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Employee Benefit Plans (Policies)	12 Months Ended
Employee Benefit Plans (Policies)	Dec. 31, 2019
Defined Benefit Post-Retirement Plans [Abstract]
Postemployment Benefit Plans, Policy	The Company has a qualified, noncontributory, defined benefit pension plan (“the Plan”) covering substantially all of its employees at December 31, 2019. Benefits paid from the plan are based on age, years of service, compensation, social security benefits and are determined in accordance with defined formulas. The Company’s policy is to fund the Plan in accordance with Employee Retirement Income Security Act of 1974 standards. Assets of the Plan are invested in publicly traded stocks and mutual funds. Prior to January 1, 2000, the Plan was a traditional defined benefit plan based on final average compensation. On January 1, 2000, the Plan was converted to a cash balance plan with grandfathering provisions for existing participants. Effective March 1, 2013, the Plan was amended. Benefit accruals for participants who, as of January 1, 2000, elected to continue participating in the traditional defined benefit plan design were frozen as of March 1, 2013. In May 2013, the noncontributory, frozen, defined benefit pension plan assumed from Alliance in the acquisition was merged into the Plan. In addition to the Plan, the Company provides supplemental employee retirement plans to certain current and former executives. The Company also assumed supplemental retirement plans for certain former executives in the Alliance acquisition. These supplemental employee retirement plans and the Plan are collectively referred to herein as “Pension Benefits.” In addition, the Company provides certain health care benefits for retired employees. Benefits were accrued over the employees’ active service period. Only employees that were employed by the Company on or before January 1, 2000 are eligible to receive post-retirement health care benefits. The Plan is contributory for participating retirees, requiring participants to absorb certain deductibles and coinsurance amounts with contributions adjusted annually to reflect cost sharing provisions and benefit limitations called for in the Plan. Employees become eligible for these benefits if they reach normal retirement age while working for the Company. For eligible employees described above, the Company funds the cost of post-retirement health care as benefits are paid. The Company elected to recognize the transition obligation on a delayed basis over twenty years. In addition, the Company assumed post-retirement medical life insurance benefits for certain Alliance employees, retirees and their spouses, if applicable, in the Alliance acquisition. These post-retirement benefits are referred to herein as “Other Benefits.” Accounting standards require an employer to: (1) recognize the overfunded or underfunded status of defined benefit post-retirement plans, which is measured as the difference between plan assets at fair value and the benefit obligation, as an asset or liability in its balance sheet; (2) recognize changes in that funded status in the year in which the changes occur through comprehensive income; and (3) measure the defined benefit plan assets and obligations as of the date of its year-end balance sheet.

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets
Cash and due from banks	$ 170,595	$ 175,550
Short-term interest bearing accounts	46,248	5,405
Equity securities, at fair value	27,771	23,053
Securities available for sale, at fair value	975,340	998,496
Securities held to maturity (fair value $641,262 and $778,675, respectively)	630,074	783,599
Federal Reserve and Federal Home Loan Bank stock	44,620	53,229
Loans held for sale	11,731	6,943
Loans	7,136,098	6,887,709
Less allowance for loan losses	72,965	72,505
Net loans	7,063,133	6,815,204
Premises and equipment, net	75,631	78,970
Goodwill	274,769	274,769
Intangible assets, net	12,020	15,599
Bank owned life insurance	181,748	177,479
Other assets	202,245	148,067
Total assets	9,715,925	9,556,363
Liabilities
Demand (noninterest bearing)	2,414,383	2,361,099
Savings, NOW and money market	4,312,244	4,076,434
Time	861,193	930,678
Total deposits	7,587,820	7,368,211
Short-term borrowings	655,275	871,696
Long-term debt	64,211	73,724
Junior subordinated debt	101,196	101,196
Other liabilities	187,026	123,627
Total liabilities	8,595,528	8,538,454
Stockholders' equity
Preferred stock, $0.01 par value; authorized 2,500,000 shares at December 31, 2019 and 2018	0	0
Common stock, $0.01 par value; authorized 100,000,000 shares at December 31, 2019 and 2018, respectively; issued 49,651,493 at December 31, 2019 and 2018	497	497
Additional paid-in-capital	576,708	575,466
Retained earnings	696,214	621,203
Accumulated other comprehensive loss	(19,026)	(43,174)
Common stock in treasury, at cost, 5,854,882 and 5,978,527 shares at December 31, 2019 and 2018, respectively	(133,996)	(136,083)
Total stockholders' equity	1,120,397	1,017,909
Total liabilities and stockholders' equity	$ 9,715,925	$ 9,556,363

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 121,021	$ 112,566	$ 82,151
Securities available for sale:
Unrealized net holding gains (losses) arising during the period, gross	25,836	(11,985)	(6,915)
Tax effect	(6,459)	2,996	2,845
Unrealized net holding gains (losses) arising during the period, net	19,377	(8,989)	(4,070)
Reclassification adjustment for net (gains) losses in net income, gross	79	6,622	(1,869)
Tax effect	(20)	(1,655)	716
Reclassification adjustment for net (gains) losses in net income, net	59	4,967	(1,153)
Amortization of unrealized net gains for the reclassification of available for sale securities to held to maturity, gross	737	688	875
Tax effect	(184)	(172)	(335)
Amortization of unrealized net gains for the reclassification of available for sale securities to held to maturity, net	553	516	540
Reclassification adjustment for an impairment write-down of equity security, gross	0	0	1,312
Tax effect	0	0	(501)
Reclassification adjustment for an impairment write-down of equity security, net	0	0	811
Total securities available for sale, net	19,989	(3,506)	(3,872)
Cash flow hedges:
Unrealized (losses) gains on derivatives (cash flow hedges), gross	(459)	1,218	901
Tax effect	115	(304)	(350)
Unrealized (losses) gains on derivatives (cash flow hedges), net	(344)	914	551
Reclassification of net unrealized (gains) on cash flow hedges to interest (income), gross	(2,012)	(2,300)	(292)
Tax effect	503	575	113
Reclassification of net unrealized (gains) on cash flow hedges to interest (income), net	(1,509)	(1,725)	(179)
Total cash flow hedges, net	(1,853)	(811)	372
Pension and other benefits:
Amortization of prior service cost and actuarial losses, gross	2,686	1,145	1,852
Tax effect	(672)	(286)	(740)
Amortization of prior service cost and actuarial losses, net	2,014	859	1,112
Decrease (increase) in unrecognized actuarial loss, gross	5,331	(12,457)	2,401
Tax effect	(1,333)	3,038	(570)
Decrease (increase) in unrecognized actuarial loss, net	3,998	(9,419)	1,831
Total pension and other benefits, net	6,012	(8,560)	2,943
Total other comprehensive income (loss)	24,148	(12,877)	(557)
Comprehensive income	$ 145,169	$ 99,689	$ 81,594

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2019

Stockholders' Equity [Abstract]

Components of Accumulated Other Comprehensive (Loss) Income

In accordance with GAAP, unrecognized prior service costs and net actuarial gains or losses associated with the Company’s pension and postretirement benefit plans and unrealized gains on derivatives and on AFS securities are included in AOCI, net of tax. For the years ended December 31, components of AOCI are:

(In thousands)	2019			2018			2017
Unrecognized prior service cost and net actuarial (losses) on pension plans	$	(21,677	)	$	(27,689	)	$	(15,284	)
Unrealized (losses) gains on derivatives (cash flow hedges)		(32	)		1,821			2,144
Unrealized net holding gains (losses) on AFS securities		2,683			(17,306	)		(8,937	)
AOCI	$	(19,026	)	$	(43,174	)	$	(22,077	)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income	$ 121,021	$ 112,566	$ 82,151
Adjustments to reconcile net income to net cash provided by operating activities
Provision for loan losses	25,412	28,828	30,988
Depreciation and amortization of premises and equipment	9,497	9,280	9,056
Net amortization on securities	3,375	4,007	4,786
Amortization of intangible assets	3,579	4,042	3,960
Amortization of operating lease right-of-use assets	7,239	0	0
Excess tax benefit on stock-based compensation	(409)	(543)	(1,769)
Stock-based compensation expense	4,210	3,936	3,644
Bank owned life insurance income	(5,355)	(5,091)	(5,175)
Trading security purchases	0	0	(1,586)
Net unrealized losses on trading securities	0	0	(623)
Proceeds from sale of loans held for sale	175,829	102,547	111,284
Originations of loans held for sale	(181,261)	(108,070)	(111,206)
Net gains on sale of loans held for sale	(786)	(286)	(349)
Net security (gains) losses	(4,213)	6,341	(1,867)
Net losses (gains) on sales and write-down of other real estate owned	227	(230)	(221)
Gain on sale of equity investment	0	0	(818)
Impairment write-down of equity security	0	0	1,312
Impairment write-down of goodwill and intangible assets	0	0	1,530
Re-evaluation of deferred tax amounts from Tax Act	0	0	4,407
Net change in other assets and other liabilities	(4,902)	(9,554)	7,400
Net cash provided by operating activities	153,463	147,773	136,904
Investing activities
Net cash used in acquisitions	0	(7,884)	(4,000)
Securities available for sale:
Proceeds from maturities, calls and principal paydowns	273,578	259,446	290,613
Proceeds from sales	26,203	101,315	14,788
Purchases	(252,963)	(132,448)	(233,804)
Securities held to maturity:
Proceeds from maturities, calls and principal paydowns	223,733	100,738	103,759
Proceeds from sales	0	0	764
Purchases	(70,660)	(400,602)	(60,706)
Equity securities:
Proceeds from sales	3,966	3,318	0
Purchases	(93)	(2)	0
Other:
Net increase in loans	(272,698)	(331,166)	(419,114)
Proceeds from Federal Home Loan Bank stock redemption	182,752	246,844	248,887
Purchases of Federal Reserve and Federal Home Loan Bank stock	(174,143)	(253,367)	(248,560)
Proceeds from settlement of bank owned life insurance	1,086	0	799
Purchases of premises and equipment, net	(6,647)	(7,402)	(6,691)
Proceeds from sale of equity investment	0	0	818
Proceeds from sales of other real estate owned	1,543	3,591	7,254
Net cash (used in) provided by investing activities	(64,343)	(417,619)	(305,193)
Financing activities
Net increase in deposits	219,609	197,575	196,948
Net (decrease) increase in short-term borrowings	(216,421)	152,573	37,419
Proceeds from issuance of long-term debt	10,598	25,000	25,000
Repayments of long-term debt	(20,111)	(40,145)	(40,218)
Proceeds from the issuance of shares to employee and other stock plans	725	1,296	3,309
Cash paid by employer for tax-withholdings on stock issuance	(1,622)	(1,893)	(3,582)
Cash dividends	(46,010)	(43,269)	(40,104)
Net cash (used in) provided by financing activities	(53,232)	291,137	178,772
Net increase (decrease) in cash and cash equivalents	35,888	21,291	10,483
Cash and cash equivalents at beginning of year	180,955	159,664	149,181
Cash and cash equivalents at end of year	216,843	180,955	159,664
Cash paid during the period for:
Interest expense	55,908	36,691	25,887
Income taxes paid	28,374	31,898	33,675
Noncash investing activities:
Loans transferred to other real estate owned	787	1,273	5,981
Acquisitions:
Fair value of assets acquired	$ 0	$ 6,274	$ 3,096

Securities, AFS Debt Securities, Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Available-for-sale Securities, Debt Maturities, Amortized Cost [Abstract]
Within one year	$ 268
From one to five years	28,692
From five to ten years	170,771
After ten years	768,823
Amortized cost	968,554	$ 1,017,626
Available-for-sale Securities, Debt Maturities, Estimated Fair Value [Abstract]
Within one year	272
From one to five years	28,668
From five to ten years	171,943
After ten years	774,457
Fair value	$ 975,340	$ 998,496

Premises, Equipment and Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Premises and Equipment [Abstract]
Premises and equipment before accumulated depreciation	$ 179,910	$ 177,385
Accumulated depreciation	104,279	98,415
Total premises and equipment	75,631	78,970
Operating lease ROU assets	$ 34,800
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets
Net Lease Cost [Abstract]
Operating lease cost	$ 7,239
Variable lease cost	2,231
Short-term lease cost	356
Sublease income	(448)
Total operating lease cost	9,378
Future Minimum Rental Commitments Related to Non-cancelable Operating Leases [Abstract]
2020	7,435
2021	6,646
2022	5,870
2023	4,969
2024	4,365
Thereafter	12,876
Total lease payments	42,161
Less: interest	(4,838)
Present value of lease liabilities	$ 37,323
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilities
Additional Information Related to Operating Leases [Abstract]
Weighted average remaining lease term, in years	7 years 8 months 8 days
Weighted average discount rate	3.00%
Cash paid for amounts included in the measurement of lease liabilities [Abstract]
Operating cash flows from operating leases	$ 6,211
ROU assets obtained in exchange for lease liabilities	41,008
Rental expense	8,000	8,600	$ 8,500
Land, Buildings and Improvements [Member]
Premises and Equipment [Abstract]
Premises and equipment before accumulated depreciation	121,479	121,808
Equipment [Member]
Premises and Equipment [Abstract]
Premises and equipment before accumulated depreciation	$ 58,431	$ 55,577
Equipment [Member] \| Minimum [Member]
Premises and Equipment [Abstract]
Property, plant and equipment, useful life	3 years
Equipment [Member] \| Maximum [Member]
Premises and Equipment [Abstract]
Property, plant and equipment, useful life	10 years
Building and Improvements [Member] \| Minimum [Member]
Premises and Equipment [Abstract]
Property, plant and equipment, useful life	5 years
Building and Improvements [Member] \| Maximum [Member]
Premises and Equipment [Abstract]
Property, plant and equipment, useful life	20 years

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Taxes [Abstract]

Components of Income Tax Expense Attributable to Operations

The significant components of income tax expense attributable to operations are as follows:

	Years ended December 31,
(In thousands)	2019			2018		2017
Current
Federal	$	28,475		$	15,762	$	35,839
State		7,653			5,977		6,599
Total Current	$	36,128		$	21,739	$	42,438

Deferred
Federal	$	(1,379	)	$	2,281	$	3,850
State		(338	)		416		(278	)
Total Deferred	$	(1,717	)	$	2,697	$	3,572
Total income tax expense	$	34,411		$	24,436	$	46,010

Components of Deferred Tax Assets and Liabilities

The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities are as follows:

	December 31,
(In thousands)	2019			2018
Deferred tax assets:
Allowance for loan losses	$	18,535		$	18,042
Lease liability		9,331			-
Deferred compensation		8,336			7,340
Postretirement benefit obligation		1,631			1,962
Fair value adjustments from acquisitions		422			663
Unrealized losses on securities		-			4,893
Accrued liabilities		1,176			913
Stock-based compensation expense		3,032			2,821
Other		1,498			1,008
Total deferred tax assets	$	43,961		$	37,642
Deferred tax liabilities:
Pension benefits	$	13,014		$	10,782
Lease right-of-use asset		9,259			-
Amortization of intangible assets		12,202			11,525
Premises and equipment, primarily due to accelerated depreciation		5,137			4,973
Unrealized gain on securities		1,770			-
Other		45			1,567
Total deferred tax liabilities	$	41,427		$	28,847
Net deferred tax asset at year-end	$	2,534		$	8,795
Net deferred tax asset at beginning of year		8,795			7,293
(Decrease) increase in net deferred tax asset	$	(6,261	)	$	1,502

Reconciliation of the Provision for Income taxes to the Amount Computed by Applying the Federal Statutory Rate

The following is a reconciliation of the provision for income taxes to the amount computed by applying the applicable Federal statutory rate to income before taxes:

	Years ended December 31
(In thousands)	2019			2018			2017
Federal income tax at statutory rate	$	32,641		$	28,770		$	44,857
Tax exempt income		(1,233	)		(1,456	)		(2,303	)
Net increase in cash surrender value of life insurance		(927	)		(973	)		(1,780	)
Federal tax credit		(1,458	)		(1,499	)		(1,343	)
State taxes, net of federal tax benefit		5,773			5,051			4,107
Federal tax reform (Tax Act)		-			-			4,407
Accounting method changes - tax rate change impact		-			(5,326	)		-
Stock-based compensation, excess tax benefit		(342	)		(456	)		(1,619	)
Other, net		(43	)		325			(316	)
Income tax expense	$	34,411		$	24,436		$	46,010

Reconciliation of Gross Unrecognized Tax Benefits

A reconciliation of the beginning and ending balance of Federal and State gross unrecognized tax benefits ("UTBs") is as follows:

(In thousands)	2019		2018
Balance at January 1	$	641	$	665
Additions for tax positions of prior years		26		27
Reduction for tax positions of prior years		-		(159	)
Current period tax positions		112		108
Balance at December 31	$	779	$	641
Amount that would affect the effective tax rate if recognized, gross of tax	$	615	$	506

Goodwill and Other Intangible Assets

12 Months Ended

Dec. 31, 2019

Goodwill and Other Intangible Assets [Abstract]

Goodwill and Other Intangible Assets

7. Goodwill and Other Intangible Assets

A summary of goodwill is as follows:

(In thousands)
January 1, 2019	$	274,769
Goodwill acquired		-
December 31, 2019	$	274,769

January 1, 2018	$	268,043
Goodwill acquired		6,726
December 31, 2018	$	274,769

The Company has intangible assets with definite useful lives capitalized on its consolidated balance sheet in the form of core deposit and other identified intangible assets. These intangible assets are amortized over their estimated useful lives, which range primarily from one to twenty years.

There was no impairment of goodwill recorded during the year ended December 31, 2019 and 2018.

A summary of core deposit and other intangible assets follows:

	December 31,
(In thousands)	2019		2018
Core deposit intangibles:
Gross carrying amount	$	8,951	$	8,975
Less: accumulated amortization		7,988		7,377
Net carrying amount	$	963	$	1,598

Identified intangible assets:
Gross carrying amount	$	34,623	$	34,623
Less: accumulated amortization		23,566		20,622
Net carrying amount	$	11,057	$	14,001

Total intangibles:
Gross carrying amount	$	43,574	$	43,598
Less: accumulated amortization		31,554		27,999
Net carrying amount	$	12,020	$	15,599

Amortization expense on intangible assets with definite useful lives totaled $3.6 million for 2019, $4.0 million for 2018 and $4.0 million for 2017. Amortization expense on intangible assets with definite useful lives is expected to total $3.0 million for 2020, $2.3 million for 2021, $1.8 million for 2022, $1.4 million for 2023, $1.1 million for 2024 and $2.4 million thereafter. Other identified intangible assets include customer lists and non-compete agreements.

During the years ended December 31, 2019 and 2018, there was no impairment of intangible assets.

Securities, HTM Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2019 USD ($) Position	Dec. 31, 2018 USD ($) Position
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 20,297	$ 23,293
12 months or longer	47,759	286,233
Total	68,056	309,526
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(187)	(91)
12 months or longer	(442)	(8,195)
Total	$ (629)	$ (8,286)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months \| Position	7	32
12 months or longer \| Position	7	118
Total \| Position	14	150
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 0	$ 0
12 months or longer	25,370	82,579
Total	25,370	82,579
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	0	0
12 months or longer	(155)	(2,773)
Total	$ (155)	$ (2,773)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months \| Position	0	0
12 months or longer \| Position	2	6
Total \| Position	2	6
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 18,040	$ 4,386
12 months or longer	22,389	145,396
Total	40,429	149,782
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(181)	(7)
12 months or longer	(287)	(3,890)
Total	$ (468)	$ (3,897)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months \| Position	3	2
12 months or longer \| Position	5	26
Total \| Position	8	28
State & Municipal [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 2,257	$ 18,907
12 months or longer	0	58,258
Total	2,257	77,165
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(6)	(84)
12 months or longer	0	(1,532)
Total	$ (6)	$ (1,616)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months \| Position	4	30
12 months or longer \| Position	0	86
Total \| Position	4	116

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current [Abstract]
Federal	$ 28,475	$ 15,762	$ 35,839
State	7,653	5,977	6,599
Total Current	36,128	21,739	42,438
Deferred [Abstract]
Federal	(1,379)	2,281	3,850
State	(338)	416	(278)
Total Deferred	(1,717)	2,697	3,572
Total income tax expense	$ 34,411	24,436	$ 46,010
Components of income taxes [Abstract]
Federal statutory income tax rate	21.00%		35.00%
Non-cash adjustment for remeasurement of deferred tax assets and liabilities for corporate rate reduction	$ 0	0	$ 4,407
Tax benefit primarily related to changes in accounting method		5,500
Deferred tax assets [Abstract]
Allowance for loan losses	18,535	18,042
Lease liability	9,331	0
Deferred compensation	8,336	7,340
Postretirement benefit obligation	1,631	1,962
Fair value adjustments from acquisitions	422	663
Unrealized losses on securities	0	4,893
Accrued liabilities	1,176	913
Stock-based compensation expense	3,032	2,821
Other	1,498	1,008
Total deferred tax assets	43,961	37,642
Deferred tax liabilities [Abstract]
Pension benefits	13,014	10,782
Lease right-of-use asset	9,259	0
Amortization of intangible assets	12,202	11,525
Premises and equipment, primarily due to accelerated depreciation	5,137	4,973
Unrealized gain on securities	1,770	0
Other	45	1,567
Total deferred tax liabilities	41,427	28,847
Net deferred tax asset at year-end	2,534	8,795	7,293
Net deferred tax asset at beginning of year	8,795	7,293
(Decrease) increase in net deferred tax asset	(6,261)	1,502
Income tax reconciliation [Abstract]
Federal income tax at statutory rate	32,641	28,770	44,857
Tax exempt income	(1,233)	(1,456)	(2,303)
Net increase in cash surrender value of life insurance	(927)	(973)	(1,780)
Federal tax credit	(1,458)	(1,499)	(1,343)
State taxes, net of federal tax benefit	5,773	5,051	4,107
Federal tax reform (Tax Act)	0	0	4,407
Accounting method changes - tax rate change impact	0	(5,326)	0
Stock-based compensation, excess tax benefit	(342)	(456)	(1,619)
Other, net	(43)	325	(316)
Total income tax expense	34,411	24,436	46,010
Reconciliation of gross unrecognized tax benefits [Roll Forward]
Beginning balance	641	665
Additions for tax positions of prior years	26	27
Reduction for tax positions of prior years	0	(159)
Current period tax positions	112	108
Ending balance	779	641	$ 665
Amount that would affect the effective tax rate if recognized, gross of tax	$ 615	$ 506
State and Local Jurisdiction [Member] \| New York State Division of Taxation and Finance [Member]
Income Tax Examination [Abstract]
Tax years under examination	2014 2015 2016

Stockholders' Equity (Details) - USD ($) $ in Thousands	12 Months Ended
Stockholders' Equity (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stockholders' Equity [Abstract]
Unrecognized prior service cost and net actuarial (losses) on pension plans	$ (21,677)	$ (27,689)	$ (15,284)
Unrealized (losses) gains on derivatives (cash flow hedges)	(32)	1,821	2,144
Unrealized net holding gains (losses) on AFS securities	2,683	(17,306)	(8,937)
AOCI	$ (19,026)	$ (43,174)	$ (22,077)
Preceding period of retained net profits for approval of Office of Comptroller of the Currency	2 years
Statutory amount available for dividend payments	$ 175,000
Number of shares available for repurchase under stock repurchase program (in shares)	1,000,000

Short-Term Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
Short-Term Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Short-term borrowings [Abstract]
Balance at year-end	$ 655,275	$ 871,696
FHLB, unused lines of credit available for short-term financing	2,400,000	1,900,000
Federal Funds Purchased [Member]
Short-term borrowings [Abstract]
Balance at year-end	65,000	80,000	$ 60,000
Average during the year	47,137	66,839	54,162
Maximum month end balance	$ 80,000	$ 80,000	$ 80,000
Weighted average rate during the year	3.90%	3.43%	2.16%
Weighted average rate at year-end	2.84%	4.25%	2.41%
Securities Sold Under Repurchase Agreements [Member]
Short-term borrowings [Abstract]
Balance at year-end	$ 143,775	$ 160,696	$ 182,123
Average during the year	123,337	146,135	175,539
Maximum month end balance	$ 146,410	$ 170,350	$ 190,326
Weighted average rate during the year	0.33%	0.16%	0.07%
Weighted average rate at year-end	0.40%	0.38%	0.07%
Other Short-Term Borrowings [Member]
Short-term borrowings [Abstract]
Balance at year-end	$ 446,500	$ 631,000	$ 477,000
Average during the year	403,453	514,662	460,334
Maximum month end balance	$ 576,000	$ 653,000	$ 591,000
Weighted average rate during the year	1.85%	1.56%	1.02%
Weighted average rate at year-end	1.73%	1.82%	1.18%

Regulatory Capital Requirements (Tables)

12 Months Ended

Dec. 31, 2019

Regulatory Capital Requirements [Abstract]

Compliance with Regulatory Compliance Requirements Under Banking Regulations

The Company and NBT Bank’s actual capital amounts and ratios are presented as follows:

	Actual					Regulatory Ratio Requirements
(Dollars in thousands)	Amount		Ratio			Minimum Capital Adequacy			Minimum plus Buffer			For Classification as Well- Capitalized
As of December 31, 2019
Tier I Capital (to average assets)
Company	$	963,147		10.33	%		4.00	%					5.00	%
NBT Bank		894,407		9.64	%		4.00	%					5.00	%
Common Equity Tier 1 Capital
Company		866,147		11.29	%		4.50	%		7.000	%		6.50	%
NBT Bank		894,407		11.76	%		4.50	%		7.000	%		6.50	%
Tier I Capital (to risk-weighted assets)
Company		963,147		12.56	%		6.00	%		8.500	%		8.00	%
NBT Bank		894,407		11.76	%		6.00	%		8.500	%		8.00	%
Total Capital (to risk-weighted assets)
Company		1,037,041		13.52	%		8.00	%		10.500	%		10.00	%
NBT Bank		968,301		12.73	%		8.00	%		10.500	%		10.00	%

As of December 31, 2018
Tier I Capital (to average assets)
Company	$	880,448		9.52	%		4.00	%					5.00	%
NBT Bank		825,863		8.98	%		4.00	%					5.00	%
Common Equity Tier 1 Capital
Company		783,448		10.49	%		4.50	%		6.375	%		6.50	%
NBT Bank		825,863		11.14	%		4.50	%		6.375	%		6.50	%
Tier I Capital (to risk-weighted assets)
Company		880,448		11.79	%		6.00	%		7.875	%		8.00	%
NBT Bank		825,863		11.14	%		6.00	%		7.875	%		8.00	%
Total Capital (to risk-weighted assets)
Company		954,232		12.78	%		8.00	%		9.875	%		10.00	%
NBT Bank		899,647		12.14	%		8.00	%		9.875	%		10.00	%

Loans (Details) - USD ($) $ in Thousands	12 Months Ended
Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Summary of Loans [Abstract]
Net Loans	$ 7,136,098	$ 6,887,709
Deferred loan origination costs, net	35,300	43,500
Residential loans held for sale	11,500	6,900
Loans serviced for unrelated third parties	612,300	557,900
Mortgage servicing rights	800	500
Loans and Leases Receivable, Related Parties [Roll Forward]
Balance at January 1	1,638	1,577
New loans	587	260
Adjustment due to change in composition of related parties	389	0
Repayments	(448)	(199)
Balance at December 31	2,166	1,638
Commercial Loans [Member]
Summary of Loans [Abstract]
Net Loans	3,444,266	3,222,310
Commercial Loans [Member] \| Commercial [Member]
Summary of Loans [Abstract]
Net Loans	1,302,209	1,291,568
Commercial Loans [Member] \| Commercial Real Estate [Member]
Summary of Loans [Abstract]
Net Loans	2,142,057	1,930,742
Commercial Loans [Member] \| Agricultural and Agricultural Real Estate Mortgages [Member]
Summary of Loans [Abstract]
Loans serviced for unrelated third parties	25,600	27,200
Residential Real Estate [Member]
Summary of Loans [Abstract]
Net Loans	1,445,156	1,380,836
Consumer Loans [Member]
Summary of Loans [Abstract]
Net Loans	2,246,676	2,284,563
Consumer Loans [Member] \| Indirect Auto [Member]
Summary of Loans [Abstract]
Net Loans	1,193,635	1,216,144
Consumer Loans [Member] \| Specialty Lending [Member]
Summary of Loans [Abstract]
Net Loans	542,063	524,928
Consumer Loans [Member] \| Home Equity [Member]
Summary of Loans [Abstract]
Net Loans	444,082	474,566
Consumer Loans [Member] \| Other Consumer [Member]
Summary of Loans [Abstract]
Net Loans	$ 66,896	$ 68,925

Regulatory Capital Requirements

12 Months Ended

Dec. 31, 2019

Regulatory Capital Requirements [Abstract]

Regulatory Capital Requirements

16. Regulatory Capital Requirements

The Company and the Bank are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the consolidated financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Bank must meet specific capital guidelines that involve quantitative measures of NBT Bank’s assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. The capital amounts and classifications are also subject to qualitative judgments by the regulators about components, risk weightings and other factors.

Quantitative measures established by regulation to ensure capital adequacy require the Company and the Bank to maintain minimum amounts and ratios (set forth in the table below) of total and Tier 1 Capital to risk-weighted assets and of Tier 1 capital to average assets. As of December 31, 2019 and 2018, the Company and the Bank meet all capital adequacy requirements to which they were subject.

Under their prompt corrective action regulations, regulatory authorities are required to take certain supervisory actions (and may take additional discretionary actions) with respect to an undercapitalized institution. Such actions could have a direct material effect on an institution’s financial statements. The regulations establish a framework for the classification of banks into five categories: well-capitalized, adequately capitalized, undercapitalized, significantly undercapitalized and critically undercapitalized. As of December 31, 2019 and 2018, the most recent notifications from the Bank’s regulators categorized the Bank as well-capitalized under the regulatory framework for prompt corrective action. To be categorized as well-capitalized the Bank must maintain minimum total risk-based, Tier 1 risk-based and Tier 1 Capital to Average Asset ratios as set forth in the table below. There are no conditions or events since that notification that management believes have changed the Bank’s category.

Beginning in 2016, in addition to maintaining minimum capital ratios, the Company began to be subject to a capital conservation buffer ("Buffer") above the minimum to avoid restriction on capital distributions and discretionary bonus paychecks to officers. At December 31, 2019 and 2018 the Buffer was 2.500% and 1.875%, respectively. The Buffer regulatory minimum ratio is in the process of being phased in over four years, which started in 2016 with the minimum requirement of 0.625%, and is fully phased in for fiscal year 2019 with a requirement of 2.500%.

The Company and NBT Bank’s actual capital amounts and ratios are presented as follows:

	Actual					Regulatory Ratio Requirements
(Dollars in thousands)	Amount		Ratio			Minimum Capital Adequacy			Minimum plus Buffer			For Classification as Well- Capitalized
As of December 31, 2019
Tier I Capital (to average assets)
Company	$	963,147		10.33	%		4.00	%					5.00	%
NBT Bank		894,407		9.64	%		4.00	%					5.00	%
Common Equity Tier 1 Capital
Company		866,147		11.29	%		4.50	%		7.000	%		6.50	%
NBT Bank		894,407		11.76	%		4.50	%		7.000	%		6.50	%
Tier I Capital (to risk-weighted assets)
Company		963,147		12.56	%		6.00	%		8.500	%		8.00	%
NBT Bank		894,407		11.76	%		6.00	%		8.500	%		8.00	%
Total Capital (to risk-weighted assets)
Company		1,037,041		13.52	%		8.00	%		10.500	%		10.00	%
NBT Bank		968,301		12.73	%		8.00	%		10.500	%		10.00	%

As of December 31, 2018
Tier I Capital (to average assets)
Company	$	880,448		9.52	%		4.00	%					5.00	%
NBT Bank		825,863		8.98	%		4.00	%					5.00	%
Common Equity Tier 1 Capital
Company		783,448		10.49	%		4.50	%		6.375	%		6.50	%
NBT Bank		825,863		11.14	%		4.50	%		6.375	%		6.50	%
Tier I Capital (to risk-weighted assets)
Company		880,448		11.79	%		6.00	%		7.875	%		8.00	%
NBT Bank		825,863		11.14	%		6.00	%		7.875	%		8.00	%
Total Capital (to risk-weighted assets)
Company		954,232		12.78	%		8.00	%		9.875	%		10.00	%
NBT Bank		899,647		12.14	%		8.00	%		9.875	%		10.00	%

- Definition

The entire disclosure for regulatory capital requirement for depository and lending institutions. Institutions include, but not are not limited to, finance company, insured depository institution, bank holding company, savings and loan association holding company, bank and savings institution not federally insured, mortgage company, foreign financial institution and credit union.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1C
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958572-112826

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1D
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958573-112826

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958570-112826

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958569-112826

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1G
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958577-112826

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1F
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958575-112826

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1E
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958574-112826

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958568-112826

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-URI http://asc.fasb.org/extlink&oid=117337116&loc=d3e65071-112826

+ Details

Deposits (Tables)

12 Months Ended

Dec. 31, 2019

Deposits [Abstract]

Maturity Distribution of Time Deposits

The following table sets forth the maturity distribution of time deposits:

(In thousands)	December 31, 2019
Within one year	$	554,132
After one but within two years		220,769
After two but within three years		50,593
After three but within four years		15,064
After four but within five years		20,453
After five years		182
Total	$	861,193

Securities, Unrealized Gains (Losses) Related to Equity Securities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Issuer	Dec. 31, 2018 USD ($) Issuer
Gains and losses on equity securities [Abstract]
Net gains and losses recognized on equity securities	$ 4,280	$ 281
Less: Net gains and losses recognized during the period on equity securities sold during the period	3,966	555
Unrealized gains and losses recognized on equity securities still held	314	(274)
Equity Securities without Readily Determinable Fair Value, Annual Amount [Abstract]
Impairment adjustments of equity securities without readily determinable fair values	0	0
Carrying amount of equity securities without readily determinable fair values	4,000	4,000
Downward adjustments of equity securities without readily determinable fair values	0	0
Upward adjustments of equity securities without readily determinable fair values	$ 0	$ 0
Number of issuers whose holdings exceeded 10% of consolidated stockholders' equity, excluding U.S. Government securities \| Issuer	0	0
Visa Class B Common Stock [Member]
Equity Securities without Readily Determinable Fair Value, Annual Amount [Abstract]
Gain from sale of equity securities without readily determinable fair value	$ 4,000

Stockholders' Equity

12 Months Ended

Dec. 31, 2019

Stockholders' Equity [Abstract]

Stockholders' Equity

15. Stockholders’ Equity

(In thousands)	2019			2018			2017
Unrecognized prior service cost and net actuarial (losses) on pension plans	$	(21,677	)	$	(27,689	)	$	(15,284	)
Unrealized (losses) gains on derivatives (cash flow hedges)		(32	)		1,821			2,144
Unrealized net holding gains (losses) on AFS securities		2,683			(17,306	)		(8,937	)
AOCI	$	(19,026	)	$	(43,174	)	$	(22,077	)

Certain restrictions exist regarding the ability of the subsidiary bank to transfer funds to the Company in the form of cash dividends. The approval of the Office of Comptroller of the Currency (the “OCC") is required to pay dividends when a bank fails to meet certain minimum regulatory capital standards or when such dividends are in excess of a subsidiary bank's earnings retained in the current year plus retained net profits for the preceding two years as specified in applicable OCC regulations. At December 31, 2019, approximately $175.0 million of the total stockholders’ equity of the Bank was available for payment of dividends to the Company without approval by the OCC. The Bank’s ability to pay dividends also is subject to the Bank being in compliance with regulatory capital requirements. The Bank is currently in compliance with these requirements. Under the State of Delaware General Corporation Law, the Company may declare and pay dividends either out of accumulated net retained earnings or capital surplus.

The Company did not purchase any shares of its common stock during the year ended December 31, 2019. There are 1,000,000 shares available for repurchase under this plan, which expires on December 31, 2021.

Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2019

Defined Benefit Post-Retirement Plans [Abstract]

Components of Accumulated Other Comprehensive Income (Loss), Net Periodic Benefit Cost

The components of AOCI, which have not yet been recognized as components of net periodic benefit cost, related to pensions and other post-retirement benefits are summarized below:

	Pension Benefits				Other Benefits
(In thousands)	2019		2018		2019		2018
Net actuarial loss	$	28,334	$	35,538	$	125	$	844
Prior service cost		491		570		94		145
Total amounts recognized in AOCI (pre-tax)	$	28,825	$	36,108	$	219	$	989

Changes in Benefit Obligations, Changes in Plan Assets, and the Funded Status of the Pension Plans and Postretirement Benefits

A December 31 measurement date is used for the pension, supplemental pension and post-retirement benefit plans. The following table sets forth changes in benefit obligations, changes in plan assets and the funded status of the pension plans and other post-retirement benefits:

	Pension Benefits						Other Benefits
(In thousands)	2019			2018			2019			2018
Change in benefit obligation:
Benefit obligation at beginning of year	$	85,134		$	90,950		$	7,034		$	8,050
Service cost		1,723			1,659			7			10
Interest cost		3,942			3,645			272			327
Plan participants' contributions		-			-			201			209
Actuarial loss (gain)		6,030			(3,977	)		(719	)		(762	)
Amendments		-			337			-			-
Benefits paid		(6,243	)		(7,480	)		(712	)		(800	)
Projected benefit obligation at end of year	$	90,586		$	85,134		$	6,083		$	7,034
Change in plan assets:
Fair value of plan assets at beginning of year	$	109,746		$	124,226		$	-		$	-
Gain (loss) on plan assets		18,120			(8,381	)		-			-
Employer contributions		1,372			1,381			511			591
Plan participants' contributions		-			-			201			209
Benefits paid		(6,243	)		(7,480	)		(712	)		(800	)
Fair value of plan assets at end of year	$	122,995		$	109,746		$	-		$	-

Funded (unfunded) status at year end	$	32,409		$	24,612		$	(6,083	)	$	(7,034	)

Amounts Recognized in Balance Sheet

An asset is recognized for an overfunded plan and a liability is recognized for an underfunded plan. The accumulated benefit obligation for pension benefits was $90.6 million and $85.1 million at December 31, 2019 and 2018, respectively. The accumulated benefit obligation for other post-retirement benefits was $6.1 million and $7.0 million at December 31, 2019 and 2018, respectively. The funded status of the pension and other post-retirement benefit plans has been recognized as follows in the consolidated balance sheets at December 31, 2019 and 2018.

	Pension Benefits						Other Benefits
(In thousands)	2019			2018			2019			2018
Other assets	$	51,988		$	42,900		$	-		$	-
Other liabilities		(19,579	)		(18,288	)		(6,083	)		(7,034	)
Funded status	$	32,409		$	24,612		$	(6,083	)	$	(7,034	)

Assumptions used to Determine Benefit Obligations and Net Periodic Pension Cost

The following assumptions were used to determine the benefit obligation and the net periodic pension cost for the years indicated:

	Years ended December 31,
	2019	2018	2017
Weighted average assumptions:
The following assumptions were used to determine benefit obligations:
Discount rate	3.69% - 3.73%	4.79% - 4.80%	4.20% - 4.21%
Expected long-term return on plan assets	7.00%	7.00%	7.00%
Rate of compensation increase	3.00%	3.00%	3.00%

The following assumptions were used to determine net periodic pension cost:
Discount rate	4.79% - 4.80%	4.20% - 4.21%	4.76% - 4.84%
Expected long-term return on plan assets	7.00%	7.00%	7.00%
Rate of compensation increase	3.00%	3.00%	3.00%

Net Periodic Pension Benefits and Other Benefit Costs

Net periodic benefit cost and other amounts recognized in OCI for the years ended December 31 included the following components:

	Pension Benefits									Other Benefits
(In thousands)	2019			2018			2017			2019			2018			2017
Components of net periodic benefit cost:
Service cost	$	1,723		$	1,659		$	1,511		$	7		$	10		$	12
Interest cost		3,942			3,645			4,168			272			327			357
Expected return on plan assets		(7,480	)		(8,478	)		(7,929	)		-			-			-
Amortization of prior service cost		43			40			46			50			51			51
Amortization of unrecognized net loss		2,593			930			1,668			-			124			87
Net periodic pension cost (benefit)	$	821		$	(2,204	)	$	(536	)	$	329		$	512		$	507

Other changes in plan assets and benefit obligations recognized in OCI (pre-tax):
Net (gain) loss	$	(4,611	)	$	12,882		$	(3,075	)	$	(720	)	$	(762	)	$	388
Prior service cost		-			337			-			-			-			286
Amortization of prior service (cost)		(43	)		(40	)		(46	)		(50	)		(51	)		(51	)
Amortization of unrecognized net (loss)		(2,593	)		(930	)		(1,668	)		-			(124	)		(87	)
Total recognized in OCI	$	(7,247	)	$	12,249		$	(4,789	)	$	(770	)	$	(937	)	$	536

Total recognized in net periodic benefit cost and OCI, pre-tax	$	(6,426	)	$	10,045		$	(5,325	)	$	(441	)	$	(425	)	$	1,043

Estimated Future Benefit Payments for the Pension Plans and Other Postretirement Benefit Plans

The following table sets forth estimated future benefit payments for the pension plans and other post-retirement benefit plans as of December 31, 2019:

(In thousands)	Pension Benefits		Other Benefits
2020	$	6,916	$	497
2021		6,722		464
2022		6,722		462
2023		6,582		457
2024		7,827		451
2025 - 2029		35,215		2,070

Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates

For measurement purposes, the annual rates of increase in the per capita cost of covered medical and prescription drug benefits for fiscal year 2019 were assumed to be 4.5% to 7.0% percent. The rates were assumed to decrease gradually to 3.8% for fiscal year 2075 and remain at that level thereafter. Assumed health care cost trend rates have a significant effect on amounts reported for health care plans. A one-percentage point change in the health care trend rates would have the following effects as of and for the year ended December 31, 2019:

(In thousands)	One Percentage Point Increase		One Percentage Point Decrease
Increase (decrease) on total service and interest cost components	$	29	$	(25	)
Increase (decrease) on post-retirement accumulated benefit obligation		628		(543	)

Target and Actual Allocations of Defined Benefit Pension Plan's Assets

The target and actual allocations expressed as a percentage of the defined benefit pension plan’s assets are as follows:

	Target 2019	2019	2018
Cash and cash equivalents	0 - 15%	3%	4%
Fixed income securities	30 - 60%	40%	39%
Equities	40 - 70%	57%	57%
Total		100%	100%

Financial Instruments Recorded at Fair Value on a Recurring Basis by the Plan

The following table presents the financial instruments recorded at fair value on a recurring basis by the Plan:

(In thousands)	Level 1		Level 2		December 31, 2019
Cash and cash equivalents	$	4,143	$	-	$	4,143
Foreign equity mutual funds		40,239		-		40,239
Equity mutual funds		29,886		-		29,886
U.S. government bonds		-		58		58
Corporate bonds		-		48,669		48,669
Total	$	74,268	$	48,727	$	122,995

	Level 1		Level 2		December 31, 2018
Cash and cash equivalents	$	4,095	$	-	$	4,095
Foreign equity mutual funds		38,861		-		38,861
Equity mutual funds		24,124		-		24,124
U.S. government bonds		-		76		76
Corporate bonds		-		42,590		42,590
Total	$	67,080	$	42,666	$	109,746

Reclassification Adjustments Out of Other Comprehensive Income (Loss) (Tables)

12 Months Ended

Dec. 31, 2019

Reclassification Adjustments Out of Other Comprehensive Income (Loss) [Abstract]

Reclassification Out of Accumulated Other Comprehensive Income

The following table summarizes the reclassification adjustments out of AOCI:

Detail About AOCI Components	Amount Reclassified From AOCI									Affected Line Item in the Consolidated Statements of Comprehensive Income (Loss)
(In thousands)	Years ended December 31,
(In thousands)	2019			2018			2017
AFS securities:
Losses (gains) on AFS securities	$	79		$	6,622		$	(1,869	)	Net securities (gains) losses
Amortization of unrealized gains related to securities transfer		737			688			875		Interest income
Impairment write-down of an equity security		-			-			1,312		Other noninterest income
Tax effect	$	(204	)	$	(1,827	)	$	(120	)	Income tax (benefit)
Net of tax	$	612		$	5,483		$	198

Cash flow hedges:
Net unrealized (gains) on cash flow hedges reclassified to interest expense	$	(2,012	)	$	(2,300	)	$	(292	)	Interest expense
Tax effect	$	503		$	575		$	113		Income tax expense
Net of tax	$	(1,509	)	$	(1,725	)	$	(179	)

Pension and other benefits:
Amortization of net losses	$	2,593		$	1,054		$	1,755		Other noninterest expense
Amortization of prior service costs		93			91			97		Other noninterest expense
Tax effect	$	(672	)	$	(286	)	$	(740	)	Income tax (benefit)
Net of tax	$	2,014		$	859		$	1,112

Total reclassifications, net of tax	$	1,117		$	4,617		$	1,131

Derivative Instruments and Hedging Activities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Agreement	Dec. 31, 2018 USD ($) Agreement	Dec. 31, 2017 USD ($)
Interest rate derivatives - Included Component [Abstract]
Amount of (loss) or gain recognized in OCI	$ (459)	$ 1,218	$ 901
Amount of gain reclassified from AOCI into interest expense	(2,012)	(2,300)	(292)
Derivatives Designated as Hedging Instruments [Member] \| Interest Rate Swaps [Member]
Fair value adjustment recorded related to notional amount of derivatives outstanding and notional amount of risk participation agreements [Abstract]
Fair value adjustment included in other assets	4	2,428
Fair value adjustment included in other liabilities	45	0
Notional amount	50,000	225,000
Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedging [Member]
Interest rate derivatives - Included Component [Abstract]
Amount of (loss) or gain recognized in OCI	(459)	1,218	901
Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedging [Member] \| Interest (Income) Expense [Member]
Interest rate derivatives - Included Component [Abstract]
Amount of gain reclassified from AOCI into interest expense	(2,012)	(2,300)	(292)
Derivatives Designated as Hedging Instruments [Member] \| Cash Flow Hedging [Member] \| Interest Rate Swaps [Member]
Fair value adjustment recorded related to notional amount of derivatives outstanding and notional amount of risk participation agreements [Abstract]
Amount to be reclassified from AOCI as a reduction to interest expense during next twelve months	39
Derivatives Not Designated as Hedging Instruments [Member] \| Other Income [Member]
Gain or loss recognized in income on derivatives not designating as a hedging relationship [Abstract]
Decrease (increase) in other income	$ 295	$ (120)	$ 101
Derivatives Not Designated as Hedging Instruments [Member] \| Interest Rate Swaps [Member]
Interest rate derivatives [Abstract]
Number of risk participation agreements held \| Agreement	15	9
Fair value adjustment recorded related to notional amount of derivatives outstanding and notional amount of risk participation agreements [Abstract]
Fair value adjustment included in other assets and other liabilities	$ 41,650	$ 17,572
Notional amount	963,209	653,369
Derivatives Not Designated as Hedging Instruments [Member] \| Interest Rate Swaps [Member] \| Other Assets [Member]
Interest rate derivatives [Abstract]
Fair value of derivative asset	112	36
Derivatives Not Designated as Hedging Instruments [Member] \| Interest Rate Swaps [Member] \| Other Liabilities [Member]
Interest rate derivatives [Abstract]
Fair value of derivative liability	82	17
Derivatives Not Designated as Hedging Instruments [Member] \| Risk Participation Agreements [Member]
Fair value adjustment recorded related to notional amount of derivatives outstanding and notional amount of risk participation agreements [Abstract]
Notional amount	$ 97,614	$ 70,785

Commitments and Contingent Liabilities (Tables)

12 Months Ended

Dec. 31, 2019

Commitments and Contingent Liabilities [Abstract]

Maximum Commitments Potential Obligation

The Company is a party to certain financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit, unused lines of credit, standby letters of credit and certain agricultural real estate loans sold to investors with recourse, with the sold portion having a government guarantee that is assignable back to the Company upon repurchase of the loan in the event of default. The Company’s exposure to credit loss in the event of nonperformance by the other party to the commitments to extend credit, unused lines of credit, standby letters of credit and loans sold with recourse is represented by the contractual amount of those instruments. The credit risk associated with commitments to extend credit and standby and commercial letters of credit is essentially the same as that involved with extending loans to customers and is subject to normal credit policies. Collateral may be obtained based on management’s assessment of the customer’s creditworthiness.

	At December 31,
(In thousands)	2019		2018
Unused lines of credit	$	340,703	$	313,987
Commitments to extend credits, primarily variable rate		1,579,414		1,420,795
Standby letters of credit		34,479		41,194
Loans sold with recourse		25,639		27,223

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2019

Long-Term Debt [Abstract]

Summary of Long-term Debt

Long-term debt consists of obligations having an original maturity at issuance of more than one year. A majority of the Company’s long-term debt is comprised of FHLB advances collateralized by the FHLB stock owned by the Company, and a blanket lien on its residential real estate mortgage loans. As of December 31, 2019 the Company had no callable long-term debt. A summary is as follows:

(Dollars in thousands)	December 31, 2019			December 31, 2018
Maturity	Amount		Weighted Average Rate	Amount		Weighted Average Rate
2019	$	-	-	$	20,000	1.96%
2020		25,000	2.34%		25,000	2.34%
2021		25,021	2.56%		25,039	2.56%
2022		10,598	2.53%		-	-
2031		3,592	2.45%		3,685	2.45%
Total	$	64,211		$	73,724

Securities, Available for Sale (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt securities, available-for-sale [Abstract]
Amortized cost	$ 968,554	$ 1,017,626
Unrealized gains	8,319	1,216
Unrealized losses	1,533	20,346
Estimated fair value	975,340	998,496
Components of net realized gains (losses) on sale of AFS securities [Abstract]
Gross realized gains	73	0	$ 2,241
Gross realized (losses)	(152)	(6,622)	(372)
Net AFS realized (losses) gains	(79)	(6,622)	1,869
Gains from calls on securities available for sale	25	0	100
OTTI loss realized on equity investment	0	0	$ 1,300
Federal Agency [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	34,998	84,982
Unrealized gains	3	10
Unrealized losses	243	693
Estimated fair value	34,758	84,299
State & Municipal [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	2,533	30,136
Unrealized gains	0	16
Unrealized losses	20	237
Estimated fair value	2,513	29,915
Mortgage-Backed, Government Sponsored Enterprises [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	453,614	493,225
Unrealized gains	4,982	439
Unrealized losses	239	10,354
Estimated fair value	458,357	483,310
Mortgage-backed Securities, U.S. Government Agency Securities [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	44,758	29,190
Unrealized gains	667	270
Unrealized losses	156	475
Estimated fair value	45,269	28,985
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	328,499	332,409
Unrealized gains	1,949	344
Unrealized losses	467	7,211
Estimated fair value	329,981	325,542
Collateralized Mortgage Obligations, U.S. Government Agency Securities [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	104,152	47,684
Unrealized gains	718	137
Unrealized losses	408	1,376
Estimated fair value	$ 104,462	$ 46,445

Allowance for Loan Losses and Credit Quality of Loans, Allowance for Loan Losses and Recorded Investment in Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	$ 72,965	$ 72,505	$ 69,500	$ 65,200
Allowance for loans individually evaluated for impairment	0	25
Allowance for loans collectively evaluated for impairment	72,965	72,480
Ending balance of loans	7,136,098	6,887,709
Commercial Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	34,525	32,759	27,606	25,444
Allowance for loans individually evaluated for impairment	0	25
Allowance for loans collectively evaluated for impairment	34,525	32,734
Ending balance of loans	3,444,266	3,222,310
Consumer Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	35,647	37,178	36,830	33,375
Allowance for loans individually evaluated for impairment	0	0
Allowance for loans collectively evaluated for impairment	35,647	37,178
Ending balance of loans	2,246,676	2,284,563
Residential Real Estate [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	2,793	2,568	$ 5,064	$ 6,381
Allowance for loans individually evaluated for impairment	0	0
Allowance for loans collectively evaluated for impairment	2,793	2,568
Ending balance of loans	1,445,156	1,380,836
Originated Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans	6,871,220	6,565,118
Ending balance of loans individually evaluated for impairment	18,253	20,578
Ending balance of loans collectively evaluated for impairment	6,852,967	6,544,540
Originated Loans [Member] \| Commercial Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans	3,329,000	3,078,620
Ending balance of loans individually evaluated for impairment	3,488	5,786
Ending balance of loans collectively evaluated for impairment	3,325,512	3,072,834
Originated Loans [Member] \| Consumer Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans	2,222,943	2,252,939
Ending balance of loans individually evaluated for impairment	7,044	7,887
Ending balance of loans collectively evaluated for impairment	2,215,899	2,245,052
Originated Loans [Member] \| Residential Real Estate [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans	1,319,277	1,233,559
Ending balance of loans individually evaluated for impairment	7,721	6,905
Ending balance of loans collectively evaluated for impairment	1,311,556	1,226,654
Acquired Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	0	0
Ending balance of loans	264,878	322,591
Ending balance of loans collectively evaluated for impairment	264,878	322,591
Acquired Loans [Member] \| Commercial Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans	115,266	143,690
Ending balance of loans collectively evaluated for impairment	115,266	143,690
Acquired Loans [Member] \| Consumer Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans	23,733	31,624
Ending balance of loans collectively evaluated for impairment	23,733	31,624
Acquired Loans [Member] \| Residential Real Estate [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans	125,879	147,277
Ending balance of loans collectively evaluated for impairment	$ 125,879	$ 147,277

Long-Term Debt

12 Months Ended

Dec. 31, 2019

Long-Term Debt [Abstract]

Long-Term Debt

10. Long-Term Debt

(Dollars in thousands)	December 31, 2019			December 31, 2018
Maturity	Amount		Weighted Average Rate	Amount		Weighted Average Rate
2019	$	-	-	$	20,000	1.96%
2020		25,000	2.34%		25,000	2.34%
2021		25,021	2.56%		25,039	2.56%
2022		10,598	2.53%		-	-
2031		3,592	2.45%		3,685	2.45%
Total	$	64,211		$	73,724

Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Long-term debt by maturity, amount [Abstract]
Due in next 12 months	$ 25,000	$ 20,000
Due in year two	25,021	25,000
Due in year three	10,598	25,039
Due in year four		0
Due in year twelve	3,592
Due in year thirteen		3,685
Total	$ 64,211	$ 73,724
Long-term debt by maturity, weighted average rate [Abstract]
Due in next 12 months	2.34%	1.96%
Due in year two	2.56%	2.34%
Due in year three	2.53%	2.56%
Due in year four		0.00%
Due in year twelve	2.45%
Due in year thirteen		2.45%

Junior Subordinated Debt (Tables)

12 Months Ended

Dec. 31, 2019

Junior Subordinated Debt [Abstract]

Schedule of Debt of VIE where Entity is not Primary Beneficiary

As of December 31, 2019, the Trusts had the following trust preferred securities outstanding and held the following junior subordinated debentures of the Company (dollars in thousands):

Description	Issuance Date	Trust Preferred Securities Outstanding		Interest Rate	Trust Preferred Debt Owed To Trust		Final Maturity Date
CNBF Capital Trust I	August 1999	$	18,000	3-month LIBOR plus 2.75%	$	18,720	August 2029
NBT Statutory Trust I	November 2005		5,000	3-month LIBOR plus 1.40%		5,155	December 2035
NBT Statutory Trust II	February 2006		50,000	3-month LIBOR plus 1.40%		51,547	March 2036
Alliance Financial Capital Trust I	December 2003		10,000	3-month LIBOR plus 2.85%		10,310	January 2034
Alliance Financial Capital Trust II	September 2006		15,000	3-month LIBOR plus 1.65%		15,464	September 2036

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
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-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21538-112644

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Employee Benefit Plans, Financial Instruments Recorded At Fair Value On A Recurring Basis By The Plan (Details) - Pension Benefits [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	$ 122,995	$ 109,746	$ 124,226
Recurring Basis [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	122,995	109,746
Recurring Basis [Member] \| Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	74,268	67,080
Recurring Basis [Member] \| Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	48,727	42,666
Recurring Basis [Member] \| Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	4,143	4,095
Recurring Basis [Member] \| Cash and Cash Equivalents [Member] \| Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	4,143	4,095
Recurring Basis [Member] \| Cash and Cash Equivalents [Member] \| Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] \| Foreign Equity Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	40,239	38,861
Recurring Basis [Member] \| Foreign Equity Mutual Funds [Member] \| Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	40,239	38,861
Recurring Basis [Member] \| Foreign Equity Mutual Funds [Member] \| Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] \| Equity Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	29,886	24,124
Recurring Basis [Member] \| Equity Mutual Funds [Member] \| Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	29,886	24,124
Recurring Basis [Member] \| Equity Mutual Funds [Member] \| Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] \| US Government Bonds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	58	76
Recurring Basis [Member] \| US Government Bonds [Member] \| Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] \| US Government Bonds [Member] \| Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	58	76
Recurring Basis [Member] \| Corporate Bonds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	48,669	42,590
Recurring Basis [Member] \| Corporate Bonds [Member] \| Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] \| Corporate Bonds [Member] \| Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	$ 48,669	$ 42,590

Commitments and Contingent Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Commitments and Contingent Liabilities [Abstract]
Percentage of the Company's loans secured by real estate	60.00%
Federal Reserve Bank Requirement [Abstract]
Federal Reserve Bank maintenance period	14 days
Average reserve at Federal Reserve Bank for maintenance period	$ 37,300
Maximum [Member]
Guarantor Obligations [Abstract]
Obligation instrument term	1 year
Unused lines of Credit [Member]
Guarantor Obligations [Abstract]
Commitments - maximum potential obligation	$ 340,703	$ 313,987
Commitment to Extend Credits, Primarily Variable Rate [Member]
Guarantor Obligations [Abstract]
Commitments - maximum potential obligation	1,579,414	1,420,795
Standby Letters of Credit [Member]
Guarantor Obligations [Abstract]
Commitments - maximum potential obligation	34,479	41,194
Loans Sold with Recourse [Member]
Guarantor Obligations [Abstract]
Commitments - maximum potential obligation	$ 25,639	$ 27,223

Allowance for Loan Losses and Credit Quality of Loans

12 Months Ended

Dec. 31, 2019

Allowance for Loan Losses and Credit Quality of Loans [Abstract]

Allowance for Loan Losses and Credit Quality of Loans

5. Allowance for Loan Losses and Credit Quality of Loans

Allowance for Loan Losses

The allowance for loan losses is maintained at a level estimated by management to provide adequately for probable incurred losses inherent in the current loan portfolio. The appropriateness of the allowance for loan losses is continuously monitored. It is assessed for appropriateness using a methodology designed to ensure the level of the allowance reasonably reflects the loan portfolio’s risk profile and can absorb all reasonably estimable credit losses inherent in the current loan portfolio.

To develop and document a systematic methodology for determining the allowance for loan losses, the Company has divided the loan portfolio into three segments, each with different risk characteristics and methodologies for assessing risk. Those segments are further segregated between our loans accounted for under the amortized cost method (referred to as “originated” loans) and loans acquired in a business combination (referred to as “acquired” loans). Each portfolio segment is broken down into class segments where appropriate. Class segments contain unique measurement attributes, risk characteristics and methods for monitoring and assessing risk that are necessary to develop the allowance for loan losses. Unique characteristics such as borrower type, loan type, collateral type and risk characteristics define each class segment.

During the first quarter of 2018, the Company made adjustments to the class segments within the portfolios to better align risk characteristics and reflect the monitoring and assessment of risks as the portfolios continue to evolve. Agricultural and Agricultural Real Estate were consolidated with Commercial and Industrial and Commercial Real Estate, respectively. Agricultural loans are a type of Commercial loan with some specific underwriting guidelines; however, as of March 31, 2018, the portfolio had decreased to less than 3% of the Commercial portfolio and separation was no longer warranted. The Indirect class segment was further separated into Indirect Auto and Specialty Lending class segments. The growth in our Specialty Lending portfolio to 21% of Consumer Loans as of March 31, 2018 warranted evaluation of this class separately due to different risk characteristics from Indirect Auto class segments. The Direct and Home Equity class segments were consolidated into Direct to reflect common management, similar underwriting and in-market focus. The change to the class segments in the allowance methodology did not have a significant impact on the allowance for loan losses. The following table illustrates the portfolio and class segments for the Company’s loan portfolio in 2019 and 2018 compared to 2017:

Portfolio	Class - 2019 & 2018	Class - 2017
Commercial Loans	Commercial and Industrial	Commercial
	Commercial Real Estate	Commercial Real Estate
	Business Banking	Agricultural
		Agricultural Real Estate
		Business Banking
Consumer Loans	Indirect Auto	Indirect
	Specialty Lending	Home Equity
	Direct	Direct
Residential Real Estate

Commercial Loans

The Company offers a variety of Commercial loan products. The Company’s underwriting analysis for commercial loans typically includes credit verification, independent appraisals, a review of the borrower’s financial condition and a detailed analysis of the borrower’s underlying cash flows.

Commercial and Industrial ("C&I") – The Company offers a variety of loan options to meet the specific needs of our C&I customers including term loans, time notes and lines of credit. Such loans are made available to businesses for working capital needs such as inventory and receivables, business expansion, equipment purchases, livestock purchases and seasonal crop expenses. These loans typically are usually collateralized by business assets such as equipment, accounts receivable and perishable agricultural products, which are exposed to industry price volatility. To reduce these risks, management also attempts to obtain personal guarantees of the owners or obtain government loan guarantees to provide further support. In 2018, the Commercial and Agricultural class segments were combined to create the C&I class segment.

Commercial Real Estate ("CRE") – The Company offers CRE loans to finance real estate purchases, refinancings, expansions and improvements to commercial and agricultural properties. CRE loans are loans are secured by liens on the real estate, which may include both owner occupied and non-owner-occupied properties, such as apartments, commercial structures, health care facilities and other facilities. The Company's underwriting analysis includes credit verification, independent appraisals, a review of the borrower's financial condition and a detailed analysis of the borrower's underlying cash flows. These loans are typically originated in amounts of no more than 80% of the appraised value of the property. Government loan guarantees may be obtained to provide further support for agricultural property. In 2018, the Commercial Real Estate and Agricultural Real Estate class segments were combined to create the CRE segment.

Business Banking – The Company offers a variety of loan options to meet the specific needs of our Business Banking customers including term loans, mortgages and lines of credit. Such loans are generally less than $1.0 million and are made available to businesses for working capital such as inventory and receivables, business expansion, equipment purchases and agricultural needs. Generally, a collateral lien is placed on assets owned by the borrower and can include real estate, equipment, inventory, receivables or other business assets. These loans carry a higher risk than C&I and CRE loans due to the smaller size of the borrower and lower levels of capital.

Consumer Loans

The Company offers a variety of Consumer loan products including Indirect Auto, Specialty Lending and Direct loans.

Indirect Auto – The Company maintains relationships with many dealers primarily in the communities that we serve. Through these relationships, the Company primarily finances the purchases of automobiles indirectly through dealer relationships. Approximately 95% of the Indirect Auto relationships represent automobile financing. Most of these loans carry a fixed rate of interest with principal repayment terms typically ranging from three to six years, based upon the nature of the collateral and the size of the loan. The majority of Indirect Auto Consumer loans are underwritten on a secured basis using the underlying collateral being financed. In 2018, the Indirect class segment was further separated into Indirect Auto and Specialty Lending class segments (see above and below).

Specialty Lending – The Company offers unsecured Consumer loans across a national footprint originated through our relationships with national technology-driven consumer lending companies to finance such things as dental and medical procedures, K-12 tuition, solar energy installations and other consumer purpose loans. Advances of credit through this specialty lending business line are subject to the Company's underwriting standards including criteria such as FICO score and debt to income thresholds. In 2018, the Indirect class segment has been further separated into Indirect Auto (see above) and Specialty Lending class segments.

Direct – The Company offers a variety of consumer installment loans to finance vehicle purchases, mobile home purchases and personal expenditures. In addition to installment loans, the Company also offers personal lines of credit, overdraft protection, home equity lines of credit and second mortgage loans (loans secured by a lien position on one-to-four family residential real estate) to finance home improvements, debt consolidation, education and other uses. For home equity loans, consumers are able to borrow up to 85% of the equity in their homes, and are generally tied to Prime with a ten year draw followed by a fifteen year amortization. These loans carry a higher risk than first mortgage residential loans as they are often in a second position with respect to collateral. Consumer installment loans carry a fixed rate of interest with principal repayment terms typically ranging from one to ten years, based upon the nature of the collateral and the size of the loan. Consumer installment loans are often secured with collateral consisting of a perfected lien on the asset being purchased or a perfected lien on a consumer's deposit account. Risk is reduced through underwriting criteria, which include credit verification, appraisals, a review of the borrower's financial condition and personal cash flows. A security interest, with title insurance when necessary, is taken in the underlying real estate. In 2018, the Home Equity segment was consolidated into the Direct class segment.

Residential Real Estate

Residential real estate loans consist primarily of loans secured by a first or second mortgage on primary residences. We originate adjustable-rate and fixed-rate, one-to-four-family residential real estate loans for the construction, purchase or refinancing of a mortgage. These loans are collateralized by properties located in the Company’s market area. When market conditions are favorable, for longer term, fixed-rate residential real estate mortgages without escrow, the Company retains the servicing, but sells the right to receive principal and interest to Government-sponsored enterprises. This practice allows the Company to manage interest rate risk, liquidity risk and credit risk. Loans on one-to-four-family residential real estate are generally originated in amounts of no more than 85% of the purchase price or appraised value (whichever is lower) or have private mortgage insurance. Mortgage title insurance and hazard insurance are normally required. Construction loans have a unique risk, because they are secured by an incomplete dwelling. This risk is reduced through periodic site inspections, including one at each loan draw period.

Allowance for Loan Loss Calculation

For purposes of evaluating the adequacy of the allowance, the Company considers a number of significant factors that affect the collectability of the portfolio. For individually impaired loans, these include estimates of impairment, if any, which reflect the facts and circumstances that affect the likelihood of repayment of such loans as of the evaluation date. For homogeneous pools of loans, estimates of the Company’s exposure to credit loss reflect a current assessment of a number of factors, which could affect collectability. These factors include: past loss experience, size, trend, composition and nature of loans; changes in lending policies and procedures, including underwriting standards and collection, charge-offs and recoveries; trends experienced in nonperforming and delinquent loans; current economic conditions in the Company’s market; portfolio concentrations that may affect loss experienced across one or more components of the portfolio; the effect of external factors such as competition, legal and regulatory requirements; and the experience, ability and depth of lending management and staff. In addition, various regulatory agencies, as an integral component of their examination process, periodically review the Company’s allowance for loan losses. Such agencies may require the Company to make loan grade changes as well as recognize additions to the allowance based on their examinations.

After a thorough consideration of the factors discussed above, any required additions or reductions to the allowance for loan losses are made periodically by charges or credits to the provision for loan losses. These charges are necessary to maintain the allowance at a level that management believes is reflective of overall level of incurred loss in the portfolio. While management uses available information to recognize losses on loans, additions and reductions of the allowance may fluctuate from one reporting period to another. These fluctuations are reflective of changes in risk associated with portfolio content or changes in management’s assessment of any or all of the determining factors discussed above.

The following tables illustrate the changes in the allowance for loan losses by our portfolio segments:

(In thousands)	Commercial Loans			Consumer Loans			Residential Real Estate			Total
Balance as of December 31, 2018	$	32,759		$	37,178		$	2,568		$	72,505
Charge-offs		(3,151	)		(28,398	)		(991	)		(32,540	)
Recoveries		534			6,913			141			7,588
Provision		4,383			19,954			1,075			25,412
Ending Balance as of December 31, 2019	$	34,525		$	35,647		$	2,793		$	72,965

Balance as of December 31, 2017	$	27,606		$	36,830		$	5,064		$	69,500
Charge-offs		(3,463	)		(29,752	)		(913	)		(34,128	)
Recoveries		1,178			6,821			306			8,305
Provision		7,438			23,279			(1,889	)		28,828
Ending Balance as of December 31, 2018	$	32,759		$	37,178		$	2,568		$	72,505

Balance as of December 31, 2016	$	25,444		$	33,375		$	6,381		$	65,200
Charge-offs		(4,169	)		(27,072	)		(1,846	)		(33,087	)
Recoveries		1,077			5,142			180			6,399
Provision		5,254			25,385			349			30,988
Ending Balance as of December 31, 2017	$	27,606		$	36,830		$	5,064		$	69,500

For acquired loans, to the extent that we experience deterioration in borrower credit quality resulting in a decrease in our expected cash flows subsequent to the acquisition of the loans, an allowance for loan losses is established based on our estimate of incurred losses at the balance sheet date. There was no allowance for loan losses for the acquired loan portfolio as of December 31, 2019 and 2018. Net charge-offs related to acquired loans totaled approximately $0.1 million, $0.1 million and $0.7 million during the years ended December 31, 2019, 2018 and 2017, respectively, and are included in the table above.

The following table illustrates the allowance for loan losses and the recorded investment by portfolio segment:

(In thousands)	Commercial Loans		Consumer Loans		Residential Real Estate		Total
As of December 31, 2019
Allowance for loan losses	$	34,525	$	35,647	$	2,793	$	72,965
Allowance for loans individually evaluated for impairment		-		-		-		-
Allowance for loans collectively evaluated for impairment	$	34,525	$	35,647	$	2,793	$	72,965
Ending balance of loans	$	3,444,266	$	2,246,676	$	1,445,156	$	7,136,098
Ending balance of originated loans individually evaluated for impairment		3,488		7,044		7,721		18,253
Ending balance of acquired loans collectively evaluated for impairment		115,266		23,733		125,879		264,878
Ending balance of originated loans collectively evaluated for impairment	$	3,325,512	$	2,215,899	$	1,311,556	$	6,852,967

As of December 31, 2018
Allowance for loan losses	$	32,759	$	37,178	$	2,568	$	72,505
Allowance for loans individually evaluated for impairment		25		-		-		25
Allowance for loans collectively evaluated for impairment	$	32,734	$	37,178	$	2,568	$	72,480
Ending balance of loans	$	3,222,310	$	2,284,563	$	1,380,836	$	6,887,709
Ending balance of originated loans individually evaluated for impairment		5,786		7,887		6,905		20,578
Ending balance of acquired loans collectively evaluated for impairment		143,690		31,624		147,277		322,591
Ending balance of originated loans collectively evaluated for impairment	$	3,072,834	$	2,245,052	$	1,226,654	$	6,544,540

The following table sets forth information with regard to past due and nonperforming loans by loan class:

(In thousands)	31-60 Days Past Due Accruing		61-90 Days Past Due Accruing		Greater Than 90 Days Past Due Accruing		Total Past Due Accruing		Nonaccrual		Current		Recorded Total Loans
As of December 31, 2019
Originated
Commercial Loans:
C&I	$	1,227	$	-	$	-	$	1,227	$	1,177	$	838,502	$	840,906
CRE		3,576		-		-		3,576		4,847		1,941,143		1,949,566
Business Banking		794		162		-		956		7,035		530,537		538,528
Total Commercial Loans	$	5,597	$	162	$	-	$	5,759	$	13,059	$	3,310,182	$	3,329,000
Consumer Loans:
Indirect Auto	$	11,860	$	2,108	$	1,005	$	14,973	$	2,175	$	1,176,487	$	1,193,635
Specialty Lending		3,153		2,087		1,307		6,547		-		535,516		542,063
Direct		2,564		564		478		3,606		2,475		481,164		487,245
Total Consumer Loans	$	17,577	$	4,759	$	2,790	$	25,126	$	4,650	$	2,193,167	$	2,222,943
Residential Real Estate	$	1,179	$	190	$	663	$	2,032	$	5,872	$	1,311,373	$	1,319,277
Total Originated Loans	$	24,353	$	5,111	$	3,453	$	32,917	$	23,581	$	6,814,722	$	6,871,220

Acquired
Commercial Loans:
C&I	$	149	$	-	$	-	$	149	$	-	$	19,215	$	19,364
CRE		-		-		-		-		-		60,937		60,937
Business Banking		397		287		-		684		382		33,899		34,965
Total Commercial Loans	$	546	$	287	$	-	$	833	$	382	$	114,051	$	115,266
Consumer Loans:
Direct	$	136	$	58	$	-	$	194	$	105	$	23,434	$	23,733
Total Consumer Loans	$	136	$	58	$	-	$	194	$	105	$	23,434	$	23,733
Residential Real Estate	$	575	$	20	$	264	$	859	$	1,106	$	123,914	$	125,879
Total Acquired Loans	$	1,257	$	365	$	264	$	1,886	$	1,593	$	261,399	$	264,878

Total Loans	$	25,610	$	5,476	$	3,717	$	34,803	$	25,174	$	7,076,121	$	7,136,098

(In thousands)	31-60 Days Past Due Accruing		61-90 Days Past Due Accruing		Greater Than 90 Days Past Due Accruing		Total Past Due Accruing		Nonaccrual		Current		Recorded Total Loans
As of December 31, 2018
Originated
Commercial Loans:
C&I	$	909	$	-	$	-	$	909	$	1,062	$	846,148	$	848,119
CRE		1,089		-		588		1,677		4,995		1,734,558		1,741,230
Business Banking		1,092		302		-		1,394		5,974		481,903		489,271
Total Commercial Loans	$	3,090	$	302	$	588	$	3,980	$	12,031	$	3,062,609	$	3,078,620
Consumer Loans:
Indirect Auto	$	14,519	$	2,300	$	1,186	$	18,005	$	1,971	$	1,196,136	$	1,216,112
Specialty Lending		3,479		1,773		1,562		6,814		-		518,114		524,928
Direct		2,962		1,437		552		4,951		2,592		504,356		511,899
Total Consumer Loans	$	20,960	$	5,510	$	3,300	$	29,770	$	4,563	$	2,218,606	$	2,252,939
Residential Real Estate	$	1,426	$	157	$	1,182	$	2,765	$	6,778	$	1,224,016	$	1,233,559
Total Originated Loans	$	25,476	$	5,969	$	5,070	$	36,515	$	23,372	$	6,505,231	$	6,565,118

Acquired
Commercial Loans:
C&I	$	-	$	-	$	-	$	-	$	-	$	26,124	$	26,124
CRE		-		-		-		-		-		84,492		84,492
Business Banking		466		288		-		754		390		31,930		33,074
Total Commercial Loans	$	466	$	288	$	-	$	754	$	390	$	142,546	$	143,690
Consumer Loans:
Indirect Auto	$	1	$	1	$	-	$	2	$	-	$	30	$	32
Direct		152		41		15		208		227		31,157		31,592
Total Consumer Loans	$	153	$	42	$	15	$	210	$	227	$	31,187	$	31,624
Residential Real Estate	$	546	$	42	$	-	$	588	$	1,498	$	145,191	$	147,277
Total Acquired Loans	$	1,165	$	372	$	15	$	1,552	$	2,115	$	318,924	$	322,591

Total Loans	$	26,641	$	6,341	$	5,085	$	38,067	$	25,487	$	6,824,155	$	6,887,709

There were no material commitments to extend further credit to borrowers with nonperforming loans as of December 31, 2019 and 2018.

Impaired Loans

The methodology used to establish the allowance for loan losses on impaired loans incorporates specific allocations on loans analyzed individually. Classified loans, including all TDRs and nonaccrual Commercial loans that are graded Substandard, Doubtful or Loss, with outstanding balances of $1.0 million or more are evaluated for impairment through the Company’s quarterly status review process. The Company considers Commercial loans less than $1.0 million to be homogeneous loans. In the third quarter of 2019 the threshold for evaluating loans for impairment was increased from $750 thousand. In determining that we will be unable to collect all principal and/or interest payments due in accordance with the contractual terms of the loan agreements, we consider factors such as payment history and changes in the financial condition of individual borrowers, local economic conditions, historical loss experience and the conditions of the various markets in which the collateral may be liquidated. For loans that are identified as impaired, impairment is measured by one of three methods: 1) the fair value of collateral less cost to sell, 2) present value of expected future cash flows or 3) the loan’s observable market price. These impaired loans are reviewed on a quarterly basis for changes in the level of impairment. Impaired amounts are charged off immediately if such amounts are determined by management to be uncollectable. Any change to the previously recognized impairment loss is recognized as a component of the provision for loan losses.

The following table provides information on loans specifically evaluated for impairment:

	December 31, 2019						December 31, 2018
(In thousands)	Recorded Investment Balance (Book)		Unpaid Principal Balance (Legal)		Related Allowance		Recorded Investment Balance (Book)		Unpaid Principal Balance (Legal)		Related Allowance
Originated
With no related allowance recorded:
Commercial Loans:
C&I	$	76	$	302			$	228	$	497
CRE		2,410		2,437		-		4,312		6,330		-
Business Banking		1,002		1,443				1,013		2,001
Total Commercial Loans	$	3,488	$	4,182			$	5,553	$	8,828
Consumer Loans:
Indirect Auto	$	154	$	242			$	143	$	241
Direct		6,862		8,335				7,744		9,831
Specialty Lending		28		28				-		-
Total Consumer Loans	$	7,044	$	8,605			$	7,887	$	10,072
Residential Real Estate	$	7,721	$	9,754			$	6,905	$	9,414
Total	$	18,253	$	22,541			$	20,345	$	28,314
With an allowance recorded:
Commercial Loans:
C&I	$	-	$	-	$	-	$	233	$	238	$	25
Total Commercial Loans	$	-	$	-	$	-	$	233	$	238	$	25

Total Loans	$	18,253	$	22,541	$	-	$	20,578	$	28,552	$	25

There were no acquired impaired loans specifically evaluated for impairment as of December 31, 2019 and 2018.

The following table summarizes the average recorded investments on loans specifically evaluated for impairment and the interest income recognized:

	December 31, 2019				December 31, 2018				December 31, 2017
(In thousands)	Average Recorded Investment		Interest Income Recognized		Average Recorded Investment		Interest Income Recognized		Average Recorded Investment		Interest Income Recognized
Originated
Commercial Loans:
C&I	$	242	$	1	$	453	$	1	$	-	$	-
CRE		3,311		123		4,078		128		-		-
Commercial		-		-		-		-		1,841		-
Commercial Real Estate		-		-		-		-		3,534		115
Agricultural		-		-		-		-		224		1
Agricultural Real Estate		-		-		-		-		1,709		43
Business Banking		1,089		24		1,018		26		875		12
Total Commercial Loans	$	4,642	$	148	$	5,549	$	155	$	8,183	$	171
Consumer Loans:
Indirect Auto	$	192	$	10	$	179	$	10	$	-	$	-
Direct		7,387		382		7,922		431		-		-
Specialty Lending		7		1		-		-		-		-
Indirect		-		-		-		-		35		3
Home Equity		-		-		-		-		8,226		446
Direct		-		-		-		-		178		8
Total Consumer Loans	$	7,586	$	393	$	8,101	$	441	$	8,439	$	457
Residential Real Estate	$	7,505	$	350	$	6,779	$	305	$	6,523	$	296
Total Originated	$	19,733	$	891	$	20,429	$	901	$	23,145	$	924

Acquired
Commercial Loans:
Commercial Real Estate	$	-	$	-	$	-	$	-	$	93	$	-
Total Commercial Loans	$	-	$	-	$	-	$	-	$	93	$	-
Total Acquired Loans	$	-	$	-	$	-	$	-	$	93	$	-

Total Loans	$	19,733	$	891	$	20,429	$	901	$	23,238	$	924

Credit Quality Indicators

The Company has developed an internal loan grading system to evaluate and quantify the Company’s loan portfolio with respect to quality and risk. The system focuses on, among other things, financial strength of borrowers, experience and depth of borrower’s management, primary and secondary sources of repayment, payment history, nature of the business and outlook on particular industries. The internal grading system enables the Company to monitor the quality of the entire loan portfolio on a consistent basis and provide management with an early warning system, enabling recognition and response to problem loans and potential problem loans.

Commercial Grading System

For C&I and CRE loans, the Company uses a grading system that relies on quantifiable and measurable characteristics when available. This includes comparison of financial strength to available industry averages, comparison of transaction factors (loan terms and conditions) to loan policy and comparison of credit history to stated repayment terms and industry averages. Some grading factors are necessarily more subjective such as economic and industry factors, regulatory environment and management. C&I and CRE loans are graded Doubtful, Substandard, Special Mention and Pass.

●

Doubtful

A Doubtful loan has a high probability of total or substantial loss, but because of specific pending events that may strengthen the asset, its classification as a loss is deferred. Doubtful borrowers are usually in default, lack adequate liquidity or capital and lack the resources necessary to remain an operating entity. Pending events can include mergers, acquisitions, liquidations, capital injections, the perfection of liens on additional collateral, the valuation of collateral and refinancing. Generally, pending events should be resolved within a relatively short period and the ratings will be adjusted based on the new information. Nonaccrual treatment is required for Doubtful assets because of the high probability of loss.

●

Substandard

Substandard loans have a high probability of payment default or they have other well-defined weaknesses. They require more intensive supervision by bank management. Substandard loans are generally characterized by current or expected unprofitable operations, inadequate debt service coverage, inadequate liquidity or marginal capitalization. Repayment may depend on collateral or other credit risk mitigants. For some Substandard loans, the likelihood of full collection of interest and principal may be in doubt and those loans should be placed on nonaccrual. Although Substandard assets in the aggregate will have a distinct potential for loss, an individual asset’s loss potential does not have to be distinct for the asset to be rated Substandard.

●

Special Mention

Special Mention loans have potential weaknesses that may, if not checked or corrected, weaken the asset or inadequately protect the Company’s position at some future date. These loans pose elevated risk, but their weakness does not yet justify a Substandard classification. Borrowers may be experiencing adverse operating trends (i.e., declining revenues or margins) or may be struggling with an ill-proportioned balance sheet (i.e., increasing inventory without an increase in sales, high leverage, tight liquidity). Adverse economic or market conditions, such as interest rate increases or the entry of a new competitor, may also support a Special Mention rating. Although a Special Mention loan has a higher probability of default than a Pass asset, its default is not imminent.

●

Pass

Loans graded as Pass encompass all loans not graded as Doubtful, Substandard or Special Mention. Pass loans are in compliance with loan covenants and payments are generally made as agreed. Pass loans range from superior quality to fair quality.

Business Banking Grading System

Business Banking loans are graded as either Classified or Non-classified:

●

Classified

Classified loans are inadequately protected by the current worth and paying capacity of the obligor or, if applicable, the collateral pledged. These loans have a well-defined weakness or weaknesses, that jeopardize the liquidation of the debt or in some cases make collection or liquidation in full, on the basis of currently existing facts, conditions and values, highly questionable and improbable. They are characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected. Classified loans have a high probability of payment default or a substantial loss. These loans require more intensive supervision by management and are generally characterized by current or expected unprofitable operations, inadequate debt service coverage, inadequate liquidity or marginal capitalization. Repayment may depend on collateral or other credit risk mitigants. Classified loans where the full collection of interest and principal is in doubt are considered to have a nonaccrual status. In some cases, Classified loans are considered uncollectable and of such little value that their continuance as assets is not warranted.

●

Non-classified

Loans graded as Non-classified encompass all loans not graded as Classified. Payments on non-classified loans are generally made as agreed.

Consumer and Residential Real Estate Grading System

Consumer and Residential Real Estate loans are graded as either Nonperforming or Performing.

●

Nonperforming

Nonperforming loans are loans that are 1) over 90 days past due and interest is still accruing or 2) on nonaccrual status.

●

Performing

All loans not meeting any of these criteria are considered Performing.

The following tables illustrate the Company’s credit quality by loan class:

(In thousands)	As of December 31, 2019
Originated
Commercial Credit Exposure
By Internally Assigned Grade:	C&I		CRE		Total
Pass	$	782,763	$	1,868,678	$	2,651,441
Special Mention		28,380		30,519		58,899
Substandard		29,257		50,369		79,626
Doubtful		506		-		506
Total	$	840,906	$	1,949,566	$	2,790,472

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking		Total
Non-classified	$	524,725	$	524,725
Classified		13,803		13,803
Total	$	538,528	$	538,528

Consumer Credit Exposure
By Payment Activity:	Indirect Auto		Specialty Lending		Direct		Total
Performing	$	1,190,455	$	540,756	$	484,292	$	2,215,503
Nonperforming		3,180		1,307		2,953		7,440
Total	$	1,193,635	$	542,063	$	487,245	$	2,222,943

Residential Real Estate Credit Exposure
By Payment Activity:	Residential Real Estate		Total
Performing	$	1,312,742	$	1,312,742
Nonperforming		6,535		6,535
Total	$	1,319,277	$	1,319,277

Acquired
Commercial Credit Exposure
By Internally Assigned Grade:	C&I		CRE		Total
Pass	$	17,801	$	60,545	$	78,346
Special Mention		1,269		-		1,269
Substandard		294		392		686
Total	$	19,364	$	60,937	$	80,301

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking		Total
Non-classified	$	32,030	$	32,030
Classified		2,935		2,935
Total	$	34,965	$	34,965

Consumer Credit Exposure
By Payment Activity:	Direct		Total
Performing	$	23,628	$	23,628
Nonperforming		105		105
Total	$	23,733	$	23,733

Residential Real Estate Credit Exposure
By Payment Activity:	Residential Real Estate		Total
Performing	$	124,509	$	124,509
Nonperforming		1,370		1,370
Total	$	125,879	$	125,879

(In thousands)	As of December 31, 2018
Originated
Commercial Credit Exposure
By Internally Assigned Grade:	C&I		CRE		Total
Pass	$	796,778	$	1,681,330	$	2,478,108
Special Mention		11,348		13,894		25,242
Substandard		39,993		46,006		85,999
Total	$	848,119	$	1,741,230	$	2,589,349

Business Banking Credit Exposure	Business
By Internally Assigned Grade:	Banking		Total
Non-classified	$	476,052	$	476,052
Classified		13,219		13,219
Total	$	489,271	$	489,271

Consumer Credit Exposure
By Payment Activity:	Indirect Auto		Specialty Lending		Direct		Total
Performing	$	1,212,955	$	523,366	$	508,755	$	2,245,076
Nonperforming		3,157		1,562		3,144		7,863
Total	$	1,216,112	$	524,928	$	511,899	$	2,252,939

Residential Real Estate Credit Exposure	Residential
By Payment Activity:	Real Estate		Total
Performing	$	1,225,599	$	1,225,599
Nonperforming		7,960		7,960
Total	$	1,233,559	$	1,233,559

Acquired
Commercial Credit Exposure
By Internally Assigned Grade:	C&I		CRE		Total
Pass	$	23,283	$	83,762	$	107,045
Special Mention		2,831		92		2,923
Substandard		10		638		648
Total	$	26,124	$	84,492	$	110,616

Business Banking Credit Exposure	Business
By Internally Assigned Grade:	Banking		Total
Non-classified	$	29,945	$	29,945
Classified		3,129		3,129
Total	$	33,074	$	33,074

Consumer Credit Exposure
By Payment Activity:	Indirect Auto		Direct		Total
Performing	$	32	$	31,350	$	31,382
Nonperforming		-		242		242
Total	$	32	$	31,592	$	31,624

Residential Real Estate Credit Exposure	Residential
By Payment Activity:	Real Estate		Total
Performing	$	145,779	$	145,779
Nonperforming		1,498		1,498
Total	$	147,277	$	147,277

Troubled Debt Restructuring

When the Company modifies a loan in a troubled debt restructuring, such modifications generally include one or a combination of the following: an extension of the maturity date at a stated rate of interest lower than the current market rate for new debt with similar risk; temporary reduction in the interest rate; or change in scheduled payment amount. Residential Real Estate and Consumer TDRs occurring during 2019 and 2018 were due to the reduction in the interest rate or extension of the term. Commercial TDRs during 2019 and 2018 were both a reduction of the interest rate and change in terms.

When the Company modifies a loan in a troubled debt restructuring, management measures for impairment, if any, based on the present value of the expected future cash flows, discounted at the contractual interest rate of the original loan agreement, except when the sole (remaining) source of repayment for the loan is the operation or liquidation of the collateral. In these cases, management uses the current fair value of the collateral, less selling costs. If management determines that the value of the modified loan is less than the recorded investment in the loan an impairment charge would be recorded.

The following tables illustrate the recorded investment and number of modifications for modified loans, including the recorded investment in the loans prior to a modification and the recorded investment in the loans after restructuring:

	Year ended December 31, 2019
(Dollars in thousands)	Number of Contracts		Pre- Modification Outstanding Recorded Investment		Post- Modification Outstanding Recorded Investment
Commercial Loans:
C&I		1	$	65	$	65
CRE		1		402		402
Business Banking		3		425		431
Total Commercial Loans		5	$	892	$	898
Consumer Loans:
Indirect Auto		9	$	134	$	134
Direct		11		450		480
Total Consumer Loans		20	$	584	$	614
Residential Real Estate		12	$	1,032	$	1,091
Total Troubled Debt Restructurings		37	$	2,508	$	2,603

	Year ended December 31, 2018
(Dollars In thousands)	Number of Contracts		Pre- Modification Outstanding Recorded Investment		Post- Modification Outstanding Recorded Investment
Commercial Loans:
Business Banking		5	$	581	$	581
Total Commercial Loans		5	$	581	$	581
Consumer Loans:
Indirect Auto		17	$	204	$	202
Direct		10		401		399
Total Consumer Loans		27	$	605	$	601
Residential Real Estate		14	$	1,099	$	1,098
Total Troubled Debt Restructurings		46	$	2,285	$	2,280

The following table illustrates the recorded investment and number of modifications for TDRs where a concession has been made and subsequently defaulted during the period:

	Year ended December 31, 2019				Year ended December 31, 2018
(Dollars in thousands)	Number of Contracts		Recorded Investment		Number of Contracts		Recorded Investment
Commercial Loans:
Business Banking		-	$	-		3	$	338
Total Commercial Loans		-	$	-		3	$	338
Consumer Loans:
Indirect Auto		3	$	18		-	$	-
Direct		29		1,385		37		1,931
Total Consumer Loans		32	$	1,403		37	$	1,931
Residential Real Estate		23	$	1,203		26	$	1,786
Total Troubled Debt Restructurings		55	$	2,606		66	$	4,055

Employee Benefit Plans, 401(k) Plan and Other Retirement Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Retirement Benefits [Abstract]
Supplemental retirement benefits for retired executives under other retirement benefits plan	$ 1.7	$ 2.0
Expense related to other retirement benefits plan	0.1	0.1	$ 0.1
401(K) Plan [Member]
Defined benefit plan disclosure [Abstract]
Employer contribution to plan	$ 3.6	$ 3.2	$ 2.8

Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Maturities of Time Deposits [Abstract]
Within one year	$ 554,132
After one but within two years	220,769
After two but within three years	50,593
After three but within four years	15,064
After four but within five years	20,453
After five years	182
Total	861,193	$ 930,678
Time Deposits, $250,000 or More [Abstract]
Time deposits of $250,000 or more	$ 140,400	$ 146,100

Employee Benefit Plans

12 Months Ended

Dec. 31, 2019

Defined Benefit Post-Retirement Plans [Abstract]

Employee Benefit Plans

13. Employee Benefit Plans

Defined Benefit Post-Retirement Plans

The Company has a qualified, noncontributory, defined benefit pension plan (“the Plan”) covering substantially all of its employees at December 31, 2019. Benefits paid from the plan are based on age, years of service, compensation, social security benefits and are determined in accordance with defined formulas. The Company’s policy is to fund the Plan in accordance with Employee Retirement Income Security Act of 1974 standards. Assets of the Plan are invested in publicly traded stocks and mutual funds. Prior to January 1, 2000, the Plan was a traditional defined benefit plan based on final average compensation. On January 1, 2000, the Plan was converted to a cash balance plan with grandfathering provisions for existing participants. Effective March 1, 2013, the Plan was amended. Benefit accruals for participants who, as of January 1, 2000, elected to continue participating in the traditional defined benefit plan design were frozen as of March 1, 2013. In May 2013, the noncontributory, frozen, defined benefit pension plan assumed from Alliance in the acquisition was merged into the Plan.

In addition to the Plan, the Company provides supplemental employee retirement plans to certain current and former executives. The Company also assumed supplemental retirement plans for certain former executives in the Alliance acquisition.

These supplemental employee retirement plans and the Plan are collectively referred to herein as “Pension Benefits.”

In addition, the Company provides certain health care benefits for retired employees. Benefits were accrued over the employees’ active service period. Only employees that were employed by the Company on or before January 1, 2000 are eligible to receive post-retirement health care benefits. The Plan is contributory for participating retirees, requiring participants to absorb certain deductibles and coinsurance amounts with contributions adjusted annually to reflect cost sharing provisions and benefit limitations called for in the Plan. Employees become eligible for these benefits if they reach normal retirement age while working for the Company. For eligible employees described above, the Company funds the cost of post-retirement health care as benefits are paid. The Company elected to recognize the transition obligation on a delayed basis over twenty years. In addition, the Company assumed post-retirement medical life insurance benefits for certain Alliance employees, retirees and their spouses, if applicable, in the Alliance acquisition. These post-retirement benefits are referred to herein as “Other Benefits.”

Accounting standards require an employer to: (1) recognize the overfunded or underfunded status of defined benefit post-retirement plans, which is measured as the difference between plan assets at fair value and the benefit obligation, as an asset or liability in its balance sheet; (2) recognize changes in that funded status in the year in which the changes occur through comprehensive income; and (3) measure the defined benefit plan assets and obligations as of the date of its year-end balance sheet.

The components of AOCI, which have not yet been recognized as components of net periodic benefit cost, related to pensions and other post-retirement benefits are summarized below:

	Pension Benefits				Other Benefits
(In thousands)	2019		2018		2019		2018
Net actuarial loss	$	28,334	$	35,538	$	125	$	844
Prior service cost		491		570		94		145
Total amounts recognized in AOCI (pre-tax)	$	28,825	$	36,108	$	219	$	989

	Pension Benefits						Other Benefits
(In thousands)	2019			2018			2019			2018
Change in benefit obligation:
Benefit obligation at beginning of year	$	85,134		$	90,950		$	7,034		$	8,050
Service cost		1,723			1,659			7			10
Interest cost		3,942			3,645			272			327
Plan participants' contributions		-			-			201			209
Actuarial loss (gain)		6,030			(3,977	)		(719	)		(762	)
Amendments		-			337			-			-
Benefits paid		(6,243	)		(7,480	)		(712	)		(800	)
Projected benefit obligation at end of year	$	90,586		$	85,134		$	6,083		$	7,034
Change in plan assets:
Fair value of plan assets at beginning of year	$	109,746		$	124,226		$	-		$	-
Gain (loss) on plan assets		18,120			(8,381	)		-			-
Employer contributions		1,372			1,381			511			591
Plan participants' contributions		-			-			201			209
Benefits paid		(6,243	)		(7,480	)		(712	)		(800	)
Fair value of plan assets at end of year	$	122,995		$	109,746		$	-		$	-

Funded (unfunded) status at year end	$	32,409		$	24,612		$	(6,083	)	$	(7,034	)

	Pension Benefits						Other Benefits
(In thousands)	2019			2018			2019			2018
Other assets	$	51,988		$	42,900		$	-		$	-
Other liabilities		(19,579	)		(18,288	)		(6,083	)		(7,034	)
Funded status	$	32,409		$	24,612		$	(6,083	)	$	(7,034	)

The following assumptions were used to determine the benefit obligation and the net periodic pension cost for the years indicated:

	Years ended December 31,
	2019	2018	2017
Weighted average assumptions:
The following assumptions were used to determine benefit obligations:
Discount rate	3.69% - 3.73%	4.79% - 4.80%	4.20% - 4.21%
Expected long-term return on plan assets	7.00%	7.00%	7.00%
Rate of compensation increase	3.00%	3.00%	3.00%

The following assumptions were used to determine net periodic pension cost:
Discount rate	4.79% - 4.80%	4.20% - 4.21%	4.76% - 4.84%
Expected long-term return on plan assets	7.00%	7.00%	7.00%
Rate of compensation increase	3.00%	3.00%	3.00%

Net periodic benefit cost and other amounts recognized in OCI for the years ended December 31 included the following components:

	Pension Benefits									Other Benefits
(In thousands)	2019			2018			2017			2019			2018			2017
Components of net periodic benefit cost:
Service cost	$	1,723		$	1,659		$	1,511		$	7		$	10		$	12
Interest cost		3,942			3,645			4,168			272			327			357
Expected return on plan assets		(7,480	)		(8,478	)		(7,929	)		-			-			-
Amortization of prior service cost		43			40			46			50			51			51
Amortization of unrecognized net loss		2,593			930			1,668			-			124			87
Net periodic pension cost (benefit)	$	821		$	(2,204	)	$	(536	)	$	329		$	512		$	507

Other changes in plan assets and benefit obligations recognized in OCI (pre-tax):
Net (gain) loss	$	(4,611	)	$	12,882		$	(3,075	)	$	(720	)	$	(762	)	$	388
Prior service cost		-			337			-			-			-			286
Amortization of prior service (cost)		(43	)		(40	)		(46	)		(50	)		(51	)		(51	)
Amortization of unrecognized net (loss)		(2,593	)		(930	)		(1,668	)		-			(124	)		(87	)
Total recognized in OCI	$	(7,247	)	$	12,249		$	(4,789	)	$	(770	)	$	(937	)	$	536

Total recognized in net periodic benefit cost and OCI, pre-tax	$	(6,426	)	$	10,045		$	(5,325	)	$	(441	)	$	(425	)	$	1,043

The Company expects that $1.6 million in net actuarial loss and nominal prior service costs will be recognized as components of net periodic benefit cost in 2020.

The following table sets forth estimated future benefit payments for the pension plans and other post-retirement benefit plans as of December 31, 2019:

(In thousands)	Pension Benefits		Other Benefits
2020	$	6,916	$	497
2021		6,722		464
2022		6,722		462
2023		6,582		457
2024		7,827		451
2025 - 2029		35,215		2,070

The Company made no voluntary contributions to the pension and other benefit plans during the year ended December 31, 2019 and 2018.

(In thousands)	One Percentage Point Increase		One Percentage Point Decrease
Increase (decrease) on total service and interest cost components	$	29	$	(25	)
Increase (decrease) on post-retirement accumulated benefit obligation		628		(543	)

Plan Investment Policy

The Company’s key investment objectives in managing its defined benefit plan assets are to ensure that present and future benefit obligations to all participants and beneficiaries are met as they become due; to provide a total return that, over the long-term, maximizes the ratio of the plan assets to liabilities, while minimizing the present value of required Company contributions, at the appropriate levels of risk; to meet statutory requirements and regulatory agencies’ requirements; and to satisfy applicable accounting standards. The Company periodically evaluates the asset allocations, funded status, rate of return assumption and contribution strategy for satisfaction of our investment objectives.

The target and actual allocations expressed as a percentage of the defined benefit pension plan’s assets are as follows:

	Target 2019	2019	2018
Cash and cash equivalents	0 - 15%	3%	4%
Fixed income securities	30 - 60%	40%	39%
Equities	40 - 70%	57%	57%
Total		100%	100%

Only high-quality bonds are to be included in the portfolio. All issues that are rated lower than A by Standard and Poor’s are to be excluded. Equity securities at December 31, 2019 and 2018 do not include any Company common stock.

The following table presents the financial instruments recorded at fair value on a recurring basis by the Plan:

(In thousands)	Level 1		Level 2		December 31, 2019
Cash and cash equivalents	$	4,143	$	-	$	4,143
Foreign equity mutual funds		40,239		-		40,239
Equity mutual funds		29,886		-		29,886
U.S. government bonds		-		58		58
Corporate bonds		-		48,669		48,669
Total	$	74,268	$	48,727	$	122,995

	Level 1		Level 2		December 31, 2018
Cash and cash equivalents	$	4,095	$	-	$	4,095
Foreign equity mutual funds		38,861		-		38,861
Equity mutual funds		24,124		-		24,124
U.S. government bonds		-		76		76
Corporate bonds		-		42,590		42,590
Total	$	67,080	$	42,666	$	109,746

The plan had no financial instruments recorded at fair value on a non-recurring basis as of December 31, 2019 and 2018.

Determination of Assumed Rate of Return

The expected long-term rate-of-return on assets was 7.0% at December 31, 2019 and 2018. This assumption represents the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the projected benefit obligation. The assumption has been determined by reflecting expectations regarding future rates of return for the portfolio considering the asset distribution and related historical rates of return. The appropriateness of the assumption is reviewed annually.

Employee 401(k) and Employee Stock Ownership Plans

The Company maintains a 401(k) and employee stock ownership plan (the “401(k) Plan”). The Company contributes to the 401(k) Plan based on employees’ contributions out of their annual salaries. In addition, the Company may also make discretionary contributions to the 401(k) Plan based on profitability. Participation in the 401(k) Plan is contingent upon certain age and service requirements. The employer contributions associated with the 401(k) Plan were $3.6 million in 2019, $3.2 million in 2018 and $2.8 million in 2017.

Other Retirement Benefits

Included in other liabilities is $1.7 million and $2.0 million at December 31, 2019 and 2018, respectively, for supplemental retirement benefits for retired executives from legacy plans assumed in acquisitions. The Company recognized $0.1 million in expense for each of the years ended December 31, 2019, 2018 and 2017 related to these plans.

Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Tier I Capital (to average assets) [Abstract]
Tier I capital to average assets	$ 963,147	$ 880,448
Tier I capital to average assets ratio	10.33%	9.52%
Minimum Tier I leverage capital required for capital adequacy to average assets	4.00%	4.00%
Tier I leverage capital required for classification as well capitalized to average assets	5.00%	5.00%
Common Equity Tier I Capital [Abstract]
Common equity Tier I capital	$ 866,147	$ 783,448
Common equity Tier I capital ratio	11.29%	10.49%
Minimum Tier I capital required for capital adequacy	4.50%	4.50%
Minimum Tier I capital required for capital adequacy plus buffer	7.00%	6.375%
Tier I capital required for classification as well capitalized	6.50%	6.50%
Tier I Capital (to risk weighted assets) [Abstract]
Tier I capital to risk weighted assets	$ 963,147	$ 880,448
Tier I capital to risk weighted assets ratio	12.56%	11.79%
Minimum Tier I capital required for capital adequacy to risk weighted assets	6.00%	6.00%
Minimum Tier I capital required for capital adequacy plus buffer to risk weighted assets	8.50%	7.875%
Tier I capital required for classification as well capitalized to risk weighted assets	8.00%	8.00%
Total Capital (to risk weighted assets) [Abstract]
Total capital to risk weighted assets	$ 1,037,041	$ 954,232
Total capital to risk weighted assets ratio	13.52%	12.78%
Minimum capital required for capital adequacy to risk weighted assets	8.00%	8.00%
Total capital required for capital adequacy plus buffer to average assets	10.50%	9.875%
Capital required for classification as well capitalized to risk weighted assets	10.00%	10.00%
NBT Bank [Member]
Tier I Capital (to average assets) [Abstract]
Tier I capital to average assets	$ 894,407	$ 825,863
Tier I capital to average assets ratio	9.64%	8.98%
Minimum Tier I leverage capital required for capital adequacy to average assets	4.00%	4.00%
Tier I leverage capital required for classification as well capitalized to average assets	5.00%	5.00%
Common Equity Tier I Capital [Abstract]
Common equity Tier I capital	$ 894,407	$ 825,863
Common equity Tier I capital ratio	11.76%	11.14%
Minimum Tier I capital required for capital adequacy	4.50%	4.50%
Minimum Tier I capital required for capital adequacy plus buffer	7.00%	6.375%
Tier I capital required for classification as well capitalized	6.50%	6.50%
Tier I Capital (to risk weighted assets) [Abstract]
Tier I capital to risk weighted assets	$ 894,407	$ 825,863
Tier I capital to risk weighted assets ratio	11.76%	11.14%
Minimum Tier I capital required for capital adequacy to risk weighted assets	6.00%	6.00%
Minimum Tier I capital required for capital adequacy plus buffer to risk weighted assets	8.50%	7.875%
Tier I capital required for classification as well capitalized to risk weighted assets	8.00%	8.00%
Total Capital (to risk weighted assets) [Abstract]
Total capital to risk weighted assets	$ 968,301	$ 899,647
Total capital to risk weighted assets ratio	12.73%	12.14%
Minimum capital required for capital adequacy to risk weighted assets	8.00%	8.00%
Total capital required for capital adequacy plus buffer to average assets	10.50%	9.875%
Capital required for classification as well capitalized to risk weighted assets	10.00%	10.00%

Premises, Equipment and Leases

12 Months Ended

Dec. 31, 2019

Premises, Equipment and Leases [Abstract]

Premises, Equipment and Leases

6. Premises, Equipment and Leases

A summary of premises and equipment follows:

	December 31,
(In thousands)	2019		2018
Land, buildings and improvements	$	121,479	$	121,808
Equipment		58,431		55,577
Premises and equipment before accumulated depreciation	$	179,910	$	177,385
Accumulated depreciation		104,279		98,415
Total premises and equipment	$	75,631	$	78,970

Buildings and improvements are depreciated based on useful lives of five to twenty years. Equipment is depreciated based on useful lives of three to ten years.

Operating leases in which we are the lessee are recorded as operating lease ROU assets and operating lease liabilities, included in other assets and other liabilities, respectively, on the consolidated balance sheets. The Company does not have any significant finance leases in which we are the lessee as of December 31, 2019 and December 31, 2018.

Operating lease ROU assets represent the Company's right to use an underlying asset during the lease term and operating lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and operating lease liabilities are recognized at lease commencement based on the present value of the remaining lease payments using a discount rate that represents the Company's incremental borrowing rate at the lease commencement date. ROU assets are further adjusted for lease incentives. Operating lease expense, which is comprised of amortization of the ROU asset and the implicit interest accreted on the operating lease liability, is recognized on a straight-line basis over the lease term, and is recorded in occupancy expense in the consolidated statements of income.

We have made a policy election to exclude the recognition requirements to all classes of leases with original terms of 12 months or less. Instead, the short-term lease payments are recognized in profit or loss on a straight-line basis over the lease term.

Our leases relate primarily to office space and bank branches, and some contain options to renew the lease. These options to renew are generally not considered reasonably certain to exercise, and are therefore not included in the lease term until such time that the option to renew is reasonably certain. As of December 31, 2019, operating lease ROU assets and liabilities were $34.8 million and $37.3 million, respectively.

The table below summarizes our net lease cost:

(In thousands)	Year Ended December 31, 2019
Operating lease cost	$	7,239
Variable lease cost		2,231
Short-term lease cost		356
Sublease income		(448	)
Total operating lease cost	$	9,378

The table below show future minimum rental commitments related to non-cancelable operating leases for the next five years and thereafter as of December 31, 2019.

(In thousands)
2020	$	7,435
2021		6,646
2022		5,870
2023		4,969
2024		4,365
Thereafter		12,876
Total lease payments	$	42,161
Less: interest		(4,838	)
Present value of lease liabilities	$	37,323

The following table shows the weighted average remaining operating lease term, the weighted average discount rate and supplemental information on the consolidated statements of cash flows for operating leases:

(In thousands except for percent and period data)	December 31, 2019
Weighted average remaining lease term, in years		7.69
Weighted average discount rate		3.00	%
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	6,211
ROU assets obtained in exchange for lease liabilities		41,008

As of December 31, 2019 there are no new significant leases that have not yet commenced.

Rental expense included in occupancy expense amounted to $8.0 million in 2019, $8.6 million in December 31, 2018 and $8.5 million in December 31, 2017.

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Reconciliation of Basic and Diluted Earnings Per Share

The following is a reconciliation of basic and diluted EPS for the years presented in the consolidated statements of income:

	Years ended December 31,
	2019						2018						2017
(In thousands except per share data)	Net Income		Weighted Average Shares		Per Share Amount		Net Income		Weighted Average Shares		Per Share Amount		Net Income		Weighted Average Shares		Per Share Amount
Basic EPS	$	121,021		43,815	$	2.76	$	112,566		43,701	$	2.58	$	82,151		43,575	$	1.89
Effect of dilutive securities:
Stock-based compensation				309						319						330
Diluted EPS	$	121,021		44,124	$	2.74	$	112,566		44,020	$	2.56	$	82,151		43,905	$	1.87

Securities (Tables)

12 Months Ended

Dec. 31, 2019

Securities [Abstract]

Amortized Cost, Estimated Fair Value and Unrealized Gains (Losses) of Available for Sale ("AFS") Securities

The amortized cost, estimated fair value and unrealized gains (losses) of AFS securities are as follows:

(In thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
As of December 31, 2019
Federal agency	$	34,998	$	3	$	243	$	34,758
State & municipal		2,533		-		20		2,513
Mortgage-backed:
Government-sponsored enterprises		453,614		4,982		239		458,357
U.S. government agency securities		44,758		667		156		45,269
Collateralized mortgage obligations:
Government-sponsored enterprises		328,499		1,949		467		329,981
U.S. government agency securities		104,152		718		408		104,462
Total AFS securities	$	968,554	$	8,319	$	1,533	$	975,340
As of December 31, 2018
Federal agency	$	84,982	$	10	$	693	$	84,299
State & municipal		30,136		16		237		29,915
Mortgage-backed:
Government-sponsored enterprises		493,225		439		10,354		483,310
U.S. government securities		29,190		270		475		28,985
Collateralized mortgage obligations:
Government-sponsored enterprises		332,409		344		7,211		325,542
U.S. government securities		47,684		137		1,376		46,445
Total AFS securities	$	1,017,626	$	1,216	$	20,346	$	998,496

Components of Net Realized Gains (Losses) on Sale of AFS Securities

The components of net realized gains (losses) on the sale of AFS securities are as follows. These amounts were reclassified out of AOCI and into earnings:

	Years Ended December 31,
(In thousands)	2019			2018			2017
Gross realized gains	$	73		$	-		$	2,241
Gross realized (losses)		(152	)		(6,622	)		(372	)
Net AFS realized (losses) gains	$	(79	)	$	(6,622	)	$	1,869

Amortized Cost, Estimated Fair Value, and Unrealized Gains (Losses) of Held to Maturity Securities

The amortized cost, estimated fair value and unrealized gains (losses) of HTM securities are as follows:

(In thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
As of December 31, 2019
Mortgage-backed:
Government-sponsored enterprises	$	149,448	$	3,184	$	155	$	152,477
U.S. government agency securities		13,667		584		-		14,251
Collateralized mortgage obligations:
Government-sponsored enterprises		189,402		2,165		368		191,199
U.S. government agency securities		110,498		3,256		100		113,654
State & municipal		167,059		2,628		6		169,681
Total HTM securities	$	630,074	$	11,817	$	629	$	641,262
As of December 31, 2018
Federal agency	$	19,995	$	52	$	-	$	20,047
Mortgage-backed:
Government-sponsored enterprises		164,618		712		2,773		162,557
U.S. government agency securities		15,230		403		-		15,633
Collateralized mortgage obligations:
Government-sponsored enterprises		257,475		1,097		3,897		254,675
U.S. government agency securities		83,148		767		-		83,915
State & municipal		243,133		331		1,616		241,848
Total HTM securities	$	783,599	$	3,362	$	8,286	$	778,675

Investment Securities with Unrealized Losses

The following table sets forth information with regard to investment securities with unrealized losses segregated according to the length of time the securities had been in a continuous unrealized loss position:

	Less Than 12 Months							12 Months or Longer							Total
(In thousands)	Fair Value		Unrealized Losses			Number of Positions		Fair Value		Unrealized Losses			Number of Positions		Fair Value		Unrealized Losses			Number of Positions
As of December 31, 2019
AFS securities:
Federal agency	$	14,891	$	(109	)		2	$	9,866	$	(134	)		1	$	24,757	$	(243	)		3
State & municipal		2,503		(20	)		1		-		-			-		2,503		(20	)		1
Mortgage-backed		67,986		(273	)		21		37,745		(122	)		16		105,731		(395	)		37
Collateralized Mortgage obligations		113,121		(316	)		24		49,632		(559	)		17		162,753		(875	)		41
Total securities with unrealized losses	$	198,501	$	(718	)		48	$	97,243	$	(815	)		34	$	295,744	$	(1,533	)		82

HTM securities:
Mortgage-backed	$	-	$	-			-	$	25,370	$	(155	)		2	$	25,370	$	(155	)		2
Collateralized mortgage obligations		18,040		(181	)		3		22,389		(287	)		5		40,429		(468	)		8
State & municipal		2,257		(6	)		4		-		-			-		2,257		(6	)		4
Total securities with unrealized losses	$	20,297	$	(187	)		7	$	47,759	$	(442	)		7	$	68,056	$	(629	)		14

As of December 31, 2018
AFS securities:
Federal agency	$	-	$	-			-	$	64,294	$	(693	)		6	$	64,294	$	(693	)		6
State & municipal		1,715		(3	)		3		22,324		(234	)		35		24,039		(237	)		38
Mortgage-backed		18,462		(65	)		12		428,440		(10,764	)		101		446,902		(10,829	)		113
Collateralized mortgage obligations		12,118		(69	)		5		320,908		(8,518	)		62		333,026		(8,587	)		67
Total securities with unrealized losses	$	32,295	$	(137	)		20	$	835,966	$	(20,209	)		204	$	868,261	$	(20,346	)		224

HTM securities:
Mortgage-backed	$	-	$	-			-	$	82,579	$	(2,773	)		6	$	82,579	$	(2,773	)		6
Collateralized mortgage obligations		4,386		(7	)		2		145,396		(3,890	)		26		149,782		(3,897	)		28
State & municipal		18,907		(84	)		30		58,258		(1,532	)		86		77,165		(1,616	)		116
Total securities with unrealized losses	$	23,293	$	(91	)		32	$	286,233	$	(8,195	)		118	$	309,526	$	(8,286	)		150

Gains and Losses on Equity Securities

The following tables set forth information with regard to gains and losses on equity securities:

	Years ended December 31,
(In thousands)	2019		2018
Net gains and losses recognized on equity securities	$	4,280	$	281
Less: Net gains and losses recognized during the period on equity securities sold during the period		3,966		555
Unrealized gains and losses recognized on equity securities still held	$	314	$	(274	)

Contractual Maturities of Debt Securities

The following tables set forth information with regard to contractual maturities of debt securities at December 31, 2019:

(In thousands)	Amortized Cost		Estimated Fair Value
AFS debt securities:
Within one year	$	268	$	272
From one to five years		28,692		28,668
From five to ten years		170,771		171,943
After ten years		768,823		774,457
Total AFS debt securities	$	968,554	$	975,340
HTM debt securities:
Within one year	$	27,010	$	27,010
From one to five years		53,895		54,358
From five to ten years		171,942		175,630
After ten years		377,227		384,264
Total HTM debt securities	$	630,074	$	641,262

Allowance for Loan Losses and Credit Quality of Loans (Policies)

12 Months Ended

Dec. 31, 2019

Allowance for Loan Losses and Credit Quality of Loans [Abstract]

Portfolio and Class Segments

Portfolio	Class - 2019 & 2018	Class - 2017
Commercial Loans	Commercial and Industrial	Commercial
	Commercial Real Estate	Commercial Real Estate
	Business Banking	Agricultural
		Agricultural Real Estate
		Business Banking
Consumer Loans	Indirect Auto	Indirect
	Specialty Lending	Home Equity
	Direct	Direct
Residential Real Estate

Allowance for Loan Losses

Commercial Loans

Consumer Loans

The Company offers a variety of Consumer loan products including Indirect Auto, Specialty Lending and Direct loans.

Residential Real Estate

Allowance for Loan Loss Calculation

Impaired Loans

Credit Quality Indicators

Commercial Grading System

●

Doubtful

●

Substandard

●

Special Mention

●

Pass

Business Banking Grading System

Business Banking loans are graded as either Classified or Non-classified:

●

Classified

●

Non-classified

Loans graded as Non-classified encompass all loans not graded as Classified. Payments on non-classified loans are generally made as agreed.

Consumer and Residential Real Estate Grading System

Consumer and Residential Real Estate loans are graded as either Nonperforming or Performing.

●

Nonperforming

Nonperforming loans are loans that are 1) over 90 days past due and interest is still accruing or 2) on nonaccrual status.

●

Performing

All loans not meeting any of these criteria are considered Performing.

Troubled Debt Restructuring

- Definition

Describes an entity's accounting policy and methodology for estimating its allowance for loan and lease losses, and its accounting policy for nonperforming loans. The description identifies the factors that influenced management of the entity in establishing the level of the allowance (for example, historical losses and existing economic conditions) and also may include discussion of the risk elements relevant to particular categories of receivables. The disclosure also may describe any liability the entity has recorded for off-balance sheet credit losses and may include the basis for determining each element of the allowance for loan and lease losses. The disclosure also could discuss the entity's policy for (1) placing loans on nonaccrual status (or discontinuing accrual of interest) and recording payments received on nonaccrual loans, and the policy for resuming accrual of interest, (2) charging-off uncollectible loans, and (3) determining past due or delinquency status (that is, whether past due status is based on how recently payments have been received or contractual terms).

+ References + Details

Junior Subordinated Debt (Details) $ in Thousands	12 Months Ended
Junior Subordinated Debt (Details) $ in Thousands	Dec. 31, 2019 USD ($) Trust Period
Junior Subordinated Debt [Abstract]
Number of statutory business trusts included in the Trusts \| Trust	5
Minimum assets for bank holding companies to be subject to the same capital requirements as insured depository institutions	$ 500,000
CNBF Capital Trust I [Member]
Junior Subordinated Debt [Abstract]
Number of wholly owned Delaware statutory business trusts	one
CNBF Capital Trust I [Member] \| LIBOR [Member]
Junior Subordinated Debt [Abstract]
Issuance Date	Aug. 01, 1999
Trust Preferred Securities Outstanding	$ 18,000
Variable rate basis	3-month LIBOR
Basis spread on variable rate	2.75%
Trust Preferred Debt Owed To Trust	$ 18,720
Final Maturity Date	Aug. 01, 2029
NBT Statutory Trust I [Member] \| LIBOR [Member]
Junior Subordinated Debt [Abstract]
Issuance Date	Nov. 01, 2005
Trust Preferred Securities Outstanding	$ 5,000
Variable rate basis	3-month LIBOR
Basis spread on variable rate	1.40%
Trust Preferred Debt Owed To Trust	$ 5,155
Final Maturity Date	Dec. 01, 2035
NBT Statutory Trust II [Member] \| LIBOR [Member]
Junior Subordinated Debt [Abstract]
Issuance Date	Feb. 01, 2006
Trust Preferred Securities Outstanding	$ 50,000
Variable rate basis	3-month LIBOR
Basis spread on variable rate	1.40%
Trust Preferred Debt Owed To Trust	$ 51,547
Final Maturity Date	Mar. 01, 2036
Alliance Financial Capital Trust I [Member] \| LIBOR [Member]
Junior Subordinated Debt [Abstract]
Issuance Date	Dec. 01, 2003
Trust Preferred Securities Outstanding	$ 10,000
Variable rate basis	3-month LIBOR
Basis spread on variable rate	2.85%
Trust Preferred Debt Owed To Trust	$ 10,310
Final Maturity Date	Jan. 01, 2034
Alliance Financial Capital Trust II [Member] \| LIBOR [Member]
Junior Subordinated Debt [Abstract]
Issuance Date	Sep. 01, 2006
Trust Preferred Securities Outstanding	$ 15,000
Variable rate basis	3-month LIBOR
Basis spread on variable rate	1.65%
Trust Preferred Debt Owed To Trust	$ 15,464
Final Maturity Date	Sep. 01, 2036
Alliance Financial Capital [Member]
Junior Subordinated Debt [Abstract]
Number of wholly owned Delaware statutory business trusts	two
Trusts [Member]
Junior Subordinated Debt [Abstract]
Trust Preferred Securities Outstanding	$ 98,000
Trust Preferred Debt Owed To Trust	101,000
Trust equity method investment	$ 3,200
Debentures period semi-annual deferral periods \| Period	10
Trust preferred securities included in Tier I capital	$ 97,000
NBT Bancorp Inc [Member]
Junior Subordinated Debt [Abstract]
Trust equity method investment	$ 1,000

Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Recent Accounting Pronouncements [Abstract]
Right-of-use assets	$ 34,800
Lease liabilities	37,323
ASU 2016-02 [Member]
Recent Accounting Pronouncements [Abstract]
Right-of-use assets		$ 34,000
Lease liabilities		$ 37,000
ASU 2016-13 [Member] \| Minimum [Member]
Recent Accounting Pronouncements [Abstract]
Cumulative effect adjustment for ASU implementation	1,000
ASU 2016-13 [Member] \| Maximum [Member]
Recent Accounting Pronouncements [Abstract]
Cumulative effect adjustment for ASU implementation	$ 8,000

Parent Company Financial Information, Condensed Income Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Income Statements [Abstract]
Net securities gains	$ 4,213	$ (6,341)	$ 1,867
Interest, dividends and other income	367,534	344,255	309,407
Income before income tax benefit and equity in undistributed income of subsidiaries	155,432	137,002	128,161
Income tax expense (benefit)	34,411	24,436	46,010
Net income	121,021	112,566	82,151
NBT Bancorp Inc [Member]
Condensed Income Statements [Abstract]
Dividends from subsidiaries	50,200	43,000	38,300
Management fee from subsidiaries	7,981	7,907	99,319
Net securities gains	165	399	2,237
Interest, dividends and other income	876	905	928
Total revenue	59,222	52,211	140,784
Operating expenses	14,262	14,226	100,667
Income before income tax benefit and equity in undistributed income of subsidiaries	44,960	37,985	40,117
Income tax expense (benefit)	(1,588)	(1,608)	2,233
Dividends in excess of income (equity in undistributed income) of subsidiaries	74,473	72,973	44,267
Net income	$ 121,021	$ 112,566	$ 82,151

Allowance for Loan Losses and Credit Quality of Loans (Tables)

12 Months Ended

Dec. 31, 2019

Allowance for Loan Losses and Credit Quality of Loans [Abstract]

Portfolio and Class Segments

Portfolio	Class - 2019 & 2018	Class - 2017
Commercial Loans	Commercial and Industrial	Commercial
	Commercial Real Estate	Commercial Real Estate
	Business Banking	Agricultural
		Agricultural Real Estate
		Business Banking
Consumer Loans	Indirect Auto	Indirect
	Specialty Lending	Home Equity
	Direct	Direct
Residential Real Estate

Allowance for Loan Losses by Portfolio

The following tables illustrate the changes in the allowance for loan losses by our portfolio segments:

(In thousands)	Commercial Loans			Consumer Loans			Residential Real Estate			Total
Balance as of December 31, 2018	$	32,759		$	37,178		$	2,568		$	72,505
Charge-offs		(3,151	)		(28,398	)		(991	)		(32,540	)
Recoveries		534			6,913			141			7,588
Provision		4,383			19,954			1,075			25,412
Ending Balance as of December 31, 2019	$	34,525		$	35,647		$	2,793		$	72,965

Balance as of December 31, 2017	$	27,606		$	36,830		$	5,064		$	69,500
Charge-offs		(3,463	)		(29,752	)		(913	)		(34,128	)
Recoveries		1,178			6,821			306			8,305
Provision		7,438			23,279			(1,889	)		28,828
Ending Balance as of December 31, 2018	$	32,759		$	37,178		$	2,568		$	72,505

Balance as of December 31, 2016	$	25,444		$	33,375		$	6,381		$	65,200
Charge-offs		(4,169	)		(27,072	)		(1,846	)		(33,087	)
Recoveries		1,077			5,142			180			6,399
Provision		5,254			25,385			349			30,988
Ending Balance as of December 31, 2017	$	27,606		$	36,830		$	5,064		$	69,500

The following table illustrates the allowance for loan losses and the recorded investment by portfolio segment:

(In thousands)	Commercial Loans		Consumer Loans		Residential Real Estate		Total
As of December 31, 2019
Allowance for loan losses	$	34,525	$	35,647	$	2,793	$	72,965
Allowance for loans individually evaluated for impairment		-		-		-		-
Allowance for loans collectively evaluated for impairment	$	34,525	$	35,647	$	2,793	$	72,965
Ending balance of loans	$	3,444,266	$	2,246,676	$	1,445,156	$	7,136,098
Ending balance of originated loans individually evaluated for impairment		3,488		7,044		7,721		18,253
Ending balance of acquired loans collectively evaluated for impairment		115,266		23,733		125,879		264,878
Ending balance of originated loans collectively evaluated for impairment	$	3,325,512	$	2,215,899	$	1,311,556	$	6,852,967

As of December 31, 2018
Allowance for loan losses	$	32,759	$	37,178	$	2,568	$	72,505
Allowance for loans individually evaluated for impairment		25		-		-		25
Allowance for loans collectively evaluated for impairment	$	32,734	$	37,178	$	2,568	$	72,480
Ending balance of loans	$	3,222,310	$	2,284,563	$	1,380,836	$	6,887,709
Ending balance of originated loans individually evaluated for impairment		5,786		7,887		6,905		20,578
Ending balance of acquired loans collectively evaluated for impairment		143,690		31,624		147,277		322,591
Ending balance of originated loans collectively evaluated for impairment	$	3,072,834	$	2,245,052	$	1,226,654	$	6,544,540

Past due and Nonperforming Loans by Loan Class

The following table sets forth information with regard to past due and nonperforming loans by loan class:

(In thousands)	31-60 Days Past Due Accruing		61-90 Days Past Due Accruing		Greater Than 90 Days Past Due Accruing		Total Past Due Accruing		Nonaccrual		Current		Recorded Total Loans
As of December 31, 2019
Originated
Commercial Loans:
C&I	$	1,227	$	-	$	-	$	1,227	$	1,177	$	838,502	$	840,906
CRE		3,576		-		-		3,576		4,847		1,941,143		1,949,566
Business Banking		794		162		-		956		7,035		530,537		538,528
Total Commercial Loans	$	5,597	$	162	$	-	$	5,759	$	13,059	$	3,310,182	$	3,329,000
Consumer Loans:
Indirect Auto	$	11,860	$	2,108	$	1,005	$	14,973	$	2,175	$	1,176,487	$	1,193,635
Specialty Lending		3,153		2,087		1,307		6,547		-		535,516		542,063
Direct		2,564		564		478		3,606		2,475		481,164		487,245
Total Consumer Loans	$	17,577	$	4,759	$	2,790	$	25,126	$	4,650	$	2,193,167	$	2,222,943
Residential Real Estate	$	1,179	$	190	$	663	$	2,032	$	5,872	$	1,311,373	$	1,319,277
Total Originated Loans	$	24,353	$	5,111	$	3,453	$	32,917	$	23,581	$	6,814,722	$	6,871,220

Acquired
Commercial Loans:
C&I	$	149	$	-	$	-	$	149	$	-	$	19,215	$	19,364
CRE		-		-		-		-		-		60,937		60,937
Business Banking		397		287		-		684		382		33,899		34,965
Total Commercial Loans	$	546	$	287	$	-	$	833	$	382	$	114,051	$	115,266
Consumer Loans:
Direct	$	136	$	58	$	-	$	194	$	105	$	23,434	$	23,733
Total Consumer Loans	$	136	$	58	$	-	$	194	$	105	$	23,434	$	23,733
Residential Real Estate	$	575	$	20	$	264	$	859	$	1,106	$	123,914	$	125,879
Total Acquired Loans	$	1,257	$	365	$	264	$	1,886	$	1,593	$	261,399	$	264,878

Total Loans	$	25,610	$	5,476	$	3,717	$	34,803	$	25,174	$	7,076,121	$	7,136,098

(In thousands)	31-60 Days Past Due Accruing		61-90 Days Past Due Accruing		Greater Than 90 Days Past Due Accruing		Total Past Due Accruing		Nonaccrual		Current		Recorded Total Loans
As of December 31, 2018
Originated
Commercial Loans:
C&I	$	909	$	-	$	-	$	909	$	1,062	$	846,148	$	848,119
CRE		1,089		-		588		1,677		4,995		1,734,558		1,741,230
Business Banking		1,092		302		-		1,394		5,974		481,903		489,271
Total Commercial Loans	$	3,090	$	302	$	588	$	3,980	$	12,031	$	3,062,609	$	3,078,620
Consumer Loans:
Indirect Auto	$	14,519	$	2,300	$	1,186	$	18,005	$	1,971	$	1,196,136	$	1,216,112
Specialty Lending		3,479		1,773		1,562		6,814		-		518,114		524,928
Direct		2,962		1,437		552		4,951		2,592		504,356		511,899
Total Consumer Loans	$	20,960	$	5,510	$	3,300	$	29,770	$	4,563	$	2,218,606	$	2,252,939
Residential Real Estate	$	1,426	$	157	$	1,182	$	2,765	$	6,778	$	1,224,016	$	1,233,559
Total Originated Loans	$	25,476	$	5,969	$	5,070	$	36,515	$	23,372	$	6,505,231	$	6,565,118

Acquired
Commercial Loans:
C&I	$	-	$	-	$	-	$	-	$	-	$	26,124	$	26,124
CRE		-		-		-		-		-		84,492		84,492
Business Banking		466		288		-		754		390		31,930		33,074
Total Commercial Loans	$	466	$	288	$	-	$	754	$	390	$	142,546	$	143,690
Consumer Loans:
Indirect Auto	$	1	$	1	$	-	$	2	$	-	$	30	$	32
Direct		152		41		15		208		227		31,157		31,592
Total Consumer Loans	$	153	$	42	$	15	$	210	$	227	$	31,187	$	31,624
Residential Real Estate	$	546	$	42	$	-	$	588	$	1,498	$	145,191	$	147,277
Total Acquired Loans	$	1,165	$	372	$	15	$	1,552	$	2,115	$	318,924	$	322,591

Total Loans	$	26,641	$	6,341	$	5,085	$	38,067	$	25,487	$	6,824,155	$	6,887,709

Impaired Loans and Specific Reserve Allocations

The following table provides information on loans specifically evaluated for impairment:

	December 31, 2019						December 31, 2018
(In thousands)	Recorded Investment Balance (Book)		Unpaid Principal Balance (Legal)		Related Allowance		Recorded Investment Balance (Book)		Unpaid Principal Balance (Legal)		Related Allowance
Originated
With no related allowance recorded:
Commercial Loans:
C&I	$	76	$	302			$	228	$	497
CRE		2,410		2,437		-		4,312		6,330		-
Business Banking		1,002		1,443				1,013		2,001
Total Commercial Loans	$	3,488	$	4,182			$	5,553	$	8,828
Consumer Loans:
Indirect Auto	$	154	$	242			$	143	$	241
Direct		6,862		8,335				7,744		9,831
Specialty Lending		28		28				-		-
Total Consumer Loans	$	7,044	$	8,605			$	7,887	$	10,072
Residential Real Estate	$	7,721	$	9,754			$	6,905	$	9,414
Total	$	18,253	$	22,541			$	20,345	$	28,314
With an allowance recorded:
Commercial Loans:
C&I	$	-	$	-	$	-	$	233	$	238	$	25
Total Commercial Loans	$	-	$	-	$	-	$	233	$	238	$	25

Total Loans	$	18,253	$	22,541	$	-	$	20,578	$	28,552	$	25

There were no acquired impaired loans specifically evaluated for impairment as of December 31, 2019 and 2018.

The following table summarizes the average recorded investments on loans specifically evaluated for impairment and the interest income recognized:

	December 31, 2019				December 31, 2018				December 31, 2017
(In thousands)	Average Recorded Investment		Interest Income Recognized		Average Recorded Investment		Interest Income Recognized		Average Recorded Investment		Interest Income Recognized
Originated
Commercial Loans:
C&I	$	242	$	1	$	453	$	1	$	-	$	-
CRE		3,311		123		4,078		128		-		-
Commercial		-		-		-		-		1,841		-
Commercial Real Estate		-		-		-		-		3,534		115
Agricultural		-		-		-		-		224		1
Agricultural Real Estate		-		-		-		-		1,709		43
Business Banking		1,089		24		1,018		26		875		12
Total Commercial Loans	$	4,642	$	148	$	5,549	$	155	$	8,183	$	171
Consumer Loans:
Indirect Auto	$	192	$	10	$	179	$	10	$	-	$	-
Direct		7,387		382		7,922		431		-		-
Specialty Lending		7		1		-		-		-		-
Indirect		-		-		-		-		35		3
Home Equity		-		-		-		-		8,226		446
Direct		-		-		-		-		178		8
Total Consumer Loans	$	7,586	$	393	$	8,101	$	441	$	8,439	$	457
Residential Real Estate	$	7,505	$	350	$	6,779	$	305	$	6,523	$	296
Total Originated	$	19,733	$	891	$	20,429	$	901	$	23,145	$	924

Acquired
Commercial Loans:
Commercial Real Estate	$	-	$	-	$	-	$	-	$	93	$	-
Total Commercial Loans	$	-	$	-	$	-	$	-	$	93	$	-
Total Acquired Loans	$	-	$	-	$	-	$	-	$	93	$	-

Total Loans	$	19,733	$	891	$	20,429	$	901	$	23,238	$	924

Financing Receivable Credit Quality by Loan Class

The following tables illustrate the Company’s credit quality by loan class:

(In thousands)	As of December 31, 2019
Originated
Commercial Credit Exposure
By Internally Assigned Grade:	C&I		CRE		Total
Pass	$	782,763	$	1,868,678	$	2,651,441
Special Mention		28,380		30,519		58,899
Substandard		29,257		50,369		79,626
Doubtful		506		-		506
Total	$	840,906	$	1,949,566	$	2,790,472

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking		Total
Non-classified	$	524,725	$	524,725
Classified		13,803		13,803
Total	$	538,528	$	538,528

Consumer Credit Exposure
By Payment Activity:	Indirect Auto		Specialty Lending		Direct		Total
Performing	$	1,190,455	$	540,756	$	484,292	$	2,215,503
Nonperforming		3,180		1,307		2,953		7,440
Total	$	1,193,635	$	542,063	$	487,245	$	2,222,943

Residential Real Estate Credit Exposure
By Payment Activity:	Residential Real Estate		Total
Performing	$	1,312,742	$	1,312,742
Nonperforming		6,535		6,535
Total	$	1,319,277	$	1,319,277

Acquired
Commercial Credit Exposure
By Internally Assigned Grade:	C&I		CRE		Total
Pass	$	17,801	$	60,545	$	78,346
Special Mention		1,269		-		1,269
Substandard		294		392		686
Total	$	19,364	$	60,937	$	80,301

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking		Total
Non-classified	$	32,030	$	32,030
Classified		2,935		2,935
Total	$	34,965	$	34,965

Consumer Credit Exposure
By Payment Activity:	Direct		Total
Performing	$	23,628	$	23,628
Nonperforming		105		105
Total	$	23,733	$	23,733

Residential Real Estate Credit Exposure
By Payment Activity:	Residential Real Estate		Total
Performing	$	124,509	$	124,509
Nonperforming		1,370		1,370
Total	$	125,879	$	125,879

(In thousands)	As of December 31, 2018
Originated
Commercial Credit Exposure
By Internally Assigned Grade:	C&I		CRE		Total
Pass	$	796,778	$	1,681,330	$	2,478,108
Special Mention		11,348		13,894		25,242
Substandard		39,993		46,006		85,999
Total	$	848,119	$	1,741,230	$	2,589,349

Business Banking Credit Exposure	Business
By Internally Assigned Grade:	Banking		Total
Non-classified	$	476,052	$	476,052
Classified		13,219		13,219
Total	$	489,271	$	489,271

Consumer Credit Exposure
By Payment Activity:	Indirect Auto		Specialty Lending		Direct		Total
Performing	$	1,212,955	$	523,366	$	508,755	$	2,245,076
Nonperforming		3,157		1,562		3,144		7,863
Total	$	1,216,112	$	524,928	$	511,899	$	2,252,939

Residential Real Estate Credit Exposure	Residential
By Payment Activity:	Real Estate		Total
Performing	$	1,225,599	$	1,225,599
Nonperforming		7,960		7,960
Total	$	1,233,559	$	1,233,559

Acquired
Commercial Credit Exposure
By Internally Assigned Grade:	C&I		CRE		Total
Pass	$	23,283	$	83,762	$	107,045
Special Mention		2,831		92		2,923
Substandard		10		638		648
Total	$	26,124	$	84,492	$	110,616

Business Banking Credit Exposure	Business
By Internally Assigned Grade:	Banking		Total
Non-classified	$	29,945	$	29,945
Classified		3,129		3,129
Total	$	33,074	$	33,074

Consumer Credit Exposure
By Payment Activity:	Indirect Auto		Direct		Total
Performing	$	32	$	31,350	$	31,382
Nonperforming		-		242		242
Total	$	32	$	31,592	$	31,624

Residential Real Estate Credit Exposure	Residential
By Payment Activity:	Real Estate		Total
Performing	$	145,779	$	145,779
Nonperforming		1,498		1,498
Total	$	147,277	$	147,277

Troubled Debt Restructurings on Financing Receivables

	Year ended December 31, 2019
(Dollars in thousands)	Number of Contracts		Pre- Modification Outstanding Recorded Investment		Post- Modification Outstanding Recorded Investment
Commercial Loans:
C&I		1	$	65	$	65
CRE		1		402		402
Business Banking		3		425		431
Total Commercial Loans		5	$	892	$	898
Consumer Loans:
Indirect Auto		9	$	134	$	134
Direct		11		450		480
Total Consumer Loans		20	$	584	$	614
Residential Real Estate		12	$	1,032	$	1,091
Total Troubled Debt Restructurings		37	$	2,508	$	2,603

	Year ended December 31, 2018
(Dollars In thousands)	Number of Contracts		Pre- Modification Outstanding Recorded Investment		Post- Modification Outstanding Recorded Investment
Commercial Loans:
Business Banking		5	$	581	$	581
Total Commercial Loans		5	$	581	$	581
Consumer Loans:
Indirect Auto		17	$	204	$	202
Direct		10		401		399
Total Consumer Loans		27	$	605	$	601
Residential Real Estate		14	$	1,099	$	1,098
Total Troubled Debt Restructurings		46	$	2,285	$	2,280

The following table illustrates the recorded investment and number of modifications for TDRs where a concession has been made and subsequently defaulted during the period:

	Year ended December 31, 2019				Year ended December 31, 2018
(Dollars in thousands)	Number of Contracts		Recorded Investment		Number of Contracts		Recorded Investment
Commercial Loans:
Business Banking		-	$	-		3	$	338
Total Commercial Loans		-	$	-		3	$	338
Consumer Loans:
Indirect Auto		3	$	18		-	$	-
Direct		29		1,385		37		1,931
Total Consumer Loans		32	$	1,403		37	$	1,931
Residential Real Estate		23	$	1,203		26	$	1,786
Total Troubled Debt Restructurings		55	$	2,606		66	$	4,055

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2019	Feb. 10, 2020	Jun. 30, 2019
Cover [Abstract]
Entity Registrant Name	NBT BANCORP INC
Entity Central Index Key	0000790359
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Public Float			$ 1,594,211,159
Entity Common Stock, Shares Outstanding		43,844,649
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Document Annual Report	true
Document Transition Report	false
Entity File Number	0-14703
Entity Tax Identification Number	16-1268674
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	52 SOUTH BROAD STREET
Entity Address, City or Town	NORWICH
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	13815
City Area Code	607
Local Phone Number	337-2265
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	NBTB
Security Exchange Name	NASDAQ

Recent Accounting Pronouncements	12 Months Ended
Recent Accounting Pronouncements	Dec. 31, 2019
Recent Accounting Pronouncements [Abstract]
Recent Accounting Pronouncements	23. Recent Accounting Pronouncements Recently Adopted Accounting Standards In February 2016, the FASB issued Accounting Standards Update ("ASU") 2016-02, Leases (Topic 842). ASU 2016-02 requires lessees to recognize right-of-use assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize a right-of-use asset and lease liability. Additionally, when measuring assets and liabilities arising from a lease, optional payments should be included only if the lessee is reasonably certain to exercise an option to extend the lease, exercise a purchase option or not exercise an option to terminate the lease. In January 2018, the FASB issued ASU 2018-01, Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842. ASU 2018-01 was issued to address concerns about the cost and complexity of complying with the transition provisions of ASU 2016-02. Both ASU 2016-02 and ASU 2018-01 are effective for the Company on January 1, 2019. Lessees and lessors are required to apply the provisions of ASU 2016-02 at the beginning of the earliest period presented using a modified retrospective approach. At its November 29, 2017 meeting, the FASB proposed allowing entities the option of applying the provisions of ASU 2016-02 at the effective date without adjusting the comparative periods presented. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases. ASU 2018-10 was issued to provide more detailed guidance and additional clarification for implementing ASU 2016-02. Also in July 2018, the FASB issued ASU 2018-11, Targeted Improvements, which allows for an optional transition method in which the provisions of ASC Topic 842 would be applied upon the adoption date and would not have to be retroactively applied to the earliest reporting period presented in the consolidated financial statements. The Company adopted ASU 2016-02 as of January 1, 2019 and elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allows the carryforward of the historical lease classification, the practical expedient related to land easements and the hindsight practical expedient to determine the reasonably certain lease term for existing leases. The Company made an accounting policy election to keep leases with an initial term of 12 months or less off of the balance sheet and recognize those lease payments in the consolidated statements of income on a straight-line basis over the lease term. The adoption of ASU 2016-02 and related transition guidance resulted in the recognition of additional net lease assets and liabilities of approximately $34 million and $37 million, respectively, as of January 1, 2019. The standard did not materially affect our 2019 consolidated net earnings or regulatory capital ratios. Refer to Note 6, Premises, Equipment and Leases for more information. In March 2017, the FASB issued ASU 2017-08, Receivables – Nonrefundable Fees and Other Costs (Subtopic 310-20). ASU 2017-08 requires amortization of premiums to the earliest call date on debt securities with call features that are explicit, on contingent and callable at fixed prices on present dates. The ASU does not impact securities held at a discount; the discount continues to be amortized to the contractual maturity. The guidance is required to be applied with a modified retrospective approach through a cumulative effect adjustment to retained earnings as of the beginning of the period of adoption. ASU 2017-08 is effective for the Company on January 1, 2019. The adoption did not have an impact on the consolidated financial statements and related disclosures and no cumulative effect adjustment was required upon adoption. In October 2018, the FASB issued ASU 2018-16, Derivatives and Hedging (Topic 815) - Inclusion of the Secured Overnight Financing Rate (“SOFR”) Overnight Index Swap (“OIS”) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes. The ASU 2018-16 amends existing guidance and permits the use of the OIS rate based on SOFR as a United States benchmark interest rate for hedge accounting purposes under Topic 815 in addition to other allowable rates stated in the guidance. ASU 2018-16 is effective for the Company on January 1, 2019 and should be applied prospectively for qualifying new or redesignated hedging relationships entered into on or after the date of adoption. The adoption did not have an impact on the Company's consolidated financial statements. Accounting Standards Issued Not Yet Adopted In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. This ASU removes specific exceptions to the general principles in Topic 740 in GAAP. It eliminates the need for an organization to analyze whether the following apply in a given period: (1) exception to the incremental approach for intraperiod tax allocation; (2) exceptions to accounting for basis differences when there are ownership changes in foreign investments; and (3) exception in interim period income tax accounting for year-to-date losses that exceed anticipated losses. The ASU also improves financial statement preparers’ application of income tax-related guidance and simplifies GAAP for: (1) franchise taxes that are partially based on income; (2) transactions with a government that result in a step up in the tax basis of goodwill; (3) separate financial statements of legal entities that are not subject to tax; and (4) enacted changes in tax laws in interim periods. The amendments in this update become effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact of adopting the new guidance on the consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair value Measurement (Topic 820) – Disclosure Framework – Changes to the Disclosure Requirements for Fair value Measurement. The provisions of ASU 2018-13 modify the disclosure requirements on fair value measurements in ASC 820. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. ASU 2018-13 is effective January 1, 2020 but may be early adopted in any interim period. The adoption did not have a material impact on the consolidated financial statements and related disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“CECL”). ASU 2016-13 introduces new guidance that make substantive changes to the accounting for credit losses. ASU 2016-13 introduces the CECL model, which applies to financial assets subject to credit losses and measured at amortized cost, as well as certain off-balance sheet credit exposures. This includes loans, loan commitments, standby letters of credit, net investments in leases recognized by a lessor and HTM debt securities. The CECL model requires an entity to estimate credit losses expected over the life of an exposure, considering information about historical events, current conditions and reasonable and supportable forecasts and is generally expected to result in earlier recognition of credit losses. ASU 2016-13 also modifies certain provisions of the current OTTI model for AFS debt securities. Credit losses on AFS debt securities will be limited to the difference between the security's amortized cost basis and its fair value and will be recognized through an allowance for credit losses rather than as a direct reduction in amortized cost basis. ASU 2016-13 also provides for a simplified accounting model for purchased financial assets with more than insignificant credit deterioration since their origination. ASU 2016-13 requires expanded disclosures including, but not limited to, (i) information about the methods and assumptions used to estimate expected credit losses, including changes in the factors that influenced management's estimate and the reasons for those changes, (ii) for financing receivables and net investment in leases measured at amortized cost, further disaggregation of information about the credit quality of those assets and (iii) a rollforward of the allowance for credit losses for HTM and AFS securities. ASU 2016-13 is effective for the Company on January 1, 2020. In April 2019, the FASB issued ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, which, among other things, clarifies that recoveries should be incorporated within the estimation of the allowance for credit losses. Expected recoveries should not exceed the aggregate amount of prior write offs and expected future write offs. The inclusion of expected recoveries in the measurement of expected credit losses may result in a negative credit allowance in certain circumstances. The effective date and transition requirements for ASU 2019-04 are consistent with the requirements for ASU 2016-13 and the Company incorporated these changes and revisions within its implementation efforts. In May 2019, the FASB issued ASU 2019-05, Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief. The Company did not elect to apply the fair value option to any asset class that are in scope for CECL. In November 2019, the FASB issued ASU 2019-11, “Codification Improvements to Topic 326, Financial Instruments-Credit Losses” which clarifies that expected recoveries should be included in the amortized cost basis previously written off or expected to be written off in the valuation allowance for PCD assets. ASU 2019-11 also clarifies that recoveries or expected recoveries of the unamortized noncredit discount or premium should not be included in the allowance for credit losses. ASU 2019-11 provides specific transition relief for existing troubled debt restructurings and extends the disclosure relief of ASU 2019-04 for accrued interest receivable balances to additional relevant disclosures involving amortized cost basis. Related to the assessment of credit risk for collateralized assets, ASU 2019-11 indicates that an entity should assess whether it reasonably expects the borrower will be able to continually replenish collateral securing the financial asset to apply the practical expedient of ASU 2016-13 while also requiring an estimation of expected credit losses for any differences between the amount of the amortized cost basis that is greater than the fair value of the collateral securing the financial asset. ASU 2019-11 provides specific transition relief for existing troubled debt restructurings and extends the disclosure relief of ASU 2019-04 for accrued interest receivable balances to additional relevant disclosures involving amortized cost basis. The effective date and transition requirements of ASU 2019-11 are consistent with the requirements of ASU 2016-13 and the Company incorporated these changes and revisions within its implementation efforts. The Company has approved an accounting policy for credit losses in compliance with CECL and established a CECL governance and approval process. The Company has selected a life of loan discounted probability of default, loss given default econometric model, adjusted for prepayments, for the majority of its portfolio segments. The Company will utilize a multiple economic forecast over a six quarter reasonable and supportable forecast period followed by a four quarter straight line reversion to historical losses. The Company expects to incur a $1.0 million to $8.0 million after-tax reduction to stockholders’ equity balance, upon the adoption of ASU 2016-13 on January 1, 2020, inclusive of the estimate for off-balance sheet exposures. Longer lived loans such as Residential Real Estate loans experience increases in the allowance for credit losses compared to the incurred loss model while shorter lived loans such as Indirect Auto and C&I loans generally experience little change in the allowance for credit losses from the incurred loss model. The Company has established a control framework and is finalizing testing of controls related to the adoption of CECL. The Company is also completing its final review of the most recent model run including evaluation of model back-testing and sensitivity analysis results, and finalizing certain assumptions primarily related to qualitative adjustments and probable troubled debt restructurings. In addition, the Company is completing the analysis of the results from the third party model validation. The Company does not expect to incur a material adjustment to the stockholders’ equity balance as of January 1, 2020 for the adoption of CECL related to HTM securities. Additionally, the Company has also evaluated the composition of its AFS securities and determined that the changes in ASU 2016-13 will not have a significant effect on the current portfolio. Management expects that the CECL model may create more volatility in the level of our allowance for loan losses from quarter to quarter as changes in the level of allowance for loan losses will be dependent upon, among other things, macroeconomic forecasts and conditions, loan portfolio volumes and credit quality. In August 2018, the FASB issued ASU 2018-14, Compensation – Retirement Benefits – Defined Benefit Plans - General (Subtopic 715-20), provides changes to the disclosure requirements for defined benefit plans. The amended guidance modifies the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. The amendments are a result of the disclosure framework project that focuses on improvements to the effectiveness of disclosures in the notes to financial statements. The amendments remove and add certain disclosure requirements. The disclosure requirements being removed relating to public companies are (1) the amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit cost over the next fiscal year, (2) the amount and timing of plan assets expected to be returned to the employer, (3) the 2001 disclosure requirement relating to Japanese Welfare Pension Insurance Law, (4) related party disclosures about the amount of future annual benefits covered by insurance, and (5) the effects of a one-percentage-point change in assumed health care cost trends on the benefit cost and obligation. The disclosure requirements being added relating to public companies are (1) the weighted-average interest crediting rates for cash balance plans, and (2) an explanation of the reasons for significant gains and losses related to changes in the benefit obligation for the period. ASU 2018-14 is effective for the Company on January 1, 2021 and early adoption is permitted. The amendments should be applied retrospectively and the Company does not expect the guidance to have a material impact on its disclosures to the consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40) – Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract. ASU 2018-15 amends existing guidance and requires a hosting arrangement that is a service contract to follow the guidance in Subtopic 350-40 to determine which implementation costs to capitalize and which costs to expense. ASU 2018-15 is effective for the Company on January 1, 2020, and early adoption is permitted. The amendments should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The adoption did not have a material impact on the consolidated financial statements and related disclosures.

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Taxes [Abstract]

Income Taxes

12. Income Taxes

The significant components of income tax expense attributable to operations are as follows:

	Years ended December 31,
(In thousands)	2019			2018		2017
Current
Federal	$	28,475		$	15,762	$	35,839
State		7,653			5,977		6,599
Total Current	$	36,128		$	21,739	$	42,438

Deferred
Federal	$	(1,379	)	$	2,281	$	3,850
State		(338	)		416		(278	)
Total Deferred	$	(1,717	)	$	2,697	$	3,572
Total income tax expense	$	34,411		$	24,436	$	46,010

On December 22, 2017, the U.S. government enacted the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act includes significant changes to the U.S. corporate income tax system including: a federal corporate rate reduction from 35% to 21% and establishing other tax laws affecting years subsequent to 2017. ASC 740, Income Taxes, requires a company to record the effects of a tax law change in the period of enactment, however shortly after the enactment of the Tax Act, the SEC staff issued Staff Accounting Bulletin 118 ("SAB 118"), which allows a company to record a provisional amount when it does not have the necessary information available, prepared, or analyzed in reasonable detail to complete its accounting for the change in the tax law. The one year remeasurement period allowed under SAB 118 ended December 31, 2018 and the Company did not make any significant changes to the provisional amounts recorded.

In connection with the analysis of the impact of the Tax Act, the Company recorded a $4.4 million non-cash adjustment in the year ended December 31, 2017 for remeasurement of deferred tax assets and liabilities for the corporate rate reduction. During 2018, the Company recorded a $5.5 million benefit primarily related to changes in accounting methods approved by the Internal Revenue Services in the fourth quarter of 2018.

The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities are as follows:

	December 31,
(In thousands)	2019			2018
Deferred tax assets:
Allowance for loan losses	$	18,535		$	18,042
Lease liability		9,331			-
Deferred compensation		8,336			7,340
Postretirement benefit obligation		1,631			1,962
Fair value adjustments from acquisitions		422			663
Unrealized losses on securities		-			4,893
Accrued liabilities		1,176			913
Stock-based compensation expense		3,032			2,821
Other		1,498			1,008
Total deferred tax assets	$	43,961		$	37,642
Deferred tax liabilities:
Pension benefits	$	13,014		$	10,782
Lease right-of-use asset		9,259			-
Amortization of intangible assets		12,202			11,525
Premises and equipment, primarily due to accelerated depreciation		5,137			4,973
Unrealized gain on securities		1,770			-
Other		45			1,567
Total deferred tax liabilities	$	41,427		$	28,847
Net deferred tax asset at year-end	$	2,534		$	8,795
Net deferred tax asset at beginning of year		8,795			7,293
(Decrease) increase in net deferred tax asset	$	(6,261	)	$	1,502

Realization of deferred tax assets is dependent upon the generation of future taxable income. A valuation allowance is recorded when it is more likely than not that some portion of the deferred tax asset will not be realized. Based on available evidence, gross deferred tax assets will ultimately be realized and a valuation allowance was not deemed necessary at December 31, 2019 and 2018.

The following is a reconciliation of the provision for income taxes to the amount computed by applying the applicable Federal statutory rate to income before taxes:

	Years ended December 31
(In thousands)	2019			2018			2017
Federal income tax at statutory rate	$	32,641		$	28,770		$	44,857
Tax exempt income		(1,233	)		(1,456	)		(2,303	)
Net increase in cash surrender value of life insurance		(927	)		(973	)		(1,780	)
Federal tax credit		(1,458	)		(1,499	)		(1,343	)
State taxes, net of federal tax benefit		5,773			5,051			4,107
Federal tax reform (Tax Act)		-			-			4,407
Accounting method changes - tax rate change impact		-			(5,326	)		-
Stock-based compensation, excess tax benefit		(342	)		(456	)		(1,619	)
Other, net		(43	)		325			(316	)
Income tax expense	$	34,411		$	24,436		$	46,010

A reconciliation of the beginning and ending balance of Federal and State gross unrecognized tax benefits ("UTBs") is as follows:

(In thousands)	2019		2018
Balance at January 1	$	641	$	665
Additions for tax positions of prior years		26		27
Reduction for tax positions of prior years		-		(159	)
Current period tax positions		112		108
Balance at December 31	$	779	$	641
Amount that would affect the effective tax rate if recognized, gross of tax	$	615	$	506

The Company recognizes interest and penalties on the income tax expense line in the accompanying consolidated statements of income. The Company monitors changes in tax statutes and regulations to determine if significant changes will occur over the next 12 months. As of December 31, 2019, no significant changes to UTBs are projected; however, tax audit examinations are possible. The Company recognized an insignificant amount of interest expense related to UTBs in the consolidated statement of income for the year ended December 31, 2019.

During the year ended December 31, 2019, the Company recognized an insignificant benefit related to the resolution of state income tax positions. The Company is no longer subject to U.S. Federal tax examination by tax authorities for years prior to 2016 and New York State for years prior to 2014. The 2014, 2015 and 2016 tax years are currently being audited by New York State.

Allowance for Loan Losses and Credit Quality of Loans, Troubled Debt Restructurings (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Contract	Dec. 31, 2018 USD ($) Contract
Troubled Debt Restructured Loans [Abstract]
Number of contracts \| Contract	37	46
Pre-modification outstanding recorded investment	$ 2,508	$ 2,285
Post-modification outstanding recorded investment	$ 2,603	$ 2,280
Number of contracts \| Contract	55	66
Recorded Investment	$ 2,606	$ 4,055
Commercial Loans [Member]
Troubled Debt Restructured Loans [Abstract]
Number of contracts \| Contract	5	5
Pre-modification outstanding recorded investment	$ 892	$ 581
Post-modification outstanding recorded investment	$ 898	$ 581
Number of contracts \| Contract	0	3
Recorded Investment	$ 0	$ 338
Commercial Loans [Member] \| C&I [Member]
Troubled Debt Restructured Loans [Abstract]
Number of contracts \| Contract	1
Pre-modification outstanding recorded investment	$ 65
Post-modification outstanding recorded investment	$ 65
Commercial Loans [Member] \| CRE [Member]
Troubled Debt Restructured Loans [Abstract]
Number of contracts \| Contract	1
Pre-modification outstanding recorded investment	$ 402
Post-modification outstanding recorded investment	$ 402
Commercial Loans [Member] \| Business Banking [Member]
Troubled Debt Restructured Loans [Abstract]
Number of contracts \| Contract	3	5
Pre-modification outstanding recorded investment	$ 425	$ 581
Post-modification outstanding recorded investment	$ 431	$ 581
Number of contracts \| Contract	0	3
Recorded Investment	$ 0	$ 338
Consumer Loans [Member]
Troubled Debt Restructured Loans [Abstract]
Number of contracts \| Contract	20	27
Pre-modification outstanding recorded investment	$ 584	$ 605
Post-modification outstanding recorded investment	$ 614	$ 601
Number of contracts \| Contract	32	37
Recorded Investment	$ 1,403	$ 1,931
Consumer Loans [Member] \| Indirect Auto [Member]
Troubled Debt Restructured Loans [Abstract]
Number of contracts \| Contract	9	17
Pre-modification outstanding recorded investment	$ 134	$ 204
Post-modification outstanding recorded investment	$ 134	$ 202
Number of contracts \| Contract	3	0
Recorded Investment	$ 18	$ 0
Consumer Loans [Member] \| Direct [Member]
Troubled Debt Restructured Loans [Abstract]
Number of contracts \| Contract	11	10
Pre-modification outstanding recorded investment	$ 450	$ 401
Post-modification outstanding recorded investment	$ 480	$ 399
Number of contracts \| Contract	29	37
Recorded Investment	$ 1,385	$ 1,931
Residential Real Estate [Member]
Troubled Debt Restructured Loans [Abstract]
Number of contracts \| Contract	12	14
Pre-modification outstanding recorded investment	$ 1,032	$ 1,099
Post-modification outstanding recorded investment	$ 1,091	$ 1,098
Number of contracts \| Contract	23	26
Recorded Investment	$ 1,203	$ 1,786

Parent Company Financial Information, Condensed Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities [Abstract]
Net income	$ 121,021	$ 112,566	$ 82,151
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Depreciation and amortization of premises and equipment	9,497	9,280	9,056
Excess tax benefit on stock-based compensation	(409)	(543)	(1,769)
Stock-based compensation expense	4,210	3,936	3,644
Net security (gains) losses	(4,213)	6,341	(1,867)
Re-evaluation of deferred tax amounts from Tax Act	0	0	4,407
Bank owned life insurance income	(5,355)	(5,091)	(5,175)
Net change in other assets and other liabilities	(4,902)	(9,554)	7,400
Net cash provided by operating activities	153,463	147,773	136,904
Investing activities [Abstract]
Proceeds on sales of equity securities	3,966	3,318	0
Purchases of equity securities	(93)	(2)	0
Proceeds on sales and maturities of AFS securities	273,578	259,446	290,613
Purchases of AFS securities	(252,963)	(132,448)	(233,804)
Proceeds from settlement of bank owned life insurance	1,086	0	799
Net purchases of premises and equipment	(6,647)	(7,402)	(6,691)
Net cash (used in) provided by investing activities	(64,343)	(417,619)	(305,193)
Financing activities [Abstract]
Proceeds from the issuance of shares to employee and other stock plans	725	1,296	3,309
Cash paid by employer for tax-withholdings on stock issuance	(1,622)	(1,893)	(3,582)
Cash dividends	(46,010)	(43,269)	(40,104)
Net cash (used in) provided by financing activities	(53,232)	291,137	178,772
Net increase (decrease) in cash and cash equivalents	35,888	21,291	10,483
Cash and cash equivalents at beginning of year	180,955	159,664	149,181
Cash and cash equivalents at end of year	216,843	180,955	159,664
NBT Bancorp Inc [Member]
Operating activities [Abstract]
Net income	121,021	112,566	82,151
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Depreciation and amortization of premises and equipment	2,298	2,814	2,974
Excess tax benefit on stock-based compensation	(409)	(543)	(1,769)
Stock-based compensation expense	4,210	3,936	3,644
Net security (gains) losses	(165)	(399)	(2,238)
Re-evaluation of deferred tax amounts from Tax Act	0	0	3,339
Equity in undistributed income of subsidiaries	(124,673)	(115,972)	(82,567)
Cash dividend from subsidiaries	50,200	43,000	38,300
Bank owned life insurance income	(398)	(424)	(328)
Net change in other assets and other liabilities	(1,573)	(6,124)	(2,454)
Net cash provided by operating activities	50,511	38,854	41,052
Investing activities [Abstract]
Proceeds on sales of equity securities	0	3,318	0
Purchases of equity securities	(93)	(2)	0
Proceeds on sales and maturities of AFS securities	0	0	4,710
Purchases of AFS securities	0	0	(9)
Proceeds from settlement of bank owned life insurance	0	0	308
Net purchases of premises and equipment	0	0	(2,264)
Net cash (used in) provided by investing activities	(93)	3,316	2,745
Financing activities [Abstract]
Proceeds from the issuance of shares to employee and other stock plans	725	1,296	3,309
Cash paid by employer for tax-withholdings on stock issuance	(1,622)	(1,893)	(3,582)
Cash dividends	(46,010)	(43,269)	(40,104)
Net cash (used in) provided by financing activities	(46,907)	(43,866)	(40,377)
Net increase (decrease) in cash and cash equivalents	3,511	(1,696)	3,420
Cash and cash equivalents at beginning of year	5,876	7,572	4,152
Cash and cash equivalents at end of year	$ 9,387	$ 5,876	$ 7,572

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Assets
Securities held to maturity fair value	$ 641,262	$ 778,675
Stockholders' equity
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	2,500,000	2,500,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	49,651,493	49,651,493
Common stock in treasury, at cost (in shares)	5,854,882	5,978,527

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Consolidated Statements of Changes in Stockholders' Equity [Abstract]
Cash dividends - per share (in dollars per share)	$ 1.05	$ 0.99	$ 0.92
Net issuance of shares to employee benefit plans and other stock plans (in shares)	123,645	130,157	285,059

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies [Abstract]

Noninterest Income, Segregated by Revenue Streams in-Scope and Out-of-Scope of ASC 606

The following table presents noninterest income, segregated by revenue streams in-scope and out-of-scope of ASC 606:

	Years ended December 31,
(In thousands)	2019		2018			2017
Noninterest income
In-Scope of ASC 606:
Insurance and other financial services revenue	$	25,006	$	24,345		$	23,532
Service charges on deposit accounts		17,151		17,224			16,750
ATM and debit card fees		23,893		22,699			21,372
Retirement plan administration fees		30,388		26,992			20,213
Trust		19,164		19,524			19,586
Other		18,853		15,228			11,991
Total noninterest income in-scope of ASC 606	$	134,455	$	126,012		$	113,444
Total noninterest income out-of-scope of ASC 606	$	9,568	$	(1,250	)	$	7,860
Total noninterest income	$	144,023	$	124,762		$	121,304

Earnings Per Share

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Earnings Per Share

17. Earnings Per Share

The following is a reconciliation of basic and diluted EPS for the years presented in the consolidated statements of income:

	Years ended December 31,
	2019						2018						2017
(In thousands except per share data)	Net Income		Weighted Average Shares		Per Share Amount		Net Income		Weighted Average Shares		Per Share Amount		Net Income		Weighted Average Shares		Per Share Amount
Basic EPS	$	121,021		43,815	$	2.76	$	112,566		43,701	$	2.58	$	82,151		43,575	$	1.89
Effect of dilutive securities:
Stock-based compensation				309						319						330
Diluted EPS	$	121,021		44,124	$	2.74	$	112,566		44,020	$	2.56	$	82,151		43,905	$	1.87

There was a nominal number of weighted average stock options outstanding for the years ended December 31, 2019, 2018 and 2017, respectively, that were not considered in the calculation of diluted EPS since the stock options’ exercise prices were greater than the average market price during these periods.

Securities (Policies)	12 Months Ended
Securities (Policies)	Dec. 31, 2019
Securities [Abstract]
Investment, Policy	Declines in the fair value of HTM securities below their amortized cost, less any current period credit loss, that are deemed to be other-than-temporary are reflected in earnings as realized losses or in OCI. The classification is dependent upon whether the Company intends to sell the security, or whether it is more likely than not, that the Company will be required to sell the security before recovery. The OTTI shall be recognized in earnings equal to the entire difference between the investment's amortized cost basis and its fair value at the balance sheet date. If the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the OTTI shall be separated into (i) the amount representing the credit loss and (ii) the amount related to all other factors. The amount of the total OTTI related to the credit loss shall be recognized in earnings. The amount of the total OTTI related to other factors shall be recognized in OCI, net of applicable taxes. In estimating OTTI losses, management considers, among other things, (i) the length of time and the extent to which the fair value has been less than cost, (ii) the financial condition and near-term prospects of the issuer and (iii) the historical and implied volatility of the fair value of the security. Management has the intent to hold the securities classified as HTM until they mature, at which time it is believed the Company will receive full value for the securities. The unrealized losses on HTM debt securities are due to increases in market interest rates over yields at the time the underlying securities were purchased. When necessary, the Company has performed a discounted cash flow analysis to determine whether or not it will receive the contractual principal and interest on certain securities. The fair value is expected to recover as the bond approaches its maturity date or repricing date or if market yields for such investments declines. Management also has the intent to hold and will not be required to sell, the debt securities classified as AFS for a period of time sufficient for a recovery of cost, which may be until maturity. The unrealized losses on AFS debt securities are due to increases in market interest rates over the yields available at the time the underlying securities were purchased. When necessary, the Company has performed a discounted cash flow analysis to determine whether or not it will receive the contractual principal and interest on certain securities. For AFS debt securities, OTTI losses are recognized in earnings if the Company intends to sell the security. In other cases the Company considers the relevant factors noted above, as well as the Company's intent and ability to retain its investment for a period of time sufficient to allow for any anticipated recovery in market value and whether evidence exists to support a realizable value equal to or greater than the cost basis. Any impairment loss on an equity security is equal to the full difference between the cost basis and the fair value of the security. Maturities of mortgage-backed, collateralized mortgage obligations and asset-backed securities are stated based on their estimated average lives. Actual maturities may differ from estimated average lives or contractual maturities because, in certain cases, borrowers have the right to call or prepay obligations with or without call or prepayment penalties.

Short-Term Borrowings

12 Months Ended

Dec. 31, 2019

Short-Term Borrowings [Abstract]

Short-Term Borrowings

9. Short-Term Borrowings

In addition to the liquidity provided by balance sheet cash flows, liquidity must also be supplemented with additional sources such as credit lines from correspondent banks as well as borrowings from the FHLB and the Federal Reserve Bank. Other funding alternatives may also be appropriate from time to time, including wholesale and retail repurchase agreements and brokered certificate of deposit (“CD”) accounts.

Short-term borrowings totaled $655.3 million and $871.7 million at December 31, 2019 and 2018, respectively, and consist of Federal funds purchased and securities sold under repurchase agreements, which generally represent overnight borrowing transactions and other short-term borrowings, primarily FHLB advances, with original maturities of one year or less.

The Company has unused lines of credit with the FHLB and access to brokered deposits available for short-term financing. Those sources totaled approximately $2.4 billion and $1.9 billion at December 31, 2019 and 2018, respectively. Borrowings on the FHLB lines are secured by FHLB stock, certain securities and one-to-four family first lien mortgage loans. Securities collateralizing repurchase agreements are held in safekeeping by nonaffiliated financial institutions and are under the Company’s control.

Information related to short-term borrowings is summarized as follows as of December 31:

(Dollars in thousands)	2019			2018			2017
Federal funds purchased:
Balance at year-end	$	65,000		$	80,000		$	60,000
Average during the year		47,137			66,839			54,162
Maximum month end balance		80,000			80,000			80,000
Weighted average rate during the year		3.90	%		3.43	%		2.16	%
Weighted average rate at year-end		2.84	%		4.25	%		2.41	%

Securities sold under repurchase agreements:
Balance at year-end	$	143,775		$	160,696		$	182,123
Average during the year		123,337			146,135			175,539
Maximum month end balance		146,410			170,350			190,326
Weighted average rate during the year		0.33	%		0.16	%		0.07	%
Weighted average rate at year-end		0.40	%		0.38	%		0.07	%

Other short-term borrowings:
Balance at year-end	$	446,500		$	631,000		$	477,000
Average during the year		403,453			514,662			460,334
Maximum month end balance		576,000			653,000			591,000
Weighted average rate during the year		1.85	%		1.56	%		1.02	%
Weighted average rate at year-end		1.73	%		1.82	%		1.18	%

See Note 3 for additional information regarding securities pledged as collateral for securities sold under the repurchase agreements.

Reclassification Adjustments Out of Other Comprehensive Income (Loss)

12 Months Ended

Dec. 31, 2019

Reclassification Adjustments Out of Other Comprehensive Income (Loss) [Abstract]

Reclassification Adjustments Out of Other Comprehensive Income (Loss)

18. Reclassification Adjustments Out of Other Comprehensive Income (Loss)

The following table summarizes the reclassification adjustments out of AOCI:

Detail About AOCI Components	Amount Reclassified From AOCI									Affected Line Item in the Consolidated Statements of Comprehensive Income (Loss)
(In thousands)	Years ended December 31,
(In thousands)	2019			2018			2017
AFS securities:
Losses (gains) on AFS securities	$	79		$	6,622		$	(1,869	)	Net securities (gains) losses
Amortization of unrealized gains related to securities transfer		737			688			875		Interest income
Impairment write-down of an equity security		-			-			1,312		Other noninterest income
Tax effect	$	(204	)	$	(1,827	)	$	(120	)	Income tax (benefit)
Net of tax	$	612		$	5,483		$	198

Cash flow hedges:
Net unrealized (gains) on cash flow hedges reclassified to interest expense	$	(2,012	)	$	(2,300	)	$	(292	)	Interest expense
Tax effect	$	503		$	575		$	113		Income tax expense
Net of tax	$	(1,509	)	$	(1,725	)	$	(179	)

Pension and other benefits:
Amortization of net losses	$	2,593		$	1,054		$	1,755		Other noninterest expense
Amortization of prior service costs		93			91			97		Other noninterest expense
Tax effect	$	(672	)	$	(286	)	$	(740	)	Income tax (benefit)
Net of tax	$	2,014		$	859		$	1,112

Total reclassifications, net of tax	$	1,117		$	4,617		$	1,131

Deposits

12 Months Ended

Dec. 31, 2019

Deposits [Abstract]

Deposits

8. Deposits

The following table sets forth the maturity distribution of time deposits:

(In thousands)	December 31, 2019
Within one year	$	554,132
After one but within two years		220,769
After two but within three years		50,593
After three but within four years		15,064
After four but within five years		20,453
After five years		182
Total	$	861,193

Time deposits of $250,000 or more aggregated $140.4 million and $146.1 million December 31, 2019 and 2018, respectively.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2019

Stock-Based Compensation [Abstract]

Stock-Based Compensation

14. Stock-Based Compensation

In May 2018, the Company adopted the NBT Bancorp Inc. 2018 Omnibus Incentive Plan (the “Stock Plan”) replacing the 2008 Omnibus Incentive Plan which automatically expired in April 2018. Under the terms of the Stock Plan, equity-based awards are granted to directors and employees to increase their direct proprietary interest in the operations and success of the Company. The Stock Plan assumed all prior equity-based incentive plans and any new equity-based awards are granted under the terms of the Stock Plan. Restricted shares granted under the Plan typically vest after three or five years for employees and three years for non-employee directors. Restricted stock units granted under the Stock Plan may have different terms and conditions. Performance shares and units granted under the Stock Plan for executives may have different terms and conditions. Since 2011, the Company primarily grants restricted stock unit awards. Stock option grants since that time were reloads of existing grants which terminate ten years from the date of the grant. Under terms of the Stock Plan, stock options are granted to purchase shares of the Company’s common stock at a price equal to the fair market value of the common stock on the date of the grant. Shares issued as a result of stock option exercises and vesting of restricted shares and stock unit awards are funded from the Company’s treasury stock.

The Company has outstanding restricted stock granted from various plans at December 31, 2019. The Company recognized $4.2 million, $3.9 million and $3.5 million in stock-based compensation expense related to these stock awards for the years ended December 31, 2019, 2018 and 2017, respectively. Tax benefits recognized with respect to restricted stock awards and stock units were $1.1 million, $1.2 million and $2.5 million for the years ended December 31, 2019, 2018 and 2017, respectively. Unrecognized compensation cost related to restricted stock units totaled $5.5 million at December 31, 2019 and will be recognized over 1.8 years on a weighted average basis. Shares issued are funded from the Company’s treasury stock. The following table summarizes information for unvested restricted stock units outstanding as of December 31, 2019:

	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested at January 1, 2019		546,054		$	28.39
Forfeited		(10,886	)		31.06
Vested		(121,774	)		25.66
Granted		142,046			33.04
Unvested at December 31, 2019		555,440		$	30.11

The following table summarizes information concerning stock options outstanding:

(In thousands, except share and per share data)	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Outstanding at January 1, 2019		66,900		$	23.07
Exercised		(32,505	)		22.31
Expired		(1,250	)		25.38
Outstanding at December 31, 2019		33,145		$	23.73		1.86	$	558,066

Exercisable at December 31, 2019		33,145		$	23.73		1.86	$	558,066

Total stock-based compensation expense for stock option awards totaled $1 thousand, $11 thousand and $18 thousand for the years ended December 31, 2019, 2018 and 2017, respectively. Cash proceeds, tax benefits and intrinsic value related to total stock options exercised is as follows:

	Years ended December 31,
(In thousands)	2019		2018		2017
Proceeds from stock options exercised	$	725	$	999	$	3,083
Tax benefits related to stock options exercised		123		173		650
Intrinsic value of stock options exercised		490		692		1,699
Fair value of shares vested during the year		13		16		329

The Company has 988,494 securities remaining available to be granted as part of the Plan at December 31, 2019.

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
Consolidated Statements of Income - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest, fee and dividend income
Interest and fees on loans	$ 321,474	$ 300,827	$ 267,096
Securities available for sale	23,303	26,920	28,564
Securities held to maturity	19,105	13,242	10,934
Other	3,652	3,266	2,813
Total interest, fee and dividend income	367,534	344,255	309,407
Interest expense
Deposits	39,986	22,144	14,475
Short-term borrowings	9,693	10,552	5,996
Long-term debt	1,875	1,790	2,299
Junior subordinated debt	4,425	4,140	3,144
Total interest expense	55,979	38,626	25,914
Net interest income	311,555	305,629	283,493
Provision for loan losses	25,412	28,828	30,988
Net interest income after provision for loan losses	286,143	276,801	252,505
Noninterest income
Insurance and other financial services revenue	25,006	24,345	23,532
Service charges on deposit accounts	17,151	17,224	16,750
ATM and debit card fees	23,893	22,699	21,372
Retirement plan administration fees	30,388	26,992	20,213
Trust	19,164	19,524	19,586
Bank owned life insurance	5,355	5,091	5,175
Net securities gains (losses)	4,213	(6,341)	1,867
Gain on the sale of equity investment	0	0	818
Other	18,853	15,228	11,991
Total noninterest income	144,023	124,762	121,304
Noninterest expense
Salaries and employee benefits	156,867	151,685	135,222
Occupancy	22,706	22,318	21,808
Data processing and communications	18,318	17,652	17,068
Professional fees and outside services	14,785	14,376	13,499
Equipment	18,583	17,037	15,225
Office supplies and postage	6,579	6,204	6,284
FDIC expenses	1,946	4,651	4,767
Advertising	2,773	2,782	2,744
Amortization of intangible assets	3,579	4,042	3,960
Loan collection and other real estate owned, net	4,158	4,217	4,763
Other	24,440	19,597	20,308
Total noninterest expense	274,734	264,561	245,648
Income before income tax expense	155,432	137,002	128,161
Income tax expense	34,411	24,436	46,010
Net income	$ 121,021	$ 112,566	$ 82,151
Earnings per share
Basic (in dollars per share)	$ 2.76	$ 2.58	$ 1.89
Diluted (in dollars per share)	$ 2.74	$ 2.56	$ 1.87

Fair Values of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2019

Fair Values of Financial Instruments [Abstract]

Fair Value of Financial Assets and Liabilities Measured on a Recurring Basis

The following tables sets forth the Company’s financial assets and liabilities measured on a recurring basis that were accounted for at fair value. Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement:

(In thousands)	Level 1		Level 2		Level 3		December 31, 2019
Assets:
AFS securities:
Federal agency	$	-	$	34,758	$	-	$	34,758
State & municipal		-		2,513		-		2,513
Mortgage-backed		-		503,626		-		503,626
Collateralized mortgage obligations		-		434,443		-		434,443
Total AFS securities	$	-	$	975,340	$	-	$	975,340
Equity securities		23,771		4,000		-		27,771
Derivatives		-		41,766		-		41,766
Total	$	23,771	$	1,021,106	$	-	$	1,044,877

Liabilities:
Derivatives	$	-	$	41,777	$	-	$	41,777
Total	$	-	$	41,777	$	-	$	41,777

(In thousands)	Level 1		Level 2		Level 3		December 31, 2018
Assets:
AFS securities:
Federal agency	$	-	$	84,299	$	-	$	84,299
State & municipal		-		29,915		-		29,915
Mortgage-backed		-		512,295		-		512,295
Collateralized mortgage obligations		-		371,987		-		371,987
Total AFS securities	$	-	$	998,496	$	-	$	998,496
Equity securities		19,053		4,000		-		23,053
Derivatives		-		20,000		-		20,000
Total	$	19,053	$	1,022,496	$	-	$	1,041,549

Liabilities:
Derivatives	$	-	$	17,572	$	-	$	17,572
Total	$	-	$	17,572	$	-	$	17,572

Information with Regard to Estimated Fair Values of Financial Instruments

The following table sets forth information with regard to estimated fair values of financial instruments. This table excludes financial instruments for which the carrying amount approximates fair value. Financial instruments for which the fair value approximates carrying value include cash and cash equivalents, AFS securities, equity securities, accrued interest receivable, non-maturity deposits, short-term borrowings, accrued interest payable and derivatives.

		December 31, 2019				December 31, 2018
(In thousands)	Fair Value Hierarchy		Carrying Amount	Estimated Fair Value		Carrying Amount		Estimated Fair Value
Financial assets:
HTM securities	2	$	630,074	$	$641,262	$	783,599	$	778,675
Net loans	3		7,074,864		6,999,690		6,822,147		6,754,460
Financial liabilities:
Time deposits	2	$	861,193	$	$858,085	$	930,678	$	920,534
Long-term debt	2		64,211		64,373		73,724		73,927
Junior subordinated debt	2		101,196		105,694		101,196		100,114

Allowance for Loan Losses and Credit Quality of Loans, Average Recorded Investments on Loans Specifically Evaluated for Impairment and Interest Income Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	$ 19,733	$ 20,429	$ 23,238
Interest income recognized accrual	891	901	924
Originated Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	19,733	20,429	23,145
Interest income recognized accrual	891	901	924
Originated Loans [Member] \| Commercial Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	4,642	5,549	8,183
Interest income recognized accrual	148	155	171
Originated Loans [Member] \| Commercial Loans [Member] \| C&I [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	242	453	0
Interest income recognized accrual	1	1	0
Originated Loans [Member] \| Commercial Loans [Member] \| CRE [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	3,311	4,078	0
Interest income recognized accrual	123	128	0
Originated Loans [Member] \| Commercial Loans [Member] \| Commercial [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	1,841
Interest income recognized accrual	0	0	0
Originated Loans [Member] \| Commercial Loans [Member] \| Commercial Real Estate [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	3,534
Interest income recognized accrual	0	0	115
Originated Loans [Member] \| Commercial Loans [Member] \| Agricultural [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	224
Interest income recognized accrual	0	0	1
Originated Loans [Member] \| Commercial Loans [Member] \| Agricultural Real Estate [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	1,709
Interest income recognized accrual	0	0	43
Originated Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	1,089	1,018	875
Interest income recognized accrual	24	26	12
Originated Loans [Member] \| Consumer Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7,586	8,101	8,439
Interest income recognized accrual	393	441	457
Originated Loans [Member] \| Consumer Loans [Member] \| Indirect Auto [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	192	179	0
Interest income recognized accrual	10	10	0
Originated Loans [Member] \| Consumer Loans [Member] \| Direct [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7,387	7,922	0
Interest income recognized accrual	382	431	0
Originated Loans [Member] \| Consumer Loans [Member] \| Specialty Lending [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7	0	0
Interest income recognized accrual	1	0	0
Originated Loans [Member] \| Consumer Loans [Member] \| Indirect [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	35
Interest income recognized accrual	0	0	3
Originated Loans [Member] \| Consumer Loans [Member] \| Home Equity [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	8,226
Interest income recognized accrual	0	0	446
Originated Loans [Member] \| Consumer Loans [Member] \| Direct [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	178
Interest income recognized accrual	0	0	8
Originated Loans [Member] \| Residential Real Estate [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7,505	6,779	6,523
Interest income recognized accrual	350	305	296
Acquired Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	93
Interest income recognized accrual	0	0	0
Acquired Loans [Member] \| Commercial Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	93
Interest income recognized accrual	0	0	0
Acquired Loans [Member] \| Commercial Loans [Member] \| Commercial Real Estate [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	0	0	93
Interest income recognized accrual	$ 0	$ 0	$ 0

Allowance for Loan Losses and Credit Quality of Loans (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) Segment	Mar. 31, 2018
Allowance for Loan Losses [Abstract]
Loan portfolio segments \| Segment	3
Agricultural [Member] \| Maximum [Member]
Allowance for Loan Losses [Abstract]
Loan amount, percentage of commercial portfolio		3.00%
Specialty Lending [Member]
Allowance for Loan Losses [Abstract]
Loan amount, percentage of consumer portfolio		21.00%
Commercial Loans [Member] \| Commercial Real Estate [Member] \| Maximum [Member]
Allowance for Loan Losses [Abstract]
Loan amount, percentage of appraised value or purchase price of the property	80.00%
Commercial Loans [Member] \| Business Banking [Member] \| Maximum [Member]
Allowance for Loan Losses [Abstract]
Business banking loans, amount available \| $	$ 1.0
Consumer Loans [Member] \| Indirect Auto [Member]
Allowance for Loan Losses [Abstract]
Percentage of automobile financing to indirect relationships with dealers	95.00%
Consumer Loans [Member] \| Indirect Auto [Member] \| Minimum [Member]
Allowance for Loan Losses [Abstract]
Principal repayment term of loan	3 years
Consumer Loans [Member] \| Indirect Auto [Member] \| Maximum [Member]
Allowance for Loan Losses [Abstract]
Principal repayment term of loan	6 years
Consumer Loans [Member] \| Direct [Member] \| Minimum [Member]
Allowance for Loan Losses [Abstract]
Principal repayment term of loan	1 year
Consumer Loans [Member] \| Direct [Member] \| Maximum [Member]
Allowance for Loan Losses [Abstract]
Principal repayment term of loan	10 years
Consumer Loans [Member] \| Home Equity [Member]
Allowance for Loan Losses [Abstract]
Term of draw	10 years
Term of amortization	15 years
Consumer Loans [Member] \| Home Equity [Member] \| Maximum [Member]
Allowance for Loan Losses [Abstract]
Loan amount, percentage of equity in property	85.00%
Residential Real Estate [Member] \| Maximum [Member]
Allowance for Loan Losses [Abstract]
Loan amount, percentage of appraised value or purchase price of the property	85.00%

Junior Subordinated Debt

12 Months Ended

Dec. 31, 2019

Junior Subordinated Debt [Abstract]

Junior Subordinated Debt

11. Junior Subordinated Debt

The Company sponsors five business trusts, CNBF Capital Trust I, NBT Statutory Trust I, NBT Statutory Trust II, Alliance Financial Capital Trust I and Alliance Financial Capital Trust II (collectively, the “Trusts”). The Company’s junior subordinated debentures include amounts related to the Company’s NBT Statutory Trust I and II as well as junior subordinated debentures associated with one statutory trust affiliate that was acquired from our merger with CNB Financial Corp. and two statutory trusts that were acquired from our acquisition of Alliance Financial Corporation (“Alliance”). The Trusts were formed for the purpose of issuing company-obligated mandatorily redeemable trust preferred securities to third-party investors and investing in the proceeds from the sale of such preferred securities solely in junior subordinated debt securities of the Company for general corporate purposes. The Company guarantees, on a limited basis, payments of distributions on the trust preferred securities and payments on redemption of the trust preferred securities. The Trusts are VIEs for which the Company is not the primary beneficiary, as defined by GAAP. In accordance with GAAP, the accounts of the Trusts are not included in the Company’s consolidated financial statements. See Note 1 for additional information about the Company’s consolidation policy.

The debentures held by each trust are the sole assets of that trust. The Trusts hold, as their sole assets, junior subordinated debentures of the Company with face amounts totaling $98.0 million at December 31, 2019. The Company owns all of the common securities of the Trusts and has accordingly recorded $3.2 million in equity method investments classified as other assets in our consolidated balance sheets at December 31, 2019. The Company owns all of the common stock of the Trusts, which have issued trust preferred securities in conjunction with the Company issuing trust preferred debentures to the Trusts. The terms of the trust preferred debentures are substantially the same as the terms of the trust preferred securities.

As of December 31, 2019, the Trusts had the following trust preferred securities outstanding and held the following junior subordinated debentures of the Company (dollars in thousands):

Description	Issuance Date	Trust Preferred Securities Outstanding		Interest Rate	Trust Preferred Debt Owed To Trust		Final Maturity Date
CNBF Capital Trust I	August 1999	$	18,000	3-month LIBOR plus 2.75%	$	18,720	August 2029
NBT Statutory Trust I	November 2005		5,000	3-month LIBOR plus 1.40%		5,155	December 2035
NBT Statutory Trust II	February 2006		50,000	3-month LIBOR plus 1.40%		51,547	March 2036
Alliance Financial Capital Trust I	December 2003		10,000	3-month LIBOR plus 2.85%		10,310	January 2034
Alliance Financial Capital Trust II	September 2006		15,000	3-month LIBOR plus 1.65%		15,464	September 2036

The Company’s junior subordinated debentures are redeemable prior to the maturity date at our option upon each trust’s stated option repurchase dates and from time to time thereafter. These debentures are also redeemable in whole at any time upon the occurrence of specific events defined within the trust indenture. Our obligations under the debentures and related documents, taken together, constitute a full and unconditional guarantee by the Company of the issuers’ obligations under the trust preferred securities. The Company owns all of the common stock of the Trusts, which have issued trust preferred securities in conjunction with the Company issuing trust preferred debentures to the Trusts. The terms of the trust preferred debentures are substantially the same as the terms of the trust preferred securities.

With respect to the Trusts, the Company has the right to defer payments of interest on the debentures issued to the Trusts at any time or from time to time for a period of up to ten consecutive semi-annual periods with respect to each deferral period. Under the terms of the debentures, if in certain circumstances there is an event of default under the debentures or the Company elects to defer interest on the debentures, the Company may not, with certain exceptions, declare or pay any dividends or distributions on its capital stock or purchase or acquire any of its capital stock.

Despite the fact that the Trusts are not included in the Company’s consolidated financial statements, $97 million of the $101 million in trust preferred securities issued by these subsidiary trusts is included in the Tier 1 capital of the Company for regulatory capital purposes as allowed by the Federal Reserve Board (NBT Bank owns $1.0 million of CNBF Trust I securities). The Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 requires bank holding companies with assets greater than $500 million to be subject to the same capital requirements as insured depository institutions, meaning, for instance, that such bank holding companies will not be able to count trust preferred securities issued after May 19, 2010 as Tier 1 capital. The aforementioned Trusts are grandfathered with respect to this enactment based on their date of issuance.

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
Minimum number of days past due for nonaccrual loan status	90 days
Period of sustained repayment performance for nonperforming TDRs to be returned to performing status	6 months
Standby letters of credit expiration period	1 year
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	$ 134,455	$ 126,012	$ 113,444
Total noninterest income out-of-scope of ASC 606	9,568	(1,250)	7,860
Total noninterest income	144,023	124,762	121,304
Insurance and Other Financial Services Revenue [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	25,006	24,345	23,532
Service Charges on Deposit Accounts [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	17,151	17,224	16,750
ATM and Debit Card Fees [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	23,893	22,699	21,372
Retirement Plan Administration Fees [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	30,388	26,992	20,213
Trust [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	19,164	19,524	19,586
Other [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	$ 18,853	$ 15,228	$ 11,991

Derivative Instruments and Hedging Activities

12 Months Ended

Dec. 31, 2019

Derivative Instruments and Hedging Activities [Abstract]

Derivative Instruments and Hedging Activities

20. Derivative Instruments and Hedging Activities

The Company is exposed to certain risks arising from both its business operations and economic conditions. The Company principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The Company manages economic risks, including interest rate, primarily by managing the amount, sources and duration of its assets and liabilities and through the use of derivative instruments. Specifically, the Company enters into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The Company’s derivative financial instruments are used to manage differences in the amount, timing and duration of the Company’s known or expected cash receipts and its known or expected cash payments principally related to certain fixed rate borrowings. The Company also has interest rate derivatives that result from a service provided to certain qualifying customers and, therefore, are not used to manage interest rate risk in the Company’s assets or liabilities. The Company manages a matched book with respect to its derivative instruments in order to minimize its net risk exposure resulting from such transactions.

Derivatives Not Designated as Hedging Instruments

The Company enters into interest rate swaps to facilitate customer transactions and meet their financing needs. These swaps are considered derivatives, but are not designated in hedging relationships. These instruments have interest rate and credit risk associated with them. To mitigate the interest rate risk, the Company enters into offsetting interest rate swaps with counterparties. The counterparty swaps are also considered derivatives and are also not designated in hedging relationships. Interest rate swaps are recorded within other assets or other liabilities on the consolidated balance sheet at their estimated fair value. Changes to the fair value of assets and liabilities arising from these derivatives are included, net, in other operating income in the consolidated statement of income.

As of December 31, 2019 the Company had fifteen risk participation agreements with financial institution counterparties for interest rate swaps related to participated loans. The fair values included in other assets and other liabilities on the consolidated balance sheet applicable to these agreements amount to $112 thousand and $82 thousand, respectively as of December 31, 2019. As of December 31, 2018 the Company had nine risk participation agreements with financial institution counterparties for interest rate swaps related to participated loans. The fair values included in other assets and other liabilities on the consolidated balance sheet applicable to these agreements amount to $36 thousand and $17 thousand, respectively. Risk participation agreements provides credit protection to the financial institution that originated the swap transaction should the borrower fail to perform on its obligation. The Company enters into both risk participation agreements in which it purchases credit protection from other financial institutions and those in which it provides credit protection to other financial institutions.

Derivatives Designated as Hedging Instruments

The Company has entered into interest rate swaps to modify the interest rate characteristics of certain short-term FHLB advances from variable rate to fixed rate in order to reduce the impact of changes in future cash flows due to market interest rate changes. These agreements are designated as cash flow hedges.

The following table depicts the fair value adjustment recorded related to the notional amount of derivatives outstanding as well as the notional amount of risk participation agreements:

	December 31,
(In thousands)	2019		2018
Derivatives Not Designated as Hedging Instruments:
Fair value adjustment included in other assets and other liabilities
Interest rate derivatives	$	41,650	$	17,572
Notional amount:
Interest rate derivatives		963,209		653,369
Risk participation agreements		97,614		70,785
Derivatives Designated as Hedging Instruments:
Fair value adjustment included in other assets
Interest rate derivatives		4		2,428
Fair value adjustment included in other liabilities
Interest rate derivatives		45		-
Notional amount:
Interest rate derivatives		50,000		225,000

For derivatives designated and that qualify as cash flow hedges of interest rate risk, the gain or loss on the derivative is recorded in AOCI and subsequently reclassified into interest expense in the same period during which the hedge transaction affects earnings. Amounts reported in AOCI related to derivatives will be reclassified to interest expense as interest payments are made on the Company's short-term rate borrowings. During the next twelve months, the Company estimates that an additional $39 thousand will be reclassified from AOCI as a reduction to interest expense.

The following table indicates the effect of cash flow hedge accounting on AOCI and on the consolidated statement of income:

	December 31,
(In thousands)	2019			2018			2017
Derivatives Designated as Hedging Instruments:
Interest rate derivatives - included component
Amount of (loss) or gain recognized in OCI	$	(459	)	$	1,218		$	901
Amount of gain reclassified from AOCI into interest expense		(2,012	)		(2,300	)		(292	)

The following table indicates the gain or loss recognized in income on derivatives not designating as a hedging relationship:

	December 31,
(In thousands)	2019		2018			2017
Derivatives Not Designated as Hedging Instruments:
Decrease (increase) in other income	$	295	$	(120	)	$	101

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies [Abstract]

Summary of Significant Accounting Policies

1. Summary of Significant Accounting Policies

The accounting and reporting policies of NBT Bancorp Inc. (“NBT Bancorp”) and its subsidiaries, NBT Bank, National Association (“NBT Bank” or the “Bank"), NBT Holdings, Inc. and NBT Financial Services, Inc., conform, in all material respects, with accounting principles generally accepted in the United States of America (“GAAP”) and to general practices within the banking industry. Collectively, NBT Bancorp and its subsidiaries are referred to herein as “the Company.”

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates.

Estimates associated with the allowance for loan losses, income taxes, pension expense, fair values of financial instruments, status of contingencies and other-than-temporary impairment ("OTTI") on investments are particularly susceptible to material change in the near term.

The following is a description of significant policies and practices:

Consolidation

The accompanying consolidated financial statements include the accounts of NBT Bancorp and its wholly-owned subsidiaries mentioned above. All material intercompany transactions have been eliminated in consolidation. Amounts previously reported in the consolidated financial statements are reclassified whenever necessary to conform to the current year’s presentation. In the “Parent Company Financial Information,” the investment in subsidiaries is recorded using the equity method of accounting.

The Company determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting interest entity or a variable interest entity under GAAP. Voting interest entities are entities in which the total equity investment at risk is sufficient to enable the entity to finance itself independently and provides the equity holders with the obligation to absorb losses, the right to receive residual returns and the right to make decisions about the entity’s activities. The Company consolidates voting interest entities in which it has all, or at least a majority of, the voting interest. As defined in applicable accounting standards, variable interest entities (“VIEs”) are entities that lack one or more of the characteristics of a voting interest entity. A controlling financial interest in a VIE is present when the Company has both the power and ability to direct the activities of the VIE that most significantly impact the VIE's economic performance and an obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. The Company’s wholly-owned subsidiaries CNBF Capital Trust I, NBT Statutory Trust I, NBT Statutory Trust II, Alliance Financial Capital Trust I and Alliance Financial Capital Trust II are VIEs for which the Company is not the primary beneficiary. Accordingly, the accounts of these entities are not included in the Company’s consolidated financial statements.

Segment Reporting

The Company’s operations are primarily in the community banking industry and include the provision of traditional banking services. The Company also provides other services through its subsidiaries such as insurance, retirement plan administration and trust administration. The Company operates solely in the geographical regions of central and upstate New York, northeastern Pennsylvania, western Massachusetts, southern New Hampshire, Vermont and southern coastal Maine. The Company has no reportable operating segments.

Cash Equivalents

The Company considers amounts due from correspondent banks, cash items in process of collection and institutional money market mutual funds to be cash equivalents for purposes of the consolidated statements of cash flows.

Securities

The Company classifies its securities at date of purchase as either held to maturity ("HTM"), trading, available for sale ("AFS") or equity. HTM debt securities are those that the Company has the ability and intent to hold until maturity. Trading securities are securities purchased with the intent to sell within a short period of time. AFS debt securities are securities that are not classified as HTM or trading securities. AFS securities are recorded at fair value. Unrealized holding gains and losses, net of the related tax effect, on AFS securities are excluded from earnings and are reported in the consolidated statements of stockholders’ equity and the consolidated statements of comprehensive income as a component of accumulated other comprehensive income or loss ("AOCI"). HTM securities are recorded at amortized cost. Trading securities and equity securities are recorded at fair value, with net unrealized gains and losses recognized in income. Transfers of securities between categories are recorded at fair value at the date of transfer. Non-marketable equity securities are carried at cost. Equity securities without readily determinable fair values are carried at cost. The Company performs a qualitative assessment to determine whether investments are impaired. Downward or upward adjustments are recognized through the income statement.

Declines in the fair value of AFS and HTM securities below their amortized cost, less any current period credit loss, that are deemed to be other-than-temporary are reflected in earnings as realized losses, or in other comprehensive income ("OCI"). The classification is dependent upon whether the Company intends to sell the security, or whether it is more likely than not, that the Company will be required to sell the security before recovery. The OTTI shall be recognized in earnings equal to the entire difference between the investment’s amortized cost basis and its fair value at the balance sheet date. If the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the OTTI shall be separated into (i) the amount representing the credit loss and (ii) the amount related to all other factors. The amount of the total OTTI impairment related to the credit loss shall be recognized in earnings. The amount of the total OTTI related to other factors shall be recognized in OCI, net of applicable taxes.

In estimating OTTI losses, management considers, among other things, (i) the length of time and the extent to which the fair value has been less than cost, (ii) the financial condition and near-term prospects of the issuer and (iii) the historical and implied volatility of the fair value of the security.

Premiums and discounts are amortized or accreted over the life of the related security as an adjustment to yield using the interest method. Dividend and interest income are recognized when earned. Realized gains and losses on securities sold are derived using the specific identification method for determining the cost of securities sold.

Investments in Federal Reserve Bank and Federal Home Loan Bank (“FHLB”) stock are required for membership in those organizations and are carried at cost since there is no market value available. The FHLB New York continues to pay dividends and repurchase stock. As such, the Company has not recognized any impairment on its holdings of Federal Reserve Bank and FHLB stock.

Loan Held for Sale and Loan Servicing

Loans held for sale are recorded at the lower of cost or fair value on an individual basis. Loan sales are recorded when the sales are funded. Gains and losses on sales of loans held for sale are included in other noninterest income in the Consolidated Statements of Income. Mortgage loans held for sale are generally sold with servicing rights retained. Mortgage servicing rights are recorded at fair value upon sale of the loan, and are amortized in proportion to and over the period of estimated net servicing income.

Loans

Loans are recorded at their current unpaid principal balance, net of unearned income and unamortized loan fees and expenses, which are amortized under the effective interest method over the estimated lives of the loans. Interest income on loans is accrued based on the principal amount outstanding.

For all loan classes within the Company’s loan portfolio, loans are placed on nonaccrual status when timely collection of principal and/or interest in accordance with contractual terms is in doubt. Loans are transferred to nonaccrual status generally when principal or interest payments become ninety days delinquent, unless the loan is well secured and in the process of collection or sooner when management concludes circumstances indicate that borrowers may be unable to meet contractual principal or interest payments. When a loan is transferred to a nonaccrual status, all interest previously accrued in the current period but not collected is reversed against interest income in that period. Interest accrued in a prior period and not collected is charged-off against the allowance for loan losses.

If ultimate repayment of a nonaccrual loan is expected, any payments received are applied in accordance with contractual terms. If ultimate repayment of principal is not expected, any payment received on a nonaccrual loan is applied to principal until ultimate repayment becomes expected. For all loan classes within the Company’s loan portfolio, nonaccrual loans are returned to accrual status when they become current as to principal and interest and demonstrate a period of performance under the contractual terms and, in the opinion of management, are fully collectible as to principal and interest. For loans in all portfolios, the principal amount is charged off in full or in part as soon as management determines, based on available facts, that the collection of principal in full or in part is improbable. For Commercial loans, management considers specific facts and circumstances relative to individual credits in making such a determination. For Consumer and Residential Real Estate loan classes, management uses specific guidance and thresholds from the Federal Financial Institutions Examination Council’s Uniform Retail Credit Classification and Account Management Policy.

Commercial type loans are considered impaired when it is probable that the borrower will not repay the loan according to the original contractual terms of the loan agreement and all loan types are considered impaired if the loan is restructured in a troubled debt restructuring (“TDR”). In determining that the Company will be unable to collect all principal and/or interest payments due in accordance with the contractual terms of the loan agreements, the Company considers factors such as payment history and changes in the financial condition of individual borrowers, local economic conditions, historical loss experience and the conditions of the various markets in which the collateral may be liquidated.

A loan is considered to be a TDR when the Company grants a concession to the borrower because of the borrower’s financial condition that the Company would not otherwise consider. Such concessions generally include one or a combination of the following: an extension of the maturity date at a stated rate of interest lower than the current market rate for new debt with similar risk; a temporary reduction in the interest rate; or a change in scheduled payment amount. TDR loans are nonaccrual loans; however, they can be returned to accrual status after a period of performance, generally evidenced by six months of compliance with their modified terms.

Acquired Loans

Acquired loans are initially measured at fair value as of the acquisition date without carryover of historical allowance for loan losses.

For loans that meet the criteria stipulated in Accounting Standards Codification (“ASC”) 310-30, Receivables - Loans and Debt Securities Acquired with Deteriorated Credit Quality, the Company shall recognize the accretable yield, which is defined as the excess of all cash flows expected at acquisition over the initial fair value of the loan, as interest income on a level-yield basis over the expected remaining life of the loan. The excess of the loan's contractually required payments over the cash flows expected to be collected is the nonaccretable difference. The nonaccretable difference shall not be recognized as an adjustment of yield, a loss accrual or a valuation allowance. Decreases in the expected cash flows in subsequent periods require the establishment of an allowance for loan losses. Improvements in expected cash flows in future periods result in a reduction of the nonaccretable discount, with such amount reclassified as part of the accretable yield and subsequently recognized in interest income over the remaining lives of the acquired loans on a level-yield basis if the amount and timing of future cash flows is reasonably estimable.

Acquired loans that met the criteria for nonaccrual of interest prior to the acquisition are considered performing upon acquisition, regardless of whether the customer is contractually delinquent, if the Company can reasonably estimate the timing and amount of the expected cash flows on such loans and if the Company expects to fully collect the new carrying value of the loans. As such, the Company may no longer consider the loan to be nonaccrual or nonperforming and may accrue interest on these loans, including the impact of any accretable yield. As such, charge-offs on acquired loans are first applied to the nonaccretable difference and then to any allowance for loan losses recognized subsequent to acquisition.

For loans that meet the criteria stipulated in ASC 310-20 - Receivables - Nonrefundable Fees and Other Costs ("ASC 310-20"), the Company shall amortize/accrete into interest income the premium/discount determined at the date of purchase on a level-yield basis over the life of the loan. Subsequent to the acquisition date, the methods utilized to estimate the required allowance for loan losses are similar to originated loans. Loans accounted for under ASC 310-20 are placed on nonaccrual status when past due in accordance with the Company's nonaccrual policy.

An acquired loan may be resolved either through receipt of payment (in full or in part) from the borrower, the sale of the loan to a third party, or foreclosure of the collateral. In the event of a sale of the loan, a gain or loss on sale is recognized and reported within noninterest income based on the difference between the sales proceeds and the carrying amount of the loan. In other cases, individual loans are removed from the pool based on comparing the amount received from its resolution (fair value of the underlying collateral less costs to sell in the case of a foreclosure) with its outstanding balance. Any difference between these amounts is recorded as a charge-off through the allowance for loan losses. Acquired loans subject to modification are not removed from the pool even if those loans would otherwise be deemed TDRs as the pool and not the individual loan, represents the unit of account.

Allowance for Loan Losses

The allowance for loan losses is maintained at a level estimated by management to provide adequately for probable incurred losses inherent in the current loan portfolio. The allowance is determined based upon numerous considerations, including local and regional conditions, the growth and composition of the loan portfolio with respect to the mix between the various types of loans and their related risk characteristics, a review of the value of collateral supporting the loans, comprehensive reviews of the loan portfolio by the independent loan review staff and management, as well as consideration of volume and trends of delinquencies, nonperforming loans and loan charge-offs. Loan losses are charged off against the allowance, while recoveries of amounts previously charged off are credited to the allowance. As a result of tests of adequacy, required additions to the allowance for loan losses are made periodically by charges to the provision for loan losses.

The allowance for loan losses related to impaired loans specifically allocated for impairment is based on discounted expected cash flows using the loan’s initial effective interest rate or the fair value of the collateral for certain loans where repayment of the loan is expected to be provided solely by the underlying collateral ("collateral dependent"). The Company’s impaired loans, if any, are generally collateral dependent. The Company considers the estimated cost to sell, on a discounted basis, when determining the fair value of collateral in the measurement of impairment if those costs are expected to reduce the cash flows available to repay or otherwise satisfy the loans.

The allowance for loan losses for collectively evaluated for impairment loans is calculated using a systematic methodology with both a quantitative and a qualitative analysis that is applied on a quarterly basis. For purposes of our allowance methodology, the loan portfolio is segmented as described in Note 5. Each segment has a distinct set of risk characteristics monitored by management. The Company further assess and monitor risk and performance at a more disaggregated level, which includes our internal risk grading system for the Commercial segments.

Historical loss rates are first applied to pools of loans with similar risk characteristics. Loss rates are calculated by historical charge-offs that have occurred within each pool of loans over the lookback period ("LBP"), multiplied by the loss emergence period ("LEP"). The LBP represents the historical data period utilized to calculate loss rates. The LEP is an estimate of the average amount of time from the point at which a loss is incurred on a loan to the point at which the loss is confirmed. In general, the LEP will be shorter in an economic slowdown or recession and longer during times of economic stability or growth, as customers are better able to delay loss confirmation after a potential loss event has occurred. In conjunction with our annual review of the allowance for loan loss assumptions, the Company updates our study of LEPs for each portfolio segment using our loan charge-off history.

After consideration of the historic loss analysis, management applies additional qualitative adjustments so that the allowance for loan losses is reflective of the estimate of incurred losses that exist in the loan portfolio at the balance sheet date. Qualitative adjustments are made if, in the judgment of management, incurred loan losses inherent in the loan portfolio are not fully captured in the historical loss analysis. Qualitative considerations include the loan portfolio trends, composition and nature of loans; changes in lending policies and procedures, including underwriting standards and collection, charge-offs and recoveries; trends experienced in nonperforming and delinquent loans; current economic conditions in the Company’s market; portfolio concentrations that may affect loss experience across one of more components of the portfolio; the effect of external factors such as competition, legal and regulatory requirements; and the experience, ability and depth of lending management and staff. The evaluation of the various components of the allowance for loan losses requires considerable judgment in order to estimate inherent loss exposures.

Management believes that the allowance for loan losses is adequate. While management uses available information to recognize losses on loans, additions and reductions of the allowance for loan losses may fluctuate from one reporting period to another based on changes in economic conditions or changes in the values of properties securing loans in the process of foreclosure. In addition, various regulatory agencies, as an integral part of their examination process, periodically review the Company’s allowance for loan losses. Such agencies may require the Company to recognize additions to the allowance for loan losses based on their judgments about information available to them at the time of their examination, which may not be currently available to management.

Premises and Equipment

Premises and equipment are stated at cost, less accumulated depreciation. Depreciation of premises and equipment is determined using the straight-line method over the estimated useful lives of the respective assets. Expenditures for maintenance, repairs and minor replacements are charged to expense as incurred.

Leases

The Company determines if a lease is present at the inception of an agreement. Right-of-use ("ROU") assets and lease liabilities are recognized at lease commencement based on the present value of the remaining lease payments using a discount rate that represents the Company's incremental borrowing rate at the lease commencement date. ROU assets and operating lease liabilities, are included in other assets and other liabilities, respectively, on the consolidated balance sheets. Leases with original terms of 12 months or less are recognized in profit or loss on a straight-line basis over the lease term.

Operating lease ROU assets represent the Company's right to use an underlying asset during the lease term and operating lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets are further adjusted for lease incentives. Operating lease expense, which is comprised of amortization of the ROU asset and the implicit interest accreted on the operating lease liability, is recognized on a straight-line basis over the lease term, and is recorded in occupancy expense in the consolidated statements of income.

The Company has lease agreements with lease and non-lease components, which are generally accounted for separately. For real estate leases, non-lease components and other non-components, such as common area maintenance charges, real estate taxes and insurance are not included in the measurement of the lease liability since they are generally able to be segregated. Our leases relate primarily to office space and bank branches, and some contain options to renew the lease. These options to renew are generally not considered reasonably certain to exercise, and are therefore not included in the lease term until such time that the option to renew is reasonably certain.

Other Real Estate Owned

Other real estate owned ("OREO") consists of properties acquired through foreclosure or by acceptance of a deed in lieu of foreclosure. These assets are recorded at the lower of fair value of the asset acquired less estimated costs to sell or “cost” (defined as the fair value at initial foreclosure). At the time of foreclosure, or when foreclosure occurs in-substance, the excess, if any, of the loan over the fair market value of the assets received, less estimated selling costs, is charged to the allowance for loan losses and any subsequent valuation write-downs are charged to other expense. In connection with the determination of the allowance for loan losses and the valuation of OREO, management obtains appraisals for properties. Operating costs associated with the properties are charged to expense as incurred. Gains on the sale of OREO are included in income when title has passed and the sale has met the minimum down payment requirements prescribed by GAAP. The balance of OREO is recorded in other assets on the consolidated balance sheets.

Goodwill and Other Intangible Assets

Goodwill represents the cost of acquired business in excess of the fair value of the related net assets acquired. Goodwill is not amortized but tested at the reporting unit level for impairment on an annual basis and on an interim basis or when events or circumstances dictate. The Company has elected June 30 as the annual impairment testing date for the insurance and retirement services reporting units and December 31 for the Bank reporting unit.

The Company has the option to first assess qualitative factors, by performing a qualitative analysis, to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the events or circumstances, the Company determines it is more likely than not that the fair value of a reporting unit is greater than its carrying amount, the impairment test is not required. If the Company concludes otherwise, the Company is required to perform a quantitative impairment test. In the quantitative impairment test, the estimated fair value of a reporting unit is compared to the carrying amount in order to determine if impairment is indicated. If the estimated fair value exceeds the carrying amount, the reporting unit is not deemed to be impaired. If the estimated fair value is below the carrying value of the reporting unit, the difference is the amount of impairment.

Intangible assets that have indefinite useful lives are not amortized, but are tested at least annually for impairment. Intangible assets that have finite useful lives are amortized over their useful lives. Core deposit intangibles and trust intangibles at the Company are amortized using the sum-of-the-years’-digits method. Covenants not to compete are amortized on a straight-line basis. Customer lists are amortized using an accelerated method. When facts and circumstances indicate potential impairment of amortizable intangible assets, the Company evaluates the recoverability of the asset carrying value, using estimates of undiscounted future cash flows over the remaining asset life. Any impairment loss is measured by the excess of carrying value over fair value.

Determining the fair value of a reporting unit under the goodwill impairment tests and determining the fair value of other intangible assets are judgmental and often involve the use of significant estimates and assumptions. Estimates of fair value are primarily determined using the discounted cash flows method, which uses significant estimates and assumptions including projected future cash flows, discount rates reflecting the market rate of return and projected growth rates. Future events may impact such estimates and assumptions and could cause the Company to conclude that our goodwill or intangible assets have become impaired, which would result in recording an impairment loss.

Bank-Owned Life Insurance

The Bank has purchased life insurance policies on certain employees, key executives and directors. Bank-owned life insurance is recorded at the amount that can be realized under the insurance contract at the balance sheet date, which is the cash surrender value adjusted for other charges or other amounts due that are probable at settlement.

Treasury Stock

Treasury stock acquisitions are recorded at cost. Subsequent sales of treasury stock are recorded on an average cost basis. Gains on the sale of treasury stock are credited to additional paid-in-capital. Losses on the sale of treasury stock are charged to additional paid-in-capital to the extent of previous gains, otherwise charged to retained earnings.

Income Taxes

Income taxes are accounted for under the asset and liability method. Deferred income taxes are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred taxes of a change in tax rates is recognized in income in the period that includes the enactment date. The Company recognizes interest accrued and penalties related to unrecognized tax benefits in income tax expense.

Tax positions are recognized as a benefit only if it is “more likely than not” that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount recognized is the largest amount of tax benefit that is greater than 50 percent likely of being realized on examination. For tax positions not meeting the “more likely than not” test, no tax benefit is recorded.

Pension Costs

The Company has a qualified, noncontributory, defined benefit pension plan covering substantially all of its employees, as well as supplemental employee retirement plans to certain current and former executives and a defined benefit postretirement healthcare plan that covers certain employees. Costs associated with these plans, based on actuarial computations of current and future benefits for employees, are charged to current operating expenses.

Stock-Based Compensation

The Company maintains various long-term incentive stock benefit plans under which restricted stock units are granted to certain directors and key employees. Compensation expense are recognized in the consolidated statements of income over the requisite service period, based on the grant-date fair value of the award. For restricted stock units, compensation expense is recognized ratably over the vesting period for the fair value of the award, measured at the grant date.

Earnings Per Share

Basic earnings per share ("EPS") excludes dilution and is computed by dividing income available to common stockholders by the weighted average number of common shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in the earnings of the entity (such as the Company’s dilutive stock options and restricted stock units).

Comprehensive Income

At the Company, comprehensive income represents net income plus OCI, which consists primarily of the net change in unrealized gains (losses) on AFS debt securities for the period, changes in the funded status of employee benefit plans and unrealized gains (losses) on derivatives designated as hedging instruments. AOCI represents the net unrealized gains (losses) on AFS debt securities, the previously unrecognized portion of the funded status of employee benefit plans and the fair value of instruments designated as hedging instruments, net of income taxes, as of the consolidated balance sheet dates.

Derivative Instruments and Hedging Activities

The Company records all derivatives on the balance sheet at fair value. The accounting for changes in the fair value of derivatives depends on the intended use of the derivative, whether the Company has elected to designate a derivative in a hedging relationship and apply hedge accounting and whether the hedging relationship has satisfied the criteria necessary to apply hedge accounting. Derivatives designated and qualifying as a hedge of the exposure to changes in the fair value of an asset, liability or firm commitment attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivatives designated and qualifying as a hedge of the exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Hedge accounting generally provides for the matching of the timing of gain or loss recognition on the hedging instrument with the recognition of the changes in the fair value of the hedged asset or liability that are attributable to the hedged risk in a fair value hedge or the earnings effect of the hedged forecasted transactions in a cash flow hedge. The Company may enter into derivative contracts that are intended to economically hedge certain of its risks, even though hedge accounting does not apply or the Company elects not to apply hedge accounting.

For derivatives designated as fair value hedges, changes in the fair value of the derivative and the hedged item related to the hedged risk are recognized in earnings. For derivatives designated as cash flow hedges, changes in fair value of the effective portion of the cash flow hedges are reported in OCI. When the cash flows associated with the hedged item are realized, the gain or loss included in OCI is recognized in the consolidated statements of income.

When the Company purchases or sells a portion of a commercial loan that has an existing interest rate swap, it may enter into a risk participation agreement with the counterparty and assumes the credit risk of the loan customer related to the swap. Any fee paid to the Company under a risk participation agreement is in consideration of the credit risk of the counterparties and is recognized in the income statement. Credit risk on the risk participation agreements is determined after considering the risk rating, probability of default and loss given default of the counterparties.

Fair Value Measurements

GAAP states that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value measurements are not adjusted for transaction costs. A fair value hierarchy exists within GAAP that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are described below:

Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;

Level 2 - Quoted prices for similar assets or liabilities in active markets, quoted prices in markets that are not active or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability;

Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement.

The types of instruments valued based on quoted market prices in active markets include most U.S. government and agency securities, many other sovereign government obligations, liquid mortgage products, active listed equities and most money market securities. Such instruments are generally classified within Level 1 or Level 2 of the fair value hierarchy. The Company does not adjust the quoted price for such instruments.

Certain common equity securities are reported at fair value utilizing Level 1 inputs (exchange quoted prices). Other investment securities are reported at fair value utilizing Level 1 and Level 2 inputs. The prices for Level 2 instruments are obtained through an independent pricing service or dealer market participants with whom the Company has historically transacted both purchases and sales of investment securities. Prices obtained from these sources include prices derived from market quotations and matrix pricing. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond's terms and conditions, among other things. Management reviews the methodologies used in pricing the securities by its third party providers.

Level 3 is for positions that are not traded in active markets or are subject to transfer restrictions. Valuations are adjusted to reflect illiquidity and/or non-transferability and such adjustments are generally based on available market evidence. In the absence of such evidence, management’s best estimate will be used. Management’s best estimate consists of both internal and external support on certain Level 3 investments. Subsequent to inception, management only changes Level 3 inputs and assumptions when corroborated by evidence such as transactions in similar instruments, completed or pending third-party transactions in the underlying investment or comparable entities, subsequent rounds of financing, recapitalizations and other transactions across the capital structure, offerings in the equity or debt markets and changes in financial ratios or cash flows.

Other Financial Instruments

The Company is a party to certain instruments with off-balance-sheet risk such as commitments to extend credit, unused lines of credit, standby letter of credit and certain Commercial loans sold to investors with recourse. The Company’s policy is to record such instruments when funded.

Standby letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party. The risk involved in issuing standby letters of credit is essentially the same as the credit risk involved in extending loan facilities to customers. Under the standby letters of credit, the Company is required to make payments to the beneficiary of the letters of credit upon request by the beneficiary contingent upon the customer's failure to perform under the terms of the underlying contract with the beneficiary. Standby letters of credit typically have one year expirations with an option to renew upon annual review. The Company typically receives a fee for these transactions. The fair value of standby letters of credit is recorded upon inception.

Repurchase Agreements

Repurchase agreements are accounted for as secured financing transactions since the Company maintains effective control over the transferred securities and the transfer meets the other criteria for such accounting. Obligations to repurchase securities sold are reflected as a liability in the consolidated balance sheets. The securities underlying the agreements are delivered to a custodial account for the benefit of the counterparties with whom each transaction is executed. The counterparties, who may sell, loan or otherwise dispose of such securities to other parties in the normal course of their operations, agree to resell to the Company the same securities at the maturities of the agreements.

Revenue from Contracts with Customers

Effective January 1, 2018, the Company adopted Financial Accounting Standards Board ("FASB") Accounting Standards Update ("ASU") 2014-09, Revenue from Contracts with Customers (ASC Topic 606) ("ASC 606” and “ASU 2014-09"), and all subsequent ASUs that modified ASC 606. The implementation of ASC 606 did not have a material impact on the measurement or recognition of revenue; as such, a cumulative effect adjustment to opening retained earnings was not deemed necessary. Results for reporting periods beginning after January 1, 2018 are presented under ASC 606, while prior period amounts were not adjusted and continue to be reported in accordance with our historic accounting under ASC 605. ASC 606 does not apply to revenue associated with financial instruments, including revenue from loans and securities and certain noninterest income streams such as fees associated with mortgage servicing rights, financial guarantees, derivatives and certain credit card fees are also not in scope. ASC 606 is applicable to noninterest revenue streams such as retirement plan administration fees, trust and asset management income, deposit related fees and annuity and insurance commissions; however, the recognition of these revenue streams did not change significantly upon adoption of ASC 606.

Insurance and Other Financial Services Revenue

Insurance and other financial services revenue primarily consists of commissions received on insurance and brokered investment product sales. The Company acts as an intermediary between the Company's customer and the insurance carrier. The Company's performance obligation related to insurance sales for both property and casualty insurance and employee benefit plans is generally satisfied upon the later of the issuance or effective date of the policy. The Company earns performance based incentives, commonly known as contingency payments, which usually are based on certain criteria established by the insurance carrier such as premium volume, growth and insured loss ratios. Contingent payments are accrued for based upon management's expectations for the year. Commission expense associated with sales of insurance products is expensed as incurred. For other financial services revenue, the Company's performance obligation is generally satisfied upon the issuance of the annuity policy. Shortly after the policy is issued, the carrier remits the commission payment to the Company, and the Company recognizes the revenue. The Company does not earn a significant amount of trailing commission fees on insurance or brokered investment product sales. The majority of the trailing commission fees are calculated based on a percentage of market value of a period end and revenue is recognized when an investment product's market value can be determined.

Service Charges on Deposit Accounts

Service charges on deposit accounts consist of overdraft fees, monthly service fees, check orders and other deposit account related fees. Overdraft, monthly service, check orders and other deposit account related fees are transactional based, and therefore, the Company’s performance obligation is satisfied, and related revenue recognized, at a point in time. Payment for service charges on deposit accounts is primarily received immediately or in the following month through a direct charge to customers’ accounts.

ATM and Debit Card Fees

ATM fees are primarily generated when a Company cardholder uses a non-Company ATM or a non-Company cardholder uses a Company ATM. Debit card income is primarily comprised of interchange fees earned whenever the Company’s debit cards are processed through card payment networks. The Company’s performance obligations for these revenue streams are satisfied, and related revenue recognized, when the services are rendered or upon completion. Payment is typically received immediately or in the following month.

Retirement Plan Administration Fees

Retirement plan administration fees are primarily generated for services related to the recordkeeping, administration and plan design solutions of defined benefit, defined contribution and revenue sharing plans. Revenue is recognized in arrears for services already provided in accordance with fees established in contracts with customers or based on rates agreed to with investment trade platforms based on ending investment balances held. The Company’s performance obligation is satisfied, and related revenue recognized based on services completed or ending investment balances, for which receivables are recorded at the time of revenue recognition.

Trust

Trust and asset management income is primarily comprised of fees earned from the management and administration of trusts, pensions and other customer assets. The Company’s performance obligation is generally satisfied with the resulting fees recognized monthly, based upon services completed or the month-end market value of the assets under management and the applicable fee rate. Payment is generally received shortly after services are rendered or a few days after month end through a direct charge to customers’ accounts. The Company does not earn performance-based incentives.

Other

Other noninterest income consists of other recurring revenue streams such as account and loan fees, interest rate swap fees, safety deposit box rental fees and other miscellaneous revenue streams. These revenue streams are primarily transactional based and payment is received immediately or in the following month, and therefore, the Company’s performance obligation is satisfied, and related revenue recognized, at a point in time.

The following table presents noninterest income, segregated by revenue streams in-scope and out-of-scope of ASC 606:

	Years ended December 31,
(In thousands)	2019		2018			2017
Noninterest income
In-Scope of ASC 606:
Insurance and other financial services revenue	$	25,006	$	24,345		$	23,532
Service charges on deposit accounts		17,151		17,224			16,750
ATM and debit card fees		23,893		22,699			21,372
Retirement plan administration fees		30,388		26,992			20,213
Trust		19,164		19,524			19,586
Other		18,853		15,228			11,991
Total noninterest income in-scope of ASC 606	$	134,455	$	126,012		$	113,444
Total noninterest income out-of-scope of ASC 606	$	9,568	$	(1,250	)	$	7,860
Total noninterest income	$	144,023	$	124,762		$	121,304

Contract Balances

A contract asset balance occurs when an entity performs a service for a customer before the customer pays consideration or before payment is due, which would result in contract receivables or assets, respectively. A contract liability balance is an entity’s obligation to transfer a service to a customer for which the entity has already received payment or for which payment is due from the customer. The Company’s noninterest revenue streams are largely based on transactional activity, or standard month-end revenue accruals such as asset management fees based on month-end market values. Consideration is often received immediately or shortly after the Company satisfies its performance obligation and revenue is recognized. The Company does not typically enter into long-term revenue contracts with customers, and therefore, does not experience significant contract balances.

Contract Acquisition Costs

ASC 606 requires the capitalization, and subsequently amortization into expense, certain incremental costs of obtaining a contract with a customer if these costs are expected to be recovered. The incremental costs of obtaining a contract are those costs that an entity incurs to obtain a contract with a customer that it would not have incurred if the contract had not been obtained. The Company elected the practical expedient, which allows immediate expensing of contract acquisition costs when the asset that would have resulted from capitalizing these costs would have been amortized in one year or less, and did not capitalize any contract acquisition costs upon adoption of ASC 606 as of or during the year ended December 31, 2019.

Trust Operations

Assets held by the Company in a fiduciary or agency capacity for its customers are not included in the accompanying consolidated balance sheets, since such assets are not assets of the Company. Trust income is recognized on the accrual method based on contractual rates applied to the balances of trust accounts.

Subsequent Events

The Company has evaluated subsequent events for potential recognition and/or disclosure and there were none identified.

Securities

12 Months Ended

Dec. 31, 2019

Securities [Abstract]

Securities

3. Securities

The amortized cost, estimated fair value and unrealized gains (losses) of AFS securities are as follows:

(In thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
As of December 31, 2019
Federal agency	$	34,998	$	3	$	243	$	34,758
State & municipal		2,533		-		20		2,513
Mortgage-backed:
Government-sponsored enterprises		453,614		4,982		239		458,357
U.S. government agency securities		44,758		667		156		45,269
Collateralized mortgage obligations:
Government-sponsored enterprises		328,499		1,949		467		329,981
U.S. government agency securities		104,152		718		408		104,462
Total AFS securities	$	968,554	$	8,319	$	1,533	$	975,340
As of December 31, 2018
Federal agency	$	84,982	$	10	$	693	$	84,299
State & municipal		30,136		16		237		29,915
Mortgage-backed:
Government-sponsored enterprises		493,225		439		10,354		483,310
U.S. government securities		29,190		270		475		28,985
Collateralized mortgage obligations:
Government-sponsored enterprises		332,409		344		7,211		325,542
U.S. government securities		47,684		137		1,376		46,445
Total AFS securities	$	1,017,626	$	1,216	$	20,346	$	998,496

The components of net realized gains (losses) on the sale of AFS securities are as follows. These amounts were reclassified out of AOCI and into earnings:

	Years Ended December 31,
(In thousands)	2019			2018			2017
Gross realized gains	$	73		$	-		$	2,241
Gross realized (losses)		(152	)		(6,622	)		(372	)
Net AFS realized (losses) gains	$	(79	)	$	(6,622	)	$	1,869

Included in net realized gains (losses) on AFS securities, the Company recorded gains from calls of approximately $25 thousand for the year ended December 31, 2019, none for the year ended December 31, 2018 and approximately $0.1 million for the year ended December 31, 2017.

The amortized cost, estimated fair value and unrealized gains (losses) of HTM securities are as follows:

(In thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
As of December 31, 2019
Mortgage-backed:
Government-sponsored enterprises	$	149,448	$	3,184	$	155	$	152,477
U.S. government agency securities		13,667		584		-		14,251
Collateralized mortgage obligations:
Government-sponsored enterprises		189,402		2,165		368		191,199
U.S. government agency securities		110,498		3,256		100		113,654
State & municipal		167,059		2,628		6		169,681
Total HTM securities	$	630,074	$	11,817	$	629	$	641,262
As of December 31, 2018
Federal agency	$	19,995	$	52	$	-	$	20,047
Mortgage-backed:
Government-sponsored enterprises		164,618		712		2,773		162,557
U.S. government agency securities		15,230		403		-		15,633
Collateralized mortgage obligations:
Government-sponsored enterprises		257,475		1,097		3,897		254,675
U.S. government agency securities		83,148		767		-		83,915
State & municipal		243,133		331		1,616		241,848
Total HTM securities	$	783,599	$	3,362	$	8,286	$	778,675

At December 31, 2019 and 2018, all of the mortgaged-backed HTM securities were comprised of U.S. government agency and Government-sponsored enterprises securities.

There were no sales of HTM securities in the years ended December 31, 2019 and 2018. In the year ended December 31, 2017, the Company recognized a loss of $2 thousand on HTM securities sales transactions.

Included in net realized gains (losses), the Company recorded gains from calls on HTM securities of approximately $12 thousand for the year ended December 31, 2019. There were no recorded gains from calls on HTM securities included in net realized gains (losses) for the years ended December 31, 2018, and 2017.

AFS and HTM securities with amortized costs totaling $1.3 billion at December 31, 2019 and $1.5 billion at December 31, 2018, were pledged to secure public deposits and for other purposes required or permitted by law. Additionally, at December 31, 2019 and 2018, AFS and HTM securities with an amortized cost of $189.8 million and $215.3 million, respectively, were pledged as collateral for securities sold under repurchase agreements.

	Less Than 12 Months							12 Months or Longer							Total
(In thousands)	Fair Value		Unrealized Losses			Number of Positions		Fair Value		Unrealized Losses			Number of Positions		Fair Value		Unrealized Losses			Number of Positions
As of December 31, 2019
AFS securities:
Federal agency	$	14,891	$	(109	)		2	$	9,866	$	(134	)		1	$	24,757	$	(243	)		3
State & municipal		2,503		(20	)		1		-		-			-		2,503		(20	)		1
Mortgage-backed		67,986		(273	)		21		37,745		(122	)		16		105,731		(395	)		37
Collateralized Mortgage obligations		113,121		(316	)		24		49,632		(559	)		17		162,753		(875	)		41
Total securities with unrealized losses	$	198,501	$	(718	)		48	$	97,243	$	(815	)		34	$	295,744	$	(1,533	)		82

HTM securities:
Mortgage-backed	$	-	$	-			-	$	25,370	$	(155	)		2	$	25,370	$	(155	)		2
Collateralized mortgage obligations		18,040		(181	)		3		22,389		(287	)		5		40,429		(468	)		8
State & municipal		2,257		(6	)		4		-		-			-		2,257		(6	)		4
Total securities with unrealized losses	$	20,297	$	(187	)		7	$	47,759	$	(442	)		7	$	68,056	$	(629	)		14

As of December 31, 2018
AFS securities:
Federal agency	$	-	$	-			-	$	64,294	$	(693	)		6	$	64,294	$	(693	)		6
State & municipal		1,715		(3	)		3		22,324		(234	)		35		24,039		(237	)		38
Mortgage-backed		18,462		(65	)		12		428,440		(10,764	)		101		446,902		(10,829	)		113
Collateralized mortgage obligations		12,118		(69	)		5		320,908		(8,518	)		62		333,026		(8,587	)		67
Total securities with unrealized losses	$	32,295	$	(137	)		20	$	835,966	$	(20,209	)		204	$	868,261	$	(20,346	)		224

HTM securities:
Mortgage-backed	$	-	$	-			-	$	82,579	$	(2,773	)		6	$	82,579	$	(2,773	)		6
Collateralized mortgage obligations		4,386		(7	)		2		145,396		(3,890	)		26		149,782		(3,897	)		28
State & municipal		18,907		(84	)		30		58,258		(1,532	)		86		77,165		(1,616	)		116
Total securities with unrealized losses	$	23,293	$	(91	)		32	$	286,233	$	(8,195	)		118	$	309,526	$	(8,286	)		150

Declines in the fair value of HTM securities below their amortized cost, less any current period credit loss, that are deemed to be other-than-temporary are reflected in earnings as realized losses or in OCI. The classification is dependent upon whether the Company intends to sell the security, or whether it is more likely than not, that the Company will be required to sell the security before recovery. The OTTI shall be recognized in earnings equal to the entire difference between the investment's amortized cost basis and its fair value at the balance sheet date. If the Company does not intend to sell the security and it is not more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the OTTI shall be separated into (i) the amount representing the credit loss and (ii) the amount related to all other factors. The amount of the total OTTI related to the credit loss shall be recognized in earnings. The amount of the total OTTI related to other factors shall be recognized in OCI, net of applicable taxes.

Management has the intent to hold the securities classified as HTM until they mature, at which time it is believed the Company will receive full value for the securities. The unrealized losses on HTM debt securities are due to increases in market interest rates over yields at the time the underlying securities were purchased. When necessary, the Company has performed a discounted cash flow analysis to determine whether or not it will receive the contractual principal and interest on certain securities. The fair value is expected to recover as the bond approaches its maturity date or repricing date or if market yields for such investments declines.

Management also has the intent to hold and will not be required to sell, the debt securities classified as AFS for a period of time sufficient for a recovery of cost, which may be until maturity. The unrealized losses on AFS debt securities are due to increases in market interest rates over the yields available at the time the underlying securities were purchased. When necessary, the Company has performed a discounted cash flow analysis to determine whether or not it will receive the contractual principal and interest on certain securities. For AFS debt securities, OTTI losses are recognized in earnings if the Company intends to sell the security. In other cases the Company considers the relevant factors noted above, as well as the Company's intent and ability to retain its investment for a period of time sufficient to allow for any anticipated recovery in market value and whether evidence exists to support a realizable value equal to or greater than the cost basis. Any impairment loss on an equity security is equal to the full difference between the cost basis and the fair value of the security.

As of December 31, 2019 and 2018, management believes the impairments detailed in the table above are temporary. For the years ended December 31, 2019 and 2018, there were no OTTI losses realized in the Company’s consolidated statements of income. For the year ended December 31, 2017, $1.3 million of an OTTI loss on an AFS equity investment was realized in the Company’s consolidated statements of income.

There were no sales of HTM securities in the years ended December 31, 2019 and 2018. During the year ended December 31, 2017, the Company sold HTM securities with an amortized cost of $0.8 million and an unrealized loss of $2 thousand. Due to significant deterioration in the creditworthiness of the issuers of the HTM securities, the circumstances caused the Company to change its intent to hold the HTM securities to maturity, which did not affect the Company's intent to hold the remainder of the HTM portfolio to maturity.

The following tables set forth information with regard to gains and losses on equity securities:

	Years ended December 31,
(In thousands)	2019		2018
Net gains and losses recognized on equity securities	$	4,280	$	281
Less: Net gains and losses recognized during the period on equity securities sold during the period		3,966		555
Unrealized gains and losses recognized on equity securities still held	$	314	$	(274	)

Included in the net realized gains and losses recognized on equity securities during the year ended December 31, 2019 the Company recorded a $4.0 million gain from the sale of Visa Class B common stock, which had no readily determinable fair value at the time of the sale. As of December 31, 2019 and 2018, the carrying value of equity securities without readily determinable fair values was $4.0 million. The Company performed a qualitative assessment to determine whether the investments were impaired and identified no areas of concern as of December 31, 2019 and 2018. There were no impairments, downward or upward adjustments recognized for equity securities without readily determinable fair values during the year ended December 31, 2019 and 2018.

The following tables set forth information with regard to contractual maturities of debt securities at December 31, 2019:

(In thousands)	Amortized Cost		Estimated Fair Value
AFS debt securities:
Within one year	$	268	$	272
From one to five years		28,692		28,668
From five to ten years		170,771		171,943
After ten years		768,823		774,457
Total AFS debt securities	$	968,554	$	975,340
HTM debt securities:
Within one year	$	27,010	$	27,010
From one to five years		53,895		54,358
From five to ten years		171,942		175,630
After ten years		377,227		384,264
Total HTM debt securities	$	630,074	$	641,262

Maturities of mortgage-backed, collateralized mortgage obligations and asset-backed securities are stated based on their estimated average lives. Actual maturities may differ from estimated average lives or contractual maturities because, in certain cases, borrowers have the right to call or prepay obligations with or without call or prepayment penalties.

Except for U.S. Government and Government-sponsored enterprises securities, there were no holdings, when taken in the aggregate, of any single issuer that exceeded 10% of consolidated stockholders’ equity at December 31, 2019 and 2018.

Parent Company Financial Information (Tables)

12 Months Ended

Dec. 31, 2019

Parent Company Financial Information [Abstract]

Parent Company Financial Information

Condensed Balance Sheets

	December 31,
(In thousands)	2019		2018
Assets
Cash and cash equivalents	$	9,387	$	5,876
Equity securities, at estimated fair value		22,441		18,221
Investment in subsidiaries, on equity basis		1,209,752		1,117,350
Other assets		30,855		34,237
Total assets	$	1,272,435	$	1,175,684
Liabilities and Stockholders’ Equity
Total liabilities	$	152,038	$	157,775
Stockholders’ equity		1,120,397		1,017,909
Total liabilities and stockholders’ equity	$	1,272,435	$	1,175,684

Condensed Statements of Income

	Years ended December 31,
(In thousands)	2019			2018			2017
Dividends from subsidiaries	$	50,200		$	43,000		$	38,300
Management fee from subsidiaries		7,981			7,907			99,319
Net securities gains		165			399			2,237
Interest, dividends and other income		876			905			928
Total revenue	$	59,222		$	52,211		$	140,784
Operating expenses		14,262			14,226			100,667
Income before income tax benefit and equity in undistributed income of subsidiaries	$	44,960		$	37,985		$	40,117
Income tax (benefit) expense		(1,588	)		(1,608	)		2,233
Dividends in excess of income (equity in undistributed income) of subsidiaries		74,473			72,973			44,267
Net income	$	121,021		$	112,566		$	82,151

Condensed Statements of Cash Flow

	Years ended December 31,
(In thousands)	2019			2018			2017
Operating activities
Net income	$	121,021		$	112,566		$	82,151
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization of premises and equipment		2,298			2,814			2,974
Excess tax benefit on stock-based compensation		(409	)		(543	)		(1,769	)
Stock-based compensation expense		4,210			3,936			3,644
Net securities gains		(165	)		(399	)		(2,238	)
Re-evaluation of deferred tax amounts from Tax Act		-			-			3,339
Equity in undistributed income of subsidiaries		(124,673	)		(115,972	)		(82,567	)
Cash dividend from subsidiaries		50,200			43,000			38,300
Bank owned life insurance income		(398	)		(424	)		(328	)
Net change in other assets and other liabilities		(1,573	)		(6,124	)		(2,454	)
Net cash provided by operating activities	$	50,511		$	38,854		$	41,052
Investing activities
Proceeds on sales of equity securities	$	-		$	3,318		$	-
Purchases of equity securities		(93	)		(2	)		-
Proceeds on sales and maturities of AFS securities		-			-			4,710
Purchases of AFS securities		-			-			(9	)
Proceeds from settlement of bank owned life insurance		-			-			308
Net purchases of premises and equipment		-			-			(2,264	)
Net cash (used in) provided by investing activities	$	(93	)	$	3,316		$	2,745
Financing activities
Proceeds from the issuance of shares to employee and other stock plans	$	725		$	1,296		$	3,309
Cash paid by employer for tax-withholding on stock issuance		(1,622	)		(1,893	)		(3,582	)
Cash dividends		(46,010	)		(43,269	)		(40,104	)
Net cash (used in) financing activities	$	(46,907	)	$	(43,866	)	$	(40,377	)
Net increase (decrease) in cash and cash equivalents	$	3,511		$	(1,696	)	$	3,420
Cash and cash equivalents at beginning of year		5,876			7,572			4,152
Cash and cash equivalents at end of year	$	9,387		$	5,876		$	7,572

Reclassification Adjustments Out of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustments out of AOCI [Abstract]
Net securities (gains) losses	$ (4,213)	$ 6,341	$ (1,867)
Interest income	311,555	305,629	283,493
Other noninterest income	18,853	15,228	11,991
Other noninterest expense	24,440	19,597	20,308
Interest expense	(55,979)	(38,626)	(25,914)
Income tax expense (benefit)	34,411	24,436	46,010
Net Income	121,021	112,566	82,151
Total reclassifications, net of tax	1,117	4,617	1,131
Accumulated Net Unrealized Investment Gain (Loss) [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Income tax expense (benefit)	(204)	(1,827)	(120)
Net Income	612	5,483	198
Losses (Gains) on AFS Securities [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Net securities (gains) losses	79	6,622	(1,869)
Amortization of Unrealized Gains Related to Securities Transfer [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Interest income	737	688	875
Impairment Write-Down of an Equity Security [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Other noninterest income	0	0	1,312
Net Unrealized (Gains) on Cash Flow Hedges Reclassified to Interest Expense [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Interest expense	(2,012)	(2,300)	(292)
Income tax expense (benefit)	503	575	113
Net Income	(1,509)	(1,725)	(179)
Accumulated Defined Benefit Plans Adjustment [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Income tax expense (benefit)	(672)	(286)	(740)
Net Income	2,014	859	1,112
Amortization of Net Losses [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Other noninterest expense	2,593	1,054	1,755
Amortization of Prior Service Costs [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Other noninterest expense	$ 93	$ 91	$ 97

Short-Term Borrowings (Tables)

12 Months Ended

Dec. 31, 2019

Short-Term Borrowings [Abstract]

Information related to short-term borrowings is summarized as follows as of December 31:

(Dollars in thousands)	2019			2018			2017
Federal funds purchased:
Balance at year-end	$	65,000		$	80,000		$	60,000
Average during the year		47,137			66,839			54,162
Maximum month end balance		80,000			80,000			80,000
Weighted average rate during the year		3.90	%		3.43	%		2.16	%
Weighted average rate at year-end		2.84	%		4.25	%		2.41	%

Securities sold under repurchase agreements:
Balance at year-end	$	143,775		$	160,696		$	182,123
Average during the year		123,337			146,135			175,539
Maximum month end balance		146,410			170,350			190,326
Weighted average rate during the year		0.33	%		0.16	%		0.07	%
Weighted average rate at year-end		0.40	%		0.38	%		0.07	%

Other short-term borrowings:
Balance at year-end	$	446,500		$	631,000		$	477,000
Average during the year		403,453			514,662			460,334
Maximum month end balance		576,000			653,000			591,000
Weighted average rate during the year		1.85	%		1.56	%		1.02	%
Weighted average rate at year-end		1.73	%		1.82	%		1.18	%

Fair Values of Financial Instruments

12 Months Ended

Dec. 31, 2019

Fair Values of Financial Instruments [Abstract]

Fair Values of Financial Instruments

21. Fair Values of Financial Instruments

Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;

Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement.

The types of instruments valued based on quoted prices in markets that are not active, broker or dealer quotations or alternative pricing sources with reasonable levels of price transparency include most investment-grade and high-yield corporate bonds, less liquid mortgage products, less liquid agency securities, less liquid listed equities, state, municipal and provincial obligations and certain physical commodities. Such instruments are generally classified within Level 2 of the fair value hierarchy. Certain common equity securities are reported at fair value utilizing Level 1 inputs (exchange quoted prices). Other investment securities are reported at fair value utilizing Level 1 and Level 2 inputs. The prices for Level 2 instruments are obtained through an independent pricing service or dealer market participants with whom the Company has historically transacted both purchases and sales of investment securities. Prices obtained from these sources include prices derived from market quotations and matrix pricing. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. Management reviews the methodologies used in pricing the securities by its third party providers.

For the year ended December 31, 2019, the Company made no transfers of assets between the levels of the fair value hierarchy. For the year ended December 31, 2018, the Company made no transfers of assets from Level 1 to Level 2 and made a $4.0 million transfer from Level 2 to Level 1.

(In thousands)	Level 1		Level 2		Level 3		December 31, 2019
Assets:
AFS securities:
Federal agency	$	-	$	34,758	$	-	$	34,758
State & municipal		-		2,513		-		2,513
Mortgage-backed		-		503,626		-		503,626
Collateralized mortgage obligations		-		434,443		-		434,443
Total AFS securities	$	-	$	975,340	$	-	$	975,340
Equity securities		23,771		4,000		-		27,771
Derivatives		-		41,766		-		41,766
Total	$	23,771	$	1,021,106	$	-	$	1,044,877

Liabilities:
Derivatives	$	-	$	41,777	$	-	$	41,777
Total	$	-	$	41,777	$	-	$	41,777

(In thousands)	Level 1		Level 2		Level 3		December 31, 2018
Assets:
AFS securities:
Federal agency	$	-	$	84,299	$	-	$	84,299
State & municipal		-		29,915		-		29,915
Mortgage-backed		-		512,295		-		512,295
Collateralized mortgage obligations		-		371,987		-		371,987
Total AFS securities	$	-	$	998,496	$	-	$	998,496
Equity securities		19,053		4,000		-		23,053
Derivatives		-		20,000		-		20,000
Total	$	19,053	$	1,022,496	$	-	$	1,041,549

Liabilities:
Derivatives	$	-	$	17,572	$	-	$	17,572
Total	$	-	$	17,572	$	-	$	17,572

GAAP requires disclosure of assets and liabilities measured and recorded at fair value on a non-recurring basis such as goodwill, loans held for sale, OREO, collateral-dependent impaired loans, mortgage servicing rights and HTM securities. The only non-recurring fair value measurements recorded during the years ended December 31, 2019 and 2018 were related to impaired loans and write-downs of OREO. The Company uses the fair value of underlying collateral, less costs to sell, to estimate the specific reserves for collateral dependent impaired loans. The appraisals may be adjusted by management for qualitative factors such as economic conditions and estimated liquidation expenses ranging from 10% to 35%. Based on the valuation techniques used, the fair value measurements for collateral dependent impaired loans are classified as Level 3.

As of December 31, 2019 the company had no collateral dependent impaired loans. As of December 31, 2018 the Company had collateral dependent impaired loans with a carrying value of $0.2 million, which had specific reserves included in the allowance for loan losses of $25 thousand.

During the year ended December 31, 2019, the Company recorded a $1.0 million write-down of a branch location to fair value of $0.2 million due to a pending disposition of the location.

		December 31, 2019				December 31, 2018
(In thousands)	Fair Value Hierarchy		Carrying Amount	Estimated Fair Value		Carrying Amount		Estimated Fair Value
Financial assets:
HTM securities	2	$	630,074	$	$641,262	$	783,599	$	778,675
Net loans	3		7,074,864		6,999,690		6,822,147		6,754,460
Financial liabilities:
Time deposits	2	$	861,193	$	$858,085	$	930,678	$	920,534
Long-term debt	2		64,211		64,373		73,724		73,927
Junior subordinated debt	2		101,196		105,694		101,196		100,114

Fair value estimates are made at a specific point in time, based on relevant market information and information about the financial instrument. These estimates do not reflect any premium or discount that could result from offering for sale at one time the Company’s entire holdings of a particular financial instrument. Because no market exists for a significant portion of the Company’s financial instruments, fair value estimates are based on judgments regarding future expected loss experience, current economic conditions, risk characteristics of various financial instruments and other factors. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. Changes in assumptions could significantly affect the estimates.

Fair value estimates are based on existing on and off-balance sheet financial instruments without attempting to estimate the value of anticipated future business and the value of assets and liabilities that are not considered financial instruments. For example, the Company has a substantial trust and investment management operation that contributes net fee income annually. The trust and investment management operation is not considered a financial instrument and its value has not been incorporated into the fair value estimates. Other significant assets and liabilities include the benefits resulting from the low-cost funding of deposit liabilities as compared to the cost of borrowing funds in the market and premises and equipment. In addition, the tax ramifications related to the realization of the unrealized gains and losses can have a significant effect on fair value estimates and have not been considered in the estimate of fair value.

HTM Securities

The fair value of the Company’s HTM securities is primarily measured using information from a third party pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things.

Net Loans

The fair value of the Company’s loans was estimated in accordance with the exit price notion as defined by FASB ASC 820, Fair Value Measurement ("ASC 820"). Net loans include portfolio loans and loans held for sale. Loans were first segregated by type and then further segmented into fixed and variable rate and loan quality categories. Expected future cash flows were projected based on contractual cash flows, adjusted for estimated prepayments, which also includes credit risk, illiquidity risk and other market factors to calculate the exit price fair value in accordance with ASC 820.

Time Deposits

The fair value of time deposits was estimated using a discounted cash flow approach that applies prevailing market interest rates for similar maturity instruments. The fair values of the Company’s time deposit liabilities do not take into consideration the value of the Company’s long-term relationships with depositors, which may have significant value.

Long-Term Debt

The fair value of long-term debt was estimated using a discounted cash flow approach that applies prevailing market interest rates for similar maturity instruments.

Junior Subordinated Debt

The fair value of junior subordinated debt has been estimated using a discounted cash flow analysis.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Derivative Instruments and Hedging Activities (Tables)

12 Months Ended

Dec. 31, 2019

Derivative Instruments and Hedging Activities Disclosures [Line Items]

Fair Value Adjustment Recorded Related to Notional Amount of Derivatives Outstanding and Notional Amount of Risk Participation Agreements

The following table depicts the fair value adjustment recorded related to the notional amount of derivatives outstanding as well as the notional amount of risk participation agreements:

	December 31,
(In thousands)	2019		2018
Derivatives Not Designated as Hedging Instruments:
Fair value adjustment included in other assets and other liabilities
Interest rate derivatives	$	41,650	$	17,572
Notional amount:
Interest rate derivatives		963,209		653,369
Risk participation agreements		97,614		70,785
Derivatives Designated as Hedging Instruments:
Fair value adjustment included in other assets
Interest rate derivatives		4		2,428
Fair value adjustment included in other liabilities
Interest rate derivatives		45		-
Notional amount:
Interest rate derivatives		50,000		225,000

Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]

Derivative Instruments and Hedging Activities Disclosures [Line Items]

Effect of Derivatives on AOCI and on Consolidated Statement of Income

The following table indicates the effect of cash flow hedge accounting on AOCI and on the consolidated statement of income:

	December 31,
(In thousands)	2019			2018			2017
Derivatives Designated as Hedging Instruments:
Interest rate derivatives - included component
Amount of (loss) or gain recognized in OCI	$	(459	)	$	1,218		$	901
Amount of gain reclassified from AOCI into interest expense		(2,012	)		(2,300	)		(292	)

Not Designated as Hedging Instrument [Member]

Derivative Instruments and Hedging Activities Disclosures [Line Items]

Effect of Derivatives on AOCI and on Consolidated Statement of Income

The following table indicates the gain or loss recognized in income on derivatives not designating as a hedging relationship:

	December 31,
(In thousands)	2019		2018			2017
Derivatives Not Designated as Hedging Instruments:
Decrease (increase) in other income	$	295	$	(120	)	$	101

Commitments and Contingent Liabilities

12 Months Ended

Dec. 31, 2019

Commitments and Contingent Liabilities [Abstract]

Commitments and Contingent Liabilities

19. Commitments and Contingent Liabilities

The Company’s concentrations of credit risk are reflected in the consolidated balance sheets. The concentrations of credit risk with standby letters of credit, unused lines of credit, commitments to originate new loans and loans sold with recourse generally follow the loan classifications.

At December 31, 2019, approximately 60% of the Company’s loans were secured by real estate located in central and upstate New York, northeastern Pennsylvania, southern New Hampshire, western Massachusetts, Vermont and southern coastal Maine. Accordingly, the ultimate collectability of a substantial portion of the Company’s portfolio is susceptible to changes in market conditions of those areas. Management is not aware of any material concentrations of credit to any industry or individual borrowers.

	At December 31,
(In thousands)	2019		2018
Unused lines of credit	$	340,703	$	313,987
Commitments to extend credits, primarily variable rate		1,579,414		1,420,795
Standby letters of credit		34,479		41,194
Loans sold with recourse		25,639		27,223

Since many loan commitments, standby letters of credit and guarantees and indemnification contracts expire without being funded in whole or in part, the contract amounts are not necessarily indicative of future cash flows. The Company does not issue any guarantees that would require liability-recognition or disclosure, other than its standby letters of credit.

The Company guarantees the obligations or performance of customers by issuing standby letters of credit to third parties. These standby letters of credit are frequently issued in support of third party debt, such as corporate debt issuances, industrial revenue bonds and municipal securities. The risk involved in issuing standby letters of credit is essentially the same as the credit risk involved in extending loan facilities to customers and letters of credit are subject to the same credit origination, portfolio maintenance and management procedures in effect to monitor other credit and off-balance sheet products. Typically, these instruments have one year expirations with an option to renew upon annual review; therefore, the total amounts do not necessarily represent future cash requirements. The fair value of the Company’s standby letters of credit at December 31, 2019 and 2018 was not significant.

In the normal course of business there are various outstanding legal proceedings. If legal costs are deemed material by management, the Company accrues for the estimated loss from a loss contingency if the information available indicates that it is probable that a liability had been incurred at the date of the financial statements and the amount of loss can be reasonably estimated.

The Company is required to maintain reserve balances with the Federal Reserve Bank. The required average total reserve for NBT Bank for the 14-day maintenance period ending December 18, 2019 was $37.3 million.

Fair Values of Financial Instruments, Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial assets [Abstract]
HTM securities	$ 641,262	$ 778,675
Carrying Amount [Member] \| Level 2 [Member]
Financial assets [Abstract]
HTM securities	630,074	783,599
Financial liabilities: [Abstract]
Time deposits	861,193	930,678
Long-term debt	64,211	73,724
Junior subordinated debt	101,196	101,196
Carrying Amount [Member] \| Level 3 [Member]
Financial assets [Abstract]
Net Loans	7,074,864	6,822,147
Estimated Fair Value [Member] \| Level 2 [Member]
Financial assets [Abstract]
HTM securities	641,262	778,675
Financial liabilities: [Abstract]
Time deposits	858,085	920,534
Long-term debt	64,373	73,927
Junior subordinated debt	105,694	100,114
Estimated Fair Value [Member] \| Level 3 [Member]
Financial assets [Abstract]
Net Loans	$ 6,999,690	$ 6,754,460

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Common Stock in Treasury [Member]	Total
Balance at Dec. 31, 2016	$ 497	$ 575,078	$ 501,761	$ (21,520)	$ (142,500)	$ 913,316
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	82,151	0	0	82,151
Cash dividends	0	0	(40,104)	0	0	(40,104)
Net issuance of shares to employee and other stock plans	0	(4,608)	0	0	4,335	(273)
Stock-based compensation	0	3,739	(95)	0	0	3,644
Other comprehensive income (loss)	0	0	0	(557)	0	(557)
Balance at Dec. 31, 2017	497	574,209	543,713	(22,077)	(138,165)	958,177
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment for ASU implementation \| ASU 2016-01 [Member]	0	0	2,618	(2,645)	0	(27)
Cumulative effect adjustment for ASU implementation \| ASU 2018-02 [Member]	0	0	5,575	(5,575)	0	0
Net income	0	0	112,566	0	0	112,566
Cash dividends	0	0	(43,269)	0	0	(43,269)
Net issuance of shares to employee and other stock plans	0	(2,679)	0	0	2,082	(597)
Stock-based compensation	0	3,936	0	0	0	3,936
Other comprehensive income (loss)	0	0	0	(12,877)	0	(12,877)
Balance at Dec. 31, 2018	497	575,466	621,203	(43,174)	(136,083)	1,017,909
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	121,021	0	0	121,021
Cash dividends	0	0	(46,010)	0	0	(46,010)
Net issuance of shares to employee and other stock plans	0	(2,968)	0	0	2,087	(881)
Stock-based compensation	0	4,210	0	0	0	4,210
Other comprehensive income (loss)	0	0	0	24,148	0	24,148
Balance at Dec. 31, 2019	$ 497	$ 576,708	$ 696,214	$ (19,026)	$ (133,996)	$ 1,120,397

Loans (Tables)

12 Months Ended

Dec. 31, 2019

Loans [Abstract]

Loans, Net of Deferred Fees and Origination Costs

A summary of loans, net of deferred fees and origination costs, by category is as follows:

	At December 31,
(In thousands)	2019		2018
Commercial	$	1,302,209	$	1,291,568
Commercial Real Estate		2,142,057		1,930,742
Residential Real Estate		1,445,156		1,380,836
Indirect Auto		1,193,635		1,216,144
Specialty Lending		542,063		524,928
Home Equity		444,082		474,566
Other Consumer		66,896		68,925
Total loans	$	7,136,098	$	6,887,709

Related Party Loans

In the ordinary course of business, the Company has made loans at prevailing rates and terms to directors, officers and other related parties. Such loans, in management’s opinion, do not present more than the normal risk of collectability or incorporate other unfavorable features. The aggregate amount of loans outstanding to qualifying related parties and changes during the years are summarized as follows:

(In thousands)	2019			2018
Balance at January 1	$	1,638		$	1,577
New loans		587			260
Adjustment due to change in composition of related parties		389			-
Repayments		(448	)		(199	)
Balance at December 31	$	2,166		$	1,638

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Summary of Significant Accounting Policies [Abstract]

Basis of Presentation

Loan Held for Sale and Loan Servicing

Loans

Acquired Loans

Acquired loans are initially measured at fair value as of the acquisition date without carryover of historical allowance for loan losses.

Allowance for Loan Losses

Premises and Equipment

Leases

Operating lease ROU assets represent the Company's right to use an underlying asset during the lease term and operating lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets are further adjusted for lease incentives. Operating lease expense, which is comprised of amortization of the ROU asset and the implicit interest accreted on the operating lease liability, is recognized on a straight-line basis over the lease term, and is recorded in occupancy expense in the consolidated statements of income.

Other Real Estate Owned

Goodwill and Other Intangible Assets

Bank-Owned Life Insurance

Treasury Stock

Income Taxes

Pension Costs

Stock-Based Compensation

Earnings Per Share

Comprehensive Income

Derivative Instruments and Hedging Activities

Fair Value Measurements

Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;

Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement.

Other Financial Instruments

Repurchase Agreements

Revenue from Contracts with Customers

Insurance and Other Financial Services Revenue

Service Charges on Deposit Accounts

ATM and Debit Card Fees

Retirement Plan Administration Fees

Trust

Other

The following table presents noninterest income, segregated by revenue streams in-scope and out-of-scope of ASC 606:

	Years ended December 31,
(In thousands)	2019		2018			2017
Noninterest income
In-Scope of ASC 606:
Insurance and other financial services revenue	$	25,006	$	24,345		$	23,532
Service charges on deposit accounts		17,151		17,224			16,750
ATM and debit card fees		23,893		22,699			21,372
Retirement plan administration fees		30,388		26,992			20,213
Trust		19,164		19,524			19,586
Other		18,853		15,228			11,991
Total noninterest income in-scope of ASC 606	$	134,455	$	126,012		$	113,444
Total noninterest income out-of-scope of ASC 606	$	9,568	$	(1,250	)	$	7,860
Total noninterest income	$	144,023	$	124,762		$	121,304

Contract Balances

Contract Acquisition Costs

Trust Operations

Subsequent Events

The Company has evaluated subsequent events for potential recognition and/or disclosure and there were none identified.

Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
Employee Benefit Plans (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined benefit plan disclosure [Abstract]
Transition obligation period of recognition	20 years
Assumptions used to determine benefit obligations [Abstract]
Expected long-term return on plan assets	7.00%	7.00%	7.00%
Rate of compensation increase	3.00%	3.00%	3.00%
Assumptions used to determine net periodic pension cost [Abstract]
Expected long-term return on plan assets	7.00%	7.00%	7.00%
Rate of compensation increase	3.00%	3.00%	3.00%
Other changes in plan assets and benefit obligation recognized in OCI (pre-tax) [Abstract]
Net (gain) loss	$ (5,331)	$ 12,457	$ (2,401)
Amortization of unrecognized net (loss)	1,333	$ (3,038)	$ 570
Net actuarial loss and prior service costs that will be amortized from Accumulated other comprehensive income (loss) in next fiscal year	$ 1,600
Estimate future benefit payments [Abstract]
Ultimate health care cost trend rate	3.80%
Effect of one-percentage point change in assumed health care cost trend rates [Abstract]
One-percentage point increase on total service and interest cost components	$ 29
One-percentage point (decrease) on total service and interest cost components	(25)
One-percentage point increase on post-retirement accumulated benefit obligation	628
One-percentage point (decrease) on post-retirement accumulated benefit obligation	$ (543)
Actual plan asset allocations [Abstract]
Actual plan asset allocations	100.00%	100.00%
Minimum [Member]
Assumptions used to determine benefit obligations [Abstract]
Discount rate	3.69%	4.79%	4.20%
Assumptions used to determine net periodic pension cost [Abstract]
Discount rate	4.79%	4.20%	4.76%
Estimate future benefit payments [Abstract]
Annual rates of increase in the per capita cost of covered medical and prescription drug benefits,	4.50%
Maximum [Member]
Assumptions used to determine benefit obligations [Abstract]
Discount rate	3.73%	4.80%	4.21%
Assumptions used to determine net periodic pension cost [Abstract]
Discount rate	4.80%	4.21%	4.84%
Estimate future benefit payments [Abstract]
Annual rates of increase in the per capita cost of covered medical and prescription drug benefits,	7.00%
Pension Benefits [Member]
Accumulated other comprehensive income (loss), before tax [Abstract]
Net actuarial loss	$ 28,334	$ 35,538
Prior service cost	491	570
Total amounts recognized in AOCI (pre-tax)	28,825	36,108
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of year	85,134	90,950
Service cost	1,723	1,659	$ 1,511
Interest cost	3,942	3,645	4,168
Plan participants' contributions	0	0
Actuarial loss (gain)	6,030	(3,977)
Amendments	0	337
Benefits paid	(6,243)	(7,480)
Projected benefit obligation at end of year	90,586	85,134	90,950
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	109,746	124,226
Actual return on plan assets	18,120	(8,381)
Employer contributions	1,372	1,381
Plan participants' contributions	0	0
Benefits paid	(6,243)	(7,480)
Fair value of plan assets at end of year	122,995	109,746	124,226
Funded (unfunded) status at year end	32,409	24,612
Accumulated benefit obligation	90,600	85,100
Amounts recognized in Balance Sheet [Abstract]
Funded (unfunded) status at year end	32,409	24,612
Components of net periodic cost (benefit) [Abstract]
Service cost	1,723	1,659	1,511
Interest cost	3,942	3,645	4,168
Expected return on plan assets	(7,480)	(8,478)	(7,929)
Amortization of prior service cost	43	40	46
Amortization of unrecognized net loss	2,593	930	1,668
Net periodic pension cost (benefit)	821	(2,204)	(536)
Other changes in plan assets and benefit obligation recognized in OCI (pre-tax) [Abstract]
Net (gain) loss	(4,611)	12,882	(3,075)
Prior service cost	0	337	0
Amortization of prior service (cost)	(43)	(40)	(46)
Amortization of unrecognized net (loss)	(2,593)	(930)	(1,668)
Total recognized in OCI	(7,247)	12,249	(4,789)
Total recognized in net periodic benefit cost and OCI pre-tax	(6,426)	10,045	(5,325)
Estimate future benefit payments [Abstract]
2020	6,916
2021	6,722
2022	6,722
2023	6,582
2024	7,827
2025 - 2029	35,215
Employer voluntary contribution to plan	0	0
Pension Benefits [Member] \| Other Assets [Member]
Amounts recognized in Balance Sheet [Abstract]
Assets recognized	51,988	42,900
Pension Benefits [Member] \| Other Liabilities [Member]
Amounts recognized in Balance Sheet [Abstract]
Liabilities recognized	$ (19,579)	$ (18,288)
Pension Benefits [Member] \| Cash and Cash Equivalents [Member]
Actual plan asset allocations [Abstract]
Actual plan asset allocations	3.00%	4.00%
Pension Benefits [Member] \| Cash and Cash Equivalents [Member] \| Minimum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	0.00%
Pension Benefits [Member] \| Cash and Cash Equivalents [Member] \| Maximum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	15.00%
Pension Benefits [Member] \| Fixed Income Securities [Member]
Actual plan asset allocations [Abstract]
Actual plan asset allocations	40.00%	39.00%
Pension Benefits [Member] \| Fixed Income Securities [Member] \| Minimum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	30.00%
Pension Benefits [Member] \| Fixed Income Securities [Member] \| Maximum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	60.00%
Pension Benefits [Member] \| Equities [Member]
Actual plan asset allocations [Abstract]
Actual plan asset allocations	57.00%	57.00%
Pension Benefits [Member] \| Equities [Member] \| Minimum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	40.00%
Pension Benefits [Member] \| Equities [Member] \| Maximum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	70.00%
Other Benefits [Member]
Accumulated other comprehensive income (loss), before tax [Abstract]
Net actuarial loss	$ 125	$ 844
Prior service cost	94	145
Total amounts recognized in AOCI (pre-tax)	219	989
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of year	7,034	8,050
Service cost	7	10	12
Interest cost	272	327	357
Plan participants' contributions	201	209
Actuarial loss (gain)	(719)	(762)
Amendments	0	0
Benefits paid	(712)	(800)
Projected benefit obligation at end of year	6,083	7,034	8,050
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	511	591
Plan participants' contributions	201	209
Benefits paid	(712)	(800)
Fair value of plan assets at end of year	0	0	0
Funded (unfunded) status at year end	(6,083)	(7,034)
Accumulated benefit obligation	6,100	7,000
Amounts recognized in Balance Sheet [Abstract]
Funded (unfunded) status at year end	(6,083)	(7,034)
Components of net periodic cost (benefit) [Abstract]
Service cost	7	10	12
Interest cost	272	327	357
Expected return on plan assets	0	0	0
Amortization of prior service cost	50	51	51
Amortization of unrecognized net loss	0	124	87
Net periodic pension cost (benefit)	329	512	507
Other changes in plan assets and benefit obligation recognized in OCI (pre-tax) [Abstract]
Net (gain) loss	(720)	(762)	388
Prior service cost	0	0	286
Amortization of prior service (cost)	(50)	(51)	(51)
Amortization of unrecognized net (loss)	0	(124)	(87)
Total recognized in OCI	(770)	(937)	536
Total recognized in net periodic benefit cost and OCI pre-tax	(441)	(425)	$ 1,043
Estimate future benefit payments [Abstract]
2020	497
2021	464
2022	462
2023	457
2024	451
2025 - 2029	2,070
Employer voluntary contribution to plan	0	0
Other Benefits [Member] \| Other Assets [Member]
Amounts recognized in Balance Sheet [Abstract]
Assets recognized	0	0
Other Benefits [Member] \| Other Liabilities [Member]
Amounts recognized in Balance Sheet [Abstract]
Liabilities recognized	$ (6,083)	$ (7,034)

Premises, Equipment and Leases (Tables)

12 Months Ended

Dec. 31, 2019

Premises, Equipment and Leases [Abstract]

Summary of Premises and Equipment

A summary of premises and equipment follows:

	December 31,
(In thousands)	2019		2018
Land, buildings and improvements	$	121,479	$	121,808
Equipment		58,431		55,577
Premises and equipment before accumulated depreciation	$	179,910	$	177,385
Accumulated depreciation		104,279		98,415
Total premises and equipment	$	75,631	$	78,970

Net Lease Cost

The table below summarizes our net lease cost:

(In thousands)	Year Ended December 31, 2019
Operating lease cost	$	7,239
Variable lease cost		2,231
Short-term lease cost		356
Sublease income		(448	)
Total operating lease cost	$	9,378

Future Minimum Rental Commitments Related to Non-cancelable Operating Leases

The table below show future minimum rental commitments related to non-cancelable operating leases for the next five years and thereafter as of December 31, 2019.

(In thousands)
2020	$	7,435
2021		6,646
2022		5,870
2023		4,969
2024		4,365
Thereafter		12,876
Total lease payments	$	42,161
Less: interest		(4,838	)
Present value of lease liabilities	$	37,323

Additional Information for Operating Leases

(In thousands except for percent and period data)	December 31, 2019
Weighted average remaining lease term, in years		7.69
Weighted average discount rate		3.00	%
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$	6,211
ROU assets obtained in exchange for lease liabilities		41,008

Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Roll Forward]
Beginning balance	$ 274,769	$ 268,043
Goodwill acquired	0	6,726
Ending balance	274,769	274,769	$ 268,043
Finite-Lived Intangible Assets [Abstract]
Gross carrying amount	43,574	43,598
Less: accumulated amortization	31,554	27,999
Net carrying amount	12,020	15,599
Impairment of goodwill	0	0
Amortization Expense [Abstract]
Amortization of intangible assets	3,579	4,042	$ 3,960
Future Amortization Expense [Abstract]
2020	3,000
2021	2,300
2022	1,800
2023	1,400
2024	1,100
Thereafter	2,400
Impairment of intangible assets	$ 0	0
Minimum [Member]
Finite-Lived Intangible Assets [Abstract]
Intangible asset useful life	1 year
Maximum [Member]
Finite-Lived Intangible Assets [Abstract]
Intangible asset useful life	20 years
Core Deposits Intangibles [Member]
Finite-Lived Intangible Assets [Abstract]
Gross carrying amount	$ 8,951	8,975
Less: accumulated amortization	7,988	7,377
Net carrying amount	963	1,598
Identified Intangible Assets [Member]
Finite-Lived Intangible Assets [Abstract]
Gross carrying amount	34,623	34,623
Less: accumulated amortization	23,566	20,622
Net carrying amount	$ 11,057	$ 14,001

Fair Values of Financial Instruments, Fair Value of Financial Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Transfers between Levels [Abstract]
Transfers from Level 1 to Level 2	$ 0	$ 0
Transfers from Level 2 to Level 1	0	4,000
Transfers into Level 3	0
Transfers out of Level 3	0
AFS securities [Abstract]
AFS securities	975,340	998,496
Equity securities	27,771	23,053
Fair Value Measurements [Abstract]
Loans and Leases Receivable, Collateral Dependent Impaired Loans	$ 0	200
Reserves on collateral dependent impaired loans		25
Minimum [Member]
Fair Value Measurements [Abstract]
Liquidation expense ratio on impaired collateral	10.00%
Maximum [Member]
Fair Value Measurements [Abstract]
Liquidation expense ratio on impaired collateral	35.00%
Changes Measurement [Member]
Fair Value Measurements [Abstract]
Branch location with pending disposition	$ (1,000)
Fair Value [Member]
Fair Value Measurements [Abstract]
Branch location with pending disposition	200
Recurring Basis [Member]
AFS securities [Abstract]
AFS securities	975,340	998,496
Equity securities	27,771	23,053
Derivatives	41,766	20,000
Total	1,044,877	1,041,549
Liabilities [Abstract]
Derivatives	41,777	17,572
Total	41,777	17,572
Recurring Basis [Member] \| Level 1 [Member]
AFS securities [Abstract]
AFS securities	0	0
Equity securities	23,771	19,053
Derivatives	0	0
Total	23,771	19,053
Liabilities [Abstract]
Derivatives	0	0
Total	0	0
Recurring Basis [Member] \| Level 2 [Member]
AFS securities [Abstract]
AFS securities	975,340	998,496
Equity securities	4,000	4,000
Derivatives	41,766	20,000
Total	1,021,106	1,022,496
Liabilities [Abstract]
Derivatives	41,777	17,572
Total	41,777	17,572
Recurring Basis [Member] \| Level 3 [Member]
AFS securities [Abstract]
AFS securities	0	0
Equity securities	0	0
Derivatives	0	0
Total	0	0
Liabilities [Abstract]
Derivatives	0	0
Total	0	0
Recurring Basis [Member] \| Federal Agency [Member]
AFS securities [Abstract]
AFS securities	34,758	84,299
Recurring Basis [Member] \| Federal Agency [Member] \| Level 1 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] \| Federal Agency [Member] \| Level 2 [Member]
AFS securities [Abstract]
AFS securities	34,758	84,299
Recurring Basis [Member] \| Federal Agency [Member] \| Level 3 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] \| State & Municipal [Member]
AFS securities [Abstract]
AFS securities	2,513	29,915
Recurring Basis [Member] \| State & Municipal [Member] \| Level 1 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] \| State & Municipal [Member] \| Level 2 [Member]
AFS securities [Abstract]
AFS securities	2,513	29,915
Recurring Basis [Member] \| State & Municipal [Member] \| Level 3 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] \| Mortgage-Backed [Member]
AFS securities [Abstract]
AFS securities	503,626	512,295
Recurring Basis [Member] \| Mortgage-Backed [Member] \| Level 1 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] \| Mortgage-Backed [Member] \| Level 2 [Member]
AFS securities [Abstract]
AFS securities	503,626	512,295
Recurring Basis [Member] \| Mortgage-Backed [Member] \| Level 3 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] \| Collateralized Mortgage Obligations [Member]
AFS securities [Abstract]
AFS securities	434,443	371,987
Recurring Basis [Member] \| Collateralized Mortgage Obligations [Member] \| Level 1 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] \| Collateralized Mortgage Obligations [Member] \| Level 2 [Member]
AFS securities [Abstract]
AFS securities	434,443	371,987
Recurring Basis [Member] \| Collateralized Mortgage Obligations [Member] \| Level 3 [Member]
AFS securities [Abstract]
AFS securities	$ 0	$ 0

Securities, AFS Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2019 USD ($) Position	Dec. 31, 2018 USD ($) Position
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 198,501	$ 32,295
12 months or longer	97,243	835,966
Total	295,744	868,261
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(718)	(137)
12 months or longer	(815)	(20,209)
Total	$ (1,533)	$ (20,346)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months \| Position	48	20
12 months or longer \| Position	34	204
Total \| Position	82	224
Federal Agency [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 14,891	$ 0
12 months or longer	9,866	64,294
Total	24,757	64,294
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(109)	0
12 months or longer	(134)	(693)
Total	$ (243)	$ (693)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months \| Position	2	0
12 months or longer \| Position	1	6
Total \| Position	3	6
State & Municipal [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 2,503	$ 1,715
12 months or longer	0	22,324
Total	2,503	24,039
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(20)	(3)
12 months or longer	0	(234)
Total	$ (20)	$ (237)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months \| Position	1	3
12 months or longer \| Position	0	35
Total \| Position	1	38
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 67,986	$ 18,462
12 months or longer	37,745	428,440
Total	105,731	446,902
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(273)	(65)
12 months or longer	(122)	(10,764)
Total	$ (395)	$ (10,829)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months \| Position	21	12
12 months or longer \| Position	16	101
Total \| Position	37	113
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 113,121	$ 12,118
12 months or longer	49,632	320,908
Total	162,753	333,026
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(316)	(69)
12 months or longer	(559)	(8,518)
Total	$ (875)	$ (8,587)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months \| Position	24	5
12 months or longer \| Position	17	62
Total \| Position	41	67

Parent Company Financial Information, Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets [Abstract]
Cash and cash equivalents	$ 216,843	$ 180,955	$ 159,664	$ 149,181
Equity securities, at estimated fair value	27,771	23,053
Other assets	202,245	148,067
Total assets	9,715,925	9,556,363
Liabilities and Stockholders' Equity [Abstract]
Total liabilities	8,595,528	8,538,454
Stockholders' equity	1,120,397	1,017,909	958,177	913,316
Total liabilities and stockholders' equity	9,715,925	9,556,363
NBT Bancorp Inc [Member]
Assets [Abstract]
Cash and cash equivalents	9,387	5,876	$ 7,572	$ 4,152
Equity securities, at estimated fair value	22,441	18,221
Investment in subsidiaries, on equity basis	1,209,752	1,117,350
Other assets	30,855	34,237
Total assets	1,272,435	1,175,684
Liabilities and Stockholders' Equity [Abstract]
Total liabilities	152,038	157,775
Stockholders' equity	1,120,397	1,017,909
Total liabilities and stockholders' equity	$ 1,272,435	$ 1,175,684

Fair Values of Financial Instruments (Policies)	12 Months Ended
Fair Values of Financial Instruments (Policies)	Dec. 31, 2019
Fair Values of Financial Instruments [Abstract]
Fair Value of Financial Instruments, Policy	GAAP states that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value measurements are not adjusted for transaction costs. A fair value hierarchy exists within GAAP that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are described below: Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2 - Quoted prices for similar assets or liabilities in active markets, quoted prices in markets that are not active or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability; Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The types of instruments valued based on quoted market prices in active markets include most U.S. government and agency securities, many other sovereign government obligations, liquid mortgage products, active listed equities and most money market securities. Such instruments are generally classified within Level 1 or Level 2 of the fair value hierarchy. The Company does not adjust the quoted prices for such instruments. The types of instruments valued based on quoted prices in markets that are not active, broker or dealer quotations or alternative pricing sources with reasonable levels of price transparency include most investment-grade and high-yield corporate bonds, less liquid mortgage products, less liquid agency securities, less liquid listed equities, state, municipal and provincial obligations and certain physical commodities. Such instruments are generally classified within Level 2 of the fair value hierarchy. Certain common equity securities are reported at fair value utilizing Level 1 inputs (exchange quoted prices). Other investment securities are reported at fair value utilizing Level 1 and Level 2 inputs. The prices for Level 2 instruments are obtained through an independent pricing service or dealer market participants with whom the Company has historically transacted both purchases and sales of investment securities. Prices obtained from these sources include prices derived from market quotations and matrix pricing. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. Management reviews the methodologies used in pricing the securities by its third party providers. Level 3 is for positions that are not traded in active markets or are subject to transfer restrictions. Valuations are adjusted to reflect illiquidity and/or non-transferability and such adjustments are generally based on available market evidence. In the absence of such evidence, management’s best estimate will be used. Management’s best estimate consists of both internal and external support on certain Level 3 investments. Subsequent to inception, management only changes Level 3 inputs and assumptions when corroborated by evidence such as transactions in similar instruments, completed or pending third-party transactions in the underlying investment or comparable entities, subsequent rounds of financing, recapitalizations and other transactions across the capital structure, offerings in the equity or debt markets and changes in financial ratios or cash flows. Fair value estimates are made at a specific point in time, based on relevant market information and information about the financial instrument. These estimates do not reflect any premium or discount that could result from offering for sale at one time the Company’s entire holdings of a particular financial instrument. Because no market exists for a significant portion of the Company’s financial instruments, fair value estimates are based on judgments regarding future expected loss experience, current economic conditions, risk characteristics of various financial instruments and other factors. These estimates are subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. Changes in assumptions could significantly affect the estimates. Fair value estimates are based on existing on and off-balance sheet financial instruments without attempting to estimate the value of anticipated future business and the value of assets and liabilities that are not considered financial instruments. For example, the Company has a substantial trust and investment management operation that contributes net fee income annually. The trust and investment management operation is not considered a financial instrument and its value has not been incorporated into the fair value estimates. Other significant assets and liabilities include the benefits resulting from the low-cost funding of deposit liabilities as compared to the cost of borrowing funds in the market and premises and equipment. In addition, the tax ramifications related to the realization of the unrealized gains and losses can have a significant effect on fair value estimates and have not been considered in the estimate of fair value. HTM Securities The fair value of the Company’s HTM securities is primarily measured using information from a third party pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. Net Loans The fair value of the Company’s loans was estimated in accordance with the exit price notion as defined by FASB ASC 820, Fair Value Measurement ("ASC 820"). Net loans include portfolio loans and loans held for sale. Loans were first segregated by type and then further segmented into fixed and variable rate and loan quality categories. Expected future cash flows were projected based on contractual cash flows, adjusted for estimated prepayments, which also includes credit risk, illiquidity risk and other market factors to calculate the exit price fair value in accordance with ASC 820. Time Deposits The fair value of time deposits was estimated using a discounted cash flow approach that applies prevailing market interest rates for similar maturity instruments. The fair values of the Company’s time deposit liabilities do not take into consideration the value of the Company’s long-term relationships with depositors, which may have significant value. Long-Term Debt The fair value of long-term debt was estimated using a discounted cash flow approach that applies prevailing market interest rates for similar maturity instruments. Junior Subordinated Debt The fair value of junior subordinated debt has been estimated using a discounted cash flow analysis.

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Stock-Based Compensation [Abstract]

Unvested Restricted Stock Units Activity

	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested at January 1, 2019		546,054		$	28.39
Forfeited		(10,886	)		31.06
Vested		(121,774	)		25.66
Granted		142,046			33.04
Unvested at December 31, 2019		555,440		$	30.11

Stock Option Activity

The following table summarizes information concerning stock options outstanding:

(In thousands, except share and per share data)	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Outstanding at January 1, 2019		66,900		$	23.07
Exercised		(32,505	)		22.31
Expired		(1,250	)		25.38
Outstanding at December 31, 2019		33,145		$	23.73		1.86	$	558,066

Exercisable at December 31, 2019		33,145		$	23.73		1.86	$	558,066

Cash Proceeds, Tax Benefits and Intrinsic Value of Stock Options Exercised

	Years ended December 31,
(In thousands)	2019		2018		2017
Proceeds from stock options exercised	$	725	$	999	$	3,083
Tax benefits related to stock options exercised		123		173		650
Intrinsic value of stock options exercised		490		692		1,699
Fair value of shares vested during the year		13		16		329

Acquisitions (Details) - USD ($) $ in Thousands	12 Months Ended
Acquisitions (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisitions [Abstract]
Goodwill acquired	$ 0	$ 6,726
Retirement Plan Services, LLC [Member]
Business Acquisitions [Abstract]
Total consideration paid		13,000
Goodwill acquired		6,700
Contingent consideration, liability		$ 5,100
Downeast Pension Services, Inc.[Member]
Business Acquisitions [Abstract]
Total consideration paid			$ 5,700
Goodwill acquired			2,600
Contingent consideration, liability			$ 1,700

Acquisitions	12 Months Ended
Acquisitions	Dec. 31, 2019
Acquisitions [Abstract]
Acquisitions	2. Acquisitions In 2018, the Company acquired Retirement Plan Services, LLC for a total consideration of $13.0 million. As part of the acquisition, the Company recorded goodwill of $6.7 million and $5.1 million contingent consideration recorded in other liabilities on the consolidated balance sheet as of December 31, 2018. In 2017, the Company acquired Downeast Pension Services, Inc. for total consideration of $5.7 million. As part of the acquisition, the Company recorded goodwill of $2.6 million and $1.7 million contingent consideration recorded in other liabilities on the consolidated balance sheet as of December 31, 2017. The operating results of acquired companies are included in the consolidated results after the dates of acquisition.

Recent Accounting Pronouncements (Policies)	12 Months Ended
Recent Accounting Pronouncements (Policies)	Dec. 31, 2019
Recent Accounting Pronouncements [Abstract]
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards In February 2016, the FASB issued Accounting Standards Update ("ASU") 2016-02, Leases (Topic 842). ASU 2016-02 requires lessees to recognize right-of-use assets and lease liabilities on the balance sheet for all leases with terms longer than 12 months. For leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election by class of underlying asset not to recognize a right-of-use asset and lease liability. Additionally, when measuring assets and liabilities arising from a lease, optional payments should be included only if the lessee is reasonably certain to exercise an option to extend the lease, exercise a purchase option or not exercise an option to terminate the lease. In January 2018, the FASB issued ASU 2018-01, Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842. ASU 2018-01 was issued to address concerns about the cost and complexity of complying with the transition provisions of ASU 2016-02. Both ASU 2016-02 and ASU 2018-01 are effective for the Company on January 1, 2019. Lessees and lessors are required to apply the provisions of ASU 2016-02 at the beginning of the earliest period presented using a modified retrospective approach. At its November 29, 2017 meeting, the FASB proposed allowing entities the option of applying the provisions of ASU 2016-02 at the effective date without adjusting the comparative periods presented. In July 2018, the FASB issued ASU 2018-10, Codification Improvements to Topic 842, Leases. ASU 2018-10 was issued to provide more detailed guidance and additional clarification for implementing ASU 2016-02. Also in July 2018, the FASB issued ASU 2018-11, Targeted Improvements, which allows for an optional transition method in which the provisions of ASC Topic 842 would be applied upon the adoption date and would not have to be retroactively applied to the earliest reporting period presented in the consolidated financial statements. The Company adopted ASU 2016-02 as of January 1, 2019 and elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allows the carryforward of the historical lease classification, the practical expedient related to land easements and the hindsight practical expedient to determine the reasonably certain lease term for existing leases. The Company made an accounting policy election to keep leases with an initial term of 12 months or less off of the balance sheet and recognize those lease payments in the consolidated statements of income on a straight-line basis over the lease term. The adoption of ASU 2016-02 and related transition guidance resulted in the recognition of additional net lease assets and liabilities of approximately $34 million and $37 million, respectively, as of January 1, 2019. The standard did not materially affect our 2019 consolidated net earnings or regulatory capital ratios. Refer to Note 6, Premises, Equipment and Leases for more information. In March 2017, the FASB issued ASU 2017-08, Receivables – Nonrefundable Fees and Other Costs (Subtopic 310-20). ASU 2017-08 requires amortization of premiums to the earliest call date on debt securities with call features that are explicit, on contingent and callable at fixed prices on present dates. The ASU does not impact securities held at a discount; the discount continues to be amortized to the contractual maturity. The guidance is required to be applied with a modified retrospective approach through a cumulative effect adjustment to retained earnings as of the beginning of the period of adoption. ASU 2017-08 is effective for the Company on January 1, 2019. The adoption did not have an impact on the consolidated financial statements and related disclosures and no cumulative effect adjustment was required upon adoption. In October 2018, the FASB issued ASU 2018-16, Derivatives and Hedging (Topic 815) - Inclusion of the Secured Overnight Financing Rate (“SOFR”) Overnight Index Swap (“OIS”) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes. The ASU 2018-16 amends existing guidance and permits the use of the OIS rate based on SOFR as a United States benchmark interest rate for hedge accounting purposes under Topic 815 in addition to other allowable rates stated in the guidance. ASU 2018-16 is effective for the Company on January 1, 2019 and should be applied prospectively for qualifying new or redesignated hedging relationships entered into on or after the date of adoption. The adoption did not have an impact on the Company's consolidated financial statements.
Accounting Standards Issued Not Yet Adopted	Accounting Standards Issued Not Yet Adopted In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. This ASU removes specific exceptions to the general principles in Topic 740 in GAAP. It eliminates the need for an organization to analyze whether the following apply in a given period: (1) exception to the incremental approach for intraperiod tax allocation; (2) exceptions to accounting for basis differences when there are ownership changes in foreign investments; and (3) exception in interim period income tax accounting for year-to-date losses that exceed anticipated losses. The ASU also improves financial statement preparers’ application of income tax-related guidance and simplifies GAAP for: (1) franchise taxes that are partially based on income; (2) transactions with a government that result in a step up in the tax basis of goodwill; (3) separate financial statements of legal entities that are not subject to tax; and (4) enacted changes in tax laws in interim periods. The amendments in this update become effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact of adopting the new guidance on the consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair value Measurement (Topic 820) – Disclosure Framework – Changes to the Disclosure Requirements for Fair value Measurement. The provisions of ASU 2018-13 modify the disclosure requirements on fair value measurements in ASC 820. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. ASU 2018-13 is effective January 1, 2020 but may be early adopted in any interim period. The adoption did not have a material impact on the consolidated financial statements and related disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“CECL”). ASU 2016-13 introduces new guidance that make substantive changes to the accounting for credit losses. ASU 2016-13 introduces the CECL model, which applies to financial assets subject to credit losses and measured at amortized cost, as well as certain off-balance sheet credit exposures. This includes loans, loan commitments, standby letters of credit, net investments in leases recognized by a lessor and HTM debt securities. The CECL model requires an entity to estimate credit losses expected over the life of an exposure, considering information about historical events, current conditions and reasonable and supportable forecasts and is generally expected to result in earlier recognition of credit losses. ASU 2016-13 also modifies certain provisions of the current OTTI model for AFS debt securities. Credit losses on AFS debt securities will be limited to the difference between the security's amortized cost basis and its fair value and will be recognized through an allowance for credit losses rather than as a direct reduction in amortized cost basis. ASU 2016-13 also provides for a simplified accounting model for purchased financial assets with more than insignificant credit deterioration since their origination. ASU 2016-13 requires expanded disclosures including, but not limited to, (i) information about the methods and assumptions used to estimate expected credit losses, including changes in the factors that influenced management's estimate and the reasons for those changes, (ii) for financing receivables and net investment in leases measured at amortized cost, further disaggregation of information about the credit quality of those assets and (iii) a rollforward of the allowance for credit losses for HTM and AFS securities. ASU 2016-13 is effective for the Company on January 1, 2020. In April 2019, the FASB issued ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, which, among other things, clarifies that recoveries should be incorporated within the estimation of the allowance for credit losses. Expected recoveries should not exceed the aggregate amount of prior write offs and expected future write offs. The inclusion of expected recoveries in the measurement of expected credit losses may result in a negative credit allowance in certain circumstances. The effective date and transition requirements for ASU 2019-04 are consistent with the requirements for ASU 2016-13 and the Company incorporated these changes and revisions within its implementation efforts. In May 2019, the FASB issued ASU 2019-05, Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief. The Company did not elect to apply the fair value option to any asset class that are in scope for CECL. In November 2019, the FASB issued ASU 2019-11, “Codification Improvements to Topic 326, Financial Instruments-Credit Losses” which clarifies that expected recoveries should be included in the amortized cost basis previously written off or expected to be written off in the valuation allowance for PCD assets. ASU 2019-11 also clarifies that recoveries or expected recoveries of the unamortized noncredit discount or premium should not be included in the allowance for credit losses. ASU 2019-11 provides specific transition relief for existing troubled debt restructurings and extends the disclosure relief of ASU 2019-04 for accrued interest receivable balances to additional relevant disclosures involving amortized cost basis. Related to the assessment of credit risk for collateralized assets, ASU 2019-11 indicates that an entity should assess whether it reasonably expects the borrower will be able to continually replenish collateral securing the financial asset to apply the practical expedient of ASU 2016-13 while also requiring an estimation of expected credit losses for any differences between the amount of the amortized cost basis that is greater than the fair value of the collateral securing the financial asset. ASU 2019-11 provides specific transition relief for existing troubled debt restructurings and extends the disclosure relief of ASU 2019-04 for accrued interest receivable balances to additional relevant disclosures involving amortized cost basis. The effective date and transition requirements of ASU 2019-11 are consistent with the requirements of ASU 2016-13 and the Company incorporated these changes and revisions within its implementation efforts. The Company has approved an accounting policy for credit losses in compliance with CECL and established a CECL governance and approval process. The Company has selected a life of loan discounted probability of default, loss given default econometric model, adjusted for prepayments, for the majority of its portfolio segments. The Company will utilize a multiple economic forecast over a six quarter reasonable and supportable forecast period followed by a four quarter straight line reversion to historical losses. The Company expects to incur a $1.0 million to $8.0 million after-tax reduction to stockholders’ equity balance, upon the adoption of ASU 2016-13 on January 1, 2020, inclusive of the estimate for off-balance sheet exposures. Longer lived loans such as Residential Real Estate loans experience increases in the allowance for credit losses compared to the incurred loss model while shorter lived loans such as Indirect Auto and C&I loans generally experience little change in the allowance for credit losses from the incurred loss model. The Company has established a control framework and is finalizing testing of controls related to the adoption of CECL. The Company is also completing its final review of the most recent model run including evaluation of model back-testing and sensitivity analysis results, and finalizing certain assumptions primarily related to qualitative adjustments and probable troubled debt restructurings. In addition, the Company is completing the analysis of the results from the third party model validation. The Company does not expect to incur a material adjustment to the stockholders’ equity balance as of January 1, 2020 for the adoption of CECL related to HTM securities. Additionally, the Company has also evaluated the composition of its AFS securities and determined that the changes in ASU 2016-13 will not have a significant effect on the current portfolio. Management expects that the CECL model may create more volatility in the level of our allowance for loan losses from quarter to quarter as changes in the level of allowance for loan losses will be dependent upon, among other things, macroeconomic forecasts and conditions, loan portfolio volumes and credit quality. In August 2018, the FASB issued ASU 2018-14, Compensation – Retirement Benefits – Defined Benefit Plans - General (Subtopic 715-20), provides changes to the disclosure requirements for defined benefit plans. The amended guidance modifies the disclosure requirements for employers that sponsor defined benefit pension or other postretirement plans. The amendments are a result of the disclosure framework project that focuses on improvements to the effectiveness of disclosures in the notes to financial statements. The amendments remove and add certain disclosure requirements. The disclosure requirements being removed relating to public companies are (1) the amounts in accumulated other comprehensive income expected to be recognized as components of net periodic benefit cost over the next fiscal year, (2) the amount and timing of plan assets expected to be returned to the employer, (3) the 2001 disclosure requirement relating to Japanese Welfare Pension Insurance Law, (4) related party disclosures about the amount of future annual benefits covered by insurance, and (5) the effects of a one-percentage-point change in assumed health care cost trends on the benefit cost and obligation. The disclosure requirements being added relating to public companies are (1) the weighted-average interest crediting rates for cash balance plans, and (2) an explanation of the reasons for significant gains and losses related to changes in the benefit obligation for the period. ASU 2018-14 is effective for the Company on January 1, 2021 and early adoption is permitted. The amendments should be applied retrospectively and the Company does not expect the guidance to have a material impact on its disclosures to the consolidated financial statements. In August 2018, the FASB issued ASU 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40) – Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract. ASU 2018-15 amends existing guidance and requires a hosting arrangement that is a service contract to follow the guidance in Subtopic 350-40 to determine which implementation costs to capitalize and which costs to expense. ASU 2018-15 is effective for the Company on January 1, 2020, and early adoption is permitted. The amendments should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The adoption did not have a material impact on the consolidated financial statements and related disclosures.

Securities, HTM Debt Securities, Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Held-to-maturity Securities, Debt Maturities, Amortized Cost [Abstract]
Within one year	$ 27,010
From one to five years	53,895
From five to ten years	171,942
After ten years	377,227
Amortized cost	630,074	$ 783,599
Held-to-maturity Securities, Debt Maturities, Estimated Fair Value [Abstract]
Within one year	27,010
From one to five years	54,358
From five to ten years	175,630
After ten years	384,264
Fair value	$ 641,262	$ 778,675

Securities, Held to Maturity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	$ 630,074	$ 783,599
Unrealized gains	11,817	3,362
Unrealized losses	629	8,286
Estimated fair value	641,262	778,675
Transactions of HTM securities [Abstract]
Held-to-maturity securities sold, amortized cost	0	0	$ 800
Held-to-maturity securities sold, realized loss			(2)
Held-to-maturity securities sold, unrealized loss			(2)
Gains from calls on HTM securities	12	0	$ 0
Federal Agency [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost		19,995
Unrealized gains		52
Unrealized losses		0
Estimated fair value		20,047
Mortgage-backed Securities, Government-Sponsored Enterprises [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	149,448	164,618
Unrealized gains	3,184	712
Unrealized losses	155	2,773
Estimated fair value	152,477	162,557
Mortgage-Backed, U.S. Government Agency Securities [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	13,667	15,230
Unrealized gains	584	403
Unrealized losses	0	0
Estimated fair value	14,251	15,633
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	189,402	257,475
Unrealized gains	2,165	1,097
Unrealized losses	368	3,897
Estimated fair value	191,199	254,675
Collateralized Mortgage Obligations, U.S. Government Agency Securities [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	110,498	83,148
Unrealized gains	3,256	767
Unrealized losses	100	0
Estimated fair value	113,654	83,915
State & Municipal [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	167,059	243,133
Unrealized gains	2,628	331
Unrealized losses	6	1,616
Estimated fair value	169,681	241,848
Public Deposits and Other Purposes [Member]
Securities pledged [Abstract]
Amortized costs of securities available for sale and held to maturity pledged	1,300,000	1,500,000
Securities Sold under Repurchase Agreements [Member]
Securities pledged [Abstract]
Amortized costs of securities available for sale and held to maturity pledged	$ 189,800	$ 215,300

Parent Company Financial Information

12 Months Ended

Dec. 31, 2019

Parent Company Financial Information [Abstract]

Parent Company Financial Information

22. Parent Company Financial Information

Condensed Balance Sheets

	December 31,
(In thousands)	2019		2018
Assets
Cash and cash equivalents	$	9,387	$	5,876
Equity securities, at estimated fair value		22,441		18,221
Investment in subsidiaries, on equity basis		1,209,752		1,117,350
Other assets		30,855		34,237
Total assets	$	1,272,435	$	1,175,684
Liabilities and Stockholders’ Equity
Total liabilities	$	152,038	$	157,775
Stockholders’ equity		1,120,397		1,017,909
Total liabilities and stockholders’ equity	$	1,272,435	$	1,175,684

Condensed Statements of Income

	Years ended December 31,
(In thousands)	2019			2018			2017
Dividends from subsidiaries	$	50,200		$	43,000		$	38,300
Management fee from subsidiaries		7,981			7,907			99,319
Net securities gains		165			399			2,237
Interest, dividends and other income		876			905			928
Total revenue	$	59,222		$	52,211		$	140,784
Operating expenses		14,262			14,226			100,667
Income before income tax benefit and equity in undistributed income of subsidiaries	$	44,960		$	37,985		$	40,117
Income tax (benefit) expense		(1,588	)		(1,608	)		2,233
Dividends in excess of income (equity in undistributed income) of subsidiaries		74,473			72,973			44,267
Net income	$	121,021		$	112,566		$	82,151

Condensed Statements of Cash Flow

	Years ended December 31,
(In thousands)	2019			2018			2017
Operating activities
Net income	$	121,021		$	112,566		$	82,151
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation and amortization of premises and equipment		2,298			2,814			2,974
Excess tax benefit on stock-based compensation		(409	)		(543	)		(1,769	)
Stock-based compensation expense		4,210			3,936			3,644
Net securities gains		(165	)		(399	)		(2,238	)
Re-evaluation of deferred tax amounts from Tax Act		-			-			3,339
Equity in undistributed income of subsidiaries		(124,673	)		(115,972	)		(82,567	)
Cash dividend from subsidiaries		50,200			43,000			38,300
Bank owned life insurance income		(398	)		(424	)		(328	)
Net change in other assets and other liabilities		(1,573	)		(6,124	)		(2,454	)
Net cash provided by operating activities	$	50,511		$	38,854		$	41,052
Investing activities
Proceeds on sales of equity securities	$	-		$	3,318		$	-
Purchases of equity securities		(93	)		(2	)		-
Proceeds on sales and maturities of AFS securities		-			-			4,710
Purchases of AFS securities		-			-			(9	)
Proceeds from settlement of bank owned life insurance		-			-			308
Net purchases of premises and equipment		-			-			(2,264	)
Net cash (used in) provided by investing activities	$	(93	)	$	3,316		$	2,745
Financing activities
Proceeds from the issuance of shares to employee and other stock plans	$	725		$	1,296		$	3,309
Cash paid by employer for tax-withholding on stock issuance		(1,622	)		(1,893	)		(3,582	)
Cash dividends		(46,010	)		(43,269	)		(40,104	)
Net cash (used in) financing activities	$	(46,907	)	$	(43,866	)	$	(40,377	)
Net increase (decrease) in cash and cash equivalents	$	3,511		$	(1,696	)	$	3,420
Cash and cash equivalents at beginning of year		5,876			7,572			4,152
Cash and cash equivalents at end of year	$	9,387		$	5,876		$	7,572

A statement of changes in stockholders’ equity has not been presented since it is the same as the consolidated statement of changes in stockholders’ equity previously presented.

Loans

12 Months Ended

Dec. 31, 2019

Loans [Abstract]

Loans

4. Loans

A summary of loans, net of deferred fees and origination costs, by category is as follows:

	At December 31,
(In thousands)	2019		2018
Commercial	$	1,302,209	$	1,291,568
Commercial Real Estate		2,142,057		1,930,742
Residential Real Estate		1,445,156		1,380,836
Indirect Auto		1,193,635		1,216,144
Specialty Lending		542,063		524,928
Home Equity		444,082		474,566
Other Consumer		66,896		68,925
Total loans	$	7,136,098	$	6,887,709

Included in the above loans are net deferred loan origination costs totaling $35.3 million and $43.5 million at December 31, 2019 and 2018, respectively. The Company had $11.5 million residential loans held for sale as of December 31, 2019. The Company had $6.9 million of residential loans held for sale as of December 31, 2018.

The total amount of loans serviced by the Company for unrelated third parties was $612.3 million and $557.9 million at December 31, 2019 and 2018, respectively. At December 31, 2019 and 2018, the Company had $0.8 million and $0.5 million, respectively, of mortgage servicing rights.

At December 31, 2019 and 2018, the Company serviced $25.6 million and $27.2 million, respectively, of agricultural loans sold with recourse. Due to sufficient collateral on these loans and government guarantees, no reserve is considered necessary at December 31, 2019 and 2018.

FHLB advances are collateralized by a blanket lien on the Company’s residential real estate mortgages.

(In thousands)	2019			2018
Balance at January 1	$	1,638		$	1,577
New loans		587			260
Adjustment due to change in composition of related parties		389			-
Repayments		(448	)		(199	)
Balance at December 31	$	2,166		$	1,638

Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2019

Goodwill and Other Intangible Assets [Abstract]

Summary of Goodwill

A summary of goodwill is as follows:

(In thousands)
January 1, 2019	$	274,769
Goodwill acquired		-
December 31, 2019	$	274,769

January 1, 2018	$	268,043
Goodwill acquired		6,726
December 31, 2018	$	274,769

Summary of Core Deposit and Other Intangible Assets

A summary of core deposit and other intangible assets follows:

	December 31,
(In thousands)	2019		2018
Core deposit intangibles:
Gross carrying amount	$	8,951	$	8,975
Less: accumulated amortization		7,988		7,377
Net carrying amount	$	963	$	1,598

Identified intangible assets:
Gross carrying amount	$	34,623	$	34,623
Less: accumulated amortization		23,566		20,622
Net carrying amount	$	11,057	$	14,001

Total intangibles:
Gross carrying amount	$	43,574	$	43,598
Less: accumulated amortization		31,554		27,999
Net carrying amount	$	12,020	$	15,599

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic EPS [Abstract]
Net income	$ 121,021	$ 112,566	$ 82,151
Weighted average shares, basic (in shares)	43,815	43,701	43,575
Basic EPS (in dollars per share)	$ 2.76	$ 2.58	$ 1.89
Diluted earnings per share [Abstract]
Net income	$ 121,021	$ 112,566	$ 82,151
Dilutive effect of stock based compensation (in shares)	309	319	330
Weighted average shares, diluted (in shares)	44,124	44,020	43,905
Diluted EPS (in dollars per share)	$ 2.74	$ 2.56	$ 1.87

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Allowance for Loan Losses and Credit Quality of Loans, Impairment Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Allowance for Loan Losses and Credit Quality of Loans [Abstract]
Threshold balance for classified loans to be evaluated individually for impairment	$ 1,000	$ 750
Total Loans [Abstract]
Recorded investment balance (book)	18,253		$ 20,578
Unpaid principal balance (legal)	22,541		28,552
Related allowance	0		25
Acquired impaired loans specifically evaluated for impairment	0		0
Originated Loans [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	18,253		20,345
Unpaid principal balance (legal)	22,541		28,314
Originated Loans [Member] \| Commercial Loans [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	3,488		5,553
Unpaid principal balance (legal)	4,182		8,828
With an allowance recorded [Abstract]
Recorded investment balance (book)	0		233
Unpaid principal balance (legal)	0		238
Total Loans [Abstract]
Related allowance	0		25
Originated Loans [Member] \| Commercial Loans [Member] \| C&I [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	76		228
Unpaid principal balance (legal)	302		497
With an allowance recorded [Abstract]
Recorded investment balance (book)	0		233
Unpaid principal balance (legal)	0		238
Total Loans [Abstract]
Related allowance	0		25
Originated Loans [Member] \| Commercial Loans [Member] \| CRE [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	2,410		4,312
Unpaid principal balance (legal)	2,437		6,330
Originated Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	1,002		1,013
Unpaid principal balance (legal)	1,443		2,001
Originated Loans [Member] \| Consumer Loans [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	7,044		7,887
Unpaid principal balance (legal)	8,605		10,072
Originated Loans [Member] \| Consumer Loans [Member] \| Indirect Auto [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	154		143
Unpaid principal balance (legal)	242		241
Originated Loans [Member] \| Consumer Loans [Member] \| Direct [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	6,862		7,744
Unpaid principal balance (legal)	8,335		9,831
Originated Loans [Member] \| Consumer Loans [Member] \| Specialty Lending [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	28		0
Unpaid principal balance (legal)	28		0
Originated Loans [Member] \| Residential Real Estate [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)	7,721		6,905
Unpaid principal balance (legal)	$ 9,754		$ 9,414

Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Additional disclosures [Abstract]
Stock-based compensation expense	$ 4,210	$ 3,936	$ 3,644
Number of shares available for future grant (in shares)	988,494
Stock Options [Member]
Share-based compensation [Abstract]
Stock awards termination period	10 years
Stock options [Roll Forward]
Outstanding, beginning of period (in shares)	66,900
Exercised (in shares)	(32,505)
Expired (in shares)	(1,250)
Outstanding, end of period (in shares)	33,145	66,900
Exercisable, end of period (in shares)	33,145
Stock options, weighted average exercise price [Abstract]
Outstanding, beginning of period (in dollars per share)	$ 23.07
Exercised (in dollars per share)	22.31
Expired (in dollars per share)	25.38
Outstanding, end of period (in dollars per share)	23.73	$ 23.07
Exercisable, end of period (in dollars per share)	$ 23.73
Additional disclosures [Abstract]
Weighted average remaining contractual term, outstanding, end of period	1 year 10 months 9 days
Weighted average remaining contractual term, exercisable, end of period	1 year 10 months 9 days
Aggregate intrinsic value, outstanding, end of period	$ 558,066
Aggregate intrinsic value, exercisable, end of period	558,066
Stock-based compensation expense	1	$ 11	18
Proceeds from stock options exercised	725	999	3,083
Tax benefits related to stock options exercised	123	173	650
Intrinsic value of stock options exercised	490	692	1,699
Fair value of shares vested during the year	13	16	329
Restricted Stock [Member]
Additional disclosures [Abstract]
Stock-based compensation expense	$ 4,200	$ 3,900	3,500
Restricted Stock [Member] \| Employees [Member] \| Minimum [Member]
Share-based compensation [Abstract]
Stock awards vesting period	3 years
Restricted Stock [Member] \| Employees [Member] \| Maximum [Member]
Share-based compensation [Abstract]
Stock awards vesting period	5 years
Restricted Stock [Member] \| Non-employee Directors [Member]
Share-based compensation [Abstract]
Stock awards vesting period	3 years
Restricted Stock Units (RSUs) [Member]
Restricted stock and restricted stock units [Roll Forward]
Unvested, beginning of period (in shares)	546,054
Forfeited (in shares)	(10,886)
Vested (in shares)	(121,774)
Granted (in shares)	142,046
Unvested, end of period (in shares)	555,440	546,054
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]
Unvested, beginning of period (in dollars per share)	$ 28.39
Forfeited (in dollars per share)	31.06
Vested (in dollars per share)	25.66
Granted (in dollars per share)	33.04
Unvested, end of period (in dollars per share)	$ 30.11	$ 28.39
Restricted Stock Awards and Stock Units [Member]
Additional disclosures [Abstract]
Tax benefit on restricted stock awards	$ 1,100	$ 1,200	$ 2,500
Unrecognized compensation cost	$ 5,500
Unrecognized compensation cost, weighted average period of recognition	1 year 9 months 18 days

Allowance for Loan Losses and Credit Quality of Loans, Allowance for Loan Losses by Portfolio Segments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	$ 72,505	$ 69,500	$ 65,200
Charge-offs	(32,540)	(34,128)	(33,087)
Recoveries	7,588	8,305	6,399
Provision	25,412	28,828	30,988
Balance, end of period	72,965	72,505	69,500
Commercial Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	32,759	27,606	25,444
Charge-offs	(3,151)	(3,463)	(4,169)
Recoveries	534	1,178	1,077
Provision	4,383	7,438	5,254
Balance, end of period	34,525	32,759	27,606
Consumer Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	37,178	36,830	33,375
Charge-offs	(28,398)	(29,752)	(27,072)
Recoveries	6,913	6,821	5,142
Provision	19,954	23,279	25,385
Balance, end of period	35,647	37,178	36,830
Residential Real Estate [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	2,568	5,064	6,381
Charge-offs	(991)	(913)	(1,846)
Recoveries	141	306	180
Provision	1,075	(1,889)	349
Balance, end of period	2,793	2,568	5,064
Acquired Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	0
Charge-offs	(100)	(100)	$ (700)
Balance, end of period	$ 0	$ 0

Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Aging [Abstract]
Minimum number of days past due for nonaccrual loan status	90 days
Total past due accruing	$ 34,803	$ 38,067
Nonaccrual	25,174	25,487
Current	7,076,121	6,824,155
Recorded total loans	7,136,098	6,887,709
31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	25,610	26,641
61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	5,476	6,341
Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	3,717	5,085
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded total loans	3,444,266	3,222,310
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded total loans	2,246,676	2,284,563
Consumer Loans [Member] \| Indirect Auto [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded total loans	1,193,635	1,216,144
Consumer Loans [Member] \| Specialty Lending [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded total loans	542,063	524,928
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded total loans	1,445,156	1,380,836
Originated Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	32,917	36,515
Nonaccrual	23,581	23,372
Current	6,814,722	6,505,231
Recorded total loans	6,871,220	6,565,118
Originated Loans [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	24,353	25,476
Originated Loans [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	5,111	5,969
Originated Loans [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	3,453	5,070
Originated Loans [Member] \| Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	5,759	3,980
Nonaccrual	13,059	12,031
Current	3,310,182	3,062,609
Recorded total loans	3,329,000	3,078,620
Originated Loans [Member] \| Commercial Loans [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	5,597	3,090
Originated Loans [Member] \| Commercial Loans [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	162	302
Originated Loans [Member] \| Commercial Loans [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	588
Originated Loans [Member] \| Commercial Loans [Member] \| C&I [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,227	909
Nonaccrual	1,177	1,062
Current	838,502	846,148
Recorded total loans	840,906	848,119
Originated Loans [Member] \| Commercial Loans [Member] \| C&I [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,227	909
Originated Loans [Member] \| Commercial Loans [Member] \| C&I [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Originated Loans [Member] \| Commercial Loans [Member] \| C&I [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Originated Loans [Member] \| Commercial Loans [Member] \| CRE [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	3,576	1,677
Nonaccrual	4,847	4,995
Current	1,941,143	1,734,558
Recorded total loans	1,949,566	1,741,230
Originated Loans [Member] \| Commercial Loans [Member] \| CRE [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	3,576	1,089
Originated Loans [Member] \| Commercial Loans [Member] \| CRE [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Originated Loans [Member] \| Commercial Loans [Member] \| CRE [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	588
Originated Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	956	1,394
Nonaccrual	7,035	5,974
Current	530,537	481,903
Recorded total loans	538,528	489,271
Originated Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	794	1,092
Originated Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	162	302
Originated Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Originated Loans [Member] \| Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	25,126	29,770
Nonaccrual	4,650	4,563
Current	2,193,167	2,218,606
Recorded total loans	2,222,943	2,252,939
Originated Loans [Member] \| Consumer Loans [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	17,577	20,960
Originated Loans [Member] \| Consumer Loans [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	4,759	5,510
Originated Loans [Member] \| Consumer Loans [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,790	3,300
Originated Loans [Member] \| Consumer Loans [Member] \| Indirect Auto [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	14,973	18,005
Nonaccrual	2,175	1,971
Current	1,176,487	1,196,136
Recorded total loans	1,193,635	1,216,112
Originated Loans [Member] \| Consumer Loans [Member] \| Indirect Auto [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	11,860	14,519
Originated Loans [Member] \| Consumer Loans [Member] \| Indirect Auto [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,108	2,300
Originated Loans [Member] \| Consumer Loans [Member] \| Indirect Auto [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,005	1,186
Originated Loans [Member] \| Consumer Loans [Member] \| Specialty Lending [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	6,547	6,814
Nonaccrual	0	0
Current	535,516	518,114
Recorded total loans	542,063	524,928
Originated Loans [Member] \| Consumer Loans [Member] \| Specialty Lending [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	3,153	3,479
Originated Loans [Member] \| Consumer Loans [Member] \| Specialty Lending [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,087	1,773
Originated Loans [Member] \| Consumer Loans [Member] \| Specialty Lending [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,307	1,562
Originated Loans [Member] \| Consumer Loans [Member] \| Direct [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	3,606	4,951
Nonaccrual	2,475	2,592
Current	481,164	504,356
Recorded total loans	487,245	511,899
Originated Loans [Member] \| Consumer Loans [Member] \| Direct [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,564	2,962
Originated Loans [Member] \| Consumer Loans [Member] \| Direct [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	564	1,437
Originated Loans [Member] \| Consumer Loans [Member] \| Direct [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	478	552
Originated Loans [Member] \| Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,032	2,765
Nonaccrual	5,872	6,778
Current	1,311,373	1,224,016
Recorded total loans	1,319,277	1,233,559
Originated Loans [Member] \| Residential Real Estate [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,179	1,426
Originated Loans [Member] \| Residential Real Estate [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	190	157
Originated Loans [Member] \| Residential Real Estate [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	663	1,182
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,886	1,552
Nonaccrual	1,593	2,115
Current	261,399	318,924
Recorded total loans	264,878	322,591
Acquired Loans [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,257	1,165
Acquired Loans [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	365	372
Acquired Loans [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	264	15
Acquired Loans [Member] \| Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	833	754
Nonaccrual	382	390
Current	114,051	142,546
Recorded total loans	115,266	143,690
Acquired Loans [Member] \| Commercial Loans [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	546	466
Acquired Loans [Member] \| Commercial Loans [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	287	288
Acquired Loans [Member] \| Commercial Loans [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Acquired Loans [Member] \| Commercial Loans [Member] \| C&I [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	149	0
Nonaccrual	0	0
Current	19,215	26,124
Recorded total loans	19,364	26,124
Acquired Loans [Member] \| Commercial Loans [Member] \| C&I [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	149	0
Acquired Loans [Member] \| Commercial Loans [Member] \| C&I [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Acquired Loans [Member] \| Commercial Loans [Member] \| C&I [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Acquired Loans [Member] \| Commercial Loans [Member] \| CRE [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Nonaccrual	0	0
Current	60,937	84,492
Recorded total loans	60,937	84,492
Acquired Loans [Member] \| Commercial Loans [Member] \| CRE [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Acquired Loans [Member] \| Commercial Loans [Member] \| CRE [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Acquired Loans [Member] \| Commercial Loans [Member] \| CRE [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Acquired Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	684	754
Nonaccrual	382	390
Current	33,899	31,930
Recorded total loans	34,965	33,074
Acquired Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	397	466
Acquired Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	287	288
Acquired Loans [Member] \| Commercial Loans [Member] \| Business Banking [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	0
Acquired Loans [Member] \| Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	194	210
Nonaccrual	105	227
Current	23,434	31,187
Recorded total loans	23,733	31,624
Acquired Loans [Member] \| Consumer Loans [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	136	153
Acquired Loans [Member] \| Consumer Loans [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	58	42
Acquired Loans [Member] \| Consumer Loans [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	15
Acquired Loans [Member] \| Consumer Loans [Member] \| Indirect Auto [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		2
Nonaccrual		0
Current		30
Recorded total loans		32
Acquired Loans [Member] \| Consumer Loans [Member] \| Indirect Auto [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		1
Acquired Loans [Member] \| Consumer Loans [Member] \| Indirect Auto [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		1
Acquired Loans [Member] \| Consumer Loans [Member] \| Indirect Auto [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Acquired Loans [Member] \| Consumer Loans [Member] \| Direct [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	194	208
Nonaccrual	105	227
Current	23,434	31,157
Recorded total loans	23,733	31,592
Acquired Loans [Member] \| Consumer Loans [Member] \| Direct [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	136	152
Acquired Loans [Member] \| Consumer Loans [Member] \| Direct [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	58	41
Acquired Loans [Member] \| Consumer Loans [Member] \| Direct [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0	15
Acquired Loans [Member] \| Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	859	588
Nonaccrual	1,106	1,498
Current	123,914	145,191
Recorded total loans	125,879	147,277
Acquired Loans [Member] \| Residential Real Estate [Member] \| 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	575	546
Acquired Loans [Member] \| Residential Real Estate [Member] \| 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	20	42
Acquired Loans [Member] \| Residential Real Estate [Member] \| Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	$ 264	$ 0

Allowance for Loan Losses and Credit Quality of Loans, Credit Quality by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Credit Quality by Loan Class [Abstract]
Net Loans	$ 7,136,098	$ 6,887,709
Consumer Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,246,676	2,284,563
Consumer Credit Exposure [Member] \| Indirect Auto [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,193,635	1,216,144
Consumer Credit Exposure [Member] \| Specialty Lending [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	542,063	524,928
Residential Real Estate Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,445,156	1,380,836
Originated Loans [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	6,871,220	6,565,118
Originated Loans [Member] \| Commercial Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,790,472	2,589,349
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,651,441	2,478,108
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	58,899	25,242
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	79,626	85,999
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| Doubtful [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	506
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| C&I [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	840,906	848,119
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| C&I [Member] \| Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	782,763	796,778
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| C&I [Member] \| Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	28,380	11,348
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| C&I [Member] \| Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	29,257	39,993
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| C&I [Member] \| Doubtful [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	506
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| CRE [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,949,566	1,741,230
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| CRE [Member] \| Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,868,678	1,681,330
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| CRE [Member] \| Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	30,519	13,894
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| CRE [Member] \| Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	50,369	46,006
Originated Loans [Member] \| Commercial Credit Exposure [Member] \| CRE [Member] \| Doubtful [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	0
Originated Loans [Member] \| Business Banking Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	538,528	489,271
Originated Loans [Member] \| Business Banking Credit Exposure [Member] \| Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	524,725	476,052
Originated Loans [Member] \| Business Banking Credit Exposure [Member] \| Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	13,803	13,219
Originated Loans [Member] \| Business Banking Credit Exposure [Member] \| Business Banking [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	538,528	489,271
Originated Loans [Member] \| Business Banking Credit Exposure [Member] \| Business Banking [Member] \| Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	524,725	476,052
Originated Loans [Member] \| Business Banking Credit Exposure [Member] \| Business Banking [Member] \| Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	13,803	13,219
Originated Loans [Member] \| Consumer Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,222,943	2,252,939
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,215,503	2,245,076
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	7,440	7,863
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Indirect Auto [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,193,635	1,216,112
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Indirect Auto [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,190,455	1,212,955
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Indirect Auto [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	3,180	3,157
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Specialty Lending [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	542,063	524,928
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Specialty Lending [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	540,756	523,366
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Specialty Lending [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,307	1,562
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Direct [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	487,245	511,899
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Direct [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	484,292	508,755
Originated Loans [Member] \| Consumer Credit Exposure [Member] \| Direct [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,953	3,144
Originated Loans [Member] \| Residential Real Estate Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,319,277	1,233,559
Originated Loans [Member] \| Residential Real Estate Credit Exposure [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,312,742	1,225,599
Originated Loans [Member] \| Residential Real Estate Credit Exposure [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	6,535	7,960
Originated Loans [Member] \| Residential Real Estate Credit Exposure [Member] \| Residential Real Estate [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,319,277	1,233,559
Originated Loans [Member] \| Residential Real Estate Credit Exposure [Member] \| Residential Real Estate [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,312,742	1,225,599
Originated Loans [Member] \| Residential Real Estate Credit Exposure [Member] \| Residential Real Estate [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	6,535	7,960
Acquired Loans [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	264,878	322,591
Acquired Loans [Member] \| Commercial Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	80,301	110,616
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	78,346	107,045
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,269	2,923
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	686	648
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| C&I [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	19,364	26,124
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| C&I [Member] \| Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	17,801	23,283
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| C&I [Member] \| Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,269	2,831
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| C&I [Member] \| Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	294	10
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| CRE [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	60,937	84,492
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| CRE [Member] \| Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	60,545	83,762
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| CRE [Member] \| Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	0	92
Acquired Loans [Member] \| Commercial Credit Exposure [Member] \| CRE [Member] \| Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	392	638
Acquired Loans [Member] \| Business Banking Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	34,965	33,074
Acquired Loans [Member] \| Business Banking Credit Exposure [Member] \| Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	32,030	29,945
Acquired Loans [Member] \| Business Banking Credit Exposure [Member] \| Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,935	3,129
Acquired Loans [Member] \| Business Banking Credit Exposure [Member] \| Business Banking [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	34,965	33,074
Acquired Loans [Member] \| Business Banking Credit Exposure [Member] \| Business Banking [Member] \| Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	32,030	29,945
Acquired Loans [Member] \| Business Banking Credit Exposure [Member] \| Business Banking [Member] \| Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,935	3,129
Acquired Loans [Member] \| Consumer Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	23,733	31,624
Acquired Loans [Member] \| Consumer Credit Exposure [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	23,628	31,382
Acquired Loans [Member] \| Consumer Credit Exposure [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	105	242
Acquired Loans [Member] \| Consumer Credit Exposure [Member] \| Indirect Auto [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		32
Acquired Loans [Member] \| Consumer Credit Exposure [Member] \| Indirect Auto [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		32
Acquired Loans [Member] \| Consumer Credit Exposure [Member] \| Indirect Auto [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		0
Acquired Loans [Member] \| Consumer Credit Exposure [Member] \| Direct [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	23,733	31,592
Acquired Loans [Member] \| Consumer Credit Exposure [Member] \| Direct [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	23,628	31,350
Acquired Loans [Member] \| Consumer Credit Exposure [Member] \| Direct [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	105	242
Acquired Loans [Member] \| Residential Real Estate Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	125,879	147,277
Acquired Loans [Member] \| Residential Real Estate Credit Exposure [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	124,509	145,779
Acquired Loans [Member] \| Residential Real Estate Credit Exposure [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,370	1,498
Acquired Loans [Member] \| Residential Real Estate Credit Exposure [Member] \| Residential Real Estate [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	125,879	147,277
Acquired Loans [Member] \| Residential Real Estate Credit Exposure [Member] \| Residential Real Estate [Member] \| Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	124,509	145,779
Acquired Loans [Member] \| Residential Real Estate Credit Exposure [Member] \| Residential Real Estate [Member] \| Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	$ 1,370	$ 1,498