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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2014	Feb. 13, 2015	Jun. 30, 2014
Document And Entity Information [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 Filer Category	Large Accelerated Filer
Entity Public Float			$ 1,001,148,554
Entity Common Stock, Shares Outstanding		44,213,717
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2014

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Assets
Cash and due from banks	$ 139,635	$ 157,625
Short-term interest bearing accounts	7,001	1,301
Securities available for sale, at fair value	1,013,171	1,364,881
Securities held to maturity (fair value $454,994 and $113,276)	454,361	117,283
Trading securities	7,793	5,779
Federal Reserve and Federal Home Loan Bank stock	32,626	46,864
Loans	5,595,271	5,406,795
Less allowance for loan losses	66,359	69,434
Net loans	5,528,912	5,337,361
Premises and equipment, net	89,258	88,327
Goodwill	263,634	264,997
Intangible assets, net	20,317	25,557
Bank owned life insurance	114,251	114,966
Other assets	126,967	127,234
Total assets	7,797,926	7,652,175
Liabilities
Demand (noninterest bearing)	1,838,622	1,645,641
Savings, NOW, and money market	3,417,160	3,223,441
Time	1,043,823	1,021,142
Total deposits	6,299,605	5,890,224
Short-term borrowings	316,802	456,042
Long-term debt	130,945	308,823
Junior subordinated debt	101,196	101,196
Other liabilities	85,197	79,321
Total liabilities	6,933,745	6,835,606
Stockholders' equity
Preferred stock, $0.01 par value; authorized 2,500,000 shares at December 31, 2014 and 2013	0	0
Common stock, $0.01 par value. Authorized 100,000,000 shares at December 31, 2014 and December 31, 2013; issued 49,651,494 at December 31, 2014 and December 31, 2013	497	497
Additional paid-in-capital	576,504	574,152
Retained earnings	423,956	385,787
Accumulated other comprehensive loss	(17,027)	(16,765)
Common stock in treasury, at cost, 5,755,040 and 6,138,444 shares at December 31, 2014 and 2013, respectively	(119,749)	(127,102)
Total stockholders' equity	864,181	816,569
Total liabilities and stockholders' equity	$ 7,797,926	$ 7,652,175

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Assets
Securities held to maturity fair value	$ 454,994	$ 113,276
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)	49,651,494	49,651,494
Common stock in treasury, at cost (in shares)	5,755,040	6,138,444

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
Consolidated Statements of Income - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest, fee, and dividend income
Interest and fees on loans and leases	$ 243,324	$ 238,672	$ 208,458
Securities available for sale	24,464	25,510	27,005
Securities held to maturity	5,261	2,660	2,378
Other	2,032	1,881	1,556
Total interest, fee, and dividend income	275,081	268,723	239,397
Interest expense
Deposits	13,638	16,290	18,848
Short-term borrowings	845	515	188
Long-term debt	6,555	11,755	14,428
Trust preferred debentures	2,165	2,084	1,730
Total interest expense	23,203	30,644	35,194
Net interest income	251,878	238,079	204,203
Provision for loan and lease losses	19,539	22,424	20,269
Net interest income after provision for loan and lease losses	232,339	215,655	183,934
Noninterest income
Insurance and other financial services revenue	24,517	24,447	22,387
Service charges on deposit accounts	17,941	19,307	18,225
ATM and debit card fees	17,135	15,558	12,358
Retirement plan administration fees	12,129	11,497	10,097
Trust	18,950	16,682	9,172
Bank owned life insurance income	5,349	3,793	3,077
Net securities gains	92	1,426	599
Gain on the sale of Springstone investment	19,401	0	0
Other	10,513	10,505	11,412
Total noninterest income	126,027	103,215	87,327
Noninterest expense
Salaries and employee benefits	119,667	113,580	104,815
Occupancy	22,128	20,720	17,415
Data processing and communications	16,137	15,353	13,437
Professional fees and outside services	14,426	13,309	10,463
Equipment	12,658	11,493	9,627
Office supplies and postage	6,983	6,563	6,489
FDIC expenses	4,944	4,960	3,832
Advertising	2,831	3,204	2,889
Amortization of intangible assets	5,047	4,872	3,394
Loan collection and other real estate owned	3,248	2,619	2,560
Merger expenses	0	12,364	2,608
Prepayment penalties on long-term debt	17,902	0	0
Other	20,092	19,890	16,358
Total noninterest expense	246,063	228,927	193,887
Income before income tax expense	112,303	89,943	77,374
Income tax expense	37,229	28,196	22,816
Net income	$ 75,074	$ 61,747	$ 54,558
Earnings per share
Basic (in dollars per share)	$ 1.71	$ 1.47	$ 1.63
Diluted (in dollars per share)	$ 1.69	$ 1.46	$ 1.62

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 75,074	$ 61,747	$ 54,558
Other comprehensive (loss) income, net of tax
Unrealized net holding gains (losses) arising during the year (pre-tax amounts of $18,069, ($41,059), and ($2,471)	11,447	(24,794)	(1,492)
Reclassification adjustment for net gains related to securities available for sale included in net income (pre-tax amounts of $92, $1,426, and $599)	(56)	(861)	(362)
Amortization of unrealized net gains and losses related to the reclassification of available for sale investment securities to held to maturity (pre-tax amounts of ($421), $0, and $0)	(257)	0	0
Amortization of prior service cost and actuarial gains (pre-tax amounts of $75, $2,790, and $3,593)	46	1,601	2,092
(Increase) Decrease in prior service cost and unrecognized actuarial loss (pre-tax amounts of ($19,245), $21,923, and $(24))	(11,442)	13,169	(14)
Total other comprehensive (loss) income	(262)	(10,885)	224
Comprehensive income	$ 74,812	$ 50,862	$ 54,782

Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other comprehensive (loss) income, before tax
Unrealized net holding (losses) gains arising during the period, pre-tax amounts	$ 18,069	$ (41,059)	$ (2,471)
Reclassification adjustment for net gains related to securities available for sale included in net income, pre-tax amounts	92	1,426	599
Amortization of unrealized net gains and losses related to the reclassification of available for sale investment securities to held to maturity, pre-tax amounts	(421)	0	0
Amortization of prior service cost and actuarial gains, pre-tax amounts	75	2,790	3,593
Decrease (Increase) in prior service costs and unrecognized actuarial loss, pre-tax amounts	$ (19,245)	$ 21,923	$ (24)

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
Beginning Balance at Dec. 31, 2011	$ 380	$ 317,329	$ 329,981	$ (6,104)	$ (103,476)	$ 538,110
Net income	0	0	54,558	0	0	54,558
Cash dividends	0	0	(26,712)	0	0	(26,712)
Purchases of treasury shares	0	0	0	0	(15,490)	(15,490)
Net issuance of shares for acquisition	13	25,811	0	0	0	25,824
Net issuance of shares to employee stock plans, including tax benefit	0	(812)	(269)	0	2,476	1,395
Stock-based compensation	0	4,364	0	0	0	4,364
Other comprehensive income	0	0	0	224	0	224
Ending Balance at Dec. 31, 2012	393	346,692	357,558	(5,880)	(116,490)	582,273
Net income	0	0	61,747	0	0	61,747
Cash dividends	0	0	(33,518)	0	0	(33,518)
Purchases of treasury shares	0	0	0	0	(12,459)	(12,459)
Net issuance of shares for acquisition	104	225,447	0	0	(5,779)	219,772
Net issuance of shares to employee stock plans, including tax benefit	0	(2,292)	0	0	7,626	5,334
Stock-based compensation	0	4,305	0	0	0	4,305
Other comprehensive income	0	0	0	(10,885)	0	(10,885)
Ending Balance at Dec. 31, 2013	497	574,152	385,787	(16,765)	(127,102)	816,569
Net income	0	0	75,074	0	0	75,074
Cash dividends	0	0	(36,905)	0	0	(36,905)
Purchases of treasury shares	0	0	0	0	(72)	(72)
Net issuance of shares to employee stock plans, including tax benefit	0	(1,169)	0	0	7,425	6,256
Stock-based compensation	0	3,521	0	0	0	3,521
Other comprehensive income	0	0	0	(262)	0	(262)
Ending Balance at Dec. 31, 2014	$ 497	$ 576,504	$ 423,956	$ (17,027)	$ (119,749)	$ 864,181

- Definition

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

+ References + Details

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Changes in Stockholders' Equity [Abstract]
Cash dividends - per share (in dollars per share)	$ 0.84	$ 0.81	$ 0.80
Purchase of treasury shares (in shares)	3,288	584,925	769,568
Net issuance of shares for acquisition (in shares)	0	10,346,363	1,269,592
Treasury stock reissued in acquisition of Alliance (in shares)	0	408,957	0
Net issuance of shares to employee stock plans, including tax benefit (in shares)	386,692	385,219	118,616

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net income	$ 75,074,000	$ 61,747,000	$ 54,558,000
Adjustments to reconcile net income to net cash provided by operating activities
Provision for loan and lease losses	19,539,000	22,424,000	20,269,000
Depreciation and amortization of premises and equipment	8,324,000	7,948,000	6,276,000
Net accretion on securities	3,216,000	5,058,000	2,408,000
Amortization of intangible assets	5,047,000	4,872,000	3,394,000
Stock based compensation	3,521,000	4,305,000	4,364,000
Bank owned life insurance income	(5,349,000)	(3,793,000)	(3,077,000)
Trading security purchases	(1,626,000)	(1,085,000)	(753,000)
Unrealized (gains) losses in trading securities	(388,000)	(776,000)	(103,000)
Deferred income tax benefit	8,347,000	2,344,000	(10,000)
Proceeds from sale of loans held for sale	7,050,000	71,342,000	65,160,000
Originations and purchases of loans held for sale	(10,215,000)	(66,512,000)	(66,252,000)
Net gains on sales of loans held for sale	(17,000)	(1,288,000)	(2,469,000)
Net security gains	(92,000)	(1,426,000)	(599,000)
Net gains on sales of other real estate owned	(459,000)	(1,106,000)	(988,000)
Gain on sale of equity investment	(19,401,000)	0	0
Prepayment penalties on long-term debt	17,903,000	0	0
Net decrease (increase) in other assets	(27,949,000)	20,463,000	6,804,000
Net (decrease) increase in other liabilities	5,286,000	(5,219,000)	(128,000)
Net cash provided by operating activities	87,811,000	119,298,000	88,854,000
Investing activities
Net cash provided by acquisitions	0	80,883,000	52,871,000
Securities available for sale:
Proceeds from maturities, calls, and principal paydowns	236,133,000	376,509,000	573,828,000
Proceeds from sales	189,000	27,593,000	1,790,000
Purchases	(197,652,000)	(353,714,000)	(483,858,000)
Securities held to maturity:
Proceeds from maturities, calls, and principal paydowns	44,756,000	34,413,000	31,506,000
Purchases	(49,479,000)	(84,621,000)	(20,193,000)
Other:
Net increase in loans	(212,238,000)	(255,318,000)	(277,530,000)
Proceeds from FHLB stock redemption	78,441,000	27,409,000	0
Purchases of Federal Reserve and FHLB stock	(64,203,000)	(36,366,000)	(1,886,000)
Proceeds from bank owned life insurance	6,064,000	0	0
Purchases of premises and equipment, net	(9,003,000)	(5,766,000)	(6,994,000)
Proceeds from sales of equity investment	19,639,000	0	0
Proceeds from sales of other real estate owned	3,612,000	5,224,000	3,616,000
Net cash used in investing activities	(143,741,000)	(183,754,000)	(126,850,000)
Financing activities
Net (decrease) increase in deposits	409,381,000	(7,545,000)	135,095,000
Net increase (decrease) in short-term borrowings	(139,240,000)	271,497,000	(18,651,000)
Proceeds from issuance of long-term debt	120,051,000	0	0
Repayments of long-term debt	(315,831,000)	(163,595,000)	(3,354,000)
Proceeds from the issuance of shares to employee benefit plans and other stock plans	6,256,000	5,334,000	1,395,000
Purchase of treasury stock	(72,000)	(12,459,000)	(15,490,000)
Cash dividends and payment for fractional shares	(36,905,000)	(33,518,000)	(26,712,000)
Net cash provided by financing activities	43,640,000	59,714,000	72,283,000
Net (decrease) increase in cash and cash equivalents	(12,290,000)	(4,742,000)	34,287,000
Cash and cash equivalents at beginning of year	158,926,000	163,668,000	129,381,000
Cash and cash equivalents at end of year	146,636,000	158,926,000	163,668,000
Cash paid during the period for:
Interest	23,387,000	31,307,000	35,344,000
Income taxes, net of refund	38,912,000	20,848,000	25,512,000
Noncash investing activities:
Loans transferred to other real estate owned	4,330,000	4,746,000	2,734,000
Preferred stock acquired from sale of equity investment	2,762,000	0	0
Transfer of available for sale securities to held to maturity portfolio	332,115,000	0	0
Acquisitions:
Fair value of assets acquired	0	1,505,490,000	258,467,000
Fair value of liabilities assumed	0	1,285,718,000	285,012,000
Fair value of debt issued in purchase combination	$ 0	$ 0	$ 502,000

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2014
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”), NBT Holdings, Inc., and NBT Financial Services, Inc., conform, in all material respects, to U.S. generally accepted accounting principles (“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 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 Report 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 the greater Portland, Maine area. 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 available for sale, held to maturity or trading. Held to maturity 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, and unrealized gains and losses are included in earnings. Available for sale securities are securities that are not classified as a held to maturity or trading securities. Available for sale securities are recorded at fair value. Unrealized holding gains and losses, net of the related tax effect, on available for sale securities are excluded from earnings and are reported in stockholders’ equity and the statement of comprehensive income as a component of accumulated other comprehensive income or loss. Held to maturity securities are recorded at amortized cost. Trading 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. Declines in the fair value of held-to-maturity and available-for-sale securities below their cost that are deemed to be other than temporary are reflected in earnings as realized losses or in other comprehensive income, depending on whether the Company intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss. If the Company intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the other-than-temporary impairment 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 entity will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the other-than-temporary impairment shall be separated into (a) the amount representing the credit loss and (b) the amount related to all other factors. The amount of the total other-than-temporary impairment related to the credit loss shall be recognized in earnings. The amount of the total other-than-temporary impairment related to other factors shall be recognized in other comprehensive income, net of applicable taxes. In estimating other-than-temporary impairment 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. Non-marketable equity securities are carried at cost. 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 (“FRB”) 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 FHLB stock. 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 interest in accordance with contractual terms is doubtful. 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 is improbable. For commercial loans, management considers specific facts and circumstances relative to individual credits in making such a determination. For consumer and residential 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 we will be unable to collect all principal and 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. 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 include the reduction of interest rates, forgiveness of all or a portion of principal or interest, or other modifications at interest rates that are less than the current market rate for new obligations with similar risk. 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. When the Company modifies a loan, management evaluates any possible impairment 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, instead of discounted cash flows. If management determines that the value of the modified loan is less than the recorded investment in the loan (net of previous charge-offs, deferred loan fees or costs and unamortized premium or discount), impairment is recognized by segment or class of loan as applicable, through an allowance estimate or a charge-off to the allowance. Segment and class status is determined by the loan’s classification at origination. 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 ASC 310-30, 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, 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 troubled debt restructurings as the pool, and not the individual loan, represents the unit of account. Allowance for Loan Losses The allowance for loan losses is the amount which, in the opinion of management, is necessary to absorb probable losses inherent in the 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 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 loans). The Company’s impaired loans 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 homogeneous non impaired 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, Allowance for Loan Loss and Credit Quality of Loans. Each segment has a distinct set of risk characteristics monitored by management. We further assess and monitor risk and performance at a more disaggregated level which includes our internal risk grading system for the commercial segments. We first apply historical loss rates 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 loss emergence period, or LEP. 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 ALL assumptions, we update our study of LEPs for each portfolio segment using our loan charge-off history. Another key assumption is the look-back period, or LBP, which represents the historical data period utilized to calculate loss rates. After consideration of the historic loss analysis, management applies additional qualitative adjustments so that the allowance for loan losses is reflective of the inherent losses that exist in the loan portfolio at the balance sheet date. Qualitative adjustments are made based upon 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 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. 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. Management believes that the allowance for loan losses is adequate. While management uses available information to recognize loan losses, future additions to the allowance for loan losses may be necessary 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. 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 other real estate owned, 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 at December 31, 2014 and 2013 was approximately $4.0 million and $2.9 million, respectively, and is recorded in Other Assets on the Consolidated Balance Sheet. Goodwill and Other Intangible Assets Goodwill and 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. Goodwill impairment tests are performed on an annual basis or when events or circumstances dictate. In these tests, the fair values of each reporting unit, or segment, is compared to the carrying amount of that reporting unit in order to determine if impairment is indicated. If so, the implied fair value of the reporting unit’s goodwill is compared to its carrying amount and the impairment loss is measured by the excess of the carrying value over fair value. 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. Stock-Based Compensation We maintain various long-term incentive stock benefit plans under which we grant stock options, restricted stock awards, and restricted stock units to certain directors and key employees. We recognize compensation expense in our income statement over the requisite service period, based on the grant-date fair value of the award. For restricted stock awards and units, we recognize compensation expense ratably over the vesting period for the fair value of the award, measured at the grant date. The fair values of options are estimated using the Black-Scholes option pricing model. The Company’s stock-based employee compensation plan is described in Note 14 “Stock-Based Compensation,” of this Report. Interest Rate Swaps The Bank offers interest rate swap agreements to its customers. These agreements allow the Bank’s customers to effectively fix the interest rate on a variable rate loan by entering into a separate agreement. Simultaneous with the execution of such an agreement with a customer, the Bank enters into a matching interest rate swap agreement with an unrelated third party provider, which allows the Bank to continue to receive the historical variable rate under the loan agreement with the customer. The agreement with the third party is not a hedge contract therefore changes in fair value are recorded through earnings. Assets and liabilities associated with the agreements are recorded in other assets and other liabilities on the balance sheet. Gains and losses are recorded as other noninterest income. The Bank is not subject to any fee or penalty should the customer elect to terminate the interest rate swap agreement prior to maturity. The Bank is exposed to credit loss equal to the fair value of the derivatives (not the notional amount of the derivatives) in the event of nonperformance by the counterparty to the interest rate swap agreements. Additionally, the Bank receives a fee from the customer that is recognized when the Bank has fulfilled its obligations under each agreement, which is generally upon execution of the agreement with the Bank’s customer. Since the terms of the thirty three interest rate swap agreements with the customers are identical to the related swaps with the third party, the income statement impact to the Bank is generally limited to the fees it receives from the customer. Other Financial Instruments The Company is a party to certain other financial instruments with off-balance-sheet risk such as commitments to extend credit, unused lines of credit, as well as certain mortgage 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 credit risk involved in issuing letters of credit is essentially the same as that 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 stand-by letters of credit is recorded upon inception. Loan Sales and Loan Servicing The Company originates and services residential mortgage loans for consumers and sells 15-year, 20-year and 30-year residential real estate mortgages in the secondary market when the interest rate environment is determined to be favorable by management, while retaining servicing rights on the sold loans. Loan sales are recorded when the sales are funded. Mortgage servicing rights are recorded at fair value upon sale of the loan. Loans held for sale are recorded at the lower of cost or market. 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 dealer or bank with whom each transaction is executed. The dealers or banks, 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. 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). Subsequent Events The Company has evaluated subsequent events for potential recognition and/or disclosure and there were none identified. Comprehensive Income At the Company, comprehensive income represents net income plus other comprehensive income (loss), which consists primarily of the net change in unrealized gains or losses on securities available for sale for the period and changes in the funded status of employee benefit plans. Accumulated other comprehensive (loss) income represents the net unrealized gains or losses on securities available for sale and the previously unrecognized portion of the funded status of employee benefit plans, net of income taxes, as of the consolidated balance sheet dates. Pension Costs The Company maintains a noncontributory, defined benefit pension plan covering substantially all employees, as well as supplemental employee retirement plans covering certain 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. 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. Fair Value Measurements 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 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. 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. 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.

Acquisitions	12 Months Ended
Acquisitions	Dec. 31, 2014
Acquisitions [Abstract]
Acquisitions	(2) Acquisitions Acquisition of Alliance Financial Corporation On March 8, 2013, the Company acquired Alliance Financial Corporation (“Alliance”), the parent company of Alliance Bank, N.A., for total consideration of $226 million. As part of the acquisition, Alliance was merged with and into the Company and Alliance Bank, with 26 branch locations in the central New York counties of Onondaga, Cortland, Madison, Oneida and Oswego, was merged with and into the Bank. The merger with Alliance enabled the Company to expand its footprint into demographically attractive and contiguous markets located in the aforementioned New York counties. Alliance operations were integrated into the Company and were included in the Consolidated Statements of Income from the date of acquisition. Other Goodwill Adjustments During the twelve months ended December 31, 2014, the Company recorded deferred tax adjustments totaling approximately ($1.0) million and valuation adjustments totaling ($0.4) related to the 2013 acquisition of Alliance resulting in a decrease in goodwill of approximately ($1.4) million in 2014. During the twelve months ended December 31, 2013, the Company recorded a deferred tax adjustment related to the 2012 acquisition of Hampshire First Bank resulting in a decrease in goodwill of approximately $(1.0) million. In addition, the Company recorded a goodwill adjustment of approximately $0.1 million related to the 2012 acquisition of a financial services company.

- Definition

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

+ References

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+ Details

Securities

12 Months Ended

Dec. 31, 2014

Securities [Abstract]

Securities

(3) Securities

The amortized cost, estimated fair value, and unrealized gains and losses of securities available for sale are as follows:

(In thousands)	Amortized cost		Unrealized gains		Unrealized losses		Estimated fair value
December 31, 2014
U.S. Treasury	$	23,041	$	70	$	-	$	23,111
Federal agency		332,193		327		2,606		329,914
State & municipal		37,035		587		52		37,570
Mortgage-backed:
Government-sponsored enterprises		339,190		7,597		224		346,563
U.S. government agency securities		17,367		863		66		18,164
Collateralized mortgage obligations:
Government-sponsored enterprises		199,837		1,828		234		201,431
U.S. government agency securities		40,237		497		36		40,698
Other securities		12,818		3,054		152		15,720
Total securities available for sale	$	1,001,718	$	14,823	$	3,370	$	1,013,171
December 31, 2013
U.S. Treasury	$	43,279	$	337	$	-	$	43,616
Federal agency		285,880		343		7,308		278,915
State & municipal		113,435		1,842		1,612		113,665
Mortgage-backed:
Government-sponsored enterprises		337,666		5,788		2,131		341,323
U.S. government securities		21,924		1,002		85		22,841
Collateralized mortgage obligations:
Government-sponsored enterprises		521,257		1,777		18,141		504,893
U.S. government securities		43,943		794		102		44,635
Other securities		12,367		2,854		228		14,993
Total securities available for sale	$	1,379,751	$	14,737	$	29,607	$	1,364,881

The following table sets forth information with regard to sales transactions of securities available for sale:

	Years ended December 31
(In thousands)	2014		2013		2012
Proceeds from sales	$	189	$	27,593	$	1,790
Gross realized gains	$	49	$	1,283	$	442
Gross realized losses		-		-		-
Net securities gains	$	49	$	1,283	$	442

In addition to gains (losses) from sales transactions, the Company also recorded gains from calls on securities available for sale of approximately $0.1 million for the year ended December 31, 2014, $0.1 million for the year ended December 31, 2013, and $0.2 million for the year ended December 31, 2012.

At December 31, 2014 and 2013, securities available for sale and held to maturity with amortized costs totaling $1.4 billion and $1.4 billion, respectively, were pledged to secure public deposits and for other purposes required or permitted by law. Additionally, at December 31, 2014, securities available for sale and held to maturity with an amortized cost of $208.8 million were pledged as collateral for securities sold under the repurchase agreements.

The amortized cost, estimated fair value, and unrealized gains and losses of securities held to maturity are as follows:

(In thousands)	Amortized cost		Unrealized gains		Unrealized losses		Estimated fair value
December 31, 2014
Mortgage-backed	$	755	$	113	$	-	$	868
Collateralized mortgage obligations		317,628		1,934		1,965		317,597
State & municipal		135,978		674		123		136,529
Total securities held to maturity	$	454,361	$	2,721	$	2,088	$	454,994
December 31, 2013
Mortgage-backed	$	953	$	128	$	-	$	1,081
Collateralized mortgage obligations		62,025		-		4,569		57,456
State & municipal		54,305		442		8		54,739
Total securities held to maturity	$	117,283	$	570	$	4,577	$	113,276

At December 31, 2014 and 2013, all of the mortgaged-backed securities held to maturity were comprised of U.S. government agency securities.

The following table sets forth information with regard to investment securities with unrealized losses at December 31, 2014 and 2013, 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
Security Type:	Fair Value		Unrealized losses			Number of Positions		Fair Value		Unrealized losses			Number of Positions		Fair Value		Unrealized losses			Number of Positions

December 31, 2014
Investment securities available for sale:
Federal agency	$	66,528	$	(226	)		8	$	198,151	$	(2,380	)		16	$	264,679	$	(2,606	)		24
State & municipal		8,818		(42	)		33		1,321		(10	)		5		10,139		(52	)		38
Mortgage-backed		10,400		(36	)		10		35,565		(254	)		31		45,965		(290	)		41
Collateralized mortgage obligations		57,682		(196	)		8		6,598		(74	)		4		64,280		(270	)		12
Other securities		-		-			-		3,201		(152	)		2		3,201		(152	)		2
Total securities with unrealized losses	$	143,428	$	(500	)		59	$	244,836	$	(2,870	)		58	$	388,264	$	(3,370	)		117

December 31, 2014
Investment securities held to maturity:
Collateralized mortgage obligations	$	26,052	$	(49	)		2	$	46,415	$	(1,916	)		4	$	72,467	$	(1,965	)		6
State & municipal		43,514		(116	)		110		1,619		(7	)		6		45,133		(123	)		116
Total securities with unrealized losses	$	69,566	$	(165	)		112	$	48,034	$	(1,923	)		10	$	117,600	$	(2,088	)		122

December 31, 2013
Investment securities available for sale:
Federal agency	$	233,935	$	(6,927	)		20	$	9,619	$	(381	)		1	$	243,554	$	(7,308	)		21
State & municipal		50,328		(1,612	)		177		-		-			-		50,328		(1,612	)		177
Mortgage-backed		143,080		(2,216	)		79		-		-			-		143,080		(2,216	)		79
Collateralized mortgage obligations		379,273		(18,243	)		36		-		-			-		379,273		(18,243	)		36
Other securities		5,490		(203	)		2		223		(25	)		1		5,713		(228	)		3
Total securities with unrealized losses	$	812,106	$	(29,201	)		314	$	9,842	$	(406	)		2	$	821,948	$	(29,607	)		316

December 31, 2013
Investment securities held to maturity:
Collateralized mortgage obligations	$	57,456	$	(4,569	)		5	$	-	$	-			-	$	57,456	$	(4,569	)		5
State & municipal		1,012		(8	)		1		-		-			-		1,012		(8	)		1
Total securities with unrealized losses	$	58,468	$	(4,577	)		6	$	-	$	-			-	$	58,468	$	(4,577	)		6

Management has the intent to hold the securities classified as held to maturity until they mature, at which time it is believed the Company will receive full value for the securities. Furthermore, as of December 31, 2014, management also had intent to hold, and will not be required to sell, the securities classified as available for sale for a period of time sufficient for a recovery of cost, which may be until maturity. The unrealized losses 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. The fair value is expected to recover as the bonds approach their maturity date or repricing date or if market yields for such investments decline. As of December 31, 2014, management believes the impairments detailed in the table above are temporary and no other-than-temporary impairment losses have been realized in the Company’s consolidated statements of income.

During 2014, the Company transferred approximately $340 million in securities from the available for sale portfolio to the held to maturity portfolio, which had unrealized losses at the time of transfer of approximately $8.3 million. This unrealized loss is amortized into interest income over the lives of the transferred securities.

The following tables set forth information with regard to contractual maturities of debt securities at December 31, 2014:

(In thousands)	Amortized cost		Estimated fair value
Debt securities classified as available for sale
Within one year	$	28,193	$	28,310
From one to five years		356,696		356,107
From five to ten years		160,816		163,924
After ten years		443,195		449,110
	$	988,900	$	997,451
Debt securities classified as held to maturity
Within one year	$	22,999	$	23,075
From one to five years		15,506		15,606
From five to ten years		87,326		87,640
After ten years		328,530		328,673
	$	454,361	$	454,994

Maturities of mortgage-backed, CMOs 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 securities, there were no holdings, when taken in the aggregate, of any single issuer that exceeded 10% of consolidated stockholders’ equity at December 31, 2014 and December 31, 2013.

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References + Details

Loans

12 Months Ended

Dec. 31, 2014

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)	2014		2013
Residential real estate mortgages	$	1,115,589	$	1,041,637
Commercial		839,770		859,026
Commercial real estate		1,442,989		1,328,313
Real estate construction and development		83,750		93,247
Agricultural and agricultural real estate mortgages		107,195		112,035
Consumer		1,436,382		1,352,638
Home equity		569,596		619,899
Total loans	$	5,595,271	$	5,406,795

Included in the above loans are net deferred loan origination costs totaling $35.6 million and $31.8 million at December 31, 2014 and 2013, respectively. The Company had residential loans held for sale totaling $3.2 million as of December 31, 2014 and $0.1 million as of December 31, 2013.

At December 31, 2014 and 2013, the Company serviced $23.4 million and $15.7 million, respectively, of agricultural loans sold with recourse. Due to sufficient collateral on these loans, no reserve is considered necessary at December 31, 2014 and 2013.

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

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)	2014			2013
Balance at January 1	$	3,372		$	2,790
New loans		522			569
Adjustment due to change in composition of related parties		253			376
Repayments		(571	)		(363	)
Balance at December 31	$	3,576		$	3,372

Allowance for Loan Losses and Credit Quality of Loans

12 Months Ended

Dec. 31, 2014

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

Allowance for Loan Losses and Credit Quality of Loans and Leases

(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 risk of probable losses inherent in the current loan portfolio. The adequacy of the allowance for loan losses is continuously monitored. It is assessed for adequacy using a methodology designed to ensure the level of the allowance reasonably reflects the loan portfolio’s risk profile. It is evaluated to ensure that it is sufficient to 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). Prior to 2013, separate disclosures for acquired loans were not significant and were included with originated loans in the Company’s asset quality disclosures. 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. The following table illustrates the portfolio and class segments for the Company’s loan portfolio:

Portfolio	Class
Commercial Loans	Commercial
	Commercial Real Estate
	Agricultural
	Agricultural Real Estate
	Business Banking

Consumer Loans	Indirect
	Home Equity
	Direct

Residential Real Estate Mortgages

COMMERCIAL LOANS

Commercial – The Company offers a variety of loan options to meet the specific needs of our commercial customers including term loans, time notes and lines of credit. Such loans are made available to businesses for working capital such as inventory and receivables, business expansion and equipment purchases. Generally, a collateral lien is placed on equipment or other assets owned by the borrower. These loans carry a higher risk than commercial real estate loans by the nature of the underlying collateral, which can be business assets such as equipment and accounts receivable and is generally less liquid than real estate. To reduce the risk, management also attempts to secure real estate as collateral and obtain personal guarantees of the borrowers.

Commercial Real Estate – The Company offers commercial real estate loans to finance real estate purchases, refinancings, expansions and improvements to commercial properties. Commercial real estate loans are made to finance the purchases of real property which generally consists of real estate with completed structures. These commercial real estate loans are secured by first liens on the real estate, which may include apartments, commercial structures, housing businesses, healthcare facilities, and other non owner-occupied facilities. These loans are typically less risky than commercial loans, since they are secured by real estate and buildings. 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.

Agricultural – The Company offers a variety of agricultural loans to meet the needs of our agricultural customers including term loans, time notes, and lines of credit. These loans are made to purchase livestock, purchase and modernize equipment, and finance seasonal crop expenses. Generally, a collateral lien is placed on the livestock, equipment, produce inventories, and/or receivables owned by the borrower. These loans may carry a higher risk than commercial and agricultural real estate loans due to the industry price volatility and the perishable nature of the underlying collateral. To reduce these risks, management may attempt to secure these loans with additional real estate collateral, obtain personal guarantees of the borrowers, or obtain government loan guarantees to provide further support.

Agricultural Real Estate – The Company offers real estate loans to our agricultural customers to finance farm related real estate purchases, refinancings, expansions, and improvements to agricultural properties. Agricultural real estate loans are made to finance the purchases and improvements of farm properties that generally consist of barns, production facilities, and land. The agricultural real estate loans are secured by first liens on the farm real estate. Because they are secured by land and buildings, these loans may be less risky than agricultural loans. 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 75% of the appraised value of the property. Government loan guarantees may be obtained to provide further support.

Business Banking - The Company offers a variety of loan options to meet the specific needs of our small business customers including term loans, small business mortgages and lines of credit. Such loans are generally less than $500 thousand 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 equipment or other assets owned by the borrower such as inventory and/or receivables. These loans carry a higher risk than commercial loans due to the smaller size of the borrower and lower levels of capital. To reduce the risk, the Company obtains personal guarantees of the owners for a majority of the loans.

CONSUMER LOANS

Indirect – The Company maintains relationships with many dealers primarily in the communities that we serve. Through these relationships, the company finances the purchases of automobiles and recreational vehicles (such as campers, boats, etc.) indirectly through dealer relationships. Approximately 70% of the indirect 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 consumer loans are underwritten on a secured basis using the underlying collateral being financed.

Home Equity – The Company offers fixed home equity loans as well as home equity lines of credit to consumers to finance home improvements, debt consolidation, education and other uses. Consumers are able to borrower up to 85% of the equity in their homes. The Company originates home equity lines of credit and second mortgage loans (loans secured by a second lien position on one-to-four-family residential real estate). These loans carry a higher risk than first mortgage residential loans as they are in a second position with respect to collateral. 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.

Direct – The Company offers a variety of consumer installment loans to finance vehicle purchases, mobile home purchases and personal expenditures. Most of these 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. The majority of consumer loans are underwritten on a secured basis using the underlying collateral being financed or a customer's deposit account. In addition to installment loans, the Company also offers personal lines of credit and overdraft protection. A minimal amount of loans are unsecured, which carry a higher risk of loss.

RESIDENTIAL REAL ESTATE LOANS

Residential real estate loans consist primarily of loans secured by first or second deeds of trust 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 owner-occupied properties located in the Company’s market area. When market conditions are favorable, for longer term, fixed-rate residential mortgages without escrow, the Company retains the servicing, but sells the right to receive principal and interest to Freddie Mac when market conditions are favorable. 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

Management considers the accounting policy relating to the allowance for loan losses to be a critical accounting policy given the inherent uncertainty in evaluating the levels of the allowance required to cover credit losses in the portfolio and the material effect that such judgments can have on the consolidated results of operations.

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

The following table illustrates the changes in the allowance for loan losses by portfolio segment for the years ended December 31, 2014, 2013 and 2012:

Allowance for Loan Losses

(in thousands)

	Commercial Loans			Consumer Loans			Residential Real Estate Mortgages			Unallocated			Total
Balance as of December 31, 2013	$	35,090		$	27,694		$	6,520		$	130		$	69,434
Charge-offs		(9,414	)		(16,642	)		(1,417	)		-			(27,473	)
Recoveries		1,774			2,800			285			-			4,859
Provision		4,983			12,868			1,742			(54	)		19,539
Ending Balance as of December 31, 2014	$	32,433		$	26,720		$	7,130		$	76		$	66,359

Balance as of December 31, 2012	$	35,624		$	27,162		$	6,252		$	296		$	69,334
Charge-offs		(10,459	)		(15,459	)		(1,771	)		-			(27,689	)
Recoveries		1,957			3,136			272			-			5,365
Provision		7,968			12,855			1,767			(166	)		22,424
Ending Balance as of December 31, 2013	$	35,090		$	27,694		$	6,520		$	130		$	69,434

Balance as of December 31, 2011	$	38,831		$	26,049		$	6,249		$	205		$	71,334
Charge-offs		(8,750	)		(15,848	)		(1,906	)		-			(26,504	)
Recoveries		1,641			2,556			38			-			4,235
Provision		3,902			14,405			1,871			91			20,269
Ending Balance as of December 31, 2012	$	35,624		$	27,162		$	6,252		$	296		$	69,334

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 acquisition of the loans, an allowance for loan losses would be established based on our estimate of future credit losses over the remaining life of the loans. As of December 31, 2014 the allowance for loan losses for the acquired loan portfolio totaled $0.5 million. There was no allowance for the acquired loan portfolio as of December 31, 2013. Net charge-offs related to acquired loans totaled approximately $4.8 million and $0.4 million during the years ended December 31, 2014 and December 31, 2013, respectively, and are included in the table above.

The following table illustrates the allowance for loan losses and the recorded investment by portfolio segment as of December 31, 2014 and 2013:

Allowance for Loan Losses and Recorded Investment in Loans

(in thousands)

	Commercial Loans		Consumer Loans		Residential Real Estate Mortgages		Unallocated		Total
As of December 31, 2014
Allowance for loan losses	$	32,433	$	26,720	$	7,130	$	76	$	66,359

Allowance for loans individually evaluated for impairment		1,100		-		-				1,100

Allowance for loans collectively evaluated for impairment	$	31,333	$	26,720	$	7,130	$	76	$	65,259


Ending balance of loans	$	2,473,702	$	2,005,980	$	1,115,589			$	5,595,271

Ending balance of originated loans individually evaluated for impairment		11,079		5,498		3,544				20,121
Ending balance of acquired loans individually evaluated for impairment		5,675		-		-				5,675
Ending balance of acquired loans collectively evaluated for impairment		327,656		147,256		266,747				741,659
Ending balance of originated loans collectively evaluated for impairment	$	2,129,292	$	1,853,226	$	845,298			$	4,827,816


As of December 31, 2013
Allowance for loan losses	$	35,090	$	27,694	$	6,520	$	130	$	69,434

Allowance for loans individually evaluated for impairment		715		-		-				715

Allowance for loans collectively evaluated for impairment	$	34,375	$	27,694	$	6,520	$	130	$	68,719


Ending balance of loans	$	2,392,621	$	1,972,537	$	1,041,637			$	5,406,795

Ending balance of originated loans individually evaluated for impairment		16,120		3,248		2,012				21,380
Ending balance of acquired loans individually evaluated for impairment		10,060		-		-				10,060
Ending balance of acquired loans collectively evaluated for impairment		392,329		219,587		308,416				920,332
Ending balance of originated loans collectively evaluated for impairment	$	1,974,112	$	1,749,702	$	731,209			$	4,455,023

The following table illustrates the Company’s nonaccrual loans by loan class as of December 31, 2014 and 2013:

(In thousands)	December 31, 2014		December 31, 2013
ORIGINATED
Commercial Loans
Commercial	$	1,012	$	3,669
Commercial Real Estate		4,127		7,834
Agricultural		817		1,135
Agricultural Real Estate		565		961
Business Banking		6,910		5,701
		13,431		19,300

Consumer Loans
Indirect		1,964		1,461
Home Equity		6,596		5,931
Direct		84		86
		8,644		7,478

Residential Real Estate Mortgages		8,770		7,105

	$	30,845	$	33,883

ACQUIRED
Commercial Loans
Commercial	$	3,009	$	6,599
Commercial Real Estate		2,666		3,559
Business Banking		665		1,340
		6,340		11,498

Consumer Loans
Indirect		106		93
Home Equity		557		570
Direct		33		49
		696		712

Residential Real Estate Mortgages		3,193		3,872

	$	10,229	$	16,082

TOTAL NONACCRUAL LOANS	$	41,074	$	49,965

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

Age Analysis of Past Due Financing Receivables

As of December 31, 2014

(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		Non-Accrual		Current		Recorded Total Loans
ORIGINATED
Commercial Loans
Commercial	$	-	$	735	$	-	$	735	$	1,012	$	613,400	$	615,147
Commercial Real Estate		192		-		-		192		4,127		1,064,549		1,068,868
Agricultural		-		-		-		-		817		32,130		32,947
Agricultural Real Estate		19		-		-		19		565		24,390		24,974
Business Banking		799		235		84		1,118		6,910		390,407		398,435
		1,010		970		84		2,064		13,431		2,124,876		2,140,371

Consumer Loans
Indirect		16,434		3,154		1,991		21,579		1,964		1,286,507		1,310,050
Home Equity		4,591		1,428		821		6,840		6,596		479,444		492,880
Direct		560		157		52		769		84		54,941		55,794
		21,585		4,739		2,864		29,188		8,644		1,820,892		1,858,724
Residential Real Estate Mortgages		2,901		96		1,256		4,253		8,770		835,819		848,842
	$	25,496	$	5,805	$	4,204	$	35,505	$	30,845	$	4,781,587	$	4,847,937


ACQUIRED
Commercial Loans
Commercial	$	-	$	-	$	-	$	-	$	3,009	$	72,255	$	75,264
Commercial Real Estate		-		-		-		-		2,666		197,222		199,888
Business Banking		5		15		-		20		665		57,494		58,179
		5		15		-		20		6,340		326,971		333,331

Consumer Loans
Indirect		518		5		54		577		106		64,540		65,223
Home Equity		190		60		5		255		557		75,904		76,716
Direct		31		-		7		38		33		5,246		5,317
		739		65		66		870		696		145,690		147,256
Residential Real Estate Mortgages		1,162		265		671		2,098		3,193		261,456		266,747
	$	1,906	$	345	$	737	$	2,988	$	10,229	$	734,117	$	747,334
Total Loans	$	27,402	$	6,150	$	4,941	$	38,493	$	41,074	$	5,515,704	$	5,595,271

Age Analysis of Past Due Financing Receivables

As of December 31, 2013

(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		Non-Accrual		Current		Recorded Total Loans
ORIGINATED
Commercial Loans
Commercial	$	105	$	247	$	-	$	352	$	3,669	$	612,402	$	616,423
Commercial Real Estate		1,366		-		-		1,366		7,834		925,116		934,316
Agricultural		150		21		-		171		1,135		63,856		65,162
Agricultural Real Estate		519		-		-		519		961		35,172		36,652
Business Banking		1,228		122		105		1,455		5,701		330,523		337,679
		3,368		390		105		3,863		19,300		1,967,069		1,990,232

Consumer Loans
Indirect		14,093		2,878		1,583		18,554		1,461		1,141,829		1,161,844
Home Equity		6,033		1,888		1,115		9,036		5,931		517,856		532,823
Direct		679		125		46		850		86		57,347		58,283
		20,805		4,891		2,744		28,440		7,478		1,717,032		1,752,950
Residential Real Estate Mortgages		3,951		379		808		5,138		7,105		720,978		733,221
	$	28,124	$	5,660	$	3,657	$	37,441	$	33,883	$	4,405,079	$	4,476,403


ACQUIRED
Commercial Loans
Commercial	$	24	$	-	$	-	$	24	$	6,599	$	96,603	$	103,226
Commercial Real Estate		-		-		-		-		3,559		225,455		229,014
Business Banking		320		2		-		322		1,340		68,487		70,149
		344		2		-		346		11,498		390,545		402,389

Consumer Loans
Indirect		939		113		71		1,123		93		123,870		125,086
Home Equity		753		63		-		816		570		85,690		87,076
Direct		76		56		9		141		49		7,235		7,425
		1,768		232		80		2,080		712		216,795		219,587
Residential Real Estate Mortgages		1,725		-		-		1,725		3,872		302,819		308,416
	$	3,837	$	234	$	80	$	4,151	$	16,082	$	910,159	$	930,392
Total Loans	$	31,961	$	5,894	$	3,737	$	41,592	$	49,965	$	5,315,238	$	5,406,795

There were no material commitments to extend further credit to borrowers with nonperforming 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 or below, with outstanding balances of $500 thousand or more are evaluated for impairment through the Company’s quarterly status review process. In determining that we will be unable to collect all principal and 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 evaluated for impairment, 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 measurement of impairment. For impaired loans measured using the present value of expected cash flow method, any change to the previously recognized impairment loss is recognized as a change to the allowance account and recorded in the consolidated statement of income as a component of the provision for credit losses.

The following provides additional information on loans specifically evaluated for impairment for the years ended December 31, 2014 and 2013

Impaired Loans

	December 31, 2014							December 31, 2013
(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
Commercial	$	1,748	$	1,901				$	4,721	$	4,777
Commercial Real Estate		4,505		4,520					4,613		5,164
Agricultural		20		26					125		195
Agricultural Real Estate		1,147		1,441					1,431		1,708
Business Banking		896		1,301					210		602
Total Commercial Loans		8,316		9,189					11,100		12,446

Consumer Loans
Home Equity		5,498		6,033					3,248		3,472

Residential Real Estate Mortgages		3,544		3,959					2,012		2,255
Total		17,358		19,181					16,360		18,173

With an allowance recorded:
Commercial Loans
Commercial Real Estate		2,763		4,611			600		5,020		6,877			715

ACQUIRED
With no related allowance recorded:
Commercial Loans
Commercial		-		-					6,501		6,538
Commercial Real Estate		2,666		3,830					3,559		3,842
Total Commercial Loans		2,666		3,830					10,060		10,380

With an allowance recorded:
Commercial Loans
Commercial		3,009		4,668			500		-		-			-

Total	$	25,796	$	32,290		$	1,100	$	31,440	$	35,430		$	715

The following table summarizes the average recorded investments on loans specifically evaluated for impairment and the interest income recognized for the years ended December 31, 2014, 2013 and 2012:

	December 31, 2014				December 31, 2013				December 31, 2012
(in thousands)	Average Recorded Investment		Interest Income Recognized Accrual		Average Recorded Investment		Interest Income Recognized Accrual		Average Recorded Investment		Interest Income Recognized Accrual
ORIGINATED
Commercial Loans
Commercial	$	1,954	$	115	$	3,488	$	-	$	6,682	$	56
Commercial Real Estate		9,679		169		11,085		95		4,944		230
Agricultural		91		1		1,035		1		1,767		43
Agricultural Real Estate		1,346		46		1,067		47		922		72
Business Banking		610		55		127		61		68		65
Consumer Loans
Home Equity		5,198		267		3,120		145		1,877		123
Residential Real Estate Mortgages		3,039		119		2,085		69		1,143		54
ACQUIRED
Commercial Loans
Commercial		5,756		-		-		-		-		-
Commercial Real Estate		3,386		-		1,310		-		-		-
Total	$	31,059	$	772	$	23,317	$	418	$	17,403	$	643

While we continue to adhere to prudent underwriting standards, as a lender we may be adversely impacted by general economic weaknesses and, in particular, a sharp downturn in the housing market nationally. Decreases in real estate values could adversely affect the value of property used as collateral for our loans. Adverse changes in the economy may have a negative effect on the ability of our borrowers to make timely loan payments, which would have an adverse impact on our earnings. A further increase in loan delinquencies would decrease our net interest income and adversely impact our loan loss experience, causing increases in our provision and allowance for loan losses.

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

Commercial Grading System

For commercial and agricultural loans, the Company uses a grading system that relies on quantifiable and measurable characteristics when available. This would include 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. The grading system for commercial and agricultural loans is as follows:

●

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 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. Because of high probability of loss, nonaccrual treatment is required for doubtful assets.

●

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 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 (declining revenues or margins) or may be struggling with an ill-proportioned balance sheet (e.g., 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 high probability of total or 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. When the likelihood of full collection of interest and principal may be in doubt; classified loans are considered to have a nonaccrual status. In some cases, classified loans are considered uncollectible 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. Non-classified loans are in compliance with loan covenants, and payments are generally made as agreed.

Consumer and Residential Mortgage Grading System

Consumer and Residential Mortgage loans are graded as either Performing or Nonperforming. Nonperforming loans are loans that are 1) over 90 days past due and interest is still accruing or 2) on nonaccrual status. All loans not meeting any of these three criteria are considered Performing.

The following tables illustrate the Company’s credit quality by loan class for the years ended December 31, 2014 and 2013:

Credit Quality Indicators

December 31, 2014

(In thousands)
ORIGINATED
Commercial Credit Exposure
By Internally Assigned Grade:	Commercial		Commercial Real Estate		Agricultural		Agricultural Real Estate		Total
Pass	$	$570,884	$	1,023,856	$	30,481	$	23,443	$	1,648,664
Special Mention		6,022		17,341		275		42		23,680
Substandard		38,241		27,671		2,183		1,489		69,584
Doubtful		-		-		8		-		8
Total	$	615,147	$	1,068,868	$	32,947	$	24,974	$	1,741,936

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking						Total
Non-classified	$	379,445					$	379,445
Classified		18,990						18,990
Total	$	398,435					$	398,435

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct		Total
Performing	$	1,306,095	$	485,463	$	55,658	$	1,847,216
Nonperforming		3,955		7,417		136		11,508
Total	$	1,310,050	$	492,880	$	55,794	$	1,858,724

Residential Mortgage Credit Exposure
By Payment Activity:	Residential Mortgage		Total
Performing	$	838,816	$	838,816
Nonperforming		10,026		10,026
Total	$	848,842	$	848,842

Credit Quality Indicators

December 31, 2014

(In thousands)

ACQUIRED
Commercial Credit Exposure
By Internally Assigned Grade:	Commercial		Commercial Real Estate		Agricultural		Total
Pass	$	63,630	$	186,036	$	-	$	249,666
Special Mention		2,840		2,646		-		5,486
Substandard		8,794		11,206		-		20,000
Doubtful		-		-		-		-
Total	$	75,264	$	199,888	$	-	$	275,152

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking		Total
Non-classified	$	53,264	$	53,264
Classified		4,915		4,915
Total	$	58,179	$	58,179

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct		Total
Performing	$	65,063	$	76,154	$	5,277	$	146,494
Nonperforming		160		562		40		762
Total	$	65,223	$	76,716	$	5,317	$	147,256

Residential Mortgage Credit Exposure
By Payment Activity:	Residential Mortgage		Total
Performing	$	262,883	$	262,883
Nonperforming		3,864		3,864
Total	$	266,747	$	266,747

Credit Quality Indicators

December 31, 2013

(In thousands)

Commercial Credit Exposure
By Internally Assigned Grade:	Commercial		Commercial Real Estate		Agricultural		Agricultural Real Estate		Total
Pass	$	576,079	$	878,411	$	60,043	$	33,136	$	1,547,669
Special Mention		16,836		22,777		381		43		40,037
Substandard		23,508		33,128		4,726		3,473		64,835
Doubtful		-		-		12		-		12
Total	$	616,423	$	934,316	$	65,162	$	36,652	$	1,652,553

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking						Total
Non-classified	$	319,578					$	319,578
Classified		18,101						18,101
Total	$	337,679					$	337,679

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct		Total
Performing	$	1,158,800	$	525,777	$	58,151	$	1,742,728
Nonperforming		3,044		7,046		132		10,222
Total	$	1,161,844	$	532,823	$	58,283	$	1,752,950

Residential Mortgage Credit Exposure
By Payment Activity:	Residential Mortgage		Total
Performing	$	725,308	$	725,308
Nonperforming		7,913		7,913
Total	$	733,221	$	733,221

Credit Quality Indicators

December 31, 2013

(In thousands)

ACQUIRED
Commercial Credit Exposure
By Internally Assigned Grade:	Commercial		Commercial Real Estate		Agricultural		Total
Pass	$	85,692	$	205,010	$	-	$	290,702
Special Mention		2,230		6,183		-		8,413
Substandard		15,304		17,821		-		33,125
Doubtful		-		-		-		-
Total	$	103,226	$	229,014	$	-	$	332,240

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking		Total
Non-classified	$	65,437	$	65,437
Classified		4,712		4,712
Total	$	70,149	$	70,149

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct		Total
Performing	$	124,922	$	86,506	$	7,367	$	218,795
Nonperforming		164		570		58		792
Total	$	125,086	$	87,076	$	7,425	$	219,587

Residential Mortgage Credit Exposure
By Payment Activity:	Residential Mortgage		Total
Performing	$	304,544	$	304,544
Nonperforming		3,872		3,872
Total	$	308,416	$	308,416

Troubled Debt Restructuring

Troubled debt restructurings made during the year ended December 31, 2014 consisted of three business banking loans totaling $0.9 million, 9 home equity loans totaling $0.3 million, one indirect consumer loan totaling less than $0.1 million, 47 direct consumer loans totaling $3.0 million and 27 residential real estate mortgages totaling $2.7 million. During the year ended December 31, 2014, there was one indirect consumer loan classified as TDRs totaling less than $0.1 million, one home equity loan classified as a TDR totaling less than $0.1 million, 5 direct consumer loans classified as TDRs totaling $0.2 million, and six residential real estate mortgages classified as TDRs totaling $0.4 million that subsequently defaulted on their renegotiated terms.

Troubled debt restructurings made during the year ended December 31, 2013 consisted of four commercial loans totaling $7.0 million, 23 home equity loans totaling $1.0 million, and six residential real estate mortgages totaling $0.5 million. During the year ended December 31, 2013, there was one commercial loan classified as a TDR totaling $0.9 million and eight home equity loans classified as TDRs totaling $0.4 million that subsequently defaulted on their renegotiated terms.

Substantially all modifications 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.

Premises and Equipment, Net

12 Months Ended

Dec. 31, 2014

Premises and Equipment, Net [Abstract]

Premises and Equipment, Net

(6) Premises and Equipment, Net

A summary of premises and equipment follows:

	December 31,
(In thousands)	2014		2013
Land, buildings, and improvements	$	122,400	$	120,098
Equipment		58,835		55,729
Premises and equipment before accumulated depreciation		181,235		175,827
Accumulated depreciation		91,977		87,500
Total premises and equipment	$	89,258	$	88,327

Buildings and improvements are depreciated based on useful lives of 15 to 40 years. Equipment is depreciated based on useful lives of three to ten years.

Rental expense included in occupancy expense amounted to $8.0 million in 2014, $7.5 million in 2013, and $6.4 million in 2012. The future minimum rental payments related to noncancelable operating leases with original terms of one year or more are as follows at December 31, 2014 (in thousands):

Future Minimum Rental Payments

2015	$	7,369
2016		7,215
2017		6,811
2018		6,122
2019		5,655
Thereafter		26,257
Total	$	59,429

Goodwill and other Intangible Assets

12 Months Ended

Dec. 31, 2014

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, 2014	$	264,997
Goodwill Adjustments		(1,363	)
December 31, 2014	$	263,634

January 1, 2013	$	152,373
Goodwill Acquired		112,624
December 31, 2013	$	264,997

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 twelve years.

A summary of core deposit and other intangible assets follows:

	December 31,
(In thousands)	2014		2013
Core deposit intangibles
Gross carrying amount	$	19,401	$	19,401
Less: accumulated amortization		12,522		10,083
Net carrying amount		6,879		9,318

Identified intangible assets
Gross carrying amount		28,316		28,509
Less: accumulated amortization		14,878		12,270
Net carrying amount		13,438		16,239

Total intangibles
Gross carrying amount		47,717		47,910
Less: accumulated amortization		27,400		22,353
Net carrying amount	$	20,317	$	25,557

Amortization expense on intangible assets with definite useful lives totaled $5.0 million for 2014, $4.9 million for 2013 and $3.4 million for 2012. Amortization expense on intangible assets with definite useful lives is expected to total $4.8 million for 2015, $3.3 million for 2016, $2.8 million for 2017, $2.2 million for 2018, $1.7 million for 2019 and $3.7million thereafter. Other identified intangible assets include customer lists, non-competes, and trademark intangibles, of which $1.8 million will not amortize.

- Definition

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

+ References + Details

Deposits

12 Months Ended

Dec. 31, 2014

Deposits [Abstract]

Deposits

(8) Deposits

The following table sets forth the maturity distribution of time deposits at December 31, 2014 (in thousands):

Time deposits
Within one year	$	464,853
After one but within two years		132,999
After two but within three years		143,142
After three but within four years		80,804
After four but within five years		204,492
After five years		17,533
Total	$	1,043,823

Time deposits of $100,000 or more aggregated $269.8 million and $375.4 million December 31, 2014 and 2013, respectively.

Short-Term Borrowings

12 Months Ended

Dec. 31, 2014

Short-Term Borrowings [Abstract]

Short-Term Borrowings

(9) Short-Term Borrowings

Short-term borrowings totaled $316.8 million and $456.0 million at December 31, 2014 and 2013, 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 had unused lines of credit with the FHLB available for short-term financing of approximately $958 million and $497 million at December 31, 2014 and 2013, respectively. Borrowings on these 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:

(In thousands)	2014			2013			2012
Federal funds purchased
Balance at year-end	$	68,000		$	130,000		$	10,000
Average during the year		110,154			39,907			12,658
Maximum month end balance		183,000			130,000			60,000
Weighted average rate during the year		0.29	%		0.26	%		0.27	%
Weighted average rate at December 31		0.34	%		0.18	%		0.27	%

Securities sold under repurchase agreements
Balance at year-end	$	148,802		$	176,042		$	152,941
Average during the year		165,858			169,352			153,084
Maximum month end balance		182,861			185,871			165,977
Weighted average rate during the year		0.06	%		0.06	%		0.10	%
Weighted average rate at December 31		0.06	%		0.05	%		0.10	%

Other short-term borrowings
Balance at year-end	$	100,000		$	150,000		$	-
Average during the year		106,438			71,589			-
Maximum month end balance		320,000			210,000			-
Weighted average rate during the year		0.40	%		0.43	%		0.00	%
Weighted average rate at December 31		0.36	%		0.55	%		0.00	%

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

Long-Term Debt

12 Months Ended

Dec. 31, 2014

Long-Term Debt [Abstract]

Long-Term Debt

(10) 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, certain of its mortgage-backed securities and a blanket lien on its residential real estate mortgage loans. A summary as of December 31, 2014 and 2013 is as follows:

(In thousands)	As of December 31, 2014										As of December 31, 2013
Maturity	Amount		Weighted Average Rate			Callable Amount		Weighted Average Rate			Amount		Weighted Average Rate			Callable Amount		Weighted Average Rate
2014		-		-			-		-			12,460		1.33	%		-		-
2015		217		-			-		-			308		-			-		-
2016		50,626		2.91	%		30,000		4.15	%		90,313		3.52	%		70,000		4.21	%
2017		40,000		2.68	%		25,000		3.48	%		115,312		3.55	%		75,000		3.73	%
2018		40,000		2.57	%		25,000		3.15	%		90,313		3.26	%		75,000		3.61	%
2021		102		4.00	%		-		-			117		4.00	%		-		-
	$	130,945				$	80,000				$	308,823				$	220,000

Junior Subordinated Debt

12 Months Ended

Dec. 31, 2014

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. The trusts were formed for the purpose of issuing company-obligated mandatorily redeemable 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. The debentures held by each trust are the sole assets of that trust. These five statutory business trusts are collectively referred herein to as “the Trusts.” 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 variable interest entities (“VIEs”) for which the Company is not the primary beneficiary, as defined by U.S. GAAP. In accordance with U.S. GAAP, the accounts of the Trusts are not included in the Company’s consolidated financial statements. See Note 1 — Summary of Significant Accounting Policies for additional information about the Company’s consolidation policy.

As of December 31, 2014, the Trusts had the following issues of trust preferred debentures, all held by the Trusts, outstanding (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 include amounts related to the Company’s NBT Statutory Trust I and II as well as junior subordinated debentures associated with one statutory trust affiliates that were acquired from our merger with CNB Financial Corp. and two statutory trusts acquired from Alliance (the “Trusts”). The Trusts qualify as variable interest entities and were formed to issue mandatorily redeemable trust preferred securities to investors and loan the proceeds to us for general corporate purposes. The Trusts hold, as their sole assets, junior subordinated debentures of the Company with face amounts totaling $98 million at December 31, 2014. The Company owns all of the common securities of the Trusts and have accordingly recorded $3.2 million in equity method investments classified as other assets in our Consolidated Balance Sheets at December 31, 2014. 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.

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 Act 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.

Income Taxes

12 Months Ended

Dec. 31, 2014

Income Taxes [Abstract]

Income Taxes

(12) Income Taxes

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

	Years ended December 31,
(In thousands)	2014		2013		2012
Current
Federal	$	26,059	$	23,536	$	21,011
State		2,823		2,316		1,815
		28,882		25,852		22,826

Deferred
Federal		6,648		2,334		(13	)
State		1,699		10		3
		8,347		2,344		(10	)
Total income tax expense	$	37,229	$	28,196	$	22,816

Not included in the above table are items that were recorded to stockholders’ equity of approximately $(1.1) million, $7.0 million, and $(0.1) million for 2014, 2013, and 2012, respectively, relating to deferred taxes on the unrealized (gain) loss on available for sale securities, tax benefits recognized with respect to stock options exercised, and deferred taxes related to pension plans.

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)	2014			2013
Deferred tax assets
Allowance for loan losses	$	25,689		$	26,729
Deferred compensation		8,744			7,931
Postretirement benefit obligation		2,377			2,596
Unrealized losses on securities available for sale		-			5,900
Accrued liabilities		1,778			3,265
Stock-based compensation expense		6,457			7,862
Equipment leasing		1,416			1,661
Other		1,325			2,125
Total deferred tax assets		47,786			58,069
Deferred tax liabilities
Pension and executive retirement		12,192			17,417
Fair value adjustments from acquisitions		1,243			2,070
Unrealized gains on securities available for sale		1,331			-
Premises and equipment, primarily due to accelerated depreciation		2,491			2,270
Deferred loan costs		1,460			1,624
Intangible amortization		14,162			12,007
Other		390			892
Total deferred tax liabilities		33,269			36,280
Net deferred tax asset at year-end		14,517			21,789
Net deferred tax asset at beginning of year		21,789			11,115
(Decrease) Increase in net deferred tax asset	$	(7,272	)	$	10,674

Realization of deferred tax assets is dependent upon the generation of future taxable income or the existence of sufficient taxable income within the available carryback period. A valuation allowance is provided 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, 2014 and 2013.

At December 31, 2014, 2013, and 2012 the Company had no ASC 740-10 unrecognized tax benefits. The Company does not expect the total amount of unrecognized tax benefits to significantly increase within the next twelve months. During 2012 there was a reduction of reserves for Federal tax benefits for expiration of the statute of limitations of prior years’ tax filings. As a result, unrecognized tax benefits were reduced $0.9 million for 2012 with a reduction of tax expense of $0.8 million in 2012.

The Company is no longer subject to U.S. Federal tax examination by tax authorities for years prior to 2010 and New York State for years prior to 2010. The Company recognizes interest expense penalties related to unrecognized tax benefits, if any, in income tax expense.

The following is a reconciliation of the provision for income taxes to the amount computed by applying the applicable Federal statutory rate of 35 % to income before taxes:

	Years ended December 31
(In thousands)	2014			2013			2012
Federal income tax at statutory rate	$	39,306		$	31,482		$	27,081
Tax exempt income		(2,250	)		(2,433	)		(2,536	)
Net increase in CSV of life insurance		(1,734	)		(1,166	)		(908	)
Low income housing tax credits		(880	)		(819	)		(629	)
State taxes, net of federal tax benefit		2,939			1,512			1,182
Other, net		(152	)		(380	)		(1,374	)
Income tax expense	$	37,229		$	28,196		$	22,816

Employee Benefit Plans

12 Months Ended

Dec. 31, 2014

Employee Benefit Plans [Abstract]

Employee Benefit Plans

(13) Employee Benefit Plans

Defined Benefit Postretirement Plans

The Company has a qualified, noncontributory, defined benefit pension plan (“the Plan”) covering substantially all of its employees at December 31, 2014. 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 pension plan in accordance with ERISA standards. Assets of the plan are invested in bonds and 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 pension 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.

The Company assumed a noncontributory, defined benefit pension plan in the Alliance acquisition. This plan covers certain Alliance full-time employees who met eligibility requirements on October 6, 2006, at which time all benefits were frozen. Under this plan, retirement benefits are primarily a function of both the years of service and the level of compensation. Effective May 1, 2013, this plan was merged into the Plan. The merging of the plans required a valuation as of the merger date and resulted in a $2.4 million adjustment to accumulated other comprehensive income in 2013. The merging of the plans did not have a significant impact on the Company’s financial statements and related footnotes.

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 current and former executives in the Alliance acquisition.

The supplemental employee retirement plans and the defined benefit pension plan are collectively referred to herein as “Pension Benefits.”

Also, the Company provides certain health care benefits for retired employees. Benefits are accrued over the employees’ active service period. Only employees that were employed by NBT Bank on or before January 1, 2000 are eligible to receive postretirement 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 postretirement 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 postretirement benefits are referred to herein as “Other Benefits.”

Accounting standards require an employer to: (1) recognize the overfunded or underfunded status of defined benefit postretirement 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 accumulated other comprehensive loss, which have not yet been recognized as components of net periodic benefit cost, related to pensions and other postretirement benefits at December 31, 2014 are summarized below.

The Company expects that $2.4 million in net actuarial loss and $0.2 million in prior service costs will be recognized as components of net periodic benefit cost in 2015.

	Pension Benefits						Other Benefits
(In thousands)	2014			2013			2014				2013
Net actuarial loss		$	28,767		$	11,286		$	2,929			$	1,628
Prior service cost			97			118			(314	)			(521	)
Total amounts recognized in accumulated other comprehensive loss (pre-tax)		$	28,864		$	11,404		$	2,615			$	1,107

A December 31 measurement date is used for the pension, supplemental pension and postretirement 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 postretirement benefits:

	Pension Benefits						Other Benefits
(In thousands)	2014			2013			2014			2013
Change in benefit obligation
Benefit obligation at beginning of year	$	85,667		$	85,130		$	7,428		$	4,071
Service cost		2,290			2,493			16			23
Interest cost		4,142			3,223			347			286
Plan participants' contributions		-			-			266			269
Actuarial(gain) loss		12,501			(10,853	)		1,452			(369	)
Amendments		-			-			-			(54	)
Acquisition		-			10,958			-			3,928
Benefits paid		(6,044	)		(5,284	)		(799	)		(726	)
Projected benefit obligation at end of year		98,556			85,667			8,710			7,428
Change in plan assets
Fair value of plan assets at beginning of year		118,574			99,705			-			-
Actual return on plan assets		3,950			18,451			-			-
Acquisition		-			4,994			-			-
Employer contributions		752			708			533			457
Plan participants' contributions		-			-			266			269
Benefits paid		(6,044	)		(5,284	)		(799	)		(726	)
Fair value of plan assets at end of year		117,232			118,574			-			-

Funded status at year end	$	18,676		$	32,907		$	(8,710	)	$	(7,428	)

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 $98.6 million and $85.7 million at December 31, 2014 and 2013, respectively. The accumulated benefit obligation for other postretirement benefits was $8.7 million and $7.4 million at December 31, 2014 and 2013, respectively. The funded status of the pension and other postretirement benefit plans has been recognized as follows in the consolidated balance sheets at December 31, 2014 and 2013.

	Pension Benefits								Other Benefits
(In thousands)	2014				2013				2014				2013
Other assets		$	39,044			$	48,189			$	-			$	-
Other liabilities			(20,368	)			(15,282	)			(8,710	)			(7,428	)
Funded status		$	18,676			$	32,907			$	(8,710	)		$	(7,428	)

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

	Years ended December 31,
	2014			2013			2012
Weighted average assumptions:
The following assumptions were used to determine benefit obligations:
Discount rate		4.19% - 4.30	%		4.90%-5.05	%		3.50	%
Expected long-term return on plan assets		7.50	%		7.50	%		7.50	%
Rate of compensation increase		3.00%-3.75	%		3.00	%		3.00	%

The following assumptions were used to determine net periodic pension cost:
Discount rate		4.90%-5.05	%		3.50	%		4.10	%
Expected long-term return on plan assets		7.50	%		7.50	%		7.50	%
Rate of compensation increase		3.00%-3.75	%		3.00	%		3.00	%

Net periodic benefit cost and other amounts recognized in other comprehensive income (loss) for the years ended December 31 included the following components:

	Pension Benefits									Other Benefits
(In thousands)	2014			2013			2012			2014			2013			2012
Components of net periodic benefit cost
Service cost	$	2,290		$	2,493		$	3,122		$	16		$	23		$	20
Interest cost		4,142			3,223			3,145			347			286			155
Expected return on plan assets		(8,681	)		(7,804	)		(6,686	)		-			-			-
Amortization of prior service cost		23			23			283			(206	)		(205	)		(202	)
Amortization of unrecognized net loss		79			2,692			3,330			151			280			182
Net periodic pension cost	$	(2,147	)	$	627		$	3,194		$	308		$	384		$	155

Other changes in plan assets and benefit obligations recognized in other comprehensive income (pre-tax)
Net loss (gain)	$	17,233		$	(21,500	)	$	894		$	1,452		$	(369	)	$	136
Prior service cost		-			-			(1,006	)		-			(54	)		-
Amortization of prior service cost		(23	)		(23	)		(283	)		206			205			202
Amortization of unrecognized net gain		(79	)		(2,692	)		(3,330	)		(151	)		(280	)		(182	)
Total recognized in other comprehensive loss (income)		17,131			(24,215	)		(3,725	)		1,507			(498	)		156

Total recognized in net periodic benefit cost and other comprehensive income (loss) - pre-tax	$	14,984		$	(23,588	)	$	(531	)	$	1,815		$	(114	)	$	311

The following table sets forth estimated future benefit payments for the pension plans and other postretirement benefit plans:

(In thousands)	Pension Benefits		Other Benefits
2015		6,011		538
2016		6,221		549
2017		9,473		571
2018		7,100		592
2019		6,953		578
2020 - 2024		40,351		2,881

The Company is not required to make contributions to the defined benefit plan in 2015.

For measurement purposes, the annual rates of increase in the per capita cost of covered medical and prescription drug benefits for fiscal year 2014 were assumed to be 7.0 to 9.0 percent. The rates were assumed to decrease gradually to 3.9 percent 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, 2014:

(In thousands)	One Percentage point increase		One Percentage point decrease
Increase (decrease) on total service and interest cost components	$	39	$	(33	)
Increase (decrease) on postretirement accumulated benefit obligation		895		(764	)

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 2014			2014			2013
Cash and cash equivalents		0 - 20	%		4	%		6	%
Fixed income securities		20 - 40	%		38	%		27	%
Equities		40 - 80	%		58	%		67	%
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, 2014 and 2013 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 as of December 31, 2014 and 2013:

(In thousands)	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Balance as of December 31, 2014
Cash and cash equivalents	$	4,423	$	-	$	4,423
Foreign equity mutual funds		38,581		-		38,581
Equity mutual funds		29,718		-		29,718
U.S. government bonds		-		4,420		4,420
Corporate bonds		-		40,090		40,090
Totals	$	72,722	$	44,510	$	117,232

(In thousands)	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Balance as of December 31, 2013
Cash and cash equivalents	$	7,533	$	-	$	7,533
Foreign equity mutual funds		15,653		-		15,653
Equity mutual funds		16,727		-		16,727
U.S. government bonds		-		9,355		9,355
Corporate bonds		-		19,665		19,665
Common stock		44,532		-		44,532
Municipal bonds and notes		-		1,451		1,451
Foreign bonds and notes		-		1,392		1,392
Foreign equity		2,266		-		2,266
Totals	$	86,711	$	31,863	$	118,574

The plan had no financial instruments recorded at fair value on a nonrecurring basis as of December 31, 2014.

Determination of Assumed Rate of Return

The expected long-term rate-of-return on assets was 7.5% at December 31, 2014 and December 31, 2013. 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 $2.2 million in 2014, $2.1 million in 2013, and $1.8 million in 2012.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2014

Stock-Based Compensation [Abstract]

Stock-Based Compensation

(14) Stock-Based Compensation

In April 2008, the Company adopted the NBT Bancorp Inc. 2008 Omnibus Incentive Plan (the “Plan”). Under the terms of the Plan, options and other equity-based awards are granted to directors and employees to increase their direct proprietary interest in the operations and success of the Company. The Plan assumed all prior equity-based incentive plans and any new equity-based awards are granted under the terms of the Plan. Under terms of the 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. Options granted have a vesting period of four years and terminate ten years from 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. Restricted shares granted under the Plan vest after five years for employees and three years for non-employee directors. Restricted stock units granted under the Plan may have different terms and conditions. Performance shares and units granted under the 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.

The following table summarizes information concerning stock options outstanding at December 31, 2014:

	Number of Shares			Weighted average exercise price		Weighted Average Remaining Contractual Term (in yrs)		Aggregate Intrinsic Value
Outstanding at January 1, 2014		1,341,500		$	22.98
Granted		3,296			24.80
Exercised		(290,243	)		22.58
Forfeited		(105	)		20.19
Expired		(16,106	)		22.36
Outstanding at December 31, 2014		1,038,342		$	23.10		3.40		$	3,353,951

Exercisable at December 31, 2014		1,031,726		$	23.09		3.37		$	3,342,258

Expected to Vest		5,249		$	24.50		7.32		$	9,354

Total stock-based compensation expense for stock option awards totaled $0.1 million, $0.2 million, and $0.5 million for the years ended December 31, 2014, 2013, and 2012, respectively. Cash proceeds, tax benefits and intrinsic value related to total stock options exercised is as follows:

	Years ended December 31,
(dollars in thousands)	2014		2013		2012
Proceeds from stock options exercised	$	6,554	$	7,927	$	1,908
Tax benefits related to stock options exercised		313		178		8
Intrinsic value of stock options exercised		789		905		498
Fair value of shares vested during the year		393		766		1,656

The Company has outstanding restricted and deferred stock awards granted from various plans at December 31, 2014. The Company recognized $4.2 million, $3.8 million, and $3.7 million in stock-based compensation expense related to these stock awards for the years ended December 31, 2014, 2013, and 2012, respectively. Tax benefits recognized with respect to restricted stock awards and stock units were $2.9 million, $2.4 million and $1.5 million for the years ended December 31, 2014, 2013 and 2012, respectively. Unrecognized compensation cost related to restricted stock awards and stock units totaled $4.4 million at December 31, 2014 and will be recognized over 1.7 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 awards outstanding as of December 31, 2014:

	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested Restricted Stock Awards
Unvested at January 1, 2014		66,650		$	23.15
Forfeited		-			-
Vested		(14,650	)		22.16
Unvested at December 31, 2014		52,000		$	23.43

The following table summarizes information for unvested restricted stock units outstanding as of December 31, 2014:

	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested Restricted Stock Units
Unvested at January 1, 2014		539,850		$	27.36
Forfeited		(5,090	)		-
Vested		(105,013	)		-
Granted		209,228			24.11
Unvested at December 31, 2014		638,975		$	31.01

The Company has 3.8 million securities remaining available to be granted as part of the Plan at December 31, 2014.

Stockholders Equity

12 Months Ended

Dec. 31, 2014

Stockholders Equity [Abstract]

Stockholders Equity

(15) Stockholders’ Equity

In accordance with accounting standards, unrealized gains on available for sale securities and unrecognized actuarial gains or losses and prior service costs associated with the Company’s pension and postretirement benefit plans are included in accumulated other comprehensive loss, net of tax. For the years ended December 31, components of accumulated other comprehensive loss are:

(In thousands)	2014			2013
Unrecognized prior service cost and net actuarial loss on pension plans	$	(19,181	)	$	(7,785	)
Unrealized net holding gains (losses) on available for sale securities		2,154			(8,980	)
Accumulated other comprehensive loss	$	(17,027	)	$	(16,765	)

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 (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, 2014, approximately $88.7 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.

Under a previously disclosed stock repurchase plan, the Company purchased 3,288 shares of its common stock during the twelve month period ended December 31, 2014, for a total of $0.1 million at an average price of $22.02 per share. This plan expired on December 31, 2014. On October 27, 2014, the NBT Board of Directors authorized a new repurchase program for NBT to repurchase up to an additional 1,000,000 shares of its outstanding common stock. This plan expires on December 31, 2016.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Subparagraph (SAB TOPIC 4.E)
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 505
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-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Subparagraph (SAB TOPIC 4.C)
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Paragraph 1
-Subparagraph (SX 210.3-04)
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
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-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph d
-Article 4

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30, 31
-Article 5

Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 17: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Article 4

Reference 18: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

Reference 19: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

+ Details

Regulatory Capital Requirements

12 Months Ended

Dec. 31, 2014

Regulatory Capital Requirements [Abstract]

Regulatory Capital Requirements

(16) Regulatory Capital Requirements

The Company and NBT 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, NBT 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 NBT 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, 2014 and 2013, the Company and NBT 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, under capitalized, significantly under capitalized, and critically under capitalized. As of December 31, 2014, the most recent notification from NBT Bank’s regulators categorized NBT Bank as well capitalized under the regulatory framework for prompt corrective action. To be categorized as well capitalized NBT 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 NBT Bank’s category.

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			For classification as well capitalized
As of December 31, 2014
Total Capital (to risk weighted assets):
Company	$	777,651		13.50	%		8.00	%		10.00	%
NBT Bank		727,771		12.72	%		8.00	%		10.00	%
Tier I Capital (to risk weighted assets)
Company		709,965		12.32	%		4.00	%		6.00	%
NBT Bank		660,086		11.54	%		4.00	%		6.00	%
Tier I Capital (to average assets)
Company		709,965		9.39	%		4.00	%		5.00	%
NBT Bank		660,086		8.79	%		4.00	%		5.00	%

As of December 31, 2013
Total Capital (to risk weighted assets):
Company	$	723,580		12.99	%		8.00	%		10.00	%
NBT Bank		686,194		12.41	%		8.00	%		10.00	%
Tier I Capital (to risk weighted assets)
Company		653,950		11.74	%		4.00	%		6.00	%
NBT Bank		617,038		11.16	%		4.00	%		6.00	%
Tier I Capital (to average assets)
Company		653,950		8.93	%		4.00	%		5.00	%
NBT Bank		617,038		8.47	%		4.00	%		5.00	%

- Definition

The entire disclosure for banks, savings institutions, and credit unions, for regulatory capital requirements imposed by the Federal Reserve System (FRB), the Federal Deposit Insurance Corporation (FDIC), the Office of Thrift Supervision (OTS) or for any state imposed capital requirements, as applicable. The disclosure may include (1) a description of regulatory capital requirements (a) for capital adequacy purposes and (b) established by the prompt corrective action provisions of Section 38 of the Federal Depository Insurance Act; (2) the actual or possible material effects of noncompliance with such requirements; (3) whether the entity is in compliance with the regulatory capital requirements including (a) required and actual ratios and amounts of Tier 1 leverage, Tier 1 risk-based, and total risk-based capital, tangible capital (for savings institutions), and Tier 3 capital for market risk (for certain banks and bank holding companies), (b) factors that may significantly affect capital adequacy; (4) the prompt corrective action category in which the entity was classified as of its most recent notification; (5) whether management believes any conditions or events since notification have changed the entity's category. Also may include additional information that might be disclosed in situations where substantial doubt about the entity's ability to continue as a going concern for a reasonable period of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1G
-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958577-112826

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1C
-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958572-112826

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1E
-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958574-112826

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1H
-URI http://asc.fasb.org/extlink&oid=35709795&loc=d3e65071-112826

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958569-112826

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958570-112826

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1F
-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958575-112826

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958568-112826

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1D
-URI http://asc.fasb.org/extlink&oid=35709795&loc=SL5958573-112826

+ Details

Earnings Per Share

12 Months Ended

Dec. 31, 2014

Earnings Per Share [Abstract]

Earnings Per Share

(17) Earnings Per Share

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

	Years ended December 31,
	2014								2013								2012
(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 earnings per share		$	75,074		43,877		$	1.71		$	61,747		41,930		$	1.47		$	54,558		33,379		$	1.63
Effect of dilutive securities

Stock based compensation					518								420								340
Diluted earnings per share		$	75,074		44,395		$	1.69		$	61,747		42,350		$	1.46		$	54,558		33,719		$	1.62

There were approximately 0.5 million, 1.0 million, and 1.2 million weighted average stock options for the years ended December 31, 2014, 2013, and 2012, respectively, that were not considered in the calculation of diluted earnings per share since the stock options’ exercise prices were greater than the average market price during these periods.

Reclassification Adjustments Out of Other Comprehensive (Loss) Income

12 Months Ended

Dec. 31, 2014

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

Reclassification Adjustments Out of Other Comprehensive (Loss) Income

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

The following table summarizes the reclassification adjustments out of accumulated other comprehensive loss (in thousands):

Detail About Accumulated Other Comprehensive (Loss) Income Components	Amount reclassified from accumulated other comprehensive income (loss)						Affected line item in the consolidated statement of comprehensive income
	Years ended
	December 31, 2014			December 31, 2013
Available for sale securities:
Gains on available for sale securities	$	(92	)	$	(1,426	)	Net securities gains
Amortization of unrealized gains and losses related to securities transfer		(421	)		-		Interest Income
Tax benefit		200			565		Income tax expense
Net of tax	$	(313	)	$	(861	)

Pension and other benefits:
Amortization of net gains	$	94		$	2,972		Salaries and employee benefits
Amortization of prior service costs		(19	)		(182	)	Salaries and employee benefits
Tax expense		29			1,189		Income tax expense
Net of tax	$	46		$	1,601

Total reclassifications during the period, net of tax	$	(267	)	$	740

Commitments and Contingent Liabilities

12 Months Ended

Dec. 31, 2014

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, 2014, approximately 59% of the Company’s loans were secured by real estate located in central and upstate New York, northeastern Pennsylvania, western Massachusetts, southern New Hampshire, and Vermont. 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.

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 mortgage loans sold to investors with recourse. 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)	2014		2013
Unused lines of credit	$	214,175	$	216,658
Commitments to extend credits, primarily variable rate		972,912		849,092
Standby letters of credit		35,244		36,837
Commercial letters of credit		22,486		41,263
Loans sold with recourse		23,351		15,741

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 stand-by letters of credit to third parties. These stand-by 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 stand-by 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 terms of five years or less and expire unused; therefore, the total amounts do not necessarily represent future cash requirements. The fair value of the Company’s stand-by letters of credit at December 31, 2014 and 2013 was not significant.

The total amount of loans serviced by the Company for unrelated third parties was approximately $626.0 million and $685.6 million at December 31, 2014 and 2013, respectively. At December 31, 2014 and 2013, the Company had approximately $1.5 million and $2.2 million, respectively, of mortgage servicing rights.

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 of New York. The required average total reserve for NBT Bank for the 14-day maintenance period ending December 24, 2014 was $46.9 million.

Fair Values of Financial Instruments

12 Months Ended

Dec. 31, 2014

Fair Values of Financial Instruments [Abstract]

Fair Values of Financial Instruments

(20) Fair Values of Financial Instruments

The following table sets forth information with regard to estimated fair values of financial instruments at December 31, 2014 and December 31, 2013. 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, securities available for sale, trading securities, accrued interest receivable, non-maturity deposits, short-term borrowings, accrued interest payable, and interest rate swaps.

			December 31, 2014				December 31, 2013
(In thousands)	Fair Value Hierarchy		Carrying amount		Estimated fair value		Carrying amount		Estimated fair value
Financial assets
Securities held to maturity		2	$	454,361	$	454,994	$	117,283	$	113,276
Net loans		3		5,528,912		5,584,777		5,337,361		5,386,520
Financial liabilities
Time deposits		2	$	1,043,823	$	1,038,877	$	1,021,142	$	1,023,982
Long-term debt		2		130,945		132,562		308,823		325,195
Junior subordinated debt		2		101,196		103,770		101,196		105,121

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.

Securities Held to Maturity

The fair value of the Company’s investment securities held to maturity 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 by discounting the expected future cash flows using the current interest rates at which similar loans would be made for the same remaining maturities. 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.

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.

Trust Preferred Debentures

The fair value of trust preferred debentures has been estimated using a discounted cash flow analysis.

The following table sets forth the Company’s financial assets and liabilities measured on a recurring basis that were accounted for at fair value as of December 31, 2014 and December 31, 2013. 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):

	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of December 31, 2014
Assets:
Securities Available for Sale:
U.S. Treasury	$	23,111	$	-	$	-	$	23,111
Federal Agency		-		329,914		-		329,914
State & municipal		-		37,570		-		37,570
Mortgage-backed		-		364,727		-		364,727
Collateralized mortgage obligations		-		242,129		-		242,129
Other securities		7,612		8,108		-		15,720
Total Securities Available for Sale	$	30,723	$	982,448	$	-	$	1,013,171
Trading Securities		7,793		-		-		7,793
Interest Rate Swaps		-		4,707		-		4,707
Total	$	38,516	$	987,155	$	-	$	1,025,671

Liabilities:
Interest Rate Swaps	$	-	$	4,707	$	-	$	4,707
Total	$	-	$	4,707	$	-	$	4,707

	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of December 31, 2013
Assets:
Securities Available for Sale:
U.S. Treasury	$	43,616	$	-	$	-	$	43,616
Federal Agency		-		278,915		-		278,915
State & municipal		-		113,665		-		113,665
Mortgage-backed		-		364,164		-		364,164
Collateralized mortgage obligations		-		549,528		-		549,528
Other securities		6,796		8,197		-		14,993
Total Securities Available for Sale	$	50,412	$	1,314,469	$	-	$	1,364,881
Trading Securities		5,779		-		-		5,779
Interest Rate Swaps		-		281		-		281
Total	$	56,191	$	1,314,750	$	-	$	1,370,941

Liabilities:
Interest Rate Swaps	$	-	$	281	$	-	$	281
Total	$	-	$	281	$	-	$	281

Fair values for securities are based on quoted market prices or dealer quotes, where available. Where quoted market prices are not available, fair values are based on quoted market prices of comparable instruments. When necessary, the Company utilizes matrix pricing from a third party pricing vendor to determine fair value pricing. Matrix prices are based on quoted prices for securities with similar coupons, ratings, and maturities, rather than on specific bids and offers for the designated security.

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.

FASB ASC Topic 820 requires disclosure of assets and liabilities measured and recorded at fair value on a nonrecurring basis. In accordance with the provisions of FASB ASC Topic 310, the Company had collateral dependent impaired loans with a carrying value of approximately $5.8 million which had specific reserves included in the allowance for loan losses of $1.1 million at December 31, 2014. The Company uses the fair value of underlying collateral to estimate the specific reserves for collateral dependent impaired loans. The fair value of underlying collateral is generally determined through independent appraisals, which generally include various Level 3 inputs which are not identifiable. 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.

FASB ASC Topic 825 gives entities the option to measure eligible financial assets, financial liabilities and Company commitments at fair value (i.e., the fair value option), on an instrument-by-instrument basis, that are otherwise not permitted to be accounted for at fair value under other accounting standards. The election to use the fair value option is available when an entity first recognizes a financial asset or financial liability or upon entering into a Company commitment. Subsequent changes in fair value must be recorded in earnings. As of December 31, 2014 and 2013, the Company did not elect the fair value option for any eligible items.

- 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

Sale of Equity Investments	12 Months Ended
Sale of Equity Investments	Dec. 31, 2014
Sale of Equity Investment [Abstract]
Sale of Equity Investments Disclosure [Text Block]	(21) Sale of Equity Investment On April 17, 2014, NBT Capital Corp., a wholly-owned subsidiary of NBT, sold to LendingClub Corporation, its 20% ownership interest in Springstone Financial, LLC, which NBT originally acquired in exchange for a $3 million investment, as part of LendingClub's acquisition of all of the outstanding equity in Springstone. In total, LendingClub paid the group of selling equityholders a purchase price equal to $140 million in cash and preferred stock. As a result of this sale, the Company recognized a gain of $19.4 million during the second quarter of 2014. There is $5.2 million in proceeds being held in escrow for indemnification provisions of the sale contract which will be recognized into income in 2015 when the conditions of the contract have been deemed to be satisfied.

Parent Company Financial Information

12 Months Ended

Dec. 31, 2014

Parent Company Financial Information [Abstract]

Parent Company Financial Information

(22) Parent Company Financial Information

Condensed Balance Sheets

	December 31,
(In thousands)	2014		2013
Assets
Cash and cash equivalents	$	3,586	$	3,741
Securities available for sale, at estimated fair value		11,649		11,008
Trading securities		6,761		4,742
Investment in subsidiaries, on equity basis		947,880		896,479
Other assets		61,829		49,530
Total assets	$	1,031,705	$	965,500
Liabilities and Stockholders’ Equity
Total liabilities	$	167,524	$	148,931
Stockholders’ equity		864,181		816,569
Total liabilities and stockholders’ equity	$	1,031,705	$	965,500

Condensed Income Statements

	Years ended December 31,
(In thousands)	2014		2013			2012
Dividends from subsidiaries	$	35,400	$	13,500		$	79,175
Management fee from subsidiaries		87,116		84,778			78,665
Securities gains		49		1,273			442
Interest, dividend and other income		800		636			720
Total revenue		123,365		100,187			159,002
Operating expense		89,834		83,679			79,015
Income before income tax benefit and equity in undistributed income of subsidiaries		33,531		16,508			79,987
Income tax benefit (expense)		631		(1,046	)		(284	)
Dividends in excess of income (equity in undistributed income) of subsidiaries		40,912		46,285			(25,145	)
Net income	$	75,074	$	61,747		$	54,558

Statements of Cash Flow

	Years ended December 31,
(In thousands)	2014			2013			2012
Operating activities
Net income	$	75,074		$	61,747		$	54,558
Adjustments to reconcile net income to net cash provided by operating activities
Stock-based compensation		3,521			4,305			4,364
Gain on sales of available-for-sale securities		49			1,273			442
Equity in undistributed income of subsidiaries		(75,824	)		(59,785	)		(54,030	)
Cash dividend from subsidiaries		35,400			13,500			79,175
Net change in other liabilities		18,594			(18,077	)		(3,181	)
Net change in other assets		(25,151	)		14,928			2,030
Net cash provided by operating activities		31,663			17,891			83,358
Investing activities
Purchases of available-for-sale securities		(597	)		-			(4,163	)
Sales and maturities of available-for-sale securities		140			1,948			1,445
Net cash provided by (used in) acquisitions		-			2,232			(14,612	)
Purchases of premises and equipment		(640	)		(782	)		(1,240	)
Net cash (used in) provided by investing activities		(1,097	)		3,398			(18,570	)
Financing activities
Proceeds from the issuance of shares to employee benefit plans and other stock plans		5,943			5,512			1,387
Payments on long-term debt		-			-			(3,340	)
Purchases of treasury shares		(72	)		(12,459	)		(15,490	)
Cash dividends and payments for fractional shares		(36,905	)		(33,518	)		(26,712	)
Excess tax benefit from exercise of stock options		313			(178	)		8
Net cash used in financing activities		(30,721	)		(40,643	)		(44,147	)
Net (decrease) increase in cash and cash equivalents		(155	)		(19,354	)		20,641
Cash and cash equivalents at beginning of year		3,741			23,095			2,454
Cash and cash equivalents at end of year	$	3,586		$	3,741		$	23,095

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.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2014
Summary of Significant Accounting Policies [Abstract]
Consolidation	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 Report	Segment Report 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 the greater Portland, Maine area. The Company has no reportable operating segments.
Cash Equivalents	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	Securities The Company classifies its securities at date of purchase as either available for sale, held to maturity or trading. Held to maturity 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, and unrealized gains and losses are included in earnings. Available for sale securities are securities that are not classified as a held to maturity or trading securities. Available for sale securities are recorded at fair value. Unrealized holding gains and losses, net of the related tax effect, on available for sale securities are excluded from earnings and are reported in stockholders’ equity and the statement of comprehensive income as a component of accumulated other comprehensive income or loss. Held to maturity securities are recorded at amortized cost. Trading 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. Declines in the fair value of held-to-maturity and available-for-sale securities below their cost that are deemed to be other than temporary are reflected in earnings as realized losses or in other comprehensive income, depending on whether the Company intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss. If the Company intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the other-than-temporary impairment 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 entity will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the other-than-temporary impairment shall be separated into (a) the amount representing the credit loss and (b) the amount related to all other factors. The amount of the total other-than-temporary impairment related to the credit loss shall be recognized in earnings. The amount of the total other-than-temporary impairment related to other factors shall be recognized in other comprehensive income, net of applicable taxes. In estimating other-than-temporary impairment 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. Non-marketable equity securities are carried at cost. 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 (“FRB”) 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 FHLB stock.
Loans	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 interest in accordance with contractual terms is doubtful. 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 is improbable. For commercial loans, management considers specific facts and circumstances relative to individual credits in making such a determination. For consumer and residential 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 we will be unable to collect all principal and 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. 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 include the reduction of interest rates, forgiveness of all or a portion of principal or interest, or other modifications at interest rates that are less than the current market rate for new obligations with similar risk. 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. When the Company modifies a loan, management evaluates any possible impairment 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, instead of discounted cash flows. If management determines that the value of the modified loan is less than the recorded investment in the loan (net of previous charge-offs, deferred loan fees or costs and unamortized premium or discount), impairment is recognized by segment or class of loan as applicable, through an allowance estimate or a charge-off to the allowance. Segment and class status is determined by the loan’s classification at origination.
Acquired Loans	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 ASC 310-30, 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, 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 troubled debt restructurings as the pool, and not the individual loan, represents the unit of account.
Allowance for Loan Losses	Allowance for Loan Losses The allowance for loan losses is the amount which, in the opinion of management, is necessary to absorb probable losses inherent in the 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 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 loans). The Company’s impaired loans 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 homogeneous non impaired 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, Allowance for Loan Loss and Credit Quality of Loans. Each segment has a distinct set of risk characteristics monitored by management. We further assess and monitor risk and performance at a more disaggregated level which includes our internal risk grading system for the commercial segments. We first apply historical loss rates 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 loss emergence period, or LEP. 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 ALL assumptions, we update our study of LEPs for each portfolio segment using our loan charge-off history. Another key assumption is the look-back period, or LBP, which represents the historical data period utilized to calculate loss rates. After consideration of the historic loss analysis, management applies additional qualitative adjustments so that the allowance for loan losses is reflective of the inherent losses that exist in the loan portfolio at the balance sheet date. Qualitative adjustments are made based upon 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 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. 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. Management believes that the allowance for loan losses is adequate. While management uses available information to recognize loan losses, future additions to the allowance for loan losses may be necessary 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 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.
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 other real estate owned, 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 at December 31, 2014 and 2013 was approximately $4.0 million and $2.9 million, respectively, and is recorded in Other Assets on the Consolidated Balance Sheet.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill and 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. Goodwill impairment tests are performed on an annual basis or when events or circumstances dictate. In these tests, the fair values of each reporting unit, or segment, is compared to the carrying amount of that reporting unit in order to determine if impairment is indicated. If so, the implied fair value of the reporting unit’s goodwill is compared to its carrying amount and the impairment loss is measured by the excess of the carrying value over fair value.
Bank-Owned Life Insurance	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 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 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.
Stock-Based Compensation	Stock-Based Compensation We maintain various long-term incentive stock benefit plans under which we grant stock options, restricted stock awards, and restricted stock units to certain directors and key employees. We recognize compensation expense in our income statement over the requisite service period, based on the grant-date fair value of the award. For restricted stock awards and units, we recognize compensation expense ratably over the vesting period for the fair value of the award, measured at the grant date. The fair values of options are estimated using the Black-Scholes option pricing model. The Company’s stock-based employee compensation plan is described in Note 14 “Stock-Based Compensation,” of this Report.
Interest Rate Swaps	Interest Rate Swaps The Bank offers interest rate swap agreements to its customers. These agreements allow the Bank’s customers to effectively fix the interest rate on a variable rate loan by entering into a separate agreement. Simultaneous with the execution of such an agreement with a customer, the Bank enters into a matching interest rate swap agreement with an unrelated third party provider, which allows the Bank to continue to receive the historical variable rate under the loan agreement with the customer. The agreement with the third party is not a hedge contract therefore changes in fair value are recorded through earnings. Assets and liabilities associated with the agreements are recorded in other assets and other liabilities on the balance sheet. Gains and losses are recorded as other noninterest income. The Bank is not subject to any fee or penalty should the customer elect to terminate the interest rate swap agreement prior to maturity. The Bank is exposed to credit loss equal to the fair value of the derivatives (not the notional amount of the derivatives) in the event of nonperformance by the counterparty to the interest rate swap agreements. Additionally, the Bank receives a fee from the customer that is recognized when the Bank has fulfilled its obligations under each agreement, which is generally upon execution of the agreement with the Bank’s customer. Since the terms of the thirty three interest rate swap agreements with the customers are identical to the related swaps with the third party, the income statement impact to the Bank is generally limited to the fees it receives from the customer.
Other Financial Instruments	Other Financial Instruments The Company is a party to certain other financial instruments with off-balance-sheet risk such as commitments to extend credit, unused lines of credit, as well as certain mortgage 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 credit risk involved in issuing letters of credit is essentially the same as that 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 stand-by letters of credit is recorded upon inception.
Loan Sales and Loan Servicing	Loan Sales and Loan Servicing The Company originates and services residential mortgage loans for consumers and sells 15-year, 20-year and 30-year residential real estate mortgages in the secondary market when the interest rate environment is determined to be favorable by management, while retaining servicing rights on the sold loans. Loan sales are recorded when the sales are funded. Mortgage servicing rights are recorded at fair value upon sale of the loan. Loans held for sale are recorded at the lower of cost or market.
Repurchase Agreements	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 dealer or bank with whom each transaction is executed. The dealers or banks, 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.
Earnings Per Share	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).
Subsequent Events	Subsequent Events The Company has evaluated subsequent events for potential recognition and/or disclosure and there were none identified.
Comprehensive Income	Comprehensive Income At the Company, comprehensive income represents net income plus other comprehensive income (loss), which consists primarily of the net change in unrealized gains or losses on securities available for sale for the period and changes in the funded status of employee benefit plans. Accumulated other comprehensive (loss) income represents the net unrealized gains or losses on securities available for sale and the previously unrecognized portion of the funded status of employee benefit plans, net of income taxes, as of the consolidated balance sheet dates.
Pension Costs	Pension Costs The Company maintains a noncontributory, defined benefit pension plan covering substantially all employees, as well as supplemental employee retirement plans covering certain 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.
Trust Operations	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.
Fair Value Measurements	Fair Value Measurements 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 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. 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. 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.

Securities (Tables)

12 Months Ended

Dec. 31, 2014

Securities [Abstract]

Amortized cost, estimated fair value, and unrealized gains and losses of securities available for sale

The amortized cost, estimated fair value, and unrealized gains and losses of securities available for sale are as follows:

(In thousands)	Amortized cost		Unrealized gains		Unrealized losses		Estimated fair value
December 31, 2014
U.S. Treasury	$	23,041	$	70	$	-	$	23,111
Federal agency		332,193		327		2,606		329,914
State & municipal		37,035		587		52		37,570
Mortgage-backed:
Government-sponsored enterprises		339,190		7,597		224		346,563
U.S. government agency securities		17,367		863		66		18,164
Collateralized mortgage obligations:
Government-sponsored enterprises		199,837		1,828		234		201,431
U.S. government agency securities		40,237		497		36		40,698
Other securities		12,818		3,054		152		15,720
Total securities available for sale	$	1,001,718	$	14,823	$	3,370	$	1,013,171
December 31, 2013
U.S. Treasury	$	43,279	$	337	$	-	$	43,616
Federal agency		285,880		343		7,308		278,915
State & municipal		113,435		1,842		1,612		113,665
Mortgage-backed:
Government-sponsored enterprises		337,666		5,788		2,131		341,323
U.S. government securities		21,924		1,002		85		22,841
Collateralized mortgage obligations:
Government-sponsored enterprises		521,257		1,777		18,141		504,893
U.S. government securities		43,943		794		102		44,635
Other securities		12,367		2,854		228		14,993
Total securities available for sale	$	1,379,751	$	14,737	$	29,607	$	1,364,881

Schedule of sales transactions of securities available for sale

The following table sets forth information with regard to sales transactions of securities available for sale:

	Years ended December 31
(In thousands)	2014		2013		2012
Proceeds from sales	$	189	$	27,593	$	1,790
Gross realized gains	$	49	$	1,283	$	442
Gross realized losses		-		-		-
Net securities gains	$	49	$	1,283	$	442

Amortized cost, estimated fair value, and unrealized gains and losses of securities held to maturity

The amortized cost, estimated fair value, and unrealized gains and losses of securities held to maturity are as follows:

(In thousands)	Amortized cost		Unrealized gains		Unrealized losses		Estimated fair value
December 31, 2014
Mortgage-backed	$	755	$	113	$	-	$	868
Collateralized mortgage obligations		317,628		1,934		1,965		317,597
State & municipal		135,978		674		123		136,529
Total securities held to maturity	$	454,361	$	2,721	$	2,088	$	454,994
December 31, 2013
Mortgage-backed	$	953	$	128	$	-	$	1,081
Collateralized mortgage obligations		62,025		-		4,569		57,456
State & municipal		54,305		442		8		54,739
Total securities held to maturity	$	117,283	$	570	$	4,577	$	113,276

Investment securities with unrealized losses

	Less than 12 months							12 months or longer							Total
Security Type:	Fair Value		Unrealized losses			Number of Positions		Fair Value		Unrealized losses			Number of Positions		Fair Value		Unrealized losses			Number of Positions

December 31, 2014
Investment securities available for sale:
Federal agency	$	66,528	$	(226	)		8	$	198,151	$	(2,380	)		16	$	264,679	$	(2,606	)		24
State & municipal		8,818		(42	)		33		1,321		(10	)		5		10,139		(52	)		38
Mortgage-backed		10,400		(36	)		10		35,565		(254	)		31		45,965		(290	)		41
Collateralized mortgage obligations		57,682		(196	)		8		6,598		(74	)		4		64,280		(270	)		12
Other securities		-		-			-		3,201		(152	)		2		3,201		(152	)		2
Total securities with unrealized losses	$	143,428	$	(500	)		59	$	244,836	$	(2,870	)		58	$	388,264	$	(3,370	)		117

December 31, 2014
Investment securities held to maturity:
Collateralized mortgage obligations	$	26,052	$	(49	)		2	$	46,415	$	(1,916	)		4	$	72,467	$	(1,965	)		6
State & municipal		43,514		(116	)		110		1,619		(7	)		6		45,133		(123	)		116
Total securities with unrealized losses	$	69,566	$	(165	)		112	$	48,034	$	(1,923	)		10	$	117,600	$	(2,088	)		122

December 31, 2013
Investment securities available for sale:
Federal agency	$	233,935	$	(6,927	)		20	$	9,619	$	(381	)		1	$	243,554	$	(7,308	)		21
State & municipal		50,328		(1,612	)		177		-		-			-		50,328		(1,612	)		177
Mortgage-backed		143,080		(2,216	)		79		-		-			-		143,080		(2,216	)		79
Collateralized mortgage obligations		379,273		(18,243	)		36		-		-			-		379,273		(18,243	)		36
Other securities		5,490		(203	)		2		223		(25	)		1		5,713		(228	)		3
Total securities with unrealized losses	$	812,106	$	(29,201	)		314	$	9,842	$	(406	)		2	$	821,948	$	(29,607	)		316

December 31, 2013
Investment securities held to maturity:
Collateralized mortgage obligations	$	57,456	$	(4,569	)		5	$	-	$	-			-	$	57,456	$	(4,569	)		5
State & municipal		1,012		(8	)		1		-		-			-		1,012		(8	)		1
Total securities with unrealized losses	$	58,468	$	(4,577	)		6	$	-	$	-			-	$	58,468	$	(4,577	)		6

Contractual maturities of debt securities

The following tables set forth information with regard to contractual maturities of debt securities at December 31, 2014:

(In thousands)	Amortized cost		Estimated fair value
Debt securities classified as available for sale
Within one year	$	28,193	$	28,310
From one to five years		356,696		356,107
From five to ten years		160,816		163,924
After ten years		443,195		449,110
	$	988,900	$	997,451
Debt securities classified as held to maturity
Within one year	$	22,999	$	23,075
From one to five years		15,506		15,606
From five to ten years		87,326		87,640
After ten years		328,530		328,673
	$	454,361	$	454,994

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

- Definition

Tabular disclosure of all investments in certain debt and equity securities for which the entity has the positive intent and ability to hold until maturity.

+ References + Details

Loans (Tables)

12 Months Ended

Dec. 31, 2014

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)	2014		2013
Residential real estate mortgages	$	1,115,589	$	1,041,637
Commercial		839,770		859,026
Commercial real estate		1,442,989		1,328,313
Real estate construction and development		83,750		93,247
Agricultural and agricultural real estate mortgages		107,195		112,035
Consumer		1,436,382		1,352,638
Home equity		569,596		619,899
Total loans	$	5,595,271	$	5,406,795

Related party loans

The aggregate amount of loans outstanding to qualifying related parties and changes during the years are summarized as follows:

(In thousands)	2014			2013
Balance at January 1	$	3,372		$	2,790
New loans		522			569
Adjustment due to change in composition of related parties		253			376
Repayments		(571	)		(363	)
Balance at December 31	$	3,576		$	3,372

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

12 Months Ended

Dec. 31, 2014

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

Allowance for loan losses by portfolio

The following table illustrates the changes in the allowance for loan losses by portfolio segment for the years ended December 31, 2014, 2013 and 2012:

Allowance for Loan Losses

(in thousands)

	Commercial Loans			Consumer Loans			Residential Real Estate Mortgages			Unallocated			Total
Balance as of December 31, 2013	$	35,090		$	27,694		$	6,520		$	130		$	69,434
Charge-offs		(9,414	)		(16,642	)		(1,417	)		-			(27,473	)
Recoveries		1,774			2,800			285			-			4,859
Provision		4,983			12,868			1,742			(54	)		19,539
Ending Balance as of December 31, 2014	$	32,433		$	26,720		$	7,130		$	76		$	66,359

Balance as of December 31, 2012	$	35,624		$	27,162		$	6,252		$	296		$	69,334
Charge-offs		(10,459	)		(15,459	)		(1,771	)		-			(27,689	)
Recoveries		1,957			3,136			272			-			5,365
Provision		7,968			12,855			1,767			(166	)		22,424
Ending Balance as of December 31, 2013	$	35,090		$	27,694		$	6,520		$	130		$	69,434

Balance as of December 31, 2011	$	38,831		$	26,049		$	6,249		$	205		$	71,334
Charge-offs		(8,750	)		(15,848	)		(1,906	)		-			(26,504	)
Recoveries		1,641			2,556			38			-			4,235
Provision		3,902			14,405			1,871			91			20,269
Ending Balance as of December 31, 2012	$	35,624		$	27,162		$	6,252		$	296		$	69,334

The following table illustrates the allowance for loan losses and the recorded investment by portfolio segment as of December 31, 2014 and 2013:

Allowance for Loan Losses and Recorded Investment in Loans

(in thousands)

	Commercial Loans		Consumer Loans		Residential Real Estate Mortgages		Unallocated		Total
As of December 31, 2014
Allowance for loan losses	$	32,433	$	26,720	$	7,130	$	76	$	66,359

Allowance for loans individually evaluated for impairment		1,100		-		-				1,100

Allowance for loans collectively evaluated for impairment	$	31,333	$	26,720	$	7,130	$	76	$	65,259


Ending balance of loans	$	2,473,702	$	2,005,980	$	1,115,589			$	5,595,271

Ending balance of originated loans individually evaluated for impairment		11,079		5,498		3,544				20,121
Ending balance of acquired loans individually evaluated for impairment		5,675		-		-				5,675
Ending balance of acquired loans collectively evaluated for impairment		327,656		147,256		266,747				741,659
Ending balance of originated loans collectively evaluated for impairment	$	2,129,292	$	1,853,226	$	845,298			$	4,827,816


As of December 31, 2013
Allowance for loan losses	$	35,090	$	27,694	$	6,520	$	130	$	69,434

Allowance for loans individually evaluated for impairment		715		-		-				715

Allowance for loans collectively evaluated for impairment	$	34,375	$	27,694	$	6,520	$	130	$	68,719


Ending balance of loans	$	2,392,621	$	1,972,537	$	1,041,637			$	5,406,795

Ending balance of originated loans individually evaluated for impairment		16,120		3,248		2,012				21,380
Ending balance of acquired loans individually evaluated for impairment		10,060		-		-				10,060
Ending balance of acquired loans collectively evaluated for impairment		392,329		219,587		308,416				920,332
Ending balance of originated loans collectively evaluated for impairment	$	1,974,112	$	1,749,702	$	731,209			$	4,455,023

Past due and nonperforming loans by loan class

The following table illustrates the Company’s nonaccrual loans by loan class as of December 31, 2014 and 2013:

(In thousands)	December 31, 2014		December 31, 2013
ORIGINATED
Commercial Loans
Commercial	$	1,012	$	3,669
Commercial Real Estate		4,127		7,834
Agricultural		817		1,135
Agricultural Real Estate		565		961
Business Banking		6,910		5,701
		13,431		19,300

Consumer Loans
Indirect		1,964		1,461
Home Equity		6,596		5,931
Direct		84		86
		8,644		7,478

Residential Real Estate Mortgages		8,770		7,105

	$	30,845	$	33,883

ACQUIRED
Commercial Loans
Commercial	$	3,009	$	6,599
Commercial Real Estate		2,666		3,559
Business Banking		665		1,340
		6,340		11,498

Consumer Loans
Indirect		106		93
Home Equity		557		570
Direct		33		49
		696		712

Residential Real Estate Mortgages		3,193		3,872

	$	10,229	$	16,082

TOTAL NONACCRUAL LOANS	$	41,074	$	49,965

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

Age Analysis of Past Due Financing Receivables

As of December 31, 2014

(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		Non-Accrual		Current		Recorded Total Loans
ORIGINATED
Commercial Loans
Commercial	$	-	$	735	$	-	$	735	$	1,012	$	613,400	$	615,147
Commercial Real Estate		192		-		-		192		4,127		1,064,549		1,068,868
Agricultural		-		-		-		-		817		32,130		32,947
Agricultural Real Estate		19		-		-		19		565		24,390		24,974
Business Banking		799		235		84		1,118		6,910		390,407		398,435
		1,010		970		84		2,064		13,431		2,124,876		2,140,371

Consumer Loans
Indirect		16,434		3,154		1,991		21,579		1,964		1,286,507		1,310,050
Home Equity		4,591		1,428		821		6,840		6,596		479,444		492,880
Direct		560		157		52		769		84		54,941		55,794
		21,585		4,739		2,864		29,188		8,644		1,820,892		1,858,724
Residential Real Estate Mortgages		2,901		96		1,256		4,253		8,770		835,819		848,842
	$	25,496	$	5,805	$	4,204	$	35,505	$	30,845	$	4,781,587	$	4,847,937


ACQUIRED
Commercial Loans
Commercial	$	-	$	-	$	-	$	-	$	3,009	$	72,255	$	75,264
Commercial Real Estate		-		-		-		-		2,666		197,222		199,888
Business Banking		5		15		-		20		665		57,494		58,179
		5		15		-		20		6,340		326,971		333,331

Consumer Loans
Indirect		518		5		54		577		106		64,540		65,223
Home Equity		190		60		5		255		557		75,904		76,716
Direct		31		-		7		38		33		5,246		5,317
		739		65		66		870		696		145,690		147,256
Residential Real Estate Mortgages		1,162		265		671		2,098		3,193		261,456		266,747
	$	1,906	$	345	$	737	$	2,988	$	10,229	$	734,117	$	747,334
Total Loans	$	27,402	$	6,150	$	4,941	$	38,493	$	41,074	$	5,515,704	$	5,595,271

Age Analysis of Past Due Financing Receivables

As of December 31, 2013

(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		Non-Accrual		Current		Recorded Total Loans
ORIGINATED
Commercial Loans
Commercial	$	105	$	247	$	-	$	352	$	3,669	$	612,402	$	616,423
Commercial Real Estate		1,366		-		-		1,366		7,834		925,116		934,316
Agricultural		150		21		-		171		1,135		63,856		65,162
Agricultural Real Estate		519		-		-		519		961		35,172		36,652
Business Banking		1,228		122		105		1,455		5,701		330,523		337,679
		3,368		390		105		3,863		19,300		1,967,069		1,990,232

Consumer Loans
Indirect		14,093		2,878		1,583		18,554		1,461		1,141,829		1,161,844
Home Equity		6,033		1,888		1,115		9,036		5,931		517,856		532,823
Direct		679		125		46		850		86		57,347		58,283
		20,805		4,891		2,744		28,440		7,478		1,717,032		1,752,950
Residential Real Estate Mortgages		3,951		379		808		5,138		7,105		720,978		733,221
	$	28,124	$	5,660	$	3,657	$	37,441	$	33,883	$	4,405,079	$	4,476,403


ACQUIRED
Commercial Loans
Commercial	$	24	$	-	$	-	$	24	$	6,599	$	96,603	$	103,226
Commercial Real Estate		-		-		-		-		3,559		225,455		229,014
Business Banking		320		2		-		322		1,340		68,487		70,149
		344		2		-		346		11,498		390,545		402,389

Consumer Loans
Indirect		939		113		71		1,123		93		123,870		125,086
Home Equity		753		63		-		816		570		85,690		87,076
Direct		76		56		9		141		49		7,235		7,425
		1,768		232		80		2,080		712		216,795		219,587
Residential Real Estate Mortgages		1,725		-		-		1,725		3,872		302,819		308,416
	$	3,837	$	234	$	80	$	4,151	$	16,082	$	910,159	$	930,392
Total Loans	$	31,961	$	5,894	$	3,737	$	41,592	$	49,965	$	5,315,238	$	5,406,795

Impaired loans and specific reserve allocations

The following provides additional information on loans specifically evaluated for impairment for the years ended December 31, 2014 and 2013

Impaired Loans

	December 31, 2014							December 31, 2013
(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
Commercial	$	1,748	$	1,901				$	4,721	$	4,777
Commercial Real Estate		4,505		4,520					4,613		5,164
Agricultural		20		26					125		195
Agricultural Real Estate		1,147		1,441					1,431		1,708
Business Banking		896		1,301					210		602
Total Commercial Loans		8,316		9,189					11,100		12,446

Consumer Loans
Home Equity		5,498		6,033					3,248		3,472

Residential Real Estate Mortgages		3,544		3,959					2,012		2,255
Total		17,358		19,181					16,360		18,173

With an allowance recorded:
Commercial Loans
Commercial Real Estate		2,763		4,611			600		5,020		6,877			715

ACQUIRED
With no related allowance recorded:
Commercial Loans
Commercial		-		-					6,501		6,538
Commercial Real Estate		2,666		3,830					3,559		3,842
Total Commercial Loans		2,666		3,830					10,060		10,380

With an allowance recorded:
Commercial Loans
Commercial		3,009		4,668			500		-		-			-

Total	$	25,796	$	32,290		$	1,100	$	31,440	$	35,430		$	715

The following table summarizes the average recorded investments on loans specifically evaluated for impairment and the interest income recognized for the years ended December 31, 2014, 2013 and 2012:

	December 31, 2014				December 31, 2013				December 31, 2012
(in thousands)	Average Recorded Investment		Interest Income Recognized Accrual		Average Recorded Investment		Interest Income Recognized Accrual		Average Recorded Investment		Interest Income Recognized Accrual
ORIGINATED
Commercial Loans
Commercial	$	1,954	$	115	$	3,488	$	-	$	6,682	$	56
Commercial Real Estate		9,679		169		11,085		95		4,944		230
Agricultural		91		1		1,035		1		1,767		43
Agricultural Real Estate		1,346		46		1,067		47		922		72
Business Banking		610		55		127		61		68		65
Consumer Loans
Home Equity		5,198		267		3,120		145		1,877		123
Residential Real Estate Mortgages		3,039		119		2,085		69		1,143		54
ACQUIRED
Commercial Loans
Commercial		5,756		-		-		-		-		-
Commercial Real Estate		3,386		-		1,310		-		-		-
Total	$	31,059	$	772	$	23,317	$	418	$	17,403	$	643

Financing receivable credit quality by loan class

The following tables illustrate the Company’s credit quality by loan class for the years ended December 31, 2014 and 2013:

Credit Quality Indicators

December 31, 2014

(In thousands)
ORIGINATED
Commercial Credit Exposure
By Internally Assigned Grade:	Commercial		Commercial Real Estate		Agricultural		Agricultural Real Estate		Total
Pass	$	$570,884	$	1,023,856	$	30,481	$	23,443	$	1,648,664
Special Mention		6,022		17,341		275		42		23,680
Substandard		38,241		27,671		2,183		1,489		69,584
Doubtful		-		-		8		-		8
Total	$	615,147	$	1,068,868	$	32,947	$	24,974	$	1,741,936

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking						Total
Non-classified	$	379,445					$	379,445
Classified		18,990						18,990
Total	$	398,435					$	398,435

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct		Total
Performing	$	1,306,095	$	485,463	$	55,658	$	1,847,216
Nonperforming		3,955		7,417		136		11,508
Total	$	1,310,050	$	492,880	$	55,794	$	1,858,724

Residential Mortgage Credit Exposure
By Payment Activity:	Residential Mortgage		Total
Performing	$	838,816	$	838,816
Nonperforming		10,026		10,026
Total	$	848,842	$	848,842

Credit Quality Indicators

December 31, 2014

(In thousands)

ACQUIRED
Commercial Credit Exposure
By Internally Assigned Grade:	Commercial		Commercial Real Estate		Agricultural		Total
Pass	$	63,630	$	186,036	$	-	$	249,666
Special Mention		2,840		2,646		-		5,486
Substandard		8,794		11,206		-		20,000
Doubtful		-		-		-		-
Total	$	75,264	$	199,888	$	-	$	275,152

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking		Total
Non-classified	$	53,264	$	53,264
Classified		4,915		4,915
Total	$	58,179	$	58,179

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct		Total
Performing	$	65,063	$	76,154	$	5,277	$	146,494
Nonperforming		160		562		40		762
Total	$	65,223	$	76,716	$	5,317	$	147,256

Residential Mortgage Credit Exposure
By Payment Activity:	Residential Mortgage		Total
Performing	$	262,883	$	262,883
Nonperforming		3,864		3,864
Total	$	266,747	$	266,747

Credit Quality Indicators

December 31, 2013

(In thousands)

Commercial Credit Exposure
By Internally Assigned Grade:	Commercial		Commercial Real Estate		Agricultural		Agricultural Real Estate		Total
Pass	$	576,079	$	878,411	$	60,043	$	33,136	$	1,547,669
Special Mention		16,836		22,777		381		43		40,037
Substandard		23,508		33,128		4,726		3,473		64,835
Doubtful		-		-		12		-		12
Total	$	616,423	$	934,316	$	65,162	$	36,652	$	1,652,553

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking						Total
Non-classified	$	319,578					$	319,578
Classified		18,101						18,101
Total	$	337,679					$	337,679

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct		Total
Performing	$	1,158,800	$	525,777	$	58,151	$	1,742,728
Nonperforming		3,044		7,046		132		10,222
Total	$	1,161,844	$	532,823	$	58,283	$	1,752,950

Residential Mortgage Credit Exposure
By Payment Activity:	Residential Mortgage		Total
Performing	$	725,308	$	725,308
Nonperforming		7,913		7,913
Total	$	733,221	$	733,221

Credit Quality Indicators

December 31, 2013

(In thousands)

ACQUIRED
Commercial Credit Exposure
By Internally Assigned Grade:	Commercial		Commercial Real Estate		Agricultural		Total
Pass	$	85,692	$	205,010	$	-	$	290,702
Special Mention		2,230		6,183		-		8,413
Substandard		15,304		17,821		-		33,125
Doubtful		-		-		-		-
Total	$	103,226	$	229,014	$	-	$	332,240

Business Banking Credit Exposure
By Internally Assigned Grade:	Business Banking		Total
Non-classified	$	65,437	$	65,437
Classified		4,712		4,712
Total	$	70,149	$	70,149

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct		Total
Performing	$	124,922	$	86,506	$	7,367	$	218,795
Nonperforming		164		570		58		792
Total	$	125,086	$	87,076	$	7,425	$	219,587

Residential Mortgage Credit Exposure
By Payment Activity:	Residential Mortgage		Total
Performing	$	304,544	$	304,544
Nonperforming		3,872		3,872
Total	$	308,416	$	308,416

Premises and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2014

Premises and Equipment, Net [Abstract]

Summary of premises and equipment

A summary of premises and equipment follows:

	December 31,
(In thousands)	2014		2013
Land, buildings, and improvements	$	122,400	$	120,098
Equipment		58,835		55,729
Premises and equipment before accumulated depreciation		181,235		175,827
Accumulated depreciation		91,977		87,500
Total premises and equipment	$	89,258	$	88,327

Future minimum rental payments related to noncancelable operating leases

The future minimum rental payments related to noncancelable operating leases with original terms of one year or more are as follows at December 31, 2014 (in thousands):

Future Minimum Rental Payments

2015	$	7,369
2016		7,215
2017		6,811
2018		6,122
2019		5,655
Thereafter		26,257
Total	$	59,429

- Definition

Tabular disclosure of a lessee's leasing arrangements including: (1) the basis on which contingent rental payments are determined, (2) the existence and terms of renewal or purchase options and escalation clauses, (3) restrictions imposed by lease arrangements, such as those concerning dividends, additional debt, and further leasing, (4) rent holidays, rent concessions, or leasehold improvement incentives and unusual provisions or conditions. Disclosure may also include the specific period used to amortize material leasehold improvements made at the inception of the lease or during the lease term. Additionally, for operating leases having initial or remaining noncancelable lease terms in excess of one year: (a) future minimum rental payments required as of the date of the latest balance sheet presented, in the aggregate and for each of the five succeeding fiscal years, (b) the total of minimum rentals to be received in the future under noncancelable subleases as of the date of the latest balance sheet presented, and (c) for all operating leases, rental expense for each period for which an income statement is presented, with separate amounts for minimum rentals, contingent rentals, and sublease rentals. Rental payments under leases with terms of a month or less that were not renewed need not be included.

+ References + Details

Goodwill and other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2014

Goodwill and other Intangible Assets [Abstract]

Summary of goodwill

A summary of goodwill is as follows:

(In thousands)
January 1, 2014	$	264,997
Goodwill Adjustments		(1,363	)
December 31, 2014	$	263,634

January 1, 2013	$	152,373
Goodwill Acquired		112,624
December 31, 2013	$	264,997

Summary of core deposit and other intangible assets

A summary of core deposit and other intangible assets follows:

	December 31,
(In thousands)	2014		2013
Core deposit intangibles
Gross carrying amount	$	19,401	$	19,401
Less: accumulated amortization		12,522		10,083
Net carrying amount		6,879		9,318

Identified intangible assets
Gross carrying amount		28,316		28,509
Less: accumulated amortization		14,878		12,270
Net carrying amount		13,438		16,239

Total intangibles
Gross carrying amount		47,717		47,910
Less: accumulated amortization		27,400		22,353
Net carrying amount	$	20,317	$	25,557

Deposits (Tables)

12 Months Ended

Dec. 31, 2014

Deposits [Abstract]

Maturity distribution of time deposits

The following table sets forth the maturity distribution of time deposits at December 31, 2014 (in thousands):

Time deposits
Within one year	$	464,853
After one but within two years		132,999
After two but within three years		143,142
After three but within four years		80,804
After four but within five years		204,492
After five years		17,533
Total	$	1,043,823

Short-Term Borrowings (Tables)

12 Months Ended

Dec. 31, 2014

Short-Term Borrowings [Abstract]

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

(In thousands)	2014			2013			2012
Federal funds purchased
Balance at year-end	$	68,000		$	130,000		$	10,000
Average during the year		110,154			39,907			12,658
Maximum month end balance		183,000			130,000			60,000
Weighted average rate during the year		0.29	%		0.26	%		0.27	%
Weighted average rate at December 31		0.34	%		0.18	%		0.27	%

Securities sold under repurchase agreements
Balance at year-end	$	148,802		$	176,042		$	152,941
Average during the year		165,858			169,352			153,084
Maximum month end balance		182,861			185,871			165,977
Weighted average rate during the year		0.06	%		0.06	%		0.10	%
Weighted average rate at December 31		0.06	%		0.05	%		0.10	%

Other short-term borrowings
Balance at year-end	$	100,000		$	150,000		$	-
Average during the year		106,438			71,589			-
Maximum month end balance		320,000			210,000			-
Weighted average rate during the year		0.40	%		0.43	%		0.00	%
Weighted average rate at December 31		0.36	%		0.55	%		0.00	%

Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2014

Long-Term Debt [Abstract]

Schedule of long-term debt

A summary as of December 31, 2014 and 2013 is as follows:

(In thousands)	As of December 31, 2014										As of December 31, 2013
Maturity	Amount		Weighted Average Rate			Callable Amount		Weighted Average Rate			Amount		Weighted Average Rate			Callable Amount		Weighted Average Rate
2014		-		-			-		-			12,460		1.33	%		-		-
2015		217		-			-		-			308		-			-		-
2016		50,626		2.91	%		30,000		4.15	%		90,313		3.52	%		70,000		4.21	%
2017		40,000		2.68	%		25,000		3.48	%		115,312		3.55	%		75,000		3.73	%
2018		40,000		2.57	%		25,000		3.15	%		90,313		3.26	%		75,000		3.61	%
2021		102		4.00	%		-		-			117		4.00	%		-		-
	$	130,945				$	80,000				$	308,823				$	220,000

Junior Subordinated Debt (Tables)

12 Months Ended

Dec. 31, 2014

Junior Subordinated Debt [Abstract]

Schedule of debt of VIE where entity is not primary beneficiary

As of December 31, 2014, the Trusts had the following issues of trust preferred debentures, all held by the Trusts, outstanding (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://www.xbrl.org/2003/role/presentationRef
-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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

+ Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2014

Income Taxes [Abstract]

Components of income tax expense attributable to operations

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

	Years ended December 31,
(In thousands)	2014		2013		2012
Current
Federal	$	26,059	$	23,536	$	21,011
State		2,823		2,316		1,815
		28,882		25,852		22,826

Deferred
Federal		6,648		2,334		(13	)
State		1,699		10		3
		8,347		2,344		(10	)
Total income tax expense	$	37,229	$	28,196	$	22,816

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)	2014			2013
Deferred tax assets
Allowance for loan losses	$	25,689		$	26,729
Deferred compensation		8,744			7,931
Postretirement benefit obligation		2,377			2,596
Unrealized losses on securities available for sale		-			5,900
Accrued liabilities		1,778			3,265
Stock-based compensation expense		6,457			7,862
Equipment leasing		1,416			1,661
Other		1,325			2,125
Total deferred tax assets		47,786			58,069
Deferred tax liabilities
Pension and executive retirement		12,192			17,417
Fair value adjustments from acquisitions		1,243			2,070
Unrealized gains on securities available for sale		1,331			-
Premises and equipment, primarily due to accelerated depreciation		2,491			2,270
Deferred loan costs		1,460			1,624
Intangible amortization		14,162			12,007
Other		390			892
Total deferred tax liabilities		33,269			36,280
Net deferred tax asset at year-end		14,517			21,789
Net deferred tax asset at beginning of year		21,789			11,115
(Decrease) Increase in net deferred tax asset	$	(7,272	)	$	10,674

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 of 35 % to income before taxes:

	Years ended December 31
(In thousands)	2014			2013			2012
Federal income tax at statutory rate	$	39,306		$	31,482		$	27,081
Tax exempt income		(2,250	)		(2,433	)		(2,536	)
Net increase in CSV of life insurance		(1,734	)		(1,166	)		(908	)
Low income housing tax credits		(880	)		(819	)		(629	)
State taxes, net of federal tax benefit		2,939			1,512			1,182
Other, net		(152	)		(380	)		(1,374	)
Income tax expense	$	37,229		$	28,196		$	22,816

Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2014

Employee Benefit Plans [Abstract]

Components of accumulated other comprehensive income (loss), net periodic benefit cost

The Company expects that $2.4 million in net actuarial loss and $0.2 million in prior service costs will be recognized as components of net periodic benefit cost in 2015.

	Pension Benefits						Other Benefits
(In thousands)	2014			2013			2014				2013
Net actuarial loss		$	28,767		$	11,286		$	2,929			$	1,628
Prior service cost			97			118			(314	)			(521	)
Total amounts recognized in accumulated other comprehensive loss (pre-tax)		$	28,864		$	11,404		$	2,615			$	1,107

Changes in benefit obligations, changes in plan assets, and the funded status of the pension plans and postretirement benefits

	Pension Benefits						Other Benefits
(In thousands)	2014			2013			2014			2013
Change in benefit obligation
Benefit obligation at beginning of year	$	85,667		$	85,130		$	7,428		$	4,071
Service cost		2,290			2,493			16			23
Interest cost		4,142			3,223			347			286
Plan participants' contributions		-			-			266			269
Actuarial(gain) loss		12,501			(10,853	)		1,452			(369	)
Amendments		-			-			-			(54	)
Acquisition		-			10,958			-			3,928
Benefits paid		(6,044	)		(5,284	)		(799	)		(726	)
Projected benefit obligation at end of year		98,556			85,667			8,710			7,428
Change in plan assets
Fair value of plan assets at beginning of year		118,574			99,705			-			-
Actual return on plan assets		3,950			18,451			-			-
Acquisition		-			4,994			-			-
Employer contributions		752			708			533			457
Plan participants' contributions		-			-			266			269
Benefits paid		(6,044	)		(5,284	)		(799	)		(726	)
Fair value of plan assets at end of year		117,232			118,574			-			-

Funded status at year end	$	18,676		$	32,907		$	(8,710	)	$	(7,428	)

Amounts recognized in balance sheet

The funded status of the pension and other postretirement benefit plans has been recognized as follows in the consolidated balance sheets at December 31, 2014 and 2013.

	Pension Benefits								Other Benefits
(In thousands)	2014				2013				2014				2013
Other assets		$	39,044			$	48,189			$	-			$	-
Other liabilities			(20,368	)			(15,282	)			(8,710	)			(7,428	)
Funded status		$	18,676			$	32,907			$	(8,710	)		$	(7,428	)

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,
	2014			2013			2012
Weighted average assumptions:
The following assumptions were used to determine benefit obligations:
Discount rate		4.19% - 4.30	%		4.90%-5.05	%		3.50	%
Expected long-term return on plan assets		7.50	%		7.50	%		7.50	%
Rate of compensation increase		3.00%-3.75	%		3.00	%		3.00	%

The following assumptions were used to determine net periodic pension cost:
Discount rate		4.90%-5.05	%		3.50	%		4.10	%
Expected long-term return on plan assets		7.50	%		7.50	%		7.50	%
Rate of compensation increase		3.00%-3.75	%		3.00	%		3.00	%

Components of net periodic pension benefits and other benefit costs

Net periodic benefit cost and other amounts recognized in other comprehensive income (loss) for the years ended December 31 included the following components:

	Pension Benefits									Other Benefits
(In thousands)	2014			2013			2012			2014			2013			2012
Components of net periodic benefit cost
Service cost	$	2,290		$	2,493		$	3,122		$	16		$	23		$	20
Interest cost		4,142			3,223			3,145			347			286			155
Expected return on plan assets		(8,681	)		(7,804	)		(6,686	)		-			-			-
Amortization of prior service cost		23			23			283			(206	)		(205	)		(202	)
Amortization of unrecognized net loss		79			2,692			3,330			151			280			182
Net periodic pension cost	$	(2,147	)	$	627		$	3,194		$	308		$	384		$	155

Other changes in plan assets and benefit obligations recognized in other comprehensive income (pre-tax)
Net loss (gain)	$	17,233		$	(21,500	)	$	894		$	1,452		$	(369	)	$	136
Prior service cost		-			-			(1,006	)		-			(54	)		-
Amortization of prior service cost		(23	)		(23	)		(283	)		206			205			202
Amortization of unrecognized net gain		(79	)		(2,692	)		(3,330	)		(151	)		(280	)		(182	)
Total recognized in other comprehensive loss (income)		17,131			(24,215	)		(3,725	)		1,507			(498	)		156

Total recognized in net periodic benefit cost and other comprehensive income (loss) - pre-tax	$	14,984		$	(23,588	)	$	(531	)	$	1,815		$	(114	)	$	311

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 postretirement benefit plans:

(In thousands)	Pension Benefits		Other Benefits
2015		6,011		538
2016		6,221		549
2017		9,473		571
2018		7,100		592
2019		6,953		578
2020 - 2024		40,351		2,881

Effect of one-percentage point change in assumed health care cost trend rates

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, 2014:

(In thousands)	One Percentage point increase		One Percentage point decrease
Increase (decrease) on total service and interest cost components	$	39	$	(33	)
Increase (decrease) on postretirement accumulated benefit obligation		895		(764	)

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 2014			2014			2013
Cash and cash equivalents		0 - 20	%		4	%		6	%
Fixed income securities		20 - 40	%		38	%		27	%
Equities		40 - 80	%		58	%		67	%
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 as of December 31, 2014 and 2013:

(In thousands)	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Balance as of December 31, 2014
Cash and cash equivalents	$	4,423	$	-	$	4,423
Foreign equity mutual funds		38,581		-		38,581
Equity mutual funds		29,718		-		29,718
U.S. government bonds		-		4,420		4,420
Corporate bonds		-		40,090		40,090
Totals	$	72,722	$	44,510	$	117,232

(In thousands)	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Balance as of December 31, 2013
Cash and cash equivalents	$	7,533	$	-	$	7,533
Foreign equity mutual funds		15,653		-		15,653
Equity mutual funds		16,727		-		16,727
U.S. government bonds		-		9,355		9,355
Corporate bonds		-		19,665		19,665
Common stock		44,532		-		44,532
Municipal bonds and notes		-		1,451		1,451
Foreign bonds and notes		-		1,392		1,392
Foreign equity		2,266		-		2,266
Totals	$	86,711	$	31,863	$	118,574

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

Stock-Based Compensation [Abstract]

Stock option activity

The following table summarizes information concerning stock options outstanding at December 31, 2014:

	Number of Shares			Weighted average exercise price		Weighted Average Remaining Contractual Term (in yrs)		Aggregate Intrinsic Value
Outstanding at January 1, 2014		1,341,500		$	22.98
Granted		3,296			24.80
Exercised		(290,243	)		22.58
Forfeited		(105	)		20.19
Expired		(16,106	)		22.36
Outstanding at December 31, 2014		1,038,342		$	23.10		3.40		$	3,353,951

Exercisable at December 31, 2014		1,031,726		$	23.09		3.37		$	3,342,258

Expected to Vest		5,249		$	24.50		7.32		$	9,354

Cash proceeds, tax benefits and intrinsic value of stock options exercised

Cash proceeds, tax benefits and intrinsic value related to total stock options exercised is as follows:

	Years ended December 31,
(dollars in thousands)	2014		2013		2012
Proceeds from stock options exercised	$	6,554	$	7,927	$	1,908
Tax benefits related to stock options exercised		313		178		8
Intrinsic value of stock options exercised		789		905		498
Fair value of shares vested during the year		393		766		1,656

Unvested restricted awards and unvested restricted units activity

The following table summarizes information for unvested restricted stock awards outstanding as of December 31, 2014:

	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested Restricted Stock Awards
Unvested at January 1, 2014		66,650		$	23.15
Forfeited		-			-
Vested		(14,650	)		22.16
Unvested at December 31, 2014		52,000		$	23.43

The following table summarizes information for unvested restricted stock units outstanding as of December 31, 2014:

	Number of Shares			Weighted- Average Grant Date Fair Value
Unvested Restricted Stock Units
Unvested at January 1, 2014		539,850		$	27.36
Forfeited		(5,090	)		-
Vested		(105,013	)		-
Granted		209,228			24.11
Unvested at December 31, 2014		638,975		$	31.01

Stockholders Equity (Tables)

12 Months Ended

Dec. 31, 2014

Stockholders Equity [Abstract]

Components of accumulated other comprehensive (loss) income

For the years ended December 31, components of accumulated other comprehensive loss are:

(In thousands)	2014			2013
Unrecognized prior service cost and net actuarial loss on pension plans	$	(19,181	)	$	(7,785	)
Unrealized net holding gains (losses) on available for sale securities		2,154			(8,980	)
Accumulated other comprehensive loss	$	(17,027	)	$	(16,765	)

Regulatory Capital Requirements (Tables)

12 Months Ended

Dec. 31, 2014

Regulatory Capital Requirements [Abstract]

Schedule of 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			For classification as well capitalized
As of December 31, 2014
Total Capital (to risk weighted assets):
Company	$	777,651		13.50	%		8.00	%		10.00	%
NBT Bank		727,771		12.72	%		8.00	%		10.00	%
Tier I Capital (to risk weighted assets)
Company		709,965		12.32	%		4.00	%		6.00	%
NBT Bank		660,086		11.54	%		4.00	%		6.00	%
Tier I Capital (to average assets)
Company		709,965		9.39	%		4.00	%		5.00	%
NBT Bank		660,086		8.79	%		4.00	%		5.00	%

As of December 31, 2013
Total Capital (to risk weighted assets):
Company	$	723,580		12.99	%		8.00	%		10.00	%
NBT Bank		686,194		12.41	%		8.00	%		10.00	%
Tier I Capital (to risk weighted assets)
Company		653,950		11.74	%		4.00	%		6.00	%
NBT Bank		617,038		11.16	%		4.00	%		6.00	%
Tier I Capital (to average assets)
Company		653,950		8.93	%		4.00	%		5.00	%
NBT Bank		617,038		8.47	%		4.00	%		5.00	%

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2014

Earnings Per Share [Abstract]

Reconciliation of basic and diluted earnings per share

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

	Years ended December 31,
	2014								2013								2012
(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 earnings per share		$	75,074		43,877		$	1.71		$	61,747		41,930		$	1.47		$	54,558		33,379		$	1.63
Effect of dilutive securities

Stock based compensation					518								420								340
Diluted earnings per share		$	75,074		44,395		$	1.69		$	61,747		42,350		$	1.46		$	54,558		33,719		$	1.62

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

12 Months Ended

Dec. 31, 2014

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 accumulated other comprehensive loss (in thousands):

Detail About Accumulated Other Comprehensive (Loss) Income Components	Amount reclassified from accumulated other comprehensive income (loss)						Affected line item in the consolidated statement of comprehensive income
	Years ended
	December 31, 2014			December 31, 2013
Available for sale securities:
Gains on available for sale securities	$	(92	)	$	(1,426	)	Net securities gains
Amortization of unrealized gains and losses related to securities transfer		(421	)		-		Interest Income
Tax benefit		200			565		Income tax expense
Net of tax	$	(313	)	$	(861	)

Pension and other benefits:
Amortization of net gains	$	94		$	2,972		Salaries and employee benefits
Amortization of prior service costs		(19	)		(182	)	Salaries and employee benefits
Tax expense		29			1,189		Income tax expense
Net of tax	$	46		$	1,601

Total reclassifications during the period, net of tax	$	(267	)	$	740

Commitments and Contingent Liabilities (Tables)

12 Months Ended

Dec. 31, 2014

Commitments and Contingent Liabilities [Abstract]

Schedule of maximum commitments potential obligation

	At December 31,
(In thousands)	2014		2013
Unused lines of credit	$	214,175	$	216,658
Commitments to extend credits, primarily variable rate		972,912		849,092
Standby letters of credit		35,244		36,837
Commercial letters of credit		22,486		41,263
Loans sold with recourse		23,351		15,741

Fair Values of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2014

Fair Values of Financial Instruments [Abstract]

Fair Value of Financial Instruments By Balance Sheet Grouping

			December 31, 2014				December 31, 2013
(In thousands)	Fair Value Hierarchy		Carrying amount		Estimated fair value		Carrying amount		Estimated fair value
Financial assets
Securities held to maturity		2	$	454,361	$	454,994	$	117,283	$	113,276
Net loans		3		5,528,912		5,584,777		5,337,361		5,386,520
Financial liabilities
Time deposits		2	$	1,043,823	$	1,038,877	$	1,021,142	$	1,023,982
Long-term debt		2		130,945		132,562		308,823		325,195
Junior subordinated debt		2		101,196		103,770		101,196		105,121

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

	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of December 31, 2014
Assets:
Securities Available for Sale:
U.S. Treasury	$	23,111	$	-	$	-	$	23,111
Federal Agency		-		329,914		-		329,914
State & municipal		-		37,570		-		37,570
Mortgage-backed		-		364,727		-		364,727
Collateralized mortgage obligations		-		242,129		-		242,129
Other securities		7,612		8,108		-		15,720
Total Securities Available for Sale	$	30,723	$	982,448	$	-	$	1,013,171
Trading Securities		7,793		-		-		7,793
Interest Rate Swaps		-		4,707		-		4,707
Total	$	38,516	$	987,155	$	-	$	1,025,671

Liabilities:
Interest Rate Swaps	$	-	$	4,707	$	-	$	4,707
Total	$	-	$	4,707	$	-	$	4,707

	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Balance as of December 31, 2013
Assets:
Securities Available for Sale:
U.S. Treasury	$	43,616	$	-	$	-	$	43,616
Federal Agency		-		278,915		-		278,915
State & municipal		-		113,665		-		113,665
Mortgage-backed		-		364,164		-		364,164
Collateralized mortgage obligations		-		549,528		-		549,528
Other securities		6,796		8,197		-		14,993
Total Securities Available for Sale	$	50,412	$	1,314,469	$	-	$	1,364,881
Trading Securities		5,779		-		-		5,779
Interest Rate Swaps		-		281		-		281
Total	$	56,191	$	1,314,750	$	-	$	1,370,941

Liabilities:
Interest Rate Swaps	$	-	$	281	$	-	$	281
Total	$	-	$	281	$	-	$	281

Parent Company Financial Information (Tables)

12 Months Ended

Dec. 31, 2014

Parent Company Financial Information [Abstract]

Parent company financial information

Condensed Balance Sheets

	December 31,
(In thousands)	2014		2013
Assets
Cash and cash equivalents	$	3,586	$	3,741
Securities available for sale, at estimated fair value		11,649		11,008
Trading securities		6,761		4,742
Investment in subsidiaries, on equity basis		947,880		896,479
Other assets		61,829		49,530
Total assets	$	1,031,705	$	965,500
Liabilities and Stockholders’ Equity
Total liabilities	$	167,524	$	148,931
Stockholders’ equity		864,181		816,569
Total liabilities and stockholders’ equity	$	1,031,705	$	965,500

Condensed Income Statements

	Years ended December 31,
(In thousands)	2014		2013			2012
Dividends from subsidiaries	$	35,400	$	13,500		$	79,175
Management fee from subsidiaries		87,116		84,778			78,665
Securities gains		49		1,273			442
Interest, dividend and other income		800		636			720
Total revenue		123,365		100,187			159,002
Operating expense		89,834		83,679			79,015
Income before income tax benefit and equity in undistributed income of subsidiaries		33,531		16,508			79,987
Income tax benefit (expense)		631		(1,046	)		(284	)
Dividends in excess of income (equity in undistributed income) of subsidiaries		40,912		46,285			(25,145	)
Net income	$	75,074	$	61,747		$	54,558

Statements of Cash Flow

	Years ended December 31,
(In thousands)	2014			2013			2012
Operating activities
Net income	$	75,074		$	61,747		$	54,558
Adjustments to reconcile net income to net cash provided by operating activities
Stock-based compensation		3,521			4,305			4,364
Gain on sales of available-for-sale securities		49			1,273			442
Equity in undistributed income of subsidiaries		(75,824	)		(59,785	)		(54,030	)
Cash dividend from subsidiaries		35,400			13,500			79,175
Net change in other liabilities		18,594			(18,077	)		(3,181	)
Net change in other assets		(25,151	)		14,928			2,030
Net cash provided by operating activities		31,663			17,891			83,358
Investing activities
Purchases of available-for-sale securities		(597	)		-			(4,163	)
Sales and maturities of available-for-sale securities		140			1,948			1,445
Net cash provided by (used in) acquisitions		-			2,232			(14,612	)
Purchases of premises and equipment		(640	)		(782	)		(1,240	)
Net cash (used in) provided by investing activities		(1,097	)		3,398			(18,570	)
Financing activities
Proceeds from the issuance of shares to employee benefit plans and other stock plans		5,943			5,512			1,387
Payments on long-term debt		-			-			(3,340	)
Purchases of treasury shares		(72	)		(12,459	)		(15,490	)
Cash dividends and payments for fractional shares		(36,905	)		(33,518	)		(26,712	)
Excess tax benefit from exercise of stock options		313			(178	)		8
Net cash used in financing activities		(30,721	)		(40,643	)		(44,147	)
Net (decrease) increase in cash and cash equivalents		(155	)		(19,354	)		20,641
Cash and cash equivalents at beginning of year		3,741			23,095			2,454
Cash and cash equivalents at end of year	$	3,586		$	3,741		$	23,095

Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2014 USD ($) Agreement	Dec. 31, 2013 USD ($)
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
Balance of OREO \| $	$ 4.0	$ 2.9
Number of interest rate swap agreements \| Agreement	33
Standby letters of credit expiration period	1 year
Mortgage loans on real estate, by loan disclosure	The Company originates and services residential mortgage loans for consumers and sells 15-year, 20-year and 30-year residential real estate mortgages in the secondary market when the interest rate environment is determined to be favorable by management, while retaining servicing rights on the sold loans.

Acquisitions (Details) $ in Millions		12 Months Ended
Acquisitions (Details) $ in Millions	Mar. 08, 2013 USD ($) Branch	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Alliance Financial Corporation [Member]
Business Acquisition [Line Items]
Date of acquisition		Mar. 08, 2013
Total consideration paid	$ 226.0
Number of banking centers operated by acquiree \| Branch	26
Other goodwill adjustments [Abstract]
Deferred tax adjustments		$ (1.0)
Valuation adjustments		(0.4)
Decrease in goodwill		$ (1.4)
Hampshire First Bank [Member]
Other goodwill adjustments [Abstract]
Decrease in goodwill			$ (1.0)
Acquisition of Financial Services Company [Member]
Other goodwill adjustments [Abstract]
Goodwill adjustment related to business acquisition			$ 0.1

Securities (Details) $ in Thousands	12 Months Ended
Securities (Details) $ in Thousands	Dec. 31, 2014 USD ($) Position	Dec. 31, 2013 USD ($) Position	Dec. 31, 2012 USD ($)
Available-for-sale securities, fair value to amortized cost basis [Abstract]
Amortized cost	$ 1,001,718	$ 1,379,751
Unrealized gains	14,823	14,737
Unrealized losses	3,370	29,607
Estimated fair value	1,013,171	1,364,881
Available-for-sale securities in continuous unrealized loss position, fair value [Abstract]
Less than 12 months	143,428	812,106
12 months or longer	244,836	9,842
Total	388,264	821,948
Available-for-sale securities in continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	(500)	(29,201)
12 months or longer	(2,870)	(406)
Total	$ (3,370)	$ (29,607)
Available-for-sale securities in continuous unrealized loss position, number of positions [Abstract]
Less than 12 months \| Position	59	314
12 months or longer \| Position	58	2
Total \| Position	117	316
Sales transactions of securities available for sale [Abstract]
Proceeds from sales	$ 189	$ 27,593	$ 1,790
Gross realized gains	49	1,283	442
Gross realized losses	0	0	0
Net securities (losses) gains	49	1,283	442
Gains from calls on securities available for sale	100	100	$ 200
Amortized costs of securities available for sale pledged to secure public deposits	1,400,000	1,400,000
Amortized costs of securities available for sale pledged as collateral for repurchase agreements	208,800
Held-to-maturity securities, fair value to amortized cost basis [Abstract]
Amortized cost	454,361	117,283
Unrealized gains	2,721	570
Unrealized losses	2,088	4,577
Total, Estimated Fair Value	454,994	113,276
Held-to-maturity securities in continuous unrealized loss position, fair value [Abstract]
Less than 12 months	69,566	58,468
12 months or longer	48,034	0
Total	117,600	58,468
Held-to-maturity securities in continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	(165)	(4,577)
12 months or longer	(1,923)	0
Total	$ (2,088)	$ (4,577)
Held-to-maturity securities in continuous unrealized loss position, number of positions [Abstract]
Less than 12 months \| Position	112	6
12 months or longer \| Position	10	0
Total \| Position	122	6
Securities transferred from available for sale portfolio to held to maturity portfolio	$ 340,000
Unrealized losses of securities available for sale portfolio before transfer to held to maturity portfolio	8,300
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Within one year	28,193
From one to five years	356,696
From five to ten years	160,816
After ten years	443,195
Total, Amortized Cost	988,900
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Within one year	28,310
From one to five years	356,107
From five to ten years	163,924
After ten years	449,110
Total, Fair Value	997,451
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Within one year	22,999
From one to five years	15,506
From five to ten years	87,326
After ten years	328,530
Amortized cost	454,361	$ 117,283
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Within one year	23,075
From one to five years	15,606
From five to ten years	87,640
After ten years	328,673
Total, Estimated Fair Value	$ 454,994	$ 113,276
Consolidated stockholders' equity threshold percentage that no single issuer of securities exceeded except for U.S. Government securities. (in hundredths)	10.00%	10.00%
US Treasury [Member]
Available-for-sale securities, fair value to amortized cost basis [Abstract]
Amortized cost	$ 23,041	$ 43,279
Unrealized gains	70	337
Unrealized losses	0	0
Estimated fair value	23,111	43,616
Federal Agency [Member]
Available-for-sale securities, fair value to amortized cost basis [Abstract]
Amortized cost	332,193	285,880
Unrealized gains	327	343
Unrealized losses	2,606	7,308
Estimated fair value	329,914	278,915
Available-for-sale securities in continuous unrealized loss position, fair value [Abstract]
Less than 12 months	66,528	233,935
12 months or longer	198,151	9,619
Total	264,679	243,554
Available-for-sale securities in continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	(226)	(6,927)
12 months or longer	(2,380)	(381)
Total	$ (2,606)	$ (7,308)
Available-for-sale securities in continuous unrealized loss position, number of positions [Abstract]
Less than 12 months \| Position	8	20
12 months or longer \| Position	16	1
Total \| Position	24	21
State & Municipal [Member]
Available-for-sale securities, fair value to amortized cost basis [Abstract]
Amortized cost	$ 37,035	$ 113,435
Unrealized gains	587	1,842
Unrealized losses	52	1,612
Estimated fair value	37,570	113,665
Available-for-sale securities in continuous unrealized loss position, fair value [Abstract]
Less than 12 months	8,818	50,328
12 months or longer	1,321	0
Total	10,139	50,328
Available-for-sale securities in continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	(42)	(1,612)
12 months or longer	(10)	0
Total	$ (52)	$ (1,612)
Available-for-sale securities in continuous unrealized loss position, number of positions [Abstract]
Less than 12 months \| Position	33	177
12 months or longer \| Position	5	0
Total \| Position	38	177
Mortgage-Backed [Member]
Available-for-sale securities in continuous unrealized loss position, fair value [Abstract]
Less than 12 months	$ 10,400	$ 143,080
12 months or longer	35,565	0
Total	45,965	143,080
Available-for-sale securities in continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	(36)	(2,216)
12 months or longer	(254)	0
Total	$ (290)	$ (2,216)
Available-for-sale securities in continuous unrealized loss position, number of positions [Abstract]
Less than 12 months \| Position	10	79
12 months or longer \| Position	31	0
Total \| Position	41	79
Mortgage-backed Securities, Issued by US Government-Sponsored Enterprises [Member]
Available-for-sale securities, fair value to amortized cost basis [Abstract]
Amortized cost	$ 339,190	$ 337,666
Unrealized gains	7,597	5,788
Unrealized losses	224	2,131
Estimated fair value	346,563	341,323
Mortgage-backed Securities, Issued by US Government Securities [Member]
Available-for-sale securities, fair value to amortized cost basis [Abstract]
Amortized cost	17,367	21,924
Unrealized gains	863	1,002
Unrealized losses	66	85
Estimated fair value	18,164	22,841
Collateralized Mortgage Obligations [Member]
Available-for-sale securities in continuous unrealized loss position, fair value [Abstract]
Less than 12 months	57,682	379,273
12 months or longer	6,598	0
Total	64,280	379,273
Available-for-sale securities in continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	(196)	(18,243)
12 months or longer	(74)	0
Total	$ (270)	$ (18,243)
Available-for-sale securities in continuous unrealized loss position, number of positions [Abstract]
Less than 12 months \| Position	8	36
12 months or longer \| Position	4	0
Total \| Position	12	36
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member]
Available-for-sale securities, fair value to amortized cost basis [Abstract]
Amortized cost	$ 199,837	$ 521,257
Unrealized gains	1,828	1,777
Unrealized losses	234	18,141
Estimated fair value	201,431	504,893
Collateralized Mortgage Obligations, U.S. Government Securities [Member]
Available-for-sale securities, fair value to amortized cost basis [Abstract]
Amortized cost	40,237	43,943
Unrealized gains	497	794
Unrealized losses	36	102
Estimated fair value	40,698	44,635
Other Securities [Member]
Available-for-sale securities, fair value to amortized cost basis [Abstract]
Amortized cost	12,818	12,367
Unrealized gains	3,054	2,854
Unrealized losses	152	228
Estimated fair value	15,720	14,993
Available-for-sale securities in continuous unrealized loss position, fair value [Abstract]
Less than 12 months	0	5,490
12 months or longer	3,201	223
Total	3,201	5,713
Available-for-sale securities in continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	0	(203)
12 months or longer	(152)	(25)
Total	$ (152)	$ (228)
Available-for-sale securities in continuous unrealized loss position, number of positions [Abstract]
Less than 12 months \| Position	0	2
12 months or longer \| Position	2	1
Total \| Position	2	3
Mortgage-Backed [Member]
Held-to-maturity securities, fair value to amortized cost basis [Abstract]
Amortized cost	$ 755	$ 953
Unrealized gains	113	128
Unrealized losses	0	0
Total, Estimated Fair Value	868	1,081
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	755	953
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Estimated Fair Value	868	1,081
State & Municipal [Member]
Held-to-maturity securities, fair value to amortized cost basis [Abstract]
Amortized cost	135,978	54,305
Unrealized gains	674	442
Unrealized losses	123	8
Total, Estimated Fair Value	136,529	54,739
Held-to-maturity securities in continuous unrealized loss position, fair value [Abstract]
Less than 12 months	43,514	1,012
12 months or longer	1,619	0
Total	45,133	1,012
Held-to-maturity securities in continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	(116)	(8)
12 months or longer	(7)	0
Total	$ (123)	$ (8)
Held-to-maturity securities in continuous unrealized loss position, number of positions [Abstract]
Less than 12 months \| Position	110	1
12 months or longer \| Position	6	0
Total \| Position	116	1
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	$ 135,978	$ 54,305
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Estimated Fair Value	136,529	54,739
Collateralized Mortgage Obligations [Member]
Held-to-maturity securities, fair value to amortized cost basis [Abstract]
Amortized cost	317,628	62,025
Unrealized gains	1,934	0
Unrealized losses	1,965	4,569
Total, Estimated Fair Value	317,597	57,456
Held-to-maturity securities in continuous unrealized loss position, fair value [Abstract]
Less than 12 months	26,052	57,456
12 months or longer	46,415	0
Total	72,467	57,456
Held-to-maturity securities in continuous unrealized loss position, unrealized losses [Abstract]
Less than 12 months	(49)	(4,569)
12 months or longer	(1,916)	0
Total	$ (1,965)	$ (4,569)
Held-to-maturity securities in continuous unrealized loss position, number of positions [Abstract]
Less than 12 months \| Position	2	5
12 months or longer \| Position	4	0
Total \| Position	6	5
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	$ 317,628	$ 62,025
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Estimated Fair Value	$ 317,597	$ 57,456

Loans (Details) - USD ($) $ in Thousands	12 Months Ended
Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loans	$ 5,595,271	$ 5,406,795
Deferred loan origination costs, net	35,600	31,800
Residential loans held for sale	3,200	100
Loans and Leases Receivable, Related Parties [Roll Forward]
Balance at January 1	3,372	2,790
New loans	522	569
Adjustment due to change in composition of related parties	253	376
Repayments	(571)	(363)
Balance at December 31	3,576	3,372
Residential Real Estate Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loans	1,115,589	1,041,637
Commercial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loans	839,770	859,026
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loans	1,442,989	1,328,313
Real Estate Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loans	83,750	93,247
Agricultural and Agricultural Real Estate Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loans	107,195	112,035
Loans serviced	23,400	15,700
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loans	1,436,382	1,352,638
Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Loans	$ 569,596	$ 619,899

Allowance for Loan Losses and Credit Quality of Loans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2014 USD ($) Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio segments \| Segment	3
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate loan amount, percentage of appraised value or purchase price of the property, maximum (in hundredths)	80.00%
Agricultural Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate loan amount, percentage of appraised value or purchase price of the property, maximum (in hundredths)	75.00%
Business Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Business banking loans, maximum amount \| $	$ 500
Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of automobile financing to indirect relationships with dealers (in hundredths)	70.00%
Principal repayment term of loan, minimum	3 years
Principal repayment term of loan, maximum	6 years
Home Equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Home equity loan amount, percentage of equity in home, maximum (in hundredths)	85.00%
Direct [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Principal repayment term of loan, minimum	1 year
Principal repayment term of loan, maximum	10 years
Residential Real Estate Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Real estate loan amount, percentage of appraised value or purchase price of the property, maximum (in hundredths)	85.00%

Allowance for Loan Losses and Credit Quality of Loans, Allowance for Loan Losses (Details) - USD ($)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	$ 69,434,000	$ 69,334,000	$ 71,334,000
Charge-offs	(27,473,000)	(27,689,000)	(26,504,000)
Recoveries	4,859,000	5,365,000	4,235,000
Provision	19,539,000	22,424,000	20,269,000
Balance, end of period	66,359,000	69,434,000	69,334,000
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	69,434,000	69,434,000	69,334,000	$ 66,359,000	$ 69,434,000
Allowance for loans individually evaluated for impairment				1,100,000	715,000
Allowance for loans collectively evaluated for impairment				65,259,000	68,719,000
Ending balance of loans				5,595,271,000	5,406,795,000
Commercial Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	35,090,000	35,624,000	38,831,000
Charge-offs	(9,414,000)	(10,459,000)	(8,750,000)
Recoveries	1,774,000	1,957,000	1,641,000
Provision	4,983,000	7,968,000	3,902,000
Balance, end of period	32,433,000	35,090,000	35,624,000
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	35,090,000	35,090,000	38,831,000	32,433,000	35,090,000
Allowance for loans individually evaluated for impairment				1,100,000	715,000
Allowance for loans collectively evaluated for impairment				31,333,000	34,375,000
Ending balance of loans				2,473,702,000	2,392,621,000
Consumer Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	27,694,000	27,162,000	26,049,000
Charge-offs	(16,642,000)	(15,459,000)	(15,848,000)
Recoveries	2,800,000	3,136,000	2,556,000
Provision	12,868,000	12,855,000	14,405,000
Balance, end of period	26,720,000	27,694,000	27,162,000
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	27,694,000	27,694,000	26,049,000	26,720,000	27,694,000
Allowance for loans individually evaluated for impairment				0	0
Allowance for loans collectively evaluated for impairment				26,720,000	27,694,000
Ending balance of loans				2,005,980,000	1,972,537,000
Residential Real Estate Mortgages [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	6,520,000	6,252,000	6,249,000
Charge-offs	(1,417,000)	(1,771,000)	(1,906,000)
Recoveries	285,000	272,000	38,000
Provision	1,742,000	1,767,000	1,871,000
Balance, end of period	7,130,000	6,520,000	6,252,000
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	6,520,000	6,520,000	6,249,000	7,130,000	6,520,000
Allowance for loans individually evaluated for impairment				0	0
Allowance for loans collectively evaluated for impairment				7,130,000	6,520,000
Ending balance of loans				1,115,589,000	1,041,637,000
Unallocated [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	130,000	296,000	205,000
Charge-offs	0	0	0
Recoveries	0	0	0
Provision	(54,000)	(166,000)	91,000
Balance, end of period	76,000	130,000	296,000
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	130,000	130,000	$ 296,000	76,000	130,000
Allowance for loans collectively evaluated for impairment				76,000	130,000
Originated Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans				4,847,937,000	4,476,403,000
Ending balance of loans individually evaluated for impairment				20,121,000	21,380,000
Ending balance of loans collectively evaluated for impairment				4,827,816,000	4,455,023,000
Originated Loans [Member] \| Commercial Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans				2,140,371,000	1,990,232,000
Ending balance of loans individually evaluated for impairment				11,079,000	16,120,000
Ending balance of loans collectively evaluated for impairment				2,129,292,000	1,974,112,000
Originated Loans [Member] \| Consumer Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans				1,858,724,000	1,752,950,000
Ending balance of loans individually evaluated for impairment				5,498,000	3,248,000
Ending balance of loans collectively evaluated for impairment				1,853,226,000	1,749,702,000
Originated Loans [Member] \| Residential Real Estate Mortgages [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans				848,842,000	733,221,000
Ending balance of loans individually evaluated for impairment				3,544,000	2,012,000
Ending balance of loans collectively evaluated for impairment				845,298,000	731,209,000
Acquired Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period	0
Charge-offs	(4,800,000)	(400,000)
Balance, end of period	500	0
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	$ 500	$ 0		500	0
Ending balance of loans				747,334,000	930,392,000
Ending balance of loans individually evaluated for impairment				5,675,000	10,060,000
Ending balance of loans collectively evaluated for impairment				741,659,000	920,332,000
Acquired Loans [Member] \| Commercial Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans				333,331,000	402,389,000
Ending balance of loans individually evaluated for impairment				5,675,000	10,060,000
Ending balance of loans collectively evaluated for impairment				327,656,000	392,329,000
Acquired Loans [Member] \| Consumer Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans				147,256,000	219,587,000
Ending balance of loans individually evaluated for impairment				0	0
Ending balance of loans collectively evaluated for impairment				147,256,000	219,587,000
Acquired Loans [Member] \| Residential Real Estate Mortgages [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans				266,747,000	308,416,000
Ending balance of loans individually evaluated for impairment				0	0
Ending balance of loans collectively evaluated for impairment				$ 266,747,000	$ 308,416,000

Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Aging [Abstract]
Minimum number of days past due for nonaccrual loan status	90 days
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	$ 27,402	$ 31,961
61 - 90 Days Past Due Accruing	6,150	5,894
Greater Than 90 Days Past Due Accruing	4,941	3,737
Total Past Due Accruing	38,493	41,592
Non-Accrual	41,074	49,965
Current	5,515,704	5,315,238
Recorded Total Loans and Leases	5,595,271	5,406,795
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Recorded Total Loans and Leases	2,473,702	2,392,621
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Recorded Total Loans and Leases	2,005,980	1,972,537
Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Recorded Total Loans and Leases	1,115,589	1,041,637
Originated Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	25,496	28,124
61 - 90 Days Past Due Accruing	5,805	5,660
Greater Than 90 Days Past Due Accruing	4,204	3,657
Total Past Due Accruing	35,505	37,441
Non-Accrual	30,845	33,883
Current	4,781,587	4,405,079
Recorded Total Loans and Leases	4,847,937	4,476,403
Originated Loans [Member] \| Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,010	3,368
61 - 90 Days Past Due Accruing	970	390
Greater Than 90 Days Past Due Accruing	84	105
Total Past Due Accruing	2,064	3,863
Non-Accrual	13,431	19,300
Current	2,124,876	1,967,069
Recorded Total Loans and Leases	2,140,371	1,990,232
Originated Loans [Member] \| Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	0	105
61 - 90 Days Past Due Accruing	735	247
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	735	352
Non-Accrual	1,012	3,669
Current	613,400	612,402
Recorded Total Loans and Leases	615,147	616,423
Originated Loans [Member] \| Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	192	1,366
61 - 90 Days Past Due Accruing	0	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	192	1,366
Non-Accrual	4,127	7,834
Current	1,064,549	925,116
Recorded Total Loans and Leases	1,068,868	934,316
Originated Loans [Member] \| Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	0	150
61 - 90 Days Past Due Accruing	0	21
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	0	171
Non-Accrual	817	1,135
Current	32,130	63,856
Recorded Total Loans and Leases	32,947	65,162
Originated Loans [Member] \| Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	19	519
61 - 90 Days Past Due Accruing	0	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	19	519
Non-Accrual	565	961
Current	24,390	35,172
Recorded Total Loans and Leases	24,974	36,652
Originated Loans [Member] \| Business Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	799	1,228
61 - 90 Days Past Due Accruing	235	122
Greater Than 90 Days Past Due Accruing	84	105
Total Past Due Accruing	1,118	1,455
Non-Accrual	6,910	5,701
Current	390,407	330,523
Recorded Total Loans and Leases	398,435	337,679
Originated Loans [Member] \| Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	21,585	20,805
61 - 90 Days Past Due Accruing	4,739	4,891
Greater Than 90 Days Past Due Accruing	2,864	2,744
Total Past Due Accruing	29,188	28,440
Non-Accrual	8,644	7,478
Current	1,820,892	1,717,032
Recorded Total Loans and Leases	1,858,724	1,752,950
Originated Loans [Member] \| Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	16,434	14,093
61 - 90 Days Past Due Accruing	3,154	2,878
Greater Than 90 Days Past Due Accruing	1,991	1,583
Total Past Due Accruing	21,579	18,554
Non-Accrual	1,964	1,461
Current	1,286,507	1,141,829
Recorded Total Loans and Leases	1,310,050	1,161,844
Originated Loans [Member] \| Home Equity Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	4,591	6,033
61 - 90 Days Past Due Accruing	1,428	1,888
Greater Than 90 Days Past Due Accruing	821	1,115
Total Past Due Accruing	6,840	9,036
Non-Accrual	6,596	5,931
Current	479,444	517,856
Recorded Total Loans and Leases	492,880	532,823
Originated Loans [Member] \| Direct [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	560	679
61 - 90 Days Past Due Accruing	157	125
Greater Than 90 Days Past Due Accruing	52	46
Total Past Due Accruing	769	850
Non-Accrual	84	86
Current	54,941	57,347
Recorded Total Loans and Leases	55,794	58,283
Originated Loans [Member] \| Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	2,901	3,951
61 - 90 Days Past Due Accruing	96	379
Greater Than 90 Days Past Due Accruing	1,256	808
Total Past Due Accruing	4,253	5,138
Non-Accrual	8,770	7,105
Current	835,819	720,978
Recorded Total Loans and Leases	848,842	733,221
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,906	3,837
61 - 90 Days Past Due Accruing	345	234
Greater Than 90 Days Past Due Accruing	737	80
Total Past Due Accruing	2,988	4,151
Non-Accrual	10,229	16,082
Current	734,117	910,159
Recorded Total Loans and Leases	747,334	930,392
Acquired Loans [Member] \| Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	5	344
61 - 90 Days Past Due Accruing	15	2
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	20	346
Non-Accrual	6,340	11,498
Current	326,971	390,545
Recorded Total Loans and Leases	333,331	402,389
Acquired Loans [Member] \| Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	0	24
61 - 90 Days Past Due Accruing	0	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	0	24
Non-Accrual	3,009	6,599
Current	72,255	96,603
Recorded Total Loans and Leases	75,264	103,226
Acquired Loans [Member] \| Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	0	0
61 - 90 Days Past Due Accruing	0	0
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	0	0
Non-Accrual	2,666	3,559
Current	197,222	225,455
Recorded Total Loans and Leases	199,888	229,014
Acquired Loans [Member] \| Business Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	5	320
61 - 90 Days Past Due Accruing	15	2
Greater Than 90 Days Past Due Accruing	0	0
Total Past Due Accruing	20	322
Non-Accrual	665	1,340
Current	57,494	68,487
Recorded Total Loans and Leases	58,179	70,149
Acquired Loans [Member] \| Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	739	1,768
61 - 90 Days Past Due Accruing	65	232
Greater Than 90 Days Past Due Accruing	66	80
Total Past Due Accruing	870	2,080
Non-Accrual	696	712
Current	145,690	216,795
Recorded Total Loans and Leases	147,256	219,587
Acquired Loans [Member] \| Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	518	939
61 - 90 Days Past Due Accruing	5	113
Greater Than 90 Days Past Due Accruing	54	71
Total Past Due Accruing	577	1,123
Non-Accrual	106	93
Current	64,540	123,870
Recorded Total Loans and Leases	65,223	125,086
Acquired Loans [Member] \| Home Equity Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	190	753
61 - 90 Days Past Due Accruing	60	63
Greater Than 90 Days Past Due Accruing	5	0
Total Past Due Accruing	255	816
Non-Accrual	557	570
Current	75,904	85,690
Recorded Total Loans and Leases	76,716	87,076
Acquired Loans [Member] \| Direct [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	31	76
61 - 90 Days Past Due Accruing	0	56
Greater Than 90 Days Past Due Accruing	7	9
Total Past Due Accruing	38	141
Non-Accrual	33	49
Current	5,246	7,235
Recorded Total Loans and Leases	5,317	7,425
Acquired Loans [Member] \| Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,162	1,725
61 - 90 Days Past Due Accruing	265	0
Greater Than 90 Days Past Due Accruing	671	0
Total Past Due Accruing	2,098	1,725
Non-Accrual	3,193	3,872
Current	261,456	302,819
Recorded Total Loans and Leases	$ 266,747	$ 308,416

Allowance for Loan Losses and Credit Quality of Loans, Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Loan Losses and Credit Quality of Loans [Abstract]
Minimum balance for classified loans to be evaluated individually for impairment	$ 500
With an allowance recorded [Abstract]
Recorded investment balance (book)	25,796	$ 31,440
Unpaid principal balance (legal)	32,290	35,430
Related allowance	1,100	715
Average recorded investment	31,059	23,317	$ 17,403
Interest income recognized accrual	772	418	643
Originated Loans [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	17,358	16,360
Unpaid principal balance (legal)	19,181	18,173
Originated Loans [Member] \| Commercial Loans [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	8,316	11,100
Unpaid principal balance (legal)	9,189	12,446
Originated Loans [Member] \| Commercial [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	1,748	4,721
Unpaid principal balance (legal)	1,901	4,777
With an allowance recorded [Abstract]
Average recorded investment	1,954	3,488	6,682
Interest income recognized accrual	115	0	56
Originated Loans [Member] \| Commercial Real Estate [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	4,505	4,613
Unpaid principal balance (legal)	4,520	5,164
With an allowance recorded [Abstract]
Recorded investment balance (book)	2,763	5,020
Unpaid principal balance (legal)	4,611	6,877
Related allowance	600	715
Average recorded investment	9,679	11,085	4,944
Interest income recognized accrual	169	95	230
Originated Loans [Member] \| Agricultural [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	20	125
Unpaid principal balance (legal)	26	195
With an allowance recorded [Abstract]
Average recorded investment	91	1,035	1,767
Interest income recognized accrual	1	1	43
Originated Loans [Member] \| Agricultural Real Estate [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	1,147	1,431
Unpaid principal balance (legal)	1,441	1,708
With an allowance recorded [Abstract]
Average recorded investment	1,346	1,067	922
Interest income recognized accrual	46	47	72
Originated Loans [Member] \| Business Banking [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	896	210
Unpaid principal balance (legal)	1,301	602
With an allowance recorded [Abstract]
Average recorded investment	610	127	68
Interest income recognized accrual	55	61	65
Originated Loans [Member] \| Consumer Loans [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	5,498	3,248
Unpaid principal balance (legal)	6,033	3,472
Originated Loans [Member] \| Home Equity [Member]
With an allowance recorded [Abstract]
Average recorded investment	5,198	3,120	1,877
Interest income recognized accrual	267	145	123
Originated Loans [Member] \| Residential Real Estate Mortgages [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	3,544	2,012
Unpaid principal balance (legal)	3,959	2,255
With an allowance recorded [Abstract]
Average recorded investment	3,039	2,085	1,143
Interest income recognized accrual	119	69	54
Acquired Loans [Member] \| Commercial Loans [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	2,666	10,060
Unpaid principal balance (legal)	3,830	10,380
Acquired Loans [Member] \| Commercial [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	0	6,501
Unpaid principal balance (legal)	0	6,538
With an allowance recorded [Abstract]
Recorded investment balance (book)	3,009	0
Unpaid principal balance (legal)	4,668	0
Related allowance	500	0
Average recorded investment	5,756	0	0
Interest income recognized accrual	0	0	0
Acquired Loans [Member] \| Commercial Real Estate [Member]
With no allowance recorded [Abstract]
Recorded investment balance (book)	2,666	3,559
Unpaid principal balance (legal)	3,830	3,842
With an allowance recorded [Abstract]
Average recorded investment	3,386	1,310	0
Interest income recognized accrual	$ 0	$ 0	$ 0

Allowance for Loan Losses and Credit Quality of Loans, Credit Quality by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Originated Loans [Member] \| Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 1,741,936	$ 1,652,553
Originated Loans [Member] \| Commercial Loans [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,648,664	1,547,669
Originated Loans [Member] \| Commercial Loans [Member] \| Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	23,680	40,037
Originated Loans [Member] \| Commercial Loans [Member] \| Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	69,584	64,835
Originated Loans [Member] \| Commercial Loans [Member] \| Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	8	12
Originated Loans [Member] \| Business Banking Credit Exposure [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	398,435	337,679
Originated Loans [Member] \| Business Banking Credit Exposure [Member] \| Non-classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	379,445	319,578
Originated Loans [Member] \| Business Banking Credit Exposure [Member] \| Classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	18,990	18,101
Originated Loans [Member] \| Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,858,724	1,752,950
Originated Loans [Member] \| Consumer Loans [Member] \| Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	1,847,216	1,742,728
Originated Loans [Member] \| Consumer Loans [Member] \| Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	11,508	10,222
Originated Loans [Member] \| Residential Mortgage Credit Exposure [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	848,842	733,221
Originated Loans [Member] \| Residential Mortgage Credit Exposure [Member] \| Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	838,816	725,308
Originated Loans [Member] \| Residential Mortgage Credit Exposure [Member] \| Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10,026	7,913
Originated Loans [Member] \| Residential Mortgage Credit Exposure [Member] \| Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	848,842	733,221
Originated Loans [Member] \| Residential Mortgage Credit Exposure [Member] \| Residential Mortgage [Member] \| Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	838,816	725,308
Originated Loans [Member] \| Residential Mortgage Credit Exposure [Member] \| Residential Mortgage [Member] \| Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	10,026	7,913
Acquired Loans [Member] \| Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	275,152	332,240
Acquired Loans [Member] \| Commercial Loans [Member] \| Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	249,666	290,702
Acquired Loans [Member] \| Commercial Loans [Member] \| Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	5,486	8,413
Acquired Loans [Member] \| Commercial Loans [Member] \| Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	20,000	33,125
Acquired Loans [Member] \| Commercial Loans [Member] \| Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	0	0
Acquired Loans [Member] \| Business Banking Credit Exposure [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	58,179	70,149
Acquired Loans [Member] \| Business Banking Credit Exposure [Member] \| Non-classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	53,264	65,437
Acquired Loans [Member] \| Business Banking Credit Exposure [Member] \| Classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	4,915	4,712
Acquired Loans [Member] \| Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	147,256	219,587
Acquired Loans [Member] \| Consumer Loans [Member] \| Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	146,494	218,795
Acquired Loans [Member] \| Consumer Loans [Member] \| Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	762	792
Acquired Loans [Member] \| Residential Mortgage Credit Exposure [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	266,747	308,416
Acquired Loans [Member] \| Residential Mortgage Credit Exposure [Member] \| Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	262,883	304,544
Acquired Loans [Member] \| Residential Mortgage Credit Exposure [Member] \| Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,864	3,872
Acquired Loans [Member] \| Residential Mortgage Credit Exposure [Member] \| Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	266,747	308,416
Acquired Loans [Member] \| Residential Mortgage Credit Exposure [Member] \| Residential Mortgage [Member] \| Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	262,883	304,544
Acquired Loans [Member] \| Residential Mortgage Credit Exposure [Member] \| Residential Mortgage [Member] \| Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 3,864	$ 3,872

Allowance for Loan Losses and Credit Quality of Loans, Troubled Debt Restructurings (Details) $ in Millions	12 Months Ended
	Dec. 31, 2014 USD ($) Contract	Dec. 31, 2013 USD ($) Contract
Commercial Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract		4
Pre-modification outstanding recorded investment \| $		$ 7.0
Number of contracts, subsequent default \| Contract		1
Outstanding recorded investment, subsequent default \| $		$ 0.9
Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract	9	23
Pre-modification outstanding recorded investment \| $	$ 0.3	$ 1.0
Number of contracts, subsequent default \| Contract	1	8
Outstanding recorded investment, subsequent default \| $	$ 0.1	$ 0.4
Residential Real Estate Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract	27	6
Pre-modification outstanding recorded investment \| $	$ 2.7	$ 0.5
Number of contracts, subsequent default \| Contract	6
Outstanding recorded investment, subsequent default \| $	$ 0.4
Business Banking [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract	3
Pre-modification outstanding recorded investment \| $	$ 0.9
Indirect Consumer Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract	1
Pre-modification outstanding recorded investment \| $	$ 0.1
Number of contracts, subsequent default \| Contract	1
Outstanding recorded investment, subsequent default \| $	$ 0.1
Direct Consumer Loan [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract	47
Pre-modification outstanding recorded investment \| $	$ 3.0
Number of contracts, subsequent default \| Contract	5
Outstanding recorded investment, subsequent default \| $	$ 0.2

Premises and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Premises and equipment before accumulated depreciation	$ 181,235	$ 175,827
Accumulated depreciation	91,977	87,500
Total premises and equipment	89,258	88,327
Rental expense	8,000	7,500	$ 6,400
Future Minimum Rental Payments [Abstract]
2015	7,369
2016	7,215
2017	6,811
2018	6,122
2019	5,655
Thereafter	26,257
Total	59,429
Land, Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment before accumulated depreciation	122,400	120,098
Equipment [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment before accumulated depreciation	$ 58,835	$ 55,729
Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	10 years
Building and Improvements [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	15 years
Building and Improvements [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	40 years

Goodwill and other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Roll Forward]
Beginning Balance	$ 264,997	$ 152,373
Goodwill acquired	(1,363)	112,624
Ending Balance	263,634	264,997	$ 152,373
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	47,717	47,910
Less: accumulated amortization	27,400	22,353
Net carrying amount	20,317	25,557
Amortization Expense [Abstract]
Amortization of intangible assets	5,047	4,872	$ 3,394
Future Amortization Expense [Abstract]
2015	4,800
2016	3,300
2017	2,800
2018	2,200
2019	1,700
Thereafter	3,700
Indefinite-lived intangible assets (Excluding goodwill)	$ 1,800
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life	1 year
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life	12 years
Core Deposits Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 19,401	19,401
Less: accumulated amortization	12,522	10,083
Net carrying amount	6,879	9,318
Identified Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	28,316	28,509
Less: accumulated amortization	14,878	12,270
Net carrying amount	$ 13,438	$ 16,239

Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Maturities of Time Deposits [Abstract]
Within one year	$ 464,853
After one but within two years	132,999
After two but within three years	143,142
After three but within four years	80,804
After four but within five years	204,492
After five years	17,533
Total	1,043,823	$ 1,021,142
Time Deposits, $100,000 or More [Abstract]
Time deposits of $100,000 or more	$ 269,800	$ 375,400

Short-Term Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
Short-Term Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Short-term Debt [Line Items]
Balance at year-end	$ 316,802	$ 456,042
FHLB, unused lines of credit available for short-term financing	958,000	497,000
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Balance at year-end	68,000	130,000	$ 10,000
Average during the year	110,154	39,907	12,658
Maximum month end balance	$ 183,000	$ 130,000	$ 60,000
Weighted average rate during the year (in hundredths)	0.29%	0.26%	0.27%
Weighted average rate at December 31 (in hundredths)	0.34%	0.18%	0.27%
Securities Sold under Repurchase Agreements [Member]
Short-term Debt [Line Items]
Balance at year-end	$ 148,802	$ 176,042	$ 152,941
Average during the year	165,858	169,352	153,084
Maximum month end balance	$ 182,861	$ 185,871	$ 165,977
Weighted average rate during the year (in hundredths)	0.06%	0.06%	0.10%
Weighted average rate at December 31 (in hundredths)	0.06%	0.05%	0.10%
Other Short-Term Borrowings [Member]
Short-term Debt [Line Items]
Balance at year-end	$ 100,000	$ 150,000	$ 0
Average during the year	106,438	71,589	0
Maximum month end balance	$ 320,000	$ 210,000	$ 0
Weighted average rate during the year (in hundredths)	0.40%	0.43%	0.00%
Weighted average rate at December 31 (in hundredths)	0.36%	0.55%	0.00%

Long-Term Debt (Details) - USD ($) $ in Thousands	12 Months Ended
Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Long-Term Debt by Maturity Periods [Abstract]
Amount	$ 130,945	$ 308,823
Callable Amount	$ 80,000	220,000
2013 [Member]
Long-Term Debt by Maturity Periods [Abstract]
Maturity	Dec. 31, 2014
Amount	$ 0	$ 12,460
Weighted Average Rate (in hundredths)	0.00%	1.33%
Callable Amount	$ 0	$ 0
Weighted Average Rate Callable Portion (in hundredths)	0.00%	0.00%
2014 [Member]
Long-Term Debt by Maturity Periods [Abstract]
Maturity	Dec. 31, 2015
Amount	$ 217	$ 308
Weighted Average Rate (in hundredths)	0.00%	0.00%
Callable Amount	$ 0	$ 0
Weighted Average Rate Callable Portion (in hundredths)	0.00%	0.00%
2015 [Member]
Long-Term Debt by Maturity Periods [Abstract]
Maturity	Dec. 31, 2016
Amount	$ 50,626	$ 90,313
Weighted Average Rate (in hundredths)	2.91%	3.52%
Callable Amount	$ 30,000	$ 70,000
Weighted Average Rate Callable Portion (in hundredths)	4.15%	4.21%
2016 [Member]
Long-Term Debt by Maturity Periods [Abstract]
Maturity	Dec. 31, 2017
Amount	$ 40,000	$ 115,312
Weighted Average Rate (in hundredths)	2.68%	3.55%
Callable Amount	$ 25,000	$ 75,000
Weighted Average Rate Callable Portion (in hundredths)	3.48%	3.73%
2017 [Member]
Long-Term Debt by Maturity Periods [Abstract]
Maturity	Dec. 31, 2018
Amount	$ 40,000	$ 90,313
Weighted Average Rate (in hundredths)	2.57%	3.26%
Callable Amount	$ 25,000	$ 75,000
Weighted Average Rate Callable Portion (in hundredths)	3.15%	3.61%
2018 [Member]
Long-Term Debt by Maturity Periods [Abstract]
Maturity	Dec. 31, 2021
Amount	$ 102	$ 117
Weighted Average Rate (in hundredths)	4.00%	4.00%
Callable Amount	$ 0	$ 0
Weighted Average Rate Callable Portion (in hundredths)	0.00%	0.00%

Junior Subordinated Debt (Details) $ in Thousands	12 Months Ended
Junior Subordinated Debt (Details) $ in Thousands	Dec. 31, 2014 USD ($) Trust Period
Debt Instrument [Line Items]
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 Debenture [Member]
Debt Instrument [Line Items]
Issuance Date	Aug. 01, 1999
Trust Preferred Securities Outstanding	$ 18,000
Interest Rate	3-month LIBOR plus 2.75%
Trust Preferred Debt Owed To Trust	$ 18,720
Final Maturity Date	Aug. 01, 2029
Number of wholly owned Delaware statutory business trusts	1
NBT Statutory Trust I Debenture [Member]
Debt Instrument [Line Items]
Issuance Date	Nov. 01, 2005
Trust Preferred Securities Outstanding	$ 5,000
Interest Rate	3-month LIBOR plus 1.40%
Trust Preferred Debt Owed To Trust	$ 5,155
Final Maturity Date	Dec. 01, 2035
NBT Statutory Trust II Debenture [Member]
Debt Instrument [Line Items]
Issuance Date	Feb. 01, 2006
Trust Preferred Securities Outstanding	$ 50,000
Interest Rate	3-month LIBOR plus 1.40%
Trust Preferred Debt Owed To Trust	$ 51,547
Final Maturity Date	Mar. 01, 2036
Alliance Financial Capital Trust I [Member]
Debt Instrument [Line Items]
Issuance Date	Dec. 01, 2003
Trust Preferred Securities Outstanding	$ 10,000
Interest Rate	3-month LIBOR plus 2.85%
Trust Preferred Debt Owed To Trust	$ 10,310
Final Maturity Date	Jan. 01, 2034
Alliance Financial Capital Trust II [Member]
Debt Instrument [Line Items]
Issuance Date	Sep. 01, 2006
Trust Preferred Securities Outstanding	$ 15,000
Interest Rate	3-month LIBOR plus 1.65%
Trust Preferred Debt Owed To Trust	$ 15,464
Final Maturity Date	Sep. 01, 2036
NBT Bancorp Inc [Member]
Debt Instrument [Line Items]
Trust equity method investment	$ 1,000
Alliance Financial Capital [Member]
Debt Instrument [Line Items]
Number of wholly owned Delaware statutory business trusts	2
Trusts [Member]
Debt Instrument [Line Items]
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

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current [Abstract]
Federal	$ 26,059	$ 23,536	$ 21,011
State	2,823	2,316	1,815
Current tax expense (benefit)	28,882	25,852	22,826
Deferred [Abstract]
Federal	6,648	2,334	(13)
State	1,699	10	3
Deferred tax expense (benefit)	8,347	2,344	(10)
Total income tax expense	37,229	28,196	22,816
Income tax recorded to stockholders' equity	(1,100)	7,000	(100)
Deferred tax assets [Abstract]
Allowance for loan and lease losses	25,689	26,729
Deferred compensation	8,744	7,931
Postretirement benefit obligation	2,377	2,596
Unrealized losses on securities available for sale	0	5,900
Accrued liabilities	1,778	3,265
Stock-based compensation expense	6,457	7,862
Equipment leasing	1,416	1,661
Other	1,325	2,125
Total deferred tax assets	47,786	58,069
Deferred tax liabilities [Abstract]
Pension and executive retirement	12,192	17,417
Fair value adjustments from acquisitions	1,243	2,070
Unrealized gains on securities available for sale	1,331	0
Premises and equipment, primarily due to accelerated depreciation	2,491	2,270
Deferred loan costs	1,460	1,624
Intangible amortization	14,162	12,007
Other	390	892
Total deferred tax liabilities	33,269	36,280
Net deferred tax asset at year-end	14,517	21,789	11,115
Net deferred tax asset (liability) at beginning of year	21,789	11,115
Increase in net deferred tax asset	$ (7,272)	10,674
Reconciliation of gross unrecognized tax benefits [Roll Forward]
Reduction in unrecognized tax benefits resulting from expiration of statute of limitations of prior years' tax filings			(900)
Decrease in tax expense			(800)
Federal statutory income tax rate (in hundredths)	35.00%
Income tax reconciliation [Abstract]
Federal income tax at statutory rate	$ 39,306	31,482	27,081
Tax exempt income	(2,250)	(2,433)	(2,536)
Net increase in CSV of life insurance	(1,734)	(1,166)	(908)
Low income housing tax credits	(880)	(819)	(629)
State taxes, net of federal tax benefit	2,939	1,512	1,182
Other, net	(152)	(380)	(1,374)
Total income tax expense	$ 37,229	$ 28,196	$ 22,816

Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
Employee Benefit Plans (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Adjustment of accumulated other comprehensive income				$ 2,400
Transition obligation period of recognition	20 years
Net actuarial loss that will be amortized from Accumulated other comprehensive income (loss) in next fiscal year	$ 2,400
Prior service credit that will be amortized from Accumulated other comprehensive income (loss) in next fiscal year	$ 200
Assumptions used to determine benefit obligations [Abstract]
Discount rate (in hundredths)						3.50%
Expected long-term return on plan assets (in hundredths)				7.50%	7.50%	7.50%
Rate of compensation increase (in hundredths)					3.00%	3.00%
Assumptions used to determine net periodic pension cost [Abstract]
Discount rate (in hundredths)		3.50%	4.10%
Expected long-term return on plan assets (in hundredths)	7.50%	7.50%	7.50%
Rate of compensation increase (in hundredths)		3.00%	3.00%
Other changes in plan assets and benefit obligation recognized in other comprehensive income (pre-tax) [Abstract]
Amortization of prior service cost	$ (75)	$ (2,790)	$ (3,593)
Amortization of unrecognized net gain	$ (19,245)	21,923	(24)
Estimate future benefit payments [Abstract]
Annual rates of increase in the per capita cost of covered medical and prescription drug benefits, minimum (in hundredths)	7.00%
Annual rates of increase in the per capita cost of covered medical and prescription drug benefits, maximum (in hundredths)	9.00%
Ultimate health care cost trend rate (in hundredths)	3.90%
Actual plan asset allocations [Abstract]
Actual plan asset allocations (in hundredths)				100.00%	100.00%
Employer contributions to 401 (k) plan	$ 2,200	2,100	1,800
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	39
One-percentage point (decrease) on total service and interest cost components	(33)
One-percentage point Increase on postretirement accumulated benefit obligation	895
One-percentage point (decrease) on postretirement accumulated benefit obligation	$ (764)
Minimum [Member]
Assumptions used to determine benefit obligations [Abstract]
Discount rate (in hundredths)				4.19%	4.90%
Rate of compensation increase (in hundredths)				3.00%
Assumptions used to determine net periodic pension cost [Abstract]
Discount rate (in hundredths)	4.90%
Rate of compensation increase (in hundredths)	3.00%
Maximum [Member]
Assumptions used to determine benefit obligations [Abstract]
Discount rate (in hundredths)				4.30%	5.05%
Rate of compensation increase (in hundredths)				3.75%
Assumptions used to determine net periodic pension cost [Abstract]
Discount rate (in hundredths)	5.05%
Rate of compensation increase (in hundredths)	3.75%
Pension Benefits [Member]
Accumulated other comprehensive income (loss), before tax [Abstract]
Net actuarial loss				$ 28,767	$ 11,286
Prior service cost				97	118
Total amounts recognized in accumulated other comprehensive loss (pre-tax)				28,864	11,404
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of period	$ 85,667	85,130
Service cost	2,290	2,493	3,122
Interest cost	4,142	3,223	3,145
Plan participants' contributions	0	0
Actuarial(gain) loss	12,501	(10,853)
Amendments	0	0
Acquisition	0	10,958
Benefits paid	(6,044)	(5,284)
Projected benefit obligation at end of period	98,556	85,667	85,130
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	118,574	99,705
Actual return on plan assets	3,950	18,451
Acquisition	0	4,994
Employer contributions	752	708
Plan participants' contributions	0	0
Benefits paid	(6,044)	(5,284)
Fair value of plan assets at end of period	117,232	118,574	99,705
Funded status				18,676	32,907
Accumulated benefit obligation				98,600	85,700
Amounts recognized in Balance Sheet [Abstract]
Other assets				39,044	48,189
Other liabilities				(20,368)	(15,282)
Funded status				18,676	32,907
Components of net periodic benefit cost [Abstract]
Service cost	2,290	2,493	3,122
Interest cost	4,142	3,223	3,145
Expected return on plan assets	(8,681)	(7,804)	(6,686)
Amortization of prior service cost	23	23	283
Amortization of unrecognized net loss	79	2,692	3,330
Net periodic pension cost	(2,147)	627	3,194
Other changes in plan assets and benefit obligation recognized in other comprehensive income (pre-tax) [Abstract]
Net loss (gain)	17,233	(21,500)	894
Prior service cost	0	0	(1,006)
Amortization of prior service cost	(23)	(23)	(283)
Amortization of unrecognized net gain	(79)	(2,692)	(3,330)
Total recognized in other comprehensive loss (income)	17,131	(24,215)	(3,725)
Total recognized in net periodic benefit cost and other comprehensive income (loss) - pre-tax	14,984	(23,588)	(531)
Estimate future benefit payments [Abstract]
2014				6,011
2015				6,221
2016				9,473
2017				7,100
2018				6,953
2019 - 2022				40,351
Actual plan asset allocations [Abstract]
Fair value of plan assets	118,574	118,574	99,705	117,232	118,574	$ 99,705
Pension Benefits [Member] \| Level 1 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	86,711
Fair value of plan assets at end of period	72,722	86,711
Actual plan asset allocations [Abstract]
Fair value of plan assets	86,711	86,711		72,722	86,711
Pension Benefits [Member] \| Level 2 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	31,863
Fair value of plan assets at end of period	44,510	31,863
Actual plan asset allocations [Abstract]
Fair value of plan assets	44,510	31,863		$ 44,510	$ 31,863
Pension Benefits [Member] \| Cash and Cash Equivalents [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	7,533
Fair value of plan assets at end of period	$ 4,423	7,533
Target asset allocations [Abstract]
Target allocation percentage of assets, range minimum (in hundredths)	0.00%
Target allocation percentage of assets, range maximum (in hundredths)	20.00%
Actual plan asset allocations [Abstract]
Actual plan asset allocations (in hundredths)				4.00%	6.00%
Fair value of plan assets	$ 4,423	7,533		$ 4,423	$ 7,533
Pension Benefits [Member] \| Cash and Cash Equivalents [Member] \| Level 1 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	7,533
Fair value of plan assets at end of period	4,423	7,533
Actual plan asset allocations [Abstract]
Fair value of plan assets	4,423	7,533		4,423	7,533
Pension Benefits [Member] \| Cash and Cash Equivalents [Member] \| Level 2 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	0
Fair value of plan assets at end of period	0	0
Actual plan asset allocations [Abstract]
Fair value of plan assets	$ 0	0		$ 0	$ 0
Pension Benefits [Member] \| Fixed Income Securities [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets, range minimum (in hundredths)	20.00%
Target allocation percentage of assets, range maximum (in hundredths)	40.00%
Actual plan asset allocations [Abstract]
Actual plan asset allocations (in hundredths)				38.00%	27.00%
Pension Benefits [Member] \| Equity [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets, range minimum (in hundredths)	40.00%
Target allocation percentage of assets, range maximum (in hundredths)	80.00%
Actual plan asset allocations [Abstract]
Actual plan asset allocations (in hundredths)				58.00%	67.00%
Pension Benefits [Member] \| Foreign Equity Mutual Funds [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	$ 15,653
Fair value of plan assets at end of period	38,581	15,653
Actual plan asset allocations [Abstract]
Fair value of plan assets	15,653	15,653		$ 38,581	$ 15,653
Pension Benefits [Member] \| Foreign Equity Mutual Funds [Member] \| Level 1 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	15,653
Fair value of plan assets at end of period	38,581	15,653
Actual plan asset allocations [Abstract]
Fair value of plan assets	15,653	15,653		38,581	15,653
Pension Benefits [Member] \| Foreign Equity Mutual Funds [Member] \| Level 2 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	0
Fair value of plan assets at end of period	0	0
Actual plan asset allocations [Abstract]
Fair value of plan assets	0	0		0	0
Pension Benefits [Member] \| Equity Mutual Funds [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	16,727
Fair value of plan assets at end of period	29,718	16,727
Actual plan asset allocations [Abstract]
Fair value of plan assets	16,727	16,727		29,718	16,727
Pension Benefits [Member] \| Equity Mutual Funds [Member] \| Level 1 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	16,727
Fair value of plan assets at end of period	29,718	16,727
Actual plan asset allocations [Abstract]
Fair value of plan assets	29,718	16,727		29,718	16,727
Pension Benefits [Member] \| Equity Mutual Funds [Member] \| Level 2 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	0
Fair value of plan assets at end of period	0	0
Actual plan asset allocations [Abstract]
Fair value of plan assets	0	0		0	0
Pension Benefits [Member] \| US Government Bonds [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	9,355
Fair value of plan assets at end of period	4,420	9,355
Actual plan asset allocations [Abstract]
Fair value of plan assets	9,355	9,355		4,420	9,355
Pension Benefits [Member] \| US Government Bonds [Member] \| Level 1 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	0
Fair value of plan assets at end of period	0	0
Actual plan asset allocations [Abstract]
Fair value of plan assets	0	0		0	0
Pension Benefits [Member] \| US Government Bonds [Member] \| Level 2 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	9,355
Fair value of plan assets at end of period	4,420	9,355
Actual plan asset allocations [Abstract]
Fair value of plan assets	9,355	9,355		4,420	9,355
Pension Benefits [Member] \| Corporate Bonds [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	19,665
Fair value of plan assets at end of period	40,090	19,665
Actual plan asset allocations [Abstract]
Fair value of plan assets	19,665	19,665		40,090	19,665
Pension Benefits [Member] \| Corporate Bonds [Member] \| Level 1 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	0
Fair value of plan assets at end of period	0	0
Actual plan asset allocations [Abstract]
Fair value of plan assets	0	0		0	0
Pension Benefits [Member] \| Corporate Bonds [Member] \| Level 2 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	19,665
Fair value of plan assets at end of period	40,090	19,665
Actual plan asset allocations [Abstract]
Fair value of plan assets	40,090	19,665		40,090	19,665
Pension Benefits [Member] \| Common Stock [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	44,532
Fair value of plan assets at end of period		44,532
Actual plan asset allocations [Abstract]
Fair value of plan assets	44,532	44,532			44,532
Pension Benefits [Member] \| Common Stock [Member] \| Level 1 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	44,532
Fair value of plan assets at end of period		44,532
Actual plan asset allocations [Abstract]
Fair value of plan assets	44,532	44,532			44,532
Pension Benefits [Member] \| Common Stock [Member] \| Level 2 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	0
Fair value of plan assets at end of period		0
Actual plan asset allocations [Abstract]
Fair value of plan assets	0	0			0
Pension Benefits [Member] \| Municipal Bonds and Notes [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	1,451
Fair value of plan assets at end of period		1,451
Actual plan asset allocations [Abstract]
Fair value of plan assets	1,451	1,451			1,451
Pension Benefits [Member] \| Municipal Bonds and Notes [Member] \| Level 1 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	0
Fair value of plan assets at end of period		0
Actual plan asset allocations [Abstract]
Fair value of plan assets	0	0			0
Pension Benefits [Member] \| Municipal Bonds and Notes [Member] \| Level 2 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	1,451
Fair value of plan assets at end of period		1,451
Actual plan asset allocations [Abstract]
Fair value of plan assets	1,451	1,451			1,451
Pension Benefits [Member] \| Foreign Bonds and Notes [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	1,392
Fair value of plan assets at end of period		1,392
Actual plan asset allocations [Abstract]
Fair value of plan assets	1,392	1,392			1,392
Pension Benefits [Member] \| Foreign Bonds and Notes [Member] \| Level 1 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	0
Fair value of plan assets at end of period		0
Actual plan asset allocations [Abstract]
Fair value of plan assets	0	0			0
Pension Benefits [Member] \| Foreign Bonds and Notes [Member] \| Level 2 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	1,392
Fair value of plan assets at end of period		1,392
Actual plan asset allocations [Abstract]
Fair value of plan assets	1,392	1,392			1,392
Pension Benefits [Member] \| Foreign Equity [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	2,266
Fair value of plan assets at end of period		2,266
Actual plan asset allocations [Abstract]
Fair value of plan assets	2,266	2,266			2,266
Pension Benefits [Member] \| Foreign Equity [Member] \| Level 1 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	2,266
Fair value of plan assets at end of period		2,266
Actual plan asset allocations [Abstract]
Fair value of plan assets	2,266	2,266			2,266
Pension Benefits [Member] \| Foreign Equity [Member] \| Level 2 [Member]
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	0
Fair value of plan assets at end of period		0
Actual plan asset allocations [Abstract]
Fair value of plan assets	0	0			0
Other Benefits [Member]
Accumulated other comprehensive income (loss), before tax [Abstract]
Net actuarial loss				2,929	1,628
Prior service cost				(314)	(521)
Total amounts recognized in accumulated other comprehensive loss (pre-tax)				2,615	1,107
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of period	7,428	4,071
Service cost	16	23	20
Interest cost	347	286	155
Plan participants' contributions	266	269
Actuarial(gain) loss	1,452	(369)
Amendments	0	(54)
Acquisition	0	3,928
Benefits paid	(799)	(726)
Projected benefit obligation at end of period	8,710	7,428	4,071
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of period	0	0
Actual return on plan assets	0	0
Acquisition	0	0
Employer contributions	533	457
Plan participants' contributions	266	269
Benefits paid	(799)	(726)
Fair value of plan assets at end of period	0	0	0
Funded status				(8,710)	(7,428)
Accumulated benefit obligation				8,700	7,400
Amounts recognized in Balance Sheet [Abstract]
Other assets				0	0
Other liabilities				(8,710)	(7,428)
Funded status				(8,710)	(7,428)
Components of net periodic benefit cost [Abstract]
Service cost	16	23	20
Interest cost	347	286	155
Expected return on plan assets	0	0	0
Amortization of prior service cost	(206)	(205)	(202)
Amortization of unrecognized net loss	151	280	182
Net periodic pension cost	308	384	155
Other changes in plan assets and benefit obligation recognized in other comprehensive income (pre-tax) [Abstract]
Net loss (gain)	1,452	(369)	136
Prior service cost	0	(54)	0
Amortization of prior service cost	206	205	202
Amortization of unrecognized net gain	(151)	(280)	(182)
Total recognized in other comprehensive loss (income)	1,507	(498)	156
Total recognized in net periodic benefit cost and other comprehensive income (loss) - pre-tax	1,815	(114)	311
Estimate future benefit payments [Abstract]
2014				538
2015				549
2016				571
2017				592
2018				578
2019 - 2022				2,881
Actual plan asset allocations [Abstract]
Fair value of plan assets	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0

Stock-Based Compensation (Details) - USD ($)	12 Months Ended
Stock-Based Compensation (Details) - USD ($)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock options additional disclosures [Abstract]
Stock-based compensation expense	$ 3,521,000	$ 4,305,000	$ 4,364,000
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]
Number of shares available for future grant (in shares)	3,800,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting period	4 years
Stock awards termination period	10 years
Stock options [Roll Forward]
Outstanding, beginning of period (in shares)	1,341,500
Granted (in shares)	3,296
Exercised (in shares)	(290,243)
Forfeited (in shares)	(105)
Expired (in shares)	(16,106)
Outstanding, end of period (in shares)	1,038,342	1,341,500
Exercisable, end of period (in shares)	1,031,726
Expected to vest (in shares)	5,249
Stock options, weighted average exercise price [Abstract]
Outstanding, beginning of period (in dollars per share)	$ 22.98
Granted (in dollars per share)	24.80
Exercised (in dollars per share)	22.58
Forfeited (in dollars per share)	20.19
Expired (in dollars per share)	22.36
Outstanding, end of period (in dollars per share)	23.10	$ 22.98
Exercisable, end of period (in dollars per share)	23.09
Expected to vest (in dollars per share)	$ 24.50
Stock options additional disclosures [Abstract]
Weighted average remaining contractual term, outstanding, end of period (in years)	3 years 4 months 24 days
Weighted average remaining contractual term, exercisable, end of period (in years)	3 years 4 months 13 days
Weighted average remaining contractual term, expected to vest (in years)	7 years 3 months 25 days
Aggregate intrinsic value, outstanding, end of period	$ 3,353,951
Aggregate intrinsic value, exercisable, end of period	3,342,258
Aggregate intrinsic value, expected to vest	9,354
Stock-based compensation expense	100,000	$ 200,000	500,000
Proceeds from stock options exercised	6,554,000	7,927,000	1,908,000
Tax benefits related to stock options exercised	313,000	178,000	8,000
Intrinsic value of stock options exercised	789,000	905,000	498,000
Fair value of shares vested during the year	393,000	$ 766,000	1,656,000
Restricted Stock [Member]
Stock options additional disclosures [Abstract]
Unrecognized compensation cost	$ 4,400,000
Unrecognized compensation cost, weighted average period of recognition (in years)	1 year 8 months 12 days
Restricted stock and restricted stock units [Roll Forward]
Unvested, beginning of period (in shares)	66,650
Forfeited (in shares)	0
Vested (in shares)	(14,650)
Unvested, end of period (in shares)	52,000	66,650
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]
Unvested, beginning of period (in dollars per share)	$ 23.15
Forfeited (in dollars per share)	0
Vested (in dollars per share)	22.16
Unvested, end of period (in dollars per share)	$ 23.43	$ 23.15
Restricted Stock [Member] \| Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting period	5 years
Restricted Stock [Member] \| Non-employee Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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)	539,850
Forfeited (in shares)	(5,090)
Vested (in shares)	(105,013)
Granted (in shares)	209,228
Unvested, end of period (in shares)	638,975	539,850
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]
Unvested, beginning of period (in dollars per share)	$ 27.36
Forfeited (in dollars per share)	0
Vested (in dollars per share)	0
Granted (in dollars per share)	24.11
Unvested, end of period (in dollars per share)	$ 31.01	$ 27.36
Restricted and Deferred Stock Awards [Member]
Stock options additional disclosures [Abstract]
Stock-based compensation expense	$ 4,200,000	$ 3,800,000	3,700,000
Tax benefit from compensation expense	$ 2,900,000	$ 2,400,000	$ 1,500,000

Stockholders Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Oct. 27, 2014
Stockholders Equity [Abstract]
Unrecognized prior service cost and net actuarial loss on pension plans	$ (19,181)	$ (7,785)
Unrealized net holding (losses) gains on available for sale securities	2,154	(8,980)
Accumulated other comprehensive loss	$ (17,027)	$ (16,765)
Class of Warrant or Right [Line Items]
Future dividend payment restrictions	The approval of the Office of Comptroller of the Currency (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.
Preceding period of retained net profits for approval of Office of Comptroller of the Currency (in years)	2 years
Statutory amount available for dividend payments	$ 88,700
Common stock repurchased during period (in shares)	3,288	584,925	769,568
Common stock repurchased during period	$ 100
Treasury Stock Acquired, Average Cost Per Share	$ 22.02
Stock Repurchase Program, Number Of Additional Shares Authorized To Be Repurchased				1,000,000

Regulatory Capital Requirements (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Total Capital (to risk weighted assets) [Abstract]
Total capital to risk weighted assets	$ 777,651	$ 723,580
Total capital to risk weighted assets (in hundredths)	13.50%	12.99%
Minimum capital required for capital adequacy to risk weighted assets (in hundredths)	8.00%	8.00%
Capital required for classification as well capitalized to risk weighted assets (in hundredths)	10.00%	10.00%
Tier I Capital (to risk weighted assets) [Abstract]
Tier I capital to risk weighted assets	$ 709,965	$ 653,950
Tier I capital to risk weighted assets (in hundredths)	12.32%	11.74%
Minimum Tier one capital required for capital adequacy to risk weighted assets(in hundredths)	4.00%	4.00%
Tier one capital required for classification as well capitalized to risk weighted assets (in hundredths)	6.00%	6.00%
Tier I Capital (to average assets) [Abstract]
Tier I capital to average assets	$ 709,965	$ 653,950
Tier I capital to average assets (in hundredths)	9.39%	8.93%
Minimum Tier I leverage capital required for capital adequacy to average assets (in hundredths)	4.00%	4.00%
Tier I leverage capital required for classification as well capitalized to average assets (in hundredths)	5.00%	5.00%
NBT Bank [Member]
Total Capital (to risk weighted assets) [Abstract]
Total capital to risk weighted assets	$ 727,771	$ 686,194
Total capital to risk weighted assets (in hundredths)	12.72%	12.41%
Minimum capital required for capital adequacy to risk weighted assets (in hundredths)	8.00%	8.00%
Capital required for classification as well capitalized to risk weighted assets (in hundredths)	10.00%	10.00%
Tier I Capital (to risk weighted assets) [Abstract]
Tier I capital to risk weighted assets	$ 660,086	$ 617,038
Tier I capital to risk weighted assets (in hundredths)	11.54%	11.16%
Minimum Tier one capital required for capital adequacy to risk weighted assets(in hundredths)	4.00%	4.00%
Tier one capital required for classification as well capitalized to risk weighted assets (in hundredths)	6.00%	6.00%
Tier I Capital (to average assets) [Abstract]
Tier I capital to average assets	$ 660,086	$ 617,038
Tier I capital to average assets (in hundredths)	8.79%	8.47%
Minimum Tier I leverage capital required for capital adequacy to average assets (in hundredths)	4.00%	4.00%
Tier I leverage capital required for classification as well capitalized to average assets (in hundredths)	5.00%	5.00%

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Basic earnings per share [Abstract]
Net income available to common shareholders	$ 75,074	$ 61,747	$ 54,558
Weighted average common shares, basic (in shares)	43,877,000	41,930,000	33,379,000
Basic EPS (in dollars per share)	$ 1.71	$ 1.47	$ 1.63
Diluted earnings per share [Abstract]
Net income available to common shareholders	$ 75,074	$ 61,747	$ 54,558
Dilutive effect of stock based compensation (in shares)	518,000	420,000	340,000
Weighted average common shares, diluted (in shares)	44,395,000	42,350,000	33,719,000
Diluted EPS (in dollars per share)	$ 1.69	$ 1.46	$ 1.62
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock options excluded from calculation of diluted EPS (in shares)	493,000	1,048,000	1,193,000

Reclassification Adjustments Out of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains	$ (92)	$ (1,426)	$ (599)
Interest income	(251,878)	(238,079)	(204,203)
Salaries and employee benefits	119,667	113,580	104,815
Income tax expense	37,229	28,196	22,816
Net Income	75,074	61,747	$ 54,558
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	200	565
Total reclassification during the period, net of tax	(267)	740
Accumulated Net Unrealized Investment Gain (Loss) [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income	(313)	(861)
Gains on Available for Sale Securities [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net securities gains	(92)	(1,426)
Amortization of Unrealized Gains and Losses Related to Securities Transfer [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest income	(421)	0
Accumulated Defined Benefit Plans Adjustment [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	29	1,189
Net Income	46	1,601
Amortization of Net Gains [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	94	2,972
Amortization of Prior Service Costs [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	$ (19)	$ (182)

Commitments and Contingent Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 24, 2014
Commitments and Contingent Liabilities [Abstract]
Percentage of the Company's loans secured by real estate (in hundredths)	59.00%
Guarantor Obligations [Line Items]
Loans serviced by the Company for unrelated third parties	$ 626,000	$ 685,600
Mortgage servicing rights	$ 1,500	2,200
Federal Reserve Bank Requirement [Abstract]
Federal Reserve Bank maintenance period	14 days
Average reserve at Federal Reserve Bank for maintenance period			$ 46,900
Unused lines of Credit [Member]
Guarantor Obligations [Line Items]
Commitments - maximum potential obligation	$ 214,175	216,658
Commitment to Extend Credits [Member]
Guarantor Obligations [Line Items]
Commitments - maximum potential obligation	972,912	849,092
Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Commitments - maximum potential obligation	35,244	$ 36,837
Obligation instrument term		5 years
Commercial Letters of Credit [Member]
Guarantor Obligations [Line Items]
Commitments - maximum potential obligation	22,486	$ 41,263
Loans Sold with Recourse [Member]
Guarantor Obligations [Line Items]
Commitments - maximum potential obligation	$ 23,351	$ 15,741

Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Financial assets [Abstract]
Securities held to maturity	$ 454,994	$ 113,276
Financial liabilities [Abstract]
Time deposits	1,043,823	1,021,142
Long-term debt	130,945	308,823
Junior subordinated debt	101,196	101,196
Securities Available for Sale [Abstract]
Total Securities Available for Sale	1,013,171	1,364,881
Trading Securities	7,793	5,779
Liabilities [Abstract]
Collateral dependent impaired financing receivable with specific reserves	5,800
Allowance for loan and lease losses collateral dependent impaired loans with specific reserves	$ 1,100
Liquidation expense ratio on impaired collateral minimum (in hundredths)	10.00%
Liquidation expense ratio on impaired collateral maximum (in hundredths)	35.00%
Carrying Amount [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Financial assets [Abstract]
Securities held to maturity	$ 454,361	117,283
Financial liabilities [Abstract]
Time deposits	1,043,823	1,021,142
Long-term debt	130,945	308,823
Junior subordinated debt	101,196	101,196
Carrying Amount [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Financial assets [Abstract]
Net Loans	5,528,912	5,337,361
Estimated Fair Value [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Financial assets [Abstract]
Securities held to maturity	454,994	113,276
Financial liabilities [Abstract]
Time deposits	1,038,877	1,023,982
Long-term debt	132,562	325,195
Junior subordinated debt	103,770	105,121
Estimated Fair Value [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Financial assets [Abstract]
Net Loans	5,584,777	5,386,520
Recurring Basis [Member]
Securities Available for Sale [Abstract]
U.S. Treasury	23,111	43,616
Federal Agency	329,914	278,915
State & municipal	37,570	113,665
Mortgage-backed	364,727	364,164
Collateralized mortgage obligations	242,129	549,528
Other securities	15,720	14,993
Total Securities Available for Sale	1,013,171	1,364,881
Trading Securities	7,793	5,779
Interest Rate Swaps	4,707	281
Total	1,025,671	1,370,941
Liabilities [Abstract]
Interest Rate Swaps	4,707	281
Total	4,707	281
Recurring Basis [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Securities Available for Sale [Abstract]
U.S. Treasury	23,111	43,616
Federal Agency	0	0
State & municipal	0	0
Mortgage-backed	0	0
Collateralized mortgage obligations	0	0
Other securities	7,612	6,796
Total Securities Available for Sale	30,723	50,412
Trading Securities	7,793	5,779
Interest Rate Swaps	0	0
Total	38,516	56,191
Liabilities [Abstract]
Interest Rate Swaps	0	0
Total	0	0
Recurring Basis [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Securities Available for Sale [Abstract]
U.S. Treasury	0	0
Federal Agency	329,914	278,915
State & municipal	37,570	113,665
Mortgage-backed	364,727	364,164
Collateralized mortgage obligations	242,129	549,528
Other securities	8,108	8,197
Total Securities Available for Sale	982,448	1,314,469
Trading Securities	0	0
Interest Rate Swaps	4,707	281
Total	987,155	1,314,750
Liabilities [Abstract]
Interest Rate Swaps	4,707	281
Total	4,707	281
Recurring Basis [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Securities Available for Sale [Abstract]
U.S. Treasury	0	0
Federal Agency	0	0
State & municipal	0	0
Mortgage-backed	0	0
Collateralized mortgage obligations	0	0
Other securities	0	0
Total Securities Available for Sale	0	0
Trading Securities	0	0
Interest Rate Swaps	0	0
Total	0	0
Liabilities [Abstract]
Interest Rate Swaps	0	0
Total	$ 0	$ 0

Sale of Equity Investment (Details) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
Sale of Equity Investment (Details) - USD ($)	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Sale of Equity Investment [Abstract]
Date of disposal		Apr. 17, 2014
Percentage of ownership interest sold (in hundredths)	20.00%	20.00%	20.00%
Book value	$ 3,000,000	$ 3,000,000	$ 3,000,000
Total sale price of investment	140,000,000	140,000,000	140,000,000
Gain on sale of equity investments	19,401,000		19,401,000	$ 0	$ 0
Proceeds of sale held in escrow	$ 5,200,000	$ 5,200,000	$ 5,200,000

Parent Company Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets [Abstract]
Cash and cash equivalents	$ 158,926	$ 158,926	$ 129,381	$ 146,636	$ 158,926	$ 163,668	$ 129,381
Securities available for sale, at estimated fair value				1,013,171	1,364,881
Trading securities				7,793	5,779
Other assets				126,967	127,234
Total assets				7,797,926	7,652,175
Liabilities and Stockholders' Equity [Abstract]
Total liabilities				6,933,745	6,835,606
Stockholders' equity				864,181	816,569	582,273	538,110
Total liabilities and stockholders' equity				7,797,926	7,652,175
Condensed Income Statements [Abstract]
Securities gains (losses)	92	1,426	599
Interest, dividend and other income	275,081	268,723	239,397
Income before income tax benefit and equity in undistributed income of subsidiaries	112,303	89,943	77,374
Income tax (expense) benefit	(37,229)	(28,196)	(22,816)
Net income	75,074	61,747	54,558
Operating activities [Abstract]
Net income	75,074	61,747	54,558
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Stock-based compensation	3,521	4,305	4,364
Gain (Loss) on sales of available-for-sale securities	(49)	(1,283)	(442)
Net change in other liabilities	5,286	(5,219)	(128)
Net change in other assets	(27,949)	20,463	6,804
Net cash provided by operating activities	87,811	119,298	88,854
Investing activities [Abstract]
Purchases of available-for-sale securities	(197,652)	(353,714)	(483,858)
Sales and maturities of available-for-sale securities	236,133	376,509	573,828
Purchases of premises and equipment	(9,003)	(5,766)	(6,994)
Net cash used in investing activities	(143,741)	(183,754)	(126,850)
Financing activities [Abstract]
Payments on long-term debt	(315,831)	(163,595)	(3,354)
Purchases of treasury shares	72	12,459	15,490
Cash dividends and payments for fractional shares	(36,905)	(33,518)	(26,712)
Net cash provided by financing activities	43,640	59,714	72,283
Net (decrease) increase in cash and cash equivalents	(12,290)	(4,742)	34,287
Cash and cash equivalents at beginning of year	158,926	163,668	129,381
Cash and cash equivalents at end of year	146,636	158,926	163,668
NBT Bancorp Inc [Member]
Assets [Abstract]
Cash and cash equivalents	3,741	3,741	23,095	3,586	3,741	$ 23,095	$ 2,454
Securities available for sale, at estimated fair value				11,649	11,008
Trading securities				6,761	4,742
Investment in subsidiaries, on equity basis				947,880	896,479
Other assets				61,829	49,530
Total assets				1,031,705	965,500
Liabilities and Stockholders' Equity [Abstract]
Total liabilities				167,524	148,931
Stockholders' equity				864,181	816,569
Total liabilities and stockholders' equity				$ 1,031,705	$ 965,500
Condensed Income Statements [Abstract]
Dividends from subsidiaries	35,400	13,500	79,175
Management fee from subsidiaries	87,116	84,778	78,665
Securities gains (losses)	49	1,273	442
Interest, dividend and other income	800	636	720
Total revenue	123,365	100,187	159,002
Operating expense	89,834	83,679	79,015
Income before income tax benefit and equity in undistributed income of subsidiaries	33,531	16,508	79,987
Income tax (expense) benefit	631	(1,046)	(284)
Dividends in excess of income (equity in undistributed income) of subsidiaries	40,912	46,285	(25,145)
Net income	75,074	61,747	54,558
Operating activities [Abstract]
Net income	75,074	61,747	54,558
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Stock-based compensation	3,521	4,305	4,364
Gain (Loss) on sales of available-for-sale securities	49	1,273	442
Equity in undistributed income	(75,824)	(59,785)	(54,030)
Cash dividend from subsidiaries	35,400	13,500	79,175
Net change in other liabilities	18,594	(18,077)	(3,181)
Net change in other assets	(25,151)	14,928	2,030
Net cash provided by operating activities	31,663	17,891	83,358
Investing activities [Abstract]
Purchases of available-for-sale securities	(597)	0	(4,163)
Sales and maturities of available-for-sale securities	140	1,948	1,445
Net cash used in acquisitions	0	2,232	(14,612)
Purchases of premises and equipment	(640)	(782)	(1,240)
Net cash used in investing activities	(1,097)	3,398	(18,570)
Financing activities [Abstract]
Proceeds from the issuance of shares to employee benefit plans and other stock plans	5,943	5,512	1,387
Payments on long-term debt	0	0	(3,340)
Purchases of treasury shares	(72)	(12,459)	(15,490)
Cash dividends and payments for fractional shares	(36,905)	(33,518)	(26,712)
Excess tax benefit from exercise of stock options	313	(178)	8
Net cash provided by financing activities	(30,721)	(40,643)	(44,147)
Net (decrease) increase in cash and cash equivalents	(155)	(19,354)	20,641
Cash and cash equivalents at beginning of year	3,741	23,095	2,454
Cash and cash equivalents at end of year	$ 3,586	$ 3,741	$ 23,095

Label	Element	Value
Agricultural Financing Receivable [Member] \| Acquired Loans [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	$ 0
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Agricultural Financing Receivable [Member] \| Acquired Loans [Member] \| Pass [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Agricultural Financing Receivable [Member] \| Acquired Loans [Member] \| Doubtful [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Agricultural Financing Receivable [Member] \| Acquired Loans [Member] \| Substandard [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Agricultural Financing Receivable [Member] \| Acquired Loans [Member] \| Special Mention [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Agricultural Financing Receivable [Member] \| Originated Loans [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	65,162,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	32,947,000
Agricultural Financing Receivable [Member] \| Originated Loans [Member] \| Pass [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	60,043,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	30,481,000
Agricultural Financing Receivable [Member] \| Originated Loans [Member] \| Doubtful [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	12,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	8,000
Agricultural Financing Receivable [Member] \| Originated Loans [Member] \| Substandard [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	4,726,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	2,183,000
Agricultural Financing Receivable [Member] \| Originated Loans [Member] \| Special Mention [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	275,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	381,000
Commercial Real Estate Other Receivable [Member] \| Acquired Loans [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	199,888,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	229,014,000
Commercial Real Estate Other Receivable [Member] \| Acquired Loans [Member] \| Pass [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	205,010,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	186,036,000
Commercial Real Estate Other Receivable [Member] \| Acquired Loans [Member] \| Doubtful [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Commercial Real Estate Other Receivable [Member] \| Acquired Loans [Member] \| Substandard [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	17,821,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	11,206,000
Commercial Real Estate Other Receivable [Member] \| Acquired Loans [Member] \| Special Mention [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	2,646,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	6,183,000
Commercial Real Estate Other Receivable [Member] \| Originated Loans [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	1,068,868,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	934,316,000
Commercial Real Estate Other Receivable [Member] \| Originated Loans [Member] \| Pass [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	1,023,856,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	878,411,000
Commercial Real Estate Other Receivable [Member] \| Originated Loans [Member] \| Doubtful [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Commercial Real Estate Other Receivable [Member] \| Originated Loans [Member] \| Substandard [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	27,671,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	33,128,000
Commercial Real Estate Other Receivable [Member] \| Originated Loans [Member] \| Special Mention [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	17,341,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	22,777,000
Indirect Financing Receivable [Member] \| Acquired Loans [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	125,086,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	65,223,000
Indirect Financing Receivable [Member] \| Acquired Loans [Member] \| Nonperforming Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	160,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	164,000
Indirect Financing Receivable [Member] \| Acquired Loans [Member] \| Performing Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	124,922,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	65,063,000
Indirect Financing Receivable [Member] \| Originated Loans [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	1,161,844,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	1,310,050,000
Indirect Financing Receivable [Member] \| Originated Loans [Member] \| Nonperforming Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	3,955,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	3,044,000
Indirect Financing Receivable [Member] \| Originated Loans [Member] \| Performing Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	1,306,095,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	1,158,800,000
Commercial Financing Receivable [Member] \| Acquired Loans [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	75,264,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	103,226,000
Commercial Financing Receivable [Member] \| Acquired Loans [Member] \| Pass [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	63,630,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	85,692,000
Commercial Financing Receivable [Member] \| Acquired Loans [Member] \| Doubtful [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Commercial Financing Receivable [Member] \| Acquired Loans [Member] \| Substandard [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	8,794,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	15,304,000
Commercial Financing Receivable [Member] \| Acquired Loans [Member] \| Special Mention [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	2,230,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	2,840,000
Commercial Financing Receivable [Member] \| Originated Loans [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	616,423,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	615,147,000
Commercial Financing Receivable [Member] \| Originated Loans [Member] \| Pass [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	570,884,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	576,079,000
Commercial Financing Receivable [Member] \| Originated Loans [Member] \| Doubtful [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Commercial Financing Receivable [Member] \| Originated Loans [Member] \| Substandard [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	23,508,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	38,241,000
Commercial Financing Receivable [Member] \| Originated Loans [Member] \| Special Mention [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	6,022,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	16,836,000
Agricultural Real Estate Financing Receivable [Member] \| Originated Loans [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	24,974,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	36,652,000
Agricultural Real Estate Financing Receivable [Member] \| Originated Loans [Member] \| Pass [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	23,443,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	33,136,000
Agricultural Real Estate Financing Receivable [Member] \| Originated Loans [Member] \| Doubtful [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Financing Receivable, Net	us-gaap_NotesReceivableNet	0
Agricultural Real Estate Financing Receivable [Member] \| Originated Loans [Member] \| Substandard [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	3,473,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	1,489,000
Agricultural Real Estate Financing Receivable [Member] \| Originated Loans [Member] \| Special Mention [Member] \| Commercial [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	43,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	42,000
Direct Financing Receivable Member [Member] \| Acquired Loans [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	5,317,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	7,425,000
Direct Financing Receivable Member [Member] \| Acquired Loans [Member] \| Nonperforming Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	40,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	58,000
Direct Financing Receivable Member [Member] \| Acquired Loans [Member] \| Performing Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	5,277,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	7,367,000
Direct Financing Receivable Member [Member] \| Originated Loans [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	58,283,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	55,794,000
Direct Financing Receivable Member [Member] \| Originated Loans [Member] \| Nonperforming Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	132,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	136,000
Direct Financing Receivable Member [Member] \| Originated Loans [Member] \| Performing Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	58,151,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	55,658,000
Small Business Financing Receivable [Member] \| Acquired Loans [Member] \| Business Banking Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	58,179,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	70,149,000
Small Business Financing Receivable [Member] \| Acquired Loans [Member] \| Classified [Member] \| Business Banking Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	4,915,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	4,712,000
Small Business Financing Receivable [Member] \| Acquired Loans [Member] \| Non classified [Member] \| Business Banking Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	65,437,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	53,264,000
Small Business Financing Receivable [Member] \| Originated Loans [Member] \| Business Banking Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	398,435,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	337,679,000
Small Business Financing Receivable [Member] \| Originated Loans [Member] \| Classified [Member] \| Business Banking Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	18,101,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	18,990,000
Small Business Financing Receivable [Member] \| Originated Loans [Member] \| Non classified [Member] \| Business Banking Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	319,578,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	379,445,000
Home Equity Financing Receivables [Member] \| Acquired Loans [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	87,076,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	76,716,000
Home Equity Financing Receivables [Member] \| Acquired Loans [Member] \| Nonperforming Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	570,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	562,000
Home Equity Financing Receivables [Member] \| Acquired Loans [Member] \| Performing Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	76,154,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	86,506,000
Home Equity Financing Receivables [Member] \| Originated Loans [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	492,880,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	532,823,000
Home Equity Financing Receivables [Member] \| Originated Loans [Member] \| Nonperforming Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	7,417,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	7,046,000
Home Equity Financing Receivables [Member] \| Originated Loans [Member] \| Performing Financing Receivable [Member] \| Consumer Credit Exposure [Member]
Financing Receivable, Net	us-gaap_NotesReceivableNet	485,463,000
Financing Receivable, Net	us-gaap_NotesReceivableNet	$ 525,777,000