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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2013	Oct. 31, 2013
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 Common Stock, Shares Outstanding		43,315,895
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2013

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012
Assets
Cash and due from banks	$ 205,884	$ 157,094
Short-term interest bearing accounts	2,358	6,574
Securities available for sale, at fair value	1,385,734	1,147,999
Securities held to maturity (fair value $115,620 and $61,535, respectively)	118,259	60,563
Trading securities	5,285	3,918
Federal Reserve and Federal Home Loan Bank stock	43,490	29,920
Loans	5,367,231	4,277,616
Less allowance for loan losses	70,184	69,334
Net loans	5,297,047	4,208,282
Premises and equipment, net	86,891	77,875
Goodwill	265,052	152,373
Intangible assets, net	26,857	16,962
Bank owned life insurance	113,821	80,702
Other assets	118,225	99,997
Total assets	7,668,903	6,042,259
Liabilities
Demand (noninterest bearing)	1,595,571	1,242,712
Savings, NOW, and money market	3,343,837	2,558,376
Time	1,063,730	983,261
Total deposits	6,003,138	4,784,349
Short-term borrowings	373,234	162,941
Long-term debt	309,009	367,492
Junior subordinated debt	101,196	75,422
Other liabilities	86,767	69,782
Total liabilities	6,873,344	5,459,986
Stockholders' equity
Preferred stock, $0.01 par value. Authorized 2,500,000 shares at September 30, 2013 and December 31, 2012	0	0
Common stock, $0.01 par value. Authorized 100,000,000 shares at September 30, 2013 and December 31, 2012; issued 49,651,494 at September 30, 2013 and 39,305,131 at December 31, 2012	497	393
Additional paid-in-capital	573,241	346,692
Retained earnings	377,046	357,558
Accumulated other comprehensive loss	(23,120)	(5,880)
Common stock in treasury, at cost, 6,377,701 and 5,529,781 shares at September 30, 2013 and December 31, 2012, respectively	(132,105)	(116,490)
Total stockholders' equity	795,559	582,273
Total liabilities and stockholders' equity	$ 7,668,903	$ 6,042,259

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012
Assets
Securities held to maturity fair value	$ 115,620	$ 61,535
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	39,305,131
Common stock in treasury, at cost (in shares)	6,377,701	5,529,781

Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Interest, fee, and dividend income
Interest and fees on loans	$ 61,773	$ 53,817	$ 177,499	$ 154,534
Securities available for sale	6,520	6,550	18,803	21,024
Securities held to maturity	804	572	1,877	1,829
Other	472	348	1,363	1,153
Total interest, fee, and dividend income	69,569	61,287	199,542	178,540
Interest expense
Deposits	3,999	4,544	12,445	14,521
Short-term borrowings	232	60	341	149
Long-term debt	2,561	3,640	9,196	10,801
Trust preferred debentures	551	436	1,539	1,319
Total interest expense	7,343	8,680	23,521	26,790
Net interest income	62,226	52,607	176,021	151,750
Provision for loan losses	5,198	4,755	17,258	13,329
Net interest income after provision for loan losses	57,028	47,852	158,763	138,421
Noninterest income
Insurance and other financial services revenue	6,038	5,591	18,686	17,024
Service charges on deposit accounts	5,055	4,626	14,311	13,538
ATM and debit card fees	4,276	3,378	11,562	9,403
Retirement plan administration fees	3,062	2,718	8,701	7,462
Trust	4,345	2,242	11,957	6,683
Bank owned life insurance	913	639	2,648	2,228
Net securities gains	329	26	1,413	578
Other	3,129	2,407	8,635	8,449
Total noninterest income	27,147	21,627	77,913	65,365
Noninterest expense
Salaries and employee benefits	29,267	26,641	85,474	78,358
Occupancy	5,262	4,437	15,458	13,150
Data processing and communications	4,059	3,352	11,368	10,041
Professional fees and outside services	3,202	2,735	9,340	7,848
Equipment	2,988	2,435	8,480	7,224
Office supplies and postage	1,640	1,597	4,886	4,842
FDIC expenses	1,285	939	3,688	2,812
Advertising	722	701	2,445	2,308
Amortization of intangible assets	1,346	870	3,548	2,530
Loan collection and other real estate owned	886	614	2,025	2,051
Merger expenses	326	558	12,276	1,895
Other	5,303	4,552	14,453	12,236
Total noninterest expense	56,286	49,431	173,441	145,295
Income before income tax expense	27,889	20,048	63,235	58,491
Income tax expense	8,632	5,513	19,413	17,049
Net income	$ 19,257	$ 14,535	$ 43,822	$ 41,442
Earnings per share
Basic (in dollars per share)	$ 0.44	$ 0.43	$ 1.06	$ 1.24
Diluted (in dollars per share)	$ 0.44	$ 0.43	$ 1.05	$ 1.23

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income	$ 19,257	$ 14,535	$ 43,822	$ 41,442
Other comprehensive income, net of tax
Unrealized net holding (losses) gains arising during the period (pre-tax amounts of ($6,927), $1,463, (33,391) and $1,798)	(4,184)	878	(20,167)	1,079
Reclassification adjustment for net gains related to securities available for sale included in net income (pre-tax amounts of $329, $26, $1,413 and $578)	(197)	(16)	(848)	(347)
Pension and other benefits:
Amortization of prior service cost and actuarial gains (pre-tax amounts of $709, $989, $2,244 and $2,702)	426	599	1,354	1,626
Increase in unrecognized actuarial gains (pre-tax amounts of $4,036, $0, $4,036 and $0)	2,421	0	2,421	0
Total other comprehensive (loss) income	(1,534)	1,461	(17,240)	2,358
Comprehensive income	$ 17,723	$ 15,996	$ 26,582	$ 43,800

Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Other comprehensive (loss) income, before tax
Unrealized net holding (losses) gains arising during the period, pre-tax amounts	$ (6,927)	$ 1,463	$ (33,391)	$ 1,798
Reclassification adjustment for net gains related to securities available for sale included in net income, pre-tax amounts	329	26	1,413	578
Amortization of prior service cost and actuarial gains, pre-tax amounts	709	989	2,244	2,702
Increase in unrecognized actuarial loss, pre-tax amounts	$ 4,036	$ 0	$ 4,036	$ 0

Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [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	41,442	0	0	41,442
Cash dividends	0	0	(19,966)	0	0	(19,966)
Purchase 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 benefit plans and other stock plans, including tax benefit	0	(764)	(196)	0	1,785	825
Stock-based compensation	0	3,558	0	0	0	3,558
Other comprehensive (loss) income	0	0	0	2,358	0	2,358
Ending Balance at Sep. 30, 2012	393	345,934	351,261	(3,746)	(117,181)	576,661
Beginning Balance at Dec. 31, 2012	393	346,692	357,558	(5,880)	(116,490)	582,273
Net income	0	0	43,822	0	0	43,822
Cash dividends	0	0	(24,334)	0	0	(24,334)
Purchase 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 benefit plans and other stock plans, including tax benefit	0	(2,469)	0	0	2,623	154
Stock-based compensation	0	3,571	0	0	0	3,571
Other comprehensive (loss) income	0	0	0	(17,240)	0	(17,240)
Ending Balance at Sep. 30, 2013	$ 497	$ 573,241	$ 377,046	$ (23,120)	$ (132,105)	$ 795,559

- Definition

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

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+ Details

Consolidated Statements of Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Consolidated Statements of Stockholders' Equity (Unaudited) [Abstract]
Cash dividends - per share (in dollars per share)	$ 0.60	$ 0.60
Purchase of treasury shares (in shares)	584,925	769,568
Net issuance of shares for acquisition (in shares)	10,346,363	1,269,592
Treasury stock reissued in acquisition of Alliance (in shares)	408,957
Net issuance of shares to employee benefit plans and other stock plans, including tax benefit (in shares)	145,962	85,943

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating activities
Net income	$ 43,822	$ 41,442
Adjustments to reconcile net income to net cash provided by operating activities
Provision for loan losses	17,258	13,329
Depreciation and amortization of premises and equipment	5,885	4,636
Net accretion on securities	4,082	1,766
Amortization of intangible assets	3,548	2,530
Stock based compensation	3,571	3,558
Bank owned life insurance income	(2,648)	(2,228)
Purchases of trading securities	(1,022)	(705)
Unrealized gains in trading securities	(345)	(84)
Deferred income tax expense (benefit)	1,126	(2,735)
Proceeds from sale of loans held for sale	59,231	37,922
Originations of loans held for sale	(65,722)	(47,263)
Net gains on sales of loans held for sale	(1,168)	(1,352)
Net security gains	(1,413)	(578)
Net gains on sales of other real estate owned	(654)	(602)
Net decrease in other assets	12,016	9,316
Net increase (decrease) in other liabilities	8,694	(1,213)
Net cash provided by operating activities	86,261	57,739
Investing activities
Net cash provided by acquisitions	80,909	53,121
Securities available for sale:
Proceeds from maturities, calls, and principal paydowns	314,104	381,160
Proceeds from sales	27,593	1,791
Purchases	(303,497)	(329,378)
Securities held to maturity:
Proceeds from maturities, calls, and principal paydowns	24,582	24,428
Purchases	(75,808)	(14,959)
Net increase in loans	(198,057)	(234,330)
Net increase in Federal Reserve and FHLB stock	(5,584)	(672)
Purchases of premises and equipment	(3,409)	(4,805)
Proceeds from sales of other real estate owned	3,470	2,411
Net cash used in investing activities	(135,697)	(121,233)
Financing activities
Net increase in deposits	105,369	156,761
Net increase (decrease) in short-term borrowings	188,689	(44,227)
Repayments of long-term debt	(163,409)	(3,350)
Proceeds from the issuance of shares to employee benefit plans and other stock plans	154	825
Purchase of treasury stock	(12,459)	(15,490)
Cash dividends	(24,334)	(19,966)
Net cash provided by financing activities	94,010	74,553
Net increase in cash and cash equivalents	44,574	11,059
Cash and cash equivalents at beginning of period	163,668	129,381
Cash and cash equivalents at end of period	208,242	140,440
Cash paid during the period for:
Interest	24,335	26,951
Income taxes paid	12,885	18,457
Acquisitions:
Fair value of assets acquired	1,504,415	257,865
Fair value of liabilities assumed	1,284,632	285,012
Fair value of debt issued in asset purchase	$ 0	$ 150

Description of Business

9 Months Ended

Sep. 30, 2013

Description of Business [Abstract]

Description of Business

Note 1.

Description of Business

NBT Bancorp Inc. (the “Registrant”) is a registered financial holding company incorporated in the State of Delaware in 1986, with its principal headquarters located in Norwich, New York. The Registrant is the parent holding company of NBT Bank, N.A. (the “Bank”), NBT Financial Services, Inc. (“NBT Financial”), NBT Holdings, Inc. (“NBT Holdings”), 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”). Through the Bank, the Company is focused on community banking operations. Through NBT Financial, the Company operates EPIC Advisors, Inc. (“EPIC”), a retirement plan administrator. Through NBT Holdings, the Company operates Mang Insurance Agency, LLC (“Mang”), a full-service insurance agency. The Trusts were organized to raise additional regulatory capital and to provide funding for certain acquisitions. The Registrant’s primary business consists of providing commercial banking and financial services to customers in its market area. The principal assets of the Registrant are all of the outstanding shares of common stock of its direct subsidiaries, and its principal sources of revenue are the management fees and dividends it receives from the Bank, NBT Financial, and NBT Holdings.

The Bank is a full service commercial bank formed in 1856, which provides a broad range of financial products to individuals, corporations and municipalities throughout the central and upstate New York, northeastern Pennsylvania, northwestern Vermont, western Massachusetts, and southern New Hampshire market areas.

Basis of Presentation

9 Months Ended

Sep. 30, 2013

Basis of Presentation [Abstract]

Basis of Presentation

Note 2.

Basis of Presentation

The accompanying unaudited interim consolidated financial statements include the accounts of the Registrant and its wholly owned subsidiaries, the Bank, NBT Financial and NBT Holdings. Collectively, the Registrant and its subsidiaries are referred to herein as “the Company.” The interim data includes all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement of the results for the interim periods in accordance with generally accepted accounting principles (“GAAP”). These consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in our 2012 Annual Report on Form 10-K. The results of operations for the interim periods are not necessarily indicative of the results that may be expected for the full year or any other interim period. All intercompany transactions have been eliminated in consolidation. Amounts in the prior period financial statements are reclassified whenever necessary to conform to current period presentation. The Company has evaluated subsequent events for potential recognition and/or disclosure and there were none identified.

- Definition

The entire disclosure for organization, consolidation and basis of presentation of financial statements disclosure.

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+ Details

Acquisition

9 Months Ended

Sep. 30, 2013

Acquisition [Abstract]

Acquisition

Note 3.

Acquisitions

Alliance Financial Corporation (“Alliance”)

On March 8, 2013, the Company acquired 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.

Under the terms of the merger agreement, each outstanding share of Alliance common stock was converted into the right to receive 2.1779 shares of the Company’s common stock. As a result, Alliance shareholders received 10.3 million shares of Company common stock valued at $226 million.

In connection with the merger, the consideration paid and the fair value of the assets acquired and the liabilities assumed on the date of acquisition are as summarized in the following table, in thousands:

Consideration paid:
NBT Bancorp common stock issued to Alliance common shareholders	$	225,551
Cash in lieu of fractional shares paid to Alliance common shareholders		11
Less treasury shares		5,779

Net consideration paid	$	219,783

Recognized Amounts of Identifiable Assets Acquired and (Liabilities Assumed) At Fair Value:
Cash and short term investments	$	81,060
Securities		320,618
Loans		904,473
Intangible assets		13,161
Other assets		71,589
Deposits		(1,113,420	)
Borrowings		(126,530	)
Trust preferred debentures		(25,774	)
Other liabilities		(18,908	)
Total identifiable net assets	$	106,269

Goodwill	$	113,514

The above recognized amounts of loans, other assets and other liabilities, at fair value, are preliminary estimates and are subject to adjustment but actual amounts are not expected to differ materially from those shown.

The estimated fair value of loans acquired from Alliance was determined by utilizing a methodology wherein similar loans were aggregated into pools. Cash flows for each pool were determined by estimating future credit losses and the rate of prepayments. Projected monthly cash flows were then discounted to present value based on a current market rate for similar loans. There was no carryover of Alliance’s allowance for credit losses associated with the loans acquired as loans were initially recorded at fair value.

Information about the acquired loan portfolio as of March 8, 2013 is as follows (in thousands):

Contractually required principal and interest at acquisition	$	908,614
Contractual cash flows not expected to be collected		(15,466	)
Expected cash flows at acquisition		893,148
Interest component of expected cash flows (accretable premium)		11,325
Fair value of acquired loans	$	904,473

The following table presents changes in the accretable discount (in thousands):

Balance at January 1, 2013	$	-
Alliance acquisition		11,325
Accretion recognized to date		(1,950	)
Balance at September 30, 2013	$	9,375

The core deposit and trust intangible assets recognized as part of the Alliance merger are being amortized over their estimated useful lives of approximately 10 and 15 years, respectively, utilizing an accelerated method. The goodwill, which is not amortized for book purposes, is not deductible for tax purposes.

The fair value of savings and transaction deposit accounts acquired from Alliance was assumed to approximate the carrying value as these accounts have no stated maturity and are payable on demand. Certificates of deposit were valued by projecting the expected cash flows based on the contractual terms of the certificates of deposit. These cash flows were discounted based on a current market rate for a certificate of deposit with a corresponding maturity.

The fair value of borrowings, which was comprised of FHLB advances, was determined by obtaining settlement quotes from the FHLB.

Direct costs related to the Alliance acquisition were expensed as incurred and amounted to $12.3 million for the nine months ended September 30, 2013.

The following table presents unaudited pro forma information as if the acquisition had occurred on January 1, 2012 under the “Pro forma” columns. This pro forma information gives effect to certain adjustments, including purchase accounting fair value adjustments, amortization of core deposit and other intangibles and related income tax effects. Merger and acquisition integration costs related to the Alliance acquisition are excluded from the periods in which they were incurred. The pro forma information does not necessarily reflect the results of operations that would have occurred had the Company merged with Alliance at the beginning of 2012. Cost savings are also not reflected in the unaudited pro forma amounts for the nine months ended September 30, 2012 and 2013.

	Pro forma
	Nine months ended September 30,
	2013		2012

Net interest income	$	182,610	$	182,081
Noninterest income		82,592		78,950
Net income		52,933		48,609

Supplemental financial information regarding the former Alliance operations included in our Consolidated Statement of Income from the date of acquisition through September 30, 2013 has not been provided as it would be impracticable to do so. The operations of Alliance have been integrated into the Bank’s operations and therefore financial information specific to revenues and expense associated with the former Alliance operations is not accessible.

Other Goodwill Adjustments

During the nine months ended September 30, 2013, the Company recorded a deferred tax adjustment related to the 2012 acquistion 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1497-128463

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1490-128463

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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+ Details

Commitments and Contingencies

9 Months Ended

Sep. 30, 2013

Commitments and Contingencies [Abstract]

Commitments and Contingencies

Note 4.

Commitments and Contingencies

The Company is a party to financial instruments in the normal course of business to meet the financing needs of its customers and to reduce its own exposure to fluctuating interest rates. These financial instruments include commitments to extend credit, unused lines of credit, and standby letters of credit. Exposure to credit loss in the event of nonperformance by the other party to the financial instrument for commitments to make loans and standby letters of credit is represented by the contractual amount of those instruments. The Company uses the same credit origination guidelines, portfolio maintenance and management procedures as other credit and off-balance sheet products. Commitments to extend credit and unused lines of credit totaled $1.1 billion at September 30, 2013 and $841.7 million at December 31, 2012. Since commitments to extend credit and unused lines of credit may expire without being fully drawn upon, this amount does not necessarily represent future cash commitments. Collateral obtained upon exercise of the commitment is determined using management’s credit evaluation of the borrower and may include accounts receivable, inventory, property, land and other items.

The Company guarantees the obligations or performance of customers by issuing standby letters of credit to third parties. These standby letters of credit are frequently issued in support of third party debt, such as corporate debt issuances, industrial revenue bonds and municipal securities. The credit risk involved in issuing standby letters of credit is essentially the same as the credit risk involved in extending loan facilities to customers, and they are subject to the same credit origination guidelines, portfolio maintenance and management procedures as 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 commitments. Standby letters of credit totaled $40.7 million at September 30, 2013 and $37.5 million at December 31, 2012. As of September 30, 2013, the fair value of standby letters of credit was not significant to the Company’s consolidated financial statements.

The Company has also entered into commercial letter of credit agreements on behalf of its customers. Under these agreements, the Company, on the request of its customer, opens the letter of credit and makes a commitment to honor draws made under the agreement, whereby the beneficiary is normally the provider of goods and/or services and the Company essentially replaces the customer as the payee. The credit risk involved in issuing commercial letters of credit is essentially the same as the credit risk involved in extending loan facilities to customers, and they are subject to the same credit origination guidelines, portfolio maintenance and management procedures as other credit and off-balance sheet products. Typically, these agreements vary in terms and the total amounts do not necessarily represent future cash commitments. Commercial letters of credit totaled $41.5 million at September 30, 2013 and $16.6 million at December 31, 2012. As of September 30, 2013, the fair value of commercial letters of credit was not significant to the Company’s consolidated financial statements.

Allowance for Loan Losses and Credit Quality of Loans

9 Months Ended

Sep. 30, 2013

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

Allowance for Loan Losses and Credit Quality of Loans

Note 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

The Company offers a variety of commercial loan products including commercial (non-real estate), commercial real estate, agricultural, agricultural real estate, and business banking loans. The Company’s underwriting analysis for commercial loans typically includes credit verification, independent appraisals, a review of the borrower’s financial condition, and a detailed analysis of the borrower’s underlying cash flows.

Commercial – 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 needs 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 due to 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, and are generally 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 in some cases, 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 such as 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. 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 business banking customers including term loans, business banking mortgages and lines of credit. Such loans are generally less than $0.5 million and are made available to businesses for working capital such as inventory and receivables, business expansion, equipment purchases, and agricultural needs. Generally, a collateral lien is placed on 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

The Company offers a variety of consumer loan products including indirect, home equity, and direct 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 75% 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 borrow 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 junior 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 Mortgages

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. 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. The Company’s underwriting analysis for residential mortgage loans typically includes credit verification, independent appraisals, and a review of the borrower’s financial condition. 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.

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

After a thorough consideration of the factors discussed above, any required additions or reductions to the allowance for loan losses are made periodically by charges or credits to the provision for loan losses. These charges or credits 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 and reductions of the allowance may fluctuate from one reporting period to another. These fluctuations are reflective of changes in risk associated with portfolio content and/or changes in management’s assessment of any or all of the determining factors discussed above.

The following tables illustrate the changes in the allowance for loan losses by our portfolio segments for the three and nine months ended September 30, 2013 and 2012:

							Residential
Three months ended September 30	Commercial			Consumer			Real Estate
	Loans			Loans			Mortgages			Unallocated			Total
Balance as of June 30, 2013	$	37,704		$	26,456		$	6,806		$	218		$	71,184
Charge-offs		(3,489	)		(3,746	)		(374	)		-			(7,609	)
Recoveries		602			733			76			-			1,411
Provision		980			3,744			402			72			5,198
Ending Balance as of September 30, 2013	$	35,797		$	27,187		$	6,910		$	290		$	70,184

Balance as of June 30, 2012	$	37,495		$	27,235		$	5,943		$	61		$	70,734
Charge-offs		(1,904	)		(3,446	)		(480	)		-			(5,830	)
Recoveries		492			574			9			-			1,075
Provision		1,734			2,213			809			(1	)		4,755
Ending Balance as of September 30, 2012	$	37,817		$	26,576		$	6,281		$	60		$	70,734

							Residential
Nine months ended September 30	Commercial			Consumer			Real Estate
	Loans			Loans			Mortgages			Unallocated			Total
Balance as of December 31, 2012	$	35,624		$	27,162		$	6,252		$	296		$	69,334
Charge-offs		(8,009	)		(11,122	)		(1,347	)		-			(20,478	)
Recoveries		1,485			2,363			179			43			4,070
Provision		6,697			8,784			1,826			(49	)		17,258
Ending Balance as of September 30, 2013	$	35,797		$	27,187		$	6,910		$	290		$	70,184

Balance as of December 31, 2011	$	38,831		$	26,049		$	6,249		$	205		$	71,334
Charge-offs		(4,685	)		(11,237	)		(1,130	)		-			(17,052	)
Recoveries		1,180			1,918			25			-			3,123
Provision		2,491			9,846			1,137			(145	)		13,329
Ending Balance as of September 30, 2012	$	37,817		$	26,576		$	6,281		$	60		$	70,734

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 September 30, 2013 and 2012, there was no allowance for loan losses for the acquired loan portfolio. Net charge-offs related to acquired loans totaled approximately $47,000 and $0.3 million during the three and nine months ended September 30, 2013, respectively, and are included in the table above.

The following tables illustrate the allowance for loan losses and the recorded investment by portfolio segments as of September 30, 2013 and December 31, 2012:

Allowance for Loan Losses and Recorded Investment in Loans
(in thousands)

					Residential
	Commercial		Consumer		Real Estate
	Loans		Loans		Mortgages		Unallocated		Total
As of September 30, 2013
Allowance for loan losses	$	35,797	$	27,187	$	6,910	$	290	$	70,184

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

Allowance for loans collectively evaluated for impairment	$	34,697	$	27,187	$	6,910	$	290	$	69,084

Ending balance of loans	$	2,378,848	$	1,960,225	$	1,028,158			$	5,367,231

Ending balance of loans individually evaluated for impairment	$	15,323	$	-	$	-			$	15,323
Ending balance of acquired loans	$	432,806	$	243,469	$	325,491			$	1,001,766
Ending balance of loans collectively evaluated for impairment	$	1,930,719	$	1,716,756	$	702,667			$	4,350,142

As of December 31, 2012
Allowance for loan losses	$	35,624	$	27,162	$	6,252	$	296	$	69,334

Allowance for loans individually evaluated for impairment	$	2,848	$	-	$	-			$	2,848

Allowance for loans collectively evaluated for impairment	$	32,776	$	27,162	$	6,252	$	296	$	66,486

Ending balance of loans	$	2,003,371	$	1,623,138	$	651,107			$	4,277,616

Ending balance of loans individually evaluated for impairment	$	11,972	$	-	$	-			$	11,972

Ending balance of loans collectively evaluated for impairment	$	1,991,399	$	1,623,138	$	651,107			$	4,265,644

Credit Quality of Loans

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 or 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. The Company’s nonaccrual policies are the same for all classes of financing receivable.

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. 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. When in the opinion of management the collection of principal appears unlikely, the loan balance is charged-off in total or in part. 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.

The following table illustrates the Company’s nonaccrual loans by loan class:

Loans on Nonaccrual Status as of:

(In thousands)	September 30, 2013		December 31, 2012
ORIGINATED
Commercial Loans
Commercial	$	4,409	$	4,985
Commercial Real Estate		8,642		7,977
Agricultural		1,076		699
Agricultural Real Estate		868		1,038
Business Banking		4,949		6,738
		19,944		21,437

Consumer Loans
Indirect		1,440		1,557
Home Equity		5,965		7,247
Direct		92		266
		7,497		9,070

Residential Real Estate Mortgages		6,666		9,169

	$	34,107	$	39,676

ACQUIRED
Commercial Loans
Commercial	$	102
Commercial Real Estate		1,329
Business Banking		1,338
		2,769

Consumer Loans
Indirect		258
Home Equity		353
Direct		71
		682

Residential Real Estate Mortgages		3,860

	$	7,311

Total nonaccrual loans	$	41,418	$	39,676

The following tables set forth information with regard to past due and nonperforming loans by loan class as of September 30, 2013 and December 31, 2012:

Age Analysis of Past Due Financing Receivables
As of September 30, 2013
(in thousands)

					Greater Than
	31-60 Days		61-90 Days		90 Days		Total						Recorded
	Past Due		Past Due		Past Due		Past Due						Total
	Accruing		Accruing		Accruing		Accruing		Non-Accrual		Current		Loans
ORIGINATED
Commercial Loans
Commercial	$	76	$	1,031	$	-	$	1,107	$	4,409	$	589,008	$	594,524
Commercial Real Estate		478		-		-		478		8,642		910,134		919,254
Agricultural		140		-		-		140		1,076		63,576		64,792
Agricultural Real Estate		-		-		-		-		868		34,071		34,939
Business Banking		1,900		675		-		2,575		4,949		325,009		332,533
		2,594		1,706		-		4,300		19,944		1,921,798		1,946,042

Consumer Loans
Indirect		10,530		2,331		1,229		14,090		1,440		1,098,286		1,113,816
Home Equity		6,513		1,648		768		8,929		5,965		527,428		542,322
Direct		625		156		107		888		92		59,638		60,618
		17,668		4,135		2,104		23,907		7,497		1,685,352		1,716,756
Residential Real Estate Mortgages		2,955		172		994		4,121		6,666		691,880		702,667
	$	23,217	$	6,013	$	3,098	$	32,328	$	34,107	$	4,299,030	$	4,365,465


ACQUIRED
Commercial Loans
Commercial	$	70	$	-	$	-	$	70	$	102	$	114,202	$	114,374
Commercial Real Estate		232		-		-		232		1,329		243,233		244,794
Business Banking		246		-		-		246		1,338		72,054		73,638
		548		-		-		548		2,769		429,489		432,806

Consumer Loans
Indirect		526		116		32		674		258		143,588		144,520
Home Equity		750		-		154		904		353		89,443		90,700
Direct		113		16		2		131		71		8,047		8,249
		1,389		132		188		1,709		682		241,078		243,469
Residential Real Estate Mortgages		2,479		317		-		2,796		3,860		318,835		325,491
	$	4,416	$	449	$	188	$	5,053	$	7,311	$	989,402	$	1,001,766
Total Loans	$	27,633	$	6,462	$	3,286	$	37,381	$	41,418	$	5,288,432	$	5,367,231

As of December 31, 2012
(in thousands)

					Greater Than
	31-60 Days		61-90 Days		90 Days		Total						Recorded
	Past Due		Past Due		Past Due		Past Due						Total
	Accruing		Accruing		Accruing		Accruing		Non-Accrual		Current		Loans
Commercial Loans
Commercial	$	-	$	-	$	-	$	-	$	4,985	$	556,496	$	561,481
Commercial Real Estate		126		-		-		126		7,977		966,692		974,795
Agricultural		22		-		-		22		699		63,037		63,758
Agricultural Real Estate		108		-		103		211		1,038		36,128		37,377
Business Banking		3,019		708		45		3,772		6,738		355,450		365,960
		3,275		708		148		4,131		21,437		1,977,803		2,003,371

Consumer Loans
Indirect		10,956		2,477		1,205		14,638		1,557		964,802		980,997
Home Equity		6,065		1,223		681		7,969		7,247		560,066		575,282
Direct		717		144		84		945		266		65,648		66,859
		17,738		3,844		1,970		23,552		9,070		1,590,516		1,623,138
Residential Real Estate Mortgages		1,839		725		330		2,894		9,169		639,044		651,107
	$	22,852	$	5,277	$	2,448	$	30,577	$	39,676	$	4,207,363	$	4,277,616

There were no material commitments to extend further credit to borrowers with nonperforming loans.

Impaired Loans

The methodology used to establish the allowance for loan losses on impaired loans incorporates specific allocations on loans analyzed individually. Classified loans with outstanding balances of $0.5 million 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 impaired as defined by accounting standards, 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. All impaired loans are reviewed on a quarterly basis for changes in the measurement of impairment. 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 table provides information on impaired loans and specific reserve allocations as of September 30, 2013 and December 31, 2012:

	September 30, 2013						December 31, 2012
	Recorded		Unpaid				Recorded		Unpaid
	Investment		Principal				Investment		Principal
	Balance		Balance		Related		Balance		Balance		Related
(in thousands)	(Book)		(Legal)		Allowance		(Book)		(Legal)		Allowance
With no related allowance recorded:
Commercial Loans
Commercial	$	5,507	$	5,549			$	1,651	$	1,710
Commercial Real Estate		5,427		5,431				8,709		9,553
Agricultural		1,097		1,460				940		1,286
Agricultural Real Estate		1,529		1,936				1,713		2,026
Business Banking		6,533		8,927				7,048		9,579
Total Commercial Loans		20,093		23,303				20,061		24,154

Consumer Loans
Home Equity		3,304		3,496				2,553		2,657

Residential Real Estate Mortgages		2,234		2,626				2,011		2,308
	$	25,631	$	29,425			$	24,625	$	29,119

With an allowance recorded:
Commercial Loans
Commercial	$	-	$	-	$	-	$	4,335	$	4,340	$	2,241
Commercial Real Estate		6,216		7,838		1,100		4,068		5,689		607
Agricultural		-		-		-		-		-		-
Agricultural Real Estate		-		-		-		-		-		-
		6,216		7,838		1,100		8,403		10,029		2,848

Total:	$	31,847	$	37,263	$	1,100	$	33,028	$	39,148	$	2,848

The following tables summarize the average recorded investments on impaired loans and the interest income recognized for the three and nine months ended September 30, 2013 and 2012:

	For the three months ended
	September 30, 2013				September 30, 2012
	Average		Interest		Average		Interest Income
	Recorded		Income		Recorded		Recognized
(in thousands)	Investment		Recognized		Investment		Accrual
Commercial Loans
Commercial	$	3,348	$	15	$	1,128	$	32
Commercial Real Estate		10,751		-		7,140		-
Agricultural		1,526		-		2,876		4
Agricultural Real Estate		897		12		1,876		12
Business Banking		6,581		13		6,572		-
Consumer Loans
Home Equity		3,064		8		1,828		5
Residential Real Estate Mortgages		2,066		15		1,055		1
Total:	$	28,233	$	63	$	22,475	$	54

	For the nine months ended
	September 30, 2013				September 30, 2012
	Average		Interest		Average		Interest Income
	Recorded		Income		Recorded		Recognized
(in thousands)	Investment		Recognized		Investment		Accrual
Commercial Loans
Commercial	$	4,069	$	45	$	1,551	$	101
Commercial Real Estate		10,660		51		6,481		-
Agricultural		1,100		1		2,997		40
Agricultural Real Estate		1,287		36		1,926		65
Business Banking		7,538		43		7,151		-
Consumer Loans
Home Equity		2,871		20		1,869		17
Residential Real Estate Mortgages		2,015		42		1,043		4
Total:	$	29,540	$	238	$	23,018	$	227

Credit Quality Indicators

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

Commercial Grading System

For 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. Classified commercial loans consist of loans graded substandard and below. 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 a loss is deferred. Doubtful borrowers are usually in default, lack adequate liquidity or capital, and lack the resources necessary to remain an operating entity. Pending events can include mergers, acquisitions, liquidations, capital injections, the perfection of liens on additional collateral, the valuation of collateral, and refinancing. Generally, pending events should be resolved within a relatively short period and the ratings will be adjusted based on the new information. Nonaccrual treatment is required for doubtful assets because of the high probability of loss.

•

Substandard

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

•

Special Mention

Special Mention loans have potential weaknesses that may, if not checked or corrected, weaken the asset or inadequately protect the Company’s position at some future date. These loans pose elevated risk, but their weakness does not yet justify a Substandard classification. Borrowers may be experiencing adverse operating trends (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, 2) on nonaccrual status or 3) restructured. All loans not meeting any of these three criteria are considered Performing.

The following tables illustrate the Company’s credit quality by loan class as of September 30, 2013 and December 31, 2012:

Credit Quality Indicators
As of September 30, 2013

ORIGINATED
			Commercial				Agricultural
Commercial Credit Exposure	Commercial		Real Estate		Agricultural		Real Estate		Total
By Internally Assigned Grade:
Pass	$	574,229	$	903,073	$	59,797	$	31,418	$	1,568,517
Special Mention		10,098		50		389		43		10,580
Substandard		10,197		16,131		4,594		3,478		34,400
Doubtful		-		-		12		-		12
Total	$	594,524	$	919,254	$	64,792	$	34,939	$	1,613,509


Business Banking Credit Exposure	Small Business								Total
By Internally Assigned Grade:
Non-classified	$	313,250							$	313,250
Classified		19,283								19,283
Total	$	332,533							$	332,533

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct				Total
Performing	$	1,111,147	$	535,589	$	60,419			$	1,707,155
Nonperforming		2,669		6,733		199				9,601
Total	$	1,113,816	$	542,322	$	60,618			$	1,716,756

	Residential
Residential Mortgage Credit Exposure	Mortgage								Total
By Payment Activity:
Performing	$	695,007							$	695,007
Nonperforming		7,660								7,660
Total	$	702,667							$	702,667

Credit Quality Indicators
As of September 30, 2013
ACQUIRED
Commercial Credit Exposure			Commercial
By Internally Assigned Grade:	Commercial		Real Estate		Agricultural		Total
Pass	$	98,128	$	221,777	$	-	$	319,905
Special Mention		1,602		4,762		-		6,364
Substandard		14,644		18,255		-		32,899
Doubtful		-		-		-		-
Total	$	114,374	$	244,794	$	-	$	359,168

Business Banking Credit Exposure
By Internally Assigned Grade:	Small Business						Total
Non-classified	$	68,917					$	68,917
Classified		4,721						4,721
Total	$	73,638					$	73,638

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct		Total
Performing	$	144,230	$	90,193	$	8,176	$	242,599
Nonperforming		290		507		73		870
Total	$	144,520	$	90,700	$	8,249	$	243,469

Residential Mortgage Credit Exposure	Residential
By Payment Activity:	Mortgage						Total
Performing	$	321,631					$	321,631
Nonperforming		3,860						3,860
Total	$	325,491					$	325,491

Credit Quality Indicators
As of December 31, 2012

Commercial Credit Exposure			Commercial				Agricultural
By Internally Assigned Grade:	Commercial		Real Estate		Agricultural		Real Estate		Total
Pass	$	522,985	$	901,928	$	57,347	$	33,472	$	1,515,732
Special Mention		18,401		32,135		13		3		50,552
Substandard		17,351		40,732		6,362		3,902		68,347
Doubtful		2,744		-		36		-		2,780
Total	$	561,481	$	974,795	$	63,758	$	37,377	$	1,637,411

Business Banking. Credit Exposure
By Internally Assigned Grade:	Small Business								Total
Non-classified	$	342,528							$	342,528
Classified		23,432								23,432
Total	$	365,960							$	365,960

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct				Total
Performing	$	978,235	$	567,354	$	66,509			$	1,612,098
Nonperforming		2,762		7,928		350				11,040
Total	$	980,997	$	575,282	$	66,859			$	1,623,138

Residential Mortgage Credit Exposure	Residential
By Payment Activity:	Mortgage								Total
Performing	$	641,608							$	641,608
Nonperforming		9,499								9,499
Total	$	651,107							$	651,107

Troubled Debt Restructured Loans

The Company’s loan portfolio includes certain loans that have been modified where economic concessions have been granted to borrowers who have experienced or are expected to experience financial difficulties. These concessions typically result from the Company’s loss mitigation activities and could include reductions in the interest rate, payment extensions, forgiveness of principal, forbearance or other actions. Certain troubled debt restructured loans (“TDRs”) are classified as nonperforming at the time of restructure and may only be returned to performing status after considering the borrower’s sustained repayment performance for a reasonable period, generally six months. Substantially all of these modifications included 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.

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.

TDRs that occurred during the three month period ending September 30, 2013 consisted of 9 home equity loans, five residential real estate mortgage, and three commercial loans totaling $0.4 million, $0.3 million, and $6.1 million, respectively. For all such modifications, the pre and post outstanding recorded investment amount remained unchanged. During the three month period ending September 30, 2013 there was one default on a home equity loan totaling $0.1 million.

There were no TDRs that occurred during the three month period ending September 30, 2012. During the three month period ending September 30, 2012 there were no defaults on previously modified loans.

TDRs that occurred during the nine month period ending September 30, 2013 consisted of 20 home equity loans, six residential real estate mortgage, and four commercial loans totaling $1.0 million, $0.5 million, and $7.0 million, respectively. For all such modifications, the pre and post outstanding recorded investment amount remained unchanged. During the nine month period ending September 30, 2013 there were seven defaults on home equity loans totaling $0.5 million.

TDRs that occurred during the nine month period ending September 30, 2012 consisted of one commercial loan totaling $1.0 million and one residential real estate mortgage totaling $0.2 million. The pre and post outstanding recorded investment amount remained unchanged. During the nine month period ending September 30, 2012 there was one default on a home equity loan totaling $25,000 and three residential real estate mortgages totaling $0.4 million that were previously modified.

Earnings Per Share

9 Months Ended

Sep. 30, 2013

Earnings Per Share [Abstract]

Earnings Per Share

Note 6.

Earnings Per Share

Basic earnings per share 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 earnings per share reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in the earnings of the entity (such as the Company’s dilutive stock options and restricted stock units).

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

Three months ended September 30,	2013		2012
(in thousands, except per share data)
Basic EPS:
Weighted average common shares outstanding		43,711		33,619
Net income available to common shareholders		19,257		14,535
Basic EPS	$	0.44	$	0.43
Diluted EPS:
Weighted average common shares outstanding		43,711		33,619
Dilutive effect of common stock options and restricted stock		424		342

Weighted average common shares and common share equivalents		44,135		33,961
Net income available to common shareholders		19,257		14,535
Diluted EPS	$	0.44	$	0.43

Nine months ended September 30,		2013		2012
(in thousands, except per share data)
Basic EPS:
Weighted average common shares outstanding		41,375		33,293
Net income available to common shareholders		43,822		41,442
Basic EPS	$	1.06	$	1.24
Diluted EPS:
Weighted average common shares outstanding		41,375		33,293
Dilutive effect of common stock options and restricted stock		394		333

Weighted average common shares and common share equivalents		41,769		33,626
Net income available to common shareholders		43,822		41,442
Diluted EPS	$	1.05	$	1.23

There were 972,403 stock options for the quarter ended September 30, 2013 and 1,176,670 stock options for the quarter ended September 30, 2012 that were not considered in the calculation of diluted earnings per share since the stock options’ exercise price was greater than the average market price during these periods.

There were 1,157,135 stock options for the nine months ended September 30, 2013 and 1,197,417 stock options for the nine months ended September 30, 2012 that were not considered in the calculation of diluted earnings per share since the stock options’ exercise price was greater than the average market price during these periods.

Defined Benefit Postretirement Plans

9 Months Ended

Sep. 30, 2013

Defined Benefit Postretirement Plans [Abstract]

Defined Benefit Postretirement Plans

Note 7.

Defined Benefit Postretirement Plans

The Company has a qualified, noncontributory, defined benefit pension plan covering substantially all of its employees at September 30, 2013, including eligible Alliance employees as of March 8, 2013. Benefits paid from the plan are based on age, years of service, compensation and social security benefits, and are determined in accordance with defined formulas. The Company’s policy is to fund the pension plan in accordance with Employee Retirement Income Security Act of 1974 (“ERISA”) standards. Assets of the plan are invested in publicly traded stocks and bonds.

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 the 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 NBT Bancorp Inc. Defined Benefit Pension Plan (“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. The merging of the plans did not have a significant impact on the Company’s financial statements and related footnotes. The Company is not required to make contributions to the Plan in 2013, and did not do so during the nine months ended September 30, 2013.

Market conditions can result in an unusually high degree of volatility and increase the risks and short term liquidity associated with certain investments held by the Plan which could impact the value of these investments.

In addition to the Plan, the Company also provides supplemental employee retirement plans to certain current and former executives. These supplemental employee retirement plans and the Plans 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 the Company on or before January 1, 2000 are eligible to receive postretirement health care benefits. This health care benefits 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. Eligibility is contingent upon the direct transition from active employment status to retirement without any break in employment from the Company. Employees also must be participants in the Company’s medical plan prior to their retirement. 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.” The components of expense for Pension Benefits and Other Benefits are set forth below (in thousands):

	Pension Benefits						Other Benefits
	Three months ended September 30,						Three months ended September 30,
Components of net periodic benefit cost:	2013			2012			2013			2012
Service cost	$	604		$	757		$	6		$	6
Interest cost		830			774			75			40
Expected return on plan assets		(1,929	)		(1,676	)		-			-
Net amortization		711			992			(2	)		(3	)
Total cost (benefit)	$	216		$	847		$	79		$	43

	Pension Benefits						Other Benefits
	Nine months ended September 30,						Nine months ended September 30,
Components of net periodic benefit cost:		2013			2012			2013			2012
Service cost	$	1,813		$	2,270		$	18		$	16
Interest cost		2,489			2,322			224			119
Expected return on plan assets		(5,786	)		(5,026	)		-			-
Net amortization		2,025			2,710			219			(8	)
Total cost (benefit)	$	541		$	2,276		$	461		$	127

The Company is not required to make contributions to the plans in 2013, and did not do so during the nine months ended September 30, 2013.

Junior Subordinated Debt

9 Months Ended

Sep. 30, 2013

Junior Subordinated Debt [Abstract]

Junior Subordinated Debt

Note 8.

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.

As of September 30, 2013, 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-99	$	18,000	3-month LIBOR plus 2.75%	$	18,720	August-29

NBT Statutory Trust I	November-05		5,000	3-month LIBOR plus 1.40%		5,155	December-35

NBT Statutory Trust II	February-06		50,000	3-month LIBOR plus 1.40%		51,547	March-36

Alliance Financial Capital Trust I	December-03		10,000	3-month LIBOR plus 2.85%		10,310	January-34

Alliance Financial Capital Trust II	September-06		15,000	3-month LIBOR plus 1.65%		15,464	September-36

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.

Fair Values Measurements and Fair Value of Financial Instruments

9 Months Ended

Sep. 30, 2013

Fair Value Measurements and Fair Value of Financial Instruments [Abstract]

Fair Value Measurements and Fair Value of Financial Instruments

Note 9.

Fair Value Measurements and Fair Value of Financial Instruments

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

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

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

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

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

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

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.

For the nine month period ending September 30, 2013, the Company has made no transfers of assets between Level 1 and Level 2, and has had no Level 3 activity.

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

September 30, 2013:

	Quoted Prices in		Significant Other		Significant
	Active Markets for		Observable		Unobservable		Balance
	Identical Assets		Inputs		Inputs		as of
	(Level 1)		(Level 2)		(Level 3)		September 30, 2013
Assets:
Securities Available for Sale:
U.S. Treasury	$	43,804	$	-	$	-	$	43,804
Federal Agency		-		295,194		-		295,194
State & municipal		-		118,602		-		118,602
Mortgage-backed		-		335,206		-		335,206
Collateralized mortgage obligations		-		578,210		-		578,210
Other securities		9,671		5,047		-		14,718
Total Securities Available for Sale	$	53,475	$	1,332,259	$	-	$	1,385,734
Trading Securities		5,285		-		-		5,285
Interest Rate Swaps		-		1,038		-		1,038
Total	$	58,760	$	1,333,297	$	-	$	1,392,057

Liabilities:
Interest Rate Swaps	$	-	$	1,038	$	-	$	1,038
Total	$	-	$	1,038	$	-	$	1,038

December 31, 2012:

	Quoted Prices in		Significant		Significant
	Active Markets for		Other		Unobservable		Balance
	Identical Assets		Observable Inputs		Inputs		as of
	(Level 1)		(Level 2)		(Level 3)		December 31, 2012
Assets:
Securities Available for Sale:
U.S. Treasury	$	64,425	$	-	$	-	$	64,425
Federal Agency		-		282,814		-		282,814
State & municipal		-		86,802		-		86,802
Mortgage-backed		-		250,281		-		250,281
Collateralized mortgage obligations		-		449,723		-		449,723
Other securities		11,866		2,088		-		13,954
Total Securities Available for Sale	$	76,291	$	1,071,708	$	-	$	1,147,999
Trading Securities		3,918		-		-		3,918
Interest Rate Swaps		-		1,490		-		1,490
Total	$	80,209	$	1,073,198	$	-	$	1,153,407

Liabilities:
Interest Rate Swaps	$	-	$	1,490	$	-	$	1,490
Total	$	-	$	1,490	$	-	$	1,490

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

U.S. GAAP requires disclosure of assets and liabilities measured and recorded at fair value on a nonrecurring basis such as goodwill, loans held for sale, other real estate owned, collateral-dependent impaired loans, mortgage servicing rights, and held-to-maturity securities. The only nonrecurring fair value measurement recorded during the nine month period ended September 30, 2013 and December 31, 2012 was related to impaired loans. The Company had collateral dependent impaired loans with a carrying value of approximately $6.2 million which had specific reserves included in the allowance for loan losses of $1.1 million at September 30, 2013. The Company had collateral dependent impaired loans with a carrying value of approximately $8.4 million which had specific reserves included in the allowance for loan losses of $2.8 million at December 31, 2012. The Company uses the fair value of underlying collateral, less costs to sell, to estimate the specific reserves for collateral dependent impaired loans. The appraisals may be adjusted by management for qualitative factors such as economic conditions and estimated liquidation expenses ranging from 10% to 35%. Based on the valuation techniques used, the fair value measurements for collateral dependent impaired loans are classified as Level 3.

The following table sets forth information with regard to estimated fair values of financial instruments at September 30, 2013 and December 31, 2012. 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.

			September 30, 2013				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	$	118,259	$	115,620	$	60,563	$	61,535
Net loans		3		5,297,047		5,358,132		4,208,282		4,313,244
Financial liabilities
Time deposits		2	$	1,063,730	$	1,068,888	$	983,261	$	994,376
Long-term debt		2		309,009		336,128		367,492		407,404
Trust preferred debentures		2		101,196		103,364		75,422		74,147

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.

- 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

Securities

9 Months Ended

Sep. 30, 2013

Securities [Abstract]

Securities

Note 10.

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
September 30, 2013
U.S. Treasury	$	43,359	$	445	$	-	$	43,804
Federal Agency		300,964		369		6,139		295,194
State & municipal		117,936		2,083		1,417		118,602
Mortgage-backed:
Government-sponsored enterprises		303,907		7,652		960		310,599
U.S. government securities		23,613		1,080		86		24,607
Collateralized mortgage obligations:
Government-sponsored enterprises		543,447		1,792		15,211		530,028
U.S. government securities		47,330		914		62		48,182
Other securities		12,367		2,551		200		14,718
Total securities available for sale	$	1,392,923	$	16,886	$	24,075	$	1,385,734
December 31, 2012
U.S. Treasury	$	63,668	$	757	$	-	$	64,425
Federal Agency		281,398		1,507		91		282,814
State & municipal		82,675		4,127		-		86,802
Mortgage-backed:
Government-sponsored enterprises		221,110		11,175		-		232,285
U.S. government securities		16,351		1,645		-		17,996
Collateralized mortgage obligations:
Government-sponsored enterprises		399,147		4,418		-		403,565
U.S. government securities		44,825		1,333		-		46,158
Other securities		11,210		2,832		88		13,954
Total securities available for sale	$	1,120,384	$	27,794	$	179	$	1,147,999

Other securities primarily represent marketable equity securities.

Proceeds from the sales of securities available for sale were $27.6 million during the nine months ended September 30, 2013, and gains on the sales were $1.4 million. Proceeds from the sales of securities available for sale were $1.8 million during the nine months ended September 30, 2012, and gains on the sales were $0.6 million. There were no losses on the sales during 2013 or 2012.

Securities with amortized costs totaling $1.2 billion at September 30, 2013 and $0.9 billion at December 31, 2012 were pledged to secure public deposits and for other purposes required or permitted by law. Additionally, at September 30, 2013 and December 31, 2012, securities with an amortized cost of $222.2 million and $209.0 million, respectively, were pledged as collateral for securities sold under repurchase agreements.

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

	Amortized		Unrealized		Unrealized		Estimated
(In thousands)	cost		gains		losses		fair value
September 30, 2013
Mortgage-backed	$	983	$	122	$	-	$	1,105
Collateralized mortgage oblications		63,048		-		3,251		59,797
State & municipal		54,228		490		-		54,718
Total securities held to maturity	$	118,259	$	612	$	3,251	$	115,620
December 31, 2012
Mortgage-backed	$	1,168	$	184	$	-	$	1,352
State & municipal		59,395		788		-		60,183
Total securities held to maturity	$	60,563	$	972	$	-	$	61,535

The following table sets forth information with regard to investment securities with unrealized losses at September 30, 2013 and December 31, 2012:

	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

September 30, 2013
Investment securities available for sale:
Federal agency	$	300,964	$	(6,139	)		20	$	-	$	-			-	$	300,964	$	(6,139	)		20
State & municipal		117,936		(1,417	)		189		-		-			-		117,936		(1,417	)		189
Mortgage-backed		327,504		(1,046	)		81		-		-			-		327,504		(1,046	)		81
Collateralized mortgage obligations		590,777		(15,273	)		40		-		-			-		590,777		(15,273	)		40
Other securities		5,523		(170	)		2		218		(30	)		1		5,741		(200	)		3
Total securities with unrealized losses	$	1,342,704	$	(24,045	)		332	$	218	$	(30	)		1	$	1,342,922	$	(24,075	)		333

September 30, 2013
Investment securities held to maturity:
Collateralized mortgage obligations	$	63,048	$	(3,251	)		5	$	-	$	-			-	$	63,048	$	(3,251	)		5
Total securities with unrealized losses	$	63,048	$	(3,251	)		5	$	-	$	-			-	$	63,048	$	(3,251	)		5

	Less than 12 months							12 months or longer							Total
	Fair Value		Unrealized losses			Number of Positions		Fair Value		Unrealized losses			Number of Positions		Fair Value		Unrealized losses			Number of Positions
December 31, 2012
Investment securities available for sale:
U.S. Treasury	$	-	$	-			-	$	-	$	-			-	$	-	$	-			-
Federal agency		39,906		(91	)		4		-		-			-		39,906		(91	)		4
State & municipal		-		-			-		-		-			-		-		-			-
Mortgage-backed		-		-			-		-		-			-		-		-			-
Collateralized mortgage obligations		23		-			2		-		-			-		23		-			2
Other securities		468		(6	)		1		167		(82	)		1		635		(88	)		2
Total securities with unrealized losses	$	40,397	$	(97	)		7	$	167	$	(82	)		1	$	40,564	$	(179	)		8

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.

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 September 30, 2013, management also had the 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 September 30, 2013, 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.

The following tables set forth information with regard to contractual maturities of debt securities at September 30, 2013:

(In thousands)	Amortized cost		Estimated fair value
Debt securities classified as available for sale
Within one year	$	26,527	$	26,704
From one to five years		272,953		274,104
From five to ten years		295,191		293,558
After ten years		785,885		776,650
	$	1,380,556	$	1,371,016
Debt securities classified as held to maturity
Within one year	$	25,305	$	25,412
From one to five years		22,364		22,744
From five to ten years		5,054		5,059
After ten years		65,536		62,405
	$	118,259	$	115,620

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

Except for U.S. Government securities, there were no holdings, when taken in the aggregate, of any single issuer that exceeded 10% of consolidated stockholders’ equity at September 30, 2013.

- Definition

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

+ References + Details

Reclassification Adjustments Out of Other Comprehensive (Loss) Income

9 Months Ended

Sep. 30, 2013

Reclassification Adjustments Out of Other Comprehensive Loss income [Abstract]

Reclassification Adjustments Out of Other Comprehensive (Loss) Income

Note 11.

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
	Three months ended
	September 30, 2013			September 30, 2012
Available for sale securities:
Gains on available for sale securities	$	(329	)	$	(26	)	Net securities gains
Tax benefit		132			10		Income tax expense
Net of tax	$	(197	)	$	(16	)

Pension and other benefits:
Amortization of net gains	$	765		$	1,044		Salaries and employee benefits
Amortization of prior service costs		(56	)		(55	)	Salaries and employee benefits
Tax expense		283			390		Income tax expense
Net of tax	$	426		$	599

Total reclassifications during the period, net of tax	$	229		$	583

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
	Nine months ended
	September 30, 2013			September 30, 2012
Available for sale securities:
Gains on available for sale securities	$	(1,413	)	$	(578	)	Net securities gains
Tax expense		565			231		Income tax expense
Net of tax	$	(848	)	$	(347	)

Pension and other benefits:
Amortization of net gains	$	2,411		$	2,869		Salaries and employee benefits
Amortization of prior service costs		(167	)		(167	)	Salaries and employee benefits
Tax expense		890			1076		Income tax expense
Net of tax	$	1,354		$	1,626

Total reclassifications during the period, net of tax	$	506		$	1,279

Description of Business (Policies)

9 Months Ended

Sep. 30, 2013

Description of Business [Abstract]

Nature of Operations [Policy Text Block]

Description of Business

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

9 Months Ended

Sep. 30, 2013

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

Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block]

Allowance for Loan Losses

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

Consumer Loans

The Company offers a variety of consumer loan products including indirect, home equity, and direct loans.

Residential Real Estate Mortgages

Credit Quality of Loans

Impaired Loans

Credit Quality Indicators [Policy Text Block]

Credit Quality Indicators

Commercial Grading System

•

Doubtful

•

Substandard

•

Special Mention

•

Pass

Business Banking Grading System

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

•

Classified

•

Non-classified

Loans graded as Non-classified encompass all loans not graded as Classified. Non-classified loans are in compliance with loan covenants, and payments are generally made as agreed.

Consumer and Residential Mortgage Grading System

Loans and Leases Receivable, Troubled Debt Restructuring Policy [Policy Text Block]

Troubled Debt Restructured Loans

Defined Benefit Postretirement Plans (Policies)	9 Months Ended
Defined Benefit Postretirement Plans (Policies)	Sep. 30, 2013
Defined Benefit Postretirement Plans [Abstract]
Postemployment Benefit Plans, Policy [Policy Text Block]	The Company has a qualified, noncontributory, defined benefit pension plan covering substantially all of its employees at September 30, 2013, including eligible Alliance employees as of March 8, 2013. Benefits paid from the plan are based on age, years of service, compensation and social security benefits, and are determined in accordance with defined formulas. The Company’s policy is to fund the pension plan in accordance with Employee Retirement Income Security Act of 1974 (“ERISA”) standards. Assets of the plan are invested in publicly traded stocks and bonds. 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 the 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 NBT Bancorp Inc. Defined Benefit Pension Plan (“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. The merging of the plans did not have a significant impact on the Company’s financial statements and related footnotes. The Company is not required to make contributions to the Plan in 2013, and did not do so during the nine months ended September 30, 2013. Market conditions can result in an unusually high degree of volatility and increase the risks and short term liquidity associated with certain investments held by the Plan which could impact the value of these investments. In addition to the Plan, the Company also provides supplemental employee retirement plans to certain current and former executives. These supplemental employee retirement plans and the Plans 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 the Company on or before January 1, 2000 are eligible to receive postretirement health care benefits. This health care benefits 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. Eligibility is contingent upon the direct transition from active employment status to retirement without any break in employment from the Company. Employees also must be participants in the Company’s medical plan prior to their retirement. 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.” The components of expense for Pension Benefits and Other Benefits are set forth below (in thousands):

Fair Values Measurements and Fair Value of Financial Instruments (Policies)	9 Months Ended
	Sep. 30, 2013
Fair Value Measurements and Fair Value of Financial Instruments [Abstract]
Fair Value of Financial Instruments, Policy [Policy Text Block]	U.S. GAAP states that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value measurements are not adjusted for transaction costs. A fair value hierarchy exists within U.S. GAAP that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (level 1 measurements) and the lowest priority to unobservable inputs (level 3 measurements). The three levels of the fair value hierarchy are described below: Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2 - Quoted prices for similar assets or liabilities in active markets, quoted prices in markets that are not active, or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability; Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The types of instruments valued based on quoted market prices in active markets include most U.S. government and agency securities, many other sovereign government obligations, liquid mortgage products, active listed equities and most money market securities. Such instruments are generally classified within level 1 or level 2 of the fair value hierarchy. The Company does not adjust the quoted price for such instruments. 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. Certain common equity securities are reported at fair value utilizing Level 1 inputs (exchange quoted prices). The majority of the other investment securities are reported at fair value utilizing Level 2 inputs. The prices for these instruments are obtained through an independent pricing service or dealer market participants with whom the Company has historically transacted both purchases and sales of investment securities. Prices obtained from these sources include prices derived from market quotations and matrix pricing. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. Management reviews the methodologies used in pricing the securities by its third party providers. U.S. GAAP requires disclosure of assets and liabilities measured and recorded at fair value on a nonrecurring basis such as goodwill, loans held for sale, other real estate owned, collateral-dependent impaired loans, mortgage servicing rights, and held-to-maturity securities. The only nonrecurring fair value measurement recorded during the nine month period ended September 30, 2013 and December 31, 2012 was related to impaired loans. The Company had collateral dependent impaired loans with a carrying value of approximately $6.2 million which had specific reserves included in the allowance for loan losses of $1.1 million at September 30, 2013. The Company had collateral dependent impaired loans with a carrying value of approximately $8.4 million which had specific reserves included in the allowance for loan losses of $2.8 million at December 31, 2012. The Company uses the fair value of underlying collateral, less costs to sell, to estimate the specific reserves for collateral dependent impaired loans. The appraisals may be adjusted by management for qualitative factors such as economic conditions and estimated liquidation expenses ranging from 10% to 35%. Based on the valuation techniques used, the fair value measurements for collateral dependent impaired loans are classified as Level 3. 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.

Securities (Policies)	9 Months Ended
Securities (Policies)	Sep. 30, 2013
Securities [Abstract]
Investment, Policy [Policy Text Block]	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. 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 September 30, 2013, management also had the 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 September 30, 2013, 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.

- Definition

Disclosure of accounting policy for investments in financial assets, including marketable securities (debt and equity securities with readily determinable fair values), investments accounted for under the equity method and cost method, securities borrowed and loaned, and repurchase and resale agreements. For marketable securities, the disclosure may include the entity's accounting treatment for transfers between investment categories and how the fair values for such securities are determined. Also, for all investments, an entity may describe its policy for assessing, recognizing and measuring impairment of the investment.

+ References + Details

Acquisition (Tables)

9 Months Ended

Sep. 30, 2013

Acquisition [Abstract]

Consideration paid, assets acquired, and liabilities assumed

Consideration paid:
NBT Bancorp common stock issued to Alliance common shareholders	$	225,551
Cash in lieu of fractional shares paid to Alliance common shareholders		11
Less treasury shares		5,779

Net consideration paid	$	219,783

Recognized Amounts of Identifiable Assets Acquired and (Liabilities Assumed) At Fair Value:
Cash and short term investments	$	81,060
Securities		320,618
Loans		904,473
Intangible assets		13,161
Other assets		71,589
Deposits		(1,113,420	)
Borrowings		(126,530	)
Trust preferred debentures		(25,774	)
Other liabilities		(18,908	)
Total identifiable net assets	$	106,269

Goodwill	$	113,514

Acquired loan portfolio

Information about the acquired loan portfolio as of March 8, 2013 is as follows (in thousands):

Contractually required principal and interest at acquisition	$	908,614
Contractual cash flows not expected to be collected		(15,466	)
Expected cash flows at acquisition		893,148
Interest component of expected cash flows (accretable premium)		11,325
Fair value of acquired loans	$	904,473

Schedule of changes in accretable discount

The following table presents changes in the accretable discount (in thousands):

Balance at January 1, 2013	$	-
Alliance acquisition		11,325
Accretion recognized to date		(1,950	)
Balance at September 30, 2013	$	9,375

Schedule of unaudited pro forma amounts related to acquisition

	Pro forma
	Nine months ended September 30,
	2013		2012

Net interest income	$	182,610	$	182,081
Noninterest income		82,592		78,950
Net income		52,933		48,609

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

9 Months Ended

Sep. 30, 2013

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

Allowance for loan losses by portfolio

The following tables illustrate the changes in the allowance for loan losses by our portfolio segments for the three and nine months ended September 30, 2013 and 2012:

							Residential
Three months ended September 30	Commercial			Consumer			Real Estate
	Loans			Loans			Mortgages			Unallocated			Total
Balance as of June 30, 2013	$	37,704		$	26,456		$	6,806		$	218		$	71,184
Charge-offs		(3,489	)		(3,746	)		(374	)		-			(7,609	)
Recoveries		602			733			76			-			1,411
Provision		980			3,744			402			72			5,198
Ending Balance as of September 30, 2013	$	35,797		$	27,187		$	6,910		$	290		$	70,184

Balance as of June 30, 2012	$	37,495		$	27,235		$	5,943		$	61		$	70,734
Charge-offs		(1,904	)		(3,446	)		(480	)		-			(5,830	)
Recoveries		492			574			9			-			1,075
Provision		1,734			2,213			809			(1	)		4,755
Ending Balance as of September 30, 2012	$	37,817		$	26,576		$	6,281		$	60		$	70,734

							Residential
Nine months ended September 30	Commercial			Consumer			Real Estate
	Loans			Loans			Mortgages			Unallocated			Total
Balance as of December 31, 2012	$	35,624		$	27,162		$	6,252		$	296		$	69,334
Charge-offs		(8,009	)		(11,122	)		(1,347	)		-			(20,478	)
Recoveries		1,485			2,363			179			43			4,070
Provision		6,697			8,784			1,826			(49	)		17,258
Ending Balance as of September 30, 2013	$	35,797		$	27,187		$	6,910		$	290		$	70,184

Balance as of December 31, 2011	$	38,831		$	26,049		$	6,249		$	205		$	71,334
Charge-offs		(4,685	)		(11,237	)		(1,130	)		-			(17,052	)
Recoveries		1,180			1,918			25			-			3,123
Provision		2,491			9,846			1,137			(145	)		13,329
Ending Balance as of September 30, 2012	$	37,817		$	26,576		$	6,281		$	60		$	70,734

The following tables illustrate the allowance for loan losses and the recorded investment by portfolio segments as of September 30, 2013 and December 31, 2012:

Allowance for Loan Losses and Recorded Investment in Loans
(in thousands)

					Residential
	Commercial		Consumer		Real Estate
	Loans		Loans		Mortgages		Unallocated		Total
As of September 30, 2013
Allowance for loan losses	$	35,797	$	27,187	$	6,910	$	290	$	70,184

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

Allowance for loans collectively evaluated for impairment	$	34,697	$	27,187	$	6,910	$	290	$	69,084

Ending balance of loans	$	2,378,848	$	1,960,225	$	1,028,158			$	5,367,231

Ending balance of loans individually evaluated for impairment	$	15,323	$	-	$	-			$	15,323
Ending balance of acquired loans	$	432,806	$	243,469	$	325,491			$	1,001,766
Ending balance of loans collectively evaluated for impairment	$	1,930,719	$	1,716,756	$	702,667			$	4,350,142

As of December 31, 2012
Allowance for loan losses	$	35,624	$	27,162	$	6,252	$	296	$	69,334

Allowance for loans individually evaluated for impairment	$	2,848	$	-	$	-			$	2,848

Allowance for loans collectively evaluated for impairment	$	32,776	$	27,162	$	6,252	$	296	$	66,486

Ending balance of loans	$	2,003,371	$	1,623,138	$	651,107			$	4,277,616

Ending balance of loans individually evaluated for impairment	$	11,972	$	-	$	-			$	11,972

Ending balance of loans collectively evaluated for impairment	$	1,991,399	$	1,623,138	$	651,107			$	4,265,644

Past due and nonperforming loans by loan class

The following table illustrates the Company’s nonaccrual loans by loan class:

Loans on Nonaccrual Status as of:

(In thousands)	September 30, 2013		December 31, 2012
ORIGINATED
Commercial Loans
Commercial	$	4,409	$	4,985
Commercial Real Estate		8,642		7,977
Agricultural		1,076		699
Agricultural Real Estate		868		1,038
Business Banking		4,949		6,738
		19,944		21,437

Consumer Loans
Indirect		1,440		1,557
Home Equity		5,965		7,247
Direct		92		266
		7,497		9,070

Residential Real Estate Mortgages		6,666		9,169

	$	34,107	$	39,676

ACQUIRED
Commercial Loans
Commercial	$	102
Commercial Real Estate		1,329
Business Banking		1,338
		2,769

Consumer Loans
Indirect		258
Home Equity		353
Direct		71
		682

Residential Real Estate Mortgages		3,860

	$	7,311

Total nonaccrual loans	$	41,418	$	39,676

The following tables set forth information with regard to past due and nonperforming loans by loan class as of September 30, 2013 and December 31, 2012:

Age Analysis of Past Due Financing Receivables
As of September 30, 2013
(in thousands)

					Greater Than
	31-60 Days		61-90 Days		90 Days		Total						Recorded
	Past Due		Past Due		Past Due		Past Due						Total
	Accruing		Accruing		Accruing		Accruing		Non-Accrual		Current		Loans
ORIGINATED
Commercial Loans
Commercial	$	76	$	1,031	$	-	$	1,107	$	4,409	$	589,008	$	594,524
Commercial Real Estate		478		-		-		478		8,642		910,134		919,254
Agricultural		140		-		-		140		1,076		63,576		64,792
Agricultural Real Estate		-		-		-		-		868		34,071		34,939
Business Banking		1,900		675		-		2,575		4,949		325,009		332,533
		2,594		1,706		-		4,300		19,944		1,921,798		1,946,042

Consumer Loans
Indirect		10,530		2,331		1,229		14,090		1,440		1,098,286		1,113,816
Home Equity		6,513		1,648		768		8,929		5,965		527,428		542,322
Direct		625		156		107		888		92		59,638		60,618
		17,668		4,135		2,104		23,907		7,497		1,685,352		1,716,756
Residential Real Estate Mortgages		2,955		172		994		4,121		6,666		691,880		702,667
	$	23,217	$	6,013	$	3,098	$	32,328	$	34,107	$	4,299,030	$	4,365,465


ACQUIRED
Commercial Loans
Commercial	$	70	$	-	$	-	$	70	$	102	$	114,202	$	114,374
Commercial Real Estate		232		-		-		232		1,329		243,233		244,794
Business Banking		246		-		-		246		1,338		72,054		73,638
		548		-		-		548		2,769		429,489		432,806

Consumer Loans
Indirect		526		116		32		674		258		143,588		144,520
Home Equity		750		-		154		904		353		89,443		90,700
Direct		113		16		2		131		71		8,047		8,249
		1,389		132		188		1,709		682		241,078		243,469
Residential Real Estate Mortgages		2,479		317		-		2,796		3,860		318,835		325,491
	$	4,416	$	449	$	188	$	5,053	$	7,311	$	989,402	$	1,001,766
Total Loans	$	27,633	$	6,462	$	3,286	$	37,381	$	41,418	$	5,288,432	$	5,367,231

As of December 31, 2012
(in thousands)

					Greater Than
	31-60 Days		61-90 Days		90 Days		Total						Recorded
	Past Due		Past Due		Past Due		Past Due						Total
	Accruing		Accruing		Accruing		Accruing		Non-Accrual		Current		Loans
Commercial Loans
Commercial	$	-	$	-	$	-	$	-	$	4,985	$	556,496	$	561,481
Commercial Real Estate		126		-		-		126		7,977		966,692		974,795
Agricultural		22		-		-		22		699		63,037		63,758
Agricultural Real Estate		108		-		103		211		1,038		36,128		37,377
Business Banking		3,019		708		45		3,772		6,738		355,450		365,960
		3,275		708		148		4,131		21,437		1,977,803		2,003,371

Consumer Loans
Indirect		10,956		2,477		1,205		14,638		1,557		964,802		980,997
Home Equity		6,065		1,223		681		7,969		7,247		560,066		575,282
Direct		717		144		84		945		266		65,648		66,859
		17,738		3,844		1,970		23,552		9,070		1,590,516		1,623,138
Residential Real Estate Mortgages		1,839		725		330		2,894		9,169		639,044		651,107
	$	22,852	$	5,277	$	2,448	$	30,577	$	39,676	$	4,207,363	$	4,277,616

Impaired loans and specific reserve allocations

The following table provides information on impaired loans and specific reserve allocations as of September 30, 2013 and December 31, 2012:

	September 30, 2013						December 31, 2012
	Recorded		Unpaid				Recorded		Unpaid
	Investment		Principal				Investment		Principal
	Balance		Balance		Related		Balance		Balance		Related
(in thousands)	(Book)		(Legal)		Allowance		(Book)		(Legal)		Allowance
With no related allowance recorded:
Commercial Loans
Commercial	$	5,507	$	5,549			$	1,651	$	1,710
Commercial Real Estate		5,427		5,431				8,709		9,553
Agricultural		1,097		1,460				940		1,286
Agricultural Real Estate		1,529		1,936				1,713		2,026
Business Banking		6,533		8,927				7,048		9,579
Total Commercial Loans		20,093		23,303				20,061		24,154

Consumer Loans
Home Equity		3,304		3,496				2,553		2,657

Residential Real Estate Mortgages		2,234		2,626				2,011		2,308
	$	25,631	$	29,425			$	24,625	$	29,119

With an allowance recorded:
Commercial Loans
Commercial	$	-	$	-	$	-	$	4,335	$	4,340	$	2,241
Commercial Real Estate		6,216		7,838		1,100		4,068		5,689		607
Agricultural		-		-		-		-		-		-
Agricultural Real Estate		-		-		-		-		-		-
		6,216		7,838		1,100		8,403		10,029		2,848

Total:	$	31,847	$	37,263	$	1,100	$	33,028	$	39,148	$	2,848

The following tables summarize the average recorded investments on impaired loans and the interest income recognized for the three and nine months ended September 30, 2013 and 2012:

	For the three months ended
	September 30, 2013				September 30, 2012
	Average		Interest		Average		Interest Income
	Recorded		Income		Recorded		Recognized
(in thousands)	Investment		Recognized		Investment		Accrual
Commercial Loans
Commercial	$	3,348	$	15	$	1,128	$	32
Commercial Real Estate		10,751		-		7,140		-
Agricultural		1,526		-		2,876		4
Agricultural Real Estate		897		12		1,876		12
Business Banking		6,581		13		6,572		-
Consumer Loans
Home Equity		3,064		8		1,828		5
Residential Real Estate Mortgages		2,066		15		1,055		1
Total:	$	28,233	$	63	$	22,475	$	54

	For the nine months ended
	September 30, 2013				September 30, 2012
	Average		Interest		Average		Interest Income
	Recorded		Income		Recorded		Recognized
(in thousands)	Investment		Recognized		Investment		Accrual
Commercial Loans
Commercial	$	4,069	$	45	$	1,551	$	101
Commercial Real Estate		10,660		51		6,481		-
Agricultural		1,100		1		2,997		40
Agricultural Real Estate		1,287		36		1,926		65
Business Banking		7,538		43		7,151		-
Consumer Loans
Home Equity		2,871		20		1,869		17
Residential Real Estate Mortgages		2,015		42		1,043		4
Total:	$	29,540	$	238	$	23,018	$	227

Financing receivable credit quality by loan class

The following tables illustrate the Company’s credit quality by loan class as of September 30, 2013 and December 31, 2012:

Credit Quality Indicators
As of September 30, 2013

ORIGINATED
			Commercial				Agricultural
Commercial Credit Exposure	Commercial		Real Estate		Agricultural		Real Estate		Total
By Internally Assigned Grade:
Pass	$	574,229	$	903,073	$	59,797	$	31,418	$	1,568,517
Special Mention		10,098		50		389		43		10,580
Substandard		10,197		16,131		4,594		3,478		34,400
Doubtful		-		-		12		-		12
Total	$	594,524	$	919,254	$	64,792	$	34,939	$	1,613,509


Business Banking Credit Exposure	Small Business								Total
By Internally Assigned Grade:
Non-classified	$	313,250							$	313,250
Classified		19,283								19,283
Total	$	332,533							$	332,533

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct				Total
Performing	$	1,111,147	$	535,589	$	60,419			$	1,707,155
Nonperforming		2,669		6,733		199				9,601
Total	$	1,113,816	$	542,322	$	60,618			$	1,716,756

	Residential
Residential Mortgage Credit Exposure	Mortgage								Total
By Payment Activity:
Performing	$	695,007							$	695,007
Nonperforming		7,660								7,660
Total	$	702,667							$	702,667

Credit Quality Indicators
As of September 30, 2013
ACQUIRED
Commercial Credit Exposure			Commercial
By Internally Assigned Grade:	Commercial		Real Estate		Agricultural		Total
Pass	$	98,128	$	221,777	$	-	$	319,905
Special Mention		1,602		4,762		-		6,364
Substandard		14,644		18,255		-		32,899
Doubtful		-		-		-		-
Total	$	114,374	$	244,794	$	-	$	359,168

Business Banking Credit Exposure
By Internally Assigned Grade:	Small Business						Total
Non-classified	$	68,917					$	68,917
Classified		4,721						4,721
Total	$	73,638					$	73,638

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct		Total
Performing	$	144,230	$	90,193	$	8,176	$	242,599
Nonperforming		290		507		73		870
Total	$	144,520	$	90,700	$	8,249	$	243,469

Residential Mortgage Credit Exposure	Residential
By Payment Activity:	Mortgage						Total
Performing	$	321,631					$	321,631
Nonperforming		3,860						3,860
Total	$	325,491					$	325,491

Credit Quality Indicators
As of December 31, 2012

Commercial Credit Exposure			Commercial				Agricultural
By Internally Assigned Grade:	Commercial		Real Estate		Agricultural		Real Estate		Total
Pass	$	522,985	$	901,928	$	57,347	$	33,472	$	1,515,732
Special Mention		18,401		32,135		13		3		50,552
Substandard		17,351		40,732		6,362		3,902		68,347
Doubtful		2,744		-		36		-		2,780
Total	$	561,481	$	974,795	$	63,758	$	37,377	$	1,637,411

Business Banking. Credit Exposure
By Internally Assigned Grade:	Small Business								Total
Non-classified	$	342,528							$	342,528
Classified		23,432								23,432
Total	$	365,960							$	365,960

Consumer Credit Exposure
By Payment Activity:	Indirect		Home Equity		Direct				Total
Performing	$	978,235	$	567,354	$	66,509			$	1,612,098
Nonperforming		2,762		7,928		350				11,040
Total	$	980,997	$	575,282	$	66,859			$	1,623,138

Residential Mortgage Credit Exposure	Residential
By Payment Activity:	Mortgage								Total
Performing	$	641,608							$	641,608
Nonperforming		9,499								9,499
Total	$	651,107							$	651,107

Earnings Per Share (Tables)

9 Months Ended

Sep. 30, 2013

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 periods presented in the consolidated statements of income.

Three months ended September 30,	2013		2012
(in thousands, except per share data)
Basic EPS:
Weighted average common shares outstanding		43,711		33,619
Net income available to common shareholders		19,257		14,535
Basic EPS	$	0.44	$	0.43
Diluted EPS:
Weighted average common shares outstanding		43,711		33,619
Dilutive effect of common stock options and restricted stock		424		342

Weighted average common shares and common share equivalents		44,135		33,961
Net income available to common shareholders		19,257		14,535
Diluted EPS	$	0.44	$	0.43

Nine months ended September 30,		2013		2012
(in thousands, except per share data)
Basic EPS:
Weighted average common shares outstanding		41,375		33,293
Net income available to common shareholders		43,822		41,442
Basic EPS	$	1.06	$	1.24
Diluted EPS:
Weighted average common shares outstanding		41,375		33,293
Dilutive effect of common stock options and restricted stock		394		333

Weighted average common shares and common share equivalents		41,769		33,626
Net income available to common shareholders		43,822		41,442
Diluted EPS	$	1.05	$	1.23

Defined Benefit Postretirement Plans (Tables)

9 Months Ended

Sep. 30, 2013

Defined Benefit Postretirement Plans [Abstract]

Components of Net Periodic Pension Benefits and Other Benefit Costs

The components of expense for Pension Benefits and Other Benefits are set forth below (in thousands):

	Pension Benefits						Other Benefits
	Three months ended September 30,						Three months ended September 30,
Components of net periodic benefit cost:	2013			2012			2013			2012
Service cost	$	604		$	757		$	6		$	6
Interest cost		830			774			75			40
Expected return on plan assets		(1,929	)		(1,676	)		-			-
Net amortization		711			992			(2	)		(3	)
Total cost (benefit)	$	216		$	847		$	79		$	43

	Pension Benefits						Other Benefits
	Nine months ended September 30,						Nine months ended September 30,
Components of net periodic benefit cost:		2013			2012			2013			2012
Service cost	$	1,813		$	2,270		$	18		$	16
Interest cost		2,489			2,322			224			119
Expected return on plan assets		(5,786	)		(5,026	)		-			-
Net amortization		2,025			2,710			219			(8	)
Total cost (benefit)	$	541		$	2,276		$	461		$	127

Junior Subordinated Debt (Tables)

9 Months Ended

Sep. 30, 2013

Junior Subordinated Debt [Abstract]

Schedule of Debt of VIE Where Entity is Not Primary Beneficiary

As of September 30, 2013, 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-99	$	18,000	3-month LIBOR plus 2.75%	$	18,720	August-29

NBT Statutory Trust I	November-05		5,000	3-month LIBOR plus 1.40%		5,155	December-35

NBT Statutory Trust II	February-06		50,000	3-month LIBOR plus 1.40%		51,547	March-36

Alliance Financial Capital Trust I	December-03		10,000	3-month LIBOR plus 2.85%		10,310	January-34

Alliance Financial Capital Trust II	September-06		15,000	3-month LIBOR plus 1.65%		15,464	September-36

- 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=6584090&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

Fair Values Measurements and Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2013

Fair Value Measurements and Fair Value of Financial Instruments [Abstract]

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

September 30, 2013:

	Quoted Prices in		Significant Other		Significant
	Active Markets for		Observable		Unobservable		Balance
	Identical Assets		Inputs		Inputs		as of
	(Level 1)		(Level 2)		(Level 3)		September 30, 2013
Assets:
Securities Available for Sale:
U.S. Treasury	$	43,804	$	-	$	-	$	43,804
Federal Agency		-		295,194		-		295,194
State & municipal		-		118,602		-		118,602
Mortgage-backed		-		335,206		-		335,206
Collateralized mortgage obligations		-		578,210		-		578,210
Other securities		9,671		5,047		-		14,718
Total Securities Available for Sale	$	53,475	$	1,332,259	$	-	$	1,385,734
Trading Securities		5,285		-		-		5,285
Interest Rate Swaps		-		1,038		-		1,038
Total	$	58,760	$	1,333,297	$	-	$	1,392,057

Liabilities:
Interest Rate Swaps	$	-	$	1,038	$	-	$	1,038
Total	$	-	$	1,038	$	-	$	1,038

December 31, 2012:

	Quoted Prices in		Significant		Significant
	Active Markets for		Other		Unobservable		Balance
	Identical Assets		Observable Inputs		Inputs		as of
	(Level 1)		(Level 2)		(Level 3)		December 31, 2012
Assets:
Securities Available for Sale:
U.S. Treasury	$	64,425	$	-	$	-	$	64,425
Federal Agency		-		282,814		-		282,814
State & municipal		-		86,802		-		86,802
Mortgage-backed		-		250,281		-		250,281
Collateralized mortgage obligations		-		449,723		-		449,723
Other securities		11,866		2,088		-		13,954
Total Securities Available for Sale	$	76,291	$	1,071,708	$	-	$	1,147,999
Trading Securities		3,918		-		-		3,918
Interest Rate Swaps		-		1,490		-		1,490
Total	$	80,209	$	1,073,198	$	-	$	1,153,407

Liabilities:
Interest Rate Swaps	$	-	$	1,490	$	-	$	1,490
Total	$	-	$	1,490	$	-	$	1,490

Fair Value of Financial Instruments By Balance Sheet Grouping

			September 30, 2013				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	$	118,259	$	115,620	$	60,563	$	61,535
Net loans		3		5,297,047		5,358,132		4,208,282		4,313,244
Financial liabilities
Time deposits		2	$	1,063,730	$	1,068,888	$	983,261	$	994,376
Long-term debt		2		309,009		336,128		367,492		407,404
Trust preferred debentures		2		101,196		103,364		75,422		74,147

Securities (Tables)

9 Months Ended

Sep. 30, 2013

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
September 30, 2013
U.S. Treasury	$	43,359	$	445	$	-	$	43,804
Federal Agency		300,964		369		6,139		295,194
State & municipal		117,936		2,083		1,417		118,602
Mortgage-backed:
Government-sponsored enterprises		303,907		7,652		960		310,599
U.S. government securities		23,613		1,080		86		24,607
Collateralized mortgage obligations:
Government-sponsored enterprises		543,447		1,792		15,211		530,028
U.S. government securities		47,330		914		62		48,182
Other securities		12,367		2,551		200		14,718
Total securities available for sale	$	1,392,923	$	16,886	$	24,075	$	1,385,734
December 31, 2012
U.S. Treasury	$	63,668	$	757	$	-	$	64,425
Federal Agency		281,398		1,507		91		282,814
State & municipal		82,675		4,127		-		86,802
Mortgage-backed:
Government-sponsored enterprises		221,110		11,175		-		232,285
U.S. government securities		16,351		1,645		-		17,996
Collateralized mortgage obligations:
Government-sponsored enterprises		399,147		4,418		-		403,565
U.S. government securities		44,825		1,333		-		46,158
Other securities		11,210		2,832		88		13,954
Total securities available for sale	$	1,120,384	$	27,794	$	179	$	1,147,999

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:

	Amortized		Unrealized		Unrealized		Estimated
(In thousands)	cost		gains		losses		fair value
September 30, 2013
Mortgage-backed	$	983	$	122	$	-	$	1,105
Collateralized mortgage oblications		63,048		-		3,251		59,797
State & municipal		54,228		490		-		54,718
Total securities held to maturity	$	118,259	$	612	$	3,251	$	115,620
December 31, 2012
Mortgage-backed	$	1,168	$	184	$	-	$	1,352
State & municipal		59,395		788		-		60,183
Total securities held to maturity	$	60,563	$	972	$	-	$	61,535

Investment securities with unrealized losses

The following table sets forth information with regard to investment securities with unrealized losses at September 30, 2013 and December 31, 2012:

	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

September 30, 2013
Investment securities available for sale:
Federal agency	$	300,964	$	(6,139	)		20	$	-	$	-			-	$	300,964	$	(6,139	)		20
State & municipal		117,936		(1,417	)		189		-		-			-		117,936		(1,417	)		189
Mortgage-backed		327,504		(1,046	)		81		-		-			-		327,504		(1,046	)		81
Collateralized mortgage obligations		590,777		(15,273	)		40		-		-			-		590,777		(15,273	)		40
Other securities		5,523		(170	)		2		218		(30	)		1		5,741		(200	)		3
Total securities with unrealized losses	$	1,342,704	$	(24,045	)		332	$	218	$	(30	)		1	$	1,342,922	$	(24,075	)		333

September 30, 2013
Investment securities held to maturity:
Collateralized mortgage obligations	$	63,048	$	(3,251	)		5	$	-	$	-			-	$	63,048	$	(3,251	)		5
Total securities with unrealized losses	$	63,048	$	(3,251	)		5	$	-	$	-			-	$	63,048	$	(3,251	)		5

	Less than 12 months							12 months or longer							Total
	Fair Value		Unrealized losses			Number of Positions		Fair Value		Unrealized losses			Number of Positions		Fair Value		Unrealized losses			Number of Positions
December 31, 2012
Investment securities available for sale:
U.S. Treasury	$	-	$	-			-	$	-	$	-			-	$	-	$	-			-
Federal agency		39,906		(91	)		4		-		-			-		39,906		(91	)		4
State & municipal		-		-			-		-		-			-		-		-			-
Mortgage-backed		-		-			-		-		-			-		-		-			-
Collateralized mortgage obligations		23		-			2		-		-			-		23		-			2
Other securities		468		(6	)		1		167		(82	)		1		635		(88	)		2
Total securities with unrealized losses	$	40,397	$	(97	)		7	$	167	$	(82	)		1	$	40,564	$	(179	)		8

Contractual maturities of debt securities

The following tables set forth information with regard to contractual maturities of debt securities at September 30, 2013:

(In thousands)	Amortized cost		Estimated fair value
Debt securities classified as available for sale
Within one year	$	26,527	$	26,704
From one to five years		272,953		274,104
From five to ten years		295,191		293,558
After ten years		785,885		776,650
	$	1,380,556	$	1,371,016
Debt securities classified as held to maturity
Within one year	$	25,305	$	25,412
From one to five years		22,364		22,744
From five to ten years		5,054		5,059
After ten years		65,536		62,405
	$	118,259	$	115,620

- 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

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

9 Months Ended

Sep. 30, 2013

Reclassification Adjustments Out of Other Comprehensive Loss income [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
	Three months ended
	September 30, 2013			September 30, 2012
Available for sale securities:
Gains on available for sale securities	$	(329	)	$	(26	)	Net securities gains
Tax benefit		132			10		Income tax expense
Net of tax	$	(197	)	$	(16	)

Pension and other benefits:
Amortization of net gains	$	765		$	1,044		Salaries and employee benefits
Amortization of prior service costs		(56	)		(55	)	Salaries and employee benefits
Tax expense		283			390		Income tax expense
Net of tax	$	426		$	599

Total reclassifications during the period, net of tax	$	229		$	583

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
	Nine months ended
	September 30, 2013			September 30, 2012
Available for sale securities:
Gains on available for sale securities	$	(1,413	)	$	(578	)	Net securities gains
Tax expense		565			231		Income tax expense
Net of tax	$	(848	)	$	(347	)

Pension and other benefits:
Amortization of net gains	$	2,411		$	2,869		Salaries and employee benefits
Amortization of prior service costs		(167	)		(167	)	Salaries and employee benefits
Tax expense		890			1076		Income tax expense
Net of tax	$	1,354		$	1,626

Total reclassifications during the period, net of tax	$	506		$	1,279

Acquisition (Details) $ in Thousands		3 Months Ended		9 Months Ended
Acquisition (Details) $ in Thousands	Mar. 08, 2013 USD ($) Branch shares	Sep. 30, 2013 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2013 USD ($) shares	Sep. 30, 2012 USD ($)	Dec. 31, 2012 USD ($)
Business Acquisition [Line Items]
Direct costs related acquisition		$ 326	$ 558	$ 12,276	$ 1,895
Recognized Amounts of Identifiable Assets Acquired and (Liabilities Assumed), At Fair Value [Abstract]
Goodwill		265,052		$ 265,052		$ 152,373
Alliance Financial Corporation [Member]
Business Acquisition [Line Items]
Date of acquisition				Mar. 08, 2013
Number of banking centers operated by acquiree \| Branch	26
Business acquisition shares converted right to receive entity's common stock (in shares) \| shares	2.1779
Number of shares of common stock issued to acquiree shareholders (in shares) \| shares				10,300,000
Direct costs related acquisition				$ 12,300
Core deposit and trust intangible assets useful Live, Minimum				10 years
Core deposit and trust intangible assets useful Lives, Maximum				15 years
Consideration paid [Abstract]
NBT Bancorp common stock issued to Alliance common shareholders	$ 225,551
Cash in lieu of fractional shares paid to Alliance common shareholders	11
Less treasury shares	5,779
Net consideration paid	219,783
Recognized Amounts of Identifiable Assets Acquired and (Liabilities Assumed), At Fair Value [Abstract]
Cash and short term investments	81,060
Securities	320,618
Loans	904,473
Intangible assets	13,161
Other assets	71,589
Deposits	(1,113,420)
Borrowings	(126,530)
Trust Preferred debentures	(25,774)
Other liabilities	(18,908)
Total identifiable net assets	106,269
Goodwill	113,514
Information about acquired loan portfolio [Abstract]
Contractually required principal and interest at acquisition	908,614
Contractual cash flows not expected to be collected	(15,466)
Expected cash flows at acquisition	893,148
Interest component of expected cash flows (accretable premium)	11,325
Fair value of acquired loans	$ 904,473
Changes in accretable discount [Abstract]
Balance at January 1, 2013				$ 0
Alliance acquisition				11,325
Accretion recognized to date				(1,950)
Balance at September 30, 2013		$ 9,375		9,375
Net Income (Loss) [Abstract]
Net interest income				182,610	182,081
Noninterest income				82,592	78,950
Net income				52,933	$ 48,609
Hampshire First Bank [Member]
Other goodwill adjustments [Abstract]
Goodwill, purchase accounting adjustments				(1,000)
Acquisition of Financial Services Company [Member]
Other goodwill adjustments [Abstract]
Goodwill, purchase accounting adjustments				$ 100

Commitments and Contingencies (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Commitment to Extend Credits and Unused Lines of Credit [Member]
Guarantor Obligations [Line Items]
Commitments - maximum potential obligation	$ 1,100.0	$ 841.7
Standby Letters of Credit [Member]
Guarantor Obligations [Line Items]
Commitments - maximum potential obligation	$ 40.7	37.5
Obligation instrument term	5 years
Commercial Letters of Credit [Member]
Guarantor Obligations [Line Items]
Commitments - maximum potential obligation	$ 41.5	$ 16.6

Allowance for Loan Losses and Credit Quality of Loans, Allowance for Loan Losses (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2013 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2013 USD ($) Segment	Sep. 30, 2012 USD ($)	Sep. 30, 2013 USD ($)	Dec. 31, 2012 USD ($)
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance as of Beginning of Period	$ 71,184,000	$ 70,734,000	$ 69,334,000	$ 71,334,000
Charge-offs	(7,609,000)	(5,830,000)	(20,478,000)	(17,052,000)
Recoveries	1,411,000	1,075,000	4,070,000	3,123,000
Provision	5,198,000	4,755,000	17,258,000	13,329,000
Balance as of Ending of Period	70,184,000	70,734,000	70,184,000	70,734,000
Allowance for loan losses for acquired loan portfolio			0	0
Provision expense and net charge-offs related to acquired loans	47,000		300,000
Allowance loan losses [Abstract]
Allowance for loan losses	71,184,000	70,734,000	69,334,000	71,334,000	$ 70,184,000	$ 69,334,000
Allowance for loans individually evaluated for impairment					1,100,000	2,848,000
Allowance for loans collectively evaluated for impairment					69,084,000	66,486,000
Ending balance of loans					5,367,231,000	4,277,616,000
Ending balance of loans individually evaluated for impairment					15,323,000	11,972,000
Ending balance of acquired loans					1,001,766,000
Ending balance of loans collectively evaluated for impairment					4,350,142,000	4,265,644,000
Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance as of Beginning of Period	37,704,000	37,495,000	35,624,000	38,831,000
Charge-offs	(3,489,000)	(1,904,000)	(8,009,000)	(4,685,000)
Recoveries	602,000	492,000	1,485,000	1,180,000
Provision	980,000	1,734,000	6,697,000	2,491,000
Balance as of Ending of Period	35,797,000	37,817,000	35,797,000	37,817,000
Allowance loan losses [Abstract]
Allowance for loan losses	37,704,000	37,817,000	$ 35,624,000	38,831,000	35,797,000	35,624,000
Allowance for loans individually evaluated for impairment					1,100,000	2,848,000
Allowance for loans collectively evaluated for impairment					34,697,000	32,776,000
Ending balance of loans					2,378,848,000	2,003,371,000
Ending balance of loans individually evaluated for impairment					15,323,000	11,972,000
Ending balance of acquired loans					432,806,000
Ending balance of loans collectively evaluated for impairment					$ 1,930,719,000	1,991,399,000
Commercial Loans [Member] \| Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan portfolio segments \| Segment			3
Real estate loan amount, percentage of appraised value or purchase price of the property, maximum (in hundredths)					80.00%
Commercial Loans [Member] \| 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%
Allowance loan losses [Abstract]
Ending balance of loans						37,377,000
Commercial Loans [Member] \| Business Banking [Member]
Allowance loan losses [Abstract]
Ending balance of loans						365,960,000
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance as of Beginning of Period	26,456,000	27,235,000	$ 27,162,000	26,049,000
Charge-offs	(3,746,000)	(3,446,000)	(11,122,000)	(11,237,000)
Recoveries	733,000	574,000	2,363,000	1,918,000
Provision	3,744,000	2,213,000	8,784,000	9,846,000
Balance as of Ending of Period	27,187,000	26,576,000	27,187,000	26,576,000
Allowance loan losses [Abstract]
Allowance for loan losses	$ 26,456,000	26,576,000	$ 27,162,000	26,049,000	$ 27,187,000	27,162,000
Allowance for loans individually evaluated for impairment					0	0
Allowance for loans collectively evaluated for impairment					27,187,000	27,162,000
Ending balance of loans					1,960,225,000	1,623,138,000
Ending balance of loans individually evaluated for impairment					0	0
Ending balance of acquired loans					243,469,000
Ending balance of loans collectively evaluated for impairment					1,716,756,000	1,623,138,000
Consumer Loans [Member] \| Business Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Business banking loans, maximum amount					$ 500,000
Consumer Loans [Member] \| Indirect [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of automobile financing to indirect relationships with dealers (in hundredths)					75.00%
Principal repayment term of loan, minimum			3 years
Principal repayment term of loan, maximum			6 years
Allowance loan losses [Abstract]
Ending balance of loans						980,997,000
Consumer Loans [Member] \| 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%		85.00%
Consumer Loans [Member] \| 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
Allowance loan losses [Abstract]
Ending balance of loans						66,859,000
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%
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance as of Beginning of Period	$ 6,806,000	5,943,000	$ 6,252,000	6,249,000
Charge-offs	(374,000)	(480,000)	(1,347,000)	(1,130,000)
Recoveries	76,000	9,000	179,000	25,000
Provision	402,000	809,000	1,826,000	1,137,000
Balance as of Ending of Period	6,910,000	6,281,000	6,910,000	6,281,000
Allowance loan losses [Abstract]
Allowance for loan losses	6,806,000	6,281,000	6,252,000	6,249,000	$ 6,910,000	6,252,000
Allowance for loans individually evaluated for impairment					0	0
Allowance for loans collectively evaluated for impairment					6,910,000	6,252,000
Ending balance of loans					1,028,158,000	651,107,000
Ending balance of loans individually evaluated for impairment					0	0
Ending balance of acquired loans					325,491,000
Ending balance of loans collectively evaluated for impairment					702,667,000	651,107,000
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance as of Beginning of Period	218,000	61,000	296,000	205,000
Charge-offs	0	0	0	0
Recoveries	0	0	43,000	0
Provision	72,000	(1,000)	(49,000)	(145,000)
Balance as of Ending of Period	290,000	60,000	290,000	60,000
Allowance loan losses [Abstract]
Allowance for loan losses	$ 218,000	$ 60,000	$ 296,000	$ 205,000	290,000	296,000
Allowance for loans collectively evaluated for impairment					$ 290,000	$ 296,000

Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
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	$ 27,633	$ 22,852
61 - 90 Days Past Due Accruing	6,462	5,277
Greater Than 90 Days Past Due Accruing	3,286	2,448
Total Past Due Accruing	37,381	30,577
Non-Accrual	41,418	39,676
Current	5,288,432	4,207,363
Ending balance of loans	5,367,231	4,277,616
Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	23,217
61 - 90 Days Past Due Accruing	6,013
Greater Than 90 Days Past Due Accruing	3,098
Total Past Due Accruing	32,328
Non-Accrual	34,107	39,676
Current	4,299,030
Ending balance of loans	4,365,465
ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	4,416
61 - 90 Days Past Due Accruing	449
Greater Than 90 Days Past Due Accruing	188
Total Past Due Accruing	5,053
Non-Accrual	7,311
Current	989,402
Ending balance of loans	1,001,766
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Ending balance of loans	2,378,848	2,003,371
Commercial Loans [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Non-Accrual	19,944	21,437
Commercial Loans [Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Non-Accrual	2,769
Commercial Loans [Member] \| Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		0
61 - 90 Days Past Due Accruing		0
Greater Than 90 Days Past Due Accruing		0
Total Past Due Accruing		0
Non-Accrual		4,985
Current		556,496
Ending balance of loans		561,481
Commercial Loans [Member] \| Commercial [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	76
61 - 90 Days Past Due Accruing	1,031
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	1,107
Non-Accrual	4,409	4,985
Current	589,008
Ending balance of loans	594,524
Commercial Loans [Member] \| Commercial [Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	70
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	70
Non-Accrual	102
Current	114,202
Ending balance of loans	114,374
Commercial Loans [Member] \| Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		126
61 - 90 Days Past Due Accruing		0
Greater Than 90 Days Past Due Accruing		0
Total Past Due Accruing		126
Non-Accrual		7,977
Current		966,692
Ending balance of loans		974,795
Commercial Loans [Member] \| Commercial Real Estate [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	478
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	478
Non-Accrual	8,642	7,977
Current	910,134
Ending balance of loans	919,254
Commercial Loans [Member] \| Commercial Real Estate [Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	232
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	232
Non-Accrual	1,329
Current	243,233
Ending balance of loans	244,794
Commercial Loans [Member] \| Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		22
61 - 90 Days Past Due Accruing		0
Greater Than 90 Days Past Due Accruing		0
Total Past Due Accruing		22
Non-Accrual		699
Current		63,037
Ending balance of loans		63,758
Commercial Loans [Member] \| Agricultural [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	140
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	140
Non-Accrual	1,076	699
Current	63,576
Ending balance of loans	64,792
Commercial Loans [Member] \| Agricultural Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		108
61 - 90 Days Past Due Accruing		0
Greater Than 90 Days Past Due Accruing		103
Total Past Due Accruing		211
Non-Accrual		1,038
Current		36,128
Ending balance of loans		37,377
Commercial Loans [Member] \| Agricultural Real Estate [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	0
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	0
Non-Accrual	868	1,038
Current	34,071
Ending balance of loans	34,939
Commercial Loans [Member] \| Business Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		3,019
61 - 90 Days Past Due Accruing		708
Greater Than 90 Days Past Due Accruing		45
Total Past Due Accruing		3,772
Non-Accrual		6,738
Current		355,450
Ending balance of loans		365,960
Commercial Loans [Member] \| Business Banking [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,900
61 - 90 Days Past Due Accruing	675
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	2,575
Non-Accrual	4,949	6,738
Current	325,009
Ending balance of loans	332,533
Commercial Loans [Member] \| Business Banking [Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	246
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	246
Non-Accrual	1,338
Current	72,054
Ending balance of loans	73,638
Commercial Loans [Member] \| Total Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		3,275
61 - 90 Days Past Due Accruing		708
Greater Than 90 Days Past Due Accruing		148
Total Past Due Accruing		4,131
Non-Accrual		21,437
Current		1,977,803
Ending balance of loans		2,003,371
Commercial Loans [Member] \| Total Commercial Loan [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	2,594
61 - 90 Days Past Due Accruing	1,706
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	4,300
Non-Accrual	19,944
Current	1,921,798
Ending balance of loans	1,946,042
Commercial Loans [Member] \| Total Commercial Loan [Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	548
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	548
Non-Accrual	2,769
Current	429,489
Ending balance of loans	432,806
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Ending balance of loans	1,960,225	1,623,138
Consumer Loans [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Non-Accrual	7,497	9,070
Consumer Loans [Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
Non-Accrual	682
Consumer Loans [Member] \| Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		10,956
61 - 90 Days Past Due Accruing		2,477
Greater Than 90 Days Past Due Accruing		1,205
Total Past Due Accruing		14,638
Non-Accrual		1,557
Current		964,802
Ending balance of loans		980,997
Consumer Loans [Member] \| Indirect [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	10,530
61 - 90 Days Past Due Accruing	2,331
Greater Than 90 Days Past Due Accruing	1,229
Total Past Due Accruing	14,090
Non-Accrual	1,440	1,557
Current	1,098,286
Ending balance of loans	1,113,816
Consumer Loans [Member] \| Indirect [Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	526
61 - 90 Days Past Due Accruing	116
Greater Than 90 Days Past Due Accruing	32
Total Past Due Accruing	674
Non-Accrual	258
Current	143,588
Ending balance of loans	144,520
Consumer Loans [Member] \| Home Equity Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		6,065
61 - 90 Days Past Due Accruing		1,223
Greater Than 90 Days Past Due Accruing		681
Total Past Due Accruing		7,969
Non-Accrual		7,247
Current		560,066
Ending balance of loans		575,282
Consumer Loans [Member] \| Home Equity Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	6,513
61 - 90 Days Past Due Accruing	1,648
Greater Than 90 Days Past Due Accruing	768
Total Past Due Accruing	8,929
Non-Accrual	5,965	7,247
Current	527,428
Ending balance of loans	542,322
Consumer Loans [Member] \| Home Equity Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	750
61 - 90 Days Past Due Accruing	0
Greater Than 90 Days Past Due Accruing	154
Total Past Due Accruing	904
Non-Accrual	353
Current	89,443
Ending balance of loans	90,700
Consumer Loans [Member] \| Direct [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		717
61 - 90 Days Past Due Accruing		144
Greater Than 90 Days Past Due Accruing		84
Total Past Due Accruing		945
Non-Accrual		266
Current		65,648
Ending balance of loans		66,859
Consumer Loans [Member] \| Direct [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	625
61 - 90 Days Past Due Accruing	156
Greater Than 90 Days Past Due Accruing	107
Total Past Due Accruing	888
Non-Accrual	92	266
Current	59,638
Ending balance of loans	60,618
Consumer Loans [Member] \| Direct [Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	113
61 - 90 Days Past Due Accruing	16
Greater Than 90 Days Past Due Accruing	2
Total Past Due Accruing	131
Non-Accrual	71
Current	8,047
Ending balance of loans	8,249
Consumer Loans [Member] \| Total Consumer Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		17,738
61 - 90 Days Past Due Accruing		3,844
Greater Than 90 Days Past Due Accruing		1,970
Total Past Due Accruing		23,552
Non-Accrual		9,070
Current		1,590,516
Ending balance of loans		1,623,138
Consumer Loans [Member] \| Total Consumer Loan [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	17,668
61 - 90 Days Past Due Accruing	4,135
Greater Than 90 Days Past Due Accruing	2,104
Total Past Due Accruing	23,907
Non-Accrual	7,497
Current	1,685,352
Ending balance of loans	1,716,756
Consumer Loans [Member] \| Total Consumer Loan [Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	1,389
61 - 90 Days Past Due Accruing	132
Greater Than 90 Days Past Due Accruing	188
Total Past Due Accruing	1,709
Non-Accrual	682
Current	241,078
Ending balance of loans	243,469
Residential Real Estate Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing		1,839
61 - 90 Days Past Due Accruing		725
Greater Than 90 Days Past Due Accruing		330
Total Past Due Accruing		2,894
Non-Accrual		9,169
Current		639,044
Ending balance of loans	1,028,158	651,107
Residential Real Estate Mortgages [Member] \| Originated loans [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	2,955
61 - 90 Days Past Due Accruing	172
Greater Than 90 Days Past Due Accruing	994
Total Past Due Accruing	4,121
Non-Accrual	6,666	$ 9,169
Current	691,880
Ending balance of loans	702,667
Residential Real Estate Mortgages [Member] \| ACQUIRED [Member]
Financing Receivable, Recorded Investment, Past Due [Abstract]
31 - 60 Days Past Due Accruing	2,479
61 - 90 Days Past Due Accruing	317
Greater Than 90 Days Past Due Accruing	0
Total Past Due Accruing	2,796
Non-Accrual	3,860
Current	318,835
Ending balance of loans	$ 325,491

Allowance for Loan Losses and Credit Quality of Loans, Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	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		$ 500
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	28,233	$ 22,475	29,540	$ 23,018
Interest Income Recognized	63	54	238	227
Commercial Loans [Member] \| Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	3,348	1,128	4,069	1,551
Interest Income Recognized	15	32	45	101
Commercial Loans [Member] \| Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	10,751	7,140	10,660	6,481
Interest Income Recognized	0	0	51	0
Commercial Loans [Member] \| Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,526	2,876	1,100	2,997
Interest Income Recognized	0	4	1	40
Commercial Loans [Member] \| Agricultural Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	897	1,876	1,287	1,926
Interest Income Recognized	12	12	36	65
Commercial Loans [Member] \| Business Banking [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	6,581	6,572	7,538	7,151
Interest Income Recognized	13	0	43	0
Consumer Loans [Member] \| Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	3,064	1,828	2,871	1,869
Interest Income Recognized	8	5	20	17
Residential Real Estate Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,066	1,055	2,015	1,043
Interest Income Recognized	15	$ 1	42	$ 4
With No Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	25,631		25,631		$ 24,625
Unpaid Principal Balance (Legal)	29,425		29,425		29,119
With No Allowance Recorded [Member] \| Commercial Loans [Member] \| Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	5,507		5,507		1,651
Unpaid Principal Balance (Legal)	5,549		5,549		1,710
With No Allowance Recorded [Member] \| Commercial Loans [Member] \| Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	5,427		5,427		8,709
Unpaid Principal Balance (Legal)	5,431		5,431		9,553
With No Allowance Recorded [Member] \| Commercial Loans [Member] \| Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	1,097		1,097		940
Unpaid Principal Balance (Legal)	1,460		1,460		1,286
With No Allowance Recorded [Member] \| Commercial Loans [Member] \| Agricultural Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	1,529		1,529		1,713
Unpaid Principal Balance (Legal)	1,936		1,936		2,026
With No Allowance Recorded [Member] \| Commercial Loans [Member] \| Business Banking [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	6,533		6,533		7,048
Unpaid Principal Balance (Legal)	8,927		8,927		9,579
With No Allowance Recorded [Member] \| Commercial Loans [Member] \| Total Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	20,093		20,093		20,061
Unpaid Principal Balance (Legal)	23,303		23,303		24,154
With No Allowance Recorded [Member] \| Consumer Loans [Member] \| Home Equity [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	3,304		3,304		2,553
Unpaid Principal Balance (Legal)	3,496		3,496		2,657
With No Allowance Recorded [Member] \| Residential Real Estate Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	2,234		2,234		2,011
Unpaid Principal Balance (Legal)	2,626		2,626		2,308
With An Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	31,847		31,847		33,028
Unpaid Principal Balance (Legal)	37,263		37,263		39,148
Related Allowance	1,100		1,100		2,848
With An Allowance Recorded [Member] \| Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	6,216		6,216		8,403
Unpaid Principal Balance (Legal)	7,838		7,838		10,029
Related Allowance	1,100		1,100		2,848
With An Allowance Recorded [Member] \| Commercial Loans [Member] \| Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	0		0		4,335
Unpaid Principal Balance (Legal)	0		0		4,340
Related Allowance	0		0		2,241
With An Allowance Recorded [Member] \| Commercial Loans [Member] \| Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	6,216		6,216		4,068
Unpaid Principal Balance (Legal)	7,838		7,838		5,689
Related Allowance	1,100		1,100		607
With An Allowance Recorded [Member] \| Commercial Loans [Member] \| Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	0		0		0
Unpaid Principal Balance (Legal)	0		0		0
Related Allowance	0		0		0
With An Allowance Recorded [Member] \| Commercial Loans [Member] \| Agricultural Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment Balance (Book)	0		0		0
Unpaid Principal Balance (Legal)	0		0		0
Related Allowance	$ 0		$ 0		$ 0

Allowance for Loan Losses and Credit Quality of Loans, Troubled Debt Restructurings (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2013 USD ($) Contract	Sep. 30, 2012 USD ($) Contract	Sep. 30, 2013 USD ($) Contract	Sep. 30, 2012 USD ($) Contract
Financing Receivable, Modifications [Line Items]
Period of sustained repayment performance for nonperforming TDRs to be returned to performing status			6 months
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Pre-modification outstanding recorded investment			$ 7,000,000
Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract			20
Pre-modification outstanding recorded investment			$ 1,000,000
Commercial Loans [Member]
Financing Receivable, Modifications [Line Items]
Pre-modification outstanding recorded investment				$ 1,000,000
Residential Real Estate Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract	5		6	1
Pre-modification outstanding recorded investment			$ 500,000	$ 200,000
Subsequent Default [Member] \| Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract		0
Pre-modification outstanding recorded investment		$ 0	$ 500,000	$ 25,000
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract				1
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract	3		4
Pre-modification outstanding recorded investment	$ 6,100,000
Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract	9
Pre-modification outstanding recorded investment	$ 400,000
Home Equity [Member] \| Subsequent Default [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract	1		7	1
Pre-modification outstanding recorded investment	$ 100,000
Commercial Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract		0
Pre-modification outstanding recorded investment		$ 0
Residential Real Estate Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Pre-modification outstanding recorded investment	$ 300,000
Residential Real Estate Mortgages [Member] \| Subsequent Default [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract		0
Pre-modification outstanding recorded investment		$ 0
Residential Real Estate Mortgages [Member] \| Subsequent Default [Member] \| Home Equity [Member]
Financing Receivable, Modifications [Line Items]
Pre-modification outstanding recorded investment				$ 400,000
Residential Real Estate Mortgages [Member] \| Home Equity [Member] \| Subsequent Default [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts \| Contract				3

Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basic EPS [Abstract]
Weighted average common shares outstanding (in shares)	43,711,000	33,619,000	41,375,000	33,293,000
Net income available to common shareholders	$ 19,257	$ 14,535	$ 43,822	$ 41,442
Basic EPS (in dollars per share)	$ 0.44	$ 0.43	$ 1.06	$ 1.24
Diluted EPS [Abstract]
Weighted average common shares outstanding (in shares)	43,711,000	33,619,000	41,375,000	33,293,000
Dilutive effect of common stock option and restricted stock (in shares)	424,000	342,000	394,000	333,000
Weighted average common shares and common share equivalent (in shares)	44,135,000	33,961,000	41,769,000	33,626,000
Net income available to common shareholders	$ 19,257	$ 14,535	$ 43,822	$ 41,442
Diluted EPS (in dollars per share)	$ 0.44	$ 0.43	$ 1.05	$ 1.23
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock options excluded from calculation of diluted EPS (in shares)	972,403	1,176,670	1,157,135	1,197,417

Defined Benefit Postretirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Defined Benefit Plan Disclosure [Line Items]
Transition obligation amortization period			20 years
Pension Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	$ 604	$ 757	$ 1,813	$ 2,270
Interest cost	830	774	2,489	2,322
Expected return on plan assets	(1,929)	(1,676)	(5,786)	(5,026)
Net amortization	711	992	2,025	2,710
Total cost (benefit)	216	847	541	2,276
Other Benefits [Member]
Components of net periodic benefit cost [Abstract]
Service cost	6	6	18	16
Interest cost	75	40	224	119
Expected return on plan assets	0	0	0	0
Net amortization	(2)	(3)	219	(8)
Total cost (benefit)	$ 79	$ 43	$ 461	$ 127

Junior Subordinated Debt (Details) $ in Thousands	9 Months Ended
Junior Subordinated Debt (Details) $ in Thousands	Sep. 30, 2013 USD ($) Trust
Limited Guarantee Trust Preferred Debentures [Abstract]
Number of statutory business trusts included in the Trusts \| Trust	5
CNBF Capital Trust I VIE Entity Not Primary Beneficiary [Member] \| CNBF Capital Trust I [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
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
NBT Statutory Trust I VIE Entity Not Primary Beneficiary [Member] \| NBT Statutory Trust I [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
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 VIE Entity Not Primary Beneficiary [Member] \| NBT Statutory Trust II [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
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 VIE Entity Not Primary Beneficiary [Member] \| Alliance Financial Capital Trust I [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
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 VIE Entity Not Primary Beneficiary [Member] \| Alliance Financial Capital Trust II [Member]
Limited Guarantee Trust Preferred Debentures [Abstract]
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

Fair Values Measurements and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2013	Dec. 31, 2012
Securities Available for Sale [Abstract]
Total Securities Available for Sale	$ 1,385,734	$ 1,147,999
Trading Securities	5,285	3,918
Liabilities [Abstract]
Collateral dependent impaired financing receivable with specific reserves	6,200	8,400
Allowance for loan and lease losses collateral dependent impaired loans with specific reserves	$ 1,100	2,800
Liquidation expense ratio on impaired collateral minimum (in hundredths)	10.00%
Liquidation expense ratio on impaired collateral maximum (in hundredths)	35.00%
Financial assets [Abstract]
Securities held to maturity	$ 115,620	61,535
Financial liabilities [Abstract]
Time deposits	1,063,730	983,261
Long-term debt	309,009	367,492
Trust preferred debentures	101,196	75,422
Carrying Amount [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Financial assets [Abstract]
Securities held to maturity	118,259	60,563
Financial liabilities [Abstract]
Time deposits	1,063,730	983,261
Long-term debt	309,009	367,492
Trust preferred debentures	101,196	75,422
Carrying Amount [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Financial assets [Abstract]
Net Loans	5,297,047	4,208,282
Estimated Fair Value [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Financial assets [Abstract]
Securities held to maturity	115,620	61,535
Financial liabilities [Abstract]
Time deposits	1,068,888	994,376
Long-term debt	336,128	407,404
Trust preferred debentures	103,364	74,147
Estimated Fair Value [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Financial assets [Abstract]
Net Loans	5,358,132	4,313,244
Recurring Basis [Member]
Securities Available for Sale [Abstract]
U.S. Treasury	43,804	64,425
Federal Agency	295,194	282,814
State & municipal	118,602	86,802
Mortgage-backed	335,206	250,281
Collateralized mortgage obligations	578,210	449,723
Other securities	14,718	13,954
Total Securities Available for Sale	1,385,734	1,147,999
Trading Securities	5,285	3,918
Interest Rate Swaps	1,038	1,490
Total	1,392,057	1,153,407
Liabilities [Abstract]
Interest Rate Swaps	1,038	1,490
Total	1,038	1,490
Recurring Basis [Member] \| Quoted Prices in Active Market for Identical Assets (Level I) [Member]
Securities Available for Sale [Abstract]
U.S. Treasury	43,804	64,425
Federal Agency	0	0
State & municipal	0	0
Mortgage-backed	0	0
Collateralized mortgage obligations	0	0
Other securities	9,671	11,866
Total Securities Available for Sale	53,475	76,291
Trading Securities	5,285	3,918
Interest Rate Swaps	0	0
Total	58,760	80,209
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	295,194	282,814
State & municipal	118,602	86,802
Mortgage-backed	335,206	250,281
Collateralized mortgage obligations	578,210	449,723
Other securities	5,047	2,088
Total Securities Available for Sale	1,332,259	1,071,708
Trading Securities	0	0
Interest Rate Swaps	1,038	1,490
Total	1,333,297	1,073,198
Liabilities [Abstract]
Interest Rate Swaps	1,038	1,490
Total	1,038	1,490
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

Securities (Details) $ in Thousands	9 Months Ended		12 Months Ended
Securities (Details) $ in Thousands	Sep. 30, 2013 USD ($) Position	Sep. 30, 2012 USD ($)	Dec. 31, 2012 USD ($) Position
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 1,392,923		$ 1,120,384
Unrealized gains	16,886		27,794
Unrealized losses	24,075		179
Estimated fair value	1,385,734		1,147,999
Sales transactions of securities available for sale [Abstract]
Proceeds from sales	27,600	$ 1,800
Gross realized gains	1,400	600
Loss on sales	0	$ 0
Amortized costs of securities available for sale pledged to secure public deposits	1,200,000		900,000
Amortized costs of securities available for sale pledged as collateral for repurchase agreements	222,200		209,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	1,342,704		40,397
12 Months or Longer, Fair Value	218		167
Total, Fair Value	1,342,922		40,564
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(24,045)		(97)
12 Months or Longer, Unrealized Losses	(30)		(82)
Total, Unrealized Losses	$ (24,075)		$ (179)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions \| Position	332		7
12 Months or Longer, Number of Positions \| Position	1		1
Total, Number of Positions \| Position	333		8
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	$ 118,259		$ 60,563
Unrealized gains	612		972
Unrealized losses	3,251		0
Estimated fair value	115,620		61,535
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	63,048
12 Months or Longer, Fair Value	0
Total, Fair Value	63,048
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(3,251)
12 Months or Longer, Unrealized Losses	0
Total, Unrealized Losses	$ (3,251)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions \| Position	5
12 Months or Longer, Number of Positions \| Position	0
Total, Number of Positions \| Position	5
Consolidated stockholders' equity threshold percentage that no single issuer of securities exceeded except for U.S. Government securities. (in hundredths)	10.00%
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Within one year	$ 26,527
From one to five years	272,953
From five to ten years	295,191
After ten years	785,885
Total, Amortized Cost	1,380,556
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Within one year	26,704
From one to five years	274,104
From five to ten years	293,558
After ten years	776,650
Total, Fair Value	1,371,016
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Within one year	25,305
From one to five years	22,364
From five to ten years	5,054
After ten years	65,536
Securities held to maturity	118,259		60,563
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Within one year	25,412
From one to five years	22,744
From five to ten years	5,059
After ten years	62,405
Total, Fair Value	115,620		61,535
State & Municipal [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	54,228		59,395
Unrealized gains	490		788
Unrealized losses	0		0
Estimated fair value	54,718		60,183
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Securities held to maturity	54,228		59,395
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	54,718		60,183
Mortgage backed [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	983		1,168
Unrealized gains	122		184
Unrealized losses	0		0
Estimated fair value	1,105		1,352
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Securities held to maturity	983		1,168
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	1,105		1,352
US Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	43,359		63,668
Unrealized gains	445		757
Unrealized losses	0		0
Estimated fair value	43,804		64,425
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value			0
12 Months or Longer, Fair Value			0
Total, Fair Value			0
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses			0
12 Months or Longer, Unrealized Losses			0
Total, Unrealized Losses			$ 0
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions \| Position			0
12 Months or Longer, Number of Positions \| Position			0
Total, Number of Positions \| Position			0
Federal Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	300,964		$ 281,398
Unrealized gains	369		1,507
Unrealized losses	6,139		91
Estimated fair value	295,194		282,814
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	300,964		39,906
12 Months or Longer, Fair Value	0		0
Total, Fair Value	300,964		39,906
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(6,139)		(91)
12 Months or Longer, Unrealized Losses	0		0
Total, Unrealized Losses	$ (6,139)		$ (91)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions \| Position	20		4
12 Months or Longer, Number of Positions \| Position	0		0
Total, Number of Positions \| Position	20		4
Mortgage backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	$ 327,504		$ 0
12 Months or Longer, Fair Value	0		0
Total, Fair Value	327,504		0
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(1,046)		0
12 Months or Longer, Unrealized Losses	0		0
Total, Unrealized Losses	$ (1,046)		$ 0
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions \| Position	81		0
12 Months or Longer, Number of Positions \| Position	0		0
Total, Number of Positions \| Position	81		0
Mortgage backed [Member] \| Government-sponsored enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 303,907		$ 221,110
Unrealized gains	7,652		11,175
Unrealized losses	960		0
Estimated fair value	310,599		232,285
Mortgage backed [Member] \| U.S. government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	23,613		16,351
Unrealized gains	1,080		1,645
Unrealized losses	86		0
Estimated fair value	24,607		17,996
State & Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	117,936		82,675
Unrealized gains	2,083		4,127
Unrealized losses	1,417		0
Estimated fair value	118,602		86,802
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	117,936		0
12 Months or Longer, Fair Value	0		0
Total, Fair Value	117,936		0
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(1,417)		0
12 Months or Longer, Unrealized Losses	0		0
Total, Unrealized Losses	$ (1,417)		$ 0
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions \| Position	189		0
12 Months or Longer, Number of Positions \| Position	0		0
Total, Number of Positions \| Position	189		0
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	$ 590,777		$ 23
12 Months or Longer, Fair Value	0		0
Total, Fair Value	590,777		23
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(15,273)		0
12 Months or Longer, Unrealized Losses	0		0
Total, Unrealized Losses	$ (15,273)		$ 0
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions \| Position	40		2
12 Months or Longer, Number of Positions \| Position	0		0
Total, Number of Positions \| Position	40		2
Collateralized Mortgage Obligations [Member] \| Government-sponsored enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 543,447		$ 399,147
Unrealized gains	1,792		4,418
Unrealized losses	15,211		0
Estimated fair value	530,028		403,565
Collateralized Mortgage Obligations [Member] \| U.S. government securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	47,330		44,825
Unrealized gains	914		1,333
Unrealized losses	62		0
Estimated fair value	48,182		46,158
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	12,367		11,210
Unrealized gains	2,551		2,832
Unrealized losses	200		88
Estimated fair value	14,718		13,954
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	5,523		468
12 Months or Longer, Fair Value	218		167
Total, Fair Value	5,741		635
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(170)		(6)
12 Months or Longer, Unrealized Losses	(30)		(82)
Total, Unrealized Losses	$ (200)		$ (88)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions \| Position	2		1
12 Months or Longer, Number of Positions \| Position	1		1
Total, Number of Positions \| Position	3		2
Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	$ 63,048
Unrealized gains	0
Unrealized losses	3,251
Estimated fair value	59,797
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	63,048
12 Months or Longer, Fair Value	0
Total, Fair Value	63,048
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(3,251)
12 Months or Longer, Unrealized Losses	0
Total, Unrealized Losses	$ (3,251)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions \| Position	5
12 Months or Longer, Number of Positions \| Position	0
Total, Number of Positions \| Position	5
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Securities held to maturity	$ 63,048
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	$ 59,797

Reclassification Adjustments Out of Other Comprehensive (Loss) Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain (Loss) on Sale of Securities, Net	$ 329	$ 26	$ 1,413	$ 578
Salaries and employee benefits	29,267	26,641	85,474	78,358
Income tax expense	8,632	5,513	19,413	17,049
Net Income	19,257	14,535	43,822	41,442
Total reclassification during the period, net of tax	229	583	506	1,279
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]
Gain (Loss) on Sale of Securities, Net	(329)	(26)	(1,413)	(578)
Income tax expense	132	10	565	231
Net Income	(197)	(16)	(848)	(347)
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	283	390	890	1,076
Net Income	426	599	1,354	1,626
Accumulated Defined Benefit Plans Adjustment [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Amortization of net gains [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	765	1,044	2,411	2,869
Accumulated Defined Benefit Plans Adjustment [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Amortization of prior service costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	$ (56)	$ (55)	$ (167)	$ (167)