NBT Bancorp (NBTB) 10-Q 12 Nov 13 2013 Q3 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	9 Months Ended
	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	30-Sep-13	'

Consolidated_Balance_Sheets_Un

Consolidated Balance Sheets (Unaudited) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
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_Un1

Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	Sep. 30, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
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_Inc

Consolidated Statements of Income (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Per Share data, unless otherwise specified	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_Com

Consolidated Statements of Comprehensive Income (Unaudited) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	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_Com1

Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	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_Sto

Consolidated Statements of Stockholders' Equity (Unaudited) (USD $)	Common Stock [Member]	Additional Paid-in-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Common Stock in Treasury [Member]	Total
In Thousands
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

Consolidated_Statements_of_Sto1

Consolidated Statements of Stockholders' Equity (Unaudited) (Parenthetical) (USD $)	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_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	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

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

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.

Acquisition

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.

Commitments_and_Contingencies

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_

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)		30-Sep-13			31-Dec-12
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:
		30-Sep-13									31-Dec-12
		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
		30-Sep-13						30-Sep-12
		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
		30-Sep-13						30-Sep-12
		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

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

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

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		Interest Rate	Trust		Final
			Preferred			Preferred		Maturity
			Securities			Debt		Date
			Outstanding			Owed To
						Trust
	CNBF Capital Trust I	Aug-99	$	18,000	3-month LIBOR plus 2.75%	$	18,720	29-Aug
	NBT Statutory Trust I	5-Nov		5,000	3-month LIBOR plus 1.40%		5,155	Dec-35
	NBT Statutory Trust II	6-Feb		50,000	3-month LIBOR plus 1.40%		51,547	Mar-36
	Alliance Financial Capital Trust I	3-Dec		10,000	3-month LIBOR plus 2.85%		10,310	Jan-34
	Alliance Financial Capital Trust II	6-Sep		15,000	3-month LIBOR plus 1.65%		15,464	Sep-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_F

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)		30-Sep-13
	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)		31-Dec-12
	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.
					30-Sep-13				31-Dec-13
	(In thousands)		Fair		Carrying		Estimated		Carrying		Estimated
			Value		amount		fair value		amount		fair value
			Hierarchy
	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.

Securities

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
	30-Sep-13
	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
	31-Dec-12
	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
	30-Sep-13
	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
	31-Dec-12
	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			Number		Fair		Unrealized			Number		Fair Value		Unrealized			Number
					losses			of		Value		losses			of				losses			of
								Positions							Positions							Positions
	30-Sep-13
	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
	30-Sep-13
	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			Number		Fair		Unrealized			Number		Fair Value		Unrealized			Number
					losses			of		Value		losses			of				losses			of
								Positions							Positions							Positions
31-Dec-12
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		Estimated fair
		cost		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.

Reclassification_Adjustments_O

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
			30-Sep-13			30-Sep-12
	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
			30-Sep-13			30-Sep-12
	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_Polici

Description of Business (Policies)	9 Months Ended
	Sep. 30, 2013
Description of Business [Abstract]	'
Nature of Operations [Policy Text Block]	'
	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.

Allowance_for_Loan_Losses_and_1

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
	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.
	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.
	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.
	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.
Credit Quality Indicators [Policy Text Block]	'
	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.
Loans and Leases Receivable, Troubled Debt Restructuring Policy [Policy Text Block]	'
	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.

Defined_Benefit_Postretirement1

Defined Benefit Postretirement Plans (Policies)	9 Months Ended
	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_F1

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

Securities (Policies)	9 Months Ended
	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.

Acquisition_Tables

Acquisition (Tables)	9 Months Ended
	Sep. 30, 2013
Acquisition [Abstract]	'
Consideration paid, assets acquired, and liabilities assumed	'
	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
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	'
	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

Allowance_for_Loan_Losses_and_2

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)	30-Sep-13			31-Dec-12
	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:
		30-Sep-13									31-Dec-12
		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
		30-Sep-13						30-Sep-12
		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
		30-Sep-13						30-Sep-12
		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

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_Postretirement2

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_Table

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		Interest Rate	Trust		Final
			Preferred			Preferred		Maturity
			Securities			Debt		Date
			Outstanding			Owed To
						Trust
	CNBF Capital Trust I	Aug-99	$	18,000	3-month LIBOR plus 2.75%	$	18,720	29-Aug
	NBT Statutory Trust I	5-Nov		5,000	3-month LIBOR plus 1.40%		5,155	Dec-35
	NBT Statutory Trust II	6-Feb		50,000	3-month LIBOR plus 1.40%		51,547	Mar-36
	Alliance Financial Capital Trust I	3-Dec		10,000	3-month LIBOR plus 2.85%		10,310	Jan-34
	Alliance Financial Capital Trust II	6-Sep		15,000	3-month LIBOR plus 1.65%		15,464	Sep-36

Fair_Values_Measurements_and_F2

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	'
	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)		30-Sep-13
	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)		31-Dec-12
	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	'
	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.
				30-Sep-13				31-Dec-13
	(In thousands)	Fair		Carrying		Estimated		Carrying		Estimated
		Value		amount		fair value		amount		fair value
		Hierarchy
	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

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
	30-Sep-13
	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
	31-Dec-12
	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
	30-Sep-13
	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
	31-Dec-12
	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			Number		Fair		Unrealized			Number		Fair Value		Unrealized			Number
				losses			of		Value		losses			of				losses			of
							Positions							Positions							Positions
	30-Sep-13
	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
	30-Sep-13
	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			Number		Fair		Unrealized			Number		Fair Value		Unrealized			Number
				losses			of		Value		losses			of				losses			of
							Positions							Positions							Positions
	31-Dec-12
	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		Estimated fair
		cost		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

Reclassification_Adjustments_O1

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
		30-Sep-13			30-Sep-12
	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
		30-Sep-13			30-Sep-12
	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

Acquisition (Details) (USD $)	3 Months Ended		9 Months Ended			0 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Mar. 08, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2013
						Alliance Financial Corporation [Member]	Alliance Financial Corporation [Member]	Alliance Financial Corporation [Member]	Hampshire First Bank [Member]	Acquisition of Financial Services Company [Member]
						Branch
Business Acquisition [Line Items]	'	'	'	'	'	'	'	'	'	'
Date of acquisition	'	'	'	'	'	'	8-Mar-13	'	'	'
Number of banking centers operated by acquiree	'	'	'	'	'	26	'	'	'	'
Business acquisition shares converted right to receive entity's common stock (in shares)	'	'	'	'	'	2.1779	'	'	'	'
Number of shares of common stock issued to acquiree shareholders (in shares)	'	'	'	'	'	'	10,300,000	'	'	'
Direct costs related acquisition	$326,000	$558,000	$12,276,000	$1,895,000	'	'	$12,300,000	'	'	'
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	'	'	'	'	'	225,551,000	'	'	'	'
Cash in lieu of fractional shares paid to Alliance common shareholders	'	'	'	'	'	11,000	'	'	'	'
Less treasury shares	'	'	'	'	'	5,779,000	'	'	'	'
Net consideration paid	'	'	'	'	'	219,783,000	'	'	'	'
Recognized Amounts of Identifiable Assets Acquired and (Liabilities Assumed), At Fair Value [Abstract]	'	'	'	'	'	'	'	'	'	'
Cash and short term investments	'	'	'	'	'	81,060,000	'	'	'	'
Securities	'	'	'	'	'	320,618,000	'	'	'	'
Loans	'	'	'	'	'	904,473,000	'	'	'	'
Intangible assets	'	'	'	'	'	13,161,000	'	'	'	'
Other assets	'	'	'	'	'	71,589,000	'	'	'	'
Deposits	'	'	'	'	'	-1,113,420,000	'	'	'	'
Borrowings	'	'	'	'	'	-126,530,000	'	'	'	'
Trust Preferred debentures	'	'	'	'	'	-25,774,000	'	'	'	'
Other liabilities	'	'	'	'	'	-18,908,000	'	'	'	'
Total identifiable net assets	'	'	'	'	'	106,269,000	'	'	'	'
Goodwill	265,052,000	'	265,052,000	'	152,373,000	113,514,000	'	'	'	'
Information about acquired loan portfolio [Abstract]	'	'	'	'	'	'	'	'	'	'
Contractually required principal and interest at acquisition	'	'	'	'	'	908,614,000	'	'	'	'
Contractual cash flows not expected to be collected	'	'	'	'	'	-15,466,000	'	'	'	'
Expected cash flows at acquisition	'	'	'	'	'	893,148,000	'	'	'	'
Interest component of expected cash flows (accretable premium)	'	'	'	'	'	11,325,000	'	'	'	'
Fair value of acquired loans	'	'	'	'	'	904,473,000	'	'	'	'
Changes in accretable discount [Abstract]	'	'	'	'	'	'	'	'	'	'
Balance at January 1, 2013	'	'	'	'	'	'	0	'	'	'
Alliance acquisition	'	'	'	'	'	'	11,325,000	'	'	'
Accretion recognized to date	'	'	'	'	'	'	-1,950,000	'	'	'
Balance at September 30, 2013	'	'	'	'	'	'	9,375,000	'	'	'
Net Income (Loss) [Abstract]	'	'	'	'	'	'	'	'	'	'
Net interest income	'	'	'	'	'	'	182,610,000	182,081,000	'	'
Noninterest income	'	'	'	'	'	'	82,592,000	78,950,000	'	'
Net income	'	'	'	'	'	'	52,933,000	48,609,000	'	'
Other goodwill adjustments [Abstract]	'	'	'	'	'	'	'	'	'	'
Goodwill, purchase accounting adjustments	'	'	'	'	'	'	'	'	($1,000,000)	$100,000

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)	9 Months Ended
In Millions, unless otherwise specified	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	$841.70
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	$41.50	$16.60

Allowance_for_Loan_Losses_and_3

Allowance for Loan Losses and Credit Quality of Loans, Allowance for Loan Losses (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
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	70,184,000	70,734,000	70,184,000	70,734,000	'
Allowance for loans individually evaluated for impairment	1,100,000	'	1,100,000	'	2,848,000
Allowance for loans collectively evaluated for impairment	69,084,000	'	69,084,000	'	66,486,000
Ending balance of loans	5,367,231,000	'	5,367,231,000	'	4,277,616,000
Ending balance of loans individually evaluated for impairment	15,323,000	'	15,323,000	'	11,972,000
Ending balance of acquired loans	1,001,766,000	'	1,001,766,000	'	'
Ending balance of loans collectively evaluated for impairment	4,350,142,000	'	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	35,797,000	37,817,000	35,797,000	37,817,000	'
Allowance for loans individually evaluated for impairment	1,100,000	'	1,100,000	'	2,848,000
Allowance for loans collectively evaluated for impairment	34,697,000	'	34,697,000	'	32,776,000
Ending balance of loans	2,378,848,000	'	2,378,848,000	'	2,003,371,000
Ending balance of loans individually evaluated for impairment	15,323,000	'	15,323,000	'	11,972,000
Ending balance of acquired loans	432,806,000	'	432,806,000	'	'
Ending balance of loans collectively evaluated for impairment	1,930,719,000	'	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	'	'	3	'	'
Real estate loan amount, percentage of appraised value or purchase price of the property, maximum (in hundredths)	80.00%	'	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%	'	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	27,187,000	26,576,000	27,187,000	26,576,000	'
Allowance for loans individually evaluated for impairment	0	'	0	'	0
Allowance for loans collectively evaluated for impairment	27,187,000	'	27,187,000	'	27,162,000
Ending balance of loans	1,960,225,000	'	1,960,225,000	'	1,623,138,000
Ending balance of loans individually evaluated for impairment	0	'	0	'	0
Ending balance of acquired loans	243,469,000	'	243,469,000	'	'
Ending balance of loans collectively evaluated for impairment	1,716,756,000	'	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	'	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%	'	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%	'	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	6,910,000	6,281,000	6,910,000	6,281,000	'
Allowance for loans individually evaluated for impairment	0	'	0	'	0
Allowance for loans collectively evaluated for impairment	6,910,000	'	6,910,000	'	6,252,000
Ending balance of loans	1,028,158,000	'	1,028,158,000	'	651,107,000
Ending balance of loans individually evaluated for impairment	0	'	0	'	0
Ending balance of acquired loans	325,491,000	'	325,491,000	'	'
Ending balance of loans collectively evaluated for impairment	702,667,000	'	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	290,000	60,000	290,000	60,000	'
Allowance for loans collectively evaluated for impairment	$290,000	'	$290,000	'	$296,000

Allowance_for_Loan_Losses_and_4

Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	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_5

Allowance for Loan Losses and Credit Quality of Loans, Impaired Loans (Details) (USD $)

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Consumer Loans [Member]

Consumer Loans [Member]

Consumer Loans [Member]

Consumer Loans [Member]

Residential Real Estate Mortgages [Member]

Residential Real Estate Mortgages [Member]

Residential Real Estate Mortgages [Member]

Residential Real Estate Mortgages [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With No Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

With An Allowance Recorded [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Home Equity [Member]

Home Equity [Member]

Home Equity [Member]

Home Equity [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Consumer Loans [Member]

Consumer Loans [Member]

Residential Real Estate Mortgages [Member]

Residential Real Estate Mortgages [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial Loans [Member]

Commercial [Member]

Commercial [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Business Banking [Member]

Business Banking [Member]

Total Commercial Loans [Member]

Total Commercial Loans [Member]

Home Equity [Member]

Home Equity [Member]

Commercial [Member]

Commercial [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Minimum balance for classified loans to be evaluated individually for impairment

$500,000

'

$500,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Financing Receivable, Impaired [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Recorded Investment Balance (Book)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25,631,000

24,625,000

5,507,000

1,651,000

5,427,000

8,709,000

1,097,000

940,000

1,529,000

1,713,000

6,533,000

7,048,000

20,093,000

20,061,000

3,304,000

2,553,000

2,234,000

2,011,000

31,847,000

33,028,000

6,216,000

8,403,000

0

4,335,000

6,216,000

4,068,000

0

0

0

0

Unpaid Principal Balance (Legal)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

29,425,000

29,119,000

5,549,000

1,710,000

5,431,000

9,553,000

1,460,000

1,286,000

1,936,000

2,026,000

8,927,000

9,579,000

23,303,000

24,154,000

3,496,000

2,657,000

2,626,000

2,308,000

37,263,000

39,148,000

7,838,000

10,029,000

0

4,340,000

7,838,000

5,689,000

0

0

0

0

Related Allowance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,100,000

2,848,000

1,100,000

2,848,000

0

2,241,000

1,100,000

607,000

0

0

0

0

Average Recorded Investment

28,233,000

22,475,000

29,540,000

23,018,000

3,348,000

1,128,000

4,069,000

1,551,000

10,751,000

7,140,000

10,660,000

6,481,000

1,526,000

2,876,000

1,100,000

2,997,000

897,000

1,876,000

1,287,000

1,926,000

6,581,000

6,572,000

7,538,000

7,151,000

3,064,000

1,828,000

2,871,000

1,869,000

2,066,000

1,055,000

2,015,000

1,043,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest Income Recognized

$63,000

$54,000

$238,000

$227,000

$15,000

$32,000

$45,000

$101,000

$0

$0

$51,000

$0

$0

$4,000

$1,000

$40,000

$12,000

$12,000

$36,000

$65,000

$13,000

$0

$43,000

$0

$8,000

$5,000

$20,000

$17,000

$15,000

$1,000

$42,000

$4,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Allowance_for_Loan_Losses_and_6

Allowance for Loan Losses and Credit Quality of Loans, Credit Quality by Loan Class (Details) (USD $)

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

Dec. 31, 2012

Sep. 30, 2013

Sep. 30, 2013

In Thousands, unless otherwise specified

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Commercial Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Consumer Credit Exposure [Member]

Residential Mortgage Credit Exposure [Member]

Residential Mortgage Credit Exposure [Member]

Residential Mortgage Credit Exposure [Member]

Residential Mortgage Credit Exposure [Member]

Residential Mortgage Credit Exposure [Member]

Residential Mortgage Credit Exposure [Member]

Residential Mortgage Credit Exposure [Member]

Residential Mortgage Credit Exposure [Member]

Residential Mortgage Credit Exposure [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Pass [Member]

Pass [Member]

Pass [Member]

Special Mention [Member]

Special Mention [Member]

Special Mention [Member]

Substandard [Member]

Substandard [Member]

Substandard [Member]

Doubtful [Member]

Doubtful [Member]

Doubtful [Member]

Non-classified [Member]

Non-classified [Member]

Classified [Member]

Classified [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Agricultural Real Estate [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Total Small Business Receivable [Member]

Total Small Business Receivable [Member]

Total Small Business Receivable [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Performing [Member]

Performing [Member]

Performing [Member]

Nonperforming [Member]

Nonperforming [Member]

Nonperforming [Member]

Indirect [Member]

Indirect [Member]

Indirect [Member]

Indirect [Member]

Indirect [Member]

Indirect [Member]

Indirect [Member]

Indirect [Member]

Indirect [Member]

Home Equity Member]

Home Equity Member]

Home Equity Member]

Home Equity Member]

Home Equity Member]

Home Equity Member]

Home Equity Member]

Home Equity Member]

Home Equity Member]

Direct [Member]

Direct [Member]

Direct [Member]

Direct [Member]

Direct [Member]

Direct [Member]

Direct [Member]

Direct [Member]

Direct [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Performing [Member]

Performing [Member]

Performing [Member]

Nonperforming [Member]

Nonperforming [Member]

Nonperforming [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ACQUIRED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Pass [Member]

Pass [Member]

Pass [Member]

Special Mention [Member]

Special Mention [Member]

Special Mention [Member]

Substandard [Member]

Substandard [Member]

Substandard [Member]

Doubtful [Member]

Doubtful [Member]

Doubtful [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Pass [Member]

Pass [Member]

Pass [Member]

Special Mention [Member]

Special Mention [Member]

Special Mention [Member]

Substandard [Member]

Substandard [Member]

Substandard [Member]

Doubtful [Member]

Doubtful [Member]

Doubtful [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Pass [Member]

Pass [Member]

Pass [Member]

Special Mention [Member]

Special Mention [Member]

Special Mention [Member]

Substandard [Member]

Substandard [Member]

Substandard [Member]

Doubtful [Member]

Doubtful [Member]

Doubtful [Member]

ORIGINATED [Member]

Pass [Member]

Pass [Member]

Special Mention [Member]

Special Mention [Member]

Substandard [Member]

Substandard [Member]

Doubtful [Member]

Doubtful [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Non-classified [Member]

Non-classified [Member]

Non-classified [Member]

Classified [Member]

Classified [Member]

Classified [Member]

ORIGINATED [Member]

Non-classified [Member]

Classified [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Performing [Member]

Performing [Member]

Performing [Member]

Nonperforming [Member]

Nonperforming [Member]

Nonperforming [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Performing [Member]

Performing [Member]

Performing [Member]

Nonperforming [Member]

Nonperforming [Member]

Nonperforming [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Performing [Member]

Performing [Member]

Performing [Member]

Nonperforming [Member]

Nonperforming [Member]

Nonperforming [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ORIGINATED [Member]

ORIGINATED [Member]

ORIGINATED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ORIGINATED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

ACQUIRED [Member]

ORIGINATED [Member]

Financing Receivable, Recorded Investment [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Financing Receivable

$1,637,411

$359,168

$1,613,509

$1,515,732

$319,905

$1,568,517

$50,552

$6,364

$10,580

$68,347

$32,899

$34,400

$2,780

$0

$12

$342,528

$68,917

$23,432

$4,721

$561,481

$114,374

$594,524

$522,985

$98,128

$574,229

$18,401

$1,602

$10,098

$17,351

$14,644

$10,197

$2,744

$0

$0

$974,795

$244,794

$919,254

$901,928

$221,777

$903,073

$32,135

$4,762

$50

$40,732

$18,255

$16,131

$0

$0

$0

$63,758

$0

$64,792

$57,347

$0

$59,797

$13

$0

$389

$6,362

$0

$4,594

$36

$0

$12

$37,377

$34,939

$33,472

$31,418

$3

$43

$3,902

$3,478

$0

$0

$365,960

$73,638

$332,533

$342,528

$68,917

$313,250

$23,432

$4,721

$19,283

$332,533

$313,250

$19,283

$1,623,138

$243,469

$1,716,756

$1,612,098

$242,599

$1,707,155

$11,040

$870

$9,601

$980,997

$144,520

$1,113,816

$978,235

$144,230

$1,111,147

$2,762

$290

$2,669

$575,282

$90,700

$542,322

$567,354

$90,193

$535,589

$7,928

$507

$6,733

$66,859

$8,249

$60,618

$66,509

$8,176

$60,419

$350

$73

$199

$651,107

$325,491

$702,667

$641,608

$321,631

$695,007

$9,499

$3,860

$7,660

Allowance_for_Loan_Losses_and_7

Allowance for Loan Losses and Credit Quality of Loans, Troubled Debt Restructurings (Details) (USD $)

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

3 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2012

Sep. 30, 2013

Sep. 30, 2012

Sep. 30, 2012

Sep. 30, 2012

Commercial Real Estate [Member]

Home Equity [Member]

Commercial Loans [Member]

Residential Real Estate Mortgages [Member]

Residential Real Estate Mortgages [Member]

Residential Real Estate Mortgages [Member]

Subsequent Default [Member]

Subsequent Default [Member]

Subsequent Default [Member]

Commercial [Member]

Commercial Real Estate [Member]

Commercial Real Estate [Member]

Home Equity [Member]

Home Equity [Member]

Home Equity [Member]

Home Equity [Member]

Commercial Loans [Member]

Residential Real Estate Mortgages [Member]

Residential Real Estate Mortgages [Member]

Residential Real Estate Mortgages [Member]

Residential Real Estate Mortgages [Member]

Contract

Contract

Contract

Contract

Home Equity [Member]

Home Equity [Member]

Home Equity [Member]

Contract

Contract

Contract

Contract

Subsequent Default [Member]

Subsequent Default [Member]

Subsequent Default [Member]

Contract

Subsequent Default [Member]

Subsequent Default [Member]

Home Equity [Member]

Contract

Contract

Contract

Contract

Contract

Home Equity [Member]

Subsequent Default [Member]

Contract

Financing Receivable, Modifications [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Period of sustained repayment performance for nonperforming TDRs to be returned to performing status

'6 months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of contracts

'

'

20

'

5

6

1

0

'

'

1

3

4

9

1

7

1

0

'

0

'

3

Pre-modification outstanding recorded investment

'

$7,000,000

$1,000,000

$1,000,000

'

$500,000

$200,000

$0

$500,000

$25,000

'

$6,100,000

'

$400,000

$100,000

'

'

$0

$300,000

$0

$400,000

'

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	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_Postretirement3

Defined Benefit Postretirement Plans (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	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_Detai

Junior Subordinated Debt (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2013
Limited Guarantee Trust Preferred Debentures [Abstract]	'
Number of statutory business trusts included in the Trusts	5
CNBF Capital Trust I VIE Entity Not Primary Beneficiary [Member] | CNBF Capital Trust I [Member]	'
Limited Guarantee Trust Preferred Debentures [Abstract]	'
Issuance Date	1-Aug-99
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	1-Aug-29
NBT Statutory Trust I VIE Entity Not Primary Beneficiary [Member] | NBT Statutory Trust I [Member]	'
Limited Guarantee Trust Preferred Debentures [Abstract]	'
Issuance Date	1-Nov-05
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	1-Dec-35
NBT Statutory Trust II VIE Entity Not Primary Beneficiary [Member] | NBT Statutory Trust II [Member]	'
Limited Guarantee Trust Preferred Debentures [Abstract]	'
Issuance Date	1-Feb-06
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	1-Mar-36
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	1-Dec-03
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	1-Jan-34
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	1-Sep-06
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	1-Sep-36

Fair_Values_Measurements_and_F3

Fair Values Measurements and Fair Value of Financial Instruments (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Securities Available for Sale [Abstract]	'	'
Total Securities Available for Sale	$1,385,734,000	$1,147,999,000
Trading Securities	5,285,000	3,918,000
Liabilities [Abstract]	'	'
Collateral dependent impaired financing receivable with specific reserves	6,200,000	8,400,000
Allowance for loan and lease losses collateral dependent impaired loans with specific reserves	1,100,000	2,800,000
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	115,620,000	61,535,000
Financial liabilities [Abstract]	'	'
Time deposits	1,063,730,000	983,261,000
Long-term debt	309,009,000	367,492,000
Trust preferred debentures	101,196,000	75,422,000
Significant Other Observable Inputs (Level 2) [Member] | Carrying Amount [Member]	'	'
Financial assets [Abstract]	'	'
Securities held to maturity	118,259,000	60,563,000
Financial liabilities [Abstract]	'	'
Time deposits	1,063,730,000	983,261,000
Long-term debt	309,009,000	367,492,000
Trust preferred debentures	101,196,000	75,422,000
Significant Other Observable Inputs (Level 2) [Member] | Estimated Fair Value [Member]	'	'
Financial assets [Abstract]	'	'
Securities held to maturity	115,620,000	61,535,000
Financial liabilities [Abstract]	'	'
Time deposits	1,068,888,000	994,376,000
Long-term debt	336,128,000	407,404,000
Trust preferred debentures	103,364,000	74,147,000
Significant Unobservable Inputs (Level 3) [Member] | Carrying Amount [Member]	'	'
Financial assets [Abstract]	'	'
Net Loans	5,297,047,000	4,208,282,000
Significant Unobservable Inputs (Level 3) [Member] | Estimated Fair Value [Member]	'	'
Financial assets [Abstract]	'	'
Net Loans	5,358,132,000	4,313,244,000
Recurring Basis [Member]	'	'
Securities Available for Sale [Abstract]	'	'
U.S. Treasury	43,804,000	64,425,000
Federal Agency	295,194,000	282,814,000
State & municipal	118,602,000	86,802,000
Mortgage-backed	335,206,000	250,281,000
Collateralized mortgage obligations	578,210,000	449,723,000
Other securities	14,718,000	13,954,000
Total Securities Available for Sale	1,385,734,000	1,147,999,000
Trading Securities	5,285,000	3,918,000
Interest Rate Swaps	1,038,000	1,490,000
Total	1,392,057,000	1,153,407,000
Liabilities [Abstract]	'	'
Interest Rate Swaps	1,038,000	1,490,000
Total	1,038,000	1,490,000
Recurring Basis [Member] | Quoted Prices in Active Market for Identical Assets (Level I) [Member]	'	'
Securities Available for Sale [Abstract]	'	'
U.S. Treasury	43,804,000	64,425,000
Federal Agency	0	0
State & municipal	0	0
Mortgage-backed	0	0
Collateralized mortgage obligations	0	0
Other securities	9,671,000	11,866,000
Total Securities Available for Sale	53,475,000	76,291,000
Trading Securities	5,285,000	3,918,000
Interest Rate Swaps	0	0
Total	58,760,000	80,209,000
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	295,194,000	282,814,000
State & municipal	118,602,000	86,802,000
Mortgage-backed	335,206,000	250,281,000
Collateralized mortgage obligations	578,210,000	449,723,000
Other securities	5,047,000	2,088,000
Total Securities Available for Sale	1,332,259,000	1,071,708,000
Trading Securities	0	0
Interest Rate Swaps	1,038,000	1,490,000
Total	1,333,297,000	1,073,198,000
Liabilities [Abstract]	'	'
Interest Rate Swaps	1,038,000	1,490,000
Total	1,038,000	1,490,000
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

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

Reclassification_Adjustments_O2

Reclassification Adjustments Out of Other Comprehensive (Loss) Income (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	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)