NBT Bancorp (NBTB) 10-K 3 Mar 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Feb. 14, 2014	Jun. 30, 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 Public Float	'	'	$887,440,734
Entity Common Stock, Shares Outstanding	'	43,867,910	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Document Type	'10-K	'	'
Amendment Flag	'false	'	'
Document Period End Date	31-Dec-13	'	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Assets	'	'
Cash and due from banks	$157,625	$157,094
Short-term interest bearing accounts	1,301	6,574
Securities available for sale, at fair value	1,364,881	1,147,999
Securities held to maturity (fair value $113,276 and $61,535)	117,283	60,563
Trading securities	5,779	3,918
Federal Reserve and Federal Home Loan Bank stock	46,864	29,920
Loans	5,406,795	4,277,616
Less allowance for loan losses	69,434	69,334
Net loans	5,337,361	4,208,282
Premises and equipment, net	88,327	77,875
Goodwill	264,997	152,373
Intangible assets, net	25,557	16,962
Bank owned life insurance	114,966	80,702
Other assets	127,234	99,997
Total assets	7,652,175	6,042,259
Liabilities	'	'
Demand (noninterest bearing)	1,645,641	1,242,712
Savings, NOW, and money market	3,223,441	2,558,376
Time	1,021,142	983,261
Total deposits	5,890,224	4,784,349
Short-term borrowings	456,042	162,941
Long-term debt	308,823	367,492
Junior subordinated debt	101,196	75,422
Other liabilities	79,321	69,782
Total liabilities	6,835,606	5,459,986
Stockholders' equity	'	'
Preferred stock, $0.01 par value; authorized 2,500,000 shares at December 31, 2013 and 2012	0	0
Common stock, $0.01 par value. Authorized 100,000,000 shares at December 31, 2013 and December 31, 2012; issued 49,651,494 at December 31, 2013 and 39,305,131 at December 31, 2012	497	393
Additional paid-in-capital	574,152	346,692
Retained earnings	385,787	357,558
Accumulated other comprehensive loss	-16,765	-5,880
Common stock in treasury, at cost, 6,138,444 and 5,529,781 shares at December 31, 2013 and 2012, respectively	-127,102	-116,490
Total stockholders' equity	816,569	582,273
Total liabilities and stockholders' equity	$7,652,175	$6,042,259

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Assets	'	'
Securities held to maturity fair value	$113,276	$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)	6,138,444	5,529,781

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Interest, fee, and dividend income	'	'	'
Interest and fees on loans and leases	$238,672	$208,458	$204,370
Securities available for sale	25,510	27,005	31,083
Securities held to maturity	2,660	2,378	2,886
Other	1,881	1,556	1,658
Total interest, fee, and dividend income	268,723	239,397	239,997
Interest expense	'	'	'
Deposits	16,290	18,848	23,020
Short-term borrowings	515	188	205
Long-term debt	11,755	14,428	14,404
Trust preferred debentures	2,084	1,730	2,092
Total interest expense	30,644	35,194	39,721
Net interest income	238,079	204,203	200,276
Provision for loan and lease losses	22,424	20,269	20,737
Net interest income after provision for loan and lease losses	215,655	183,934	179,539
Noninterest income	'	'	'
Insurance and other financial services revenue	24,447	22,387	20,843
Service charges on deposit accounts	19,307	18,225	21,464
ATM and debit card fees	15,558	12,358	11,642
Retirement plan administration fees	11,497	10,097	8,918
Trust	16,682	9,172	8,864
Bank owned life insurance income	3,793	3,077	3,085
Net securities gains	1,426	599	150
Other	10,505	11,412	5,345
Total noninterest income	103,215	87,327	80,311
Noninterest expense	'	'	'
Salaries and employee benefits	113,580	104,815	99,212
Occupancy	20,720	17,415	16,363
Data processing and communications	15,353	13,437	12,271
Professional fees and outside services	13,309	10,463	8,921
Equipment	11,493	9,627	8,864
Office supplies and postage	6,563	6,489	6,073
FDIC expenses	4,960	3,832	4,267
Advertising	3,204	2,889	3,460
Amortization of intangible assets	4,872	3,394	3,046
Loan collection and other real estate owned	2,619	2,560	2,631
Merger expenses	12,364	2,608	804
Other	19,890	16,358	14,764
Total noninterest expense	228,927	193,887	180,676
Income before income tax expense	89,943	77,374	79,174
Income tax expense	28,196	22,816	21,273
Net income	$61,747	$54,558	$57,901
Earnings per share	'	'	'
Basic (in dollars per share)	$1.47	$1.63	$1.72
Diluted (in dollars per share)	$1.46	$1.62	$1.71

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Statements of Comprehensive Income [Abstract]	'	'	'
Net income	$61,747	$54,558	$57,901
Other comprehensive (loss) income, net of tax	'	'	'
Unrealized net holding (losses) gains arising during the year (pre-tax amounts of $(41,059), $(2,471), and $12,757)	-24,794	-1,492	7,703
Reclassification adjustment for net gains related to securities available for sale included in net income (pre-tax amounts of $1,426, $599, and $150)	-861	-362	-90
Amortization of prior service cost and actuarial gains (pre-tax amounts of $2,790, $3,593, and $1,665)	1,601	2,092	999
Decrease (Increase) in prior service cost and unrecognized actuarial loss (pre-tax amounts of $21,923, $(24), and $(15,546))	13,169	-14	-9,381
Total other comprehensive income (loss)	-10,885	224	-769
Comprehensive income	$50,862	$54,782	$57,132

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other comprehensive (loss) income, before tax	'	'	'
Unrealized net holding (losses) gains arising during the period, pre-tax amounts	($41,059)	($2,471)	$12,757
Reclassification adjustment for net gains related to securities available for sale included in net income, pre-tax amounts	1,426	599	150
Amortization of prior service cost and actuarial gains, pre-tax amounts	2,790	3,593	1,665
Decrease (Increase) in prior service costs and unrecognized actuarial loss, pre-tax amounts	$21,923	($24)	($15,546)

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Stockholders' Equity (USD $)	Common Stock [Member]	Additional Paid-in-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Common Stock in Treasury [Member]	Total
In Thousands
Beginning Balance at Dec. 31, 2010	$380	$314,023	$299,797	($5,335)	($75,293)	$533,572
Net income	0	0	57,901	0	0	57,901
Cash dividends	0	0	-27,063	0	0	-27,063
Purchases of treasury shares	0	0	0	0	-30,502	-30,502
Net issuance of shares to employee stock plans, including tax benefit	0	62	-654	0	2,319	1,727
Stock-based compensation	0	3,244	0	0	0	3,244
Other comprehensive income	0	0	0	-769	0	-769
Ending Balance at Dec. 31, 2011	380	317,329	329,981	-6,104	-103,476	538,110
Net income	0	0	54,558	0	0	54,558
Cash dividends	0	0	-26,712	0	0	-26,712
Purchases of treasury shares	0	0	0	0	-15,490	-15,490
Net issuance of shares for acquisition	13	25,811	0	0	0	25,824
Net issuance of shares to employee stock plans, including tax benefit	0	-812	-269	0	2,476	1,395
Stock-based compensation	0	4,364	0	0	0	4,364
Other comprehensive income	0	0	0	224	0	224
Ending Balance at Dec. 31, 2012	393	346,692	357,558	-5,880	-116,490	582,273
Net income	0	0	61,747	0	0	61,747
Cash dividends	0	0	-33,518	0	0	-33,518
Purchases of treasury shares	0	0	0	0	-12,459	-12,459
Net issuance of shares for acquisition	104	225,447	0	0	-5,779	219,772
Net issuance of shares to employee stock plans, including tax benefit	0	-2,292	0	0	7,626	5,334
Stock-based compensation	0	4,305	0	0	0	4,305
Other comprehensive income	0	0	0	-10,885	0	-10,885
Ending Balance at Dec. 31, 2013	$497	$574,152	$385,787	($16,765)	($127,102)	$816,569

Consolidated_Statements_of_Cha1

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Consolidated Statements of Changes in Stockholders' Equity [Abstract]	'	'	'
Cash dividends - per share (in dollars per share)	$0.81	$0.80	$0.80
Purchase of treasury shares (in shares)	584,925	769,568	1,458,639
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 stock plans, including tax benefit (in shares)	385,219	118,616	112,512

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities	'	'	'
Net income	$61,747	$54,558	$57,901
Adjustments to reconcile net income to net cash provided by operating activities	'	'	'
Provision for loan and lease losses	22,424	20,269	20,737
Depreciation and amortization of premises and equipment	7,948	6,276	5,463
Net accretion on securities	5,058	2,408	1,597
Amortization of intangible assets	4,872	3,394	3,046
Stock based compensation	4,305	4,364	3,244
Bank owned life insurance income	-3,793	-3,077	-3,085
Trading security purchases	-1,085	-753	-447
Unrealized (gains) losses in trading securities	-776	-103	193
Deferred income tax benefit	2,344	-10	-9,478
Proceeds from sale of loans held for sale	71,342	65,160	13,545
Originations and purchases of loans held for sale	-66,512	-66,252	-14,167
Net gains on sales of loans held for sale	-1,288	-2,469	-329
Net security gains	-1,426	-599	-151
Net gains on sales of other real estate owned	-1,106	-988	-2,531
Net decrease (increase) in other assets	20,463	6,804	-3,579
Net (decrease) increase in other liabilities	-5,219	-128	11,806
Net cash provided by operating activities	119,298	88,854	83,765
Investing activities	'	'	'
Net cash provided by acquisitions	80,883	52,871	81,467
Securities available for sale:	'	'	'
Proceeds from maturities, calls, and principal paydowns	376,509	573,828	541,555
Proceeds from sales	27,593	1,790	2,437
Purchases	-353,714	-483,858	-648,048
Securities held to maturity:	'	'	'
Proceeds from maturities, calls, and principal paydowns	34,413	31,506	47,186
Purchases	-84,621	-20,193	-20,736
Net increase in loans	-255,318	-277,530	-172,920
Net (increase) decrease in Federal Reserve and FHLB stock	-8,957	-1,886	226
Proceeds from bank owned life insurance	0	0	758
Purchases of premises and equipment, net	-5,766	-6,994	-9,954
Proceeds from sales of other real estate owned	5,224	3,616	2,531
Net cash used in investing activities	-183,754	-126,850	-175,498
Financing activities	'	'	'
Net (decrease) increase in deposits	-7,545	135,095	87,992
Net increase (decrease) in short-term borrowings	271,497	-18,651	22,158
Proceeds from issuance of long-term debt	0	0	156
Repayments of long-term debt	-163,595	-3,354	-2,146
Excess tax benefit from exercise of stock options	-178	8	341
Proceeds from the issuance of shares to employee benefit plans and other stock plans	5,512	1,387	1,386
Purchase of treasury stock	-12,459	-15,490	-30,502
Cash dividends and payment for fractional shares	-33,518	-26,712	-27,063
Net cash provided by financing activities	59,714	72,283	52,322
Net (decrease) increase in cash and cash equivalents	-4,742	34,287	-39,411
Cash and cash equivalents at beginning of year	163,668	129,381	168,792
Cash and cash equivalents at end of year	158,926	163,668	129,381
Cash paid during the period for:	'	'	'
Interest	31,307	35,344	40,135
Income taxes, net of refund	20,848	25,512	31,258
Noncash investing activities:	'	'	'
Loans transferred to other real estate owned	4,746	2,734	2,927
Acquisitions:	'	'	'
Fair value of assets acquired	1,505,490	258,467	67,020
Fair value of liabilities assumed	1,285,718	285,012	148,487
Fair value of debt issued in purchase combination	$0	$502	$2,460

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies [Abstract]	'
Summary of Significant Accounting Policies	'
	(1)  Summary of Significant Accounting Policies
	The accounting and reporting policies of NBT Bancorp Inc. (“NBT Bancorp”) and its subsidiaries, NBT Bank, National Association (“NBT Bank”), NBT Holdings, Inc., and NBT Financial Services, Inc., conform, in all material respects, to U.S. generally accepted accounting principles (“GAAP”) and to general practices within the banking industry. Collectively, NBT Bancorp and its subsidiaries are referred to herein as “the Company.”
	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates.
	Estimates associated with the allowance for loan losses, income taxes, pension expense, fair values of financial instruments, status of contingencies and other-than-temporary impairment on investments and other real estate owned (OREO) are particularly susceptible to material change in the near term.
	The following is a description of significant policies and practices:
	Consolidation
	The accompanying consolidated financial statements include the accounts of NBT Bancorp and its wholly owned subsidiaries mentioned above.  All material intercompany transactions have been eliminated in consolidation. Amounts previously reported in the consolidated financial statements are reclassified whenever necessary to conform to the current year’s presentation. In the “Parent Company Financial Information,” the investment in subsidiaries is recorded using the equity method of accounting.
	The Company determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting interest entity or a variable interest entity under GAAP. Voting interest entities are entities in which the total equity investment at risk is sufficient to enable the entity to finance itself independently and provides the equity holders with the obligation to absorb losses, the right to receive residual returns and the right to make decisions about the entity’s activities. The Company consolidates voting interest entities in which it has all, or at least a majority of, the voting interest. As defined in applicable accounting standards, variable interest entities (“VIEs”) are entities that lack one or more of the characteristics of a voting interest entity. A controlling financial interest in a VIE is present when the Company has both the power and ability to direct the activities of the VIE that most significantly impact the VIE's economic performance and an obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. The Company’s wholly owned subsidiaries CNBF Capital Trust I, NBT Statutory Trust I, NBT Statutory Trust II, Alliance Financial Capital Trust I and Alliance Financial Capital Trust II are VIEs for which the Company is not the primary beneficiary. Accordingly, the accounts of these entities are not included in the Company’s consolidated financial statements.
	Segment Report
	The Company’s operations are primarily in the community banking industry and include the provision of traditional banking services.  The Company also provides other services through its subsidiaries such as insurance, retirement plan administration, and trust administration. The Company operates solely in the geographical regions of central and upstate New York, northeastern Pennsylvania, western Massachusetts, southern New Hampshire and Burlington, Vermont.  The Company has no reportable operating segments.
	Cash Equivalents
	The Company considers amounts due from correspondent banks, cash items in process of collection, and institutional money market mutual funds to be cash equivalents for purposes of the consolidated statements of cash flows.
	Securities
	The Company classifies its securities at date of purchase as either available for sale, held to maturity or trading.  Held to maturity debt securities are those that the Company has the ability and intent to hold until maturity.  Available for sale securities are recorded at fair value. Unrealized holding gains and losses, net of the related tax effect, on available for sale securities are excluded from earnings and are reported in stockholders’ equity and the statement of comprehensive income as a component of accumulated other comprehensive income or loss. Held to maturity securities are recorded at amortized cost. Trading securities are recorded at fair value, with net unrealized gains and losses recognized in income.  Transfers of securities between categories are recorded at fair value at the date of transfer. Declines in the fair value of held-to-maturity and available-for-sale securities below their cost that are deemed to be other than temporary are reflected in earnings as realized losses or in other comprehensive income, depending on whether the Company intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss.  If the Company intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the other-than-temporary impairment shall be recognized in earnings equal to the entire difference between the investment’s amortized cost basis and its fair value at the balance sheet date.  If the Company does not intend to sell the security and it is not more likely than not that the entity will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the other-than-temporary impairment shall be separated into (a) the amount representing the credit loss and (b) the amount related to all other factors.  The amount of the total other-than-temporary impairment related to the credit loss shall be recognized in earnings. The amount of the total other-than-temporary impairment related to other factors shall be recognized in other comprehensive income, net of applicable taxes.
	In estimating other-than-temporary impairment losses, management considers, among other things, (i) the length of time and the extent to which the fair value has been less than cost, (ii) the financial condition and near-term prospects of the issuer, and (iii) the historical and implied volatility of the fair value of the security.
	Non-marketable equity securities are carried at cost.
	Premiums and discounts are amortized or accreted over the life of the related security as an adjustment to yield using the interest method. Dividend and interest income are recognized when earned. Realized gains and losses on securities  sold  are  derived  using  the  specific  identification  method for determining  the  cost  of  securities  sold.
	Investments in Federal Reserve Bank (“FRB”) and Federal Home Loan Bank (“FHLB”) stock are required for membership in those organizations and are carried at cost since there is no market value available.  The FHLB New York continues to pay dividends and repurchase stock.  As such, the Company has not recognized any impairment on its holdings of FHLB stock.
	Loans
	Loans are recorded at their current unpaid principal balance, net of unearned income and unamortized loan fees and expenses, which are amortized under the effective interest method over the estimated lives of the loans. Interest income on loans is accrued based on the principal amount outstanding.
	For all loan classes within the Company’s loan portfolio, loans are placed on nonaccrual status when timely collection of principal and interest in accordance with contractual terms is doubtful. Loans are transferred to nonaccrual status generally when principal or interest payments become ninety days delinquent, unless the loan is well secured and in the process of collection, or sooner when management concludes circumstances indicate that borrowers may be unable to meet contractual principal or interest payments.  When a loan is transferred to a nonaccrual status, all interest previously accrued in the current period but not collected is reversed against interest income in that period. Interest accrued in a prior period and not collected is charged-off against the allowance for loan losses.
	If ultimate repayment of a nonaccrual loan is expected, any payments received are applied in accordance with contractual terms. If ultimate repayment of principal is not expected, any payment received on a nonaccrual loan is applied to principal until ultimate repayment becomes expected.  For all loan classes within the Company’s loan portfolio, nonaccrual loans are returned to accrual status when they become current as to principal and interest and demonstrate a period of performance under the contractual terms and, in the opinion of management, are fully collectible as to principal and interest.  For loans in all portfolios, the principal amount is charged off in full or in part as soon as management determines, based on available facts, that the collection of principal in full is improbable.  For commercial loans, management considers specific facts and circumstances relative to individual credits in making such a determination.  For consumer and residential loan classes, management uses specific guidance and thresholds from the Federal Financial Institutions Examination Council’s Uniform Retail Credit Classification and Account Management Policy.
	Commercial type loans are considered impaired when it is probable that the borrower will not repay the loan according to the original contractual terms of the loan agreement, and all loan types are considered impaired if the loan is restructured in a troubled debt restructuring (“TDR”).  In determining that we will be unable to collect all principal and interest payments due in accordance with the contractual terms of the loan agreements, we consider factors such as payment history and changes in the financial condition of individual borrowers, local economic conditions, historical loss experience and the conditions of the various markets in which the collateral may be liquidated.
	A loan is considered to be a TDR when the Company grants a concession to the borrower because of the borrower’s financial condition that the Company would not otherwise consider. Such concessions include the reduction of interest rates, forgiveness of all or a portion of principal or interest, or other modifications at interest rates that are less than the current market rate for new obligations with similar risk. TDR loans are nonaccrual loans; however, they can be returned to accrual status after a period of performance, generally evidenced by six months of compliance with their modified terms.
	When the Company modifies a loan, management evaluates any possible impairment based on the present value of the expected future cash flows, discounted at the contractual interest rate of the original loan agreement, except when the sole (remaining) source of repayment for the loan is the operation or liquidation of the collateral.  In these cases, management uses the current fair value of the collateral, less selling costs, instead of discounted cash flows.  If management determines that the value of the modified loan is less than the recorded investment in the loan (net of previous charge-offs, deferred loan fees or costs and unamortized premium or discount), impairment is recognized by segment or class of loan as applicable, through an allowance estimate or a charge-off to the allowance.  Segment and class status is determined by the loan’s classification at origination.
	Allowance for Loan Losses
	The allowance for loan losses is the amount which, in the opinion of management, is necessary to absorb probable losses inherent in the loan portfolio. The allowance is determined based upon numerous considerations, including local and regional conditions, the growth and composition of the loan portfolio  with  respect to the mix between the various types of loans and their related risk characteristics, a review of the value of collateral supporting the loans, comprehensive reviews of the loan portfolio by the independent loan review staff and management, as well as consideration of volume and trends of delinquencies, nonperforming loans, and loan charge-offs.  Loan losses are charged off against the allowance, while recoveries of amounts previously charged off are credited to the allowance.  As a result of tests of adequacy, required additions to the allowance for loan losses are made periodically by charges to the provision for loan losses.
	The allowance for loan losses related to impaired loans specifically allocated for impairment is based on discounted cash flows using the loan’s initial effective interest rate or the fair value of the collateral for certain loans where repayment of the loan is expected to be provided solely by the underlying collateral (collateral dependent loans). The Company’s impaired loans are generally collateral dependent. The Company considers the estimated cost to sell, on a discounted basis, when determining the fair value of collateral in the measurement of impairment if those costs are expected to reduce the cash flows available to repay or otherwise satisfy the loans.
	Management believes that the allowance for loan losses is adequate.  While management uses available information to recognize loan losses, future additions to the allowance for loan losses may be necessary based on changes in economic conditions or changes in the values of properties securing loans in the process of foreclosure. In addition, various regulatory agencies, as an integral part of their examination process, periodically review the Company’s allowance for loan losses. Such agencies may require the Company to recognize additions to the allowance for loan losses based on their judgments about information available to them at the time of their examination which may not be currently available to management.
	Premises and Equipment
	Premises and equipment are stated at cost, less accumulated depreciation.  Depreciation of premises and equipment is determined using the straight-line method over the estimated useful lives of the respective assets. Expenditures for maintenance, repairs, and minor replacements are charged to expense as incurred.
	Other Real Estate Owned
	OREO consists of properties acquired through foreclosure or by acceptance of a deed in lieu of foreclosure. These assets are recorded at the lower of fair value of the asset acquired less estimated costs to sell or “cost” (defined as the fair value at initial foreclosure). At the time of foreclosure, or when foreclosure occurs in-substance, the excess, if any, of the loan over the fair market value of the assets received, less estimated selling costs, is charged to the allowance for loan losses and any subsequent valuation write-downs are charged to other expense.  In connection with the determination of the allowance for loan losses and the valuation of other real estate owned, management obtains appraisals for properties.  Operating costs associated with the properties are charged to expense as incurred. Gains on the sale of OREO are included in income when title has passed and the sale has met the minimum down payment requirements prescribed by GAAP.  The balance of OREO at December 31, 2013 and 2012 was approximately $2.9 million and $2.3 million, respectively, and is recorded in Other Assets on the Consolidated Balance Sheet.
	Acquired Loans
	Acquired loans are initially measured at fair value as of the acquisition date without carryover of historical allowance for loan losses.
	For loans that meet the criteria stipulated in ASC 310-30, the Company shall recognize the accretable yield, which is defined as the excess of all cash flows expected at acquisition over the initial fair value of the loan, as interest income on a level-yield basis over the expected remaining life of the loan. The excess of the loan's contractually required payments over the cash flows expected to be collected is the nonaccretable difference. The nonaccretable difference shall not be recognized as an adjustment of yield, a loss accrual, or a valuation allowance. Decreases in the expected cash flows in subsequent periods require the establishment of an allowance for loan losses. Improvements in expected cash flows in future periods result in a reduction of the nonaccretable discount, with such amount reclassified as part of the accretable yield and subsequently recognized in interest income over the remaining lives of the acquired loans on a level-yield basis if the amount and timing of future cash flows is reasonably estimable.
	Acquired loans that met the criteria for nonaccrual of interest prior to the acquisition are considered performing upon acquisition, regardless of whether the customer is contractually delinquent, if the Company can reasonably estimate the timing and amount of the expected cash flows on such loans and if the Company expects to fully collect the new carrying value of the loans. As such, the Company may no longer consider the loan to be nonaccrual or nonperforming and may accrue interest on these loans, including the impact of any accretable yield. As such, charge-offs on acquired loans are first applied to the nonaccretable difference and then to any allowance for loan losses recognized subsequent to acquisition.
	For loans that meet the criteria stipulated in ASC 310-20, the Company shall amortize/accrete into interest income the premium/discount determined at the date of purchase on a level-yield basis over the life of the loan. Subsequent to the acquisition date, the methods utilized to estimate the required allowance for loan losses are similar to originated loans.  Loans accounted for under ASC 310-20 are placed on nonaccrual status when past due in accordance with the Company's nonaccrual policy.
	Subsequent to acquisition the estimate of cash flows expected to be collected on loans accounted for in accordance with ASC 310-20 is periodically re-assessed. These re-assessments involve the use of key assumptions and estimates, similar to those used in the initial estimate of fair value. A decrease in expected cash flows in subsequent periods may indicate that the loan pool is impaired, which would require the establishment of an allowance for loan losses by a charge to the provision for credit losses.
	An acquired loan may be resolved either through receipt of payment (in full or in part) from the borrower, the sale of the loan to a third party, or foreclosure of the collateral. In the event of a sale of the loan, a gain or loss on sale is recognized and reported within noninterest income based on the difference between the sales proceeds and the carrying amount of the loan. In other cases, individual loans are removed from the pool based on comparing the amount received from its resolution (fair value of the underlying collateral less costs to sell in the case of a foreclosure) with its outstanding balance. Any difference between these amounts is recorded as a charge-off through the allowance for loan losses.  Acquired loans subject to modification are not removed from the pool even if those loans would otherwise be deemed troubled debt restructurings as the pool, and not the individual loan, represents the unit of account.
	Goodwill and Other Intangible Assets
	Goodwill and intangible assets that have indefinite useful lives are not amortized, but are tested at least annually for impairment. Intangible assets that have finite useful lives are amortized over their useful lives.  Core deposit intangibles and trust intangibles at the Company are amortized using the sum-of-the-years’-digits method.  Covenants not to compete are amortized on a straight-line basis.  Customer lists are amortized using an accelerated method.
	When facts and circumstances indicate potential impairment of amortizable intangible assets, the Company evaluates the recoverability of the asset carrying value, using estimates of undiscounted future cash flows over the remaining asset life. Any impairment loss is measured by the excess of carrying value over fair value. Goodwill impairment tests are performed on an annual basis or when events or circumstances dictate. In these tests, the fair values of each reporting unit, or segment, is compared to the carrying amount of that reporting unit in order to determine if impairment is indicated. If so, the implied fair value of the reporting unit’s goodwill is compared to its carrying amount and the impairment loss is measured by the excess of the carrying value over fair value.
	Treasury Stock
	Treasury stock acquisitions are recorded at cost. Subsequent sales of treasury stock are recorded on an average cost basis. Gains on the sale of treasury stock are credited to additional paid-in-capital. Losses on the sale of treasury stock are charged to additional paid-in-capital to the extent of previous gains, otherwise charged to retained earnings.
	Income Taxes
	Income taxes are accounted for under the asset and liability method. Deferred income taxes are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases.  Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred taxes of a change in tax rates is recognized in income in the period that includes the enactment date.  The Company recognizes interest accrued and penalties related to unrecognized tax benefits in income tax expense.
	Stock-Based Compensation
	We maintain various long-term incentive stock benefit plans under which we grant stock options, restricted stock awards, and restricted stock units to certain directors and key employees.  We recognize compensation expense in our income statement over the requisite service period, based on the grant-date fair value of the award.  The fair values of options are estimated using the Black-Scholes option pricing model.  For restricted stock awards and units, we recognize compensation expense ratably over the vesting period for the fair value of the award, measured at the grant date.
	The Company’s stock-based employee compensation plan is described in Note 14 “Stock-Based Compensation,” of this Report.
	Interest Rate Swaps
	The Bank offers interest rate swap agreements to its customers.  These agreements allow the Bank’s customers to effectively fix the interest rate on a variable rate loan by entering into a separate agreement.  Simultaneous with the execution of such an agreement with a customer, the Bank enters into a matching interest rate swap agreement with an unrelated third party provider, which allows the Bank to continue to receive the historical variable rate under the loan agreement with the customer.  The agreement with the third party is not a hedge contract therefore changes in fair value are recorded through earnings.  Assets and liabilities associated with the agreements are recorded in other assets and other liabilities on the balance sheet.  Gains and losses are recorded as other noninterest income.  The Bank is not subject to any fee or penalty should the customer elect to terminate the interest rate swap agreement prior to maturity.  The Bank is exposed to credit loss equal to the fair value of the derivatives (not the notional amount of the derivatives) in the event of nonperformance by the counterparty to the interest rate swap agreements.  Additionally, the Bank receives a fee from the customer that is recognized when the Bank has fulfilled its obligations under each agreement, which is generally upon execution of the agreement with the Bank’s customer.  Since the terms of the two interest rate swap agreements are identical, the income statement impact to the Bank is generally limited to the fees it receives from the customer.
	Other Financial Instruments
	The Company is a party to certain other financial instruments with off-balance-sheet risk such as commitments to extend credit, unused lines of credit, as well as certain mortgage loans sold to investors with recourse. The Company’s policy is to record such instruments when funded.
	Standby letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party.  The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loan facilities to customers.  Under the standby letters of credit, the Company is required to make payments to the beneficiary of the letters of credit upon request by the beneficiary contingent upon the customer's failure to perform under the terms of the underlying contract with the beneficiary.  Standby letters of credit typically have one year expirations with an option to renew upon annual review.  The Company typically receives a fee for these transactions.  The fair value of stand-by letters of credit is recorded upon inception.
	Loan Sales and Loan Servicing
	The Company originates and services residential mortgage loans for consumers and sells 15-year, 20-year and 30-year residential real estate mortgages in the secondary market when the interest rate environment is determined to be favorable by management, while retaining servicing rights on the sold loans.  Loan sales are recorded when the sales are funded.  Mortgage servicing rights are recorded at fair value upon sale of the loan.  Loans held for sale are recorded at the lower of cost or market.
	Repurchase Agreements
	Repurchase agreements are accounted for as secured financing transactions since the Company maintains effective control over the transferred securities and the transfer meets the other criteria for such accounting.  Obligations to repurchase securities sold are reflected as a liability in the Consolidated Balance Sheets.  The securities underlying the agreements are delivered to a custodial account for the benefit of the dealer or bank with whom each transaction is executed.  The dealers or banks, who may sell, loan or otherwise dispose of such securities to other parties in the normal course of their operations, agree to resell to the Company the same securities at the maturities of the agreements.
	Earnings Per Share
	Basic earnings per share (“EPS”) excludes dilution and is computed by dividing income available to common stockholders by the weighted average number of common shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in the earnings of the entity (such as the Company’s dilutive stock options and restricted stock).
	Subsequent Events
	The Company has evaluated subsequent events for potential recognition and/or disclosure and there were none identified.
Comprehensive Income
At the Company, comprehensive income represents net income plus other comprehensive income (loss), which consists primarily of the net change in unrealized gains or losses on securities available for sale for the period and changes in the funded status of employee benefit plans. Accumulated other comprehensive (loss) income represents the net unrealized gains or losses on securities available for sale and the previously unrecognized portion of the funded status of employee benefit plans, net of income taxes, as of the consolidated balance sheet dates.
Pension Costs
The Company maintains a noncontributory, defined benefit pension plan covering substantially all employees, as well as supplemental employee retirement plans covering certain executives and a defined benefit postretirement healthcare plan that covers certain employees.  Costs associated with these plans, based on actuarial computations of current and future benefits for employees, are charged to current operating expenses.
Trust Operations
Assets held by the Company in a fiduciary or agency capacity for its customers are not included in the accompanying consolidated balance sheets, since such assets are not assets of the Company.  Trust income is recognized on the accrual method based on contractual rates applied to the balances of trust accounts.
Fair Value Measurements
Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value measurements are not adjusted for transaction costs.  A fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (level 1 measurements) and the lowest priority to unobservable inputs (level 3 measurements). The three levels of the fair value hierarchy are described below:
Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;
Level 2 -  Quoted prices for similar assets or liabilities in active markets, quoted prices in markets that are not active, or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability;
Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).
A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement.
The types of instruments valued based on quoted market prices in active markets include most U.S. government and agency securities, many other sovereign government obligations, liquid mortgage products, active listed equities and most money market securities. Such instruments are generally classified within level 1 or level 2 of the fair value hierarchy.  The Company does not adjust the quoted price for such instruments.
The types of instruments valued based on quoted prices in markets that are not active, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency include most investment-grade and high-yield corporate bonds, less liquid mortgage products, less liquid agency securities, less liquid listed equities, state, municipal and provincial obligations, and certain physical commodities. Such instruments are generally classified within level 2 of the fair value hierarchy.
Level 3 is for positions that are not traded in active markets or are subject to transfer restrictions, valuations are adjusted to reflect illiquidity and/or non-transferability, and such adjustments are generally based on available market evidence. In the absence of such evidence, management’s best estimate will be used. Management’s best estimate consists of both internal and external support on certain Level 3 investments. Subsequent to inception, management only changes level 3 inputs and assumptions when corroborated by evidence such as transactions in similar instruments, completed or pending third-party transactions in the underlying investment or comparable entities, subsequent rounds of financing, recapitalizations and other transactions across the capital structure, offerings in the equity or debt markets, and changes in financial ratios or cash flows.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2013
Acquisitions [Abstract]	'
Acquisitions	'
	(2)  Acquisitions
	Acquisition of Alliance Financial Corporation
	On March 8, 2013, the Company acquired Alliance Financial Corporation (“Alliance”), the parent company of Alliance Bank, N.A., for total consideration of $226 million.  As part of the acquisition, Alliance was merged with and into the Company and Alliance Bank, with 26 branch locations in the central New York counties of Onondaga, Cortland, Madison, Oneida and Oswego, was merged with and into the Bank.  The merger with Alliance enabled the Company to expand its footprint into demographically attractive and contiguous markets located in the aforementioned New York counties.  Alliance operations were integrated into the Company and were included in the Consolidated Statements of Income from the date of acquisition.
	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 and leases		904,473
	Intangible assets		13,161
	Other assets		72,731
	Deposits		(1,113,420	)
	Borrowings		(126,530	)
	Junior subordinated debt		(25,774	)
	Other liabilities		(19,994	)
	Total identifiable net assets	$	106,325
	Goodwill	$	113,458
	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.  During the measurement period, the Company recorded net adjustments for the fair value of premises, litigation accrual and other operational liabilities that resulted in an increase to goodwill totaling approximately $1.2 million.
	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.  Loans acquired with deteriorated credit quality totaled $0.4 million.
	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		11,325
	Fair value of acquired loans	$	904,473
	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 $12.4 million for the year ended December 31, 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 twelve months ended December 31, 2012 and 2013.
		Pro forma
		Years Ended December 31,
		2013			2012
	Net interest income	$	244,383		$	244,142
	Noninterest income		107,894			106,178
	Net income		70,341			62,694
	Supplemental financial information regarding the former Alliance operations included in our Consolidated Statement of Income from the date of acquisition through December 31, 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 twelve months ended December 31, 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.

Securities

Securities	12 Months Ended
	Dec. 31, 2013
Securities [Abstract]	'
Securities	'
	(3) Securities
	The amortized cost, estimated fair value, and unrealized gains and losses of securities available for sale are as follows:
	(In thousands)	Amortized cost		Unrealized gains			Unrealized losses			Estimated fair value
	31-Dec-13
	U.S. Treasury	$	43,279	$	337		$	-		$	43,616
	Federal Agency		285,880		343			7,308			278,915
	State & municipal		113,435		1,842			1,612			113,665
	Mortgage-backed:
	Government-sponsored enterprises		337,666		5,788			2,131			341,323
	U.S. government agency securities		21,924		1,002			85			22,841
	Collateralized mortgage obligations:
	Government-sponsored enterprises		521,257		1,777			18,141			504,893
	U.S. government agency securities		43,943		794			102			44,635
	Other securities		12,367		2,854			228			14,993
	Total securities available for sale	$	1,379,751	$	14,737		$	29,607		$	1,364,881
	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
	The following table sets forth information with regard to sales transactions of securities available for sale:
		Years ended December 31
	(In thousands)	2013		2012			2011
	Proceeds from sales	$	27,593	$	1,790		$	2,437
	Gross realized gains	$	1,283	$	442		$	7
	Gross realized losses		-		-			(165	)
	Net securities (losses) gains	$	1,283	$	442		$	(158	)
	In addition to gains (losses) from sales transactions, the Company also recorded gains from calls on securities available for sale of approximately $0.1 million for the year ended December 31, 2013, $0.2 million for the year ended December 31, 2012, and $0.3 million for the year ended December 31, 2011.
	At December 31, 2013 and 2012, securities available for sale and held to maturity with amortized costs totaling $1.4 billion and $1.2 billion, respectively, were pledged to secure public deposits and for other purposes required or permitted by law.  Additionally, at December 31, 2013, securities available for sale and held to maturity with an amortized cost of $218.4 million were pledged as collateral for securities sold under the repurchase agreements.
	The amortized cost, estimated fair value, and unrealized gains and losses of securities held to maturity are as follows:
		Amortized		Unrealized			Unrealized			Estimated
	(In thousands)	cost		gains			losses			fair value
	31-Dec-13
	Mortgage-backed	$	953	$	128		$	-		$	1,081
	Collateralized mortgage obligations		62,025		-			4,569			57,456
	State & municipal		54,305		442			8			54,739
	Total securities held to maturity	$	117,283	$	570		$	4,577		$	113,276
	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
	At December 31, 2013 and 2012, all of the mortgaged-backed securities held to maturity were comprised of U.S. Government Agency securities.
	The following table sets forth information with regard to investment securities with unrealized losses at December 31, 2013 and 2012, segregated according to the length of time the securities had been in a continuous unrealized loss position:
		Less than 12 months								12 months or longer							Total
	Security Type:	Fair		Unrealized			Number			Fair		Unrealized			Number		Fair		Unrealized			Number
		Value		losses			of			Value		losses			of		Value		losses			of
							Positions								Positions							Positions
	31-Dec-13
	Investment securities available for sale:
	Federal agency	$	233,935	$	(6,927	)		20		$	9,619	$	(381	)		1	$	243,554	$	(7,308	)		21
	State & municipal		50,328		(1,612	)		177			-		-			-		50,328		(1,612	)		177
	Mortgage-backed		143,080		(2,216	)		79			-		-			-		143,080		(2,216	)		79
	Collateralized mortgage obligations		379,273		(18,243	)		36			-		-			-		379,273		(18,243	)		36
	Other securities		5,490		(203	)		2			223		(25	)		1		5,713		(228	)		3
	Total securities with unrealized losses	$	812,106	$	(29,201	)		314		$	9,842	$	(406	)		2	$	821,948	$	(29,607	)		316
	31-Dec-13
Investment securities held to maturity:
Collateralized mortgage obligations	$	57,456	$	(4,569	)		5		$	-	$	-			-	$	57,456	$	(4,569	)		5
State & municipal		1,012		(8	)		1			-		-			-		1,012		(8	)		1
Total securities with unrealized losses	$	58,468	$	(4,577	)		6		$	-	$	-			-	$	58,468	$	(4,577	)		6
31-Dec-12
Investment securities available for sale:
Federal agency	$	39,906	$	(91	)		4		$	-	$	-			-	$	39,906	$	(91	)		4
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
Management has the intent to hold the securities classified as held to maturity until they mature, at which time it is believed the Company will receive full value for the securities. Furthermore, as of December 31, 2013, management also had intent to hold, and will not be required to sell, the securities classified as available for sale for a period of time sufficient for a recovery of cost, which may be until maturity.  The unrealized losses are due to increases in market interest rates over the yields available at the time the underlying securities were purchased. When necessary, the Company has performed a discounted cash flow analysis to determine whether or not it will receive the contractual principal and interest on certain securities.  The fair value is expected to recover as the bonds approach their maturity date or repricing date or if market yields for such investments decline.  As of December 31, 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 December 31, 2013:
(In thousands)	Amortized		Estimated fair
	cost		value
Debt securities classified as available for sale
Within one year	$	27,894	$	28,030
From one to five years		261,703		261,526
From five to ten years		300,051		297,837
After ten years		777,736		762,495
	$	1,367,384	$	1,349,888
Debt securities classified as held to maturity
Within one year	$	24,680	$	24,766
From one to five years		22,791		23,148
From five to ten years		5,489		5,481
After ten years		64,323		59,881
	$	117,283	$	113,276
Maturities of mortgage-backed, CMOs and asset-backed securities are stated based on their estimated average lives.  Actual maturities may differ from estimated average lives or contractual maturities because, in certain cases, borrowers have the right to call or prepay obligations with or without call or prepayment penalties.
Except for U.S. Government securities, there were no holdings, when taken in the aggregate, of any single issuer that exceeded 10% of consolidated stockholders’ equity at December 31, 2013 and 2012.

Loans

Loans	12 Months Ended
	Dec. 31, 2013
Loans [Abstract]	'
Loans	'
	(4)  Loans
	A summary of loans, net of deferred fees and origination costs, by category is as follows:
		At December 31,
	(In thousands)	2013			2012
	Residential real estate mortgages	$	1,041,637		$	651,107
	Commercial		859,026			694,799
	Commercial real estate		1,328,313			1,072,807
	Real estate construction and development		93,247			123,078
	Agricultural and agricultural real estate mortgages		112,035			112,687
	Consumer		1,352,638			1,047,856
	Home equity		619,899			575,282
	Total loans	$	5,406,795		$	4,277,616
	Included in the above loans are net deferred loan origination costs totaling $31.8 million and $25.5 million at December 31, 2013 and 2012, respectively.  The Company had residential loans held for sale totaling $0.1 million as of December 31, 2013 and $3.6 million as of December 31, 2012.
	FHLB advances are collateralized by a blanket lien on the Company’s residential real estate mortgages.
	In the ordinary course of business, the Company has made loans at prevailing rates and terms to directors, officers, and other related parties. Such loans, in management’s opinion, do not present more than the normal risk of collectability or incorporate other unfavorable features. The aggregate amount of loans outstanding to qualifying related parties and changes during the years are summarized as follows:
	(In thousands)	2013			2012
	Balance at January 1	$	2,790		$	2,537
	New loans		569			750
	Adjustment due to change in composition of related parties		376			(130	)
	Repayments		(363	)		(367	)
	Balance at December 31	$	3,372		$	2,790

Allowance_for_Loan_Losses_and_

Allowance for Loan Losses and Credit Quality of Loans	12 Months Ended
	Dec. 31, 2013
Allowance for Loan Losses and Credit Quality of Loans and Leases [Abstract]	'
Allowance for Loan Losses and Credit Quality of Loans and Leases	'
	(5)  Allowance for Loan Losses and Credit Quality of Loans
	Allowance for Loan Losses
	The allowance for loan losses is maintained at a level estimated by management to provide adequately for risk of probable losses inherent in the current loan portfolio. The adequacy of the allowance for loan losses is continuously monitored.  It is assessed for adequacy using a methodology designed to ensure the level of the allowance reasonably reflects the loan portfolio’s risk profile. It is evaluated to ensure that it is sufficient to absorb all reasonably estimable credit losses inherent in the current loan portfolio.
	To develop and document a systematic methodology for determining the allowance for loan losses, the Company has divided the loan portfolio into three segments, each with different risk characteristics and methodologies for assessing risk.  Those segments are further segregated between our loans accounted for under the amortized cost method (referred to as “originated” loans) and loans acquired in a business combination (referred to as “acquired” loans).  Prior to 2013, separate disclosures for acquired loans were not significant and were included with originated loans in the Company’s asset quality disclosures.  Each portfolio segment is broken down into class segments where appropriate.  Class segments contain unique measurement attributes, risk characteristics and methods for monitoring and assessing risk that are necessary to develop the allowance for loan losses.  Unique characteristics such as borrower type, loan type, collateral type, and risk characteristics define each class segment.  The following table illustrates the portfolio and class segments for the Company’s loan portfolio:
	Portfolio	Class
	Commercial Loans	Commercial
		Commercial Real Estate
		Agricultural
		Agricultural Real Estate
		Business Banking
	Consumer Loans	Indirect
		Home Equity
		Direct
	Residential Real Estate Mortgages
	COMMERCIAL LOANS
	Commercial – The Company offers a variety of loan options to meet the specific needs of our commercial customers including term loans, time notes and lines of credit.  Such loans are made available to businesses for working capital such as inventory and receivables, business expansion and equipment purchases. Generally, a collateral lien is placed on equipment or other assets owned by the borrower.  These loans carry a higher risk than commercial real estate loans by the nature of the underlying collateral, which can be business assets such as equipment and accounts receivable and is generally less liquid than real estate. To reduce the risk, management also attempts to secure real estate as collateral and obtain personal guarantees of the borrowers.
	Commercial Real Estate – The Company offers commercial real estate loans to finance real estate purchases, refinancings, expansions and improvements to commercial properties.  Commercial real estate loans are made to finance the purchases of real property which generally consists of real estate with completed structures. These commercial real estate loans are secured by first liens on the real estate, which may include apartments, commercial structures, housing businesses, healthcare facilities, and other non owner-occupied facilities.  These loans are typically less risky than commercial loans, since they are secured by real estate and buildings. The Company’s underwriting analysis includes credit verification, independent appraisals, a review of the borrower's financial condition, and a detailed analysis of the borrower’s underlying cash flows. These loans are typically originated in amounts of no more than 80% of the appraised value of the property.
	Agricultural – The Company offers a variety of agricultural loans to meet the needs of our agricultural customers including term loans, time notes, and lines of credit.  These loans are made to purchase livestock, purchase and modernize equipment, and finance seasonal crop expenses.  Generally, a collateral lien is placed on the livestock, equipment, produce inventories, and/or receivables owned by the borrower.  These loans may carry a higher risk than commercial and agricultural real estate loans due to the industry price volatility and the perishable nature of the underlying collateral.  To reduce these risks, management may attempt to secure these loans with additional real estate collateral, obtain personal guarantees of the borrowers, or obtain government loan guarantees to provide further support.
	Agricultural Real Estate – The Company offers real estate loans to our agricultural customers to finance farm related real estate purchases, refinancings, expansions, and improvements to agricultural properties.  Agricultural real estate loans are made to finance the purchases and improvements of farm properties that generally consist of barns, production facilities, and land.  The agricultural real estate loans are secured by first liens on the farm real estate.  Because they are secured by land and buildings, these loans may be less risky than agricultural loans.  The Company's underwriting analysis includes credit verification, independent appraisals, a review of the borrower's financial condition, and a detailed analysis of the borrower’s underlying cash flows.  These loans are typically originated in amounts of no more than 75% of the appraised value of the property.  Government loan guarantees may be obtained to provide further support.
	Business Banking - The Company offers a variety of loan options to meet the specific needs of our small business customers including term loans, small business mortgages and lines of credit.  Such loans are generally less than $500 thousand and are made available to businesses for working capital such as inventory and receivables, business expansion, equipment purchases, and agricultural needs.  Generally, a collateral lien is placed on equipment or other assets owned by the borrower such as inventory and/or receivables.  These loans carry a higher risk than commercial loans due to the smaller size of the borrower and lower levels of capital.  To reduce the risk, the Company obtains personal guarantees of the owners for a majority of the loans.
	CONSUMER LOANS
	Indirect – The Company maintains relationships with many dealers primarily in the communities that we serve.  Through these relationships, the company finances the purchases of automobiles and recreational vehicles (such as campers, boats, etc.) indirectly through dealer relationships.  Approximately 70% of the indirect relationships represent automobile financing.  Most of these loans carry a fixed rate of interest with principal repayment terms typically ranging from three to six years, based upon the nature of the collateral and the size of the loan. The majority of indirect consumer loans are underwritten on a secured basis using the underlying collateral being financed.
	Home Equity – The Company offers fixed home equity loans as well as home equity lines of credit to consumers to finance home improvements, debt consolidation, education and other uses.  Consumers are able to borrower up to 85% of the equity in their homes.  The Company originates home equity lines of credit and second mortgage loans (loans secured by a second lien position on one-to-four-family residential real estate).  These loans carry a higher risk than first mortgage residential loans as they are in a second position with respect to collateral.  Risk is reduced through underwriting criteria, which include credit verification, appraisals, a review of the borrower's financial condition, and personal cash flows.  A security interest, with title insurance when necessary, is taken in the underlying real estate.
	Direct – The Company offers a variety of consumer installment loans to finance vehicle purchases, mobile home purchases and personal expenditures.  Most of these loans carry a fixed rate of interest with principal repayment terms typically ranging from one to ten years, based upon the nature of the collateral and the size of the loan. The majority of consumer loans are underwritten on a secured basis using the underlying collateral being financed or a customer's deposit account. In addition to installment loans, the Company also offers personal lines of credit and overdraft protection.  A minimal amount of loans are unsecured, which carry a higher risk of loss.
	RESIDENTIAL REAL ESTATE LOANS
	Residential real estate loans consist primarily of loans secured by first or second deeds of trust on primary residences.  We originate adjustable-rate and fixed-rate, one-to-four-family residential real estate loans for the construction, purchase or refinancing of a mortgage.  These loans are collateralized by owner-occupied properties located in the Company’s market area. When market conditions are favorable, for longer term, fixed-rate residential mortgages without escrow, the Company retains the servicing, but sells the right to receive principal and interest to Freddie Mac when market conditions are favorable.   This practice allows the Company to manage interest rate risk, liquidity risk, and credit risk.  Loans on one-to-four-family residential real estate are generally originated in amounts of no more than 85% of the purchase price or appraised value (whichever is lower), or have private mortgage insurance.  Mortgage title insurance and hazard insurance are normally required. Construction loans have a unique risk, because they are secured by an incomplete dwelling. This risk is reduced through periodic site inspections, including one at each loan draw period.
	Allowance for Loan Loss Calculation
	Management considers the accounting policy relating to the allowance for loan losses to be a critical accounting policy given the inherent uncertainty in evaluating the levels of the allowance required to cover credit losses in the portfolio and the material effect that such judgments can have on the consolidated results of operations.
	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 to the allowance for loan losses are made periodically by charges to the provision for loan losses. These charges are necessary to maintain the allowance at a level which management believes is reasonably reflective of overall inherent risk of probable loss in the portfolio. While management uses available information to recognize losses on loans, additions to the allowance may fluctuate from one reporting period to another.  These fluctuations are reflective of changes in risk associated with portfolio content and/or changes in management’s assessment of any or all of the determining factors discussed above.  The following table illustrates the changes in the allowance for loan losses by portfolio segment for the years ended December 31, 2013, 2012 and 2011:
	Allowance for Loan Losses
	(in thousands)
									Residential
	Years ended December 31		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			(10,459	)		(15,459	)		(1,771	)		-			(27,689	)
	Recoveries			1,957			3,136			272			-			5,365
	Provision			7,968			12,855			1,767			(166	)		22,424
	Ending Balance as of December 31, 2013		$	35,090		$	27,694		$	6,520		$	130		$	69,434
	Balance as of December 31, 2011		$	38,831		$	26,049		$	6,249		$	205		$	71,334
	Charge-offs			(8,750	)		(15,848	)		(1,906	)		-			(26,504	)
	Recoveries			1,641			2,556			38			-			4,235
	Provision			3,902			14,405			1,871			91			20,269
	Ending Balance as of December 30, 2012		$	35,624		$	27,162		$	6,252		$	296		$	69,334
	Balance as of December 31, 2010		$	40,101		$	26,126		$	4,627		$	380		$	71,234
	Charge-offs			(8,969	)		(14,209	)		(1,310	)		-			(24,488	)
	Recoveries			1,438			2,406			7			-			3,851
	Provision			6,261			11,726			2,925			(175	)		20,737
	Ending Balance as of December 30, 2011		$	38,831		$	26,049		$	6,249		$	205		$	71,334
	For acquired loans, to the extent that we experience deterioration in borrower credit quality resulting in a decrease in our expected cash flows subsequent to acquisition of the loans, an allowance for loan losses would be established based on our estimate of future credit losses over the remaining life of the loans.  As of December 31, 2013 and 2012, there was no allowance for loan losses for the acquired loan portfolio. Net charge-offs related to acquired loans totaled approximately $0.6 million during the year ended December 31, 2013, and are included in the table above.
	The following table illustrates the allowance for loan losses and the recorded investment by portfolio segment as of December 31, 2013 and 2012:
	Allowance for Loan Losses and Recorded Investment in Loans
	(in thousands)
									Residential
			Commercial			Consumer			Real Estate
			Loans			Loans			Mortgages			Unallocated			Total
	As of December 31, 2013
	Allowance for loan losses		$	35,090		$	27,694		$	6,520		$	130		$	69,434
	Allowance for loans individually evaluated for impairment			715			-			-						715
	Allowance for loans collectively evaluated for impairment		$	34,375		$	27,694		$	6,520		$	130		$	68,719
	Ending balance of loans		$	2,392,621		$	1,972,537		$	1,041,637					$	5,406,795
	Ending balance of originated loans individually evaluated for impairment			16,120			3,248			2,012						21,380
Ending balance of acquired loans individually evaluated for impairment			10,060			-			-						10,060
Ending balance of acquired loans collectively evaluated for impairment			392,329			219,587			308,416						920,332
Ending balance of originated loans collectively evaluated for impairment		$	1,974,112		$	1,749,702		$	731,209					$	4,455,023
As of December 31, 2012
Allowance for loan and lease losses		$	35,624		$	27,162		$	6,252		$	296		$	69,334
Allowance for loans and leases individually evaluated for impairment			2,848			-			-						2,848
Allowance for loans and leases collectively evaluated for impairment		$	32,776		$	27,162		$	6,252		$	296		$	66,486
Ending balance of loans and leases		$	2,003,371		$	1,623,138		$	651,107					$	4,277,616
Ending balance of loans individually evaluated for impairment			18,505			2,553			2,011						23,069
Ending balance of loans collectively evaluated for impairment		$	1,984,866		$	1,620,585		$	649,096					$	4,254,547
The following table illustrates the Company’s nonaccrual loans by loan class as of December 31, 2013 and 2012:
(In thousands)		31-Dec-13			31-Dec-12
ORIGINATED
Commercial Loans
Commercial		$	3,669		$	4,985
Commercial Real Estate			7,834			7,977
Agricultural			1,135			699
Agricultural Real Estate			961			1,038
Business Banking			5,701			6,738
			19,300			21,437
Consumer Loans
Indirect			1,461			1,557
Home Equity			5,931			7,247
Direct			86			266
			7,478			9,070
Residential Real Estate Mortgages			7,105			9,169
		$	33,883		$	39,676
ACQUIRED
Commercial Loans
Commercial		$	6,599
Commercial Real Estate			3,559
Business Banking			1,340
			11,498
Consumer Loans
Indirect			93
Home Equity			570
Direct			49
			712
Residential Real Estate Mortgages			3,872
		$	16,082
TOTAL NONACCRUAL LOANS		$	49,965		$	39,676
The following table sets forth information with regard to past due and nonperforming loans by loan class:
Age Analysis of Past Due Financing Receivables
As of December 31, 2013
(in thousands)
								Greater
		31-60 Days			61-90 Days			Than			Total								Recorded Total
								90 Days
		Past Due			Past Due			Past Due			Past Due								Loans and
		Accruing			Accruing			Accruing			Accruing			Non-Accrual			Current		Leases
ORIGINATED
Commercial Loans
Commercial		$	105		$	247		$	-		$	352		$	3,669		$	612,402	$	616,423
Commercial Real Estate			1,366			-			-			1,366			7,834			925,116		934,316
Agricultural			150			21			-			171			1,135			63,856		65,162
Agricultural Real Estate			519			-			-			519			961			35,172		36,652
Business Banking			1,228			122			105			1,455			5,701			330,523		337,679
			3,368			390			105			3,863			19,300			1,967,069		1,990,232
Consumer Loans
Indirect			14,093			2,878			1,583			18,554			1,461			1,141,829		1,161,844
Home Equity			6,033			1,888			1,115			9,036			5,931			517,856		532,823
Direct			679			125			46			850			86			57,347		58,283
			20,805			4,891			2,744			28,440			7,478			1,717,032		1,752,950
Residential Real Estate Mortgages			3,951			379			808			5,138			7,105			720,978		733,221
		$	28,124		$	5,660		$	3,657		$	37,441		$	33,883		$	4,405,079	$	4,476,403
ACQUIRED
Commercial Loans
Commercial		$	24		$	-		$	-		$	24		$	6,599		$	96,603	$	103,226
Commercial Real Estate			-			-			-			-			3,559			225,455		229,014
Business Banking			320			2			-			322			1,340			68,487		70,149
			344			2			-			346			11,498			390,545		402,389
Consumer Loans
Indirect			939			113			71			1,123			93			123,870		125,086
Home Equity			753			63			-			816			570			85,690		87,076
Direct			76			56			9			141			49			7,235		7,425
			1,768			232			80			2,080			712			216,795		219,587
Residential Real Estate Mortgages			1,725			-			-			1,725			3,872			302,819		308,416
		$	3,837		$	234		$	80		$	4,151		$	16,082		$	910,159	$	930,392
Total Loans		$	31,961		$	5,894		$	3,737		$	41,592		$	49,965		$	5,315,238	$	5,406,795
Age Analysis of Past Due Loans
As of December 31, 2012
(in thousands)
								Greater Than											Recorded
		31-60 Days			61-90 Days			90 Days			Total								Total
		Past Due			Past Due			Past Due			Past Due								Loans and
		Accruing			Accruing			Accruing			Accruing			Non-Accrual			Current		Leases
Commercial
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
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.
The methodology used to establish the allowance for loan losses on impaired loans incorporates specific allocations on loans analyzed individually.  Classified loans, including all TDRs and nonaccrual commercial loans that are graded substandard or below, with outstanding balances of $500 thousand or more are evaluated for impairment through the Company’s quarterly status review process.  In determining that we will be unable to collect all principal and interest payments due in accordance with the contractual terms of the loan agreements, we consider factors such as payment history and changes in the financial condition of individual borrowers, local economic conditions, historical loss experience and the conditions of the various markets in which the collateral may be liquidated.  For loans that are evaluated for impairment, impairment is measured by one of three methods: 1) the fair value of collateral less cost to sell, 2) present value of expected future cash flows or 3) the loan’s observable market price.  These impaired loans are reviewed on a quarterly basis for changes in the measurement of impairment.  For impaired loans measured using the present value of expected cash flow method, any change to the previously recognized impairment loss is recognized as a change to the allowance account and recorded in the consolidated statement of income as a component of the provision for credit losses.
The following provides additional information on loans specifically evaluated for impairment for the years ended December 31, 2013 and 2012:
Impaired Loans
		31-Dec-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
ORIGINATED
With no related allowance recorded:
Commercial Loans
Commercial		$	4,721		$	4,777					$	1,000		$	1,000
Commercial Real Estate			4,613			5,164						7,362			7,366
Agricultural			125			195						446			540
Agricultural Real Estate			1,431			1,708						903			1,029
Business Banking			210			602						391			783
Total Commercial Loans			11,100			12,446						10,102			10,718
Consumer Loans
Home Equity			3,248			3,472						2,553			2,657
Residential Real Estate Mortgages			2,012			2,255						2,011			2,308
Total			16,360			18,173						14,666			15,683
With an allowance recorded:
Commercial Loans
Commercial			-			-			-			4,335			4,340			2,241
Commercial Real Estate			5,020			6,877			715			4,068			5,689			607
Agricultural			-			-			-			-			-			-
Agricultural Real Estate			-			-			-			-			-			-
			5,020			6,877			715			8,403			10,029			2,848
ACQUIRED
With no related allowance recorded:
Commercial Loans
Commercial			6,501			6,538
Commercial Real Estate			3,559			3,842
Total Commercial Loans			10,060			10,380
Total		$	31,440		$	35,430		$	715		$	23,069		$	25,712		$	2,848
The following table summarizes the average recorded investments on loans specifically evaluated for impairment and the interest income recognized for the years ended December 31, 2013, 2012 and 2011:
		31-Dec-13						31-Dec-12						31-Dec-11
		Average			Interest Income			Average			Interest Income			Average			Interest Income
		Recorded			Recognized			Recorded			Recognized			Recorded			Recognized
(in thousands)		Investment			Accrual			Investment			Accrual			Investment			Accrual
ORIGINATED
Commercial Loans
Commercial		$	3,722		$	17		$	6,682		$	56		$	1,507		$	-
Commercial Real Estate			11,010			130			4,944			230			3,763			-
Agricultural			207			1			1,767			43			2,070			-
Agricultural Real Estate			1,167			52			922			72			695			-
Business Banking			295			57			68			65			17			-
Consumer Loans
Home Equity			2,969			143			1,877			123			1,924			60
Residential Real Estate Mortgages			2,024			69			1,143			54			933			4
ACQUIRED
Commercial Loans
Commercial			1,625			-			-			-			-			-
Commercial Real Estate			1,222			-			-			-			-			-
Total		$	24,240		$	469		$	17,403		$	643		$	10,909		$	64
There has been significant disruption and volatility in the financial and capital markets since the second half of 2008.  Turmoil in the mortgage market adversely impacted both domestic and global markets and led to a significant credit and liquidity crisis in many domestic markets.  These market conditions were attributable to a variety of factors, in particular the fallout associated with subprime mortgage loans (a type of lending we have never actively pursued).  The disruption was exacerbated by the decline of the real estate and housing market.  However, in the markets in which the Company does business, the disruption has been less significant than in the national market.  For example, our real estate market has not suffered the extreme declines seen nationally and our unemployment rate, while notably higher than in prior periods, is still below the national average.
While we continue to adhere to prudent underwriting standards, as a lender we may be adversely impacted by general economic weaknesses and, in particular, a sharp downturn in the housing market nationally.  Decreases in real estate values could adversely affect the value of property used as collateral for our loans.  Adverse changes in the economy may have a negative effect on the ability of our borrowers to make timely loan payments, which would have an adverse impact on our earnings.  A further increase in loan delinquencies would decrease our net interest income and adversely impact our loan loss experience, causing increases in our provision and allowance for loan losses.
The Company has developed an internal loan grading system to evaluate and quantify the Bank’s loan portfolio with respect to quality and risk.  The system focuses on, among other things, financial strength of borrowers, experience and depth of management, primary and secondary sources of repayment, payment history, nature of the business, outlook on particular industries.  The internal grading system enables the Company to monitor the quality of the entire loan portfolio on a continuous basis and provide management with an early warning system, enabling recognition and response to problem loans and potential problem loans.
Commercial Grading System
For commercial and agricultural loans, the Company uses a grading system that relies on quantifiable and measurable characteristics when available.  This would include comparison of financial strength to available industry averages, comparison of transaction factors (loan terms and conditions) to loan policy, and comparison of credit history to stated repayment terms and industry averages. Some grading factors are necessarily more subjective such as economic and industry factors, regulatory environment, and management.  The grading system for commercial and agricultural loans is as follows:
	·	Doubtful
A doubtful loan has a high probability of total or substantial loss, but because of specific pending events that may strengthen the asset, its classification as loss is deferred. Doubtful borrowers are usually in default, lack adequate liquidity or capital, and lack the resources necessary to remain an operating entity. Pending events can include mergers, acquisitions, liquidations, capital injections, the perfection of liens on additional collateral, the valuation of collateral, and refinancing. Generally, pending events should be resolved within a relatively short period and the ratings will be adjusted based on the new information. Because of high probability of loss, nonaccrual treatment is required for doubtful assets.
	·	Substandard
Substandard loans have a high probability of payment default, or they have other well-defined weaknesses. They require more intensive supervision by bank management. Substandard loans are generally characterized by current or expected unprofitable operations, inadequate debt service coverage, inadequate liquidity, or marginal capitalization. Repayment may depend on collateral or other credit risk mitigants. For some substandard loans, the likelihood of full collection of interest and principal may be in doubt and should be placed on nonaccrual. Although substandard assets in the aggregate will have a distinct potential for loss, an individual asset’s loss potential does not have to be distinct for the asset to be rated substandard.
	·	Special Mention
Special Mention loans have potential weaknesses that may, if not checked or corrected, weaken the asset or inadequately protect the Company’s position at some future date. These loans pose elevated risk, but their weakness does not yet justify a substandard classification. Borrowers may be experiencing adverse operating trends (declining revenues or margins) or may be struggling with an ill-proportioned balance sheet (e.g., increasing inventory without an increase in sales, high leverage, tight liquidity). Adverse economic or market conditions, such as interest rate increases or the entry of a new competitor, may also support a special mention rating. Although a Special Mention loan has a higher probability of default than a pass asset, its default is not imminent.
	·	Pass
Loans graded as Pass encompass all loans not graded as Doubtful, Substandard, or Special Mention.  Pass loans are in compliance with loan covenants, and payments are generally made as agreed.  Pass loans range from superior quality to fair quality.
Business Banking Grading System
Business Banking loans are graded as either Classified or Non-classified:
	·	Classified
Classified loans are inadequately protected by the current worth and paying capacity of the obligor or, if applicable, the collateral pledged.   These loans have a well-defined weakness, or weaknesses, that jeopardize the liquidation of the debt, or in some cases make collection or liquidation in full, on the basis of currently existing facts, conditions, and values, highly questionable and improbable. They are characterized by the distinct possibility that the Company will sustain some loss if the deficiencies are not corrected.   Classified loans have a high probability of payment default, or a high probability of total or substantial loss.  These loans require more intensive supervision by management and are generally characterized by current or expected unprofitable operations, inadequate debt service coverage, inadequate liquidity, or marginal capitalization.  Repayment may depend on collateral or other credit risk mitigants.  When the likelihood of full collection of interest and principal may be in doubt; classified loans are considered to have a nonaccrual status.   In some cases, classified loans are considered uncollectible and of such little value that their continuance as assets is not warranted.
	·	Non-classified
Loans graded as Non-classified encompass all loans not graded as Classified.  Non-classified loans are in compliance with loan covenants, and payments are generally made as agreed.
Consumer and Residential Mortgage Grading System
Consumer and Residential Mortgage loans are graded as either Performing or Nonperforming.   Nonperforming loans are loans that are 1) over 90 days past due and interest is still accruing or 2) on nonaccrual status.  All loans not meeting any of these three criteria are considered Performing.
The following tables illustrate the Company’s credit quality by loan class for the years ended December 31, 2013 and 2012:
Credit Quality Indicators
As of December 31, 2013
ORIGINATED
Commercial Credit Exposure					Commercial						Agricultural
By Internally Assigned Grade:		Commercial			Real Estate			Agricultural			Real Estate			Total
Pass		$	576,079		$	878,411		$	60,043		$	33,136		$	1,547,669
Special Mention			16,836			22,777			381			43			40,037
Substandard			23,508			33,128			4,726			3,473			64,835
Doubtful			-			-			12			-			12
Total		$	616,423		$	934,316		$	65,162		$	36,652		$	1,652,553
Business Banking Credit Exposure
By Internally Assigned Grade:		Business Banking												Total
Non-classified		$	319,578											$	319,578
Classified			18,101												18,101
Total		$	337,679											$	337,679
Consumer Credit Exposure
By Payment Activity:		Indirect			Home Equity			Direct						Total
Performing		$	1,158,800		$	525,777		$	58,151					$	1,742,728
Nonperforming			3,044			7,046			132						10,222
Total		$	1,161,844		$	532,823		$	58,283					$	1,752,950
Residential Mortgage Credit Exposure		Residential
By Payment Activity:		Mortgage												Total
Performing		$	725,308											$	725,308
Nonperforming			7,913												7,913
Total		$	733,221											$	733,221
Credit Quality Indicators
As of December 31, 2013
ACQUIRED
Commercial Credit Exposure					Commercial
By Internally Assigned Grade:		Commercial			Real Estate			Agricultural						Total
Pass		$	85,692		$	205,010		$	-					$	290,702
Special Mention			2,230			6,183			-						8,413
Substandard			15,304			17,821			-						33,125
Doubtful			-			-			-						-
Total		$	103,226		$	229,014		$	-					$	332,240
Business Banking Credit Exposure
By Internally Assigned Grade:		Business Banking												Total
Non-classified		$	65,437											$	65,437
Classified			4,712												4,712
Total		$	70,149											$	70,149
Consumer Credit Exposure
By Payment Activity:		Indirect			Home Equity			Direct						Total
Performing		$	124,922		$	86,506		$	7,367					$	218,795
Nonperforming			164			570			58						792
Total		$	125,086		$	87,076		$	7,425					$	219,587
Residential Mortgage Credit Exposure		Residential
By Payment Activity:		Mortgage												Total
Performing		$	304,544											$	304,544
Nonperforming			3,872												3,872
Total		$	308,416											$	308,416
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		Business
By Internally Assigned Grade:		Banking												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 Restructuring
Troubled debt restructurings made during the year ended December 31, 2013 consisted of four commercial loans totaling $7.0 million, 23 home equity loans totaling $1.0 million and 6 residential real estate mortgages totaling $0.5 million.  For all such modifications, the pre-and post-outstanding recorded investment amount remained unchanged.  During the year ended December 31, 2013, there was one commercial loan classified as TDRs totaling $0.9 million and eight home equity loans totaling $0.4 million that subsequently defaulted on their renegotiated terms.
Troubled debt restructurings made during the year ended December 31, 2012 consisted of four commercial loans totaling $6.6 million, one business banking loan totaling $0.1 million, 18 home equity loans totaling $0.9 million and 12 residential real estate mortgages totaling $1.2 million.  For all such modifications, the pre-and post-outstanding recorded investment amount remained unchanged.  During the year ended December 31, 2012, there were two residential real estate loans classified as TDRs totaling $0.3 million and one home equity loan totaling less than $0.1 million that subsequently defaulted on their renegotiated terms.
Substantially all modifications include one or a combination of the following: an extension of the maturity date at a stated rate of interest lower than the current market rate for new debt with similar risk; temporary reduction in the interest rate; or change in scheduled payment amount.

Premises_and_Equipment_Net

Premises and Equipment, Net	12 Months Ended
	Dec. 31, 2013
Premises and Equipment, Net [Abstract]	'
Premises and Equipment, Net	'
	(6) Premises and Equipment, Net
	A summary of premises and equipment follows:
		December 31,
	(In thousands)	2013		2012
	Land, buildings, and improvements	$	120,098	$	109,601
	Equipment		55,729		51,321
	Premises and equipment before accumulated depreciation		175,827		160,922
	Accumulated depreciation		87,500		83,047
	Total premises and equipment	$	88,327	$	77,875
	Buildings and improvements are depreciated based on useful lives of 15 to 40 years.  Equipment is depreciated based on useful lives of three to ten years.
	Rental expense included in occupancy expense amounted to $7.5 million in 2013, $6.4 million in 2012, and $5.6 million in 2011. The future minimum rental payments related to noncancelable operating leases with original terms of one year or more are as follows at December 31, 2013 (in thousands):
	Future Minimum Rental Payments
	2014	$	7,156
	2015		7,012
	2016		6,985
	2017		6,859
	2018		6,791
	Thereafter		53,132
	Total	$	87,935

Goodwill_and_other_Intangible_

Goodwill and other Intangible Assets	12 Months Ended
	Dec. 31, 2013
Goodwill and other Intangible Assets [Abstract]	'
Goodwill and other Intangible Assets	'
	(7) Goodwill and other Intangible Assets
	A summary of goodwill is as follows:
	(In thousands)
	1-Jan-13		152,373
	Goodwill Acquired		112,624
	31-Dec-13	$	264,997
	1-Jan-12		132,029
	Goodwill Acquired		20,344
	31-Dec-12	$	152,373
	The Company has intangible assets with definite useful lives capitalized on its consolidated balance sheet in the form of core deposit and other identified intangible assets.  These intangible assets are amortized over their estimated useful lives, which range primarily from one to twelve years.
	A summary of core deposit and other intangible assets follows:
		December 31,
	(In thousands)	2013		2012
	Core deposit intangibles
	Gross carrying amount	$	19,401	$	13,240
	Less: accumulated amortization		10,083		7,794
	Net carrying amount		9,318		5,446
	Identified intangible assets
	Gross carrying amount		28,509		21,743
	Less: accumulated amortization		12,270		10,227
	Net carrying amount		16,239		11,516
	Total intangibles
	Gross carrying amount		47,910		34,983
	Less: accumulated amortization		22,353		18,021
	Net carrying amount	$	25,557	$	16,962
	Amortization expense on intangible assets with definite useful lives totaled $4.9 million for 2013, $3.4 million for 2012 and $3.0 million for 2011.  Amortization expense on intangible assets with definite useful lives is expected to total $5.0 million for 2014, $4.6 million for 2015, $3.3 million for 2016, $2.8 million for 2017, $2.2 million for 2018 and $5.4 million thereafter.  Other identified intangible assets include customer lists, non-competes, and trademark intangibles, of which $2.0 million will not amortize.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2013
Deposits [Abstract]	'
Deposits	'
	(8)  Deposits
	The following table sets forth the maturity distribution of time deposits at December 31, 2013 (in thousands):
	Time deposits
	Within one year	$	661,619
	After one but within two years		184,796
	After two but within three years		86,689
	After three but within four years		52,024
	After four but within five years		20,656
	After five years		15,358
	Total	$	1,021,142
	Time deposits of $100,000 or more aggregated $375.4 million and $352.3 million December 31, 2013 and 2012, respectively.

ShortTerm_Borrowings

Short-Term Borrowings	12 Months Ended
	Dec. 31, 2013
Short-Term Borrowings [Abstract]	'
Short-Term Borrowings	'
	(9) Short-Term Borrowings
	Short-term borrowings totaled $456.0 million and $162.9 million at December 31, 2013 and 2012, respectively, and consist of Federal funds purchased and securities sold under repurchase agreements, which generally represent overnight borrowing transactions, and other short-term borrowings, primarily FHLB advances, with original maturities of one year or less.
	The Company had unused lines of credit with the FHLB available for short-term financing of approximately $497 million and $418 million at December 31, 2013 and 2012, respectively.  Borrowings on these lines are secured by FHLB stock, certain securities and one-to-four family first lien mortgage loans.  Securities  collateralizing  repurchase  agreements  are  held in safekeeping by nonaffiliated  financial  institutions  and  are  under  the  Company’s control.
	Information related to short-term borrowings is summarized as follows:
	(In thousands)	2013			2012			2011
	Federal funds purchased
	Balance at year-end	$	130,000		$	10,000		$	27,000
	Average during the year		39,907			12,658			3,017
	Maximum month end balance		130,000			60,000			28,000
	Weighted average rate during the year		0.26	%		0.27	%		0.11	%
	Weighted average rate at December 31		0.18	%		0.27	%		0.13	%
	Securities sold under repurchase agreements
	Balance at year-end	$	176,042		$	152,941		$	154,592
	Average during the year		169,352			153,084			150,663
	Maximum month end balance		185,871			165,977			178,414
	Weighted average rate during the year		0.06	%		0.1	%		0.13	%
	Weighted average rate at December 31		0.05	%		0.1	%		0.1	%
	Other short-term borrowings
	Balance at year-end	$	150,000		$	-		$	-
	Average during the year		71,589			-			249
	Maximum month end balance		210,000			-			250
	Weighted average rate during the year		0.43	%		-			-
	Weighted average rate at December 31		0.55	%		-			-
	See Note 3 for additional information regarding securities pledged as collateral for securities sold under the repurchase agreements.

LongTerm_Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2013
Long-Term Debt [Abstract]	'
Long-Term Debt	'
	(10) Long-Term Debt
	Long-term debt consists of obligations having an original maturity at issuance of more than one year. A majority of the Company’s long-term debt is comprised of FHLB advances collateralized by the FHLB stock owned by the Company, certain of its mortgage-backed securities and a blanket lien on its residential real estate mortgage loans.  A summary as of December 31, 2013 and 2012 is as follows:
		As of December 31, 2013										As of December 31, 2012
	Maturity	Amount		Weighted Average Rate			Callable Amount		Weighted Average Rate			Amount		Weighted Average Rate			Callable Amount		Weighted Average Rate
	2013		-		-			-		-			119,502		3.87	%		100,000		3.71	%
	2014		12,460		1.33	%		-		-			2,610		1.89	%		-		-
	2015		308		0	%		-		-			250		0	%		-		-
	2016		90,313		3.52	%		70,000		4.21	%		70,000		4.21	%		70,000		4.21	%
	2017		115,312		3.55	%		75,000		3.73	%		100,000		3.89	%		100,000		3.89	%
	2018		90,313		3.26	%		75,000		3.61	%		75,000		3.61	%		75,000		3.61	%
	2021		117		4	%		-		-			130		4	%		-		-
		$	308,823				$	220,000				$	367,492				$	345,000

Junior_Subordinated_Debt

Junior Subordinated Debt	12 Months Ended
	Dec. 31, 2013
Junior Subordinated Debt [Abstract]	'
Junior Subordinated Debt	'
	(11) Junior Subordinated Debt
	The Company sponsors five business trusts, CNBF Capital Trust I, NBT Statutory Trust I, NBT Statutory Trust II, Alliance Financial Capital Trust I and Alliance Financial Capital Trust II.  The trusts were formed for the purpose of issuing company-obligated mandatorily redeemable preferred securities to third-party investors and investing in the proceeds from the sale of such preferred securities solely in junior subordinated debt securities of the Company.  The debentures held by each trust are the sole assets of that trust.  These five statutory business trusts are collectively referred herein to as “the Trusts.”  The Company guarantees, on a limited basis, payments of distributions on the trust preferred securities and payments on redemption of the trust preferred securities.  The Trusts are variable interest entities (“VIEs”) for which the Company is not the primary beneficiary, as defined by U.S. GAAP.  In accordance with U.S. GAAP, the accounts of the Trusts are not included in the Company’s consolidated financial statements. See Note 1 — Summary of Significant Accounting Policies for additional information about the Company’s consolidation policy. As of December 31, 2013, the Trusts had the following issues of trust preferred debentures, all held by the Trusts, outstanding (dollars in thousands):
	Description	Issuance Date	Trust Preferred Securities Outstanding		Interest Rate	Trust Preferred Debt Owed To Trust		Final Maturity Date
	CNBF Capital Trust I	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’s junior subordinated debentures include amounts related to the Company’s NBT Statutory Trust I and II as well as junior subordinated debentures associated with one statutory trust affiliates that were acquired from our merger with CNB Financial Corp. and two statutory trusts acquired from Alliance (the “Trusts”). The Trusts qualify as variable interest entities and were formed to issue mandatorily redeemable trust preferred securities to investors and loan the proceeds to us for general corporate purposes. The Trusts hold, as their sole assets, junior subordinated debentures of the Company with face amounts totaling $98 million at December 31, 2013. The Company owns all of the common securities of the Trusts and have accordingly recorded $3.2 million in equity method investments classified as other assets in our Consolidated Balance Sheets at December 31, 2013. The Company owns all of the common stock of the Trusts, which have issued trust preferred securities in conjunction with the Company issuing trust preferred debentures to the Trusts. The terms of the trust preferred debentures are substantially the same as the terms of the trust preferred securities.
	The Company’s junior subordinated debentures are redeemable prior to the maturity date at our option upon each trust’s stated option repurchase dates, and from time to time thereafter. These debentures are also redeemable in whole at any time upon the occurrence of specific events defined within the trust indenture. Our obligations under the debentures and related documents, taken together, constitute a full and unconditional guarantee by the Company of the issuers’ obligations under the trust preferred securities.  The Company owns all of the common stock of the Trusts, which have issued trust preferred securities in conjunction with the Company issuing trust preferred debentures to the Trusts. The terms of the trust preferred debentures are substantially the same as the terms of the trust preferred securities.
	With respect to the Trusts, the Company has the right to defer payments of interest on the debentures issued to the Trusts at any time or from time to time for a period of up to ten consecutive semi-annual periods with respect to each deferral period. Under the terms of the debentures, if in certain circumstances there is an event of default under the debentures or the Company elects to defer interest on the debentures, the Company may not, with certain exceptions, declare or pay any dividends or distributions on its capital stock or purchase or acquire any of its capital stock.
	Despite the fact that the Trusts are not included in the Company’s consolidated financial statements, $97 million of the $101 million in trust preferred securities issued by these subsidiary trusts is included in the Tier 1 capital of the Company for regulatory capital purposes as allowed by the Federal Reserve Board (NBT Bank owns $1.0 million of CNBF Trust I securities).  The Dodd-Frank Act requires bank holding companies with assets greater than $500 million to be subject to the same capital requirements as insured depository institutions, meaning, for instance, that such bank holding companies will not be able to count trust preferred securities issued after May 19, 2010 as Tier 1 capital.  The aforementioned Trusts are grandfathered with respect to this enactment based on their date of issuance.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Taxes [Abstract]	'
Income Taxes	'
	(12) Income Taxes
	The significant components of income tax expense attributable to operations are:
		Years ended December 31,
		2013			2012			2011
	Current
	Federal	$	23,536		$	21,011		$	29,274
	State		2,316			1,815			1,477
			25,852			22,826			30,751
	Deferred
	Federal		2,334			(13	)		(8,129	)
	State		10			3			(1,349	)
			2,344			(10	)		(9,478	)
	Total income tax expense	$	28,196		$	22,816		$	21,273
	Not included in the above table are items that were recorded to stockholders’ equity of approximately $7.0 million, ($0.1 million), and ($0.5 million) for 2013, 2012, and 2011, respectively, relating to deferred taxes on the unrealized (gain) loss on available for sale securities, tax benefits recognized with respect to stock options exercised, and deferred taxes related to pension plans.
	The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities are as follows:
		December 31,
	(In thousands)	2013			2012
	Deferred tax assets
	Allowance for loan and lease losses	$	26,729		$	26,687
	Deferred compensation		7,931			5,362
	Postretirement benefit obligation		2,596			1,600
	Unrealized losses on securities available for sale		5,900			-
	Fair value adjustments from acquisitions		-			3,633
	Accrued liabilities		3,265			1,524
	Stock-based compensation expense		7,862			5,726
	Equipment leasing		1,661			-
	Other		2,125			1,933
	Total deferred tax assets		58,069			46,465
	Deferred tax liabilities
	Pension and executive retirement		17,417			7,676
	Fair value adjustments from acquisitions		2,070			-
	Unrealized gains on securities available for sale		-			10,939
	Premises and equipment, primarily due to accelerated depreciation		2,270			1,980
	Equipment leasing		-			582
	Deferred loan costs		1,624			873
	Intangible amortization		12,007			13,146
	Other		892			154
	Total deferred tax liabilities		36,280			35,350
	Net deferred tax asset at year-end		21,789			11,115
	Net deferred tax asset (liability) at beginning of year		11,115			5,953
	Increase in net deferred tax asset	$	10,674		$	5,162
	Realization of deferred tax assets is dependent upon the generation of future taxable income or the existence of sufficient taxable income within the available carryback period.  A valuation allowance is provided when it is more likely than not that some portion of the deferred tax asset will not be realized.  Based on available evidence, gross deferred tax assets will ultimately be realized and a valuation allowance was not deemed necessary at December 31, 2013 and 2012.
	A reconciliation of the beginning and ending balance of gross unrecognized tax benefits is as follows:
	(In thousands)	2013			2012			2011
	Balance at January 1	$	-		$	888		$	3,081
	Additions for tax positions of prior years		-			-			-
	Reduction for tax positions of prior years		-			(888	)		(2,193	)
	Balance at December 31	$	-		$	-		$	888
	At December 31, 2013 and 2012, the Company had no ASC 740-10 unrecognized tax benefits with $.9 million of unrecognized tax benefits at December 31, 2011.   The Company does not expect the total amount of unrecognized tax benefits to significantly increase within the next twelve months.   During 2012 and 2011 there was a reduction of reserves for Federal tax benefits for expiration of the statute of limitations of prior years’ tax filings and in 2011 the Company reached a settlement with New York State on franchise tax examinations for the years 2003 through 2007.  As a result, unrecognized tax benefits were reduced $0.9 million and $2.2 million for 2012 and 2011, respectively, with a reduction of tax expense of $0.8 million in 2012 and $1.5 million in 2011.
	The Company is no longer subject to U.S. Federal tax examination by tax authorities for years prior to 2010 and New York State for years prior to 2008.
	The Company recognizes interest accrued and penalties related to unrecognized tax benefits in income tax expense.  The total amount of accrued interest at December 31, 2011 was approximately $0.1 million.  Net interest impacting the Company’s 2011 tax expense was $0.3 million.
	The following is a reconciliation of the provision for income taxes to the amount computed by applying the applicable Federal statutory rate of 35% to income before taxes:
		Years ended December 31
	(In thousands)	2013			2012			2011
	Federal income tax at statutory rate	$	31,482		$	27,081		$	27,711
	Tax exempt income		(2,433	)		(2,536	)		(2,925	)
	Net increase in CSV of life insurance		(1,166	)		(908	)		(919	)
	Low income housing tax credits		(819	)		(629	)		(782	)
	State taxes, net of federal tax benefit		1,512			1,182			764
	State audit settlements		-			-			(681	)
	Other, net		(380	)		(1,374	)		(1,895	)
	Income tax expense	$	28,196		$	22,816		$	21,273

Employee_Benefit_Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2013
Employee Benefit Plans [Abstract]	'
Employee Benefit Plans	'
	(13) Employee Benefit Plans
	Defined Benefit Postretirement Plans
	The Company has a qualified, noncontributory, defined benefit pension plan (“the Plan”) covering substantially all of its employees at December 31, 2013. Benefits paid from the plan are based on age, years of service, compensation, social security benefits, and are determined in accordance with defined formulas. The Company’s policy is to fund the pension plan in accordance with ERISA standards. Assets of the plan are invested in publicly traded stocks and bonds. Prior to January 1, 2000, the Plan was a traditional defined benefit plan based on final average compensation.  On January 1, 2000, the Plan was converted to a cash balance plan with grandfathering provisions for existing participants.
	The Company assumed a noncontributory, defined benefit pension plan in the Alliance acquisition.  This plan covers certain Alliance full-time employees who met eligibility requirements on October 6, 2006, at which time all benefits were frozen.  Under this plan, retirement benefits are primarily a function of both the years of service and the level of compensation.  Effective May 1, 2013, this plan was merged into the Plan.  The merging of the plans required a valuation as of the merger date and resulted in a $2.4 million adjustment to accumulated other comprehensive income.  The merging of the plans did not have a significant impact on the Company’s financial statements and related footnotes.
	In addition to the Plan, the Company provides supplemental employee retirement plans to certain current and former executives.  The Company also assumed supplemental retirement plans for certain current and former executives in the Alliance acquisition.
	The supplemental employee retirement plans and the defined benefit pension plan are collectively referred to herein as “Pension Benefits.”
	Also, the Company provides certain health care benefits for retired employees.  Benefits are accrued over the employees’ active service period. Only employees that were employed by NBT Bank on or before January 1, 2000 are eligible to receive postretirement health care benefits.  The plan is contributory for participating retirees, requiring participants to absorb certain deductibles and coinsurance amounts with contributions adjusted annually to reflect cost sharing provisions and benefit limitations called for in the plan. Employees become eligible for these benefits if they reach normal retirement age while working for the Company.  For eligible employees described above, the Company funds the cost of postretirement health care as benefits are paid. The Company elected to recognize the transition obligation on a delayed basis over twenty years.  In addition, the Company assumed post-retirement medical life insurance benefits for certain Alliance employees, retirees and their spouses, if applicable, in the Alliance acquisition.  These postretirement benefits are referred to herein as “Other Benefits.”
	Accounting standards require an employer to: (1) recognize the overfunded or underfunded status of defined benefit postretirement plans, which is measured as the difference between plan assets at fair value and the benefit obligation, as an asset or liability in its balance sheet; (2) recognize changes in that funded status in the year in which the changes occur through comprehensive income; and (3) measure the defined benefit plan assets and obligations as of the date of its year-end balance sheet.
	The components of accumulated other comprehensive loss, which have not yet been recognized as components of net periodic benefit cost, related to pensions and other postretirement benefits at December 31, 2013 are summarized below.  The Company expects that $0.3 million in net actuarial loss and $0.2 million in prior service costs will be recognized as components of net periodic benefit cost in 2014.
		Pension Benefits						Other Benefits
	(In thousands)	2013			2012			2013			2012
	Net actuarial loss	$	11,286		$	35,478		$	1,628		$	2,277
	Prior service cost		118			141			(521	)		(672	)
	Total amounts recognized in accumulated other comprehensive loss (pre-tax)	$	11,404		$	35,619		$	1,107		$	1,605
	A December 31 measurement date is used for the pension, supplemental pension and postretirement benefit plans.  The following table sets forth changes in benefit obligations, changes in plan assets, and the funded status of the pension plans and other postretirement benefits:
		Pension Benefits						Other Benefits
	(In thousands)	2013			2012			2013			2012
	Change in benefit obligation
	Benefit obligation at beginning of year	$	85,129		$	78,024		$	4,071		$	3,985
	Service cost		2,493			3,122			23			20
	Interest cost		3,223			3,145			286			155
	Plan participants' contributions		-			-			269			233
	Actuarial(gain) loss		(10,853	)		5,941			(369	)		136
	Amendments		-			(1,006	)		(54	)		-
	Acquisition		10,958			-			3,928			-
	Benefits paid		(5,283	)		(4,097	)		(726	)		(458	)
	Projected benefit obligation at end of year		85,667			85,129			7,428			4,071
	Change in plan assets
	Fair value of plan assets at beginning of year		99,704			91,575			-			-
	Actual return on plan assets		18,451			11,733			-			-
	Acquisition		4,994			-			-			-
	Employer contributions		708			493			457			225
	Plan participants' contributions		-			-			269			233
	Benefits paid		(5,283	)		(4,097	)		(726	)		(458	)
	Fair value of plan assets at end of year		118,574			99,704			-			-
	Funded status at year end	$	32,907		$	14,575		$	(7,428	)	$	(4,071	)
	Effective March 1, 2013, the pension plan was amended.  Benefit accruals for participants who, as of January 1, 2000, elected to continue participating in the traditional defined benefit plan design were frozen as of March 1, 2013.  This amendment resulted in a reduction to the projected benefit obligation as of December 31, 2012 as noted in the table above.
	The funded status of the pension and other postretirement benefit plans has been recognized as follows in the consolidated balance sheets at December 31, 2013 and 2012.  An asset is recognized for an overfunded plan and a liability is recognized for an underfunded plan.  The accumulated benefit obligation for pension benefits was $85.7 million and $85.1 million at December 31, 2013 and 2012, respectively.  The accumulated benefit obligation for other postretirement benefits was $7.4 million and $4.1 million at December 31, 2013 and 2012, respectively.
		Pension Benefits						Other Benefits
	(In thousands)	2013			2012			2013			2012
	Other assets	$	48,189		$	27,062		$	-		$	-
	Other liabilities		(15,282	)		(12,487	)		(7,428	)		(4,071	)
	Funded status	$	32,907		$	14,575		$	(7,428	)	$	(4,071	)
	The following assumptions were used to determine the benefit obligation and the net periodic pension cost for the years indicated:
		Years ended December 31,
		2013			2012			2011
	Weighted average assumptions:
	The following assumptions were used to determine benefit obligations:
	Discount rate		4.90% - 5.05	%		3.5	%		4.1	%
	Expected long-term return on plan assets		7.5	%		7.5	%		7.5	%
	Rate of compensation increase		3	%		3	%		3	%
	The following assumptions were used to determine net periodic pension cost:
	Discount rate		3.5	%		4.1	%		5.15	%
	Expected long-term return on plan assets		7.5	%		7.5	%		8	%
	Rate of compensation increase		3	%		3	%		3	%
	Net periodic benefit cost and other amounts recognized in other comprehensive income (loss) for the years ended December 31 included the following components:
		Pension Benefits									Other Benefits
	(In thousands)	2013			2012			2011			2013			2012			2011
	Components of net periodic benefit cost
	Service cost	$	2,493		$	3,122		$	2,589		$	23		$	20		$	17
	Interest cost		3,223			3,145			3,544			286			155			202
	Expected return on plan assets		(7,804	)		(6,686	)		(7,720	)		-			-			-
	Amortization of prior service cost		23			283			309			(205	)		(202	)		(202	)
Amortization of unrecognized net loss		2,692			3,330			1,353			280			182			205
Net periodic pension cost	$	627		$	3,194		$	75		$	384		$	155		$	222
Other changes in plan assets and benefit obligations recognized in other comprehensive income (pre-tax)
Net loss (gain)	$	(21,500	)	$	894		$	16,108		$	(369	)	$	136		$	(562	)
Prior service cost		-			(1,006	)		-			(54	)		-			-
Amortization of prior service cost		(23	)		(283	)		(309	)		205			202			202
Amortization of unrecognized net gain		(2,692	)		(3,330	)		(1,353	)		(280	)		(182	)		(205	)
Total recognized in other comprehensive loss (income)		(24,215	)		(3,725	)		14,446			(498	)		156			(565	)
Total recognized in net periodic benefit cost and other comprehensive income (loss) - pre-tax	$	(23,588	)	$	(531	)	$	14,521		$	(114	)	$	311		$	(343	)
The following table sets forth estimated future benefit payments for the pension plans and other postretirement benefit plans:
	Pension			Other
	Benefits			Benefits
2014		5,950			555
2015		6,090			565
2016		6,143			560
2017		9,199			576
2018		6,899			590
2019 - 2023		34,827			2,771
The Company is not required to make contributions to the defined benefit plan in 2014.
For measurement purposes, the annual rates of increase in the per capita cost of covered medical and prescription drug benefits for fiscal year 2013 were assumed to be 5.9 to 8.5 percent. The rates were assumed to decrease gradually to 5.0 percent for fiscal year 2021 and remain at that level thereafter.  Assumed health care cost trend rates have a significant effect on amounts reported for health care plans. A one-percentage point change in the health care trend rates would have the following effects as of and for the year ended December 31, 2014:
(In thousands)	One Percentage point increase			One Percentage point decrease
Increase (decrease) on total service and interest cost components	$	37		$	(27	)
Increase (decrease) on postretirement accumulated benefit obligation		768			(567	)
Plan Investment Policy
The Company’s key investment objectives in managing its defined benefit plan assets are to ensure that present and future benefit obligations to all participants and beneficiaries are met as they become due; to provide a total return that, over the long-term, maximizes the ratio of the plan assets to liabilities, while minimizing the present value of required Company contributions, at the appropriate levels of risk; to meet statutory requirements and regulatory agencies’ requirements; and to satisfy applicable accounting standards.  The Company periodically evaluates the asset allocations, funded status, rate of return assumption and contribution strategy for satisfaction of our investment objectives.  The target and actual allocations expressed as a percentage of the defined benefit pension plan’s assets are as follows:
	Target 2013			2013			2012
Cash and cash equivalents		0 - 20	%		6	%		5	%
Fixed income securities		20 - 40	%		27	%		29	%
Equities		40 - 80	%		67	%		66	%
Total					100	%		100	%
Only high-quality bonds are to be included in the portfolio.  All issues that are rated lower than A by Standard and Poor’s are to be excluded.  Equity securities at December 31, 2013 and 2012 do not include any Company common stock.  The following table presents the financial instruments recorded at fair value on a recurring basis by the Plan as of December 31, 2013 and 2012:
	Quoted Prices in			Significant
	Active Markets for			Other			Balance
	Identical Assets			Observable Inputs			as of
	(Level 1)			(Level 2)			31-Dec-13
Cash and cash equivalents	$	7,533		$	-		$	7,533
Foreign equity mutual funds		15,653			-			15,653
Equity mutual funds		16,727			-			16,727
US government bonds		-			9,355			9,355
Corporate bonds		-			19,665			19,665
Common stock		44,532			-			44,532
Municipal bonds and notes		-			1,451			1,451
Foreign bonds and notes		-			1,392			1,392
Foreign equity		2,266			-			2,266
Totals	$	86,711		$	31,863		$	118,574
	Quoted Prices in			Significant
	Active Markets for			Other			Balance
	Identical Assets			Observable Inputs			as of
	(Level 1)			(Level 2)			31-Dec-12
Cash and cash equivalents	$	5,464		$	-		$	5,464
Foreign equity mutual funds		9,763			-			9,763
Equity mutual funds		13,110			-			13,110
US government bonds		-			12,744			12,744
Corporate bonds		-			13,604			13,604
Common stock		40,430			-			40,430
Municipal bonds and notes		-			1,805			1,805
Foreign bonds and notes		-			1,137			1,137
Foreign equity		1,647			-			1,647
Totals	$	70,414		$	29,290		$	99,704
The plan had no financial instruments recorded at fair value on a nonrecurring basis as of December 31, 2013.
Determination of Assumed Rate of Return
The expected long-term rate-of-return on assets is 7.5% at December 31, 2013.  This assumption represents the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the projected benefit obligation.  The assumption has been determined by reflecting expectations regarding future rates of return for the portfolio considering the asset distribution and related historical rates of return.  The appropriateness of the assumption is reviewed annually.
Employee 401(k) and Employee Stock Ownership Plans
The Company maintains a 401(k) and employee stock ownership plan (the “401(k) Plan”).  The Company contributes to the 401(k) Plan based on employees’ contributions out of their annual salaries.  In addition, the Company may also make discretionary contributions to the 401(k) Plan based on profitability.  Participation in the 401(k) Plan is contingent upon certain age and service requirements.  The employer contributions associated with the 401(k) Plan were $2.1 million in 2013, $1.8 million in 2012, and $3.7 million in 2011.

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2013
Stock-Based Compensation [Abstract]	'
Stock-Based Compensation	'
	(14) Stock-Based Compensation
	In April 2008, the Company adopted the NBT Bancorp Inc. 2008 Omnibus Incentive Plan (the “Plan”). Under the terms of the Plan, options and other equity-based awards are granted to directors and employees to increase their direct proprietary interest in the operations and success of the Company.  The Plan assumed all prior equity-based incentive plans and any new equity-based awards are granted under the terms of the Plan.  Under terms of the Plan, stock options are granted to purchase shares of the Company’s common stock at a price equal to the fair market value of the common stock on the date of the grant. Options granted have a vesting period of four years and terminate ten years from the date of the grant.  Shares issued as a result of stock option exercises and vesting of restricted shares and stock unit awards are funded from the Company’s treasury stock.  Restricted shares granted under the Plan vest after five years for employees and three years for non-employee directors.  Restricted stock units granted under the Plan may have different terms and conditions.  Performance shares and units granted under the Plan for executives may have different terms and conditions.
	The per share weighted average fair value of stock options granted during 2013, 2012, and 2011 was $7.09, $4.57, and $5.45, respectively. The fair value of each award is estimated on the grant date using the Black-Scholes option pricing model with the following weighted average assumptions used for grants in the years ended December 31.  Historical information was the primary basis for the selection of the expected volatility, expected dividend yield and the expected lives of the options. The risk-free interest rate was selected based upon yields of the U.S. Treasury issues with a term equal to the expected life of the option being valued:
		Years ended December 31,
		2013			2012			2011
	Dividend yield		3.2	%		3.94	%		3.31%–3.82	%
	Expected volatility		34.6	%		34.64	%		33.75%–34.36	%
	Risk-free interest rates		2.43	%		1.24	%		1.48%–2.81	%
	Expected life	7 years			7 years			7 years
	The following table summarizes information concerning stock options outstanding at December 31, 2013:
		Number of Shares			Weighted average exercise price			Weighted Average Remaining Contractual Term (in yrs)			Aggregate Intrinsic Value
	Outstanding at January 1, 2013		1,695,562		$	22.72
	Granted		120			26.29
	Exercised		(335,103	)		21.77
	Forfeited		(495	)		20.19
	Expired		(18,584	)		21.58
	Outstanding at December 31, 2013		1,341,500		$	22.98			3.89		$	3,996,816
	Exercisable at December 31, 2013		1,279,560		$	23.08			3.78		$	3,683,178
	Expected to Vest		61,044		$	20.8			5.54		$	311,352
	Total stock-based compensation expense for stock option awards totaled $0.2 million, $0.5 million, and $0.9 million for the years ended December 31, 2013, 2012, and 2011, respectively.  Cash proceeds, tax benefits and intrinsic value related to total stock options exercised is as follows:
		Years ended
	(dollars in thousands)	2013			2012			2011
	Proceeds from stock options exercised	$	7,927		$	1,908		$	2,255
	Tax benefits related to stock options exercised		178			8			341
	Intrinsic value of stock options exercised		905			498			897
	Fair value of shares vested during the year		766			1,656			1,597
	The Company has outstanding restricted and deferred stock awards granted from various plans at December 31, 2013. The Company recognized $3.8 million, $3.7 million, and $3.2 million in stock-based compensation expense related to these stock awards for the years ended December 31, 2013, 2012, and 2011, respectively.  Tax benefits recognized with respect to restricted stock awards and stock units were $1.5 million, $1.5 million and $1.2 million for the years ended December 31, 2013, 2012 and 2011, respectively.  Unrecognized compensation cost related to restricted stock awards and stock units totaled $4.6 million at December 31, 2013 and will be recognized over 2.1 years on a weighted average basis.  Shares issued are funded from the Company’s treasury stock.  The following table summarizes information for unvested restricted stock awards outstanding as of December 31, 2013:
		Number			Weighted-
					Average
		of			Grant Date Fair
		Shares			Value
	Unvested Restricted Stock Awards
	Unvested at January 1, 2013		117,150		$	24.37
	Forfeited		(2,033	)		23.25
	Vested		(48,467	)		26.1
	Unvested at December 31, 2013		66,650		$	23.15
	The following table summarizes information for unvested restricted stock units outstanding as of December 31, 2013:
		Number			Weighted-
					Average
		of			Grant Date Fair
		Shares			Value
	Unvested Restricted Stock Units
	Unvested at January 1, 2013		406,058		$	25.64
	Forfeited		(6,467	)		-
	Vested		(69,333	)		-
	Granted		209,592			20.81
	Unvested at December 31, 2013		539,850		$	27.36
	The Company has 4.1 million securities remaining available to be granted as part of the Plan at December 31, 2013.

Stockholders_Equity

Stockholders Equity	12 Months Ended
	Dec. 31, 2013
Stockholders Equity [Abstract]	'
Stockholders Equity	'
	(15)  Stockholders’ Equity
	In accordance with accounting standards, unrealized gains on available for sale securities and unrecognized actuarial gains or losses and prior service costs associated with the Company’s pension and postretirement benefit plans are included in accumulated other comprehensive loss.  For the years ended December 31, components of accumulated other comprehensive loss are:
	(In thousands)	2013			2012
	Unrecognized prior service cost and net actuarial loss on pension plans	$	(7,785	)	$	(22,555	)
	Unrealized net holding (losses) gains on available for sale securities		(8,980	)		16,675
	Accumulated other comprehensive loss	$	(16,765	)	$	(5,880	)
	Certain restrictions exist regarding the ability of the subsidiary bank to transfer funds to the Company in the form of cash dividends. The approval of the Office of Comptroller of the Currency (“OCC”) is required to pay dividends when a bank fails to meet certain minimum regulatory capital standards or when such dividends are in excess of a subsidiary bank’s earnings retained in the current year plus retained net profits for the preceding two years as specified in applicable OCC regulations.  At December 31, 2013, approximately $56.7 million of the total stockholders’ equity of the Bank was available for payment of dividends to the Company without approval by the OCC. The Bank’s ability to pay dividends also is subject to the Bank being in compliance with regulatory capital requirements.  The Bank is currently in compliance with these requirements. Under the State of Delaware General Corporation Law, the Company may declare and pay dividends either out of accumulated net retained earnings or capital surplus.
	In October 2004, the Company adopted a Stockholder Rights Plan (the “Plan”) designed to ensure that any potential acquirer of the Company negotiate with the board of directors and that all Company stockholders are treated equitably in the event of a takeover attempt. At that time, the Company paid a dividend of one Preferred Share Purchase Right (a “Right”) for each outstanding share of common stock of the Company. Similar rights are attached to each share of the Company’s common stock issued after November 16, 2004. Under the Plan, the Rights will not be exercisable until a person or group acquires beneficial ownership of 15% or more of the Company’s outstanding common stock or begins a tender or exchange offer for 15% or more of the Company’s outstanding common stock. Additionally, until the occurrence of such an event, the Rights are not severable from the Company’s common stock and, therefore, the Rights will be transferred upon the transfer of shares of the Company’s common stock. Upon the occurrence of such events, each Right entitles the holder to purchase one one-hundredth of a share of Series A Junior Participating Preferred Stock of the Company, no par value and $0.01 stated value per share, at a price of $70.
	The Plan also provides that upon the occurrence of certain specified events, the holders of Rights will be entitled to acquire additional equity interests in the Company or in the acquiring entity and such interests will have a market value of two times the Right’s exercise price of $70. The Rights, which expire October 24, 2014, are redeemable in whole, but not in part, at the Company’s option prior to the time they are exercisable, for a price of $0.001 per Right.
	Under a previously disclosed stock repurchase plan, the Company purchased 584,925 shares of its common stock during the twelve month period ended December 31, 2013, for a total of $12.5 million at an average price of $21.30 per share.  This plan expired on December 31, 2013.  On July 22, 2013, the NBT Board of Directors authorized a new repurchase program for NBT to repurchase up to an additional 1,000,000 shares of its outstanding common stock.  This plan expires on December 31, 2014.

Regulatory_Capital_Requirement

Regulatory Capital Requirements	12 Months Ended
	Dec. 31, 2013
Regulatory Capital Requirements [Abstract]	'
Regulatory Capital Requirements	'
	(16)  Regulatory Capital Requirements
	The Company and NBT Bank are subject to various regulatory capital requirements administered by the federal banking agencies.  Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the consolidated financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, NBT Bank must meet specific capital guidelines that involve quantitative measures of NBT Bank’s assets, liabilities, and certain off-balance sheet items as calculated under regulatory accounting practices. The capital amounts and classifications are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors.
	Quantitative measures established by regulation to ensure capital adequacy require the Company and NBT Bank to maintain minimum amounts and ratios (set forth in the table below) of total and Tier 1 Capital to risk-weighted assets and of Tier 1 capital to average assets. As of December 31, 2013 and 2012, the Company and NBT Bank meet all capital adequacy requirements to which they were subject.
	Under their prompt corrective action regulations, regulatory authorities are required to take certain supervisory actions (and may take additional discretionary actions) with respect to an undercapitalized institution. Such actions could have a direct material effect on an institution’s financial statements.  The regulations establish a framework for the classification of banks into five categories:  well capitalized, adequately capitalized, under capitalized, significantly under capitalized, and critically under capitalized.  As of December 31, 2013, the most recent notification from NBT Bank’s regulators categorized NBT Bank as well capitalized under the regulatory framework for prompt corrective action.  To be categorized as well capitalized NBT Bank must maintain minimum total risk-based, Tier 1 risk-based, and Tier 1 capital to average asset ratios as set forth in the table below. There are no conditions or events since that notification that management believes have changed NBT Bank’s category.
	The Company and NBT Bank’s actual capital amounts and ratios are presented as follows:
		Actual					Regulatory ratio requirements
	(Dollars in thousands)	Amount		Ratio			Minimum			For classification
							capital adequacy			as well capitalized
	As of December 31, 2013
	Total Capital (to risk weighted assets):
	Company	$	723,580		12.99	%		8	%		10	%
	NBT Bank		686,194		12.41	%		8	%		10	%
	Tier I Capital (to risk weighted assets)
	Company		653,950		11.74	%		4	%		6	%
	NBT Bank		617,038		11.16	%		4	%		6	%
	Tier I Capital (to average assets)
	Company		653,950		8.93	%		4	%		5	%
	NBT Bank		617,038		8.47	%		4	%		5	%
	As of December 31, 2012
	Total Capital (to risk weighted assets):
	Company	$	560,745		12.25	%		8	%		10	%
	NBT Bank		505,027		11.08	%		8	%		10	%
	Tier I Capital (to risk weighted assets)
	Company		503,359		11	%		4	%		6	%
	NBT Bank		447,909		9.83	%		4	%		6	%
	Tier I Capital (to average assets)
	Company		503,359		8.54	%		4	%		5	%
	NBT Bank		447,909		7.62	%		4	%		5	%

Earnings_Per_Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2013
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	(17) Earnings Per Share
	The following is a reconciliation of basic and diluted earnings per share for the years presented in the consolidated statements of income:
		Years ended December 31,
		2013						2012						2011
				Weighted						Weighted						Weighted
		Net		average		Per share		Net		average		Per share		Net		average		Per share
	(In thousands, except per share data)	income		shares		amount		income		shares		amount		income		shares		amount
	Basic earnings per share	$	61,747		41,930	$	1.47	$	54,558		33,379	$	1.63	$	57,901		33,662	$	1.72
	Effect of dilutive securities
	Stock based compensation				420						340						262
	Diluted earnings per share	$	61,747		42,350	$	1.46	$	54,558		33,719	$	1.62	$	57,901		33,924	$	1.71
	There were approximately 1.0 million, 1.2 million, and 1.3 million weighted average stock options for the years ended December 31, 2013, 2012, and 2011, respectively, that were not considered in the calculation of diluted earnings per share since the stock options’ exercise prices were greater than the average market price during  these  periods.

Reclassification_Adjustments_O

Reclassification Adjustments Out of Other Comprehensive (Loss) Income	12 Months Ended
	Dec. 31, 2013
Reclassification Adjustments Out of Other Comprehensive Loss income [Abstract]	'
Reclassification Adjustments Out of Other Comprehensive (Loss) Income	'
	(18) Reclassification Adjustments Out of Other Comprehensive (Loss) Income
	The following table summarizes the reclassification adjustments out of accumulated other comprehensive loss (in thousands):
	Detail About Accumulated Other Comprehensive (Loss)	Amount reclassified from accumulated other comprehensive income (loss)						Affected line item in the consolidated statement of comprehensive income
	Income Components
		Years ended
		31-Dec-13			31-Dec-12
	Available for sale securities:
	Gains on available for sale securities	$	(1,426	)	$	(599	)	Net securities gains
	Tax benefit		565			237		Income tax expense
	Net of tax	$	(861	)	$	(362	)
	Pension and other benefits:
	Amortization of net gains	$	2,972		$	3,512		Salaries and employee benefits
	Amortization of prior service costs		(182	)		81		Salaries and employee benefits
	Tax expense		1,189			1,419		Income tax expense
	Net of tax	$	1,601		$	2,174
	Total reclassifications during the period, net of tax	$	740		$	1,812

Commitments_and_Contingent_Lia

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2013
Commitments and Contingent Liabilities [Abstract]	'
Commitments and Contingent Liabilities	'
	(19) Commitments and Contingent Liabilities
	The Company’s concentrations of credit risk are reflected in the consolidated balance sheets.  The concentrations of credit risk with standby letters of credit, unused lines of credit, commitments to originate new loans and loans sold with recourse generally follow the loan classifications.
	At December 31, 2013, approximately 59% of the Company’s loans were secured by real estate located in central and upstate New York, northeastern Pennsylvania, western Massachusetts, southern New Hampshire, and the greater Burlington, Vermont area.  Accordingly, the ultimate collectability of a substantial portion of the Company’s portfolio is susceptible to changes in market conditions of those areas. Management is not aware of any material concentrations of credit to any industry or individual borrowers.
	The Company is a party to certain financial instruments with off balance sheet risk in the normal course of business to meet the financing needs of its customers.  These financial instruments include commitments to extend credit, unused lines of credit, standby letters of credit, and certain mortgage loans sold to investors with recourse. The Company’s exposure to credit loss in the event of nonperformance by the other party to the commitments to extend credit, unused lines of credit, standby letters of credit, and loans sold with recourse is represented by the contractual amount of those instruments. The credit risk associated with commitments to extend credit and standby and commercial letters of credit is essentially the same as that involved with extending loans to customers and is subject to normal credit policies.  Collateral may be obtained based on management’s assessment of the customer’s creditworthiness.
		At December 31,
	(In thousands)	2013		2012
	Unused lines of credit	$	216,658	$	163,626
	Commitments to extend credits, primarily variable rate		849,092		678,093
	Standby letters of credit		36,837		37,510
	Commercial letters of credit		41,263		16,607
	Loans sold with recourse		15,741		13,690
	Since many loan commitments, standby letters of credit, and guarantees and indemnification contracts expire without being funded in whole or in part, the contract amounts are not necessarily indicative of future cash flows.  The Company does not issue any guarantees that would require liability-recognition or disclosure, other than its standby letters of credit.
	The Company guarantees the obligations or performance of customers by issuing stand-by letters of credit to third parties. These stand-by letters of credit are frequently issued in support of third party debt, such as corporate debt issuances, industrial revenue bonds, and municipal securities. The risk involved in issuing stand-by letters of credit is essentially the same as the credit risk involved in extending loan facilities to customers, and letters of credit are subject to the same credit origination, portfolio maintenance and management procedures in effect to monitor other credit and off-balance sheet products.  Typically, these instruments have terms of five years or less and expire unused; therefore, the total amounts do not necessarily represent future cash requirements.  The fair value of the Company’s stand-by letters of credit at December 31, 2013 and 2012 was not significant.
	The total amount of loans serviced by the Company for unrelated third parties was approximately $554.4 million and $309.2 million at December 31, 2013 and 2012, respectively.  At December 31, 2013 and 2012, the Company had approximately $2.2 million and $1.2 million, respectively, of mortgage servicing rights.
	In the normal course of business there are various outstanding legal proceedings. If legal costs are deemed material by management, the Company accrues for the estimated loss from a loss contingency if the information available indicates that it is probable that a liability had been incurred at the date of the financial statements, and the amount of loss can be reasonably estimated.  The Company is a defendant to a class action lawsuit related to a previously disclosed class action lawsuit arising from its assessment and collection of fees on its checking account customers.  As of December 31, 2013, the Company has accrued for the full amount of a preliminarily approved settlement, which if and when finally approved would entirely dispose of the action.  A hearing with respect to such approval has been scheduled for June 27, 2014.  In the opinion of management, the aggregate amount involved in such proceedings at December 31, 2013 is not material to the consolidated balance sheets or results of operations of the Company.
	The Company is required to maintain reserve balances with the Federal Reserve Bank of New York. The required average total reserve for NBT Bank for the 14-day maintenance period ending December 25, 2013 was $48.7 million.

Fair_Values_of_Financial_Instr

Fair Values of Financial Instruments	12 Months Ended
	Dec. 31, 2013
Fair Values of Financial Instruments [Abstract]	'
Fair Values of Financial Instruments	'
	(20) Fair Values of Financial Instruments
	The following table sets forth information with regard to estimated fair values of financial instruments at December 31, 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.
				31-Dec-13				31-Dec-12
	(In thousands)	Fair Value Hierarchy		Carrying amount		Estimated fair value		Carrying amount		Estimated fair value
	Financial assets
	Securities held to maturity		2	$	117,283	$	113,276	$	60,563	$	61,535
	Net loans		3		5,337,361		5,386,520		4,208,282		4,313,244
	Financial liabilities
	Time deposits		2	$	1,021,142	$	1,023,982	$	983,261	$	994,376
	Long-term debt		2		308,823		325,195		367,492		407,404
	Junior subordinated debt		2		101,196		105,121		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.
	The following table sets forth the Company’s financial assets and liabilities measured on a recurring basis that were accounted for at fair value as of December 31, 2013 and December 31, 2012.  Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement (in thousands):
		Quoted Prices in		Significant		Significant
		Active Markets for		Other		Unobservable		Balance
		Identical Assets		Observable Inputs		Inputs		as of
		(Level 1)		(Level 2)		(Level 3)		31-Dec-13
	Assets:
	Securities Available for Sale:
	U.S. Treasury	$	43,616	$	-	$	-	$	43,616
	Federal Agency		-		278,915		-		278,915
	State & municipal		-		113,665		-		113,665
	Mortgage-backed		-		364,164		-		364,164
	Collateralized mortgage obligations		-		549,528		-		549,528
	Other securities		6,796		8,197		-		14,993
	Total Securities Available for Sale	$	50,412	$	1,314,750	$	-	$	1,364,881
	Trading Securities		5,779		-		-		5,779
	Interest Rate Swaps		-		281		-		281
	Total	$	56,191	$	1,314,750	$	-	$	1,370,941
	Liabilities:
	Interest Rate Swaps	$	-	$	281	$	-	$	281
	Total	$	-	$	281	$	-	$	281
		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		8,672		5,282		-		13,954
	Total Securities Available for Sale	$	73,097	$	1,074,902	$	-	$	1,147,999
	Trading Securities		3,918		-		-		3,918
	Interest Rate Swaps		-		1,490		-		1,490
	Total	$	77,015	$	1,076,392	$	-	$	1,153,407
	Liabilities:
	Interest Rate Swaps	$	-	$	1,490	$	-	$	1,490
	Total	$	-	$	1,490	$	-	$	1,490
	Fair values for securities are based on quoted market prices or dealer quotes, where available.  Where quoted market prices are not available, fair values are based on quoted market prices of comparable instruments.  When necessary, the Company utilizes matrix pricing from a third party pricing vendor to determine fair value pricing.  Matrix prices are based on quoted prices for securities with similar coupons, ratings, and maturities, rather than on specific bids and offers for the designated security.
FASB ASC Topic 820 requires disclosure of assets and liabilities measured and recorded at fair value on a nonrecurring basis.  In accordance with the provisions of FASB ASC Topic 310, the Company had collateral dependent impaired loans with a carrying value of approximately $5.0 million which had specific reserves included in the allowance for loan losses of $0.7 million at December 31, 2013.  The Company uses the fair value of underlying collateral to estimate the specific reserves for collateral dependent impaired loans.  The fair value of underlying collateral is generally determined through independent appraisals, which generally include various Level 3 inputs which are not identifiable. The appraisals may be adjusted by management for qualitative factors such as economic conditions and estimated liquidation expenses ranging from 10% to 35%.  Based on the valuation techniques used, the fair value measurements for collateral dependent impaired loans are classified as Level 3.
FASB ASC Topic 825 gives entities the option to measure eligible financial assets, financial liabilities and Company commitments at fair value (i.e., the fair value option), on an instrument-by-instrument basis, that are otherwise not permitted to be accounted for at fair value under other accounting standards.  The election to use the fair value option is available when an entity first recognizes a financial asset or financial liability or upon entering into a Company commitment.  Subsequent changes in fair value must be recorded in earnings.  As of December 31, 2013 and 2012, the Company did not elect the fair value option for any eligible items.

Parent_Company_Financial_Infor

Parent Company Financial Information	12 Months Ended
	Dec. 31, 2013
Parent Company Financial Information [Abstract]	'
Parent Company Financial Information	'
	(21)  Parent Company Financial Information
	Condensed Balance Sheets
		December 31,
	(In thousands)	2013			2012
	Assets
	Cash and cash equivalents	$	3,741		$	23,095
	Securities available for sale, at estimated fair value		11,008			12,866
	Trading securities		4,742			3,371
	Investment in subsidiaries, on equity basis		896,479			635,851
	Other assets		49,530			48,324
	Total assets	$	965,500		$	723,507
	Liabilities and Stockholders’ Equity
	Total liabilities	$	148,931		$	141,234
	Stockholders’ equity		816,569			582,273
	Total liabilities and stockholders’ equity	$	965,500		$	723,507
	Condensed Income Statements
		Years ended December 31,
	(In thousands)	2013			2012			2011
	Dividends from subsidiaries	$	13,500		$	79,175		$	54,400
	Management fee from subsidiaries		84,778			78,665			69,430
	Securities gains (losses)		1,273			442			(31	)
	Interest, dividend and other income		636			720			628
	Total revenue		100,187			159,002			124,427
	Operating expense		83,675			79,015			75,254
	Income before income tax benefit and equity in undistributed income of subsidiaries		16,512			79,987			49,173
	Income tax (expense) benefit		(1,046	)		(284	)		1,340
	Dividends in excess of income (equity in undistributed income) of subsidiaries		46,285			(25,145	)		7,388
	Net income	$	61,751		$	54,558		$	57,901
	Statements of Cash Flow
		Years ended December 31,
	(In thousands)	2013			2012			2011
	Operating activities
	Net income	$	61,751		$	54,558		$	57,901
	Adjustments to reconcile net income to net cash provided by operating activities
	Stock-based compensation		4,305			4,364			3,244
	Gain on sales of available-for-sale securities		1,273			442			31
	Equity in undistributed income of subsidiaries		(59,785	)		(54,030	)		(61,788	)
	Cash dividend from subsidiaries		13,500			79,175			54,400
	Net change in other liabilities		(18,077	)		(3,181	)		15,311
	Net change in other assets		14,924			2,030			(11,607	)
	Net cash provided by operating activities		17,891			83,358			57,492
	Investing activities
	Purchases of available-for-sale securities		-			(4,163	)		(968	)
	Sales and maturities of available-for-sale securities		1,948			1,445			71
	Net cash provided by (used in) acquisitions		2,232			(14,612	)		-
	Purchases of premises and equipment		(782	)		(1,240	)		(1,656	)
	Net cash provided by (used in) investing activities		3,398			(18,570	)		(2,553	)
	Financing activities
	Proceeds from the issuance of shares to employee benefit plans and other stock plans		5,512			1,387			1,386
	Payments on long-term debt		-			(3,340	)		(140	)
	Purchases of treasury shares		(12,459	)		(15,490	)		(30,502	)
	Cash dividends and payments for fractional shares		(33,518	)		(26,712	)		(27,063	)
	Excess tax benefit from exercise of stock options		(178	)		8			341
	Net cash used in financing activities		(40,643	)		(44,147	)		(55,978	)
	Net (decrease )increase in cash and cash equivalents		(19,354	)		20,641			(1,039	)
	Cash and cash equivalents at beginning of year		23,095			2,454			3,493
	Cash and cash equivalents at end of year	$	3,741		$	23,095		$	2,454
	A statement of changes in stockholders’ equity has not been presented since it is the same as the consolidated statement of changes in stockholders’ equity previously presented.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
Summary of Significant Accounting Policies [Abstract]	'
Consolidation	'
	Consolidation
	The accompanying consolidated financial statements include the accounts of NBT Bancorp and its wholly owned subsidiaries mentioned above.  All material intercompany transactions have been eliminated in consolidation. Amounts previously reported in the consolidated financial statements are reclassified whenever necessary to conform to the current year’s presentation. In the “Parent Company Financial Information,” the investment in subsidiaries is recorded using the equity method of accounting.
	The Company determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting interest entity or a variable interest entity under GAAP. Voting interest entities are entities in which the total equity investment at risk is sufficient to enable the entity to finance itself independently and provides the equity holders with the obligation to absorb losses, the right to receive residual returns and the right to make decisions about the entity’s activities. The Company consolidates voting interest entities in which it has all, or at least a majority of, the voting interest. As defined in applicable accounting standards, variable interest entities (“VIEs”) are entities that lack one or more of the characteristics of a voting interest entity. A controlling financial interest in a VIE is present when the Company has both the power and ability to direct the activities of the VIE that most significantly impact the VIE's economic performance and an obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. The Company’s wholly owned subsidiaries CNBF Capital Trust I, NBT Statutory Trust I, NBT Statutory Trust II, Alliance Financial Capital Trust I and Alliance Financial Capital Trust II are VIEs for which the Company is not the primary beneficiary. Accordingly, the accounts of these entities are not included in the Company’s consolidated financial statements.
Segment Report	'
	Segment Report
	The Company’s operations are primarily in the community banking industry and include the provision of traditional banking services.  The Company also provides other services through its subsidiaries such as insurance, retirement plan administration, and trust administration. The Company operates solely in the geographical regions of central and upstate New York, northeastern Pennsylvania, western Massachusetts, southern New Hampshire and Burlington, Vermont.  The Company has no reportable operating segments.
Cash Equivalents	'
	Cash Equivalents
	The Company considers amounts due from correspondent banks, cash items in process of collection, and institutional money market mutual funds to be cash equivalents for purposes of the consolidated statements of cash flows.
Securities	'
	Securities
	The Company classifies its securities at date of purchase as either available for sale, held to maturity or trading.  Held to maturity debt securities are those that the Company has the ability and intent to hold until maturity.  Available for sale securities are recorded at fair value. Unrealized holding gains and losses, net of the related tax effect, on available for sale securities are excluded from earnings and are reported in stockholders’ equity and the statement of comprehensive income as a component of accumulated other comprehensive income or loss. Held to maturity securities are recorded at amortized cost. Trading securities are recorded at fair value, with net unrealized gains and losses recognized in income.  Transfers of securities between categories are recorded at fair value at the date of transfer. Declines in the fair value of held-to-maturity and available-for-sale securities below their cost that are deemed to be other than temporary are reflected in earnings as realized losses or in other comprehensive income, depending on whether the Company intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss.  If the Company intends to sell the security or more likely than not will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the other-than-temporary impairment shall be recognized in earnings equal to the entire difference between the investment’s amortized cost basis and its fair value at the balance sheet date.  If the Company does not intend to sell the security and it is not more likely than not that the entity will be required to sell the security before recovery of its amortized cost basis less any current-period credit loss, the other-than-temporary impairment shall be separated into (a) the amount representing the credit loss and (b) the amount related to all other factors.  The amount of the total other-than-temporary impairment related to the credit loss shall be recognized in earnings. The amount of the total other-than-temporary impairment related to other factors shall be recognized in other comprehensive income, net of applicable taxes.
	In estimating other-than-temporary impairment losses, management considers, among other things, (i) the length of time and the extent to which the fair value has been less than cost, (ii) the financial condition and near-term prospects of the issuer, and (iii) the historical and implied volatility of the fair value of the security.
	Non-marketable equity securities are carried at cost.
	Premiums and discounts are amortized or accreted over the life of the related security as an adjustment to yield using the interest method. Dividend and interest income are recognized when earned. Realized gains and losses on securities  sold  are  derived  using  the  specific  identification  method for determining  the  cost  of  securities  sold.
	Investments in Federal Reserve Bank (“FRB”) and Federal Home Loan Bank (“FHLB”) stock are required for membership in those organizations and are carried at cost since there is no market value available.  The FHLB New York continues to pay dividends and repurchase stock.  As such, the Company has not recognized any impairment on its holdings of FHLB stock.
Loans	'
	Loans
	Loans are recorded at their current unpaid principal balance, net of unearned income and unamortized loan fees and expenses, which are amortized under the effective interest method over the estimated lives of the loans. Interest income on loans is accrued based on the principal amount outstanding.
	For all loan classes within the Company’s loan portfolio, loans are placed on nonaccrual status when timely collection of principal and interest in accordance with contractual terms is doubtful. Loans are transferred to nonaccrual status generally when principal or interest payments become ninety days delinquent, unless the loan is well secured and in the process of collection, or sooner when management concludes circumstances indicate that borrowers may be unable to meet contractual principal or interest payments.  When a loan is transferred to a nonaccrual status, all interest previously accrued in the current period but not collected is reversed against interest income in that period. Interest accrued in a prior period and not collected is charged-off against the allowance for loan losses.
	If ultimate repayment of a nonaccrual loan is expected, any payments received are applied in accordance with contractual terms. If ultimate repayment of principal is not expected, any payment received on a nonaccrual loan is applied to principal until ultimate repayment becomes expected.  For all loan classes within the Company’s loan portfolio, nonaccrual loans are returned to accrual status when they become current as to principal and interest and demonstrate a period of performance under the contractual terms and, in the opinion of management, are fully collectible as to principal and interest.  For loans in all portfolios, the principal amount is charged off in full or in part as soon as management determines, based on available facts, that the collection of principal in full is improbable.  For commercial loans, management considers specific facts and circumstances relative to individual credits in making such a determination.  For consumer and residential loan classes, management uses specific guidance and thresholds from the Federal Financial Institutions Examination Council’s Uniform Retail Credit Classification and Account Management Policy.
	Commercial type loans are considered impaired when it is probable that the borrower will not repay the loan according to the original contractual terms of the loan agreement, and all loan types are considered impaired if the loan is restructured in a troubled debt restructuring (“TDR”).  In determining that we will be unable to collect all principal and interest payments due in accordance with the contractual terms of the loan agreements, we consider factors such as payment history and changes in the financial condition of individual borrowers, local economic conditions, historical loss experience and the conditions of the various markets in which the collateral may be liquidated.
	A loan is considered to be a TDR when the Company grants a concession to the borrower because of the borrower’s financial condition that the Company would not otherwise consider. Such concessions include the reduction of interest rates, forgiveness of all or a portion of principal or interest, or other modifications at interest rates that are less than the current market rate for new obligations with similar risk. TDR loans are nonaccrual loans; however, they can be returned to accrual status after a period of performance, generally evidenced by six months of compliance with their modified terms.
	When the Company modifies a loan, management evaluates any possible impairment based on the present value of the expected future cash flows, discounted at the contractual interest rate of the original loan agreement, except when the sole (remaining) source of repayment for the loan is the operation or liquidation of the collateral.  In these cases, management uses the current fair value of the collateral, less selling costs, instead of discounted cash flows.  If management determines that the value of the modified loan is less than the recorded investment in the loan (net of previous charge-offs, deferred loan fees or costs and unamortized premium or discount), impairment is recognized by segment or class of loan as applicable, through an allowance estimate or a charge-off to the allowance.  Segment and class status is determined by the loan’s classification at origination.
Allowance for LoanLosses	'
	Allowance for Loan Losses
	The allowance for loan losses is the amount which, in the opinion of management, is necessary to absorb probable losses inherent in the loan portfolio. The allowance is determined based upon numerous considerations, including local and regional conditions, the growth and composition of the loan portfolio  with  respect to the mix between the various types of loans and their related risk characteristics, a review of the value of collateral supporting the loans, comprehensive reviews of the loan portfolio by the independent loan review staff and management, as well as consideration of volume and trends of delinquencies, nonperforming loans, and loan charge-offs.  Loan losses are charged off against the allowance, while recoveries of amounts previously charged off are credited to the allowance.  As a result of tests of adequacy, required additions to the allowance for loan losses are made periodically by charges to the provision for loan losses.
	The allowance for loan losses related to impaired loans specifically allocated for impairment is based on discounted cash flows using the loan’s initial effective interest rate or the fair value of the collateral for certain loans where repayment of the loan is expected to be provided solely by the underlying collateral (collateral dependent loans). The Company’s impaired loans are generally collateral dependent. The Company considers the estimated cost to sell, on a discounted basis, when determining the fair value of collateral in the measurement of impairment if those costs are expected to reduce the cash flows available to repay or otherwise satisfy the loans.
	Management believes that the allowance for loan losses is adequate.  While management uses available information to recognize loan losses, future additions to the allowance for loan losses may be necessary based on changes in economic conditions or changes in the values of properties securing loans in the process of foreclosure. In addition, various regulatory agencies, as an integral part of their examination process, periodically review the Company’s allowance for loan losses. Such agencies may require the Company to recognize additions to the allowance for loan losses based on their judgments about information available to them at the time of their examination which may not be currently available to management.
Premises and Equipment	'
	Premises and Equipment
	Premises and equipment are stated at cost, less accumulated depreciation.  Depreciation of premises and equipment is determined using the straight-line method over the estimated useful lives of the respective assets. Expenditures for maintenance, repairs, and minor replacements are charged to expense as incurred.
Other Real Estate Owned	'
	Other Real Estate Owned
	OREO consists of properties acquired through foreclosure or by acceptance of a deed in lieu of foreclosure. These assets are recorded at the lower of fair value of the asset acquired less estimated costs to sell or “cost” (defined as the fair value at initial foreclosure). At the time of foreclosure, or when foreclosure occurs in-substance, the excess, if any, of the loan over the fair market value of the assets received, less estimated selling costs, is charged to the allowance for loan losses and any subsequent valuation write-downs are charged to other expense.  In connection with the determination of the allowance for loan losses and the valuation of other real estate owned, management obtains appraisals for properties.  Operating costs associated with the properties are charged to expense as incurred. Gains on the sale of OREO are included in income when title has passed and the sale has met the minimum down payment requirements prescribed by GAAP.  The balance of OREO at December 31, 2013 and 2012 was approximately $2.9 million and $2.3 million, respectively, and is recorded in Other Assets on the Consolidated Balance Sheet.
Acquired Loans	'
	Acquired Loans
	Acquired loans are initially measured at fair value as of the acquisition date without carryover of historical allowance for loan losses.
	For loans that meet the criteria stipulated in ASC 310-30, the Company shall recognize the accretable yield, which is defined as the excess of all cash flows expected at acquisition over the initial fair value of the loan, as interest income on a level-yield basis over the expected remaining life of the loan. The excess of the loan's contractually required payments over the cash flows expected to be collected is the nonaccretable difference. The nonaccretable difference shall not be recognized as an adjustment of yield, a loss accrual, or a valuation allowance. Decreases in the expected cash flows in subsequent periods require the establishment of an allowance for loan losses. Improvements in expected cash flows in future periods result in a reduction of the nonaccretable discount, with such amount reclassified as part of the accretable yield and subsequently recognized in interest income over the remaining lives of the acquired loans on a level-yield basis if the amount and timing of future cash flows is reasonably estimable.
	Acquired loans that met the criteria for nonaccrual of interest prior to the acquisition are considered performing upon acquisition, regardless of whether the customer is contractually delinquent, if the Company can reasonably estimate the timing and amount of the expected cash flows on such loans and if the Company expects to fully collect the new carrying value of the loans. As such, the Company may no longer consider the loan to be nonaccrual or nonperforming and may accrue interest on these loans, including the impact of any accretable yield. As such, charge-offs on acquired loans are first applied to the nonaccretable difference and then to any allowance for loan losses recognized subsequent to acquisition.
	For loans that meet the criteria stipulated in ASC 310-20, the Company shall amortize/accrete into interest income the premium/discount determined at the date of purchase on a level-yield basis over the life of the loan. Subsequent to the acquisition date, the methods utilized to estimate the required allowance for loan losses are similar to originated loans.  Loans accounted for under ASC 310-20 are placed on nonaccrual status when past due in accordance with the Company's nonaccrual policy.
	Subsequent to acquisition the estimate of cash flows expected to be collected on loans accounted for in accordance with ASC 310-20 is periodically re-assessed. These re-assessments involve the use of key assumptions and estimates, similar to those used in the initial estimate of fair value. A decrease in expected cash flows in subsequent periods may indicate that the loan pool is impaired, which would require the establishment of an allowance for loan losses by a charge to the provision for credit losses.
	An acquired loan may be resolved either through receipt of payment (in full or in part) from the borrower, the sale of the loan to a third party, or foreclosure of the collateral. In the event of a sale of the loan, a gain or loss on sale is recognized and reported within noninterest income based on the difference between the sales proceeds and the carrying amount of the loan. In other cases, individual loans are removed from the pool based on comparing the amount received from its resolution (fair value of the underlying collateral less costs to sell in the case of a foreclosure) with its outstanding balance. Any difference between these amounts is recorded as a charge-off through the allowance for loan losses.  Acquired loans subject to modification are not removed from the pool even if those loans would otherwise be deemed troubled debt restructurings as the pool, and not the individual loan, represents the unit of account.
Goodwill and Other Intangible Assets	'
	Goodwill and Other Intangible Assets
	Goodwill and intangible assets that have indefinite useful lives are not amortized, but are tested at least annually for impairment. Intangible assets that have finite useful lives are amortized over their useful lives.  Core deposit intangibles and trust intangibles at the Company are amortized using the sum-of-the-years’-digits method.  Covenants not to compete are amortized on a straight-line basis.  Customer lists are amortized using an accelerated method.
	When facts and circumstances indicate potential impairment of amortizable intangible assets, the Company evaluates the recoverability of the asset carrying value, using estimates of undiscounted future cash flows over the remaining asset life. Any impairment loss is measured by the excess of carrying value over fair value. Goodwill impairment tests are performed on an annual basis or when events or circumstances dictate. In these tests, the fair values of each reporting unit, or segment, is compared to the carrying amount of that reporting unit in order to determine if impairment is indicated. If so, the implied fair value of the reporting unit’s goodwill is compared to its carrying amount and the impairment loss is measured by the excess of the carrying value over fair value.
Treasury Stock	'
	Treasury Stock
	Treasury stock acquisitions are recorded at cost. Subsequent sales of treasury stock are recorded on an average cost basis. Gains on the sale of treasury stock are credited to additional paid-in-capital. Losses on the sale of treasury stock are charged to additional paid-in-capital to the extent of previous gains, otherwise charged to retained earnings.
Income Taxes	'
	Income Taxes
	Income taxes are accounted for under the asset and liability method. Deferred income taxes are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases.  Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred taxes of a change in tax rates is recognized in income in the period that includes the enactment date.  The Company recognizes interest accrued and penalties related to unrecognized tax benefits in income tax expense.
Stock-Based Compensation	'
	Stock-Based Compensation
	We maintain various long-term incentive stock benefit plans under which we grant stock options, restricted stock awards, and restricted stock units to certain directors and key employees.  We recognize compensation expense in our income statement over the requisite service period, based on the grant-date fair value of the award.  The fair values of options are estimated using the Black-Scholes option pricing model.  For restricted stock awards and units, we recognize compensation expense ratably over the vesting period for the fair value of the award, measured at the grant date.
	The Company’s stock-based employee compensation plan is described in Note 14 “Stock-Based Compensation,” of this Report.
Interest Rate Swaps	'
	Interest Rate Swaps
	The Bank offers interest rate swap agreements to its customers.  These agreements allow the Bank’s customers to effectively fix the interest rate on a variable rate loan by entering into a separate agreement.  Simultaneous with the execution of such an agreement with a customer, the Bank enters into a matching interest rate swap agreement with an unrelated third party provider, which allows the Bank to continue to receive the historical variable rate under the loan agreement with the customer.  The agreement with the third party is not a hedge contract therefore changes in fair value are recorded through earnings.  Assets and liabilities associated with the agreements are recorded in other assets and other liabilities on the balance sheet.  Gains and losses are recorded as other noninterest income.  The Bank is not subject to any fee or penalty should the customer elect to terminate the interest rate swap agreement prior to maturity.  The Bank is exposed to credit loss equal to the fair value of the derivatives (not the notional amount of the derivatives) in the event of nonperformance by the counterparty to the interest rate swap agreements.  Additionally, the Bank receives a fee from the customer that is recognized when the Bank has fulfilled its obligations under each agreement, which is generally upon execution of the agreement with the Bank’s customer.  Since the terms of the two interest rate swap agreements are identical, the income statement impact to the Bank is generally limited to the fees it receives from the customer.
Other Financial Instruments	'
	Other Financial Instruments
	The Company is a party to certain other financial instruments with off-balance-sheet risk such as commitments to extend credit, unused lines of credit, as well as certain mortgage loans sold to investors with recourse. The Company’s policy is to record such instruments when funded.
	Standby letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party.  The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loan facilities to customers.  Under the standby letters of credit, the Company is required to make payments to the beneficiary of the letters of credit upon request by the beneficiary contingent upon the customer's failure to perform under the terms of the underlying contract with the beneficiary.  Standby letters of credit typically have one year expirations with an option to renew upon annual review.  The Company typically receives a fee for these transactions.  The fair value of stand-by letters of credit is recorded upon inception.
Loan Sales and Loan Servicing	'
	Loan Sales and Loan Servicing
	The Company originates and services residential mortgage loans for consumers and sells 15-year, 20-year and 30-year residential real estate mortgages in the secondary market when the interest rate environment is determined to be favorable by management, while retaining servicing rights on the sold loans.  Loan sales are recorded when the sales are funded.  Mortgage servicing rights are recorded at fair value upon sale of the loan.  Loans held for sale are recorded at the lower of cost or market.
Repurchase Agreements	'
	Repurchase Agreements
	Repurchase agreements are accounted for as secured financing transactions since the Company maintains effective control over the transferred securities and the transfer meets the other criteria for such accounting.  Obligations to repurchase securities sold are reflected as a liability in the Consolidated Balance Sheets.  The securities underlying the agreements are delivered to a custodial account for the benefit of the dealer or bank with whom each transaction is executed.  The dealers or banks, who may sell, loan or otherwise dispose of such securities to other parties in the normal course of their operations, agree to resell to the Company the same securities at the maturities of the agreements.
Earnings Per Share	'
	Earnings Per Share
	Basic earnings per share (“EPS”) excludes dilution and is computed by dividing income available to common stockholders by the weighted average number of common shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in the earnings of the entity (such as the Company’s dilutive stock options and restricted stock).
Subsequent Events	'
	Subsequent Events
	The Company has evaluated subsequent events for potential recognition and/or disclosure and there were none identified.
Comprehensive Income	'
	Comprehensive Income
	At the Company, comprehensive income represents net income plus other comprehensive income (loss), which consists primarily of the net change in unrealized gains or losses on securities available for sale for the period and changes in the funded status of employee benefit plans. Accumulated other comprehensive (loss) income represents the net unrealized gains or losses on securities available for sale and the previously unrecognized portion of the funded status of employee benefit plans, net of income taxes, as of the consolidated balance sheet dates.
Pension Costs	'
	Pension Costs
	The Company maintains a noncontributory, defined benefit pension plan covering substantially all employees, as well as supplemental employee retirement plans covering certain executives and a defined benefit postretirement healthcare plan that covers certain employees.  Costs associated with these plans, based on actuarial computations of current and future benefits for employees, are charged to current operating expenses.
Trust Operations	'
	Trust Operations
	Assets held by the Company in a fiduciary or agency capacity for its customers are not included in the accompanying consolidated balance sheets, since such assets are not assets of the Company.  Trust income is recognized on the accrual method based on contractual rates applied to the balances of trust accounts.
Fair Value Measurements	'
	Fair Value Measurements
	Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value measurements are not adjusted for transaction costs.  A fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (level 1 measurements) and the lowest priority to unobservable inputs (level 3 measurements). The three levels of the fair value hierarchy are described below:
	Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;
	Level 2 -  Quoted prices for similar assets or liabilities in active markets, quoted prices in markets that are not active, or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability;
	Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).
	A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement.
	The types of instruments valued based on quoted market prices in active markets include most U.S. government and agency securities, many other sovereign government obligations, liquid mortgage products, active listed equities and most money market securities. Such instruments are generally classified within level 1 or level 2 of the fair value hierarchy.  The Company does not adjust the quoted price for such instruments.
	The types of instruments valued based on quoted prices in markets that are not active, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency include most investment-grade and high-yield corporate bonds, less liquid mortgage products, less liquid agency securities, less liquid listed equities, state, municipal and provincial obligations, and certain physical commodities. Such instruments are generally classified within level 2 of the fair value hierarchy.
	Level 3 is for positions that are not traded in active markets or are subject to transfer restrictions, valuations are adjusted to reflect illiquidity and/or non-transferability, and such adjustments are generally based on available market evidence. In the absence of such evidence, management’s best estimate will be used. Management’s best estimate consists of both internal and external support on certain Level 3 investments. Subsequent to inception, management only changes level 3 inputs and assumptions when corroborated by evidence such as transactions in similar instruments, completed or pending third-party transactions in the underlying investment or comparable entities, subsequent rounds of financing, recapitalizations and other transactions across the capital structure, offerings in the equity or debt markets, and changes in financial ratios or cash flows.

Acquisitions_Tables

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2013
Acquisitions [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 and leases		904,473
	Intangible assets		13,161
	Other assets		72,731
	Deposits		(1,113,420	)
	Borrowings		(126,530	)
	Junior subordinated debt		(25,774	)
	Other liabilities		(19,994	)
	Total identifiable net assets	$	106,325
	Goodwill	$	113,458
Schedule of 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		11,325
	Fair value of acquired loans	$	904,473
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 twelve months ended December 31, 2012 and 2013.
		Pro forma
		Years Ended December 31,
		2013			2012
	Net interest income	$	244,383		$	244,142
	Noninterest income		107,894			106,178
	Net income		70,341			62,694

Securities_Tables

Securities (Tables)	12 Months Ended
	Dec. 31, 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
	31-Dec-13
	U.S. Treasury	$	43,279	$	337		$	-		$	43,616
	Federal Agency		285,880		343			7,308			278,915
	State & municipal		113,435		1,842			1,612			113,665
	Mortgage-backed:
	Government-sponsored enterprises		337,666		5,788			2,131			341,323
	U.S. government agency securities		21,924		1,002			85			22,841
	Collateralized mortgage obligations:
	Government-sponsored enterprises		521,257		1,777			18,141			504,893
	U.S. government agency securities		43,943		794			102			44,635
	Other securities		12,367		2,854			228			14,993
	Total securities available for sale	$	1,379,751	$	14,737		$	29,607		$	1,364,881
	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
Schedule of sales transactions of securities available for sale	'
	The following table sets forth information with regard to sales transactions of securities available for sale:
		Years ended December 31
	(In thousands)	2013		2012			2011
	Proceeds from sales	$	27,593	$	1,790		$	2,437
	Gross realized gains	$	1,283	$	442		$	7
	Gross realized losses		-		-			(165	)
	Net securities (losses) gains	$	1,283	$	442		$	(158	)
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
	31-Dec-13
	Mortgage-backed	$	953	$	128		$	-		$	1,081
	Collateralized mortgage obligations		62,025		-			4,569			57,456
	State & municipal		54,305		442			8			54,739
	Total securities held to maturity	$	117,283	$	570		$	4,577		$	113,276
	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 December 31, 2013 and 2012, segregated according to the length of time the securities had been in a continuous unrealized loss position:
		Less than 12 months								12 months or longer							Total
	Security Type:	Fair		Unrealized			Number			Fair		Unrealized			Number		Fair		Unrealized			Number
		Value		losses			of			Value		losses			of		Value		losses			of
							Positions								Positions							Positions
	31-Dec-13
	Investment securities available for sale:
	Federal agency	$	233,935	$	(6,927	)		20		$	9,619	$	(381	)		1	$	243,554	$	(7,308	)		21
	State & municipal		50,328		(1,612	)		177			-		-			-		50,328		(1,612	)		177
	Mortgage-backed		143,080		(2,216	)		79			-		-			-		143,080		(2,216	)		79
	Collateralized mortgage obligations		379,273		(18,243	)		36			-		-			-		379,273		(18,243	)		36
	Other securities		5,490		(203	)		2			223		(25	)		1		5,713		(228	)		3
	Total securities with unrealized losses	$	812,106	$	(29,201	)		314		$	9,842	$	(406	)		2	$	821,948	$	(29,607	)		316
	31-Dec-13
	Investment securities held to maturity:
	Collateralized mortgage obligations	$	57,456	$	(4,569	)		5		$	-	$	-			-	$	57,456	$	(4,569	)		5
	State & municipal		1,012		(8	)		1			-		-			-		1,012		(8	)		1
	Total securities with unrealized losses	$	58,468	$	(4,577	)		6		$	-	$	-			-	$	58,468	$	(4,577	)		6
	31-Dec-12
	Investment securities available for sale:
	Federal agency	$	39,906	$	(91	)		4		$	-	$	-			-	$	39,906	$	(91	)		4
	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 December 31, 2013:
	(In thousands)	Amortized		Estimated fair
		cost		value
	Debt securities classified as available for sale
	Within one year	$	27,894	$	28,030
	From one to five years		261,703		261,526
	From five to ten years		300,051		297,837
	After ten years		777,736		762,495
		$	1,367,384	$	1,349,888
	Debt securities classified as held to maturity
	Within one year	$	24,680	$	24,766
	From one to five years		22,791		23,148
	From five to ten years		5,489		5,481
	After ten years		64,323		59,881
		$	117,283	$	113,276

Loans_Tables

Loans (Tables)	12 Months Ended
	Dec. 31, 2013
Loans [Abstract]	'
Loans, net of deferred fees and origination costs	'
	A summary of loans, net of deferred fees and origination costs, by category is as follows:
		At December 31,
	(In thousands)	2013			2012
	Residential real estate mortgages	$	1,041,637		$	651,107
	Commercial		859,026			694,799
	Commercial real estate		1,328,313			1,072,807
	Real estate construction and development		93,247			123,078
	Agricultural and agricultural real estate mortgages		112,035			112,687
	Consumer		1,352,638			1,047,856
	Home equity		619,899			575,282
	Total loans	$	5,406,795		$	4,277,616
Related Party Loans	'
	In the ordinary course of business, the Company has made loans at prevailing rates and terms to directors, officers, and other related parties. Such loans, in management’s opinion, do not present more than the normal risk of collectability or incorporate other unfavorable features. The aggregate amount of loans outstanding to qualifying related parties and changes during the years are summarized as follows:
	(In thousands)	2013			2012
	Balance at January 1	$	2,790		$	2,537
	New loans		569			750
	Adjustment due to change in composition of related parties		376			(130	)
	Repayments		(363	)		(367	)
	Balance at December 31	$	3,372		$	2,790

Allowance_for_Loan_Losses_and_1

Allowance for Loan Losses and Credit Quality of Loans (Tables)	12 Months Ended
	Dec. 31, 2013
Allowance for Loan Losses and Credit Quality of Loans and Leases [Abstract]	'
Allowance for loan losses by portfolio	'
	The following table illustrates the changes in the allowance for loan losses by portfolio segment for the years ended December 31, 2013, 2012 and 2011:
	Allowance for Loan Losses
	(in thousands)
								Residential
	Years ended December 31	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		(10,459	)		(15,459	)		(1,771	)		-			(27,689	)
	Recoveries		1,957			3,136			272			-			5,365
	Provision		7,968			12,855			1,767			(166	)		22,424
	Ending Balance as of December 31, 2013	$	35,090		$	27,694		$	6,520		$	130		$	69,434
	Balance as of December 31, 2011	$	38,831		$	26,049		$	6,249		$	205		$	71,334
	Charge-offs		(8,750	)		(15,848	)		(1,906	)		-			(26,504	)
	Recoveries		1,641			2,556			38			-			4,235
	Provision		3,902			14,405			1,871			91			20,269
	Ending Balance as of December 30, 2012	$	35,624		$	27,162		$	6,252		$	296		$	69,334
	Balance as of December 31, 2010	$	40,101		$	26,126		$	4,627		$	380		$	71,234
	Charge-offs		(8,969	)		(14,209	)		(1,310	)		-			(24,488	)
	Recoveries		1,438			2,406			7			-			3,851
	Provision		6,261			11,726			2,925			(175	)		20,737
	Ending Balance as of December 30, 2011	$	38,831		$	26,049		$	6,249		$	205		$	71,334
	The following table illustrates the allowance for loan losses and the recorded investment by portfolio segment as of December 31, 2013 and 2012:
	Allowance for Loan Losses and Recorded Investment in Loans
	(in thousands)
								Residential
		Commercial			Consumer			Real Estate
		Loans			Loans			Mortgages			Unallocated			Total
	As of December 31, 2013
	Allowance for loan losses	$	35,090		$	27,694		$	6,520		$	130		$	69,434
	Allowance for loans individually evaluated for impairment		715			-			-						715
	Allowance for loans collectively evaluated for impairment	$	34,375		$	27,694		$	6,520		$	130		$	68,719
	Ending balance of loans	$	2,392,621		$	1,972,537		$	1,041,637					$	5,406,795
	Ending balance of originated loans individually evaluated for impairment		16,120			3,248			2,012						21,380
	Ending balance of acquired loans individually evaluated for impairment		10,060			-			-						10,060
	Ending balance of acquired loans collectively evaluated for impairment		392,329			219,587			308,416						920,332
	Ending balance of originated loans collectively evaluated for impairment	$	1,974,112		$	1,749,702		$	731,209					$	4,455,023
	As of December 31, 2012
	Allowance for loan and lease losses	$	35,624		$	27,162		$	6,252		$	296		$	69,334
	Allowance for loans and leases individually evaluated for impairment		2,848			-			-						2,848
	Allowance for loans and leases collectively evaluated for impairment	$	32,776		$	27,162		$	6,252		$	296		$	66,486
	Ending balance of loans and leases	$	2,003,371		$	1,623,138		$	651,107					$	4,277,616
	Ending balance of loans individually evaluated for impairment		18,505			2,553			2,011						23,069
	Ending balance of loans collectively evaluated for impairment	$	1,984,866		$	1,620,585		$	649,096					$	4,254,547
Past due and nonperforming loans by loan class	'
	The following table illustrates the Company’s nonaccrual loans by loan class as of December 31, 2013 and 2012:
	(In thousands)	31-Dec-13			31-Dec-12
	ORIGINATED
	Commercial Loans
	Commercial	$	3,669		$	4,985
	Commercial Real Estate		7,834			7,977
	Agricultural		1,135			699
	Agricultural Real Estate		961			1,038
	Business Banking		5,701			6,738
			19,300			21,437
	Consumer Loans
	Indirect		1,461			1,557
	Home Equity		5,931			7,247
	Direct		86			266
			7,478			9,070
	Residential Real Estate Mortgages		7,105			9,169
		$	33,883		$	39,676
	ACQUIRED
	Commercial Loans
	Commercial	$	6,599
	Commercial Real Estate		3,559
	Business Banking		1,340
			11,498
	Consumer Loans
	Indirect		93
	Home Equity		570
	Direct		49
			712
	Residential Real Estate Mortgages		3,872
		$	16,082
	TOTAL NONACCRUAL LOANS	$	49,965		$	39,676
	The following table sets forth information with regard to past due and nonperforming loans by loan class:
	Age Analysis of Past Due Financing Receivables
	As of December 31, 2013
	(in thousands)
								Greater
		31-60 Days			61-90 Days			Than			Total								Recorded Total
								90 Days
		Past Due			Past Due			Past Due			Past Due								Loans and
		Accruing			Accruing			Accruing			Accruing			Non-Accrual			Current		Leases
	ORIGINATED
	Commercial Loans
	Commercial	$	105		$	247		$	-		$	352		$	3,669		$	612,402	$	616,423
	Commercial Real Estate		1,366			-			-			1,366			7,834			925,116		934,316
	Agricultural		150			21			-			171			1,135			63,856		65,162
	Agricultural Real Estate		519			-			-			519			961			35,172		36,652
	Business Banking		1,228			122			105			1,455			5,701			330,523		337,679
			3,368			390			105			3,863			19,300			1,967,069		1,990,232
	Consumer Loans
	Indirect		14,093			2,878			1,583			18,554			1,461			1,141,829		1,161,844
	Home Equity		6,033			1,888			1,115			9,036			5,931			517,856		532,823
	Direct		679			125			46			850			86			57,347		58,283
			20,805			4,891			2,744			28,440			7,478			1,717,032		1,752,950
	Residential Real Estate Mortgages		3,951			379			808			5,138			7,105			720,978		733,221
		$	28,124		$	5,660		$	3,657		$	37,441		$	33,883		$	4,405,079	$	4,476,403
	ACQUIRED
	Commercial Loans
	Commercial	$	24		$	-		$	-		$	24		$	6,599		$	96,603	$	103,226
	Commercial Real Estate		-			-			-			-			3,559			225,455		229,014
	Business Banking		320			2			-			322			1,340			68,487		70,149
			344			2			-			346			11,498			390,545		402,389
	Consumer Loans
	Indirect		939			113			71			1,123			93			123,870		125,086
Home Equity		753			63			-			816			570			85,690		87,076
Direct		76			56			9			141			49			7,235		7,425
		1,768			232			80			2,080			712			216,795		219,587
Residential Real Estate Mortgages		1,725			-			-			1,725			3,872			302,819		308,416
	$	3,837		$	234		$	80		$	4,151		$	16,082		$	910,159	$	930,392
Total Loans	$	31,961		$	5,894		$	3,737		$	41,592		$	49,965		$	5,315,238	$	5,406,795
Age Analysis of Past Due Loans
As of December 31, 2012
(in thousands)
							Greater Than											Recorded
	31-60 Days			61-90 Days			90 Days			Total								Total
	Past Due			Past Due			Past Due			Past Due								Loans and
	Accruing			Accruing			Accruing			Accruing			Non-Accrual			Current		Leases
Commercial
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
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 provides additional information on loans specifically evaluated for impairment for the years ended December 31, 2013 and 2012:
	Impaired Loans
		31-Dec-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
	ORIGINATED
	With no related allowance recorded:
	Commercial Loans
	Commercial	$	4,721		$	4,777					$	1,000		$	1,000
	Commercial Real Estate		4,613			5,164						7,362			7,366
	Agricultural		125			195						446			540
	Agricultural Real Estate		1,431			1,708						903			1,029
	Business Banking		210			602						391			783
	Total Commercial Loans		11,100			12,446						10,102			10,718
	Consumer Loans
	Home Equity		3,248			3,472						2,553			2,657
	Residential Real Estate Mortgages		2,012			2,255						2,011			2,308
	Total		16,360			18,173						14,666			15,683
	With an allowance recorded:
	Commercial Loans
	Commercial		-			-			-			4,335			4,340			2,241
	Commercial Real Estate		5,020			6,877			715			4,068			5,689			607
	Agricultural		-			-			-			-			-			-
	Agricultural Real Estate		-			-			-			-			-			-
			5,020			6,877			715			8,403			10,029			2,848
	ACQUIRED
	With no related allowance recorded:
	Commercial Loans
	Commercial		6,501			6,538
	Commercial Real Estate		3,559			3,842
	Total Commercial Loans		10,060			10,380
	Total	$	31,440		$	35,430		$	715		$	23,069		$	25,712		$	2,848
	The following table summarizes the average recorded investments on loans specifically evaluated for impairment and the interest income recognized for the years ended December 31, 2013, 2012 and 2011:
		31-Dec-13						31-Dec-12						31-Dec-11
		Average			Interest Income			Average			Interest Income			Average			Interest Income
		Recorded			Recognized			Recorded			Recognized			Recorded			Recognized
	(in thousands)	Investment			Accrual			Investment			Accrual			Investment			Accrual
	ORIGINATED
	Commercial Loans
	Commercial	$	3,722		$	17		$	6,682		$	56		$	1,507		$	-
	Commercial Real Estate		11,010			130			4,944			230			3,763			-
	Agricultural		207			1			1,767			43			2,070			-
	Agricultural Real Estate		1,167			52			922			72			695			-
	Business Banking		295			57			68			65			17			-
	Consumer Loans
	Home Equity		2,969			143			1,877			123			1,924			60
	Residential Real Estate Mortgages		2,024			69			1,143			54			933			4
	ACQUIRED
	Commercial Loans
	Commercial		1,625			-			-			-			-			-
	Commercial Real Estate		1,222			-			-			-			-			-
	Total	$	24,240		$	469		$	17,403		$	643		$	10,909		$	64
Financing receivable credit quality by loan class	'
	The following tables illustrate the Company’s credit quality by loan class for the years ended December 31, 2013 and 2012:
	Credit Quality Indicators
	As of December 31, 2013
	ORIGINATED
	Commercial Credit Exposure				Commercial						Agricultural
	By Internally Assigned Grade:	Commercial			Real Estate			Agricultural			Real Estate			Total
	Pass	$	576,079		$	878,411		$	60,043		$	33,136		$	1,547,669
	Special Mention		16,836			22,777			381			43			40,037
	Substandard		23,508			33,128			4,726			3,473			64,835
	Doubtful		-			-			12			-			12
	Total	$	616,423		$	934,316		$	65,162		$	36,652		$	1,652,553
	Business Banking Credit Exposure
	By Internally Assigned Grade:	Business Banking												Total
	Non-classified	$	319,578											$	319,578
	Classified		18,101												18,101
	Total	$	337,679											$	337,679
	Consumer Credit Exposure
	By Payment Activity:	Indirect			Home Equity			Direct						Total
	Performing	$	1,158,800		$	525,777		$	58,151					$	1,742,728
	Nonperforming		3,044			7,046			132						10,222
	Total	$	1,161,844		$	532,823		$	58,283					$	1,752,950
	Residential Mortgage Credit Exposure	Residential
	By Payment Activity:	Mortgage												Total
	Performing	$	725,308											$	725,308
	Nonperforming		7,913												7,913
	Total	$	733,221											$	733,221
	Credit Quality Indicators
	As of December 31, 2013
	ACQUIRED
	Commercial Credit Exposure				Commercial
	By Internally Assigned Grade:	Commercial			Real Estate			Agricultural						Total
	Pass	$	85,692		$	205,010		$	-					$	290,702
	Special Mention		2,230			6,183			-						8,413
	Substandard		15,304			17,821			-						33,125
	Doubtful		-			-			-						-
	Total	$	103,226		$	229,014		$	-					$	332,240
	Business Banking Credit Exposure
	By Internally Assigned Grade:	Business Banking												Total
	Non-classified	$	65,437											$	65,437
	Classified		4,712												4,712
	Total	$	70,149											$	70,149
	Consumer Credit Exposure
	By Payment Activity:	Indirect			Home Equity			Direct						Total
	Performing	$	124,922		$	86,506		$	7,367					$	218,795
	Nonperforming		164			570			58						792
	Total	$	125,086		$	87,076		$	7,425					$	219,587
	Residential Mortgage Credit Exposure	Residential
	By Payment Activity:	Mortgage												Total
	Performing	$	304,544											$	304,544
	Nonperforming		3,872												3,872
	Total	$	308,416											$	308,416
	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	Business
	By Internally Assigned Grade:	Banking												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

Premises_and_Equipment_Net_Tab

Premises and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2013
Premises and Equipment, Net [Abstract]	'
Summary of premises and equipment	'
	A summary of premises and equipment follows:
		December 31,
	(In thousands)	2013		2012
	Land, buildings, and improvements	$	120,098	$	109,601
	Equipment		55,729		51,321
	Premises and equipment before accumulated depreciation		175,827		160,922
	Accumulated depreciation		87,500		83,047
	Total premises and equipment	$	88,327	$	77,875
Future minimum rental payments related to noncancelable operating leases	'
	Future Minimum Rental Payments
	2014	$	7,156
	2015		7,012
	2016		6,985
	2017		6,859
	2018		6,791
	Thereafter		53,132
	Total	$	87,935

Goodwill_and_other_Intangible_1

Goodwill and other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2013
Goodwill and other Intangible Assets [Abstract]	'
Summary of goodwill	'
	A summary of goodwill is as follows:
	(In thousands)
	1-Jan-13		152,373
	Goodwill Acquired		112,624
	31-Dec-13	$	264,997
	1-Jan-12		132,029
	Goodwill Acquired		20,344
	31-Dec-12	$	152,373
Summary of core deposit and other intangible assets	'
	A summary of core deposit and other intangible assets follows:
		December 31,
	(In thousands)	2013		2012
	Core deposit intangibles
	Gross carrying amount	$	19,401	$	13,240
	Less: accumulated amortization		10,083		7,794
	Net carrying amount		9,318		5,446
	Identified intangible assets
	Gross carrying amount		28,509		21,743
	Less: accumulated amortization		12,270		10,227
	Net carrying amount		16,239		11,516
	Total intangibles
	Gross carrying amount		47,910		34,983
	Less: accumulated amortization		22,353		18,021
	Net carrying amount	$	25,557	$	16,962

Deposits_Tables

Deposits (Tables)	12 Months Ended
	Dec. 31, 2013
Deposits [Abstract]	'
Maturity distribution of time deposits	'
	The following table sets forth the maturity distribution of time deposits at December 31, 2013 (in thousands):
	Time deposits
	Within one year	$	661,619
	After one but within two years		184,796
	After two but within three years		86,689
	After three but within four years		52,024
	After four but within five years		20,656
	After five years		15,358
	Total	$	1,021,142

ShortTerm_Borrowings_Tables

Short-Term Borrowings (Tables)	12 Months Ended
	Dec. 31, 2013
Short-Term Borrowings [Abstract]	'
Information related to short-term borrowings	'
	Information related to short-term borrowings is summarized as follows:
	(In thousands)	2013			2012			2011
	Federal funds purchased
	Balance at year-end	$	130,000		$	10,000		$	27,000
	Average during the year		39,907			12,658			3,017
	Maximum month end balance		130,000			60,000			28,000
	Weighted average rate during the year		0.26	%		0.27	%		0.11	%
	Weighted average rate at December 31		0.18	%		0.27	%		0.13	%
	Securities sold under repurchase agreements
	Balance at year-end	$	176,042		$	152,941		$	154,592
	Average during the year		169,352			153,084			150,663
	Maximum month end balance		185,871			165,977			178,414
	Weighted average rate during the year		0.06	%		0.1	%		0.13	%
	Weighted average rate at December 31		0.05	%		0.1	%		0.1	%
	Other short-term borrowings
	Balance at year-end	$	150,000		$	-		$	-
	Average during the year		71,589			-			249
	Maximum month end balance		210,000			-			250
	Weighted average rate during the year		0.43	%		-			-
	Weighted average rate at December 31		0.55	%		-			-

LongTerm_Debt_Tables

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2013
Long-Term Debt [Abstract]	'
Schedule of Long-term Debt	'
	Long-term debt consists of obligations having an original maturity at issuance of more than one year. A majority of the Company’s long-term debt is comprised of FHLB advances collateralized by the FHLB stock owned by the Company, certain of its mortgage-backed securities and a blanket lien on its residential real estate mortgage loans.  A summary as of December 31, 2013 and 2012 is as follows:
		As of December 31, 2013										As of December 31, 2012
	Maturity	Amount		Weighted Average Rate			Callable Amount		Weighted Average Rate			Amount		Weighted Average Rate			Callable Amount		Weighted Average Rate
	2013		-		-			-		-			119,502		3.87	%		100,000		3.71	%
	2014		12,460		1.33	%		-		-			2,610		1.89	%		-		-
	2015		308		0	%		-		-			250		0	%		-		-
	2016		90,313		3.52	%		70,000		4.21	%		70,000		4.21	%		70,000		4.21	%
	2017		115,312		3.55	%		75,000		3.73	%		100,000		3.89	%		100,000		3.89	%
	2018		90,313		3.26	%		75,000		3.61	%		75,000		3.61	%		75,000		3.61	%
	2021		117		4	%		-		-			130		4	%		-		-
		$	308,823				$	220,000				$	367,492				$	345,000

Junior_Subordinated_Debt_Table

Junior Subordinated Debt (Tables)	12 Months Ended
	Dec. 31, 2013
Junior Subordinated Debt [Abstract]	'
Schedule of Debt of VIE Where Entity is Not Primary Beneficiary	'
	As of December 31, 2013, the Trusts had the following issues of trust preferred debentures, all held by the Trusts, outstanding (dollars in thousands):
	Description	Issuance Date	Trust Preferred Securities Outstanding		Interest Rate	Trust Preferred Debt Owed To Trust		Final Maturity Date
	CNBF Capital Trust I	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

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Taxes [Abstract]	'
Components of income tax expense attributable to operations	'
	The significant components of income tax expense attributable to operations are:
		Years ended December 31,
		2013			2012			2011
	Current
	Federal	$	23,536		$	21,011		$	29,274
	State		2,316			1,815			1,477
			25,852			22,826			30,751
	Deferred
	Federal		2,334			(13	)		(8,129	)
	State		10			3			(1,349	)
			2,344			(10	)		(9,478	)
	Total income tax expense	$	28,196		$	22,816		$	21,273
Components of deferred tax assets and liabilities	'
	The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities are as follows:
		December 31,
	(In thousands)	2013			2012
	Deferred tax assets
	Allowance for loan and lease losses	$	26,729		$	26,687
	Deferred compensation		7,931			5,362
	Postretirement benefit obligation		2,596			1,600
	Unrealized losses on securities available for sale		5,900			-
	Fair value adjustments from acquisitions		-			3,633
	Accrued liabilities		3,265			1,524
	Stock-based compensation expense		7,862			5,726
	Equipment leasing		1,661			-
	Other		2,125			1,933
	Total deferred tax assets		58,069			46,465
	Deferred tax liabilities
	Pension and executive retirement		17,417			7,676
	Fair value adjustments from acquisitions		2,070			-
	Unrealized gains on securities available for sale		-			10,939
	Premises and equipment, primarily due to accelerated depreciation		2,270			1,980
	Equipment leasing		-			582
	Deferred loan costs		1,624			873
	Intangible amortization		12,007			13,146
	Other		892			154
	Total deferred tax liabilities		36,280			35,350
	Net deferred tax asset at year-end		21,789			11,115
	Net deferred tax asset (liability) at beginning of year		11,115			5,953
	Increase in net deferred tax asset	$	10,674		$	5,162
Reconciliation of gross unrecognized tax benefits	'
	A reconciliation of the beginning and ending balance of gross unrecognized tax benefits is as follows:
	(In thousands)	2013			2012			2011
	Balance at January 1	$	-		$	888		$	3,081
	Additions for tax positions of prior years		-			-			-
	Reduction for tax positions of prior years		-			(888	)		(2,193	)
	Balance at December 31	$	-		$	-		$	888
Reconciliation of the provision for income taxes to the amount computed by applying the federal statutory rate	'
	The following is a reconciliation of the provision for income taxes to the amount computed by applying the applicable Federal statutory rate of 35% to income before taxes:
		Years ended December 31
	(In thousands)	2013			2012			2011
	Federal income tax at statutory rate	$	31,482		$	27,081		$	27,711
	Tax exempt income		(2,433	)		(2,536	)		(2,925	)
	Net increase in CSV of life insurance		(1,166	)		(908	)		(919	)
	Low income housing tax credits		(819	)		(629	)		(782	)
	State taxes, net of federal tax benefit		1,512			1,182			764
	State audit settlements		-			-			(681	)
	Other, net		(380	)		(1,374	)		(1,895	)
	Income tax expense	$	28,196		$	22,816		$	21,273

Employee_Benefit_Plans_Tables

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2013
Employee Benefit Plans [Abstract]	'
Components of accumulated other comprehensive income (loss), net periodic benefit cost	'
	The Company expects that $0.3 million in net actuarial loss and $0.2 million in prior service costs will be recognized as components of net periodic benefit cost in 2014.
		Pension Benefits						Other Benefits
	(In thousands)	2013			2012			2013			2012
	Net actuarial loss	$	11,286		$	35,478		$	1,628		$	2,277
	Prior service cost		118			141			(521	)		(672	)
	Total amounts recognized in accumulated other comprehensive loss (pre-tax)	$	11,404		$	35,619		$	1,107		$	1,605
Changes in benefit obligations, changes in plan assets, and the funded status of the pension plans and postretirement benefits	'
	A December 31 measurement date is used for the pension, supplemental pension and postretirement benefit plans.  The following table sets forth changes in benefit obligations, changes in plan assets, and the funded status of the pension plans and other postretirement benefits:
		Pension Benefits						Other Benefits
	(In thousands)	2013			2012			2013			2012
	Change in benefit obligation
	Benefit obligation at beginning of year	$	85,129		$	78,024		$	4,071		$	3,985
	Service cost		2,493			3,122			23			20
	Interest cost		3,223			3,145			286			155
	Plan participants' contributions		-			-			269			233
	Actuarial(gain) loss		(10,853	)		5,941			(369	)		136
	Amendments		-			(1,006	)		(54	)		-
	Acquisition		10,958			-			3,928			-
	Benefits paid		(5,283	)		(4,097	)		(726	)		(458	)
	Projected benefit obligation at end of year		85,667			85,129			7,428			4,071
	Change in plan assets
	Fair value of plan assets at beginning of year		99,704			91,575			-			-
	Actual return on plan assets		18,451			11,733			-			-
	Acquisition		4,994			-			-			-
	Employer contributions		708			493			457			225
	Plan participants' contributions		-			-			269			233
	Benefits paid		(5,283	)		(4,097	)		(726	)		(458	)
	Fair value of plan assets at end of year		118,574			99,704			-			-
	Funded status at year end	$	32,907		$	14,575		$	(7,428	)	$	(4,071	)
Amounts recognized in balance sheet	'
	The funded status of the pension and other postretirement benefit plans has been recognized as follows in the consolidated balance sheets at December 31, 2013 and 2012.  An asset is recognized for an overfunded plan and a liability is recognized for an underfunded plan.  The accumulated benefit obligation for pension benefits was $85.7 million and $85.1 million at December 31, 2013 and 2012, respectively.  The accumulated benefit obligation for other postretirement benefits was $7.4 million and $4.1 million at December 31, 2013 and 2012, respectively.
		Pension Benefits						Other Benefits
	(In thousands)	2013			2012			2013			2012
	Other assets	$	48,189		$	27,062		$	-		$	-
	Other liabilities		(15,282	)		(12,487	)		(7,428	)		(4,071	)
	Funded status	$	32,907		$	14,575		$	(7,428	)	$	(4,071	)
Assumptions used to determine benefit obligations and net periodic pension cost	'
	The following assumptions were used to determine the benefit obligation and the net periodic pension cost for the years indicated:
		Years ended December 31,
		2013			2012			2011
	Weighted average assumptions:
	The following assumptions were used to determine benefit obligations:
	Discount rate		4.90% - 5.05	%		3.5	%		4.1	%
	Expected long-term return on plan assets		7.5	%		7.5	%		7.5	%
	Rate of compensation increase		3	%		3	%		3	%
	The following assumptions were used to determine net periodic pension cost:
	Discount rate		3.5	%		4.1	%		5.15	%
	Expected long-term return on plan assets		7.5	%		7.5	%		8	%
	Rate of compensation increase		3	%		3	%		3	%
Components of net periodic pension benefits and other benefit costs	'
	Net periodic benefit cost and other amounts recognized in other comprehensive income (loss) for the years ended December 31 included the following components:
		Pension Benefits									Other Benefits
	(In thousands)	2013			2012			2011			2013			2012			2011
	Components of net periodic benefit cost
	Service cost	$	2,493		$	3,122		$	2,589		$	23		$	20		$	17
	Interest cost		3,223			3,145			3,544			286			155			202
	Expected return on plan assets		(7,804	)		(6,686	)		(7,720	)		-			-			-
	Amortization of prior service cost		23			283			309			(205	)		(202	)		(202	)
	Amortization of unrecognized net loss		2,692			3,330			1,353			280			182			205
	Net periodic pension cost	$	627		$	3,194		$	75		$	384		$	155		$	222
	Other changes in plan assets and benefit obligations recognized in other comprehensive income (pre-tax)
	Net loss (gain)	$	(21,500	)	$	894		$	16,108		$	(369	)	$	136		$	(562	)
	Prior service cost		-			(1,006	)		-			(54	)		-			-
	Amortization of prior service cost		(23	)		(283	)		(309	)		205			202			202
	Amortization of unrecognized net gain		(2,692	)		(3,330	)		(1,353	)		(280	)		(182	)		(205	)
	Total recognized in other comprehensive loss (income)		(24,215	)		(3,725	)		14,446			(498	)		156			(565	)
	Total recognized in net periodic benefit cost and other comprehensive income (loss) - pre-tax	$	(23,588	)	$	(531	)	$	14,521		$	(114	)	$	311		$	(343	)
Estimated future benefit payments for the pension plans and other postretirement benefit plans	'
	The following table sets forth estimated future benefit payments for the pension plans and other postretirement benefit plans:
		Pension			Other
		Benefits			Benefits
	2014		5,950			555
	2015		6,090			565
	2016		6,143			560
	2017		9,199			576
	2018		6,899			590
	2019 - 2023		34,827			2,771
Effect of one-percentage point change in assumed health care cost trend rates	'
	For measurement purposes, the annual rates of increase in the per capita cost of covered medical and prescription drug benefits for fiscal year 2013 were assumed to be 5.9 to 8.5 percent. The rates were assumed to decrease gradually to 5.0 percent for fiscal year 2021 and remain at that level thereafter.  Assumed health care cost trend rates have a significant effect on amounts reported for health care plans. A one-percentage point change in the health care trend rates would have the following effects as of and for the year ended December 31, 2014:
	(In thousands)	One Percentage point increase			One Percentage point decrease
	Increase (decrease) on total service and interest cost components	$	37		$	(27	)
	Increase (decrease) on postretirement accumulated benefit obligation		768			(567	)
Target and actual allocations of defined benefit pension plan's assets	'
	The target and actual allocations expressed as a percentage of the defined benefit pension plan’s assets are as follows:
		Target 2013			2013			2012
	Cash and cash equivalents		0 - 20	%		6	%		5	%
	Fixed income securities		20 - 40	%		27	%		29	%
	Equities		40 - 80	%		67	%		66	%
	Total					100	%		100	%
Financial instruments recorded at fair value on a recurring basis by the Plan	'
	The following table presents the financial instruments recorded at fair value on a recurring basis by the Plan as of December 31, 2013 and 2012:
		Quoted Prices in			Significant
		Active Markets for			Other			Balance
		Identical Assets			Observable Inputs			as of
		(Level 1)			(Level 2)			31-Dec-13
	Cash and cash equivalents	$	7,533		$	-		$	7,533
	Foreign equity mutual funds		15,653			-			15,653
	Equity mutual funds		16,727			-			16,727
	US government bonds		-			9,355			9,355
	Corporate bonds		-			19,665			19,665
	Common stock		44,532			-			44,532
	Municipal bonds and notes		-			1,451			1,451
	Foreign bonds and notes		-			1,392			1,392
	Foreign equity		2,266			-			2,266
	Totals	$	86,711		$	31,863		$	118,574
		Quoted Prices in			Significant
		Active Markets for			Other			Balance
		Identical Assets			Observable Inputs			as of
		(Level 1)			(Level 2)			31-Dec-12
	Cash and cash equivalents	$	5,464		$	-		$	5,464
	Foreign equity mutual funds		9,763			-			9,763
	Equity mutual funds		13,110			-			13,110
	US government bonds		-			12,744			12,744
	Corporate bonds		-			13,604			13,604
	Common stock		40,430			-			40,430
	Municipal bonds and notes		-			1,805			1,805
	Foreign bonds and notes		-			1,137			1,137
	Foreign equity		1,647			-			1,647
	Totals	$	70,414		$	29,290		$	99,704

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2013
Stock-Based Compensation [Abstract]	'
Fair value assumptions	'
	The risk-free interest rate was selected based upon yields of the U.S. Treasury issues with a term equal to the expected life of the option being valued:
		Years ended December 31,
		2013			2012			2011
	Dividend yield		3.2	%		3.94	%		3.31%–3.82	%
	Expected volatility		34.6	%		34.64	%		33.75%–34.36	%
	Risk-free interest rates		2.43	%		1.24	%		1.48%–2.81	%
	Expected life	7 years			7 years			7 years
Stock option activity	'
	The following table summarizes information concerning stock options outstanding at December 31, 2013:
		Number of Shares			Weighted average exercise price			Weighted Average Remaining Contractual Term (in yrs)			Aggregate Intrinsic Value
	Outstanding at January 1, 2013		1,695,562		$	22.72
	Granted		120			26.29
	Exercised		(335,103	)		21.77
	Forfeited		(495	)		20.19
	Expired		(18,584	)		21.58
	Outstanding at December 31, 2013		1,341,500		$	22.98			3.89		$	3,996,816
	Exercisable at December 31, 2013		1,279,560		$	23.08			3.78		$	3,683,178
	Expected to Vest		61,044		$	20.8			5.54		$	311,352
Cash proceeds, tax benefits and intrinsic value of stock options exercised	'
	Total stock-based compensation expense for stock option awards totaled $0.2 million, $0.5 million, and $0.9 million for the years ended December 31, 2013, 2012, and 2011, respectively.  Cash proceeds, tax benefits and intrinsic value related to total stock options exercised is as follows:
		Years ended
	(dollars in thousands)	2013			2012			2011
	Proceeds from stock options exercised	$	7,927		$	1,908		$	2,255
	Tax benefits related to stock options exercised		178			8			341
	Intrinsic value of stock options exercised		905			498			897
	Fair value of shares vested during the year		766			1,656			1,597
Unvested restricted awards and unvested restricted units activity	'
	The Company has outstanding restricted and deferred stock awards granted from various plans at December 31, 2013. The Company recognized $3.8 million, $3.7 million, and $3.2 million in stock-based compensation expense related to these stock awards for the years ended December 31, 2013, 2012, and 2011, respectively.  Tax benefits recognized with respect to restricted stock awards and stock units were $1.5 million, $1.5 million and $1.2 million for the years ended December 31, 2013, 2012 and 2011, respectively.  Unrecognized compensation cost related to restricted stock awards and stock units totaled $4.6 million at December 31, 2013 and will be recognized over 2.1 years on a weighted average basis.  Shares issued are funded from the Company’s treasury stock.  The following table summarizes information for unvested restricted stock awards outstanding as of December 31, 2013:
		Number			Weighted-
					Average
		of			Grant Date Fair
		Shares			Value
	Unvested Restricted Stock Awards
	Unvested at January 1, 2013		117,150		$	24.37
	Forfeited		(2,033	)		23.25
	Vested		(48,467	)		26.1
	Unvested at December 31, 2013		66,650		$	23.15
	The following table summarizes information for unvested restricted stock units outstanding as of December 31, 2013:
		Number			Weighted-
					Average
		of			Grant Date Fair
		Shares			Value
	Unvested Restricted Stock Units
	Unvested at January 1, 2013		406,058		$	25.64
	Forfeited		(6,467	)		-
	Vested		(69,333	)		-
	Granted		209,592			20.81
	Unvested at December 31, 2013		539,850		$	27.36

Stockholders_Equity_Tables

Stockholders Equity (Tables)	12 Months Ended
	Dec. 31, 2013
Stockholders Equity [Abstract]	'
Components of accumulated other comprehensive (loss) income	'
	In accordance with accounting standards, unrealized gains on available for sale securities and unrecognized actuarial gains or losses and prior service costs associated with the Company’s pension and postretirement benefit plans are included in accumulated other comprehensive loss.  For the years ended December 31, components of accumulated other comprehensive loss are:
	(In thousands)	2013			2012
	Unrecognized prior service cost and net actuarial loss on pension plans	$	(7,785	)	$	(22,555	)
	Unrealized net holding (losses) gains on available for sale securities		(8,980	)		16,675
	Accumulated other comprehensive loss	$	(16,765	)	$	(5,880	)

Regulatory_Capital_Requirement1

Regulatory Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2013
Regulatory Capital Requirements [Abstract]	'
Schedule of compliance with regulatory compliance requirements under banking regulations	'
	The Company and NBT Bank’s actual capital amounts and ratios are presented as follows:
		Actual					Regulatory ratio requirements
	(Dollars in thousands)	Amount		Ratio			Minimum			For classification
							capital adequacy			as well capitalized
	As of December 31, 2013
	Total Capital (to risk weighted assets):
	Company	$	723,580		12.99	%		8	%		10	%
	NBT Bank		686,194		12.41	%		8	%		10	%
	Tier I Capital (to risk weighted assets)
	Company		653,950		11.74	%		4	%		6	%
	NBT Bank		617,038		11.16	%		4	%		6	%
	Tier I Capital (to average assets)
	Company		653,950		8.93	%		4	%		5	%
	NBT Bank		617,038		8.47	%		4	%		5	%
	As of December 31, 2012
	Total Capital (to risk weighted assets):
	Company	$	560,745		12.25	%		8	%		10	%
	NBT Bank		505,027		11.08	%		8	%		10	%
	Tier I Capital (to risk weighted assets)
	Company		503,359		11	%		4	%		6	%
	NBT Bank		447,909		9.83	%		4	%		6	%
	Tier I Capital (to average assets)
	Company		503,359		8.54	%		4	%		5	%
	NBT Bank		447,909		7.62	%		4	%		5	%

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 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 years presented in the consolidated statements of income:
		Years ended December 31,
		2013						2012						2011
				Weighted						Weighted						Weighted
		Net		average		Per share		Net		average		Per share		Net		average		Per share
	(In thousands, except per share data)	income		shares		amount		income		shares		amount		income		shares		amount
	Basic earnings per share	$	61,747		41,930	$	1.47	$	54,558		33,379	$	1.63	$	57,901		33,662	$	1.72
	Effect of dilutive securities
	Stock based compensation				420						340						262
	Diluted earnings per share	$	61,747		42,350	$	1.46	$	54,558		33,719	$	1.62	$	57,901		33,924	$	1.71

Reclassification_Adjustments_O1

Reclassification Adjustments Out of Other Comprehensive (Loss) Income (Tables)	12 Months Ended
	Dec. 31, 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)	Amount reclassified from accumulated other comprehensive income (loss)						Affected line item in the consolidated statement of comprehensive income
	Income Components
		Years ended
		31-Dec-13			31-Dec-12
	Available for sale securities:
	Gains on available for sale securities	$	(1,426	)	$	(599	)	Net securities gains
	Tax benefit		565			237		Income tax expense
	Net of tax	$	(861	)	$	(362	)
	Pension and other benefits:
	Amortization of net gains	$	2,972		$	3,512		Salaries and employee benefits
	Amortization of prior service costs		(182	)		81		Salaries and employee benefits
	Tax expense		1,189			1,419		Income tax expense
	Net of tax	$	1,601		$	2,174
	Total reclassifications during the period, net of tax	$	740		$	1,812

Commitments_and_Contingent_Lia1

Commitments and Contingent Liabilities (Tables)	12 Months Ended
	Dec. 31, 2013
Commitments and Contingent Liabilities [Abstract]	'
Schedule of maximum commitments potential obligation	'
	The Company is a party to certain financial instruments with off balance sheet risk in the normal course of business to meet the financing needs of its customers.  These financial instruments include commitments to extend credit, unused lines of credit, standby letters of credit, and certain mortgage loans sold to investors with recourse. The Company’s exposure to credit loss in the event of nonperformance by the other party to the commitments to extend credit, unused lines of credit, standby letters of credit, and loans sold with recourse is represented by the contractual amount of those instruments. The credit risk associated with commitments to extend credit and standby and commercial letters of credit is essentially the same as that involved with extending loans to customers and is subject to normal credit policies.  Collateral may be obtained based on management’s assessment of the customer’s creditworthiness.
		At December 31,
	(In thousands)	2013		2012
	Unused lines of credit	$	216,658	$	163,626
	Commitments to extend credits, primarily variable rate		849,092		678,093
	Standby letters of credit		36,837		37,510
	Commercial letters of credit		41,263		16,607
	Loans sold with recourse		15,741		13,690

Fair_Values_of_Financial_Instr1

Fair Values of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2013
Fair Values of Financial Instruments [Abstract]	'
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 December 31, 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.
				31-Dec-13				31-Dec-12
	(In thousands)	Fair Value Hierarchy		Carrying amount		Estimated fair value		Carrying amount		Estimated fair value
	Financial assets
	Securities held to maturity		2	$	117,283	$	113,276	$	60,563	$	61,535
	Net loans		3		5,337,361		5,386,520		4,208,282		4,313,244
	Financial liabilities
	Time deposits		2	$	1,021,142	$	1,023,982	$	983,261	$	994,376
	Long-term debt		2		308,823		325,195		367,492		407,404
	Junior subordinated debt		2		101,196		105,121		75,422		74,147
Fair Value of Financial Assets and Liabilities Measured on a Recurring Basis	'
	The following table sets forth the Company’s financial assets and liabilities measured on a recurring basis that were accounted for at fair value as of December 31, 2013 and December 31, 2012.  Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement (in thousands):
		Quoted Prices in		Significant		Significant
		Active Markets for		Other		Unobservable		Balance
		Identical Assets		Observable Inputs		Inputs		as of
		(Level 1)		(Level 2)		(Level 3)		31-Dec-13
	Assets:
	Securities Available for Sale:
	U.S. Treasury	$	43,616	$	-	$	-	$	43,616
	Federal Agency		-		278,915		-		278,915
	State & municipal		-		113,665		-		113,665
	Mortgage-backed		-		364,164		-		364,164
	Collateralized mortgage obligations		-		549,528		-		549,528
	Other securities		6,796		8,197		-		14,993
	Total Securities Available for Sale	$	50,412	$	1,314,750	$	-	$	1,364,881
	Trading Securities		5,779		-		-		5,779
	Interest Rate Swaps		-		281		-		281
	Total	$	56,191	$	1,314,750	$	-	$	1,370,941
	Liabilities:
	Interest Rate Swaps	$	-	$	281	$	-	$	281
	Total	$	-	$	281	$	-	$	281
		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		8,672		5,282		-		13,954
	Total Securities Available for Sale	$	73,097	$	1,074,902	$	-	$	1,147,999
	Trading Securities		3,918		-		-		3,918
	Interest Rate Swaps		-		1,490		-		1,490
	Total	$	77,015	$	1,076,392	$	-	$	1,153,407
	Liabilities:
	Interest Rate Swaps	$	-	$	1,490	$	-	$	1,490
	Total	$	-	$	1,490	$	-	$	1,490

Parent_Company_Financial_Infor1

Parent Company Financial Information (Tables)	12 Months Ended
	Dec. 31, 2013
Parent Company Financial Information [Abstract]	'
Parent company financial information	'
	Condensed Balance Sheets
		December 31,
	(In thousands)	2013			2012
	Assets
	Cash and cash equivalents	$	3,741		$	23,095
	Securities available for sale, at estimated fair value		11,008			12,866
	Trading securities		4,742			3,371
	Investment in subsidiaries, on equity basis		896,479			635,851
	Other assets		49,530			48,324
	Total assets	$	965,500		$	723,507
	Liabilities and Stockholders’ Equity
	Total liabilities	$	148,931		$	141,234
	Stockholders’ equity		816,569			582,273
	Total liabilities and stockholders’ equity	$	965,500		$	723,507
	Condensed Income Statements
		Years ended December 31,
	(In thousands)	2013			2012			2011
	Dividends from subsidiaries	$	13,500		$	79,175		$	54,400
	Management fee from subsidiaries		84,778			78,665			69,430
	Securities gains (losses)		1,273			442			(31	)
	Interest, dividend and other income		636			720			628
	Total revenue		100,187			159,002			124,427
	Operating expense		83,675			79,015			75,254
	Income before income tax benefit and equity in undistributed income of subsidiaries		16,512			79,987			49,173
	Income tax (expense) benefit		(1,046	)		(284	)		1,340
	Dividends in excess of income (equity in undistributed income) of subsidiaries		46,285			(25,145	)		7,388
	Net income	$	61,751		$	54,558		$	57,901
	Statements of Cash Flow
		Years ended December 31,
	(In thousands)	2013			2012			2011
	Operating activities
	Net income	$	61,751		$	54,558		$	57,901
	Adjustments to reconcile net income to net cash provided by operating activities
	Stock-based compensation		4,305			4,364			3,244
	Gain on sales of available-for-sale securities		1,273			442			31
	Equity in undistributed income of subsidiaries		(59,785	)		(54,030	)		(61,788	)
	Cash dividend from subsidiaries		13,500			79,175			54,400
	Net change in other liabilities		(18,077	)		(3,181	)		15,311
	Net change in other assets		14,924			2,030			(11,607	)
	Net cash provided by operating activities		17,891			83,358			57,492
	Investing activities
	Purchases of available-for-sale securities		-			(4,163	)		(968	)
	Sales and maturities of available-for-sale securities		1,948			1,445			71
	Net cash provided by (used in) acquisitions		2,232			(14,612	)		-
	Purchases of premises and equipment		(782	)		(1,240	)		(1,656	)
	Net cash provided by (used in) investing activities		3,398			(18,570	)		(2,553	)
	Financing activities
	Proceeds from the issuance of shares to employee benefit plans and other stock plans		5,512			1,387			1,386
	Payments on long-term debt		-			(3,340	)		(140	)
	Purchases of treasury shares		(12,459	)		(15,490	)		(30,502	)
	Cash dividends and payments for fractional shares		(33,518	)		(26,712	)		(27,063	)
	Excess tax benefit from exercise of stock options		(178	)		8			341
	Net cash used in financing activities		(40,643	)		(44,147	)		(55,978	)
	Net (decrease )increase in cash and cash equivalents		(19,354	)		20,641			(1,039	)
	Cash and cash equivalents at beginning of year		23,095			2,454			3,493
	Cash and cash equivalents at end of year	$	3,741		$	23,095		$	2,454

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
	Agreement
Summary of Significant Accounting Policies [Abstract]	'	'
Balance of OREO	$2.90	$2.30
Number of interest rate swap agreements	2	'
Standby letters of credit expiration period	'1 year	'
Standby letters of credit, description	'typically have one year expirations with an option to renew upon annual review	'
Mortgage loans on real estate, by loan disclosure	'The Company originates and services residential mortgage loans for consumers and sells 15-year, 20-year and 30-year residential real estate mortgages in the secondary market when the interest rate environment is determined to be favorable by management, while retaining servicing rights on the sold loans.	'

Acquisitions_Details

Acquisitions (Details) (USD $)	12 Months Ended			0 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Mar. 08, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 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	'	'	'
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 and Leases	'	'	'	904,473,000	'	'	'	'
Intangible assets	'	'	'	13,161,000	'	'	'	'
Other assets	'	'	'	72,731,000	'	'	'	'
Deposits	'	'	'	-1,113,420,000	'	'	'	'
Borrowings	'	'	'	-126,530,000	'	'	'	'
Trust preferred debentures	'	'	'	-25,774,000	'	'	'	'
Other liabilities	'	'	'	-19,994,000	'	'	'	'
Total identifiable net assets	'	'	'	106,325,000	'	'	'	'
Goodwill	264,997,000	152,373,000	132,029,000	113,458,000	'	'	'	'
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	'	'	'	'
Direct costs related acquisition	12,364,000	2,608,000	804,000	'	12,400,000	'	'	'
Core deposit and trust intangible assets useful life, minimum	'	'	'	'	'10 years	'	'	'
Core deposit and trust intangible assets useful life, maximum	'	'	'	'	'15 years	'	'	'
Net Income (Loss) [Abstract]	'	'	'	'	'	'	'	'
Net interest income	'	'	'	'	244,383,000	244,142,000	'	'
Noninterest income	'	'	'	'	107,894,000	106,178,000	'	'
Net income	'	'	'	'	70,341,000	62,694,000	'	'
Other goodwill adjustments [Abstract]	'	'	'	'	'	'	'	'
Goodwill, purchase accounting adjustments	'	'	'	'	'	'	($1,000,000)	$100,000

Securities_Details

Securities (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	Position	Position
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Amortized cost	$1,379,751,000	$1,120,384,000	'
Unrealized gains	14,737,000	27,794,000	'
Unrealized losses	29,607,000	179,000	'
Estimated fair value	1,364,881,000	1,147,999,000	'
Unrealized Loss Position, Fair Value [Abstract]	'	'	'
Less Than 12 Months, Fair Value	812,106,000	40,397,000	'
12 Months or Longer, Fair Value	9,842,000	167,000	'
Total, Fair Value	821,948,000	40,564,000	'
Unrealized Loss Position, Unrealized Losses [Abstract]	'	'	'
Less than 12 months Unrealized Losses	-29,201,000	-97,000	'
12 months or longer Unrealized Losses	-406,000	-82,000	'
Total Unrealized Losses	-29,607,000	-179,000	'
Unrealized Loss Position, Number of Positions [Abstract]	'	'	'
Less Than 12 Months, Number of Positions	314	7	'
12 Months or Longer, Number of Positions	2	1	'
Total, Number of Positions	316	8	'
Sales transactions of securities available for sale [Abstract]	'	'	'
Proceeds from sales	27,593,000	1,790,000	2,437,000
Gross realized gains	1,283,000	442,000	7,000
Gross realized losses	0	0	-165,000
Net securities (losses) gains	1,283,000	442,000	-158,000
Gains from calls on securities available for sale	100,000	200,000	300,000
Amortized costs of securities available for sale pledged to secure public deposits	1,400,000,000	1,200,000,000	'
Amortized costs of securities available for sale pledged as collateral for repurchase agreements	218,400,000	'	'
Schedule of Held-to-maturity Securities [Line Items]	'	'	'
Amortized cost	117,283,000	60,563,000	'
Unrealized gains	570,000	972,000	'
Unrealized losses	4,577,000	0	'
Total, Fair Value	113,276,000	61,535,000	'
Unrealized Loss Position, Fair Value [Abstract]	'	'	'
Less Than 12 Months, Fair Value	58,468,000	'	'
12 Months or Longer, Fair Value	0	'	'
Total, Fair Value	58,468,000	'	'
Unrealized Loss Position, Unrealized Losses [Abstract]	'	'	'
Less Than 12 Months, Unrealized Losses	-4,577,000	'	'
12 Months or Longer, Unrealized Losses	0	'	'
Total, Unrealized Losses	-4,577,000	'	'
Unrealized Loss Position, Number of Positions [Abstract]	'	'	'
Less Than 12 Months, Number of Positions	6	'	'
12 Months or Longer, Number of Positions	0	'	'
Total, Number of Positions	6	'	'
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]	'	'	'
Within one year	27,894,000	'	'
From one to five years	261,703,000	'	'
From five to ten years	300,051,000	'	'
After ten years	777,736,000	'	'
Total, Amortized Cost	1,367,384,000	'	'
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]	'	'	'
Within one year	28,030,000	'	'
From one to five years	261,526,000	'	'
From five to ten years	297,837,000	'	'
After ten years	762,495,000	'	'
Total, Fair Value	1,349,888,000	'	'
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]	'	'	'
Within one year	24,680,000	'	'
From one to five years	22,791,000	'	'
From five to ten years	5,489,000	'	'
After ten years	64,323,000	'	'
Securities held to maturity	117,283,000	60,563,000	'
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]	'	'	'
Within one year	24,766,000	'	'
From one to five years	23,148,000	'	'
From five to ten years	5,481,000	'	'
After ten years	59,881,000	'	'
Total, Fair Value	113,276,000	61,535,000	'
Consolidated stockholders' equity threshold percentage that no single issuer of securities exceeded except for U.S. Government securities. (in hundredths)	10.00%	10.00%	'
Mortgage-Backed [Member]	'	'	'
Schedule of Held-to-maturity Securities [Line Items]	'	'	'
Amortized cost	953,000	1,168,000	'
Unrealized gains	128,000	184,000	'
Unrealized losses	0	0	'
Total, Fair Value	1,081,000	1,352,000	'
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]	'	'	'
Securities held to maturity	953,000	1,168,000	'
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]	'	'	'
Total, Fair Value	1,081,000	1,352,000	'
State & Municipal [Member]	'	'	'
Schedule of Held-to-maturity Securities [Line Items]	'	'	'
Amortized cost	54,305,000	59,395,000	'
Unrealized gains	442,000	788,000	'
Unrealized losses	8,000	0	'
Total, Fair Value	54,739,000	60,183,000	'
Unrealized Loss Position, Fair Value [Abstract]	'	'	'
Less Than 12 Months, Fair Value	1,012,000	'	'
12 Months or Longer, Fair Value	0	'	'
Total, Fair Value	1,012,000	'	'
Unrealized Loss Position, Unrealized Losses [Abstract]	'	'	'
Less Than 12 Months, Unrealized Losses	-8,000	'	'
12 Months or Longer, Unrealized Losses	0	'	'
Total, Unrealized Losses	-8,000	'	'
Unrealized Loss Position, Number of Positions [Abstract]	'	'	'
Less Than 12 Months, Number of Positions	1	'	'
12 Months or Longer, Number of Positions	0	'	'
Total, Number of Positions	1	'	'
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]	'	'	'
Securities held to maturity	54,305,000	59,395,000	'
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]	'	'	'
Total, Fair Value	54,739,000	60,183,000	'
Collateralized Mortgage Obligations [Member]	'	'	'
Schedule of Held-to-maturity Securities [Line Items]	'	'	'
Amortized cost	62,025,000	'	'
Unrealized gains	0	'	'
Unrealized losses	4,569,000	'	'
Total, Fair Value	57,456,000	'	'
Unrealized Loss Position, Fair Value [Abstract]	'	'	'
Less Than 12 Months, Fair Value	57,456,000	'	'
12 Months or Longer, Fair Value	0	'	'
Total, Fair Value	57,456,000	'	'
Unrealized Loss Position, Unrealized Losses [Abstract]	'	'	'
Less Than 12 Months, Unrealized Losses	-4,569,000	'	'
12 Months or Longer, Unrealized Losses	0	'	'
Total, Unrealized Losses	-4,569,000	'	'
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	62,025,000	'	'
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]	'	'	'
Total, Fair Value	57,456,000	'	'
US Treasury [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Amortized cost	43,279,000	63,668,000	'
Unrealized gains	337,000	757,000	'
Unrealized losses	0	0	'
Estimated fair value	43,616,000	64,425,000	'
Federal Agency [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Amortized cost	285,880,000	281,398,000	'
Unrealized gains	343,000	1,507,000	'
Unrealized losses	7,308,000	91,000	'
Estimated fair value	278,915,000	282,814,000	'
Unrealized Loss Position, Fair Value [Abstract]	'	'	'
Less Than 12 Months, Fair Value	233,935,000	39,906,000	'
12 Months or Longer, Fair Value	9,619,000	0	'
Total, Fair Value	243,554,000	39,906,000	'
Unrealized Loss Position, Unrealized Losses [Abstract]	'	'	'
Less than 12 months Unrealized Losses	-6,927,000	-91,000	'
12 months or longer Unrealized Losses	-381,000	0	'
Total Unrealized Losses	-7,308,000	-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	1	0	'
Total, Number of Positions	21	4	'
State & Municipal [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Amortized cost	113,435,000	82,675,000	'
Unrealized gains	1,842,000	4,127,000	'
Unrealized losses	1,612,000	0	'
Estimated fair value	113,665,000	86,802,000	'
Unrealized Loss Position, Fair Value [Abstract]	'	'	'
Less Than 12 Months, Fair Value	50,328,000	'	'
12 Months or Longer, Fair Value	0	'	'
Total, Fair Value	50,328,000	'	'
Unrealized Loss Position, Unrealized Losses [Abstract]	'	'	'
Less than 12 months Unrealized Losses	-1,612,000	'	'
12 months or longer Unrealized Losses	0	'	'
Total Unrealized Losses	-1,612,000	'	'
Unrealized Loss Position, Number of Positions [Abstract]	'	'	'
Less Than 12 Months, Number of Positions	177	'	'
12 Months or Longer, Number of Positions	0	'	'
Total, Number of Positions	177	'	'
Mortgage-Backed [Member]	'	'	'
Unrealized Loss Position, Fair Value [Abstract]	'	'	'
Less Than 12 Months, Fair Value	143,080,000	'	'
12 Months or Longer, Fair Value	0	'	'
Total, Fair Value	143,080,000	'	'
Unrealized Loss Position, Unrealized Losses [Abstract]	'	'	'
Less than 12 months Unrealized Losses	-2,216,000	'	'
12 months or longer Unrealized Losses	0	'	'
Total Unrealized Losses	-2,216,000	'	'
Unrealized Loss Position, Number of Positions [Abstract]	'	'	'
Less Than 12 Months, Number of Positions	79	'	'
12 Months or Longer, Number of Positions	0	'	'
Total, Number of Positions	79	'	'
Mortgage-Backed [Member] | Government-sponsored enterprises [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Amortized cost	337,666,000	221,110,000	'
Unrealized gains	5,788,000	11,175,000	'
Unrealized losses	2,131,000	0	'
Estimated fair value	341,323,000	232,285,000	'
Mortgage-Backed [Member] | U.S. government securities [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Amortized cost	21,924,000	16,351,000	'
Unrealized gains	1,002,000	1,645,000	'
Unrealized losses	85,000	0	'
Estimated fair value	22,841,000	17,996,000	'
Collateralized Mortgage Obligations [Member]	'	'	'
Unrealized Loss Position, Fair Value [Abstract]	'	'	'
Less Than 12 Months, Fair Value	379,273,000	23,000	'
12 Months or Longer, Fair Value	0	0	'
Total, Fair Value	379,273,000	23,000	'
Unrealized Loss Position, Unrealized Losses [Abstract]	'	'	'
Less than 12 months Unrealized Losses	-18,243,000	0	'
12 months or longer Unrealized Losses	0	0	'
Total Unrealized Losses	-18,243,000	0	'
Unrealized Loss Position, Number of Positions [Abstract]	'	'	'
Less Than 12 Months, Number of Positions	36	2	'
12 Months or Longer, Number of Positions	0	0	'
Total, Number of Positions	36	2	'
Collateralized Mortgage Obligations [Member] | Government-sponsored enterprises [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Amortized cost	521,257,000	399,147,000	'
Unrealized gains	1,777,000	4,418,000	'
Unrealized losses	18,141,000	0	'
Estimated fair value	504,893,000	403,565,000	'
Collateralized Mortgage Obligations [Member] | U.S. government securities [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Amortized cost	43,943,000	44,825,000	'
Unrealized gains	794,000	1,333,000	'
Unrealized losses	102,000	0	'
Estimated fair value	44,635,000	46,158,000	'
Other Securities [Member]	'	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'	'
Amortized cost	12,367,000	11,210,000	'
Unrealized gains	2,854,000	2,832,000	'
Unrealized losses	228,000	88,000	'
Estimated fair value	14,993,000	13,954,000	'
Unrealized Loss Position, Fair Value [Abstract]	'	'	'
Less Than 12 Months, Fair Value	5,490,000	468,000	'
12 Months or Longer, Fair Value	223,000	167,000	'
Total, Fair Value	5,713,000	635,000	'
Unrealized Loss Position, Unrealized Losses [Abstract]	'	'	'
Less than 12 months Unrealized Losses	-203,000	-6,000	'
12 months or longer Unrealized Losses	-25,000	-82,000	'
Total Unrealized Losses	($228,000)	($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	'

Loans_Details

Loans (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Net Loans	$5,406,795,000	$4,277,616,000
Deferred loan origination costs, net	31,800,000	25,500,000
Residential loans held for sale	100,000	3,600,000
Loans and Leases Receivable, Related Parties [Roll Forward]	'	'
Balance at January 1	2,790,000	2,537,000
New loans	569,000	750,000
Adjustment due to change in composition of related parties	376,000	-130,000
Repayments	-363,000	-367,000
Balance at December 31	3,372,000	2,790,000
Residential Real Estate Mortgages [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Net Loans	1,041,637,000	651,107,000
Commercial [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Net Loans	859,026,000	694,799,000
Commercial Real Estate [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Net Loans	1,328,313,000	1,072,807,000
Real Estate Construction and Development [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Net Loans	93,247,000	123,078,000
Agricultural and Agricultural Real Estate Mortgages [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Net Loans	112,035,000	112,687,000
Consumer [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Net Loans	1,352,638,000	1,047,856,000
Home Equity [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Net Loans	$619,899,000	$575,282,000

Allowance_for_Loan_Losses_and_2

Allowance for Loan Losses and Credit Quality of Loans (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
	Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]	'
Loan portfolio segments	3
Commercial Loans [Member] | Commercial Real Estate [Member]	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'
Real estate loan amount, percentage of appraised value or purchase price of the property, maximum (in hundredths)	80.00%
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%
Commercial Loans [Member] | Business Banking [Member]	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'
Business banking loans, maximum amount	500
Consumer Loans [Member] | Indirect [Member]	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'
Percentage of automobile financing to indirect relationships with dealers (in hundredths)	70.00%
Principal repayment term of loan, minimum (in years)	'3 years
Principal repayment term of loan, maximum (in years)	'6 years
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%
Consumer Loans [Member] | Direct [Member]	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'
Principal repayment term of loan, minimum (in years)	'1 year
Principal repayment term of loan, maximum (in years)	'10 years
Residential Real Estate Mortgages [Member]	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'
Real estate loan amount, percentage of appraised value or purchase price of the property, maximum (in hundredths)	85.00%

Allowance_for_Loan_Losses_and_3

Allowance for Loan Losses and Credit Quality of Loans, Allowance for Loan Losses (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Roll Forward]	'	'	'
Balance as of Beginning of Period	$69,334	$71,334	$71,234
Charge-offs	-27,689	-26,504	-24,488
Recoveries	5,365	4,235	3,851
Provision	22,424	20,269	20,737
Balance as of Ending of Period	69,434	69,334	71,334
Allowance loan losses [Abstract]	'	'	'
Allowance for loan losses	69,434	69,334	71,334
Allowance for loans individually evaluated for impairment	715	2,848	'
Allowance for loans collectively evaluated for impairment	68,719	66,486	'
Ending balance of loans	5,406,795	4,277,616	'
Ending balance of loans individually evaluated for impairment	'	23,069	'
Ending balance of loans collectively evaluated for impairment	'	4,254,547	'
Commercial Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Roll Forward]	'	'	'
Balance as of Beginning of Period	35,624	38,831	40,101
Charge-offs	-10,459	-8,750	-8,969
Recoveries	1,957	1,641	1,438
Provision	7,968	3,902	6,261
Balance as of Ending of Period	35,090	35,624	38,831
Allowance loan losses [Abstract]	'	'	'
Allowance for loan losses	35,090	35,624	38,831
Allowance for loans individually evaluated for impairment	715	2,848	'
Allowance for loans collectively evaluated for impairment	34,375	32,776	'
Ending balance of loans	2,392,621	2,003,371	'
Ending balance of loans individually evaluated for impairment	'	18,505	'
Ending balance of loans collectively evaluated for impairment	'	1,984,866	'
Consumer Loans [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Roll Forward]	'	'	'
Balance as of Beginning of Period	27,162	26,049	26,126
Charge-offs	-15,459	-15,848	-14,209
Recoveries	3,136	2,556	2,406
Provision	12,855	14,405	11,726
Balance as of Ending of Period	27,694	27,162	26,049
Allowance loan losses [Abstract]	'	'	'
Allowance for loan losses	27,694	27,162	26,049
Allowance for loans individually evaluated for impairment	0	0	'
Allowance for loans collectively evaluated for impairment	27,694	27,162	'
Ending balance of loans	1,972,537	1,623,138	'
Ending balance of loans individually evaluated for impairment	'	2,553	'
Ending balance of loans collectively evaluated for impairment	'	1,620,585	'
Residential Real Estate Mortgages [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Roll Forward]	'	'	'
Balance as of Beginning of Period	6,252	6,249	4,627
Charge-offs	-1,771	-1,906	-1,310
Recoveries	272	38	7
Provision	1,767	1,871	2,925
Balance as of Ending of Period	6,520	6,252	6,249
Allowance loan losses [Abstract]	'	'	'
Allowance for loan losses	6,520	6,252	6,249
Allowance for loans individually evaluated for impairment	0	0	'
Allowance for loans collectively evaluated for impairment	6,520	6,252	'
Ending balance of loans	1,041,637	651,107	'
Ending balance of loans individually evaluated for impairment	'	2,011	'
Ending balance of loans collectively evaluated for impairment	'	649,096	'
Unallocated [Member]	'	'	'
Financing Receivable, Allowance for Credit Losses [Roll Forward]	'	'	'
Balance as of Beginning of Period	296	205	380
Charge-offs	0	0	0
Recoveries	0	0	0
Provision	-166	91	-175
Balance as of Ending of Period	130	296	205
Allowance loan losses [Abstract]	'	'	'
Allowance for loan losses	130	296	205
Allowance for loans collectively evaluated for impairment	130	296	'
Originated Loans [Member]	'	'	'
Allowance loan losses [Abstract]	'	'	'
Ending balance of loans	4,476,403	'	'
Ending balance of loans individually evaluated for impairment	21,380	'	'
Ending balance of loans collectively evaluated for impairment	4,455,023	'	'
Originated Loans [Member] | Commercial Loans [Member]	'	'	'
Allowance loan losses [Abstract]	'	'	'
Ending balance of loans individually evaluated for impairment	16,120	'	'
Ending balance of loans collectively evaluated for impairment	1,974,112	'	'
Originated Loans [Member] | Consumer Loans [Member]	'	'	'
Allowance loan losses [Abstract]	'	'	'
Ending balance of loans individually evaluated for impairment	3,248	'	'
Ending balance of loans collectively evaluated for impairment	1,749,702	'	'
Originated Loans [Member] | Residential Real Estate Mortgages [Member]	'	'	'
Allowance loan losses [Abstract]	'	'	'
Ending balance of loans individually evaluated for impairment	2,012	'	'
Ending balance of loans collectively evaluated for impairment	731,209	'	'
Acquired Loans [Member]	'	'	'
Allowance loan losses [Abstract]	'	'	'
Ending balance of loans	930,392	'	'
Ending balance of loans individually evaluated for impairment	10,060	'	'
Ending balance of loans collectively evaluated for impairment	920,332	'	'
Acquired Loans [Member] | Commercial Loans [Member]	'	'	'
Allowance loan losses [Abstract]	'	'	'
Ending balance of loans individually evaluated for impairment	10,060	'	'
Ending balance of loans collectively evaluated for impairment	392,329	'	'
Acquired Loans [Member] | Consumer Loans [Member]	'	'	'
Allowance loan losses [Abstract]	'	'	'
Ending balance of loans individually evaluated for impairment	0	'	'
Ending balance of loans collectively evaluated for impairment	219,587	'	'
Acquired Loans [Member] | Residential Real Estate Mortgages [Member]	'	'	'
Allowance loan losses [Abstract]	'	'	'
Ending balance of loans individually evaluated for impairment	0	'	'
Ending balance of loans collectively evaluated for impairment	$308,416	'	'

Allowance_for_Loan_Losses_and_4

Allowance for Loan Losses and Credit Quality of Loans, Past Due Loans (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Aging [Abstract]	'	'
Minimum number of days past due for nonaccrual loan status (in days)	'90 days	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	$31,961	$22,852
61 - 90 Days Past Due Accruing	5,894	5,277
Greater Than 90 Days Past Due Accruing	3,737	2,448
Total Past Due Accruing	41,592	30,577
Non-Accrual	49,965	39,676
Current	5,315,238	4,207,363
Recorded Total Loans and Leases	5,406,795	4,277,616
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
Recorded Total Loans and Leases	'	561,481
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
Recorded Total Loans and Leases	'	974,795
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
Recorded Total Loans and Leases	'	63,758
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
Recorded Total Loans and Leases	'	37,377
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
Recorded Total Loans and Leases	'	365,960
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
Recorded Total Loans and Leases	'	2,003,371
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
Recorded Total Loans and Leases	'	980,997
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
Recorded Total Loans and Leases	'	575,282
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
Recorded Total Loans and Leases	'	66,859
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
Recorded Total Loans and Leases	'	1,623,138
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
Recorded Total Loans and Leases	'	651,107
Originated Loans [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	28,124	'
61 - 90 Days Past Due Accruing	5,660	'
Greater Than 90 Days Past Due Accruing	3,657	'
Total Past Due Accruing	37,441	'
Non-Accrual	33,883	39,676
Current	4,405,079	'
Recorded Total Loans and Leases	4,476,403	'
Originated Loans [Member] | Commercial Loans [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
Non-Accrual	19,300	21,437
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	105	'
61 - 90 Days Past Due Accruing	247	'
Greater Than 90 Days Past Due Accruing	0	'
Total Past Due Accruing	352	'
Non-Accrual	3,669	4,985
Current	612,402	'
Recorded Total Loans and Leases	616,423	'
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	1,366	'
61 - 90 Days Past Due Accruing	0	'
Greater Than 90 Days Past Due Accruing	0	'
Total Past Due Accruing	1,366	'
Non-Accrual	7,834	7,977
Current	925,116	'
Recorded Total Loans and Leases	934,316	'
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	150	'
61 - 90 Days Past Due Accruing	21	'
Greater Than 90 Days Past Due Accruing	0	'
Total Past Due Accruing	171	'
Non-Accrual	1,135	699
Current	63,856	'
Recorded Total Loans and Leases	65,162	'
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	519	'
61 - 90 Days Past Due Accruing	0	'
Greater Than 90 Days Past Due Accruing	0	'
Total Past Due Accruing	519	'
Non-Accrual	961	1,038
Current	35,172	'
Recorded Total Loans and Leases	36,652	'
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	1,228	'
61 - 90 Days Past Due Accruing	122	'
Greater Than 90 Days Past Due Accruing	105	'
Total Past Due Accruing	1,455	'
Non-Accrual	5,701	6,738
Current	330,523	'
Recorded Total Loans and Leases	337,679	'
Originated Loans [Member] | Commercial Loans [Member] | Total Commercial Loan [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	3,368	'
61 - 90 Days Past Due Accruing	390	'
Greater Than 90 Days Past Due Accruing	105	'
Total Past Due Accruing	3,863	'
Non-Accrual	19,300	'
Current	1,967,069	'
Recorded Total Loans and Leases	1,990,232	'
Originated Loans [Member] | Consumer Loans [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
Non-Accrual	7,478	9,070
Originated Loans [Member] | Consumer Loans [Member] | Indirect [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	14,093	'
61 - 90 Days Past Due Accruing	2,878	'
Greater Than 90 Days Past Due Accruing	1,583	'
Total Past Due Accruing	18,554	'
Non-Accrual	1,461	1,557
Current	1,141,829	'
Recorded Total Loans and Leases	1,161,844	'
Originated Loans [Member] | Consumer Loans [Member] | Home Equity Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	6,033	'
61 - 90 Days Past Due Accruing	1,888	'
Greater Than 90 Days Past Due Accruing	1,115	'
Total Past Due Accruing	9,036	'
Non-Accrual	5,931	7,247
Current	517,856	'
Recorded Total Loans and Leases	532,823	'
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	679	'
61 - 90 Days Past Due Accruing	125	'
Greater Than 90 Days Past Due Accruing	46	'
Total Past Due Accruing	850	'
Non-Accrual	86	266
Current	57,347	'
Recorded Total Loans and Leases	58,283	'
Originated Loans [Member] | Consumer Loans [Member] | Total Consumer Loan [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	20,805	'
61 - 90 Days Past Due Accruing	4,891	'
Greater Than 90 Days Past Due Accruing	2,744	'
Total Past Due Accruing	28,440	'
Non-Accrual	7,478	'
Current	1,717,032	'
Recorded Total Loans and Leases	1,752,950	'
Originated Loans [Member] | Residential Real Estate Mortgages [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	3,951	'
61 - 90 Days Past Due Accruing	379	'
Greater Than 90 Days Past Due Accruing	808	'
Total Past Due Accruing	5,138	'
Non-Accrual	7,105	9,169
Current	720,978	'
Recorded Total Loans and Leases	733,221	'
Acquired Loans [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	3,837	'
61 - 90 Days Past Due Accruing	234	'
Greater Than 90 Days Past Due Accruing	80	'
Total Past Due Accruing	4,151	'
Non-Accrual	16,082	'
Current	910,159	'
Recorded Total Loans and Leases	930,392	'
Acquired Loans [Member] | Commercial Loans [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
Non-Accrual	11,498	'
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	24	'
61 - 90 Days Past Due Accruing	0	'
Greater Than 90 Days Past Due Accruing	0	'
Total Past Due Accruing	24	'
Non-Accrual	6,599	'
Current	96,603	'
Recorded Total Loans and Leases	103,226	'
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [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	3,559	'
Current	225,455	'
Recorded Total Loans and Leases	229,014	'
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	320	'
61 - 90 Days Past Due Accruing	2	'
Greater Than 90 Days Past Due Accruing	0	'
Total Past Due Accruing	322	'
Non-Accrual	1,340	'
Current	68,487	'
Recorded Total Loans and Leases	70,149	'
Acquired Loans [Member] | Commercial Loans [Member] | Total Commercial Loan [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	344	'
61 - 90 Days Past Due Accruing	2	'
Greater Than 90 Days Past Due Accruing	0	'
Total Past Due Accruing	346	'
Non-Accrual	11,498	'
Current	390,545	'
Recorded Total Loans and Leases	402,389	'
Acquired Loans [Member] | Consumer Loans [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
Non-Accrual	712	'
Acquired Loans [Member] | Consumer Loans [Member] | Indirect [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	939	'
61 - 90 Days Past Due Accruing	113	'
Greater Than 90 Days Past Due Accruing	71	'
Total Past Due Accruing	1,123	'
Non-Accrual	93	'
Current	123,870	'
Recorded Total Loans and Leases	125,086	'
Acquired Loans [Member] | Consumer Loans [Member] | Home Equity Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	753	'
61 - 90 Days Past Due Accruing	63	'
Greater Than 90 Days Past Due Accruing	0	'
Total Past Due Accruing	816	'
Non-Accrual	570	'
Current	85,690	'
Recorded Total Loans and Leases	87,076	'
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	76	'
61 - 90 Days Past Due Accruing	56	'
Greater Than 90 Days Past Due Accruing	9	'
Total Past Due Accruing	141	'
Non-Accrual	49	'
Current	7,235	'
Recorded Total Loans and Leases	7,425	'
Acquired Loans [Member] | Consumer Loans [Member] | Total Consumer Loan [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	1,768	'
61 - 90 Days Past Due Accruing	232	'
Greater Than 90 Days Past Due Accruing	80	'
Total Past Due Accruing	2,080	'
Non-Accrual	712	'
Current	216,795	'
Recorded Total Loans and Leases	219,587	'
Acquired Loans [Member] | Residential Real Estate Mortgages [Member]	'	'
Financing Receivable, Recorded Investment, Past Due [Abstract]	'	'
31 - 60 Days Past Due Accruing	1,725	'
61 - 90 Days Past Due Accruing	0	'
Greater Than 90 Days Past Due Accruing	0	'
Total Past Due Accruing	1,725	'
Non-Accrual	3,872	'
Current	302,819	'
Recorded Total Loans and Leases	$308,416	'

Allowance_for_Loan_Losses_and_5

Allowance for Loan Losses and Credit Quality of Loans, Impaired Loans (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for Loan Losses and Credit Quality of Loans and Leases [Abstract]	'	'	'
Minimum balance for classified loans to be evaluated individually for impairment	$500	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	31,440	23,069	'
Unpaid Principal Balance (Legal)	35,430	25,712	'
Related Allowance	715	2,848	'
Average Recorded Investment	24,240	17,403	10,909
Interest Income Recognized Accrual	469	643	64
Originated Loans [Member] | Commercial Loans [Member] | Commercial [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Average Recorded Investment	3,722	6,682	1,507
Interest Income Recognized Accrual	17	56	0
Originated Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Average Recorded Investment	11,010	4,944	3,763
Interest Income Recognized Accrual	130	230	0
Originated Loans [Member] | Commercial Loans [Member] | Agricultural [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Average Recorded Investment	207	1,767	2,070
Interest Income Recognized Accrual	1	43	0
Originated Loans [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Average Recorded Investment	1,167	922	695
Interest Income Recognized Accrual	52	72	0
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Average Recorded Investment	295	68	17
Interest Income Recognized Accrual	57	65	0
Originated Loans [Member] | Consumer Loans [Member] | Home Equity [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Average Recorded Investment	2,969	1,877	1,924
Interest Income Recognized Accrual	143	123	60
Originated Loans [Member] | Residential Real Estate Mortgages [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Average Recorded Investment	2,024	1,143	933
Interest Income Recognized Accrual	69	54	4
Originated Loans [Member] | With No Allowance Recorded [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	16,360	14,666	'
Unpaid Principal Balance (Legal)	18,173	15,683	'
Originated Loans [Member] | With No Allowance Recorded [Member] | Commercial Loans [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	11,100	10,102	'
Unpaid Principal Balance (Legal)	12,446	10,718	'
Originated Loans [Member] | With No Allowance Recorded [Member] | Commercial Loans [Member] | Commercial [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	4,721	1,000	'
Unpaid Principal Balance (Legal)	4,777	1,000	'
Originated Loans [Member] | With No Allowance Recorded [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	4,613	7,362	'
Unpaid Principal Balance (Legal)	5,164	7,366	'
Originated Loans [Member] | With No Allowance Recorded [Member] | Commercial Loans [Member] | Agricultural [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	125	446	'
Unpaid Principal Balance (Legal)	195	540	'
Originated Loans [Member] | With No Allowance Recorded [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	1,431	903	'
Unpaid Principal Balance (Legal)	1,708	1,029	'
Originated Loans [Member] | With No Allowance Recorded [Member] | Commercial Loans [Member] | Business Banking [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	210	391	'
Unpaid Principal Balance (Legal)	602	783	'
Originated Loans [Member] | With No Allowance Recorded [Member] | Consumer Loans [Member] | Home Equity [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	3,248	2,553	'
Unpaid Principal Balance (Legal)	3,472	2,657	'
Originated Loans [Member] | With No Allowance Recorded [Member] | Residential Real Estate Mortgages [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	2,012	2,011	'
Unpaid Principal Balance (Legal)	2,255	2,308	'
Originated Loans [Member] | With An Allowance Recorded [Member] | Commercial Loans [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	5,020	8,403	'
Unpaid Principal Balance (Legal)	6,877	10,029	'
Related Allowance	715	2,848	'
Originated Loans [Member] | With An Allowance Recorded [Member] | Commercial Loans [Member] | Commercial [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	0	4,335	'
Unpaid Principal Balance (Legal)	0	4,340	'
Related Allowance	0	2,241	'
Originated Loans [Member] | With An Allowance Recorded [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	5,020	4,068	'
Unpaid Principal Balance (Legal)	6,877	5,689	'
Related Allowance	715	607	'
Originated Loans [Member] | With An Allowance Recorded [Member] | Commercial Loans [Member] | Agricultural [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	0	0	'
Unpaid Principal Balance (Legal)	0	0	'
Related Allowance	0	0	'
Originated Loans [Member] | With An Allowance Recorded [Member] | Commercial Loans [Member] | Agricultural Real Estate [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	0	0	'
Unpaid Principal Balance (Legal)	0	0	'
Related Allowance	0	0	'
Acquired Loans [Member] | Commercial Loans [Member] | Commercial [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Average Recorded Investment	1,625	0	0
Interest Income Recognized Accrual	0	0	0
Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Average Recorded Investment	1,222	0	0
Interest Income Recognized Accrual	0	0	0
Acquired Loans [Member] | With No Allowance Recorded [Member] | Commercial Loans [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	10,060	'	'
Unpaid Principal Balance (Legal)	10,380	'	'
Acquired Loans [Member] | With No Allowance Recorded [Member] | Commercial Loans [Member] | Commercial [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	6,501	'	'
Unpaid Principal Balance (Legal)	6,538	'	'
Acquired Loans [Member] | With No Allowance Recorded [Member] | Commercial Loans [Member] | Commercial Real Estate [Member]	'	'	'
Financing Receivable, Impaired [Line Items]	'	'	'
Recorded Investment Balance (Book)	3,559	'	'
Unpaid Principal Balance (Legal)	$3,842	'	'

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

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 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]

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]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Originated Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Acquired Loans [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [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]

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]

Performing [Member]

Nonperforming [Member]

Indirect [Member]

Indirect [Member]

Indirect [Member]

Home Equity Member]

Home Equity Member]

Home Equity Member]

Direct [Member]

Direct [Member]

Direct [Member]

Performing [Member]

Nonperforming [Member]

Residential Mortgage [Member]

Residential Mortgage [Member]

Residential Mortgage [Member]

Non-classified [Member]

Classified [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [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]

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]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking 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]

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]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Business Banking Credit Exposure [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Performing [Member]

Nonperforming [Member]

Performing [Member]

Nonperforming [Member]

Performing [Member]

Nonperforming [Member]

Performing [Member]

Nonperforming [Member]

Non-classified [Member]

Classified [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [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]

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]

Performing [Member]

Nonperforming [Member]

Indirect [Member]

Indirect [Member]

Indirect [Member]

Home Equity Member]

Home Equity Member]

Home Equity Member]

Direct [Member]

Direct [Member]

Direct [Member]

Performing [Member]

Nonperforming [Member]

Residential Mortgage [Member]

Residential Mortgage [Member]

Residential Mortgage [Member]

Non-classified [Member]

Classified [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [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]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Agricultural [Member]

Performing [Member]

Nonperforming [Member]

Indirect [Member]

Indirect [Member]

Indirect [Member]

Home Equity Member]

Home Equity Member]

Home Equity Member]

Direct [Member]

Direct [Member]

Direct [Member]

Performing [Member]

Nonperforming [Member]

Residential Mortgage [Member]

Residential Mortgage [Member]

Residential Mortgage [Member]

Non-classified [Member]

Classified [Member]

Business Banking [Member]

Business Banking [Member]

Business Banking [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Performing [Member]

Nonperforming [Member]

Performing [Member]

Nonperforming [Member]

Performing [Member]

Nonperforming [Member]

Performing [Member]

Nonperforming [Member]

Non-classified [Member]

Classified [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Pass [Member]

Special Mention [Member]

Substandard [Member]

Doubtful [Member]

Performing [Member]

Nonperforming [Member]

Performing [Member]

Nonperforming [Member]

Performing [Member]

Nonperforming [Member]

Performing [Member]

Nonperforming [Member]

Non-classified [Member]

Classified [Member]

Financing Receivable, Recorded Investment [Line Items]

'

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'

'

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'

'

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'

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'

Financing Receivable

$1,637,411

$1,515,732

$50,552

$68,347

$2,780

$561,481

$522,985

$18,401

$17,351

$2,744

$974,795

$901,928

$32,135

$40,732

$0

$63,758

$57,347

$13

$6,362

$36

$37,377

$33,472

$3

$3,902

$0

$1,623,138

$1,612,098

$11,040

$980,997

$978,235

$2,762

$575,282

$567,354

$7,928

$66,859

$66,509

$350

$651,107

$641,608

$9,499

$651,107

$641,608

$9,499

$365,960

$342,528

$23,432

$365,960

$342,528

$23,432

$1,652,553

$1,547,669

$40,037

$64,835

$12

$616,423

$576,079

$16,836

$23,508

$0

$934,316

$878,411

$22,777

$33,128

$0

$65,162

$60,043

$381

$4,726

$12

$36,652

$33,136

$43

$3,473

$0

$1,752,950

$1,742,728

$10,222

$1,161,844

$1,158,800

$3,044

$532,823

$525,777

$7,046

$58,283

$58,151

$132

$733,221

$725,308

$7,913

$733,221

$725,308

$7,913

$337,679

$319,578

$18,101

$337,679

$319,578

$18,101

$332,240

$290,702

$8,413

$33,125

$0

$103,226

$85,692

$2,230

$15,304

$0

$229,014

$205,010

$6,183

$17,821

$0

$0

$0

$0

$0

$0

$219,587

$218,795

$792

$125,086

$124,922

$164

$87,076

$86,506

$570

$7,425

$7,367

$58

$308,416

$304,544

$3,872

$308,416

$304,544

$3,872

$70,149

$65,437

$4,712

$70,149

$65,437

$4,712

Allowance_for_Loan_Losses_and_7

Allowance for Loan Losses and Credit Quality of Loans, Troubled Debt Restructurings (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
	Contract	Contract
Financing Receivable, Modifications [Line Items]	'	'
Period of sustained repayment performance for nonperforming TDRs to be returned to performing status (in months)	'6 months	'
Business Banking [Member]	'	'
Financing Receivable, Modifications [Line Items]	'	'
Number of contracts	'	1
Pre-modification outstanding recorded investment	'	$0.10
Home Equity [Member]	'	'
Financing Receivable, Modifications [Line Items]	'	'
Number of contracts	23	18
Pre-modification outstanding recorded investment	1	0.9
Commercial Loans [Member]	'	'
Financing Receivable, Modifications [Line Items]	'	'
Number of contracts	4	4
Pre-modification outstanding recorded investment	7	6.6
Residential Real Estate Mortgages [Member]	'	'
Financing Receivable, Modifications [Line Items]	'	'
Number of contracts	6	12
Pre-modification outstanding recorded investment	0.5	1.2
Subsequent Default [Member] | Home Equity [Member]	'	'
Financing Receivable, Modifications [Line Items]	'	'
Number of contracts	8	1
Pre-modification outstanding recorded investment	0.4	0.1
Subsequent Default [Member] | Commercial Loans [Member]	'	'
Financing Receivable, Modifications [Line Items]	'	'
Number of contracts	1	'
Pre-modification outstanding recorded investment	0.9	'
Subsequent Default [Member] | Residential Real Estate Mortgages [Member]	'	'
Financing Receivable, Modifications [Line Items]	'	'
Number of contracts	'	2
Pre-modification outstanding recorded investment	'	$0.30

Premises_and_Equipment_Net_Det

Premises and Equipment, Net (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]	'	'	'
Premises and equipment before accumulated depreciation	$175,827,000	$160,922,000	'
Accumulated depreciation	87,500,000	83,047,000	'
Total premises and equipment	88,327,000	77,875,000	'
Rental expense	7,500,000	6,400,000	5,600,000
Future Minimum Rental Payments [Abstract]	'	'	'
2014	7,156,000	'	'
2015	7,012,000	'	'
2016	6,985,000	'	'
2017	6,859,000	'	'
2018	6,791,000	'	'
Thereafter	53,132,000	'	'
Total	87,935,000	'	'
Land, Buildings and Improvements [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Premises and equipment before accumulated depreciation	120,098,000	109,601,000	'
Equipment [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Premises and equipment before accumulated depreciation	$55,729,000	$51,321,000	'
Equipment [Member] | Minimum [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property, plant and equipment, useful life	'3 years	'	'
Equipment [Member] | Maximum [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property, plant and equipment, useful life	'10 years	'	'
Building and Improvements [Member] | Minimum [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property, plant and equipment, useful life	'15 years	'	'
Building and Improvements [Member] | Maximum [Member]	'	'	'
Property, Plant and Equipment [Line Items]	'	'	'
Property, plant and equipment, useful life	'40 years	'	'

Goodwill_and_other_Intangible_2

Goodwill and other Intangible Assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Goodwill [Roll Forward]	'	'	'
Beginning Balance	$152,373,000	$132,029,000	'
Goodwill acquired	112,624,000	20,344,000	'
Ending Balance	264,997,000	152,373,000	132,029,000
Finite-Lived Intangible Assets [Line Items]	'	'	'
Gross carrying amount	47,910,000	34,983,000	'
Less: accumulated amortization	22,353,000	18,021,000	'
Net carrying amount	25,557,000	16,962,000	'
Amortization Expense [Abstract]	'	'	'
Amortization of intangible assets	4,872,000	3,394,000	3,046,000
Future Amortization Expense [Abstract]	'	'	'
2014	5,000,000	'	'
2015	4,600,000	'	'
2016	3,300,000	'	'
2017	2,800,000	'	'
2018	2,200,000	'	'
Thereafter	5,400,000	'	'
Indefinite-lived intangible assets (Excluding goodwill)	2,000,000	'	'
Minimum [Member]	'	'	'
Finite-Lived Intangible Assets [Line Items]	'	'	'
Intangible asset useful life	'1 year	'	'
Maximum [Member]	'	'	'
Finite-Lived Intangible Assets [Line Items]	'	'	'
Intangible asset useful life	'12 years	'	'
Core Deposits Intangibles [Member]	'	'	'
Finite-Lived Intangible Assets [Line Items]	'	'	'
Gross carrying amount	19,401,000	13,240,000	'
Less: accumulated amortization	10,083,000	7,794,000	'
Net carrying amount	9,318,000	5,446,000	'
Identified Intangible Assets [Member]	'	'	'
Finite-Lived Intangible Assets [Line Items]	'	'	'
Gross carrying amount	28,509,000	21,743,000	'
Less: accumulated amortization	12,270,000	10,227,000	'
Net carrying amount	$16,239,000	$11,516,000	'

Deposits_Details

Deposits (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Maturities of Time Deposits [Abstract]	'	'
Within one year	$661,619,000	'
After one but within two years	184,796,000	'
After two but within three years	86,689,000	'
After three but within four years	52,024,000	'
After four but within five years	20,656,000	'
After five years	15,358,000	'
Total	1,021,142,000	983,261,000
Time Deposits, $100,000 or More [Abstract]	'	'
Time deposits of $100,000 or more	$374,500,000	$352,300,000

ShortTerm_Borrowings_Details

Short-Term Borrowings (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Short-term Debt [Line Items]	'	'	'
Balance at year-end	$456,042,000	$162,941,000	'
FHLB, unused lines of credit available for short-term financing	497,000,000	418,000,000	'
Federal Funds Purchased [Member]	'	'	'
Short-term Debt [Line Items]	'	'	'
Balance at year-end	130,000,000	10,000,000	27,000,000
Average during the year	39,907,000	12,658,000	3,017,000
Maximum month end balance	130,000,000	60,000,000	28,000,000
Weighted average rate during the year (in hundredths)	0.26%	0.27%	0.11%
Weighted average rate at December 31 (in hundredths)	0.18%	0.27%	0.13%
Securities Sold under Repurchase Agreements [Member]	'	'	'
Short-term Debt [Line Items]	'	'	'
Balance at year-end	176,042,000	152,941,000	154,592,000
Average during the year	169,352,000	153,084,000	150,663,000
Maximum month end balance	185,871,000	165,977,000	178,414,000
Weighted average rate during the year (in hundredths)	0.06%	0.10%	0.13%
Weighted average rate at December 31 (in hundredths)	0.05%	0.10%	0.10%
Other Short-Term Borrowings [Member]	'	'	'
Short-term Debt [Line Items]	'	'	'
Balance at year-end	150,000,000	0	0
Average during the year	71,589,000	0	249,000
Maximum month end balance	$210,000,000	$0	$250,000
Weighted average rate during the year (in hundredths)	0.43%	0.00%	0.00%
Weighted average rate at December 31 (in hundredths)	0.55%	0.00%	0.00%

LongTerm_Debt_Details

Long-Term Debt (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Long-Term Debt by Maturity Periods [Abstract]	'	'
Amount	$308,823	$367,492
Callable Amount	220,000	345,000
2013 [Member]	'	'
Long-Term Debt by Maturity Periods [Abstract]	'	'
Maturity	31-Dec-13	'
Amount	0	119,502
Weighted Average Rate (in hundredths)	0.00%	3.87%
Callable Amount	0	100,000
Weighted Average Rate Callable Portion (in hundredths)	0.00%	3.71%
2014 [Member]	'	'
Long-Term Debt by Maturity Periods [Abstract]	'	'
Maturity	31-Dec-14	'
Amount	12,460	2,610
Weighted Average Rate (in hundredths)	1.33%	1.89%
Callable Amount	0	0
Weighted Average Rate Callable Portion (in hundredths)	0.00%	0.00%
2015 [Member]	'	'
Long-Term Debt by Maturity Periods [Abstract]	'	'
Maturity	31-Dec-15	'
Amount	308	250
Weighted Average Rate (in hundredths)	0.00%	0.00%
Callable Amount	0	0
Weighted Average Rate Callable Portion (in hundredths)	0.00%	0.00%
2016 [Member]	'	'
Long-Term Debt by Maturity Periods [Abstract]	'	'
Maturity	31-Dec-16	'
Amount	90,313	70,000
Weighted Average Rate (in hundredths)	3.52%	4.21%
Callable Amount	70,000	70,000
Weighted Average Rate Callable Portion (in hundredths)	4.21%	4.21%
2017 [Member]	'	'
Long-Term Debt by Maturity Periods [Abstract]	'	'
Maturity	31-Dec-17	'
Amount	115,312	100,000
Weighted Average Rate (in hundredths)	3.55%	3.89%
Callable Amount	75,000	100,000
Weighted Average Rate Callable Portion (in hundredths)	3.73%	3.89%
2018 [Member]	'	'
Long-Term Debt by Maturity Periods [Abstract]	'	'
Maturity	31-Dec-18	'
Amount	90,313	75,000
Weighted Average Rate (in hundredths)	3.26%	3.61%
Callable Amount	75,000	75,000
Weighted Average Rate Callable Portion (in hundredths)	3.61%	3.61%
2021 [Member]	'	'
Long-Term Debt by Maturity Periods [Abstract]	'	'
Maturity	31-Dec-21	'
Amount	117	130
Weighted Average Rate (in hundredths)	4.00%	4.00%
Callable Amount	$0	$0
Weighted Average Rate Callable Portion (in hundredths)	0.00%	0.00%

Junior_Subordinated_Debt_Detai

Junior Subordinated Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2013
Debt Instrument [Line Items]	'
Number of statutory business trusts included in the Trusts	5
Minimum assets for bank holding companies to be subject to the same capital requirements as insured depository institutions	$500,000,000
CNBF Capital Trust I Debenture [Member]	'
Debt Instrument [Line Items]	'
Issuance Date	1-Aug-99
Trust Preferred Securities Outstanding	18,000,000
Interest Rate	'3-month LIBOR plus 2.75%
Trust Preferred Debt Owed To Trust	18,720,000
Final Maturity Date	29-Aug-14
Number of wholly owned Delaware statutory business trusts	'1
NBT Statutory Trust I Debenture [Member]	'
Debt Instrument [Line Items]	'
Issuance Date	5-Nov-14
Trust Preferred Securities Outstanding	5,000,000
Interest Rate	'3-month LIBOR plus 1.40%
Trust Preferred Debt Owed To Trust	5,155,000
Final Maturity Date	1-Dec-35
NBT Statutory Trust II Debenture [Member]	'
Debt Instrument [Line Items]	'
Issuance Date	6-Feb-14
Trust Preferred Securities Outstanding	50,000,000
Interest Rate	'3-month LIBOR plus 1.40%
Trust Preferred Debt Owed To Trust	51,547,000
Final Maturity Date	1-Mar-36
Alliance Financial Capital Trust I [Member]	'
Debt Instrument [Line Items]	'
Issuance Date	3-Dec-14
Trust Preferred Securities Outstanding	10,000,000
Interest Rate	'3-month LIBOR plus 2.85%
Trust Preferred Debt Owed To Trust	10,310,000
Final Maturity Date	1-Jan-34
Alliance Financial Capital Trust II [Member]	'
Debt Instrument [Line Items]	'
Issuance Date	6-Sep-14
Trust Preferred Securities Outstanding	15,000,000
Interest Rate	'3-month LIBOR plus 1.65%
Trust Preferred Debt Owed To Trust	15,464,000
Final Maturity Date	1-Sep-36
NBT Bancorp Inc [Member]	'
Debt Instrument [Line Items]	'
Trust equity method investment	1,000,000
Alliance Financial Capital [Member]	'
Debt Instrument [Line Items]	'
Number of wholly owned Delaware statutory business trusts	'2
Trusts [Member]	'
Debt Instrument [Line Items]	'
Trust Preferred Securities Outstanding	98,000,000
Trust Preferred Debt Owed To Trust	101,000,000
Trust equity method investment	3,200,000
Debentures period semi-annual deferral periods	10
Trust preferred securities included in Tier I capital	$97,000,000

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current [Abstract]	'	'	'
Federal	$23,536,000	$21,011,000	$29,274,000
State	2,316,000	1,815,000	1,477,000
Current tax expense (benefit)	25,852,000	22,826,000	30,751,000
Deferred [Abstract]	'	'	'
Federal	2,334,000	-13,000	-8,129,000
State	10,000	3,000	-1,349,000
Deferred tax expense (benefit)	2,344,000	-10,000	-9,478,000
Total income tax expense	28,196,000	22,816,000	21,273,000
Income tax recorded to stockholders' equity	7,000,000	-100,000	-500,000
Deferred tax assets [Abstract]	'	'	'
Allowance for loan and lease losses	26,729,000	26,687,000	'
Deferred compensation	7,931,000	5,362,000	'
Postretirement benefit obligation	2,596,000	1,600,000	'
Unrealized losses on securities available for sale	5,900,000	0	'
Fair value adjustments from acquisitions	0	3,633,000	'
Accrued liabilities	3,265,000	1,524,000	'
Stock-based compensation expense	7,862,000	5,726,000	'
Equipment leasing	1,661,000	0	'
Other	2,125,000	1,933,000	'
Total deferred tax assets	58,069,000	46,465,000	'
Deferred tax liabilities [Abstract]	'	'	'
Pension and executive retirement	17,417,000	7,676,000	'
Fair value adjustments from acquisitions	2,070,000	0	'
Unrealized gains on securities available for sale	0	10,939,000	'
Premises and equipment, primarily due to accelerated depreciation	2,270,000	1,980,000	'
Equipment leasing	0	582,000	'
Deferred loan costs	1,624,000	873,000	'
Intangible amortization	12,007,000	13,146,000	'
Other	892,000	154,000	'
Total deferred tax liabilities	36,280,000	35,350,000	'
Net deferred tax asset at year-end	21,789,000	11,115,000	5,953,000
Net deferred tax asset (liability) at beginning of year	11,115,000	5,953,000	'
Increase in net deferred tax asset	10,674,000	5,162,000	'
Reconciliation of gross unrecognized tax benefits [Roll Forward]	'	'	'
Balance, beginning of period	0	888,000	3,081,000
Additions for tax positions of prior years	0	0	0
Reduction for tax positions of prior years	0	-888,000	-2,193,000
Balance, end of period	0	0	888,000
Decrease in tax expense resulting from lapse of statute of limitations	'	800,000	1,500,000
Accrued interest	'	'	100,000
Net interest	'	'	300,000
Federal statutory income tax rate (in hundredths)	35.00%	'	'
Income tax reconciliation [Abstract]	'	'	'
Federal income tax at statutory rate	31,482,000	27,081,000	27,711,000
Tax exempt income	-2,433,000	-2,536,000	-2,925,000
Net increase in CSV of life insurance	-1,166,000	-908,000	-919,000
Low income housing tax credits	-819,000	-629,000	-782,000
State taxes, net of federal tax benefit	1,512,000	1,182,000	764,000
State audit settlements	0	0	-681,000
Other, net	-380,000	-1,374,000	-1,895,000
Total income tax expense	$28,196,000	$22,816,000	$21,273,000

Employee_Benefit_Plans_Details

Employee Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Adjustment of accumulated other comprehensive income	$2,400,000	'	'
Transition obligation period of recognition	'20 years	'	'
Net actuarial loss that will be amortized from Accumulated other comprehensive income (loss) in next fiscal year	300,000	'	'
Prior service credit that will be amortized from Accumulated other comprehensive income (loss) in next fiscal year	200,000	'	'
Assumptions used to determine benefit obligations [Abstract]	'	'	'
Discount rate (in hundredths)	'	3.50%	4.10%
Expected long-term return on plan assets (in hundredths)	7.50%	7.50%	7.50%
Rate of compensation increase (in hundredths)	3.00%	3.00%	3.00%
Assumptions used to determine net periodic pension cost [Abstract]	'	'	'
Discount rate (in hundredths)	3.50%	4.10%	5.15%
Expected long-term return on plan assets (in hundredths)	7.50%	7.50%	8.00%
Rate of compensation increase (in hundredths)	3.00%	3.00%	3.00%
Other changes in plan assets and benefit obligation recognized in other comprehensive income (pre-tax) [Abstract]	'	'	'
Amortization of prior service cost	-2,790,000	-3,593,000	-1,665,000
Estimate future benefit payments [Abstract]	'	'	'
Annual rates of increase in the per capita cost of covered medical and prescription drug benefits, minimum (in hundredths)	5.90%	'	'
Annual rates of increase in the per capita cost of covered medical and prescription drug benefits, maximum (in hundredths)	8.50%	'	'
Ultimate health care cost trend rate (in hundredths)	5.00%	'	'
Actual plan asset allocations [Abstract]	'	'	'
Actual plan asset allocations (in hundredths)	100.00%	100.00%	'
Employer contributions to 401 (k) plan	2,100,000	1,800,000	3,700,000
Effect of one-percentage point change in assumed health care cost trend rates [Abstract]	'	'	'
One-percentage point Increase on total service and interest cost components	37,000	'	'
One-percentage point (decrease) on total service and interest cost components	-27,000	'	'
One-percentage point Increase on postretirement accumulated benefit obligation	768,000	'	'
One-percentage point (decrease) on postretirement accumulated benefit obligation	-567,000	'	'
Minimum [Member]	'	'	'
Assumptions used to determine benefit obligations [Abstract]	'	'	'
Discount rate (in hundredths)	4.90%	'	'
Maximum [Member]	'	'	'
Assumptions used to determine benefit obligations [Abstract]	'	'	'
Discount rate (in hundredths)	5.05%	'	'
Pension Benefits [Member]	'	'	'
Accumulated other comprehensive income (loss), before tax [Abstract]	'	'	'
Net actuarial loss	11,286,000	35,478,000	'
Prior service cost	118,000	141,000	'
Total amounts recognized in accumulated other comprehensive loss (pre-tax)	11,404,000	35,619,000	'
Change in benefit obligation [Roll Forward]	'	'	'
Benefit obligation at beginning of period	85,129,000	78,024,000	'
Service cost	2,493,000	3,122,000	2,589,000
Interest cost	3,223,000	3,145,000	3,544,000
Plan participants' contributions	0	0	'
Actuarial(gain) loss	-10,853,000	5,941,000	'
Amendments	0	-1,006,000	'
Acquisition	10,958,000	0	'
Benefits paid	-5,283,000	-4,097,000	'
Projected benefit obligation at end of period	85,667,000	85,129,000	78,024,000
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at beginning of period	99,704,000	91,575,000	'
Actual return on plan assets	18,451,000	11,733,000	'
Acquisition	4,994,000	0	'
Employer contributions	708,000	493,000	'
Plan participants' contributions	0	0	'
Benefits paid	-5,283,000	-4,097,000	'
Fair value of plan assets at end of period	118,574,000	99,704,000	91,575,000
Funded status	32,907,000	14,575,000	'
Accumulated benefit obligation	85,700,000	85,100,000	'
Amounts recognized in Balance Sheet [Abstract]	'	'	'
Other assets	48,189,000	27,062,000	'
Other liabilities	-15,282,000	-12,487,000	'
Funded status	32,907,000	14,575,000	'
Components of net periodic benefit cost [Abstract]	'	'	'
Service cost	2,493,000	3,122,000	2,589,000
Interest cost	3,223,000	3,145,000	3,544,000
Expected return on plan assets	-7,804,000	-6,686,000	-7,720,000
Amortization of prior service cost	23,000	283,000	309,000
Amortization of unrecognized net loss	2,692,000	3,330,000	1,353,000
Net periodic pension cost	627,000	3,194,000	75,000
Other changes in plan assets and benefit obligation recognized in other comprehensive income (pre-tax) [Abstract]	'	'	'
Net loss (gain)	-21,500,000	894,000	16,108,000
Prior service cost	0	-1,006,000	0
Amortization of prior service cost	-23,000	-283,000	-309,000
Amortization of unrecognized net gain	-2,692,000	-3,330,000	-1,353,000
Total recognized in other comprehensive loss (income)	-24,215,000	-3,725,000	14,446,000
Total recognized in net periodic benefit cost and other comprehensive income (loss) - pre-tax	-23,588,000	-531,000	14,521,000
Estimate future benefit payments [Abstract]	'	'	'
2014	5,950,000	'	'
2015	6,090,000	'	'
2016	6,143,000	'	'
2017	9,199,000	'	'
2018	6,899,000	'	'
2019 - 2022	34,827,000	'	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	118,574,000	99,704,000	91,575,000
Pension Benefits [Member] | Level 1 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	86,711,000	70,414,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	86,711,000	70,414,000	'
Pension Benefits [Member] | Level 2 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	31,863,000	29,290,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	31,863,000	29,290,000	'
Pension Benefits [Member] | Cash and Cash Equivalents [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at beginning of period	5,464,000	'	'
Fair value of plan assets at end of period	7,533,000	'	'
Target asset allocations [Abstract]	'	'	'
Target allocation percentage of assets, range minimum (in hundredths)	0.00%	'	'
Target allocation percentage of assets, range maximum (in hundredths)	20.00%	'	'
Actual plan asset allocations [Abstract]	'	'	'
Actual plan asset allocations (in hundredths)	6.00%	5.00%	'
Fair value of plan assets	7,533,000	'	'
Pension Benefits [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	7,533,000	5,464,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	7,533,000	5,464,000	'
Pension Benefits [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	0	0	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	0	0	'
Pension Benefits [Member] | Fixed Income Securities [Member]	'	'	'
Target asset allocations [Abstract]	'	'	'
Target allocation percentage of assets, range minimum (in hundredths)	20.00%	'	'
Target allocation percentage of assets, range maximum (in hundredths)	40.00%	'	'
Actual plan asset allocations [Abstract]	'	'	'
Actual plan asset allocations (in hundredths)	27.00%	29.00%	'
Pension Benefits [Member] | Equity [Member]	'	'	'
Target asset allocations [Abstract]	'	'	'
Target allocation percentage of assets, range minimum (in hundredths)	40.00%	'	'
Target allocation percentage of assets, range maximum (in hundredths)	80.00%	'	'
Actual plan asset allocations [Abstract]	'	'	'
Actual plan asset allocations (in hundredths)	67.00%	66.00%	'
Pension Benefits [Member] | Foreign Equity Mutual Funds [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	15,653,000	9,763,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	15,653,000	9,763,000	'
Pension Benefits [Member] | Foreign Equity Mutual Funds [Member] | Level 1 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	15,653,000	9,763,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	15,653,000	9,763,000	'
Pension Benefits [Member] | Foreign Equity Mutual Funds [Member] | Level 2 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	0	0	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	0	0	'
Pension Benefits [Member] | Equity Mutual Funds [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	16,727,000	13,110,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	16,727,000	13,110,000	'
Pension Benefits [Member] | Equity Mutual Funds [Member] | Level 1 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	16,727,000	13,110,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	16,727,000	13,110,000	'
Pension Benefits [Member] | Equity Mutual Funds [Member] | Level 2 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	0	0	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	0	0	'
Pension Benefits [Member] | US Government Bonds [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	9,355,000	12,744,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	9,355,000	12,744,000	'
Pension Benefits [Member] | US Government Bonds [Member] | Level 1 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	0	0	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	0	0	'
Pension Benefits [Member] | US Government Bonds [Member] | Level 2 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	9,355,000	12,744,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	9,355,000	12,744,000	'
Pension Benefits [Member] | Corporate Bonds [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	19,665,000	13,604,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	19,665,000	13,604,000	'
Pension Benefits [Member] | Corporate Bonds [Member] | Level 1 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	0	0	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	0	0	'
Pension Benefits [Member] | Corporate Bonds [Member] | Level 2 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	19,665,000	13,604,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	19,665,000	13,604,000	'
Pension Benefits [Member] | Common Stock [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	44,532,000	40,430,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	44,532,000	40,430,000	'
Pension Benefits [Member] | Common Stock [Member] | Level 1 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	44,532,000	40,430,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	44,532,000	40,430,000	'
Pension Benefits [Member] | Common Stock [Member] | Level 2 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	0	0	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	0	0	'
Pension Benefits [Member] | Municipal Bonds and Notes [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	1,451,000	1,805,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	1,451,000	1,805,000	'
Pension Benefits [Member] | Municipal Bonds and Notes [Member] | Level 1 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	0	0	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	0	0	'
Pension Benefits [Member] | Municipal Bonds and Notes [Member] | Level 2 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	1,451,000	1,805,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	1,451,000	1,805,000	'
Pension Benefits [Member] | Foreign Bonds and Notes [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	1,392,000	1,137,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	1,392,000	1,137,000	'
Pension Benefits [Member] | Foreign Bonds and Notes [Member] | Level 1 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	0	0	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	0	0	'
Pension Benefits [Member] | Foreign Bonds and Notes [Member] | Level 2 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	1,392,000	1,137,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	1,392,000	1,137,000	'
Pension Benefits [Member] | Foreign Equity [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	2,266,000	1,647,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	2,266,000	1,647,000	'
Pension Benefits [Member] | Foreign Equity [Member] | Level 1 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	2,266,000	1,647,000	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	2,266,000	1,647,000	'
Pension Benefits [Member] | Foreign Equity [Member] | Level 2 [Member]	'	'	'
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at end of period	0	0	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	0	0	'
Other Benefits [Member]	'	'	'
Accumulated other comprehensive income (loss), before tax [Abstract]	'	'	'
Net actuarial loss	1,628,000	2,277,000	'
Prior service cost	-521,000	-672,000	'
Total amounts recognized in accumulated other comprehensive loss (pre-tax)	1,107,000	1,605,000	'
Change in benefit obligation [Roll Forward]	'	'	'
Benefit obligation at beginning of period	4,071,000	3,985,000	'
Service cost	23,000	20,000	17,000
Interest cost	286,000	155,000	202,000
Plan participants' contributions	269,000	233,000	'
Actuarial(gain) loss	-369,000	136,000	'
Amendments	-54,000	0	'
Acquisition	3,928,000	0	'
Benefits paid	-726,000	-458,000	'
Projected benefit obligation at end of period	7,428,000	4,071,000	3,985,000
Change in plan assets [Roll Forward]	'	'	'
Fair value of plan assets at beginning of period	0	0	'
Actual return on plan assets	0	0	'
Acquisition	0	0	'
Employer contributions	457,000	225,000	'
Plan participants' contributions	269,000	233,000	'
Benefits paid	-726,000	-458,000	'
Fair value of plan assets at end of period	0	0	0
Funded status	-7,428,000	-4,071,000	'
Accumulated benefit obligation	7,400,000	4,100,000	'
Amounts recognized in Balance Sheet [Abstract]	'	'	'
Other assets	0	0	'
Other liabilities	-7,428,000	-4,071,000	'
Funded status	-7,428,000	-4,071,000	'
Components of net periodic benefit cost [Abstract]	'	'	'
Service cost	23,000	20,000	17,000
Interest cost	286,000	155,000	202,000
Expected return on plan assets	0	0	0
Amortization of prior service cost	-205,000	-202,000	-202,000
Amortization of unrecognized net loss	280,000	182,000	205,000
Net periodic pension cost	384,000	155,000	222,000
Other changes in plan assets and benefit obligation recognized in other comprehensive income (pre-tax) [Abstract]	'	'	'
Net loss (gain)	-369,000	136,000	-562,000
Prior service cost	-54,000	0	0
Amortization of prior service cost	205,000	202,000	202,000
Amortization of unrecognized net gain	-280,000	-182,000	-205,000
Total recognized in other comprehensive loss (income)	-498,000	156,000	-565,000
Total recognized in net periodic benefit cost and other comprehensive income (loss) - pre-tax	-114,000	311,000	-343,000
Estimate future benefit payments [Abstract]	'	'	'
2014	555,000	'	'
2015	565,000	'	'
2016	560,000	'	'
2017	576,000	'	'
2018	590,000	'	'
2019 - 2022	2,771,000	'	'
Actual plan asset allocations [Abstract]	'	'	'
Fair value of plan assets	$0	$0	$0

StockBased_Compensation_Detail

Stock-Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Fair value assumptions [Abstract]	'	'	'
Dividend yield (in hundredths)	3.20%	3.94%	'
Dividend yield, minimum (in hundredths)	'	'	3.31%
Dividend yield, maximum (in hundredths)	'	'	3.82%
Expected volatility (in hundredths)	34.60%	34.64%	'
Expected volatility, minimum (in hundredths)	'	'	33.75%
Expected volatility, maximum (in hundredths)	'	'	34.36%
Risk-free interest rates (in hundredths)	2.43%	1.24%	'
Risk-free interest rates, minimum (in hundredths)	'	'	1.48%
Risk-free interest rates, maximum (in hundredths)	'	'	2.81%
Expected life	'7 years	'7 years	'7 years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock awards termination period	'10 years	'	'
Stock options additional disclosures [Abstract]	'	'	'
Stock-based compensation expense	$4,305,000	$4,364,000	$3,244,000
Restricted Stock and restricted stock additional disclosures [Abstract]	'	'	'
Number of shares available for future grant (in shares)	4,100,000	'	'
Stock Options [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Stock awards vesting period	'4 years	'	'
Weighted average fair value of stock options granted (in dollars per share)	$7.09	$4.57	$5.45
Stock options [Roll Forward]	'	'	'
Outstanding, Beginning of period (in shares)	1,695,562	'	'
Granted (in shares)	120	'	'
Exercised (in shares)	-335,103	'	'
Forfeited (in shares)	-495	'	'
Expired (in shares)	-18,584	'	'
Outstanding, End of period (in shares)	1,341,500	1,695,562	'
Exercisable, End of period (in shares)	1,279,560	'	'
Expected to Vest (in shares)	61,044	'	'
Stock options additional disclosures [Abstract]	'	'	'
Weighted average exercise price, Outstanding, Beginning of period (in dollars per share)	$22.72	'	'
Weighted average exercise price, Granted (in dollars per share)	$26.29	'	'
Weighted average exercise price, Exercised (in dollars per share)	$21.77	'	'
Weighted average exercise price, Forfeited (in dollars per share)	$20.19	'	'
Weighted average exercise price, Expired (in dollars per share)	$21.58	'	'
Weighted average exercise price, Outstanding, End of period (in dollars per share)	$22.98	$22.72	'
Weighted average exercise price, Exercisable, End of period (in dollars per share)	$23.08	'	'
Weighted average exercise price, Expected to Vest (in dollars per share)	$20.80	'	'
Weighted Average Remaining Contractual Term, Outstanding, End of period (in years)	'3 years 10 months 20 days	'	'
Weighted Average Remaining Contractual Term, Exercisable, End of period (in years)	'3 years 9 months 11 days	'	'
Weighted Average Remaining Contractual Term, Expected to Vest (in years)	'5 years 6 months 14 days	'	'
Aggregate Intrinsic Value, Outstanding, End of period	3,996,816	'	'
Aggregate Intrinsic Value, Exercisable, End of period	3,683,178	'	'
Aggregate Intrinsic Value, Expected to Vest	311,352	'	'
Stock-based compensation expense	200,000	500,000	900,000
Proceeds from stock options exercised	7,927,000	1,908,000	2,255,000
Tax benefits related to stock options exercised	178,000	8,000	341,000
Intrinsic value of stock options exercised	905,000	498,000	897,000
Fair value of shares vested during the year	766,000	1,656,000	1,597,000
Restricted Stock [Member]	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Restricted shares vesting period for employees, minimum	'5 years	'	'
Restricted shares vesting period for non-employee directors, minimum	'3 years	'	'
Stock options additional disclosures [Abstract]	'	'	'
Unrecognized compensation cost	4,600,000	'	'
Unrecognized compensation cost, weighted average period of recognition (in years)	'2 years 1 month 6 days	'	'
Restricted Stock and restricted stock [Roll Forward]	'	'	'
Unvested, Beginning of period (in shares)	117,150	'	'
Forfeited (in shares)	-2,033	'	'
Vested (in shares)	-48,467	'	'
Unvested, End of period (in shares)	66,650	'	'
Restricted Stock and restricted stock additional disclosures [Abstract]	'	'	'
Weighted-average grant date fair value, Unvested, Beginning of period (in dollars per share)	$24.37	'	'
Weighted-average grant date fair value, Forfeited (in dollars per share)	$23.25	'	'
Weighted-average grant date fair value, Vested (in dollars per share)	$26.10	'	'
Weighted-average grant date fair value, Unvested, End of period (in dollars per share)	$23.15	'	'
Restricted Stock Units (RSUs) [Member]	'	'	'
Restricted Stock and restricted stock [Roll Forward]	'	'	'
Unvested, Beginning of period (in shares)	406,058	'	'
Forfeited (in shares)	-6,467	'	'
Vested (in shares)	-69,333	'	'
Granted (in shares)	209,592	'	'
Unvested, End of period (in shares)	539,850	'	'
Restricted Stock and restricted stock additional disclosures [Abstract]	'	'	'
Weighted-average grant date fair value, Unvested, Beginning of period (in dollars per share)	$25.64	'	'
Weighted-average grant date fair value, Forfeited (in dollars per share)	$0	'	'
Weighted-average grant date fair value, Vested (in dollars per share)	$0	'	'
Weighted-average grant date fair value, Granted (in dollars per share)	$20.81	'	'
Weighted-average grant date fair value, Unvested, End of period (in dollars per share)	$27.36	'	'
Restricted and Deferred Stock Awards [Member]	'	'	'
Stock options additional disclosures [Abstract]	'	'	'
Stock-based compensation expense	3,800,000	3,700,000	3,200,000
Tax benefit from compensation expense	$1,500,000	$1,500,000	$1,200,000

Stockholders_Equity_Details

Stockholders Equity (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Stockholders Equity [Abstract]	'	'
Unrecognized prior service cost and net actuarial loss on pension plans	($7,785,000)	($22,555,000)
Unrealized net holding (losses) gains on available for sale securities	-8,980,000	16,675,000
Accumulated other comprehensive loss	-16,765,000	-5,880,000
Class of Warrant or Right [Line Items]	'	'
Future dividend payment restrictions	'The approval of the Office of Comptroller of the Currency (OCC) is required to pay dividends when a bank fails to meet certain minimum regulatory capital standards or when such dividends are in excess of a subsidiary bank's earnings retained in the current year plus retained net profits for the preceding two years as specified in applicable OCC regulations.	'
Preceding period of retained net profits for approval of Office of Comptroller of the Currency (in years)	'2 years	'
Statutory amount available for dividend payments	$56,700,000	'
Series A Junior Participating Preferred Stock [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Purchase entitlement (in shares)	0.01	'
Stated value of purchase entitlement (in dollars per share)	$0.01	'
Exercise price (in dollars per share)	$70	'
Stockholder Rights Plan [Member]	'	'
Class of Warrant or Right [Line Items]	'	'
Preferred share purchase right dividend per common share (in shares)	1	'
Beneficial ownership of outstanding common stock basis for right exercise, minimum (in hundredths)	15.00%	'
Tender or exchange offer of outstanding common stock rights to exercise, minimum (in hundredths)	15.00%	'
Market value of additional equity interests rights, description	'two times the Right's exercise price of $70	'
Multiplier for market value of additional equity interest	2	'
Preferred Share Purchase Right exercise price (in dollars per right)	$0.00	'

Regulatory_Capital_Requirement2

Regulatory Capital Requirements (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Total Capital (to risk weighted assets) [Abstract]	'	'
Total capital to risk weighted assets	$723,580	$560,745
Total capital to risk weighted assets (in hundredths)	12.99%	12.25%
Minimum capital required for capital adequacy to risk weighted assets (in hundredths)	8.00%	8.00%
Capital required for classification as well capitalized to risk weighted assets (in hundredths)	10.00%	10.00%
Tier I Capital (to risk weighted assets) [Abstract]	'	'
Tier I capital to risk weighted assets	653,950	503,359
Tier I capital to risk weighted assets (in hundredths)	11.74%	11.00%
Minimum Tier one capital required for capital adequacy to risk weighted assets(in hundredths)	4.00%	4.00%
Tier one capital required for classification as well capitalized to risk weighted assets (in hundredths)	6.00%	6.00%
Tier I Capital (to average assets) [Abstract]	'	'
Tier I capital to average assets	653,950	503,359
Tier I capital to average assets (in hundredths)	8.93%	8.54%
Minimum Tier I leverage capital required for capital adequacy to average assets (in hundredths)	4.00%	4.00%
Tier I leverage capital required for classification as well capitalized to average assets (in hundredths)	5.00%	5.00%
NBT Bank [Member]	'	'
Total Capital (to risk weighted assets) [Abstract]	'	'
Total capital to risk weighted assets	686,194	505,027
Total capital to risk weighted assets (in hundredths)	12.41%	11.08%
Minimum capital required for capital adequacy to risk weighted assets (in hundredths)	8.00%	8.00%
Capital required for classification as well capitalized to risk weighted assets (in hundredths)	10.00%	10.00%
Tier I Capital (to risk weighted assets) [Abstract]	'	'
Tier I capital to risk weighted assets	617,038	447,909
Tier I capital to risk weighted assets (in hundredths)	11.16%	9.83%
Minimum Tier one capital required for capital adequacy to risk weighted assets(in hundredths)	4.00%	4.00%
Tier one capital required for classification as well capitalized to risk weighted assets (in hundredths)	6.00%	6.00%
Tier I Capital (to average assets) [Abstract]	'	'
Tier I capital to average assets	$617,038	$447,909
Tier I capital to average assets (in hundredths)	8.47%	7.62%
Minimum Tier I leverage capital required for capital adequacy to average assets (in hundredths)	4.00%	4.00%
Tier I leverage capital required for classification as well capitalized to average assets (in hundredths)	5.00%	5.00%

Earnings_Per_Share_Details

Earnings Per Share (Details) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Basic earnings per share [Abstract]	'	'	'
Net income available to common shareholders	$61,747	$54,558	$57,901
Weighted average common shares, basic (in shares)	41,930,000	33,379,000	33,662,000
Basic EPS (in dollars per share)	$1.47	$1.63	$1.72
Diluted earnings per share [Abstract]	'	'	'
Net income available to common shareholders	$61,747	$54,558	$57,901
Dilutive effect of stock based compensation (in shares)	420,000	340,000	262,000
Weighted average common shares, diluted (in shares)	42,350,000	33,719,000	33,924,000
Diluted EPS (in dollars per share)	$1.46	$1.62	$1.71
Stock Options [Member]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Stock options excluded from calculation of diluted EPS (in shares)	1,048,000	1,193,000	1,258,000

Reclassification_Adjustments_O2

Reclassification Adjustments Out of Other Comprehensive (Loss) Income (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'
Net securities gains	($1,426)	($599)	($150)
Salaries and employee benefits	113,580	104,815	99,212
Income tax expense	28,196	22,816	21,273
Net Income	61,747	54,558	57,901
Total reclassification during the period, net of tax	740	1,812	'
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]	'	'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'	'	'
Net securities gains	-1,426	-599	'
Income tax expense	565	237	'
Net Income	-861	-362	'
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	1,189	1,419	'
Net Income	1,601	2,174	'
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	2,792	3,512	'
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	($182)	$81	'

Commitments_and_Contingent_Lia2

Commitments and Contingent Liabilities (Details) (USD $)

12 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 25, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Unused lines of Credit [Member]

Unused lines of Credit [Member]

Commitment to Extend Credits [Member]

Commitment to Extend Credits [Member]

Standby Letters of Credit [Member]

Standby Letters of Credit [Member]

Commercial Letters of Credit [Member]

Commercial Letters of Credit [Member]

Loans Sold with Recourse [Member]

Loans Sold with Recourse [Member]

Commitments and Contingent Liabilities [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of the Company's loans secured by real estate (in hundredths)

59.00%

'

'

'

'

'

'

'

'

'

'

'

'

Guarantor Obligations [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Commitments - maximum potential obligation

'

'

'

$216,658,000

$163,626,000

$849,092,000

$678,093,000

$37,510,000

$36,837,000

$41,263,000

$16,607,000

$15,741,000

$13,690,000

Obligation instrument term

'

'

'

'

'

'

'

'5 years

'

'

'

'

'

Loans serviced by the Company for unrelated third parties

554,400,000

'

309,200,000

'

'

'

'

'

'

'

'

'

'

Federal Reserve Bank Requirement [Abstract]

'

'

'

'

'

'

'

'

'

'

'

'

'

Federal Reserve Bank maintenance period

'14 days

'

'

'

'

'

'

'

'

'

'

'

'

Average reserve at Federal Reserve Bank for maintenance period

'

$48,700,000

'

'

'

'

'

'

'

'

'

'

'

Fair_Values_of_Financial_Instr2

Fair Values of Financial Instruments (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Financial assets [Abstract]	'	'
Securities held to maturity	$113,276,000	$61,535,000
Financial liabilities [Abstract]	'	'
Time deposits	1,021,142,000	983,261,000
Long-term debt	308,823,000	367,492,000
Junior subordinated debt	101,196,000	75,422,000
Securities Available for Sale [Abstract]	'	'
Total Securities Available for Sale	1,364,881,000	1,147,999,000
Trading Securities	5,779,000	3,918,000
Liabilities [Abstract]	'	'
Collateral dependent impaired financing receivable with specific reserves	5,000,000	'
Allowance for loan and lease losses collateral dependent impaired loans with specific reserves	700,000	'
Liquidation expense ratio on impaired collateral minimum (in hundredths)	10.00%	'
Liquidation expense ratio on impaired collateral maximum (in hundredths)	35.00%	'
Recurring Basis [Member]	'	'
Securities Available for Sale [Abstract]	'	'
U.S. Treasury	43,616,000	64,425,000
Federal Agency	278,915,000	282,814,000
State & municipal	113,665,000	86,802,000
Mortgage-backed	364,164,000	250,281,000
Collateralized mortgage obligations	549,528,000	449,723,000
Other securities	14,993,000	13,954,000
Total Securities Available for Sale	1,364,881,000	1,147,999,000
Trading Securities	5,779,000	3,918,000
Interest Rate Swaps	281,000	1,490,000
Total	1,370,941,000	1,153,407,000
Liabilities [Abstract]	'	'
Interest Rate Swaps	281,000	1,490,000
Total	281,000	1,490,000
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Recurring Basis [Member]	'	'
Securities Available for Sale [Abstract]	'	'
U.S. Treasury	43,616,000	64,425,000
Federal Agency	0	0
State & municipal	0	0
Mortgage-backed	0	0
Collateralized mortgage obligations	0	0
Other securities	6,796,000	8,672,000
Total Securities Available for Sale	50,412,000	73,097,000
Trading Securities	5,779,000	3,918,000
Interest Rate Swaps	0	0
Total	56,191,000	77,015,000
Liabilities [Abstract]	'	'
Interest Rate Swaps	0	0
Total	0	0
Significant Other Observable Inputs (Level 2) [Member] | Recurring Basis [Member]	'	'
Securities Available for Sale [Abstract]	'	'
U.S. Treasury	0	0
Federal Agency	278,915,000	282,814,000
State & municipal	113,665,000	86,802,000
Mortgage-backed	364,164,000	250,281,000
Collateralized mortgage obligations	549,528,000	449,723,000
Other securities	8,197,000	5,282,000
Total Securities Available for Sale	1,314,469,000	1,074,902,000
Trading Securities	0	0
Interest Rate Swaps	281,000	1,490,000
Total	1,314,750,000	1,076,392,000
Liabilities [Abstract]	'	'
Interest Rate Swaps	281,000	1,490,000
Total	281,000	1,490,000
Significant Unobservable Inputs (Level 3) [Member] | Recurring Basis [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
Carrying Amount [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Financial assets [Abstract]	'	'
Securities held to maturity	117,283,000	60,563,000
Financial liabilities [Abstract]	'	'
Time deposits	1,021,142,000	983,261,000
Long-term debt	308,823,000	367,492,000
Carrying Amount [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Financial assets [Abstract]	'	'
Net Loans	5,337,361,000	4,208,282,000
Financial liabilities [Abstract]	'	'
Junior subordinated debt	101,196,000	75,422,000
Estimated Fair Value [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Financial assets [Abstract]	'	'
Securities held to maturity	113,276,000	61,535,000
Financial liabilities [Abstract]	'	'
Time deposits	1,023,982,000	994,376,000
Long-term debt	325,195,000	407,404,000
Estimated Fair Value [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Financial assets [Abstract]	'	'
Net Loans	5,386,520,000	4,313,244,000
Financial liabilities [Abstract]	'	'
Junior subordinated debt	$105,121,000	$74,147,000

Parent_Company_Financial_Infor2

Parent Company Financial Information (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Assets [Abstract]	'	'	'	'
Cash and cash equivalents	$158,926	$163,668	$129,381	'
Securities available for sale, at estimated fair value	1,364,881	1,147,999	'	'
Trading securities	5,779	3,918	'	'
Other assets	127,234	99,997	'	'
Total assets	7,652,175	6,042,259	'	'
Liabilities and Stockholders' Equity [Abstract]	'	'	'	'
Total liabilities	6,835,606	5,459,986	'	'
Stockholders' equity	816,569	582,273	538,110	533,572
Total liabilities and stockholders' equity	7,652,175	6,042,259	'	'
Condensed Income Statements [Abstract]	'	'	'	'
Securities gains (losses)	1,426	599	150	'
Interest, dividend and other income	268,723	239,397	239,997	'
Income before income tax benefit and equity in undistributed income of subsidiaries	89,943	77,374	79,174	'
Income tax (expense) benefit	-28,196	-22,816	-21,273	'
Net income	61,747	54,558	57,901	'
Operating activities [Abstract]	'	'	'	'
Net income	61,747	54,558	57,901	'
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]	'	'	'	'
Stock-based compensation	4,305	4,364	3,244	'
Gain (Loss) on sales of available-for-sale securities	-1,283	-442	-7	'
Net change in other liabilities	-5,219	-128	11,806	'
Net change in other assets	20,463	6,804	-3,579	'
Net cash provided by operating activities	119,298	88,854	83,765	'
Investing activities [Abstract]	'	'	'	'
Purchases of available-for-sale securities	-353,714	-483,858	-648,048	'
Sales and maturities of available-for-sale securities	376,509	573,828	541,555	'
Purchases of premises and equipment	-5,766	-6,994	-9,954	'
Net cash used in investing activities	-183,754	-126,850	-175,498	'
Financing activities [Abstract]	'	'	'	'
Payments on long-term debt	-163,595	-3,354	-2,146	'
Purchases of treasury shares	12,459	15,490	30,502	'
Cash dividends and payments for fractional shares	-33,518	-26,712	-27,063	'
Excess tax benefit from exercise of stock options	-178	8	341	'
Net cash provided by financing activities	59,714	72,283	52,322	'
Net (decrease) increase in cash and cash equivalents	-4,742	34,287	-39,411	'
Cash and cash equivalents at beginning of year	163,668	129,381	168,792	'
Cash and cash equivalents at end of year	158,926	163,668	129,381	'
NBT Bancorp Inc [Member]	'	'	'	'
Assets [Abstract]	'	'	'	'
Cash and cash equivalents	3,741	23,095	2,454	'
Securities available for sale, at estimated fair value	11,008	12,866	'	'
Trading securities	4,742	3,371	'	'
Investment in subsidiaries, on equity basis	896,479	635,851	'	'
Other assets	49,530	48,324	'	'
Total assets	965,500	723,507	'	'
Liabilities and Stockholders' Equity [Abstract]	'	'	'	'
Total liabilities	148,931	141,234	'	'
Stockholders' equity	816,569	582,273	'	'
Total liabilities and stockholders' equity	965,500	723,507	'	'
Condensed Income Statements [Abstract]	'	'	'	'
Dividends from subsidiaries	13,500	79,175	54,400	'
Management fee from subsidiaries	84,778	78,665	69,430	'
Securities gains (losses)	1,273	442	-31	'
Interest, dividend and other income	636	720	628	'
Total revenue	100,187	159,002	124,427	'
Operating expense	83,675	79,015	75,254	'
Income before income tax benefit and equity in undistributed income of subsidiaries	16,512	79,987	49,173	'
Income tax (expense) benefit	-1,046	-284	1,340	'
Dividends in excess of income (equity in undistributed income) of subsidiaries	46,285	-25,145	7,388	'
Net income	61,751	54,558	57,901	'
Operating activities [Abstract]	'	'	'	'
Net income	61,751	54,558	57,901	'
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]	'	'	'	'
Stock-based compensation	4,305	4,364	3,244	'
Gain (Loss) on sales of available-for-sale securities	1,273	442	31	'
Equity in undistributed income	-59,785	-54,030	-61,788	'
Cash dividend from subsidiaries	13,500	79,175	54,400	'
Net change in other liabilities	-18,077	-3,181	15,311	'
Net change in other assets	14,924	2,030	-11,607	'
Net cash provided by operating activities	17,891	83,358	57,492	'
Investing activities [Abstract]	'	'	'	'
Purchases of available-for-sale securities	0	-4,163	-968	'
Sales and maturities of available-for-sale securities	1,948	1,445	71	'
Net cash used in acquisitions	2,232	-14,612	0	'
Purchases of premises and equipment	-782	-1,240	-1,656	'
Net cash used in investing activities	3,398	-18,570	-2,553	'
Financing activities [Abstract]	'	'	'	'
Proceeds from the issuance of shares to employee benefit plans and other stock plans	5,512	1,387	1,386	'
Payments on long-term debt	0	-3,340	-140	'
Purchases of treasury shares	-12,459	-15,490	-30,502	'
Cash dividends and payments for fractional shares	-33,518	-26,712	-27,063	'
Excess tax benefit from exercise of stock options	-178	8	341	'
Net cash provided by financing activities	-40,643	-44,147	-55,978	'
Net (decrease) increase in cash and cash equivalents	-19,354	20,641	-1,039	'
Cash and cash equivalents at beginning of year	23,095	2,454	3,493	'
Cash and cash equivalents at end of year	$3,741	$23,095	$2,454	'