NBT Bancorp (NBTB) 10-K 1 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 08, 2021	Jun. 30, 2020
Cover [Abstract]
Entity Registrant Name	NBT BANCORP INC
Entity Central Index Key	0000790359
Current Fiscal Year End Date	--12-31
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Document Transition Report	false
Entity File Number	0-14703
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	16-1268674
Entity Address, Address Line One	52 SOUTH BROAD STREET
Entity Address, City or Town	NORWICH
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	13815
City Area Code	607
Local Phone Number	337-2265
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	NBTB
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 1,302,040,742
Entity Common Stock, Shares Outstanding		43,581,317

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019
Assets
Cash and due from banks		$ 159,995	$ 170,595
Short-term interest bearing accounts		512,686	46,248
Equity securities, at fair value		30,737	27,771
Securities available for sale, at fair value		1,348,698	975,340
Securities held to maturity (fair value $636,827 and $641,262, respectively)		616,560	630,074
Federal Reserve and Federal Home Loan Bank stock		27,353	44,620
Loans held for sale		1,119	11,731
Loans		7,498,885	7,136,098
Less allowance for loan losses	[1]	110,000
Less allowance for loan losses	[1]		72,965
Net loans		7,388,885	7,063,133
Premises and equipment, net		74,206	75,631
Goodwill		280,541	274,769
Intangible assets, net		11,735	12,020
Bank owned life insurance		186,434	181,748
Other assets		293,957	202,245
Total assets		10,932,906	9,715,925
Liabilities
Demand (noninterest bearing)		3,241,123	2,414,383
Savings, NOW and money market		5,207,090	4,312,244
Time		633,479	861,193
Total deposits		9,081,692	7,587,820
Short-term borrowings		168,386	655,275
Long-term debt		39,097	64,211
Subordinated debt, net		98,052	0
Junior subordinated debt		101,196	101,196
Other liabilities		256,865	187,026
Total liabilities		9,745,288	8,595,528
Stockholders' equity
Preferred stock, $0.01 par value. Authorized 2,500,000 shares at December 31, 2020 and 2019		0	0
Common stock, $0.01 par value. Authorized 100,000,000 shares at December 31, 2020 and 2019, issued 49,651,493 at December 31, 2020 and 2019		497	497
Additional paid-in-capital		578,082	576,708
Retained earnings		749,056	696,214
Accumulated other comprehensive income (loss)		417	(19,026)
Common stock in treasury, at cost, 6,022,399 and 5,854,882 shares at December 31, 2020 and 2019, respectively		(140,434)	(133,996)
Total stockholders' equity		1,187,618	1,120,397
Total liabilities and stockholders' equity		$ 10,932,906	$ 9,715,925
[1]	Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets
Securities held to maturity fair value	$ 636,827	$ 641,262
Stockholders' equity
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	2,500,000	2,500,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	49,651,493	49,651,493
Common stock in treasury, at cost (in shares)	6,022,399	5,854,882

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest, fee and dividend income
Interest and fees on loans		$ 307,859	$ 321,474	$ 300,827
Securities available for sale		22,434	23,303	26,920
Securities held to maturity		15,283	19,105	13,242
Other		2,706	3,652	3,266
Total interest, fee and dividend income		348,282	367,534	344,255
Interest expense
Deposits		22,070	39,986	22,144
Short-term borrowings		3,408	9,693	10,552
Long-term debt		1,553	1,875	1,790
Subordinated debt		2,842	0	0
Junior subordinated debt		2,731	4,425	4,140
Total interest expense		32,604	55,979	38,626
Net interest income		315,678	311,555	305,629
Provision for loan losses	[1]	51,134	25,412	28,828
Net interest income after provision for loan losses		264,544	286,143	276,801
Noninterest income
Service charges on deposit accounts		13,201	17,151	17,224
ATM and debit card fees		25,960	23,893	22,699
Retirement plan administration fees		35,851	30,388	26,992
Wealth management		29,247	28,400	28,747
Insurance		14,757	15,770	15,122
Bank owned life insurance		5,743	5,355	5,091
Net securities (losses) gains		(388)	4,213	(6,341)
Other		21,905	18,853	15,228
Total noninterest income		146,276	144,023	124,762
Noninterest expense
Salaries and employee benefits		161,934	156,867	151,685
Occupancy		21,634	22,706	22,318
Data processing and communications		16,527	18,318	17,652
Professional fees and outside services		15,082	14,785	14,376
Equipment		19,889	18,583	17,037
Office supplies and postage		6,138	6,579	6,204
FDIC expenses		2,688	1,946	4,651
Advertising		2,288	2,773	2,782
Amortization of intangible assets		3,395	3,579	4,042
Loan collection and other real estate owned, net		3,295	4,158	4,217
Other		24,863	24,440	19,597
Total noninterest expense		277,733	274,734	264,561
Income before income tax expense		133,087	155,432	137,002
Income tax expense		28,699	34,411	24,436
Net income		$ 104,388	$ 121,021	$ 112,566
Earnings per share
Basic (in dollars per share)		$ 2.39	$ 2.76	$ 2.58
Diluted (in dollars per share)		$ 2.37	$ 2.74	$ 2.56
[1]	Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 104,388	$ 121,021	$ 112,566
Securities available for sale:
Unrealized net holding gains (losses) arising during the period, gross	23,204	25,836	(11,985)
Tax effect	(5,800)	(6,459)	2,996
Unrealized net holding gains (losses) arising during the period, net	17,404	19,377	(8,989)
Reclassification adjustment for net (gains) losses in net income, gross	(3)	79	6,622
Tax effect	1	(20)	(1,655)
Reclassification adjustment for net (gains) losses in net income, net	(2)	59	4,967
Amortization of unrealized net gains for the reclassification of available for sale securities to held to maturity, gross	644	737	688
Tax effect	(161)	(184)	(172)
Amortization of unrealized net gains for the reclassification of available for sale securities to held to maturity, net	483	553	516
Total securities available for sale, net	17,885	19,989	(3,506)
Cash flow hedges:
Unrealized (losses) gains on derivatives (cash flow hedges), gross	(275)	(459)	1,218
Tax effect	69	115	(304)
Unrealized (losses) gains on derivatives (cash flow hedges), net	(206)	(344)	914
Reclassification of net unrealized losses (gains) on cash flow hedges to interest (income), gross	296	(2,012)	(2,300)
Tax effect	(74)	503	575
Reclassification of net unrealized losses (gains) on cash flow hedges to interest (income), net	222	(1,509)	(1,725)
Total cash flow hedges, net	16	(1,853)	(811)
Pension and other benefits:
Amortization of prior service cost and actuarial losses, gross	1,627	2,686	1,145
Tax effect	(407)	(672)	(286)
Amortization of prior service cost and actuarial losses, net	1,220	2,014	859
Decrease (increase) in unrecognized actuarial loss, gross	429	5,331	(12,457)
Tax effect	(107)	(1,333)	3,038
Decrease (increase) in unrecognized actuarial loss, net	322	3,998	(9,419)
Total pension and other benefits, net	1,542	6,012	(8,560)
Total other comprehensive income (loss)	19,443	24,148	(12,877)
Comprehensive income	$ 123,831	$ 145,169	$ 99,689

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in-Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Common Stock in Treasury [Member]	Total	Cumulative Effect Adjustment for ASU Implementation [Member]Common Stock [Member]	Cumulative Effect Adjustment for ASU Implementation [Member]Additional Paid-in-Capital [Member]	Cumulative Effect Adjustment for ASU Implementation [Member]Retained Earnings [Member]	Cumulative Effect Adjustment for ASU Implementation [Member]Accumulated Other Comprehensive (Loss) Income [Member]	Cumulative Effect Adjustment for ASU Implementation [Member]Common Stock in Treasury [Member]	Cumulative Effect Adjustment for ASU Implementation [Member]
Balance at Dec. 31, 2017	$ 497	$ 574,209	$ 543,713	$ (22,077)	$ (138,165)	$ 958,177
Balance (ASU 2016-01 [Member]) at Dec. 31, 2017							$ 0	$ 0	$ 2,618	$ (2,645)	$ 0	$ (27)
Balance (ASU 2018-02 [Member]) at Dec. 31, 2017							0	0	5,575	(5,575)	0	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	112,566	0	0	112,566
Cash dividends	0	0	(43,269)	0	0	(43,269)
Net issuance of shares to employee and other stock plans	0	(2,679)	0	0	2,082	(597)
Stock-based compensation	0	3,936	0	0	0	3,936
Other comprehensive income (loss)	0	0	0	(12,877)	0	(12,877)
Balance at Dec. 31, 2018	497	575,466	621,203	(43,174)	(136,083)	1,017,909
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	121,021	0	0	121,021
Cash dividends	0	0	(46,010)	0	0	(46,010)
Net issuance of shares to employee and other stock plans	0	(2,968)	0	0	2,087	(881)
Stock-based compensation	0	4,210	0	0	0	4,210
Other comprehensive income (loss)	0	0	0	24,148	0	24,148
Balance at Dec. 31, 2019	497	576,708	696,214	(19,026)	(133,996)	1,120,397
Balance (ASU 2016-13 [Member]) at Dec. 31, 2019							$ 0	$ 0	$ (4,339)	$ 0	$ 0	$ (4,339)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	104,388	0	0	104,388
Cash dividends	0	0	(47,207)	0	0	(47,207)
Purchase of treasury shares	0	0	0	0	(7,980)	(7,980)
Net issuance of shares to employee and other stock plans	0	(3,207)	0	0	1,542	(1,665)
Stock-based compensation	0	4,581	0	0	0	4,581
Other comprehensive income (loss)	0	0	0	19,443	0	19,443
Balance at Dec. 31, 2020	$ 497	$ 578,082	$ 749,056	$ 417	$ (140,434)	$ 1,187,618

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Consolidated Statements of Changes in Stockholders' Equity [Abstract]
Cash dividends - per share (in dollars per share)	$ 1.08	$ 1.05	$ 0.99
Purchase of treasury shares (in shares)	263,507
Net issuance of shares to employee benefit plans and other stock plans (in shares)	95,990	123,645	130,157

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net income		$ 104,388	$ 121,021	$ 112,566
Adjustments to reconcile net income to net cash provided by operating activities
Provision for loan losses	[1]	51,134	25,412	28,828
Depreciation and amortization of premises and equipment		9,772	9,497	9,280
Net amortization on securities		4,369	3,375	4,007
Amortization of intangible assets		3,395	3,579	4,042
Amortization of operating lease right-of-use assets		7,382	7,239	0
Excess tax benefit on stock-based compensation		(181)	(409)	(543)
Stock-based compensation expense		4,581	4,210	3,936
Bank owned life insurance income		(5,743)	(5,355)	(5,091)
Amortization of subordinated debt issuance costs		230	0	0
Proceeds from sale of loans held for sale		168,707	175,829	102,547
Originations of loans held for sale		(158,279)	(181,261)	(108,070)
Net gains on sales of loans held for sale		(1,989)	(786)	(286)
Net security losses (gains)		388	(4,213)	6,341
Net (gains) losses on sale of other real estate owned		(96)	227	(230)
Lease termination loss		4,284	1,872	0
Net change in other assets and other liabilities		(49,930)	(6,774)	(9,554)
Net cash provided by operating activities		142,412	153,463	147,773
Investing activities
Net cash used in acquisitions		(3,899)	0	(7,884)
Securities available for sale:
Proceeds from maturities, calls and principal paydowns		336,410	273,578	259,446
Proceeds from sales		0	26,203	101,315
Purchases		(689,932)	(252,963)	(132,448)
Securities held to maturity:
Proceeds from maturities, calls and principal paydowns		243,136	223,733	100,738
Proceeds from sales		996	0	0
Purchases		(230,951)	(70,660)	(400,602)
Equity securities:
Proceeds from calls		2,000	0	0
Proceeds from sales		0	3,966	3,318
Purchases		0	(93)	(2)
Other:
Net increase in loans		(378,765)	(272,698)	(331,166)
Proceeds from Federal Home Loan Bank stock redemption		63,305	182,752	246,844
Purchases of Federal Reserve Bank and Federal Home Loan Bank stock		(46,038)	(174,143)	(253,367)
Proceeds from settlement of bank owned life insurance		1,057	1,086	0
Purchases of premises and equipment, net		(8,157)	(6,647)	(7,402)
Proceeds from sales of other real estate owned		1,113	1,543	3,591
Net cash used in investing activities		(709,725)	(64,343)	(417,619)
Financing activities
Net increase in deposits		1,493,872	219,609	197,575
Net (decrease) increase in short-term borrowings		(486,889)	(216,421)	152,573
Proceeds from issuance of subordinated debt		100,000	0	0
Payment of subordinated debt issuance costs		(2,178)	0	0
Proceeds from issuance of long-term debt		0	10,598	25,000
Repayments of long-term debt		(25,114)	(20,111)	(40,145)
Proceeds from the issuance of shares to employee and other stock plans		184	725	1,296
Cash paid by employer for tax-withholding on stock issuance		(1,537)	(1,622)	(1,893)
Purchase of treasury stock		(7,980)	0	0
Cash dividends		(47,207)	(46,010)	(43,269)
Net cash provided by (used in) financing activities		1,023,151	(53,232)	291,137
Net increase in cash and cash equivalents		455,838	35,888	21,291
Cash and cash equivalents at beginning of year		216,843	180,955	159,664
Cash and cash equivalents at end of year		672,681	216,843	180,955
Cash paid during the year for:
Interest expense		31,692	55,908	36,691
Income taxes paid, net of refund		45,790	28,374	31,898
Noncash investing activities:
Loans transferred to other real estate owned		1,017	787	1,273
Acquisitions:
Fair value of assets acquired		$ 3,328	$ 0	$ 6,274
[1]	Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Summary of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. Summary of Significant Accounting Policies The accounting and reporting policies of NBT Bancorp Inc. (“NBT Bancorp”) and its subsidiaries, NBT Bank, National Association (“NBT Bank” or the “Bank”), NBT Financial Services, Inc. and NBT Holdings, Inc. 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 and such estimates could be material to the financial statements. Estimates associated with the allowance for credit losses, provision for income taxes, pension accounting, fair values of financial instruments and status of contingencies are particularly susceptible to material change in the near term. The following is a description of significant policies and practices: Consolidation The accompanying consolidated financial statements include the accounts of NBT Bancorp and its wholly-owned subsidiaries mentioned above. All material intercompany transactions have been eliminated in consolidation. Amounts previously reported in the consolidated financial statements are reclassified whenever necessary to conform to the current year’s presentation. In the “Parent Company Financial Information,” the investment in subsidiaries is recorded using the equity method of accounting. The Company determines whether it has a controlling financial interest in an entity by first evaluating whether the entity is a voting interest entity or a variable interest entity under GAAP. Voting interest entities are entities in which the total equity investment at risk is sufficient to enable the entity to finance itself independently and provides the equity holders with the obligation to absorb losses, the right to receive residual returns and the right to make decisions about the entity’s activities. The Company consolidates voting interest entities in which it has all, or at least a majority of, the voting interest. As defined in applicable accounting standards, variable interest entities (“VIEs”) are entities that lack one or more of the characteristics of a voting interest entity. A controlling financial interest in a VIE is present when the Company has both the power and ability to direct the activities of the VIE that most significantly impact the VIE’s economic performance and an obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. The Company’s wholly-owned subsidiaries CNBF Capital Trust I, NBT Statutory Trust I, NBT Statutory Trust II, Alliance Financial Capital Trust I and Alliance Financial Capital Trust II are VIEs for which the Company is not the primary beneficiary. Accordingly, the accounts of these entities are not included in the Company’s consolidated financial statements. Segment Reporting The Company’s operations are primarily in the community banking industry and include the provision of traditional banking services. The Company also provides other services through its subsidiaries such as insurance, retirement plan administration and trust administration. The Company operates solely in the geographical regions of central and upstate New York, northeastern Pennsylvania, western Massachusetts, southern New Hampshire, Vermont, the southern coastal Maine area and now entering central Connecticut. Cash Equivalents The Company considers amounts due from correspondent banks, cash items in process of collection and institutional money market mutual funds to be cash equivalents for purposes of the consolidated statements of cash flows. Securities The Company classifies its securities at date of purchase as either held to maturity (“HTM”), available for sale (“AFS”) or equity. HTM debt securities are those that the Company has the ability and intent to hold until maturity. AFS debt securities are securities that are not classified as HTM. 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. Allowance for Credit Losses –HTM Debt Securities With respect to its HTM debt securities, the Company is required to utilize the Accounting Standards Update (“ASU”) 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments The mortgage-backed and collateralized mortgage obligations HTM securities are issued by U.S. government entities and agencies. These securities are either explicitly or implicitly guaranteed by the U.S. government as to timely repayment of principal and interest, are highly rated by major rating agencies, and have a long history of no credit losses. Therefore, the Company did not record a credit loss for these securities. State and municipal bonds carry a Moody’s rating of A to AAA. In addition, the Company has a limited amount of New York state local municipal bonds that are not rated. The estimate of expected credit losses on the HTM portfolio is based on the expected cash flows of each individual CUSIP over its contractual life and considers historical credit loss information, current conditions and reasonable and supportable forecasts. Given the rarity of municipal defaults and losses, the Company utilized Moody’s Municipal Loss Forecast Model as the sole source of municipal default and loss rates which provides decades of data across all municipal sectors and geographies. As with the loan portfolio, cash flows are forecast over a 6-quarter period under various weighted economic conditions, with a reversion to long-term average economic conditions over a 4-quarter period on a straight-line basis. Management may exercise discretion to make adjustments based on environmental factors. As of December 31, 2020, the Company determined that the expected credit loss on its municipal bond portfolio was de minimis, and therefore, an allowance for credit losses was not recorded. Allowance for Credit Losses –AFS Debt Securities The impairment model for AFS debt securities differs from the CECL approach utilized for HTM debt securities because AFS debt securities are measured at fair value rather than amortized cost. For AFS debt securities in an unrealized loss position, the Bank first assesses whether it intends to sell, or it is more likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through income. For AFS debt securities that do not meet the aforementioned criteria, in making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, adverse conditions specifically related to the security, failure of the issuer of the debt security to make scheduled interest or principal payments, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. The cash flows should be estimated using information relevant to the collectability of the security, including information about past events, current conditions and reasonable and supportable forecasts. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded for the credit loss, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income. Prior to the adoption of CECL on January 1, 2020, declines in the fair value of AFS and HTM securities below their amortized cost, less any current period credit loss, that are deemed to be other-than-temporary were reflected in earnings as realized losses, or in other comprehensive income (“OCI”). Investments in Federal Reserve Bank and Federal Home Loan Bank (“FHLB”) stock are required for membership in those organizations and are carried at cost since there is no market value available. The FHLB New York continues to pay dividends and repurchase stock. As such, the Company has not recognized any impairment on its holdings of Federal Reserve Bank and FHLB stock. Loan Held for Sale and Loan Servicing Loans held for sale are recorded at the lower of cost or fair value on an individual basis. Loan sales are recorded when the sales are funded. Gains and losses on sales of loans held for sale are included in other noninterest income in the Consolidated Statements of Income. Mortgage loans held for sale are generally sold with servicing rights retained. Mortgage servicing rights are recorded at fair value upon sale of the loan, and are amortized in proportion to and over the period of estimated net servicing income. Loans Loans are recorded at their current unpaid principal balance, net of unearned income and unamortized loan fees and expenses, which are amortized under the effective interest method over the estimated lives of the loans. Interest income on loans is accrued based on the principal amount outstanding. For all loan classes within the Company’s loan portfolio, loans are placed on nonaccrual status when timely collection of principal and/or interest in accordance with contractual terms is in doubt. Loans are transferred to nonaccrual status generally when principal or interest payments become ninety days delinquent, unless the loan is well secured and in the process of collection or sooner when management concludes circumstances indicate that borrowers may be unable to meet contractual principal or interest payments. When a loan is transferred to a nonaccrual status, all interest previously accrued in the current period but not collected is reversed against interest income in that period. Interest accrued in a prior period and not collected is charged-off against the allowance for credit losses. If ultimate repayment of a nonaccrual loan is expected, any payments received are applied in accordance with contractual terms. If ultimate repayment of principal is not expected, any payment received on a nonaccrual loan is applied to principal until ultimate repayment becomes expected. For all loan classes within the Company’s loan portfolio, nonaccrual loans are returned to accrual status when they become current as to principal and interest and demonstrate a period of performance under the contractual terms and, in the opinion of management, are fully collectible as to principal and interest. For loans in all portfolios, the principal amount is charged off in full or in part as soon as management determines, based on available facts, that the collection of principal in full or in part is improbable. For Commercial loans, management considers specific facts and circumstances relative to individual credits in making such a determination. For Consumer and Residential Real Estate loan classes, management uses specific guidance and thresholds from the Federal Financial Institutions Examination Council’s Uniform Retail Credit Classification and Account Management Policy. A loan is considered to be a troubled debt restructuring (“TDR”) when the Company grants a concession to the borrower because of the borrower’s financial condition that the Company would not otherwise consider. Such concessions generally include or a combination of the following: an extension of the maturity date at a stated rate of interest lower than the current market rate for new debt with similar risk; a temporary reduction in the interest rate; or a change in scheduled payment amount. TDR loans are nonaccrual loans; however, they can be returned to accrual status after a period of performance, generally evidenced by Section 4013 of the Coronavirus Aid, Relief and Economic Security Act (“CARES Act”), which was enacted on March 27, 2020, provides that a qualified loan modification is exempt by law from classification as a troubled debt restructuring as defined by GAAP. To be eligible, each loan modification must be (1) related to the coronavirus (“COVID-19”) pandemic; (2) executed on a loan that was not more than 30 days past due as of December 31, 2019; and (3) executed between March 1, 2020, and the earlier of (a) 60 days after the date of termination of the National Emergency or (b) December 31, 2020. On August 3, 2020, the Federal Financial Institutions Examination Council (“FFIEC”) issued a joint statement on additional loan accommodations related to COVID-19. The joint statement clarifies that for loan modifications in which Section 4013 is being applied, subsequent modifications could also be eligible under Section 4013. Accordingly, the Company is offering modifications made in response to COVID-19 to borrowers who were current and otherwise not past due in accordance with the criteria stated in Section 4013. These include short-term, 180 days or less, modifications in the form of payment deferrals, fee waivers, extensions of repayment terms, or other delays in payment. Accordingly, the Company did not account for such loan modifications as TDRs. As of December 31, 2020, there were $110.8 million in loans in modification programs related to COVID-19. On December 27, 2020, the Consolidated Appropriations Act amended section 2014 of the CARES Act extending the exemption of qualified loan modifications from classification as a troubled debt restructuring as defined by GAAP to the earlier of January 1, 2022, or 60 days after the National Emergency concerning COVID-19 ends. Allowance for Credit Losses - Loans The CECL approach requires an estimate of the credit losses expected over the life of a loan (or pool of loans). It replaces the incurred loss approach’s threshold that required the recognition of a credit loss when it was probable a loss event was incurred. The allowance for credit losses is a valuation account that is deducted from, or added to, the loans’ amortized cost basis to present the net, lifetime amount expected to be collected on the loans. Loan losses are charged off against the allowance when management believes a loan balance is confirmed to be uncollectible. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Management estimates the allowance balance using relevant available information, from internal and external sources, related to past events, current conditions, and reasonable and supportable forecasts. Historical credit loss experience provides the basis for the estimation of expected credit losses. Company historical loss experience was supplemented with peer information when there was insufficient loss data for the Company. Peer selection was based on a review of institutions with comparable loss experience as well as loan yield, bank size, portfolio concentration and geography. Adjustments to historical loss information are made for differences in current loan-specific risk characteristics such as differences in underwriting standards, portfolio mix, delinquency level or term as well as changes in environmental conditions, such as changes in unemployment rates, production metrics, property values, or other relevant factors. Significant management judgment is required at each point in the measurement process. Portfolio segment is defined as the level at which an entity develops and documents a systematic methodology to determine its allowance for credit losses. Upon adoption of CECL, management revised the manner in which loans were pooled for similar risk characteristics. Management developed segments for estimating loss based on type of borrower and collateral which is generally based upon federal call report segmentation and have been combined or subsegmented as needed to ensure loans of similar risk profiles are appropriately pooled. The following table illustrates the portfolio and class segments for the Company’s loan portfolio in 2020: Portfolio Segment Class Commercial Loans Commercial & Industrial Paycheck Protection Program Commercial Real Estate Consumer Loans Auto Other Consumer Residential Loans Commercial Loans The Company offers a variety of commercial loan products. The Company’s underwriting analysis for commercial loans typically includes credit verification, independent appraisals, a review of the borrower’s financial condition and a detailed analysis of the borrower’s underlying cash flows. Commercial and Industrial (“C&I”) Paycheck Protection Program (“PPP”) Commercial Real Estate (“CRE”) Consumer Loans The Company offers a variety of Consumer loan products including Auto and Other Consumer loans. Auto three Other Consumer one Residential Residential loans consist primarily of loans secured by a first or second mortgage on primary residences, home equity loans and lines of credit in first and second lien positions and residential construction loans. We originate adjustable-rate and fixed rate, one-to-four-family residential loans for the construction or purchase of a residential property or the refinancing of a mortgage. These loans are collateralized by properties located in the Company’s market area. Loans on one-to-four-family residential 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. For home equity loans, consumers are able to borrow up to 85% of the equity in their homes and are generally tied to Prime with a ten-year draw followed by a fifteen-year amortization. These loans carry a higher risk than first mortgage residential loans as they are often in a second position with respect to collateral. Historical credit loss experience for both the Company and segment-specific peers provides the basis for the estimation of expected credit losses, where observed credit losses are converted to probability of default rate (“PD”) curves through the use of segment-specific loss given default (“LGD”) risk factors that convert default rates to loss severity based on industry-level, observed relationships between the two variables for each asset class, primarily due to the nature of the underlying collateral. These risk factors were assessed for reasonableness against the Company’s own loss experience and adjusted in certain cases when the relationship between the Company’s historical default and loss severity deviate from that of the wider industry. The historical PDR curves, together with corresponding economic conditions, establish a quantitative relationship between economic conditions and loan performance through an economic cycle. Using the historical relationship between economic conditions and loan performance, management’s expectation of future loan performance is incorporated using externally developed economic forecasts which are probabilistically weighted to reflect potential forecast inaccuracy and model limitations. These forecasts are applied over a period that management has determined to be reasonable and supportable. Beyond the period over which management can develop or source a reasonable and supportable forecast, the model will revert to long-term average economic conditions using a straight-line, time-based methodology. The allowance for credit losses is measured on a collective (pool) basis, with both a quantitative and qualitative analysis that is applied on a quarterly basis, when similar risk characteristics exist. The respective quantitative allowance for each segment is measured using an econometric, discounted PD/LGD modeling methodology in which distinct, segment-specific multi-variate regression models are applied to multiple, probabilistically weighted external economic forecasts. Under the discounted cash flows methodology, expected credit losses are estimated over the effective life of the loans by measuring the difference between the net present value of modeled cash flows and amortized cost basis. Contractual cash flows over the contractual life of the loans are the basis for modeled cash flows, adjusted for modeled defaults and expected prepayments and discounted at the loan-level stated interest rate. The contractual term excludes expected extensions, renewals, and modifications unless either of the following applies: management has a reasonable expectation at the reporting date that a TDR will be executed with an individual borrower or the extension or renewal options are included in the original or modified contract at the reporting date and are not unconditionally cancellable by the Company. After quantitative considerations, management applies additional qualitative adjustments so that the allowance for credit loss is reflective of the estimate of lifetime losses that exist in the loan portfolio at the balance sheet date. Qualitative considerations include limitations inherent in the quantitative model; trends experienced in nonperforming and delinquent loans; changes in value of underlying collateral; changes in lending policies and procedures; nature and composition of loans; portfolio concentrations that may affect loss experience across one or more components of the portfolio; the experience, ability and depth of lending management and staff; the Company’s credit review system; and the effect of external factors; such as competition, legal and regulatory requirements. Loans that do not share risk characteristics and meet materiality criteria are evaluated on an individual basis and are excluded from the pooled evaluation. When management determines that foreclosure is probable, expected credit losses are based on the fair value of the collateral at the reporting date, adjusted for selling costs as appropriate. If the loan is not collateral dependent, the allowance for credit losses related to individually assessed loans is based on discounted expected cash flows using the loan’s initial effective interest rate. Generally, individually assessed loans are collateral dependent. A loan for which the terms have been modified resulting in a concession, and for which the borrower is experiencing financial difficulties is considered to be a TDR. The allowance for credit losses on a TDR is measured using the same method as all other loans held for investment, except that the original interest rate is used to discount the expected cash flows, not the rate specified within the restructuring. Allowance for Credit Losses on Off-Balance Sheet Credit Exposures The Company estimates expected credit losses over the contractual period in which the Company has exposure to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by the Company. The allowance for credit losses on off-balance sheet credit exposures is adjusted as an expense in other noninterest expense. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over their estimated lives. Estimating credit losses on unfunded commitments requires the Bank to consider the following categories of off-balance sheet credit exposure: unfunded commitments to extend credit, unfunded lines of credit, and standby letters of credit. Each of these unfunded commitments is then analyzed for a probability of funding to calculate a probable funding amount. The life of loan loss factor by related portfolio segment from the loan allowance for credit loss calculation is then applied to the probable funding amount to calculate a reserve on unfunded commitments. Accrued Interest Receivable Upon adoption of CECL on January 1, 2020, the Company made the following elections regarding accrued interest receivable: (1) presented accrued interest receivable balances separately within other assets balance sheet line item; (2) excluded interest receivable that is included in amortized cost of financing receivables from related disclosures requirements and (3) continued our policy to write off accrued interest receivable by reversing interest income. For loans, write off typically occurs upon becoming over 90 to 120 days past due and therefore the amount of such write offs are immaterial. For loans given short-term loan modifications to assist borrowers during the COVID-19 national emergency, this accounting policy would not apply as the length of time between interest recognition and the write-off of uncollectible interest could exceed 120 days. Therefore, the Company estimated an allowance for credit losses for accrued interest receivable related to loans with short-term modifications due to the pandemic. Historically, the Company has not experienced uncollectible accrued interest receivable on investment securities. Allowance for Loan Losses – Incurred Loss Method Prior to the adoption of CECL on January 1, 2020, the Company calculated the allowance for loan losses using the incurred loss method whereby the allowance represented management’s estimate of probable incurred losses inherent in the current loan portfolio. Management believes that the allowance for loan losses is adequate. While management uses available information to recognize losses on loans, additions and reductions of the allowance for loan losses may fluctuate from one reporting period to another based on changes in economic conditions or changes in the values of properties securing loans in the process of foreclosure. The evaluation of the various components of the allowance for loan losses requires considerable judgment in order to estimate inherent loss exposures. Historical loss rates are first applied to pools of loans with similar risk characteristics. Each segment has a distinct set of risk characteristics monitored by management. Unique characteristics such as borrower type, loan type, collateral type and risk characteristics define each class segment. The Company further assess and monitor risk and performance at a more disaggregated level, which includes our internal risk grading system for the Commercial segments. Under the incurred loss method, the loan portfolio was segmented into the Commercial, Consumer and Residential Real Estate portfolio segments. The Commercial segment was further pooled into three classes: Commercial and Industrial, Commercial Real Estate and Business Banking. The Consumer segment was further pooled into three classes: Indirect Auto, Specialty Lending and Direct. Those segments were 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). Loss rates are calculated by historical charge-offs that have occurred within each pool of loans over the lookback period (“LBP”), multiplied by the loss emergence period (“LEP”). The LBP represents the historical data period utilized to calculate loss rates. The LEP is an estimate of the average amount of time from the point at which a loss is incurred on a loan to the point at which the loss is confirmed. In general, the LEP will be shorter in an economic slowdown or recession and longer during times of economic stability or growth, as customers are better able to delay loss confirmation after a potential loss event has occurred. In conjunction with our annual review of the allowance for loan loss assumptions, the Company updates our study of LEPs for each portfolio segment using our loan charge-off history. After consideration of the historic loss analysis, management applies additional qualitative adjustments so that the allowance for loan losses is reflective of the estimate of incurred losses that exist in the loan portfolio at the balance sheet date. Qualitative adjustments are made if, in the judgment of management, incurred loan losses inherent in the loan portfolio are not fully captured in the historical loss analysis. Qualitative considerations include the loan portfolio trends, composition and nature of loans; changes in lending policies and procedures, including underwriting standards and collection, charge-offs and recoveries; trends experienced in nonperforming and delinquent loans; current economic conditions in the Company’s market; portfolio concentrations that may affect loss experience across one of more components of the portfolio; the effect of external factors such as competition, legal and regulatory requirements; and the experience, ability and depth of lending management and staff. The allowance for loan losses related to impaired loans specifically allocated for impairment is based on discounted expected cash flows using the loan’s initial effective interest rate or the fair value of the collateral for certain loans where repayment of the loan is expected to be provided solely by the underlying collateral (“collateral dependent”). The Company’s impaired loans, if any, are generally collateral dependent. The Company considers the estimated cost to sell, on a discounted basis, when determining the fair value of collateral in the measurement of impairment if those costs are expected to reduce the cash flows available to repay or otherwise satisfy the loans. After a thorough consideration and validation of the factors discussed above, required additions or reductions to the allowance for loan losses are made periodically by charges or credits to the provision for loan losses. These are necessary to maintain the allowance at a level which management believes is reasonably reflective of the level of incurred credit losses inherent in the portfolio. Loan losses are charged off against the allowance, while recoveries of amounts previously charged off are credited to the allowance. Premises and Equipment Premises and equipment are stated at cost, less accumulated depreciation. Depreciation of premises and equipment is determined using the straight-line method over the estimated useful lives of the respective assets. Expenditures for maintenance, repairs and minor replacements are charged to expense as incurred. Leases The Company determines if a lease is present at the inception of an agreement. Right-of-use (“ROU”) assets and lease liabilities are recognized at lease commencement based on the present value of the remaining lease payments using a discount rate that represents the Company’s incremental borrowing rate at the lease commencement date. ROU assets and operating lease liabilities, are included in other assets and other liabilities, respectively, on the consolidated balance sheets Operating lease ROU assets represent the Company’s right to use an underlying asset during the lease term and operating lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets are further adjusted for lease incentives. Operating lease expense, which is comprised of amortization of the ROU asset and the implicit interest accreted on the operating lease liability, is recognized on a straight-line basis over the lease term, and is recorded in occupancy expense in the consolidated statements of income The Company has lease agreements with lease and non-lease components, which are generally accounted for separately. For real estate leases, non-lease components and other non-components, such as common area maintenance charges, real estate taxes and insurance are not included in the measurement of the lease liability since they are generally able to be segregated. Our leases relate primarily to office space and bank branches, and some contain options to renew the lease. These options to renew are generally not considered reasonably certain to exercise, and are therefore not included in the lease term until such time that the option to renew is reasonably certain. Other Real Estate Owned Other real estate owned (“OREO”) consists of properties acquired through foreclosure or by acceptance of a deed in lieu of foreclosure. These assets are recorded at the lower of fair value of the asset acquir

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2020
Recent Accounting Pronouncements [Abstract]
Recent Accounting Pronouncements	2. Recent Accounting Pronouncements Recently Adopted Accounting Standards In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments The Company adopted CECL on January 1, 2020 (“Day 1”) using the modified retrospective method for all financial assets measured at amortized cost and off-balance-sheet credit exposures. Results for reporting periods beginning after January 1, 2020 are presented under ASC 326 while prior period amounts continue to be reported in accordance with previously applicable GAAP. The Company recorded a net decrease to retained earnings of $4.3 million as of January 1, 2020 for the cumulative effect of adopting ASC 326. The transition adjustment includes a $3.0 million impact due to the allowance for credit losses on loans, a $2.8 million impact due to the allowance for credit losses on off-balance sheet credit exposure, and a $1.5 million impact to the deferred tax asset. The Company did not record an allowance for HTM debt securities on January 1, 2020 as the amount of credit risk was deemed immaterial. The Company did not record an allowance for credit losses on its AFS debt securities under the newly codified AFS debt security impairment model, as the majority of these securities are government agency-backed securities for which the risk of loss is minimal. Refer to Note 4 Securities and Note 6 Allowance for Credit Losses and Credit Quality of Loans to the Company’s consolidated financial statements included in this Form 10-K for more information. In December 2018, the Office of Comptroller of the Currency (“OCC”), the Board of Governors of the Federal Reserve System, and the Federal Deposit Insurance Corporation (“FDIC”) approved a final rule to address changes to credit loss accounting under GAAP, including banking organizations’ implementation of CECL. The final rule provides banking organizations the option to phase in over a three-year period the day-one adverse effects on regulatory capital that may result from the adoption of the new accounting standard. In March 2020, the OCC, the Board of Governors of the Federal Reserve System, and the FDIC announced an interim final rule to delay the estimated impact on regulatory capital stemming from the implementation of CECL. The interim final rule maintains the three-year transition option in the previous rule and provides banks the option to delay for two years an estimate of CECL’s effect on regulatory capital, relative to the incurred loss methodology’s effect on regulatory capital, followed by a three-year transition period (five-year transition option). The Company adopted the capital transition relief over the permissible five-year period. On March 22, 2020, a statement was issued by the Company’s banking regulators and titled the “Interagency Statement on Loan Modifications and Reporting for Financial Institutions Working with Customers Affected by the Coronavirus” that encourages financial institutions to work prudently with borrowers who are or may be unable to meet their contractual payment obligations due to the effects of the recent COVID-19 pandemic. Additionally, Section 4013 of the CARES Act, which was enacted on March 27, 2020, further provides that a qualified loan modification is exempt by law from classification as a troubled debt restructuring as defined by GAAP. To be eligible, each loan modification must be (1) related to the COVID-19 event; (2) executed on a loan that was not more than 30 days past due as of December 31, 2019; and (3) executed between March 1, 2020, and the earlier of (a) 60 days after the date of termination of the National Emergency or (b) December 31, 2020. On August 3, 2020, the Federal Financial Institutions Examination Council (“FFIEC”) issued a joint statement on additional loan accommodations related to COVID-19. The joint statement clarifies that for loan modifications in which Section 4013 is being applied, subsequent modifications could also be eligible under Section 4013. Accordingly, the Company is offering modifications made in response to COVID-19 to borrowers who were current and otherwise not past due in accordance with the criteria stated in Section 4013. These include short-term, 180 days or less, modifications in the form of payment deferrals, fee waivers, extensions of repayment terms, or other delays in payment. Accordingly, the Company did not account for such loan modifications as TDRs. As of December 31, 2020, there were $110.8 million in loans in modification programs related to COVID-19. On December 27, 2020, the Consolidated Appropriations Act amended section 2014 of the CARES Act extending the exemption of qualified loan modifications from classification as a troubled debt restructuring as defined by GAAP to the earlier of January 1, 2022, or 60 days after the National Emergency concerning COVID-19 ends. In August 2018, the FASB issued ASU 2018-13, Fair value Measurement (Topic 820) – Disclosure Framework – Changes to the Disclosure Requirements for Fair value Measurement In August 2018, the FASB issued ASU 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40) – Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract In August 2018, the FASB issued ASU 2018-14, Compensation – Retirement Benefits – Defined Benefit Plans - General (Subtopic 715-20) Accounting Standards Issued Not Yet Adopted In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2020
Acquisitions [Abstract]
Acquisitions	3. Acquisitions In 2020, the Company acquired Alliance Benefit Group of Illinois, Inc. for a total consideration of $9.1 million. As part of the acquisition, the Company recorded goodwill of $5.8 million and $5.1 million contingent consideration recorded in other liabilities on the consolidated balance sheet as of December 31, 2020. In 2018, the Company acquired Retirement Plan Services, LLC for a total consideration of $13.0 million. As part of the acquisition, the Company recorded goodwill of $6.7 million and $5.1 million contingent consideration recorded in other liabilities on the consolidated balance sheet as of December 31, 2018. The operating results of acquired companies are included in the consolidated results after the dates of acquisition.

Securities

Securities	12 Months Ended
	Dec. 31, 2020
Securities [Abstract]
Securities	4. Securities The amortized cost, estimated fair value and unrealized gains (losses) of AFS securities are as follows: (In thousands) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value As of December 31, 2020 Federal agency $ 245,590 $ 59 $ 2,052 $ 243,597 State & municipal 42,550 630 - 43,180 Mortgage-backed: Government-sponsored enterprises 521,448 17,079 22 538,505 U.S. government agency securities 55,049 2,332 47 57,334 Collateralized mortgage obligations: Government-sponsored enterprises 311,710 7,549 58 319,201 U.S. government agency securities 114,864 3,739 - 118,603 Corporate 27,500 778 - 28,278 Total AFS securities $ 1,318,711 $ 32,166 $ 2,179 $ 1,348,698 As of December 31, 2019 Federal agency $ 34,998 $ 3 $ 243 $ 34,758 State & municipal 2,533 - 20 2,513 Mortgage-backed: Government-sponsored enterprises 453,614 4,982 239 458,357 U.S. government securities 44,758 667 156 45,269 Collateralized mortgage obligations: Government-sponsored enterprises 328,499 1,949 467 329,981 U.S. government securities 104,152 718 408 104,462 Total AFS securities $ 968,554 $ 8,319 $ 1,533 $ 975,340 There was no allowance for credit losses on AFS securities as of the year ending December 31, 2020. The components of net realized gains (losses) on AFS securities are as follows. These amounts were reclassified out of AOCI and into earnings. Years Ended December 31, (In thousands) 2020 2019 2018 Gross realized gains $ 3 $ 73 $ - Gross realized (losses) - (152 ) (6,622 ) N et AFS realized gains (losses) $ 3 $ (79 ) $ (6,622 ) Included in net realized gains (losses) on AFS securities, the Company recorded gains from calls of approximately $ thousand for the year ended , $ thousand for the year ended and for the year ended . The amortized cost, estimated fair value and unrealized gains (losses) of HTM securities are as follows: (In thousands) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value As of December 31, 2020 Federal agency $ 100,000 $ - $ 1,658 $ 98,342 Mortgage-backed: Government-sponsored enterprises 107,914 4,583 - 112,497 U.S. government agency securities 11,533 979 - 12,512 Collateralized mortgage obligations: Government-sponsored enterprises 103,105 4,477 - 107,582 U.S. government agency securities 79,145 3,950 - 83,095 State & municipal 214,863 7,953 17 222,799 Total HTM securities $ 616,560 $ 21,942 $ 1,675 $ 636,827 As of December 31, 2019 Mortgage-backed: Government-sponsored enterprises $ 149,448 $ 3,184 $ 155 $ 152,477 U.S. government agency securities 13,667 584 - 14,251 Collateralized mortgage obligations: Government-sponsored enterprises 189,402 2,165 368 191,199 U.S. government agency securities 110,498 3,256 100 113,654 State & municipal 167,059 2,628 6 169,681 Total HTM securities $ 630,074 $ 11,817 $ 629 $ 641,262 At December 31, 2020 and 2019, all of the mortgaged-backed HTM securities were comprised of U.S. government agency and Government-sponsored enterprises securities. There was no allowance for credit losses on HTM securities as of December 31, 2020. Included in net realized gains (losses), the Company recorded gains from calls on HTM securities of approximately $ thousand for the year ended and approximately $ thousand for the year ended December 31, 2019. There were recorded gains from calls on HTM securities included in the net realizes gains (losses) for the year ended D . During the year ended December 31, 2020, the Company sold HTM securities with an amortized cost of $1.0 million and resulted in a realized loss of $1 thousand. Due to significant deterioration in the creditworthiness of the issuer of the HTM securities, the circumstances caused the Company to change its intent to hold the HTM securities sold to maturity, which did not affect the Company’s intent to hold the remainder of the HTM portfolio to maturity. There were no sales of HTM securities in the years ended December 31, 2019 and 2018. AFS and HTM securities with amortized costs totaling $ billion at and $ billion at D were pledged to secure public deposits and for other purposes required or permitted by law. Additionally, at D and 2019, AFS and HTM securities with an amortized cost of $ million and $ million, respectively, were pledged as collateral for securities sold under repurchase agreements. The following tables set forth information with regard to gains and (losses) on equity securities: Years Ended December 31, (In thousands) 2020 2019 Net (losses) and gains recognized on equity securities $ (414 ) $ 4,280 Less: Net gains recognized during the period on equity securities sold during the period - 3,966 Unrealized (losses) and gains recognized on equity securities still held $ (414 ) $ 314 Included in the net realized gains and (losses) recognized on equity securities during the year ended December 31, 2019, the Company recorded a $4.0 million gain from the sale of Visa Class B common stock, which had no readily determinable fair value at the time of the sale. As of December 31, 2020 and 2019 the carrying value of equity securities without readily determinable fair values was $2.0 million and $4.0 million, respectively. The Company performed a qualitative assessment to determine whether the investments were impaired and identified no areas of concern as of December 31, 2020 and 2019. There were no impairments, downward or upward adjustments recognized for equity securities without readily determinable fair values during the years ended December 31, 2020 and 2019. The following tables set forth information with regard to contractual maturities of debt securities at December 31, 2020: (In thousands) Amortized Cost Estimated Fair Value AFS debt securities: Within one year $ 438 $ 449 From one to five years 21,476 22,324 From five to ten years 545,330 551,215 After ten years 751,467 774,710 Total AFS debt securities $ 1,318,711 $ 1,348,698 HTM debt securities: Within one year $ 18,088 $ 18,104 From one to five years 58,963 60,483 From five to ten years 231,927 237,275 After ten years 307,582 320,965 Total HTM debt securities $ 616,560 $ 636,827 Maturities of mortgage-backed, collateralized mortgage obligations and asset-backed securities are stated based on their estimated average lives. Actual maturities may differ from estimated average lives or contractual maturities because, in certain cases, borrowers have the right to call or prepay obligations with or without call or prepayment penalties. Except for U.S. Government securities and Government-sponsored enterprises securities, there were no holdings, when taken in the aggregate, of any single issuer that exceeded 10% of consolidated stockholders’ equity at December 31, 2020 and 2019. The following table sets forth information with regard to investment securities with unrealized losses, for which an allowance for credit losses has not been recorded at December 31, 2020, Less Than 12 Months 12 Months or Longer Total (In thousands) Fair Value Unrealized Losses Number of Positions Fair Value Unrealized Losses Number of Positions Fair Value Unrealized Losses Number of Positions As of December 31, 2020 AFS securities: Federal agency $ 148,537 $ (2,052 ) 10 $ - $ - - $ 148,537 $ (2,052 ) 10 Mortgage-backed 47,269 (60 ) 3 800 (9 ) 4 48,069 (69 ) 7 Collateralized mortgage obligations 17,837 (58 ) 6 - - - 17,837 (58 ) 6 Total securities with unrealized losses $ 213,643 $ (2,170 ) 19 $ 800 $ (9 ) 4 $ 214,443 $ (2,179 ) 23 HTM securities: Federal agency $ 98,342 $ (1,658 ) 4 $ - $ - - $ 98,342 $ (1,658 ) 4 State & municipal 4,805 (17 ) 5 - - - 4,805 (17 ) 5 Total securities with unrealized losses $ 103,147 $ (1,675 ) 9 $ - $ - - $ 103,147 $ (1,675 ) 9 As of December 31, 2019 AFS securities: Federal agency $ 14,891 $ (109 ) 2 $ 9,866 $ (134 ) 1 $ 24,757 $ (243 ) 3 State & municipal 2,503 (20 ) 1 - - - 2,503 (20 ) 1 Mortgage-backed 67,986 (273 ) 21 37,745 (122 ) 16 105,731 (395 ) 37 Collateralized mortgage obligations 113,121 (316 ) 24 49,632 (559 ) 17 162,753 (875 ) 41 Total securities with unrealized losses $ 198,501 $ (718 ) 48 $ 97,243 $ (815 ) 34 $ 295,744 $ (1,533 ) 82 HTM securities: Mortgage-backed $ - $ - - $ 25,370 $ (155 ) 2 $ 25,370 $ (155 ) 2 Collateralized mortgage obligations 18,040 (181 ) 3 22,389 (287 ) 5 40,429 (468 ) 8 State & municipal 2,257 (6 ) 4 - - - 2,257 (6 ) 4 Total securities with unrealized losses $ 20,297 $ (187 ) 7 $ 47,759 $ (442 ) 7 $ 68,056 $ (629 ) 14 The Company does not believe the AFS securities that were in an unrealized loss position as of December 31, 2020, which consisted of 23 individual securities, represented a credit loss impairment. AFS debt securities in unrealized loss positions are evaluated for impairment related to credit losses at least quarterly. As of December 31, 2020, the majority of the AFS securities in an unrealized loss position consisted of debt securities issued by U.S. government agencies or U.S. government-sponsored enterprises that carry the explicit and/or implicit guarantee of the U.S. government, which are widely recognized as “risk-free” and have a long history of zero credit losses. Total gross unrealized losses were primarily attributable to changes in interest rates, relative to when the investment securities were purchased, and not due to the credit quality of the investment securities. The Company does not intend to sell, nor is it more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis, which may be at maturity. The Company elected to exclude accrued interest receivable (“AIR”) from the amortized cost basis of debt securities disclosed throughout this footnote. AIR on AFS debt securities totaled $3.3 million at December 31, 2020 and is excluded from the estimate of credit losses and reported in the financial statement line for other assets. None of the bank’s HTM debt securities were past due or on nonaccrual status as of the year ended December 31, 2020. There was no accrued interest reversed against interest income for the year ended December 31, 2020 as all securities remained on accrual status. In addition, there were no collateral dependent HTM debt securities as of year ended December 31, 2020. 65% of the Company’s HTM debt securities are issued by U.S. government agencies or U.S. government-sponsored enterprises. These securities carry the explicit and/or implicit guarantee of the U.S. government, are widely recognized as “risk-free,” and have a long history of zero credit loss. Therefore, the Company did not record an allowance for credit losses for these securities as of December 31, 2020. The remaining HTM debt securities at December 31, 2020 were comprised of state and municipal obligations with bond ratings of A to AAA. Utilizing the CECL approach, the Company determined that the expected credit loss on its HTM municipal bond portfolio was immaterial and therefore no allowance for credit loss was recorded as of December 31, 2020. AIR on HTM debt securities totaled $2.7 million at December 31, 2020 and is excluded from the estimate of credit losses and reported in the financial statement line for other assets.

Loans

Loans	12 Months Ended
	Dec. 31, 2020
Loans [Abstract]
Loans	5. Loans A summary of loans, net of deferred fees and origination costs, by category is as follows: At December 31, (In thousands) 2020 2019 Commercial $ 1,267,679 $ 1,302,209 Commercial Real Estate 2,380,358 2,142,057 Paycheck Protection Program 430,810 - Residential Real Estate 1,466,662 1,445,156 Indirect Auto 931,286 1,193,635 Specialty Lending 579,644 542,063 Home Equity 387,974 444,082 Other Consumer 54,472 66,896 Total loans $ 7,498,885 $ 7,136,098 Included in the above loans are net deferred loan origination costs totaling $9.4 million and $35.3 million at December 31, 2020 and 2019, respectively. The Company had $1.1 million residential loans held for sale as of December 31, 2020. The Company had $11.5 million of residential loans held for sale as of December 31, 2019. The total amount of loans serviced by the Company for unrelated third parties was $614.5 million and $612.3 million at December 31, 2020 and 2019, respectively. At December 31, 2020 and 2019, the Company had $1.3 million and $0.8 million, respectively, of mortgage servicing rights. At December 31, 2020 and 2019, the Company serviced $25.7 million and $25.6 million, respectively, of agricultural loans sold with recourse. Due to sufficient collateral on these loans and government guarantees, no reserve is considered necessary at December 31, 2020 and 2019. 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) 2020 2019 Balance at January 1 $ 2,166 $ 1,638 New loans 1,524 587 Adjustment due to change in composition of related parties 2,448 389 Repayments (202 ) (448 ) Balance at December 31 $ 5,936 $ 2,166

Allowance for Credit Losses and

Allowance for Credit Losses and Credit Quality of Loans	12 Months Ended
	Dec. 31, 2020
Allowance for Credit Losses and Credit Quality of Loans [Abstract]
Allowance for Credit Losses and Credit Quality of Loans	6. Allowance for Credit Losses and Credit Quality of Loans As previously mentioned in Note 1 Summary of Significant Accounting Policies, the Company’s January 1, 2020 adoption of CECL resulted in a significant change to our methodology for estimating the allowance for credit losses since December 31, 2019. Portfolio segmentation has been redefined under CECL and therefore prior year tables are presented separately. The Day 1 increase in the allowance for credit loss on loans relating to adoption of ASU 2016-13 was $3.0 million, which decreased retained earnings by $2.3 million and increased the deferred tax asset by $0.7 million. There were no loans purchased with credit deterioration during the year ended December 31, 2020. During 2020, the Company purchased $51.9 million of consumer loans at a 1% discount. The allowance for credit losses recorded for these loans on the purchase date was $3.6 million. The Company made a policy election to report AIR in the other assets line item on the balance sheet. AIR on loans totaled $23.7 million at December 31, 2020 and was included in the allowance for loan credit losses to estimate the impact of accrued interest receivable related to loans with modifications due to the pandemic as the length of time between interest recognition and the write-off of uncollectible interest could exceed 120 days, exempting these loans from our policy election for accrued interest receivable. The estimated allowance for credit losses related to AIR at December 31, 2020 was $0.6 million. The Day 1 and December 31, 2020 allowance for credit losses calculation incorporated a 6-quarter forecast period to account for forecast economic conditions under each scenario utilized in the measurement. For periods beyond the 6-quarter forecast, the model reverted to long-term economic conditions over a 4-quarter reversion period on a straight-line basis. The quantitative model as of December 31, 2020 incorporated a baseline economic outlook, along with alternative upside and downside scenarios sourced from a reputable third-party to accommodate other potential economic conditions in the model. The baseline outlook reflected an unemployment rate environment above pre-COVID-19 levels for the entire forecast period, though steadily improving, before returning to low single digits by the end of 2023. Northeast GDP’s annual growth was expected to start 2021 in the low to mid-single digits, with a peak growth rate of 8% in the fourth quarter of 2021 and steadily falling back down to normalized levels through 2023 and 2024. Other utilized economic variables show improvement in their respective forecasts, namely business output. Key assumptions in the baseline economic outlook included an additional stimulus package passed at the same timing and a comparable level to that of the actual $900 billion COVID-19 relief package passed in December 2020 along with no significant secondary surge in COVID-19 cases or pandemic-related business closures. The alternative downside scenario assumed deteriorated economic and epidemiological conditions from the baseline outlook. In the same way, the alternative upside scenario assumed a faster economic recovery and more effective management of the COVID-19 virus from the baseline outlook. These scenarios and their respective weightings are evaluated at each measurement date and reflect management’s expectations as of December 31, 2020. Additional adjustments were made for COVID-19 related factors not incorporated in the forecasts, such as the mitigating impact of unprecedented stimulus in 2020, including direct payments to individuals, increased unemployment benefits, the Company’s loan deferral and modification initiatives and various government-sponsored loan programs. The commercial & industrial and consumer segment models were based upon percent change in unemployment with modeled values as of December 31, 2020 well outside the observed historical experience. Therefore, adjustments were required to produce outputs more aligned with default expectations given the forecast economic environment. Additionally, the Company identified a slightly higher level of criticized and classified loans during 2020 than those contemplated by the model during similar economic conditions in the past for which an adjustment was made for estimated expected additional losses above modeled output. These factors were considered through a separate quantitative process and incorporated into the estimate for allowance for credit losses at December 31, 2020. The allowance for credit losses totaled $110.0 million at December 31, 2020, compared to $73.0 million at December 31, 2019. The allowance for credit losses as a percentage of loans was 1.47% at December 31, 2020, compared to 1.02% at December 31, 2019. The increase in the allowance for credit losses from January 1, 2020 to December 31, 2020 was primarily due to the deteriorated economic forecast due to the COVID-19 pandemic. The provision for loan losses was $51.1 million for the twelve months ended December 31, 2020, compared to $25.4 million for the twelve months ended December 31, 2019. The increase to provision expense was driven by the deteriorated economic forecast due to the COVID-19 pandemic. The Company expects that with the adoption of CECL beginning on January 1, 2020, provision expense may become more volatile due to changes in CECL model assumptions of credit quality, macroeconomic factors and conditions, and loan composition, which drive the allowance for credit losses balance. The following table illustrate the changes in the allowance for credit losses by our portfolio segments: (In thousands) Commercial Loans Consumer Loans Residential Total Balance as of January 1, 2020 (after adoption of ASC 326) $ 27,156 $ 32,122 $ 16,721 $ 75,999 Charge-offs (4,005 ) (21,938 ) (1,135 ) (27,078 ) Recoveries 786 8,541 618 9,945 Provision 27,005 19,078 5,051 51,134 Ending Balance as of December 31, 2020 $ 50,942 $ 37,803 $ 21,255 $ 110,000 The increase in the allowance for credit losses from Day 1 to December 31, 2020 was primarily due to the deterioration of macroeconomic factors surrounding the COVID-19 pandemic. Individually Evaluated Loans As of December 31, 2020, there were five relationships identified to be evaluated for loss on an individual basis which had an amortized cost basis of $15.2 million. The allowance for credit loss was $3.2 million and was determined by an estimate of the fair value of the collateral which consisted of business assets (accounts receivable, inventory and machinery, real estate and equipment). As of Day 1, there were no relationships identified to be evaluated for loss on an individual basis. The following table sets forth information with regard to past due and nonperforming loans by loan segment: (In thousands) 31-60 Days Past Due Accruing 61-90 Days Past Due Accruing Greater Than 90 Days Past Due Accruing Total Past Due Accruing Nonaccrual Current Recorded Total Loans As of December 31, 2020 Commercial Loans: C&I $ 2,235 $ 2,394 $ 23 $ 4,652 $ 4,278 $ 1,116,686 $ 1,125,616 CRE 682 - 470 1,152 19,971 2,391,162 2,412,285 PPP - - - - - 430,810 430,810 Total Commercial Loans $ 2,917 $ 2,394 $ 493 $ 5,804 $ 24,249 $ 3,938,658 $ 3,968,711 Consumer Loans: Auto $ 9,125 $ 1,553 $ 866 $ 11,544 $ 2,730 $ 877,831 $ 892,105 Other Consumer 3,711 1,929 1,272 6,912 290 640,952 648,154 Total Consumer Loans $ 12,836 $ 3,482 $ 2,138 $ 18,456 $ 3,020 $ 1,518,783 $ 1,540,259 Residential $ 2,719 $ 309 $ 518 $ 3,546 $ 17,378 $ 1,968,991 $ 1,989,915 Total Loans $ 18,472 $ 6,185 $ 3,149 $ 27,806 $ 44,647 $ 7,426,432 $ 7,498,885 As of December 31, 2020, there were no loans in nonaccrual without an allowance for credit losses. Credit Quality Indicators The Company has developed an internal loan grading system to evaluate and quantify the Company’s loan portfolio with respect to quality and risk. The system focuses on, among other things, financial strength of borrowers, experience and depth of borrower’s management, primary and secondary sources of repayment, payment history, nature of the business and outlook on particular industries. The internal grading system enables the Company to monitor the quality of the entire loan portfolio on a consistent basis and provide management with an early warning system, enabling recognition and response to problem loans and potential problem loans. Commercial Grading System For C&I, PPP and CRE loans, the Company uses a grading system that relies on quantifiable and measurable characteristics when available. This includes comparison of financial strength to available industry averages, comparison of transaction factors (loan terms and conditions) to loan policy and comparison of credit history to stated repayment terms and industry averages. Some grading factors are necessarily more subjective such as economic and industry factors, regulatory environment and management. C&I and CRE loans are graded Doubtful, Substandard, Special Mention and Pass. The increase in non-pass credits from December 31, 2019 was primarily due to the Company’s proactive approach to downgrade loans that were both in payment deferral due to the COVID-19 pandemic and in higher risk industries such as entertainment, restaurants, retail, healthcare and accommodations. Doubtful A Doubtful loan has a high probability of total or substantial loss, but because of specific pending events that may strengthen the asset, its classification as a loss is deferred. Doubtful borrowers are usually in default, lack adequate liquidity or capital and lack the resources necessary to remain an operating entity. Pending events can include mergers, acquisitions, liquidations, capital injections, the perfection of liens on additional collateral, the valuation of collateral and refinancing. Generally, pending events should be resolved within a relatively short period and the ratings will be adjusted based on the new information. Nonaccrual treatment is required for Doubtful assets because of the high probability of loss. Substandard Substandard loans have a high probability of payment default or they have other well-defined weaknesses. They require more intensive supervision by bank management. Substandard loans are generally characterized by current or expected unprofitable operations, inadequate debt service coverage, inadequate liquidity or marginal capitalization. Repayment may depend on collateral or other credit risk mitigants. For some Substandard loans, the likelihood of full collection of interest and principal may be in doubt and those loans should be placed on nonaccrual. Although Substandard assets in the aggregate will have a distinct potential for loss, an individual asset’s loss potential does not have to be distinct for the asset to be rated Substandard. Special Mention Special Mention loans have potential weaknesses that may, if not checked or corrected, weaken the asset or inadequately protect the Company’s position at some future date. These loans pose elevated risk, but their weakness does not yet justify a Substandard classification. Borrowers may be experiencing adverse operating trends (i.e., declining revenues or margins) or may be struggling with an ill-proportioned balance sheet (i.e., increasing inventory without an increase in sales, high leverage, tight liquidity). Adverse economic or market conditions, such as interest rate increases or the entry of a new competitor, may also support a Special Mention rating. Although a Special Mention loan has a higher probability of default than a Pass asset, its default is not imminent. Pass Loans graded as Pass encompass all loans not graded as Doubtful, Substandard or Special Mention. Pass loans are in compliance with loan covenants and payments are generally made as agreed. Pass loans range from superior quality to fair quality. Pass loans also include any portion of a government guaranteed loan, including PPP loans. Consumer and Residential Grading System Consumer and Residential loans are graded as either Nonperforming or Performing. Nonperforming Nonperforming loans are loans that are 1) over 90 days past due and interest is still accruing or 2) on nonaccrual status. Performing All loans not meeting any of the above criteria are considered Performing. The following tables illustrate the Company’s credit quality by loan class by vintage a (In thousands) 2020 2019 2018 2017 2016 Prior Revolving Loans Amortized Cost Basis Revolving Loans Converted to Term Total C&I By Internally Assigned Grade: Pass $ 331,921 $ 182,329 $ 91,230 $ 41,856 $ 32,625 $ 32,609 $ 322,674 $ 412 $ 1,035,656 Special Mention 20,064 6,534 5,053 4,702 1,624 2,830 13,614 - 54,421 Substandard 338 6,364 10,219 3,388 791 4,272 9,945 14 35,331 Doubtful - - - 207 - 1 - - 208 Total C&I $ 352,323 $ 195,227 $ 106,502 $ 50,153 $ 35,040 $ 39,712 $ 346,233 $ 426 $ 1,125,616 CRE By Internally Assigned Grade: Pass $ 469,919 $ 361,187 $ 256,154 $ 271,874 $ 212,197 $ 383,690 $ 113,128 $ 4,034 $ 2,072,183 Special Mention 2,051 44,034 22,260 55,039 36,830 43,537 1,297 11,524 216,572 Substandard 536 5,307 18,298 15,691 6,018 62,168 1,501 4,642 114,161 Doubtful - 1,897 - - - 7,472 - - 9,369 Total CRE $ 472,506 $ 412,425 $ 296,712 $ 342,604 $ 255,045 $ 496,867 $ 115,926 $ 20,200 $ 2,412,285 PPP By Internally Assigned Grade: Pass $ 430,810 $ - $ - $ - $ - $ - $ - $ - $ 430,810 Total PPP $ 430,810 $ - $ - $ - $ - $ - $ - $ - $ 430,810 Auto By Payment Activity: Performing $ 197,881 $ 314,034 $ 201,850 $ 115,977 $ 45,495 $ 13,250 $ 22 $ - $ 888,509 Nonperforming 359 1,140 1,135 525 437 - - - 3,596 Total Auto $ 198,240 $ 315,174 $ 202,985 $ 116,502 $ 45,932 $ 13,250 $ 22 $ - $ 892,105 Other Consumer By Payment Activity: Performing $ 234,628 $ 178,411 $ 127,549 $ 55,676 $ 14,255 $ 17,414 $ 18,588 $ 71 $ 646,592 Nonperforming 339 418 307 265 90 133 10 - 1,562 Total Other Consumer $ 234,967 $ 178,829 $ 127,856 $ 55,941 $ 14,345 $ 17,547 $ 18,598 $ 71 $ 648,154 Residential By Payment Activity: Performing $ 237,338 $ 210,505 $ 213,437 $ 182,993 $ 164,424 $ 684,495 $ 268,878 $ 9,991 $ 1,972,061 Nonperforming 1,245 659 2,318 2,535 902 10,195 - - 17,854 Total Residential $ 238,583 $ 211,164 $ 215,755 $ 185,528 $ 165,326 $ 694,690 $ 268,878 $ 9,991 $ 1,989,915 Total Loans $ 1,927,429 $ 1,312,819 $ 949,810 $ 750,728 $ 515,688 $ 1,262,066 $ 749,657 $ 30,688 $ 7,498,885 Allowance for Credit Losses on Off-Balance Sheet Credit Exposures As of December 31, 2020, the allowance for losses on unfunded commitments totaled $6.4 million, compared to $0.9 million as of December 31, 2019. Prior to January 1, 2020, the Company calculated the allowance for losses on unfunded commitments using the incurred loss methodology. Troubled Debt Restructuring When the Company modifies a loan in a troubled debt restructuring, such modifications generally include one or a combination of the following: an extension of the maturity date at a stated rate of interest lower than the current market rate for new debt with similar risk; temporary reduction in the interest rate; or change in scheduled payment amount. Residential and Consumer TDRs occurring during 2020 were due to the reduction in the interest rate or extension of the term. An allowance for impaired commercial and consumer loans that have been modified in a TDR is measured based on the present value of the expected future cash flows, discounted at the contractual interest rate of the original loan agreement, except when the sole (remaining) source of repayment for the loan is the operation or liquidation of the collateral. In these cases, management uses the current fair value of the collateral, less selling costs. If management determines that the value of the modified loan is less than the recorded investment in the loan an impairment charge would be recorded. The Company began offering loan modifications to assist borrowers during the COVID-19 national emergency. The CARES Act, along with a joint agency statement issued by banking regulatory agencies, provides that modifications made in response to COVID-19 do not need to be accounted for as a TDR. The Company evaluated the modification programs provided to its borrowers and has concluded the modifications were generally made in accordance with the CARES Act guidance to borrowers who were in good standing prior to the COVID-19 pandemic and are not required to be designated as TDRs. See Note 2 Recent Accounting Pronouncements for more information. The following tables illustrate the recorded investment and number of modifications designated as TDRs, including the recorded investment in the loans prior to a modification and the recorded investment in the loans after restructuring: Year Ended December 31, 2020 (Dollars in thousands) Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Commercial Loans: C&I 1 $ 22 $ 22 Total Commercial Loans 1 $ 22 $ 22 Consumer Loans: Auto 1 $ 44 $ 44 Total Consumer Loans 1 $ 44 $ 44 Residential 35 $ 2,834 $ 2,960 Total Troubled Debt Restructurings 37 $ 2,900 $ 3,026 The following table illustrates the recorded investment and number of modifications for TDRs where a concession has been made and subsequently defaulted during the year: Year Ended December 31, 2020 (Dollars in thousands) Number of Contracts Recorded Investment Commercial Loans: C&I 1 $ 387 CRE 1 168 Total Commercial Loans 2 $ 555 Consumer Loans: Auto 1 $ 6 Total Consumer Loans 1 $ 6 Residential 61 $ 3,213 Total Trouble Debt Restructurings 64 $ 3,774 Allowance for Loan Losses Prior to the adoption of ASU 2016-13 on January 1, 2020, the Company’s calculated allowance for loan losses under the incurred loss methodology. The following tables are disclosures related to the allowance for loan losses in prior periods. The following tables illustrate the changes in the allowance for loan losses by our portfolio segments: (In thousands) Commercial Loans Consumer Loans Residential Real Estate Total Balance as of December 31, 2018 $ 32,759 $ 37,178 $ 2,568 $ 72,505 Charge-offs (3,151 ) (28,398 ) (991 ) (32,540 ) Recoveries 534 6,913 141 7,588 Provision 4,383 19,954 1,075 25,412 Ending Balance as of December 31, 2019 $ 34,525 $ 35,647 $ 2,793 $ 72,965 Balance as of December 31, 2017 $ 27,606 $ 36,830 $ 5,064 $ 69,500 Charge-offs (3,463 ) (29,752 ) (913 ) (34,128 ) Recoveries 1,178 6,821 306 8,305 Provision 7,438 23,279 (1,889 ) 28,828 Ending Balance as of December 31, 2018 $ 32,759 $ 37,178 $ 2,568 $ 72,505 The following table illustrates the allowance for loan losses and the recorded investment by portfolio segments: (In thousands) Commercial Loans Consumer Loans Residential Real Estate Total As of December 31, 2019 Allowance for loan losses $ 34,525 $ 35,647 $ 2,793 $ 72,965 Allowance for loans individually evaluated for impairment - - - - Allowance for loans collectively evaluated for impairment $ 34,525 $ 35,647 $ 2,793 $ 72,965 Ending balance of loans $ 3,444,266 $ 2,246,676 $ 1,445,156 $ 7,136,098 Ending balance of originated loans individually evaluated for impairment 3,488 7,044 7,721 18,253 Ending balance of acquired loans collectively evaluated for impairment 115,266 23,733 125,879 264,878 Ending balance of originated loans collectively evaluated for impairment $ 3,325,512 $ 2,215,899 $ 1,311,556 $ 6,852,967 The following table sets forth information with regard to past due and nonperforming loans by loan class: (In thousands) 31-60 Days Past Due Accruing 61-90 Days Past Due Accruing Greater Than 90 Days Past Due Accruing Total Past Due Accruing Nonaccrual Current Recorded Total Loans As of December 31, 2019 Originated Commercial Loans: C&I $ 1,227 $ - $ - $ 1,227 $ 1,177 $ 838,502 $ 840,906 CRE 3,576 - - 3,576 4,847 1,941,143 1,949,566 Business Banking 794 162 - 956 7,035 530,537 538,528 Total Commercial Loans $ 5,597 $ 162 $ - $ 5,759 $ 13,059 $ 3,310,182 $ 3,329,000 Consumer Loans: Indirect Auto $ 11,860 $ 2,108 $ 1,005 $ 14,973 $ 2,175 $ 1,176,487 $ 1,193,635 Specialty Lending 3,153 2,087 1,307 6,547 - 535,516 542,063 Direct 2,564 564 478 3,606 2,475 481,164 487,245 Total Consumer Loans $ 17,577 $ 4,759 $ 2,790 $ 25,126 $ 4,650 $ 2,193,167 $ 2,222,943 Residential Real Estate $ 1,179 $ 190 $ 663 $ 2,032 $ 5,872 $ 1,311,373 $ 1,319,277 Total Originated Loans $ 24,353 $ 5,111 $ 3,453 $ 32,917 $ 23,581 $ 6,814,722 $ 6,871,220 Acquired Commercial Loans: C&I $ 149 $ - $ - $ 149 $ - $ 19,215 $ 19,364 CRE - - - - - 60,937 60,937 Business Banking 397 287 - 684 382 33,899 34,965 Total Commercial Loans $ 546 $ 287 $ - $ 833 $ 382 $ 114,051 $ 115,266 Consumer Loans: Direct $ 136 $ 58 $ - $ 194 $ 105 $ 23,434 $ 23,733 Total Consumer Loans $ 136 $ 58 $ - $ 194 $ 105 $ 23,434 $ 23,733 Residential Real Estate $ 575 $ 20 $ 264 $ 859 $ 1,106 $ 123,914 $ 125,879 Total Acquired Loans $ 1,257 $ 365 $ 264 $ 1,886 $ 1,593 $ 261,399 $ 264,878 Total Loans $ 25,610 $ 5,476 $ 3,717 $ 34,803 $ 25,174 $ 7,076,121 $ 7,136,098 The following table provides information on loans specifically evaluated for impairment: December 31, 2019 (In thousands) Recorded Investment Balance (Book) Unpaid Principal Balance (Legal) Related Allowance Originated With no related allowance recorded: Commercial Loans: C&I $ 76 $ 302 CRE 2,410 2,437 - Business Banking 1,002 1,443 Total Commercial Loans $ 3,488 $ 4,182 Consumer Loans: Indirect Auto $ 154 $ 242 Direct 6,862 8,335 Specialty Lending 28 28 Total Consumer Loans $ 7,044 $ 8,605 Residential Real Estate $ 7,721 $ 9,754 Total $ 18,253 $ 22,541 Total Loans $ 18,253 $ 22,541 $ - The following table summarizes the average recorded investments on loans specifically evaluated for impairment and the interest income recognized: December 31, 2019 December 31, 2018 (In thousands) Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized Originated Commercial Loans: C&I $ 242 $ 1 $ 453 $ 1 CRE 3,311 123 4,078 128 Business Banking 1,089 24 1,018 26 Total Commercial Loans $ 4,642 $ 148 $ 5,549 $ 155 Consumer Loans: Indirect Auto $ 192 $ 10 $ 179 $ 10 Direct 7,387 382 7,922 431 Specialty Lending 7 1 - - Total Consumer Loans $ 7,586 $ 393 $ 8,101 $ 441 Residential Real Estate $ 7,505 $ 350 $ 6,779 $ 305 Total Originated $ 19,733 $ 891 $ 20,429 $ 901 Total Loans $ 19,733 $ 891 $ 20,429 $ 901 Under the incurred loss method, classified loans, including all TDRs and nonaccrual Commercial loans that are graded Substandard, Doubtful or Loss, with outstanding balances of $1.0 million or more are evaluated for impairment through the Company’s quarterly status review process. In the third quarter of 2019 the threshold for evaluating loans for impairment was increased from $750 thousand. In determining that we will be unable to collect all principal and/or interest payments due in accordance with the contractual terms of the loan agreements, we consider factors such as payment history and changes in the financial condition of individual borrowers, local economic conditions, historical loss experience and the conditions of the various markets in which the collateral may be liquidated. For loans that are identified as impaired, impairment is measured by one of three methods: 1) the fair value of collateral less cost to sell, 2) present value of expected future cash flows or 3) the loan’s observable market price. These impaired loans are reviewed on a quarterly basis for changes in the level of impairment. Impaired amounts are charged off immediately if such amounts are determined by management to be uncollectable. Any change to the previously recognized impairment loss is recognized as a component of the provision for loan losses. The following tables illustrate the Company’s credit quality by loan class: (In thousands) As of December 31, 2019 Originated Commercial Credit Exposure By Internally Assigned Grade: C&I CRE Total Pass $ 782,763 $ 1,868,678 $ 2,651,441 Special Mention 28,380 30,519 58,899 Substandard 29,257 50,369 79,626 Doubtful 506 - 506 Total $ 840,906 $ 1,949,566 $ 2,790,472 Business Banking Credit Exposure Business By Internally Assigned Grade: Banking Total Non-classified $ 524,725 $ 524,725 Classified 13,803 13,803 Total $ 538,528 $ 538,528 Consumer Credit Exposure Specialty By Payment Activity: Indirect Auto Lending Direct Total Performing $ 1,190,455 $ 540,756 $ 484,292 $ 2,215,503 Nonperforming 3,180 1,307 2,953 7,440 Total $ 1,193,635 $ 542,063 $ 487,245 $ 2,222,943 Residential Real Estate Credit Exposure Residential By Payment Activity: Real Estate Total Performing $ 1,312,742 $ 1,312,742 Nonperforming 6,535 6,535 Total $ 1,319,277 $ 1,319,277 Acquired Commercial Credit Exposure By Internally Assigned Grade: C&I CRE Total Pass $ 17,801 $ 60,545 $ 78,346 Special Mention 1,269 - 1,269 Substandard 294 392 686 Total $ 19,364 $ 60,937 $ 80,301 Business Banking Credit Exposure Business By Internally Assigned Grade: Banking Total Non-classified $ 32,030 $ 32,030 Classified 2,935 2,935 Total $ 34,965 $ 34,965 Consumer Credit Exposure By Payment Activity: Direct Total Performing $ 23,628 $ 23,628 Nonperforming 105 105 Total $ 23,733 $ 23,733 Residential Real Estate Credit Exposure Residential By Payment Activity: Real Estate Total Performing $ 124,509 $ 124,509 Nonperforming 1,370 1,370 Total $ 125,879 $ 125,879 The following tables illustrate the recorded investment and number of modifications for modified loans, including the recorded investment in the loans prior to a modification and the recorded investment in the loans after restructuring: Year Ended December 31, 2019 (Dollars in thousands) Number of Contracts Pre- Modification Outstanding Recorded Investment Post- Modification Outstanding Recorded Investment Commercial Loans: C&I 1 $ 65 $ 65 CRE 1 402 402 Business Banking 3 425 431 Total Commercial Loans 5 $ 892 $ 898 Consumer Loans: Indirect Auto 9 $ 134 $ 134 Direct 11 450 480 Total Consumer Loans 20 $ 584 $ 614 Residential Real Estate 12 $ 1,032 $ 1,091 Total Troubled Debt Restructurings 37 $ 2,508 $ 2,603 The following table illustrates the recorded investment and number of modifications for TDRs where a concession has been made and subsequently defaulted during the period: Year Ended December 31, 2019 (Dollars in thousands) Number of Contracts Recorded Investment Consumer Loans: Indirect Auto 3 $ 18 Direct 29 1,385 Total Consumer Loans 32 $ 1,403 Residential Real Estate 23 $ 1,203 Total Troubled Debt Restructurings 55 $ 2,606

Premises, Equipment and Leases

Premises, Equipment and Leases	12 Months Ended
	Dec. 31, 2020
Premises, Equipment and Leases [Abstract]
Premises, Equipment and Leases	7. Premises, Equipment and Leases A summary of premises and equipment follows: December 31, (In thousands) 2020 2019 Land, buildings and improvements $ 125,002 $ 121,479 Equipment 55,195 58,431 Premises and equipment before accumulated depreciation $ 180,197 $ 179,910 Accumulated depreciation 105,991 104,279 Total premises and equipment $ 74,206 $ 75,631 Buildings and improvements are depreciated based on useful lives of five three Operating leases in which we are the lessee are recorded as operating lease ROU assets and operating lease liabilities, included in other assets other liabilities Operating lease ROU assets represent the Company’s right to use an underlying asset during the lease term and operating lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and operating lease liabilities are recognized at lease commencement based on the present value of the remaining lease payments using a discount rate that represents the Company’s incremental borrowing rate at the lease commencement date. ROU assets are further adjusted for lease incentives. Operating lease expense, which is comprised of amortization of the ROU asset and the implicit interest accreted on the operating lease liability, is recognized on a straight-line basis over the lease term, and is recorded in occupancy expense in the consolidated statements of income. We have made a policy election to exclude the recognition requirements to all classes of leases with original terms of 12 months or less. Instead, the short-term lease payments are recognized in profit or loss on a straight-line basis over the lease term. The Company has lease agreements with lease and non-lease components, which are generally accounted for separately. For real estate leases, non-lease components and other non-components, such as common area maintenance charges, real estate taxes and insurance are not included in the measurement of the lease liability since they are generally able to be segregated. Our leases relate primarily to office space and bank branches, and some contain options to renew the lease. These options to renew are generally not considered reasonably certain to exercise, and are therefore not included in the lease term until such time that the option to renew is reasonably certain. As of December 31, 2020, operating lease ROU assets and liabilities were $26.4 million and $32.8 million, respectively. As of December 31, 2019 operating lease ROU assets and liabilities were $34.8 million and $37.3 million, respectively. The table below summarizes our net lease cost: December 31, (In thousands) 2020 2019 Operating lease cost $ 7,382 $ 7,239 Variable lease cost 2,141 2,231 Short-term lease cost 453 356 Sublease income (502 ) (448 ) Total premises and equipment $ 9,474 $ 9,378 The table below show future minimum rental commitments related to non-cancelable operating leases for the next five years and thereafter as of December 31, 2020. (In thousands) 2021 $ 7,209 2022 6,339 2023 5,251 2024 4,581 2025 3,411 Thereafter 10,023 Total lease payments $ 36,814 Less: interest (3,990 ) Present value of lease liabilities $ 32,824 The following table shows the weighted average remaining operating lease term, the weighted average discount rate and supplemental information on the consolidated statements of cash flows for operating leases: December 31, (In thousands except for percent and period data) 2020 2019 Weighted average remaining lease term, in years 7.21 7.69 Weighted average discount rate 3.02 % 3.00 % Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 7,934 $ 6,211 ROU assets obtained in exchange for lease liabilities 3,441 41,008 As of December 31, 2020 there are no new significant leases that have not yet commenced. Rental expense included in occupancy expense amounted to $8.0 million in 2020, $8.0 million in December 31, 2019 and $8.6 million in December 31, 2018.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	12 Months Ended
	Dec. 31, 2020
Goodwill and Other Intangible Assets [Abstract]
Goodwill and Other Intangible Assets	8. Goodwill and Other Intangible Assets A summary of goodwill is as follows: (In thousands) January 1, 2020 $ 274,769 Goodwill acquired 5,772 December 31, 2020 $ 280,541 January 1, 2019 $ 274,769 Goodwill acquired - December 31, 2019 $ 274,769 The Company has intangible assets with definite useful lives capitalized on its consolidated balance sheet in the form of core deposit and other identified intangible assets. These intangible assets are amortized over their estimated useful lives, which range primarily from one There was no impairment of goodwill recorded during the year ended December 31, 2020 and 2019. A summary of core deposit and other intangible assets follows: December 31, (In thousands) 2020 2019 Core deposit intangibles: Gross carrying amount $ 8,951 $ 8,951 Less: accumulated amortization 8,463 7,988 Net carrying amount $ 488 $ 963 Identified intangible assets: Gross carrying amount $ 27,057 $ 34,623 Less: accumulated amortization 15,810 23,566 Net carrying amount $ 11,247 $ 11,057 Total intangibles: Gross carrying amount $ 36,008 $ 43,574 Less: accumulated amortization 24,273 31,554 Net carrying amount $ 11,735 $ 12,020 Amortization expense on intangible assets with definite useful lives totaled $3.4 million for 2020, $3.6 million for 2019 and $4.0 million for 2018. Amortization expense on intangible assets with definite useful lives is expected to total $2.8 million for 2021, $2.2 million for 2022, $1.8 million for 2023, $1.5 million for 2024, $1.2 million for 2025 and $2.3 million thereafter. Other identified intangible assets include customer lists and non-compete agreements. During the years ended December 31, 2020 and 2019, there was no impairment of intangible assets.

Deposits

Deposits	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Deposits	9. Deposits The following table sets forth the maturity distribution of time deposits: (In thousands) December 31, 2020 Within one year $ 476,983 After one but within two years 77,081 After two but within three years 36,857 After three but within four years 27,888 After four but within five years 14,381 After five years 289 Total $ 633,479 Time deposits of $250,000 or more aggregated $104.1 million and $140.4 million December 31, 2020 and 2019, respectively.

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2020
Borrowings [Abstract]
Borrowings	10. Borrowings Short-Term Borrowings In addition to the liquidity provided by balance sheet cash flows, liquidity must also be supplemented with additional sources such as credit lines from correspondent banks as well as borrowings from the FHLB and the Federal Reserve Bank. Other funding alternatives may also be appropriate from time to time, including wholesale and retail repurchase agreements and brokered certificate of deposit (“CD”) accounts. Short-term borrowings totaled $168.4 million and $655.3 million at December 31, 2020 and 2019, respectively, and consist of Federal funds purchased and securities sold under repurchase agreements, which generally represent overnight borrowing transactions and other short-term borrowings, primarily FHLB advances, with original maturities of one year or less. The Company has unused lines of credit with the FHLB and access to brokered deposits available for short-term financing. Those sources totaled approximately $3.1 billion and $2.4 billion at December 31, 2020 and 2019, respectively. Borrowings on the FHLB lines are secured by FHLB stock, certain securities and one-to-four family first lien mortgage loans. Securities collateralizing repurchase agreements are held in safekeeping by nonaffiliated financial institutions and are under the Company’s control. Information related to short-term borrowings is summarized as follows as of December 31: (Dollars in thousands) 2020 2019 2018 Federal funds purchased: Balance at year-end $ - $ 65,000 $ 80,000 Average during the year 14,727 47,137 66,839 Maximum month end balance 40,000 80,000 80,000 Weighted average rate during the year 2.05 % 3.90 % 3.43 % Weighted average rate at year-end - 2.84 % 4.25 % Securities sold under repurchase agreements: Balance at year-end $ 143,386 $ 143,775 $ 160,696 Average during the year 154,383 123,337 146,135 Maximum month end balance 176,840 146,410 170,350 Weighted average rate during the year 0.17 % 0.33 % 0.16 % Weighted average rate at year-end 0.20 % 0.40 % 0.38 % Other short-term borrowings: Balance at year-end $ 25,000 $ 446,500 $ 631,000 Average during the year 183,699 403,453 514,662 Maximum month end balance 366,500 576,000 653,000 Weighted average rate during the year 1.55 % 1.85 % 1.56 % Weighted average rate at year-end 1.99 % 1.73 % 1.82 % See Note 4 for additional information regarding securities pledged as collateral for securities sold under the repurchase agreements. Long-Term Debt Long-term debt consists of obligations having an original maturity at issuance of more than one year. A majority of the Company’s long-term debt is comprised of FHLB advances collateralized by the FHLB stock owned by the Company, and a blanket lien on its residential real estate mortgage loans. As of December 31, 2020 the Company had no callable long-term debt. A summary is as follows: (Dollars in thousands) December 31, 2020 December 31, 2019 Maturity Amount Weighted Average Rate Amount Weighted Average Rate 2020 $ - - $ 25,000 2.34% 2021 25,003 2.56% 25,021 2.56% 2022 10,598 2.53% 10,598 2.53% 2031 3,496 2.45% 3,592 2.45% Total $ 39,097 $ 64,211 Subordinated Debt On June 23, 2020, the Company issued $100.0 million aggregate principal amount of 5.00% fixed-to-floating rate subordinated notes due 2030. The subordinated notes, which qualify as Tier 2 capital, bear interest at an annual rate of 5.00%, payable semi-annually in arrears commencing on January 1, 2021, and a floating rate of interest equivalent to the three-month Secured Overnight Financing Rate (“SOFR”) plus a spread of 4.85%, payable quarterly in arrears commencing on October 1, 2025. The subordinated notes issuance costs of $2.2 million are being amortized on a straight-line basis into interest expense over five years. The Company may redeem the subordinated notes (1) in whole or in part beginning with the interest payment date of July 1, 2025, and on any interest payment date thereafter or (2) in whole but not in part upon the occurrence of a “Tax Event”, a “Tier 2 Capital Event” or in the event the Company is required to register as an investment company pursuant to the Investment Company Act of 1940, as amended. The redemption price for any redemption is 100% of the principal amount of the subordinated notes being redeemed, plus accrued and unpaid interest thereon to, but excluding, the date of redemption. Any redemption of the subordinated notes will be subject to the receipt of the approval of the Board of Governors of the Federal Reserve System to the extent then required under applicable laws or regulations, including capital regulations. The following table summarizes the Company’s subordinated debt: (Dollars in thousands) December 31, 2020 Subordinated notes issued June 2020 – fixed interest rate of 5.00% through June 2025 and a variable interest rate equivalent to three-month SOFR plus 4.85% thereafter, maturing July 1, 2030 - $ 100,000 Unamortized debt issuance costs (1,948 ) Total subordinated debt, net $ 98,052 Junior Subordinated Debt The Company sponsors five business trusts, CNBF Capital Trust I, NBT Statutory Trust I, NBT Statutory Trust II, Alliance Financial Capital Trust I and Alliance Financial Capital Trust II (collectively, the “Trusts”). The Company’s junior subordinated debentures include amounts related to the Company’s NBT Statutory Trust I and II as well as junior subordinated debentures associated with one statutory trust affiliate that was acquired from our merger with CNB Financial Corp. and two statutory trusts that were acquired from our acquisition of Alliance Financial Corporation (“Alliance”). The Trusts were formed for the purpose of issuing company-obligated mandatorily redeemable trust preferred securities to third-party investors and investing in the proceeds from the sale of such preferred securities solely in junior subordinated debt securities of the Company for general corporate purposes. The Company guarantees, on a limited basis, payments of distributions on the trust preferred securities and payments on redemption of the trust preferred securities. The Trusts are VIEs for which the Company is not the primary beneficiary, as defined by GAAP. In accordance with GAAP, the accounts of the Trusts are not included in the Company’s consolidated financial statements. See Note 1 for additional information about the Company’s consolidation policy. The debentures held by each trust are the sole assets of that trust. The Trusts hold, as their sole assets, junior subordinated debentures of the Company with face amounts totaling $98.0 million at December 31, 2020. The Company owns all of the common securities of the Trusts and has accordingly recorded $3.2 million in equity method investments classified as other assets in our consolidated balance sheets at December 31, 2020. The Company owns all of the common stock of the Trusts, which have issued trust preferred securities in conjunction with the Company issuing trust preferred debentures to the Trusts. The terms of the trust preferred debentures are substantially the same as the terms of the trust preferred securities. As of December 31, 2020, the Trusts had the following trust preferred securities outstanding and held the following junior subordinated debentures of the Company (dollars in thousands): Description Issuance Date Trust Preferred Securities Outstanding Interest Rate Trust Preferred Debt Owed To Trust Final Maturity Date CNBF Capital Trust I August 1999 $ 18,000 3-month LIBOR plus 2.75% $ 18,720 August 2029 NBT Statutory Trust I November 2005 5,000 3-month LIBOR plus 1.40% 5,155 December 2035 NBT Statutory Trust II February 2006 50,000 3-month LIBOR plus 1.40% 51,547 March 2036 Alliance Financial Capital Trust I December 2003 10,000 3-month LIBOR plus 2.85% 10,310 January 2034 Alliance Financial Capital Trust II September 2006 15,000 3-month LIBOR plus 1.65% 15,464 September 2036 The Company’s junior subordinated debentures are redeemable prior to the maturity date at our option upon each trust’s stated option repurchase dates and from time to time thereafter. These debentures are also redeemable in whole at any time upon the occurrence of specific events defined within the trust indenture. Our obligations under the debentures and related documents, taken together, constitute a full and unconditional guarantee by the Company of the issuers’ obligations under the trust preferred securities. The Company owns all of the common stock of the Trusts, which have issued trust preferred securities in conjunction with the Company issuing trust preferred debentures to the Trusts. The terms of the trust preferred debentures are substantially the same as the terms of the trust preferred securities. With respect to the Trusts, the Company has the right to defer payments of interest on the debentures issued to the Trusts at any time or from time to time for a period of up to ten consecutive semi-annual periods with respect to each deferral period. Under the terms of the debentures, if in certain circumstances there is an event of default under the debentures or the Company elects to defer interest on the debentures, the Company may not, with certain exceptions, declare or pay any dividends or distributions on its capital stock or purchase or acquire any of its capital stock. Despite the fact that the Trusts are not included in the Company’s consolidated financial statements, $97 million of the $101 million in trust preferred securities issued by these subsidiary trusts is included in the Tier 1 capital of the Company for regulatory capital purposes as allowed by the Federal Reserve Board (NBT Bank owns $1.0 million of CNBF Trust I securities). The Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010 requires bank holding companies with assets greater than $500 million to be subject to the same capital requirements as insured depository institutions, meaning, for instance, that such bank holding companies will not be able to count trust preferred securities issued after May 19, 2010 as Tier 1 capital. The aforementioned Trusts are grandfathered with respect to this enactment based on their date of issuance.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Taxes [Abstract]
Income Taxes	11. Income Taxes The significant components of income tax expense attributable to operations are as follows: Years Ended December 31, (In thousands) 2020 2019 2018 Current Federal $ 36,358 $ 28,475 $ 15,762 State 9,768 7,653 5,977 Total Current $ 46,126 $ 36,128 $ 21,739 Deferred Federal $ (14,021 ) $ (1,379 ) $ 2,281 State (3,406 ) (338 ) 416 Total Deferred $ (17,427 ) $ (1,717 ) $ 2,697 Total income tax expense $ 28,699 $ 34,411 $ 24,436 During 2018, the Company recorded a $5.5 million benefit primarily related to changes in accounting methods approved by the Internal Revenue Services in the fourth quarter of 2018. The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and deferred tax liabilities are as follows: December 31, (In thousands) 2020 2019 Deferred tax assets: Allowance for loan losses $ 27,282 $ 18,535 Lease liability 8,141 9,331 Deferred compensation 11,602 8,336 Postretirement benefit obligation 1,511 1,631 Fair value adjustments from acquisitions 259 422 Loan fees 5,400 1,384 Accrued liabilities 1,307 1,176 Stock-based compensation expense 3,213 3,032 Other 3,558 1,498 Total deferred tax assets $ 62,273 $ 45,345 Deferred tax liabilities: Pension benefits $ 14,406 $ 13,014 Lease right-of-use asset 6,567 9,259 Amortization of intangible assets 12,725 12,202 Premises and equipment, primarily due to accelerated depreciation 4,774 5,137 Unrealized gain on securities 7,732 1,770 Other 952 1,429 Total deferred tax liabilities $ 47,156 $ 42,811 Net deferred tax asset at year-end $ 15,117 $ 2,534 Net deferred tax asset at beginning of year 2,534 8,795 Increase (decrease) in net deferred tax asset $ 12,583 $ (6,261 ) Realization of deferred tax assets is dependent upon the generation of future taxable income. A valuation allowance is recorded when it is more likely than not that some portion of the deferred tax asset will not be realized. Based on available evidence, gross deferred tax assets will ultimately be realized and a valuation allowance was not deemed necessary at December 31, 2020 and 2019. The following is a reconciliation of the provision for income taxes to the amount computed by applying the applicable Federal statutory rate to income before taxes: Years Ended December 31 (In thousands) 2020 2019 2018 Federal income tax at statutory rate $ 27,948 $ 32,641 $ 28,770 Tax exempt income (981 ) (1,233 ) (1,456 ) Net increase in cash surrender value of life insurance (1,135 ) (927 ) (973 ) Federal tax credit (1,705 ) (1,458 ) (1,499 ) State taxes, net of federal tax benefit 5,026 5,773 5,051 Accounting method changes - tax rate change impact - - (5,326 ) Stock-based compensation, excess tax benefit (152 ) (342 ) (456 ) Other, net (302 ) (43 ) 325 Income tax expense $ 28,699 $ 34,411 $ 24,436 A reconciliation of the beginning and ending balance of Federal and State gross unrecognized tax benefits (“UTBs”) is as follows: (In thousands) 2020 2019 Balance at January 1 $ 779 $ 641 Additions for tax positions of prior years 254 26 Current period tax positions 145 112 Balance at December 31 $ 1,178 $ 779 Amount that would affect the effective tax rate if recognized, gross of tax $ 931 $ 615 The Company recognizes interest and penalties on the income tax expense line in the accompanying consolidated statements of income. The Company monitors changes in tax statutes and regulations to determine if significant changes will occur over the next 12 months. As of December 31, 2020, no significant changes to UTBs are projected; however, tax audit examinations are possible, but it is not reasonably possible to estimate when examinations in subsequent years will be completed As of December 31, 2020, the Company is no longer subject to U.S. Federal tax examination by tax authorities for years prior to 2016 and New York State for years prior to 2015. The tax years 2015 to 2019

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Employee Benefit Plans [Abstract]
Employee Benefit Plans	12. Employee Benefit Plans Defined Benefit Post-Retirement Plans The Company has a qualified, noncontributory, defined benefit pension plan (“the Plan”) covering substantially all of its employees at December 31, 2020. Benefits paid from the plan are based on age, years of service, compensation and social security benefits and are determined in accordance with defined formulas. The Company’s policy is to fund the Plan in accordance with Employee Retirement Income Security Act of 1974 standards. Assets of the Plan are invested in publicly traded stocks and mutual funds. Prior to January 1, 2000, the Plan was a traditional defined benefit plan based on final average compensation. On January 1, 2000, the Plan was converted to a cash balance plan with grandfathering provisions for existing participants. Effective March 1, 2013, the Plan was amended. Benefit accruals for participants who, as of January 1, 2000, elected to continue participating in the traditional defined benefit plan design were frozen as of March 1, 2013. In May 2013, the noncontributory, frozen, defined benefit pension plan assumed from Alliance in the acquisition was merged into the Plan. In addition to the Plan, the Company provides supplemental employee retirement plans to certain current and former executives. The Company also assumed supplemental retirement plans for certain former executives in the Alliance acquisition. These supplemental employee retirement plans and the Plan are collectively referred to herein as “Pension Benefits.” In addition, the Company provides certain health care benefits for retired employees. Benefits were accrued over the employees’ active service period. Only employees that were employed by the Company on or before January 1, 2000 are eligible to receive post-retirement health care benefits. The Plan is contributory for participating retirees, requiring participants to absorb certain deductibles and coinsurance amounts with contributions adjusted annually to reflect cost sharing provisions and benefit limitations called for in the Plan. Employees become eligible for these benefits if they reach normal retirement age while working for the Company. For eligible employees described above, the Company funds the cost of post-retirement health care as benefits are paid. The Company elected to recognize the transition obligation on a delayed basis over twenty years. In addition, the Company assumed post-retirement medical life insurance benefits for certain Alliance employees, retirees and their spouses, if applicable, in the Alliance acquisition. These post-retirement benefits are referred to herein as “Other Benefits.” Accounting standards require an employer to: (1) recognize the overfunded or underfunded status of defined benefit post-retirement plans, which is measured as the difference between plan assets at fair value and the benefit obligation, as an asset or liability in its balance sheet; (2) recognize changes in that funded status in the year in which the changes occur through comprehensive income; and (3) measure the defined benefit plan assets and obligations as of the date of its year-end balance sheet. In August 2018, the FASB issued ASU 2018-14, Compensation – Retirement Benefits – Defined Benefit Plans - General (Subtopic 715-20), provides changes to the disclosure requirements for defined benefit plans. The Company adopted the provisions of ASU 2018-14 as of December 31, 2020 and it did not have a material impact on its disclosures to the consolidated financial statements. The components of AOCI, which have not yet been recognized as components of net periodic benefit cost, related to pensions and other post-retirement benefits are summarized below: Pension Benefits Other Benefits (In thousands) 2020 2019 2020 2019 Net actuarial loss $ 26,108 $ 28,334 $ 317 $ 125 Prior service cost 378 491 43 94 Total amounts recognized in AOCI (pre-tax) $ 26,486 $ 28,825 $ 360 $ 219 A December 31 measurement date is used for the pension, supplemental pension and post-retirement benefit plans. The following table sets forth changes in benefit obligations, changes in plan assets and the funded status of the pension plans and other post-retirement benefits: Pension Benefits Other Benefits (In thousands) 2020 2019 2020 2019 Change in benefit obligation: Benefit obligation at beginning of year $ 90,586 $ 85,134 $ 6,083 $ 7,034 Service cost 1,840 1,723 8 7 Interest cost 3,237 3,942 213 272 Plan participants’ contributions - - 173 201 Actuarial loss (gain) 3,411 6,030 191 (719 ) Curtailments (67 ) - - - Benefits paid (8,813 ) (6,243 ) (669 ) (712 ) Projected benefit obligation at end of year $ 90,194 $ 90,586 $ 5,999 $ 6,083 Change in plan assets: Fair value of plan assets at beginning of year $ 122,995 $ 109,746 $ - $ - Gain on plan assets 12,449 18,120 - - Employer contributions 1,932 1,372 496 511 Plan participants’ contributions - - 173 201 Benefits paid (8,813 ) (6,243 ) (669 ) (712 ) Fair value of plan assets at end of year $ 128,563 $ 122,995 $ - $ - Funded (unfunded) status at year end $ 38,369 $ 32,409 $ (5,999 ) $ (6,083 ) An asset is recognized for an overfunded plan and a liability is recognized for an underfunded plan. The accumulated benefit obligation for pension benefits was $90.2 million and $90.6 million at December 31, 2020 and 2019, respectively. The accumulated benefit obligation for other post-retirement benefits was $6.0 million and $6.1 million at December 31, 2020 and 2019, respectively. The funded status of the pension and other post-retirement benefit plans has been recognized as follows in the consolidated balance sheets at December 31, 2020 and 2019. Pension Benefits Other Benefits (In thousands) 2020 2019 2020 2019 Other assets $ 57,456 $ 51,988 $ - $ - Other liabilities (19,087 ) (19,579 ) (5,999 ) (6,083 ) Funded status $ 38,369 $ 32,409 $ (5,999 ) $ (6,083 ) The following assumptions were used to determine the benefit obligation and the net periodic pension cost for the years indicated: Years Ended December 31, 2020 2019 2018 Weighted average assumptions: The following assumptions were used to determine benefit obligations: Discount rate 3.08% - 3.25% 3.69% - 3.73% 4.79% - 4.80% Expected long-term return on plan assets 7.00% 7.00% 7.00% Rate of compensation increase 3.00% 3.00% 3.00% Interest rate of credit for cash balance plan 1.62% 2.28% 3.36% The following assumptions were used to determine net periodic pension cost: Discount rate 3.69% - 3.73% 4.79% - 4.80% 4.20% - 4.21% Expected long-term return on plan assets 7.00% 7.00% 7.00% Rate of compensation increase 3.00% 3.00% 3.00% Interest rate of credit for cash balance plan 2.28% 3.36% 2.80% Net periodic benefit cost and other amounts recognized in OCI for the years ended December 31 included the following components: Pension Benefits Other Benefits (In thousands) 2020 2019 2018 2020 2019 2018 Components of net periodic (benefit) cost: Service cost $ 1,840 $ 1,723 $ 1,659 $ 8 $ 7 $ 10 Interest cost 3,237 3,942 3,645 213 272 327 Expected return on plan assets (8,410 ) (7,480 ) (8,478 ) - - - Additional gain due to curtailment (74 ) - - - - - Amortization of prior service cost 41 43 40 51 50 51 Amortization of unrecognized net loss 1,535 2,593 930 - - 124 Net periodic pension (benefit) cost $ (1,831 ) $ 821 $ (2,204 ) $ 272 $ 329 $ 512 Other changes in plan assets and benefit obligations recognized in OCI (pre-tax): Net (gain) loss $ (628 ) $ (4,611 ) $ 12,882 $ 192 $ (720 ) $ (762 ) Prior service cost - - 337 - - - Additional gain due to curtailment 7 - - - - - Amortization of prior service cost (41 ) (43 ) (40 ) (51 ) (50 ) (51 ) Amortization of unrecognized net (loss) (1,535 ) (2,593 ) (930 ) - - (124 ) Total recognized in OCI $ (2,197 ) $ (7,247 ) $ 12,249 $ 141 $ (770 ) $ (937 ) Total recognized in net periodic (benefit) cost and OCI, pre-tax $ (4,028 ) $ (6,426 ) $ 10,045 $ 413 $ (441 ) $ (425 ) The service cost component of the net periodic (benefit) cost is included in Salaries and Employee Benefits and the interest cost, expected return on plan assets and net amortization components are included in Other Noninterest Expense on the consolidated statements of income. The following table sets forth estimated future benefit payments for the pension plans and other post-retirement benefit plans as of December 31, 2020: (In thousands) Pension Benefits Other Benefits 2021 $ 6,910 $ 453 2022 6,977 451 2023 6,807 448 2024 7,083 443 2025 7,409 436 2026 - 2030 33,579 1,962 The Company made no voluntary contributions to the pension and other benefit plans during the year ended December 31, 2020 and 2019. For measurement purposes, the annual rates of increase in the per capita cost of covered medical and prescription drug benefits for fiscal year 2020 were assumed to be 4.5% to 7.0% percent. The rates were assumed to decrease gradually to 3.8% for fiscal year 2075 and remain at that level thereafter. Assumed health care cost trend rates have a significant effect on amounts reported for health care plans. 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 2020 2020 2019 Cash and cash equivalents 0 - 15% 3% 3% Fixed income securities 30 - 60% 38% 40% Equities 40 - 70% 59% 57% Total 100% 100% Only high-quality bonds are to be included in the portfolio. All issues that are rated lower than A by Standard and Poor’s are to be excluded. Equity securities at December 31, 2020 and 2019 do not include any Company common stock. The following table presents the financial instruments recorded at fair value on a recurring basis by the Plan: (In thousands) Level 1 Level 2 December 31, 2020 Cash and cash equivalents $ 3,461 $ - $ 3,461 Foreign equity mutual funds 41,000 - 41,000 Equity mutual funds 35,637 - 35,637 U.S. government bonds - 47 47 Corporate bonds - 48,418 48,418 Total $ 80,098 $ 48,465 $ 128,563 Level 1 Level 2 December 31, 2019 Cash and cash equivalents $ 4,143 $ - $ 4,143 Foreign equity mutual funds 40,239 - 40,239 Equity mutual funds 29,886 - 29,886 U.S. government bonds - 58 58 Corporate bonds - 48,669 48,669 Total $ 74,268 $ 48,727 $ 122,995 The plan had no financial instruments recorded at fair value on a non-recurring basis as of December 31, 2020 and 2019. Determination of Assumed Rate of Return The expected long-term rate-of-return on assets was 7.0% at December 31, 2020 and 2019. This assumption represents the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the projected benefit obligation. The assumption has been determined by reflecting expectations regarding future rates of return for the portfolio considering the asset distribution and related historical rates of return. The appropriateness of the assumption is reviewed annually. Employee 401(k) and Employee Stock Ownership Plans The Company maintains a 401(k) and employee stock ownership plan (the “401(k) Plan”). The Company contributes to the 401(k) Plan based on employees’ contributions out of their annual salaries. In addition, the Company may also make discretionary contributions to the 401(k) Plan based on profitability. Participation in the 401(k) Plan is contingent upon certain age and service requirements. The employer contributions associated with the 401(k) Plan were $3.6 million in 2020, $3.6 million in 2019 and $3.2 million in 2018. Other Retirement Benefits Included in other liabilities is $1.6 million and $1.7 million at December 31, 2020 and 2019, respectively, for supplemental retirement benefits for retired executives from legacy plans assumed in acquisitions. The Company recognized $0.2 million, $0.1 million and $0.1 million in expense for each of the years ended December 31, 2020, 2019 and 2018 respectively, related to these plans.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2020
Stock-Based Compensation [Abstract]
Stock-Based Compensation	13. Stock-Based Compensation In May 2018, the Company adopted the NBT Bancorp Inc. 2018 Omnibus Incentive Plan (the “Stock Plan”) replacing the 2008 Omnibus Incentive Plan which automatically expired in April 2018. Under the terms of the Stock Plan, equity-based awards are granted to directors and employees to increase their direct proprietary interest in the operations and success of the Company. The Stock Plan assumed all prior equity-based incentive plans and any new equity-based awards are granted under the terms of the Stock Plan. Restricted shares granted under the Plan typically vest after three or The Company has outstanding restricted stock granted from various plans at December 31, 2020. The Company recognized $4.6 million, $4.2 million and $3.9 million in stock-based compensation expense related to these stock awards for the years ended December 31, 2020, 2019 and 2018, respectively. Tax benefits recognized with respect to restricted stock awards and stock units were $1.0 million, $1.1 million and $1.2 million for the years ended December 31, 2020, 2019 and 2018, respectively. Unrecognized compensation cost related to restricted stock units totaled $5.1 million at December 31, 2020 and will be recognized over 1.5 years on a weighted average basis. Shares issued are funded from the Company’s treasury stock. The following table summarizes information for unvested restricted stock units outstanding as of December 31, 2020: Number of Shares Weighted- Average Grant Date Fair Value Unvested at January 1, 2020 555,440 $ 30.11 Forfeited (2,315 ) 34.82 Vested (115,432 ) 29.93 Granted 147,562 28.61 Unvested at December 31, 2020 585,255 $ 29.78 The following table summarizes information concerning stock options outstanding: (In thousands, except share and per share data) Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in Years) Aggregate Intrinsic Value Outstanding at January 1, 2020 33,145 $ 23.73 Exercised (8,845 ) 20.87 Expired (10,500 ) 20.74 Outstanding at December 31, 2020 13,800 $ 27.83 3.36 $ 75 Exercisable at December 31, 2020 13,800 $ 27.83 3.36 $ 75 T here was stock-based compensation expense for stock option awards for the year ended Years Ended December 31, (In thousands) 2020 2019 2018 Proceeds from stock options exercised $ 185 $ 725 $ 999 Tax benefits related to stock options exercised 41 123 173 Intrinsic value of stock options exercised 165 490 692 Fair value of shares vested during the year - 13 16 The Company has 781,123 securities remaining available to be granted as part of the Plan at December 31, 2020.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2020
Stockholders' Equity [Abstract]
Stockholders' Equity	14. Stockholders’ Equity In accordance with GAAP, unrecognized prior service costs and net actuarial gains or losses associated with the Company’s pension and postretirement benefit plans and unrealized gains on derivatives and on AFS securities are included in AOCI, net of tax. For the years ended December 31, components of AOCI are: (In thousands) 2020 2019 2018 Unrecognized prior service cost and net actuarial (losses) on pension plans $ (20,134 ) $ (21,677 ) $ (27,689 ) Unrealized (losses) gains on derivatives (cash flow hedges) (16 ) (32 ) 1,821 Unrealized net holding gains (losses) on AFS securities 20,567 2,683 (17,306 ) AOCI $ 417 $ (19,026 ) $ (43,174 ) 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 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, 2020, approximately $194.2 million of the total stockholders’ equity of the Bank was available for payment of dividends to the Company without approval by the OCC. The Bank’s ability to pay dividends also is subject to the Bank being in compliance with regulatory capital requirements. The Bank is currently in compliance with these requirements. Under the State of Delaware General Corporation Law, the Company may declare and pay dividends either out of accumulated net retained earnings or capital surplus. The Company purchased 263,507 shares of its common stock during the year ended December 31, 2020, for a total of $ million at an average price of $ per share under its previously announced plan. As of December 31 , t . On January 27, 2021 , the NBT Board of Directors approved an increase to the total number of shares authorized under the stock repurchase program to million shares from million shares, previously

Regulatory Capital Requirements

Regulatory Capital Requirements	12 Months Ended
	Dec. 31, 2020
Regulatory Capital Requirements [Abstract]
Regulatory Capital Requirements	15. Regulatory Capital Requirements The Company and the Bank are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the consolidated financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Bank must meet specific capital guidelines that involve quantitative measures of NBT Bank’s assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. The capital amounts and classifications are also subject to qualitative judgments by the regulators about components, risk weightings and other factors. Quantitative measures established by regulation to ensure capital adequacy require the Company and the Bank to maintain minimum amounts and ratios (set forth in the table below) of total and Tier 1 Capital to risk-weighted assets and of Tier 1 capital to average assets. In addition to maintaining minimum capital ratios, the Company is subject to a capital conservation buffer (“Buffer”) of 2.50% above the minimum to avoid restriction on capital distributions and discretionary bonus paychecks to officers. At and Under their prompt corrective action regulations, regulatory authorities are required to take certain supervisory actions (and may take additional discretionary actions) with respect to an undercapitalized institution. Such actions could have a direct material effect on an institution’s financial statements. The regulations establish a framework for the classification of banks into five categories: well-capitalized, adequately capitalized, undercapitalized, significantly undercapitalized and critically undercapitalized. As of December 31, 2020 and 2019, the most recent notifications from the Bank’s regulators categorized the Bank as well-capitalized under the regulatory framework for prompt corrective action. To be categorized as well-capitalized the Bank must maintain minimum total risk-based, Tier 1 risk-based and Tier 1 Capital to Average Asset ratios as set forth in the table below. There are no conditions or events since that notification that management believes have changed the Bank’s category. In March 2020, the OCC, the Board of Governors of the Federal Reserve System, and the FDIC announced an interim final rule to delay the estimated impact on regulatory capital stemming from the implementation of CECL. Under the modified CECL transition provision, the regulatory capital impact of the January 1, 2020 CECL adoption date adjustment to the allowance for credit losses (after-tax) has been deferred and will phase into regulatory capital at 25% per year commencing January 1, 2022. For the ongoing impact of CECL, the Company is allowed to defer the regulatory capital impact of the allowance for credit losses in an amount equal to 25% of the change in the allowance for credit losses (pre-tax) recognized through earnings for each period between January 1, 2020 and December 31, 2021. The cumulative adjustment to the allowance for credit losses between January 1, 2020 and December 31, 2021, will also phase into regulatory capital at 25% per year commencing January 1, 2022. The Company adopted the capital transition relief over the permissible period The Company and NBT Bank’s actual capital amounts and ratios are presented as follows: Actual Regulatory Ratio Requirements (Dollars in thousands) Amount Ratio Minimum Capital Adequacy Minimum plus Buffer For Classification as Well- Capitalized As of December 31, 2020 Tier I Capital (to average assets) Company $ 1,018,320 9.56 % 4.00 % 5.00 % NBT Bank 1,054,097 9.95 % 4.00 % 5.00 % Common Equity Tier 1 Capital Company 921,320 11.84 % 4.50 % 7.00 % 6.50 % NBT Bank 1,054,097 13.67 % 4.50 % 7.00 % 6.50 % Tier I Capital (to risk-weighted assets) Company 1,018,320 13.09 % 6.00 % 8.50 % 8.00 % NBT Bank 1,054,097 13.67 % 6.00 % 8.50 % 8.00 % Total Capital (to risk-weighted assets) Company 1,215,672 15.62 % 8.00 % 10.50 % 10.00 % NBT Bank 1,150,544 14.93 % 8.00 % 10.50 % 10.00 % As of December 31, 2019 Tier I Capital (to average assets) Company $ 963,147 10.33 % 4.00 % 5.00 % NBT Bank 894,407 9.64 % 4.00 % 5.00 % Common Equity Tier 1 Capital Company 866,147 11.29 % 4.50 % 7.00 % 6.50 % NBT Bank 894,407 11.76 % 4.50 % 7.00 % 6.50 % Tier I Capital (to risk-weighted assets) Company 963,147 12.56 % 6.00 % 8.50 % 8.00 % NBT Bank 894,407 11.76 % 6.00 % 8.50 % 8.00 % Total Capital (to risk-weighted assets) Company 1,037,041 13.52 % 8.00 % 10.50 % 10.00 % NBT Bank 968,301 12.73 % 8.00 % 10.50 % 10.00 %

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Earnings Per Share	16. Earnings Per Share The following is a reconciliation of basic and diluted EPS for the years presented in the consolidated statements of income: Years Ended December 31, 2020 2019 2018 (In thousands except per share data) Net Income Weighted Average Shares Per Share Amount Net Income Weighted Average Shares Per Share Amount Net Income Weighted Average Shares Per Share Amount Basic EPS $ 104,388 43,693 $ 2.39 $ 121,021 43,815 $ 2.76 $ 112,566 43,701 $ 2.58 Effect of dilutive securities: Stock-based compensation 296 309 319 Diluted EPS $ 104,388 43,989 $ 2.37 $ 121,021 44,124 $ 2.74 $ 112,566 44,020 $ 2.56 There was a nominal number of weighted average stock options outstanding for the years ended December 31, 2020, 2019 and 2018, respectively, that were not considered in the calculation of diluted EPS since the stock options’ exercise prices were greater than the average market price during these periods.

Reclassification Adjustments Ou

Reclassification Adjustments Out of Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2020
Reclassification Adjustments Out of Other Comprehensive Income (Loss) [Abstract]
Reclassification Adjustments Out of Other Comprehensive Income (Loss)	17. Reclassification Adjustments Out of Other Comprehensive Income (Loss) The following table summarizes the reclassification adjustments out of AOCI: Detail About AOCI Components Amount Reclassified From AOCI Affected Line Item in the Consolidated Statements of Comprehensive Income (Loss) (In thousands) Years Ended December 31, 2020 2019 2018 AFS securities: (Gains) losses on AFS securities $ (3 ) $ 79 $ 6,622 Net securities (gains) losses Amortization of unrealized gains related to securities transfer 644 737 688 Interest income Tax effect $ (160 ) $ (204 ) $ (1,827 ) Income tax (benefit) Net of tax $ 481 $ 612 $ 5,483 Cash flow hedges: Net unrealized losses (gains) on cash flow hedges reclassified to interest expense $ 296 $ (2,012 ) $ (2,300 ) Interest expense Tax effect $ (74 ) $ 503 $ 575 Income tax (benefit) expense Net of tax $ 222 $ (1,509 ) $ (1,725 ) Pension and other benefits: Amortization of net losses $ 1,535 $ 2,593 $ 1,054 Other noninterest expense Amortization of prior service costs 92 93 91 Other noninterest expense Tax effect $ (407 ) $ (672 ) $ (286 ) Income tax (benefit) Net of tax $ 1,220 $ 2,014 $ 859 Total reclassifications, net of tax $ 1,923 $ 1,117 $ 4,617

Commitments and Contingent Liab

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2020
Commitments and Contingent Liabilities [Abstract]
Commitments and Contingent Liabilities	18. 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, 2020, approximately 59% of the Company’s loans were secured by real estate located in central and upstate New York, northeastern Pennsylvania, southern New Hampshire, western Massachusetts, Vermont and southern coastal Maine 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 agricultural real estate loans sold to investors with recourse, with the sold portion having a government guarantee that is assignable back to the Company upon repurchase of the loan in the event of default. The Company’s exposure to credit loss in the event of nonperformance by the other party to the commitments to extend credit, unused lines of credit, standby letters of credit and loans sold with recourse is represented by the contractual amount of those instruments. The credit risk associated with commitments to extend credit and standby and commercial letters of credit is essentially the same as that involved with extending loans to customers and is subject to normal credit policies. Collateral may be obtained based on management’s assessment of the customer’s creditworthiness. At December 31, (In thousands) 2020 2019 Unused lines of credit $ 351,876 $ 340,703 Commitments to extend credits, primarily variable rate 1,831,671 1,579,414 Standby letters of credit 54,009 34,479 Loans sold with recourse 25,659 25,639 Since many loan commitments, standby letters of credit and guarantees and indemnification contracts expire without being funded in whole or in part, the contract amounts are not necessarily indicative of future cash flows. The Company does not issue any guarantees that would require liability-recognition or disclosure, other than its standby letters of credit. The Company guarantees the obligations or performance of customers by issuing standby letters of credit to third-parties. These standby letters of credit are frequently issued in support of third-party debt, such as corporate debt issuances, industrial revenue bonds and municipal securities. The risk involved in issuing standby letters of credit is essentially the same as the credit risk involved in extending loan facilities to customers and letters of credit are subject to the same credit origination, portfolio maintenance and management procedures in effect to monitor other credit and off-balance sheet products. Typically, these instruments have one year expirations with an option to renew upon annual review; therefore, the total amounts do not necessarily represent future cash requirements. The fair value of the Company’s standby letters of credit at December 31, 2020 and 2019 was not significant. In the normal course of business there are various outstanding legal proceedings. If legal costs are deemed material by management, the Company accrues for the estimated loss from a loss contingency if the information available indicates that it is probable that a liability had been incurred at the date of the financial statements and the amount of loss can be reasonably estimated. The Company is required to maintain reserve balances with the Federal Reserve Bank. The required average total reserve for NBT Bank for the 14-day maintenance period ending December 30, 2020 was $64.6 million.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities [Abstract]
Derivative Instruments and Hedging Activities	19. Derivative Instruments and Hedging Activities The Company is exposed to certain risks arising from both its business operations and economic conditions. The Company principally manages its exposures to a wide variety of business and operational risks through management of its core business activities. The Company manages economic risks, including interest rate, primarily by managing the amount, sources and duration of its assets and liabilities and through the use of derivative instruments. Specifically, the Company enters into derivative financial instruments to manage exposures that arise from business activities that result in the receipt or payment of future known and uncertain cash amounts, the value of which are determined by interest rates. The Company’s derivative financial instruments are used to manage differences in the amount, timing and duration of the Company’s known or expected cash receipts and its known or expected cash payments principally related to certain fixed rate borrowings. The Company also has interest rate derivatives that result from a service provided to certain qualifying customers and, therefore, are not used to manage interest rate risk in the Company’s assets or liabilities. The Company manages a matched book with respect to its derivative instruments in order to minimize its net risk exposure resulting from such transactions. Derivatives Not Designated as Hedging Instruments The Company enters into interest rate swaps to facilitate customer transactions and meet their financing needs. These swaps are considered derivatives, but are not designated in hedging relationships. These instruments have interest rate and credit risk associated with them. To mitigate the interest rate risk, the Company enters into offsetting interest rate swaps with counterparties. The counterparty swaps are also considered derivatives and are also not designated in hedging relationships. Interest rate swaps are recorded within other assets or other liabilities on the consolidated balance sheet at their estimated fair value. Changes to the fair value of assets and liabilities arising from these derivatives are included, net, in other operating income in the consolidated statement of income. As of December 31, 2020 the Company had seventeen risk participation agreements with financial institution counterparties for interest rate swaps related to participated loans. The fair values included in other assets and other liabilities on the consolidated balance sheet applicable to these agreements amount to $292 thousand and $125 thousand, respectively as of December 31, 2020. As of December 31, 2019 the Company had fifteen risk participation agreements with financial institution counterparties for interest rate swaps related to participated loans. The fair values included in other assets and other liabilities on the consolidated balance sheet applicable to these agreements amount to $112 thousand and $82 thousand, respectively. Risk participation agreements provide credit protection to the financial institution that originated the swap transaction should the borrower fail to perform on its obligation. The Company enters into both risk participation agreements in which it purchases credit protection from other financial institutions and those in which it provides credit protection to other financial institutions. Derivatives Designated as Hedging Instruments The Company has entered into interest rate swaps to modify the interest rate characteristics of certain short-term FHLB advances from variable rate to fixed rate in order to reduce the impact of changes in future cash flows due to market interest rate changes. These agreements are designated as cash flow hedges. The following table depicts the fair value adjustment recorded related to the notional amount of derivatives outstanding as well as the notional amount of risk participation agreements: December 31, (In thousands) 2020 2019 Derivatives Not Designated as Hedging Instruments: Fair value adjustment included in other assets and other liabilities Interest rate derivatives $ 108,487 $ 41,650 Notional amount Interest rate derivatives 2,447,168 963,209 Risk participation agreements 112,313 97,614 Derivatives Designated as Hedging Instruments: Fair value adjustment included in other assets Interest rate derivatives - 4 Fair value adjustment included in other liabilities Interest rate derivatives 34 45 Notional amount Interest rate derivatives 25,000 50,000 For derivatives designated and that qualify as cash flow hedges of interest rate risk, the gain or loss on the derivative is recorded in AOCI and subsequently reclassified into interest expense in the same period during which the hedge transaction affects earnings. Amounts reported in AOCI related to derivatives will be reclassified to interest expense as interest payments are made on the Company’s short-term rate borrowings. During the next twelve months, the Company estimates that an additional $21 thousand will be reclassified from AOCI as a reduction to interest expense. The following table indicates the effect of cash flow hedge accounting on AOCI and on the consolidated statement of income: December 31, (In thousands) 2020 2019 2018 Derivatives Designated as Hedging Instruments: Interest rate derivatives - included component Amount of (loss) gain recognized in OCI $ (275 ) $ (459 ) $ 1,218 Amount of loss (gain) reclassified from AOCI into interest expense 296 (2,012 ) (2,300 ) The following table indicates the gain or loss recognized in income on derivatives not designated as a hedging relationship: December 31, (In thousands) 2020 2019 2018 Derivatives Not Designated as Hedging Instruments: Increase (decrease) in other income $ 1 $ 295 $ (120 )

Fair Values of Financial Instru

Fair Values of Financial Instruments	12 Months Ended
	Dec. 31, 2020
Fair Values of Financial Instruments [Abstract]
Fair Values of Financial Instruments	20. Fair Values of Financial Instruments GAAP states that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value measurements are not adjusted for transaction costs. A fair value hierarchy exists within GAAP that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are described below: Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2 - Quoted prices for similar assets or liabilities in active markets, quoted prices in markets that are not active or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability; Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The types of instruments valued based on quoted market prices in active markets include most U.S. government and agency securities, many other sovereign government obligations, liquid mortgage products, active listed equities and most money market securities. Such instruments are generally classified within Level 1 or Level 2 of the fair value hierarchy. The Company does not adjust the quoted prices for such instruments. The types of instruments valued based on quoted prices in markets that are not active, broker or dealer quotations or alternative pricing sources with reasonable levels of price transparency include most investment-grade and high-yield corporate bonds, less liquid mortgage products, less liquid agency securities, less liquid listed equities, state, municipal and provincial obligations and certain physical commodities. Such instruments are generally classified within Level 2 of the fair value hierarchy. Certain common equity securities are reported at fair value utilizing Level 1 inputs (exchange quoted prices). Other investment securities are reported at fair value utilizing Level 1 and Level 2 inputs. The prices for Level 2 instruments are obtained through an independent pricing service or dealer market participants with whom the Company has historically transacted both purchases and sales of investment securities. Prices obtained from these sources include prices derived from market quotations and matrix pricing. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. Management reviews the methodologies used in pricing the securities by its third party providers. Level 3 is for positions that are not traded in active markets or are subject to transfer restrictions. Valuations are adjusted to reflect illiquidity and/or non-transferability and such adjustments are generally based on available market evidence. In the absence of such evidence, management’s best estimate will be used. Management’s best estimate consists of both internal and external support on certain Level 3 investments. Subsequent to inception, management only changes Level 3 inputs and assumptions when corroborated by evidence such as transactions in similar instruments, completed or pending third-party transactions in the underlying investment or comparable entities, subsequent rounds of financing, recapitalizations and other transactions across the capital structure, offerings in the equity or debt markets and changes in financial ratios or cash flows. The following tables sets forth the Company’s financial assets and liabilities measured on a recurring basis that were accounted for at fair value. Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement: (In thousands) Level 1 Level 2 Level 3 December 31, 2020 Assets: AFS securities: Federal agency $ - $ 243,597 $ - $ 243,597 State & municipal - 43,180 - 43,180 Mortgage-backed - 595,839 - 595,839 Collateralized mortgage obligations - 437,804 - 437,804 Corporate - 28,278 - 28,278 Total AFS securities $ - $ 1,348,698 $ - $ 1,348,698 Equity securities 28,737 2,000 - 30,737 Derivatives - 108,779 - 108,779 Total $ 28,737 $ 1,459,477 $ - $ 1,488,214 Liabilities: Derivatives $ - $ 108,646 $ - $ 108,646 Total $ - $ 108,646 $ - $ 108,646 (In thousands) Level 1 Level 2 Level 3 December 31, 2019 Assets: AFS securities: Federal agency $ - $ 34,758 $ - $ 34,758 State & municipal - 2,513 - 2,513 Mortgage-backed - 503,626 - 503,626 Collateralized mortgage obligations - 434,443 - 434,443 Total AFS securities $ - $ 975,340 $ - $ 975,340 Equity securities 23,771 4,000 - 27,771 Derivatives - 41,766 - 41,766 Total $ 23,771 $ 1,021,106 $ - $ 1,044,877 Liabilities: Derivatives $ - $ 41,777 $ - $ 41,777 Total $ - $ 41,777 $ - $ 41,777 GAAP requires disclosure of assets and liabilities measured and recorded at fair value on a non-recurring basis such as goodwill, loans held for sale, other real estate owned, collateral-dependent impaired loans, mortgage servicing rights and HTM securities. The non-recurring fair value measurements recorded during the years ended were related to impaired loans, write-downs of other real estate owned and write-down of branch assets to fair value. The Company uses the fair value of underlying collateral, less costs to sell, to estimate the allowance for credit losses for individually evaluated collateral dependent loans. The appraisals may be adjusted by management for qualitative factors such as economic conditions and estimated liquidation expenses ranging from Based on the valuation techniques used, the fair value measurements for collateral dependent individually evaluated loans are classified as Level 3. As of December 31, 2020 the Company had collateral dependent individually evaluated loans with a carrying value of $15.2 million, which had an estimated allowance for credit loss of $3.2 million. As of December 31, 2019 the Company had no collateral dependent loans. During the year ended December 31, 2020, the Company recorded a $0.5 million write-off of branch locations due to a pending disposition of the locations. During the year ended December 31, 2019, the Company recorded a $1.0 million write-down of a branch location to fair value of $0.2 million due to a pending disposition of the location. The following table sets forth information with regard to estimated fair values of financial instruments. This table excludes financial instruments for which the carrying amount approximates fair value. Financial instruments for which the fair value approximates carrying value include cash and cash equivalents, AFS securities, equity securities, accrued interest receivable, non-maturity deposits, short-term borrowings, accrued interest payable and derivatives. December 31, 2020 December 31, 2019 (In thousands) Fair Value Hierarchy Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Financial assets: HTM securities 2 $ 616,560 $ 636,827 $ 630,074 $ 641,262 Net loans 3 7,390,004 7,530,033 7,074,864 6,999,690 Financial liabilities: Time deposits 2 $ 633,479 $ 638,721 $ 861,193 $ 858,085 Long-term debt 2 39,097 39,820 64,211 64,373 Subordinated debt 1 100,000 103,277 - - Junior subordinated debt 2 101,196 108,926 101,196 105,694 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 wealth operation that contributes net fee income annually. The wealth management operation is not considered a financial instrument and its value has not been incorporated into the fair value estimates. Other significant assets and liabilities include the benefits resulting from the low-cost funding of deposit liabilities as compared to the cost of borrowing funds in the market and premises and equipment. In addition, the tax ramifications related to the realization of the unrealized gains and losses can have a significant effect on fair value estimates and have not been considered in the estimate of fair value. HTM Securities The fair value of the Company’s HTM securities is primarily measured using information from a third-party pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. Net Loans Net loans include portfolio loans and loans held for sale. Loans were first segregated by type and then further segmented into fixed and variable rate and loan quality categories. Expected future cash flows were projected based on contractual cash flows, adjusted for estimated prepayments, which also includes credit risk, illiquidity risk and other market factors to calculate the exit price fair value in accordance with ASC 820. Time Deposits The fair value of time deposits was estimated using a discounted cash flow approach that applies prevailing market interest rates for similar maturity instruments. The fair values of the Company’s time deposit liabilities do not take into consideration the value of the Company’s long-term relationships with depositors, which may have significant value. Long-Term Debt The fair value of long-term debt was estimated using a discounted cash flow approach that applies prevailing market interest rates for similar maturity instruments. Subordinated Debt The fair value of subordinated debt has been measured using the observable market price as of the period reported. Junior Subordinated Debt The fair value of junior subordinated debt has been estimated using a discounted cash flow analysis.

Parent Company Financial Inform

Parent Company Financial Information	12 Months Ended
	Dec. 31, 2020
Parent Company Financial Information [Abstract]
Parent Company Financial Information	21. Parent Company Financial Information Condensed Balance Sheets December 31, (In thousands) 2020 2019 Assets Cash and cash equivalents $ 37,915 $ 9,387 Equity securities, at estimated fair value 25,111 22,441 Investment in subsidiaries, on equity basis 1,345,317 1,209,752 Other assets 30,577 30,855 Total assets $ 1,438,920 $ 1,272,435 Liabilities and Stockholders’ Equity Total liabilities $ 251,302 $ 152,038 Stockholders’ equity 1,187,618 1,120,397 Total liabilities and stockholders’ equity $ 1,438,920 $ 1,272,435 Condensed Statements of Income Years Ended December 31, (In thousands) 2020 2019 2018 Dividends from subsidiaries $ 77,000 $ 50,200 $ 43,000 Management fee from subsidiaries 4,151 7,981 7,907 Net securities (losses) gains (483 ) 165 399 Interest, dividends and other income 824 876 905 Total revenue $ 81,492 $ 59,222 $ 52,211 Operating expenses 11,825 14,262 14,226 Income before income tax benefit and equity in undistributed income of subsidiaries $ 69,667 $ 44,960 $ 37,985 Income tax benefit (2,653 ) (1,588 ) (1,608 ) Equity in undistributed income of subsidiaries 32,068 74,473 72,973 Net income $ 104,388 $ 121,021 $ 112,566 Condensed Statements of Cash Flow Years Ended December 31, (In thousands) 2020 2019 2018 Operating activities Net income $ 104,388 $ 121,021 $ 112,566 Adjustments to reconcile net income to net cash provided by operating activities Depreciation and amortization of premises and equipment 1,739 2,298 2,814 Excess tax benefit on stock-based compensation (181 ) (409 ) (543 ) Stock-based compensation expense 4,581 4,210 3,936 Net securities losses (gains) 483 (165 ) (399 ) Equity in undistributed income of subsidiaries (32,068 ) (74,473 ) (72,973 ) Bank owned life insurance income (391 ) (398 ) (424 ) Amortization of subordinated debt issuance costs 230 - - Net change in other assets and other liabilities (3,535 ) (1,573 ) (6,124 ) Net cash provided by operating activities $ 75,246 $ 50,511 $ 38,853 Investing activities Investment in the Bank $ (90,000 ) $ - $ - Proceeds from calls of equity securities 2,000 - - Proceeds on sales of equity securities - - 3,318 Purchases of equity securities - (93 ) (2 ) Net cash (used in) provided by investing activities $ (88,000 ) $ (93 ) $ 3,316 Financing activities Proceeds from issuance of subordinated debt $ 100,000 $ - $ - Payment of subordinated debt issuance costs (2,178 ) - - Proceeds from the issuance of shares to employee and other stock plans 184 725 1,296 Cash paid by employer for tax-withholding on stock issuance (1,537 ) (1,622 ) (1,893 ) Purchases of treasury shares (7,980 ) - - Cash dividends (47,207 ) (46,010 ) (43,269 ) Net cash provided by (used in) financing activities $ 41,282 $ (46,907 ) $ (43,866 ) Net increase (decrease) in cash and cash equivalents $ 28,528 $ 3,511 $ (1,697 ) Cash and cash equivalents at beginning of year 9,387 5,876 7,572 Cash and cash equivalents at end of year $ 37,915 $ 9,387 $ 5,876 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 Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Summary of Significant Accounting Policies [Abstract]
Basis of Presentation	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 and such estimates could be material to the financial statements.
Use of Estimates	Estimates associated with the allowance for credit losses, provision for income taxes, pension accounting, fair values of financial instruments and status of contingencies are particularly susceptible to material change in the near term.
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 Reporting	Segment Reporting The Company’s operations are primarily in the community banking industry and include the provision of traditional banking services. The Company also provides other services through its subsidiaries such as insurance, retirement plan administration and trust administration. The Company operates solely in the geographical regions of central and upstate New York, northeastern Pennsylvania, western Massachusetts, southern New Hampshire, Vermont, the southern coastal Maine area and now entering central Connecticut.
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 held to maturity (“HTM”), available for sale (“AFS”) or equity. HTM debt securities are those that the Company has the ability and intent to hold until maturity. AFS debt securities are securities that are not classified as HTM. 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. Allowance for Credit Losses –HTM Debt Securities With respect to its HTM debt securities, the Company is required to utilize the Accounting Standards Update (“ASU”) 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments The mortgage-backed and collateralized mortgage obligations HTM securities are issued by U.S. government entities and agencies. These securities are either explicitly or implicitly guaranteed by the U.S. government as to timely repayment of principal and interest, are highly rated by major rating agencies, and have a long history of no credit losses. Therefore, the Company did not record a credit loss for these securities. State and municipal bonds carry a Moody’s rating of A to AAA. In addition, the Company has a limited amount of New York state local municipal bonds that are not rated. The estimate of expected credit losses on the HTM portfolio is based on the expected cash flows of each individual CUSIP over its contractual life and considers historical credit loss information, current conditions and reasonable and supportable forecasts. Given the rarity of municipal defaults and losses, the Company utilized Moody’s Municipal Loss Forecast Model as the sole source of municipal default and loss rates which provides decades of data across all municipal sectors and geographies. As with the loan portfolio, cash flows are forecast over a 6-quarter period under various weighted economic conditions, with a reversion to long-term average economic conditions over a 4-quarter period on a straight-line basis. Management may exercise discretion to make adjustments based on environmental factors. As of December 31, 2020, the Company determined that the expected credit loss on its municipal bond portfolio was de minimis, and therefore, an allowance for credit losses was not recorded. Allowance for Credit Losses –AFS Debt Securities The impairment model for AFS debt securities differs from the CECL approach utilized for HTM debt securities because AFS debt securities are measured at fair value rather than amortized cost. For AFS debt securities in an unrealized loss position, the Bank first assesses whether it intends to sell, or it is more likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through income. For AFS debt securities that do not meet the aforementioned criteria, in making this assessment, management considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, adverse conditions specifically related to the security, failure of the issuer of the debt security to make scheduled interest or principal payments, among other factors. If this assessment indicates that a credit loss exists, the present value of cash flows expected to be collected from the security are compared to the amortized cost basis of the security. The cash flows should be estimated using information relevant to the collectability of the security, including information about past events, current conditions and reasonable and supportable forecasts. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded for the credit loss, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income. Prior to the adoption of CECL on January 1, 2020, declines in the fair value of AFS and HTM securities below their amortized cost, less any current period credit loss, that are deemed to be other-than-temporary were reflected in earnings as realized losses, or in other comprehensive income (“OCI”). Investments in Federal Reserve Bank and Federal Home Loan Bank (“FHLB”) stock are required for membership in those organizations and are carried at cost since there is no market value available. The FHLB New York continues to pay dividends and repurchase stock. As such, the Company has not recognized any impairment on its holdings of Federal Reserve Bank and FHLB stock.
Loan Held for Sale and Loan Servicing	Loan Held for Sale and Loan Servicing Loans held for sale are recorded at the lower of cost or fair value on an individual basis. Loan sales are recorded when the sales are funded. Gains and losses on sales of loans held for sale are included in other noninterest income in the Consolidated Statements of Income. Mortgage loans held for sale are generally sold with servicing rights retained. Mortgage servicing rights are recorded at fair value upon sale of the loan, and are amortized in proportion to and over the period of estimated net servicing income.
Loans	Loans Loans are recorded at their current unpaid principal balance, net of unearned income and unamortized loan fees and expenses, which are amortized under the effective interest method over the estimated lives of the loans. Interest income on loans is accrued based on the principal amount outstanding. For all loan classes within the Company’s loan portfolio, loans are placed on nonaccrual status when timely collection of principal and/or interest in accordance with contractual terms is in doubt. Loans are transferred to nonaccrual status generally when principal or interest payments become ninety days delinquent, unless the loan is well secured and in the process of collection or sooner when management concludes circumstances indicate that borrowers may be unable to meet contractual principal or interest payments. When a loan is transferred to a nonaccrual status, all interest previously accrued in the current period but not collected is reversed against interest income in that period. Interest accrued in a prior period and not collected is charged-off against the allowance for credit losses. If ultimate repayment of a nonaccrual loan is expected, any payments received are applied in accordance with contractual terms. If ultimate repayment of principal is not expected, any payment received on a nonaccrual loan is applied to principal until ultimate repayment becomes expected. For all loan classes within the Company’s loan portfolio, nonaccrual loans are returned to accrual status when they become current as to principal and interest and demonstrate a period of performance under the contractual terms and, in the opinion of management, are fully collectible as to principal and interest. For loans in all portfolios, the principal amount is charged off in full or in part as soon as management determines, based on available facts, that the collection of principal in full or in part is improbable. For Commercial loans, management considers specific facts and circumstances relative to individual credits in making such a determination. For Consumer and Residential Real Estate loan classes, management uses specific guidance and thresholds from the Federal Financial Institutions Examination Council’s Uniform Retail Credit Classification and Account Management Policy. A loan is considered to be a troubled debt restructuring (“TDR”) when the Company grants a concession to the borrower because of the borrower’s financial condition that the Company would not otherwise consider. Such concessions generally include or a combination of the following: an extension of the maturity date at a stated rate of interest lower than the current market rate for new debt with similar risk; a temporary reduction in the interest rate; or a change in scheduled payment amount. TDR loans are nonaccrual loans; however, they can be returned to accrual status after a period of performance, generally evidenced by Section 4013 of the Coronavirus Aid, Relief and Economic Security Act (“CARES Act”), which was enacted on March 27, 2020, provides that a qualified loan modification is exempt by law from classification as a troubled debt restructuring as defined by GAAP. To be eligible, each loan modification must be (1) related to the coronavirus (“COVID-19”) pandemic; (2) executed on a loan that was not more than 30 days past due as of December 31, 2019; and (3) executed between March 1, 2020, and the earlier of (a) 60 days after the date of termination of the National Emergency or (b) December 31, 2020. On August 3, 2020, the Federal Financial Institutions Examination Council (“FFIEC”) issued a joint statement on additional loan accommodations related to COVID-19. The joint statement clarifies that for loan modifications in which Section 4013 is being applied, subsequent modifications could also be eligible under Section 4013. Accordingly, the Company is offering modifications made in response to COVID-19 to borrowers who were current and otherwise not past due in accordance with the criteria stated in Section 4013. These include short-term, 180 days or less, modifications in the form of payment deferrals, fee waivers, extensions of repayment terms, or other delays in payment. Accordingly, the Company did not account for such loan modifications as TDRs. As of December 31, 2020, there were $110.8 million in loans in modification programs related to COVID-19. On December 27, 2020, the Consolidated Appropriations Act amended section 2014 of the CARES Act extending the exemption of qualified loan modifications from classification as a troubled debt restructuring as defined by GAAP to the earlier of January 1, 2022, or 60 days after the National Emergency concerning COVID-19 ends.
Allowance for Credit Losses - Loans	Allowance for Credit Losses - Loans The CECL approach requires an estimate of the credit losses expected over the life of a loan (or pool of loans). It replaces the incurred loss approach’s threshold that required the recognition of a credit loss when it was probable a loss event was incurred. The allowance for credit losses is a valuation account that is deducted from, or added to, the loans’ amortized cost basis to present the net, lifetime amount expected to be collected on the loans. Loan losses are charged off against the allowance when management believes a loan balance is confirmed to be uncollectible. Expected recoveries do not exceed the aggregate of amounts previously charged-off and expected to be charged-off. Management estimates the allowance balance using relevant available information, from internal and external sources, related to past events, current conditions, and reasonable and supportable forecasts. Historical credit loss experience provides the basis for the estimation of expected credit losses. Company historical loss experience was supplemented with peer information when there was insufficient loss data for the Company. Peer selection was based on a review of institutions with comparable loss experience as well as loan yield, bank size, portfolio concentration and geography. Adjustments to historical loss information are made for differences in current loan-specific risk characteristics such as differences in underwriting standards, portfolio mix, delinquency level or term as well as changes in environmental conditions, such as changes in unemployment rates, production metrics, property values, or other relevant factors. Significant management judgment is required at each point in the measurement process. Portfolio segment is defined as the level at which an entity develops and documents a systematic methodology to determine its allowance for credit losses. Upon adoption of CECL, management revised the manner in which loans were pooled for similar risk characteristics. Management developed segments for estimating loss based on type of borrower and collateral which is generally based upon federal call report segmentation and have been combined or subsegmented as needed to ensure loans of similar risk profiles are appropriately pooled. The following table illustrates the portfolio and class segments for the Company’s loan portfolio in 2020: Portfolio Segment Class Commercial Loans Commercial & Industrial Paycheck Protection Program Commercial Real Estate Consumer Loans Auto Other Consumer Residential Loans Commercial Loans The Company offers a variety of commercial loan products. The Company’s underwriting analysis for commercial loans typically includes credit verification, independent appraisals, a review of the borrower’s financial condition and a detailed analysis of the borrower’s underlying cash flows. Commercial and Industrial (“C&I”) Paycheck Protection Program (“PPP”) Commercial Real Estate (“CRE”) Consumer Loans The Company offers a variety of Consumer loan products including Auto and Other Consumer loans. Auto three Other Consumer one Residential Residential loans consist primarily of loans secured by a first or second mortgage on primary residences, home equity loans and lines of credit in first and second lien positions and residential construction loans. We originate adjustable-rate and fixed rate, one-to-four-family residential loans for the construction or purchase of a residential property or the refinancing of a mortgage. These loans are collateralized by properties located in the Company’s market area. Loans on one-to-four-family residential 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. For home equity loans, consumers are able to borrow up to 85% of the equity in their homes and are generally tied to Prime with a ten-year draw followed by a fifteen-year amortization. These loans carry a higher risk than first mortgage residential loans as they are often in a second position with respect to collateral. Historical credit loss experience for both the Company and segment-specific peers provides the basis for the estimation of expected credit losses, where observed credit losses are converted to probability of default rate (“PD”) curves through the use of segment-specific loss given default (“LGD”) risk factors that convert default rates to loss severity based on industry-level, observed relationships between the two variables for each asset class, primarily due to the nature of the underlying collateral. These risk factors were assessed for reasonableness against the Company’s own loss experience and adjusted in certain cases when the relationship between the Company’s historical default and loss severity deviate from that of the wider industry. The historical PDR curves, together with corresponding economic conditions, establish a quantitative relationship between economic conditions and loan performance through an economic cycle. Using the historical relationship between economic conditions and loan performance, management’s expectation of future loan performance is incorporated using externally developed economic forecasts which are probabilistically weighted to reflect potential forecast inaccuracy and model limitations. These forecasts are applied over a period that management has determined to be reasonable and supportable. Beyond the period over which management can develop or source a reasonable and supportable forecast, the model will revert to long-term average economic conditions using a straight-line, time-based methodology. The allowance for credit losses is measured on a collective (pool) basis, with both a quantitative and qualitative analysis that is applied on a quarterly basis, when similar risk characteristics exist. The respective quantitative allowance for each segment is measured using an econometric, discounted PD/LGD modeling methodology in which distinct, segment-specific multi-variate regression models are applied to multiple, probabilistically weighted external economic forecasts. Under the discounted cash flows methodology, expected credit losses are estimated over the effective life of the loans by measuring the difference between the net present value of modeled cash flows and amortized cost basis. Contractual cash flows over the contractual life of the loans are the basis for modeled cash flows, adjusted for modeled defaults and expected prepayments and discounted at the loan-level stated interest rate. The contractual term excludes expected extensions, renewals, and modifications unless either of the following applies: management has a reasonable expectation at the reporting date that a TDR will be executed with an individual borrower or the extension or renewal options are included in the original or modified contract at the reporting date and are not unconditionally cancellable by the Company. After quantitative considerations, management applies additional qualitative adjustments so that the allowance for credit loss is reflective of the estimate of lifetime losses that exist in the loan portfolio at the balance sheet date. Qualitative considerations include limitations inherent in the quantitative model; trends experienced in nonperforming and delinquent loans; changes in value of underlying collateral; changes in lending policies and procedures; nature and composition of loans; portfolio concentrations that may affect loss experience across one or more components of the portfolio; the experience, ability and depth of lending management and staff; the Company’s credit review system; and the effect of external factors; such as competition, legal and regulatory requirements. Loans that do not share risk characteristics and meet materiality criteria are evaluated on an individual basis and are excluded from the pooled evaluation. When management determines that foreclosure is probable, expected credit losses are based on the fair value of the collateral at the reporting date, adjusted for selling costs as appropriate. If the loan is not collateral dependent, the allowance for credit losses related to individually assessed loans is based on discounted expected cash flows using the loan’s initial effective interest rate. Generally, individually assessed loans are collateral dependent. A loan for which the terms have been modified resulting in a concession, and for which the borrower is experiencing financial difficulties is considered to be a TDR. The allowance for credit losses on a TDR is measured using the same method as all other loans held for investment, except that the original interest rate is used to discount the expected cash flows, not the rate specified within the restructuring. Allowance for Credit Losses on Off-Balance Sheet Credit Exposures The Company estimates expected credit losses over the contractual period in which the Company has exposure to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by the Company. The allowance for credit losses on off-balance sheet credit exposures is adjusted as an expense in other noninterest expense. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over their estimated lives. Estimating credit losses on unfunded commitments requires the Bank to consider the following categories of off-balance sheet credit exposure: unfunded commitments to extend credit, unfunded lines of credit, and standby letters of credit. Each of these unfunded commitments is then analyzed for a probability of funding to calculate a probable funding amount. The life of loan loss factor by related portfolio segment from the loan allowance for credit loss calculation is then applied to the probable funding amount to calculate a reserve on unfunded commitments. Accrued Interest Receivable Upon adoption of CECL on January 1, 2020, the Company made the following elections regarding accrued interest receivable: (1) presented accrued interest receivable balances separately within other assets balance sheet line item; (2) excluded interest receivable that is included in amortized cost of financing receivables from related disclosures requirements and (3) continued our policy to write off accrued interest receivable by reversing interest income. For loans, write off typically occurs upon becoming over 90 to 120 days past due and therefore the amount of such write offs are immaterial. For loans given short-term loan modifications to assist borrowers during the COVID-19 national emergency, this accounting policy would not apply as the length of time between interest recognition and the write-off of uncollectible interest could exceed 120 days. Therefore, the Company estimated an allowance for credit losses for accrued interest receivable related to loans with short-term modifications due to the pandemic. Historically, the Company has not experienced uncollectible accrued interest receivable on investment securities. Allowance for Loan Losses – Incurred Loss Method Prior to the adoption of CECL on January 1, 2020, the Company calculated the allowance for loan losses using the incurred loss method whereby the allowance represented management’s estimate of probable incurred losses inherent in the current loan portfolio. Management believes that the allowance for loan losses is adequate. While management uses available information to recognize losses on loans, additions and reductions of the allowance for loan losses may fluctuate from one reporting period to another based on changes in economic conditions or changes in the values of properties securing loans in the process of foreclosure. The evaluation of the various components of the allowance for loan losses requires considerable judgment in order to estimate inherent loss exposures. Historical loss rates are first applied to pools of loans with similar risk characteristics. Each segment has a distinct set of risk characteristics monitored by management. Unique characteristics such as borrower type, loan type, collateral type and risk characteristics define each class segment. The Company further assess and monitor risk and performance at a more disaggregated level, which includes our internal risk grading system for the Commercial segments. Under the incurred loss method, the loan portfolio was segmented into the Commercial, Consumer and Residential Real Estate portfolio segments. The Commercial segment was further pooled into three classes: Commercial and Industrial, Commercial Real Estate and Business Banking. The Consumer segment was further pooled into three classes: Indirect Auto, Specialty Lending and Direct. Those segments were 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). Loss rates are calculated by historical charge-offs that have occurred within each pool of loans over the lookback period (“LBP”), multiplied by the loss emergence period (“LEP”). The LBP represents the historical data period utilized to calculate loss rates. The LEP is an estimate of the average amount of time from the point at which a loss is incurred on a loan to the point at which the loss is confirmed. In general, the LEP will be shorter in an economic slowdown or recession and longer during times of economic stability or growth, as customers are better able to delay loss confirmation after a potential loss event has occurred. In conjunction with our annual review of the allowance for loan loss assumptions, the Company updates our study of LEPs for each portfolio segment using our loan charge-off history. After consideration of the historic loss analysis, management applies additional qualitative adjustments so that the allowance for loan losses is reflective of the estimate of incurred losses that exist in the loan portfolio at the balance sheet date. Qualitative adjustments are made if, in the judgment of management, incurred loan losses inherent in the loan portfolio are not fully captured in the historical loss analysis. Qualitative considerations include the loan portfolio trends, composition and nature of loans; changes in lending policies and procedures, including underwriting standards and collection, charge-offs and recoveries; trends experienced in nonperforming and delinquent loans; current economic conditions in the Company’s market; portfolio concentrations that may affect loss experience across one of more components of the portfolio; the effect of external factors such as competition, legal and regulatory requirements; and the experience, ability and depth of lending management and staff. The allowance for loan losses related to impaired loans specifically allocated for impairment is based on discounted expected cash flows using the loan’s initial effective interest rate or the fair value of the collateral for certain loans where repayment of the loan is expected to be provided solely by the underlying collateral (“collateral dependent”). The Company’s impaired loans, if any, are generally collateral dependent. The Company considers the estimated cost to sell, on a discounted basis, when determining the fair value of collateral in the measurement of impairment if those costs are expected to reduce the cash flows available to repay or otherwise satisfy the loans. After a thorough consideration and validation of the factors discussed above, required additions or reductions to the allowance for loan losses are made periodically by charges or credits to the provision for loan losses. These are necessary to maintain the allowance at a level which management believes is reasonably reflective of the level of incurred credit losses inherent in the portfolio. Loan losses are charged off against the allowance, while recoveries of amounts previously charged off are credited to the allowance.
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.
Leases	Leases The Company determines if a lease is present at the inception of an agreement. Right-of-use (“ROU”) assets and lease liabilities are recognized at lease commencement based on the present value of the remaining lease payments using a discount rate that represents the Company’s incremental borrowing rate at the lease commencement date. ROU assets and operating lease liabilities, are included in other assets and other liabilities, respectively, on the consolidated balance sheets Operating lease ROU assets represent the Company’s right to use an underlying asset during the lease term and operating lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets are further adjusted for lease incentives. Operating lease expense, which is comprised of amortization of the ROU asset and the implicit interest accreted on the operating lease liability, is recognized on a straight-line basis over the lease term, and is recorded in occupancy expense in the consolidated statements of income The Company has lease agreements with lease and non-lease components, which are generally accounted for separately. For real estate leases, non-lease components and other non-components, such as common area maintenance charges, real estate taxes and insurance are not included in the measurement of the lease liability since they are generally able to be segregated. Our leases relate primarily to office space and bank branches, and some contain options to renew the lease. These options to renew are generally not considered reasonably certain to exercise, and are therefore not included in the lease term until such time that the option to renew is reasonably certain.
Other Real Estate Owned	Other Real Estate Owned Other real estate owned (“OREO”) consists of properties acquired through foreclosure or by acceptance of a deed in lieu of foreclosure. These assets are recorded at the lower of fair value of the asset acquired less estimated costs to sell or “cost” (defined as the fair value at initial foreclosure). At the time of foreclosure, or when foreclosure occurs in-substance, the excess, if any, of the loan over the fair market value of the assets received, less estimated selling costs, is charged to the allowance for loan losses and any subsequent valuation write-downs are charged to other expense. In connection with the determination of the allowance for loan losses and the valuation of OREO, management obtains appraisals for properties. Operating costs associated with the properties are charged to expense as incurred. Gains on the sale of OREO are included in income when title has passed and the sale has met the minimum down payment requirements prescribed by GAAP. The balance of OREO is recorded in other assets on the consolidated balance sheets.
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets Goodwill represents the cost of acquired business in excess of the fair value of the related net assets acquired. Goodwill is not amortized but tested at the reporting unit level for impairment on an annual basis and on an interim basis or when events or circumstances dictate. The Company has elected June 30 as the annual impairment testing date for the insurance and retirement services reporting units and December 31 for the Bank reporting unit. The Company has the option to first assess qualitative factors, by performing a qualitative analysis, to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the events or circumstances, the Company determines it is more likely than not that the fair value of a reporting unit is greater than its carrying amount, the impairment test is not required. If the Company concludes otherwise, the Company is required to perform a quantitative impairment test. In the quantitative impairment test, the estimated fair value of a reporting unit is compared to the carrying amount in order to determine if impairment is indicated. If the estimated fair value exceeds the carrying amount, the reporting unit is not deemed to be impaired. If the estimated fair value is below the carrying value of the reporting unit, the difference is the amount of impairment. Intangible assets that have indefinite useful lives are not amortized, but are tested at least annually for impairment. Intangible assets that have finite useful lives are amortized over their useful lives. Core deposit intangibles and trust intangibles at the Company are amortized using the sum-of-the-years’-digits method. Covenants not to compete are amortized on a straight-line basis. Customer lists are amortized using an accelerated method. When facts and circumstances indicate potential impairment of amortizable intangible assets, the Company evaluates the recoverability of the asset carrying value, using estimates of undiscounted future cash flows over the remaining asset life. Any impairment loss is measured by the excess of carrying value over fair value. Determining the fair value of a reporting unit under the goodwill impairment tests and determining the fair value of other intangible assets are judgmental and often involve the use of significant estimates and assumptions. Estimates of fair value are primarily determined using the discounted cash flows method, which uses significant estimates and assumptions including projected future cash flows, discount rates reflecting the market rate of return and projected growth rates. Future events may impact such estimates and assumptions and could cause the Company to conclude that our goodwill or intangible assets have become impaired, which would result in recording an impairment loss.
Bank-Owned Life Insurance	Bank-Owned Life Insurance The Bank has purchased life insurance policies on certain employees, key executives and directors. Bank-owned life insurance is recorded at the amount that can be realized under the insurance contract at the balance sheet date, which is the cash surrender value adjusted for other charges or other amounts due that are probable at settlement.
Treasury Stock	Treasury Stock Treasury stock acquisitions are recorded at cost. Subsequent sales of treasury stock are recorded on an average cost basis. Gains on the sale of treasury stock are credited to additional paid-in-capital. Losses on the sale of treasury stock are charged to additional paid-in-capital to the extent of previous gains, otherwise charged to retained earnings.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred income taxes are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred taxes of a change in tax rates is recognized in income in the period that includes the enactment date. The Company recognizes interest accrued and penalties related to unrecognized tax benefits in income tax expense. Tax positions are recognized as a benefit only if it is “more likely than not” that the tax position would be sustained in a tax examination, with a tax examination being presumed to occur. The amount recognized is the largest amount of tax benefit that is greater than 50 percent likely of being realized on examination. For tax positions not meeting the “more likely than not” test, no tax benefit is recorded.
Pension Costs	Pension Costs The Company has a qualified, noncontributory, defined benefit pension plan covering substantially all of its employees, as well as supplemental employee retirement plans to certain current and former executives and a defined benefit postretirement healthcare plan that covers certain employees. Costs associated with these plans, based on actuarial computations of current and future benefits for employees, are charged to current operating expenses.
Stock-Based Compensation	Stock-Based Compensation The Company maintains various long-term incentive stock benefit plans under which restricted stock units are granted to certain directors and key employees. Compensation expense are recognized in the consolidated statements of income over the requisite service period, based on the grant-date fair value of the award. For restricted stock units, compensation expense is recognized ratably over the vesting period for the fair value of the award, measured at the grant date.
Earnings Per Share	Earnings Per Share Basic earnings per share (“EPS”) excludes dilution and is computed by dividing income available to common stockholders by the weighted average number of common shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur if securities or other contracts to issue common stock were exercised or converted into common stock or resulted in the issuance of common stock that then shared in the earnings of the entity (such as the Company’s dilutive stock options and restricted stock units).
Comprehensive Income	Comprehensive Income At the Company, comprehensive income represents net income plus OCI, which consists primarily of the net change in unrealized gains (losses) on AFS debt securities for the period, changes in the funded status of employee benefit plans and unrealized gains (losses) on derivatives designated as hedging instruments. AOCI represents the net unrealized gains (losses) on AFS debt securities, the previously unrecognized portion of the funded status of employee benefit plans and the fair value of instruments designated as hedging instruments, net of income taxes, as of the consolidated balance sheet dates.
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities The Company records all derivatives on the balance sheet at fair value. The accounting for changes in the fair value of derivatives depends on the intended use of the derivative, whether the Company has elected to designate a derivative in a hedging relationship and apply hedge accounting and whether the hedging relationship has satisfied the criteria necessary to apply hedge accounting. Derivatives designated and qualifying as a hedge of the exposure to changes in the fair value of an asset, liability or firm commitment attributable to a particular risk, such as interest rate risk, are considered fair value hedges. Derivatives designated and qualifying as a hedge of the exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Hedge accounting generally provides for the matching of the timing of gain or loss recognition on the hedging instrument with the recognition of the changes in the fair value of the hedged asset or liability that are attributable to the hedged risk in a fair value hedge or the earnings effect of the hedged forecasted transactions in a cash flow hedge. The Company may enter into derivative contracts that are intended to economically hedge certain of its risks, even though hedge accounting does not apply or the Company elects not to apply hedge accounting. For derivatives designated as fair value hedges, changes in the fair value of the derivative and the hedged item related to the hedged risk are recognized in earnings. For derivatives designated as cash flow hedges, changes in fair value of the cash flow hedges are reported in OCI. When the cash flows associated with the hedged item are realized, the gain or loss included in OCI is recognized in the consolidated statements of income. When the Company purchases or sells a portion of a commercial loan that has an existing interest rate swap, it may enter into a risk participation agreement to provide credit protection to the financial institution that originated the swap transaction should the borrower fail to perform on its obligation. The Company enters into both risk participation agreements in which it purchases credit protection from other financial institutions and those in which it provides credit protection to other financial institutions
Fair Value Measurements	Fair Value Measurements GAAP states that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value measurements are not adjusted for transaction costs. A fair value hierarchy exists within GAAP that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are described below: Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2 - Quoted prices for similar assets or liabilities in active markets, quoted prices in markets that are not active or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability; Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The types of instruments valued based on quoted market prices in active markets include most U.S. government and agency securities, many other sovereign government obligations, liquid mortgage products, active listed equities and most money market securities. Such instruments are generally classified within Level 1 or Level 2 of the fair value hierarchy. The Company does not adjust the quoted price for such instruments. The types of instruments valued based on quoted prices in markets that are not active, broker or dealer quotations or alternative pricing sources with reasonable levels of price transparency include most investment-grade and high-yield corporate bonds, less liquid mortgage products, less liquid agency securities, less liquid listed equities, state, municipal and provincial obligations and certain physical commodities. Such instruments are generally classified within Level 2 of the fair value hierarchy. Certain common equity securities are reported at fair value utilizing Level 1 inputs (exchange quoted prices). Other investment securities are reported at fair value utilizing Level 1 and Level 2 inputs. The prices for Level 2 instruments are obtained through an independent pricing service or dealer market participants with whom the Company has historically transacted both purchases and sales of investment securities. Prices obtained from these sources include prices derived from market quotations and matrix pricing. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. Management reviews the methodologies used in pricing the securities by its third party providers. Level 3 is for positions that are not traded in active markets or are subject to transfer restrictions. Valuations are adjusted to reflect illiquidity and/or non-transferability and such adjustments are generally based on available market evidence. In the absence of such evidence, management’s best estimate will be used. Management’s best estimate consists of both internal and external support on certain Level 3 investments. Subsequent to inception, management only changes Level 3 inputs and assumptions when corroborated by evidence such as transactions in similar instruments, completed or pending third-party transactions in the underlying investment or comparable entities, subsequent rounds of financing, recapitalizations and other transactions across the capital structure, offerings in the equity or debt markets and changes in financial ratios or cash flows.
Other Financial Instruments	Other Financial Instruments The Company is a party to certain instruments with off-balance-sheet risk such as commitments to extend credit, unused lines of credit, standby letter of credit and certain agricultural real estate loans sold to investors with recourse. The Company’s policy is to record such instruments when funded. Standby letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party. The risk involved in issuing standby letters of credit is essentially the same as the credit risk involved in extending loan facilities to customers. Under the standby letters of credit, the Company is required to make payments to the beneficiary of the letters of credit upon request by the beneficiary contingent upon the customer’s failure to perform under the terms of the underlying contract with the beneficiary. Standby letters of credit typically have one year expirations with an option to renew upon annual review. The Company typically receives a fee for these transactions. The fair value of standby letters of credit is recorded upon inception.
Repurchase Agreements	Repurchase Agreements Repurchase agreements are accounted for as secured financing transactions since the Company maintains effective control over the transferred securities and the transfer meets the other criteria for such accounting. Obligations to repurchase securities sold are reflected as a liability in the consolidated balance sheets. The securities underlying the agreements are delivered to a custodial account for the benefit of the counterparties with whom each transaction is executed. The counterparties, who may sell, loan or otherwise dispose of such securities to other parties in the normal course of their operations, agree to resell to the Company the same securities at the maturities of the agreements.
Revenue from Contracts with Customers	Revenue from Contracts with Customers Effective January 1, 2018, the Company adopted Financial Accounting Standards Board (“FASB”) Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Accounting Standards Codification (“ASC”) Topic 606) Service Charges on Deposit Accounts Service charges on deposit accounts consist of overdraft fees, monthly service fees, check orders and other deposit account related fees. Overdraft, monthly service, check orders and other deposit account related fees are transactional based, and therefore, the Company’s performance obligation is satisfied, and related revenue recognized, at a point in time. Payment for service charges on deposit accounts is primarily received immediately or in the following month through a direct charge to customers’ accounts. ATM and Debit Card Fees ATM fees are primarily generated when a Company cardholder uses a non-Company ATM or a non-Company cardholder uses a Company ATM. Debit card income is primarily comprised of interchange fees earned whenever the Company’s debit cards are processed through card payment networks. The Company’s performance obligations for these revenue streams are satisfied, and related revenue recognized, when the services are rendered or upon completion. Payment is typically received immediately or in the following month. Retirement Plan Administration Fees Retirement plan administration fees are primarily generated for services related to the recordkeeping, administration and plan design solutions of defined benefit, defined contribution and revenue sharing plans. Revenue is recognized in arrears for services already provided in accordance with fees established in contracts with customers or based on rates agreed to with investment trade platforms based on ending investment balances held. The Company’s performance obligation is satisfied, and related revenue recognized based on services completed or ending investment balances, for which receivables are recorded at the time of revenue recognition. Wealth Management Wealth Management revenue primarily is comprised of trust and other financial services revenue. Trust and asset management income is primarily comprised of fees earned from the management and administration of trusts, pensions and other customer assets. The Company’s performance obligation is generally satisfied with the resulting fees recognized monthly, based upon services completed or the month-end market value of the assets under management and the applicable fee rate. Payment is generally received shortly after services are rendered or a few days after month end through a direct charge to customers’ accounts. The Company does not earn performance-based incentives. Financial services revenue primarily consists of commissions received on brokered investment product sales. For other financial services revenue, the Company’s performance obligation is generally satisfied upon the issuance of the annuity policy. Shortly after the policy is issued, the carrier remits the commission payment to the Company, and the Company recognizes the revenue. The Company does not earn a significant amount of trailing commission fees on brokered investment product sales. The majority of the trailing commission fees are calculated based on a percentage of market value of a period end and revenue is recognized when an investment product’s market value can be determined. Insurance Revenue Insurance and other financial services revenue primarily consists of commissions received on insurance. The Company acts as an intermediary between the Company’s customer and the insurance carrier. The Company’s performance obligation related to insurance sales for both property and casualty insurance and employee benefit plans is generally satisfied upon the later of the issuance or effective date of the policy. The Company earns performance based incentives, commonly known as contingency payments, which usually are based on certain criteria established by the insurance carrier such as premium volume, growth and insured loss ratios. Contingent payments are accrued for based upon management’s expectations for the year. Commission expense associated with sales of insurance products is expensed as incurred. The Company does not earn a significant amount of trailing commission fees on insurance product sales. The majority of the trailing commission fees are calculated based on a percentage of market value of a period end and revenue is recognized when an investment product’s market value can be determined. Other Other noninterest income consists of other recurring revenue streams such as account and loan fees, interest rate swap fees, safe deposit box rental fees and other miscellaneous revenue streams. These revenue streams are primarily transactional based and payment is received immediately or in the following month, and therefore, the Company’s performance obligation is satisfied, and related revenue recognized, at a point in time. The following table presents noninterest income, segregated by revenue streams in-scope and out-of-scope of ASC 606: Years Ended December 31, (In thousands) 2020 2019 2018 Noninterest income In-Scope of ASC 606: Service charges on deposit accounts $ 13,201 $ 17,151 $ 17,224 ATM and debit card fees 25,960 23,893 22,699 Retirement plan administration fees 35,851 30,388 26,992 Wealth management 29,247 28,400 28,747 Insurance 14,757 15,770 15,122 Other 21,905 18,853 15,228 Total noninterest income in-scope of ASC 606 $ 140,921 $ 134,455 $ 126,012 Total noninterest income out-of-scope of ASC 606 $ 5,355 $ 9,568 $ (1,250 ) Total noninterest income $ 146,276 $ 144,023 $ 124,762 Contract Balances A contract asset balance occurs when an entity performs a service for a customer before the customer pays consideration or before payment is due, which would result in contract receivables or assets, respectively. A contract liability balance is an entity’s obligation to transfer a service to a customer for which the entity has already received payment or for which payment is due from the customer. The Company’s noninterest revenue streams are largely based on transactional activity, or standard month-end revenue accruals such as asset management fees based on month-end market values. Consideration is often received immediately or shortly after the Company satisfies its performance obligation and revenue is recognized. The Company does not typically enter into long-term revenue contracts with customers, and therefore, does not experience significant contract balances. Contract Acquisition Costs ASC 606 requires the capitalization, and subsequently amortization into expense, certain incremental costs of obtaining a contract with a customer if these costs are expected to be recovered. The incremental costs of obtaining a contract are those costs that an entity incurs to obtain a contract with a customer that it would not have incurred if the contract had not been obtained. The Company elected the practical expedient, which allows immediate expensing of contract acquisition costs when the asset that would have resulted from capitalizing these costs would have been amortized in one year or less, and did not capitalize any contract acquisition costs upon adoption of ASC 606 as of or during the year ended December 31, 2020.
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.
Subsequent Events	Subsequent Events The Company has evaluated subsequent events for potential recognition and/or disclosure and there were none identified.

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements (Policies)	12 Months Ended
	Dec. 31, 2020
Recent Accounting Pronouncements [Abstract]
Recently Adopted Accounting Standards and Accounting Standards Issued Not Yet Adopted	Recently Adopted Accounting Standards In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments The Company adopted CECL on January 1, 2020 (“Day 1”) using the modified retrospective method for all financial assets measured at amortized cost and off-balance-sheet credit exposures. Results for reporting periods beginning after January 1, 2020 are presented under ASC 326 while prior period amounts continue to be reported in accordance with previously applicable GAAP. The Company recorded a net decrease to retained earnings of $4.3 million as of January 1, 2020 for the cumulative effect of adopting ASC 326. The transition adjustment includes a $3.0 million impact due to the allowance for credit losses on loans, a $2.8 million impact due to the allowance for credit losses on off-balance sheet credit exposure, and a $1.5 million impact to the deferred tax asset. The Company did not record an allowance for HTM debt securities on January 1, 2020 as the amount of credit risk was deemed immaterial. The Company did not record an allowance for credit losses on its AFS debt securities under the newly codified AFS debt security impairment model, as the majority of these securities are government agency-backed securities for which the risk of loss is minimal. Refer to Note 4 Securities and Note 6 Allowance for Credit Losses and Credit Quality of Loans to the Company’s consolidated financial statements included in this Form 10-K for more information. In December 2018, the Office of Comptroller of the Currency (“OCC”), the Board of Governors of the Federal Reserve System, and the Federal Deposit Insurance Corporation (“FDIC”) approved a final rule to address changes to credit loss accounting under GAAP, including banking organizations’ implementation of CECL. The final rule provides banking organizations the option to phase in over a three-year period the day-one adverse effects on regulatory capital that may result from the adoption of the new accounting standard. In March 2020, the OCC, the Board of Governors of the Federal Reserve System, and the FDIC announced an interim final rule to delay the estimated impact on regulatory capital stemming from the implementation of CECL. The interim final rule maintains the three-year transition option in the previous rule and provides banks the option to delay for two years an estimate of CECL’s effect on regulatory capital, relative to the incurred loss methodology’s effect on regulatory capital, followed by a three-year transition period (five-year transition option). The Company adopted the capital transition relief over the permissible five-year period. On March 22, 2020, a statement was issued by the Company’s banking regulators and titled the “Interagency Statement on Loan Modifications and Reporting for Financial Institutions Working with Customers Affected by the Coronavirus” that encourages financial institutions to work prudently with borrowers who are or may be unable to meet their contractual payment obligations due to the effects of the recent COVID-19 pandemic. Additionally, Section 4013 of the CARES Act, which was enacted on March 27, 2020, further provides that a qualified loan modification is exempt by law from classification as a troubled debt restructuring as defined by GAAP. To be eligible, each loan modification must be (1) related to the COVID-19 event; (2) executed on a loan that was not more than 30 days past due as of December 31, 2019; and (3) executed between March 1, 2020, and the earlier of (a) 60 days after the date of termination of the National Emergency or (b) December 31, 2020. On August 3, 2020, the Federal Financial Institutions Examination Council (“FFIEC”) issued a joint statement on additional loan accommodations related to COVID-19. The joint statement clarifies that for loan modifications in which Section 4013 is being applied, subsequent modifications could also be eligible under Section 4013. Accordingly, the Company is offering modifications made in response to COVID-19 to borrowers who were current and otherwise not past due in accordance with the criteria stated in Section 4013. These include short-term, 180 days or less, modifications in the form of payment deferrals, fee waivers, extensions of repayment terms, or other delays in payment. Accordingly, the Company did not account for such loan modifications as TDRs. As of December 31, 2020, there were $110.8 million in loans in modification programs related to COVID-19. On December 27, 2020, the Consolidated Appropriations Act amended section 2014 of the CARES Act extending the exemption of qualified loan modifications from classification as a troubled debt restructuring as defined by GAAP to the earlier of January 1, 2022, or 60 days after the National Emergency concerning COVID-19 ends. In August 2018, the FASB issued ASU 2018-13, Fair value Measurement (Topic 820) – Disclosure Framework – Changes to the Disclosure Requirements for Fair value Measurement In August 2018, the FASB issued ASU 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40) – Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract In August 2018, the FASB issued ASU 2018-14, Compensation – Retirement Benefits – Defined Benefit Plans - General (Subtopic 715-20) Accounting Standards Issued Not Yet Adopted In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

Securities (Policies)

Securities (Policies)	12 Months Ended
	Dec. 31, 2020
Securities [Abstract]
Investment, Policy	The Company does not believe the AFS securities that were in an unrealized loss position as of December 31, 2020, which consisted of 23 individual securities, represented a credit loss impairment. AFS debt securities in unrealized loss positions are evaluated for impairment related to credit losses at least quarterly. As of December 31, 2020, the majority of the AFS securities in an unrealized loss position consisted of debt securities issued by U.S. government agencies or U.S. government-sponsored enterprises that carry the explicit and/or implicit guarantee of the U.S. government, which are widely recognized as “risk-free” and have a long history of zero credit losses. Total gross unrealized losses were primarily attributable to changes in interest rates, relative to when the investment securities were purchased, and not due to the credit quality of the investment securities. The Company does not intend to sell, nor is it more likely than not that the Company will be required to sell the security before recovery of its amortized cost basis, which may be at maturity. The Company elected to exclude accrued interest receivable (“AIR”) from the amortized cost basis of debt securities disclosed throughout this footnote. AIR on AFS debt securities totaled $3.3 million at December 31, 2020 and is excluded from the estimate of credit losses and reported in the financial statement line for other assets. None of the bank’s HTM debt securities were past due or on nonaccrual status as of the year ended December 31, 2020. There was no accrued interest reversed against interest income for the year ended December 31, 2020 as all securities remained on accrual status. In addition, there were no collateral dependent HTM debt securities as of year ended December 31, 2020. 65% of the Company’s HTM debt securities are issued by U.S. government agencies or U.S. government-sponsored enterprises. These securities carry the explicit and/or implicit guarantee of the U.S. government, are widely recognized as “risk-free,” and have a long history of zero credit loss. Therefore, the Company did not record an allowance for credit losses for these securities as of December 31, 2020. The remaining HTM debt securities at December 31, 2020 were comprised of state and municipal obligations with bond ratings of A to AAA. Utilizing the CECL approach, the Company determined that the expected credit loss on its HTM municipal bond portfolio was immaterial and therefore no allowance for credit loss was recorded as of December 31, 2020. AIR on HTM debt securities totaled $2.7 million at December 31, 2020 and is excluded from the estimate of credit losses and reported in the financial statement line for other assets.

Allowance for Credit Losses a_2

Allowance for Credit Losses and Credit Quality of Loans (Policies)	12 Months Ended
	Dec. 31, 2020
Allowance for Credit Losses and Credit Quality of Loans [Abstract]
Allowance for Credit Losses	The Day 1 increase in the allowance for credit loss on loans relating to adoption of ASU 2016-13 was $3.0 million, which decreased retained earnings by $2.3 million and increased the deferred tax asset by $0.7 million. There were no loans purchased with credit deterioration during the year ended December 31, 2020. During 2020, the Company purchased $51.9 million of consumer loans at a 1% discount. The allowance for credit losses recorded for these loans on the purchase date was $3.6 million. The Company made a policy election to report AIR in the other assets line item on the balance sheet. AIR on loans totaled $23.7 million at December 31, 2020 and was included in the allowance for loan credit losses to estimate the impact of accrued interest receivable related to loans with modifications due to the pandemic as the length of time between interest recognition and the write-off of uncollectible interest could exceed 120 days, exempting these loans from our policy election for accrued interest receivable. The estimated allowance for credit losses related to AIR at December 31, 2020 was $0.6 million. The Day 1 and December 31, 2020 allowance for credit losses calculation incorporated a 6-quarter forecast period to account for forecast economic conditions under each scenario utilized in the measurement. For periods beyond the 6-quarter forecast, the model reverted to long-term economic conditions over a 4-quarter reversion period on a straight-line basis. The quantitative model as of December 31, 2020 incorporated a baseline economic outlook, along with alternative upside and downside scenarios sourced from a reputable third-party to accommodate other potential economic conditions in the model. The baseline outlook reflected an unemployment rate environment above pre-COVID-19 levels for the entire forecast period, though steadily improving, before returning to low single digits by the end of 2023. Northeast GDP’s annual growth was expected to start 2021 in the low to mid-single digits, with a peak growth rate of 8% in the fourth quarter of 2021 and steadily falling back down to normalized levels through 2023 and 2024. Other utilized economic variables show improvement in their respective forecasts, namely business output. Key assumptions in the baseline economic outlook included an additional stimulus package passed at the same timing and a comparable level to that of the actual $900 billion COVID-19 relief package passed in December 2020 along with no significant secondary surge in COVID-19 cases or pandemic-related business closures. The alternative downside scenario assumed deteriorated economic and epidemiological conditions from the baseline outlook. In the same way, the alternative upside scenario assumed a faster economic recovery and more effective management of the COVID-19 virus from the baseline outlook. These scenarios and their respective weightings are evaluated at each measurement date and reflect management’s expectations as of December 31, 2020. Additional adjustments were made for COVID-19 related factors not incorporated in the forecasts, such as the mitigating impact of unprecedented stimulus in 2020, including direct payments to individuals, increased unemployment benefits, the Company’s loan deferral and modification initiatives and various government-sponsored loan programs. The commercial & industrial and consumer segment models were based upon percent change in unemployment with modeled values as of December 31, 2020 well outside the observed historical experience. Therefore, adjustments were required to produce outputs more aligned with default expectations given the forecast economic environment. Additionally, the Company identified a slightly higher level of criticized and classified loans during 2020 than those contemplated by the model during similar economic conditions in the past for which an adjustment was made for estimated expected additional losses above modeled output. These factors were considered through a separate quantitative process and incorporated into the estimate for allowance for credit losses at December 31, 2020. The allowance for credit losses totaled $110.0 million at December 31, 2020, compared to $73.0 million at December 31, 2019. The allowance for credit losses as a percentage of loans was 1.47% at December 31, 2020, compared to 1.02% at December 31, 2019. The increase in the allowance for credit losses from January 1, 2020 to December 31, 2020 was primarily due to the deteriorated economic forecast due to the COVID-19 pandemic. The provision for loan losses was $51.1 million for the twelve months ended December 31, 2020, compared to $25.4 million for the twelve months ended December 31, 2019. The increase to provision expense was driven by the deteriorated economic forecast due to the COVID-19 pandemic. The Company expects that with the adoption of CECL beginning on January 1, 2020, provision expense may become more volatile due to changes in CECL model assumptions of credit quality, macroeconomic factors and conditions, and loan composition, which drive the allowance for credit losses balance. The increase in the allowance for credit losses from Day 1 to December 31, 2020 was primarily due to the deterioration of macroeconomic factors surrounding the COVID-19 pandemic. Individually Evaluated Loans As of December 31, 2020, there were five relationships identified to be evaluated for loss on an individual basis which had an amortized cost basis of $15.2 million. The allowance for credit loss was $3.2 million and was determined by an estimate of the fair value of the collateral which consisted of business assets (accounts receivable, inventory and machinery, real estate and equipment). As of Day 1, there were no relationships identified to be evaluated for loss on an individual basis. As of December 31, 2020, there were no loans in nonaccrual without an allowance for credit losses. Credit Quality Indicators The Company has developed an internal loan grading system to evaluate and quantify the Company’s loan portfolio with respect to quality and risk. The system focuses on, among other things, financial strength of borrowers, experience and depth of borrower’s management, primary and secondary sources of repayment, payment history, nature of the business and outlook on particular industries. The internal grading system enables the Company to monitor the quality of the entire loan portfolio on a consistent basis and provide management with an early warning system, enabling recognition and response to problem loans and potential problem loans. Commercial Grading System For C&I, PPP and CRE loans, the Company uses a grading system that relies on quantifiable and measurable characteristics when available. This includes comparison of financial strength to available industry averages, comparison of transaction factors (loan terms and conditions) to loan policy and comparison of credit history to stated repayment terms and industry averages. Some grading factors are necessarily more subjective such as economic and industry factors, regulatory environment and management. C&I and CRE loans are graded Doubtful, Substandard, Special Mention and Pass. The increase in non-pass credits from December 31, 2019 was primarily due to the Company’s proactive approach to downgrade loans that were both in payment deferral due to the COVID-19 pandemic and in higher risk industries such as entertainment, restaurants, retail, healthcare and accommodations. Doubtful A Doubtful loan has a high probability of total or substantial loss, but because of specific pending events that may strengthen the asset, its classification as a loss is deferred. Doubtful borrowers are usually in default, lack adequate liquidity or capital and lack the resources necessary to remain an operating entity. Pending events can include mergers, acquisitions, liquidations, capital injections, the perfection of liens on additional collateral, the valuation of collateral and refinancing. Generally, pending events should be resolved within a relatively short period and the ratings will be adjusted based on the new information. Nonaccrual treatment is required for Doubtful assets because of the high probability of loss. Substandard Substandard loans have a high probability of payment default or they have other well-defined weaknesses. They require more intensive supervision by bank management. Substandard loans are generally characterized by current or expected unprofitable operations, inadequate debt service coverage, inadequate liquidity or marginal capitalization. Repayment may depend on collateral or other credit risk mitigants. For some Substandard loans, the likelihood of full collection of interest and principal may be in doubt and those loans should be placed on nonaccrual. Although Substandard assets in the aggregate will have a distinct potential for loss, an individual asset’s loss potential does not have to be distinct for the asset to be rated Substandard. Special Mention Special Mention loans have potential weaknesses that may, if not checked or corrected, weaken the asset or inadequately protect the Company’s position at some future date. These loans pose elevated risk, but their weakness does not yet justify a Substandard classification. Borrowers may be experiencing adverse operating trends (i.e., declining revenues or margins) or may be struggling with an ill-proportioned balance sheet (i.e., increasing inventory without an increase in sales, high leverage, tight liquidity). Adverse economic or market conditions, such as interest rate increases or the entry of a new competitor, may also support a Special Mention rating. Although a Special Mention loan has a higher probability of default than a Pass asset, its default is not imminent. Pass Loans graded as Pass encompass all loans not graded as Doubtful, Substandard or Special Mention. Pass loans are in compliance with loan covenants and payments are generally made as agreed. Pass loans range from superior quality to fair quality. Pass loans also include any portion of a government guaranteed loan, including PPP loans. Consumer and Residential Grading System Consumer and Residential loans are graded as either Nonperforming or Performing. Nonperforming Nonperforming loans are loans that are 1) over 90 days past due and interest is still accruing or 2) on nonaccrual status. Performing All loans not meeting any of the above criteria are considered Performing. Allowance for Credit Losses on Off-Balance Sheet Credit Exposures As of December 31, 2020, the allowance for losses on unfunded commitments totaled $6.4 million, compared to $0.9 million as of December 31, 2019. Prior to January 1, 2020, the Company calculated the allowance for losses on unfunded commitments using the incurred loss methodology.
Troubled Debt Restructuring	Troubled Debt Restructuring When the Company modifies a loan in a troubled debt restructuring, such modifications generally include one or a combination of the following: an extension of the maturity date at a stated rate of interest lower than the current market rate for new debt with similar risk; temporary reduction in the interest rate; or change in scheduled payment amount. Residential and Consumer TDRs occurring during 2020 were due to the reduction in the interest rate or extension of the term. An allowance for impaired commercial and consumer loans that have been modified in a TDR is measured based on the present value of the expected future cash flows, discounted at the contractual interest rate of the original loan agreement, except when the sole (remaining) source of repayment for the loan is the operation or liquidation of the collateral. In these cases, management uses the current fair value of the collateral, less selling costs. If management determines that the value of the modified loan is less than the recorded investment in the loan an impairment charge would be recorded. The Company began offering loan modifications to assist borrowers during the COVID-19 national emergency. The CARES Act, along with a joint agency statement issued by banking regulatory agencies, provides that modifications made in response to COVID-19 do not need to be accounted for as a TDR. The Company evaluated the modification programs provided to its borrowers and has concluded the modifications were generally made in accordance with the CARES Act guidance to borrowers who were in good standing prior to the COVID-19 pandemic and are not required to be designated as TDRs. See Note 2 Recent Accounting Pronouncements for more information.

Employee Benefit Plans (Policie

Employee Benefit Plans (Policies)	12 Months Ended
	Dec. 31, 2020
Employee Benefit Plans [Abstract]
Postemployment Benefit Plans, Policy	The Company has a qualified, noncontributory, defined benefit pension plan (“the Plan”) covering substantially all of its employees at December 31, 2020. Benefits paid from the plan are based on age, years of service, compensation and social security benefits and are determined in accordance with defined formulas. The Company’s policy is to fund the Plan in accordance with Employee Retirement Income Security Act of 1974 standards. Assets of the Plan are invested in publicly traded stocks and mutual funds. Prior to January 1, 2000, the Plan was a traditional defined benefit plan based on final average compensation. On January 1, 2000, the Plan was converted to a cash balance plan with grandfathering provisions for existing participants. Effective March 1, 2013, the Plan was amended. Benefit accruals for participants who, as of January 1, 2000, elected to continue participating in the traditional defined benefit plan design were frozen as of March 1, 2013. In May 2013, the noncontributory, frozen, defined benefit pension plan assumed from Alliance in the acquisition was merged into the Plan. In addition to the Plan, the Company provides supplemental employee retirement plans to certain current and former executives. The Company also assumed supplemental retirement plans for certain former executives in the Alliance acquisition. These supplemental employee retirement plans and the Plan are collectively referred to herein as “Pension Benefits.” In addition, the Company provides certain health care benefits for retired employees. Benefits were accrued over the employees’ active service period. Only employees that were employed by the Company on or before January 1, 2000 are eligible to receive post-retirement health care benefits. The Plan is contributory for participating retirees, requiring participants to absorb certain deductibles and coinsurance amounts with contributions adjusted annually to reflect cost sharing provisions and benefit limitations called for in the Plan. Employees become eligible for these benefits if they reach normal retirement age while working for the Company. For eligible employees described above, the Company funds the cost of post-retirement health care as benefits are paid. The Company elected to recognize the transition obligation on a delayed basis over twenty years. In addition, the Company assumed post-retirement medical life insurance benefits for certain Alliance employees, retirees and their spouses, if applicable, in the Alliance acquisition. These post-retirement benefits are referred to herein as “Other Benefits.” Accounting standards require an employer to: (1) recognize the overfunded or underfunded status of defined benefit post-retirement plans, which is measured as the difference between plan assets at fair value and the benefit obligation, as an asset or liability in its balance sheet; (2) recognize changes in that funded status in the year in which the changes occur through comprehensive income; and (3) measure the defined benefit plan assets and obligations as of the date of its year-end balance sheet.

Fair Values of Financial Inst_2

Fair Values of Financial Instruments (Policies)	12 Months Ended
	Dec. 31, 2020
Fair Values of Financial Instruments [Abstract]
Fair Value of Financial Instruments, Policy	GAAP states that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. Fair value measurements are not adjusted for transaction costs. A fair value hierarchy exists within GAAP that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are described below: Level 1 - Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2 - Quoted prices for similar assets or liabilities in active markets, quoted prices in markets that are not active or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability; Level 3 - Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). A financial instrument’s level within the fair value hierarchy is based on the lowest level of input that is significant to the fair value measurement. The types of instruments valued based on quoted market prices in active markets include most U.S. government and agency securities, many other sovereign government obligations, liquid mortgage products, active listed equities and most money market securities. Such instruments are generally classified within Level 1 or Level 2 of the fair value hierarchy. The Company does not adjust the quoted prices for such instruments. The types of instruments valued based on quoted prices in markets that are not active, broker or dealer quotations or alternative pricing sources with reasonable levels of price transparency include most investment-grade and high-yield corporate bonds, less liquid mortgage products, less liquid agency securities, less liquid listed equities, state, municipal and provincial obligations and certain physical commodities. Such instruments are generally classified within Level 2 of the fair value hierarchy. Certain common equity securities are reported at fair value utilizing Level 1 inputs (exchange quoted prices). Other investment securities are reported at fair value utilizing Level 1 and Level 2 inputs. The prices for Level 2 instruments are obtained through an independent pricing service or dealer market participants with whom the Company has historically transacted both purchases and sales of investment securities. Prices obtained from these sources include prices derived from market quotations and matrix pricing. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. Management reviews the methodologies used in pricing the securities by its third party providers. Level 3 is for positions that are not traded in active markets or are subject to transfer restrictions. Valuations are adjusted to reflect illiquidity and/or non-transferability and such adjustments are generally based on available market evidence. In the absence of such evidence, management’s best estimate will be used. Management’s best estimate consists of both internal and external support on certain Level 3 investments. Subsequent to inception, management only changes Level 3 inputs and assumptions when corroborated by evidence such as transactions in similar instruments, completed or pending third-party transactions in the underlying investment or comparable entities, subsequent rounds of financing, recapitalizations and other transactions across the capital structure, offerings in the equity or debt markets and changes in financial ratios or cash flows. GAAP requires disclosure of assets and liabilities measured and recorded at fair value on a non-recurring basis such as goodwill, loans held for sale, other real estate owned, collateral-dependent impaired loans, mortgage servicing rights and HTM securities. The non-recurring fair value measurements recorded during the years ended were related to impaired loans, write-downs of other real estate owned and write-down of branch assets to fair value. The Company uses the fair value of underlying collateral, less costs to sell, to estimate the allowance for credit losses for individually evaluated collateral dependent loans. The appraisals may be adjusted by management for qualitative factors such as economic conditions and estimated liquidation expenses ranging from Based on the valuation techniques used, the fair value measurements for collateral dependent individually evaluated loans are classified as Level 3. As of December 31, 2020 the Company had collateral dependent individually evaluated loans with a carrying value of $15.2 million, which had an estimated allowance for credit loss of $3.2 million. As of December 31, 2019 the Company had no collateral dependent loans. During the year ended December 31, 2020, the Company recorded a $0.5 million write-off of branch locations due to a pending disposition of the locations. During the year ended December 31, 2019, the Company recorded a $1.0 million write-down of a branch location to fair value of $0.2 million due to a pending disposition of the location. 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 wealth operation that contributes net fee income annually. The wealth management operation is not considered a financial instrument and its value has not been incorporated into the fair value estimates. Other significant assets and liabilities include the benefits resulting from the low-cost funding of deposit liabilities as compared to the cost of borrowing funds in the market and premises and equipment. In addition, the tax ramifications related to the realization of the unrealized gains and losses can have a significant effect on fair value estimates and have not been considered in the estimate of fair value. HTM Securities The fair value of the Company’s HTM securities is primarily measured using information from a third-party pricing service. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the bond’s terms and conditions, among other things. Net Loans Net loans include portfolio loans and loans held for sale. Loans were first segregated by type and then further segmented into fixed and variable rate and loan quality categories. Expected future cash flows were projected based on contractual cash flows, adjusted for estimated prepayments, which also includes credit risk, illiquidity risk and other market factors to calculate the exit price fair value in accordance with ASC 820. Time Deposits The fair value of time deposits was estimated using a discounted cash flow approach that applies prevailing market interest rates for similar maturity instruments. The fair values of the Company’s time deposit liabilities do not take into consideration the value of the Company’s long-term relationships with depositors, which may have significant value. Long-Term Debt The fair value of long-term debt was estimated using a discounted cash flow approach that applies prevailing market interest rates for similar maturity instruments. Subordinated Debt The fair value of subordinated debt has been measured using the observable market price as of the period reported. Junior Subordinated Debt The fair value of junior subordinated debt has been estimated using a discounted cash flow analysis.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Summary of Significant Accounting Policies [Abstract]
Portfolio and Class Segments	The following table illustrates the portfolio and class segments for the Company’s loan portfolio in 2020: Portfolio Segment Class Commercial Loans Commercial & Industrial Paycheck Protection Program Commercial Real Estate Consumer Loans Auto Other Consumer Residential Loans
Noninterest Income, Segregated by Revenue Streams in-Scope and Out-of-Scope of ASC 606	The following table presents noninterest income, segregated by revenue streams in-scope and out-of-scope of ASC 606: Years Ended December 31, (In thousands) 2020 2019 2018 Noninterest income In-Scope of ASC 606: Service charges on deposit accounts $ 13,201 $ 17,151 $ 17,224 ATM and debit card fees 25,960 23,893 22,699 Retirement plan administration fees 35,851 30,388 26,992 Wealth management 29,247 28,400 28,747 Insurance 14,757 15,770 15,122 Other 21,905 18,853 15,228 Total noninterest income in-scope of ASC 606 $ 140,921 $ 134,455 $ 126,012 Total noninterest income out-of-scope of ASC 606 $ 5,355 $ 9,568 $ (1,250 ) Total noninterest income $ 146,276 $ 144,023 $ 124,762

Securities (Tables)

Securities (Tables)	12 Months Ended
	Dec. 31, 2020
Securities [Abstract]
Amortized Cost, Estimated Fair Value and Unrealized Gains (Losses) of Available for Sale ("AFS") Securities	The amortized cost, estimated fair value and unrealized gains (losses) of AFS securities are as follows: (In thousands) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value As of December 31, 2020 Federal agency $ 245,590 $ 59 $ 2,052 $ 243,597 State & municipal 42,550 630 - 43,180 Mortgage-backed: Government-sponsored enterprises 521,448 17,079 22 538,505 U.S. government agency securities 55,049 2,332 47 57,334 Collateralized mortgage obligations: Government-sponsored enterprises 311,710 7,549 58 319,201 U.S. government agency securities 114,864 3,739 - 118,603 Corporate 27,500 778 - 28,278 Total AFS securities $ 1,318,711 $ 32,166 $ 2,179 $ 1,348,698 As of December 31, 2019 Federal agency $ 34,998 $ 3 $ 243 $ 34,758 State & municipal 2,533 - 20 2,513 Mortgage-backed: Government-sponsored enterprises 453,614 4,982 239 458,357 U.S. government securities 44,758 667 156 45,269 Collateralized mortgage obligations: Government-sponsored enterprises 328,499 1,949 467 329,981 U.S. government securities 104,152 718 408 104,462 Total AFS securities $ 968,554 $ 8,319 $ 1,533 $ 975,340
Components of Net Realized Gains (Losses) on Sale of AFS Securities	The components of net realized gains (losses) on AFS securities are as follows. These amounts were reclassified out of AOCI and into earnings. Years Ended December 31, (In thousands) 2020 2019 2018 Gross realized gains $ 3 $ 73 $ - Gross realized (losses) - (152 ) (6,622 ) N et AFS realized gains (losses) $ 3 $ (79 ) $ (6,622 )
Amortized Cost, Estimated Fair Value, and Unrealized Gains (Losses) of Held to Maturity Securities	The amortized cost, estimated fair value and unrealized gains (losses) of HTM securities are as follows: (In thousands) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value As of December 31, 2020 Federal agency $ 100,000 $ - $ 1,658 $ 98,342 Mortgage-backed: Government-sponsored enterprises 107,914 4,583 - 112,497 U.S. government agency securities 11,533 979 - 12,512 Collateralized mortgage obligations: Government-sponsored enterprises 103,105 4,477 - 107,582 U.S. government agency securities 79,145 3,950 - 83,095 State & municipal 214,863 7,953 17 222,799 Total HTM securities $ 616,560 $ 21,942 $ 1,675 $ 636,827 As of December 31, 2019 Mortgage-backed: Government-sponsored enterprises $ 149,448 $ 3,184 $ 155 $ 152,477 U.S. government agency securities 13,667 584 - 14,251 Collateralized mortgage obligations: Government-sponsored enterprises 189,402 2,165 368 191,199 U.S. government agency securities 110,498 3,256 100 113,654 State & municipal 167,059 2,628 6 169,681 Total HTM securities $ 630,074 $ 11,817 $ 629 $ 641,262
Gains and (Losses) on Equity Securities	The following tables set forth information with regard to gains and (losses) on equity securities: Years Ended December 31, (In thousands) 2020 2019 Net (losses) and gains recognized on equity securities $ (414 ) $ 4,280 Less: Net gains recognized during the period on equity securities sold during the period - 3,966 Unrealized (losses) and gains recognized on equity securities still held $ (414 ) $ 314
Contractual Maturities of Debt Securities	The following tables set forth information with regard to contractual maturities of debt securities at December 31, 2020: (In thousands) Amortized Cost Estimated Fair Value AFS debt securities: Within one year $ 438 $ 449 From one to five years 21,476 22,324 From five to ten years 545,330 551,215 After ten years 751,467 774,710 Total AFS debt securities $ 1,318,711 $ 1,348,698 HTM debt securities: Within one year $ 18,088 $ 18,104 From one to five years 58,963 60,483 From five to ten years 231,927 237,275 After ten years 307,582 320,965 Total HTM debt securities $ 616,560 $ 636,827
Investment Securities with Unrealized Losses	The following table sets forth information with regard to investment securities with unrealized losses, for which an allowance for credit losses has not been recorded at December 31, 2020, Less Than 12 Months 12 Months or Longer Total (In thousands) Fair Value Unrealized Losses Number of Positions Fair Value Unrealized Losses Number of Positions Fair Value Unrealized Losses Number of Positions As of December 31, 2020 AFS securities: Federal agency $ 148,537 $ (2,052 ) 10 $ - $ - - $ 148,537 $ (2,052 ) 10 Mortgage-backed 47,269 (60 ) 3 800 (9 ) 4 48,069 (69 ) 7 Collateralized mortgage obligations 17,837 (58 ) 6 - - - 17,837 (58 ) 6 Total securities with unrealized losses $ 213,643 $ (2,170 ) 19 $ 800 $ (9 ) 4 $ 214,443 $ (2,179 ) 23 HTM securities: Federal agency $ 98,342 $ (1,658 ) 4 $ - $ - - $ 98,342 $ (1,658 ) 4 State & municipal 4,805 (17 ) 5 - - - 4,805 (17 ) 5 Total securities with unrealized losses $ 103,147 $ (1,675 ) 9 $ - $ - - $ 103,147 $ (1,675 ) 9 As of December 31, 2019 AFS securities: Federal agency $ 14,891 $ (109 ) 2 $ 9,866 $ (134 ) 1 $ 24,757 $ (243 ) 3 State & municipal 2,503 (20 ) 1 - - - 2,503 (20 ) 1 Mortgage-backed 67,986 (273 ) 21 37,745 (122 ) 16 105,731 (395 ) 37 Collateralized mortgage obligations 113,121 (316 ) 24 49,632 (559 ) 17 162,753 (875 ) 41 Total securities with unrealized losses $ 198,501 $ (718 ) 48 $ 97,243 $ (815 ) 34 $ 295,744 $ (1,533 ) 82 HTM securities: Mortgage-backed $ - $ - - $ 25,370 $ (155 ) 2 $ 25,370 $ (155 ) 2 Collateralized mortgage obligations 18,040 (181 ) 3 22,389 (287 ) 5 40,429 (468 ) 8 State & municipal 2,257 (6 ) 4 - - - 2,257 (6 ) 4 Total securities with unrealized losses $ 20,297 $ (187 ) 7 $ 47,759 $ (442 ) 7 $ 68,056 $ (629 ) 14

Loans (Tables)

Loans (Tables)	12 Months Ended
	Dec. 31, 2020
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) 2020 2019 Commercial $ 1,267,679 $ 1,302,209 Commercial Real Estate 2,380,358 2,142,057 Paycheck Protection Program 430,810 - Residential Real Estate 1,466,662 1,445,156 Indirect Auto 931,286 1,193,635 Specialty Lending 579,644 542,063 Home Equity 387,974 444,082 Other Consumer 54,472 66,896 Total loans $ 7,498,885 $ 7,136,098
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) 2020 2019 Balance at January 1 $ 2,166 $ 1,638 New loans 1,524 587 Adjustment due to change in composition of related parties 2,448 389 Repayments (202 ) (448 ) Balance at December 31 $ 5,936 $ 2,166

Allowance for Credit Losses a_3

Allowance for Credit Losses and Credit Quality of Loans (Tables)	12 Months Ended
	Dec. 31, 2020
Allowance for Credit Losses and Credit Quality of Loans [Abstract]
Allowance for Loan Losses by Portfolio	The following table illustrate the changes in the allowance for credit losses by our portfolio segments: (In thousands) Commercial Loans Consumer Loans Residential Total Balance as of January 1, 2020 (after adoption of ASC 326) $ 27,156 $ 32,122 $ 16,721 $ 75,999 Charge-offs (4,005 ) (21,938 ) (1,135 ) (27,078 ) Recoveries 786 8,541 618 9,945 Provision 27,005 19,078 5,051 51,134 Ending Balance as of December 31, 2020 $ 50,942 $ 37,803 $ 21,255 $ 110,000 The following tables illustrate the changes in the allowance for loan losses by our portfolio segments: (In thousands) Commercial Loans Consumer Loans Residential Real Estate Total Balance as of December 31, 2018 $ 32,759 $ 37,178 $ 2,568 $ 72,505 Charge-offs (3,151 ) (28,398 ) (991 ) (32,540 ) Recoveries 534 6,913 141 7,588 Provision 4,383 19,954 1,075 25,412 Ending Balance as of December 31, 2019 $ 34,525 $ 35,647 $ 2,793 $ 72,965 Balance as of December 31, 2017 $ 27,606 $ 36,830 $ 5,064 $ 69,500 Charge-offs (3,463 ) (29,752 ) (913 ) (34,128 ) Recoveries 1,178 6,821 306 8,305 Provision 7,438 23,279 (1,889 ) 28,828 Ending Balance as of December 31, 2018 $ 32,759 $ 37,178 $ 2,568 $ 72,505 The following table illustrates the allowance for loan losses and the recorded investment by portfolio segments: (In thousands) Commercial Loans Consumer Loans Residential Real Estate Total As of December 31, 2019 Allowance for loan losses $ 34,525 $ 35,647 $ 2,793 $ 72,965 Allowance for loans individually evaluated for impairment - - - - Allowance for loans collectively evaluated for impairment $ 34,525 $ 35,647 $ 2,793 $ 72,965 Ending balance of loans $ 3,444,266 $ 2,246,676 $ 1,445,156 $ 7,136,098 Ending balance of originated loans individually evaluated for impairment 3,488 7,044 7,721 18,253 Ending balance of acquired loans collectively evaluated for impairment 115,266 23,733 125,879 264,878 Ending balance of originated loans collectively evaluated for impairment $ 3,325,512 $ 2,215,899 $ 1,311,556 $ 6,852,967
Past due and Nonperforming Loans by Loan Class	The following table sets forth information with regard to past due and nonperforming loans by loan segment: (In thousands) 31-60 Days Past Due Accruing 61-90 Days Past Due Accruing Greater Than 90 Days Past Due Accruing Total Past Due Accruing Nonaccrual Current Recorded Total Loans As of December 31, 2020 Commercial Loans: C&I $ 2,235 $ 2,394 $ 23 $ 4,652 $ 4,278 $ 1,116,686 $ 1,125,616 CRE 682 - 470 1,152 19,971 2,391,162 2,412,285 PPP - - - - - 430,810 430,810 Total Commercial Loans $ 2,917 $ 2,394 $ 493 $ 5,804 $ 24,249 $ 3,938,658 $ 3,968,711 Consumer Loans: Auto $ 9,125 $ 1,553 $ 866 $ 11,544 $ 2,730 $ 877,831 $ 892,105 Other Consumer 3,711 1,929 1,272 6,912 290 640,952 648,154 Total Consumer Loans $ 12,836 $ 3,482 $ 2,138 $ 18,456 $ 3,020 $ 1,518,783 $ 1,540,259 Residential $ 2,719 $ 309 $ 518 $ 3,546 $ 17,378 $ 1,968,991 $ 1,989,915 Total Loans $ 18,472 $ 6,185 $ 3,149 $ 27,806 $ 44,647 $ 7,426,432 $ 7,498,885 The following table sets forth information with regard to past due and nonperforming loans by loan class: (In thousands) 31-60 Days Past Due Accruing 61-90 Days Past Due Accruing Greater Than 90 Days Past Due Accruing Total Past Due Accruing Nonaccrual Current Recorded Total Loans As of December 31, 2019 Originated Commercial Loans: C&I $ 1,227 $ - $ - $ 1,227 $ 1,177 $ 838,502 $ 840,906 CRE 3,576 - - 3,576 4,847 1,941,143 1,949,566 Business Banking 794 162 - 956 7,035 530,537 538,528 Total Commercial Loans $ 5,597 $ 162 $ - $ 5,759 $ 13,059 $ 3,310,182 $ 3,329,000 Consumer Loans: Indirect Auto $ 11,860 $ 2,108 $ 1,005 $ 14,973 $ 2,175 $ 1,176,487 $ 1,193,635 Specialty Lending 3,153 2,087 1,307 6,547 - 535,516 542,063 Direct 2,564 564 478 3,606 2,475 481,164 487,245 Total Consumer Loans $ 17,577 $ 4,759 $ 2,790 $ 25,126 $ 4,650 $ 2,193,167 $ 2,222,943 Residential Real Estate $ 1,179 $ 190 $ 663 $ 2,032 $ 5,872 $ 1,311,373 $ 1,319,277 Total Originated Loans $ 24,353 $ 5,111 $ 3,453 $ 32,917 $ 23,581 $ 6,814,722 $ 6,871,220 Acquired Commercial Loans: C&I $ 149 $ - $ - $ 149 $ - $ 19,215 $ 19,364 CRE - - - - - 60,937 60,937 Business Banking 397 287 - 684 382 33,899 34,965 Total Commercial Loans $ 546 $ 287 $ - $ 833 $ 382 $ 114,051 $ 115,266 Consumer Loans: Direct $ 136 $ 58 $ - $ 194 $ 105 $ 23,434 $ 23,733 Total Consumer Loans $ 136 $ 58 $ - $ 194 $ 105 $ 23,434 $ 23,733 Residential Real Estate $ 575 $ 20 $ 264 $ 859 $ 1,106 $ 123,914 $ 125,879 Total Acquired Loans $ 1,257 $ 365 $ 264 $ 1,886 $ 1,593 $ 261,399 $ 264,878 Total Loans $ 25,610 $ 5,476 $ 3,717 $ 34,803 $ 25,174 $ 7,076,121 $ 7,136,098
Financing Receivable Credit Quality by Loan Class	The following tables illustrate the Company’s credit quality by loan class by vintage a (In thousands) 2020 2019 2018 2017 2016 Prior Revolving Loans Amortized Cost Basis Revolving Loans Converted to Term Total C&I By Internally Assigned Grade: Pass $ 331,921 $ 182,329 $ 91,230 $ 41,856 $ 32,625 $ 32,609 $ 322,674 $ 412 $ 1,035,656 Special Mention 20,064 6,534 5,053 4,702 1,624 2,830 13,614 - 54,421 Substandard 338 6,364 10,219 3,388 791 4,272 9,945 14 35,331 Doubtful - - - 207 - 1 - - 208 Total C&I $ 352,323 $ 195,227 $ 106,502 $ 50,153 $ 35,040 $ 39,712 $ 346,233 $ 426 $ 1,125,616 CRE By Internally Assigned Grade: Pass $ 469,919 $ 361,187 $ 256,154 $ 271,874 $ 212,197 $ 383,690 $ 113,128 $ 4,034 $ 2,072,183 Special Mention 2,051 44,034 22,260 55,039 36,830 43,537 1,297 11,524 216,572 Substandard 536 5,307 18,298 15,691 6,018 62,168 1,501 4,642 114,161 Doubtful - 1,897 - - - 7,472 - - 9,369 Total CRE $ 472,506 $ 412,425 $ 296,712 $ 342,604 $ 255,045 $ 496,867 $ 115,926 $ 20,200 $ 2,412,285 PPP By Internally Assigned Grade: Pass $ 430,810 $ - $ - $ - $ - $ - $ - $ - $ 430,810 Total PPP $ 430,810 $ - $ - $ - $ - $ - $ - $ - $ 430,810 Auto By Payment Activity: Performing $ 197,881 $ 314,034 $ 201,850 $ 115,977 $ 45,495 $ 13,250 $ 22 $ - $ 888,509 Nonperforming 359 1,140 1,135 525 437 - - - 3,596 Total Auto $ 198,240 $ 315,174 $ 202,985 $ 116,502 $ 45,932 $ 13,250 $ 22 $ - $ 892,105 Other Consumer By Payment Activity: Performing $ 234,628 $ 178,411 $ 127,549 $ 55,676 $ 14,255 $ 17,414 $ 18,588 $ 71 $ 646,592 Nonperforming 339 418 307 265 90 133 10 - 1,562 Total Other Consumer $ 234,967 $ 178,829 $ 127,856 $ 55,941 $ 14,345 $ 17,547 $ 18,598 $ 71 $ 648,154 Residential By Payment Activity: Performing $ 237,338 $ 210,505 $ 213,437 $ 182,993 $ 164,424 $ 684,495 $ 268,878 $ 9,991 $ 1,972,061 Nonperforming 1,245 659 2,318 2,535 902 10,195 - - 17,854 Total Residential $ 238,583 $ 211,164 $ 215,755 $ 185,528 $ 165,326 $ 694,690 $ 268,878 $ 9,991 $ 1,989,915 Total Loans $ 1,927,429 $ 1,312,819 $ 949,810 $ 750,728 $ 515,688 $ 1,262,066 $ 749,657 $ 30,688 $ 7,498,885 (In thousands) As of December 31, 2019 Originated Commercial Credit Exposure By Internally Assigned Grade: C&I CRE Total Pass $ 782,763 $ 1,868,678 $ 2,651,441 Special Mention 28,380 30,519 58,899 Substandard 29,257 50,369 79,626 Doubtful 506 - 506 Total $ 840,906 $ 1,949,566 $ 2,790,472 Business Banking Credit Exposure Business By Internally Assigned Grade: Banking Total Non-classified $ 524,725 $ 524,725 Classified 13,803 13,803 Total $ 538,528 $ 538,528 Consumer Credit Exposure Specialty By Payment Activity: Indirect Auto Lending Direct Total Performing $ 1,190,455 $ 540,756 $ 484,292 $ 2,215,503 Nonperforming 3,180 1,307 2,953 7,440 Total $ 1,193,635 $ 542,063 $ 487,245 $ 2,222,943 Residential Real Estate Credit Exposure Residential By Payment Activity: Real Estate Total Performing $ 1,312,742 $ 1,312,742 Nonperforming 6,535 6,535 Total $ 1,319,277 $ 1,319,277 Acquired Commercial Credit Exposure By Internally Assigned Grade: C&I CRE Total Pass $ 17,801 $ 60,545 $ 78,346 Special Mention 1,269 - 1,269 Substandard 294 392 686 Total $ 19,364 $ 60,937 $ 80,301 Business Banking Credit Exposure Business By Internally Assigned Grade: Banking Total Non-classified $ 32,030 $ 32,030 Classified 2,935 2,935 Total $ 34,965 $ 34,965 Consumer Credit Exposure By Payment Activity: Direct Total Performing $ 23,628 $ 23,628 Nonperforming 105 105 Total $ 23,733 $ 23,733 Residential Real Estate Credit Exposure Residential By Payment Activity: Real Estate Total Performing $ 124,509 $ 124,509 Nonperforming 1,370 1,370 Total $ 125,879 $ 125,879
Troubled Debt Restructurings on Financing Receivables	The following tables illustrate the recorded investment and number of modifications designated as TDRs, including the recorded investment in the loans prior to a modification and the recorded investment in the loans after restructuring: Year Ended December 31, 2020 (Dollars in thousands) Number of Contracts Pre-Modification Outstanding Recorded Investment Post-Modification Outstanding Recorded Investment Commercial Loans: C&I 1 $ 22 $ 22 Total Commercial Loans 1 $ 22 $ 22 Consumer Loans: Auto 1 $ 44 $ 44 Total Consumer Loans 1 $ 44 $ 44 Residential 35 $ 2,834 $ 2,960 Total Troubled Debt Restructurings 37 $ 2,900 $ 3,026 The following table illustrates the recorded investment and number of modifications for TDRs where a concession has been made and subsequently defaulted during the year: Year Ended December 31, 2020 (Dollars in thousands) Number of Contracts Recorded Investment Commercial Loans: C&I 1 $ 387 CRE 1 168 Total Commercial Loans 2 $ 555 Consumer Loans: Auto 1 $ 6 Total Consumer Loans 1 $ 6 Residential 61 $ 3,213 Total Trouble Debt Restructurings 64 $ 3,774 The following tables illustrate the recorded investment and number of modifications for modified loans, including the recorded investment in the loans prior to a modification and the recorded investment in the loans after restructuring: Year Ended December 31, 2019 (Dollars in thousands) Number of Contracts Pre- Modification Outstanding Recorded Investment Post- Modification Outstanding Recorded Investment Commercial Loans: C&I 1 $ 65 $ 65 CRE 1 402 402 Business Banking 3 425 431 Total Commercial Loans 5 $ 892 $ 898 Consumer Loans: Indirect Auto 9 $ 134 $ 134 Direct 11 450 480 Total Consumer Loans 20 $ 584 $ 614 Residential Real Estate 12 $ 1,032 $ 1,091 Total Troubled Debt Restructurings 37 $ 2,508 $ 2,603 The following table illustrates the recorded investment and number of modifications for TDRs where a concession has been made and subsequently defaulted during the period: Year Ended December 31, 2019 (Dollars in thousands) Number of Contracts Recorded Investment Consumer Loans: Indirect Auto 3 $ 18 Direct 29 1,385 Total Consumer Loans 32 $ 1,403 Residential Real Estate 23 $ 1,203 Total Troubled Debt Restructurings 55 $ 2,606
Impaired Loans and Specific Reserve Allocations	The following table provides information on loans specifically evaluated for impairment: December 31, 2019 (In thousands) Recorded Investment Balance (Book) Unpaid Principal Balance (Legal) Related Allowance Originated With no related allowance recorded: Commercial Loans: C&I $ 76 $ 302 CRE 2,410 2,437 - Business Banking 1,002 1,443 Total Commercial Loans $ 3,488 $ 4,182 Consumer Loans: Indirect Auto $ 154 $ 242 Direct 6,862 8,335 Specialty Lending 28 28 Total Consumer Loans $ 7,044 $ 8,605 Residential Real Estate $ 7,721 $ 9,754 Total $ 18,253 $ 22,541 Total Loans $ 18,253 $ 22,541 $ - The following table summarizes the average recorded investments on loans specifically evaluated for impairment and the interest income recognized: December 31, 2019 December 31, 2018 (In thousands) Average Recorded Investment Interest Income Recognized Average Recorded Investment Interest Income Recognized Originated Commercial Loans: C&I $ 242 $ 1 $ 453 $ 1 CRE 3,311 123 4,078 128 Business Banking 1,089 24 1,018 26 Total Commercial Loans $ 4,642 $ 148 $ 5,549 $ 155 Consumer Loans: Indirect Auto $ 192 $ 10 $ 179 $ 10 Direct 7,387 382 7,922 431 Specialty Lending 7 1 - - Total Consumer Loans $ 7,586 $ 393 $ 8,101 $ 441 Residential Real Estate $ 7,505 $ 350 $ 6,779 $ 305 Total Originated $ 19,733 $ 891 $ 20,429 $ 901 Total Loans $ 19,733 $ 891 $ 20,429 $ 901

Premises, Equipment and Leases

Premises, Equipment and Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Premises, Equipment and Leases [Abstract]
Summary of Premises and Equipment	A summary of premises and equipment follows: December 31, (In thousands) 2020 2019 Land, buildings and improvements $ 125,002 $ 121,479 Equipment 55,195 58,431 Premises and equipment before accumulated depreciation $ 180,197 $ 179,910 Accumulated depreciation 105,991 104,279 Total premises and equipment $ 74,206 $ 75,631
Net Lease Cost	The table below summarizes our net lease cost: December 31, (In thousands) 2020 2019 Operating lease cost $ 7,382 $ 7,239 Variable lease cost 2,141 2,231 Short-term lease cost 453 356 Sublease income (502 ) (448 ) Total premises and equipment $ 9,474 $ 9,378
Future Minimum Rental Commitments Related to Non-cancelable Operating Leases	The table below show future minimum rental commitments related to non-cancelable operating leases for the next five years and thereafter as of December 31, 2020. (In thousands) 2021 $ 7,209 2022 6,339 2023 5,251 2024 4,581 2025 3,411 Thereafter 10,023 Total lease payments $ 36,814 Less: interest (3,990 ) Present value of lease liabilities $ 32,824
Additional Information for Operating Leases	The following table shows the weighted average remaining operating lease term, the weighted average discount rate and supplemental information on the consolidated statements of cash flows for operating leases: December 31, (In thousands except for percent and period data) 2020 2019 Weighted average remaining lease term, in years 7.21 7.69 Weighted average discount rate 3.02 % 3.00 % Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 7,934 $ 6,211 ROU assets obtained in exchange for lease liabilities 3,441 41,008

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Other Intangible Assets [Abstract]
Summary of Goodwill	A summary of goodwill is as follows: (In thousands) January 1, 2020 $ 274,769 Goodwill acquired 5,772 December 31, 2020 $ 280,541 January 1, 2019 $ 274,769 Goodwill acquired - December 31, 2019 $ 274,769
Summary of Core Deposit and Other Intangible Assets	A summary of core deposit and other intangible assets follows: December 31, (In thousands) 2020 2019 Core deposit intangibles: Gross carrying amount $ 8,951 $ 8,951 Less: accumulated amortization 8,463 7,988 Net carrying amount $ 488 $ 963 Identified intangible assets: Gross carrying amount $ 27,057 $ 34,623 Less: accumulated amortization 15,810 23,566 Net carrying amount $ 11,247 $ 11,057 Total intangibles: Gross carrying amount $ 36,008 $ 43,574 Less: accumulated amortization 24,273 31,554 Net carrying amount $ 11,735 $ 12,020

Deposits (Tables)

Deposits (Tables)	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Maturity Distribution of Time Deposits	The following table sets forth the maturity distribution of time deposits: (In thousands) December 31, 2020 Within one year $ 476,983 After one but within two years 77,081 After two but within three years 36,857 After three but within four years 27,888 After four but within five years 14,381 After five years 289 Total $ 633,479

Borrowings (Tables)

Borrowings (Tables)	12 Months Ended
	Dec. 31, 2020
Borrowings [Abstract]
Information Related to Short-term Borrowings	Information related to short-term borrowings is summarized as follows as of December 31: (Dollars in thousands) 2020 2019 2018 Federal funds purchased: Balance at year-end $ - $ 65,000 $ 80,000 Average during the year 14,727 47,137 66,839 Maximum month end balance 40,000 80,000 80,000 Weighted average rate during the year 2.05 % 3.90 % 3.43 % Weighted average rate at year-end - 2.84 % 4.25 % Securities sold under repurchase agreements: Balance at year-end $ 143,386 $ 143,775 $ 160,696 Average during the year 154,383 123,337 146,135 Maximum month end balance 176,840 146,410 170,350 Weighted average rate during the year 0.17 % 0.33 % 0.16 % Weighted average rate at year-end 0.20 % 0.40 % 0.38 % Other short-term borrowings: Balance at year-end $ 25,000 $ 446,500 $ 631,000 Average during the year 183,699 403,453 514,662 Maximum month end balance 366,500 576,000 653,000 Weighted average rate during the year 1.55 % 1.85 % 1.56 % Weighted average rate at year-end 1.99 % 1.73 % 1.82 %
Summary of Long-term Debt	Long-term debt consists of obligations having an original maturity at issuance of more than one year. A majority of the Company’s long-term debt is comprised of FHLB advances collateralized by the FHLB stock owned by the Company, and a blanket lien on its residential real estate mortgage loans. As of December 31, 2020 the Company had no callable long-term debt. A summary is as follows: (Dollars in thousands) December 31, 2020 December 31, 2019 Maturity Amount Weighted Average Rate Amount Weighted Average Rate 2020 $ - - $ 25,000 2.34% 2021 25,003 2.56% 25,021 2.56% 2022 10,598 2.53% 10,598 2.53% 2031 3,496 2.45% 3,592 2.45% Total $ 39,097 $ 64,211
Subordinated Debt	The following table summarizes the Company’s subordinated debt: (Dollars in thousands) December 31, 2020 Subordinated notes issued June 2020 – fixed interest rate of 5.00% through June 2025 and a variable interest rate equivalent to three-month SOFR plus 4.85% thereafter, maturing July 1, 2030 - $ 100,000 Unamortized debt issuance costs (1,948 ) Total subordinated debt, net $ 98,052
Schedule of Debt of VIE where Entity is not Primary Beneficiary	As of December 31, 2020, the Trusts had the following trust preferred securities outstanding and held the following junior subordinated debentures of the Company (dollars in thousands): Description Issuance Date Trust Preferred Securities Outstanding Interest Rate Trust Preferred Debt Owed To Trust Final Maturity Date CNBF Capital Trust I August 1999 $ 18,000 3-month LIBOR plus 2.75% $ 18,720 August 2029 NBT Statutory Trust I November 2005 5,000 3-month LIBOR plus 1.40% 5,155 December 2035 NBT Statutory Trust II February 2006 50,000 3-month LIBOR plus 1.40% 51,547 March 2036 Alliance Financial Capital Trust I December 2003 10,000 3-month LIBOR plus 2.85% 10,310 January 2034 Alliance Financial Capital Trust II September 2006 15,000 3-month LIBOR plus 1.65% 15,464 September 2036

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Taxes [Abstract]
Components of Income Tax Expense Attributable to Operations	The significant components of income tax expense attributable to operations are as follows: Years Ended December 31, (In thousands) 2020 2019 2018 Current Federal $ 36,358 $ 28,475 $ 15,762 State 9,768 7,653 5,977 Total Current $ 46,126 $ 36,128 $ 21,739 Deferred Federal $ (14,021 ) $ (1,379 ) $ 2,281 State (3,406 ) (338 ) 416 Total Deferred $ (17,427 ) $ (1,717 ) $ 2,697 Total income tax expense $ 28,699 $ 34,411 $ 24,436
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) 2020 2019 Deferred tax assets: Allowance for loan losses $ 27,282 $ 18,535 Lease liability 8,141 9,331 Deferred compensation 11,602 8,336 Postretirement benefit obligation 1,511 1,631 Fair value adjustments from acquisitions 259 422 Loan fees 5,400 1,384 Accrued liabilities 1,307 1,176 Stock-based compensation expense 3,213 3,032 Other 3,558 1,498 Total deferred tax assets $ 62,273 $ 45,345 Deferred tax liabilities: Pension benefits $ 14,406 $ 13,014 Lease right-of-use asset 6,567 9,259 Amortization of intangible assets 12,725 12,202 Premises and equipment, primarily due to accelerated depreciation 4,774 5,137 Unrealized gain on securities 7,732 1,770 Other 952 1,429 Total deferred tax liabilities $ 47,156 $ 42,811 Net deferred tax asset at year-end $ 15,117 $ 2,534 Net deferred tax asset at beginning of year 2,534 8,795 Increase (decrease) in net deferred tax asset $ 12,583 $ (6,261 )
Reconciliation of the Provision for Income taxes to the Amount Computed by Applying the Federal Statutory Rate	The following is a reconciliation of the provision for income taxes to the amount computed by applying the applicable Federal statutory rate to income before taxes: Years Ended December 31 (In thousands) 2020 2019 2018 Federal income tax at statutory rate $ 27,948 $ 32,641 $ 28,770 Tax exempt income (981 ) (1,233 ) (1,456 ) Net increase in cash surrender value of life insurance (1,135 ) (927 ) (973 ) Federal tax credit (1,705 ) (1,458 ) (1,499 ) State taxes, net of federal tax benefit 5,026 5,773 5,051 Accounting method changes - tax rate change impact - - (5,326 ) Stock-based compensation, excess tax benefit (152 ) (342 ) (456 ) Other, net (302 ) (43 ) 325 Income tax expense $ 28,699 $ 34,411 $ 24,436
Reconciliation of Gross Unrecognized Tax Benefits	A reconciliation of the beginning and ending balance of Federal and State gross unrecognized tax benefits (“UTBs”) is as follows: (In thousands) 2020 2019 Balance at January 1 $ 779 $ 641 Additions for tax positions of prior years 254 26 Current period tax positions 145 112 Balance at December 31 $ 1,178 $ 779 Amount that would affect the effective tax rate if recognized, gross of tax $ 931 $ 615

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Employee Benefit Plans [Abstract]
Components of Accumulated Other Comprehensive Income (Loss), Net Periodic Benefit Cost	The components of AOCI, which have not yet been recognized as components of net periodic benefit cost, related to pensions and other post-retirement benefits are summarized below: Pension Benefits Other Benefits (In thousands) 2020 2019 2020 2019 Net actuarial loss $ 26,108 $ 28,334 $ 317 $ 125 Prior service cost 378 491 43 94 Total amounts recognized in AOCI (pre-tax) $ 26,486 $ 28,825 $ 360 $ 219
Changes in Benefit Obligations, Changes in Plan Assets, and the Funded Status of the Pension Plans and Postretirement Benefits	A December 31 measurement date is used for the pension, supplemental pension and post-retirement benefit plans. The following table sets forth changes in benefit obligations, changes in plan assets and the funded status of the pension plans and other post-retirement benefits: Pension Benefits Other Benefits (In thousands) 2020 2019 2020 2019 Change in benefit obligation: Benefit obligation at beginning of year $ 90,586 $ 85,134 $ 6,083 $ 7,034 Service cost 1,840 1,723 8 7 Interest cost 3,237 3,942 213 272 Plan participants’ contributions - - 173 201 Actuarial loss (gain) 3,411 6,030 191 (719 ) Curtailments (67 ) - - - Benefits paid (8,813 ) (6,243 ) (669 ) (712 ) Projected benefit obligation at end of year $ 90,194 $ 90,586 $ 5,999 $ 6,083 Change in plan assets: Fair value of plan assets at beginning of year $ 122,995 $ 109,746 $ - $ - Gain on plan assets 12,449 18,120 - - Employer contributions 1,932 1,372 496 511 Plan participants’ contributions - - 173 201 Benefits paid (8,813 ) (6,243 ) (669 ) (712 ) Fair value of plan assets at end of year $ 128,563 $ 122,995 $ - $ - Funded (unfunded) status at year end $ 38,369 $ 32,409 $ (5,999 ) $ (6,083 )
Amounts Recognized in Balance Sheet	An asset is recognized for an overfunded plan and a liability is recognized for an underfunded plan. The accumulated benefit obligation for pension benefits was $90.2 million and $90.6 million at December 31, 2020 and 2019, respectively. The accumulated benefit obligation for other post-retirement benefits was $6.0 million and $6.1 million at December 31, 2020 and 2019, respectively. The funded status of the pension and other post-retirement benefit plans has been recognized as follows in the consolidated balance sheets at December 31, 2020 and 2019. Pension Benefits Other Benefits (In thousands) 2020 2019 2020 2019 Other assets $ 57,456 $ 51,988 $ - $ - Other liabilities (19,087 ) (19,579 ) (5,999 ) (6,083 ) Funded status $ 38,369 $ 32,409 $ (5,999 ) $ (6,083 )
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, 2020 2019 2018 Weighted average assumptions: The following assumptions were used to determine benefit obligations: Discount rate 3.08% - 3.25% 3.69% - 3.73% 4.79% - 4.80% Expected long-term return on plan assets 7.00% 7.00% 7.00% Rate of compensation increase 3.00% 3.00% 3.00% Interest rate of credit for cash balance plan 1.62% 2.28% 3.36% The following assumptions were used to determine net periodic pension cost: Discount rate 3.69% - 3.73% 4.79% - 4.80% 4.20% - 4.21% Expected long-term return on plan assets 7.00% 7.00% 7.00% Rate of compensation increase 3.00% 3.00% 3.00% Interest rate of credit for cash balance plan 2.28% 3.36% 2.80%
Net Periodic Pension Benefits and Other Benefit Costs	Net periodic benefit cost and other amounts recognized in OCI for the years ended December 31 included the following components: Pension Benefits Other Benefits (In thousands) 2020 2019 2018 2020 2019 2018 Components of net periodic (benefit) cost: Service cost $ 1,840 $ 1,723 $ 1,659 $ 8 $ 7 $ 10 Interest cost 3,237 3,942 3,645 213 272 327 Expected return on plan assets (8,410 ) (7,480 ) (8,478 ) - - - Additional gain due to curtailment (74 ) - - - - - Amortization of prior service cost 41 43 40 51 50 51 Amortization of unrecognized net loss 1,535 2,593 930 - - 124 Net periodic pension (benefit) cost $ (1,831 ) $ 821 $ (2,204 ) $ 272 $ 329 $ 512 Other changes in plan assets and benefit obligations recognized in OCI (pre-tax): Net (gain) loss $ (628 ) $ (4,611 ) $ 12,882 $ 192 $ (720 ) $ (762 ) Prior service cost - - 337 - - - Additional gain due to curtailment 7 - - - - - Amortization of prior service cost (41 ) (43 ) (40 ) (51 ) (50 ) (51 ) Amortization of unrecognized net (loss) (1,535 ) (2,593 ) (930 ) - - (124 ) Total recognized in OCI $ (2,197 ) $ (7,247 ) $ 12,249 $ 141 $ (770 ) $ (937 ) Total recognized in net periodic (benefit) cost and OCI, pre-tax $ (4,028 ) $ (6,426 ) $ 10,045 $ 413 $ (441 ) $ (425 )
Estimated Future Benefit Payments for the Pension Plans and Other Postretirement Benefit Plans	The following table sets forth estimated future benefit payments for the pension plans and other post-retirement benefit plans as of December 31, 2020: (In thousands) Pension Benefits Other Benefits 2021 $ 6,910 $ 453 2022 6,977 451 2023 6,807 448 2024 7,083 443 2025 7,409 436 2026 - 2030 33,579 1,962
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 2020 2020 2019 Cash and cash equivalents 0 - 15% 3% 3% Fixed income securities 30 - 60% 38% 40% Equities 40 - 70% 59% 57% Total 100% 100%
Financial Instruments Recorded at Fair Value on a Recurring Basis by the Plan	The following table presents the financial instruments recorded at fair value on a recurring basis by the Plan: (In thousands) Level 1 Level 2 December 31, 2020 Cash and cash equivalents $ 3,461 $ - $ 3,461 Foreign equity mutual funds 41,000 - 41,000 Equity mutual funds 35,637 - 35,637 U.S. government bonds - 47 47 Corporate bonds - 48,418 48,418 Total $ 80,098 $ 48,465 $ 128,563 Level 1 Level 2 December 31, 2019 Cash and cash equivalents $ 4,143 $ - $ 4,143 Foreign equity mutual funds 40,239 - 40,239 Equity mutual funds 29,886 - 29,886 U.S. government bonds - 58 58 Corporate bonds - 48,669 48,669 Total $ 74,268 $ 48,727 $ 122,995

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Stock-Based Compensation [Abstract]
Unvested Restricted Stock Units Activity	The Company has outstanding restricted stock granted from various plans at December 31, 2020. The Company recognized $4.6 million, $4.2 million and $3.9 million in stock-based compensation expense related to these stock awards for the years ended December 31, 2020, 2019 and 2018, respectively. Tax benefits recognized with respect to restricted stock awards and stock units were $1.0 million, $1.1 million and $1.2 million for the years ended December 31, 2020, 2019 and 2018, respectively. Unrecognized compensation cost related to restricted stock units totaled $5.1 million at December 31, 2020 and will be recognized over 1.5 years on a weighted average basis. Shares issued are funded from the Company’s treasury stock. The following table summarizes information for unvested restricted stock units outstanding as of December 31, 2020: Number of Shares Weighted- Average Grant Date Fair Value Unvested at January 1, 2020 555,440 $ 30.11 Forfeited (2,315 ) 34.82 Vested (115,432 ) 29.93 Granted 147,562 28.61 Unvested at December 31, 2020 585,255 $ 29.78
Stock Option Activity	The following table summarizes information concerning stock options outstanding: (In thousands, except share and per share data) Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in Years) Aggregate Intrinsic Value Outstanding at January 1, 2020 33,145 $ 23.73 Exercised (8,845 ) 20.87 Expired (10,500 ) 20.74 Outstanding at December 31, 2020 13,800 $ 27.83 3.36 $ 75 Exercisable at December 31, 2020 13,800 $ 27.83 3.36 $ 75
Cash Proceeds, Tax Benefits and Intrinsic Value of Stock Options Exercised	T here was stock-based compensation expense for stock option awards for the year ended Years Ended December 31, (In thousands) 2020 2019 2018 Proceeds from stock options exercised $ 185 $ 725 $ 999 Tax benefits related to stock options exercised 41 123 173 Intrinsic value of stock options exercised 165 490 692 Fair value of shares vested during the year - 13 16

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Stockholders' Equity [Abstract]
Components of Accumulated Other Comprehensive (Loss) Income	In accordance with GAAP, unrecognized prior service costs and net actuarial gains or losses associated with the Company’s pension and postretirement benefit plans and unrealized gains on derivatives and on AFS securities are included in AOCI, net of tax. For the years ended December 31, components of AOCI are: (In thousands) 2020 2019 2018 Unrecognized prior service cost and net actuarial (losses) on pension plans $ (20,134 ) $ (21,677 ) $ (27,689 ) Unrealized (losses) gains on derivatives (cash flow hedges) (16 ) (32 ) 1,821 Unrealized net holding gains (losses) on AFS securities 20,567 2,683 (17,306 ) AOCI $ 417 $ (19,026 ) $ (43,174 )

Regulatory Capital Requiremen_2

Regulatory Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2020
Regulatory Capital Requirements [Abstract]
Compliance with Regulatory Compliance Requirements Under Banking Regulations	The Company and NBT Bank’s actual capital amounts and ratios are presented as follows: Actual Regulatory Ratio Requirements (Dollars in thousands) Amount Ratio Minimum Capital Adequacy Minimum plus Buffer For Classification as Well- Capitalized As of December 31, 2020 Tier I Capital (to average assets) Company $ 1,018,320 9.56 % 4.00 % 5.00 % NBT Bank 1,054,097 9.95 % 4.00 % 5.00 % Common Equity Tier 1 Capital Company 921,320 11.84 % 4.50 % 7.00 % 6.50 % NBT Bank 1,054,097 13.67 % 4.50 % 7.00 % 6.50 % Tier I Capital (to risk-weighted assets) Company 1,018,320 13.09 % 6.00 % 8.50 % 8.00 % NBT Bank 1,054,097 13.67 % 6.00 % 8.50 % 8.00 % Total Capital (to risk-weighted assets) Company 1,215,672 15.62 % 8.00 % 10.50 % 10.00 % NBT Bank 1,150,544 14.93 % 8.00 % 10.50 % 10.00 % As of December 31, 2019 Tier I Capital (to average assets) Company $ 963,147 10.33 % 4.00 % 5.00 % NBT Bank 894,407 9.64 % 4.00 % 5.00 % Common Equity Tier 1 Capital Company 866,147 11.29 % 4.50 % 7.00 % 6.50 % NBT Bank 894,407 11.76 % 4.50 % 7.00 % 6.50 % Tier I Capital (to risk-weighted assets) Company 963,147 12.56 % 6.00 % 8.50 % 8.00 % NBT Bank 894,407 11.76 % 6.00 % 8.50 % 8.00 % Total Capital (to risk-weighted assets) Company 1,037,041 13.52 % 8.00 % 10.50 % 10.00 % NBT Bank 968,301 12.73 % 8.00 % 10.50 % 10.00 %

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Reconciliation of Basic and Diluted Earnings Per Share	The following is a reconciliation of basic and diluted EPS for the years presented in the consolidated statements of income: Years Ended December 31, 2020 2019 2018 (In thousands except per share data) Net Income Weighted Average Shares Per Share Amount Net Income Weighted Average Shares Per Share Amount Net Income Weighted Average Shares Per Share Amount Basic EPS $ 104,388 43,693 $ 2.39 $ 121,021 43,815 $ 2.76 $ 112,566 43,701 $ 2.58 Effect of dilutive securities: Stock-based compensation 296 309 319 Diluted EPS $ 104,388 43,989 $ 2.37 $ 121,021 44,124 $ 2.74 $ 112,566 44,020 $ 2.56

Reclassification Adjustments _2

Reclassification Adjustments Out of Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2020
Reclassification Adjustments Out of Other Comprehensive Income (Loss) [Abstract]
Reclassification Adjustments out of AOCI	The following table summarizes the reclassification adjustments out of AOCI: Detail About AOCI Components Amount Reclassified From AOCI Affected Line Item in the Consolidated Statements of Comprehensive Income (Loss) (In thousands) Years Ended December 31, 2020 2019 2018 AFS securities: (Gains) losses on AFS securities $ (3 ) $ 79 $ 6,622 Net securities (gains) losses Amortization of unrealized gains related to securities transfer 644 737 688 Interest income Tax effect $ (160 ) $ (204 ) $ (1,827 ) Income tax (benefit) Net of tax $ 481 $ 612 $ 5,483 Cash flow hedges: Net unrealized losses (gains) on cash flow hedges reclassified to interest expense $ 296 $ (2,012 ) $ (2,300 ) Interest expense Tax effect $ (74 ) $ 503 $ 575 Income tax (benefit) expense Net of tax $ 222 $ (1,509 ) $ (1,725 ) Pension and other benefits: Amortization of net losses $ 1,535 $ 2,593 $ 1,054 Other noninterest expense Amortization of prior service costs 92 93 91 Other noninterest expense Tax effect $ (407 ) $ (672 ) $ (286 ) Income tax (benefit) Net of tax $ 1,220 $ 2,014 $ 859 Total reclassifications, net of tax $ 1,923 $ 1,117 $ 4,617

Commitments and Contingent Li_2

Commitments and Contingent Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingent Liabilities [Abstract]
Maximum Commitments Potential Obligation	The Company is a party to certain financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit, unused lines of credit, standby letters of credit and certain agricultural real estate loans sold to investors with recourse, with the sold portion having a government guarantee that is assignable back to the Company upon repurchase of the loan in the event of default. The Company’s exposure to credit loss in the event of nonperformance by the other party to the commitments to extend credit, unused lines of credit, standby letters of credit and loans sold with recourse is represented by the contractual amount of those instruments. The credit risk associated with commitments to extend credit and standby and commercial letters of credit is essentially the same as that involved with extending loans to customers and is subject to normal credit policies. Collateral may be obtained based on management’s assessment of the customer’s creditworthiness. At December 31, (In thousands) 2020 2019 Unused lines of credit $ 351,876 $ 340,703 Commitments to extend credits, primarily variable rate 1,831,671 1,579,414 Standby letters of credit 54,009 34,479 Loans sold with recourse 25,659 25,639

Derivative Instruments and He_2

Derivative Instruments and Hedging Activities (Tables)	12 Months Ended
	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value Adjustment Recorded Related to Notional Amount of Derivatives Outstanding and Notional Amount of Risk Participation Agreements	The following table depicts the fair value adjustment recorded related to the notional amount of derivatives outstanding as well as the notional amount of risk participation agreements: December 31, (In thousands) 2020 2019 Derivatives Not Designated as Hedging Instruments: Fair value adjustment included in other assets and other liabilities Interest rate derivatives $ 108,487 $ 41,650 Notional amount Interest rate derivatives 2,447,168 963,209 Risk participation agreements 112,313 97,614 Derivatives Designated as Hedging Instruments: Fair value adjustment included in other assets Interest rate derivatives - 4 Fair value adjustment included in other liabilities Interest rate derivatives 34 45 Notional amount Interest rate derivatives 25,000 50,000
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Effect of Derivatives on AOCI and on Consolidated Statement of Income	The following table indicates the effect of cash flow hedge accounting on AOCI and on the consolidated statement of income: December 31, (In thousands) 2020 2019 2018 Derivatives Designated as Hedging Instruments: Interest rate derivatives - included component Amount of (loss) gain recognized in OCI $ (275 ) $ (459 ) $ 1,218 Amount of loss (gain) reclassified from AOCI into interest expense 296 (2,012 ) (2,300 )
Not Designated as Hedging Instrument [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Effect of Derivatives on AOCI and on Consolidated Statement of Income	The following table indicates the gain or loss recognized in income on derivatives not designated as a hedging relationship: December 31, (In thousands) 2020 2019 2018 Derivatives Not Designated as Hedging Instruments: Increase (decrease) in other income $ 1 $ 295 $ (120 )

Fair Values of Financial Inst_3

Fair Values of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Values of Financial Instruments [Abstract]
Fair Value of Financial Assets and Liabilities Measured on a Recurring Basis	The following tables sets forth the Company’s financial assets and liabilities measured on a recurring basis that were accounted for at fair value. Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement: (In thousands) Level 1 Level 2 Level 3 December 31, 2020 Assets: AFS securities: Federal agency $ - $ 243,597 $ - $ 243,597 State & municipal - 43,180 - 43,180 Mortgage-backed - 595,839 - 595,839 Collateralized mortgage obligations - 437,804 - 437,804 Corporate - 28,278 - 28,278 Total AFS securities $ - $ 1,348,698 $ - $ 1,348,698 Equity securities 28,737 2,000 - 30,737 Derivatives - 108,779 - 108,779 Total $ 28,737 $ 1,459,477 $ - $ 1,488,214 Liabilities: Derivatives $ - $ 108,646 $ - $ 108,646 Total $ - $ 108,646 $ - $ 108,646 (In thousands) Level 1 Level 2 Level 3 December 31, 2019 Assets: AFS securities: Federal agency $ - $ 34,758 $ - $ 34,758 State & municipal - 2,513 - 2,513 Mortgage-backed - 503,626 - 503,626 Collateralized mortgage obligations - 434,443 - 434,443 Total AFS securities $ - $ 975,340 $ - $ 975,340 Equity securities 23,771 4,000 - 27,771 Derivatives - 41,766 - 41,766 Total $ 23,771 $ 1,021,106 $ - $ 1,044,877 Liabilities: Derivatives $ - $ 41,777 $ - $ 41,777 Total $ - $ 41,777 $ - $ 41,777
Information with Regard to Estimated Fair Values of Financial Instruments	The following table sets forth information with regard to estimated fair values of financial instruments. This table excludes financial instruments for which the carrying amount approximates fair value. Financial instruments for which the fair value approximates carrying value include cash and cash equivalents, AFS securities, equity securities, accrued interest receivable, non-maturity deposits, short-term borrowings, accrued interest payable and derivatives. December 31, 2020 December 31, 2019 (In thousands) Fair Value Hierarchy Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value Financial assets: HTM securities 2 $ 616,560 $ 636,827 $ 630,074 $ 641,262 Net loans 3 7,390,004 7,530,033 7,074,864 6,999,690 Financial liabilities: Time deposits 2 $ 633,479 $ 638,721 $ 861,193 $ 858,085 Long-term debt 2 39,097 39,820 64,211 64,373 Subordinated debt 1 100,000 103,277 - - Junior subordinated debt 2 101,196 108,926 101,196 105,694

Parent Company Financial Info_2

Parent Company Financial Information (Tables)	12 Months Ended
	Dec. 31, 2020
Parent Company Financial Information [Abstract]
Parent Company Financial Information	Condensed Balance Sheets December 31, (In thousands) 2020 2019 Assets Cash and cash equivalents $ 37,915 $ 9,387 Equity securities, at estimated fair value 25,111 22,441 Investment in subsidiaries, on equity basis 1,345,317 1,209,752 Other assets 30,577 30,855 Total assets $ 1,438,920 $ 1,272,435 Liabilities and Stockholders’ Equity Total liabilities $ 251,302 $ 152,038 Stockholders’ equity 1,187,618 1,120,397 Total liabilities and stockholders’ equity $ 1,438,920 $ 1,272,435 Condensed Statements of Income Years Ended December 31, (In thousands) 2020 2019 2018 Dividends from subsidiaries $ 77,000 $ 50,200 $ 43,000 Management fee from subsidiaries 4,151 7,981 7,907 Net securities (losses) gains (483 ) 165 399 Interest, dividends and other income 824 876 905 Total revenue $ 81,492 $ 59,222 $ 52,211 Operating expenses 11,825 14,262 14,226 Income before income tax benefit and equity in undistributed income of subsidiaries $ 69,667 $ 44,960 $ 37,985 Income tax benefit (2,653 ) (1,588 ) (1,608 ) Equity in undistributed income of subsidiaries 32,068 74,473 72,973 Net income $ 104,388 $ 121,021 $ 112,566 Condensed Statements of Cash Flow Years Ended December 31, (In thousands) 2020 2019 2018 Operating activities Net income $ 104,388 $ 121,021 $ 112,566 Adjustments to reconcile net income to net cash provided by operating activities Depreciation and amortization of premises and equipment 1,739 2,298 2,814 Excess tax benefit on stock-based compensation (181 ) (409 ) (543 ) Stock-based compensation expense 4,581 4,210 3,936 Net securities losses (gains) 483 (165 ) (399 ) Equity in undistributed income of subsidiaries (32,068 ) (74,473 ) (72,973 ) Bank owned life insurance income (391 ) (398 ) (424 ) Amortization of subordinated debt issuance costs 230 - - Net change in other assets and other liabilities (3,535 ) (1,573 ) (6,124 ) Net cash provided by operating activities $ 75,246 $ 50,511 $ 38,853 Investing activities Investment in the Bank $ (90,000 ) $ - $ - Proceeds from calls of equity securities 2,000 - - Proceeds on sales of equity securities - - 3,318 Purchases of equity securities - (93 ) (2 ) Net cash (used in) provided by investing activities $ (88,000 ) $ (93 ) $ 3,316 Financing activities Proceeds from issuance of subordinated debt $ 100,000 $ - $ - Payment of subordinated debt issuance costs (2,178 ) - - Proceeds from the issuance of shares to employee and other stock plans 184 725 1,296 Cash paid by employer for tax-withholding on stock issuance (1,537 ) (1,622 ) (1,893 ) Purchases of treasury shares (7,980 ) - - Cash dividends (47,207 ) (46,010 ) (43,269 ) Net cash provided by (used in) financing activities $ 41,282 $ (46,907 ) $ (43,866 ) Net increase (decrease) in cash and cash equivalents $ 28,528 $ 3,511 $ (1,697 ) Cash and cash equivalents at beginning of year 9,387 5,876 7,572 Cash and cash equivalents at end of year $ 37,915 $ 9,387 $ 5,876

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)Loan	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Loans [Abstract]
Minimum number of days past due for loans to be considered nonperforming	90 days
Period of sustained repayment performance for nonperforming TDRs to be returned to performing status	6 months
Other Financial Instruments [Abstract]
Standby letters of credit expiration period	1 year
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	$ 140,921	$ 134,455	$ 126,012
Total noninterest income out-of-scope of ASC 606	5,355	9,568	(1,250)
Total noninterest income	$ 146,276	144,023	124,762
Minimum [Member]
Allowance for Credit Losses [Abstract]
Threshold period past due for loans to be written off	90 days
Maximum [Member]
Allowance for Credit Losses [Abstract]
Threshold period past due for loans to be written off	120 days
Paycheck Protection Program [Member]
Allowance for Credit Losses [Abstract]
Number of loans processed | Loan	3,000
Paycheck Protection Program [Member] | Minimum [Member]
Allowance for Credit Losses [Abstract]
Amount of loans processed	$ 548,000
COVID-19 [Member]
Loans [Abstract]
Loans in modification programs related to COVID-19	110,800
Service Charges on Deposit Accounts [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	13,201	17,151	17,224
ATM and Debit Card Fees [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	25,960	23,893	22,699
Retirement Plan Administration Fees [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	35,851	30,388	26,992
Wealth Management [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	29,247	28,400	28,747
Insurance [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	14,757	15,770	15,122
Other [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	$ 21,905	$ 18,853	$ 15,228
Commercial Loans [Member] | Commercial Real Estate [Member] | Maximum [Member]
Allowance for Credit Losses [Abstract]
Loan amount, percentage of appraised value or purchase price of the property	80.00%
Consumer Loans [Member] | Auto [Member] | Minimum [Member]
Allowance for Credit Losses [Abstract]
Principal repayment term of loan	3 years
Consumer Loans [Member] | Auto [Member] | Maximum [Member]
Allowance for Credit Losses [Abstract]
Principal repayment term of loan	6 years
Consumer Loans [Member] | Installment Loans [Member] | Minimum [Member]
Allowance for Credit Losses [Abstract]
Principal repayment term of loan	1 year
Consumer Loans [Member] | Installment Loans [Member] | Maximum [Member]
Allowance for Credit Losses [Abstract]
Principal repayment term of loan	15 years
Residential [Member] | Maximum [Member]
Allowance for Credit Losses [Abstract]
Loan amount, percentage of appraised value or purchase price of the property	85.00%
Residential [Member] | Home Equity [Member] | Maximum [Member]
Allowance for Credit Losses [Abstract]
Loan amount, percentage of equity in property	85.00%
Term of draw	10 years
Term of amortization	15 years

Recent Accounting Pronounceme_3

Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019
Recent Accounting Pronouncements [Abstract]
Retained earnings		$ 749,056	$ 696,214
Allowance for credit losses	[1]	110,000
COVID-19 [Member]
Recent Accounting Pronouncements [Abstract]
Loans in modification programs related to COVID-19		110,800
ASU 2016-13 [Member]
Recent Accounting Pronouncements [Abstract]
Allowance for credit losses		$ 110,000	75,999
ASU 2016-13 [Member] | Cumulative Effect Adjustment for ASU Implementation [Member]
Recent Accounting Pronouncements [Abstract]
Retained earnings			(4,300)
Allowance for credit losses			3,000
Allowance for credit losses on off-balance sheet credit exposure			2,800
Deferred tax asset			$ (1,500)
[1]	Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.

Acquisitions (Details)

Acquisitions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisitions [Abstract]
Goodwill acquired	$ 5,772	$ 0
Alliance Benefit Group of Illinois, Inc. [Member]
Business Acquisitions [Abstract]
Total consideration paid	9,100
Goodwill acquired	5,800
Contingent consideration, liability	$ 5,100
Retirement Plan Services, LLC [Member]
Business Acquisitions [Abstract]
Total consideration paid			$ 13,000
Goodwill acquired			6,700
Contingent consideration, liability			$ 5,100

Securities, Available for Sale

Securities, Available for Sale (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt securities, available-for-sale [Abstract]
Amortized cost	$ 1,318,711	$ 968,554
Unrealized gains	32,166	8,319
Unrealized losses	2,179	1,533
Estimated fair value	1,348,698	975,340
Allowance for credit losses on AFS securities	0
Components of net realized gains (losses) on sale of AFS securities [Abstract]
Gross realized gains	3	73	$ 0
Gross realized (losses)	0	(152)	(6,622)
Net AFS realized gains (losses)	3	(79)	(6,622)
Gains from calls on securities available for sale	3	25	$ 0
Federal Agency [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	245,590	34,998
Unrealized gains	59	3
Unrealized losses	2,052	243
Estimated fair value	243,597	34,758
State & Municipal [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	42,550	2,533
Unrealized gains	630	0
Unrealized losses	0	20
Estimated fair value	43,180	2,513
Mortgage-Backed, Government Sponsored Enterprises [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	521,448	453,614
Unrealized gains	17,079	4,982
Unrealized losses	22	239
Estimated fair value	538,505	458,357
Mortgage-backed Securities, U.S. Government Agency Securities [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	55,049	44,758
Unrealized gains	2,332	667
Unrealized losses	47	156
Estimated fair value	57,334	45,269
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	311,710	328,499
Unrealized gains	7,549	1,949
Unrealized losses	58	467
Estimated fair value	319,201	329,981
Collateralized Mortgage Obligations, U.S. Government Agency Securities [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	114,864	104,152
Unrealized gains	3,739	718
Unrealized losses	0	408
Estimated fair value	118,603	$ 104,462
Corporate [Member]
Debt securities, available-for-sale [Abstract]
Amortized cost	27,500
Unrealized gains	778
Unrealized losses	0
Estimated fair value	$ 28,278

Securities, Held to Maturity (D

Securities, Held to Maturity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	$ 616,560	$ 630,074
Unrealized gains	21,942	11,817
Unrealized losses	1,675	629
Estimated fair value	636,827	641,262
Allowance for credit losses on HTM securities	0
Transactions of HTM securities [Abstract]
Gains from calls on HTM securities	24	12	$ 0
Held-to-maturity securities sold, amortized cost	1,000	0	$ 0
Held-to-maturity securities sold, realized loss	1
Federal Agency [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	100,000
Unrealized gains	0
Unrealized losses	1,658
Estimated fair value	98,342
Mortgage-backed Securities, Government-Sponsored Enterprises [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	107,914	149,448
Unrealized gains	4,583	3,184
Unrealized losses	0	155
Estimated fair value	112,497	152,477
Mortgage-Backed, U.S. Government Agency Securities [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	11,533	13,667
Unrealized gains	979	584
Unrealized losses	0	0
Estimated fair value	12,512	14,251
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	103,105	189,402
Unrealized gains	4,477	2,165
Unrealized losses	0	368
Estimated fair value	107,582	191,199
Collateralized Mortgage Obligations, U.S. Government Agency Securities [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	79,145	110,498
Unrealized gains	3,950	3,256
Unrealized losses	0	100
Estimated fair value	83,095	113,654
State & Municipal [Member]
Held-to-maturity securities, fair value to amortized cost [Abstract]
Amortized cost	214,863	167,059
Unrealized gains	7,953	2,628
Unrealized losses	17	6
Estimated fair value	222,799	169,681
Public Deposits and Other Purposes [Member]
Securities pledged [Abstract]
Amortized costs of securities available for sale and held to maturity pledged	1,400,000	1,300,000
Securities Sold under Repurchase Agreements [Member]
Securities pledged [Abstract]
Amortized costs of securities available for sale and held to maturity pledged	$ 305,200	$ 189,800

Securities, Gains and (Losses)

Securities, Gains and (Losses) on Equity Securities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)Issuer	Dec. 31, 2019USD ($)Issuer
Gains (losses) on equity securities [Abstract]
Net (losses) and gains recognized on equity securities	$ (414)	$ 4,280
Less: Net gains recognized during the period on equity securities sold during the period	0	3,966
Unrealized (losses) and gains recognized on equity securities still held	(414)	314
Equity Securities without Readily Determinable Fair Value, Annual Amount [Abstract]
Carrying amount of equity securities without readily determinable fair values	2,000	4,000
Impairment adjustments of equity securities without readily determinable fair values	0	0
Downward adjustments of equity securities without readily determinable fair values	0	0
Upward adjustments of equity securities without readily determinable fair values	$ 0	$ 0
Number of issuers whose holdings exceeded 10% of consolidated stockholders' equity, excluding U.S. Government securities | Issuer	0	0
Visa Class B Common Stock [Member]
Equity Securities without Readily Determinable Fair Value, Annual Amount [Abstract]
Gain from sale of equity securities without readily determinable fair value		$ 4,000

Securities, AFS Debt Securities

Securities, AFS Debt Securities, Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Available-for-sale Securities, Debt Maturities, Amortized Cost [Abstract]
Within one year	$ 438
From one to five years	21,476
From five to ten years	545,330
After ten years	751,467
Amortized cost	1,318,711	$ 968,554
Available-for-sale Securities, Debt Maturities, Estimated Fair Value [Abstract]
Within one year	449
From one to five years	22,324
From five to ten years	551,215
After ten years	774,710
Fair value	$ 1,348,698	$ 975,340

Securities, HTM Debt Securities

Securities, HTM Debt Securities, Contractual Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Held-to-maturity Securities, Debt Maturities, Amortized Cost [Abstract]
Within one year	$ 18,088
From one to five years	58,963
From five to ten years	231,927
After ten years	307,582
Amortized cost	616,560	$ 630,074
Held-to-maturity Securities, Debt Maturities, Estimated Fair Value [Abstract]
Within one year	18,104
From one to five years	60,483
From five to ten years	237,275
After ten years	320,965
Fair value	$ 636,827	$ 641,262

Securities, AFS Securities in C

Securities, AFS Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2020USD ($)Position	Dec. 31, 2019USD ($)Position
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 213,643	$ 198,501
12 months or longer	800	97,243
Total	214,443	295,744
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(2,170)	(718)
12 months or longer	(9)	(815)
Total	$ (2,179)	$ (1,533)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	19	48
12 months or longer | Position	4	34
Total | Position	23	82
AIR on AFS debt securities	$ 3,300
Federal Agency [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	148,537	$ 14,891
12 months or longer	0	9,866
Total	148,537	24,757
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(2,052)	(109)
12 months or longer	0	(134)
Total	$ (2,052)	$ (243)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	10	2
12 months or longer | Position	0	1
Total | Position	10	3
State & Municipal [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months		$ 2,503
12 months or longer		0
Total		2,503
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months		(20)
12 months or longer		0
Total		$ (20)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position		1
12 months or longer | Position		0
Total | Position		1
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 47,269	$ 67,986
12 months or longer	800	37,745
Total	48,069	105,731
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(60)	(273)
12 months or longer	(9)	(122)
Total	$ (69)	$ (395)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	3	21
12 months or longer | Position	4	16
Total | Position	7	37
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 17,837	$ 113,121
12 months or longer	0	49,632
Total	17,837	162,753
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(58)	(316)
12 months or longer	0	(559)
Total	$ (58)	$ (875)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	6	24
12 months or longer | Position	0	17
Total | Position	6	41

Securities, HTM Securities in C

Securities, HTM Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)Position	Dec. 31, 2019USD ($)Position
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 103,147	$ 20,297
12 months or longer	0	47,759
Total	103,147	68,056
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(1,675)	(187)
12 months or longer	0	(442)
Total	$ (1,675)	$ (629)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	9	7
12 months or longer | Position	0	7
Total | Position	9	14
Held-to-maturity, past due	$ 0
Accrued interest reversed against interest income	0
Collateral-dependent HTM debt securities	0
AIR on HTM debt securities	2,700
Federal Agency [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	98,342
12 months or longer	0
Total	98,342
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(1,658)
12 months or longer	0
Total	$ (1,658)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	4
12 months or longer | Position	0
Total | Position	4
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months		$ 0
12 months or longer		25,370
Total		25,370
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months		0
12 months or longer		(155)
Total		$ (155)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position		0
12 months or longer | Position		2
Total | Position		2
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months		$ 18,040
12 months or longer		22,389
Total		40,429
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months		(181)
12 months or longer		(287)
Total		$ (468)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position		3
12 months or longer | Position		5
Total | Position		8
State & Municipal [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 4,805	$ 2,257
12 months or longer	0	0
Total	4,805	2,257
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	(17)	(6)
12 months or longer	0	0
Total	$ (17)	$ (6)
Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	5	4
12 months or longer | Position	0	0
Total | Position	5	4
US Government Agencies Debt Securities and US Government-sponsored Enterprises Debt Securities [Member]
Unrealized Loss Position, Number of Positions [Abstract]
Held-to-maturity debt securities, percentage	65.00%

Loans (Details)

Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Summary of Loans [Abstract]
Net Loans	$ 7,498,885	$ 7,136,098
Deferred loan origination costs, net	9,400	35,300
Residential loans held for sale	1,100	11,500
Loans serviced for unrelated third parties	614,500	612,300
Mortgage servicing rights	1,300	800
Loans and Leases Receivable, Related Parties [Roll Forward]
Balance at January 1	2,166	1,638
New loans	1,524	587
Adjustment due to change in composition of related parties	2,448	389
Repayments	(202)	(448)
Balance at December 31	5,936	2,166
Commercial [Member]
Summary of Loans [Abstract]
Net Loans	1,267,679	1,302,209
Commercial Real Estate [Member]
Summary of Loans [Abstract]
Net Loans	2,380,358	2,142,057
Paycheck Protection Program [Member]
Summary of Loans [Abstract]
Net Loans	430,810	0
Residential Real Estate [Member]
Summary of Loans [Abstract]
Net Loans	1,466,662	1,445,156
Indirect Auto [Member]
Summary of Loans [Abstract]
Net Loans	931,286	1,193,635
Specialty Lending [Member]
Summary of Loans [Abstract]
Net Loans	579,644	542,063
Home Equity [Member]
Summary of Loans [Abstract]
Net Loans	387,974	444,082
Other Consumer [Member]
Summary of Loans [Abstract]
Net Loans	54,472	66,896
Agricultural and Agricultural Real Estate Mortgages [Member]
Summary of Loans [Abstract]
Loans serviced for unrelated third parties	$ 25,700	$ 25,600

Allowance for Credit Losses a_4

Allowance for Credit Losses and Credit Quality of Loans (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Allowance for Credit Losses [Abstract]
Allowance for credit losses	[1]	$ 110,000
Allowance for credit losses			$ 72,965	[1]	$ 72,505	$ 69,500
Retained earnings		749,056	$ 696,214
Loans purchased with credit deterioration		$ 0
Percentage of allowance of credit losses		1.47%	1.02%
Provision for loan and lease losses		$ 51,100	$ 25,400
ASU 2016-13 [Member]
Allowance for Credit Losses [Abstract]
Allowance for credit losses		110,000	75,999
ASU 2016-13 [Member] | Loans [Member]
Allowance for Credit Losses [Abstract]
Allowance for credit losses		3,000
Retained earnings		(2,300)
Deferred tax asset		700
ASU 2016-13 [Member] | Accrued Interest Receivable [Member]
Allowance for Credit Losses [Abstract]
Allowance for credit losses		600
AIR on loans		$ 23,700
Write-off of uncollectible interest period		120 days
Consumer Loans [Member]
Allowance for Credit Losses [Abstract]
Allowance for credit losses			35,647		$ 37,178	$ 36,830
Amount of loans purchased		$ 51,900
Discount on loans purchased		1.00%
Allowance for credit losses on loans purchased		$ 3,600
Consumer Loans [Member] | ASU 2016-13 [Member]
Allowance for Credit Losses [Abstract]
Allowance for credit losses		$ 37,803	$ 32,122
[1]	Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.

Allowance for Credit Losses a_5

Allowance for Credit Losses and Credit Quality of Loans, Allowance for Loan Losses by Portfolio Segments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Activity in allowance for credit losses by portfolio segment [Roll Forward]
Balance, end of period	$ 110,000	[1]
ASU 2016-13 [Member]
Activity in allowance for credit losses by portfolio segment [Roll Forward]
Balance, beginning of period	75,999
Charge-offs	(27,078)
Recoveries	9,945
Provision	51,134
Balance, end of period	110,000
Commercial Loans [Member] | ASU 2016-13 [Member]
Activity in allowance for credit losses by portfolio segment [Roll Forward]
Balance, beginning of period	27,156
Charge-offs	(4,005)
Recoveries	786
Provision	27,005
Balance, end of period	50,942
Consumer Loans [Member] | ASU 2016-13 [Member]
Activity in allowance for credit losses by portfolio segment [Roll Forward]
Balance, beginning of period	32,122
Charge-offs	(21,938)
Recoveries	8,541
Provision	19,078
Balance, end of period	37,803
Residential Real Estate [Member] | ASU 2016-13 [Member]
Activity in allowance for credit losses by portfolio segment [Roll Forward]
Balance, beginning of period	16,721
Charge-offs	(1,135)
Recoveries	618
Provision	5,051
Balance, end of period	$ 21,255
[1]	Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.

Allowance for Credit Losses a_6

Allowance for Credit Losses and Credit Quality of Loans, Past Due Loans (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)Relationship	Dec. 31, 2019USD ($)Relationship
Allowance for Credit Losses and Credit Quality of Loans [Abstract]
Individually evaluated loans, number of relationships | Relationship	5	0
Individually evaluated loans, amortized cost	$ 15,200
Individually evaluated loans, allowance for credit losses	3,200
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	27,806	$ 34,803
Nonaccrual	44,647	25,174
Current	7,426,432	7,076,121
Recorded total loans	7,498,885	7,136,098
Loans in non-accrual without an allowance for credit losses	$ 0
Minimum number of days past due for loans to be considered nonperforming	90 days
31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	$ 18,472	25,610
61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	6,185	5,476
Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	3,149	3,717
Indirect Auto [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded total loans	931,286	1,193,635
Specialty Lending [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Recorded total loans	579,644	542,063
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	5,804
Nonaccrual	24,249
Current	3,938,658
Recorded total loans	3,968,711
Commercial Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,917
Commercial Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,394
Commercial Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	493
Commercial Loans [Member] | C&I [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	4,652
Nonaccrual	4,278
Current	1,116,686
Recorded total loans	1,125,616
Commercial Loans [Member] | C&I [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,235
Commercial Loans [Member] | C&I [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,394
Commercial Loans [Member] | C&I [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	23
Commercial Loans [Member] | CRE [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,152
Nonaccrual	19,971
Current	2,391,162
Recorded total loans	2,412,285
Commercial Loans [Member] | CRE [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	682
Commercial Loans [Member] | CRE [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0
Commercial Loans [Member] | CRE [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	470
Commercial Loans [Member] | PPP [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0
Nonaccrual	0
Current	430,810
Recorded total loans	430,810
Commercial Loans [Member] | PPP [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0
Commercial Loans [Member] | PPP [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0
Commercial Loans [Member] | PPP [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	0
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	18,456
Nonaccrual	3,020
Current	1,518,783
Recorded total loans	1,540,259
Consumer Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	12,836
Consumer Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	3,482
Consumer Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,138
Consumer Loans [Member] | Auto [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	11,544
Nonaccrual	2,730
Current	877,831
Recorded total loans	892,105
Consumer Loans [Member] | Auto [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	9,125
Consumer Loans [Member] | Auto [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,553
Consumer Loans [Member] | Auto [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	866
Consumer Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	6,912
Nonaccrual	290
Current	640,952
Recorded total loans	648,154
Consumer Loans [Member] | Other Consumer [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	3,711
Consumer Loans [Member] | Other Consumer [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,929
Consumer Loans [Member] | Other Consumer [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	1,272
Residential [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	3,546
Nonaccrual	17,378
Current	1,968,991
Recorded total loans	1,989,915
Residential [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	2,719
Residential [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	309
Residential [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing	$ 518
Originated Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		32,917
Nonaccrual		23,581
Current		6,814,722
Recorded total loans		6,871,220
Originated Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		24,353
Originated Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		5,111
Originated Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		3,453
Originated Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		5,759
Nonaccrual		13,059
Current		3,310,182
Recorded total loans		3,329,000
Originated Loans [Member] | Commercial Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		5,597
Originated Loans [Member] | Commercial Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		162
Originated Loans [Member] | Commercial Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		1,227
Nonaccrual		1,177
Current		838,502
Recorded total loans		840,906
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		1,227
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		3,576
Nonaccrual		4,847
Current		1,941,143
Recorded total loans		1,949,566
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		3,576
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		956
Nonaccrual		7,035
Current		530,537
Recorded total loans		538,528
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		794
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		162
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Originated Loans [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		25,126
Nonaccrual		4,650
Current		2,193,167
Recorded total loans		2,222,943
Originated Loans [Member] | Consumer Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		17,577
Originated Loans [Member] | Consumer Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		4,759
Originated Loans [Member] | Consumer Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		2,790
Originated Loans [Member] | Consumer Loans [Member] | Indirect Auto [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		14,973
Nonaccrual		2,175
Current		1,176,487
Recorded total loans		1,193,635
Originated Loans [Member] | Consumer Loans [Member] | Indirect Auto [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		11,860
Originated Loans [Member] | Consumer Loans [Member] | Indirect Auto [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		2,108
Originated Loans [Member] | Consumer Loans [Member] | Indirect Auto [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		1,005
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		6,547
Nonaccrual		0
Current		535,516
Recorded total loans		542,063
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		3,153
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		2,087
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		1,307
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		3,606
Nonaccrual		2,475
Current		481,164
Recorded total loans		487,245
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		2,564
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		564
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		478
Originated Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		2,032
Nonaccrual		5,872
Current		1,311,373
Recorded total loans		1,319,277
Originated Loans [Member] | Residential [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		1,179
Originated Loans [Member] | Residential [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		190
Originated Loans [Member] | Residential [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		663
Acquired Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		1,886
Nonaccrual		1,593
Current		261,399
Recorded total loans		264,878
Acquired Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		1,257
Acquired Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		365
Acquired Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		264
Acquired Loans [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		833
Nonaccrual		382
Current		114,051
Recorded total loans		115,266
Acquired Loans [Member] | Commercial Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		546
Acquired Loans [Member] | Commercial Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		287
Acquired Loans [Member] | Commercial Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Acquired Loans [Member] | Commercial Loans [Member] | C&I [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		149
Nonaccrual		0
Current		19,215
Recorded total loans		19,364
Acquired Loans [Member] | Commercial Loans [Member] | C&I [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		149
Acquired Loans [Member] | Commercial Loans [Member] | C&I [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Acquired Loans [Member] | Commercial Loans [Member] | C&I [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Acquired Loans [Member] | Commercial Loans [Member] | CRE [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Nonaccrual		0
Current		60,937
Recorded total loans		60,937
Acquired Loans [Member] | Commercial Loans [Member] | CRE [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Acquired Loans [Member] | Commercial Loans [Member] | CRE [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Acquired Loans [Member] | Commercial Loans [Member] | CRE [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		684
Nonaccrual		382
Current		33,899
Recorded total loans		34,965
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		397
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		287
Acquired Loans [Member] | Commercial Loans [Member] | Business Banking [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Acquired Loans [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		194
Nonaccrual		105
Current		23,434
Recorded total loans		23,733
Acquired Loans [Member] | Consumer Loans [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		136
Acquired Loans [Member] | Consumer Loans [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		58
Acquired Loans [Member] | Consumer Loans [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		194
Nonaccrual		105
Current		23,434
Recorded total loans		23,733
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		136
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		58
Acquired Loans [Member] | Consumer Loans [Member] | Direct [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		0
Acquired Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		859
Nonaccrual		1,106
Current		123,914
Recorded total loans		125,879
Acquired Loans [Member] | Residential [Member] | 31-60 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		575
Acquired Loans [Member] | Residential [Member] | 61-90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		20
Acquired Loans [Member] | Residential [Member] | Greater Than 90 Days Past Due Accruing [Member]
Financing Receivable, Recorded Investment, Aging [Abstract]
Total past due accruing		$ 264

Allowance for Credit Losses a_7

Allowance for Credit Losses and Credit Quality of Loans, Credit Quality Indicators (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Minimum number of days past due for loans to be considered nonperforming	90 days
Credit Quality by Loan Class [Abstract]
2020	$ 1,927,429
2019	1,312,819
2018	949,810
2017	750,728
2016	515,688
Prior	1,262,066
Revolving Loans Amortized Cost Basis	749,657
Revolving Loans Converted to Term	30,688
Total	7,498,885
C&I [Member]
Credit Quality by Loan Class [Abstract]
2020	352,323
2019	195,227
2018	106,502
2017	50,153
2016	35,040
Prior	39,712
Revolving Loans Amortized Cost Basis	346,233
Revolving Loans Converted to Term	426
Total	1,125,616
C&I [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
2020	331,921
2019	182,329
2018	91,230
2017	41,856
2016	32,625
Prior	32,609
Revolving Loans Amortized Cost Basis	322,674
Revolving Loans Converted to Term	412
Total	1,035,656
C&I [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
2020	20,064
2019	6,534
2018	5,053
2017	4,702
2016	1,624
Prior	2,830
Revolving Loans Amortized Cost Basis	13,614
Revolving Loans Converted to Term	0
Total	54,421
C&I [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
2020	338
2019	6,364
2018	10,219
2017	3,388
2016	791
Prior	4,272
Revolving Loans Amortized Cost Basis	9,945
Revolving Loans Converted to Term	14
Total	35,331
C&I [Member] | Doubtful [Member]
Credit Quality by Loan Class [Abstract]
2020	0
2019	0
2018	0
2017	207
2016	0
Prior	1
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term	0
Total	208
CRE [Member]
Credit Quality by Loan Class [Abstract]
2020	472,506
2019	412,425
2018	296,712
2017	342,604
2016	255,045
Prior	496,867
Revolving Loans Amortized Cost Basis	115,926
Revolving Loans Converted to Term	20,200
Total	2,412,285
CRE [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
2020	469,919
2019	361,187
2018	256,154
2017	271,874
2016	212,197
Prior	383,690
Revolving Loans Amortized Cost Basis	113,128
Revolving Loans Converted to Term	4,034
Total	2,072,183
CRE [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
2020	2,051
2019	44,034
2018	22,260
2017	55,039
2016	36,830
Prior	43,537
Revolving Loans Amortized Cost Basis	1,297
Revolving Loans Converted to Term	11,524
Total	216,572
CRE [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
2020	536
2019	5,307
2018	18,298
2017	15,691
2016	6,018
Prior	62,168
Revolving Loans Amortized Cost Basis	1,501
Revolving Loans Converted to Term	4,642
Total	114,161
CRE [Member] | Doubtful [Member]
Credit Quality by Loan Class [Abstract]
2020	0
2019	1,897
2018	0
2017	0
2016	0
Prior	7,472
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term	0
Total	9,369
PPP [Member]
Credit Quality by Loan Class [Abstract]
2020	430,810
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term	0
Total	430,810
PPP [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
2020	430,810
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term	0
Total	430,810
Auto [Member]
Credit Quality by Loan Class [Abstract]
2020	198,240
2019	315,174
2018	202,985
2017	116,502
2016	45,932
Prior	13,250
Revolving Loans Amortized Cost Basis	22
Revolving Loans Converted to Term	0
Total	892,105
Auto [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
2020	197,881
2019	314,034
2018	201,850
2017	115,977
2016	45,495
Prior	13,250
Revolving Loans Amortized Cost Basis	22
Revolving Loans Converted to Term	0
Total	888,509
Auto [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
2020	359
2019	1,140
2018	1,135
2017	525
2016	437
Prior	0
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term	0
Total	3,596
Other Consumer [Member]
Credit Quality by Loan Class [Abstract]
2020	234,967
2019	178,829
2018	127,856
2017	55,941
2016	14,345
Prior	17,547
Revolving Loans Amortized Cost Basis	18,598
Revolving Loans Converted to Term	71
Total	648,154
Other Consumer [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
2020	234,628
2019	178,411
2018	127,549
2017	55,676
2016	14,255
Prior	17,414
Revolving Loans Amortized Cost Basis	18,588
Revolving Loans Converted to Term	71
Total	646,592
Other Consumer [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
2020	339
2019	418
2018	307
2017	265
2016	90
Prior	133
Revolving Loans Amortized Cost Basis	10
Revolving Loans Converted to Term	0
Total	1,562
Residential [Member]
Credit Quality by Loan Class [Abstract]
2020	238,583
2019	211,164
2018	215,755
2017	185,528
2016	165,326
Prior	694,690
Revolving Loans Amortized Cost Basis	268,878
Revolving Loans Converted to Term	9,991
Total	1,989,915
Residential [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
2020	237,338
2019	210,505
2018	213,437
2017	182,993
2016	164,424
Prior	684,495
Revolving Loans Amortized Cost Basis	268,878
Revolving Loans Converted to Term	9,991
Total	1,972,061
Residential [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
2020	1,245
2019	659
2018	2,318
2017	2,535
2016	902
Prior	10,195
Revolving Loans Amortized Cost Basis	0
Revolving Loans Converted to Term	0
Total	$ 17,854

Allowance for Credit Losses a_8

Allowance for Credit Losses and Credit Quality of Loans, Allowance for Credit Losses on Off-Balance Sheet Credit Exposures (Details) - USD ($) $ in Thousands		Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Allowance for Credit Losses and Credit Quality of Loans [Abstract]
Allowance for credit losses	[1]	$ 110,000
Allowance for credit losses			$ 72,965	[1]	$ 72,505	$ 69,500
Unfunded Commitment [Member]
Allowance for Credit Losses and Credit Quality of Loans [Abstract]
Allowance for credit losses		$ 6,400
Allowance for credit losses			$ 900
[1]	Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.

Allowance for Credit Losses a_9

Allowance for Credit Losses and Credit Quality of Loans, Troubled Debt Restructurings (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)Contract	Dec. 31, 2019USD ($)Contract
Troubled Debt Restructuring [Abstract]
Number of contracts | Contract	37	37
Pre-modification outstanding recorded investment	$ 2,900	$ 2,508
Post-modification outstanding recorded investment	$ 3,026	$ 2,603
Number of contracts | Contract	64	55
Recorded Investment	$ 3,774	$ 2,606
Commercial Loans [Member]
Troubled Debt Restructuring [Abstract]
Number of contracts | Contract	1	5
Pre-modification outstanding recorded investment	$ 22	$ 892
Post-modification outstanding recorded investment	$ 22	$ 898
Number of contracts | Contract	2
Recorded Investment	$ 555
Commercial Loans [Member] | C&I [Member]
Troubled Debt Restructuring [Abstract]
Number of contracts | Contract	1	1
Pre-modification outstanding recorded investment	$ 22	$ 65
Post-modification outstanding recorded investment	$ 22	$ 65
Number of contracts | Contract	1
Recorded Investment	$ 387
Commercial Loans [Member] | CRE [Member]
Troubled Debt Restructuring [Abstract]
Number of contracts | Contract		1
Pre-modification outstanding recorded investment		$ 402
Post-modification outstanding recorded investment		$ 402
Number of contracts | Contract	1
Recorded Investment	$ 168
Commercial Loans [Member] | Business Banking [Member]
Troubled Debt Restructuring [Abstract]
Number of contracts | Contract		3
Pre-modification outstanding recorded investment		$ 425
Post-modification outstanding recorded investment		$ 431
Consumer Loans [Member]
Troubled Debt Restructuring [Abstract]
Number of contracts | Contract	1	20
Pre-modification outstanding recorded investment	$ 44	$ 584
Post-modification outstanding recorded investment	$ 44	$ 614
Number of contracts | Contract	1	32
Recorded Investment	$ 6	$ 1,403
Consumer Loans [Member] | Auto [Member]
Troubled Debt Restructuring [Abstract]
Number of contracts | Contract	1
Pre-modification outstanding recorded investment	$ 44
Post-modification outstanding recorded investment	$ 44
Number of contracts | Contract	1
Recorded Investment	$ 6
Consumer Loans [Member] | Indirect Auto [Member]
Troubled Debt Restructuring [Abstract]
Number of contracts | Contract		9
Pre-modification outstanding recorded investment		$ 134
Post-modification outstanding recorded investment		$ 134
Number of contracts | Contract		3
Recorded Investment		$ 18
Consumer Loans [Member] | Direct [Member]
Troubled Debt Restructuring [Abstract]
Number of contracts | Contract		11
Pre-modification outstanding recorded investment		$ 450
Post-modification outstanding recorded investment		$ 480
Number of contracts | Contract		29
Recorded Investment		$ 1,385
Residential [Member]
Troubled Debt Restructuring [Abstract]
Number of contracts | Contract	35	12
Pre-modification outstanding recorded investment	$ 2,834	$ 1,032
Post-modification outstanding recorded investment	$ 2,960	$ 1,091
Number of contracts | Contract	61	23
Recorded Investment	$ 3,213	$ 1,203

Allowance for Credit Losses _10

Allowance for Credit Losses and Credit Quality of Loans, Changes in Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period		$ 72,965	[1]	$ 72,505		$ 69,500
Charge-offs				(32,540)		(34,128)
Recoveries				7,588		8,305
Provision	[1]	51,134		25,412		28,828
Balance, end of period				72,965	[1]	72,505
Commercial Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period		34,525		32,759		27,606
Charge-offs				(3,151)		(3,463)
Recoveries				534		1,178
Provision				4,383		7,438
Balance, end of period				34,525		32,759
Consumer Loans [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period		35,647		37,178		36,830
Charge-offs				(28,398)		(29,752)
Recoveries				6,913		6,821
Provision				19,954		23,279
Balance, end of period				35,647		37,178
Residential Real Estate [Member]
Changes in allowance for loan losses by portfolio segment [Roll Forward]
Balance, beginning of period		$ 2,793		2,568		5,064
Charge-offs				(991)		(913)
Recoveries				141		306
Provision				1,075		(1,889)
Balance, end of period				$ 2,793		$ 2,568
[1]	Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.

Allowance for Credit Losses _11

Allowance for Credit Losses and Credit Quality of Loans, Allowance for Loan Losses and Recorded Investment in Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	$ 72,965	[1]	$ 72,505	$ 69,500
Allowance for loans individually evaluated for impairment	0
Allowance for loans collectively evaluated for impairment	72,965
Ending balance of loans	7,136,098
Commercial Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	34,525		32,759	27,606
Allowance for loans individually evaluated for impairment	0
Allowance for loans collectively evaluated for impairment	34,525
Ending balance of loans	3,444,266
Consumer Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	35,647		37,178	36,830
Allowance for loans individually evaluated for impairment	0
Allowance for loans collectively evaluated for impairment	35,647
Ending balance of loans	2,246,676
Residential Real Estate [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Allowance for loan losses	2,793		$ 2,568	$ 5,064
Allowance for loans individually evaluated for impairment	0
Allowance for loans collectively evaluated for impairment	2,793
Ending balance of loans	1,445,156
Originated Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans individually evaluated for impairment	18,253
Ending balance of loans collectively evaluated for impairment	6,852,967
Originated Loans [Member] | Commercial Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans individually evaluated for impairment	3,488
Ending balance of loans collectively evaluated for impairment	3,325,512
Originated Loans [Member] | Consumer Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans individually evaluated for impairment	7,044
Ending balance of loans collectively evaluated for impairment	2,215,899
Originated Loans [Member] | Residential Real Estate [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans individually evaluated for impairment	7,721
Ending balance of loans collectively evaluated for impairment	1,311,556
Acquired Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans collectively evaluated for impairment	264,878
Acquired Loans [Member] | Commercial Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans collectively evaluated for impairment	115,266
Acquired Loans [Member] | Consumer Loans [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans collectively evaluated for impairment	23,733
Acquired Loans [Member] | Residential Real Estate [Member]
Allowance for loan losses and recorded investment by portfolio segment [Abstract]
Ending balance of loans collectively evaluated for impairment	$ 125,879
[1]	Beginning January 1, 2020, calculation is based on current expected loss methodology. Prior to January 1, 2020, calculation was based on incurred loss methodology.

Allowance for Credit Losses _12

Allowance for Credit Losses and Credit Quality of Loans, Impairment Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2019
Total Loans [Abstract]
Recorded investment balance (book)		$ 18,253
Unpaid principal balance (legal)		22,541
Related allowance		0
Threshold balance for classified loans to be evaluated individually for impairment	$ 1,000		$ 750
Originated Loans [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		18,253
Unpaid principal balance (legal)		22,541
Originated Loans [Member] | Commercial Loans [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		3,488
Unpaid principal balance (legal)		4,182
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		76
Unpaid principal balance (legal)		302
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		2,410
Unpaid principal balance (legal)		2,437
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		1,002
Unpaid principal balance (legal)		1,443
Originated Loans [Member] | Consumer Loans [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		7,044
Unpaid principal balance (legal)		8,605
Originated Loans [Member] | Consumer Loans [Member] | Indirect Auto [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		154
Unpaid principal balance (legal)		242
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		6,862
Unpaid principal balance (legal)		8,335
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		28
Unpaid principal balance (legal)		28
Originated Loans [Member] | Residential Real Estate [Member]
With no related allowance recorded [Abstract]
Recorded investment balance (book)		7,721
Unpaid principal balance (legal)		$ 9,754

Allowance for Credit Losses _13

Allowance for Credit Losses and Credit Quality of Loans, Average Recorded Investments on Loans Specifically Evaluated for Impairment and Interest Income Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	$ 19,733	$ 20,429
Interest income recognized	891	901
Originated Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	19,733	20,429
Interest income recognized	891	901
Originated Loans [Member] | Commercial Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	4,642	5,549
Interest income recognized	148	155
Originated Loans [Member] | Commercial Loans [Member] | C&I [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	242	453
Interest income recognized	1	1
Originated Loans [Member] | Commercial Loans [Member] | CRE [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	3,311	4,078
Interest income recognized	123	128
Originated Loans [Member] | Commercial Loans [Member] | Business Banking [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	1,089	1,018
Interest income recognized	24	26
Originated Loans [Member] | Consumer Loans [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7,586	8,101
Interest income recognized	393	441
Originated Loans [Member] | Consumer Loans [Member] | Indirect Auto [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	192	179
Interest income recognized	10	10
Originated Loans [Member] | Consumer Loans [Member] | Direct [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7,387	7,922
Interest income recognized	382	431
Originated Loans [Member] | Consumer Loans [Member] | Specialty Lending [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7	0
Interest income recognized	1	0
Originated Loans [Member] | Residential Real Estate [Member]
Average Recorded Investment and Interest Income Recognized [Abstract]
Average recorded investment	7,505	6,779
Interest income recognized	$ 350	$ 305

Allowance for Credit Losses _14

Allowance for Credit Losses and Credit Quality of Loans, Credit Quality by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Credit Quality by Loan Class [Abstract]
Net Loans	$ 7,498,885	$ 7,136,098
Indirect Auto [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	931,286	1,193,635
Specialty Lending [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	$ 579,644	542,063
Originated Loans [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		6,871,220
Originated Loans [Member] | Commercial Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,790,472
Originated Loans [Member] | Commercial Credit Exposure [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,651,441
Originated Loans [Member] | Commercial Credit Exposure [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		58,899
Originated Loans [Member] | Commercial Credit Exposure [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		79,626
Originated Loans [Member] | Commercial Credit Exposure [Member] | Doubtful [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		506
Originated Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		840,906
Originated Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		782,763
Originated Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		28,380
Originated Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		29,257
Originated Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Doubtful [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		506
Originated Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,949,566
Originated Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,868,678
Originated Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		30,519
Originated Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		50,369
Originated Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Doubtful [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		0
Originated Loans [Member] | Business Banking Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		538,528
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		524,725
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		13,803
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		538,528
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		524,725
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		13,803
Originated Loans [Member] | Consumer Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,222,943
Originated Loans [Member] | Consumer Credit Exposure [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,215,503
Originated Loans [Member] | Consumer Credit Exposure [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		7,440
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect Auto [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,193,635
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect Auto [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,190,455
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect Auto [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		3,180
Originated Loans [Member] | Consumer Credit Exposure [Member] | Specialty Lending [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		542,063
Originated Loans [Member] | Consumer Credit Exposure [Member] | Specialty Lending [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		540,756
Originated Loans [Member] | Consumer Credit Exposure [Member] | Specialty Lending [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,307
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		487,245
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		484,292
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,953
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,319,277
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,312,742
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		6,535
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,319,277
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,312,742
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		6,535
Acquired Loans [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		264,878
Acquired Loans [Member] | Commercial Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		80,301
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		78,346
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,269
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		686
Acquired Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		19,364
Acquired Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		17,801
Acquired Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,269
Acquired Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		294
Acquired Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		60,937
Acquired Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		60,545
Acquired Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		0
Acquired Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		392
Acquired Loans [Member] | Business Banking Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		34,965
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		32,030
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,935
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		34,965
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		32,030
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,935
Acquired Loans [Member] | Consumer Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		23,733
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		23,628
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		105
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		23,733
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		23,628
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		105
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		125,879
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		124,509
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,370
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		125,879
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		124,509
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		$ 1,370

Premises, Equipment and Lease_2

Premises, Equipment and Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Premises and Equipment [Abstract]
Premises and equipment before accumulated depreciation	$ 180,197	$ 179,910
Accumulated depreciation	105,991	104,279
Total premises and equipment	74,206	75,631
Operating lease ROU assets	$ 26,400	$ 34,800
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets	us-gaap:OtherAssets
Net Lease Cost [Abstract]
Operating lease cost	$ 7,382	$ 7,239
Variable lease cost	2,141	2,231
Short-term lease cost	453	356
Sublease income	(502)	(448)
Total premises and equipment	9,474	9,378
Future Minimum Rental Commitments Related to Non-cancelable Operating Leases [Abstract]
2021	7,209
2022	6,339
2023	5,251
2024	4,581
2025	3,411
Thereafter	10,023
Total lease payments	36,814
Less: interest	(3,990)
Present value of lease liabilities	$ 32,824	$ 37,300
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilities	us-gaap:OtherLiabilities
Additional Information Related to Operating Leases [Abstract]
Weighted average remaining lease term, in years	7 years 2 months 15 days	7 years 8 months 8 days
Weighted average discount rate	3.02%	3.00%
Cash paid for amounts included in the measurement of lease liabilities [Abstract]
Operating cash flows from operating leases	$ 7,934	$ 6,211
ROU assets obtained in exchange for lease liabilities	3,441	41,008
Rental expense	8,000	8,000	$ 8,600
Land, Buildings and Improvements [Member]
Premises and Equipment [Abstract]
Premises and equipment before accumulated depreciation	125,002	121,479
Equipment [Member]
Premises and Equipment [Abstract]
Premises and equipment before accumulated depreciation	$ 55,195	$ 58,431
Equipment [Member] | Minimum [Member]
Premises and Equipment [Abstract]
Property, plant and equipment, useful life	3 years
Equipment [Member] | Maximum [Member]
Premises and Equipment [Abstract]
Property, plant and equipment, useful life	10 years
Building and Improvements [Member] | Minimum [Member]
Premises and Equipment [Abstract]
Property, plant and equipment, useful life	5 years
Building and Improvements [Member] | Maximum [Member]
Premises and Equipment [Abstract]
Property, plant and equipment, useful life	20 years

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Beginning balance	$ 274,769	$ 274,769
Goodwill acquired	5,772	0
Ending balance	280,541	274,769	$ 274,769
Finite-Lived Intangible Assets [Abstract]
Gross carrying amount	36,008	43,574
Less: accumulated amortization	24,273	31,554
Net carrying amount	11,735	12,020
Impairment of goodwill	0	0
Amortization Expense [Abstract]
Amortization of intangible assets	3,395	3,579	$ 4,042
Future Amortization Expense [Abstract]
2021	2,800
2022	2,200
2023	1,800
2024	1,500
2025	1,200
Thereafter	2,300
Impairment of intangible assets	$ 0	0
Minimum [Member]
Finite-Lived Intangible Assets [Abstract]
Intangible asset useful life	1 year
Maximum [Member]
Finite-Lived Intangible Assets [Abstract]
Intangible asset useful life	20 years
Core Deposits Intangibles [Member]
Finite-Lived Intangible Assets [Abstract]
Gross carrying amount	$ 8,951	8,951
Less: accumulated amortization	8,463	7,988
Net carrying amount	488	963
Identified Intangible Assets [Member]
Finite-Lived Intangible Assets [Abstract]
Gross carrying amount	27,057	34,623
Less: accumulated amortization	15,810	23,566
Net carrying amount	$ 11,247	$ 11,057

Deposits (Details)

Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Maturities of Time Deposits [Abstract]
Within one year	$ 476,983
After one but within two years	77,081
After two but within three years	36,857
After three but within four years	27,888
After four but within five years	14,381
After five years	289
Total	633,479	$ 861,193
Time Deposits, $250,000 or More [Abstract]
Time deposits of $250,000 or more	$ 104,100	$ 140,400

Borrowings, Short-Term Borrowin

Borrowings, Short-Term Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Short-term borrowings [Abstract]
Balance at year-end	$ 168,386	$ 655,275
FHLB, unused lines of credit available for short-term financing	3,100,000	2,400,000
Federal Funds Purchased [Member]
Short-term borrowings [Abstract]
Balance at year-end	0	65,000	$ 80,000
Average during the year	14,727	47,137	66,839
Maximum month end balance	$ 40,000	$ 80,000	$ 80,000
Weighted average rate during the year	2.05%	3.90%	3.43%
Weighted average rate at year-end	0.00%	2.84%	4.25%
Securities Sold Under Repurchase Agreements [Member]
Short-term borrowings [Abstract]
Balance at year-end	$ 143,386	$ 143,775	$ 160,696
Average during the year	154,383	123,337	146,135
Maximum month end balance	$ 176,840	$ 146,410	$ 170,350
Weighted average rate during the year	0.17%	0.33%	0.16%
Weighted average rate at year-end	0.20%	0.40%	0.38%
Other Short-Term Borrowings [Member]
Short-term borrowings [Abstract]
Balance at year-end	$ 25,000	$ 446,500	$ 631,000
Average during the year	183,699	403,453	514,662
Maximum month end balance	$ 366,500	$ 576,000	$ 653,000
Weighted average rate during the year	1.55%	1.85%	1.56%
Weighted average rate at year-end	1.99%	1.73%	1.82%

Borrowings, Long-Term Debt (Det

Borrowings, Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Long-term debt by maturity, amount [Abstract]
Due in next 12 months	$ 25,003	$ 25,000
Due in year two	10,598	25,021
Due in year three		10,598
Due in year eleven	3,496
Due in year twelve		3,592
Total	$ 39,097	$ 64,211
Long-term debt by maturity, weighted average rate [Abstract]
Due in next 12 months	2.56%	2.34%
Due in year two	2.53%	2.56%
Due in year three		2.53%
Due in year eleven	2.45%
Due in year twelve		2.45%

Borrowings, Subordinated Debt (

Borrowings, Subordinated Debt (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Summary of Subordinated Notes [Abstract]
Total subordinated debt, net	$ 98,052	$ 0
Subordinated Notes [Member]
Subordinated Debt [Abstract]
Debt instrument, rate on fixed portion	5.00%
Debt issuance cost	$ 2,200
Debt instrument, redemption price percentage of principal amount	100.00%
Summary of Subordinated Notes [Abstract]
Subordinated notes issued June 2020 - fixed interest rate of 5.00% through June 2025 and a variable interest rate equivalent to three-month SOFR plus 4.85% thereafter, maturing July 1, 2030	$ 100,000
Unamortized debt issuance costs	(1,948)
Total subordinated debt, net	$ 98,052
Subordinated Notes [Member] | Minimum [Member]
Subordinated Debt [Abstract]
Debt issuance cost amortization period	5 years
Subordinated Notes [Member] | SOFR [Member]
Subordinated Debt [Abstract]
Term of variable rate basis	3 months
Basis spread on variable rate	4.85%

Borrowings, Junior Subordinated

Borrowings, Junior Subordinated Debt (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)TrustPeriod
Junior Subordinated Debt [Abstract]
Number of statutory business trusts included in the Trusts | Trust	5
Minimum assets for bank holding companies to be subject to the same capital requirements as insured depository institutions	$ 500,000
CNBF Capital Trust I [Member]
Junior Subordinated Debt [Abstract]
Number of wholly owned Delaware statutory business trusts | Trust	1
CNBF Capital Trust I [Member] | LIBOR [Member]
Junior Subordinated Debt [Abstract]
Issuance Date	Aug. 1, 1999
Trust Preferred Securities Outstanding	$ 18,000
Variable rate basis	3-month LIBOR
Basis spread on variable rate	2.75%
Trust Preferred Debt Owed To Trust	$ 18,720
Final Maturity Date	Aug. 1, 2029
NBT Statutory Trust I [Member] | LIBOR [Member]
Junior Subordinated Debt [Abstract]
Issuance Date	Nov. 1, 2005
Trust Preferred Securities Outstanding	$ 5,000
Variable rate basis	3-month LIBOR
Basis spread on variable rate	1.40%
Trust Preferred Debt Owed To Trust	$ 5,155
Final Maturity Date	Dec. 1, 2035
NBT Statutory Trust II [Member] | LIBOR [Member]
Junior Subordinated Debt [Abstract]
Issuance Date	Feb. 1, 2006
Trust Preferred Securities Outstanding	$ 50,000
Variable rate basis	3-month LIBOR
Basis spread on variable rate	1.40%
Trust Preferred Debt Owed To Trust	$ 51,547
Final Maturity Date	Mar. 1, 2036
Alliance Financial Capital Trust I [Member] | LIBOR [Member]
Junior Subordinated Debt [Abstract]
Issuance Date	Dec. 1, 2003
Trust Preferred Securities Outstanding	$ 10,000
Variable rate basis	3-month LIBOR
Basis spread on variable rate	2.85%
Trust Preferred Debt Owed To Trust	$ 10,310
Final Maturity Date	Jan. 1, 2034
Alliance Financial Capital Trust II [Member] | LIBOR [Member]
Junior Subordinated Debt [Abstract]
Issuance Date	Sep. 1, 2006
Trust Preferred Securities Outstanding	$ 15,000
Variable rate basis	3-month LIBOR
Basis spread on variable rate	1.65%
Trust Preferred Debt Owed To Trust	$ 15,464
Final Maturity Date	Sep. 1, 2036
Alliance Financial Capital [Member]
Junior Subordinated Debt [Abstract]
Number of wholly owned Delaware statutory business trusts | Trust	2
Trusts [Member]
Junior Subordinated Debt [Abstract]
Trust Preferred Securities Outstanding	$ 98,000
Trust Preferred Debt Owed To Trust	101,000
Trust equity method investment	$ 3,200
Debentures period semi-annual deferral periods | Period	10
Trust preferred securities included in Tier I capital	$ 97,000
NBT Bancorp Inc [Member]
Junior Subordinated Debt [Abstract]
Trust equity method investment	$ 1,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Current [Abstract]
Federal	$ 36,358	$ 28,475	$ 15,762
State	9,768	7,653	5,977
Total Current	46,126	36,128	21,739
Deferred [Abstract]
Federal	(14,021)	(1,379)	2,281
State	(3,406)	(338)	416
Total Deferred	(17,427)	(1,717)	2,697
Total income tax expense	28,699	34,411	24,436
Components of income taxes [Abstract]
Tax benefit primarily related to changes in accounting method			5,500
Deferred tax assets [Abstract]
Allowance for loan losses	27,282	18,535
Lease liability	8,141	9,331
Deferred compensation	11,602	8,336
Postretirement benefit obligation	1,511	1,631
Fair value adjustments from acquisitions	259	422
Loan fees	5,400	1,384
Accrued liabilities	1,307	1,176
Stock-based compensation expense	3,213	3,032
Other	3,558	1,498
Total deferred tax assets	62,273	45,345
Deferred tax liabilities [Abstract]
Pension benefits	14,406	13,014
Lease right-of-use asset	6,567	9,259
Amortization of intangible assets	12,725	12,202
Premises and equipment, primarily due to accelerated depreciation	4,774	5,137
Unrealized gain on securities	7,732	1,770
Other	952	1,429
Total deferred tax liabilities	47,156	42,811
Net deferred tax asset at year-end	15,117	2,534	8,795
Net deferred tax asset at beginning of year	2,534	8,795
Increase (decrease) in net deferred tax asset	12,583	(6,261)
Income tax reconciliation [Abstract]
Federal income tax at statutory rate	27,948	32,641	28,770
Tax exempt income	(981)	(1,233)	(1,456)
Net increase in cash surrender value of life insurance	(1,135)	(927)	(973)
Federal tax credit	(1,705)	(1,458)	(1,499)
State taxes, net of federal tax benefit	5,026	5,773	5,051
Accounting method changes - tax rate change impact	0	0	(5,326)
Stock-based compensation, excess tax benefit	(152)	(342)	(456)
Other, net	(302)	(43)	325
Total income tax expense	28,699	34,411	24,436
Reconciliation of gross unrecognized tax benefits [Roll Forward]
Beginning balance	779	641
Additions for tax positions of prior years	254	26
Current period tax positions	145	112
Ending balance	1,178	779	$ 641
Amount that would affect the effective tax rate if recognized, gross of tax	$ 931	$ 615
State and Local Jurisdiction [Member] | New York State Division of Taxation and Finance [Member]
Income Tax Examination [Abstract]
Tax years under examination	2015 2016 2017 2018 2019

Employee Benefit Plans (Details

Employee Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined benefit plan disclosure [Abstract]
Transition obligation period of recognition	20 years
Assumptions used to determine benefit obligations [Abstract]
Expected long-term return on plan assets	7.00%	7.00%	7.00%
Rate of compensation increase	3.00%	3.00%	3.00%
Interest rate of credit for cash balance plan	1.62%	2.28%	3.36%
Assumptions used to determine net periodic pension cost [Abstract]
Expected long-term return on plan assets	7.00%	7.00%	7.00%
Rate of compensation increase	3.00%	3.00%	3.00%
Interest rate of credit for cash balance plan	2.28%	3.36%	2.80%
Other changes in plan assets and benefit obligation recognized in OCI (pre-tax) [Abstract]
Net (gain) loss	$ (429)	$ (5,331)	$ 12,457
Amortization of unrecognized net (loss)	$ 107	$ 1,333	$ (3,038)
Estimate future benefit payments [Abstract]
Ultimate health care cost trend rate	3.80%
Actual plan asset allocations [Abstract]
Actual plan asset allocations	100.00%	100.00%
Minimum [Member]
Assumptions used to determine benefit obligations [Abstract]
Discount rate	3.08%	3.69%	4.79%
Assumptions used to determine net periodic pension cost [Abstract]
Discount rate	3.69%	4.79%	4.20%
Estimate future benefit payments [Abstract]
Annual rates of increase in the per capita cost of covered medical and prescription drug benefits,	4.50%
Maximum [Member]
Assumptions used to determine benefit obligations [Abstract]
Discount rate	3.25%	3.73%	4.80%
Assumptions used to determine net periodic pension cost [Abstract]
Discount rate	3.73%	4.80%	4.21%
Estimate future benefit payments [Abstract]
Annual rates of increase in the per capita cost of covered medical and prescription drug benefits,	7.00%
Pension Benefits [Member]
Accumulated other comprehensive income (loss), before tax [Abstract]
Net actuarial loss	$ 26,108	$ 28,334
Prior service cost	378	491
Total amounts recognized in AOCI (pre-tax)	26,486	28,825
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of year	90,586	85,134
Service cost	1,840	1,723	$ 1,659
Interest cost	3,237	3,942	3,645
Plan participants' contributions	0	0
Actuarial loss (gain)	3,411	6,030
Curtailments	(67)	0
Benefits paid	(8,813)	(6,243)
Projected benefit obligation at end of year	90,194	90,586	85,134
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	122,995	109,746
Gain on plan assets	12,449	18,120
Employer contributions	1,932	1,372
Plan participants' contributions	0	0
Benefits paid	(8,813)	(6,243)
Fair value of plan assets at end of year	128,563	122,995	109,746
Funded (unfunded) status at year end	38,369	32,409
Accumulated benefit obligation	90,200	90,600
Amounts recognized in Balance Sheet [Abstract]
Funded (unfunded) status at year end	38,369	32,409
Components of net periodic (benefit) cost [Abstract]
Service cost	1,840	1,723	1,659
Interest cost	3,237	3,942	3,645
Expected return on plan assets	(8,410)	(7,480)	(8,478)
Additional gain due to curtailment	(74)	0	0
Amortization of prior service cost	41	43	40
Amortization of unrecognized net loss	1,535	2,593	930
Net periodic pension (benefit) cost	(1,831)	821	(2,204)
Other changes in plan assets and benefit obligation recognized in OCI (pre-tax) [Abstract]
Net (gain) loss	(628)	(4,611)	12,882
Prior service cost	0	0	337
Additional gain due to curtailment	7	0	0
Amortization of prior service cost	(41)	(43)	(40)
Amortization of unrecognized net (loss)	(1,535)	(2,593)	(930)
Total recognized in OCI	(2,197)	(7,247)	12,249
Total recognized in net periodic (benefit) cost and OCI, pre-tax	(4,028)	(6,426)	10,045
Estimate future benefit payments [Abstract]
2021	6,910
2022	6,977
2023	6,807
2024	7,083
2025	7,409
2026 - 2030	33,579
Employer voluntary contribution to plan	0	0
Pension Benefits [Member] | Other Assets [Member]
Amounts recognized in Balance Sheet [Abstract]
Assets recognized	57,456	51,988
Pension Benefits [Member] | Other Liabilities [Member]
Amounts recognized in Balance Sheet [Abstract]
Liabilities recognized	$ (19,087)	$ (19,579)
Pension Benefits [Member] | Cash and Cash Equivalents [Member]
Actual plan asset allocations [Abstract]
Actual plan asset allocations	3.00%	3.00%
Pension Benefits [Member] | Cash and Cash Equivalents [Member] | Minimum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	0.00%
Pension Benefits [Member] | Cash and Cash Equivalents [Member] | Maximum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	15.00%
Pension Benefits [Member] | Fixed Income Securities [Member]
Actual plan asset allocations [Abstract]
Actual plan asset allocations	38.00%	40.00%
Pension Benefits [Member] | Fixed Income Securities [Member] | Minimum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	30.00%
Pension Benefits [Member] | Fixed Income Securities [Member] | Maximum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	60.00%
Pension Benefits [Member] | Equities [Member]
Actual plan asset allocations [Abstract]
Actual plan asset allocations	59.00%	57.00%
Pension Benefits [Member] | Equities [Member] | Minimum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	40.00%
Pension Benefits [Member] | Equities [Member] | Maximum [Member]
Target asset allocations [Abstract]
Target allocation percentage of assets	70.00%
Other Benefits [Member]
Accumulated other comprehensive income (loss), before tax [Abstract]
Net actuarial loss	$ 317	$ 125
Prior service cost	43	94
Total amounts recognized in AOCI (pre-tax)	360	219
Change in benefit obligation [Roll Forward]
Benefit obligation at beginning of year	6,083	7,034
Service cost	8	7	10
Interest cost	213	272	327
Plan participants' contributions	173	201
Actuarial loss (gain)	191	(719)
Curtailments	0	0
Benefits paid	(669)	(712)
Projected benefit obligation at end of year	5,999	6,083	7,034
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Gain on plan assets	0	0
Employer contributions	496	511
Plan participants' contributions	173	201
Benefits paid	(669)	(712)
Fair value of plan assets at end of year	0	0	0
Funded (unfunded) status at year end	(5,999)	(6,083)
Accumulated benefit obligation	6,000	6,100
Amounts recognized in Balance Sheet [Abstract]
Funded (unfunded) status at year end	(5,999)	(6,083)
Components of net periodic (benefit) cost [Abstract]
Service cost	8	7	10
Interest cost	213	272	327
Expected return on plan assets	0	0	0
Additional gain due to curtailment	0	0	0
Amortization of prior service cost	51	50	51
Amortization of unrecognized net loss	0	0	124
Net periodic pension (benefit) cost	272	329	512
Other changes in plan assets and benefit obligation recognized in OCI (pre-tax) [Abstract]
Net (gain) loss	192	(720)	(762)
Prior service cost	0	0	0
Additional gain due to curtailment	0	0	0
Amortization of prior service cost	(51)	(50)	(51)
Amortization of unrecognized net (loss)	0	0	(124)
Total recognized in OCI	141	(770)	(937)
Total recognized in net periodic (benefit) cost and OCI, pre-tax	413	(441)	$ (425)
Estimate future benefit payments [Abstract]
2021	453
2022	451
2023	448
2024	443
2025	436
2026 - 2030	1,962
Employer voluntary contribution to plan	0	0
Other Benefits [Member] | Other Assets [Member]
Amounts recognized in Balance Sheet [Abstract]
Assets recognized	0	0
Other Benefits [Member] | Other Liabilities [Member]
Amounts recognized in Balance Sheet [Abstract]
Liabilities recognized	$ (5,999)	$ (6,083)

Employee Benefit Plans, Financi

Employee Benefit Plans, Financial Instruments Recorded At Fair Value On A Recurring Basis By The Plan (Details) - Pension Benefits [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	$ 128,563	$ 122,995	$ 109,746
Recurring Basis [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	128,563	122,995
Recurring Basis [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	80,098	74,268
Recurring Basis [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	48,465	48,727
Recurring Basis [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	3,461	4,143
Recurring Basis [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	3,461	4,143
Recurring Basis [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] | Foreign Equity Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	41,000	40,239
Recurring Basis [Member] | Foreign Equity Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	41,000	40,239
Recurring Basis [Member] | Foreign Equity Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] | Equity Mutual Funds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	35,637	29,886
Recurring Basis [Member] | Equity Mutual Funds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	35,637	29,886
Recurring Basis [Member] | Equity Mutual Funds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] | US Government Bonds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	47	58
Recurring Basis [Member] | US Government Bonds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] | US Government Bonds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	47	58
Recurring Basis [Member] | Corporate Bonds [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	48,418	48,669
Recurring Basis [Member] | Corporate Bonds [Member] | Level 1 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	0	0
Recurring Basis [Member] | Corporate Bonds [Member] | Level 2 [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Fair value of plan assets	$ 48,418	$ 48,669

Employee Benefit Plans, 401(k)

Employee Benefit Plans, 401(k) Plan and Other Retirement Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Retirement Benefits [Abstract]
Supplemental retirement benefits for retired executives under other retirement benefits plan	$ 1.6	$ 1.7
Expense related to other retirement benefits plan	0.2	0.1	$ 0.1
401(K) Plan [Member]
Defined benefit plan disclosure [Abstract]
Employer contribution to plan	$ 3.6	$ 3.6	$ 3.2

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Additional disclosures [Abstract]
Stock-based compensation expense	$ 4,581	$ 4,210	$ 3,936
Number of shares available for future grant (in shares)	781,123
Stock Options [Member]
Share-based compensation [Abstract]
Stock awards termination period	10 years
Stock options [Roll Forward]
Outstanding, beginning of period (in shares)	33,145
Exercised (in shares)	(8,845)
Expired (in shares)	(10,500)
Outstanding, end of period (in shares)	13,800	33,145
Exercisable, end of period (in shares)	13,800
Stock options, weighted average exercise price [Abstract]
Outstanding, beginning of period (in dollars per share)	$ 23.73
Exercised (in dollars per share)	20.87
Expired (in dollars per share)	20.74
Outstanding, end of period (in dollars per share)	27.83	$ 23.73
Exercisable, end of period (in dollars per share)	$ 27.83
Additional disclosures [Abstract]
Weighted average remaining contractual term, outstanding, end of period	3 years 4 months 9 days
Weighted average remaining contractual term, exercisable, end of period	3 years 4 months 9 days
Aggregate intrinsic value, outstanding, end of period	$ 75
Aggregate intrinsic value, exercisable, end of period	75
Stock-based compensation expense	0	$ 1	11
Proceeds from stock options exercised	185	725	999
Tax benefits related to stock options exercised	41	123	173
Intrinsic value of stock options exercised	165	490	692
Fair value of shares vested during the year	0	13	16
Restricted Stock [Member]
Additional disclosures [Abstract]
Stock-based compensation expense	$ 4,600	$ 4,200	3,900
Restricted Stock [Member] | Employees [Member] | Minimum [Member]
Share-based compensation [Abstract]
Stock awards vesting period	3 years
Restricted Stock [Member] | Employees [Member] | Maximum [Member]
Share-based compensation [Abstract]
Stock awards vesting period	5 years
Restricted Stock [Member] | Non-employee Directors [Member]
Share-based compensation [Abstract]
Stock awards vesting period	3 years
Restricted Stock Units (RSUs) [Member]
Restricted stock and restricted stock units [Roll Forward]
Unvested, beginning of period (in shares)	555,440
Forfeited (in shares)	(2,315)
Vested (in shares)	(115,432)
Granted (in shares)	147,562
Unvested, end of period (in shares)	585,255	555,440
Restricted stock and restricted stock units, weighted average grant date fair value [Abstract]
Unvested, beginning of period (in dollars per share)	$ 30.11
Forfeited (in dollars per share)	34.82
Vested (in dollars per share)	29.93
Granted (in dollars per share)	28.61
Unvested, end of period (in dollars per share)	$ 29.78	$ 30.11
Restricted Stock Awards and Stock Units [Member]
Additional disclosures [Abstract]
Tax benefit on restricted stock awards	$ 1,000	$ 1,100	$ 1,200
Unrecognized compensation cost	$ 5,100
Unrecognized compensation cost, weighted average period of recognition	1 year 6 months

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Jan. 27, 2021	Dec. 31, 2019	Dec. 31, 2018
Stockholders' Equity [Abstract]
Unrecognized prior service cost and net actuarial (losses) on pension plans	$ (20,134)		$ (21,677)	$ (27,689)
Unrealized (losses) gains on derivatives (cash flow hedges)	(16)		(32)	1,821
Unrealized net holding gains (losses) on AFS securities	20,567		2,683	(17,306)
AOCI	$ 417		$ (19,026)	$ (43,174)
Preceding period of retained net profits for approval of Office of Comptroller of the Currency	2 years
Statutory amount available for dividend payments	$ 194,200
Stock Repurchase Program [Abstract]
Purchase of common stock (in shares)	263,507
Purchase of common stock value	$ 7,980
Average price per share (in dollars per share)	$ 30.28
Number of shares available for repurchase under stock repurchase program (in shares)	736,493
Number of shares authorized under stock repurchase program (in shares)	1,000,000
Subsequent Event [Member]
Stock Repurchase Program [Abstract]
Number of shares authorized under stock repurchase program (in shares)		2,000,000

Regulatory Capital Requiremen_3

Regulatory Capital Requirements (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Tier I Capital (to average assets) [Abstract]
Tier I capital to average assets	$ 1,018,320	$ 963,147
Tier I capital to average assets ratio	0.0956	0.1033
Minimum Tier I leverage capital required for capital adequacy to average assets	0.0400	0.0400
Tier I leverage capital required for classification as well capitalized to average assets	0.0500	0.0500
Common Equity Tier I Capital [Abstract]
Common equity Tier I capital	$ 921,320	$ 866,147
Common equity Tier I capital ratio	0.1184	0.1129
Minimum Tier I capital required for capital adequacy	0.0450	0.0450
Minimum Tier I capital required for capital adequacy plus buffer	0.0700	0.0700
Tier I capital required for classification as well capitalized	0.0650	0.0650
Tier I Capital (to risk weighted assets) [Abstract]
Tier I capital to risk weighted assets	$ 1,018,320	$ 963,147
Tier I capital to risk weighted assets ratio	0.1309	0.1256
Minimum Tier I capital required for capital adequacy to risk weighted assets	0.0600	0.0600
Minimum Tier I capital required for capital adequacy plus buffer to risk weighted assets	0.0850	0.0850
Tier I capital required for classification as well capitalized to risk weighted assets	0.0800	0.0800
Total Capital (to risk weighted assets) [Abstract]
Total capital to risk weighted assets	$ 1,215,672	$ 1,037,041
Total capital to risk weighted assets ratio	0.1562	0.1352
Minimum capital required for capital adequacy to risk weighted assets	0.0800	0.0800
Total capital required for capital adequacy plus buffer to average assets	0.1050	0.1050
Capital required for classification as well capitalized to risk weighted assets	0.1000	0.1000
Permissible capital transition relief period	5 years
NBT Bank [Member]
Tier I Capital (to average assets) [Abstract]
Tier I capital to average assets	$ 1,054,097	$ 894,407
Tier I capital to average assets ratio	0.0995	0.0964
Minimum Tier I leverage capital required for capital adequacy to average assets	0.0400	0.0400
Tier I leverage capital required for classification as well capitalized to average assets	0.0500	0.0500
Common Equity Tier I Capital [Abstract]
Common equity Tier I capital	$ 1,054,097	$ 894,407
Common equity Tier I capital ratio	0.1367	0.1176
Minimum Tier I capital required for capital adequacy	0.0450	0.0450
Minimum Tier I capital required for capital adequacy plus buffer	0.0700	0.0700
Tier I capital required for classification as well capitalized	0.0650	0.0650
Tier I Capital (to risk weighted assets) [Abstract]
Tier I capital to risk weighted assets	$ 1,054,097	$ 894,407
Tier I capital to risk weighted assets ratio	0.1367	0.1176
Minimum Tier I capital required for capital adequacy to risk weighted assets	0.0600	0.0600
Minimum Tier I capital required for capital adequacy plus buffer to risk weighted assets	0.0850	0.0850
Tier I capital required for classification as well capitalized to risk weighted assets	0.0800	0.0800
Total Capital (to risk weighted assets) [Abstract]
Total capital to risk weighted assets	$ 1,150,544	$ 968,301
Total capital to risk weighted assets ratio	0.1493	0.1273
Minimum capital required for capital adequacy to risk weighted assets	0.0800	0.0800
Total capital required for capital adequacy plus buffer to average assets	0.1050	0.1050
Capital required for classification as well capitalized to risk weighted assets	0.1000	0.1000

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic EPS [Abstract]
Net income	$ 104,388	$ 121,021	$ 112,566
Weighted average shares, basic (in shares)	43,693	43,815	43,701
Basic EPS (in dollars per share)	$ 2.39	$ 2.76	$ 2.58
Diluted earnings per share [Abstract]
Net income	$ 104,388	$ 121,021	$ 112,566
Dilutive effect of stock based compensation (in shares)	296	309	319
Weighted average shares, diluted (in shares)	43,989	44,124	44,020
Diluted EPS (in dollars per share)	$ 2.37	$ 2.74	$ 2.56

Reclassification Adjustments _3

Reclassification Adjustments Out of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustments out of AOCI [Abstract]
Net securities (gains) losses	$ 388	$ (4,213)	$ 6,341
Interest income (expense)	315,678	311,555	305,629
Other noninterest expense	24,863	24,440	19,597
Income tax (benefit) expense	28,699	34,411	24,436
Net Income	104,388	121,021	112,566
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Total reclassifications, net of tax	1,923	1,117	4,617
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Income tax (benefit) expense	(160)	(204)	(1,827)
Net Income	481	612	5,483
Gains (losses) on AFS securities [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Net securities (gains) losses	(3)	79	6,622
Amortization of Unrealized Gains Related to Securities Transfer [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Interest income (expense)	644	737	688
Net Unrealized Losses (Gains) on Cash Flow Hedges Reclassified to Interest Expense [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Interest income (expense)	296	(2,012)	(2,300)
Income tax (benefit) expense	(74)	503	575
Net Income	222	(1,509)	(1,725)
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Income tax (benefit) expense	(407)	(672)	(286)
Net Income	1,220	2,014	859
Amortization of Net Losses [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Other noninterest expense	1,535	2,593	1,054
Amortization of Prior Service Costs [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustments out of AOCI [Abstract]
Other noninterest expense	$ 92	$ 93	$ 91

Commitments and Contingent Li_3

Commitments and Contingent Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Commitments and Contingent Liabilities [Abstract]
Percentage of the Company's loans secured by real estate	59.00%
Guarantor Obligations [Abstract]
Obligation instrument term	1 year
Federal Reserve Bank Requirement [Abstract]
Federal Reserve Bank maintenance period	14 days
Average reserve at Federal Reserve Bank for maintenance period	$ 64,600
Unused lines of Credit [Member]
Guarantor Obligations [Abstract]
Commitments - maximum potential obligation	351,876	$ 340,703
Commitment to Extend Credits, Primarily Variable Rate [Member]
Guarantor Obligations [Abstract]
Commitments - maximum potential obligation	1,831,671	1,579,414
Standby Letters of Credit [Member]
Guarantor Obligations [Abstract]
Commitments - maximum potential obligation	54,009	34,479
Loans Sold with Recourse [Member]
Guarantor Obligations [Abstract]
Commitments - maximum potential obligation	$ 25,659	$ 25,639

Derivative Instruments and He_3

Derivative Instruments and Hedging Activities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)Agreement	Dec. 31, 2019USD ($)Agreement	Dec. 31, 2018USD ($)
Interest rate derivatives - Included Component [Abstract]
Amount of (loss) gain recognized in OCI	$ (275)	$ (459)	$ 1,218
Amount of loss (gain) reclassified from AOCI into interest expense	296	(2,012)	(2,300)
Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Fair value adjustment recorded related to notional amount of derivatives outstanding and notional amount of risk participation agreements [Abstract]
Fair value adjustment included in other assets	0	4
Fair value adjustment included in other liabilities	34	45
Notional amount	25,000	50,000
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedging [Member]
Interest rate derivatives - Included Component [Abstract]
Amount of (loss) gain recognized in OCI	(275)	(459)	1,218
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedging [Member] | Interest (Income) Expense [Member]
Interest rate derivatives - Included Component [Abstract]
Amount of loss (gain) reclassified from AOCI into interest expense	296	(2,012)	(2,300)
Derivatives Designated as Hedging Instruments [Member] | Cash Flow Hedging [Member] | Interest Rate Swaps [Member]
Fair value adjustment recorded related to notional amount of derivatives outstanding and notional amount of risk participation agreements [Abstract]
Amount to be reclassified from AOCI as a reduction to interest expense during next twelve months	21
Derivatives Not Designated as Hedging Instruments [Member] | Other Income [Member]
Gain or loss recognized in income on derivatives not designating as a hedging relationship [Abstract]
Increase (decrease) in other income	$ 1	$ 295	$ (120)
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Interest rate derivatives [Abstract]
Number of risk participation agreements held | Agreement	17	15
Fair value adjustment recorded related to notional amount of derivatives outstanding and notional amount of risk participation agreements [Abstract]
Fair value adjustment included in other assets and other liabilities	$ 108,487	$ 41,650
Notional amount	2,447,168	963,209
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member] | Other Assets [Member]
Interest rate derivatives [Abstract]
Fair value of derivative asset	292	112
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member] | Other Liabilities [Member]
Interest rate derivatives [Abstract]
Fair value of derivative liability	125	82
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member]
Fair value adjustment recorded related to notional amount of derivatives outstanding and notional amount of risk participation agreements [Abstract]
Notional amount	$ 112,313	$ 97,614

Fair Values of Financial Inst_4

Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
AFS securities [Abstract]
AFS securities	$ 1,348,698	$ 975,340
Equity securities	30,737	27,771
Fair Value Measurements [Abstract]
Collateral dependent impaired loans with specific reserve	15,200	0
Reserves on collateral dependent impaired loans	$ 3,200
Minimum [Member]
Fair Value Measurements [Abstract]
Liquidation expense ratio on impaired collateral	10.00%
Maximum [Member]
Fair Value Measurements [Abstract]
Liquidation expense ratio on impaired collateral	50.00%
Changes Measurement [Member]
Fair Value Measurements [Abstract]
Branch location with pending disposition	$ (500)	(1,000)
Fair Value [Member]
Fair Value Measurements [Abstract]
Branch location with pending disposition		200
Recurring Basis [Member]
AFS securities [Abstract]
AFS securities	1,348,698	975,340
Equity securities	30,737	27,771
Derivatives	108,779	41,766
Total	1,488,214	1,044,877
Liabilities [Abstract]
Derivatives	108,646	41,777
Total	108,646	41,777
Recurring Basis [Member] | Level 1 [Member]
AFS securities [Abstract]
AFS securities	0	0
Equity securities	28,737	23,771
Derivatives	0	0
Total	28,737	23,771
Liabilities [Abstract]
Derivatives	0	0
Total	0	0
Recurring Basis [Member] | Level 2 [Member]
AFS securities [Abstract]
AFS securities	1,348,698	975,340
Equity securities	2,000	4,000
Derivatives	108,779	41,766
Total	1,459,477	1,021,106
Liabilities [Abstract]
Derivatives	108,646	41,777
Total	108,646	41,777
Recurring Basis [Member] | Level 3 [Member]
AFS securities [Abstract]
AFS securities	0	0
Equity securities	0	0
Derivatives	0	0
Total	0	0
Liabilities [Abstract]
Derivatives	0	0
Total	0	0
Recurring Basis [Member] | Federal Agency [Member]
AFS securities [Abstract]
AFS securities	243,597	34,758
Recurring Basis [Member] | Federal Agency [Member] | Level 1 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] | Federal Agency [Member] | Level 2 [Member]
AFS securities [Abstract]
AFS securities	243,597	34,758
Recurring Basis [Member] | Federal Agency [Member] | Level 3 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] | State & Municipal [Member]
AFS securities [Abstract]
AFS securities	43,180	2,513
Recurring Basis [Member] | State & Municipal [Member] | Level 1 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] | State & Municipal [Member] | Level 2 [Member]
AFS securities [Abstract]
AFS securities	43,180	2,513
Recurring Basis [Member] | State & Municipal [Member] | Level 3 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] | Mortgage-Backed [Member]
AFS securities [Abstract]
AFS securities	595,839	503,626
Recurring Basis [Member] | Mortgage-Backed [Member] | Level 1 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] | Mortgage-Backed [Member] | Level 2 [Member]
AFS securities [Abstract]
AFS securities	595,839	503,626
Recurring Basis [Member] | Mortgage-Backed [Member] | Level 3 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] | Collateralized Mortgage Obligations [Member]
AFS securities [Abstract]
AFS securities	437,804	434,443
Recurring Basis [Member] | Collateralized Mortgage Obligations [Member] | Level 1 [Member]
AFS securities [Abstract]
AFS securities	0	0
Recurring Basis [Member] | Collateralized Mortgage Obligations [Member] | Level 2 [Member]
AFS securities [Abstract]
AFS securities	437,804	434,443
Recurring Basis [Member] | Collateralized Mortgage Obligations [Member] | Level 3 [Member]
AFS securities [Abstract]
AFS securities	0	$ 0
Recurring Basis [Member] | Corporate [Member]
AFS securities [Abstract]
AFS securities	28,278
Recurring Basis [Member] | Corporate [Member] | Level 1 [Member]
AFS securities [Abstract]
AFS securities	0
Recurring Basis [Member] | Corporate [Member] | Level 2 [Member]
AFS securities [Abstract]
AFS securities	28,278
Recurring Basis [Member] | Corporate [Member] | Level 3 [Member]
AFS securities [Abstract]
AFS securities	$ 0

Fair Values of Financial Inst_5

Fair Values of Financial Instruments, Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financial assets [Abstract]
HTM securities	$ 636,827	$ 641,262
Carrying Amount [Member] | Level 1 [Member]
Financial liabilities [Abstract]
Subordinated debt	100,000	0
Carrying Amount [Member] | Level 2 [Member]
Financial assets [Abstract]
HTM securities	616,560	630,074
Financial liabilities [Abstract]
Time deposits	633,479	861,193
Long-term debt	39,097	64,211
Junior subordinated debt	101,196	101,196
Carrying Amount [Member] | Level 3 [Member]
Financial assets [Abstract]
Net loans	7,390,004	7,074,864
Estimated Fair Value [Member] | Level 1 [Member]
Financial liabilities [Abstract]
Subordinated debt	103,277	0
Estimated Fair Value [Member] | Level 2 [Member]
Financial assets [Abstract]
HTM securities	636,827	641,262
Financial liabilities [Abstract]
Time deposits	638,721	858,085
Long-term debt	39,820	64,373
Junior subordinated debt	108,926	105,694
Estimated Fair Value [Member] | Level 3 [Member]
Financial assets [Abstract]
Net loans	$ 7,530,033	$ 6,999,690

Parent Company Financial Info_3

Parent Company Financial Information, Condensed Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets [Abstract]
Cash and cash equivalents	$ 672,681	$ 216,843	$ 180,955	$ 159,664
Equity securities, at estimated fair value	30,737	27,771
Other assets	293,957	202,245
Total assets	10,932,906	9,715,925
Liabilities and Stockholders' Equity [Abstract]
Total liabilities	9,745,288	8,595,528
Stockholders' equity	1,187,618	1,120,397	1,017,909	958,177
Total liabilities and stockholders' equity	10,932,906	9,715,925
NBT Bancorp Inc [Member]
Assets [Abstract]
Cash and cash equivalents	37,915	9,387	$ 5,876	$ 7,572
Equity securities, at estimated fair value	25,111	22,441
Investment in subsidiaries, on equity basis	1,345,317	1,209,752
Other assets	30,577	30,855
Total assets	1,438,920	1,272,435
Liabilities and Stockholders' Equity [Abstract]
Total liabilities	251,302	152,038
Stockholders' equity	1,187,618	1,120,397
Total liabilities and stockholders' equity	$ 1,438,920	$ 1,272,435

Parent Company Financial Info_4

Parent Company Financial Information, Condensed Income Statements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Income Statements [Abstract]
Net securities (losses) gains	$ (388)	$ 4,213	$ (6,341)
Interest, dividends and other income	348,282	367,534	344,255
Income before income tax expense	133,087	155,432	137,002
Income tax benefit	28,699	34,411	24,436
Net income	104,388	121,021	112,566
NBT Bancorp Inc [Member]
Condensed Income Statements [Abstract]
Dividends from subsidiaries	77,000	50,200	43,000
Management fee from subsidiaries	4,151	7,981	7,907
Net securities (losses) gains	(483)	165	399
Interest, dividends and other income	824	876	905
Total revenue	81,492	59,222	52,211
Operating expenses	11,825	14,262	14,226
Income before income tax expense	69,667	44,960	37,985
Income tax benefit	(2,653)	(1,588)	(1,608)
Equity in undistributed income of subsidiaries	32,068	74,473	72,973
Net income	$ 104,388	$ 121,021	$ 112,566

Parent Company Financial Info_5

Parent Company Financial Information, Condensed Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities [Abstract]
Net income	$ 104,388	$ 121,021	$ 112,566
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Depreciation and amortization of premises and equipment	9,772	9,497	9,280
Excess tax benefit on stock-based compensation	(181)	(409)	(543)
Stock-based compensation expense	4,581	4,210	3,936
Net securities losses (gains)	388	(4,213)	6,341
Bank owned life insurance income	(5,743)	(5,355)	(5,091)
Amortization of subordinated debt issuance costs	230	0	0
Net change in other assets and other liabilities	(49,930)	(6,774)	(9,554)
Net cash provided by operating activities	142,412	153,463	147,773
Investing activities [Abstract]
Proceeds on sales of equity securities	0	3,966	3,318
Purchases of equity securities	0	(93)	(2)
Net cash used in investing activities	(709,725)	(64,343)	(417,619)
Financing activities [Abstract]
Proceeds from issuance of subordinated debt	100,000	0	0
Payment of subordinated debt issuance costs	(2,178)	0	0
Proceeds from the issuance of shares to employee and other stock plans	184	725	1,296
Cash paid by employer for tax-withholding on stock issuance	(1,537)	(1,622)	(1,893)
Purchases of treasury shares	(7,980)	0	0
Cash dividends	(47,207)	(46,010)	(43,269)
Net cash provided by (used in) financing activities	1,023,151	(53,232)	291,137
Net increase in cash and cash equivalents	455,838	35,888	21,291
Cash and cash equivalents at beginning of year	216,843	180,955	159,664
Cash and cash equivalents at end of year	672,681	216,843	180,955
NBT Bancorp Inc [Member]
Operating activities [Abstract]
Net income	104,388	121,021	112,566
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Depreciation and amortization of premises and equipment	1,739	2,298	2,814
Excess tax benefit on stock-based compensation	(181)	(409)	(543)
Stock-based compensation expense	4,581	4,210	3,936
Net securities losses (gains)	483	(165)	(399)
Equity in undistributed income of subsidiaries	(32,068)	(74,473)	(72,973)
Bank owned life insurance income	(391)	(398)	(424)
Amortization of subordinated debt issuance costs	230	0	0
Net change in other assets and other liabilities	(3,535)	(1,573)	(6,124)
Net cash provided by operating activities	75,246	50,511	38,853
Investing activities [Abstract]
Investment in the Bank	(90,000)	0	0
Proceeds from calls of equity securities	2,000	0	0
Proceeds on sales of equity securities	0	0	3,318
Purchases of equity securities	0	(93)	(2)
Net cash used in investing activities	(88,000)	(93)	3,316
Financing activities [Abstract]
Proceeds from issuance of subordinated debt	100,000	0	0
Payment of subordinated debt issuance costs	(2,178)	0	0
Proceeds from the issuance of shares to employee and other stock plans	184	725	1,296
Cash paid by employer for tax-withholding on stock issuance	(1,537)	(1,622)	(1,893)
Purchases of treasury shares	(7,980)	0	0
Cash dividends	(47,207)	(46,010)	(43,269)
Net cash provided by (used in) financing activities	41,282	(46,907)	(43,866)
Net increase in cash and cash equivalents	28,528	3,511	(1,697)
Cash and cash equivalents at beginning of year	9,387	5,876	7,572
Cash and cash equivalents at end of year	$ 37,915	$ 9,387	$ 5,876