Community Bank System (CBU) 10-Q 9 Aug 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Jul. 31, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Quarterly Report	true
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity Registrant Name	COMMUNITY BANK SYSTEM, INC.
Entity Incorporation, State or Country Code	DE
Entity File Number	001-13695
Entity Tax Identification Number	16-1213679
Entity Address, Address Line One	5790 Widewaters Parkway
Entity Address, City or Town	DeWitt
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	13214
City Area Code	315
Local Phone Number	445-2282
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		53,918,062
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Central Index Key	0000723188
Title of 12(b) Security	Common Stock, $1.00 par value per share
Trading Symbol	CBU
Security Exchange Name	NYSE

CONSOLIDATED STATEMENTS OF COND

CONSOLIDATED STATEMENTS OF CONDITION - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets:
Cash and cash equivalents	$ 2,205,926	$ 1,645,805
Available-for-sale investment securities (cost of $4,039,978 and $3,427,779, respectively)	4,012,739	3,547,892
Equity and other securities (cost of $43,955 and $46,511, respectively)	44,923	47,455
Loans held for sale, at fair value	1,340	1,622
Loans	7,244,147	7,415,952
Allowance for credit losses	(51,750)	(60,869)
Net loans	7,192,397	7,355,083
Goodwill, net	794,892	793,708
Core deposit intangibles, net	11,267	13,831
Other intangibles, net	36,513	39,109
Intangible assets, net	842,672	846,648
Premises and equipment, net	161,007	165,655
Accrued interest and fees receivable	36,954	39,031
Other assets	303,329	281,903
Total assets	14,801,287	13,931,094
Liabilities:
Noninterest-bearing deposits	3,729,355	3,361,768
Interest-bearing deposits	8,609,670	7,863,206
Total deposits	12,339,025	11,224,974
Securities sold under agreement to repurchase, short-term	194,887	284,008
Other Federal Home Loan Bank borrowings	2,936	6,658
Subordinated notes payable	3,290	3,303
Subordinated debt held by unconsolidated subsidiary trusts	0	77,320
Accrued interest and other liabilities	200,049	230,724
Total liabilities	12,740,187	11,826,987
Commitments and contingencies (See Note J)
Shareholders' equity:
Preferred stock, $1.00 par value, 500,000 shares authorized, 0 shares issued	0	0
Common stock, $1.00 par value, 75,000,000 shares authorized; 54,063,867 and 53,754,599 shares issued, respectively	54,064	53,755
Additional paid-in capital	1,037,088	1,025,163
Retained earnings	1,015,742	960,183
Accumulated other comprehensive (loss) income	(48,400)	62,077
Treasury stock, at cost (145,172 shares, including 145,157 shares held by deferred compensation arrangements at June 30, 2021 and 161,472 shares including 161,457 shares held by deferred compensation arrangements at December 31, 2020, respectively)	(5,632)	(6,198)
Deferred compensation arrangements (145,157 and 161,457 shares, respectively)	8,238	9,127
Total shareholders' equity	2,061,100	2,104,107
Total liabilities and shareholders' equity	$ 14,801,287	$ 13,931,094

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF CONDITION (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets:
Available-for-sale investment securities, cost	$ 4,039,978	$ 3,427,779
Equity and other securities, cost	$ 43,955	$ 46,511
Shareholders' equity:
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	500,000	500,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	54,063,867	53,754,599
Treasury stock, shares at cost (in shares)	145,172	161,472
Shares held by deferred compensation arrangements (in shares)	145,157	161,457

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Interest income:
Interest and fees on loans	$ 75,907	$ 78,720	$ 155,621	$ 157,285
Interest and dividends on taxable investments	16,789	15,423	31,964	30,752
Interest and dividends on nontaxable investments	2,664	3,049	5,440	6,150
Total interest income	95,360	97,192	193,025	194,187
Interest expense:
Interest on deposits	2,963	4,173	6,075	9,718
Interest on borrowings	253	430	521	988
Interest on subordinated notes payable	39	184	77	369
Interest on subordinated debt held by unconsolidated subsidiary trusts	0	454	293	1,107
Total interest expense	3,255	5,241	6,966	12,182
Net interest income	92,105	91,951	186,059	182,005
Provision for credit losses	(4,338)	9,774	(10,057)	15,368
Net interest income after provision for credit losses	96,443	82,177	196,116	166,637
Noninterest revenues:
Deposit service fees	14,236	12,179	28,316	28,462
Mortgage banking	331	1,375	1,019	2,291
Other banking services	980	755	1,834	1,650
Employee benefit services	27,477	24,068	54,010	49,434
Insurance services	8,209	8,183	16,362	16,241
Wealth management services	8,227	6,366	16,426	13,500
Unrealized gain (loss) on equity securities	0	12	24	(18)
Total noninterest revenues	59,460	52,938	117,991	111,560
Noninterest expenses:
Salaries and employee benefits	57,892	54,721	115,524	112,972
Occupancy and equipment	10,270	9,754	21,570	20,493
Data processing and communications	12,766	10,833	25,157	21,246
Amortization of intangible assets	3,246	3,524	6,597	7,191
Legal and professional fees	2,499	3,061	5,533	6,212
Business development and marketing	2,659	1,504	4,689	4,017
Acquisition expenses	4	3,372	31	3,741
Other expenses	4,207	4,134	7,688	8,694
Total noninterest expenses	93,543	90,903	186,789	184,566
Income before income taxes	62,360	44,212	127,318	93,631
Income taxes	14,416	8,964	26,524	18,249
Net income	$ 47,944	$ 35,248	$ 100,794	$ 75,382
Basic earnings per share (in dollars per share)	$ 0.89	$ 0.67	$ 1.86	$ 1.44
Diluted earnings per share (in dollars per share)	$ 0.88	$ 0.66	$ 1.85	$ 1.43

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Pension and other post retirement obligations:
Amortization of actuarial losses included in net periodic pension cost, gross	$ 911	$ 820	$ 1,822	$ 1,640
Tax effect	(219)	(197)	(438)	(394)
Amortization of actuarial losses included in net periodic pension cost, net	692	623	1,384	1,246
Amortization of prior service cost included in net periodic pension cost, gross	50	16	100	31
Tax effect	(12)	(4)	(24)	(7)
Amortization of prior service cost included in net periodic pension cost, net	38	12	76	24
Other comprehensive income related to pension and other post retirement obligations, net of taxes	730	635	1,460	1,270
Unrealized gains (losses) on available-for-sale securities:
Net unrealized holding (losses) gains arising during period, gross	80,074	7,832	(147,353)	130,260
Tax effect	(19,247)	(1,880)	35,416	(31,273)
Net unrealized holding (losses) gains arising during period, net	60,827	5,952	(111,937)	98,987
Other comprehensive income (loss) related to unrealized gains (losses) on available-for-sale securities, net of taxes	60,827	5,952	(111,937)	98,987
Other comprehensive (loss) income, net of tax	61,557	6,587	(110,477)	100,257
Net income	47,944	35,248	100,794	75,382
Comprehensive income (loss)	109,501	$ 41,835	(9,683)	$ 175,639
Accumulated Other Comprehensive (Loss) Income By Component:
Unrealized (loss) for pension and other post-retirement obligations	(36,345)		(36,345)		$ (38,267)
Tax effect	8,932		8,932		9,394
Net unrealized (loss) for pension and other post-retirement obligations	(27,413)		(27,413)		(28,873)
Unrealized (loss) gain on available-for-sale securities	(27,239)		(27,239)		120,114
Tax effect	6,252		6,252		(29,164)
Net unrealized (loss) gain on available-for-sale securities	(20,987)		(20,987)		90,950
Accumulated other comprehensive (loss) income	$ (48,400)		$ (48,400)		$ 62,077

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock Outstanding [Member]	Common Stock Amount Issued [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Treasury Stock [Member]	Deferred Compensation Arrangements [Member]	Total
Balance at Dec. 31, 2019		$ 51,975	$ 927,337	$ 882,851	$ (10,226)	$ (6,823)	$ 10,120	$ 1,855,234
Balance (in shares) at Dec. 31, 2019	51,793,923
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income				75,382				75,382
Other comprehensive income (loss), net of tax					100,257			100,257
Cumulative effect of change in accounting Principle - Current Expected Credit Losses				530				530
Dividends declared:
Common				(43,371)				(43,371)
Common stock activity under employee stock plans		334	12,689					13,023
Common stock activity under employee stock plans (in shares)	333,556
Stock-based compensation			3,233					3,233
Stock issued for acquisition		1,363	75,579					76,942
Stock issued for acquisition (in shares)	1,363,259
Distribution of stock under deferred compensation arrangements			415			849	(1,264)	0
Distribution of stock under deferred compensation arrangements (in shares)	22,497
Treasury stock issued to benefit plans, net			38			(92)	139	85
Treasury stock issued to benefit plans, net (in shares)	981
Balance at Jun. 30, 2020		53,672	1,019,291	915,392	90,031	(6,066)	8,995	2,081,315
Balance (in shares) at Jun. 30, 2020	53,514,216
Balance at Mar. 31, 2020		52,190	935,924	902,148	83,444	(6,005)	8,930	1,976,631
Balance (in shares) at Mar. 31, 2020	52,031,092
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income				35,248				35,248
Other comprehensive income (loss), net of tax					6,587			6,587
Dividends declared:
Common				(22,004)				(22,004)
Common stock activity under employee stock plans		119	6,505					6,624
Common stock activity under employee stock plans (in shares)	118,968
Stock-based compensation			1,281					1,281
Stock issued for acquisition		1,363	75,579					76,942
Stock issued for acquisition (in shares)	1,363,259
Treasury stock issued to benefit plans, net			2			(61)	65	6
Treasury stock issued to benefit plans, net (in shares)	897
Balance at Jun. 30, 2020		53,672	1,019,291	915,392	90,031	(6,066)	8,995	2,081,315
Balance (in shares) at Jun. 30, 2020	53,514,216
Balance at Dec. 31, 2020		53,755	1,025,163	960,183	62,077	(6,198)	9,127	2,104,107
Balance (in shares) at Dec. 31, 2020	53,593,127
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income				100,794				100,794
Other comprehensive income (loss), net of tax					(110,477)			(110,477)
Dividends declared:
Common				(45,235)				(45,235)
Common stock activity under employee stock plans		309	8,360					8,669
Common stock activity under employee stock plans (in shares)	309,268
Stock-based compensation			3,242					3,242
Distribution of stock under deferred compensation arrangements			323			694	(1,017)	0
Distribution of stock under deferred compensation arrangements (in shares)	18,089
Treasury stock issued to benefit plans, net						(128)	128	0
Treasury stock issued to benefit plans, net (in shares)	(1,789)
Balance at Jun. 30, 2021		54,064	1,037,088	1,015,742	(48,400)	(5,632)	8,238	2,061,100
Balance (in shares) at Jun. 30, 2021	53,918,695
Balance at Mar. 31, 2021		54,019	1,034,225	990,504	(109,957)	(5,572)	8,178	1,971,397
Balance (in shares) at Mar. 31, 2021	53,874,979
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income				47,944				47,944
Other comprehensive income (loss), net of tax					61,557			61,557
Dividends declared:
Common				(22,706)				(22,706)
Common stock activity under employee stock plans		45	1,295					1,340
Common stock activity under employee stock plans (in shares)	44,493
Stock-based compensation			1,568					1,568
Treasury stock issued to benefit plans, net						(60)	60	0
Treasury stock issued to benefit plans, net (in shares)	777
Balance at Jun. 30, 2021		$ 54,064	$ 1,037,088	$ 1,015,742	$ (48,400)	$ (5,632)	$ 8,238	$ 2,061,100
Balance (in shares) at Jun. 30, 2021	53,918,695

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Cash dividends declared:
Dividends declared per common share (in dollars per share)	$ 0.42	$ 0.41	$ 0.84	$ 0.82

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities:
Net income	$ 100,794	$ 75,382
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	8,014	7,995
Amortization of intangible assets	6,597	7,191
Net accretion on securities, loans and borrowings	(11,729)	(5,902)
Stock-based compensation	3,242	3,233
Provision for credit losses	(10,057)	15,368
Amortization of mortgage servicing rights	269	166
Unrealized (gain) loss on equity securities	(24)	18
Income from bank-owned life insurance policies	(981)	(866)
Net gain on sale of loans and other assets	(463)	(529)
Change in other assets and other liabilities	(7,585)	(6,701)
Net cash provided by operating activities	88,077	95,355
Investing activities:
Proceeds from maturities, calls, and paydowns of available-for-sale investment securities	151,994	130,739
Proceeds from maturities and redemptions of equity and other investment securities	2,648	406
Purchases of available-for-sale investment securities	(759,022)	(65,211)
Purchases of equity and other securities	(92)	(24)
Net decrease (increase) in loans	179,167	(296,873)
Cash (paid) received for acquisitions, net of cash acquired of $0 and $55,973, respectively	(2,900)	34,360
Purchases of premises and equipment, net	(5,689)	(4,641)
Real estate tax credit investments	(320)	(550)
Net cash used in investing activities	(434,214)	(201,794)
Financing activities:
Net increase in deposits	1,114,051	1,335,437
Net decrease in borrowings	(92,843)	(83,563)
Payments on subordinated debt held by unconsolidated subsidiary trusts	(77,320)	0
Issuance of common stock	8,669	13,023
Purchases of treasury stock	(128)	(139)
Sales of treasury stock	0	85
Increase in deferred compensation arrangements	128	139
Cash dividends paid	(45,162)	(42,609)
Withholding taxes paid on share-based compensation	(1,137)	(1,084)
Net cash provided by financing activities	906,258	1,221,289
Change in cash and cash equivalents	560,121	1,114,850
Cash and cash equivalents at beginning of period	1,645,805	205,030
Cash and cash equivalents at end of period	2,205,926	1,319,880
Supplemental disclosures of cash flow information:
Cash paid for interest	7,644	12,336
Cash paid for income taxes	22,482	10,459
Supplemental disclosures of noncash financing and investing activities:
Dividends declared and unpaid	22,768	22,104
Transfers from loans to other real estate	120	990
Acquisitions:
Common stock issued	0	76,942
Fair value of assets acquired, excluding acquired cash and intangibles	199	549,983
Fair value of liabilities assumed	$ 174	$ 530,767

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Investing activities:
Cash acquired related to acquisition	$ 0	$ 55,973

BASIS OF PRESENTATION

BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2021
BASIS OF PRESENTATION
BASIS OF PRESENTATION	NOTE A: BASIS OF PRESENTATION The interim financial data as of and for the three and six months ended June 30, 2021 is unaudited; however, in the opinion of Community Bank System, Inc. (the “Company”), the interim data includes all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement of the results for the interim periods in conformity with generally accepted accounting principles in the United States of America (“GAAP”) and Article 10 of Regulation S-X. The results of operations for the interim periods are not necessarily indicative of the results that may be expected for the full year or any other interim period. The Company’s unaudited interim consolidated financial statements and notes thereto should be read in conjunction with the Company’s audited annual consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 filed with the Securities and Exchange Commission (“SEC”) on March 1, 2021.

ACQUISITIONS

ACQUISITIONS	6 Months Ended
	Jun. 30, 2021
ACQUISITIONS
ACQUISITIONS	NOTE B: ACQUISITIONS Subsequent Events On July 1, 2021, the Company, through its subsidiary Benefit Plans Administrative Services, Inc., completed its acquisition of Fringe Benefits Design of Minnesota, Inc. (“FBD”) for $15.3 million in cash, excluding contingent consideration valued up to $2.7 million. The Company expects to incur certain one-time, transaction-related costs in the third quarter of 2021 in connection with the FBD acquisition, and the effects of the acquisition will be reflected in the third quarter consolidated financial statements. On August 2, 2021, the Company, through its subsidiary OneGroup NY, Inc. (“OneGroup”), completed its acquisition of certain assets of the Thomas Gregory Associates Insurance Brokers, Inc. (“TGA”), a specialty-lines insurance broker based in the Boston, Massachusetts marketplace, for $11.6 million in cash, excluding contingent consideration valued up to $3.4 million. The Company expects to incur certain one-time, transaction-related costs in the third quarter of 2021 in connection with the TGA acquisition, and the effects of the acquisition will be reflected in the third quarter consolidated financial statements. Current and Prior Period Acquisitions On June 1, 2021, the Company, through its subsidiary OneGroup, completed its acquisition of certain assets of NuVantage Insurance Corp. ("NuVantage"), an insurance agency headquartered in Melbourne, Florida. The Company paid $2.9 million in cash and recorded a $1.4 million customer list intangible asset and $1.5 million of goodwill in conjunction with the acquisition. The effects of the acquired assets have been included in the consolidated financial statements since that date. On June 12, 2020, the Company completed its merger with Steuben Trust Corporation (“Steuben”), parent company of Steuben Trust Company, a New York State chartered bank headquartered in Hornell, New York, for $98.6 million in Company stock and cash, comprised of $21.6 million in cash and the issuance of 1.36 million shares of common stock. The merger extended the Company’s footprint into two new counties in Western New York State, and enhanced the Company’s presence in four Western New York State counties in which it had already operated. In connection with the merger, the Company added 11 full-service offices to its branch service network and acquired $607.8 million of assets, including $339.7 million of loans and $180.5 million of investment securities, as well as $516.3 million of deposits. Goodwill of $20.0 million was recognized as a result of the merger. The effects of the acquired assets and liabilities have been included in the consolidated financial statements since that date. Revenues, excluding interest income on acquired investments, interest income on acquired consumer indirect loans, and revenues associated with acquired loans and deposits consolidated into the legacy branch network, of approximately $3.3 million and $6.5 million, and direct expenses, which may not include certain shared expenses, of approximately $1.2 million and $2.5 million from Steuben were included in the consolidated income statement for the three and six months ended June 30, 2021. The Company incurred certain one-time, transaction-related costs in 2020 in connection with the Steuben acquisition. The assets and liabilities assumed in the acquisitions were recorded at their estimated fair values based on management’s best estimates using information available at the dates of the acquisitions, and were subject to adjustment based on updated information not available at the time of the acquisitions. Through the second quarter of 2021, the carrying amount of other liabilities associated with the Steuben acquisition decreased by $0.3 million as a result of an adjustment to accrued income taxes and deferred income taxes. Goodwill associated with the Steuben acquisition decreased $0.3 million as a result of this adjustment. The acquisitions expanded the Company’s geographical presence in New York and Florida and management expects that the Company will benefit from greater geographic diversity and the advantages of other synergistic business development opportunities. The following table summarizes the estimated fair value of the assets acquired and liabilities assumed after considering the measurement period adjustments described above: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 (000s omitted) ​ NuVantage ​ Steuben Consideration paid : ​ ​ ​ ​ ​ Cash ​ $ 2,900 ​ $ 21,613 Community Bank System, Inc. common stock ​ ​ 0 ​ 76,942 Total net consideration paid ​ ​ 2,900 ​ 98,555 Recognized amounts of identifiable assets acquired and liabilities assumed: ​ ​ ​ ​ Cash and cash equivalents ​ ​ 0 ​ 55,973 Investment securities ​ ​ 0 ​ 180,497 Loans, net of allowance for credit losses on PCD loans ​ ​ 0 ​ 339,017 Premises and equipment, net ​ ​ 199 ​ 7,764 Accrued interest and fees receivable ​ ​ 0 ​ 2,701 Other assets ​ ​ 0 ​ 17,675 Core deposit intangibles ​ ​ 0 ​ 2,928 Other intangibles ​ ​ 1,437 ​ 1,196 Deposits ​ ​ 0 ​ (516,274) Other liabilities ​ ​ (174) ​ (4,841) Other Federal Home Loan Bank borrowings ​ ​ 0 ​ (6,000) Subordinated debt held by unconsolidated subsidiary trusts ​ ​ 0 ​ (2,062) Total identifiable assets, net ​ ​ 1,462 ​ 78,574 Goodwill ​ $ 1,438 ​ $ 19,981 ​ The Company has acquired loans from Steuben for which there was evidence of a more-than-insignificant deterioration in credit quality since origination (purchased credit deteriorated (“PCD”) loans). PCD loans are initially recorded at the amount paid. An allowance for credit losses is determined using the same methodology as other loans. The initial allowance for credit losses determined on a collective basis is allocated to individual loans. The sum of the loan’s purchase price and allowance for credit losses becomes its initial amortized cost basis. The difference between the initial amortized cost basis and the par value of the loan is a noncredit discount or premium, which is amortized into interest income over the life of the loan. Subsequent changes to the allowance for credit losses are recorded as provision for (or reversal of) credit losses. There were no investment securities acquired from Steuben for which there was evidence of a more-than-insignificant deterioration in credit quality since origination. The carrying amount of those loans is as follows at the date of acquisition: ​ ​ ​ ​ ​ (000s omitted) PCD Loans Par value of PCD loans at acquisition ​ $ 35,906 Allowance for credit losses at acquisition ​ (668) Non-credit premium at acquisition ​ 103 Fair value of PCD loans at acquisition ​ $ 35,341 ​ Acquired loans that are deemed to not have experienced a more-than-insignificant credit deterioration since origination are considered non-PCD. At the acquisition date, a fair value adjustment is recorded that includes both credit and interest rate considerations. Fair value adjustments may be discounts (or premiums) to a loan’s cost basis and are accreted (or amortized) to net interest income (or expense) over the loan’s remaining life. Fair value adjustments for revolving loans are accreted (or amortized) using a straight line method. Term loans are accreted (or amortized) using the constant effective yield method. A provision for credit losses is also recorded at acquisition for the credit considerations on non-PCD loans. Subsequent to the purchase date, the methods utilized to estimate the required allowance for credit losses for these loans are the same as originated loans and subsequent changes to the allowance for credit losses are recorded as provision for (or reversal of) credit losses. The following is a summary of the remaining loans acquired from Steuben for which there was no evidence of a more-than-insignificant deterioration in credit quality since origination at the date of acquisition: ​ ​ ​ ​ ​ (000s omitted) Non-PCD Loans Contractually required principal and interest at acquisition ​ $ 400,738 Contractual cash flows not expected to be collected ​ (2,994) Expected cash flows at acquisition ​ 397,744 Interest component of expected cash flows ​ (94,068) Fair value of non-PCD loans at acquisition ​ $ 303,676 ​ The fair value of the Company’s common stock issued for the Steuben acquisition was determined using the market close price of the stock on June 12, 2020. The fair value of checking, savings and money market deposit accounts acquired were assumed to approximate the carrying value as these accounts have no stated maturity and are payable on demand. Certificate of deposit accounts were valued at the present value of the certificates’ expected contractual payments discounted at market rates for similar certificates. The core deposit intangibles and other intangibles related to the Steuben acquisition and the NuVantage acquisition are being amortized using an accelerated method over their estimated useful life of eight years. The goodwill, which is not amortized for book purposes, was assigned to the Banking segment for the Steuben Direct costs related to the acquisitions were expensed as incurred. Merger and acquisition integration-related expenses were immaterial during the three and six months ended June 30, 2021 and amounted to $3.4 million and $3.7 million during the three and six months ended June 30, 2020, respectively, and have been separately stated in the consolidated statements of income. Supplemental Pro Forma Financial Information The following unaudited condensed pro forma information assumes the Steuben acquisition had been completed as of January 1, 2019 for the three and six months ended June 30, 2020 and June 30, 2019. The table below has been prepared for comparative purposes only and is not necessarily indicative of the actual results that would have been attained had the acquisition occurred as of the beginning of the year presented, nor is it indicative of the Company’s future results. Furthermore, the unaudited pro forma information does not reflect management’s estimate of any revenue-enhancing opportunities nor anticipated cost savings that may have occurred as a result of the integration and consolidation of the acquisitions. The pro forma information set forth below reflects the historical results of Steuben combined with the Company’s consolidated statements of income with adjustments related to (a) certain purchase accounting fair value adjustments and (b) amortization of customer lists and core deposit intangibles. Acquisition-related expenses totaling ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pro Forma (Unaudited) ​ Pro Forma (Unaudited) ​ ​ ​ Three Months Ended Six Months Ended ​ (000's omitted) June 30, 2020 June 30, 2019 June 30, 2020 June 30, 2019 Total revenue, net of interest expense ​ $ 149,576 ​ $ 154,878 ​ $ 304,088 ​ $ 303,152 ​ Net income ​ 39,072 ​ 46,447 ​ 80,848 ​ 86,774 ​ ​

ACCOUNTING POLICIES

ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2021
ACCOUNTING POLICIES
ACCOUNTING POLICIES	NOTE C: ACCOUNTING POLICIES The accounting policies of the Company, as applied in the consolidated interim financial statements presented herein, are substantially the same as those followed on an annual basis as presented on pages 79 through 92 of the Annual Report on Form 10-K for the year ended December 31, 2020 filed with the Securities and Exchange Commission (“SEC”) on March 1, 2021 except as noted below. The extent to which the novel coronavirus (“COVID-19”) impacts the Company’s business and financial results will depend on numerous evolving factors including, but not limited to: the magnitude and duration of COVID-19, the extent to which it will impact national and international macroeconomic conditions including interest rates, unemployment rates, the speed of the anticipated recovery, and governmental and business reactions to the pandemic. The Company assessed certain accounting matters that generally require consideration of forecasted financial information in context with the information reasonably available to the Company and the unknown future impacts of COVID-19 as of June 30, 2021 and through the date of this Quarterly Report on Form 10-Q. The accounting matters assessed included, but were not limited to, the Company’s allowance for credit losses, decrease in fee and interest income, and the carrying value of the goodwill and other long-lived assets. While there was not a material impact to the Company’s consolidated financial statements as of and for the three and six months ended June 30, 2021, the Company’s future assessment of the magnitude and duration of COVID-19, as well as other factors, could result in material impacts to the Company’s consolidated financial statements in future reporting periods. Contract Balances A contract asset balance occurs when an entity performs a service for a customer before the customer pays consideration (resulting in a contract receivable) or before payment is due (resulting in a contract asset). 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 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. As of June 30, 2021, $27.4 million of accounts receivable, including $8.3 million of unbilled fee revenue, and $2.7 million of unearned revenue was recorded in the consolidated statements of condition. As of December 31, 2020, $30.3 million of accounts receivable, including $7.7 million of unbilled fee revenue, and $1.4 million of unearned revenue was recorded in the consolidated statements of condition. Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-14, Disclosure Framework - Changes to the Disclosure Requirements for Defined Benefit Plans (Subtopic 715-20) . The updated guidance removed the requirements to identify amounts that are expected to be reclassified out of accumulated other comprehensive income and recognized as components of net periodic benefit cost in the next fiscal year, as well as the effects of a one-percentage-point change in assumed health care cost trend rates on service and interest cost and on the postretirement benefit obligation. The updated guidance added annual disclosure requirements for the weighted-average interest crediting rates for cash balance plans and other plans with interest crediting rates, and explanations for significant gains and losses related to changes in the benefit obligation for the period. This new guidance is effective retrospectively for fiscal years beginning after December 15, 2020 with early adoption permitted. The Company adopted this guidance on January 1, 2021 and determined the adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (Topic 740) . The updated guidance simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740, and clarifying and amending existing guidance to improve consistent application. This new guidance is effective for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. Early adoption is permitted in any interim periods for which financial statements have not been issued. The Company adopted this guidance on January 1, 2021 and determined the adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. New Accounting Pronouncements In March 2020, the FASB issued ASU No. 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting (Topic 848)

INVESTMENT SECURITIES

INVESTMENT SECURITIES	6 Months Ended
	Jun. 30, 2021
INVESTMENT SECURITIES
INVESTMENT SECURITIES	NOTE D: INVESTMENT SECURITIES The amortized cost and estimated fair value of investment securities as of June 30, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ December 31, 2020 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Amortized ​ Unrealized ​ Unrealized ​ Fair (000's omitted) Cost Gains Losses Value Cost Gains Losses Value Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 3,082,187 ​ $ 52,960 ​ $ 110,075 ​ $ 3,025,072 ​ $ 2,423,236 ​ $ 94,741 ​ $ 16,595 ​ $ 2,501,382 Obligations of state and political subdivisions ​ 405,245 ​ 20,908 ​ 1 ​ 426,152 ​ 451,028 ​ 24,632 ​ 0 ​ 475,660 Government agency mortgage-backed securities ​ 521,056 ​ 10,999 ​ 2,916 ​ 529,139 ​ 506,540 ​ 16,280 ​ 182 ​ 522,638 Corporate debt securities ​ 3,000 ​ 94 ​ 0 ​ 3,094 ​ 4,499 ​ 137 ​ 1 ​ 4,635 Government agency collateralized mortgage obligations ​ 28,490 ​ 796 ​ 4 ​ 29,282 ​ 42,476 ​ 1,111 ​ 10 ​ 43,577 Total available-for-sale portfolio ​ $ 4,039,978 ​ $ 85,757 ​ $ 112,996 ​ $ 4,012,739 ​ $ 3,427,779 ​ $ 136,901 ​ $ 16,788 ​ $ 3,547,892 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity and other Securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity securities, at fair value ​ $ 251 ​ $ 218 ​ $ 0 ​ $ 469 ​ $ 251 ​ $ 194 ​ $ 0 ​ $ 445 Federal Home Loan Bank common stock ​ 7,262 ​ 0 ​ 0 ​ 7,262 ​ 7,468 ​ 0 ​ 0 ​ 7,468 Federal Reserve Bank common stock ​ 33,916 ​ 0 ​ 0 ​ 33,916 ​ 33,916 ​ 0 ​ 0 ​ 33,916 Other equity securities, at adjusted cost ​ 2,526 ​ 750 ​ 0 ​ 3,276 ​ 4,876 ​ 750 ​ 0 ​ 5,626 Total equity and other securities ​ $ 43,955 ​ $ 968 ​ $ 0 ​ $ 44,923 ​ $ 46,511 ​ $ 944 ​ $ 0 ​ $ 47,455 ​ A summary of investment securities that have been in a continuous unrealized loss position is as follows: As of June 30, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 Months 12 Months or Longer Total ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized (000's omitted) # Value Losses # Value Losses # Value Losses ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ 29 ​ $ 1,272,423 ​ $ 110,075 ​ 0 ​ $ 0 ​ $ 0 ​ 29 ​ $ 1,272,423 ​ $ 110,075 Obligations of state and political subdivisions ​ 4 ​ 1,651 ​ 1 ​ 0 ​ 0 ​ 0 ​ 4 ​ 1,651 ​ 1 Government agency mortgage-backed securities ​ 126 ​ 170,661 ​ 2,914 ​ 6 ​ 1,146 ​ 2 ​ 132 ​ 171,807 ​ 2,916 Government agency collateralized mortgage obligations ​ 3 ​ 1,804 ​ 3 ​ 3 ​ 182 ​ 1 ​ 6 ​ 1,986 ​ 4 Total available-for-sale investment portfolio ​ 162 ​ $ 1,446,539 ​ $ 112,993 ​ 9 ​ $ 1,328 ​ $ 3 ​ 171 ​ $ 1,447,867 ​ $ 112,996 ​ As of December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 Months 12 Months or Longer Total ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized (000's omitted) # Value Losses # Value Losses # Value Losses ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ 13 ​ $ 831,015 ​ $ 16,595 ​ 0 ​ $ 0 ​ $ 0 ​ 13 ​ $ 831,015 ​ $ 16,595 Obligations of state and political subdivisions ​ 1 ​ 358 ​ 0 ​ 0 ​ 0 ​ 0 ​ 1 ​ 358 ​ 0 Government agency mortgage-backed securities ​ 89 ​ 75,992 ​ 182 ​ 2 ​ 14 ​ 0 ​ 91 ​ 76,006 ​ 182 Corporate debt securities ​ 1 ​ ​ 1,001 ​ ​ 1 ​ 0 ​ ​ 0 ​ ​ 0 ​ 1 ​ ​ 1,001 ​ ​ 1 Government agency collateralized mortgage obligations ​ 13 ​ 5,246 ​ 10 ​ 1 ​ 0 ​ 0 ​ 14 ​ 5,246 ​ 10 Total available-for-sale investment portfolio ​ 117 ​ $ 913,612 ​ $ 16,788 ​ 3 ​ $ 14 ​ $ 0 ​ 120 ​ $ 913,626 ​ $ 16,788 ​ The unrealized losses reported pertaining to securities issued by the U.S. government and its sponsored entities include treasuries, agencies, and mortgage-backed securities issued by Ginnie Mae, Fannie Mae, and Freddie Mac, which are currently rated AAA by Moody’s Investor Services, AA+ by Standard & Poor’s and are guaranteed by the U.S. government. The majority of the obligations of state and political subdivisions and corporations carry a credit rating of A or better. Additionally, a majority of the obligations of state and political subdivisions carry a secondary level of credit enhancement. The Company does not intend to sell these securities, nor is it more likely than not that the Company will be required to sell these securities prior to recovery of the amortized cost. Timely principal and interest payments continue to be made on the securities. The unrealized losses in the portfolios are primarily attributable to changes in interest rates. As such, management does not believe any individual unrealized loss as of June 30, 2021 represents credit losses and no unrealized losses have been recognized into credit loss expense. Accordingly, there is no allowance for credit losses on the Company’s available-for-sale portfolio as of June 30, 2021. Accrued interest receivable on available-for-sale debt securities, included in accrued interest and fees receivable on the consolidated statements of condition, totaled $ The amortized cost and estimated fair value of debt securities at June 30, 2021, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Securities not due at a single maturity date are shown separately. ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale ​ ​ Amortized ​ Fair (000's omitted) Cost Value Due in one year or less ​ $ 198,566 ​ $ 199,557 Due after one through five years ​ 768,349 ​ 796,228 Due after five years through ten years ​ 1,018,820 ​ 1,037,749 Due after ten years ​ 1,504,697 ​ 1,420,784 Subtotal ​ 3,490,432 ​ 3,454,318 Government agency mortgage-backed securities ​ 521,056 ​ 529,139 Government agency collateralized mortgage obligations ​ 28,490 ​ 29,282 Total ​ $ 4,039,978 ​ $ 4,012,739 ​ Investment securities with a carrying value of $2.43 billion and $2.03 billion at June 30, 2021 and December 31, 2020, respectively, were pledged to collateralize certain deposits and borrowings. Securities pledged to collateralize certain deposits and borrowings included

LOANS

LOANS	6 Months Ended
	Jun. 30, 2021
LOANS
LOANS	NOTE E: LOANS The segments of the Company’s loan portfolio are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, (000’s omitted) ​ 2021 2020 Business lending ​ $ 3,186,487 ​ $ 3,440,077 Consumer mortgage ​ 2,408,499 ​ 2,401,499 Consumer indirect ​ 1,109,504 ​ 1,021,885 Consumer direct ​ 148,540 ​ 152,657 Home equity ​ 391,117 ​ 399,834 Gross loans, including deferred origination costs ​ 7,244,147 ​ 7,415,952 Allowance for credit losses ​ (51,750) ​ (60,869) Loans, net of allowance for credit losses ​ $ 7,192,397 ​ $ 7,355,083 ​ The following table presents the aging of the amortized cost basis of the Company’s past due loans, including PCD loans, by segment as of June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Current Total Loans Business lending ​ $ 972 ​ $ 228 ​ $ 49,877 ​ $ 51,077 ​ $ 3,135,410 ​ $ 3,186,487 Consumer mortgage ​ 8,645 ​ 1,259 ​ 16,025 ​ 25,929 ​ 2,382,570 ​ 2,408,499 Consumer indirect ​ 7,110 ​ 73 ​ 0 ​ 7,183 ​ 1,102,321 ​ 1,109,504 Consumer direct ​ 507 ​ 15 ​ 2 ​ 524 ​ 148,016 ​ 148,540 Home equity ​ 1,077 ​ 147 ​ 2,572 ​ 3,796 ​ 387,321 ​ 391,117 Total ​ $ 18,311 ​ $ 1,722 ​ $ 68,476 ​ $ 88,509 ​ $ 7,155,638 ​ $ 7,244,147 ​ The following table presents the aging of the amortized cost basis of the Company’s past due loans, including PCD loans, by segment as of December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due ​ 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Current Total Loans Business lending ​ $ 4,896 ​ $ 59 ​ $ 55,709 ​ $ 60,664 ​ $ 3,379,413 ​ $ 3,440,077 Consumer mortgage ​ 13,236 ​ 3,051 ​ 14,970 ​ 31,257 ​ 2,370,242 ​ 2,401,499 Consumer indirect ​ 13,161 ​ 219 ​ 1 ​ 13,381 ​ 1,008,504 ​ 1,021,885 Consumer direct ​ 1,170 ​ 28 ​ 3 ​ 1,201 ​ 151,456 ​ 152,657 Home equity ​ 2,296 ​ 565 ​ 2,246 ​ 5,107 ​ 394,727 ​ 399,834 Total ​ $ 34,759 ​ $ 3,922 ​ $ 72,929 ​ $ 111,610 ​ $ 7,304,342 ​ $ 7,415,952 ​ The delinquency status for loans on payment deferment due to COVID-19 financial hardship were reported at June 30, 2021 based on their delinquency status at the execution date of the payment deferment, unless subsequent to the execution date of the payment deferment, the borrower made all required past due payments to bring the loan to current status. Certain loans under extended pandemic-related forbearance were reclassified to nonaccrual status. ​ No interest income on nonaccrual loans was recognized during the three and six months ended June 30, 2021. An immaterial amount of accrued interest was written off on nonaccrual loans by reversing interest income. ​ The Company uses several credit quality indicators to assess credit risk in an ongoing manner. The Company’s primary credit quality indicator for its business lending portfolio is an internal credit risk rating system that categorizes loans as “pass”, “special mention”, “classified”, or “doubtful”. Credit risk ratings are applied individually to those classes of loans that have significant or unique credit characteristics that benefit from a case-by-case evaluation. Loans that were granted COVID- 19 related financial hardship payment deferrals were reviewed on a case-by-case basis for credit risk ratings. Loans on payment deferral will continue to be monitored for indications of deterioration that could result in future downgrades. In general, the following are the definitions of the Company’s credit quality indicators: ​ ​ ​ Pass The condition of the borrower and the performance of the loans are satisfactory or better. Special Mention ​ The condition of the borrower has deteriorated although the loan performs as agreed. Loss may be incurred at some future date, if conditions deteriorate further. Classified ​ The condition of the borrower has significantly deteriorated and the performance of the loan could further deteriorate and incur loss, if deficiencies are not corrected. Doubtful ​ The condition of the borrower has deteriorated to the point that collection of the balance is improbable based on current facts and conditions and loss is likely. ​ The following tables show the amount of business lending loans by credit quality category at June 30, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ June 30, 2021 2021 2020 2019 2018 2017 Prior Cost Basis Total Business lending: ​ ​ ​ ​ ​ ​ ​ ​ Risk rating ​ ​ ​ ​ ​ ​ ​ ​ Pass ​ $ 343,472 ​ $ 439,365 ​ $ 338,583 ​ $ 284,580 ​ $ 189,477 ​ $ 661,491 ​ $ 507,921 ​ $ 2,764,889 Special mention ​ 2,001 ​ 12,961 ​ 12,084 ​ 36,635 ​ 21,586 ​ 72,145 ​ 34,484 ​ 191,896 Classified ​ 360 ​ 2,163 ​ 21,063 ​ 49,150 ​ 27,397 ​ 84,543 ​ 42,178 ​ 226,854 Doubtful ​ 0 ​ 0 ​ 16 ​ 1,931 ​ 0 ​ 35 ​ 866 ​ 2,848 Total business lending ​ $ 345,833 ​ $ 454,489 ​ $ 371,746 ​ $ 372,296 ​ $ 238,460 ​ $ 818,214 ​ $ 585,449 ​ $ 3,186,487 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ December 31, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Business lending: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Risk rating ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pass ​ $ 860,178 ​ $ 351,350 ​ $ 312,087 ​ $ 217,138 ​ $ 231,453 ​ $ 543,999 ​ $ 483,018 ​ $ 2,999,223 Special mention ​ 14,687 ​ 36,041 ​ 28,410 ​ 21,875 ​ 29,386 ​ 51,657 ​ 52,732 ​ 234,788 Classified ​ 6,336 ​ 4,560 ​ 30,422 ​ 24,807 ​ 14,891 ​ 65,157 ​ 56,000 ​ 202,173 Doubtful ​ 0 ​ 18 ​ 2,888 ​ 0 ​ 0 ​ 108 ​ 879 ​ 3,893 Total business lending ​ $ 881,201 ​ $ 391,969 ​ $ 373,807 ​ $ 263,820 ​ $ 275,730 ​ $ 660,921 ​ $ 592,629 ​ $ 3,440,077 ​ All other loans are underwritten and structured using standardized criteria and characteristics, primarily payment performance, and are normally risk rated and monitored collectively on a monthly basis. These are typically loans to individuals in the consumer categories and are delineated as either performing or nonperforming. Performing loans include loans classified as current as well as those classified as 30 - 89 days past due. Nonperforming loans include 90+ days past due and still accruing and nonaccrual loans. The following table details the balances in all other loan categories at June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ June 30, 2021 2021 2020 2019 2018 2017 Prior Cost Basis Total Consumer mortgage: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ FICO AB ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 217,537 ​ $ 245,277 ​ $ 204,560 ​ $ 139,256 ​ $ 135,992 ​ $ 660,613 ​ $ 0 ​ $ 1,603,235 Nonperforming ​ 0 ​ 171 ​ 0 ​ 261 ​ 516 ​ 2,765 ​ 0 ​ 3,713 Total FICO AB ​ 217,537 ​ 245,448 ​ 204,560 ​ 139,517 ​ 136,508 ​ 663,378 ​ 0 ​ 1,606,948 FICO CDE ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ 58,224 ​ 128,942 ​ 94,750 ​ 73,362 ​ 64,401 ​ 346,907 ​ 21,394 ​ 787,980 Nonperforming ​ 0 ​ 234 ​ 901 ​ 744 ​ 702 ​ 10,990 ​ 0 ​ 13,571 Total FICO CDE ​ 58,224 ​ 129,176 ​ 95,651 ​ 74,106 ​ 65,103 ​ 357,897 ​ 21,394 ​ 801,551 Total consumer mortgage ​ $ 275,761 ​ $ 374,624 ​ $ 300,211 ​ $ 213,623 ​ $ 201,611 ​ $ 1,021,275 ​ $ 21,394 ​ $ 2,408,499 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer indirect: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 317,236 ​ $ 255,939 ​ $ 240,528 ​ $ 148,990 ​ $ 59,328 ​ $ 87,410 ​ $ 0 ​ $ 1,109,431 Nonperforming ​ 0 ​ 10 ​ 38 ​ 13 ​ 0 ​ 12 ​ 0 ​ 73 Total consumer indirect ​ $ 317,236 ​ $ 255,949 ​ $ 240,566 ​ $ 149,003 ​ $ 59,328 ​ $ 87,422 ​ $ 0 ​ $ 1,109,504 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer direct: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 37,644 ​ $ 37,762 ​ $ 34,503 ​ $ 18,947 ​ $ 7,557 ​ $ 6,100 ​ $ 6,010 ​ $ 148,523 Nonperforming ​ 0 ​ 0 ​ 0 ​ 2 ​ 0 ​ 15 ​ 0 ​ 17 Total consumer direct ​ $ 37,644 ​ $ 37,762 ​ $ 34,503 ​ $ 18,949 ​ $ 7,557 ​ $ 6,115 ​ $ 6,010 ​ $ 148,540 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Home equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 33,503 ​ $ 47,348 ​ $ 42,432 ​ $ 23,450 ​ $ 19,224 ​ $ 43,050 ​ $ 179,391 ​ $ 388,398 Nonperforming ​ 0 ​ 56 ​ 22 ​ 107 ​ 79 ​ 722 ​ 1,733 ​ 2,719 Total home equity ​ $ 33,503 ​ $ 47,404 ​ $ 42,454 ​ $ 23,557 ​ $ 19,303 ​ $ 43,772 ​ $ 181,124 ​ $ 391,117 ​ The following table details the balances in all other loan categories at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ December 31, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Consumer mortgage: ​ ​ ​ ​ ​ ​ ​ ​ FICO AB ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 260,588 ​ $ 227,027 ​ $ 166,638 ​ $ 163,653 ​ $ 160,911 ​ $ 614,976 ​ $ 321 ​ $ 1,594,114 Nonperforming ​ 0 ​ 0 ​ 275 ​ 398 ​ 345 ​ 2,709 ​ 0 ​ 3,727 Total FICO AB ​ 260,588 ​ 227,027 ​ 166,913 ​ 164,051 ​ 161,256 ​ 617,685 ​ 321 ​ 1,597,841 FICO CDE ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ 115,049 ​ 102,788 ​ 80,973 ​ 75,289 ​ 83,214 ​ 314,668 ​ 17,382 ​ 789,363 Nonperforming ​ 0 ​ 1,010 ​ 582 ​ 877 ​ 1,786 ​ 10,040 ​ 0 ​ 14,295 Total FICO CDE ​ 115,049 ​ 103,798 ​ 81,555 ​ 76,166 ​ 85,000 ​ 324,708 ​ 17,382 ​ 803,658 Total consumer mortgage ​ $ 375,637 ​ $ 330,825 ​ $ 248,468 ​ $ 240,217 ​ $ 246,256 ​ $ 942,393 ​ $ 17,703 ​ $ 2,401,499 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer indirect: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 303,471 ​ $ 305,901 ​ $ 202,373 ​ $ 86,497 ​ $ 61,449 ​ $ 61,975 ​ $ 0 ​ $ 1,021,666 Nonperforming ​ 51 ​ 52 ​ 82 ​ 17 ​ 16 ​ 1 ​ 0 ​ 219 Total consumer indirect ​ $ 303,522 ​ $ 305,953 ​ $ 202,455 ​ $ 86,514 ​ $ 61,465 ​ $ 61,976 ​ $ 0 ​ $ 1,021,885 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer direct: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 49,181 ​ $ 46,992 ​ $ 27,872 ​ $ 12,326 ​ $ 5,232 ​ $ 4,146 ​ $ 6,878 ​ $ 152,627 Nonperforming ​ 1 ​ 19 ​ 2 ​ 5 ​ 0 ​ 3 ​ 0 ​ 30 Total consumer direct ​ $ 49,182 ​ $ 47,011 ​ $ 27,874 ​ $ 12,331 ​ $ 5,232 ​ $ 4,149 ​ $ 6,878 ​ $ 152,657 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Home equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 48,145 ​ $ 48,780 ​ $ 28,074 ​ $ 23,524 ​ $ 17,828 ​ $ 35,900 ​ $ 194,773 ​ $ 397,024 Nonperforming ​ 0 ​ 24 ​ 73 ​ 104 ​ 183 ​ 490 ​ 1,936 ​ 2,810 Total home equity ​ $ 48,145 ​ $ 48,804 ​ $ 28,147 ​ $ 23,628 ​ $ 18,011 ​ $ 36,390 ​ $ 196,709 ​ $ 399,834 ​ All loan classes are collectively evaluated for impairment except business lending. A summary of individually evaluated impaired business loans as of June 30, 2021 and December 31, 2020 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, (000’s omitted) 2021 2020 Loans with allowance allocation ​ $ 25,534 ​ $ 27,437 Loans without allowance allocation ​ 6,529 ​ 8,138 Carrying balance ​ 32,063 ​ 35,575 Contractual balance ​ 34,228 ​ 38,362 Specifically allocated allowance ​ 2,800 ​ 3,874 ​ The average carrying balance of individually evaluated impaired loans was $32.9 million and $1.4 million for the three months ended June 30, 2021 and June 30, 2020, respectively. The average carrying balance of individually evaluated impaired loans was $34.6 million and $1.8 million for the six months ended June 30, 2021 and June 30, 2020, respectively. No interest income was recognized on individually evaluated impaired loans for the three or six months ended June 30, 2021 and June 30, 2020. In the course of working with borrowers, the Company may choose to restructure the contractual terms of certain loans. In this scenario, the Company attempts to work-out an alternative payment schedule with the borrower in order to optimize collectability of the loan. Any loans that are modified are reviewed by the Company to identify if a troubled debt restructuring (“TDR”) has occurred, which is when, for economic or legal reasons related to a borrower’s financial difficulties, the Company grants a concession to the borrower that it would not otherwise consider. Terms may be modified to fit the ability of the borrower to repay in line with its current financial standing and the restructuring of the loan may include the transfer of assets from the borrower to satisfy the debt, a modification of loan terms, or a combination of the two. In accordance with the clarified guidance issued by the Office of the Comptroller of the Currency (“OCC”), loans that have been discharged in Chapter 7 bankruptcy but not reaffirmed by the borrower, are classified as TDRs, irrespective of payment history or delinquency status, even if the repayment terms for the loan have not been otherwise modified. The Company’s lien position against the underlying collateral remains unchanged. Pursuant to that guidance, the Company records a charge-off equal to any portion of the carrying value that exceeds the net realizable value of the collateral. The amount of loss incurred in the three and six months ended June 31, 2021 and 2020 was immaterial. TDRs less than $0.5 million are collectively included in the allowance for credit loss estimate. Commercial loans greater than $0.5 million are individually evaluated for impairment, and if necessary, a specific allocation of the allowance for credit losses is provided. With regard to determination of the amount of the allowance for credit losses, TDR loans are considered to be impaired. As a result, the determination of the amount of allowance for credit losses related to impaired loans for each portfolio segment within TDRs is the same as detailed previously. With respect to the Company’s lending activities, the Company implemented a customer forbearance program allowing for loan payment deferrals up to three months per request during 2020 to assist both consumer and business borrowers that were experiencing financial hardship due to COVID-19 related challenges. Business lending, consumer direct, and consumer indirect loans in deferment status continued to accrue interest on the deferred principal during the deferment period unless otherwise classified as nonaccrual. Consumer mortgage and home equity loans did not accrue interest on the deferred payments during the deferment period. Consistent with the Coronavirus Aid, Relief and Economic Security Act ( “CARES Act”), the Consolidated Appropriations Act of 2021 (“CAA”) and industry regulatory guidance, borrowers that were otherwise current on loan payments and granted COVID-19 related financial hardship payment deferrals were reported as current loans throughout the first 180 days of the deferral period and were not classified as TDRs. Borrowers that were delinquent in their payments to the Company prior to requesting a COVID-19 related financial hardship payment deferral were reviewed on a case-by-case basis for TDR classification and non-performing loan status. As of June 30, 2021, the Company had 12 borrowers in forbearance due to COVID-19 related financial hardship, representing $2.4 million in outstanding loan balances, or 0.03% of total loans outstanding. These forbearances were comprised of 8 business borrowers representing $2.0 million in outstanding loan balances and 4 consumer borrowers representing approximately $0.4 million in outstanding loan balances. As of December 31, 2020, the Company had 74 borrowers in forbearance due to COVID-19 related financial hardship, representing $66.5 million in outstanding loan balances, or 0.9% of total loans outstanding. These forbearances were comprised of 63 business borrowers representing $65.7 million in outstanding loan balances and 11 consumer borrowers representing approximately $0.8 million in outstanding loan balances. Information regarding TDRs as of June 30, 2021 and December 31, 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 December 31, 2020 (000’s omitted) ​ Nonaccrual ​ Accruing ​ Total ​ Nonaccrual ​ Accruing ​ Total ​ # Amount # Amount # Amount # Amount # Amount # Amount Business lending ​ 6 ​ $ 445 4 ​ $ 180 10 ​ $ 625 6 ​ $ 529 4 ​ $ 191 10 ​ $ 720 Consumer mortgage ​ 58 ​ 2,553 42 ​ 2,074 100 ​ 4,627 56 ​ 2,413 48 ​ 2,266 104 ​ 4,679 Consumer indirect ​ 0 ​ 0 79 ​ 916 79 ​ 916 0 ​ 0 86 ​ 951 86 ​ 951 Consumer direct ​ 0 ​ 0 17 ​ 14 17 ​ 14 0 ​ 0 23 ​ 85 23 ​ 85 Home equity ​ 10 ​ 252 12 ​ 248 22 ​ 500 11 ​ 285 13 ​ 264 24 ​ 549 Total ​ 74 ​ $ 3,250 154 ​ $ 3,432 228 ​ $ 6,682 73 ​ $ 3,227 174 ​ $ 3,757 247 ​ $ 6,984 ​ The following table presents information related to loans modified in a TDR during the three months and six months ended June 30, 2021 and 2020. Of the loans noted in the table below, all consumer mortgage loans for the three months and six months ended June 30, 2021 and 2020 were modified due to a Chapter 7 bankruptcy as described previously. The financial effects of these restructurings were immaterial. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Three Months Ended ​ ​ June 30, 2021 ​ June 30, 2020 ​ ​ Number of ​ Outstanding ​ Number of ​ Outstanding (000’s omitted) loans modified Balance loans modified Balance Business lending 0 ​ $ 0 0 ​ $ 0 Consumer mortgage 7 ​ 366 3 ​ 174 Consumer indirect 9 ​ 116 3 ​ 47 Consumer direct 0 ​ 0 0 ​ 0 Home equity 0 ​ 0 1 ​ 28 Total 16 ​ $ 482 7 ​ $ 249 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ Six Months Ended ​ ​ June 30, 2021 ​ June 30, 2020 ​ ​ Number of ​ Outstanding ​ Number of ​ Outstanding (000’s omitted) loans modified Balance loans modified Balance Business lending 0 ​ $ 0 0 ​ $ 0 Consumer mortgage 10 ​ 474 9 ​ 738 Consumer indirect 15 ​ 177 14 ​ 151 Consumer direct 1 ​ 6 1 ​ 11 Home equity 0 ​ 0 1 ​ 28 Total 26 ​ $ 657 25 ​ $ 928 ​ Allowance for Credit Losses The following presents by segment the activity in the allowance for credit losses during the three months and six months ended June 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, 2021 ​ ​ Beginning ​ Charge- ​ ​ ​ ​ ​ ​ ​ Ending (000’s omitted) balance offs Recoveries Provision balance Business lending ​ $ 27,042 ​ $ (2) ​ $ 255 ​ $ (3,878) ​ $ 23,417 Consumer mortgage ​ 9,686 ​ (142) ​ 9 ​ 448 ​ 10,001 Consumer indirect ​ 11,120 ​ (750) ​ 1,183 ​ (450) ​ 11,103 Consumer direct ​ 2,682 ​ (195) ​ 213 ​ (152) ​ 2,548 Home equity ​ 1,543 ​ (17) ​ 5 ​ 265 ​ 1,796 Unallocated ​ 1,000 ​ 0 ​ 0 ​ 0 ​ 1,000 Purchased credit deteriorated ​ 1,996 ​ 0 ​ 33 ​ (144) ​ 1,885 Allowance for credit losses – loans ​ 55,069 ​ (1,106) ​ 1,698 ​ (3,911) ​ 51,750 Liabilities for off-balance-sheet credit exposures ​ 1,189 ​ 0 ​ 0 ​ (427) ​ 762 Total allowance for credit losses ​ $ 56,258 ​ $ (1,106) ​ $ 1,698 ​ $ (4,338) ​ $ 52,512 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, 2020 ​ Beginning Charge- ​ Steuben ​ Ending (000’s omitted) ​ balance ​ offs ​ Recoveries ​ acquisition ​ Provision ​ balance Business lending ​ $ 19,489 ​ $ (7) ​ $ 84 ​ $ 2,483 ​ $ 2,155 ​ $ 24,204 Consumer mortgage ​ 12,430 ​ (234) ​ 36 ​ 146 ​ 710 ​ 13,088 Consumer indirect ​ 13,694 ​ (1,431) ​ 833 ​ 183 ​ 2,587 ​ 15,866 Consumer direct ​ 3,737 ​ (341) ​ 171 ​ 87 ​ 374 ​ 4,028 Home equity ​ 2,484 ​ (81) ​ 12 ​ 235 ​ 40 ​ 2,690 Unallocated ​ 772 ​ 0 ​ 0 ​ 0 ​ 228 ​ 1,000 Purchased credit deteriorated ​ 3,046 ​ 0 ​ 48 ​ 528 ​ (61) ​ 3,561 Allowance for credit losses – loans ​ 55,652 ​ (2,094) ​ 1,184 ​ 3,662 ​ 6,033 ​ 64,437 Liabilities for off-balance-sheet credit exposures ​ 845 ​ 0 ​ 0 ​ 67 ​ 540 ​ 1,452 Total allowance for credit losses ​ $ 56,497 ​ $ (2,094) ​ $ 1,184 ​ $ 3,729 ​ $ 6,573 ​ $ 65,889 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended June 30, 2021 ​ Beginning Charge- ​ Ending (000’s omitted) ​ balance ​ offs ​ Recoveries ​ Provision ​ balance Business lending ​ $ 28,190 ​ $ (53) ​ $ 322 ​ $ (5,042) ​ $ 23,417 Consumer mortgage ​ 10,672 ​ (242) ​ 19 ​ (448) ​ 10,001 Consumer indirect ​ 13,696 ​ (2,149) ​ 2,429 ​ (2,873) ​ 11,103 Consumer direct ​ 3,207 ​ (513) ​ 444 ​ (590) ​ 2,548 Home equity ​ 2,222 ​ (115) ​ 9 ​ (320) ​ 1,796 Unallocated ​ 1,000 ​ 0 ​ 0 ​ 0 ​ 1,000 Purchased credit deteriorated ​ 1,882 ​ 0 ​ 60 ​ (57) ​ 1,885 Allowance for credit losses – loans ​ 60,869 ​ (3,072) ​ 3,283 ​ (9,330) ​ 51,750 Liabilities for off-balance-sheet credit exposures ​ 1,489 ​ 0 ​ 0 ​ (727) ​ 762 Total allowance for credit losses ​ $ 62,358 ​ $ (3,072) ​ $ 3,283 ​ $ (10,057) ​ $ 52,512 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended June 30, 2020 ​ ​ Beginning ​ ​ ​ ​ Beginning ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ balance, ​ ​ ​ ​ balance, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ prior to the ​ ​ ​ ​ after ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ adoption of ​ Impact of ​ adoption of ​ ​ ​ ​ ​ ​ ​ Steuben ​ ​ ​ ​ Ending (000’s omitted) ASC 326 ASC 326 ASC 326 Charge-offs Recoveries acquisition Provision balance Business lending ​ $ 19,426 ​ $ 288 ​ $ 19,714 ​ $ (183) ​ $ 222 ​ $ 2,483 ​ $ 1,968 ​ $ 24,204 Consumer mortgage ​ 10,269 ​ (1,051) ​ 9,218 ​ (420) ​ 44 ​ 146 ​ 4,100 ​ 13,088 Consumer indirect ​ 13,712 ​ (997) ​ 12,715 ​ (3,510) ​ 1,996 ​ 183 ​ 4,482 ​ 15,866 Consumer direct ​ 3,255 ​ (643) ​ 2,612 ​ (874) ​ 353 ​ 87 ​ 1,850 ​ 4,028 Home equity ​ 2,129 ​ 808 ​ 2,937 ​ (154) ​ 18 ​ 235 ​ (346) ​ 2,690 Unallocated ​ 957 ​ 43 ​ 1,000 ​ 0 ​ 0 ​ 0 ​ 0 ​ 1,000 Purchased credit deteriorated ​ 0 ​ 3,072 ​ 3,072 ​ 0 ​ 48 ​ 528 ​ (87) ​ 3,561 Purchased credit impaired ​ 163 ​ (163) ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 Allowance for credit losses – loans ​ 49,911 ​ 1,357 ​ 51,268 ​ (5,141) ​ 2,681 ​ 3,662 ​ 11,967 ​ 64,437 Liabilities for off-balance-sheet credit exposures ​ 0 ​ 1,185 ​ 1,185 ​ 0 ​ 0 ​ 67 ​ 200 ​ 1,452 Total allowance for credit losses ​ $ 49,911 ​ $ 2,542 ​ $ 52,453 ​ $ (5,141) ​ $ 2,681 ​ $ 3,729 ​ $ 12,167 ​ $ 65,889 ​ Improvements in economic forecasts have resulted in an allowance for credit losses to total loans ratio of 0.71% at June 30, 2021, 15 basis points lower than the level at June 30, 2020 and 11 basis points lower than the level at December 31, 2020. Accrued interest receivable on loans, included in accrued interest and fees receivable on the consolidated statements of condition, totaled $19.0 million at June 30, 2021 and is excluded from the estimate of credit losses and amortized cost basis of loans. Under ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) 31, 2020. Adjustments to historical loss experience were made for differences in current loan-specific risk characteristics and to address current period delinquencies, charge-off rates, risk ratings, lack of loan level data through an entire economic cycle, changes in loan sizes and underwriting standards as well as the addition of acquired loans which were not underwritten by the Company. The Company considered historical losses immediately prior, through and following the Great Recession of 2008 compared to the historical period used for modeling to adjust the historical information to account for longer-term expectations for loan credit performance. Under CECL, the Company is required to consider future economic conditions to determine current expected credit losses. Management selected an eight quarter reasonable and supportable forecast period using a two quarter lag adjustment with a four quarter reversion to the historical mean to use as part of the economic forecast. Management determined that these qualitative adjustments were needed to adjust historical information for expected losses and to reflect changes as a result of current conditions. For qualitative macroeconomic adjustments, the Company uses third party forecasted economic data scenarios utilizing a base scenario and two alternative scenarios that were weighted based on guidance from the third party provider, with forecasts available as of June 30, 2021. These forecasts were factored into the qualitative portion of the calculation of the estimated credit losses and included the impact of COVID-19, including forecasted vaccine distribution progress, and current and future Federal stimulus packages. The scenarios utilized outline a significant improvement in economic conditions with peak unemployment ranging from Management developed expected loss estimates considering factors for segments as outlined below: ● Business lending – non real estate: The Company considered and selected projected unemployment and GDP as possible indicators of forecasted losses related to business lending. The Company also considered delinquencies, the level of loan deferrals, risk rating changes, recent charge-off history and acquired loans as part of the review of estimated losses. ● Business lending – real estate: The Company considered and selected projected unemployment and commercial and multi-family real estate values as possible indicators of forecasted losses related to commercial real estate loans. The Company also considered the factors noted in business lending – non real estate. ● Consumer mortgages and home equity: The Company considered and selected projected unemployment and residential real estate values as possible indicators of forecasted losses related to mortgage lending. In addition, current delinquencies, the level of loan deferrals, charge-offs and acquired loans were considered. ● Consumer indirect: The Company considered and selected projected unemployment and vehicle valuation indices as possible indicators of forecasted losses related to indirect lending. In addition, current delinquencies, the level of loan deferrals, charge-offs and acquired loans were considered. ● Consumer direct: The Company considered and selected projected unemployment and median household income as possible indicator of forecasted losses related to direct lending. In addition, current delinquencies, the level of loan deferrals, charge-offs and acquired loans were considered. The following table presents the carrying amounts of loans purchased and sold during the six months ended June 30, 2021 by portfolio segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Business ​ Consumer ​ Consumer ​ Consumer ​ Home ​ ​ ​ (000’s omitted) lending mortgage indirect direct equity Total Purchases ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 Sales ​ ​ 848 ​ ​ 10,860 ​ ​ 0 ​ ​ 0 ​ ​ 0 ​ ​ 11,708 ​ All the sales of consumer mortgages during the six months ended June 30, 2021 were sales of secondary market eligible residential mortgage loans. The sales of business loans during the six months ended June 30, 2021 includes two business lending loans under one relationship.

GOODWILL AND IDENTIFIABLE INTAN

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS	6 Months Ended
	Jun. 30, 2021
GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS
GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS	NOTE F: GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS The gross carrying amount and accumulated amortization for each type of identifiable intangible asset are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 December 31, 2020 ​ ​ Gross ​ ​ ​ ​ Net ​ Gross ​ ​ ​ ​ Net ​ ​ Carrying Accumulated Carrying Carrying Accumulated Carrying (000’s omitted) ​ Amount Amortization Amount Amount Amortization Amount Amortizing intangible assets: ​ ​ ​ ​ ​ ​ ​ Core deposit intangibles ​ $ 69,403 ​ $ (58,136) ​ $ 11,267 ​ $ 69,403 ​ $ (55,572) ​ $ 13,831 Other intangibles ​ 91,899 ​ (55,386) ​ 36,513 ​ 90,462 ​ (51,353) ​ 39,109 Total amortizing intangibles ​ $ 161,302 ​ $ (113,522) ​ $ 47,780 ​ $ 159,865 ​ $ (106,925) ​ $ 52,940 ​ The estimated aggregate amortization expense for each of the five succeeding fiscal years ended December 31 is as follows: ​ ​ ​ ​ ​ ​ (000's omitted) Jul - Dec 2021 $ 6,229 2022 ​ 11,141 2023 ​ 9,338 2024 ​ 7,768 2025 ​ 6,550 Thereafter ​ 6,754 Total ​ $ 47,780 ​ Shown below are the components of the Company’s goodwill at December 31, 2020 and June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) December 31, 2020 Activity June 30, 2021 Goodwill, net ​ $ 793,708 ​ $ 1,184 ​ $ 794,892 ​ ​

MANDATORILY REDEEMABLE PREFERRE

MANDATORILY REDEEMABLE PREFERRED SECURITIES	6 Months Ended
	Jun. 30, 2021
MANDATORILY REDEEMABLE PREFERRED SECURITIES
MANDATORILY REDEEMABLE PREFERRED SECURITIES	NOTE G: MANDATORILY REDEEMABLE PREFERRED SECURITIES As of June 30, 2021, the Company does not sponsor any business trusts. The Company previously sponsored Community Capital Trust IV (“CCT IV”) until March 15, 2021 when the Company exercised its right to redeem all of the CCT IV debentures and associated preferred securities for a total of ​

BENEFIT PLANS

BENEFIT PLANS	6 Months Ended
	Jun. 30, 2021
BENEFIT PLANS
BENEFIT PLANS	NOTE H: BENEFIT PLANS The Company provides a qualified defined benefit pension to eligible employees and retirees, other post-retirement health and life insurance benefits to certain retirees, an unfunded supplemental pension plan for certain key executives, and an unfunded stock balance plan for certain of its nonemployee directors. The Company accrues for the estimated cost of these benefits through charges to expense during the years that employees earn these benefits. The service cost component of net periodic benefit income is included in the salaries and employee benefits line of the consolidated statements of income, while the other components of net periodic benefit income are included in other expenses. The Company made a $2.9 million contribution to its defined benefit pension plan in the first quarter of 2021. The Company made a $3.9 million contribution to its defined benefit pension plan in the second quarter of 2020. The net periodic benefit cost for the three and six months ended June 30, 2021 and 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension Benefits ​ Post-retirement Benefits ​ ​ ​ Three Months Ended ​ Six Months Ended ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ June 30, ​ June 30, ​ (000’s omitted) ​ 2021 2020 2021 ​ 2020 2021 ​ 2020 ​ 2021 2020 Service cost ​ $ 1,480 ​ $ 1,438 ​ $ 2,960 ​ $ 2,875 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 ​ Interest cost ​ 1,259 1,356 ​ 2,518 ​ 2,712 11 ​ 14 ​ 22 ​ 28 ​ Expected return on plan assets ​ (4,695) ​ (3,932) ​ ​ (9,391) ​ ​ (7,864) ​ 0 ​ 0 ​ ​ 0 ​ 0 ​ Amortization of unrecognized net loss ​ 900 ​ 810 ​ ​ 1,800 ​ ​ 1,620 ​ 11 ​ 10 ​ ​ 22 ​ 20 ​ Amortization of prior service cost ​ 94 ​ 60 ​ ​ 189 ​ ​ 120 ​ (44) ​ (44) ​ ​ (89) ​ (89) ​ Net periodic benefit ​ $ (962) ​ $ (268) ​ $ (1,924) ​ $ (537) ​ $ (22) ​ $ (20) ​ $ (45) ​ $ (41) ​ ​

EARNINGS PER SHARE

EARNINGS PER SHARE	6 Months Ended
	Jun. 30, 2021
EARNINGS PER SHARE
EARNINGS PER SHARE	NOTE I: EARNINGS PER SHARE The two class method is used in the calculations of basic and diluted earnings per share. Under the two class method, earnings available to common shareholders for the period are allocated between common shareholders and participating securities according to dividends declared and participation rights in undistributed earnings. The Company has determined that all of its outstanding non-vested stock awards are participating securities as of June 30, 2021. Basic earnings per share are computed based on the weighted-average of the common shares outstanding for the period. Diluted earnings per share are based on the weighted-average of the shares outstanding and the assumed exercise of stock options during the year. The dilutive effect of options is calculated using the treasury stock method of accounting. The treasury stock method determines the number of common shares that would be outstanding if all the dilutive options were exercised and the proceeds were used to repurchase common shares in the open market at the average market price for the applicable time period. There were approximately 0.2 million and 0.1 million weighted-average anti-dilutive stock options outstanding for the three months and six months ended June 30, 2021, respectively, compared to 0.6 million weighted-average anti-dilutive stock options outstanding for the three months and six months ended June 30, 2020 that were not included in the computation below. The following is a reconciliation of basic to diluted earnings per share for the three and six months ended June 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ (000’s omitted, except per share data) ​ 2021 2020 2021 2020 Net income ​ $ 47,944 ​ $ 35,248 ​ $ 100,794 ​ $ 75,382 ​ Income attributable to unvested stock-based compensation awards ​ (127) ​ (127) ​ (263) ​ (264) ​ Income available to common shareholders ​ $ 47,817 ​ $ 35,121 ​ $ 100,531 ​ $ 75,118 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 54,007 ​ 52,487 ​ 53,927 ​ 52,262 ​ Basic earnings per share ​ $ 0.89 ​ $ 0.67 ​ $ 1.86 ​ $ 1.44 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income ​ $ 47,944 ​ $ 35,248 ​ $ 100,794 ​ $ 75,382 ​ Income attributable to unvested stock-based compensation awards ​ (127) ​ (127) ​ (263) ​ (264) ​ Income available to common shareholders ​ $ 47,817 ​ $ 35,121 ​ $ 100,531 ​ $ 75,118 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 54,007 ​ 52,487 ​ 53,927 ​ 52,262 ​ Assumed exercise of stock options ​ 462 ​ 339 ​ 455 ​ 372 ​ Weighted-average common shares outstanding – diluted ​ 54,469 ​ 52,826 ​ 54,382 ​ 52,634 ​ Diluted earnings per share ​ $ 0.88 ​ $ 0.66 ​ $ 1.85 ​ $ 1.43 ​ ​ Stock Repurchase Program At its December 2019 meeting, the Company’s Board of Directors (the “Board”) approved a stock repurchase program authorizing the repurchase of up to 2.60 million shares of the Company’s common stock in accordance with securities laws and regulations, through December 31, 2020. At its December 2020 meeting, the Board approved a similar program for 2021, authorizing the repurchase of up to 2.68 million shares of the Company’s common stock through December 31, 2021. Any repurchased shares will be used for general corporate purposes, including those related to stock plan activities. The timing and extent of repurchases will depend on market conditions and other corporate considerations as determined at the Company’s discretion. The Company did not repurchase any shares under the authorized plan during the first six months of 2021 or 2020.

COMMITMENTS, CONTINGENT LIABILI

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS	6 Months Ended
	Jun. 30, 2021
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS	NOTE J: COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS The Company is a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments consist primarily of commitments to extend credit and standby letters of credit. Commitments to extend credit are agreements to lend to customers, generally having fixed expiration dates or other termination clauses that may require payment of a fee. These commitments consist principally of unused commercial and consumer credit lines. Standby letters of credit generally are contingent upon the failure of the customer to perform according to the terms of an underlying contract with a third party. The credit risks associated with commitments to extend credit and standby letters of credit are essentially the same as that involved with extending loans to customers and are subject to the Company’s normal credit policies. Collateral may be obtained based on management’s assessment of the customer’s creditworthiness. The fair value of the standby letters of credit is immaterial for disclosure. The contract amounts of commitments and contingencies are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, (000’s omitted) ​ 2021 ​ 2020 Commitments to extend credit ​ $ 1,199,804 ​ $ 1,313,568 ​ Standby letters of credit ​ 35,382 ​ 39,213 ​ Total ​ $ 1,235,186 ​ $ 1,352,781 ​ ​ The Company and its subsidiaries are subject in the normal course of business to various pending and threatened legal proceedings in which claims for monetary damages are asserted. As of June 30, 2021, management, after consultation with legal counsel, does not anticipate that the aggregate ultimate liability arising out of litigation pending or threatened against the Company or its subsidiaries will be material to the Company’s consolidated financial position. On at least a quarterly basis, the Company assesses its liabilities and contingencies in connection with such legal proceedings. For those matters where it is probable that the Company will incur losses and the amounts of the losses can be reasonably estimated, the Company records an expense and corresponding liability in its consolidated financial statements. To the extent the pending or threatened litigation could result in exposure in excess of that liability, the amount of such excess is not currently estimable. The range of reasonably possible losses for matters where an exposure is not currently estimable or considered probable, beyond the existing recorded liabilities, is believed to be between $0 and $1 million in the aggregate. Although the Company does not believe that the outcome of pending litigation will be material to the Company’s consolidated financial position, it cannot rule out the possibility that such outcomes will be material to the consolidated results of operations for a particular reporting period in the future. ​ The Company recorded $3.0 million in litigation accrual in 2020 related to a settlement of a purported class action lawsuit regarding the Bank’s deposit account terms and overdraft disclosures. The Company executed a settlement agreement with respect to the lawsuit in the fourth quarter 2020 providing for a release of all claims asserted by class members in the action, and the Company does not anticipate that additional amounts will be accrued for this matter in future periods. Notice of the settlement terms was provided to all class members and no objections to the settlement were received prior to expiration of the notice period. The hearing for final Court approval of the settlement is scheduled on August 25, 2021.

FAIR VALUE

FAIR VALUE	6 Months Ended
	Jun. 30, 2021
FAIR VALUE
FAIR VALUE	NOTE K: FAIR VALUE Accounting standards establish a framework for measuring fair value and require certain disclosures about such fair value instruments. It defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (i.e. exit price). Inputs used to measure fair value are classified into the following hierarchy: ● Quoted prices in active markets for identical assets or liabilities. ● Quoted prices in active markets for similar assets or liabilities, or quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs other than quoted prices that are observable for the asset or liability. ● Significant valuation assumptions not readily observable in a market. ​ A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The following tables set forth the Company’s financial assets and liabilities that were accounted for at fair value on a recurring basis. There were no transfers between any of the levels for the periods presented. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair (000's omitted) Level 1 Level 2 Level 3 Value Available-for-sale investment securities: ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 2,909,475 ​ $ 115,597 ​ $ 0 ​ $ 3,025,072 Obligations of state and political subdivisions ​ 0 ​ 426,152 ​ 0 ​ 426,152 Government agency mortgage-backed securities ​ 0 ​ 529,139 ​ 0 ​ 529,139 Corporate debt securities ​ 0 ​ 3,094 ​ 0 ​ 3,094 Government agency collateralized mortgage obligations ​ 0 ​ 29,282 ​ 0 ​ 29,282 Total available-for-sale investment securities ​ 2,909,475 ​ 1,103,264 ​ 0 ​ 4,012,739 Equity securities ​ 469 ​ 0 ​ 0 ​ 469 Mortgage loans held for sale ​ ​ 0 ​ ​ 1,340 ​ ​ 0 ​ ​ 1,340 Commitments to originate real estate loans for sale ​ ​ 0 ​ ​ 0 ​ ​ 130 ​ ​ 130 Forward sales commitments ​ ​ 0 ​ ​ 31 ​ ​ 0 ​ ​ 31 Interest rate swap agreements asset ​ 0 ​ 372 ​ 0 ​ 372 Interest rate swap agreements liability ​ 0 ​ (7) ​ 0 ​ (7) Total ​ $ 2,909,944 ​ $ 1,105,000 ​ $ 130 ​ $ 4,015,074 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair (000's omitted) Level 1 Level 2 Level 3 Value Available-for-sale investment securities: ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 2,359,912 ​ $ 141,470 ​ $ 0 ​ $ 2,501,382 Obligations of state and political subdivisions ​ 0 ​ 475,660 ​ 0 ​ 475,660 Government agency mortgage-backed securities ​ 0 ​ 522,638 ​ 0 ​ 522,638 Corporate debt securities ​ 0 ​ 4,635 ​ 0 ​ 4,635 Government agency collateralized mortgage obligations ​ 0 ​ 43,577 ​ 0 ​ 43,577 Total available-for-sale investment securities ​ 2,359,912 ​ 1,187,980 ​ 0 ​ 3,547,892 Equity securities ​ 445 ​ 0 ​ 0 ​ 445 Mortgage loans held for sale ​ 0 ​ 1,622 ​ 0 ​ 1,622 Commitments to originate real estate loans for sale ​ ​ 0 ​ ​ 0 ​ ​ 14 ​ ​ 14 Forward sales commitments ​ ​ 0 ​ ​ 2 ​ ​ 0 ​ ​ 2 Interest rate swap agreements asset ​ 0 ​ 1,572 ​ 0 ​ 1,572 Interest rate swap agreements liability ​ 0 ​ (1,074) ​ ​ 0 ​ (1,074) Total ​ $ 2,360,357 ​ $ 1,190,102 ​ $ 14 ​ $ 3,550,473 ​ The valuation techniques used to measure fair value for the items in the table above are as follows: ● Available-for-sale investment securities and equity securities – The fair values of available-for-sale investment securities are based upon quoted prices, if available. If quoted prices are not available, fair values are measured using quoted market prices for similar securities or model-based valuation techniques. Level 1 securities include U.S. Treasury obligations and marketable equity securities that are traded by dealers or brokers in active over-the-counter markets. Level 2 securities include U.S. agency securities, mortgage-backed securities issued by government-sponsored entities, municipal securities and corporate debt securities that are valued by reference to prices for similar securities or through model-based techniques in which all significant inputs, such as reported trades, trade execution data, LIBOR swap yield curve, market prepayment speeds, credit information, market spreads, and security’s terms and conditions, are observable. See Note D for further disclosure of the fair value of investment securities. ● Mortgage loans held for sale – The Company has elected to value loans held for sale at fair value in order to more closely match the gains and losses associated with loans held for sale with the gains and losses on forward sales contracts. Accordingly, the impact on the valuation will be recognized in the Company’s consolidated statements of income. All mortgage loans held for sale are current and in performing status. The fair value of mortgage loans held for sale is determined using quoted secondary-market prices of loans with similar characteristics and, as such, has been classified as a Level 2 valuation. The unpaid principal value of mortgage loans held for sale was approximately $ 1.3 million at June 30, 2021. The unpaid principal value of mortgage loans held for sale was approximately $1.6 million at December 31, 2020. The unrealized gain on mortgage loans held for sale was recognized in mortgage banking revenues in the consolidated statements of income and is immaterial. ● Forward sales commitments – The Company enters into forward sales commitments to sell certain residential real estate loans. Such commitments are considered to be derivative financial instruments and, therefore, are carried at estimated fair value in the other asset or other liability section of the consolidated statement of condition. The fair value of these forward sales commitments is primarily measured by obtaining pricing from certain government-sponsored entities and reflects the underlying price the entity would pay the Company for an immediate sale on these mortgages. As such, these instruments are classified as Level 2 in the fair value hierarchy. ● Commitments to originate real estate loans for sale – The Company enters into various commitments to originate residential real estate loans for sale. Such commitments are considered to be derivative financial instruments and, therefore, are carried at estimated fair value in the other asset or other liability section of the consolidated statement of condition. The estimated fair value of these commitments is determined using quoted secondary market prices obtained from certain government-sponsored entities. Additionally, accounting guidance requires the expected net future cash flows related to the associated servicing of the loan to be included in the fair value measurement of the derivative. The expected net future cash flows are based on a valuation model that calculates the present value of estimated net servicing income. The valuation model incorporates assumptions that market participants would use in estimating future net servicing income. Such assumptions include estimates of the cost of servicing loans, appropriate discount rate and prepayment speeds. The determination of expected net cash flows is considered a significant unobservable input contributing to the Level 3 classification of commitments to originate real estate loans for sale. ● Interest rate swaps – The interest rate swaps are reported at their fair value utilizing Level 2 inputs from third parties. The fair value of the interest rate swaps are determined using prices obtained from a third party advisor. The fair value measurement of the interest rate swap is determined by netting the discounted future fixed cash payments and the discounted expected variable cash receipts. The variable cash receipts are based on the expectation of future interest rates derived from observed market interest rate curves. The changes in Level 3 assets measured at fair value on a recurring basis are immaterial. The fair value information of assets and liabilities measured on a non-recurring basis presented below is not as of the period-end, but rather as of the date the fair value adjustment was recorded closest to the date presented. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ Total Fair ​ ​ ​ ​ ​ ​ Total Fair (000's omitted) ​ Level 1 ​ Level 2 ​ Level 3 ​ Value ​ Level 1 ​ Level 2 ​ Level 3 ​ Value Impaired loans ​ $ 0 ​ $ 0 ​ $ 21,330 $ 21,330 ​ $ 0 ​ $ 0 ​ $ 25,063 $ 25,063 Other real estate owned ​ 0 ​ 0 ​ 879 879 ​ 0 ​ 0 ​ 883 883 Mortgage servicing rights ​ 0 ​ 0 ​ 697 697 ​ 0 ​ 0 ​ 682 682 Total ​ $ 0 ​ $ 0 ​ $ 22,906 $ 22,906 ​ $ 0 ​ $ 0 ​ $ 26,628 $ 26,628 ​ Loans are generally not recorded at fair value on a recurring basis. Periodically, the Company records nonrecurring adjustments to the carrying value of loans based on fair value measurements for partial charge-offs of the uncollectible portions of those loans. Nonrecurring adjustments also include certain impairment amounts for collateral-dependent loans calculated when establishing the allowance for credit losses. Such amounts are generally based on the fair value of the underlying collateral supporting the loan and, as a result, the carrying value of the loan less the calculated valuation amount does not necessarily represent the fair value of the loan. Real estate collateral is typically valued using independent appraisals or other indications of value based on recent comparable sales of similar properties or assumptions generally observable in the marketplace, adjusted for non-observable inputs. Thus, the resulting nonrecurring fair value measurements are generally classified as Level 3. Estimates of fair value used for other collateral supporting commercial loans generally are based on assumptions not observable in the marketplace and, therefore, such valuations classify as Level 3. Other real estate owned (“OREO”) is valued at the time the loan is foreclosed upon and the asset is transferred to OREO. The value is based primarily on third party appraisals, less costs to sell. The appraisals are sometimes further discounted based on management’s historical knowledge, changes in market conditions from the time of valuation, and/or management’s expertise and knowledge of the customer and customer’s business. Such discounts are significant, ranging from 9.0% to 51.1% at June 30, 2021 and result in a Level 3 classification of the inputs for determining fair value. OREO is reviewed and evaluated on at least a quarterly basis for additional impairment and adjusted accordingly, based on the same factors identified above. The Company recovers the carrying value of OREO through the sale of the property. The ability to affect future sales prices is subject to market conditions and factors beyond the Company’s control and may impact the estimated fair value of a property. Originated mortgage servicing rights are recorded at their fair value at the time of sale of the underlying loan, and are amortized in proportion to and over the estimated period of net servicing income. The fair value of mortgage servicing rights is based on a valuation model incorporating inputs that market participants would use in estimating future net servicing income. Such inputs include estimates of the cost of servicing loans, appropriate discount rate and prepayment speeds and are considered to be unobservable and contribute to the Level 3 classification of mortgage servicing rights. In accordance with GAAP, the Company must record impairment charges, on a nonrecurring basis, when the carrying value of a stratum exceeds its estimated fair value. Impairment is recognized through a valuation allowance. There is a valuation allowance of approximately $0.1 million and $0.2 million at June 30, 2021 and December 31, 2020, respectively. The Company determines fair values based on quoted market values, where available, estimates of present values, or other valuation techniques. Those techniques are significantly affected by the assumptions used, including, but not limited to, the discount rate and estimates of future cash flows. In that regard, the derived fair value estimates cannot be substantiated by comparison to independent markets and, in many cases, may not be realized in immediate settlement of the instrument. The significant unobservable inputs used in the determination of fair value of assets classified as Level 3 on a recurring or non-recurring basis are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ ​ ​ ​ Unobservable Input ​ ​ Fair Value at ​ ​ ​ ​ ​ Range ​ (000's omitted, except per loan data) ​ June 30, 2021 ​ Valuation Technique ​ Significant Unobservable Inputs (Weighted Average) ​ Impaired loans ​ $ 21,330 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 78.7% (53.8%) ​ Other real estate owned ​ 879 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 51.1% (34.5%) ​ Commitments to originate real estate loans for sale ​ 130 Discounted cash flow Embedded servicing value ​ 1.0 % Mortgage servicing rights ​ 697 Discounted cash flow Weighted average constant prepayment rate ​ 16.9% - 49.1% (21.8%) ​ ​ ​ ​ ​ ​ ​ ​ Weighted average discount rate ​ ​ 2.2% - 2.8% (2.7%) ​ ​ ​ ​ ​ ​ ​ ​ Adequate compensation ​ $ 7/loan ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ ​ Unobservable Input ​ ​ ​ Fair Value at ​ ​ ​ ​ ​ Range ​ (000's omitted, except per loan data) ​ December 31, 2020 ​ Valuation Technique ​ Significant Unobservable Inputs ​ (Weighted Average) Impaired loans ​ $ 25,063 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 78.4% (52.7%) ​ Other real estate owned ​ 883 Fair value of collateral Estimated cost of disposal/market adjustment ​ 11.3% - 52.9% (34.0%) ​ Commitments to originate real estate loans for sale ​ ​ 14 ​ Discounted cash flow ​ Embedded servicing value ​ ​ 1.0 % Mortgage servicing rights ​ 682 Discounted cash flow Weighted average constant prepayment rate ​ 9.8% - 18.8% (17.6%) ​ ​ ​ Weighted average discount rate ​ 1.7% - 2.2% (2.1%) ​ ​ ​ ​ ​ ​ ​ Adequate compensation ​ $ 7/loan ​ ​ The significant unobservable inputs used in the determination of the fair value of assets classified as Level 3 have an inherent measurement uncertainty that if changed could result in higher or lower fair value measurements of these assets as of the reporting date. The weighted average of the estimated cost of disposal/market adjustment for impaired loans was calculated by dividing the total of the book value of the collateral of the impaired loans classified as Level 3 by the total of the fair value of the collateral of the impaired loans classified as Level 3. The weighted average of the estimated cost of disposal/market adjustment for OREO was calculated by dividing the total of the differences between the appraisal values of the real estate and the book values of the real estate divided by the totals of the appraisal values of the real estate. The weighted average of the constant prepayment rate for mortgage servicing rights was calculated by adding the constant prepayment rates used in each loan pool weighted by the balance in each loan pool. The weighted average of the discount rate for mortgage servicing rights was calculated by adding the discount rates used in each loan pool weighted by the balance in each loan pool. Certain financial instruments and all nonfinancial instruments are excluded from fair value disclosure requirements. Accordingly, the aggregate fair value amounts presented do not represent the underlying value of the Company. The carrying amounts and estimated fair values of the Company’s other financial instruments that are not accounted for at fair value at June 30, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ December 31, 2020 ​ Carrying Fair Carrying Fair (000's omitted) ​ Value ​ Value ​ Value ​ Value Financial assets: ​ ​ ​ ​ Net loans ​ $ 7,192,397 ​ $ 7,563,546 ​ $ 7,355,083 ​ $ 7,655,044 Financial liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Deposits ​ 12,339,025 ​ 12,349,413 ​ 11,224,974 ​ 11,239,628 Securities sold under agreement to repurchase, short-term ​ 194,887 ​ 194,887 ​ 284,008 ​ 284,008 Other Federal Home Loan Bank borrowings ​ 2,936 ​ 2,993 ​ 6,658 ​ 6,758 Subordinated notes payable ​ 3,290 ​ 3,290 ​ 3,303 ​ 3,303 Subordinated debt held by unconsolidated subsidiary trusts ​ 0 ​ 0 ​ 77,320 ​ 77,320 ​ The following is a further description of the principal valuation methods used by the Company to estimate the fair values of its financial instruments. Loans have been classified as a Level 3 valuation. Fair values for loans are estimated using discounted cash flows and interest rates currently being offered for loans with similar terms to borrowers of similar credit quality. Deposits have been classified as a Level 2 valuation. The fair value of demand deposits, interest-bearing checking deposits, savings accounts, and money market deposits is the amount payable on demand at the reporting date. The fair value of time deposit obligations are based on current market rates for similar products. Borrowings and subordinated debt held by unconsolidated subsidiary trusts have been classified as a Level 2 valuation. The fair value of short-term borrowings and securities sold under agreement to repurchase, short-term, is the amount payable on demand at the reporting date. Fair values for long-term debt and subordinated debt held by unconsolidated subsidiary trusts are estimated using discounted cash flows and interest rates currently being offered on similar securities. The difference between the carrying values of long-term borrowings and subordinated debt held by unconsolidated subsidiary trusts, and their fair values, are not material as of the reporting dates. Other financial assets and liabilities – Cash and cash equivalents have been classified as a Level 1 valuation, while accrued interest receivable and accrued interest payable have been classified as a Level 2 valuation. The fair values of each approximate the respective carrying values because the instruments are payable on demand or have short-term maturities and present relatively low credit risk and interest rate risk.

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	6 Months Ended
	Jun. 30, 2021
DERIVATIVE INSTRUMENTS
DERIVATIVE INSTRUMENTS	NOTE L: DERIVATIVE INSTRUMENTS The Company is party to derivative financial instruments in the normal course of its business to meet the financing needs of its customers and to manage its own exposure to fluctuations in interest rates. These financial instruments have been limited to interest rate swap agreements, commitments to originate real estate loans held for sale and forward sales commitments. The Company does not hold or issue derivative financial instruments for trading or other speculative purposes. The Company enters into forward sales commitments for the future delivery of residential mortgage loans, and interest rate lock commitments to fund loans at a specified interest rate. The forward sales commitments are utilized to reduce interest rate risk associated with interest rate lock commitments and loans held for sale. Changes in the estimated fair value of the forward sales commitments and interest rate lock commitments subsequent to inception are based on changes in the fair value of the underlying loan resulting from the fulfillment of the commitment and changes in the probability that the loan will fund within the terms of the commitment, which is affected primarily by changes in interest rates and the passage of time. At inception and during the life of the interest rate lock commitment, the Company includes the expected net future cash flows related to the associated servicing of the loan as part of the fair value measurement of the interest rate lock commitments. These derivatives are recorded at fair value, which were immaterial at June 30, 2021 and December 31, 2020. The effect of the changes to these derivatives for the three and six months then ended was also immaterial. The Company acquired interest rate swaps in 2017 with notional amounts with certain commercial customers which totaled $0.7 million at June 30, 2021 and $14.4 million at December 31, 2020. In order to minimize the Company’s risk, these customer derivatives (pay floating/receive fixed swaps) have been offset with essentially matching interest rate swaps (pay fixed/receive floating swaps) with the Company’s counterparty totaling $0.7 million at June 30, 2021 and $14.4 million at December 31, 2020. At June 30, 2021, the weighted average receive rate of these interest rate swaps was 2.34%, the weighted average pay rate was 3.54% and the weighted average maturity was 1.8 years. At December 31, 2020, the weighted average receive rate of these interest rate swaps was The Company also acquired interest rate swaps in 2017 with notional amounts totaling $5.4 million at June 30, 2021, and $5.7 million at December 31, 2020, that were designated as fair value hedges of certain fixed rate loans with municipalities which are recorded in loans in the consolidated statements of financial condition. At June 30, 2021, the weighted average receive rate of these interest rate swaps was 1.38%, the weighted average pay rate was 3.11% and the weighted average maturity was 12.0 years. At December 31, 2020, the weighted average receive rate of these interest rate swaps was 1.42%, the weighted average pay rate was 3.11% and the weighted average maturity was 12.5 years. The Company includes the gain or loss on the hedged items in interest and fees on loans, the same line item as the offsetting gain or loss on the related interest rate swaps. The effects of fair value accounting in the consolidated statements of income for the three and six months ended June 30, 2021 are immaterial. As of June 30, 2021 and December 31, 2020, the following amounts were recorded in the consolidated statement of condition related to cumulative basis adjustments for fair value hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ ​ ​ ​ ​ ​ ​ Cumulative Amount of Fair Value ​ ​ Carrying Amount of the Hedged ​ Hedging Adjustment Included in the Line Item in the Consolidated ​ Assets ​ Carrying Amount of the Hedged Assets Statement of Condition in Which ​ June 30, ​ December 31, ​ June 30, ​ December 31, the Hedged Item Is Included 2021 2020 2021 2020 Loans $ 5,809 $ 5,675 $ (365) $ (498) ​ Fair values of derivative instruments as of June 30, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ June 30, 2021 ​ ​ Derivative Assets ​ Derivative Liabilities ​ ​ Consolidated Statement ​ Fair ​ Consolidated Statement of ​ Fair ​ of Condition Location Value Condition Location Value Derivatives designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ $ 365 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ ​ Interest rate swaps Other assets ​ 7 Accrued interest and other liabilities ​ $ 7 Commitments to originate real estate loans for sale Other assets ​ 130 ​ ​ Forward sales commitments Other assets ​ 31 ​ ​ Total derivatives ​ $ 533 ​ $ 7 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ December 31, 2020 ​ ​ Derivative Assets ​ Derivative Liabilities ​ ​ Consolidated Statement ​ Fair ​ Consolidated Statement of ​ Fair ​ of Condition Location Value Condition Location Value Derivatives designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ $ 498 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ ​ ​ Interest rate swaps Other assets ​ 1,074 Accrued interest and other liabilities ​ $ 1,074 Commitments to originate real estate loans for sale ​ Other assets ​ ​ 14 ​ ​ ​ ​ ​ Forward sales commitments ​ Other assets ​ ​ 2 ​ ​ ​ ​ ​ Total derivatives ​ ​ $ 1,588 ​ $ 1,074 ​ The Company assessed its counterparty risk at June 30, 2021 and December 31, 2020 and determined any credit risk inherent in our derivative contracts was not material. Further information about the fair value of derivative financial instruments can be found in Note K to these consolidated financial statements.

SEGMENT INFORMATION

SEGMENT INFORMATION	6 Months Ended
	Jun. 30, 2021
SEGMENT INFORMATION
SEGMENT INFORMATION	NOTE M: SEGMENT INFORMATION Operating segments are components of an enterprise, which are evaluated regularly by the “chief operating decision maker” in deciding how to allocate resources and assess performance. The Company’s chief operating decision maker is the President and Chief Executive Officer of the Company. The Company has identified Banking, Employee Benefit Services and All Other as its reportable operating business segments. Community Bank, N.A. (the “Bank” or “CBNA”) operates the Banking segment that provides full-service banking to consumers, businesses, and governmental units in Upstate New York as well as Northeastern Pennsylvania, Vermont and Western Massachusetts. Employee Benefit Services, which includes the operating subsidiaries Benefit Plans Administrative Services, LLC, BPAS Actuarial and Pension Services, LLC, BPAS Trust Company of Puerto Rico, Northeast Retirement Services, LLC (“NRS”), Global Trust Company, Inc. (“GTC”), and Hand Benefits & Trust Company, provides employee benefit trust, collective investment fund, retirement plan administration, fund administration, transfer agency, actuarial, VEBA/HRA, and health and welfare consulting services. The All Other segment is comprised of: (a) wealth management services including trust services provided by the personal trust unit within the Bank, broker-dealer and investment advisory services provided by Community Investment Services, Inc., The Carta Group, Inc. and OneGroup Wealth Partners, Inc. as well as asset management provided by Nottingham Advisors, Inc., and (b) full-service insurance, risk management and employee benefit services provided by OneGroup NY, Inc. The accounting policies used in the disclosure of business segments are the same as those described in the summary of significant accounting policies (See Note A, Summary of Significant Accounting Policies Information about reportable segments and reconciliation of the information to the consolidated financial statements follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee ​ ​ ​ ​ ​ ​ ​ Consolidated (000's omitted) Banking Benefit Services All Other Eliminations Total Three Months Ended June 30, 2021 ​ ​ ​ ​ ​ Net interest income ​ $ 92,033 ​ $ 65 ​ $ 7 ​ $ 0 ​ $ 92,105 Provision for credit losses ​ (4,338) ​ 0 ​ 0 ​ 0 ​ (4,338) Noninterest revenues ​ 16,357 ​ 27,994 ​ 16,816 ​ (1,707) ​ 59,460 Amortization of intangible assets ​ 1,240 ​ 1,327 ​ 679 ​ 0 ​ 3,246 Acquisition expenses ​ 4 ​ 0 ​ 0 ​ 0 ​ 4 Other operating expenses ​ 65,158 ​ 14,846 ​ 11,996 ​ (1,707) ​ 90,293 Income before income taxes ​ $ 46,326 ​ $ 11,886 ​ $ 4,148 ​ $ 0 ​ $ 62,360 Assets ​ $ 14,588,075 ​ $ 235,141 ​ $ 78,770 ​ $ (100,699) ​ $ 14,801,287 Goodwill ​ $ 689,867 ​ $ 83,275 ​ $ 21,750 ​ $ 0 ​ $ 794,892 Core deposit intangibles & Other intangibles ​ $ 11,267 ​ $ 29,370 ​ $ 7,143 ​ $ 0 ​ $ 47,780 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net interest income ​ $ 91,645 ​ $ 246 ​ $ 60 ​ $ 0 ​ $ 91,951 Provision for credit losses ​ 9,774 ​ 0 ​ 0 ​ 0 ​ 9,774 Noninterest revenues ​ 14,991 ​ 24,504 ​ 14,817 ​ (1,374) ​ 52,938 Amortization of intangible assets ​ 1,364 ​ 1,411 ​ 749 ​ 0 ​ 3,524 Acquisition expenses ​ 3,372 ​ 0 ​ 0 ​ 0 ​ 3,372 Other operating expenses ​ 59,130 ​ 14,948 ​ 11,303 ​ (1,374) ​ 84,007 Income before income taxes ​ $ 32,996 ​ $ 8,391 ​ $ 2,825 ​ $ 0 ​ $ 44,212 Assets ​ $ 13,272,929 ​ $ 216,122 ​ $ 78,022 ​ $ (122,856) ​ $ 13,444,217 Goodwill ​ $ 689,128 ​ $ 83,275 ​ $ 20,312 ​ $ 0 ​ $ 792,715 Core deposit intangibles & Other intangibles ​ $ 16,565 ​ $ 34,870 ​ $ 8,611 ​ $ 0 ​ $ 60,046 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee ​ ​ ​ ​ Consolidated (000's omitted) ​ Banking ​ Benefit Services ​ All Other ​ Eliminations ​ Total Six Months Ended June 30, 2021 ​ ​ ​ ​ ​ Net interest income ​ $ 185,872 ​ $ 159 ​ $ 28 ​ $ 0 ​ $ 186,059 Provision for credit losses ​ (10,057) ​ 0 ​ 0 ​ 0 ​ (10,057) Noninterest revenues ​ 32,811 ​ 55,143 ​ 33,633 ​ (3,596) ​ 117,991 Amortization of intangible assets ​ 2,564 ​ 2,681 ​ 1,352 ​ 0 ​ 6,597 Acquisition expenses ​ 31 ​ 0 ​ 0 ​ 0 ​ 31 Other operating expenses ​ 130,165 ​ 29,851 ​ 23,741 ​ (3,596) ​ 180,161 Income before income taxes ​ $ 95,980 ​ $ 22,770 ​ $ 8,568 ​ $ 0 ​ $ 127,318 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended June 30, 2020 ​ ​ ​ ​ ​ Net interest income ​ $ 181,409 ​ $ 486 ​ $ 110 ​ $ 0 ​ $ 182,005 Provision for credit losses ​ 15,368 ​ 0 ​ 0 ​ 0 ​ 15,368 Noninterest revenues ​ 33,672 ​ 50,429 ​ 30,352 ​ (2,893) ​ 111,560 Amortization of intangible assets ​ 2,781 ​ 2,905 ​ 1,505 ​ 0 ​ 7,191 Acquisition expenses ​ 3,741 ​ 0 ​ 0 ​ 0 ​ 3,741 Other operating expenses ​ 123,330 ​ 30,079 ​ 23,118 ​ (2,893) ​ 173,634 Income before income taxes ​ $ 69,861 ​ $ 17,931 ​ $ 5,839 ​ $ 0 ​ $ 93,631 ​

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2021
ACCOUNTING POLICIES
Contract Balances	Contract Balances A contract asset balance occurs when an entity performs a service for a customer before the customer pays consideration (resulting in a contract receivable) or before payment is due (resulting in a contract asset). 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 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. As of June 30, 2021, $27.4 million of accounts receivable, including $8.3 million of unbilled fee revenue, and $2.7 million of unearned revenue was recorded in the consolidated statements of condition. As of December 31, 2020, $30.3 million of accounts receivable, including $7.7 million of unbilled fee revenue, and $1.4 million of unearned revenue was recorded in the consolidated statements of condition.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-14, Disclosure Framework - Changes to the Disclosure Requirements for Defined Benefit Plans (Subtopic 715-20) . The updated guidance removed the requirements to identify amounts that are expected to be reclassified out of accumulated other comprehensive income and recognized as components of net periodic benefit cost in the next fiscal year, as well as the effects of a one-percentage-point change in assumed health care cost trend rates on service and interest cost and on the postretirement benefit obligation. The updated guidance added annual disclosure requirements for the weighted-average interest crediting rates for cash balance plans and other plans with interest crediting rates, and explanations for significant gains and losses related to changes in the benefit obligation for the period. This new guidance is effective retrospectively for fiscal years beginning after December 15, 2020 with early adoption permitted. The Company adopted this guidance on January 1, 2021 and determined the adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (Topic 740) . The updated guidance simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740, and clarifying and amending existing guidance to improve consistent application. This new guidance is effective for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. Early adoption is permitted in any interim periods for which financial statements have not been issued. The Company adopted this guidance on January 1, 2021 and determined the adoption of this guidance did not have a material impact on the Company’s consolidated financial statements.
New Accounting Pronouncements	New Accounting Pronouncements In March 2020, the FASB issued ASU No. 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting (Topic 848)

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	6 Months Ended
	Jun. 30, 2021
ACQUISITIONS
Schedule of estimated fair value of assets acquired and liabilities assumed	The following table summarizes the estimated fair value of the assets acquired and liabilities assumed after considering the measurement period adjustments described above: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2021 ​ 2020 (000s omitted) ​ NuVantage ​ Steuben Consideration paid : ​ ​ ​ ​ ​ Cash ​ $ 2,900 ​ $ 21,613 Community Bank System, Inc. common stock ​ ​ 0 ​ 76,942 Total net consideration paid ​ ​ 2,900 ​ 98,555 Recognized amounts of identifiable assets acquired and liabilities assumed: ​ ​ ​ ​ Cash and cash equivalents ​ ​ 0 ​ 55,973 Investment securities ​ ​ 0 ​ 180,497 Loans, net of allowance for credit losses on PCD loans ​ ​ 0 ​ 339,017 Premises and equipment, net ​ ​ 199 ​ 7,764 Accrued interest and fees receivable ​ ​ 0 ​ 2,701 Other assets ​ ​ 0 ​ 17,675 Core deposit intangibles ​ ​ 0 ​ 2,928 Other intangibles ​ ​ 1,437 ​ 1,196 Deposits ​ ​ 0 ​ (516,274) Other liabilities ​ ​ (174) ​ (4,841) Other Federal Home Loan Bank borrowings ​ ​ 0 ​ (6,000) Subordinated debt held by unconsolidated subsidiary trusts ​ ​ 0 ​ (2,062) Total identifiable assets, net ​ ​ 1,462 ​ 78,574 Goodwill ​ $ 1,438 ​ $ 19,981
Schedule of loans acquired	​ ​ ​ ​ ​ (000s omitted) PCD Loans Par value of PCD loans at acquisition ​ $ 35,906 Allowance for credit losses at acquisition ​ (668) Non-credit premium at acquisition ​ 103 Fair value of PCD loans at acquisition ​ $ 35,341 ​ ​ ​ ​ ​ (000s omitted) Non-PCD Loans Contractually required principal and interest at acquisition ​ $ 400,738 Contractual cash flows not expected to be collected ​ (2,994) Expected cash flows at acquisition ​ 397,744 Interest component of expected cash flows ​ (94,068) Fair value of non-PCD loans at acquisition ​ $ 303,676
Schedule of pro forma financial information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pro Forma (Unaudited) ​ Pro Forma (Unaudited) ​ ​ ​ Three Months Ended Six Months Ended ​ (000's omitted) June 30, 2020 June 30, 2019 June 30, 2020 June 30, 2019 Total revenue, net of interest expense ​ $ 149,576 ​ $ 154,878 ​ $ 304,088 ​ $ 303,152 ​ Net income ​ 39,072 ​ 46,447 ​ 80,848 ​ 86,774 ​

INVESTMENT SECURITIES (Tables)

INVESTMENT SECURITIES (Tables)	6 Months Ended
	Jun. 30, 2021
INVESTMENT SECURITIES
Schedule of amortized cost and estimated fair value of investment securities	The amortized cost and estimated fair value of investment securities as of June 30, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ December 31, 2020 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Amortized ​ Unrealized ​ Unrealized ​ Fair (000's omitted) Cost Gains Losses Value Cost Gains Losses Value Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 3,082,187 ​ $ 52,960 ​ $ 110,075 ​ $ 3,025,072 ​ $ 2,423,236 ​ $ 94,741 ​ $ 16,595 ​ $ 2,501,382 Obligations of state and political subdivisions ​ 405,245 ​ 20,908 ​ 1 ​ 426,152 ​ 451,028 ​ 24,632 ​ 0 ​ 475,660 Government agency mortgage-backed securities ​ 521,056 ​ 10,999 ​ 2,916 ​ 529,139 ​ 506,540 ​ 16,280 ​ 182 ​ 522,638 Corporate debt securities ​ 3,000 ​ 94 ​ 0 ​ 3,094 ​ 4,499 ​ 137 ​ 1 ​ 4,635 Government agency collateralized mortgage obligations ​ 28,490 ​ 796 ​ 4 ​ 29,282 ​ 42,476 ​ 1,111 ​ 10 ​ 43,577 Total available-for-sale portfolio ​ $ 4,039,978 ​ $ 85,757 ​ $ 112,996 ​ $ 4,012,739 ​ $ 3,427,779 ​ $ 136,901 ​ $ 16,788 ​ $ 3,547,892 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity and other Securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity securities, at fair value ​ $ 251 ​ $ 218 ​ $ 0 ​ $ 469 ​ $ 251 ​ $ 194 ​ $ 0 ​ $ 445 Federal Home Loan Bank common stock ​ 7,262 ​ 0 ​ 0 ​ 7,262 ​ 7,468 ​ 0 ​ 0 ​ 7,468 Federal Reserve Bank common stock ​ 33,916 ​ 0 ​ 0 ​ 33,916 ​ 33,916 ​ 0 ​ 0 ​ 33,916 Other equity securities, at adjusted cost ​ 2,526 ​ 750 ​ 0 ​ 3,276 ​ 4,876 ​ 750 ​ 0 ​ 5,626 Total equity and other securities ​ $ 43,955 ​ $ 968 ​ $ 0 ​ $ 44,923 ​ $ 46,511 ​ $ 944 ​ $ 0 ​ $ 47,455
Schedule of investment securities that have been in a continuous unrealized loss position for less than or greater than twelve months	A summary of investment securities that have been in a continuous unrealized loss position is as follows: As of June 30, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 Months 12 Months or Longer Total ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized (000's omitted) # Value Losses # Value Losses # Value Losses ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ 29 ​ $ 1,272,423 ​ $ 110,075 ​ 0 ​ $ 0 ​ $ 0 ​ 29 ​ $ 1,272,423 ​ $ 110,075 Obligations of state and political subdivisions ​ 4 ​ 1,651 ​ 1 ​ 0 ​ 0 ​ 0 ​ 4 ​ 1,651 ​ 1 Government agency mortgage-backed securities ​ 126 ​ 170,661 ​ 2,914 ​ 6 ​ 1,146 ​ 2 ​ 132 ​ 171,807 ​ 2,916 Government agency collateralized mortgage obligations ​ 3 ​ 1,804 ​ 3 ​ 3 ​ 182 ​ 1 ​ 6 ​ 1,986 ​ 4 Total available-for-sale investment portfolio ​ 162 ​ $ 1,446,539 ​ $ 112,993 ​ 9 ​ $ 1,328 ​ $ 3 ​ 171 ​ $ 1,447,867 ​ $ 112,996 ​ As of December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 Months 12 Months or Longer Total ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized (000's omitted) # Value Losses # Value Losses # Value Losses ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ 13 ​ $ 831,015 ​ $ 16,595 ​ 0 ​ $ 0 ​ $ 0 ​ 13 ​ $ 831,015 ​ $ 16,595 Obligations of state and political subdivisions ​ 1 ​ 358 ​ 0 ​ 0 ​ 0 ​ 0 ​ 1 ​ 358 ​ 0 Government agency mortgage-backed securities ​ 89 ​ 75,992 ​ 182 ​ 2 ​ 14 ​ 0 ​ 91 ​ 76,006 ​ 182 Corporate debt securities ​ 1 ​ ​ 1,001 ​ ​ 1 ​ 0 ​ ​ 0 ​ ​ 0 ​ 1 ​ ​ 1,001 ​ ​ 1 Government agency collateralized mortgage obligations ​ 13 ​ 5,246 ​ 10 ​ 1 ​ 0 ​ 0 ​ 14 ​ 5,246 ​ 10 Total available-for-sale investment portfolio ​ 117 ​ $ 913,612 ​ $ 16,788 ​ 3 ​ $ 14 ​ $ 0 ​ 120 ​ $ 913,626 ​ $ 16,788 ​
Schedule of amortized cost and estimated fair value of debt securities by contractual maturity	The amortized cost and estimated fair value of debt securities at June 30, 2021, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Securities not due at a single maturity date are shown separately. ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale ​ ​ Amortized ​ Fair (000's omitted) Cost Value Due in one year or less ​ $ 198,566 ​ $ 199,557 Due after one through five years ​ 768,349 ​ 796,228 Due after five years through ten years ​ 1,018,820 ​ 1,037,749 Due after ten years ​ 1,504,697 ​ 1,420,784 Subtotal ​ 3,490,432 ​ 3,454,318 Government agency mortgage-backed securities ​ 521,056 ​ 529,139 Government agency collateralized mortgage obligations ​ 28,490 ​ 29,282 Total ​ $ 4,039,978 ​ $ 4,012,739

LOANS (Tables)

LOANS (Tables)	6 Months Ended
	Jun. 30, 2021
Loans and Leases Receivable Disclosure [Line Items]
Schedule of loans receivable, net	The segments of the Company’s loan portfolio are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, (000’s omitted) ​ 2021 2020 Business lending ​ $ 3,186,487 ​ $ 3,440,077 Consumer mortgage ​ 2,408,499 ​ 2,401,499 Consumer indirect ​ 1,109,504 ​ 1,021,885 Consumer direct ​ 148,540 ​ 152,657 Home equity ​ 391,117 ​ 399,834 Gross loans, including deferred origination costs ​ 7,244,147 ​ 7,415,952 Allowance for credit losses ​ (51,750) ​ (60,869) Loans, net of allowance for credit losses ​ $ 7,192,397 ​ $ 7,355,083 ​
Schedule of aged analysis of past due loans by class	The following table presents the aging of the amortized cost basis of the Company’s past due loans, including PCD loans, by segment as of June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Current Total Loans Business lending ​ $ 972 ​ $ 228 ​ $ 49,877 ​ $ 51,077 ​ $ 3,135,410 ​ $ 3,186,487 Consumer mortgage ​ 8,645 ​ 1,259 ​ 16,025 ​ 25,929 ​ 2,382,570 ​ 2,408,499 Consumer indirect ​ 7,110 ​ 73 ​ 0 ​ 7,183 ​ 1,102,321 ​ 1,109,504 Consumer direct ​ 507 ​ 15 ​ 2 ​ 524 ​ 148,016 ​ 148,540 Home equity ​ 1,077 ​ 147 ​ 2,572 ​ 3,796 ​ 387,321 ​ 391,117 Total ​ $ 18,311 ​ $ 1,722 ​ $ 68,476 ​ $ 88,509 ​ $ 7,155,638 ​ $ 7,244,147 ​ The following table presents the aging of the amortized cost basis of the Company’s past due loans, including PCD loans, by segment as of December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due ​ 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Current Total Loans Business lending ​ $ 4,896 ​ $ 59 ​ $ 55,709 ​ $ 60,664 ​ $ 3,379,413 ​ $ 3,440,077 Consumer mortgage ​ 13,236 ​ 3,051 ​ 14,970 ​ 31,257 ​ 2,370,242 ​ 2,401,499 Consumer indirect ​ 13,161 ​ 219 ​ 1 ​ 13,381 ​ 1,008,504 ​ 1,021,885 Consumer direct ​ 1,170 ​ 28 ​ 3 ​ 1,201 ​ 151,456 ​ 152,657 Home equity ​ 2,296 ​ 565 ​ 2,246 ​ 5,107 ​ 394,727 ​ 399,834 Total ​ $ 34,759 ​ $ 3,922 ​ $ 72,929 ​ $ 111,610 ​ $ 7,304,342 ​ $ 7,415,952 ​
Schedule of non-business impaired loans	All loan classes are collectively evaluated for impairment except business lending. A summary of individually evaluated impaired business loans as of June 30, 2021 and December 31, 2020 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, (000’s omitted) 2021 2020 Loans with allowance allocation ​ $ 25,534 ​ $ 27,437 Loans without allowance allocation ​ 6,529 ​ 8,138 Carrying balance ​ 32,063 ​ 35,575 Contractual balance ​ 34,228 ​ 38,362 Specifically allocated allowance ​ 2,800 ​ 3,874 ​
Schedule of troubled debt restructurings on financing receivables	Information regarding TDRs as of June 30, 2021 and December 31, 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 December 31, 2020 (000’s omitted) ​ Nonaccrual ​ Accruing ​ Total ​ Nonaccrual ​ Accruing ​ Total ​ # Amount # Amount # Amount # Amount # Amount # Amount Business lending ​ 6 ​ $ 445 4 ​ $ 180 10 ​ $ 625 6 ​ $ 529 4 ​ $ 191 10 ​ $ 720 Consumer mortgage ​ 58 ​ 2,553 42 ​ 2,074 100 ​ 4,627 56 ​ 2,413 48 ​ 2,266 104 ​ 4,679 Consumer indirect ​ 0 ​ 0 79 ​ 916 79 ​ 916 0 ​ 0 86 ​ 951 86 ​ 951 Consumer direct ​ 0 ​ 0 17 ​ 14 17 ​ 14 0 ​ 0 23 ​ 85 23 ​ 85 Home equity ​ 10 ​ 252 12 ​ 248 22 ​ 500 11 ​ 285 13 ​ 264 24 ​ 549 Total ​ 74 ​ $ 3,250 154 ​ $ 3,432 228 ​ $ 6,682 73 ​ $ 3,227 174 ​ $ 3,757 247 ​ $ 6,984 ​ The following table presents information related to loans modified in a TDR during the three months and six months ended June 30, 2021 and 2020. Of the loans noted in the table below, all consumer mortgage loans for the three months and six months ended June 30, 2021 and 2020 were modified due to a Chapter 7 bankruptcy as described previously. The financial effects of these restructurings were immaterial. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Three Months Ended ​ ​ June 30, 2021 ​ June 30, 2020 ​ ​ Number of ​ Outstanding ​ Number of ​ Outstanding (000’s omitted) loans modified Balance loans modified Balance Business lending 0 ​ $ 0 0 ​ $ 0 Consumer mortgage 7 ​ 366 3 ​ 174 Consumer indirect 9 ​ 116 3 ​ 47 Consumer direct 0 ​ 0 0 ​ 0 Home equity 0 ​ 0 1 ​ 28 Total 16 ​ $ 482 7 ​ $ 249 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ Six Months Ended ​ ​ June 30, 2021 ​ June 30, 2020 ​ ​ Number of ​ Outstanding ​ Number of ​ Outstanding (000’s omitted) loans modified Balance loans modified Balance Business lending 0 ​ $ 0 0 ​ $ 0 Consumer mortgage 10 ​ 474 9 ​ 738 Consumer indirect 15 ​ 177 14 ​ 151 Consumer direct 1 ​ 6 1 ​ 11 Home equity 0 ​ 0 1 ​ 28 Total 26 ​ $ 657 25 ​ $ 928 ​
Schedule of allowance for loan losses by class	The following presents by segment the activity in the allowance for credit losses during the three months and six months ended June 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, 2021 ​ ​ Beginning ​ Charge- ​ ​ ​ ​ ​ ​ ​ Ending (000’s omitted) balance offs Recoveries Provision balance Business lending ​ $ 27,042 ​ $ (2) ​ $ 255 ​ $ (3,878) ​ $ 23,417 Consumer mortgage ​ 9,686 ​ (142) ​ 9 ​ 448 ​ 10,001 Consumer indirect ​ 11,120 ​ (750) ​ 1,183 ​ (450) ​ 11,103 Consumer direct ​ 2,682 ​ (195) ​ 213 ​ (152) ​ 2,548 Home equity ​ 1,543 ​ (17) ​ 5 ​ 265 ​ 1,796 Unallocated ​ 1,000 ​ 0 ​ 0 ​ 0 ​ 1,000 Purchased credit deteriorated ​ 1,996 ​ 0 ​ 33 ​ (144) ​ 1,885 Allowance for credit losses – loans ​ 55,069 ​ (1,106) ​ 1,698 ​ (3,911) ​ 51,750 Liabilities for off-balance-sheet credit exposures ​ 1,189 ​ 0 ​ 0 ​ (427) ​ 762 Total allowance for credit losses ​ $ 56,258 ​ $ (1,106) ​ $ 1,698 ​ $ (4,338) ​ $ 52,512 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, 2020 ​ Beginning Charge- ​ Steuben ​ Ending (000’s omitted) ​ balance ​ offs ​ Recoveries ​ acquisition ​ Provision ​ balance Business lending ​ $ 19,489 ​ $ (7) ​ $ 84 ​ $ 2,483 ​ $ 2,155 ​ $ 24,204 Consumer mortgage ​ 12,430 ​ (234) ​ 36 ​ 146 ​ 710 ​ 13,088 Consumer indirect ​ 13,694 ​ (1,431) ​ 833 ​ 183 ​ 2,587 ​ 15,866 Consumer direct ​ 3,737 ​ (341) ​ 171 ​ 87 ​ 374 ​ 4,028 Home equity ​ 2,484 ​ (81) ​ 12 ​ 235 ​ 40 ​ 2,690 Unallocated ​ 772 ​ 0 ​ 0 ​ 0 ​ 228 ​ 1,000 Purchased credit deteriorated ​ 3,046 ​ 0 ​ 48 ​ 528 ​ (61) ​ 3,561 Allowance for credit losses – loans ​ 55,652 ​ (2,094) ​ 1,184 ​ 3,662 ​ 6,033 ​ 64,437 Liabilities for off-balance-sheet credit exposures ​ 845 ​ 0 ​ 0 ​ 67 ​ 540 ​ 1,452 Total allowance for credit losses ​ $ 56,497 ​ $ (2,094) ​ $ 1,184 ​ $ 3,729 ​ $ 6,573 ​ $ 65,889 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended June 30, 2021 ​ Beginning Charge- ​ Ending (000’s omitted) ​ balance ​ offs ​ Recoveries ​ Provision ​ balance Business lending ​ $ 28,190 ​ $ (53) ​ $ 322 ​ $ (5,042) ​ $ 23,417 Consumer mortgage ​ 10,672 ​ (242) ​ 19 ​ (448) ​ 10,001 Consumer indirect ​ 13,696 ​ (2,149) ​ 2,429 ​ (2,873) ​ 11,103 Consumer direct ​ 3,207 ​ (513) ​ 444 ​ (590) ​ 2,548 Home equity ​ 2,222 ​ (115) ​ 9 ​ (320) ​ 1,796 Unallocated ​ 1,000 ​ 0 ​ 0 ​ 0 ​ 1,000 Purchased credit deteriorated ​ 1,882 ​ 0 ​ 60 ​ (57) ​ 1,885 Allowance for credit losses – loans ​ 60,869 ​ (3,072) ​ 3,283 ​ (9,330) ​ 51,750 Liabilities for off-balance-sheet credit exposures ​ 1,489 ​ 0 ​ 0 ​ (727) ​ 762 Total allowance for credit losses ​ $ 62,358 ​ $ (3,072) ​ $ 3,283 ​ $ (10,057) ​ $ 52,512 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended June 30, 2020 ​ ​ Beginning ​ ​ ​ ​ Beginning ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ balance, ​ ​ ​ ​ balance, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ prior to the ​ ​ ​ ​ after ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ adoption of ​ Impact of ​ adoption of ​ ​ ​ ​ ​ ​ ​ Steuben ​ ​ ​ ​ Ending (000’s omitted) ASC 326 ASC 326 ASC 326 Charge-offs Recoveries acquisition Provision balance Business lending ​ $ 19,426 ​ $ 288 ​ $ 19,714 ​ $ (183) ​ $ 222 ​ $ 2,483 ​ $ 1,968 ​ $ 24,204 Consumer mortgage ​ 10,269 ​ (1,051) ​ 9,218 ​ (420) ​ 44 ​ 146 ​ 4,100 ​ 13,088 Consumer indirect ​ 13,712 ​ (997) ​ 12,715 ​ (3,510) ​ 1,996 ​ 183 ​ 4,482 ​ 15,866 Consumer direct ​ 3,255 ​ (643) ​ 2,612 ​ (874) ​ 353 ​ 87 ​ 1,850 ​ 4,028 Home equity ​ 2,129 ​ 808 ​ 2,937 ​ (154) ​ 18 ​ 235 ​ (346) ​ 2,690 Unallocated ​ 957 ​ 43 ​ 1,000 ​ 0 ​ 0 ​ 0 ​ 0 ​ 1,000 Purchased credit deteriorated ​ 0 ​ 3,072 ​ 3,072 ​ 0 ​ 48 ​ 528 ​ (87) ​ 3,561 Purchased credit impaired ​ 163 ​ (163) ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 Allowance for credit losses – loans ​ 49,911 ​ 1,357 ​ 51,268 ​ (5,141) ​ 2,681 ​ 3,662 ​ 11,967 ​ 64,437 Liabilities for off-balance-sheet credit exposures ​ 0 ​ 1,185 ​ 1,185 ​ 0 ​ 0 ​ 67 ​ 200 ​ 1,452 Total allowance for credit losses ​ $ 49,911 ​ $ 2,542 ​ $ 52,453 ​ $ (5,141) ​ $ 2,681 ​ $ 3,729 ​ $ 12,167 ​ $ 65,889 ​
Schedule of financing receivables purchased and Sold	The following table presents the carrying amounts of loans purchased and sold during the six months ended June 30, 2021 by portfolio segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Business ​ Consumer ​ Consumer ​ Consumer ​ Home ​ ​ ​ (000’s omitted) lending mortgage indirect direct equity Total Purchases ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 Sales ​ ​ 848 ​ ​ 10,860 ​ ​ 0 ​ ​ 0 ​ ​ 0 ​ ​ 11,708
Business Lending [Member]
Loans and Leases Receivable Disclosure [Line Items]
Schedule of loans by credit quality indicator	The following tables show the amount of business lending loans by credit quality category at June 30, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ June 30, 2021 2021 2020 2019 2018 2017 Prior Cost Basis Total Business lending: ​ ​ ​ ​ ​ ​ ​ ​ Risk rating ​ ​ ​ ​ ​ ​ ​ ​ Pass ​ $ 343,472 ​ $ 439,365 ​ $ 338,583 ​ $ 284,580 ​ $ 189,477 ​ $ 661,491 ​ $ 507,921 ​ $ 2,764,889 Special mention ​ 2,001 ​ 12,961 ​ 12,084 ​ 36,635 ​ 21,586 ​ 72,145 ​ 34,484 ​ 191,896 Classified ​ 360 ​ 2,163 ​ 21,063 ​ 49,150 ​ 27,397 ​ 84,543 ​ 42,178 ​ 226,854 Doubtful ​ 0 ​ 0 ​ 16 ​ 1,931 ​ 0 ​ 35 ​ 866 ​ 2,848 Total business lending ​ $ 345,833 ​ $ 454,489 ​ $ 371,746 ​ $ 372,296 ​ $ 238,460 ​ $ 818,214 ​ $ 585,449 ​ $ 3,186,487 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ December 31, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Business lending: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Risk rating ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pass ​ $ 860,178 ​ $ 351,350 ​ $ 312,087 ​ $ 217,138 ​ $ 231,453 ​ $ 543,999 ​ $ 483,018 ​ $ 2,999,223 Special mention ​ 14,687 ​ 36,041 ​ 28,410 ​ 21,875 ​ 29,386 ​ 51,657 ​ 52,732 ​ 234,788 Classified ​ 6,336 ​ 4,560 ​ 30,422 ​ 24,807 ​ 14,891 ​ 65,157 ​ 56,000 ​ 202,173 Doubtful ​ 0 ​ 18 ​ 2,888 ​ 0 ​ 0 ​ 108 ​ 879 ​ 3,893 Total business lending ​ $ 881,201 ​ $ 391,969 ​ $ 373,807 ​ $ 263,820 ​ $ 275,730 ​ $ 660,921 ​ $ 592,629 ​ $ 3,440,077
All Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Schedule of loans by credit quality indicator	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ June 30, 2021 2021 2020 2019 2018 2017 Prior Cost Basis Total Consumer mortgage: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ FICO AB ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 217,537 ​ $ 245,277 ​ $ 204,560 ​ $ 139,256 ​ $ 135,992 ​ $ 660,613 ​ $ 0 ​ $ 1,603,235 Nonperforming ​ 0 ​ 171 ​ 0 ​ 261 ​ 516 ​ 2,765 ​ 0 ​ 3,713 Total FICO AB ​ 217,537 ​ 245,448 ​ 204,560 ​ 139,517 ​ 136,508 ​ 663,378 ​ 0 ​ 1,606,948 FICO CDE ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ 58,224 ​ 128,942 ​ 94,750 ​ 73,362 ​ 64,401 ​ 346,907 ​ 21,394 ​ 787,980 Nonperforming ​ 0 ​ 234 ​ 901 ​ 744 ​ 702 ​ 10,990 ​ 0 ​ 13,571 Total FICO CDE ​ 58,224 ​ 129,176 ​ 95,651 ​ 74,106 ​ 65,103 ​ 357,897 ​ 21,394 ​ 801,551 Total consumer mortgage ​ $ 275,761 ​ $ 374,624 ​ $ 300,211 ​ $ 213,623 ​ $ 201,611 ​ $ 1,021,275 ​ $ 21,394 ​ $ 2,408,499 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer indirect: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 317,236 ​ $ 255,939 ​ $ 240,528 ​ $ 148,990 ​ $ 59,328 ​ $ 87,410 ​ $ 0 ​ $ 1,109,431 Nonperforming ​ 0 ​ 10 ​ 38 ​ 13 ​ 0 ​ 12 ​ 0 ​ 73 Total consumer indirect ​ $ 317,236 ​ $ 255,949 ​ $ 240,566 ​ $ 149,003 ​ $ 59,328 ​ $ 87,422 ​ $ 0 ​ $ 1,109,504 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer direct: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 37,644 ​ $ 37,762 ​ $ 34,503 ​ $ 18,947 ​ $ 7,557 ​ $ 6,100 ​ $ 6,010 ​ $ 148,523 Nonperforming ​ 0 ​ 0 ​ 0 ​ 2 ​ 0 ​ 15 ​ 0 ​ 17 Total consumer direct ​ $ 37,644 ​ $ 37,762 ​ $ 34,503 ​ $ 18,949 ​ $ 7,557 ​ $ 6,115 ​ $ 6,010 ​ $ 148,540 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Home equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 33,503 ​ $ 47,348 ​ $ 42,432 ​ $ 23,450 ​ $ 19,224 ​ $ 43,050 ​ $ 179,391 ​ $ 388,398 Nonperforming ​ 0 ​ 56 ​ 22 ​ 107 ​ 79 ​ 722 ​ 1,733 ​ 2,719 Total home equity ​ $ 33,503 ​ $ 47,404 ​ $ 42,454 ​ $ 23,557 ​ $ 19,303 ​ $ 43,772 ​ $ 181,124 ​ $ 391,117 ​ The following table details the balances in all other loan categories at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ December 31, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Consumer mortgage: ​ ​ ​ ​ ​ ​ ​ ​ FICO AB ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 260,588 ​ $ 227,027 ​ $ 166,638 ​ $ 163,653 ​ $ 160,911 ​ $ 614,976 ​ $ 321 ​ $ 1,594,114 Nonperforming ​ 0 ​ 0 ​ 275 ​ 398 ​ 345 ​ 2,709 ​ 0 ​ 3,727 Total FICO AB ​ 260,588 ​ 227,027 ​ 166,913 ​ 164,051 ​ 161,256 ​ 617,685 ​ 321 ​ 1,597,841 FICO CDE ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ 115,049 ​ 102,788 ​ 80,973 ​ 75,289 ​ 83,214 ​ 314,668 ​ 17,382 ​ 789,363 Nonperforming ​ 0 ​ 1,010 ​ 582 ​ 877 ​ 1,786 ​ 10,040 ​ 0 ​ 14,295 Total FICO CDE ​ 115,049 ​ 103,798 ​ 81,555 ​ 76,166 ​ 85,000 ​ 324,708 ​ 17,382 ​ 803,658 Total consumer mortgage ​ $ 375,637 ​ $ 330,825 ​ $ 248,468 ​ $ 240,217 ​ $ 246,256 ​ $ 942,393 ​ $ 17,703 ​ $ 2,401,499 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer indirect: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 303,471 ​ $ 305,901 ​ $ 202,373 ​ $ 86,497 ​ $ 61,449 ​ $ 61,975 ​ $ 0 ​ $ 1,021,666 Nonperforming ​ 51 ​ 52 ​ 82 ​ 17 ​ 16 ​ 1 ​ 0 ​ 219 Total consumer indirect ​ $ 303,522 ​ $ 305,953 ​ $ 202,455 ​ $ 86,514 ​ $ 61,465 ​ $ 61,976 ​ $ 0 ​ $ 1,021,885 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer direct: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 49,181 ​ $ 46,992 ​ $ 27,872 ​ $ 12,326 ​ $ 5,232 ​ $ 4,146 ​ $ 6,878 ​ $ 152,627 Nonperforming ​ 1 ​ 19 ​ 2 ​ 5 ​ 0 ​ 3 ​ 0 ​ 30 Total consumer direct ​ $ 49,182 ​ $ 47,011 ​ $ 27,874 ​ $ 12,331 ​ $ 5,232 ​ $ 4,149 ​ $ 6,878 ​ $ 152,657 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Home equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 48,145 ​ $ 48,780 ​ $ 28,074 ​ $ 23,524 ​ $ 17,828 ​ $ 35,900 ​ $ 194,773 ​ $ 397,024 Nonperforming ​ 0 ​ 24 ​ 73 ​ 104 ​ 183 ​ 490 ​ 1,936 ​ 2,810 Total home equity ​ $ 48,145 ​ $ 48,804 ​ $ 28,147 ​ $ 23,628 ​ $ 18,011 ​ $ 36,390 ​ $ 196,709 ​ $ 399,834 ​

GOODWILL AND IDENTIFIABLE INT_2

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Tables)	6 Months Ended
	Jun. 30, 2021
GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS
Schedule of gross carrying amount and accumulated amortization for each type of identifiable intangible asset	The gross carrying amount and accumulated amortization for each type of identifiable intangible asset are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 December 31, 2020 ​ ​ Gross ​ ​ ​ ​ Net ​ Gross ​ ​ ​ ​ Net ​ ​ Carrying Accumulated Carrying Carrying Accumulated Carrying (000’s omitted) ​ Amount Amortization Amount Amount Amortization Amount Amortizing intangible assets: ​ ​ ​ ​ ​ ​ ​ Core deposit intangibles ​ $ 69,403 ​ $ (58,136) ​ $ 11,267 ​ $ 69,403 ​ $ (55,572) ​ $ 13,831 Other intangibles ​ 91,899 ​ (55,386) ​ 36,513 ​ 90,462 ​ (51,353) ​ 39,109 Total amortizing intangibles ​ $ 161,302 ​ $ (113,522) ​ $ 47,780 ​ $ 159,865 ​ $ (106,925) ​ $ 52,940
Schedule of estimated aggregate amortization expense for each of five succeeding fiscal years	The estimated aggregate amortization expense for each of the five succeeding fiscal years ended December 31 is as follows: ​ ​ ​ ​ ​ ​ (000's omitted) Jul - Dec 2021 $ 6,229 2022 ​ 11,141 2023 ​ 9,338 2024 ​ 7,768 2025 ​ 6,550 Thereafter ​ 6,754 Total ​ $ 47,780
Schedule of components of goodwill	Shown below are the components of the Company’s goodwill at December 31, 2020 and June 30, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) December 31, 2020 Activity June 30, 2021 Goodwill, net ​ $ 793,708 ​ $ 1,184 ​ $ 794,892 ​

BENEFIT PLANS (Tables)

BENEFIT PLANS (Tables)	6 Months Ended
	Jun. 30, 2021
BENEFIT PLANS
Schedule of net periodic benefit cost	The net periodic benefit cost for the three and six months ended June 30, 2021 and 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension Benefits ​ Post-retirement Benefits ​ ​ ​ Three Months Ended ​ Six Months Ended ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ June 30, ​ June 30, ​ (000’s omitted) ​ 2021 2020 2021 ​ 2020 2021 ​ 2020 ​ 2021 2020 Service cost ​ $ 1,480 ​ $ 1,438 ​ $ 2,960 ​ $ 2,875 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 ​ Interest cost ​ 1,259 1,356 ​ 2,518 ​ 2,712 11 ​ 14 ​ 22 ​ 28 ​ Expected return on plan assets ​ (4,695) ​ (3,932) ​ ​ (9,391) ​ ​ (7,864) ​ 0 ​ 0 ​ ​ 0 ​ 0 ​ Amortization of unrecognized net loss ​ 900 ​ 810 ​ ​ 1,800 ​ ​ 1,620 ​ 11 ​ 10 ​ ​ 22 ​ 20 ​ Amortization of prior service cost ​ 94 ​ 60 ​ ​ 189 ​ ​ 120 ​ (44) ​ (44) ​ ​ (89) ​ (89) ​ Net periodic benefit ​ $ (962) ​ $ (268) ​ $ (1,924) ​ $ (537) ​ $ (22) ​ $ (20) ​ $ (45) ​ $ (41) ​

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2021
EARNINGS PER SHARE
Schedule of reconciliation of basic to diluted earnings per share	The following is a reconciliation of basic to diluted earnings per share for the three and six months ended June 30, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ ​ June 30, ​ June 30, ​ (000’s omitted, except per share data) ​ 2021 2020 2021 2020 Net income ​ $ 47,944 ​ $ 35,248 ​ $ 100,794 ​ $ 75,382 ​ Income attributable to unvested stock-based compensation awards ​ (127) ​ (127) ​ (263) ​ (264) ​ Income available to common shareholders ​ $ 47,817 ​ $ 35,121 ​ $ 100,531 ​ $ 75,118 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 54,007 ​ 52,487 ​ 53,927 ​ 52,262 ​ Basic earnings per share ​ $ 0.89 ​ $ 0.67 ​ $ 1.86 ​ $ 1.44 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income ​ $ 47,944 ​ $ 35,248 ​ $ 100,794 ​ $ 75,382 ​ Income attributable to unvested stock-based compensation awards ​ (127) ​ (127) ​ (263) ​ (264) ​ Income available to common shareholders ​ $ 47,817 ​ $ 35,121 ​ $ 100,531 ​ $ 75,118 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 54,007 ​ 52,487 ​ 53,927 ​ 52,262 ​ Assumed exercise of stock options ​ 462 ​ 339 ​ 455 ​ 372 ​ Weighted-average common shares outstanding – diluted ​ 54,469 ​ 52,826 ​ 54,382 ​ 52,634 ​ Diluted earnings per share ​ $ 0.88 ​ $ 0.66 ​ $ 1.85 ​ $ 1.43 ​

COMMITMENTS, CONTINGENT LIABI_2

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS (Tables)	6 Months Ended
	Jun. 30, 2021
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS
Schedule of The contract amounts of commitments and contingencies	The contract amounts of commitments and contingencies are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, December 31, (000’s omitted) ​ 2021 ​ 2020 Commitments to extend credit ​ $ 1,199,804 ​ $ 1,313,568 ​ Standby letters of credit ​ 35,382 ​ 39,213 ​ Total ​ $ 1,235,186 ​ $ 1,352,781 ​

FAIR VALUE (Tables)

FAIR VALUE (Tables)	6 Months Ended
	Jun. 30, 2021
FAIR VALUE
Fair Value Measured on a Recurring Basis	A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The following tables set forth the Company’s financial assets and liabilities that were accounted for at fair value on a recurring basis. There were no transfers between any of the levels for the periods presented. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair (000's omitted) Level 1 Level 2 Level 3 Value Available-for-sale investment securities: ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 2,909,475 ​ $ 115,597 ​ $ 0 ​ $ 3,025,072 Obligations of state and political subdivisions ​ 0 ​ 426,152 ​ 0 ​ 426,152 Government agency mortgage-backed securities ​ 0 ​ 529,139 ​ 0 ​ 529,139 Corporate debt securities ​ 0 ​ 3,094 ​ 0 ​ 3,094 Government agency collateralized mortgage obligations ​ 0 ​ 29,282 ​ 0 ​ 29,282 Total available-for-sale investment securities ​ 2,909,475 ​ 1,103,264 ​ 0 ​ 4,012,739 Equity securities ​ 469 ​ 0 ​ 0 ​ 469 Mortgage loans held for sale ​ ​ 0 ​ ​ 1,340 ​ ​ 0 ​ ​ 1,340 Commitments to originate real estate loans for sale ​ ​ 0 ​ ​ 0 ​ ​ 130 ​ ​ 130 Forward sales commitments ​ ​ 0 ​ ​ 31 ​ ​ 0 ​ ​ 31 Interest rate swap agreements asset ​ 0 ​ 372 ​ 0 ​ 372 Interest rate swap agreements liability ​ 0 ​ (7) ​ 0 ​ (7) Total ​ $ 2,909,944 ​ $ 1,105,000 ​ $ 130 ​ $ 4,015,074 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair (000's omitted) Level 1 Level 2 Level 3 Value Available-for-sale investment securities: ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 2,359,912 ​ $ 141,470 ​ $ 0 ​ $ 2,501,382 Obligations of state and political subdivisions ​ 0 ​ 475,660 ​ 0 ​ 475,660 Government agency mortgage-backed securities ​ 0 ​ 522,638 ​ 0 ​ 522,638 Corporate debt securities ​ 0 ​ 4,635 ​ 0 ​ 4,635 Government agency collateralized mortgage obligations ​ 0 ​ 43,577 ​ 0 ​ 43,577 Total available-for-sale investment securities ​ 2,359,912 ​ 1,187,980 ​ 0 ​ 3,547,892 Equity securities ​ 445 ​ 0 ​ 0 ​ 445 Mortgage loans held for sale ​ 0 ​ 1,622 ​ 0 ​ 1,622 Commitments to originate real estate loans for sale ​ ​ 0 ​ ​ 0 ​ ​ 14 ​ ​ 14 Forward sales commitments ​ ​ 0 ​ ​ 2 ​ ​ 0 ​ ​ 2 Interest rate swap agreements asset ​ 0 ​ 1,572 ​ 0 ​ 1,572 Interest rate swap agreements liability ​ 0 ​ (1,074) ​ ​ 0 ​ (1,074) Total ​ $ 2,360,357 ​ $ 1,190,102 ​ $ 14 ​ $ 3,550,473
Assets and Liabilities Measured on a Non-Recurring Basis	The fair value information of assets and liabilities measured on a non-recurring basis presented below is not as of the period-end, but rather as of the date the fair value adjustment was recorded closest to the date presented. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ Total Fair ​ ​ ​ ​ ​ ​ Total Fair (000's omitted) ​ Level 1 ​ Level 2 ​ Level 3 ​ Value ​ Level 1 ​ Level 2 ​ Level 3 ​ Value Impaired loans ​ $ 0 ​ $ 0 ​ $ 21,330 $ 21,330 ​ $ 0 ​ $ 0 ​ $ 25,063 $ 25,063 Other real estate owned ​ 0 ​ 0 ​ 879 879 ​ 0 ​ 0 ​ 883 883 Mortgage servicing rights ​ 0 ​ 0 ​ 697 697 ​ 0 ​ 0 ​ 682 682 Total ​ $ 0 ​ $ 0 ​ $ 22,906 $ 22,906 ​ $ 0 ​ $ 0 ​ $ 26,628 $ 26,628
Significant Unobservable Inputs, Fair Value Valuation Techniques	The Company determines fair values based on quoted market values, where available, estimates of present values, or other valuation techniques. Those techniques are significantly affected by the assumptions used, including, but not limited to, the discount rate and estimates of future cash flows. In that regard, the derived fair value estimates cannot be substantiated by comparison to independent markets and, in many cases, may not be realized in immediate settlement of the instrument. The significant unobservable inputs used in the determination of fair value of assets classified as Level 3 on a recurring or non-recurring basis are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ ​ ​ ​ Unobservable Input ​ ​ Fair Value at ​ ​ ​ ​ ​ Range ​ (000's omitted, except per loan data) ​ June 30, 2021 ​ Valuation Technique ​ Significant Unobservable Inputs (Weighted Average) ​ Impaired loans ​ $ 21,330 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 78.7% (53.8%) ​ Other real estate owned ​ 879 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 51.1% (34.5%) ​ Commitments to originate real estate loans for sale ​ 130 Discounted cash flow Embedded servicing value ​ 1.0 % Mortgage servicing rights ​ 697 Discounted cash flow Weighted average constant prepayment rate ​ 16.9% - 49.1% (21.8%) ​ ​ ​ ​ ​ ​ ​ ​ Weighted average discount rate ​ ​ 2.2% - 2.8% (2.7%) ​ ​ ​ ​ ​ ​ ​ ​ Adequate compensation ​ $ 7/loan ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ ​ Unobservable Input ​ ​ ​ Fair Value at ​ ​ ​ ​ ​ Range ​ (000's omitted, except per loan data) ​ December 31, 2020 ​ Valuation Technique ​ Significant Unobservable Inputs ​ (Weighted Average) Impaired loans ​ $ 25,063 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 78.4% (52.7%) ​ Other real estate owned ​ 883 Fair value of collateral Estimated cost of disposal/market adjustment ​ 11.3% - 52.9% (34.0%) ​ Commitments to originate real estate loans for sale ​ ​ 14 ​ Discounted cash flow ​ Embedded servicing value ​ ​ 1.0 % Mortgage servicing rights ​ 682 Discounted cash flow Weighted average constant prepayment rate ​ 9.8% - 18.8% (17.6%) ​ ​ ​ Weighted average discount rate ​ 1.7% - 2.2% (2.1%) ​ ​ ​ ​ ​ ​ ​ Adequate compensation ​ $ 7/loan ​
Carrying Amounts and Estimated Fair Values of Other Financial Instruments	Certain financial instruments and all nonfinancial instruments are excluded from fair value disclosure requirements. Accordingly, the aggregate fair value amounts presented do not represent the underlying value of the Company. The carrying amounts and estimated fair values of the Company’s other financial instruments that are not accounted for at fair value at June 30, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2021 ​ December 31, 2020 ​ Carrying Fair Carrying Fair (000's omitted) ​ Value ​ Value ​ Value ​ Value Financial assets: ​ ​ ​ ​ Net loans ​ $ 7,192,397 ​ $ 7,563,546 ​ $ 7,355,083 ​ $ 7,655,044 Financial liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Deposits ​ 12,339,025 ​ 12,349,413 ​ 11,224,974 ​ 11,239,628 Securities sold under agreement to repurchase, short-term ​ 194,887 ​ 194,887 ​ 284,008 ​ 284,008 Other Federal Home Loan Bank borrowings ​ 2,936 ​ 2,993 ​ 6,658 ​ 6,758 Subordinated notes payable ​ 3,290 ​ 3,290 ​ 3,303 ​ 3,303 Subordinated debt held by unconsolidated subsidiary trusts ​ 0 ​ 0 ​ 77,320 ​ 77,320 ​

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2021
DERIVATIVE INSTRUMENTS
Amounts Related to Cumulative Basis Adjustments for Fair Value Hedges	As of June 30, 2021 and December 31, 2020, the following amounts were recorded in the consolidated statement of condition related to cumulative basis adjustments for fair value hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ ​ ​ ​ ​ ​ ​ Cumulative Amount of Fair Value ​ ​ Carrying Amount of the Hedged ​ Hedging Adjustment Included in the Line Item in the Consolidated ​ Assets ​ Carrying Amount of the Hedged Assets Statement of Condition in Which ​ June 30, ​ December 31, ​ June 30, ​ December 31, the Hedged Item Is Included 2021 2020 2021 2020 Loans $ 5,809 $ 5,675 $ (365) $ (498)
Fair Value of Derivative Instruments	Fair values of derivative instruments as of June 30, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ June 30, 2021 ​ ​ Derivative Assets ​ Derivative Liabilities ​ ​ Consolidated Statement ​ Fair ​ Consolidated Statement of ​ Fair ​ of Condition Location Value Condition Location Value Derivatives designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ $ 365 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ ​ Interest rate swaps Other assets ​ 7 Accrued interest and other liabilities ​ $ 7 Commitments to originate real estate loans for sale Other assets ​ 130 ​ ​ Forward sales commitments Other assets ​ 31 ​ ​ Total derivatives ​ $ 533 ​ $ 7 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ December 31, 2020 ​ ​ Derivative Assets ​ Derivative Liabilities ​ ​ Consolidated Statement ​ Fair ​ Consolidated Statement of ​ Fair ​ of Condition Location Value Condition Location Value Derivatives designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ $ 498 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ ​ ​ Interest rate swaps Other assets ​ 1,074 Accrued interest and other liabilities ​ $ 1,074 Commitments to originate real estate loans for sale ​ Other assets ​ ​ 14 ​ ​ ​ ​ ​ Forward sales commitments ​ Other assets ​ ​ 2 ​ ​ ​ ​ ​ Total derivatives ​ ​ $ 1,588 ​ $ 1,074 ​

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2021
SEGMENT INFORMATION
Schedule of Segment Reporting Information by Segment	Information about reportable segments and reconciliation of the information to the consolidated financial statements follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee ​ ​ ​ ​ ​ ​ ​ Consolidated (000's omitted) Banking Benefit Services All Other Eliminations Total Three Months Ended June 30, 2021 ​ ​ ​ ​ ​ Net interest income ​ $ 92,033 ​ $ 65 ​ $ 7 ​ $ 0 ​ $ 92,105 Provision for credit losses ​ (4,338) ​ 0 ​ 0 ​ 0 ​ (4,338) Noninterest revenues ​ 16,357 ​ 27,994 ​ 16,816 ​ (1,707) ​ 59,460 Amortization of intangible assets ​ 1,240 ​ 1,327 ​ 679 ​ 0 ​ 3,246 Acquisition expenses ​ 4 ​ 0 ​ 0 ​ 0 ​ 4 Other operating expenses ​ 65,158 ​ 14,846 ​ 11,996 ​ (1,707) ​ 90,293 Income before income taxes ​ $ 46,326 ​ $ 11,886 ​ $ 4,148 ​ $ 0 ​ $ 62,360 Assets ​ $ 14,588,075 ​ $ 235,141 ​ $ 78,770 ​ $ (100,699) ​ $ 14,801,287 Goodwill ​ $ 689,867 ​ $ 83,275 ​ $ 21,750 ​ $ 0 ​ $ 794,892 Core deposit intangibles & Other intangibles ​ $ 11,267 ​ $ 29,370 ​ $ 7,143 ​ $ 0 ​ $ 47,780 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended June 30, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net interest income ​ $ 91,645 ​ $ 246 ​ $ 60 ​ $ 0 ​ $ 91,951 Provision for credit losses ​ 9,774 ​ 0 ​ 0 ​ 0 ​ 9,774 Noninterest revenues ​ 14,991 ​ 24,504 ​ 14,817 ​ (1,374) ​ 52,938 Amortization of intangible assets ​ 1,364 ​ 1,411 ​ 749 ​ 0 ​ 3,524 Acquisition expenses ​ 3,372 ​ 0 ​ 0 ​ 0 ​ 3,372 Other operating expenses ​ 59,130 ​ 14,948 ​ 11,303 ​ (1,374) ​ 84,007 Income before income taxes ​ $ 32,996 ​ $ 8,391 ​ $ 2,825 ​ $ 0 ​ $ 44,212 Assets ​ $ 13,272,929 ​ $ 216,122 ​ $ 78,022 ​ $ (122,856) ​ $ 13,444,217 Goodwill ​ $ 689,128 ​ $ 83,275 ​ $ 20,312 ​ $ 0 ​ $ 792,715 Core deposit intangibles & Other intangibles ​ $ 16,565 ​ $ 34,870 ​ $ 8,611 ​ $ 0 ​ $ 60,046

ACQUISITIONS (Details)

ACQUISITIONS (Details) shares in Thousands, $ in Thousands	Aug. 02, 2021USD ($)	Jul. 01, 2021USD ($)	Jun. 03, 2021USD ($)	Jun. 12, 2020USD ($)Officecountryshares	Jun. 30, 2021USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Acquisitions [Abstract]
Cash						$ 2,900	$ (34,360)
Goodwill					$ 794,892	794,892	$ 792,715	$ 793,708
NuVantage Insurance, Inc. [Member]
Acquisitions [Abstract]
Purchase price in cash			$ 2,900
Customer List Intangibles			1,400
Goodwill			$ 1,500
Steuben Trust Corporation [Member]
Acquisitions [Abstract]
Cash				$ 21,600				21,613
Issuance of common shares (in shares) | shares				1,360
Purchase price of acquisition				$ 98,600				98,555
Deposits				516,300				516,274
Goodwill				20,000				19,981
Assets acquired				607,800
Loans				339,700				339,017
Investment securities				$ 180,500				$ 180,497
Revenue earned					3,300	6,500
Direct expenses					1,200	2,500
Increase (decrease) in other liabilities as a result of reclassification and adjustment					$ 300
Increase (decrease) in goodwill as a result of fair value adjustment						$ 300
Steuben Trust Corporation [Member] | Western New York State [Member]
Acquisitions [Abstract]
Number of counties where the bank has facilities | country				4
Number of new counties where the bank has extended footprints | country				2
Number of branch locations | Office				11
Subsequent event | Fringe Benefits Design of Minnesota, Inc ("FBD") [Member]
Acquisitions [Abstract]
Purchase price of acquisition		$ 15,300
Contingent consideration		$ 2,700
Subsequent event | Thomas Gregory Associates [Member]
Acquisitions [Abstract]
Purchase price of acquisition	$ 11,600
Contingent consideration	$ 3,400

ACQUISITIONS - Estimated Fair V

ACQUISITIONS - Estimated Fair Value of Assets Acquired and Liabilities assumed (Details) - USD ($) $ in Thousands	Jun. 12, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Consideration paid :
Cash		$ 2,900	$ (34,360)
Recognized amounts of identifiable assets acquired and liabilities assumed:
Goodwill		794,892	$ 792,715	$ 793,708
Steuben Trust Corporation [Member]
Consideration paid :
Cash	$ 21,600			21,613
Community Bank System, Inc. common stock				76,942
Total net consideration paid	98,600			98,555
Recognized amounts of identifiable assets acquired and liabilities assumed:
Cash and cash equivalents				55,973
Investment securities	180,500			180,497
Loans, net of allowance for credit losses on PCD loans	339,700			339,017
Premises and equipment, net				7,764
Accrued interest and fees receivable				2,701
Other assets				17,675
Deposits	(516,300)			(516,274)
Other liabilities				(4,841)
Other Federal Home Loan Bank borrowings				(6,000)
Subordinated debt held by unconsolidated subsidiary trusts				2,062
Total identifiable assets, net				78,574
Goodwill	$ 20,000			19,981
Steuben Trust Corporation [Member] | Core deposit intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed:
Intangibles				2,928
Steuben Trust Corporation [Member] | Other intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed:
Intangibles				$ 1,196
NuVantage Insurance Corporation [Member]
Consideration paid :
Cash		2,900
Community Bank System, Inc. common stock		0
Total net consideration paid		2,900
Recognized amounts of identifiable assets acquired and liabilities assumed:
Cash and cash equivalents		0
Investment securities		0
Loans, net of allowance for credit losses on PCD loans		0
Premises and equipment, net		199
Accrued interest and fees receivable		0
Other assets		0
Deposits		0
Other liabilities		(174)
Other Federal Home Loan Bank borrowings		0
Subordinated debt held by unconsolidated subsidiary trusts		0
Total identifiable assets, net		1,462
Goodwill		1,438
NuVantage Insurance Corporation [Member] | Core deposit intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed:
Intangibles		0
NuVantage Insurance Corporation [Member] | Other intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed:
Intangibles		$ 1,437

ACQUISITIONS - Summary of Loans

ACQUISITIONS - Summary of Loans Acquired (Details) - Steuben Trust Corporation [Member] $ in Thousands	Jun. 12, 2020USD ($)
Acquired Deteriorated
Summary of loans acquired [Abstract]
Par value of loans at acquisition	$ 35,906
Allowance for credit losses at acquisition	(668)
Non-credit premium at acquisition	103
Fair value of acquired loans	35,341
Non-PCD Loans
Summary of loans acquired [Abstract]
Contractually required principal and interest at acquisition	400,738
Contractual cash flows not expected to be collected	(2,994)
Expected cash flows at acquisition	397,744
Interest component of expected cash flows	(94,068)
Fair value of acquired loans	$ 303,676

ACQUISITIONS - Intangible Asset

ACQUISITIONS - Intangible Asset, Goodwill and Acquisition-related Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Summary of loans acquired [Abstract]
Merger and acquisition integration related (recoveries) expenses	$ 4	$ 3,372	$ 31	$ 3,741
Steuben Trust Corporation [Member] | Other intangibles [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Intangible asset useful life (amortization period)			8 years
NuVantage Insurance Corporation [Member] | Core deposit intangibles [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Intangible asset useful life (amortization period)			8 years

ACQUISITIONS - Supplemental Pro

ACQUISITIONS - Supplemental Pro Forma Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Supplemental Pro Forma Financial Information [Abstract]
Acquisitions-related expenses	$ 3,300		$ 3,600
Total revenue, net of interest expense, pro forma	149,576	$ 154,878	304,088	$ 303,152
Net income, pro forma	$ 39,072	$ 46,447	$ 80,848	$ 86,774

ACCOUNTING POLICIES (Details)

ACCOUNTING POLICIES (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Contract Balances
Accounts receivable	$ 27.4	$ 30.3
Unbilled fee revenue	8.3	7.7
Unearned revenue	$ 2.7	$ 1.4

INVESTMENT SECURITIES - Availab

INVESTMENT SECURITIES - Available-for-Sale Portfolio (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Available-for-Sale Portfolio [Abstract]
Amortized cost	$ 4,039,978	$ 3,427,779
Gross unrealized gains	85,757	136,901
Gross unrealized losses	112,996	16,788
Fair value	4,012,739	3,547,892
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	4,039,978
Fair value	4,012,739
U.S. Treasury and agency securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	3,082,187	2,423,236
Gross unrealized gains	52,960	94,741
Gross unrealized losses	110,075	16,595
Fair value	3,025,072	2,501,382
Obligations of state and political subdivisions
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	405,245	451,028
Gross unrealized gains	20,908	24,632
Gross unrealized losses	1	0
Fair value	426,152	475,660
Government agency mortgage-backed securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	521,056	506,540
Gross unrealized gains	10,999	16,280
Gross unrealized losses	2,916	182
Fair value	529,139	522,638
Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	3,000	4,499
Gross unrealized gains	94	137
Gross unrealized losses	0	1
Fair value	3,094	4,635
Government agency collateralized mortgage obligations
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	28,490	42,476
Gross unrealized gains	796	1,111
Gross unrealized losses	4	10
Fair value	$ 29,282	$ 43,577

INVESTMENT SECURITIES - Equity

INVESTMENT SECURITIES - Equity and Other Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Equity and Other Securities [Abstract]
Amortized cost	$ 43,955	$ 46,511
Gross unrealized gains	968	944
Gross unrealized losses	0	0
Equity and other securities (cost of $43,955 and $46,511, respectively)	44,923	47,455
Equity Securities, at Fair Value [Abstract]
Amortized cost	251	251
Gross unrealized gains	218	194
Gross unrealized losses	0	0
Fair value	469	445
Federal Home Loan Bank Common Stock [Member]
Other Equity Securities, at Adjusted Cost [Abstract]
Amortized cost	7,262	7,468
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	7,262	7,468
Federal Reserve Bank Stock [Member]
Other Equity Securities, at Adjusted Cost [Abstract]
Amortized cost	33,916	33,916
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	33,916	33,916
Other Equity Securities [Member]
Other Equity Securities, at Adjusted Cost [Abstract]
Amortized cost	2,526	4,876
Gross unrealized gains	750	750
Gross unrealized losses	0	0
Fair value	$ 3,276	$ 5,626

INVESTMENT SECURITIES - Investm

INVESTMENT SECURITIES - Investment Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Jun. 30, 2021USD ($)	Dec. 31, 2020USD ($)
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months	162	117
12 months or longer	9	3
Total	171	120
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 1,446,539	$ 913,612
12 months or longer	1,328	14
Total	1,447,867	913,626
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	112,993	16,788
12 months or longer	3	0
Total	112,996	$ 16,788
Available-for-sale, allowance for credit losses	0
Accrued interest and fees receivable	19,000
Available-for-sale Securities [Member]
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Accrued interest and fees receivable	$ 14,500
U.S. Treasury and agency securities
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months	29	13
12 months or longer	0	0
Total	29	13
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 1,272,423	$ 831,015
12 months or longer	0	0
Total	1,272,423	831,015
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	110,075	16,595
12 months or longer	0	0
Total	$ 110,075	$ 16,595
Obligations of state and political subdivisions
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months	4	1
12 months or longer	0	0
Total	4	1
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 1,651	$ 358
12 months or longer	0	0
Total	1,651	358
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	1	0
12 months or longer	0	0
Total	$ 1	$ 0
Government agency mortgage-backed securities
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months	126	89
12 months or longer	6	2
Total	132	91
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 170,661	$ 75,992
12 months or longer	1,146	14
Total	171,807	76,006
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	2,914	182
12 months or longer	2	0
Total	$ 2,916	$ 182
Corporate debt securities
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months		1
12 months or longer		0
Total		1
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months		$ 1,001
12 months or longer		0
Total		1,001
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months		1
12 months or longer		0
Total		$ 1
Government agency collateralized mortgage obligations
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months	3	13
12 months or longer	3	1
Total	6	14
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 1,804	$ 5,246
12 months or longer	182	0
Total	1,986	5,246
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	3	10
12 months or longer	1	0
Total	$ 4	$ 10

INVESTMENT SECURITIES - Amortiz

INVESTMENT SECURITIES - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Due in one year or less	$ 198,566
Due after one through five years	768,349
Due after five years through ten years	1,018,820
Due after ten years	1,504,697
Subtotal	3,490,432
Amortized cost	4,039,978
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Due in one year or less	199,557
Due after one through five years	796,228
Due after five years through ten years	1,037,749
Due after ten years	1,420,784
Subtotal	3,454,318
Fair value	4,012,739
Government agency mortgage-backed securities
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Without single maturity date	521,056
Amortized cost	521,056	$ 506,540
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Without single maturity date	529,139
Fair value	529,139	522,638
Government agency collateralized mortgage obligations
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Without single maturity date	28,490
Amortized cost	28,490	42,476
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Without single maturity date	29,282
Fair value	$ 29,282	$ 43,577

INVESTMENT SECURITIES - Inves_2

INVESTMENT SECURITIES - Investment Securities Pledged as Collateral (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Investment Securities Pledged as Collateral
Investment securities pledged to collateralize certain deposits and borrowings	$ 2,430	$ 2,030
U.S. Treasury and agency securities | Securities Sold under Agreements to Repurchase [Member]
Investment Securities Pledged as Collateral
Investment securities pledged to collateralize certain deposits and borrowings	$ 475	$ 473.4

INVESTMENT SECURITIES - Inves_3

INVESTMENT SECURITIES - Investment Securities Pledged as Collateral (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Pledged Financial Instruments, Not Separately Reported, Securities, by Type of Security [Abstract]
Investment securities pledged to collateralize certain deposits and borrowings	$ 2,430	$ 2,030
U.S. Treasury and agency securities | Securities Sold under Agreements to Repurchase [Member]
Pledged Financial Instruments, Not Separately Reported, Securities, by Type of Security [Abstract]
Investment securities pledged to collateralize certain deposits and borrowings	$ 475	$ 473.4

LOANS - Loan Summary (Details)

LOANS - Loan Summary (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Loans receivable, net
Gross loans, including deferred origination costs	$ 7,244,147		$ 7,415,952
Allowance for credit losses	(51,750)	$ (55,069)	(60,869)	$ (64,437)	$ (55,652)	$ (49,911)
Net loans	7,192,397		7,355,083
Commercial Portfolio Segment [Member] | Business Lending [Member]
Loans receivable, net
Gross loans, including deferred origination costs	3,186,487		3,440,077
Allowance for credit losses	(23,417)	(27,042)	(28,190)	(24,204)	(19,489)	(19,426)
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Loans receivable, net
Gross loans, including deferred origination costs	2,408,499
Allowance for credit losses	(10,001)	(9,686)	(10,672)	(13,088)	(12,430)	(10,269)
Consumer Portfolio Segment [Member] | Consumer Mortgage [Member]
Loans receivable, net
Gross loans, including deferred origination costs	2,408,499		2,401,499
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Loans receivable, net
Gross loans, including deferred origination costs	1,109,504		1,021,885
Allowance for credit losses	(11,103)	(11,120)	(13,696)	(15,866)	(13,694)	(13,712)
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Loans receivable, net
Gross loans, including deferred origination costs	148,540		152,657
Allowance for credit losses	(2,548)	(2,682)	(3,207)	(4,028)	(3,737)	(3,255)
Consumer Portfolio Segment [Member] | Home Equity [Member]
Loans receivable, net
Gross loans, including deferred origination costs	391,117		399,834
Allowance for credit losses	$ (1,796)	$ (1,543)	$ (2,222)	$ (2,690)	$ (2,484)	$ (2,129)

LOANS - Credit Quality By Past

LOANS - Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Aged analysis of the company's loans
Total loans	$ 7,244,147	$ 7,415,952
Interest income on nonaccrual loans	0
Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		3,922
Nonaccrual		72,929
Total past due		111,610
Current		7,304,342
Total loans		7,415,952
Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		34,759
Acquired Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	1,722
Nonaccrual	68,476
Total past due	88,509
Current	7,155,638
Total loans	7,244,147
Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	18,311
Commercial Portfolio Segment [Member] | Business Lending [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	228
Nonaccrual	49,877
Total past due	51,077
Current	3,135,410
Total loans	3,186,487	3,440,077
Commercial Portfolio Segment [Member] | Business Lending [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	972
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		59
Nonaccrual		55,709
Total past due		60,664
Current		3,379,413
Total loans		3,440,077
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		4,896
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	1,259
Nonaccrual	16,025
Total past due	25,929
Current	2,382,570
Total loans	2,408,499
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	8,645
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		3,051
Nonaccrual		14,970
Total past due		31,257
Current		2,370,242
Total loans		2,401,499
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		13,236
Consumer Portfolio Segment [Member] | Consumer Mortgage [Member]
Aged analysis of the company's loans
Total loans	2,408,499	2,401,499
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	73
Nonaccrual	0
Total past due	7,183
Current	1,102,321
Total loans	1,109,504	1,021,885
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	7,110
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		219
Nonaccrual		1
Total past due		13,381
Current		1,008,504
Total loans		1,021,885
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		13,161
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	15
Nonaccrual	2
Total past due	524
Current	148,016
Total loans	148,540	152,657
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	507
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		28
Nonaccrual		3
Total past due		1,201
Current		151,456
Total loans		152,657
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		1,170
Consumer Portfolio Segment [Member] | Home Equity [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	147
Nonaccrual	2,572
Total past due	3,796
Current	387,321
Total loans	391,117	399,834
Consumer Portfolio Segment [Member] | Home Equity [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	$ 1,077
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		565
Nonaccrual		2,246
Total past due		5,107
Current		394,727
Total loans		399,834
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		$ 2,296

LOANS - Amount of Business Lend

LOANS - Amount of Business Lending Loans by Credit Quality Categories (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Business Lending [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	$ 345,833
2020	454,489	$ 881,201
2019	371,746	391,969
2018	372,296	373,807
2017	238,460	263,820
2016		275,730
Prior	818,214	660,921
Revolving Loans Amortized Cost Basis	585,449	592,629
Total	3,186,487	3,440,077
Business Lending [Member] | Pass [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	343,472
2020	439,365	860,178
2019	338,583	351,350
2018	284,580	312,087
2017	189,477	217,138
2016		231,453
Prior	661,491	543,999
Revolving Loans Amortized Cost Basis	507,921	483,018
Total	2,764,889	2,999,223
Business Lending [Member] | Special Mention [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	2,001
2020	12,961	14,687
2019	12,084	36,041
2018	36,635	28,410
2017	21,586	21,875
2016		29,386
Prior	72,145	51,657
Revolving Loans Amortized Cost Basis	34,484	52,732
Total	191,896	234,788
Business Lending [Member] | Classified [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	360
2020	2,163	6,336
2019	21,063	4,560
2018	49,150	30,422
2017	27,397	24,807
2016		14,891
Prior	84,543	65,157
Revolving Loans Amortized Cost Basis	42,178	56,000
Total	226,854	202,173
Business Lending [Member] | Doubtful [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	0	0
2019	16	18
2018	1,931	2,888
2017	0	0
2016		0
Prior	35	108
Revolving Loans Amortized Cost Basis	866	879
Total	2,848	3,893
Consumer Mortgage [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	275,761
2020	374,624	375,637
2019	300,211	330,825
2018	213,623	248,468
2017	201,611	240,217
2016		246,256
Prior	1,021,275	942,393
Revolving Loans Amortized Cost Basis	21,394	17,703
Total	2,408,499	2,401,499
Consumer Mortgage [Member] | FICO AB [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	217,537
2020	245,448	260,588
2019	204,560	227,027
2018	139,517	166,913
2017	136,508	164,051
2016		161,256
Prior	663,378	617,685
Revolving Loans Amortized Cost Basis	0	321
Total	1,606,948	1,597,841
Consumer Mortgage [Member] | FICO AB [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	217,537
2020	245,277	260,588
2019	204,560	227,027
2018	139,256	166,638
2017	135,992	163,653
2016		160,911
Prior	660,613	614,976
Revolving Loans Amortized Cost Basis	0	321
Total	1,603,235	1,594,114
Consumer Mortgage [Member] | FICO AB [Member] | Nonperforming Financial Instruments [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	171	0
2019	0	0
2018	261	275
2017	516	398
2016		345
Prior	2,765	2,709
Revolving Loans Amortized Cost Basis	0	0
Total	3,713	3,727
Consumer Mortgage [Member] | FICO CDE [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	58,224
2020	129,176	115,049
2019	95,651	103,798
2018	74,106	81,555
2017	65,103	76,166
2016		85,000
Prior	357,897	324,708
Revolving Loans Amortized Cost Basis	21,394	17,382
Total	801,551	803,658
Consumer Mortgage [Member] | FICO CDE [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	58,224
2020	128,942	115,049
2019	94,750	102,788
2018	73,362	80,973
2017	64,401	75,289
2016		83,214
Prior	346,907	314,668
Revolving Loans Amortized Cost Basis	21,394	17,382
Total	787,980	789,363
Consumer Mortgage [Member] | FICO CDE [Member] | Nonperforming Financial Instruments [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	234	0
2019	901	1,010
2018	744	582
2017	702	877
2016		1,786
Prior	10,990	10,040
Revolving Loans Amortized Cost Basis	0	0
Total	13,571	14,295
Consumer Indirect [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	317,236
2020	255,949	303,522
2019	240,566	305,953
2018	149,003	202,455
2017	59,328	86,514
2016		61,465
Prior	87,422	61,976
Revolving Loans Amortized Cost Basis	0	0
Total	1,109,504	1,021,885
Consumer Indirect [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	317,236
2020	255,939	303,471
2019	240,528	305,901
2018	148,990	202,373
2017	59,328	86,497
2016		61,449
Prior	87,410	61,975
Revolving Loans Amortized Cost Basis	0	0
Total	1,109,431	1,021,666
Consumer Indirect [Member] | Nonperforming Financial Instruments [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	10	51
2019	38	52
2018	13	82
2017	0	17
2016		16
Prior	12	1
Revolving Loans Amortized Cost Basis	0	0
Total	73	219
Consumer Direct [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	37,644
2020	37,762	49,182
2019	34,503	47,011
2018	18,949	27,874
2017	7,557	12,331
2016		5,232
Prior	6,115	4,149
Revolving Loans Amortized Cost Basis	6,010	6,878
Total	148,540	152,657
Consumer Direct [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	37,644
2020	37,762	49,181
2019	34,503	46,992
2018	18,947	27,872
2017	7,557	12,326
2016		5,232
Prior	6,100	4,146
Revolving Loans Amortized Cost Basis	6,010	6,878
Total	148,523	152,627
Consumer Direct [Member] | Nonperforming Financial Instruments [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	0	1
2019	0	19
2018	2	2
2017	0	5
2016		0
Prior	15	3
Revolving Loans Amortized Cost Basis	0	0
Total	17	30
Home Equity [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	33,503
2020	47,404	48,145
2019	42,454	48,804
2018	23,557	28,147
2017	19,303	23,628
2016		18,011
Prior	43,772	36,390
Revolving Loans Amortized Cost Basis	181,124	196,709
Total	391,117	399,834
Home Equity [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	33,503
2020	47,348	48,145
2019	42,432	48,780
2018	23,450	28,074
2017	19,224	23,524
2016		17,828
Prior	43,050	35,900
Revolving Loans Amortized Cost Basis	179,391	194,773
Total	388,398	397,024
Home Equity [Member] | Nonperforming Financial Instruments [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	56	0
2019	22	24
2018	107	73
2017	79	104
2016		183
Prior	722	490
Revolving Loans Amortized Cost Basis	1,733	1,936
Total	$ 2,719	$ 2,810

LOANS - Summary of Impaired Loa

LOANS - Summary of Impaired Loans, Excluding Purchased Impaired (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Impaired loans
Loans with allowance allocation	$ 25,534		$ 25,534		$ 27,437
Loans without allowance allocation	6,529		6,529		8,138
Carrying balance	32,063		32,063		35,575
Contractual balance	34,228		34,228		38,362
Specifically allocated allowance	2,800		2,800		$ 3,874
Average carrying balance of individually evaluated impaired loans	$ 32,900	$ 1,400	34,600	$ 1,800
Interest income on individually evaluated impaired loans			$ 0	$ 0

LOANS - Troubled Debt Restructu

LOANS - Troubled Debt Restructurings (TDRs) (Details) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2021USD ($)loanborrower	Jun. 30, 2020USD ($)loan	Dec. 31, 2020USD ($)loanborrower
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	228		247
TDRs, amount	$ 6,682		$ 6,984
Loans modified in TDR during the year, number | loan	16	7
Loans modified in TDR during the year, amount	$ 482	$ 249
Number of borrowers representing $75.6 million in outstanding loan balances | borrower	12
Outstanding loan balances of 47 number of borrowers	$ 2,400
Percentage of total loan outstanding	0.03%		0.90%
Number of business borrowers representing $75.1 million in outstanding loan balances | borrower	8
Outstanding loan balances of 42 number of business borrowers	$ 2,000
Number of consumer borrowers representing $0.5 million in outstanding loan balances | borrower	4
Outstanding loan balances of 5 number of consumer borrowers	$ 400
Number of borrowers representing $66.5 million in outstanding loan balances | borrower			74
Outstanding loan balances of 74 number of borrowers			$ 66,500
Number of borrowers representing $65.7 million in outstanding loan balances | borrower			63
Outstanding loan balances of 63 number of borrowers			$ 65,700
Number of borrowers representing $0.8 million in outstanding loan balances | borrower			11
Outstanding loan balances of 11 number of borrowers			$ 800
Minimum [Member]
Troubled Debt Restructurings (TDRs)
Threshold balance of loan individually evaluated for impairment	500
Maximum [Member]
Troubled Debt Restructurings (TDRs)
Threshold balance of TDR loans collectively included in general loan loss allocation and qualitative review	$ 500
Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	74		73
TDRs, amount	$ 3,250		$ 3,227
Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	154		174
TDRs, amount	$ 3,432		$ 3,757
Commercial Portfolio Segment [Member]
Troubled Debt Restructurings (TDRs)
Loans modified in TDR during the year, number | loan	26	25
Loans modified in TDR during the year, amount	$ 657	$ 928
Commercial Portfolio Segment [Member] | Business Lending [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	10		10
TDRs, amount	$ 625		$ 720
Loans modified in TDR during the year, number | loan	0	0
Loans modified in TDR during the year, amount	$ 0	$ 0
Commercial Portfolio Segment [Member] | Business Lending [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	6		6
TDRs, amount	$ 445		$ 529
Commercial Portfolio Segment [Member] | Business Lending [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	4		4
TDRs, amount	$ 180		$ 191
Commercial Portfolio Segment [Member] | Consumer Mortgage [Member]
Troubled Debt Restructurings (TDRs)
Loans modified in TDR during the year, number | loan	10	9
Loans modified in TDR during the year, amount	$ 474	$ 738
Commercial Portfolio Segment [Member] | Consumer Indirect [Member]
Troubled Debt Restructurings (TDRs)
Loans modified in TDR during the year, number | loan	15	14
Loans modified in TDR during the year, amount	$ 177	$ 151
Commercial Portfolio Segment [Member] | Consumer Direct [Member]
Troubled Debt Restructurings (TDRs)
Loans modified in TDR during the year, number | loan	1	1
Loans modified in TDR during the year, amount	$ 6	$ 11
Commercial Portfolio Segment [Member] | Home Equity [Member]
Troubled Debt Restructurings (TDRs)
Loans modified in TDR during the year, number | loan	0	1
Loans modified in TDR during the year, amount	$ 0	$ 28
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	100		104
TDRs, amount	$ 4,627		$ 4,679
Loans modified in TDR during the year, number | loan	7	3
Loans modified in TDR during the year, amount	$ 366	$ 174
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	58		56
TDRs, amount	$ 2,553		$ 2,413
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	42		48
TDRs, amount	$ 2,074		$ 2,266
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	79		86
TDRs, amount	$ 916		$ 951
Loans modified in TDR during the year, number | loan	9	3
Loans modified in TDR during the year, amount	$ 116	$ 47
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	0		0
TDRs, amount	$ 0		$ 0
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	79		86
TDRs, amount	$ 916		$ 951
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	17		23
TDRs, amount	$ 14		$ 85
Loans modified in TDR during the year, number | loan	0	0
Loans modified in TDR during the year, amount	$ 0	$ 0
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	0		0
TDRs, amount	$ 0		$ 0
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	17		23
TDRs, amount	$ 14		$ 85
Consumer Portfolio Segment [Member] | Home Equity [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	22		24
TDRs, amount	$ 500		$ 549
Loans modified in TDR during the year, number | loan	0	1
Loans modified in TDR during the year, amount	$ 0	$ 28
Consumer Portfolio Segment [Member] | Home Equity [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	10		11
TDRs, amount	$ 252		$ 285
Consumer Portfolio Segment [Member] | Home Equity [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	12		13
TDRs, amount	$ 248		$ 264

LOANS - Allowance for Credit Lo

LOANS - Allowance for Credit Losses (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Allowance for loan losses [Roll Forward]
Balance, beginning of period	$ 55,069	$ 55,652	$ 60,869	$ 49,911	$ 49,911
Charge-offs	(1,106)	(2,094)	(3,072)
Recoveries	1,698	1,184	3,283
Steuben acquisition		3,662
Provision	(3,911)	6,033	(9,330)
Balance, end of period	51,750	64,437	51,750	64,437	60,869
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance	1,189	845	1,489	0	0
Charge-offs	0	0	0
Recoveries	0	0	0
Steuben acquisition		67
Provision	(427)	540	(727)
Ending balance	762	1,452	762	1,452	1,489
Total allowance for credit losses [Roll Forward]
Beginning balance	56,258	56,497	62,358	49,911	49,911
Charge-offs	(1,106)	(2,094)	(3,072)
Recoveries	1,698	1,184	3,283
Steuben acquisition		3,729
Provision	(4,338)	6,573	(10,057)
Ending balance	$ 52,512	65,889	$ 52,512	65,889	$ 62,358
Allowance for Credit Losses
Allowance for credit losses to total loans ratio	0.71		0.71
Basis points lower level			0.15		0.11
Accrued interest and fees receivable	$ 19,000		$ 19,000
Minimum [Member] | COVID-19 [Member]
Allowance for Credit Losses
Percentage of peak unemployment			3.00%
Maximum [Member] | COVID-19 [Member]
Allowance for Credit Losses
Percentage of peak unemployment			9.00%
ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				51,268	$ 51,268
Charge-offs				(5,141)
Recoveries				2,681
Steuben acquisition				3,662
Provision				11,967
Balance, end of period		64,437		64,437
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance				1,185	1,185
Charge-offs				0
Recoveries				0
Steuben acquisition				67
Provision				200
Ending balance		1,452		1,452
Total allowance for credit losses [Roll Forward]
Beginning balance				52,453	52,453
Charge-offs				(5,141)
Recoveries				2,681
Steuben acquisition				3,729
Provision				12,167
Ending balance		65,889		65,889
ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				1,357	1,357
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance				1,185	1,185
Total allowance for credit losses [Roll Forward]
Beginning balance				2,542	2,542
Acquired Impaired Loans [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				163	163
Acquired Impaired Loans [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				0	0
Charge-offs				0
Recoveries				0
Steuben acquisition				0
Provision				0
Balance, end of period		0		0
Acquired Impaired Loans [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				(163)	(163)
Acquired Deteriorated
Allowance for loan losses [Roll Forward]
Balance, beginning of period	1,996	3,046	$ 1,882	0	0
Charge-offs	0	0	0
Recoveries	33	48	60
Steuben acquisition		528
Provision	(144)	(61)	(57)
Balance, end of period	1,885	3,561	1,885	3,561	1,882
Acquired Deteriorated | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				3,072	3,072
Charge-offs				0
Recoveries				48
Steuben acquisition				528
Provision				(87)
Balance, end of period		3,561		3,561
Acquired Deteriorated | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				3,072	3,072
Commercial Portfolio Segment [Member] | Business Lending [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	27,042	19,489	28,190	19,426	19,426
Charge-offs	(2)	(7)	(53)
Recoveries	255	84	322
Steuben acquisition		2,483
Provision	(3,878)	2,155	(5,042)
Balance, end of period	23,417	24,204	23,417	24,204	28,190
Commercial Portfolio Segment [Member] | Business Lending [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				19,714	19,714
Charge-offs				(183)
Recoveries				222
Steuben acquisition				2,483
Provision				1,968
Balance, end of period		24,204		24,204
Commercial Portfolio Segment [Member] | Business Lending [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				288	288
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	9,686	12,430	10,672	10,269	10,269
Charge-offs	(142)	(234)	(242)
Recoveries	9	36	19
Steuben acquisition		146
Provision	448	710	(448)
Balance, end of period	10,001	13,088	10,001	13,088	10,672
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				9,218	9,218
Charge-offs				(420)
Recoveries				44
Steuben acquisition				146
Provision				4,100
Balance, end of period		13,088		13,088
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				(1,051)	(1,051)
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	11,120	13,694	13,696	13,712	13,712
Charge-offs	(750)	(1,431)	(2,149)
Recoveries	1,183	833	2,429
Steuben acquisition		183
Provision	(450)	2,587	(2,873)
Balance, end of period	11,103	15,866	11,103	15,866	13,696
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				12,715	12,715
Charge-offs				(3,510)
Recoveries				1,996
Steuben acquisition				183
Provision				4,482
Balance, end of period		15,866		15,866
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				(997)	(997)
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	2,682	3,737	3,207	3,255	3,255
Charge-offs	(195)	(341)	(513)
Recoveries	213	171	444
Steuben acquisition		87
Provision	(152)	374	(590)
Balance, end of period	2,548	4,028	2,548	4,028	3,207
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				2,612	2,612
Charge-offs				(874)
Recoveries				353
Steuben acquisition				87
Provision				1,850
Balance, end of period		4,028		4,028
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				(643)	(643)
Consumer Portfolio Segment [Member] | Home Equity [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	1,543	2,484	2,222	2,129	2,129
Charge-offs	(17)	(81)	(115)
Recoveries	5	12	9
Steuben acquisition		235
Provision	265	40	(320)
Balance, end of period	1,796	2,690	1,796	2,690	2,222
Consumer Portfolio Segment [Member] | Home Equity [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				2,937	2,937
Charge-offs				(154)
Recoveries				18
Steuben acquisition				235
Provision				(346)
Balance, end of period		2,690		2,690
Consumer Portfolio Segment [Member] | Home Equity [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				808	808
Unallocated Financing Receivables [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	1,000	772	1,000	957	957
Charge-offs	0	0	0
Recoveries	0	0	0
Steuben acquisition		0
Provision	0	228	0
Balance, end of period	$ 1,000	1,000	$ 1,000	1,000	1,000
Unallocated Financing Receivables [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				1,000	1,000
Charge-offs				0
Recoveries				0
Steuben acquisition				0
Provision				0
Balance, end of period		$ 1,000		1,000
Unallocated Financing Receivables [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period				$ 43	$ 43

LOANS - Carrying Amounts of Loa

LOANS - Carrying Amounts of Loans Purchased and Sold (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)
Carrying Amounts of Loans Purchased and Sold
Purchases	$ 0
Sales	11,708
Commercial Portfolio Segment [Member] | Business Lending [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	0
Sales	848
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	0
Sales	10,860
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	0
Sales	0
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	0
Sales	0
Consumer Portfolio Segment [Member] | Home Equity [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	0
Sales	$ 0

GOODWILL AND IDENTIFIABLE INT_3

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Identifiable Intangible Assets [Abstract]
Gross Carrying Amount	$ 161,302	$ 159,865
Accumulated Amortization	(113,522)	(106,925)
Net Carrying Amount	47,780	52,940
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Jul - Dec 2021	6,229
2022	11,141
2023	9,338
2024	7,768
2025	6,550
Thereafter	6,754
Net Carrying Amount	47,780	52,940
Components of goodwill [Abstract]
Goodwill, net, beginning of period	793,708
Goodwill, net, activity	1,184
Goodwill, net, end of period	794,892
Core deposit intangibles [Member]
Identifiable Intangible Assets [Abstract]
Gross Carrying Amount	69,403	69,403
Accumulated Amortization	(58,136)	(55,572)
Net Carrying Amount	11,267	13,831
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Net Carrying Amount	11,267	13,831
Other intangibles [Member]
Identifiable Intangible Assets [Abstract]
Gross Carrying Amount	91,899	90,462
Accumulated Amortization	(55,386)	(51,353)
Net Carrying Amount	36,513	39,109
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Net Carrying Amount	$ 36,513	$ 39,109

MANDATORILY REDEEMABLE PREFER_2

MANDATORILY REDEEMABLE PREFERRED SECURITIES (Details) - USD ($) $ in Millions	Mar. 15, 2021	Sep. 15, 2020
Community Capital Trust IV
Mandatorily Redeemable Preferred Securities [Abstract]
Redemption of debentures and associated preferred securities	$ 77.3
Steuben Statutory Trust
Mandatorily Redeemable Preferred Securities [Abstract]
Redemption of debentures and associated preferred securities		$ 2.1

BENEFIT PLANS (Details)

BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Pension Plans [Abstract]
Contribution made to defined benefit pension plan by employer			$ 3,900
Pension Benefits [Member]
Pension Plans [Abstract]
Contribution made to defined benefit pension plan by employer		$ 2,900
Net periodic benefit cost [Abstract]
Service cost	$ 1,480		1,438	$ 2,960	$ 2,875
Interest cost	1,259		1,356	2,518	2,712
Expected return on plan assets	(4,695)		(3,932)	(9,391)	(7,864)
Amortization of unrecognized net loss	900		810	1,800	1,620
Amortization of prior service cost	94		60	189	120
Net periodic benefit	(962)		(268)	(1,924)	(537)
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0		0	0	0
Interest cost	11		14	22	28
Expected return on plan assets	0		0	0	0
Amortization of unrecognized net loss	11		10	22	20
Amortization of prior service cost	(44)		(44)	(89)	(89)
Net periodic benefit	$ (22)		$ (20)	$ (45)	$ (41)

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
EARNINGS PER SHARE
Weighted-average anti-dilutive stock options outstanding (in shares)	200,000	600,000	100,000	600,000
Basic earnings per share [Abstract]
Net income	$ 47,944	$ 35,248	$ 100,794	$ 75,382
Income attributable to unvested stock-based compensation awards	(127)	(127)	(263)	(264)
Income available to common shareholders	$ 47,817	$ 35,121	$ 100,531	$ 75,118
Weighted-average common shares outstanding - basic (in shares)	54,007,000	52,487,000	53,927,000	52,262,000
Basic earnings per share (in dollars per share)	$ 0.89	$ 0.67	$ 1.86	$ 1.44
Diluted earnings per share [Abstract]
Net income	$ 47,944	$ 35,248	$ 100,794	$ 75,382
Income attributable to unvested stock-based compensation awards	(127)	(127)	(263)	(264)
Income available to common shareholders	$ 47,817	$ 35,121	$ 100,531	$ 75,118
Weighted-average common shares outstanding - basic (in shares)	54,007,000	52,487,000	53,927,000	52,262,000
Assumed exercise of stock options (in shares)	462,000	339,000	455,000	372,000
Weighted-average common shares outstanding - diluted (in shares)	54,469,000	52,826,000	54,382,000	52,634,000
Diluted earnings per share (in dollars per share)	$ 0.88	$ 0.66	$ 1.85	$ 1.43
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)					2,680,000	2,600,000
Number of common shares repurchased (in shares)			0	0

COMMITMENTS, CONTINGENT LIABI_3

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Jun. 30, 2021
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	$ 1,352,781	$ 1,235,186
Expense recorded for litigation accrual	3,000
Minimum [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Range of reasonably possible losses for such matters in the aggregate, beyond the existing recorded liability		0
Maximum [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Range of reasonably possible losses for such matters in the aggregate, beyond the existing recorded liability		1,000
Commitments to Extend Credit [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	1,313,568	1,199,804
Standby Letters of Credit [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	$ 39,213	$ 35,382

FAIR VALUE - Financial Assets a

FAIR VALUE - Financial Assets and Liabilities Accounted for at Fair Value On a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	$ 4,012,739
Equity securities	469	$ 445
U.S. Treasury and agency securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,025,072	2,501,382
Obligations of state and political subdivisions
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	426,152	475,660
Government agency mortgage-backed securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	529,139	522,638
Corporate debt securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,094	4,635
Government agency collateralized mortgage obligations
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	29,282	43,577
Significant Unobservable Inputs, Level 3 [Member] | Commitments to originate real estate loans for sale
Available-for-sale investment securities [Abstract]
Derivative asset	130	14
Recurring [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	4,012,739	3,547,892
Equity securities	469	445
Mortgage loans held for sale	1,340	1,622
Total	4,015,074	3,550,473
Recurring [Member] | Commitments to originate real estate loans for sale
Available-for-sale investment securities [Abstract]
Derivative asset	130	14
Recurring [Member] | Forward sales commitments
Available-for-sale investment securities [Abstract]
Derivative asset	31	2
Recurring [Member] | Interest rate swap agreements
Available-for-sale investment securities [Abstract]
Derivative asset	372	1,572
Derivative liability	(7)	(1,074)
Recurring [Member] | U.S. Treasury and agency securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,025,072	2,501,382
Recurring [Member] | Obligations of state and political subdivisions
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	426,152	475,660
Recurring [Member] | Government agency mortgage-backed securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	529,139	522,638
Recurring [Member] | Corporate debt securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,094	4,635
Recurring [Member] | Government agency collateralized mortgage obligations
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	29,282	43,577
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,909,475	2,359,912
Equity securities	469	445
Mortgage loans held for sale	0	0
Total	2,909,944	2,360,357
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Commitments to originate real estate loans for sale
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Forward sales commitments
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Interest rate swap agreements
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Derivative liability	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | U.S. Treasury and agency securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,909,475	2,359,912
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Obligations of state and political subdivisions
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Government agency mortgage-backed securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Corporate debt securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Government agency collateralized mortgage obligations
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Significant Observable Inputs, Level 2 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,103,264	1,187,980
Equity securities	0	0
Mortgage loans held for sale	1,340	1,622
Total	1,105,000	1,190,102
Mortgage loans held for sale	1,300	1,600
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Commitments to originate real estate loans for sale
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Forward sales commitments
Available-for-sale investment securities [Abstract]
Derivative asset	31	2
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Interest rate swap agreements
Available-for-sale investment securities [Abstract]
Derivative asset	372	1,572
Derivative liability	(7)	(1,074)
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | U.S. Treasury and agency securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	115,597	141,470
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Obligations of state and political subdivisions
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	426,152	475,660
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Government agency mortgage-backed securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	529,139	522,638
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Corporate debt securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,094	4,635
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Government agency collateralized mortgage obligations
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	29,282	43,577
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Equity securities	0	0
Mortgage loans held for sale	0	0
Total	130	14
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Commitments to originate real estate loans for sale
Available-for-sale investment securities [Abstract]
Derivative asset	130	14
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Forward sales commitments
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Interest rate swap agreements
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Derivative liability	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | U.S. Treasury and agency securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Obligations of state and political subdivisions
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Government agency mortgage-backed securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Corporate debt securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Government agency collateralized mortgage obligations
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	$ 0	$ 0

FAIR VALUE - Assets and Liabili

FAIR VALUE - Assets and Liabilities Measured on Nonrecurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Valuation allowance	$ 2,800	$ 3,874
Mortgage Servicing Rights [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Valuation allowance	100	200
Significant Unobservable Inputs, Level 3 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	21,330	25,063
Other real estate owned	879	883
Mortgage servicing rights	697	682
Non-recurring [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	21,330	25,063
Other real estate owned	879	883
Mortgage servicing rights	697	682
Total	22,906	26,628
Non-recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	0	0
Other real estate owned	0	0
Mortgage servicing rights	0	0
Total	0	0
Non-recurring [Member] | Significant Observable Inputs, Level 2 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	0	0
Other real estate owned	0	0
Mortgage servicing rights	0	0
Total	0	0
Non-recurring [Member] | Significant Unobservable Inputs, Level 3 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	21,330	25,063
Other real estate owned	879	883
Mortgage servicing rights	697	682
Total	$ 22,906	$ 26,628

FAIR VALUE - Significant Unobse

FAIR VALUE - Significant Unobservable Inputs (Details)	12 Months Ended
	Dec. 31, 2020USD ($)	Jun. 30, 2021USD ($)
Minimum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Other real estate owned, measurement input		9
Maximum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Other real estate owned, measurement input		51.1
Significant Unobservable Inputs, Level 3 [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans	$ 25,063,000	$ 21,330,000
Other real estate owned	883,000	879,000
Fair value of MSRs at end of period	$ 682,000	$ 697,000
Significant Unobservable Inputs, Level 3 [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans, Valuation Technique [Extensible List]	Fair Value of Collateral [Member]	Fair Value of Collateral [Member]
Impaired loans, Measurement Input [Extensible List]	us-gaap:MeasurementInputCostToSellMember	us-gaap:MeasurementInputCostToSellMember
Other real estate owned, Valuation Technique [Extensible List]	Fair Value of Collateral [Member]	Fair Value of Collateral [Member]
Other real estate owned, Measurement Input [Extensible List]	us-gaap:MeasurementInputCostToSellMember	us-gaap:MeasurementInputCostToSellMember
Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, Valuation Technique [Extensible List]	Discounted Cash Flow [Member]	Discounted Cash Flow [Member]
Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, Measurement Input [Extensible List]	Weighted Average Constant Prepayment Rate [Member]	Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, Measurement Input [Extensible List]	Weighted Average Discount Rate [Member]	Weighted Average Discount Rate [Member]
Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member] | Adequate Compensation [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input		7
Mortgage servicing rights, measurement input	7
Mortgage servicing rights, Measurement Input [Extensible List]	Adequate Compensation [Member]	Adequate Compensation [Member]
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans, measurement input	9	9
Other real estate owned, measurement input	11.3	9
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	9.8	16.9
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	1.7	2.2
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans, measurement input	78.4	78.7
Other real estate owned, measurement input	52.9	51.1
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	18.8	49.1
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	2.2	2.8
Significant Unobservable Inputs, Level 3 [Member] | Weighted Average [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans, measurement input	52.7	53.8
Other real estate owned, measurement input	34	34.5
Significant Unobservable Inputs, Level 3 [Member] | Weighted Average [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	17.6	21.8
Significant Unobservable Inputs, Level 3 [Member] | Weighted Average [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	2.1	2.7
Commitments to originate real estate loans for sale | Significant Unobservable Inputs, Level 3 [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Commitments to originate real estate loans for sale	$ 14,000	$ 130,000
Commitments to originate real estate loans for sale | Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Commitments to originate real estate loans for sale, Valuation Technique [Extensible List]	Discounted Cash Flow [Member]	Discounted Cash Flow [Member]
Commitments to originate real estate loans for sale, measurement input	1	1
Commitments to originate real estate loans for sale | Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member] | Embedded Servicing Value [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Commitments to originate real estate loans for sale, Measurement Input [Extensible List]	Embedded Servicing Value [Member]	Embedded Servicing Value [Member]

FAIR VALUE - Carrying Amounts a

FAIR VALUE - Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Carrying Value [Member]
Financial assets:
Net loans	$ 7,192,397	$ 7,355,083
Financial liabilities:
Deposits	12,339,025	11,224,974
Securities sold under agreement to repurchase, short-term	194,887	284,008
Other Federal Home Loan Bank borrowings	2,936	6,658
Subordinated notes payable	3,290	3,303
Subordinated debt held by unconsolidated subsidiary trusts	0	77,320
Fair Value [Member]
Financial assets:
Net loans	7,563,546	7,655,044
Financial liabilities:
Deposits	12,349,413	11,239,628
Securities sold under agreement to repurchase, short-term	194,887	284,008
Other Federal Home Loan Bank borrowings	2,993	6,758
Subordinated notes payable	3,290	3,303
Subordinated debt held by unconsolidated subsidiary trusts	$ 0	$ 77,320

DERIVATIVE INSTRUMENTS (Details

DERIVATIVE INSTRUMENTS (Details) - Interest rate swap agreements - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Derivative Instruments [Abstract]
Derivative, notional amount	$ 0.7	$ 14.4
Derivative weighted average receive rate	2.34%	2.10%
Derivative weighted average pay rate	3.54%	4.44%
Weighted average maturity period	1 year 9 months 18 days	5 years 2 months 12 days
Designated As Hedging Instrument | Fair Value Hedging [Member]
Derivative Instruments [Abstract]
Derivative, notional amount	$ 5.4	$ 5.7
Derivative weighted average receive rate	1.38%	1.42%
Derivative weighted average pay rate	3.11%	3.11%
Weighted average maturity period	12 years	12 years 6 months

DERIVATIVE INSTRUMENTS - Cumula

DERIVATIVE INSTRUMENTS - Cumulative Basis Adjustments for Fair Value Hedges (Details) - Loans [Member] - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Cumulative Basis Adjustments for Fair Value Hedges [Abstract]
Carrying amount of the hedged assets	$ 5,809	$ 5,675
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets	$ (365)	$ (498)

DERIVATIVE INSTRUMENTS - Fair V

DERIVATIVE INSTRUMENTS - Fair Values of Derivative Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Values of Derivative Instruments
Derivative assets	$ 533	$ 1,588
Derivative liabilities	7	1,074
Interest rate swap agreements | Designated As Hedging Instrument | Other Assets
Fair Values of Derivative Instruments
Derivative assets	365	498
Interest rate swap agreements | Not Designated as Hedging Instrument | Other Assets
Fair Values of Derivative Instruments
Derivative assets	7	1,074
Interest rate swap agreements | Not Designated as Hedging Instrument | Accrued Interest and Other Liabilities
Fair Values of Derivative Instruments
Derivative liabilities	7	1,074
Commitments to originate real estate loans for sale | Not Designated as Hedging Instrument | Other Assets
Fair Values of Derivative Instruments
Derivative assets	130	14
Forward sales commitments | Not Designated as Hedging Instrument | Other Assets
Fair Values of Derivative Instruments
Derivative assets	$ 31	$ 2

SEGMENT INFORMATION (Details)

SEGMENT INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Segment Reporting Information, Additional Information [Abstract]
Net interest income	$ 92,105	$ 91,951	$ 186,059	$ 182,005
Provision for credit losses	(4,338)	9,774	(10,057)	15,368
Noninterest revenues	59,460	52,938	117,991	111,560
Amortization of intangible assets	3,246	3,524	6,597	7,191
Acquisition expenses	4	3,372	31	3,741
Other operating expenses	90,293	84,007	180,161	173,634
Income before income taxes	62,360	44,212	127,318	93,631
Assets	14,801,287	13,444,217	14,801,287	13,444,217	$ 13,931,094
Goodwill	794,892	792,715	794,892	792,715	$ 793,708
Core deposit intangibles & Other intangibles	47,780	60,046	47,780	60,046
Eliminations [Member]
Segment Reporting Information, Additional Information [Abstract]
Net interest income	0	0	0	0
Provision for credit losses	0	0	0	0
Noninterest revenues	(1,707)	(1,374)	(3,596)	(2,893)
Amortization of intangible assets	0	0	0	0
Acquisition expenses	0	0	0	0
Other operating expenses	(1,707)	(1,374)	(3,596)	(2,893)
Income before income taxes	0	0	0	0
Assets	(100,699)	(122,856)	(100,699)	(122,856)
Goodwill	0	0	0	0
Core deposit intangibles & Other intangibles	0	0	0	0
Banking [Member] | Operating Segments [Member]
Segment Reporting Information, Additional Information [Abstract]
Net interest income	92,033	91,645	185,872	181,409
Provision for credit losses	(4,338)	9,774	(10,057)	15,368
Noninterest revenues	16,357	14,991	32,811	33,672
Amortization of intangible assets	1,240	1,364	2,564	2,781
Acquisition expenses	4	3,372	31	3,741
Other operating expenses	65,158	59,130	130,165	123,330
Income before income taxes	46,326	32,996	95,980	69,861
Assets	14,588,075	13,272,929	14,588,075	13,272,929
Goodwill	689,867	689,128	689,867	689,128
Core deposit intangibles & Other intangibles	11,267	16,565	11,267	16,565
Employee Benefit Services [Member] | Operating Segments [Member]
Segment Reporting Information, Additional Information [Abstract]
Net interest income	65	246	159	486
Provision for credit losses	0	0	0	0
Noninterest revenues	27,994	24,504	55,143	50,429
Amortization of intangible assets	1,327	1,411	2,681	2,905
Acquisition expenses	0	0	0	0
Other operating expenses	14,846	14,948	29,851	30,079
Income before income taxes	11,886	8,391	22,770	17,931
Assets	235,141	216,122	235,141	216,122
Goodwill	83,275	83,275	83,275	83,275
Core deposit intangibles & Other intangibles	29,370	34,870	29,370	34,870
All Other [Member] | Operating Segments [Member]
Segment Reporting Information, Additional Information [Abstract]
Net interest income	7	60	28	110
Provision for credit losses	0	0	0	0
Noninterest revenues	16,816	14,817	33,633	30,352
Amortization of intangible assets	679	749	1,352	1,505
Acquisition expenses	0	0	0	0
Other operating expenses	11,996	11,303	23,741	23,118
Income before income taxes	4,148	2,825	8,568	5,839
Assets	78,770	78,022	78,770	78,022
Goodwill	21,750	20,312	21,750	20,312
Core deposit intangibles & Other intangibles	$ 7,143	$ 8,611	$ 7,143	$ 8,611