Community Bank System (CBU) 10-Q 9 Nov 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Oct. 31, 2020
Cover [Abstract]
Entity Registrant Name	COMMUNITY BANK SYSTEM, INC.
Entity Central Index Key	0000723188
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		53,541,669
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Document Quarterly Report	true
Document Transition Report	false
Entity File Number	001-13695
Entity Tax Identification Number	16-1213679
Entity Incorporation, State or Country Code	DE
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
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 (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Cash and cash equivalents	$ 1,836,521	$ 205,030
Available-for-sale investment securities (cost of $3,068,406 and $3,011,551, respectively)	3,222,722	3,044,428
Equity and other securities (cost of $46,419 and $42,965, respectively)	47,341	43,915
Loans held for sale, at fair value	8,151	0
Loans	7,458,643	6,890,543
Allowance for credit losses	(64,962)	(49,911)
Net loans	7,393,681	6,840,632
Goodwill, net	793,749	773,810
Core deposit intangibles, net	15,186	16,418
Other intangibles, net	41,279	46,695
Intangible assets, net	850,214	836,923
Premises and equipment, net	165,342	164,638
Accrued interest and fees receivable	41,420	31,647
Other assets	279,933	243,082
Total assets	13,845,325	11,410,295
Liabilities:
Noninterest-bearing deposits	3,326,517	2,465,902
Interest-bearing deposits	7,794,073	6,529,065
Total deposits	11,120,590	8,994,967
Overnight Federal Home Loan Bank borrowings	0	8,300
Securities sold under agreement to repurchase, short-term	280,767	241,708
Other Federal Home Loan Bank borrowings	7,681	3,750
Subordinated notes payable	13,735	13,795
Subordinated debt held by unconsolidated subsidiary trusts	77,320	77,320
Accrued interest and other liabilities	246,572	215,221
Total liabilities	11,746,665	9,555,061
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; 53,697,919 and 51,974,726 shares issued, respectively	53,698	51,975
Additional paid-in capital	1,021,798	927,337
Retained earnings	936,273	882,851
Accumulated other comprehensive gain (loss)	83,962	(10,226)
Treasury stock, at cost (160,326 shares, including 160,311 shares held by deferred compensation arrangements at September 30, 2020 and 180,803 shares including 179,548 shares held by deferred compensation arrangements at December 31, 2019, respectively)	(6,131)	(6,823)
Deferred compensation arrangements (160,311 and 179,548 shares, respectively)	9,060	10,120
Total shareholders' equity	2,098,660	1,855,234
Total liabilities and shareholders' equity	$ 13,845,325	$ 11,410,295

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF CONDITION (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Available-for-sale investment securities, cost	$ 3,068,406	$ 3,011,551
Equity and other securities, cost	$ 46,419	$ 42,965
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)	53,697,919	51,974,726
Treasury stock, shares at cost (in shares)	160,326	180,803
Shares held by deferred compensation arrangements (in shares)	160,311	179,548

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest income:
Interest and fees on loans	$ 79,646	$ 79,931	$ 236,931	$ 227,701
Interest and dividends on taxable investments	14,881	15,862	45,633	49,376
Interest and dividends on nontaxable investments	2,963	2,854	9,113	8,603
Total interest income	97,490	98,647	291,677	285,680
Interest expense:
Interest on deposits	3,655	5,859	13,373	14,526
Interest on borrowings	292	347	1,280	1,397
Interest on subordinated notes payable	184	161	553	161
Interest on subordinated debt held by unconsolidated subsidiary trusts	394	1,004	1,501	3,161
Total interest expense	4,525	7,371	16,707	19,245
Net interest income	92,965	91,276	274,970	266,435
Provision for credit losses	1,945	1,751	17,313	5,573
Net interest income after provision for credit losses	91,020	89,525	257,657	260,862
Noninterest revenues:
Deposit service fees	14,260	16,920	42,722	48,780
Mortgage banking	3,908	(138)	6,199	276
Other banking services	924	1,083	2,574	3,352
Employee benefit services	25,159	24,329	74,593	72,170
Insurance services	8,531	8,527	24,772	24,718
Wealth management services	6,889	6,363	20,389	19,290
Gain on sale of investment securities, net	0	0	0	4,882
Unrealized (loss) gain on equity securities	(12)	10	(30)	28
Total noninterest revenues	59,659	57,094	171,219	173,496
Noninterest expenses:
Salaries and employee benefits	57,280	56,061	170,252	163,448
Occupancy and equipment	10,134	9,801	30,627	29,708
Data processing and communications	12,096	10,675	33,342	30,475
Amortization of intangible assets	3,581	3,960	10,772	11,994
Legal and professional fees	2,365	2,595	8,577	7,999
Business development and marketing	3,145	2,604	7,162	8,532
Litigation accrual	2,950	0	2,950	0
Acquisition expenses	796	6,061	4,537	7,789
Other expenses	4,619	5,172	13,313	16,812
Total noninterest expenses	96,966	96,929	281,532	276,757
Income before income taxes	53,713	49,690	147,344	157,601
Income taxes	10,904	10,472	29,153	31,422
Net income	$ 42,809	$ 39,218	$ 118,191	$ 126,179
Basic earnings per share (in dollars per share)	$ 0.80	$ 0.76	$ 2.23	$ 2.44
Diluted earnings per share (in dollars per share)	$ 0.79	$ 0.75	$ 2.22	$ 2.41

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Pension and other post retirement obligations:
Amortization of actuarial losses included in net periodic pension cost, gross	$ 820	$ 651	$ 2,460	$ 1,954
Tax effect	(197)	(158)	(591)	(477)
Amortization of actuarial losses included in net periodic pension cost, net	623	493	1,869	1,477
Amortization of prior service cost included in net periodic pension cost, gross	15	(28)	46	(86)
Tax effect	(4)	6	(11)	21
Amortization of prior service cost included in net periodic pension cost, net	11	(22)	35	(65)
Other comprehensive income related to pension and other post-retirement obligations, net of taxes	634	471	1,904	1,412
Unrealized (losses) gains on available-for-sale securities:
Net unrealized holding (losses) gains arising during period, gross	(8,821)	8,756	121,439	66,208
Tax effect	2,118	(2,136)	(29,155)	(16,157)
Net unrealized holding (losses) gains arising during period, net	(6,703)	6,620	92,284	50,051
Reclassification adjustment for net gains included in net income, gross	0	0	0	(4,882)
Tax effect	0	0	0	1,194
Reclassification adjustment for net gains included in net income, net	0	0	0	(3,688)
Other comprehensive income related to unrealized (losses) gains on available-for-sale securities, net of taxes	(6,703)	6,620	92,284	46,363
Other comprehensive (loss) income, net of tax	(6,069)	7,091	94,188	47,775
Net income	42,809	39,218	118,191	126,179
Comprehensive income	36,740	$ 46,309	212,379	$ 173,954
Accumulated Other Comprehensive Income (Loss) By Component:
Unrealized (loss) for pension and other post-retirement obligations	(43,669)		(43,669)		$ (46,175)
Tax effect	10,691		10,691		11,293
Net unrealized (loss) for pension and other post-retirement obligations	(32,978)		(32,978)		(34,882)
Unrealized gain on available-for-sale securities	154,316		154,316		32,877
Tax effect	(37,376)		(37,376)		(8,221)
Net unrealized gain on available-for-sale securities	116,940		116,940		24,656
Accumulated other comprehensive income (loss)	$ 83,962		$ 83,962		$ (10,226)

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Cumulative Effect AdjustmentRetained Earnings [Member]	Cumulative Effect Adjustment	Common Stock Shares Outstanding [Member]	Common Stock Amount Issued [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Treasury Stock [Member]	Deferred Compensation Arrangements [Member]	Total
Balance at Dec. 31, 2018				$ 51,577	$ 911,748	$ 795,563	$ (45,305)	$ (11,528)	$ 11,728	$ 1,713,783
Balance (in shares) at Dec. 31, 2018			51,257,824
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income						126,179				126,179
Other comprehensive income (loss), net of tax							47,775			47,775
Cash dividends declared:
Common						(60,488)				(60,488)
Common stock activity under employee stock ownership plans				266	2,246					2,512
Common stock activity under employee stock ownership plans (in shares)			266,127
Stock-based compensation					3,998					3,998
Distribution of stock under deferred compensation arrangements					1,064			830	(1,894)	0
Distribution of stock under deferred compensation arrangements (in shares)			32,431
Treasury stock issued to benefit plans, net					2,626			3,823	213	6,662
Treasury stock issued to benefit plans, net (in shares)			103,672
Balance at Sep. 30, 2019				51,843	921,682	861,254	2,470	(6,875)	10,047	1,840,421
Balance (in shares) at Sep. 30, 2019			51,660,054
Balance at Jun. 30, 2019				51,806	917,855	843,288	(4,621)	(8,797)	9,979	1,809,510
Balance (in shares) at Jun. 30, 2019			51,570,608
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income						39,218				39,218
Other comprehensive income (loss), net of tax							7,091			7,091
Cash dividends declared:
Common						(21,252)				(21,252)
Common stock activity under employee stock ownership plans				37	1,254					1,291
Common stock activity under employee stock ownership plans (in shares)			37,542
Stock-based compensation					1,241					1,241
Treasury stock issued to benefit plans, net					1,332			1,922	68	3,322
Treasury stock issued to benefit plans, net (in shares)			51,904
Balance at Sep. 30, 2019				51,843	921,682	861,254	2,470	(6,875)	10,047	1,840,421
Balance (in shares) at Sep. 30, 2019			51,660,054
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						118,191				118,191
Other comprehensive income (loss), net of tax							94,188			94,188
Cash dividends declared:
Common						(65,909)				(65,909)
Common stock activity under employee stock ownership plans				360	13,781					14,141
Common stock activity under employee stock ownership plans (in shares)			359,934
Stock-based compensation					4,648					4,648
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			(157)	204	85
Treasury stock issued to benefit plans, net (in shares)			(2,020)
Balance (Topic ASC 326) at Sep. 30, 2020	$ 1,140	$ 1,140
Balance at Sep. 30, 2020				53,698	1,021,798	936,273	83,962	(6,131)	9,060	2,098,660
Balance (in shares) at Sep. 30, 2020			53,537,593
Balance at Jun. 30, 2020				53,672	1,019,291	916,002	90,031	(6,066)	8,995	2,081,925
Balance (in shares) at Jun. 30, 2020			53,514,216
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income						42,809				42,809
Other comprehensive income (loss), net of tax							(6,069)			(6,069)
Cash dividends declared:
Common						(22,538)				(22,538)
Common stock activity under employee stock ownership plans				26	1,092					1,118
Common stock activity under employee stock ownership plans (in shares)			24,584
Stock-based compensation					1,415					1,415
Treasury stock issued to benefit plans, net								(65)	65	0
Treasury stock issued to benefit plans, net (in shares)			(1,207)
Balance (Topic ASC 326) at Sep. 30, 2020	$ 1,140	$ 1,140
Balance at Sep. 30, 2020				$ 53,698	$ 1,021,798	$ 936,273	$ 83,962	$ (6,131)	$ 9,060	$ 2,098,660
Balance (in shares) at Sep. 30, 2020			53,537,593

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Cash dividends declared:
Dividends declared per common share (in dollars per share)	$ 0.42	$ 0.41	$ 1.24	$ 1.17

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities:
Net income	$ 118,191	$ 126,179
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	11,946	11,781
Amortization of intangible assets	10,772	11,994
Net accretion on securities, loans and borrowings	(7,954)	(4,545)
Stock-based compensation	4,648	3,998
Provision for credit losses	17,313	5,573
Amortization of mortgage servicing rights	266	285
Gain on sale of investment securities, net	0	(4,882)
Unrealized loss (gain) on equity securities	30	(28)
Income from bank-owned life insurance policies	(1,398)	(1,215)
Net gain on sale of loans and other assets	(1,633)	(2)
Change in other assets and other liabilities	(26,944)	(20,152)
Net cash provided by operating activities	125,237	128,986
Investing activities:
Proceeds from sales of available-for-sale investment securities	0	590,179
Proceeds from maturities, calls, and paydowns of available-for-sale investment securities	219,503	153,785
Proceeds from maturities and redemptions of equity and other investment securities	436	3,258
Purchases of available-for-sale investment securities	(91,381)	(86,073)
Purchases of equity and other securities	(3,064)	(144)
Net increase in loans	(228,235)	(100,020)
Cash received (paid) for acquisitions, net of cash acquired of $55,973 and $90,381, respectively	34,360	(4,653)
Settlement of bank-owned life insurance policies	0	1,597
Purchases of premises and equipment, net	(8,727)	(5,025)
Real estate tax credit investments	(1,071)	(1,342)
Net cash (used in) provided by investing activities	(78,179)	551,562
Financing activities:
Net increase in deposits	1,609,349	277,833
Net increase (decrease) in borrowings	28,690	(80,502)
Payments on subordinated debt held by unconsolidated subsidiary trusts	(2,062)	(22,681)
Issuance of common stock	14,141	2,512
Purchases of treasury stock	(204)	(213)
Sales of treasury stock	85	6,662
Increase in deferred compensation arrangements	204	213
Cash dividends paid	(64,593)	(59,014)
Withholding taxes paid on share-based compensation	(1,177)	(3,150)
Net cash provided by financing activities	1,584,433	121,660
Change in cash and cash equivalents	1,631,491	802,208
Cash and cash equivalents at beginning of period	205,030	211,834
Cash and cash equivalents at end of period	1,836,521	1,014,042
Supplemental disclosures of cash flow information:
Cash paid for interest	16,927	18,455
Cash paid for income taxes	28,705	34,150
Supplemental disclosures of noncash financing and investing activities:
Dividends declared and unpaid	22,658	21,282
Transfers from loans to other real estate	1,192	1,833
Acquisitions:
Common stock issued	76,942	0
Fair value of assets acquired, excluding acquired cash and intangibles	547,623	548,856
Fair value of liabilities assumed	$ 529,441	$ 589,396

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Net Cash Provided by (Used in) Investing Activities [Abstract]
Cash acquired from acquisition	$ 55,973	$ 90,381

BASIS OF PRESENTATION

BASIS OF PRESENTATION	9 Months Ended
	Sep. 30, 2020
BASIS OF PRESENTATION
BASIS OF PRESENTATION	NOTE A: BASIS OF PRESENTATION The interim financial data as of and for the three and nine months ended September 30, 2020 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”). 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.

ACQUISITIONS

ACQUISITIONS	9 Months Ended
	Sep. 30, 2020
ACQUISITIONS
ACQUISITIONS	NOTE B: ACQUISITIONS 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 currently operates. In connection with the merger, the Company added 11 full-service offices to its branch service network and acquired $607.7 million of assets, including $339.5 million of loans and $180.5 million of investment securities, as well as $516.3 million of deposits. Goodwill of $20.3 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 $3.8 million and $4.5 million, and direct expenses, which may not include certain shared expenses, of approximately $ 1.1 million and $1.4 million from Steuben were included in the consolidated income statement for three and nine months ended September 30, 2020, respectively. The Company incurred certain one-time, transaction-related costs in 2020 in connection with the Steuben acquisition. On September 18, 2019, the Company, through its subsidiary, Community Investment Services, Inc. (“CISI”), completed its acquisition of certain assets of a practice engaged in the financial services business headquartered in Syracuse, New York. The Company paid $0.5 million in cash to acquire a customer list, and recorded a $0.5 million customer list intangible asset in conjunction with the acquisition. The effects of the acquired assets have been included in the consolidated financial statements since that date. On July 12, 2019, the Company completed its merger with Kinderhook Bank Corp. (“Kinderhook”), parent company of The National Union Bank of Kinderhook, headquartered in Kinderhook, New York, for $93.4 million in cash. The merger added 11 branch locations across a five county area in the Capital District of Upstate New York. The merger resulted in the acquisition of $642.8 million of assets, including $479.9 million of loans and $39.8 million of investment securities, as well as $568.2 million of deposits. Goodwill of $40.0 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, of approximately $3.8 million, and direct expenses, which may not include certain shared expenses, of approximately $2.2 million from Kinderhook were included in the consolidated income statement for the three months ended September 30, 2020. Revenues, excluding interest income on acquired investments, of approximately $12.7 million, and direct expenses, which may not include certain shared expenses, of approximately $5.8 million from Kinderhook were included in the consolidated income statement for the nine months ended September 30, 2020. On January 2, 2019, the Company, through its subsidiary, CISI, completed its acquisition of certain assets of Wealth Resources Network, Inc. (“Wealth Resources”), a financial services business headquartered in Liverpool, New York. The Company paid $1.2 million in cash to acquire a customer list from Wealth Resources, and recorded a $1.2 million customer list intangible asset in conjunction with the acquisition. The effects of the acquired assets have been included in the consolidated financial statements since that date. 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. During the first quarter of 2020, the carrying amount of other liabilities associated with the Kinderhook acquisition decreased by $0.3 million as a result of an adjustment to accrued income taxes and deferred income taxes. Goodwill associated with the Kinderhook acquisition decreased $0.3 million as a result of this adjustment. During the third quarter of 2020, associated with the Steuben acquisition, the carrying amount of loans decreased by $0.2 million, premises and equipment decreased by $0.5 million, other assets decreased by $1.7 million, and accrued interest and other liabilities decreased by $1.3 million as a result of updated information not available at the time of acquisition. Goodwill associated with the Steuben acquisition increased $1.1 million as a result of these adjustments. The above referenced acquisitions generally expanded the Company’s geographical presence in New York 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: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ 2019 (000s omitted) Steuben Kinderhook Other (1) Total Consideration paid : ​ ​ ​ ​ Cash ​ $ 21,613 ​ $ 93,384 ​ $ 1,650 ​ $ 95,034 Community Bank System, Inc. common stock ​ 76,942 ​ 0 ​ 0 ​ 0 Total net consideration paid ​ 98,555 ​ 93,384 ​ 1,650 ​ 95,034 Recognized amounts of identifiable assets acquired and liabilities assumed: ​ ​ ​ ​ Cash and cash equivalents ​ 55,973 ​ 90,381 ​ 0 ​ 90,381 Investment securities ​ 180,497 ​ 39,770 ​ 0 ​ 39,770 Loans, net of allowance for credit losses on PCD loans (2) ​ 339,017 ​ 479,877 ​ 0 ​ 479,877 Premises and equipment, net ​ 7,764 ​ 13,970 ​ 0 ​ 13,970 Accrued interest and fees receivable ​ 2,712 ​ 1,130 ​ 0 ​ 1,130 Other assets ​ 17,633 ​ 14,109 ​ 0 ​ 14,109 Core deposit intangibles ​ 2,928 ​ 3,573 ​ 0 ​ 3,573 Other intangibles ​ 1,196 ​ 0 ​ 1,650 ​ 1,650 Deposits ​ (516,274) ​ (568,161) ​ 0 ​ (568,161) Other liabilities ​ (5,105) ​ (2,922) ​ 0 ​ (2,922) Other Federal Home Loan Bank borrowings ​ (6,000) ​ (2,420) ​ 0 ​ (2,420) Subordinated notes payable ​ 0 ​ (13,831) ​ 0 ​ (13,831) Subordinated debt held by unconsolidated subsidiary trusts ​ (2,062) ​ (2,062) ​ 0 ​ (2,062) Total identifiable assets, net ​ 78,279 ​ 53,414 ​ 1,650 ​ 55,064 Goodwill ​ $ 20,276 ​ $ 39,970 ​ $ 0 ​ $ 39,970 (1) Includes amounts related to both acquisitions completed by CISI in 2019. (2) Acquisition-related allowance for credit losses on purchased credit deteriorated (“PCD”) loans applicable beginning in 2020. Under ASC 310-30, acquired loans that have evidence of deterioration in credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all contractually required payments were aggregated by comparable characteristics and recorded at fair value without a carryover of the related allowance for credit losses. Cash flows for each loan were determined using an estimate of credit losses and rate of prepayments. Projected monthly cash flows were then discounted to present value using a market-based discount rate. The excess of the undiscounted expected cash flows over the estimated fair value is referred to as the “accretable yield” and is recognized into interest income over the remaining lives of the acquired loans. On January 1, 2020, the Company adopted ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) The Company has acquired loans from Steuben for which there was evidence of a more-than-insignificant deterioration in credit quality since origination. 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 ​ $ 24,415 Allowance for credit losses at acquisition ​ (524) Non-credit discount at acquisition ​ (115) Fair value of PCD loans at acquisition ​ $ 23,776 ​ 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 ​ $ 416,230 Contractual cash flows not expected to be collected ​ (3,131) Expected cash flows at acquisition ​ 413,099 Interest component of expected cash flows ​ (97,858) Fair value of non-PCD loans at acquisition ​ $ 315,241 ​ The following is a summary of the loans acquired from Kinderhook at the date of acquisition: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Acquired Acquired Total ​ Impaired Non-impaired Acquired (000s omitted) Loans Loans Loans Contractually required principal and interest at acquisition ​ $ 13,350 ​ $ 636,384 ​ $ 649,734 Contractual cash flows not expected to be collected ​ (4,176) ​ (5,472) ​ (9,648) Expected cash flows at acquisition ​ 9,174 ​ 630,912 ​ 640,086 Interest component of expected cash flows ​ (551) ​ (159,658) ​ (160,209) Fair value of acquired loans ​ $ 8,623 ​ $ 471,254 ​ $ 479,877 ​ 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 fair value of subordinated notes payable was estimated using discounted cash flows and interest rates being offered on similar securities. Subordinated notes payable assumed with the Kinderhook acquisition included $3.0 million of subordinated notes with a fixed interest rate of 6.0% maturing in February 2028 November 2025 The core deposit intangibles and other intangibles related to the Steuben acquisition, both acquisitions completed by CISI in 2019 Steuben and Direct costs related to the acquisitions were expensed as incurred. Merger and acquisition integration-related expenses amount to $0.8 million and $4.5 million during the three and nine months ended September 30, 2020, respectively, and have been separately stated in the consolidated statements of income. Merger and acquisition integration-related expenses amount to $6.1 million and $7.8 million during the three and nine months ended September 30, 2019, 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 nine months ended September 30, 2020 and September 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 $0.8 million and $4.4 million for the three and nine months ended September 30, 2020, respectively, related to Steuben were included in the pro forma information as if they were incurred in the first quarter of 2019. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pro Forma (Unaudited) ​ Pro Forma (Unaudited) ​ Three Months Ended Nine Months Ended (000’s omitted) September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 Total revenue, net of interest expense ​ $ 152,634 ​ $ 154,221 ​ $ 456,740 ​ $ 457,399 Net income ​ 43,472 ​ 40,695 ​ 124,338 ​ 126,874 ​

ACCOUNTING POLICIES

ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2020
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 65 through 75 of the Annual Report on Form 10-K for the year ended December 31, 2019 filed with the Securities and Exchange Commission (“SEC”) on March 2, 2020 except as noted below. The accounting policies of the Company effective for the comparative periods presented prior to the adoption of ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) 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 September 30, 2020 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 quarter ended September 30, 2020, 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. Investment Securities The Company can classify its investments in debt securities as held-to-maturity, available-for-sale, or trading. Held-to-maturity securities are those for which the Company has the positive intent and ability to hold until maturity, and are reported at cost, which is adjusted for amortization of premiums and accretion of discounts. The Company did not use the held-to-maturity classification in 2019 or through September 30, 2020. Available-for-sale debt securities are reported at fair value with net unrealized gains and losses reflected as a separate component of shareholders’ equity, net of applicable income taxes. None of the Company’s investment securities have been classified as trading securities at September 30, 2020 or December 31, 2019. Equity securities with a readily determinable fair value are reported at fair value with net unrealized gains and losses recognized in the consolidated statements of income. Certain equity securities that do not have a readily determinable fair value are stated at cost, adjusted for observable price changes in orderly transactions for identical or similar investments of the same issuer. These securities include restricted stock of the Federal Reserve Bank of New York (“Federal Reserve”) and the Federal Home Loan Bank of New York and the Federal Home Loan Bank of Boston (collectively referred to as “FHLB”), as well as other equity securities. Fair values for investment securities are based upon quoted market prices, where available. If quoted market prices are not available, fair values are based upon quoted market prices of comparable instruments, or a discounted cash flow model using market estimates of interest rates and volatility. Allowance for Credit Losses – Debt Securities For held-to-maturity debt securities, the Company measures expected credit losses on a collective basis by major security type. The estimates of expected credit losses considers historical credit loss information that is adjusted for current conditions and reasonable and supportable forecasts. Accrued interest receivable on held-to-maturity securities is excluded from the estimates of credit losses. For available-for-sale debt securities in an unrealized loss position, the Company first assesses whether it intends to sell, or it more likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through income. For available-for-sale debt securities that do not meet the aforementioned criteria, the Company evaluates whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, management considers the security structure, recent security collateral performance metrics, if applicable, external credit ratings, failure of the issuer to make scheduled interest or principal payments, judgment about and expectations of future performance, and relevant independent industry research, analysis, and forecasts. The severity of the impairment and the length of time the security has been impaired is also considered in the assessment. This assessment involves a high degree of subjectivity and judgment that is based on the information available to management at a point in time. If this assessment indicates that a credit loss exists, the present value of the cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of the cash flows expected to be collected from the security is less than the amortized cost basis of the security, a credit loss exists and an allowance for credit losses is recorded, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income. Changes in the allowance for credit losses are recorded as provision for (or reversal of) credit losses. Losses are charged against the allowance when management believes the uncollectibility of an available-for-sale security is confirmed or when either of the criteria regarding intent or requirement to sell is met. Accrued interest receivable on available-for-sale debt securities, included in accrued interest and fees receivable on the consolidated statements of condition, totaled $14.2 million at September 30, 2020 and is excluded from the estimate of credit losses. Loans Loans that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at amortized cost, net of allowance for credit losses. Amortized cost is the principal balance outstanding, net of purchase premiums and discounts, and deferred loan fees and costs. Mortgage loans held for sale are carried at fair value and are included in loans held for sale on the consolidated statements of condition. Fair values for variable rate loans that reprice frequently are based on carrying values. Fair values for fixed rate loans are estimated using discounted cash flows and interest rates currently being offered for loans with similar terms to borrowers of similar credit quality. The carrying amount of accrued interest approximates its fair value. Interest on loans is accrued and credited to operations based upon the principal amount outstanding. Nonrefundable loan fees and related direct costs are deferred and included in the loan balances where they are amortized over the life of the loan as an adjustment to loan yield using the effective yield method. Premiums and discounts on purchased loans are amortized using the effective yield method over the life of the loans. Accrued interest receivable on loans, included in accrued interest and fees receivable on the consolidated statements of condition, totaled $23.8 million at September 30, 2020 and is excluded from the estimate of credit losses and amortized cost basis of loans. An allowance for credit losses is not measured for accrued interest receivable on loans as the Company writes off the uncollectible accrued interest balance in a timely manner. The Company places a loan on nonaccrual status when the loan becomes 90 days past due (or sooner, if management concludes collection is doubtful), except when, in the opinion of management, it is well-collateralized and in the process of collection. A loan may be placed on nonaccrual status earlier than 90 days past due if there is deterioration in the financial position of the borrower or if other conditions of the loan so warrant. When a loan is placed on nonaccrual status, uncollected accrued interest is reversed against interest income and the amortization of nonrefundable loan fees and related direct costs is discontinued. Interest income during the period the loan is on nonaccrual status is recorded on a cash basis after recovery of principal is reasonably assured. Nonaccrual loans are returned to accrual status when management determines that the borrower’s performance has improved and that both principal and interest are collectible. This generally requires a sustained period of timely principal and interest payments and a well-documented credit evaluation of the borrower’s financial condition. The Company’s charge-off policy by loan type is as follows: ● Business lending loans are generally charged-off to the extent outstanding principal exceeds the fair value of estimated proceeds from collection efforts, including liquidation of collateral. The charge-off is recognized when the loss becomes reasonably quantifiable. ● Consumer installment loans are generally charged-off to the extent outstanding principal exceeds the fair value of collateral, and are recognized by the end of the month in which the loan becomes 90 days past due. ● Consumer mortgage and home equity loans are generally charged-off to the extent outstanding principal exceeds the fair value of the property, less estimated costs to sell, and are recognized when the loan becomes 180 days past due. Allowance for Credit Losses – Loans The allowance for credit losses is a valuation account that is netted against the loans’ amortized cost basis to present the net amount expected to be collected on the loans. Loans are charged off against the allowance when management believes the uncollectibility of a loan balance is confirmed. Management estimates the allowance balance using relevant available information, from internal and external sources, relating to past events, current conditions, and reasonable and supportable forecasts. Historical credit loss experience provides the basis for the estimation of expected credit losses. Adjustments are made for differences in current loan-specific risk characteristics such as differences in underwriting standards, portfolio mix, acquired loans, delinquency level, risk ratings or term of loans as well as changes in macroeconomic conditions, such as changes in unemployment rates, property values such as home prices, commercial real estate prices and automobile prices, gross domestic product, recession probability, and other relevant factors. The segments of the Company’s loan portfolio are disaggregated into the following classes that allow management to monitor risk and performance: ● Business lending is comprised of general purpose commercial and industrial loans including, but not limited to agricultural-related and dealer floor plans, loans to not-for-profit enterprises, as well as mortgages on commercial property and Paycheck Protection Program (“PPP”) loans. The portfolio segment is further broken into portfolio classes based on risks associated with the collateral supporting the loans. Each class of business lending can also have different payment structures. Business lending loans are generally higher dollar loans and a large portion are risk rated at least annually. ● Consumer mortgages consist primarily of fixed rate residential instruments, typically 10 – 30 years in contractual term, secured by first liens on real property. FICO scores are used to monitor higher risks related to this type of lending with FICO AB referring to higher tiered loans with FICO scores greater than or equal to 720 as compared to FICO CDE with lower FICO scores less than 720 and potentially higher risk. ● Consumer indirect consists primarily of installment loans originated through selected dealerships and are generally secured by automobiles, marine and other recreational vehicles. Collateral securing the loans was used to further disaggregate this portfolio as charge-offs can vary depending on the purpose of the loan. Non-auto loans often have longer terms, and generally have higher risk due to declines in collateral value given the nature of the property. ● Consumer direct consists of all other loans to consumers such as personal installment loans and check credit lines of credit. ● Home equity products are installment loans or lines of credit most often secured by a first or second lien position on residential real estate with terms up to 30 years . The allowance for credit losses is measured on a collective (pool) basis when similar risk characteristics exist, including collateral type, credit ratings/scores, size, duration, interest rate structure, industry, geography, origination vintage, and payment structure. The Company has identified the following portfolio segments and classes and measures the allowance for credit losses using the following methods: ​ ​ ​ ​ ​ ​ ​ Loan Portfolio Segment Loan Portfolio Class Allowance for Credit Losses Methodology Business lending ​ Commercial real estate multi family ​ Cumulative loss rate ​ Business lending ​ Commercial real estate non-owner occupied ​ Cumulative loss rate ​ Business lending ​ Commercial real estate owner occupied ​ Cumulative loss rate ​ Business lending ​ Commercial and industrial loans ​ Vintage loss rate ​ Business lending ​ Commercial and industrial lines of credit ​ Line loss ​ Business lending ​ Municipal ​ Cumulative loss rate ​ Business lending ​ Other business ​ Cumulative loss rate ​ Business lending ​ Paycheck Protection Program ​ Cumulative loss rate ​ Consumer mortgage ​ Consumer mortgage FICO AB ​ Cumulative loss rate ​ Consumer mortgage ​ Consumer mortgage FICO CDE ​ Cumulative loss rate ​ Consumer indirect ​ Indirect new auto ​ Vintage loss rate ​ Consumer indirect ​ Indirect used auto ​ Vintage loss rate ​ Consumer indirect ​ Indirect non-auto ​ Vintage loss rate ​ Consumer direct ​ Consumer check credit ​ Line loss ​ Consumer direct ​ Consumer direct ​ Vintage loss rate ​ Home equity ​ Home equity fixed rate ​ Vintage loss rate ​ Home equity ​ Home equity lines of credit ​ Line loss ​ ​ The cumulative loss rate method uses historical loss data applied against multiple pools of loans and uses a quantitatively based management overlay in order to capture the risk for a loan’s entire expected life. These loss rates are then applied to current balances to achieve a required reserve before qualitative adjustments. The line loss method calculates the quantitative required reserve for lines of credit. This method contains several different underlying calculations including average annual loss rate, pay-down rate, cumulative loss, average draw percentage, and undrawn liability reserve. The vintage loss rate method calculates annual loss rates by origination year. The results of this model are then applied to outstanding balances, which correspond to the origination period for each annual loss rate. In addition to the risk characteristics noted above, management considers the portion of acquired loans to the overall segment balance, as well as current delinquency and charge-off trends compared to historical time periods. Loans that do not share risk characteristics are evaluated on an individual basis. Loans evaluated individually are not also included in the collective evaluation. When management determines that foreclosure is probable or when the borrower is experiencing financial difficulty at the reporting date and repayment is expected to be provided substantially through the operation or sale of the collateral, expected credit losses are based on the fair value of the collateral at the reporting date, adjusted for selling costs as appropriate. Expected credit losses are estimated over the contractual term of the loans and adjusted for expected prepayments when appropriate. The contractual term excludes expected extensions, renewals, and modifications unless management has a reasonable expectation at the reporting date that a troubled debt restructuring will be executed with an individual borrower or the extension or renewal options are included in the original or modified contract at the reporting date and are not unconditionally cancellable by the Company. Certain business lending, consumer direct, and home equity loans do not have stated maturities. In determining the estimated life of these loans, management first estimates the future cash flows expected to be received and then applies those expected future cash flows to the balance. Expected credit losses for lines of credit with no stated maturity are determined by estimating the amount and timing of all principal payments expected to be received after the reporting period and allocating those principal payments between the balance outstanding as of the reporting period and the balance of future receivables expected to be originated through subsequent usage of the unconditionally cancellable loan commitment associated with the account until the expected payments have been fully allocated. An additional allowance for credit loss is recorded for the excess of the balance outstanding as of the reporting period over the expected principal payments allocated to that balance. Troubled Debt Restructuring A loan for which the terms have been modified resulting in a concession, and for which the borrower is experiencing financial difficulties, is considered to be a troubled debt restructuring (“TDR”). The allowance for credit loss on a TDR is measured using the same method as all other loans, except when the value of a concession cannot be measured using a method other than the discounted cash flow method. When the value of a concession is measured using the discounted cash flow method, the allowance for credit loss is determined by discounting the expected future cash flows at the original interest rate of the loan. Refer to Note E: Loans for the Company’s policy regarding COVID-19 related financial hardship payment deferrals. Allowance for Credit Losses – Off-balance-sheet credit exposures The Company estimates expected credit losses over the contractual period in which the Company is exposed to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by the Company. There are unfunded commitments for lines of credit within each of the Company’s loan portfolio segments except consumer indirect. The allowance for credit losses on off-balance-sheet credit exposures is adjusted as a provision for (or reversal of) credit losses. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over its estimated life. Management estimates the allowance balance using relevant available information, from internal and external sources, relating to past events, current conditions, and reasonable and supportable forecasts. Historical credit loss experience provides the basis for the estimation of expected credit losses. Adjustments to historical loss information are made for differences in current loan-specific risk characteristics that are the same as the adjustments considered for the loan portfolio. Purchased Credit Deteriorated (PCD) Loans The Company has purchased loans, some of which have experienced a more-than-insignificant credit deterioration since origination. The Company’s policy for reviewing what meets the threshold of the definition of a more-than-insignificant credit deterioration includes loans that are delinquent more than 30 days, loans that have historical delinquencies of more than 30 days at least three times since origination, risk rating downgrades since origination, loans with multiple payment deferrals, loans considered to be troubled debt restructurings, specifically impaired loans or loans with certain documented policy exceptions, further refined based on loan-specific facts and circumstances. 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. 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 September 30, 2020, $28.5 million of accounts receivable, including $8.3 million of unbilled fee revenue, and $2.0 million of unearned revenue was recorded in the consolidated statements of condition. As of December 31, 2019, $26.8 million of accounts receivable, including $7.5 million of unbilled fee revenue, and $1.8 million of unearned revenue was recorded in the consolidated statements of condition. Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) The Company adopted ASC 326 on January 1, 2020 using a modified retrospective approach for all financial assets measured at amortized cost and off-balance-sheet credit exposures. Results for reporting periods beginning after January 1, 2020 are presented under ASC 326 while prior period amounts continue to be reported in accordance with previously applicable GAAP. The Company recorded a net cumulative-effect adjustment that increased retained earnings by $1.1 million. This adjustment was a result of a $3.1 million adjustment to loans, partially offset by a $1.4 million increase in the allowance for credit losses and a $0.6 million increase in other liabilities related to the allowance for off-balance-sheet credit exposures and deferred taxes. The adoption of ASU No. 2016-13 did not result in a material allowance for credit losses on the Company’s available-for-sale debt securities or its other instruments carried at amortized cost. The Company’s regulators permit financial institutions to “phase-in” the impact of CECL on its regulatory capital ratios for up to 5 years with transitional relief of incremental capital requirements. The Company did not utilize the phased-in approach and recorded the entire cumulative-effect adjustment against its regulatory capital at the time of adoption. The Company adopted ASC 326 using the prospective transition approach for financial assets purchased with credit deterioration (“PCD”) that were previously classified as purchased credit impaired (“PCI”) and accounted for under ASC 310-30. In accordance with this standard, management did not reassess whether PCI assets met the criteria of PCD assets as of the date of adoption. On January 1, 2020, the amortized cost basis of the PCD assets were adjusted to reflect the addition of $3.1 million of allowance for credit losses. The remaining noncredit discount (based on the adjusted amortized cost basis) will be accreted into interest income at the effective interest rate beginning on January 1, 2020. In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350) In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurements (Topic 820) New 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) In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (Topic 740) 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	9 Months Ended
	Sep. 30, 2020
INVESTMENT SECURITIES
INVESTMENT SECURITIES	NOTE D: INVESTMENT SECURITIES The amortized cost and estimated fair value of investment securities as of September 30, 2020 and December 31, 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ December 31, 2019 ​ ​ ​ ​ ​ 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 ​ $ 2,034,512 ​ $ 114,658 ​ $ 0 ​ $ 2,149,170 ​ $ 2,030,060 ​ $ 21,674 ​ $ 7,975 ​ $ 2,043,759 Obligations of state and political subdivisions ​ 470,518 ​ 22,978 ​ 0 ​ 493,496 ​ 497,852 ​ 14,382 ​ 26 ​ 512,208 Government agency mortgage-backed securities ​ 508,738 ​ 15,514 ​ 278 ​ 523,974 ​ 428,491 ​ 5,478 ​ 1,107 ​ 432,862 Corporate debt securities ​ 4,504 ​ 98 ​ 0 ​ 4,602 ​ 2,527 ​ 1 ​ 0 ​ 2,528 Government agency collateralized mortgage obligations ​ 50,134 ​ 1,354 ​ 8 ​ 51,480 ​ 52,621 ​ 482 ​ 32 ​ 53,071 Total available-for-sale portfolio ​ $ 3,068,406 ​ $ 154,602 ​ $ 286 ​ $ 3,222,722 ​ $ 3,011,551 ​ $ 42,017 ​ $ 9,140 ​ $ 3,044,428 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity and other Securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity securities, at fair value ​ $ 251 ​ $ 192 ​ $ 20 ​ $ 423 ​ $ 251 ​ $ 200 ​ $ 0 ​ $ 451 Federal Home Loan Bank common stock ​ 7,545 ​ 0 ​ 0 ​ 7,545 ​ 7,246 ​ 0 ​ 0 ​ 7,246 Federal Reserve Bank common stock ​ 33,916 ​ 0 ​ 0 ​ 33,916 ​ 30,922 ​ 0 ​ 0 ​ 30,922 Other equity securities, at adjusted cost ​ 4,707 ​ 750 ​ 0 ​ 5,457 ​ 4,546 ​ 750 ​ 0 ​ 5,296 Total equity and other securities ​ $ 46,419 ​ $ 942 ​ $ 20 ​ $ 47,341 ​ $ 42,965 ​ $ 950 ​ $ 0 ​ $ 43,915 ​ A summary of investment securities that have been in a continuous unrealized loss position is as follows: As of September 30, 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 1 ​ $ 1,010 ​ $ 0 0 ​ $ 0 ​ $ 0 1 ​ $ 1,010 ​ $ 0 Obligations of state and political subdivisions 1 ​ 196 ​ 0 0 ​ 0 ​ 0 1 ​ 196 ​ 0 Government agency mortgage-backed securities 91 ​ 62,318 ​ 278 2 ​ 14 ​ 0 93 ​ 62,332 ​ 278 Government agency collateralized mortgage obligations 14 ​ 4,244 ​ 8 1 ​ 0 ​ 0 15 ​ 4,244 ​ 8 Total available-for-sale investment portfolio 107 ​ $ 67,768 ​ $ 286 3 ​ $ 14 ​ $ 0 110 ​ $ 67,782 ​ $ 286 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity and other Securities: ​ ​ ​ ​ ​ ​ Equity securities, at fair value 1 ​ $ 81 ​ $ 20 0 ​ $ 0 ​ $ 0 1 ​ $ 81 ​ $ 20 Total equity and other securities 1 ​ $ 81 ​ $ 20 0 ​ $ 0 ​ $ 0 1 ​ $ 81 ​ $ 20 ​ As of December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 12 ​ $ 592,678 ​ $ 7,970 5 ​ $ 25,998 ​ $ 5 17 ​ $ 618,676 ​ $ 7,975 Obligations of state and political subdivisions 21 ​ 22,716 ​ 26 0 ​ 0 ​ 0 21 ​ 22,716 ​ 26 Government agency mortgage-backed securities 50 ​ 89,237 ​ 341 52 ​ 52,975 ​ 766 102 ​ 142,212 ​ 1,107 Government agency collateralized mortgage obligations 5 ​ 5,971 ​ 14 5 ​ 4,405 ​ 18 10 ​ 10,376 ​ 32 Total available-for-sale investment portfolio 88 ​ $ 710,602 ​ $ 8,351 62 ​ $ 83,378 ​ $ 789 150 ​ $ 793,980 ​ $ 9,140 ​ 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 September 30, 2020 represents credit losses and no unrealized losses have been recognized in the provision for credit losses. Accordingly, there is no allowance for credit losses on the Company’s available-for-sale portfolio as of September 30, 2020. As of December 31, 2019, management did not believe any individual unrealized loss represents other-than-temporary impairment. The amortized cost and estimated fair value of debt securities at September 30, 2020, 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 ​ $ 760,019 ​ $ 765,009 Due after one through five years ​ 802,750 ​ 843,487 Due after five years through ten years ​ 461,012 ​ 503,778 Due after ten years ​ 485,753 ​ 534,994 Subtotal ​ 2,509,534 ​ 2,647,268 Government agency mortgage-backed securities ​ 508,738 ​ 523,974 Government agency collateralized mortgage obligations ​ 50,134 ​ 51,480 Total ​ $ 3,068,406 ​ $ 3,222,722 ​ As of September 30, 2020, $295.5 million of U.S. Treasury securities were pledged as collateral for securities sold under agreement to repurchase. All securities sold under agreement to repurchase as of September 30, 2020 have an overnight and continuous maturity. During the nine months ended September 30, 2019, the Company sold $590.2 million of U.S. Treasury and agency securities, recognizing $5.0 million of gross realized gains and $0.1 million of gross realized losses.

LOANS

LOANS	9 Months Ended
	Sep. 30, 2020
LOANS
LOANS	NOTE E: LOANS The segments of the Company’s loan portfolio are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, (000's omitted) 2020 2019 Business lending ​ $ 3,433,565 ​ $ 2,775,876 Consumer mortgage ​ 2,410,249 ​ 2,430,902 Consumer indirect ​ 1,039,925 ​ 1,113,062 Consumer direct ​ 161,639 ​ 184,378 Home equity ​ 413,265 ​ 386,325 Gross loans, including deferred origination costs ​ 7,458,643 ​ 6,890,543 Allowance for credit losses ​ (64,962) ​ (49,911) Loans, net of allowance for credit losses ​ $ 7,393,681 ​ $ 6,840,632 ​ The following table presents the aging of the amortized cost basis of the Company’s past due loans, including purchased credit deteriorated (“PCD”) loans, by segment as of September 30, 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 ​ $ 3,151 ​ $ 39 ​ $ 11,750 ​ $ 14,940 ​ $ 3,418,625 ​ $ 3,433,565 Consumer mortgage ​ 11,449 ​ 3,182 ​ 14,821 ​ 29,452 ​ 2,380,797 ​ 2,410,249 Consumer indirect ​ 8,711 ​ 12 ​ 1 ​ 8,724 ​ 1,031,201 ​ 1,039,925 Consumer direct ​ 1,060 ​ 34 ​ 3 ​ 1,097 ​ 160,542 ​ 161,639 Home equity ​ 2,179 ​ 220 ​ 2,181 ​ 4,580 ​ 408,685 ​ 413,265 Total ​ $ 26,550 ​ $ 3,487 ​ $ 28,756 ​ $ 58,793 ​ $ 7,399,850 ​ $ 7,458,643 ​ The following is an aged analysis of the Company’s past due loans by segment as of December 31, 2019: Legacy Loans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Current Total Loans Business lending ​ $ 3,936 ​ $ 126 ​ $ 3,840 ​ $ 7,902 ​ $ 1,848,683 ​ $ 1,856,585 Consumer mortgage ​ 10,990 ​ 2,052 ​ 10,131 ​ 23,173 ​ 1,973,543 ​ 1,996,716 Consumer indirect ​ 12,673 ​ 125 ​ 0 ​ 12,798 ​ 1,094,510 ​ 1,107,308 Consumer direct ​ 1,455 ​ 76 ​ 0 ​ 1,531 ​ 174,445 ​ 175,976 Home equity ​ 1,508 ​ 328 ​ 1,444 ​ 3,280 ​ 310,727 ​ 314,007 Total ​ $ 30,562 ​ $ 2,707 ​ $ 15,415 ​ $ 48,684 ​ $ 5,401,908 ​ $ 5,450,592 ​ Acquired Loans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ Acquired ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Impaired (1) Current Total Loans Business lending ​ $ 8,518 ​ $ 2,173 ​ $ 570 ​ $ 11,261 ​ $ 11,797 ​ $ 896,233 ​ $ 919,291 Consumer mortgage ​ 890 ​ 277 ​ 2,386 ​ 3,553 ​ 0 ​ 430,633 ​ 434,186 Consumer indirect ​ 79 ​ 31 ​ 0 ​ 110 ​ 0 ​ 5,644 ​ 5,754 Consumer direct ​ 59 ​ 0 ​ 52 ​ 111 ​ 0 ​ 8,291 ​ 8,402 Home equity ​ 744 ​ 238 ​ 412 ​ 1,394 ​ 0 ​ 70,924 ​ 72,318 Total ​ $ 10,290 ​ $ 2,719 ​ $ 3,420 ​ $ 16,429 ​ $ 11,797 ​ $ 1,411,725 ​ $ 1,439,951 ​ (1) Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performing under ASC 310-30. As a result interest income, through the accretion of the difference between the carrying amount of the loans and the expected cashflows, is being recognized on all acquired impaired loans. The delinquency status for loans on payment deferment due to COVID-19 financial hardship were reported at September 30, 2020 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. No interest income on nonaccrual loans was recognized during the three and nine months ended September 30, 2020. 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 initial COVID-19 related financial hardship payment deferrals were not automatically downgraded into lower credit risk ratings, but 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 September 30, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ September 30, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Business lending: ​ ​ ​ ​ ​ ​ ​ ​ Risk rating ​ ​ ​ ​ ​ ​ ​ ​ Pass ​ $ 783,726 ​ $ 351,036 ​ $ 337,662 ​ $ 243,816 ​ $ 246,551 ​ $ 576,220 ​ $ 483,163 ​ $ 3,022,174 Special mention ​ 14,008 ​ 39,130 ​ 20,714 ​ 19,157 ​ 29,987 ​ 65,627 ​ 53,293 ​ 241,916 Classified ​ 5,942 ​ 2,852 ​ 28,228 ​ 14,084 ​ 14,363 ​ 61,121 ​ 41,996 ​ 168,586 Doubtful ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 ​ 889 ​ 889 Total business lending ​ $ 803,676 ​ $ 393,018 ​ $ 386,604 ​ $ 277,057 ​ $ 290,901 ​ $ 702,968 ​ $ 579,341 ​ $ 3,433,565 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 (000’s omitted) Legacy Acquired Total Pass ​ $ 1,655,280 ​ $ 832,693 ​ $ 2,487,973 Special mention ​ 98,953 ​ 45,324 ​ 144,277 Classified ​ 102,352 ​ 29,477 ​ 131,829 Doubtful ​ 0 ​ 0 ​ 0 Acquired impaired ​ 0 ​ 11,797 ​ 11,797 Total ​ $ 1,856,585 ​ $ 919,291 ​ $ 2,775,876 ​ 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 September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ September 30, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Consumer mortgage: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ FICO AB ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 182,675 ​ $ 237,891 ​ $ 176,837 ​ $ 175,605 ​ $ 170,844 ​ $ 664,129 ​ $ 582 ​ $ 1,608,563 Nonperforming ​ 0 ​ 0 ​ 329 ​ 444 ​ 311 ​ 3,556 ​ 0 ​ 4,640 Total FICO AB ​ 182,675 ​ 237,891 ​ 177,166 ​ 176,049 ​ 171,155 ​ 667,685 ​ 582 ​ 1,613,203 FICO CDE ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ 75,419 ​ 106,072 ​ 84,280 ​ 79,292 ​ 87,578 ​ 337,097 ​ 13,945 ​ 783,683 Nonperforming ​ 0 ​ 647 ​ 482 ​ 813 ​ 1,530 ​ 9,891 ​ 0 ​ 13,363 Total FICO CDE ​ 75,419 ​ 106,719 ​ 84,762 ​ 80,105 ​ 89,108 ​ 346,988 ​ 13,945 ​ 797,046 Total consumer mortgage ​ $ 258,094 ​ $ 344,610 ​ $ 261,928 ​ $ 256,154 ​ $ 260,263 ​ $ 1,014,673 ​ $ 14,527 ​ $ 2,410,249 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer indirect: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 227,697 ​ $ 338,279 ​ $ 230,246 ​ $ 100,529 ​ $ 73,331 ​ $ 69,830 ​ $ 0 ​ $ 1,039,912 Nonperforming ​ 0 ​ 5 ​ 0 ​ 4 ​ 1 ​ 3 ​ 0 ​ 13 Total consumer indirect ​ $ 227,697 ​ $ 338,284 ​ $ 230,246 ​ $ 100,533 ​ $ 73,332 ​ $ 69,833 ​ 0 ​ $ 1,039,925 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer direct: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 42,905 ​ $ 53,421 ​ $ 32,359 ​ $ 14,773 ​ $ 6,707 ​ $ 4,722 ​ $ 6,715 ​ $ 161,602 Nonperforming ​ 0 ​ 4 ​ 9 ​ 0 ​ 24 ​ 0 ​ 0 ​ 37 Total consumer direct ​ $ 42,905 ​ $ 53,425 ​ $ 32,368 ​ $ 14,773 ​ $ 6,731 ​ $ 4,722 ​ $ 6,715 ​ $ 161,639 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Home equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 40,760 ​ $ 51,240 ​ $ 29,904 ​ $ 25,286 ​ $ 19,964 ​ $ 39,429 ​ $ 204,281 ​ $ 410,864 Nonperforming ​ 0 ​ 0 ​ 82 ​ 110 ​ 212 ​ 481 ​ 1,516 ​ 2,401 Total home equity ​ $ 40,760 ​ $ 51,240 ​ $ 29,986 ​ $ 25,396 ​ $ 20,176 ​ $ 39,910 ​ $ 205,797 ​ $ 413,265 ​ The following table details the balances in all other loan categories at December 31, 2019: Legacy Loans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer Consumer Consumer Home ​ ​ (000’s omitted) Mortgage Indirect Direct Equity Total Performing ​ $ 1,984,533 ​ $ 1,107,183 ​ $ 175,900 ​ $ 312,235 ​ $ 3,579,851 Nonperforming ​ 12,183 ​ 125 ​ 76 ​ 1,772 ​ 14,156 Total ​ $ 1,996,716 ​ $ 1,107,308 ​ $ 175,976 ​ $ 314,007 ​ $ 3,594,007 ​ Acquired Loans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer Consumer Consumer Home ​ ​ (000’s omitted) ​ Mortgage ​ Indirect ​ Direct ​ Equity ​ Total Performing ​ $ 431,523 ​ $ 5,723 ​ $ 8,350 ​ $ 71,668 ​ $ 517,264 Nonperforming ​ 2,663 ​ 31 ​ 52 ​ 650 ​ 3,396 Total ​ $ 434,186 ​ $ 5,754 ​ $ 8,402 ​ $ 72,318 ​ $ 520,660 ​ All loan classes are collectively evaluated for impairment except business lending. A summary of individually evaluated impaired business lending loans as of September 30, 2020 and December 31, 2019 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, (000’s omitted) 2020 2019 Loans with allowance allocation ​ $ 6,842 ​ $ 0 Loans without allowance allocation ​ 1,414 ​ 1,414 Carrying balance ​ 8,256 ​ 1,414 Contractual balance ​ 10,558 ​ 2,944 Specifically allocated allowance ​ 882 ​ 0 ​ The average carrying balance of individually evaluated impaired loans was $8.8 million and $5.1 million for the three months ended September 30, 2020 and September 30, 2019, respectively. The average carrying balance of individually evaluated impaired loans was $4.2 million and $5.4 million for the nine months ended September 30, 2020 and September 30, 2019, respectively. No interest income was recognized on individually evaluated impaired loans for the three or nine months ended September 30, 2020 and September 30, 2019. 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 nine months ended September 30, 2020 and 2019 was immaterial. TDRs that are less than $0.5 million are collectively included in the allowance for credit loss estimate. TDRs that are commercial loans and greater than $0.5 million are individually evaluated for impairment, and if necessary, a specific allocation of the allowance for credit losses is provided. As a result, the determination of the amount of allowance for credit losses related to TDRs is the same as detailed in the critical accounting policies. With respect to the Company’s lending activities, the Company implemented a customer payment deferral program for deferrals up to three months per request during the first nine months of 2020 to assist both consumer and business borrowers that may be experiencing financial hardship due to COVID-19 related challenges. Business lending, consumer direct, and consumer indirect loans in deferment status will continue to accrue interest on the deferred principal during the deferment period unless otherwise classified as nonaccrual. Consumer mortgage and home equity loans will not accrue interest on the deferred payments during the deferment period. Consistent with the Coronavirus Aid, Relief and Economic Security Act (the "CARES Act") and industry regulatory guidance, borrowers that were otherwise current on loan payments that were granted COVID-19 related financial hardship payment deferrals will continue to be reported as current loans throughout the agreed upon deferral period. These payment deferrals were also deemed to be an insignificant borrower concession, and therefore, not classified as TDR loans during the first nine months of 2020. Borrowers that were delinquent in their payments to Community Bank, N.A. (the "Bank") prior to requesting a COVID-19 related financial hardship payment deferral were reviewed on a case by case basis for troubled debt restructure classification and non-performing loan status. Information regarding TDRs as of September 30, 2020 and December 31, 2019 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ December 31, 2019 (000’s omitted) Nonaccrual Accruing Total Nonaccrual Accruing Total ​ # Amount # Amount # Amount # Amount # Amount # Amount Business lending 8 ​ $ 602 3 ​ $ 195 11 ​ $ 797 8 ​ $ 681 3 ​ $ 201 11 ​ $ 882 Consumer mortgage 57 ​ 2,478 47 ​ 2,330 104 ​ 4,808 59 ​ 2,638 47 ​ 1,892 106 ​ 4,530 Consumer indirect 0 ​ 0 85 ​ 935 85 ​ 935 0 ​ 0 84 ​ 941 84 ​ 941 Consumer direct 0 ​ 0 24 ​ 94 24 ​ 94 0 ​ 0 23 ​ 101 23 ​ 101 Home equity 11 ​ 277 13 ​ 272 24 ​ 549 13 ​ 290 11 ​ 238 24 ​ 528 Total 76 ​ $ 3,357 172 ​ $ 3,826 248 ​ $ 7,183 80 ​ $ 3,609 168 ​ $ 3,373 248 ​ $ 6,982 ​ The following table presents information related to loans modified in a TDR during the three months and nine months ended September 30, 2020 and 2019. Of the loans noted in the table below, all consumer mortgage loans for the three months and nine months ended September 30, 2020 and 2019 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 ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ Number of ​ Outstanding ​ Number of ​ Outstanding (000’s omitted) loans modified Balance loans modified Balance Business lending 0 ​ $ 0 1 ​ $ 415 Consumer mortgage 8 ​ 646 8 ​ 464 Consumer indirect 14 ​ 131 10 ​ 116 Consumer direct 1 ​ 2 2 ​ 25 Home equity 2 ​ 56 0 ​ 0 Total 25 ​ $ 835 21 ​ $ 1,020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ Nine Months Ended ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ Number of ​ Outstanding ​ Number of ​ Outstanding (000’s omitted) loans modified Balance loans modified Balance Business lending ​ 0 ​ $ 0 3 ​ $ 660 Consumer mortgage ​ 17 ​ 1,378 19 ​ 1,271 Consumer indirect ​ 25 ​ 261 22 ​ 206 Consumer direct ​ 2 ​ 12 5 ​ 35 Home equity ​ 2 ​ 56 4 ​ 72 Total ​ 46 ​ $ 1,707 53 ​ $ 2,244 ​ Allowance for Credit Losses The following presents by segment the activity in the allowance for credit losses: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2020 ​ ​ Beginning ​ Charge- ​ ​ ​ ​ ​ ​ ​ Ending (000’s omitted) balance offs Recoveries Provision balance Business lending ​ $ 24,204 ​ $ (736) ​ $ 67 ​ $ 3,539 ​ $ 27,074 Consumer mortgage ​ 13,088 ​ (248) ​ 23 ​ (599) ​ 12,264 Consumer indirect ​ 15,866 ​ (1,281) ​ 1,111 ​ (963) ​ 14,733 Consumer direct ​ 4,028 ​ (340) ​ 225 ​ (120) ​ 3,793 Home equity ​ 2,690 ​ (24) ​ 5 ​ (124) ​ 2,547 Unallocated ​ 1,000 ​ 0 ​ 0 ​ 4 ​ 1,004 Purchased credit deteriorated ​ 3,561 ​ (91) ​ 32 ​ 45 ​ 3,547 Allowance for credit losses ​ 64,437 ​ (2,720) ​ 1,463 ​ 1,782 ​ 64,962 Liabilities for off-balance-sheet credit exposures ​ 1,452 ​ 0 ​ 0 ​ 163 ​ 1,615 Total allowance for credit losses and liabilities for off-balance-sheet credit exposures ​ $ 65,889 ​ $ (2,720) ​ $ 1,463 ​ $ 1,945 ​ $ 66,577 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2019 ​ ​ Business ​ Consumer ​ Consumer ​ Consumer ​ Home ​ ​ ​ ​ Acquired ​ ​ ​ (000’s omitted) Lending Mortgage Indirect Direct Equity Unallocated Impaired Total Beginning balance ​ $ 17,769 ​ $ 10,763 ​ $ 14,345 ​ $ 3,184 ​ $ 2,103 ​ $ 991 ​ $ 155 ​ $ 49,310 Charge-offs ​ (305) ​ (200) ​ (2,224) ​ (456) ​ (45) ​ 0 ​ 0 ​ (3,230) Recoveries ​ 290 ​ 8 ​ 1,095 ​ 167 ​ 32 ​ 0 ​ 0 ​ 1,592 Provision ​ 301 ​ (94) ​ 1,221 ​ 383 ​ (8) ​ (53) ​ 1 ​ 1,751 Ending balance ​ $ 18,055 ​ $ 10,477 ​ $ 14,437 ​ $ 3,278 ​ $ 2,082 ​ $ 938 ​ $ 156 ​ $ 49,423 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 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 ​ $ (919) ​ $ 289 ​ $ 2,483 ​ $ 5,507 ​ $ 27,074 Consumer mortgage ​ 10,269 ​ (1,051) ​ 9,218 ​ (668) ​ 67 ​ 146 ​ 3,501 ​ 12,264 Consumer indirect ​ 13,712 ​ (997) ​ 12,715 ​ (4,791) ​ 3,107 ​ 183 ​ 3,519 ​ 14,733 Consumer direct ​ 3,255 ​ (643) ​ 2,612 ​ (1,214) ​ 578 ​ 87 ​ 1,730 ​ 3,793 Home equity ​ 2,129 ​ 808 ​ 2,937 ​ (178) ​ 23 ​ 235 ​ (470) ​ 2,547 Unallocated ​ 957 ​ 43 ​ 1,000 ​ 0 ​ 0 ​ 0 ​ 4 ​ 1,004 Purchased credit deteriorated ​ 0 ​ 3,072 ​ 3,072 ​ (91) ​ 80 ​ 528 ​ (42) ​ 3,547 Purchased credit impaired ​ 163 ​ (163) ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 Allowance for credit losses ​ 49,911 ​ 1,357 ​ 51,268 ​ (7,861) ​ 4,144 ​ 3,662 ​ 13,749 ​ 64,962 Liabilities for off-balance-sheet credit exposures ​ 0 ​ 1,185 ​ 1,185 ​ 0 ​ 0 ​ 67 ​ 363 ​ 1,615 Total allowance for credit losses and liabilities for off-balance-sheet credit exposures ​ $ 49,911 ​ $ 2,542 ​ $ 52,453 ​ $ (7,861) ​ $ 4,144 ​ $ 3,729 ​ $ 14,112 ​ $ 66,577 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2019 ​ ​ Business ​ Consumer ​ Consumer ​ Consumer ​ Home ​ ​ ​ ​ Acquired ​ ​ (000’s omitted) Lending Mortgage Indirect Direct Equity Unallocated Impaired Total Beginning balance ​ $ 18,522 ​ $ 10,124 ​ $ 14,366 ​ $ 3,095 ​ $ 2,144 ​ $ 1,000 ​ $ 33 ​ $ 49,284 Charge-offs ​ (1,774) ​ (1,040) ​ (5,529) ​ (1,436) ​ (223) ​ 0 ​ 0 ​ (10,002) Recoveries ​ 593 ​ 44 ​ 3,296 ​ 567 ​ 68 ​ 0 ​ 0 ​ 4,568 Provision ​ 714 ​ 1,349 ​ 2,304 ​ 1,052 ​ 93 ​ (62) ​ 123 ​ 5,573 Ending balance ​ $ 18,055 ​ $ 10,477 ​ $ 14,437 ​ $ 3,278 ​ $ 2,082 ​ $ 938 ​ $ 156 ​ $ 49,423 ​ The allowance for credit losses to total loans ratio of 0.87% at September 30, 2020 was 15 basis points higher than the level at both September 30, 2019 and December 31, 2019, primarily due to the decline in economic conditions associated with the COVID-19 pandemic. Under CECL, the Company utilizes the historical loss rate on its loan portfolio as the initial basis for the estimate of credit losses using the cumulative loss, vintage loss and line loss methods which is derived from the Company’s historical loss experience from January 1, 2012 to December 31, 2019. 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 expected losses under a life of loan concept. 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 to reflect changes as a result of current conditions. 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 September 30, 2020. These forecasts were factored into the qualitative portion of the calculation of the estimated credit losses and included the impact of COVID-19 and current and future Federal stimulus packages. The scenarios utilized outline a continued weakness in economic activity 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 projected unemployment and GDP as possible indicators of forecasted losses related to business lending and selected projected unemployment as the best leading indicator given the current economic environment. 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 projected unemployment and real estate values as possible indicators of forecasted losses related to commercial real estate loans and selected projected unemployment as the best leading indicator given the current economic environment. The Company also considered the factors noted in business lending – non real estate. ● Consumer mortgages and home equity: The Company considered projected unemployment and real estate values as possible indicators of forecasted losses related to mortgage lending and selected projected unemployment as the best leading indicator given the current economic environment. In addition, current delinquencies, the level of loan deferrals, charge-offs and acquired loans were considered. ● Consumer indirect: The Company considered projected unemployment and vehicle valuation indices as possible indicators of forecasted losses related to indirect lending and selected projected unemployment as the best leading indicator given the current economic environment. 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 as a 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 nine months ended September 30, 2020 by portfolio segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Business ​ Consumer ​ Consumer ​ Consumer ​ Home ​ ​ ​ (000’s omitted) lending mortgage indirect direct equity Total Purchases ​ $ 253,368 ​ $ 26,721 ​ $ 13,926 ​ $ 5,994 ​ $ 39,554 ​ $ 339,563 Sales ​ ​ 0 ​ ​ 37,409 ​ ​ 0 ​ ​ 0 ​ ​ 0 ​ ​ 37,409 ​ All the purchases during the nine months ended September 30, 2020 were associated with the Steuben acquisition on June 12, 2020 and all the sales during the nine months ended September 30, 2020 were sales of secondary market eligible residential mortgage loans.

GOODWILL AND IDENTIFIABLE INTAN

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS	9 Months Ended
	Sep. 30, 2020
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: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 December 31, 2019 ​ ​ 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 ​ $ (54,217) ​ $ 15,186 ​ $ 66,475 ​ $ (50,057) ​ $ 16,418 Other intangibles ​ 90,462 ​ (49,183) ​ 41,279 ​ 89,266 ​ (42,571) ​ 46,695 Total amortizing intangibles ​ $ 159,865 ​ $ (103,400) ​ $ 56,465 ​ $ 155,741 ​ $ (92,628) ​ $ 63,113 ​ The estimated aggregate amortization expense for each of the five succeeding fiscal years ended December 31 is as follows: ​ ​ ​ ​ ​ ​ (000's omitted) Oct - Dec 2020 ​ $ 3,525 2021 ​ 12,640 2022 ​ 10,844 2023 ​ 9,082 2024 ​ 7,551 Thereafter ​ 12,823 Total ​ $ 56,465 ​ Shown below are the components of the Company’s goodwill at December 31, 2019 and September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) December 31, 2019 Activity September 30, 2020 Goodwill, net ​ $ 773,810 ​ $ 19,939 ​ $ 793,749 ​

MANDATORILY REDEEMABLE PREFERRE

MANDATORILY REDEEMABLE PREFERRED SECURITIES	9 Months Ended
	Sep. 30, 2020
MANDATORILY REDEEMABLE PREFERRED SECURITIES
MANDATORILY REDEEMABLE PREFERRED SECURITIES	NOTE G: MANDATORILY REDEEMABLE PREFERRED SECURITIES As of September 30, 2020, the Company sponsors one business trust, Community Capital Trust IV (“CCT IV”), of which 100% of the common stock is owned by the Company. The Company previously sponsored Steuben Statutory Trust ("SST II ") until September 15, 2020 when the Company exercised its right to redeem all of the SST II debentures and associated preferred securities for a total of $2.1 million. The Company previously sponsored MBVT Statutory Trust I (“MBVT I”) and Kinderhook Capital Trust (“KCT”) until September 16, 2019 when the Company exercised its right to redeem all of the MBVT I and KCT debentures and associated preferred securities for a total of $20.6 million and $2.1 million, respectively. The common stock of MBVT I was acquired in the Merchants Bancshares, Inc. (“Merchants”) acquisition, the common stock of KCT was acquired in the Kinderhook acquisition and the common stock of SST II was acquired in the Steuben acquisition. The trusts were formed for the purpose of issuing company-obligated mandatorily redeemable preferred securities to third-party investors and investing the proceeds from the sale of such preferred securities solely in junior subordinated debt securities of the Company. The debentures held by each trust are the sole assets of such trust. Distributions on the preferred securities issued by each trust are payable quarterly at a rate per annum equal to the interest rate being earned by the trust on the debentures held by that trust and are recorded as interest expense in the consolidated financial statements. The preferred securities are subject to mandatory redemption, in whole or in part, upon repayment of the debentures. The Company has entered into agreements which, taken collectively, fully and unconditionally guarantee the preferred securities subject to the terms of each of the guarantees. As of September 30, 2020, the terms of the preferred securities of CCT IV are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Issuance Par Maturity Trust ​ Date ​ Amount ​ Interest Rate ​ Date ​ Call Price CCT IV 12/8/2006 ​ $ 75.0 million 3 month 12/15/2036 Par ​

BENEFIT PLANS

BENEFIT PLANS	9 Months Ended
	Sep. 30, 2020
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 $3.9 million contribution to its defined benefit pension plan in the second quarter of 2020, and made a $3.5 million contribution to the Steuben Trust Company Pension Plan in the third quarter of 2020. The Company made a $7.3 million contribution to its defined benefit pension plan in the first quarter of 2019. The net periodic benefit cost for the three and nine months ended September 30, 2020 and 2019 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension Benefits ​ Post-retirement Benefits ​ ​ Three Months Ended ​ Nine Months Ended ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ September 30, ​ September 30, (000's omitted) 2020 2019 2020 ​ 2019 2020 ​ 2019 ​ 2020 2019 Service cost ​ $ 1,438 ​ $ 1,270 ​ $ 4,313 ​ $ 3,811 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 Interest cost 1,356 1,566 ​ 4,068 ​ 4,698 15 ​ 18 ​ 43 ​ 53 Expected return on plan assets ​ (3,932) ​ (3,578) ​ ​ (11,796) ​ ​ (10,733) ​ 0 ​ 0 ​ ​ 0 ​ 0 Amortization of unrecognized net loss ​ 810 ​ 642 ​ ​ 2,430 ​ ​ 1,926 ​ 10 ​ 9 ​ ​ 30 ​ 28 Amortization of prior service cost ​ 60 ​ 17 ​ ​ 180 ​ ​ 48 ​ (45) ​ (45) ​ ​ (134) ​ (134) Net periodic benefit ​ $ (268) ​ $ (83) ​ $ (805) ​ $ (250) ​ $ (20) ​ $ (18) ​ $ (61) ​ $ (53) ​

EARNINGS PER SHARE

EARNINGS PER SHARE	9 Months Ended
	Sep. 30, 2020
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 September 30, 2020. 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 (those where the average market price is greater than the exercise price) 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 0.5 million and 0.7 million weighted-average anti-dilutive stock options outstanding for the three months and nine months ended September 30, 2020, respectively, compared to 0.5 million weighted-average anti-dilutive stock options outstanding for the three months and nine months ended September 30, 2019 that were not included in the computation below. The following is a reconciliation of basic to diluted earnings per share for the three and nine months ended September 30, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, (000's omitted, except per share data) 2020 2019 2020 2019 Net income ​ $ 42,809 ​ $ 39,218 ​ $ 118,191 ​ $ 126,179 Income attributable to unvested stock-based compensation awards ​ (147) ​ (102) ​ (432) ​ (331) Income available to common shareholders ​ $ 42,662 ​ $ 39,116 ​ $ 117,759 ​ $ 125,848 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 53,650 ​ 51,750 ​ 52,727 ​ 51,644 Basic earnings per share ​ $ 0.80 ​ $ 0.76 ​ $ 2.23 ​ $ 2.44 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income ​ $ 42,809 ​ $ 39,218 ​ $ 118,191 ​ $ 126,179 Income attributable to unvested stock-based compensation awards ​ (147) ​ (102) ​ (432) ​ (331) Income available to common shareholders ​ $ 42,662 ​ $ 39,116 ​ $ 117,759 ​ $ 125,848 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 53,650 ​ 51,750 ​ 52,727 ​ 51,644 Assumed exercise of stock options ​ 324 ​ 496 ​ 356 ​ 522 Weighted-average common shares outstanding – diluted ​ 53,974 ​ 52,246 ​ 53,083 ​ 52,166 Diluted earnings per share ​ $ 0.79 ​ $ 0.75 ​ $ 2.22 ​ $ 2.41 ​ Stock Repurchase Program At its December 2018 meeting, the Company’s Board of Directors (the “Board”) approved a stock repurchase program authorizing the repurchase of up to 2.5 million shares of the Company’s common stock in accordance with securities laws and regulations, through December 31, 2019. At its December 2019 meeting, the Board approved a similar program for 2020, authorizing the repurchase of up to 2.6 million shares of the Company’s common stock through December 31, 2020. 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 nine months of 2020 or 2019.

COMMITMENTS, CONTINGENT LIABILI

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS	9 Months Ended
	Sep. 30, 2020
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: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, (000's omitted) ​ 2020 ​ 2019 Commitments to extend credit ​ $ 1,201,285 ​ $ 1,143,780 Standby letters of credit ​ 43,283 ​ 37,872 Total ​ $ 1,244,568 ​ $ 1,181,652 ​ 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 September 30, 2020, 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. ​ During the three months and nine months ending September 30, 2020, the Company recorded $3.0 million in litigation accrual related to an anticipated settlement, following mediation, of a purported class action lawsuit regarding the Bank’s deposit account terms and overdraft disclosures and certain overdraft fees assessed pursuant to such terms and disclosures. The Company anticipates it will execute a settlement agreement with the plaintiffs on the matter in the fourth quarter of 2020 and does not anticipate that additional amounts will be accrued for this matter in future periods. The settlement, which is subject to documentation and Court approval, will provide for a release of all claims asserted by class members in the action. ​

FAIR VALUE

FAIR VALUE	9 Months Ended
	Sep. 30, 2020
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. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 (000's omitted) Level 1 Level 2 Level 3 Total Fair Available-for-sale investment securities: ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 1,982,893 ​ $ 166,277 ​ $ 0 ​ $ 2,149,170 Obligations of state and political subdivisions ​ 0 ​ 493,496 ​ 0 ​ 493,496 Government agency mortgage-backed securities ​ 0 ​ 523,974 ​ 0 ​ 523,974 Corporate debt securities ​ 0 ​ 4,602 ​ 0 ​ 4,602 Government agency collateralized mortgage obligations ​ 0 ​ 51,480 ​ 0 ​ 51,480 Total available-for-sale investment securities ​ 1,982,893 ​ 1,239,829 ​ 0 ​ 3,222,722 Equity securities ​ 423 ​ 0 ​ 0 ​ 423 Mortgage loans held for sale ​ 0 ​ 8,151 ​ 0 ​ 8,151 Commitments to originate real estate loans for sale ​ 0 ​ 0 ​ 2,684 ​ 2,684 Forward sales commitments ​ 0 ​ 510 ​ 0 ​ 510 Interest rate swap agreements asset ​ 0 ​ 1,756 ​ 0 ​ 1,756 Interest rate swap agreements liability ​ 0 ​ (1,194) ​ 0 ​ (1,194) Total ​ $ 1,983,316 ​ $ 1,249,052 ​ $ 2,684 ​ $ 3,235,052 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 (000's omitted) Level 1 Level 2 Level 3 Total Fair Available-for-sale investment securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 1,878,705 ​ $ 165,054 ​ $ 0 ​ $ 2,043,759 Obligations of state and political subdivisions ​ 0 ​ 512,208 ​ 0 ​ 512,208 Government agency mortgage-backed securities ​ 0 ​ 432,862 ​ 0 ​ 432,862 Corporate debt securities ​ 0 ​ 2,528 ​ 0 ​ 2,528 Government agency collateralized mortgage obligations ​ 0 ​ 53,071 ​ 0 ​ 53,071 Total available-for-sale investment securities ​ 1,878,705 ​ 1,165,723 ​ 0 ​ 3,044,428 Equity securities ​ 451 ​ 0 ​ 0 ​ 451 Interest rate swap agreements asset ​ 0 ​ 851 ​ 0 ​ 851 Interest rate swap agreements liability ​ 0 ​ (586) ​ 0 ​ (586) Total ​ $ 1,879,156 ​ $ 1,165,988 ​ 0 ​ $ 3,045,144 ​ 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 statement 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 $ 7.9 million at September 30, 2020. The Company did no t have any mortgage loans held for sale at December 31, 2019. 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. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 December 31, 2019 (000's omitted) Level 1 Level 2 Level 3 Total Fair Level 1 Level 2 Level 3 Total Fair Impaired loans ​ $ 0 ​ $ 0 ​ $ 6,808 ​ $ 6,808 ​ $ 0 ​ $ 0 ​ $ 848 ​ $ 848 Other real estate owned ​ 0 ​ 0 ​ 1,209 ​ 1,209 ​ 0 ​ 0 ​ 1,270 ​ 1,270 Mortgage servicing rights ​ 0 ​ 0 ​ 460 ​ 460 ​ 0 ​ 0 ​ 56 ​ 56 Total ​ $ 0 ​ $ 0 ​ $ 8,477 ​ $ 8,477 ​ $ 0 ​ $ 0 ​ $ 2,174 ​ $ 2,174 ​ 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 are classified 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 15.2% to 53.5% at September 30, 2020 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 $0.2 million and $0.3 million at September 30, 2020 and December 31, 2019, 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) ​ September 30, 2020 ​ Valuation Technique ​ Significant Unobservable Inputs (Weighted Average) ​ Impaired loans ​ $ 6,808 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 78.7% (58.8%) ​ Other real estate owned ​ 1,209 Fair value of collateral Estimated cost of disposal/market adjustment ​ 15.2% - 53.5% (31.3%) ​ Commitments to originate real estate loans for sale ​ 2,684 Discounted cash flow Embedded servicing value ​ 1.0 % Mortgage servicing rights ​ 460 Discounted cash flow Weighted average constant prepayment rate ​ 13.8% - 14.7% (14.6%) ​ ​ ​ ​ ​ ​ ​ ​ Weighted average discount rate ​ ​ 1.22% - 1.98% (1.92%) ​ ​ ​ ​ ​ ​ ​ ​ Adequate compensation ​ $ 7/loan ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ ​ Unobservable Input ​ ​ ​ Fair Value at ​ ​ ​ ​ ​ Range ​ (000's omitted) ​ December 31, 2019 ​ Valuation Technique ​ Significant Unobservable Inputs ​ (Weighted Average) Impaired loans ​ $ 848 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 35.0% (27.9%) ​ Other real estate owned ​ 1,270 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 85.7% (37.1%) ​ Mortgage servicing rights ​ 56 Discounted cash flow Weighted average constant prepayment rate ​ 52.8 % ​ ​ Weighted average discount rate ​ 3.00 % ​ ​ ​ ​ ​ ​ 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 other real estate owned 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 September 30, 2020 and December 31, 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 December 31, 2019 ​ ​ Carrying ​ Fair ​ Carrying ​ Fair (000's omitted) Value Value Value Value Financial assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loans ​ $ 7,393,681 ​ $ 7,710,461 ​ $ 6,840,632 ​ $ 7,028,663 Financial liabilities: ​ ​ ​ ​ Deposits ​ 11,120,590 ​ 11,135,779 ​ 8,994,967 ​ 8,997,551 Overnight Federal Home Loan Bank borrowings ​ 0 ​ 0 ​ 8,300 ​ 8,300 Securities sold under agreement to repurchase, short-term ​ 280,767 ​ 280,767 ​ 241,708 ​ 241,708 Other Federal Home Loan Bank borrowings ​ 7,681 ​ 7,810 ​ 3,750 ​ 3,755 Subordinated notes payable ​ 13,735 ​ 13,735 ​ 13,795 ​ 13,795 Subordinated debt held by unconsolidated subsidiary trusts ​ 77,320 ​ 77,320 ​ 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 variable rate loans that reprice frequently are based on carrying values. Fair values for fixed rate 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	9 Months Ended
	Sep. 30, 2020
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 September 30, 2020 and December 31, 2019. The effect of the changes to these derivatives for the three and nine months then ended was also immaterial. The Company acquired interest rate swaps in 2017 with notional amounts with certain commercial customers which totaled $14.8 million at September 30, 2020 and $16.4 million at December 31, 2019. 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 $14.8 million at September 30, 2020 and $16.4 million at December 31, 2019. At September 30, 2020, the weighted average receive rate of these interest rate swaps was 2.10%, the weighted average pay rate was 4.43% and the weighted average maturity was 5.5 years. At December 31, 2019, the weighted average receive rate of these interest rate swaps was 3.72%, the weighted average pay rate was 4.39% and the weighted average maturity was 6.1 years. Hedge accounting has not been applied for these derivatives. Since the terms of the swaps with the customer and the other financial institution offset each other, with the only difference being counterparty credit risk, changes in the fair value of the underlying derivative contracts are not materially different and do not significantly impact the Company’s results of operations. The Company also acquired interest rate swaps in 2017 with notional amounts totaling $5.7 million at September 30, 2020, and $6.2 million at December 31, 2019, that were designated as fair value hedges of certain fixed rate loans with municipalities which are recorded in loans in the consolidated statements of condition. At September 30, 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 12.8 years. At December 31, 2019, the weighted average receive rate of these interest rate swaps was 2.47%, the weighted average pay rate was 3.11% and the weighted average maturity was 13.5 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 nine months ended September 30, 2020 are immaterial. As of September 30, 2020 and December 31, 2019, 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 ​ September 30, ​ December 31, ​ September 30, ​ December 31, the Hedged Item Is Included 2020 2019 2020 2019 Loans $ 5,611 $ 6,390 $ (562) $ (265) ​ Fair values of derivative instruments as of September 30, 2020 and December 31, 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ September 30, 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 ​ $ 562 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ 1,194 Accrued interest and other liabilities ​ $ 1,194 Commitments to originate real estate loans for sale Other assets ​ 2,684 ​ Forward sales commitments Other assets ​ 510 ​ Total derivatives ​ $ 4,950 ​ $ 1,194 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ December 31, 2019 ​ ​ 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 ​ $ 265 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ 586 Accrued interest and other liabilities ​ $ 586 Total derivatives ​ $ 851 ​ $ 586 ​ The Company assessed its counterparty risk at September 30, 2020 and December 31, 2019 and determined any credit risk inherent in our derivative contracts was not material. Information about the fair value of derivative financial instruments can be found in Note K to these consolidated financial statements.

SEGMENT INFORMATION

SEGMENT INFORMATION	9 Months Ended
	Sep. 30, 2020
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. 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 CISI, 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. 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 September 30, 2020 ​ ​ ​ ​ ​ Net interest income ​ $ 92,642 ​ $ 256 ​ $ 67 ​ $ 0 ​ $ 92,965 Provision for credit losses ​ 1,945 ​ 0 ​ 0 ​ 0 ​ 1,945 Noninterest revenues ​ 19,756 ​ 25,651 ​ 15,706 ​ (1,454) ​ 59,659 Amortization of intangible assets ​ 1,379 ​ 1,409 ​ 793 ​ 0 ​ 3,581 Acquisition expenses ​ 796 ​ 0 ​ 0 ​ 0 ​ 796 Other operating expenses ​ 67,193 ​ 15,078 ​ 11,772 ​ (1,454) ​ 92,589 Income before income taxes ​ $ 41,085 ​ $ 9,420 ​ $ 3,208 ​ $ 0 ​ $ 53,713 Assets ​ $ 13,674,995 ​ $ 210,679 ​ $ 80,528 ​ $ (120,877) ​ $ 13,845,325 Goodwill ​ $ 690,162 ​ $ 83,275 ​ $ 20,312 ​ $ 0 ​ $ 793,749 Core deposit intangibles & Other intangibles ​ $ 15,186 ​ $ 33,461 ​ $ 7,818 ​ $ 0 ​ $ 56,465 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net interest income ​ $ 91,018 ​ $ 209 ​ $ 49 ​ $ 0 ​ $ 91,276 Provision for credit losses ​ 1,751 ​ 0 ​ 0 ​ 0 ​ 1,751 Noninterest revenues ​ 17,790 ​ 24,830 ​ 15,143 ​ (669) ​ 57,094 Amortization of intangible assets ​ 1,439 ​ 1,667 ​ 854 ​ 0 ​ 3,960 Acquisition expenses ​ 6,061 ​ 0 ​ 0 ​ 0 ​ 6,061 Other operating expenses ​ 61,839 ​ 14,721 ​ 11,017 ​ (669) ​ 86,908 Income before income taxes ​ $ 37,718 ​ $ 8,651 ​ $ 3,321 ​ $ 0 ​ $ 49,690 Assets ​ $ 11,398,191 ​ $ 201,442 ​ $ 74,169 ​ $ (76,505) ​ $ 11,597,297 Goodwill ​ $ 670,023 ​ $ 83,275 ​ $ 20,312 ​ $ 0 ​ $ 773,610 Core deposit intangibles & Other intangibles ​ $ 17,872 ​ $ 39,440 ​ $ 9,763 ​ $ 0 ​ $ 67,075 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee ​ ​ ​ ​ ​ ​ ​ Consolidated (000's omitted) Banking Benefit Services All Other Eliminations Total Nine Months Ended September 30, 2020 ​ ​ ​ ​ ​ Net interest income ​ $ 274,051 ​ $ 742 ​ $ 177 ​ $ 0 ​ $ 274,970 Provision for credit losses ​ 17,313 ​ 0 ​ 0 ​ 0 ​ 17,313 Noninterest revenues ​ 53,428 ​ 76,080 ​ 46,058 ​ (4,347) ​ 171,219 Amortization of intangible assets ​ 4,160 ​ 4,314 ​ 2,298 ​ 0 ​ 10,772 Acquisition expenses ​ 4,537 ​ 0 ​ 0 ​ 0 ​ 4,537 Other operating expenses ​ 190,523 ​ 45,157 ​ 34,890 ​ (4,347) ​ 266,223 Income before income taxes ​ $ 110,946 ​ $ 27,351 ​ $ 9,047 ​ $ 0 ​ $ 147,344 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ Net interest income ​ $ 265,860 ​ $ 448 ​ $ 127 ​ $ 0 ​ $ 266,435 Provision for credit losses ​ 5,573 ​ 0 ​ 0 ​ 0 ​ 5,573 Noninterest revenues ​ 57,059 ​ 73,919 ​ 44,749 ​ (2,231) ​ 173,496 Amortization of intangible assets ​ 4,297 ​ 5,105 ​ 2,592 ​ 0 ​ 11,994 Acquisition expenses ​ 7,789 ​ 0 ​ 0 ​ 0 ​ 7,789 Other operating expenses ​ 182,186 ​ 43,985 ​ 33,034 ​ (2,231) ​ 256,974 Income before income taxes ​ $ 123,074 ​ $ 25,277 ​ $ 9,250 ​ $ 0 ​ $ 157,601 ​

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2020
ACCOUNTING POLICIES
Investment Securities	Investment Securities The Company can classify its investments in debt securities as held-to-maturity, available-for-sale, or trading. Held-to-maturity securities are those for which the Company has the positive intent and ability to hold until maturity, and are reported at cost, which is adjusted for amortization of premiums and accretion of discounts. The Company did not use the held-to-maturity classification in 2019 or through September 30, 2020. Available-for-sale debt securities are reported at fair value with net unrealized gains and losses reflected as a separate component of shareholders’ equity, net of applicable income taxes. None of the Company’s investment securities have been classified as trading securities at September 30, 2020 or December 31, 2019. Equity securities with a readily determinable fair value are reported at fair value with net unrealized gains and losses recognized in the consolidated statements of income. Certain equity securities that do not have a readily determinable fair value are stated at cost, adjusted for observable price changes in orderly transactions for identical or similar investments of the same issuer. These securities include restricted stock of the Federal Reserve Bank of New York (“Federal Reserve”) and the Federal Home Loan Bank of New York and the Federal Home Loan Bank of Boston (collectively referred to as “FHLB”), as well as other equity securities. Fair values for investment securities are based upon quoted market prices, where available. If quoted market prices are not available, fair values are based upon quoted market prices of comparable instruments, or a discounted cash flow model using market estimates of interest rates and volatility.
Allowance for Credit Losses - Debt Securities	Allowance for Credit Losses – Debt Securities For held-to-maturity debt securities, the Company measures expected credit losses on a collective basis by major security type. The estimates of expected credit losses considers historical credit loss information that is adjusted for current conditions and reasonable and supportable forecasts. Accrued interest receivable on held-to-maturity securities is excluded from the estimates of credit losses. For available-for-sale debt securities in an unrealized loss position, the Company first assesses whether it intends to sell, or it more likely than not that it will be required to sell the security before recovery of its amortized cost basis. If either of the criteria regarding intent or requirement to sell is met, the security’s amortized cost basis is written down to fair value through income. For available-for-sale debt securities that do not meet the aforementioned criteria, the Company evaluates whether the decline in fair value has resulted from credit losses or other factors. In making this assessment, management considers the security structure, recent security collateral performance metrics, if applicable, external credit ratings, failure of the issuer to make scheduled interest or principal payments, judgment about and expectations of future performance, and relevant independent industry research, analysis, and forecasts. The severity of the impairment and the length of time the security has been impaired is also considered in the assessment. This assessment involves a high degree of subjectivity and judgment that is based on the information available to management at a point in time. If this assessment indicates that a credit loss exists, the present value of the cash flows expected to be collected from the security are compared to the amortized cost basis of the security. If the present value of the cash flows expected to be collected from the security is less than the amortized cost basis of the security, a credit loss exists and an allowance for credit losses is recorded, limited by the amount that the fair value is less than the amortized cost basis. Any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income. Changes in the allowance for credit losses are recorded as provision for (or reversal of) credit losses. Losses are charged against the allowance when management believes the uncollectibility of an available-for-sale security is confirmed or when either of the criteria regarding intent or requirement to sell is met. Accrued interest receivable on available-for-sale debt securities, included in accrued interest and fees receivable on the consolidated statements of condition, totaled $14.2 million at September 30, 2020 and is excluded from the estimate of credit losses.
Loans	Loans Loans that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are reported at amortized cost, net of allowance for credit losses. Amortized cost is the principal balance outstanding, net of purchase premiums and discounts, and deferred loan fees and costs. Mortgage loans held for sale are carried at fair value and are included in loans held for sale on the consolidated statements of condition. Fair values for variable rate loans that reprice frequently are based on carrying values. Fair values for fixed rate loans are estimated using discounted cash flows and interest rates currently being offered for loans with similar terms to borrowers of similar credit quality. The carrying amount of accrued interest approximates its fair value. Interest on loans is accrued and credited to operations based upon the principal amount outstanding. Nonrefundable loan fees and related direct costs are deferred and included in the loan balances where they are amortized over the life of the loan as an adjustment to loan yield using the effective yield method. Premiums and discounts on purchased loans are amortized using the effective yield method over the life of the loans. Accrued interest receivable on loans, included in accrued interest and fees receivable on the consolidated statements of condition, totaled $23.8 million at September 30, 2020 and is excluded from the estimate of credit losses and amortized cost basis of loans. An allowance for credit losses is not measured for accrued interest receivable on loans as the Company writes off the uncollectible accrued interest balance in a timely manner. The Company places a loan on nonaccrual status when the loan becomes 90 days past due (or sooner, if management concludes collection is doubtful), except when, in the opinion of management, it is well-collateralized and in the process of collection. A loan may be placed on nonaccrual status earlier than 90 days past due if there is deterioration in the financial position of the borrower or if other conditions of the loan so warrant. When a loan is placed on nonaccrual status, uncollected accrued interest is reversed against interest income and the amortization of nonrefundable loan fees and related direct costs is discontinued. Interest income during the period the loan is on nonaccrual status is recorded on a cash basis after recovery of principal is reasonably assured. Nonaccrual loans are returned to accrual status when management determines that the borrower’s performance has improved and that both principal and interest are collectible. This generally requires a sustained period of timely principal and interest payments and a well-documented credit evaluation of the borrower’s financial condition. The Company’s charge-off policy by loan type is as follows: ● Business lending loans are generally charged-off to the extent outstanding principal exceeds the fair value of estimated proceeds from collection efforts, including liquidation of collateral. The charge-off is recognized when the loss becomes reasonably quantifiable. ● Consumer installment loans are generally charged-off to the extent outstanding principal exceeds the fair value of collateral, and are recognized by the end of the month in which the loan becomes 90 days past due. ● Consumer mortgage and home equity loans are generally charged-off to the extent outstanding principal exceeds the fair value of the property, less estimated costs to sell, and are recognized when the loan becomes 180 days past due.
Allowance for Credit Losses - Loans	Allowance for Credit Losses – Loans The allowance for credit losses is a valuation account that is netted against the loans’ amortized cost basis to present the net amount expected to be collected on the loans. Loans are charged off against the allowance when management believes the uncollectibility of a loan balance is confirmed. Management estimates the allowance balance using relevant available information, from internal and external sources, relating to past events, current conditions, and reasonable and supportable forecasts. Historical credit loss experience provides the basis for the estimation of expected credit losses. Adjustments are made for differences in current loan-specific risk characteristics such as differences in underwriting standards, portfolio mix, acquired loans, delinquency level, risk ratings or term of loans as well as changes in macroeconomic conditions, such as changes in unemployment rates, property values such as home prices, commercial real estate prices and automobile prices, gross domestic product, recession probability, and other relevant factors. The segments of the Company’s loan portfolio are disaggregated into the following classes that allow management to monitor risk and performance: ● Business lending is comprised of general purpose commercial and industrial loans including, but not limited to agricultural-related and dealer floor plans, loans to not-for-profit enterprises, as well as mortgages on commercial property and Paycheck Protection Program (“PPP”) loans. The portfolio segment is further broken into portfolio classes based on risks associated with the collateral supporting the loans. Each class of business lending can also have different payment structures. Business lending loans are generally higher dollar loans and a large portion are risk rated at least annually. ● Consumer mortgages consist primarily of fixed rate residential instruments, typically 10 – 30 years in contractual term, secured by first liens on real property. FICO scores are used to monitor higher risks related to this type of lending with FICO AB referring to higher tiered loans with FICO scores greater than or equal to 720 as compared to FICO CDE with lower FICO scores less than 720 and potentially higher risk. ● Consumer indirect consists primarily of installment loans originated through selected dealerships and are generally secured by automobiles, marine and other recreational vehicles. Collateral securing the loans was used to further disaggregate this portfolio as charge-offs can vary depending on the purpose of the loan. Non-auto loans often have longer terms, and generally have higher risk due to declines in collateral value given the nature of the property. ● Consumer direct consists of all other loans to consumers such as personal installment loans and check credit lines of credit. ● Home equity products are installment loans or lines of credit most often secured by a first or second lien position on residential real estate with terms up to 30 years . The allowance for credit losses is measured on a collective (pool) basis when similar risk characteristics exist, including collateral type, credit ratings/scores, size, duration, interest rate structure, industry, geography, origination vintage, and payment structure. The Company has identified the following portfolio segments and classes and measures the allowance for credit losses using the following methods: ​ ​ ​ ​ ​ ​ ​ Loan Portfolio Segment Loan Portfolio Class Allowance for Credit Losses Methodology Business lending ​ Commercial real estate multi family ​ Cumulative loss rate ​ Business lending ​ Commercial real estate non-owner occupied ​ Cumulative loss rate ​ Business lending ​ Commercial real estate owner occupied ​ Cumulative loss rate ​ Business lending ​ Commercial and industrial loans ​ Vintage loss rate ​ Business lending ​ Commercial and industrial lines of credit ​ Line loss ​ Business lending ​ Municipal ​ Cumulative loss rate ​ Business lending ​ Other business ​ Cumulative loss rate ​ Business lending ​ Paycheck Protection Program ​ Cumulative loss rate ​ Consumer mortgage ​ Consumer mortgage FICO AB ​ Cumulative loss rate ​ Consumer mortgage ​ Consumer mortgage FICO CDE ​ Cumulative loss rate ​ Consumer indirect ​ Indirect new auto ​ Vintage loss rate ​ Consumer indirect ​ Indirect used auto ​ Vintage loss rate ​ Consumer indirect ​ Indirect non-auto ​ Vintage loss rate ​ Consumer direct ​ Consumer check credit ​ Line loss ​ Consumer direct ​ Consumer direct ​ Vintage loss rate ​ Home equity ​ Home equity fixed rate ​ Vintage loss rate ​ Home equity ​ Home equity lines of credit ​ Line loss ​ ​ The cumulative loss rate method uses historical loss data applied against multiple pools of loans and uses a quantitatively based management overlay in order to capture the risk for a loan’s entire expected life. These loss rates are then applied to current balances to achieve a required reserve before qualitative adjustments. The line loss method calculates the quantitative required reserve for lines of credit. This method contains several different underlying calculations including average annual loss rate, pay-down rate, cumulative loss, average draw percentage, and undrawn liability reserve. The vintage loss rate method calculates annual loss rates by origination year. The results of this model are then applied to outstanding balances, which correspond to the origination period for each annual loss rate. In addition to the risk characteristics noted above, management considers the portion of acquired loans to the overall segment balance, as well as current delinquency and charge-off trends compared to historical time periods. Loans that do not share risk characteristics are evaluated on an individual basis. Loans evaluated individually are not also included in the collective evaluation. When management determines that foreclosure is probable or when the borrower is experiencing financial difficulty at the reporting date and repayment is expected to be provided substantially through the operation or sale of the collateral, expected credit losses are based on the fair value of the collateral at the reporting date, adjusted for selling costs as appropriate. Expected credit losses are estimated over the contractual term of the loans and adjusted for expected prepayments when appropriate. The contractual term excludes expected extensions, renewals, and modifications unless management has a reasonable expectation at the reporting date that a troubled debt restructuring will be executed with an individual borrower or the extension or renewal options are included in the original or modified contract at the reporting date and are not unconditionally cancellable by the Company. Certain business lending, consumer direct, and home equity loans do not have stated maturities. In determining the estimated life of these loans, management first estimates the future cash flows expected to be received and then applies those expected future cash flows to the balance. Expected credit losses for lines of credit with no stated maturity are determined by estimating the amount and timing of all principal payments expected to be received after the reporting period and allocating those principal payments between the balance outstanding as of the reporting period and the balance of future receivables expected to be originated through subsequent usage of the unconditionally cancellable loan commitment associated with the account until the expected payments have been fully allocated. An additional allowance for credit loss is recorded for the excess of the balance outstanding as of the reporting period over the expected principal payments allocated to that balance.
Troubled Debt Restructuring	Troubled Debt Restructuring A loan for which the terms have been modified resulting in a concession, and for which the borrower is experiencing financial difficulties, is considered to be a troubled debt restructuring (“TDR”). The allowance for credit loss on a TDR is measured using the same method as all other loans, except when the value of a concession cannot be measured using a method other than the discounted cash flow method. When the value of a concession is measured using the discounted cash flow method, the allowance for credit loss is determined by discounting the expected future cash flows at the original interest rate of the loan. Refer to Note E: Loans for the Company’s policy regarding COVID-19 related financial hardship payment deferrals.
Allowance for Credit Losses - Off-balance-sheet Credit Exposures	Allowance for Credit Losses – Off-balance-sheet credit exposures The Company estimates expected credit losses over the contractual period in which the Company is exposed to credit risk via a contractual obligation to extend credit, unless that obligation is unconditionally cancellable by the Company. There are unfunded commitments for lines of credit within each of the Company’s loan portfolio segments except consumer indirect. The allowance for credit losses on off-balance-sheet credit exposures is adjusted as a provision for (or reversal of) credit losses. The estimate includes consideration of the likelihood that funding will occur and an estimate of expected credit losses on commitments expected to be funded over its estimated life. Management estimates the allowance balance using relevant available information, from internal and external sources, relating to past events, current conditions, and reasonable and supportable forecasts. Historical credit loss experience provides the basis for the estimation of expected credit losses. Adjustments to historical loss information are made for differences in current loan-specific risk characteristics that are the same as the adjustments considered for the loan portfolio.
Purchased Credit Deteriorated (PCD) Loans	Purchased Credit Deteriorated (PCD) Loans The Company has purchased loans, some of which have experienced a more-than-insignificant credit deterioration since origination. The Company’s policy for reviewing what meets the threshold of the definition of a more-than-insignificant credit deterioration includes loans that are delinquent more than 30 days, loans that have historical delinquencies of more than 30 days at least three times since origination, risk rating downgrades since origination, loans with multiple payment deferrals, loans considered to be troubled debt restructurings, specifically impaired loans or loans with certain documented policy exceptions, further refined based on loan-specific facts and circumstances. 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.
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 September 30, 2020, $28.5 million of accounts receivable, including $8.3 million of unbilled fee revenue, and $2.0 million of unearned revenue was recorded in the consolidated statements of condition. As of December 31, 2019, $26.8 million of accounts receivable, including $7.5 million of unbilled fee revenue, and $1.8 million of unearned revenue was recorded in the consolidated statements of condition.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) The Company adopted ASC 326 on January 1, 2020 using a modified retrospective approach for all financial assets measured at amortized cost and off-balance-sheet credit exposures. Results for reporting periods beginning after January 1, 2020 are presented under ASC 326 while prior period amounts continue to be reported in accordance with previously applicable GAAP. The Company recorded a net cumulative-effect adjustment that increased retained earnings by $1.1 million. This adjustment was a result of a $3.1 million adjustment to loans, partially offset by a $1.4 million increase in the allowance for credit losses and a $0.6 million increase in other liabilities related to the allowance for off-balance-sheet credit exposures and deferred taxes. The adoption of ASU No. 2016-13 did not result in a material allowance for credit losses on the Company’s available-for-sale debt securities or its other instruments carried at amortized cost. The Company’s regulators permit financial institutions to “phase-in” the impact of CECL on its regulatory capital ratios for up to 5 years with transitional relief of incremental capital requirements. The Company did not utilize the phased-in approach and recorded the entire cumulative-effect adjustment against its regulatory capital at the time of adoption. The Company adopted ASC 326 using the prospective transition approach for financial assets purchased with credit deterioration (“PCD”) that were previously classified as purchased credit impaired (“PCI”) and accounted for under ASC 310-30. In accordance with this standard, management did not reassess whether PCI assets met the criteria of PCD assets as of the date of adoption. On January 1, 2020, the amortized cost basis of the PCD assets were adjusted to reflect the addition of $3.1 million of allowance for credit losses. The remaining noncredit discount (based on the adjusted amortized cost basis) will be accreted into interest income at the effective interest rate beginning on January 1, 2020. In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350) In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurements (Topic 820)
New Accounting Pronouncements	New 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) In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (Topic 740)

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	9 Months Ended
	Sep. 30, 2020
ACQUISITIONS
Schedule of estimated fair value of the assets acquired and liabilities	The following table summarizes the estimated fair value of the assets acquired and liabilities assumed after considering the measurement period adjustments described above: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2020 ​ 2019 (000s omitted) Steuben Kinderhook Other (1) Total Consideration paid : ​ ​ ​ ​ Cash ​ $ 21,613 ​ $ 93,384 ​ $ 1,650 ​ $ 95,034 Community Bank System, Inc. common stock ​ 76,942 ​ 0 ​ 0 ​ 0 Total net consideration paid ​ 98,555 ​ 93,384 ​ 1,650 ​ 95,034 Recognized amounts of identifiable assets acquired and liabilities assumed: ​ ​ ​ ​ Cash and cash equivalents ​ 55,973 ​ 90,381 ​ 0 ​ 90,381 Investment securities ​ 180,497 ​ 39,770 ​ 0 ​ 39,770 Loans, net of allowance for credit losses on PCD loans (2) ​ 339,017 ​ 479,877 ​ 0 ​ 479,877 Premises and equipment, net ​ 7,764 ​ 13,970 ​ 0 ​ 13,970 Accrued interest and fees receivable ​ 2,712 ​ 1,130 ​ 0 ​ 1,130 Other assets ​ 17,633 ​ 14,109 ​ 0 ​ 14,109 Core deposit intangibles ​ 2,928 ​ 3,573 ​ 0 ​ 3,573 Other intangibles ​ 1,196 ​ 0 ​ 1,650 ​ 1,650 Deposits ​ (516,274) ​ (568,161) ​ 0 ​ (568,161) Other liabilities ​ (5,105) ​ (2,922) ​ 0 ​ (2,922) Other Federal Home Loan Bank borrowings ​ (6,000) ​ (2,420) ​ 0 ​ (2,420) Subordinated notes payable ​ 0 ​ (13,831) ​ 0 ​ (13,831) Subordinated debt held by unconsolidated subsidiary trusts ​ (2,062) ​ (2,062) ​ 0 ​ (2,062) Total identifiable assets, net ​ 78,279 ​ 53,414 ​ 1,650 ​ 55,064 Goodwill ​ $ 20,276 ​ $ 39,970 ​ $ 0 ​ $ 39,970 (1) Includes amounts related to both acquisitions completed by CISI in 2019. (2) Acquisition-related allowance for credit losses on purchased credit deteriorated (“PCD”) loans applicable beginning in 2020.
Schedule of of the loans acquired	The Company has acquired loans from Steuben for which there was evidence of a more-than-insignificant deterioration in credit quality since origination. 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 ​ $ 24,415 Allowance for credit losses at acquisition ​ (524) Non-credit discount at acquisition ​ (115) Fair value of PCD loans at acquisition ​ $ 23,776 ​ 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 ​ $ 416,230 Contractual cash flows not expected to be collected ​ (3,131) Expected cash flows at acquisition ​ 413,099 Interest component of expected cash flows ​ (97,858) Fair value of non-PCD loans at acquisition ​ $ 315,241 ​ The following is a summary of the loans acquired from Kinderhook at the date of acquisition: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Acquired Acquired Total ​ Impaired Non-impaired Acquired (000s omitted) Loans Loans Loans Contractually required principal and interest at acquisition ​ $ 13,350 ​ $ 636,384 ​ $ 649,734 Contractual cash flows not expected to be collected ​ (4,176) ​ (5,472) ​ (9,648) Expected cash flows at acquisition ​ 9,174 ​ 630,912 ​ 640,086 Interest component of expected cash flows ​ (551) ​ (159,658) ​ (160,209) Fair value of acquired loans ​ $ 8,623 ​ $ 471,254 ​ $ 479,877
Schedule of pro forma information	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 $0.8 million and $4.4 million for the three and nine months ended September 30, 2020, respectively, related to Steuben were included in the pro forma information as if they were incurred in the first quarter of 2019. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pro Forma (Unaudited) ​ Pro Forma (Unaudited) ​ Three Months Ended Nine Months Ended (000’s omitted) September 30, 2020 September 30, 2019 September 30, 2020 September 30, 2019 Total revenue, net of interest expense ​ $ 152,634 ​ $ 154,221 ​ $ 456,740 ​ $ 457,399 Net income ​ 43,472 ​ 40,695 ​ 124,338 ​ 126,874

INVESTMENT SECURITIES (Tables)

INVESTMENT SECURITIES (Tables)	9 Months Ended
	Sep. 30, 2020
INVESTMENT SECURITIES
Amortized Cost and Estimated Fair Value of Investment Securities	The amortized cost and estimated fair value of investment securities as of September 30, 2020 and December 31, 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ December 31, 2019 ​ ​ ​ ​ ​ 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 ​ $ 2,034,512 ​ $ 114,658 ​ $ 0 ​ $ 2,149,170 ​ $ 2,030,060 ​ $ 21,674 ​ $ 7,975 ​ $ 2,043,759 Obligations of state and political subdivisions ​ 470,518 ​ 22,978 ​ 0 ​ 493,496 ​ 497,852 ​ 14,382 ​ 26 ​ 512,208 Government agency mortgage-backed securities ​ 508,738 ​ 15,514 ​ 278 ​ 523,974 ​ 428,491 ​ 5,478 ​ 1,107 ​ 432,862 Corporate debt securities ​ 4,504 ​ 98 ​ 0 ​ 4,602 ​ 2,527 ​ 1 ​ 0 ​ 2,528 Government agency collateralized mortgage obligations ​ 50,134 ​ 1,354 ​ 8 ​ 51,480 ​ 52,621 ​ 482 ​ 32 ​ 53,071 Total available-for-sale portfolio ​ $ 3,068,406 ​ $ 154,602 ​ $ 286 ​ $ 3,222,722 ​ $ 3,011,551 ​ $ 42,017 ​ $ 9,140 ​ $ 3,044,428 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity and other Securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity securities, at fair value ​ $ 251 ​ $ 192 ​ $ 20 ​ $ 423 ​ $ 251 ​ $ 200 ​ $ 0 ​ $ 451 Federal Home Loan Bank common stock ​ 7,545 ​ 0 ​ 0 ​ 7,545 ​ 7,246 ​ 0 ​ 0 ​ 7,246 Federal Reserve Bank common stock ​ 33,916 ​ 0 ​ 0 ​ 33,916 ​ 30,922 ​ 0 ​ 0 ​ 30,922 Other equity securities, at adjusted cost ​ 4,707 ​ 750 ​ 0 ​ 5,457 ​ 4,546 ​ 750 ​ 0 ​ 5,296 Total equity and other securities ​ $ 46,419 ​ $ 942 ​ $ 20 ​ $ 47,341 ​ $ 42,965 ​ $ 950 ​ $ 0 ​ $ 43,915
Summary 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 September 30, 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 1 ​ $ 1,010 ​ $ 0 0 ​ $ 0 ​ $ 0 1 ​ $ 1,010 ​ $ 0 Obligations of state and political subdivisions 1 ​ 196 ​ 0 0 ​ 0 ​ 0 1 ​ 196 ​ 0 Government agency mortgage-backed securities 91 ​ 62,318 ​ 278 2 ​ 14 ​ 0 93 ​ 62,332 ​ 278 Government agency collateralized mortgage obligations 14 ​ 4,244 ​ 8 1 ​ 0 ​ 0 15 ​ 4,244 ​ 8 Total available-for-sale investment portfolio 107 ​ $ 67,768 ​ $ 286 3 ​ $ 14 ​ $ 0 110 ​ $ 67,782 ​ $ 286 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity and other Securities: ​ ​ ​ ​ ​ ​ Equity securities, at fair value 1 ​ $ 81 ​ $ 20 0 ​ $ 0 ​ $ 0 1 ​ $ 81 ​ $ 20 Total equity and other securities 1 ​ $ 81 ​ $ 20 0 ​ $ 0 ​ $ 0 1 ​ $ 81 ​ $ 20 ​ As of December 31, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 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 12 ​ $ 592,678 ​ $ 7,970 5 ​ $ 25,998 ​ $ 5 17 ​ $ 618,676 ​ $ 7,975 Obligations of state and political subdivisions 21 ​ 22,716 ​ 26 0 ​ 0 ​ 0 21 ​ 22,716 ​ 26 Government agency mortgage-backed securities 50 ​ 89,237 ​ 341 52 ​ 52,975 ​ 766 102 ​ 142,212 ​ 1,107 Government agency collateralized mortgage obligations 5 ​ 5,971 ​ 14 5 ​ 4,405 ​ 18 10 ​ 10,376 ​ 32 Total available-for-sale investment portfolio 88 ​ $ 710,602 ​ $ 8,351 62 ​ $ 83,378 ​ $ 789 150 ​ $ 793,980 ​ $ 9,140
Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity	The amortized cost and estimated fair value of debt securities at September 30, 2020, 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 ​ $ 760,019 ​ $ 765,009 Due after one through five years ​ 802,750 ​ 843,487 Due after five years through ten years ​ 461,012 ​ 503,778 Due after ten years ​ 485,753 ​ 534,994 Subtotal ​ 2,509,534 ​ 2,647,268 Government agency mortgage-backed securities ​ 508,738 ​ 523,974 Government agency collateralized mortgage obligations ​ 50,134 ​ 51,480 Total ​ $ 3,068,406 ​ $ 3,222,722

LOANS (Tables)

LOANS (Tables)	9 Months Ended
	Sep. 30, 2020
Loans and Leases Receivable Disclosure [Line Items]
Loans Receivable, Net	The segments of the Company’s loan portfolio are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, (000's omitted) 2020 2019 Business lending ​ $ 3,433,565 ​ $ 2,775,876 Consumer mortgage ​ 2,410,249 ​ 2,430,902 Consumer indirect ​ 1,039,925 ​ 1,113,062 Consumer direct ​ 161,639 ​ 184,378 Home equity ​ 413,265 ​ 386,325 Gross loans, including deferred origination costs ​ 7,458,643 ​ 6,890,543 Allowance for credit losses ​ (64,962) ​ (49,911) Loans, net of allowance for credit losses ​ $ 7,393,681 ​ $ 6,840,632 ​
Aged Analysis of Past Due Loans by Segment	The following table presents the aging of the amortized cost basis of the Company’s past due loans, including purchased credit deteriorated (“PCD”) loans, by segment as of September 30, 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 ​ $ 3,151 ​ $ 39 ​ $ 11,750 ​ $ 14,940 ​ $ 3,418,625 ​ $ 3,433,565 Consumer mortgage ​ 11,449 ​ 3,182 ​ 14,821 ​ 29,452 ​ 2,380,797 ​ 2,410,249 Consumer indirect ​ 8,711 ​ 12 ​ 1 ​ 8,724 ​ 1,031,201 ​ 1,039,925 Consumer direct ​ 1,060 ​ 34 ​ 3 ​ 1,097 ​ 160,542 ​ 161,639 Home equity ​ 2,179 ​ 220 ​ 2,181 ​ 4,580 ​ 408,685 ​ 413,265 Total ​ $ 26,550 ​ $ 3,487 ​ $ 28,756 ​ $ 58,793 ​ $ 7,399,850 ​ $ 7,458,643 ​ The following is an aged analysis of the Company’s past due loans by segment as of December 31, 2019: Legacy Loans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Current Total Loans Business lending ​ $ 3,936 ​ $ 126 ​ $ 3,840 ​ $ 7,902 ​ $ 1,848,683 ​ $ 1,856,585 Consumer mortgage ​ 10,990 ​ 2,052 ​ 10,131 ​ 23,173 ​ 1,973,543 ​ 1,996,716 Consumer indirect ​ 12,673 ​ 125 ​ 0 ​ 12,798 ​ 1,094,510 ​ 1,107,308 Consumer direct ​ 1,455 ​ 76 ​ 0 ​ 1,531 ​ 174,445 ​ 175,976 Home equity ​ 1,508 ​ 328 ​ 1,444 ​ 3,280 ​ 310,727 ​ 314,007 Total ​ $ 30,562 ​ $ 2,707 ​ $ 15,415 ​ $ 48,684 ​ $ 5,401,908 ​ $ 5,450,592 ​ Acquired Loans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ Acquired ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Impaired (1) Current Total Loans Business lending ​ $ 8,518 ​ $ 2,173 ​ $ 570 ​ $ 11,261 ​ $ 11,797 ​ $ 896,233 ​ $ 919,291 Consumer mortgage ​ 890 ​ 277 ​ 2,386 ​ 3,553 ​ 0 ​ 430,633 ​ 434,186 Consumer indirect ​ 79 ​ 31 ​ 0 ​ 110 ​ 0 ​ 5,644 ​ 5,754 Consumer direct ​ 59 ​ 0 ​ 52 ​ 111 ​ 0 ​ 8,291 ​ 8,402 Home equity ​ 744 ​ 238 ​ 412 ​ 1,394 ​ 0 ​ 70,924 ​ 72,318 Total ​ $ 10,290 ​ $ 2,719 ​ $ 3,420 ​ $ 16,429 ​ $ 11,797 ​ $ 1,411,725 ​ $ 1,439,951 ​ (1) Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performing under ASC 310-30. As a result interest income, through the accretion of the difference between the carrying amount of the loans and the expected cashflows, is being recognized on all acquired impaired loans.
Impaired business lending loans	All loan classes are collectively evaluated for impairment except business lending. A summary of individually evaluated impaired business lending loans as of September 30, 2020 and December 31, 2019 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, (000’s omitted) 2020 2019 Loans with allowance allocation ​ $ 6,842 ​ $ 0 Loans without allowance allocation ​ 1,414 ​ 1,414 Carrying balance ​ 8,256 ​ 1,414 Contractual balance ​ 10,558 ​ 2,944 Specifically allocated allowance ​ 882 ​ 0 ​
Troubled Debt Restructurings on Financing Receivables	Information regarding TDRs as of September 30, 2020 and December 31, 2019 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ December 31, 2019 (000’s omitted) Nonaccrual Accruing Total Nonaccrual Accruing Total ​ # Amount # Amount # Amount # Amount # Amount # Amount Business lending 8 ​ $ 602 3 ​ $ 195 11 ​ $ 797 8 ​ $ 681 3 ​ $ 201 11 ​ $ 882 Consumer mortgage 57 ​ 2,478 47 ​ 2,330 104 ​ 4,808 59 ​ 2,638 47 ​ 1,892 106 ​ 4,530 Consumer indirect 0 ​ 0 85 ​ 935 85 ​ 935 0 ​ 0 84 ​ 941 84 ​ 941 Consumer direct 0 ​ 0 24 ​ 94 24 ​ 94 0 ​ 0 23 ​ 101 23 ​ 101 Home equity 11 ​ 277 13 ​ 272 24 ​ 549 13 ​ 290 11 ​ 238 24 ​ 528 Total 76 ​ $ 3,357 172 ​ $ 3,826 248 ​ $ 7,183 80 ​ $ 3,609 168 ​ $ 3,373 248 ​ $ 6,982 ​ The following table presents information related to loans modified in a TDR during the three months and nine months ended September 30, 2020 and 2019. Of the loans noted in the table below, all consumer mortgage loans for the three months and nine months ended September 30, 2020 and 2019 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 ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ Number of ​ Outstanding ​ Number of ​ Outstanding (000’s omitted) loans modified Balance loans modified Balance Business lending 0 ​ $ 0 1 ​ $ 415 Consumer mortgage 8 ​ 646 8 ​ 464 Consumer indirect 14 ​ 131 10 ​ 116 Consumer direct 1 ​ 2 2 ​ 25 Home equity 2 ​ 56 0 ​ 0 Total 25 ​ $ 835 21 ​ $ 1,020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended ​ Nine Months Ended ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ Number of ​ Outstanding ​ Number of ​ Outstanding (000’s omitted) loans modified Balance loans modified Balance Business lending ​ 0 ​ $ 0 3 ​ $ 660 Consumer mortgage ​ 17 ​ 1,378 19 ​ 1,271 Consumer indirect ​ 25 ​ 261 22 ​ 206 Consumer direct ​ 2 ​ 12 5 ​ 35 Home equity ​ 2 ​ 56 4 ​ 72 Total ​ 46 ​ $ 1,707 53 ​ $ 2,244
Allowance for Credit Losses by Class	The following presents by segment the activity in the allowance for credit losses: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2020 ​ ​ Beginning ​ Charge- ​ ​ ​ ​ ​ ​ ​ Ending (000’s omitted) balance offs Recoveries Provision balance Business lending ​ $ 24,204 ​ $ (736) ​ $ 67 ​ $ 3,539 ​ $ 27,074 Consumer mortgage ​ 13,088 ​ (248) ​ 23 ​ (599) ​ 12,264 Consumer indirect ​ 15,866 ​ (1,281) ​ 1,111 ​ (963) ​ 14,733 Consumer direct ​ 4,028 ​ (340) ​ 225 ​ (120) ​ 3,793 Home equity ​ 2,690 ​ (24) ​ 5 ​ (124) ​ 2,547 Unallocated ​ 1,000 ​ 0 ​ 0 ​ 4 ​ 1,004 Purchased credit deteriorated ​ 3,561 ​ (91) ​ 32 ​ 45 ​ 3,547 Allowance for credit losses ​ 64,437 ​ (2,720) ​ 1,463 ​ 1,782 ​ 64,962 Liabilities for off-balance-sheet credit exposures ​ 1,452 ​ 0 ​ 0 ​ 163 ​ 1,615 Total allowance for credit losses and liabilities for off-balance-sheet credit exposures ​ $ 65,889 ​ $ (2,720) ​ $ 1,463 ​ $ 1,945 ​ $ 66,577 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2019 ​ ​ Business ​ Consumer ​ Consumer ​ Consumer ​ Home ​ ​ ​ ​ Acquired ​ ​ ​ (000’s omitted) Lending Mortgage Indirect Direct Equity Unallocated Impaired Total Beginning balance ​ $ 17,769 ​ $ 10,763 ​ $ 14,345 ​ $ 3,184 ​ $ 2,103 ​ $ 991 ​ $ 155 ​ $ 49,310 Charge-offs ​ (305) ​ (200) ​ (2,224) ​ (456) ​ (45) ​ 0 ​ 0 ​ (3,230) Recoveries ​ 290 ​ 8 ​ 1,095 ​ 167 ​ 32 ​ 0 ​ 0 ​ 1,592 Provision ​ 301 ​ (94) ​ 1,221 ​ 383 ​ (8) ​ (53) ​ 1 ​ 1,751 Ending balance ​ $ 18,055 ​ $ 10,477 ​ $ 14,437 ​ $ 3,278 ​ $ 2,082 ​ $ 938 ​ $ 156 ​ $ 49,423 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 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 ​ $ (919) ​ $ 289 ​ $ 2,483 ​ $ 5,507 ​ $ 27,074 Consumer mortgage ​ 10,269 ​ (1,051) ​ 9,218 ​ (668) ​ 67 ​ 146 ​ 3,501 ​ 12,264 Consumer indirect ​ 13,712 ​ (997) ​ 12,715 ​ (4,791) ​ 3,107 ​ 183 ​ 3,519 ​ 14,733 Consumer direct ​ 3,255 ​ (643) ​ 2,612 ​ (1,214) ​ 578 ​ 87 ​ 1,730 ​ 3,793 Home equity ​ 2,129 ​ 808 ​ 2,937 ​ (178) ​ 23 ​ 235 ​ (470) ​ 2,547 Unallocated ​ 957 ​ 43 ​ 1,000 ​ 0 ​ 0 ​ 0 ​ 4 ​ 1,004 Purchased credit deteriorated ​ 0 ​ 3,072 ​ 3,072 ​ (91) ​ 80 ​ 528 ​ (42) ​ 3,547 Purchased credit impaired ​ 163 ​ (163) ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 Allowance for credit losses ​ 49,911 ​ 1,357 ​ 51,268 ​ (7,861) ​ 4,144 ​ 3,662 ​ 13,749 ​ 64,962 Liabilities for off-balance-sheet credit exposures ​ 0 ​ 1,185 ​ 1,185 ​ 0 ​ 0 ​ 67 ​ 363 ​ 1,615 Total allowance for credit losses and liabilities for off-balance-sheet credit exposures ​ $ 49,911 ​ $ 2,542 ​ $ 52,453 ​ $ (7,861) ​ $ 4,144 ​ $ 3,729 ​ $ 14,112 ​ $ 66,577 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2019 ​ ​ Business ​ Consumer ​ Consumer ​ Consumer ​ Home ​ ​ ​ ​ Acquired ​ ​ (000’s omitted) Lending Mortgage Indirect Direct Equity Unallocated Impaired Total Beginning balance ​ $ 18,522 ​ $ 10,124 ​ $ 14,366 ​ $ 3,095 ​ $ 2,144 ​ $ 1,000 ​ $ 33 ​ $ 49,284 Charge-offs ​ (1,774) ​ (1,040) ​ (5,529) ​ (1,436) ​ (223) ​ 0 ​ 0 ​ (10,002) Recoveries ​ 593 ​ 44 ​ 3,296 ​ 567 ​ 68 ​ 0 ​ 0 ​ 4,568 Provision ​ 714 ​ 1,349 ​ 2,304 ​ 1,052 ​ 93 ​ (62) ​ 123 ​ 5,573 Ending balance ​ $ 18,055 ​ $ 10,477 ​ $ 14,437 ​ $ 3,278 ​ $ 2,082 ​ $ 938 ​ $ 156 ​ $ 49,423
Carrying Amounts of Loans Purchased and Sold	The following table presents the carrying amounts of loans purchased and sold during the nine months ended September 30, 2020 by portfolio segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Business ​ Consumer ​ Consumer ​ Consumer ​ Home ​ ​ ​ (000’s omitted) lending mortgage indirect direct equity Total Purchases ​ $ 253,368 ​ $ 26,721 ​ $ 13,926 ​ $ 5,994 ​ $ 39,554 ​ $ 339,563 Sales ​ ​ 0 ​ ​ 37,409 ​ ​ 0 ​ ​ 0 ​ ​ 0 ​ ​ 37,409
Business Lending [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans by Credit Quality Indicator	The following tables show the amount of business lending loans by credit quality category at September 30, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ September 30, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Business lending: ​ ​ ​ ​ ​ ​ ​ ​ Risk rating ​ ​ ​ ​ ​ ​ ​ ​ Pass ​ $ 783,726 ​ $ 351,036 ​ $ 337,662 ​ $ 243,816 ​ $ 246,551 ​ $ 576,220 ​ $ 483,163 ​ $ 3,022,174 Special mention ​ 14,008 ​ 39,130 ​ 20,714 ​ 19,157 ​ 29,987 ​ 65,627 ​ 53,293 ​ 241,916 Classified ​ 5,942 ​ 2,852 ​ 28,228 ​ 14,084 ​ 14,363 ​ 61,121 ​ 41,996 ​ 168,586 Doubtful ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 ​ 889 ​ 889 Total business lending ​ $ 803,676 ​ $ 393,018 ​ $ 386,604 ​ $ 277,057 ​ $ 290,901 ​ $ 702,968 ​ $ 579,341 ​ $ 3,433,565 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 (000’s omitted) Legacy Acquired Total Pass ​ $ 1,655,280 ​ $ 832,693 ​ $ 2,487,973 Special mention ​ 98,953 ​ 45,324 ​ 144,277 Classified ​ 102,352 ​ 29,477 ​ 131,829 Doubtful ​ 0 ​ 0 ​ 0 Acquired impaired ​ 0 ​ 11,797 ​ 11,797 Total ​ $ 1,856,585 ​ $ 919,291 ​ $ 2,775,876
All Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans by Credit Quality Indicator	The following table details the balances in all other loan categories at September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ September 30, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Consumer mortgage: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ FICO AB ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 182,675 ​ $ 237,891 ​ $ 176,837 ​ $ 175,605 ​ $ 170,844 ​ $ 664,129 ​ $ 582 ​ $ 1,608,563 Nonperforming ​ 0 ​ 0 ​ 329 ​ 444 ​ 311 ​ 3,556 ​ 0 ​ 4,640 Total FICO AB ​ 182,675 ​ 237,891 ​ 177,166 ​ 176,049 ​ 171,155 ​ 667,685 ​ 582 ​ 1,613,203 FICO CDE ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ 75,419 ​ 106,072 ​ 84,280 ​ 79,292 ​ 87,578 ​ 337,097 ​ 13,945 ​ 783,683 Nonperforming ​ 0 ​ 647 ​ 482 ​ 813 ​ 1,530 ​ 9,891 ​ 0 ​ 13,363 Total FICO CDE ​ 75,419 ​ 106,719 ​ 84,762 ​ 80,105 ​ 89,108 ​ 346,988 ​ 13,945 ​ 797,046 Total consumer mortgage ​ $ 258,094 ​ $ 344,610 ​ $ 261,928 ​ $ 256,154 ​ $ 260,263 ​ $ 1,014,673 ​ $ 14,527 ​ $ 2,410,249 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer indirect: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 227,697 ​ $ 338,279 ​ $ 230,246 ​ $ 100,529 ​ $ 73,331 ​ $ 69,830 ​ $ 0 ​ $ 1,039,912 Nonperforming ​ 0 ​ 5 ​ 0 ​ 4 ​ 1 ​ 3 ​ 0 ​ 13 Total consumer indirect ​ $ 227,697 ​ $ 338,284 ​ $ 230,246 ​ $ 100,533 ​ $ 73,332 ​ $ 69,833 ​ 0 ​ $ 1,039,925 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer direct: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 42,905 ​ $ 53,421 ​ $ 32,359 ​ $ 14,773 ​ $ 6,707 ​ $ 4,722 ​ $ 6,715 ​ $ 161,602 Nonperforming ​ 0 ​ 4 ​ 9 ​ 0 ​ 24 ​ 0 ​ 0 ​ 37 Total consumer direct ​ $ 42,905 ​ $ 53,425 ​ $ 32,368 ​ $ 14,773 ​ $ 6,731 ​ $ 4,722 ​ $ 6,715 ​ $ 161,639 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Home equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 40,760 ​ $ 51,240 ​ $ 29,904 ​ $ 25,286 ​ $ 19,964 ​ $ 39,429 ​ $ 204,281 ​ $ 410,864 Nonperforming ​ 0 ​ 0 ​ 82 ​ 110 ​ 212 ​ 481 ​ 1,516 ​ 2,401 Total home equity ​ $ 40,760 ​ $ 51,240 ​ $ 29,986 ​ $ 25,396 ​ $ 20,176 ​ $ 39,910 ​ $ 205,797 ​ $ 413,265 ​ The following table details the balances in all other loan categories at December 31, 2019: Legacy Loans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer Consumer Consumer Home ​ ​ (000’s omitted) Mortgage Indirect Direct Equity Total Performing ​ $ 1,984,533 ​ $ 1,107,183 ​ $ 175,900 ​ $ 312,235 ​ $ 3,579,851 Nonperforming ​ 12,183 ​ 125 ​ 76 ​ 1,772 ​ 14,156 Total ​ $ 1,996,716 ​ $ 1,107,308 ​ $ 175,976 ​ $ 314,007 ​ $ 3,594,007 ​ Acquired Loans ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer Consumer Consumer Home ​ ​ (000’s omitted) ​ Mortgage ​ Indirect ​ Direct ​ Equity ​ Total Performing ​ $ 431,523 ​ $ 5,723 ​ $ 8,350 ​ $ 71,668 ​ $ 517,264 Nonperforming ​ 2,663 ​ 31 ​ 52 ​ 650 ​ 3,396 Total ​ $ 434,186 ​ $ 5,754 ​ $ 8,402 ​ $ 72,318 ​ $ 520,660

GOODWILL AND IDENTIFIABLE INT_2

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Tables)	9 Months Ended
	Sep. 30, 2020
GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS
Gross Carrying Amount and Accumulated Amortization of Identifiable Intangible Assets	The gross carrying amount and accumulated amortization for each type of identifiable intangible asset are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 December 31, 2019 ​ ​ 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 ​ $ (54,217) ​ $ 15,186 ​ $ 66,475 ​ $ (50,057) ​ $ 16,418 Other intangibles ​ 90,462 ​ (49,183) ​ 41,279 ​ 89,266 ​ (42,571) ​ 46,695 Total amortizing intangibles ​ $ 159,865 ​ $ (103,400) ​ $ 56,465 ​ $ 155,741 ​ $ (92,628) ​ $ 63,113
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) Oct - Dec 2020 ​ $ 3,525 2021 ​ 12,640 2022 ​ 10,844 2023 ​ 9,082 2024 ​ 7,551 Thereafter ​ 12,823 Total ​ $ 56,465
Components of Goodwill	Shown below are the components of the Company’s goodwill at December 31, 2019 and September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) December 31, 2019 Activity September 30, 2020 Goodwill, net ​ $ 773,810 ​ $ 19,939 ​ $ 793,749

MANDATORILY REDEEMABLE PREFER_2

MANDATORILY REDEEMABLE PREFERRED SECURITIES (Tables)	9 Months Ended
	Sep. 30, 2020
MANDATORILY REDEEMABLE PREFERRED SECURITIES
Terms of Preferred Securities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Issuance Par Maturity Trust ​ Date ​ Amount ​ Interest Rate ​ Date ​ Call Price CCT IV 12/8/2006 ​ $ 75.0 million 3 month 12/15/2036 Par

BENEFIT PLANS (Tables)

BENEFIT PLANS (Tables)	9 Months Ended
	Sep. 30, 2020
BENEFIT PLANS
Net Periodic Benefit Cost	The net periodic benefit cost for the three and nine months ended September 30, 2020 and 2019 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension Benefits ​ Post-retirement Benefits ​ ​ Three Months Ended ​ Nine Months Ended ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, ​ September 30, ​ September 30, (000's omitted) 2020 2019 2020 ​ 2019 2020 ​ 2019 ​ 2020 2019 Service cost ​ $ 1,438 ​ $ 1,270 ​ $ 4,313 ​ $ 3,811 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 Interest cost 1,356 1,566 ​ 4,068 ​ 4,698 15 ​ 18 ​ 43 ​ 53 Expected return on plan assets ​ (3,932) ​ (3,578) ​ ​ (11,796) ​ ​ (10,733) ​ 0 ​ 0 ​ ​ 0 ​ 0 Amortization of unrecognized net loss ​ 810 ​ 642 ​ ​ 2,430 ​ ​ 1,926 ​ 10 ​ 9 ​ ​ 30 ​ 28 Amortization of prior service cost ​ 60 ​ 17 ​ ​ 180 ​ ​ 48 ​ (45) ​ (45) ​ ​ (134) ​ (134) Net periodic benefit ​ $ (268) ​ $ (83) ​ $ (805) ​ $ (250) ​ $ (20) ​ $ (18) ​ $ (61) ​ $ (53)

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2020
EARNINGS PER SHARE
Reconciliation of Basic to Diluted Earnings per Share	The following is a reconciliation of basic to diluted earnings per share for the three and nine months ended September 30, 2020 and 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Nine Months Ended ​ ​ September 30, ​ September 30, (000's omitted, except per share data) 2020 2019 2020 2019 Net income ​ $ 42,809 ​ $ 39,218 ​ $ 118,191 ​ $ 126,179 Income attributable to unvested stock-based compensation awards ​ (147) ​ (102) ​ (432) ​ (331) Income available to common shareholders ​ $ 42,662 ​ $ 39,116 ​ $ 117,759 ​ $ 125,848 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 53,650 ​ 51,750 ​ 52,727 ​ 51,644 Basic earnings per share ​ $ 0.80 ​ $ 0.76 ​ $ 2.23 ​ $ 2.44 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income ​ $ 42,809 ​ $ 39,218 ​ $ 118,191 ​ $ 126,179 Income attributable to unvested stock-based compensation awards ​ (147) ​ (102) ​ (432) ​ (331) Income available to common shareholders ​ $ 42,662 ​ $ 39,116 ​ $ 117,759 ​ $ 125,848 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 53,650 ​ 51,750 ​ 52,727 ​ 51,644 Assumed exercise of stock options ​ 324 ​ 496 ​ 356 ​ 522 Weighted-average common shares outstanding – diluted ​ 53,974 ​ 52,246 ​ 53,083 ​ 52,166 Diluted earnings per share ​ $ 0.79 ​ $ 0.75 ​ $ 2.22 ​ $ 2.41

COMMITMENTS, CONTINGENT LIABI_2

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS (Tables)	9 Months Ended
	Sep. 30, 2020
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS
Off Balance Sheet Financial Instruments Contract Amounts	The contract amounts of commitments and contingencies are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, December 31, (000's omitted) ​ 2020 ​ 2019 Commitments to extend credit ​ $ 1,201,285 ​ $ 1,143,780 Standby letters of credit ​ 43,283 ​ 37,872 Total ​ $ 1,244,568 ​ $ 1,181,652

FAIR VALUE (Tables)

FAIR VALUE (Tables)	9 Months Ended
	Sep. 30, 2020
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. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 (000's omitted) Level 1 Level 2 Level 3 Total Fair Available-for-sale investment securities: ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 1,982,893 ​ $ 166,277 ​ $ 0 ​ $ 2,149,170 Obligations of state and political subdivisions ​ 0 ​ 493,496 ​ 0 ​ 493,496 Government agency mortgage-backed securities ​ 0 ​ 523,974 ​ 0 ​ 523,974 Corporate debt securities ​ 0 ​ 4,602 ​ 0 ​ 4,602 Government agency collateralized mortgage obligations ​ 0 ​ 51,480 ​ 0 ​ 51,480 Total available-for-sale investment securities ​ 1,982,893 ​ 1,239,829 ​ 0 ​ 3,222,722 Equity securities ​ 423 ​ 0 ​ 0 ​ 423 Mortgage loans held for sale ​ 0 ​ 8,151 ​ 0 ​ 8,151 Commitments to originate real estate loans for sale ​ 0 ​ 0 ​ 2,684 ​ 2,684 Forward sales commitments ​ 0 ​ 510 ​ 0 ​ 510 Interest rate swap agreements asset ​ 0 ​ 1,756 ​ 0 ​ 1,756 Interest rate swap agreements liability ​ 0 ​ (1,194) ​ 0 ​ (1,194) Total ​ $ 1,983,316 ​ $ 1,249,052 ​ $ 2,684 ​ $ 3,235,052 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2019 (000's omitted) Level 1 Level 2 Level 3 Total Fair Available-for-sale investment securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 1,878,705 ​ $ 165,054 ​ $ 0 ​ $ 2,043,759 Obligations of state and political subdivisions ​ 0 ​ 512,208 ​ 0 ​ 512,208 Government agency mortgage-backed securities ​ 0 ​ 432,862 ​ 0 ​ 432,862 Corporate debt securities ​ 0 ​ 2,528 ​ 0 ​ 2,528 Government agency collateralized mortgage obligations ​ 0 ​ 53,071 ​ 0 ​ 53,071 Total available-for-sale investment securities ​ 1,878,705 ​ 1,165,723 ​ 0 ​ 3,044,428 Equity securities ​ 451 ​ 0 ​ 0 ​ 451 Interest rate swap agreements asset ​ 0 ​ 851 ​ 0 ​ 851 Interest rate swap agreements liability ​ 0 ​ (586) ​ 0 ​ (586) Total ​ $ 1,879,156 ​ $ 1,165,988 ​ 0 ​ $ 3,045,144
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. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 December 31, 2019 (000's omitted) Level 1 Level 2 Level 3 Total Fair Level 1 Level 2 Level 3 Total Fair Impaired loans ​ $ 0 ​ $ 0 ​ $ 6,808 ​ $ 6,808 ​ $ 0 ​ $ 0 ​ $ 848 ​ $ 848 Other real estate owned ​ 0 ​ 0 ​ 1,209 ​ 1,209 ​ 0 ​ 0 ​ 1,270 ​ 1,270 Mortgage servicing rights ​ 0 ​ 0 ​ 460 ​ 460 ​ 0 ​ 0 ​ 56 ​ 56 Total ​ $ 0 ​ $ 0 ​ $ 8,477 ​ $ 8,477 ​ $ 0 ​ $ 0 ​ $ 2,174 ​ $ 2,174
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) ​ September 30, 2020 ​ Valuation Technique ​ Significant Unobservable Inputs (Weighted Average) ​ Impaired loans ​ $ 6,808 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 78.7% (58.8%) ​ Other real estate owned ​ 1,209 Fair value of collateral Estimated cost of disposal/market adjustment ​ 15.2% - 53.5% (31.3%) ​ Commitments to originate real estate loans for sale ​ 2,684 Discounted cash flow Embedded servicing value ​ 1.0 % Mortgage servicing rights ​ 460 Discounted cash flow Weighted average constant prepayment rate ​ 13.8% - 14.7% (14.6%) ​ ​ ​ ​ ​ ​ ​ ​ Weighted average discount rate ​ ​ 1.22% - 1.98% (1.92%) ​ ​ ​ ​ ​ ​ ​ ​ Adequate compensation ​ $ 7/loan ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ ​ Unobservable Input ​ ​ ​ Fair Value at ​ ​ ​ ​ ​ Range ​ (000's omitted) ​ December 31, 2019 ​ Valuation Technique ​ Significant Unobservable Inputs ​ (Weighted Average) Impaired loans ​ $ 848 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 35.0% (27.9%) ​ Other real estate owned ​ 1,270 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 85.7% (37.1%) ​ Mortgage servicing rights ​ 56 Discounted cash flow Weighted average constant prepayment rate ​ 52.8 % ​ ​ Weighted average discount rate ​ 3.00 % ​ ​ ​ ​ ​ ​ 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 September 30, 2020 and December 31, 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 December 31, 2019 ​ ​ Carrying ​ Fair ​ Carrying ​ Fair (000's omitted) Value Value Value Value Financial assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loans ​ $ 7,393,681 ​ $ 7,710,461 ​ $ 6,840,632 ​ $ 7,028,663 Financial liabilities: ​ ​ ​ ​ Deposits ​ 11,120,590 ​ 11,135,779 ​ 8,994,967 ​ 8,997,551 Overnight Federal Home Loan Bank borrowings ​ 0 ​ 0 ​ 8,300 ​ 8,300 Securities sold under agreement to repurchase, short-term ​ 280,767 ​ 280,767 ​ 241,708 ​ 241,708 Other Federal Home Loan Bank borrowings ​ 7,681 ​ 7,810 ​ 3,750 ​ 3,755 Subordinated notes payable ​ 13,735 ​ 13,735 ​ 13,795 ​ 13,795 Subordinated debt held by unconsolidated subsidiary trusts ​ 77,320 ​ 77,320 ​ 77,320 ​ 77,320 ​

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2020
DERIVATIVE INSTRUMENTS
Amounts Related to Cumulative Basis Adjustments for Fair Value Hedges	As of September 30, 2020 and December 31, 2019, 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 ​ September 30, ​ December 31, ​ September 30, ​ December 31, the Hedged Item Is Included 2020 2019 2020 2019 Loans $ 5,611 $ 6,390 $ (562) $ (265)
Fair Value of Derivative Instruments	Fair values of derivative instruments as of September 30, 2020 and December 31, 2019 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ September 30, 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 ​ $ 562 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ 1,194 Accrued interest and other liabilities ​ $ 1,194 Commitments to originate real estate loans for sale Other assets ​ 2,684 ​ Forward sales commitments Other assets ​ 510 ​ Total derivatives ​ $ 4,950 ​ $ 1,194 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ December 31, 2019 ​ ​ 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 ​ $ 265 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ 586 Accrued interest and other liabilities ​ $ 586 Total derivatives ​ $ 851 ​ $ 586 ​

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	9 Months Ended
	Sep. 30, 2020
SEGMENT INFORMATION
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 September 30, 2020 ​ ​ ​ ​ ​ Net interest income ​ $ 92,642 ​ $ 256 ​ $ 67 ​ $ 0 ​ $ 92,965 Provision for credit losses ​ 1,945 ​ 0 ​ 0 ​ 0 ​ 1,945 Noninterest revenues ​ 19,756 ​ 25,651 ​ 15,706 ​ (1,454) ​ 59,659 Amortization of intangible assets ​ 1,379 ​ 1,409 ​ 793 ​ 0 ​ 3,581 Acquisition expenses ​ 796 ​ 0 ​ 0 ​ 0 ​ 796 Other operating expenses ​ 67,193 ​ 15,078 ​ 11,772 ​ (1,454) ​ 92,589 Income before income taxes ​ $ 41,085 ​ $ 9,420 ​ $ 3,208 ​ $ 0 ​ $ 53,713 Assets ​ $ 13,674,995 ​ $ 210,679 ​ $ 80,528 ​ $ (120,877) ​ $ 13,845,325 Goodwill ​ $ 690,162 ​ $ 83,275 ​ $ 20,312 ​ $ 0 ​ $ 793,749 Core deposit intangibles & Other intangibles ​ $ 15,186 ​ $ 33,461 ​ $ 7,818 ​ $ 0 ​ $ 56,465 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net interest income ​ $ 91,018 ​ $ 209 ​ $ 49 ​ $ 0 ​ $ 91,276 Provision for credit losses ​ 1,751 ​ 0 ​ 0 ​ 0 ​ 1,751 Noninterest revenues ​ 17,790 ​ 24,830 ​ 15,143 ​ (669) ​ 57,094 Amortization of intangible assets ​ 1,439 ​ 1,667 ​ 854 ​ 0 ​ 3,960 Acquisition expenses ​ 6,061 ​ 0 ​ 0 ​ 0 ​ 6,061 Other operating expenses ​ 61,839 ​ 14,721 ​ 11,017 ​ (669) ​ 86,908 Income before income taxes ​ $ 37,718 ​ $ 8,651 ​ $ 3,321 ​ $ 0 ​ $ 49,690 Assets ​ $ 11,398,191 ​ $ 201,442 ​ $ 74,169 ​ $ (76,505) ​ $ 11,597,297 Goodwill ​ $ 670,023 ​ $ 83,275 ​ $ 20,312 ​ $ 0 ​ $ 773,610 Core deposit intangibles & Other intangibles ​ $ 17,872 ​ $ 39,440 ​ $ 9,763 ​ $ 0 ​ $ 67,075 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee ​ ​ ​ ​ ​ ​ ​ Consolidated (000's omitted) Banking Benefit Services All Other Eliminations Total Nine Months Ended September 30, 2020 ​ ​ ​ ​ ​ Net interest income ​ $ 274,051 ​ $ 742 ​ $ 177 ​ $ 0 ​ $ 274,970 Provision for credit losses ​ 17,313 ​ 0 ​ 0 ​ 0 ​ 17,313 Noninterest revenues ​ 53,428 ​ 76,080 ​ 46,058 ​ (4,347) ​ 171,219 Amortization of intangible assets ​ 4,160 ​ 4,314 ​ 2,298 ​ 0 ​ 10,772 Acquisition expenses ​ 4,537 ​ 0 ​ 0 ​ 0 ​ 4,537 Other operating expenses ​ 190,523 ​ 45,157 ​ 34,890 ​ (4,347) ​ 266,223 Income before income taxes ​ $ 110,946 ​ $ 27,351 ​ $ 9,047 ​ $ 0 ​ $ 147,344 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2019 ​ ​ ​ ​ ​ ​ ​ ​ ​ Net interest income ​ $ 265,860 ​ $ 448 ​ $ 127 ​ $ 0 ​ $ 266,435 Provision for credit losses ​ 5,573 ​ 0 ​ 0 ​ 0 ​ 5,573 Noninterest revenues ​ 57,059 ​ 73,919 ​ 44,749 ​ (2,231) ​ 173,496 Amortization of intangible assets ​ 4,297 ​ 5,105 ​ 2,592 ​ 0 ​ 11,994 Acquisition expenses ​ 7,789 ​ 0 ​ 0 ​ 0 ​ 7,789 Other operating expenses ​ 182,186 ​ 43,985 ​ 33,034 ​ (2,231) ​ 256,974 Income before income taxes ​ $ 123,074 ​ $ 25,277 ​ $ 9,250 ​ $ 0 ​ $ 157,601

ACQUISITIONS (Details)

ACQUISITIONS (Details) shares in Thousands, $ in Thousands	Jun. 12, 2020USD ($)countryOfficeshares	Sep. 18, 2019USD ($)	Jul. 12, 2019USD ($)Officecountry	Jan. 02, 2019USD ($)	Sep. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Acquisitions
Cash			$ 95,034
Deposits			568,161
Goodwill			39,970		$ 793,749		$ 793,749	$ 773,610	$ 773,810
Loans acquired							339,563
Investment securities			$ 39,770
Increase in deposits							1,609,349	$ 277,833
Upstate New York
Acquisitions
Number of new counties where the bank has extended footprints | country			5
Customer Lists
Acquisitions
Cash		$ 500
Intangibles		$ 500
Steuben
Acquisitions
Issuance of common shares (in shares) | shares	1,360
Cash	$ 21,613
Deposits	516,274
Goodwill	20,276
Assets acquired	607,700
Loans acquired	339,500
Investment securities	180,497
Revenues					3,800		4,500
Direct expenses					1,100		1,400
Increase (decrease) in goodwill as a result of fair value adjustment					1,100
Decrease in loans					200
Decrease in premises and equipment					500
Decrease in other assets					1,700
Decrease in accrued interest and other liabilities					1,300
Steuben | New York
Acquisitions
Investment securities	$ 180,500
Steuben | Western New York State
Acquisitions
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
Kinderhook Bank Corp
Acquisitions
Cash			$ 93,384
Deposits			568,161
Goodwill			39,970
Assets acquired			642,800
Loans acquired			479,900
Investment securities			39,770
Revenues					3,800		12,700
Direct expenses					$ 2,200		$ 5,800
Increase in deposits			568,200
Increased in accrued interest and fees receivable						$ 300
Increase (decrease) in goodwill as a result of fair value adjustment			40,000			$ 300
Kinderhook Bank Corp | New York
Acquisitions
Cash			93,400
Investment securities			$ 39,800
Kinderhook Bank Corp | Upstate New York
Acquisitions
Number of branch locations | Office			11
Wealth Resources Network, Inc | Customer Lists
Acquisitions
Cash				$ 1,200
Intangibles				$ 1,200

ACQUISITIONS - Estimated Fair V

ACQUISITIONS - Estimated Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Jun. 12, 2020	Jul. 12, 2019	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Consideration paid [Abstract]
Cash		$ 95,034
Community Bank System, Inc. common stock		0
Total net consideration paid		95,034
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents		90,381
Investment securities		39,770
Loans, net of allowance for credit losses on PCD loans		479,877
Premises and equipment, net		13,970
Accrued interest and fees receivable		1,130
Other assets		14,109
Deposits		(568,161)
Other liabilities		(2,922)
Other Federal Home Loan Bank borrowings		(2,420)
Subordinated notes payable		(13,831)
Subordinated debt held by unconsolidated subsidiary trusts		(2,062)
Total identifiable assets, net		55,064
Goodwill		39,970	$ 793,749	$ 773,810	$ 773,610
Core Deposit Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles		3,573
Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles		1,650
Steuben
Consideration paid [Abstract]
Cash	$ 21,613
Community Bank System, Inc. common stock	76,942
Total net consideration paid	98,555
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents	55,973
Investment securities	180,497
Loans, net of allowance for credit losses on PCD loans	339,017
Premises and equipment, net	7,764
Accrued interest and fees receivable	2,712
Other assets	17,633
Deposits	(516,274)
Other liabilities	(5,105)
Other Federal Home Loan Bank borrowings	(6,000)
Subordinated notes payable	0
Subordinated debt held by unconsolidated subsidiary trusts	(2,062)
Total identifiable assets, net	78,279
Goodwill	20,276
Steuben | Core Deposit Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles	2,928
Steuben | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles	$ 1,196
Kinderhook Bank Corp
Consideration paid [Abstract]
Cash		93,384
Community Bank System, Inc. common stock		0
Total net consideration paid		93,384
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents		90,381
Investment securities		39,770
Loans, net of allowance for credit losses on PCD loans		479,877
Premises and equipment, net		13,970
Accrued interest and fees receivable		1,130
Other assets		14,109
Deposits		(568,161)
Other liabilities		(2,922)
Other Federal Home Loan Bank borrowings		(2,420)
Subordinated notes payable		(13,831)
Subordinated debt held by unconsolidated subsidiary trusts		(2,062)
Total identifiable assets, net		53,414
Goodwill		39,970
Kinderhook Bank Corp | Core Deposit Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles		3,573
Kinderhook Bank Corp | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles		0
Other
Consideration paid [Abstract]
Cash		1,650
Community Bank System, Inc. common stock		0
Total net consideration paid		1,650
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents		0
Investment securities		0
Loans, net of allowance for credit losses on PCD loans		0
Premises and equipment, net		0
Accrued interest and fees receivable		0
Other assets		0
Deposits		0
Other liabilities		0
Other Federal Home Loan Bank borrowings		0
Subordinated notes payable		0
Subordinated debt held by unconsolidated subsidiary trusts		0
Total identifiable assets, net		1,650
Goodwill		0
Other | Core Deposit Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles		0
Other | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles		$ 1,650

ACQUISITIONS - Summary of Loans

ACQUISITIONS - Summary of Loans Acquired (Details) - USD ($) $ in Thousands	Jun. 12, 2020	Jul. 12, 2019
Kinderhook Bank Corp
Summary of loans acquired [Abstract]
Contractually required principal and interest at acquisition		$ 649,734
Contractual cash flows not expected to be collected		(9,648)
Expected cash flows at acquisition		640,086
Interest component of expected cash flows		(160,209)
Fair value of acquired loans		479,877
Kinderhook Bank Corp | Acquired Impaired Loans
Summary of loans acquired [Abstract]
Contractually required principal and interest at acquisition		13,350
Contractual cash flows not expected to be collected		(4,176)
Expected cash flows at acquisition		9,174
Interest component of expected cash flows		(551)
Fair value of acquired loans		8,623
Kinderhook Bank Corp | Acquired Non Impaired Loans
Summary of loans acquired [Abstract]
Contractually required principal and interest at acquisition		636,384
Contractual cash flows not expected to be collected		(5,472)
Expected cash flows at acquisition		630,912
Interest component of expected cash flows		(159,658)
Fair value of acquired loans		$ 471,254
Steuben | Purchased Credit Deteriorated
Summary of loans acquired [Abstract]
Par value of loans at acquisition	$ 24,415
Allowance for credit losses at acquisition	(524)
Non-credit discount at acquisition	(115)
Fair value of acquired loans	23,776
Steuben | Non-PCD Loans
Summary of loans acquired [Abstract]
Contractually required principal and interest at acquisition	416,230
Contractual cash flows not expected to be collected	(3,131)
Expected cash flows at acquisition	413,099
Interest component of expected cash flows	(97,858)
Fair value of acquired loans	$ 315,241

ACQUISITIONS - Intangible Asset

ACQUISITIONS - Intangible Asset, Goodwill and Acquisition-related Expenses (Details) - USD ($) $ in Thousands	Jul. 12, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Fair Value of Subordinated Notes Payable [Abstract]
Subordinated notes payable		$ 13,735		$ 13,735		$ 13,795
Summary of loans acquired [Abstract]
Acquisition-related expenses		796	$ 6,061	$ 4,537	$ 7,789
Subordinated Notes Maturing in February 2028
Fair Value of Subordinated Notes Payable [Abstract]
Subordinated notes payable	$ 3,000
Fixed interest rate percentage	6.00%
Maturity date	Feb. 29, 2028
Subordinated Notes Maturing in November 2025
Fair Value of Subordinated Notes Payable [Abstract]
Subordinated notes payable	$ 10,000
Fixed interest rate percentage	6.375%
Maturity date	Nov. 30, 2025
Kinderhook Bank Corp | Core Deposit Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life				8 years
Kinderhook Bank Corp | Other Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life				8 years
Steuben
Summary of loans acquired [Abstract]
Acquisition-related expenses		$ 800		$ 4,400
Steuben | Core Deposit Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life				8 years
Steuben | Other Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life				8 years

ACQUISITIONS - Supplemental Pro

ACQUISITIONS - Supplemental Pro Forma Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Supplemental Pro Forma Financial Information [Abstract]
Acquisition-related expenses	$ 796	$ 6,061	$ 4,537	$ 7,789
Steuben
Supplemental Pro Forma Financial Information [Abstract]
Acquisition-related expenses	800		4,400
Total revenue, net of interest expense	152,634	154,221	456,740	457,399
Net income	$ 43,472	$ 40,695	$ 124,338	$ 126,874

ACCOUNTING POLICIES (Details)

ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2020
Loans [Abstract]
Accrued interest receivable on loans		$ 23,800
Number of days past due for loans to be placed on nonaccrual status		90 days
Number of days past due after which loans are charged off to the extent outstanding principal balance exceeds fair value of collateral/property		90 days
Contract Balances
Accounts receivable	$ 26,800	$ 28,500
Unbilled fee revenue	7,500	8,300
Unearned revenue	1,800	2,000
New Accounting Pronouncements
Retained earnings	882,851	936,273
Allowance for Credit Losses - Debt Securities
Accrued interest receivable on available-for-sale debt securities		$ 14,200
Consumer Installment Loans [Member]
Loans [Abstract]
Number of days past due after which loans are charged off to the extent outstanding principal balance exceeds fair value of collateral/property		90 days
Consumer Mortgage [Member]
Loans [Abstract]
Number of days past due after which loans are charged off to the extent outstanding principal balance exceeds fair value of collateral/property		180 days
Consumer Mortgage [Member] | Minimum [Member]
New Accounting Pronouncements
Typical contract term		10 years
Consumer Mortgage [Member] | Maximum [Member]
New Accounting Pronouncements
Typical contract term		30 years
Home Equity [Member] | Maximum [Member]
New Accounting Pronouncements
Typical contract term		30 years
Topic ASC 326 | Cumulative Effect Adjustment
New Accounting Pronouncements
Retained earnings	1,100
Increase in allowance for credit losses	1,400
Adjustment to loans	3,100
Increase in other liabilities	600
Addition to allowance for credit losses	$ 3,100

INVESTMENT SECURITIES, Availabl

INVESTMENT SECURITIES, Available-for-Sale Portfolio (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available-for-Sale Portfolio
Amortized cost	$ 3,068,406	$ 3,011,551
Gross unrealized gains	154,602	42,017
Gross unrealized losses	286	9,140
Fair value	3,222,722	3,044,428
Debt Securities, Available-for-sale, Fair Value to Amortized Cost
Amortized cost	3,068,406
Fair value	3,222,722
U.S. Treasury Securities [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost
Amortized cost	2,034,512	2,030,060
Gross unrealized gains	114,658	21,674
Gross unrealized losses	0	7,975
Fair value	2,149,170	2,043,759
Obligations of State and Political Subdivisions [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost
Amortized cost	470,518	497,852
Gross unrealized gains	22,978	14,382
Gross unrealized losses	0	26
Fair value	493,496	512,208
Government Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost
Amortized cost	508,738	428,491
Gross unrealized gains	15,514	5,478
Gross unrealized losses	278	1,107
Fair value	523,974	432,862
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost
Amortized cost	4,504	2,527
Gross unrealized gains	98	1
Gross unrealized losses	0	0
Fair value	4,602	2,528
Government Agency Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost
Amortized cost	50,134	52,621
Gross unrealized gains	1,354	482
Gross unrealized losses	8	32
Fair value	$ 51,480	$ 53,071

INVESTMENT SECURITIES, Equity a

INVESTMENT SECURITIES, Equity and Other Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Equity and Other Securities
Amortized cost	$ 46,419	$ 42,965
Gross unrealized gains	942	950
Gross unrealized losses	20	0
Equity and other securities (cost of $42,965 and $44,678, respectively)	47,341	43,915
Equity Securities, at Fair Value
Amortized cost	251	251
Gross unrealized gains	192	200
Gross unrealized losses	20	0
Fair value	423	451
Federal Home Loan Bank Common Stock [Member]
Equity Securities, at Fair Value
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Other Equity Securities, at Adjusted Cost
Amortized cost	7,545	7,246
Fair value	7,545	7,246
Federal Reserve Bank Common Stock [Member]
Equity Securities, at Fair Value
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Other Equity Securities, at Adjusted Cost
Amortized cost	33,916	30,922
Fair value	33,916	30,922
Other Equity Securities [Member]
Equity Securities, at Fair Value
Gross unrealized losses	0	0
Other Equity Securities, at Adjusted Cost
Amortized cost	4,707	4,546
Gross unrealized gains	750	750
Fair value	$ 5,457	$ 5,296

INVESTMENT SECURITIES, Investme

INVESTMENT SECURITIES, Investment Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Sep. 30, 2020USD ($)position	Dec. 31, 2019USD ($)position
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions
Less than 12 months | position	107	88
12 months or longer | position	3	62
Total | position	110	150
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value
Less than 12 months	$ 67,768	$ 710,602
12 months or longer	14	83,378
Total	67,782	793,980
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses
Less than 12 months	286	8,351
12 months or longer	0	789
Total	$ 286	$ 9,140
Equity and Other Securities, Continuous Unrealized Loss Position, Number of Positions
Less than 12 months | position	1
12 months or longer | position	0
Total | position	1
Equity and Other Securities, Continuous Unrealized Loss Position, Fair Value
Less than 12 months	$ 81
12 months or longer	0
Total	81
Equity and Other Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses
Less than 12 months	20
12 months or longer	0
Total	20
Available-for-sale, allowance for credit losses	$ 0
U.S. Treasury Securities [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions
Less than 12 months | position	1	12
12 months or longer | position	0	5
Total | position	1	17
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value
Less than 12 months	$ 1,010	$ 592,678
12 months or longer	0	25,998
Total	1,010	618,676
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses
Less than 12 months	0	7,970
12 months or longer	0	5
Total	$ 0	$ 7,975
Obligations of State and Political Subdivisions [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions
Less than 12 months | position	1	21
12 months or longer | position	0	0
Total | position	1	21
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value
Less than 12 months	$ 196	$ 22,716
12 months or longer	0	0
Total	196	22,716
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses
Less than 12 months	0	26
12 months or longer	0	0
Total	$ 0	$ 26
Government Agency Mortgage-Backed Securities [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions
Less than 12 months | position	91	50
12 months or longer | position	2	52
Total | position	93	102
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value
Less than 12 months	$ 62,318	$ 89,237
12 months or longer	14	52,975
Total	62,332	142,212
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses
Less than 12 months	278	341
12 months or longer	0	766
Total	$ 278	$ 1,107
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions
Less than 12 months | position	14	5
12 months or longer | position	1	5
Total | position	15	10
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value
Less than 12 months	$ 4,244	$ 5,971
12 months or longer	0	4,405
Total	4,244	10,376
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses
Less than 12 months	8	14
12 months or longer	0	18
Total	$ 8	$ 32
Equity Securities, at Fair Value [Member]
Equity and Other Securities, Continuous Unrealized Loss Position, Number of Positions
Less than 12 months | position	1
12 months or longer | position	0
Total | position	1
Equity and Other Securities, Continuous Unrealized Loss Position, Fair Value
Less than 12 months	$ 81
12 months or longer	0
Total	81
Equity and Other Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses
Less than 12 months	20
12 months or longer	0
Total	$ 20

INVESTMENT SECURITIES, Amortize

INVESTMENT SECURITIES, Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available-for-Sale, Debt Maturities, Amortized Cost
Due in one year or less	$ 760,019
Due after one through five years	802,750
Due after five years through ten years	461,012
Due after ten years	485,753
Subtotal	2,509,534
Amortized cost	3,068,406
Available-for-Sale, Debt Maturities, Fair Value
Due in one year or less	765,009
Due after one through five years	843,487
Due after five years through ten years	503,778
Due after ten years	534,994
Subtotal	2,647,268
Fair value	3,222,722
Government Agency Mortgage-Backed Securities [Member]
Available-for-Sale, Debt Maturities, Amortized Cost
Without single maturity date	508,738
Amortized cost	508,738	$ 428,491
Available-for-Sale, Debt Maturities, Fair Value
Without single maturity date	523,974
Fair value	523,974	432,862
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-Sale, Debt Maturities, Amortized Cost
Without single maturity date	50,134
Amortized cost	50,134	52,621
Available-for-Sale, Debt Maturities, Fair Value
Without single maturity date	51,480
Fair value	$ 51,480	$ 53,071

INVESTMENT SECURITIES, Invest_2

INVESTMENT SECURITIES, Investment Securities Pledged as Collateral (Details) - USD ($)	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Investment Securities Pledged as Collateral
Proceeds from sales of securities	$ 0	$ 590,179,000
U.S. Treasury Securities [Member] | Securities Sold under Agreements to Repurchase [Member]
Investment Securities Pledged as Collateral
Investment securities pledged to collateralize certain deposits and borrowings	$ 295,500,000
Proceeds from sales of securities		590,200,000
Gross realized gains		5,000,000
Gross realized losses		$ 100,000

LOANS, Loan Summary (Details)

LOANS, Loan Summary (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Loans receivable, net
Gross loans, including deferred origination costs	$ 7,458,643		$ 6,890,543
Allowance for credit losses	(64,962)	$ (64,437)	(49,911)	$ (49,423)	$ (49,310)	$ (49,284)
Net loans	7,393,681		6,840,632
Business Lending [Member]
Loans receivable, net
Gross loans, including deferred origination costs			2,775,876
Commercial Portfolio Segment [Member] | Business Lending [Member]
Loans receivable, net
Gross loans, including deferred origination costs	3,433,565		2,775,876
Allowance for credit losses	(27,074)	(24,204)	(19,426)	(18,055)	(17,769)	(18,522)
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Loans receivable, net
Gross loans, including deferred origination costs	2,410,249		2,430,902
Allowance for credit losses	(12,264)	(13,088)	(10,269)	(10,477)	(10,763)	(10,124)
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Loans receivable, net
Gross loans, including deferred origination costs	1,039,925		1,113,062
Allowance for credit losses	(14,733)	(15,866)	(13,712)	(14,437)	(14,345)	(14,366)
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Loans receivable, net
Gross loans, including deferred origination costs	161,639		184,378
Allowance for credit losses	(3,793)	(4,028)	(3,255)	(3,278)	(3,184)	(3,095)
Consumer Portfolio Segment [Member] | Home Equity [Member]
Loans receivable, net
Gross loans, including deferred origination costs	413,265		386,325
Allowance for credit losses	$ (2,547)	$ (2,690)	$ (2,129)	$ (2,082)	$ (2,103)	$ (2,144)

LOANS, Credit Quality By Past D

LOANS, Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2020	Dec. 31, 2019
Aged analysis of the company's loans
90 + days past due and still accruing		$ 3,487
Nonaccrual		28,756
Total past due		58,793
Current		7,399,850
Total loans		7,458,643	$ 6,890,543
Interest income on nonaccrual loans		0
Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		26,550
Legacy Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			2,707
Nonaccrual			15,415
Total past due			48,684
Current			5,401,908
Total loans			5,450,592
Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			30,562
Acquired Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			2,719
Nonaccrual			3,420
Total past due			16,429
Impaired	[1]		11,797
Current			1,411,725
Total loans			1,439,951
Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			10,290
Business Lending [Member]
Aged analysis of the company's loans
Total loans			2,775,876
Business Lending [Member] | Legacy Loans [Member]
Aged analysis of the company's loans
Total loans			1,856,585
Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans
Total loans			919,291
Consumer Mortgage [Member] | Legacy Loans [Member]
Aged analysis of the company's loans
Total loans			1,996,716
Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans
Total loans			434,186
Consumer Indirect [Member] | Legacy Loans [Member]
Aged analysis of the company's loans
Total loans			1,107,308
Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans
Total loans			5,754
Consumer Direct [Member] | Legacy Loans [Member]
Aged analysis of the company's loans
Total loans			175,976
Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans
Total loans			8,402
Home Equity [Member] | Legacy Loans [Member]
Aged analysis of the company's loans
Total loans			314,007
Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans
Total loans			72,318
Commercial Portfolio Segment [Member] | Business Lending [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		39
Nonaccrual		11,750
Total past due		14,940
Current		3,418,625
Total loans		3,433,565	2,775,876
Commercial Portfolio Segment [Member] | Business Lending [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		3,151
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			126
Nonaccrual			3,840
Total past due			7,902
Current			1,848,683
Total loans			1,856,585
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			3,936
Commercial Portfolio Segment [Member] | Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			2,173
Nonaccrual			570
Total past due			11,261
Impaired	[1]		11,797
Current			896,233
Total loans			919,291
Commercial Portfolio Segment [Member] | Business Lending [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			8,518
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		3,182
Nonaccrual		14,821
Total past due		29,452
Current		2,380,797
Total loans		2,410,249	2,430,902
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		11,449
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			2,052
Nonaccrual			10,131
Total past due			23,173
Current			1,973,543
Total loans			1,996,716
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			10,990
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			277
Nonaccrual			2,386
Total past due			3,553
Impaired	[1]		0
Current			430,633
Total loans			434,186
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			890
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		12
Nonaccrual		1
Total past due		8,724
Current		1,031,201
Total loans		1,039,925	1,113,062
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		8,711
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			125
Nonaccrual			0
Total past due			12,798
Current			1,094,510
Total loans			1,107,308
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			12,673
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			31
Nonaccrual			0
Total past due			110
Impaired	[1]		0
Current			5,644
Total loans			5,754
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			79
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		34
Nonaccrual		3
Total past due		1,097
Current		160,542
Total loans		161,639	184,378
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		1,060
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			76
Nonaccrual			0
Total past due			1,531
Current			174,445
Total loans			175,976
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			1,455
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			0
Nonaccrual			52
Total past due			111
Impaired	[1]		0
Current			8,291
Total loans			8,402
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			59
Consumer Portfolio Segment [Member] | Home Equity [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		220
Nonaccrual		2,181
Total past due		4,580
Current		408,685
Total loans		413,265	386,325
Consumer Portfolio Segment [Member] | Home Equity [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		$ 2,179
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			328
Nonaccrual			1,444
Total past due			3,280
Current			310,727
Total loans			314,007
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			1,508
Consumer Portfolio Segment [Member] | Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing			238
Nonaccrual			412
Total past due			1,394
Impaired	[1]		0
Current			70,924
Total loans			72,318
Consumer Portfolio Segment [Member] | Home Equity [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due			$ 744
[1]	Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performing under ASC 310-30. As a result interest income, through the accretion of the difference between the carrying amount of the loans and the expected cashflows, is being recognized on all acquired impaired loans.

LOANS, Amount of Business Lendi

LOANS, Amount of Business Lending Loans by Credit Quality Category (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Term Loans Amortized Cost Basis by Origination Year
Loans	$ 7,458,643	$ 6,890,543
Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		5,450,592
Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		1,439,951
Business Lending [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	803,676
2019	393,018
2018	386,604
2017	277,057
2016	290,901
Prior	702,968
Revolving loans amortized cost basis	579,341
Total	3,433,565
Loans		2,775,876
Business Lending [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		1,856,585
Business Lending [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		919,291
Business Lending [Member] | Pass [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	783,726
2019	351,036
2018	337,662
2017	243,816
2016	246,551
Prior	576,220
Revolving loans amortized cost basis	483,163
Total	3,022,174
Loans		2,487,973
Business Lending [Member] | Pass [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		1,655,280
Business Lending [Member] | Pass [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		832,693
Business Lending [Member] | Special Mention [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	14,008
2019	39,130
2018	20,714
2017	19,157
2016	29,987
Prior	65,627
Revolving loans amortized cost basis	53,293
Total	241,916
Loans		144,277
Business Lending [Member] | Special Mention [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		98,953
Business Lending [Member] | Special Mention [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		45,324
Business Lending [Member] | Classified [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	5,942
2019	2,852
2018	28,228
2017	14,084
2016	14,363
Prior	61,121
Revolving loans amortized cost basis	41,996
Total	168,586
Loans		131,829
Business Lending [Member] | Classified [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		102,352
Business Lending [Member] | Classified [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		29,477
Business Lending [Member] | Doubtful [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	889
Total	889
Loans		0
Business Lending [Member] | Doubtful [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		0
Business Lending [Member] | Doubtful [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		0
Business Lending [Member] | Acquired Impaired [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		11,797
Business Lending [Member] | Acquired Impaired [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		0
Business Lending [Member] | Acquired Impaired [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		11,797
All Other Loans [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		3,594,007
All Other Loans [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		520,660
All Other Loans [Member] | Performing [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		3,579,851
All Other Loans [Member] | Performing [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		517,264
All Other Loans [Member] | Nonperforming [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		14,156
All Other Loans [Member] | Nonperforming [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		3,396
Consumer Mortgage [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	258,094
2019	344,610
2018	261,928
2017	256,154
2016	260,263
Prior	1,014,673
Revolving loans amortized cost basis	14,527
Total	2,410,249
Consumer Mortgage [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		1,996,716
Consumer Mortgage [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		434,186
Consumer Mortgage [Member] | Performing [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		1,984,533
Consumer Mortgage [Member] | Performing [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		431,523
Consumer Mortgage [Member] | Nonperforming [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		12,183
Consumer Mortgage [Member] | Nonperforming [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		2,663
Consumer Mortgage [Member] | FICO AB [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	182,675
2019	237,891
2018	177,166
2017	176,049
2016	171,155
Prior	667,685
Revolving loans amortized cost basis	582
Total	1,613,203
Consumer Mortgage [Member] | FICO AB [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	182,675
2019	237,891
2018	176,837
2017	175,605
2016	170,844
Prior	664,129
Revolving loans amortized cost basis	582
Total	1,608,563
Consumer Mortgage [Member] | FICO AB [Member] | Nonperforming [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	0
2019	0
2018	329
2017	444
2016	311
Prior	3,556
Revolving loans amortized cost basis	0
Total	4,640
Consumer Mortgage [Member] | FICO CDE [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	75,419
2019	106,719
2018	84,762
2017	80,105
2016	89,108
Prior	346,988
Revolving loans amortized cost basis	13,945
Total	797,046
Consumer Mortgage [Member] | FICO CDE [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	75,419
2019	106,072
2018	84,280
2017	79,292
2016	87,578
Prior	337,097
Revolving loans amortized cost basis	13,945
Total	783,683
Consumer Mortgage [Member] | FICO CDE [Member] | Nonperforming [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	0
2019	647
2018	482
2017	813
2016	1,530
Prior	9,891
Revolving loans amortized cost basis	0
Total	13,363
Consumer Indirect [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	227,697
2019	338,284
2018	230,246
2017	100,533
2016	73,332
Prior	69,833
Revolving loans amortized cost basis	0
Total	1,039,925
Consumer Indirect [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		1,107,308
Consumer Indirect [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		5,754
Consumer Indirect [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	227,697
2019	338,279
2018	230,246
2017	100,529
2016	73,331
Prior	69,830
Revolving loans amortized cost basis	0
Total	1,039,912
Consumer Indirect [Member] | Performing [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		1,107,183
Consumer Indirect [Member] | Performing [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		5,723
Consumer Indirect [Member] | Nonperforming [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	0
2019	5
2018	0
2017	4
2016	1
Prior	3
Revolving loans amortized cost basis	0
Total	13
Consumer Indirect [Member] | Nonperforming [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		125
Consumer Indirect [Member] | Nonperforming [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		31
Consumer Direct [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	42,905
2019	53,425
2018	32,368
2017	14,773
2016	6,731
Prior	4,722
Revolving loans amortized cost basis	6,715
Total	161,639
Consumer Direct [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		175,976
Consumer Direct [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		8,402
Consumer Direct [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	42,905
2019	53,421
2018	32,359
2017	14,773
2016	6,707
Prior	4,722
Revolving loans amortized cost basis	6,715
Total	161,602
Consumer Direct [Member] | Performing [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		175,900
Consumer Direct [Member] | Performing [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		8,350
Consumer Direct [Member] | Nonperforming [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	0
2019	4
2018	9
2017	0
2016	24
Prior	0
Revolving loans amortized cost basis	0
Total	37
Consumer Direct [Member] | Nonperforming [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		76
Consumer Direct [Member] | Nonperforming [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		52
Home Equity [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	40,760
2019	51,240
2018	29,986
2017	25,396
2016	20,176
Prior	39,910
Revolving loans amortized cost basis	205,797
Total	413,265
Home Equity [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		314,007
Home Equity [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		72,318
Home Equity [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	40,760
2019	51,240
2018	29,904
2017	25,286
2016	19,964
Prior	39,429
Revolving loans amortized cost basis	204,281
Total	410,864
Home Equity [Member] | Performing [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		312,235
Home Equity [Member] | Performing [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		71,668
Home Equity [Member] | Nonperforming [Member]
Term Loans Amortized Cost Basis by Origination Year
2020	0
2019	0
2018	82
2017	110
2016	212
Prior	481
Revolving loans amortized cost basis	1,516
Total	$ 2,401
Home Equity [Member] | Nonperforming [Member] | Legacy Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		1,772
Home Equity [Member] | Nonperforming [Member] | Acquired Loans [Member]
Term Loans Amortized Cost Basis by Origination Year
Loans		$ 650

LOANS, Summary of Impaired Loan

LOANS, Summary of Impaired Loans, Excluding Purchased Impaired (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Impaired loans
Loans with allowance allocation	$ 6,842		$ 6,842		$ 0
Loans without allowance allocation	1,414		1,414		1,414
Carrying balance	8,256		8,256		1,414
Contractual balance	10,558		10,558		2,944
Specifically allocated allowance	882		882		$ 0
Average carrying balance of individually evaluated impaired loans	8,800	$ 5,100	4,200	$ 5,400
Interest income on individually evaluated impaired loans	$ 0	$ 0	$ 0	$ 0

LOANS, Troubled Debt Restructur

LOANS, Troubled Debt Restructurings (TDRs) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)loan	Sep. 30, 2019USD ($)loan	Sep. 30, 2020USD ($)loan	Sep. 30, 2019USD ($)loan	Dec. 31, 2019USD ($)loan
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	248		248		248
TDRs, amount	$ 7,183		$ 7,183		$ 6,982
Loans modified in TDR during the year, number | loan	25	21	46	53
Loans modified in TDR during the year, amount	$ 835	$ 1,020	$ 1,707	$ 2,244
Maximum [Member]
Troubled Debt Restructurings (TDRs)
Threshold balance of TDR loans collectively included in general loan loss allocation and qualitative review	$ 500		$ 500
Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	76		76		80
TDRs, amount	$ 3,357		$ 3,357		$ 3,609
Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	172		172		168
TDRs, amount	$ 3,826		$ 3,826		$ 3,373
Commercial Portfolio Segment [Member] | Minimum [Member]
Troubled Debt Restructurings (TDRs)
Threshold balance of loans individually evaluated for impairment	$ 500		$ 500
Commercial Portfolio Segment [Member] | Business Lending [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	11		11		11
TDRs, amount	$ 797		$ 797		$ 882
Loans modified in TDR during the year, number | loan	0	1	0	3
Loans modified in TDR during the year, amount	$ 0	$ 415	$ 0	$ 660
Commercial Portfolio Segment [Member] | Business Lending [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	8		8		8
TDRs, amount	$ 602		$ 602		$ 681
Commercial Portfolio Segment [Member] | Business Lending [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	3		3		3
TDRs, amount	$ 195		$ 195		$ 201
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	104		104		106
TDRs, amount	$ 4,808		$ 4,808		$ 4,530
Loans modified in TDR during the year, number | loan	8	8	17	19
Loans modified in TDR during the year, amount	$ 646	$ 464	$ 1,378	$ 1,271
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	57		57		59
TDRs, amount	$ 2,478		$ 2,478		$ 2,638
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	47		47		47
TDRs, amount	$ 2,330		$ 2,330		$ 1,892
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	85		85		84
TDRs, amount	$ 935		$ 935		$ 941
Loans modified in TDR during the year, number | loan	14	10	25	22
Loans modified in TDR during the year, amount	$ 131	$ 116	$ 261	$ 206
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	0		0		0
TDRs, amount	$ 0		$ 0		$ 0
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	85		85		84
TDRs, amount	$ 935		$ 935		$ 941
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	24		24		23
TDRs, amount	$ 94		$ 94		$ 101
Loans modified in TDR during the year, number | loan	1	2	2	5
Loans modified in TDR during the year, amount	$ 2	$ 25	$ 12	$ 35
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	0		0		0
TDRs, amount	$ 0		$ 0		$ 0
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	24		24		23
TDRs, amount	$ 94		$ 94		$ 101
Consumer Portfolio Segment [Member] | Home Equity [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	24		24		24
TDRs, amount	$ 549		$ 549		$ 528
Loans modified in TDR during the year, number | loan	2	0	2	4
Loans modified in TDR during the year, amount	$ 56	$ 0	$ 56	$ 72
Consumer Portfolio Segment [Member] | Home Equity [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	11		11		13
TDRs, amount	$ 277		$ 277		$ 290
Consumer Portfolio Segment [Member] | Home Equity [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	13		13		11
TDRs, amount	$ 272		$ 272		$ 238

LOANS, Allowance for Credit Los

LOANS, Allowance for Credit Losses (Details) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Allowance for credit losses - loans [Roll Forward]
Beginning balance		$ 64,437	$ 49,310	$ 49,911	$ 49,284	$ 49,284
Charge-offs		(2,720)	(3,230)		(10,002)
Recoveries		1,463	1,592		4,568
Provision		1,782	1,751		5,573
Ending balance		64,962	49,423	64,962	49,423	49,911
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance		1,452		0
Charge-offs		0
Recoveries		0
Provision		163
Ending balance		1,615		1,615		0
Total allowance for credit losses [Roll Forward]
Beginning balance		65,889		49,911
Charge-offs		(2,720)
Recoveries		1,463
Provision		1,945
Ending balance		$ 66,577		$ 66,577		$ 49,911
Allowance for Credit Losses
Allowance for credit losses to total loans ratio		0.0087		0.0087
Increase in allowance for credit losses to total loans ratio over the same quarter in prior year				15.00%		15.00%
Forecast [Member] | Minimum [Member] | COVID-19 [Member]
Allowance for Credit Losses
Percentage of peak unemployment	7.00%
Forecast [Member] | Maximum [Member] | COVID-19 [Member]
Allowance for Credit Losses
Percentage of peak unemployment	11.00%
Topic ASC 326
Allowance for credit losses - loans [Roll Forward]
Beginning balance				$ 51,268
Charge-offs				(7,861)
Recoveries				4,144
Steuben acquisition				3,662
Provision				13,749
Ending balance		$ 64,962		64,962		$ 51,268
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance				1,185
Charge-offs				0
Recoveries				0
Steuben acquisition				67
Provision				363
Ending balance		1,615		1,615		1,185
Total allowance for credit losses [Roll Forward]
Beginning balance				52,453
Charge-offs				(7,861)
Recoveries				4,144
Steuben acquisition				3,729
Provision				14,112
Ending balance		66,577		66,577		52,453
Topic ASC 326 | Cumulative Effect Adjustment
Allowance for credit losses - loans [Roll Forward]
Beginning balance				1,357
Ending balance						1,357
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance				1,185
Ending balance						1,185
Total allowance for credit losses [Roll Forward]
Beginning balance				2,542
Ending balance						2,542
Acquired Impaired Loans
Allowance for credit losses - loans [Roll Forward]
Beginning balance			155	163	33	33
Charge-offs			0		0
Recoveries			0		0
Provision			1		123
Ending balance			156		156	163
Acquired Impaired Loans | Topic ASC 326
Allowance for credit losses - loans [Roll Forward]
Beginning balance				0
Charge-offs				0
Recoveries				0
Steuben acquisition				0
Provision				0
Ending balance		0		0		0
Acquired Impaired Loans | Topic ASC 326 | Cumulative Effect Adjustment
Allowance for credit losses - loans [Roll Forward]
Beginning balance				(163)
Ending balance						(163)
Purchased Credit Deteriorated
Allowance for credit losses - loans [Roll Forward]
Beginning balance		3,561		0
Charge-offs		(91)
Recoveries		32
Provision		45
Ending balance		3,547		3,547		0
Purchased Credit Deteriorated | Topic ASC 326
Allowance for credit losses - loans [Roll Forward]
Beginning balance				3,072
Charge-offs				(91)
Recoveries				80
Steuben acquisition				528
Provision				(42)
Ending balance		3,547		3,547		3,072
Purchased Credit Deteriorated | Topic ASC 326 | Cumulative Effect Adjustment
Allowance for credit losses - loans [Roll Forward]
Beginning balance				3,072
Ending balance						3,072
Commercial Portfolio Segment [Member] | Business Lending [Member]
Allowance for credit losses - loans [Roll Forward]
Beginning balance		24,204	17,769	19,426	18,522	18,522
Charge-offs		(736)	(305)		(1,774)
Recoveries		67	290		593
Provision		3,539	301		714
Ending balance		27,074	18,055	27,074	18,055	19,426
Commercial Portfolio Segment [Member] | Business Lending [Member] | Topic ASC 326
Allowance for credit losses - loans [Roll Forward]
Beginning balance				19,714
Charge-offs				(919)
Recoveries				289
Steuben acquisition				2,483
Provision				5,507
Ending balance		27,074		27,074		19,714
Commercial Portfolio Segment [Member] | Business Lending [Member] | Topic ASC 326 | Cumulative Effect Adjustment
Allowance for credit losses - loans [Roll Forward]
Beginning balance				288
Ending balance						288
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Allowance for credit losses - loans [Roll Forward]
Beginning balance		13,088	10,763	10,269	10,124	10,124
Charge-offs		(248)	(200)		(1,040)
Recoveries		23	8		44
Provision		(599)	(94)		1,349
Ending balance		12,264	10,477	12,264	10,477	10,269
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Topic ASC 326
Allowance for credit losses - loans [Roll Forward]
Beginning balance				9,218
Charge-offs				(668)
Recoveries				67
Steuben acquisition				146
Provision				3,501
Ending balance		12,264		12,264		9,218
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Topic ASC 326 | Cumulative Effect Adjustment
Allowance for credit losses - loans [Roll Forward]
Beginning balance				(1,051)
Ending balance						(1,051)
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Allowance for credit losses - loans [Roll Forward]
Beginning balance		15,866	14,345	13,712	14,366	14,366
Charge-offs		(1,281)	(2,224)		(5,529)
Recoveries		1,111	1,095		3,296
Provision		(963)	1,221		2,304
Ending balance		14,733	14,437	14,733	14,437	13,712
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Topic ASC 326
Allowance for credit losses - loans [Roll Forward]
Beginning balance				12,715
Charge-offs				(4,791)
Recoveries				3,107
Steuben acquisition				183
Provision				3,519
Ending balance		14,733		14,733		12,715
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Topic ASC 326 | Cumulative Effect Adjustment
Allowance for credit losses - loans [Roll Forward]
Beginning balance				(997)
Ending balance						(997)
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Allowance for credit losses - loans [Roll Forward]
Beginning balance		4,028	3,184	3,255	3,095	3,095
Charge-offs		(340)	(456)		(1,436)
Recoveries		225	167		567
Provision		(120)	383		1,052
Ending balance		3,793	3,278	3,793	3,278	3,255
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Topic ASC 326
Allowance for credit losses - loans [Roll Forward]
Beginning balance				2,612
Charge-offs				(1,214)
Recoveries				578
Steuben acquisition				87
Provision				1,730
Ending balance		3,793		3,793		2,612
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Topic ASC 326 | Cumulative Effect Adjustment
Allowance for credit losses - loans [Roll Forward]
Beginning balance				(643)
Ending balance						(643)
Consumer Portfolio Segment [Member] | Home Equity [Member]
Allowance for credit losses - loans [Roll Forward]
Beginning balance		2,690	2,103	2,129	2,144	2,144
Charge-offs		(24)	(45)		(223)
Recoveries		5	32		68
Provision		(124)	(8)		93
Ending balance		2,547	2,082	2,547	2,082	2,129
Consumer Portfolio Segment [Member] | Home Equity [Member] | Topic ASC 326
Allowance for credit losses - loans [Roll Forward]
Beginning balance				2,937
Charge-offs				(178)
Recoveries				23
Steuben acquisition				235
Provision				(470)
Ending balance		2,547		2,547		2,937
Consumer Portfolio Segment [Member] | Home Equity [Member] | Topic ASC 326 | Cumulative Effect Adjustment
Allowance for credit losses - loans [Roll Forward]
Beginning balance				808
Ending balance						808
Unallocated Financing Receivables [Member]
Allowance for credit losses - loans [Roll Forward]
Beginning balance		1,000	991	957	1,000	1,000
Charge-offs		0	0		0
Recoveries		0	0		0
Provision		4	(53)		(62)
Ending balance		1,004	$ 938	1,004	$ 938	957
Unallocated Financing Receivables [Member] | Topic ASC 326
Allowance for credit losses - loans [Roll Forward]
Beginning balance				1,000
Charge-offs				0
Recoveries				0
Steuben acquisition				0
Provision				4
Ending balance		$ 1,004		1,004		1,000
Unallocated Financing Receivables [Member] | Topic ASC 326 | Cumulative Effect Adjustment
Allowance for credit losses - loans [Roll Forward]
Beginning balance				$ 43
Ending balance						$ 43

LOANS, Carrying Amounts of Loan

LOANS, Carrying Amounts of Loans Purchased and Sold (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
Carrying Amounts of Loans Purchased and Sold
Purchases	$ 339,563
Sales	37,409
Commercial Portfolio Segment [Member] | Business Lending [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	253,368
Sales	0
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	26,721
Sales	37,409
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	13,926
Sales	0
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	5,994
Sales	0
Consumer Portfolio Segment [Member] | Home Equity [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	39,554
Sales	$ 0

GOODWILL AND IDENTIFIABLE INT_3

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Identifiable Intangible Assets [Abstract]
Gross carrying amount	$ 159,865	$ 155,741
Accumulated amortization	(103,400)	(92,628)
Net carrying amount	56,465	63,113
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Oct - Dec 2020	3,525
2021	12,640
2022	10,844
2023	9,082
2024	7,551
Thereafter	12,823
Net carrying amount	56,465	63,113
Components of goodwill [Abstract]
Goodwill, net, beginning of period	773,810
Goodwill, net, activity	19,939
Goodwill, net, end of period	793,749
Core Deposit Intangibles [Member]
Identifiable Intangible Assets [Abstract]
Gross carrying amount	69,403	66,475
Accumulated amortization	(54,217)	(50,057)
Net carrying amount	15,186	16,418
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Net carrying amount	15,186	16,418
Other Intangibles [Member]
Identifiable Intangible Assets [Abstract]
Gross carrying amount	90,462	89,266
Accumulated amortization	(49,183)	(42,571)
Net carrying amount	41,279	46,695
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Net carrying amount	$ 41,279	$ 46,695

MANDATORILY REDEEMABLE PREFER_3

MANDATORILY REDEEMABLE PREFERRED SECURITIES (Details) $ in Millions	Sep. 15, 2020USD ($)	Sep. 16, 2019USD ($)	Sep. 30, 2020USD ($)trust
Mandatorily Redeemable Preferred Securities [Abstract]
Number of unconsolidated subsidiary business trusts owned | trust			1
Business Trust [Member]
Mandatorily Redeemable Preferred Securities [Abstract]
Percent ownership of unconsolidated subsidiary trusts			100.00%
MBVT Statutory Trust I [Member]
Mandatorily Redeemable Preferred Securities [Abstract]
Redemption of debentures and associated preferred securities		$ 20.6
Kinderhook Capital Trust [Member]
Mandatorily Redeemable Preferred Securities [Abstract]
Redemption of debentures and associated preferred securities		$ 2.1
Steuben Statutory Trust
Mandatorily Redeemable Preferred Securities [Abstract]
Redemption of debentures and associated preferred securities	$ 2.1
Preferred Debt [Member] | Community Capital Trust IV [Member]
Terms of preferred securities for each trust [Abstract]
Issuance date			Dec. 8, 2006
Par amount			$ 75
Effective interest rate			1.90%
Maturity date			Dec. 15, 2036
Call price			Par
Preferred Debt [Member] | Community Capital Trust IV [Member] | LIBOR [Member]
Terms of preferred securities for each trust [Abstract]
Term of variable rate			3 months
Variable interest rate, basis spread			1.65%

BENEFIT PLANS (Details)

BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	$ 1,438	$ 1,270		$ 4,313	$ 3,811
Interest cost	1,356	1,566		4,068	4,698
Expected return on plan assets	(3,932)	(3,578)		(11,796)	(10,733)
Amortization of unrecognized net loss	810	642		2,430	1,926
Amortization of prior service cost	60	17		180	48
Net periodic benefit	(268)	(83)		(805)	(250)
Pension Benefits [Member] | Nonqualified Plan [Member] | Unfunded Plan [Member]
Pension Plans [Abstract]
Contribution made to defined benefit pension plan by employer	3,900		$ 7,300
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0	0		0	0
Interest cost	15	18		43	53
Expected return on plan assets	0	0		0	0
Amortization of unrecognized net loss	10	9		30	28
Amortization of prior service cost	(45)	(45)		(134)	(134)
Net periodic benefit	(20)	$ (18)		$ (61)	$ (53)
Steuben Trust Company Pension Plan
Pension Plans [Abstract]
Contribution made to defined benefit pension plan by employer	$ 3,500

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
EARNINGS PER SHARE
Weighted-average anti-dilutive stock options outstanding (in shares)	500,000	500,000	700,000	500,000
Basic earnings per share [Abstract]
Net income	$ 42,809	$ 39,218	$ 118,191	$ 126,179
Income attributable to unvested stock-based compensation awards	(147)	(102)	(432)	(331)
Income available to common shareholders	$ 42,662	$ 39,116	$ 117,759	$ 125,848
Weighted-average common shares outstanding - basic (in shares)	53,650,000	51,750,000	52,727,000	51,644,000
Basic earnings per share (in dollars per share)	$ 0.80	$ 0.76	$ 2.23	$ 2.44
Diluted earnings per share [Abstract]
Net income	$ 42,809	$ 39,218	$ 118,191	$ 126,179
Income attributable to unvested stock-based compensation awards	(147)	(102)	(432)	(331)
Income available to common shareholders	$ 42,662	$ 39,116	$ 117,759	$ 125,848
Weighted-average common shares outstanding - basic (in shares)	53,650,000	51,750,000	52,727,000	51,644,000
Assumed exercise of stock options (in shares)	324,000	496,000	356,000	522,000
Weighted-average common shares outstanding - diluted (in shares)	53,974,000	52,246,000	53,083,000	52,166,000
Diluted earnings per share (in dollars per share)	$ 0.79	$ 0.75	$ 2.22	$ 2.41
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)					2,600,000	2,500,000
Number of common shares repurchased (in shares)			0	0

COMMITMENTS, CONTINGENT LIABI_3

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	$ 1,244,568		$ 1,244,568		$ 1,181,652
Expense recorded for litigation accrual	2,950	$ 0	2,950	$ 0
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		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		1,000
Commitments to Extend Credit [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	1,201,285		1,201,285		1,143,780
Standby Letters of Credit [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	$ 43,283		$ 43,283		$ 37,872

FAIR VALUE - Financial Assets a

FAIR VALUE - Financial Assets and Liabilities Accounted for at Fair Value On a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	$ 3,222,722
Equity securities	423	$ 451
Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	2,684
U.S. Treasury Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,149,170	2,043,759
Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	493,496	512,208
Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	523,974	432,862
Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	4,602	2,528
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	51,480	53,071
Recurring [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,222,722	3,044,428
Equity securities	423	451
Mortgage loans held for sale	8,151
Total	3,235,052	3,045,144
Recurring [Member] | Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	2,684
Recurring [Member] | Forward Sales Commitments [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	510
Recurring [Member] | Interest Rate Swap Agreements [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	1,756	851
Derivative liability	(1,194)	(586)
Recurring [Member] | U.S. Treasury Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,149,170	2,043,759
Recurring [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	493,496	512,208
Recurring [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	523,974	432,862
Recurring [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	4,602	2,528
Recurring [Member] | Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	51,480	53,071
Recurring [Member] | Level 1 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,982,893	1,878,705
Equity securities	423	451
Mortgage loans held for sale	0
Total	1,983,316	1,879,156
Recurring [Member] | Level 1 [Member] | Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0
Recurring [Member] | Level 1 [Member] | Forward Sales Commitments [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0
Recurring [Member] | Level 1 [Member] | Interest Rate Swap Agreements [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Derivative liability	0	0
Recurring [Member] | Level 1 [Member] | U.S. Treasury Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,982,893	1,878,705
Recurring [Member] | Level 1 [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 1 [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 1 [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 1 [Member] | Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 2 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,239,829	1,165,723
Equity securities	0	0
Mortgage loans held for sale	8,151
Total	1,249,052	1,165,988
Mortgage loans held for sale, at principal value	7,900	0
Recurring [Member] | Level 2 [Member] | Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0
Recurring [Member] | Level 2 [Member] | Forward Sales Commitments [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	510
Recurring [Member] | Level 2 [Member] | Interest Rate Swap Agreements [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	1,756	851
Derivative liability	(1,194)	(586)
Recurring [Member] | Level 2 [Member] | U.S. Treasury Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	166,277	165,054
Recurring [Member] | Level 2 [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	493,496	512,208
Recurring [Member] | Level 2 [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	523,974	432,862
Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	4,602	2,528
Recurring [Member] | Level 2 [Member] | Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	51,480	53,071
Recurring [Member] | 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
Total	2,684	0
Recurring [Member] | Level 3 [Member] | Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	2,684
Recurring [Member] | Level 3 [Member] | Forward Sales Commitments [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0
Recurring [Member] | Level 3 [Member] | Interest Rate Swap Agreements [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Derivative liability	0	0
Recurring [Member] | Level 3 [Member] | U.S. Treasury Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 3 [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 3 [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 3 [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 3 [Member] | Government Agency Collateralized Mortgage Obligations [Member]
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	Sep. 30, 2020	Dec. 31, 2019
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	$ 6,808	$ 848
Other real estate owned	1,209	1,270
Mortgage servicing rights	460	56
Valuation allowance	882	0
Mortgage Servicing Rights [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Valuation allowance	200	300
Non-recurring [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	6,808	848
Other real estate owned	1,209	1,270
Mortgage servicing rights	460	56
Total	8,477	2,174
Non-recurring [Member] | 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] | 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] | Level 3 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	6,808	848
Other real estate owned	1,209	1,270
Mortgage servicing rights	460	56
Total	$ 8,477	$ 2,174

FAIR VALUE - Significant Unobse

FAIR VALUE - Significant Unobservable Inputs (Details) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans	$ 6,808	$ 848
Other real estate owned	$ 1,209	$ 1,270
Other real estate owned, Valuation Technique [Extensible List]	us-gaap:MarketApproachValuationTechniqueMember	us-gaap:MarketApproachValuationTechniqueMember
Other real estate owned, Measurement Input [Extensible List]	us-gaap:MeasurementInputCostToSellMember	us-gaap:MeasurementInputCostToSellMember
Mortgage servicing rights	$ 460	$ 56
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		0.528
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		0.0300
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	7
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	0.090	0.090
Other real estate owned, measurement input	0.152	0.090
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	0.138
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	0.0122
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	0.787	0.350
Other real estate owned, measurement input	0.535	0.857
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	0.147
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	0.0198
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	0.588	0.279
Other real estate owned, measurement input	0.313	0.371
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	0.146
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	0.0192
Commitments to Originate Real Estate Loans for Sale [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	$ 2,684
Commitments to originate real estate loans for sale, Valuation Technique [Extensible List]	us-gaap:ValuationTechniqueDiscountedCashFlowMember
Commitments to originate real estate loans for sale, Measurement Input [Extensible List]	cbu:MeasurementInputEmbeddedServicingValueMember
Commitments to originate real estate loans for sale, measurement input	0.010

FAIR VALUE - Carrying Amounts a

FAIR VALUE - Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Carrying Value [Member]
Financial assets [Abstract]
Net loans	$ 7,393,681	$ 6,840,632
Financial liabilities [Abstract]
Deposits	11,120,590	8,994,967
Overnight Federal Home Loan Bank borrowings	0	8,300
Securities sold under agreement to repurchase, short-term	280,767	241,708
Other Federal Home Loan Bank borrowings	7,681	3,750
Subordinated notes payable	13,735	13,795
Subordinated debt held by unconsolidated subsidiary trusts	77,320	77,320
Fair Value [Member]
Financial assets [Abstract]
Net loans	7,710,461	7,028,663
Financial liabilities [Abstract]
Deposits	11,135,779	8,997,551
Overnight Federal Home Loan Bank borrowings	0	8,300
Securities sold under agreement to repurchase, short-term	280,767	241,708
Other Federal Home Loan Bank borrowings	7,810	3,755
Subordinated notes payable	13,735	13,795
Subordinated debt held by unconsolidated subsidiary trusts	$ 77,320	$ 77,320

DERIVATIVE INSTRUMENTS (Details

DERIVATIVE INSTRUMENTS (Details) - Interest Rate Swap Agreements [Member] - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Derivative Instruments [Abstract]
Derivative, notional amount	$ 14.8	$ 16.4
Derivative weighted average receive rate	2.10%	3.72%
Derivative weighted average pay rate	4.43%	4.39%
Weighted average maturity period	5 years 6 months	6 years 1 month 6 days
Designated as Hedging Instrument [Member] | Fair Value Hedging [Member]
Derivative Instruments [Abstract]
Derivative, notional amount	$ 5.7	$ 6.2
Derivative weighted average receive rate	1.42%	2.47%
Derivative weighted average pay rate	3.11%	3.11%
Weighted average maturity period	12 years 9 months 18 days	13 years 6 months

DERIVATIVE INSTRUMENTS - Cumula

DERIVATIVE INSTRUMENTS - Cumulative Basis Adjustments for Fair Value Hedges (Details) - Loans [Member] - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Cumulative Basis Adjustments for Fair Value Hedges [Abstract]
Carrying amount of the hedged assets	$ 5,611	$ 6,390
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets	$ (562)	$ (265)

DERIVATIVE INSTRUMENTS - Fair V

DERIVATIVE INSTRUMENTS - Fair Values of Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Values of Derivative Instruments [Abstract]
Derivative assets	$ 4,950	$ 851
Derivative liabilities	1,194	586
Interest Rate Swap Agreements [Member] | Designated as Hedging Instrument [Member] | Other Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Derivative assets	562	265
Interest Rate Swap Agreements [Member] | Not Designated as Hedging Instrument [Member] | Other Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Derivative assets	1,194	586
Interest Rate Swap Agreements [Member] | Not Designated as Hedging Instrument [Member] | Accrued Interest and Other Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Derivative liabilities	1,194	$ 586
Commitments to Originate Real Estate Loans for Sale [Member] | Not Designated as Hedging Instrument [Member] | Other Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Derivative assets	2,684
Forward Sales Commitments [Member] | Not Designated as Hedging Instrument [Member] | Other Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Derivative assets	$ 510

SEGMENT INFORMATION (Details)

SEGMENT INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Jul. 12, 2019
Information about reportable segments [Abstract]
Net interest income	$ 92,965	$ 91,276	$ 274,970	$ 266,435
Provision for credit losses	1,945	1,751	17,313	5,573
Noninterest revenues	59,659	57,094	171,219	173,496
Amortization of intangible assets	3,581	3,960	10,772	11,994
Acquisition expenses	796	6,061	4,537	7,789
Other operating expenses	92,589	86,908	266,223	256,974
Income before income taxes	53,713	49,690	147,344	157,601
Assets	13,845,325	11,597,297	13,845,325	11,597,297	$ 11,410,295
Goodwill	793,749	773,610	793,749	773,610	$ 773,810	$ 39,970
Core deposit intangibles & Other intangibles	56,465	67,075	56,465	67,075
Eliminations [Member]
Information about reportable segments [Abstract]
Net interest income	0	0	0	0
Provision for credit losses	0	0	0	0
Noninterest revenues	(1,454)	(669)	(4,347)	(2,231)
Amortization of intangible assets	0	0	0	0
Acquisition expenses	0	0	0	0
Other operating expenses	(1,454)	(669)	(4,347)	(2,231)
Income before income taxes	0	0	0	0
Assets	(120,877)	(76,505)	(120,877)	(76,505)
Goodwill	0	0	0	0
Core deposit intangibles & Other intangibles	0	0	0	0
Banking [Member] | Operating Segments [Member]
Information about reportable segments [Abstract]
Net interest income	92,642	91,018	274,051	265,860
Provision for credit losses	1,945	1,751	17,313	5,573
Noninterest revenues	19,756	17,790	53,428	57,059
Amortization of intangible assets	1,379	1,439	4,160	4,297
Acquisition expenses	796	6,061	4,537	7,789
Other operating expenses	67,193	61,839	190,523	182,186
Income before income taxes	41,085	37,718	110,946	123,074
Assets	13,674,995	11,398,191	13,674,995	11,398,191
Goodwill	690,162	670,023	690,162	670,023
Core deposit intangibles & Other intangibles	15,186	17,872	15,186	17,872
Employee Benefit Services [Member] | Operating Segments [Member]
Information about reportable segments [Abstract]
Net interest income	256	209	742	448
Provision for credit losses	0	0	0	0
Noninterest revenues	25,651	24,830	76,080	73,919
Amortization of intangible assets	1,409	1,667	4,314	5,105
Acquisition expenses	0	0	0	0
Other operating expenses	15,078	14,721	45,157	43,985
Income before income taxes	9,420	8,651	27,351	25,277
Assets	210,679	201,442	210,679	201,442
Goodwill	83,275	83,275	83,275	83,275
Core deposit intangibles & Other intangibles	33,461	39,440	33,461	39,440
All Other [Member] | Operating Segments [Member]
Information about reportable segments [Abstract]
Net interest income	67	49	177	127
Provision for credit losses	0	0	0	0
Noninterest revenues	15,706	15,143	46,058	44,749
Amortization of intangible assets	793	854	2,298	2,592
Acquisition expenses	0	0	0	0
Other operating expenses	11,772	11,017	34,890	33,034
Income before income taxes	3,208	3,321	9,047	9,250
Assets	80,528	74,169	80,528	74,169
Goodwill	20,312	20,312	20,312	20,312
Core deposit intangibles & Other intangibles	$ 7,818	$ 9,763	$ 7,818	$ 9,763