Community Bank System (CBU) 10-Q 10 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Quarterly Report	true
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity Registrant Name	COMMUNITY BANK SYSTEM, INC.
Entity Incorporation, State or Country Code	DE
Entity File Number	001-13695
Entity Tax Identification Number	16-1213679
Entity Address, Address Line One	5790 Widewaters Parkway
Entity Address, City or Town	DeWitt
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	13214
City Area Code	315
Local Phone Number	445-2282
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		53,883,259
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0000723188
Title of 12(b) Security	Common Stock, $1.00 par value per share
Trading Symbol	CBU
Security Exchange Name	NYSE

CONSOLIDATED STATEMENTS OF COND

CONSOLIDATED STATEMENTS OF CONDITION - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets:
Cash and cash equivalents	$ 2,151,347	$ 1,645,805
Available-for-sale investment securities (cost of $3,898,704 and $3,427,779, respectively)	3,791,391	3,547,892
Equity and other securities (cost of $44,138 and $46,511, respectively)	45,106	47,455
Loans held for sale, at fair value	1,140	1,622
Loans	7,368,327	7,415,952
Allowance for credit losses	(55,069)	(60,869)
Net loans	7,313,258	7,355,083
Goodwill, net	793,456	793,708
Core deposit intangibles, net	12,507	13,831
Other intangibles, net	37,082	39,109
Intangible assets, net	843,045	846,648
Premises and equipment, net	161,194	165,655
Accrued interest and fees receivable	36,405	39,031
Other assets	277,295	281,903
Total assets	14,620,181	13,931,094
Liabilities:
Noninterest-bearing deposits	3,710,292	3,361,768
Interest-bearing deposits	8,493,945	7,863,206
Total deposits	12,204,237	11,224,974
Securities sold under agreement to repurchase, short-term	257,767	284,008
Other Federal Home Loan Bank borrowings	5,959	6,658
Subordinated notes payable	3,297	3,303
Subordinated debt held by unconsolidated subsidiary trusts	0	77,320
Accrued interest and other liabilities	177,524	230,724
Total liabilities	12,648,784	11,826,987
Commitments and contingencies (See Note J)
Shareholders' equity:
Preferred stock, $1.00 par value, 500,000 shares authorized, 0 shares issued	0	0
Common stock, $1.00 par value, 75,000,000 shares authorized; 54,019,374 and 53,754,599 shares issued, respectively	54,019	53,755
Additional paid-in capital	1,034,225	1,025,163
Retained earnings	990,504	960,183
Accumulated other comprehensive (loss) income	(109,957)	62,077
Treasury stock, at cost (144,395 shares, including 144,380 shares held by deferred compensation arrangements at March 31, 2021 and 161,472 shares including 161,457 shares held by deferred compensation arrangements at December 31, 2020, respectively)	(5,572)	(6,198)
Deferred compensation arrangements (144,380 and 161,457 shares, respectively)	8,178	9,127
Total shareholders' equity	1,971,397	2,104,107
Total liabilities and shareholders' equity	$ 14,620,181	$ 13,931,094

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF CONDITION (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets:
Available-for-sale investment securities, cost	$ 3,898,704	$ 3,427,779
Equity and other securities, cost	$ 44,138	$ 46,511
Shareholders' equity:
Preferred stock, par value (in dollars per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	500,000	500,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	54,019,374	53,754,599
Treasury stock, shares at cost (in shares)	144,395	161,472
Shares held by deferred compensation arrangements (in shares)	144,380	161,457

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Interest income:
Interest and fees on loans	$ 79,714	$ 78,565
Interest and dividends on taxable investments	15,175	15,329
Interest and dividends on nontaxable investments	2,776	3,101
Total interest income	97,665	96,995
Interest expense:
Interest on deposits	3,112	5,545
Interest on borrowings	268	558
Interest on subordinated notes payable	38	185
Interest on subordinated debt held by unconsolidated subsidiary trusts	293	653
Total interest expense	3,711	6,941
Net interest income	93,954	90,054
Provision for credit losses	(5,719)	5,594
Net interest income after provision for credit losses	99,673	84,460
Noninterest revenues:
Deposit service fees	14,080	16,283
Mortgage banking	688	916
Other banking services	854	895
Employee benefit services	26,533	25,366
Insurance services	8,153	8,058
Wealth management services	8,199	7,134
Unrealized gain (loss) on equity securities	24	(30)
Total noninterest revenues	58,531	58,622
Noninterest expenses:
Salaries and employee benefits	57,632	58,251
Occupancy and equipment	11,300	10,739
Data processing and communications	12,391	10,413
Amortization of intangible assets	3,351	3,667
Legal and professional fees	3,034	3,151
Business development and marketing	2,030	2,513
Acquisition expenses	27	369
Other expenses	3,481	4,560
Total noninterest expenses	93,246	93,663
Income before income taxes	64,958	49,419
Income taxes	12,108	9,285
Net income	$ 52,850	$ 40,134
Basic earnings per share (in dollars per share)	$ 0.98	$ 0.77
Diluted earnings per share (in dollars per share)	$ 0.97	$ 0.76

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Pension and other post retirement obligations:
Amortization of actuarial losses included in net periodic pension cost, gross	$ 911	$ 820
Tax effect	(219)	(197)
Amortization of actuarial losses included in net periodic pension cost, net	692	623
Amortization of prior service cost included in net periodic pension cost, gross	50	15
Tax effect	(12)	(3)
Amortization of prior service cost included in net periodic pension cost, net	38	12
Other comprehensive income related to pension and other post retirement obligations, net of taxes	730	635
Unrealized (losses) gains on available-for-sale securities:
Net unrealized holding (losses) gains arising during period, gross	(227,427)	122,428
Tax effect	54,663	(29,393)
Net unrealized holding (losses) gains arising during period, net	(172,764)	93,035
Other comprehensive (loss) income related to unrealized gains on available-for-sale securities, net of taxes	(172,764)	93,035
Other comprehensive (loss) income, net of tax	(172,034)	93,670
Net income	52,850	40,134
Comprehensive (loss) income	(119,184)	$ 133,804
Accumulated Other Comprehensive (Loss) Income By Component:
Unrealized (loss) for pension and other postretirement obligations	(37,306)		$ (38,267)
Tax effect	9,163		9,394
Net unrealized (loss) for pension and other postretirement obligations	(28,143)		(28,873)
Unrealized (loss) gain on available-for-sale securities	(107,313)		120,114
Tax effect	25,499		(29,164)
Net unrealized (loss) gain on available-for-sale securities	(81,814)		90,950
Accumulated other comprehensive (loss) income	$ (109,957)		$ 62,077

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Cumulative Effect Adjustment [Member]Retained Earnings [Member]	Cumulative Effect Adjustment [Member]	Common Stock Outstanding [Member]	Common Stock Amount Issued [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Treasury Stock [Member]	Deferred Compensation Arrangements [Member]	Total
Balance at Dec. 31, 2019				$ 51,975	$ 927,337	$ 882,851	$ (10,226)	$ (6,823)	$ 10,120	$ 1,855,234
Balance (in shares) at Dec. 31, 2019			51,793,923
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income						40,134				40,134
Other comprehensive income (loss), net of tax							93,670			93,670
Dividends declared:
Common						(21,367)				(21,367)
Common stock activity under employee stock plans				215	6,184					6,399
Common stock activity under employee stock plans (in shares)			214,588
Stock-based compensation					1,952					1,952
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					36			(31)	74	79
Treasury stock issued to benefit plans, net (in shares)			84
Balance (ASU 2016-13 [Member]) at Mar. 31, 2020	$ 530	$ 530
Balance at Mar. 31, 2020				52,190	935,924	902,148	83,444	(6,005)	8,930	1,976,631
Balance (in shares) at Mar. 31, 2020			52,031,092
Balance at Dec. 31, 2020				53,755	1,025,163	960,183	62,077	(6,198)	9,127	2,104,107
Balance (in shares) at Dec. 31, 2020			53,593,127
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income						52,850				52,850
Other comprehensive income (loss), net of tax							(172,034)			(172,034)
Dividends declared:
Common						(22,529)				(22,529)
Common stock activity under employee stock plans				264	7,065					7,329
Common stock activity under employee stock plans (in shares)			264,775
Stock-based compensation					1,674					1,674
Distribution of stock under deferred compensation arrangements					323			694	(1,017)	0
Distribution of stock under deferred compensation arrangements (in shares)			18,089
Treasury stock issued to benefit plans, net								(68)	68	0
Treasury stock issued to benefit plans, net (in shares)			1,012
Balance at Mar. 31, 2021				$ 54,019	$ 1,034,225	$ 990,504	$ (109,957)	$ (5,572)	$ 8,178	$ 1,971,397
Balance (in shares) at Mar. 31, 2021			53,874,979

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash dividends declared:
Dividends declared per common share (in dollars per share)	$ 0.42	$ 0.41

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities:
Net income	$ 52,850	$ 40,134
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation	4,034	4,079
Amortization of intangible assets	3,351	3,667
Net accretion on securities, loans and borrowings	(7,127)	(2,113)
Stock-based compensation	1,674	1,952
Provision for credit losses	(5,719)	5,594
Amortization of mortgage servicing rights	135	82
Unrealized (gain) loss on equity securities	(24)	30
Income from bank-owned life insurance policies	(480)	(408)
Net (gain) loss on sale of loans and other assets	(280)	9
Change in other assets and other liabilities	13,396	(26,332)
Net cash provided by operating activities	61,810	26,694
Investing activities:
Proceeds from maturities, calls, and paydowns of available-for-sale investment securities	78,112	61,753
Proceeds from maturities and redemptions of equity and other investment securities	2,383	404
Purchases of available-for-sale investment securities	(546,733)	(34,597)
Purchases of equity and other securities	(10)	(18)
Net decrease in loans	52,297	25,446
Purchases of premises and equipment, net	(876)	(3,020)
Real estate tax credit investments	(155)	(550)
Net cash (used in) provided by investing activities	(414,982)	49,418
Financing activities:
Net increase in deposits	979,263	309,015
Net decrease in borrowings	(26,940)	(45,040)
Payments on subordinated debt held by unconsolidated subsidiary trusts	(77,320)	0
Issuance of common stock	7,329	6,399
Purchases of treasury stock	(68)	(74)
Sales of treasury stock	0	79
Increase in deferred compensation agreements	68	74
Cash dividends paid	(22,553)	(21,268)
Withholding taxes paid on share-based compensation	(1,065)	(991)
Net cash provided by financing activities	858,714	248,194
Change in cash and cash equivalents	505,542	324,306
Cash and cash equivalents at beginning of period	1,645,805	205,030
Cash and cash equivalents at end of period	2,151,347	529,336
Supplemental disclosures of cash flow information:
Cash paid for interest	4,351	6,888
Cash paid for income taxes	2,701	9,642
Supplemental disclosures of noncash financing activities
Dividends declared and unpaid	22,671	21,441
Transfers from loans to other real estate	$ 63	$ 779

BASIS OF PRESENTATION

BASIS OF PRESENTATION	3 Months Ended
	Mar. 31, 2021
BASIS OF PRESENTATION
BASIS OF PRESENTATION	NOTE A: BASIS OF PRESENTATION The interim financial data as of and for the three months ended March 31, 2021 is unaudited; however, in the opinion of Community Bank System, Inc. (the “Company”), the interim data includes all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement of the results for the interim periods in conformity with generally accepted accounting principles in the United States of America (“GAAP”) and Article 10 of Regulation S-X. The results of operations for the interim periods are not necessarily indicative of the results that may be expected for the full year or any other interim period. The Company’s unaudited interim consolidated financial statements and notes thereto should be read in conjunction with the Company’s audited annual consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 filed with the Securities and Exchange Commission (“SEC”) on March 1, 2021.

ACQUISITIONS

ACQUISITIONS	3 Months Ended
	Mar. 31, 2021
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 $607.8 million of assets, including $339.7 million of loans and $180.5 million of investment securities, as well as $516.3 million of deposits. Goodwill of $20.0 million was recognized as a result of the merger. The effects of the acquired assets and liabilities have been included in the consolidated financial statements since that date. Revenues, excluding interest income on acquired investments, interest income on acquired consumer indirect loans, and revenues associated with acquired loans and deposits consolidated into the legacy branch network, of approximately $3.2 million, and direct expenses, which may not include certain shared expenses, of approximately $1.3 million from Steuben were included in the consolidated income statement for the three months ended March 31, 2021. The Company incurred certain one-time, transaction-related costs in 2020 in connection with the Steuben acquisition. The assets and liabilities assumed in the acquisitions were recorded at their estimated fair values based on management’s best estimates using information available at the dates of the acquisitions, and were subject to adjustment based on updated information not available at the time of the acquisitions. During the first quarter of 2021, the carrying amount of other liabilities associated with the Steuben acquisition decreased by $0.3 million as a result of an adjustment to accrued income taxes and deferred income taxes. Goodwill associated with the Steuben acquisition decreased $0.3 million as a result of this adjustment. The acquisition 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 (000s omitted) ​ Steuben Consideration paid : ​ ​ 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: ​ 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 ​ 2,701 Other assets ​ 17,675 Core deposit intangibles ​ 2,928 Other intangibles ​ 1,196 Deposits ​ (516,274) Other liabilities ​ (4,843) Other Federal Home Loan Bank borrowings ​ (6,000) Subordinated debt held by unconsolidated subsidiary trusts ​ (2,062) Total identifiable assets, net ​ 78,572 Goodwill ​ $ 19,983 ​ The Company has acquired loans from Steuben for which there was evidence of a more-than-insignificant deterioration in credit quality since origination (purchased credit deteriorated (“PCD”) loans). PCD loans are initially recorded at the amount paid. An allowance for credit losses is determined using the same methodology as other loans. The initial allowance for credit losses determined on a collective basis is allocated to individual loans. The sum of the loan’s purchase price and allowance for credit losses becomes its initial amortized cost basis. The difference between the initial amortized cost basis and the par value of the loan is a noncredit discount or premium, which is amortized into interest income over the life of the loan. Subsequent changes to the allowance for credit losses are recorded as provision for (or reversal of) credit losses. There were no investment securities acquired from Steuben for which there was evidence of a more-than-insignificant deterioration in credit quality since origination. The carrying amount of those loans is as follows at the date of acquisition: ​ ​ ​ ​ ​ (000s omitted) PCD Loans Par value of PCD loans at acquisition ​ $ 35,906 Allowance for credit losses at acquisition ​ (668) Non-credit premium at acquisition ​ 103 Fair value of PCD loans at acquisition ​ $ 35,341 ​ Acquired loans that are deemed to not have experienced a more-than-insignificant credit deterioration since origination are considered non-PCD. At the acquisition date, a fair value adjustment is recorded that includes both credit and interest rate considerations. Fair value adjustments may be discounts (or premiums) to a loan’s cost basis and are accreted (or amortized) to net interest income (or expense) over the loan’s remaining life. Fair value adjustments for revolving loans are accreted (or amortized) using a straight line method. Term loans are accreted (or amortized) using the constant effective yield method. A provision for credit losses is also recorded at acquisition for the credit considerations on non-PCD loans. Subsequent to the purchase date, the methods utilized to estimate the required allowance for credit losses for these loans are the same as originated loans and subsequent changes to the allowance for credit losses are recorded as provision for (or reversal of) credit losses.The following is a summary of the remaining loans acquired from Steuben for which there was no evidence of a more-than-insignificant deterioration in credit quality since origination at the date of acquisition: ​ ​ ​ ​ ​ (000s omitted) Non-PCD Loans Contractually required principal and interest at acquisition ​ $ 400,738 Contractual cash flows not expected to be collected ​ (2,994) Expected cash flows at acquisition ​ 397,744 Interest component of expected cash flows ​ (94,068) Fair value of non-PCD loans at acquisition ​ $ 303,676 ​ The fair value of the Company’s common stock issued for the Steuben acquisition was determined using the market close price of the stock on June 12, 2020. The fair value of checking, savings and money market deposit accounts acquired were assumed to approximate the carrying value as these accounts have no stated maturity and are payable on demand. Certificate of deposit accounts were valued at the present value of the certificates’ expected contractual payments discounted at market rates for similar certificates. The core deposit intangibles and other intangibles related to the Steuben acquisition is being amortized using an accelerated method over their estimated useful life of eight years. The goodwill, which is not amortized for book purposes, was assigned to the Banking segment for the Steuben Direct costs related to the acquisitions were expensed as incurred. Merger and acquisition integration-related expenses were immaterial during the three months ended March 31, 2021 and amounted to $0.4 million during the three months ended March 31, 2020, and have been separately stated in the consolidated statements of income.

ACCOUNTING POLICIES

ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2021
ACCOUNTING POLICIES
ACCOUNTING POLICIES	NOTE C: ACCOUNTING POLICIES The accounting policies of the Company, as applied in the consolidated interim financial statements presented herein, are substantially the same as those followed on an annual basis as presented on pages 79 through 92 of the Annual Report on Form 10-K for the year ended December 31, 2020 filed with the Securities and Exchange Commission (“SEC”) on March 1, 2021 except as noted below. The extent to which the novel coronavirus (“COVID-19”) impacts the Company’s business and financial results will depend on numerous evolving factors including, but not limited to: the magnitude and duration of COVID-19, the extent to which it will impact national and international macroeconomic conditions including interest rates, unemployment rates, the speed of the anticipated recovery, and governmental and business reactions to the pandemic. The Company assessed certain accounting matters that generally require consideration of forecasted financial information in context with the information reasonably available to the Company and the unknown future impacts of COVID-19 as of March 31, 2021 and through the date of this Quarterly Report on Form 10-Q. The accounting matters assessed included, but were not limited to, the Company’s allowance for credit losses, decrease in fee and interest income, and the carrying value of the goodwill and other long-lived assets. While there was not a material impact to the Company’s consolidated financial statements as of and for the quarter ended March 31, 2021, the Company’s future assessment of the magnitude and duration of COVID-19, as well as other factors, could result in material impacts to the Company’s consolidated financial statements in future reporting periods. Contract Balances A contract asset balance occurs when an entity performs a service for a customer before the customer pays consideration (resulting in a contract receivable) or before payment is due (resulting in a contract asset). A contract liability balance is an entity’s obligation to transfer a service to a customer for which the entity has already received payment (or payment is due) from the customer. The Company’s noninterest revenue streams are largely based on transactional activity, or standard month-end revenue accruals such as asset management fees based on month-end market values. Consideration is often received immediately or shortly after the Company satisfies its performance obligation and revenue is recognized. The Company does not typically enter into long-term revenue contracts with customers, and therefore, does not experience significant contract balances. As of March 31, 2021, $26.8 million of accounts receivable, including $8.7 million of unbilled fee revenue, and $4.0 million of unearned revenue was recorded in the consolidated statements of condition. As of December 31, 2020, $30.3 million of accounts receivable, including $7.7 million of unbilled fee revenue, and $1.4 million of unearned revenue was recorded in the consolidated statements of condition. Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-14, Disclosure Framework - Changes to the Disclosure Requirements for Defined Benefit Plans (Subtopic 715-20) . The updated guidance removed the requirements to identify amounts that are expected to be reclassified out of accumulated other comprehensive income and recognized as components of net periodic benefit cost in the next fiscal year, as well as the effects of a one-percentage-point change in assumed health care cost trend rates on service and interest cost and on the postretirement benefit obligation. The updated guidance added disclosure requirements for the weighted-average interest crediting rates for cash balance plans and other plans with interest crediting rates, and explanations for significant gains and losses related to changes in the benefit obligation for the period. This new guidance is effective retrospectively for fiscal years beginning after December 15, 2020 with early adoption permitted. The Company adopted this guidance on January 1, 2021 and determined the adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (Topic 740) . The updated guidance simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740, and clarifying and amending existing guidance to improve consistent application. This new guidance is effective for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. Early adoption is permitted in any interim periods for which financial statements have not been issued. The Company adopted this guidance on January 1, 2021 and determined the adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. New Accounting Pronouncements In March 2020, the FASB issued ASU No. 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting (Topic 848)

INVESTMENT SECURITIES

INVESTMENT SECURITIES	3 Months Ended
	Mar. 31, 2021
INVESTMENT SECURITIES
INVESTMENT SECURITIES	NOTE D: INVESTMENT SECURITIES The amortized cost and estimated fair value of investment securities as of March 31, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ December 31, 2020 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ (000's omitted) Cost Gains Losses Value Cost Gains Losses Value Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 2,892,001 ​ $ 38,711 ​ $ 174,454 ​ $ 2,756,258 ​ $ 2,423,236 ​ $ 94,741 ​ $ 16,595 ​ $ 2,501,382 ​ Obligations of state and political subdivisions ​ 430,447 ​ 19,733 ​ 9 ​ 450,171 ​ 451,028 ​ 24,632 ​ 0 ​ 475,660 ​ Government agency mortgage-backed securities ​ 537,317 ​ 12,638 ​ 4,969 ​ 544,986 ​ 506,540 ​ 16,280 ​ 182 ​ 522,638 ​ Corporate debt securities ​ 3,000 ​ 82 ​ 0 ​ 3,082 ​ 4,499 ​ 137 ​ 1 ​ 4,635 ​ Government agency collateralized mortgage obligations ​ 35,939 ​ 962 ​ 7 ​ 36,894 ​ 42,476 ​ 1,111 ​ 10 ​ 43,577 ​ Total available-for-sale portfolio ​ $ 3,898,704 ​ $ 72,126 ​ $ 179,439 ​ $ 3,791,391 ​ $ 3,427,779 ​ $ 136,901 ​ $ 16,788 ​ $ 3,547,892 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity and other Securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity securities, at fair value ​ $ 251 ​ $ 218 ​ $ 0 ​ $ 469 ​ $ 251 ​ $ 194 ​ $ 0 ​ $ 445 ​ Federal Home Loan Bank common stock ​ 7,410 ​ 0 ​ 0 ​ 7,410 ​ 7,468 ​ 0 ​ 0 ​ 7,468 ​ Federal Reserve Bank common stock ​ 33,916 ​ 0 ​ 0 ​ 33,916 ​ 33,916 ​ 0 ​ 0 ​ 33,916 ​ Other equity securities, at adjusted cost ​ 2,561 ​ 750 ​ 0 ​ 3,311 ​ 4,876 ​ 750 ​ 0 ​ 5,626 ​ Total equity and other securities ​ $ 44,138 ​ $ 968 ​ $ 0 ​ $ 45,106 ​ $ 46,511 ​ $ 944 ​ $ 0 ​ $ 47,455 ​ ​ A summary of investment securities that have been in a continuous unrealized loss position is as follows: As of March 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 Months 12 Months or Longer Total ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized (000's omitted) # Value Losses # Value Losses # Value Losses ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ 31 ​ $ 1,440,822 ​ $ 174,454 ​ 0 ​ $ 0 ​ $ 0 ​ 31 ​ $ 1,440,822 ​ $ 174,454 Obligations of state and political subdivisions ​ 17 ​ 7,028 ​ 9 ​ 0 ​ 0 ​ 0 ​ 17 ​ 7,028 ​ 9 Government agency mortgage-backed securities ​ 162 ​ 184,325 ​ 4,969 ​ 2 ​ 13 ​ 0 ​ 164 ​ 184,338 ​ 4,969 Government agency collateralized mortgage obligations ​ 8 ​ 2,720 ​ 7 ​ 1 ​ 0 ​ 0 ​ 9 ​ 2,720 ​ 7 Total available-for-sale investment portfolio ​ 218 ​ $ 1,634,895 ​ $ 179,439 ​ 3 ​ $ 13 ​ $ 0 ​ 221 ​ $ 1,634,908 ​ $ 179,439 ​ As of December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 Months 12 Months or Longer Total ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized (000's omitted) # Value Losses # Value Losses # Value Losses ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ 13 ​ $ 831,015 ​ $ 16,595 ​ 0 ​ $ 0 ​ $ 0 ​ 13 ​ $ 831,015 ​ $ 16,595 Obligations of state and political subdivisions ​ 1 ​ 358 ​ 0 ​ 0 ​ 0 ​ 0 ​ 1 ​ 358 ​ 0 Government agency mortgage-backed securities ​ 89 ​ 75,992 ​ 182 ​ 2 ​ 14 ​ 0 ​ 91 ​ 76,006 ​ 182 Corporate debt securities ​ 1 ​ ​ 1,001 ​ ​ 1 ​ 0 ​ ​ 0 ​ ​ 0 ​ 1 ​ ​ 1,001 ​ ​ 1 Government agency collateralized mortgage obligations ​ 13 ​ 5,246 ​ 10 ​ 1 ​ 0 ​ 0 ​ 14 ​ 5,246 ​ 10 Total available-for-sale investment portfolio ​ 117 ​ $ 913,612 ​ $ 16,788 ​ 3 ​ $ 14 ​ $ 0 ​ 120 ​ $ 913,626 ​ $ 16,788 ​ The unrealized losses reported pertaining to securities issued by the U.S. government and its sponsored entities, include treasuries, agencies, and mortgage-backed securities issued by Ginnie Mae, Fannie Mae, and Freddie Mac, which are currently rated AAA by Moody’s Investor Services, AA+ by Standard & Poor’s and are guaranteed by the U.S. government. The majority of the obligations of state and political subdivisions and corporations carry a credit rating of A or better. Additionally, a majority of the obligations of state and political subdivisions carry a secondary level of credit enhancement. The Company does not intend to sell these securities, nor is it more likely than not that the Company will be required to sell these securities prior to recovery of the amortized cost. Timely principal and interest payments continue to be made on the securities. The unrealized losses in the portfolios are primarily attributable to changes in interest rates. As such, management does not believe any individual unrealized loss as of March 31, 2021 represents credit losses and no unrealized losses have been recognized into credit loss expense. Accordingly, there is no allowance for credit losses on the Company’s available-for-sale portfolio as of March 31, 2021. Accrued interest receivable on available-for-sale debt securities, included in accrued interest and fees receivable on the consolidated statements of condition, totaled $ The amortized cost and estimated fair value of debt securities at March 31, 2021, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Securities not due at a single maturity date are shown separately. ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale ​ ​ Amortized ​ Fair (000's omitted) Cost Value Due in one year or less ​ $ 201,210 ​ $ 202,974 Due after one through five years ​ 727,189 ​ 758,445 Due after five years through ten years ​ 954,210 ​ 952,781 Due after ten years ​ 1,442,839 ​ 1,295,311 Subtotal ​ 3,325,448 ​ 3,209,511 Government agency mortgage-backed securities ​ 537,317 ​ 544,986 Government agency collateralized mortgage obligations ​ 35,939 ​ 36,894 Total ​ $ 3,898,704 ​ $ 3,791,391 ​ As of March 31, 2021, $271.3 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 March 31, 2021 have an overnight and continuous maturity.

LOANS

LOANS	3 Months Ended
	Mar. 31, 2021
LOANS
LOANS	NOTE E: LOANS The segments of the Company’s loan portfolio are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ (000’s omitted) ​ 2021 2020 ​ Business lending ​ $ 3,391,786 ​ $ 3,440,077 ​ Consumer mortgage ​ 2,409,373 ​ 2,401,499 ​ Consumer indirect ​ 1,029,335 ​ 1,021,885 ​ Consumer direct ​ 142,425 ​ 152,657 ​ Home equity ​ 395,408 ​ 399,834 ​ Gross loans, including deferred origination costs ​ 7,368,327 ​ 7,415,952 ​ Allowance for credit losses ​ (55,069) ​ (60,869) ​ Loans, net of allowance for credit losses ​ $ 7,313,258 ​ $ 7,355,083 ​ ​ The following table presents the aging of the amortized cost basis of the Company’s past due loans, including PCD loans, by segment as of March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Current Total Loans Business lending ​ $ 3,681 ​ $ 88 ​ $ 54,930 ​ $ 58,699 ​ $ 3,333,087 ​ $ 3,391,786 Consumer mortgage ​ 8,022 ​ 1,688 ​ 15,836 ​ 25,546 ​ 2,383,827 ​ 2,409,373 Consumer indirect ​ 6,431 ​ 115 ​ 0 ​ 6,546 ​ 1,022,789 ​ 1,029,335 Consumer direct ​ 559 ​ 16 ​ 2 ​ 577 ​ 141,848 ​ 142,425 Home equity ​ 958 ​ 245 ​ 2,542 ​ 3,745 ​ 391,663 ​ 395,408 Total ​ $ 19,651 ​ $ 2,152 ​ $ 73,310 ​ $ 95,113 ​ $ 7,273,214 ​ $ 7,368,327 ​ The following table presents the aging of the amortized cost basis of the Company’s past due loans, including PCD loans, by segment as of December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due ​ 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Current Total Loans Business lending ​ $ 4,896 ​ $ 59 ​ $ 55,709 ​ $ 60,664 ​ $ 3,379,413 ​ $ 3,440,077 Consumer mortgage ​ 13,236 ​ 3,051 ​ 14,970 ​ 31,257 ​ 2,370,242 ​ 2,401,499 Consumer indirect ​ 13,161 ​ 219 ​ 1 ​ 13,381 ​ 1,008,504 ​ 1,021,885 Consumer direct ​ 1,170 ​ 28 ​ 3 ​ 1,201 ​ 151,456 ​ 152,657 Home equity ​ 2,296 ​ 565 ​ 2,246 ​ 5,107 ​ 394,727 ​ 399,834 Total ​ $ 34,759 ​ $ 3,922 ​ $ 72,929 ​ $ 111,610 ​ $ 7,304,342 ​ $ 7,415,952 ​ The delinquency status for loans on payment deferment due to COVID-19 financial hardship were reported at March 31, 2021 based on their delinquency status at the execution date of the payment deferment, unless subsequent to the execution date of the payment deferment, the borrower made all required past due payments to bring the loan to current status. ​ No interest income on nonaccrual loans was recognized during the three months ended March 31, 2021. An immaterial amount of accrued interest was written off on nonaccrual loans by reversing interest income. ​ The Company uses several credit quality indicators to assess credit risk in an ongoing manner. The Company’s primary credit quality indicator for its business lending portfolio is an internal credit risk rating system that categorizes loans as “pass”, “special mention”, “classified”, or “doubtful”. Credit risk ratings are applied individually to those classes of loans that have significant or unique credit characteristics that benefit from a case-by-case evaluation. Loans that were granted COVID- 19 related financial hardship payment deferrals were reviewed on a case-by-case basis for downgrades into lower credit risk ratings. Loans on payment deferral will continue to be monitored for indications of deterioration that could result in future downgrades. In general, the following are the definitions of the Company’s credit quality indicators: ​ ​ ​ Pass The condition of the borrower and the performance of the loans are satisfactory or better. Special Mention ​ The condition of the borrower has deteriorated although the loan performs as agreed. Loss may be incurred at some future date, if conditions deteriorate further. Classified ​ The condition of the borrower has significantly deteriorated and the performance of the loan could further deteriorate and incur loss, if deficiencies are not corrected. Doubtful ​ The condition of the borrower has deteriorated to the point that collection of the balance is improbable based on current facts and conditions and loss is likely. ​ The following tables show the amount of business lending loans by credit quality category at March 31, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ March 31, 2021 2021 2020 2019 2018 2017 Prior Cost Basis Total Business lending: ​ ​ ​ ​ ​ ​ ​ ​ Risk rating ​ ​ ​ ​ ​ ​ ​ ​ Pass ​ $ 289,320 ​ $ 599,626 ​ $ 344,078 ​ $ 296,523 ​ $ 202,536 ​ $ 715,334 ​ $ 491,420 ​ $ 2,938,837 Special mention ​ 1,187 ​ 13,585 ​ 16,348 ​ 24,560 ​ 25,583 ​ 76,596 ​ 44,936 ​ 202,795 Classified ​ 63 ​ 4,493 ​ 22,684 ​ 38,881 ​ 25,884 ​ 93,255 ​ 61,343 ​ 246,603 Doubtful ​ 0 ​ 0 ​ 17 ​ 88 ​ 0 ​ 71 ​ 3,375 ​ 3,551 Total business lending ​ $ 290,570 ​ $ 617,704 ​ $ 383,127 ​ $ 360,052 ​ $ 254,003 ​ $ 885,256 ​ $ 601,074 ​ $ 3,391,786 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ December 31, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Business lending: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Risk rating ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pass ​ $ 860,178 ​ $ 351,350 ​ $ 312,087 ​ $ 217,138 ​ $ 231,453 ​ $ 543,999 ​ $ 483,018 ​ $ 2,999,223 Special mention ​ 14,687 ​ 36,041 ​ 28,410 ​ 21,875 ​ 29,386 ​ 51,657 ​ 52,732 ​ 234,788 Classified ​ 6,336 ​ 4,560 ​ 30,422 ​ 24,807 ​ 14,891 ​ 65,157 ​ 56,000 ​ 202,173 Doubtful ​ 0 ​ 18 ​ 2,888 ​ 0 ​ 0 ​ 108 ​ 879 ​ 3,893 Total business lending ​ $ 881,201 ​ $ 391,969 ​ $ 373,807 ​ $ 263,820 ​ $ 275,730 ​ $ 660,921 ​ $ 592,629 ​ $ 3,440,077 ​ All other loans are underwritten and structured using standardized criteria and characteristics, primarily payment performance, and are normally risk rated and monitored collectively on a monthly basis. These are typically loans to individuals in the consumer categories and are delineated as either performing or nonperforming. Performing loans include loans classified as current as well as those classified as 30 - 89 days past due. Nonperforming loans include 90+ days past due and still accruing and nonaccrual loans. The following table details the balances in all other loan categories at March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ March 31, 2021 2021 2020 2019 2018 2017 Prior Cost Basis Total Consumer mortgage: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ FICO AB ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 106,415 ​ $ 254,218 ​ $ 213,877 ​ $ 152,748 ​ $ 149,072 ​ $ 715,345 ​ $ 95 ​ $ 1,591,770 Nonperforming ​ 0 ​ 0 ​ 0 ​ 268 ​ 649 ​ 2,880 ​ 0 ​ 3,797 Total FICO AB ​ 106,415 ​ 254,218 ​ 213,877 ​ 153,016 ​ 149,721 ​ 718,225 ​ 95 ​ 1,595,567 FICO CDE ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ 28,736 ​ 132,230 ​ 98,451 ​ 77,047 ​ 69,565 ​ 373,604 ​ 20,446 ​ 800,079 Nonperforming ​ 0 ​ 130 ​ 908 ​ 799 ​ 751 ​ 11,139 ​ 0 ​ 13,727 Total FICO CDE ​ 28,736 ​ 132,360 ​ 99,359 ​ 77,846 ​ 70,316 ​ 384,743 ​ 20,446 ​ 813,806 Total consumer mortgage ​ $ 135,151 ​ $ 386,578 ​ $ 313,236 ​ $ 230,862 ​ $ 220,037 ​ $ 1,102,968 ​ $ 20,541 ​ $ 2,409,373 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer indirect: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 119,208 ​ $ 282,934 ​ $ 273,903 ​ $ 175,721 ​ $ 72,517 ​ $ 104,937 ​ $ 0 ​ $ 1,029,220 Nonperforming ​ 0 ​ 40 ​ 17 ​ 41 ​ 11 ​ 6 ​ 0 ​ 115 Total consumer indirect ​ $ 119,208 ​ $ 282,974 ​ $ 273,920 ​ $ 175,762 ​ $ 72,528 ​ $ 104,943 ​ 0 ​ $ 1,029,335 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer direct: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 13,121 ​ $ 42,530 ​ $ 40,319 ​ $ 22,983 ​ $ 9,781 ​ $ 7,493 ​ $ 6,180 ​ $ 142,407 Nonperforming ​ 0 ​ 0 ​ 10 ​ 2 ​ 0 ​ 6 ​ 0 ​ 18 Total consumer direct ​ $ 13,121 ​ $ 42,530 ​ $ 40,329 ​ $ 22,985 ​ $ 9,781 ​ $ 7,499 ​ $ 6,180 ​ $ 142,425 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Home equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 17,564 ​ $ 49,686 ​ $ 45,846 ​ $ 25,565 ​ $ 21,395 ​ $ 48,214 ​ $ 184,351 ​ $ 392,621 Nonperforming ​ 0 ​ 0 ​ 22 ​ 111 ​ 97 ​ 701 ​ 1,856 ​ 2,787 Total home equity ​ $ 17,564 ​ $ 49,686 ​ $ 45,868 ​ $ 25,676 ​ $ 21,492 ​ $ 48,915 ​ $ 186,207 ​ $ 395,408 ​ The following table details the balances in all other loan categories at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ December 31, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Consumer mortgage: ​ ​ ​ ​ ​ ​ ​ ​ FICO AB ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 260,588 ​ $ 227,027 ​ $ 166,638 ​ $ 163,653 ​ $ 160,911 ​ $ 614,976 ​ $ 321 ​ $ 1,594,114 Nonperforming ​ 0 ​ 0 ​ 275 ​ 398 ​ 345 ​ 2,709 ​ 0 ​ 3,727 Total FICO AB ​ 260,588 ​ 227,027 ​ 166,913 ​ 164,051 ​ 161,256 ​ 617,685 ​ 321 ​ 1,597,841 FICO CDE ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ 115,049 ​ 102,788 ​ 80,973 ​ 75,289 ​ 83,214 ​ 314,668 ​ 17,382 ​ 789,363 Nonperforming ​ 0 ​ 1,010 ​ 582 ​ 877 ​ 1,786 ​ 10,040 ​ 0 ​ 14,295 Total FICO CDE ​ 115,049 ​ 103,798 ​ 81,555 ​ 76,166 ​ 85,000 ​ 324,708 ​ 17,382 ​ 803,658 Total consumer mortgage ​ $ 375,637 ​ $ 330,825 ​ $ 248,468 ​ $ 240,217 ​ $ 246,256 ​ $ 942,393 ​ $ 17,703 ​ $ 2,401,499 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer indirect: ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 303,471 ​ $ 305,901 ​ $ 202,373 ​ $ 86,497 ​ $ 61,449 ​ $ 61,975 ​ $ 0 ​ $ 1,021,666 Nonperforming ​ 51 ​ 52 ​ 82 ​ 17 ​ 16 ​ 1 ​ 0 ​ 219 Total consumer indirect ​ $ 303,522 ​ $ 305,953 ​ $ 202,455 ​ $ 86,514 ​ $ 61,465 ​ $ 61,976 ​ ​ 0 ​ $ 1,021,885 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer direct: ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 49,181 ​ $ 46,992 ​ $ 27,872 ​ $ 12,326 ​ $ 5,232 ​ $ 4,146 ​ $ 6,878 ​ $ 152,627 Nonperforming ​ 1 ​ 19 ​ 2 ​ 5 ​ 0 ​ 3 ​ 0 ​ 30 Total consumer direct ​ $ 49,182 ​ $ 47,011 ​ $ 27,874 ​ $ 12,331 ​ $ 5,232 ​ $ 4,149 ​ $ 6,878 ​ $ 152,657 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Home equity: ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 48,145 ​ $ 48,780 ​ $ 28,074 ​ $ 23,524 ​ $ 17,828 ​ $ 35,900 ​ $ 194,773 ​ $ 397,024 Nonperforming ​ 0 ​ 24 ​ 73 ​ 104 ​ 183 ​ 490 ​ 1,936 ​ 2,810 Total home equity ​ $ 48,145 ​ $ 48,804 ​ $ 28,147 ​ $ 23,628 ​ $ 18,011 ​ $ 36,390 ​ $ 196,709 ​ $ 399,834 ​ All loan classes are collectively evaluated for impairment except business lending. A summary of individually evaluated impaired business loans as of March 31, 2021 and December 31, 2020 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, (000’s omitted) 2021 2020 Loans with allowance allocation ​ $ 26,670 ​ $ 27,437 Loans without allowance allocation ​ 8,028 ​ 8,138 Carrying balance ​ 34,698 ​ 35,575 Contractual balance ​ 37,745 ​ 38,362 Specifically allocated allowance ​ 3,560 ​ 3,874 ​ The average carrying balance of individually evaluated impaired loans was $34.9 million and $2.2 million for the three months ended March 31, 2021 and March 31, 2020, respectively. No interest income was recognized on individually evaluated impaired loans for the three months ended March 31, 2021 and March 31, 2020. In the course of working with borrowers, the Company may choose to restructure the contractual terms of certain loans. In this scenario, the Company attempts to work-out an alternative payment schedule with the borrower in order to optimize collectability of the loan. Any loans that are modified are reviewed by the Company to identify if a troubled debt restructuring (“TDR”) has occurred, which is when, for economic or legal reasons related to a borrower’s financial difficulties, the Company grants a concession to the borrower that it would not otherwise consider. Terms may be modified to fit the ability of the borrower to repay in line with its current financial standing and the restructuring of the loan may include the transfer of assets from the borrower to satisfy the debt, a modification of loan terms, or a combination of the two. In accordance with the clarified guidance issued by the Office of the Comptroller of the Currency (“OCC”), loans that have been discharged in Chapter 7 bankruptcy but not reaffirmed by the borrower, are classified as TDRs, irrespective of payment history or delinquency status, even if the repayment terms for the loan have not been otherwise modified. The Company’s lien position against the underlying collateral remains unchanged. Pursuant to that guidance, the Company records a charge-off equal to any portion of the carrying value that exceeds the net realizable value of the collateral. The amount of loss incurred in the three months ended March 31, 2021 and 2020 was immaterial. TDRs less than $0.5 million are collectively included in the allowance for credit loss estimate. Commercial loans greater than $0.5 million are individually evaluated for impairment, and if necessary, a specific allocation of the allowance for credit losses is provided. With regard to determination of the amount of the allowance for credit losses, troubled debt restructured loans are considered to be impaired. As a result, the determination of the amount of allowance for credit losses related to impaired loans for each portfolio segment within TDRs is the same as detailed previously. With respect to the Company’s lending activities, the Company implemented a customer forbearance program allowing for loan payment deferrals up to three months per request during 2020 to assist both consumer and business borrowers that were experiencing financial hardship due to COVID-19 related challenges. Business lending, consumer direct, and consumer indirect loans in deferment status continued to accrue interest on the deferred principal during the deferment period unless otherwise classified as nonaccrual. Consumer mortgage and home equity loans did not accrue interest on the deferred payments during the deferment period. Consistent with the Coronavirus Aid, Relief and Economic Security Act ( “CARES Act”), the Consolidated Appropriations Act of 2021 (“CAA”) and industry regulatory guidance, borrowers that were otherwise current on loan payments and granted COVID-19 related financial hardship payment deferrals were reported as current loans throughout the first 180 days of the deferral period and were not classified as TDRs. Borrowers that were delinquent in their payments to the Bank prior to requesting a COVID-19 related financial hardship payment deferral were reviewed on a case-by-case basis for TDR classification and non-performing loan status. As of March 31, 2021, the Company had 47 borrowers in forbearance due to COVID-19 related financial hardship, representing $75.6 million in outstanding loan balances, or 1.0% of total loans outstanding. These forbearances were comprised of 42 business borrowers representing $75.1 million in outstanding loan balances and 5 consumer borrowers representing approximately $0.5 million in outstanding loan balances. As of December 31, 2020, the Company had 74 borrowers in forbearance due to COVID-19 related financial hardship, representing $66.5 million in outstanding loan balances, or 0.9% of total loans outstanding. These forbearances were comprised of 63 business borrowers representing $65.7 million in outstanding loan balances and 11 consumer borrowers representing approximately $0.8 million in outstanding loan balances. Information regarding TDRs as of March 31, 2021 and December 31, 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 (000’s omitted) ​ Nonaccrual ​ Accruing ​ Total ​ Nonaccrual ​ Accruing ​ Total ​ # Amount # Amount # Amount # Amount # Amount # Amount Business lending ​ 6 ​ $ 505 4 ​ $ 185 10 ​ $ 690 6 ​ $ 529 4 ​ $ 191 10 ​ $ 720 Consumer mortgage ​ 55 ​ 2,389 44 ​ 2,174 99 ​ 4,563 56 ​ 2,413 48 ​ 2,266 104 ​ 4,679 Consumer indirect ​ 0 ​ 0 78 ​ 882 78 ​ 882 0 ​ 0 86 ​ 951 86 ​ 951 Consumer direct ​ 0 ​ 0 20 ​ 31 20 ​ 31 0 ​ 0 23 ​ 85 23 ​ 85 Home equity ​ 10 ​ 261 12 ​ 257 22 ​ 518 11 ​ 285 13 ​ 264 24 ​ 549 Total ​ 71 ​ $ 3,155 158 ​ $ 3,529 229 ​ $ 6,684 73 ​ $ 3,227 174 ​ $ 3,757 247 ​ $ 6,984 ​ The following table presents information related to loans modified in a TDR during the three months ended March 31, 2021 and 2020. Of the loans noted in the table below, all consumer mortgage loans for the three months ended March 31, 2021 and 2020 were modified due to a Chapter 7 bankruptcy as described previously. The financial effects of these restructurings were immaterial. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Three Months Ended ​ ​ March 31, 2021 ​ March 31, 2020 ​ ​ Number of ​ Outstanding ​ Number of ​ Outstanding (000’s omitted) loans modified Balance loans modified Balance Business lending 0 ​ $ 0 0 ​ $ 0 Consumer mortgage 3 ​ 110 7 ​ 617 Consumer indirect 6 ​ 66 14 ​ 127 Consumer direct 1 ​ 7 1 ​ 12 Home equity 0 ​ 0 0 ​ 0 Total 10 ​ $ 183 22 ​ $ 756 ​ Allowance for Credit Losses The following presents by segment the activity in the allowance for credit losses during the three months ended March 31, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, 2021 ​ ​ Beginning ​ Charge- ​ ​ ​ ​ ​ ​ ​ Ending (000’s omitted) balance offs Recoveries Provision balance Business lending ​ $ 28,190 ​ $ (51) ​ $ 67 ​ $ (1,164) ​ $ 27,042 Consumer mortgage ​ 10,672 ​ (100) ​ 10 ​ (896) ​ 9,686 Consumer indirect ​ 13,696 ​ (1,399) ​ 1,246 ​ (2,423) ​ 11,120 Consumer direct ​ 3,207 ​ (318) ​ 231 ​ (438) ​ 2,682 Home equity ​ 2,222 ​ (98) ​ 4 ​ (585) ​ 1,543 Unallocated ​ 1,000 ​ 0 ​ 0 ​ 0 ​ 1,000 Purchased credit deteriorated ​ 1,882 ​ 0 ​ 27 ​ 87 ​ 1,996 Allowance for credit losses – loans ​ 60,869 ​ (1,966) ​ 1,585 ​ (5,419) ​ 55,069 Liabilities for off-balance-sheet credit exposures ​ 1,489 ​ 0 ​ 0 ​ (300) ​ 1,189 Total allowance for credit losses ​ $ 62,358 ​ $ (1,966) ​ $ 1,585 ​ $ (5,719) ​ $ 56,258 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, 2020 ​ ​ Beginning ​ ​ ​ ​ Beginning ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ balance, ​ ​ ​ ​ balance, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ prior to the ​ ​ ​ ​ after ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ adoption of ​ Impact of ​ adoption of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Ending (000’s omitted) ASC 326 ASC 326 ASC 326 Charge-offs Recoveries Provision balance Business lending ​ $ 19,426 ​ $ 288 ​ $ 19,714 ​ $ (176) ​ $ 138 ​ $ (187) ​ $ 19,489 Consumer mortgage ​ 10,269 ​ (1,051) ​ 9,218 ​ (186) ​ 8 ​ 3,390 ​ 12,430 Consumer indirect ​ 13,712 ​ (997) ​ 12,715 ​ (2,079) ​ 1,163 ​ 1,895 ​ 13,694 Consumer direct ​ 3,255 ​ (643) ​ 2,612 ​ (533) ​ 182 ​ 1,476 ​ 3,737 Home equity ​ 2,129 ​ 808 ​ 2,937 ​ (73) ​ 6 ​ (386) ​ 2,484 Unallocated ​ 957 ​ 43 ​ 1,000 ​ 0 ​ 0 ​ (228) ​ 772 Purchased credit deteriorated ​ 0 ​ 3,072 ​ 3,072 ​ 0 ​ 0 ​ (26) ​ 3,046 Purchased credit impaired ​ 163 ​ (163) ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 Allowance for credit losses – loans ​ 49,911 ​ 1,357 ​ 51,268 ​ (3,047) ​ 1,497 ​ 5,934 ​ 55,652 Liabilities for off-balance-sheet credit exposures ​ 0 ​ 1,185 ​ 1,185 ​ 0 ​ 0 ​ (340) ​ 845 Total allowance for credit losses ​ $ 49,911 ​ $ 2,542 ​ $ 52,453 ​ $ (3,047) ​ $ 1,497 ​ $ 5,594 ​ $ 56,497 ​ Improvements in economic forecasts have resulted in an allowance for credit losses to total loans ratio of 0.75% at March 31, 2021, six basis points lower than the level at March 31, 2020 and seven basis points lower than the level at December 31, 2020. Accrued interest receivable on loans, included in accrued interest and fees receivable on the consolidated statements of condition, totaled $20.9 million at March 31, 2021 and is excluded from the estimate of credit losses and amortized cost basis of loans. 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, 2020. Adjustments to historical loss experience were made for differences in current loan-specific risk characteristics and to address current period delinquencies, charge-off rates, risk ratings, lack of loan level data through an entire economic cycle, changes in loan sizes and underwriting standards as well as the addition of acquired loans which were not underwritten by the Company. The Company considered historical losses immediately prior, through and following the Great Recession of 2008 compared to the historical period used for modeling to adjust the historical information to account for longer-term expectations for loan credit performance. Under CECL, the Company is required to consider future economic conditions to determine current expected credit losses. Management selected an eight quarter reasonable and supportable forecast period using a two quarter lag adjustment with a four quarter reversion to the historical mean to use as part of the economic forecast. Management determined that these qualitative adjustments were needed to adjust historical information for expected losses and to reflect changes as a result of current conditions. For qualitative macroeconomic adjustments, the Company uses third party forecasted economic data scenarios utilizing a base scenario and two alternative scenarios that were weighted based on guidance from the third party provider, with forecasts available as of March 31, 2021. These forecasts were factored into the qualitative portion of the calculation of the estimated credit losses and included the impact of COVID-19, including forecasted vaccine distribution progress, and current and future Federal stimulus packages. The scenarios utilized outline a significant improvement in economic conditions with peak unemployment ranging from Management developed expected loss estimates considering factors for segments as outlined below: ● Business lending – non real estate: The Company considered and selected projected unemployment and GDP as possible indicators of forecasted losses related to business lending. The Company also considered delinquencies, the level of loan deferrals, risk rating changes, recent charge-off history and acquired loans as part of the review of estimated losses. ● Business lending – real estate: The Company considered and selected projected unemployment and commercial and multi-family real estate values as possible indicators of forecasted losses related to commercial real estate loans. The Company also considered the factors noted in business lending – non real estate. ● Consumer mortgages and home equity: The Company considered and selected projected unemployment and residential real estate values as possible indicators of forecasted losses related to mortgage lending. In addition, current delinquencies, the level of loan deferrals, charge-offs and acquired loans were considered. ● Consumer indirect: The Company considered and selected projected unemployment and vehicle valuation indices as possible indicators of forecasted losses related to indirect lending. In addition, current delinquencies, the level of loan deferrals, charge-offs and acquired loans were considered. ● Consumer direct: The Company considered and selected projected unemployment and median household income as possible indicator of forecasted losses related to direct lending. In addition, current delinquencies, the level of loan deferrals, charge-offs and acquired loans were considered. The following table presents the carrying amounts of loans purchased and sold during the three months ended March 31, 2021 by portfolio segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Business ​ Consumer ​ Consumer ​ Consumer ​ Home ​ ​ ​ (000’s omitted) lending mortgage indirect direct equity Total Purchases ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 Sales ​ ​ 0 ​ ​ 8,284 ​ ​ 0 ​ ​ 0 ​ ​ 0 ​ ​ 8,284 ​ All the sales during the three months ended March 31, 2021 were sales of secondary market eligible residential mortgage loans.

GOODWILL AND IDENTIFIABLE INTAN

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2021
GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS
GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS	NOTE F: GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS The gross carrying amount and accumulated amortization for each type of identifiable intangible asset are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 ​ ​ Gross ​ ​ ​ ​ Net ​ Gross ​ ​ ​ ​ Net ​ ​ Carrying Accumulated Carrying Carrying Accumulated Carrying (000’s omitted) ​ Amount Amortization Amount Amount Amortization Amount Amortizing intangible assets: ​ ​ ​ ​ ​ ​ ​ Core deposit intangibles ​ $ 69,403 ​ $ (56,896) ​ $ 12,507 ​ $ 69,403 ​ $ (55,572) ​ $ 13,831 Other intangibles ​ 90,462 ​ (53,380) ​ 37,082 ​ 90,462 ​ (51,353) ​ 39,109 Total amortizing intangibles ​ $ 159,865 ​ $ (110,276) ​ $ 49,589 ​ $ 159,865 ​ $ (106,925) ​ $ 52,940 ​ The estimated aggregate amortization expense for each of the five succeeding fiscal years ended December 31 is as follows: ​ ​ ​ ​ ​ ​ (000's omitted) Apr - Dec 2021 $ 9,289 2022 ​ 10,844 2023 ​ 9,082 2024 ​ 7,551 2025 ​ 6,374 Thereafter ​ 6,449 Total ​ $ 49,589 ​ Shown below are the components of the Company’s goodwill at December 31, 2020 and March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) December 31, 2020 Activity March 31, 2021 Goodwill, net ​ $ 793,708 ​ $ (252) ​ $ 793,456 ​ ​

MANDATORILY REDEEMABLE PREFERRE

MANDATORILY REDEEMABLE PREFERRED SECURITIES	3 Months Ended
	Mar. 31, 2021
MANDATORILY REDEEMABLE PREFERRED SECURITIES
MANDATORILY REDEEMABLE PREFERRED SECURITIES	NOTE G: MANDATORILY REDEEMABLE PREFERRED SECURITIES As of March 31, 2021, the Company does not sponsor any business trusts. The Company previously sponsored Community Capital Trust IV (“CCT IV”) until March 15, 2021 when the Company exercised its right to redeem all of the CCT IV debentures and associated preferred securities for a total of ​

BENEFIT PLANS

BENEFIT PLANS	3 Months Ended
	Mar. 31, 2021
BENEFIT PLANS
BENEFIT PLANS	NOTE H: BENEFIT PLANS The Company provides a qualified defined benefit pension to eligible employees and retirees, other post-retirement health and life insurance benefits to certain retirees, an unfunded supplemental pension plan for certain key executives, and an unfunded stock balance plan for certain of its nonemployee directors. The Company accrues for the estimated cost of these benefits through charges to expense during the years that employees earn these benefits. The service cost component of net periodic benefit income is included in the salaries and employee benefits line of the consolidated statements of income, while the other components of net periodic benefit income are included in other expenses. The Company did not make a contribution to its defined benefit pension plan in the first quarter of 2020. The Company made a $2.8 million contribution to its defined benefit pension plan and a $0.09 million contribution to the Steuben Trust Company Pension Plan in the first quarter of 2021. The net periodic benefit cost for the three months ended March 31, 2021 and 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension Benefits ​ Post-retirement Benefits ​ ​ ​ Three Months Ended ​ Three Months Ended ​ ​ ​ March 31, ​ March 31, ​ (000’s omitted) ​ 2021 2020 2021 ​ 2020 Service cost ​ $ 1,480 ​ $ 1,438 ​ $ 0 ​ $ 0 ​ Interest cost ​ 1,259 1,356 11 ​ 14 Expected return on plan assets ​ (4,696) ​ (3,932) ​ 0 ​ 0 ​ Amortization of unrecognized net loss ​ 900 ​ 810 ​ 11 ​ 10 ​ Amortization of prior service cost ​ 95 ​ 60 ​ (45) ​ (45) ​ Net periodic benefit ​ $ (962) ​ $ (268) ​ $ (23) ​ $ (21) ​ ​

EARNINGS PER SHARE

EARNINGS PER SHARE	3 Months Ended
	Mar. 31, 2021
EARNINGS PER SHARE
EARNINGS PER SHARE	NOTE I: EARNINGS PER SHARE The two class method is used in the calculations of basic and diluted earnings per share. Under the two class method, earnings available to common shareholders for the period are allocated between common shareholders and participating securities according to dividends declared and participation rights in undistributed earnings. The Company has determined that all of its outstanding non-vested stock awards are participating securities as of March 31, 2021. Basic earnings per share are computed based on the weighted-average of the common shares outstanding for the period. Diluted earnings per share are based on the weighted-average of the shares outstanding and the assumed exercise of stock options during the year. The dilutive effect of options is calculated using the treasury stock method of accounting. The treasury stock method determines the number of common shares that would be outstanding if all the dilutive options were exercised and the proceeds were used to repurchase common shares in the open market at the average market price for the applicable time period. There were approximately 0.03 million weighted-average anti-dilutive stock options outstanding for the three months ended March 31, 2021, compared to approximately 0.2 million weighted-average anti-dilutive stock options outstanding for the three months ended March 31, 2020 that were not included in the computation below. The following is a reconciliation of basic to diluted earnings per share for the three months ended March 31, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ (000’s omitted, except per share data) ​ 2021 2020 Net income ​ $ 52,850 ​ $ 40,134 ​ Income attributable to unvested stock-based compensation awards ​ (130) ​ (146) ​ Income available to common shareholders ​ $ 52,720 ​ $ 39,988 ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 53,845 ​ 52,036 ​ Basic earnings per share ​ $ 0.98 ​ $ 0.77 ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income ​ $ 52,850 ​ $ 40,134 ​ Income attributable to unvested stock-based compensation awards ​ (130) ​ (146) ​ Income available to common shareholders ​ $ 52,720 ​ $ 39,988 ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 53,845 ​ 52,036 ​ Assumed exercise of stock options ​ 438 ​ 420 ​ Weighted-average common shares outstanding – diluted ​ 54,283 ​ 52,456 ​ Diluted earnings per share ​ $ 0.97 ​ $ 0.76 ​ ​ Stock Repurchase Program At its December 2019 meeting, the Company’s Board of Directors (the “Board”) approved a stock repurchase program authorizing the repurchase of up to 2.60 million shares of the Company’s common stock in accordance with securities laws and regulations, through December 31, 2020. At its December 2020 meeting, the Board approved a similar program for 2021, authorizing the repurchase of up to 2.68 million shares of the Company’s common stock through December 31, 2021. Any repurchased shares will be used for general corporate purposes, including those related to stock plan activities. The timing and extent of repurchases will depend on market conditions and other corporate considerations as determined at the Company’s discretion. The Company did not repurchase any shares under the authorized plan during the first three months of 2021 or 2020.

COMMITMENTS, CONTINGENT LIABILI

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS	3 Months Ended
	Mar. 31, 2021
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS	NOTE J: COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS The Company is a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments consist primarily of commitments to extend credit and standby letters of credit. Commitments to extend credit are agreements to lend to customers, generally having fixed expiration dates or other termination clauses that may require payment of a fee. These commitments consist principally of unused commercial and consumer credit lines. Standby letters of credit generally are contingent upon the failure of the customer to perform according to the terms of an underlying contract with a third party. The credit risks associated with commitments to extend credit and standby letters of credit are essentially the same as that involved with extending loans to customers and are subject to the Company’s normal credit policies. Collateral may be obtained based on management’s assessment of the customer’s creditworthiness. The fair value of the standby letters of credit is immaterial for disclosure. The contract amounts of commitments and contingencies are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, (000’s omitted) ​ 2021 ​ 2020 Commitments to extend credit ​ $ 1,277,853 ​ $ 1,313,568 ​ Standby letters of credit ​ 37,638 ​ 39,213 ​ Total ​ $ 1,315,491 ​ $ 1,352,781 ​ ​ The Company and its subsidiaries are subject in the normal course of business to various pending and threatened legal proceedings in which claims for monetary damages are asserted. As of March 31, 2021, management, after consultation with legal counsel, does not anticipate that the aggregate ultimate liability arising out of litigation pending or threatened against the Company or its subsidiaries will be material to the Company’s consolidated financial position. On at least a quarterly basis, the Company assesses its liabilities and contingencies in connection with such legal proceedings. For those matters where it is probable that the Company will incur losses and the amounts of the losses can be reasonably estimated, the Company records an expense and corresponding liability in its consolidated financial statements. To the extent the pending or threatened litigation could result in exposure in excess of that liability, the amount of such excess is not currently estimable. The range of reasonably possible losses for matters where an exposure is not currently estimable or considered probable, beyond the existing recorded liabilities, is believed to be between $0 and $1 million in the aggregate. Although the Company does not believe that the outcome of pending litigation will be material to the Company’s consolidated financial position, it cannot rule out the possibility that such outcomes will be material to the consolidated results of operations for a particular reporting period in the future. ​ The Company recorded $3.0 million in litigation accrual in 2020 related to a settlement of a purported class action lawsuit regarding the Bank’s deposit account terms and overdraft disclosures. The Company executed a settlement agreement with respect to the lawsuit in the fourth quarter of 2020 and does not anticipate that additional amounts will be accrued for this matter in future periods. The settlement, which is subject to Court approval, will provide for a release of all claims asserted by class members in the action.

FAIR VALUE

FAIR VALUE	3 Months Ended
	Mar. 31, 2021
FAIR VALUE
FAIR VALUE	NOTE K: FAIR VALUE Accounting standards establish a framework for measuring fair value and require certain disclosures about such fair value instruments. It defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (i.e. exit price). Inputs used to measure fair value are classified into the following hierarchy: ● Quoted prices in active markets for identical assets or liabilities. ● Quoted prices in active markets for similar assets or liabilities, or quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs other than quoted prices that are observable for the asset or liability. ● Significant valuation assumptions not readily observable in a market. ​ A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The following tables set forth the Company’s financial assets and liabilities that were accounted for at fair value on a recurring basis. There were no transfers between any of the levels for the periods presented. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair (000’s omitted) Level 1 Level 2 Level 3 Value Available-for-sale investment securities: ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 2,632,967 ​ $ 123,291 ​ $ 0 ​ $ 2,756,258 Obligations of state and political subdivisions ​ 0 ​ 450,171 ​ 0 ​ 450,171 Government agency mortgage-backed securities ​ 0 ​ 544,986 ​ 0 ​ 544,986 Corporate debt securities ​ 0 ​ 3,082 ​ 0 ​ 3,082 Government agency collateralized mortgage obligations ​ 0 ​ 36,894 ​ 0 ​ 36,894 Total available-for-sale investment securities ​ 2,632,967 ​ 1,158,424 ​ 0 ​ 3,791,391 Equity securities ​ 469 ​ 0 ​ 0 ​ 469 Mortgage loans held for sale ​ ​ 0 ​ ​ 292 ​ ​ 0 ​ ​ 292 Commitments to originate real estate loans for sale ​ ​ 0 ​ ​ 0 ​ ​ 34 ​ ​ 34 Forward sales commitments ​ ​ 0 ​ ​ 50 ​ ​ 0 ​ ​ 50 Interest rate swap agreements asset ​ 0 ​ 707 ​ 0 ​ 707 Interest rate swap agreements liability ​ 0 ​ (388) ​ 0 ​ (388) Total ​ $ 2,633,436 ​ $ 1,159,085 ​ $ 34 ​ $ 3,792,555 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair (000’s omitted) Level 1 Level 2 Level 3 Value Available-for-sale investment securities: ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 2,359,912 ​ $ 141,470 ​ $ 0 ​ $ 2,501,382 Obligations of state and political subdivisions ​ 0 ​ 475,660 ​ 0 ​ 475,660 Government agency mortgage-backed securities ​ 0 ​ 522,638 ​ 0 ​ 522,638 Corporate debt securities ​ 0 ​ 4,635 ​ 0 ​ 4,635 Government agency collateralized mortgage obligations ​ 0 ​ 43,577 ​ 0 ​ 43,577 Total available-for-sale investment securities ​ 2,359,912 ​ 1,187,980 ​ 0 ​ 3,547,892 Equity securities ​ 445 ​ 0 ​ 0 ​ 445 Mortgage loans held for sale ​ 0 ​ 1,622 ​ 0 ​ 1,622 Commitments to originate real estate loans for sale ​ ​ 0 ​ ​ 0 ​ ​ 14 ​ ​ 14 Forward sales commitments ​ ​ 0 ​ ​ 2 ​ ​ 0 ​ ​ 2 Interest rate swap agreements asset ​ 0 ​ 1,572 ​ 0 ​ 1,572 Interest rate swap agreements liability ​ 0 ​ (1,074) ​ ​ 0 ​ (1,074) Total ​ $ 2,360,357 ​ $ 1,190,102 ​ $ 14 ​ $ 3,550,473 ​ The valuation techniques used to measure fair value for the items in the table above are as follows: ● Available-for-sale investment securities and equity securities – The fair values of available-for-sale investment securities are based upon quoted prices, if available. If quoted prices are not available, fair values are measured using quoted market prices for similar securities or model-based valuation techniques. Level 1 securities include U.S. Treasury obligations and marketable equity securities that are traded by dealers or brokers in active over-the-counter markets. Level 2 securities include U.S. agency securities, mortgage-backed securities issued by government-sponsored entities, municipal securities and corporate debt securities that are valued by reference to prices for similar securities or through model-based techniques in which all significant inputs, such as reported trades, trade execution data, LIBOR swap yield curve, market prepayment speeds, credit information, market spreads, and security’s terms and conditions, are observable. See Note D for further disclosure of the fair value of investment securities. ● Mortgage loans held for sale – The Company has elected to value loans held for sale at fair value in order to more closely match the gains and losses associated with loans held for sale with the gains and losses on forward sales contracts. Accordingly, the impact on the valuation will be recognized in the Company’s consolidated statements of income. All mortgage loans held for sale are current and in performing status. The fair value of mortgage loans held for sale is determined using quoted secondary-market prices of loans with similar characteristics and, as such, has been classified as a Level 2 valuation. The unpaid principal value of mortgage loans held for sale was approximately $ 0.3 million at March 31, 2021. The unpaid principal value of mortgage loans held for sale was approximately $1.6 million at December 31, 2020. The unrealized gain on mortgage loans held for sale was recognized in mortgage banking revenues in the consolidated statements of income and is immaterial. ● Forward sales commitments – The Company enters into forward sales commitments to sell certain residential real estate loans. Such commitments are considered to be derivative financial instruments and, therefore, are carried at estimated fair value in the other asset or other liability section of the consolidated statement of condition. The fair value of these forward sales commitments is primarily measured by obtaining pricing from certain government-sponsored entities and reflects the underlying price the entity would pay the Company for an immediate sale on these mortgages. As such, these instruments are classified as Level 2 in the fair value hierarchy. ● Commitments to originate real estate loans for sale – The Company enters into various commitments to originate residential real estate loans for sale. Such commitments are considered to be derivative financial instruments and, therefore, are carried at estimated fair value in the other asset or other liability section of the consolidated statement of condition. The estimated fair value of these commitments is determined using quoted secondary market prices obtained from certain government-sponsored entities. Additionally, accounting guidance requires the expected net future cash flows related to the associated servicing of the loan to be included in the fair value measurement of the derivative. The expected net future cash flows are based on a valuation model that calculates the present value of estimated net servicing income. The valuation model incorporates assumptions that market participants would use in estimating future net servicing income. Such assumptions include estimates of the cost of servicing loans, appropriate discount rate and prepayment speeds. The determination of expected net cash flows is considered a significant unobservable input contributing to the Level 3 classification of commitments to originate real estate loans for sale. ● Interest rate swaps – The interest rate swaps are reported at their fair value utilizing Level 2 inputs from third parties. The fair value of the interest rate swaps are determined using prices obtained from a third party advisor. The fair value measurement of the interest rate swap is determined by netting the discounted future fixed cash payments and the discounted expected variable cash receipts. The variable cash receipts are based on the expectation of future interest rates derived from observed market interest rate curves. The changes in Level 3 assets measured at fair value on a recurring basis are immaterial. The fair value information of assets and liabilities measured on a non-recurring basis presented below is not as of the period-end, but rather as of the date the fair value adjustment was recorded closest to the date presented. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ Total Fair ​ ​ ​ ​ ​ ​ Total Fair (000’s omitted) ​ Level 1 ​ Level 2 ​ Level 3 ​ Value ​ Level 1 ​ Level 2 ​ Level 3 ​ Value Impaired loans ​ $ 0 ​ $ 0 ​ $ 21,647 $ 21,647 ​ $ 0 ​ $ 0 ​ $ 25,063 $ 25,063 Business loans held for sale ​ 0 ​ 0 ​ 848 848 ​ 0 ​ 0 ​ 0 0 Other real estate owned ​ 0 ​ 0 ​ 824 824 ​ 0 ​ 0 ​ 883 883 Mortgage servicing rights ​ 0 ​ 0 ​ 807 807 ​ 0 ​ 0 ​ 682 682 Total ​ $ 0 ​ $ 0 ​ $ 24,126 $ 24,126 ​ $ 0 ​ $ 0 ​ $ 26,628 $ 26,628 ​ Loans are generally not recorded at fair value on a recurring basis. Periodically, the Company records nonrecurring adjustments to the carrying value of loans based on fair value measurements for partial charge-offs of the uncollectible portions of those loans. Nonrecurring adjustments also include certain impairment amounts for collateral-dependent loans calculated when establishing the allowance for credit losses. Such amounts are generally based on the fair value of the underlying collateral supporting the loan and, as a result, the carrying value of the loan less the calculated valuation amount does not necessarily represent the fair value of the loan. Real estate collateral is typically valued using independent appraisals or other indications of value based on recent comparable sales of similar properties or assumptions generally observable in the marketplace, adjusted for non-observable inputs. Thus, the resulting nonrecurring fair value measurements are generally classified as Level 3. Estimates of fair value used for other collateral supporting commercial loans generally are based on assumptions not observable in the marketplace and, therefore, such valuations classify as Level 3. In addition, loans held for sale includes two business lending loans under one relationship at March 31, 2021 that are on nonaccrual status. The fair value of business loans held for sale is determined using liquidation collateral values. The unpaid principal value of business lending loans held for sale was approximately 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 31.8% to 97.5% at March 31, 2021 and result in a Level 3 classification of the inputs for determining fair value. OREO is reviewed and evaluated on at least a quarterly basis for additional impairment and adjusted accordingly, based on the same factors identified above. The Company recovers the carrying value of OREO through the sale of the property. The ability to affect future sales prices is subject to market conditions and factors beyond the Company’s control and may impact the estimated fair value of a property. Originated mortgage servicing rights are recorded at their fair value at the time of sale of the underlying loan, and are amortized in proportion to and over the estimated period of net servicing income. The fair value of mortgage servicing rights is based on a valuation model incorporating inputs that market participants would use in estimating future net servicing income. Such inputs include estimates of the cost of servicing loans, appropriate discount rate and prepayment speeds and are considered to be unobservable and contribute to the Level 3 classification of mortgage servicing rights. In accordance with GAAP, the Company must record impairment charges, on a nonrecurring basis, when the carrying value of a stratum exceeds its estimated fair value. Impairment is recognized through a valuation allowance. There is a valuation allowance of approximately $0.1 million and $0.2 million at March 31, 2021 and December 31, 2020, respectively. The Company determines fair values based on quoted market values, where available, estimates of present values, or other valuation techniques. Those techniques are significantly affected by the assumptions used, including, but not limited to, the discount rate and estimates of future cash flows. In that regard, the derived fair value estimates cannot be substantiated by comparison to independent markets and, in many cases, may not be realized in immediate settlement of the instrument. The significant unobservable inputs used in the determination of fair value of assets classified as Level 3 on a recurring or non-recurring basis are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ ​ ​ ​ Unobservable Input ​ ​ Fair Value at ​ ​ ​ ​ ​ Range ​ (000's omitted, except per loan data) ​ March 31, 2021 ​ Valuation Technique ​ Significant Unobservable Inputs (Weighted Average) ​ Impaired loans ​ $ 21,647 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 78.7% (54.3%) ​ Business loans held for sale ​ 848 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 35.0% (27.9%) ​ Other real estate owned ​ 824 Fair value of collateral Estimated cost of disposal/market adjustment ​ 31.8% - 97.5% (42.0%) ​ Commitments to originate real estate loans for sale ​ 34 Discounted cash flow Embedded servicing value ​ 1 % Mortgage servicing rights ​ 807 Discounted cash flow Weighted average constant prepayment rate ​ 13.7% - 27.0% (15.7%) ​ ​ ​ ​ ​ ​ ​ ​ Weighted average discount rate ​ ​ 2.49% - 3.06% (2.97%) ​ ​ ​ ​ ​ ​ ​ ​ Adequate compensation ​ $ 7/loan ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ ​ Unobservable Input ​ ​ ​ Fair Value at ​ ​ ​ ​ ​ Range ​ (000's omitted, except per loan data) ​ December 31, 2020 ​ Valuation Technique ​ Significant Unobservable Inputs ​ (Weighted Average) Impaired loans ​ $ 25,063 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 78.4% (52.7%) ​ Other real estate owned ​ 883 Fair value of collateral Estimated cost of disposal/market adjustment ​ 11.3% - 52.9% (34.0%) ​ Commitments to originate real estate loans for sale ​ ​ 14 ​ Discounted cash flow ​ Embedded servicing value ​ ​ 1.0 % Mortgage servicing rights ​ 682 Discounted cash flow Weighted average constant prepayment rate ​ 9.8% - 18.8% (17.6%) ​ ​ ​ Weighted average discount rate ​ 1.7% - 2.2% (2.1%) ​ ​ ​ ​ ​ ​ ​ Adequate compensation ​ $ 7/loan ​ ​ The significant unobservable inputs used in the determination of the fair value of assets classified as Level 3 have an inherent measurement uncertainty that if changed could result in higher or lower fair value measurements of these assets as of the reporting date. The weighted average of the estimated cost of disposal/market adjustment for impaired loans and business loans held for sale 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 March 31, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ December 31, 2020 ​ Carrying Fair Carrying Fair (000’s omitted) ​ Value ​ Value ​ Value ​ Value Financial assets: ​ ​ ​ ​ Net loans ​ $ 7,313,258 ​ $ 7,565,204 ​ $ 7,355,083 ​ $ 7,655,044 Financial liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Deposits ​ 12,204,237 ​ 12,215,473 ​ 11,224,974 ​ 11,239,628 Securities sold under agreement to repurchase, short-term ​ 257,767 ​ 257,767 ​ 284,008 ​ 284,008 Other Federal Home Loan Bank borrowings ​ 5,959 ​ 6,031 ​ 6,658 ​ 6,758 Subordinated notes payable ​ 3,297 ​ 3,297 ​ 3,303 ​ 3,303 Subordinated debt held by unconsolidated subsidiary trusts ​ 0 ​ 0 ​ 77,320 ​ 77,320 ​ The following is a further description of the principal valuation methods used by the Company to estimate the fair values of its financial instruments. Loans have been classified as a Level 3 valuation. Fair values for 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	3 Months Ended
	Mar. 31, 2021
DERIVATIVE INSTRUMENTS
DERIVATIVE INSTRUMENTS	NOTE L: DERIVATIVE INSTRUMENTS The Company is party to derivative financial instruments in the normal course of its business to meet the financing needs of its customers and to manage its own exposure to fluctuations in interest rates. These financial instruments have been limited to interest rate swap agreements, commitments to originate real estate loans held for sale and forward sales commitments. The Company does not hold or issue derivative financial instruments for trading or other speculative purposes. The Company enters into forward sales commitments for the future delivery of residential mortgage loans, and interest rate lock commitments to fund loans at a specified interest rate. The forward sales commitments are utilized to reduce interest rate risk associated with interest rate lock commitments and loans held for sale. Changes in the estimated fair value of the forward sales commitments and interest rate lock commitments subsequent to inception are based on changes in the fair value of the underlying loan resulting from the fulfillment of the commitment and changes in the probability that the loan will fund within the terms of the commitment, which is affected primarily by changes in interest rates and the passage of time. At inception and during the life of the interest rate lock commitment, the Company includes the expected net future cash flows related to the associated servicing of the loan as part of the fair value measurement of the interest rate lock commitments. These derivatives are recorded at fair value, which were immaterial at March 31, 2021 and December 31, 2020. The effect of the changes to these derivatives for the three months ended March 31, 2021 and March 31, 2020 was also immaterial. The Company acquired interest rate swaps in 2017 with notional amounts with certain commercial customers which totaled $7.5 million at March 31, 2021 and $14.4 million at December 31, 2020. In order to minimize the Company’s risk, these customer derivatives (pay floating/receive fixed swaps) have been offset with essentially matching interest rate swaps (pay fixed/receive floating swaps) with the Company’s counterparty totaling $7.5 million at March 31, 2021 and $14.4 million at December 31, 2020. At March 31, 2021, the weighted average receive rate of these interest rate swaps was 2.14%, the weighted average pay rate was 4.44% and the weighted average maturity was 2.7 years. At December 31, 2020, the weighted average receive rate of these interest rate swaps was The Company also acquired interest rate swaps in 2017 with notional amounts totaling $5.7 million at March 31, 2021, and $5.7 million at December 31, 2020, that were designated as fair value hedges of certain fixed rate loans with municipalities which are recorded in loans in the consolidated statements of financial condition. At March 31, 2021, the weighted average receive rate of these interest rate swaps was 1.40%, the weighted average pay rate was 3.11% and the weighted average maturity was 12.3 years. At December 31, 2020, the weighted average receive rate of these interest rate swaps was 1.42%, the weighted average pay rate was 3.11% and the weighted average maturity was 12.5 years. The Company includes the gain or loss on the hedged items in interest and fees on loans, the same line item as the offsetting gain or loss on the related interest rate swaps. The effects of fair value accounting in the consolidated statements of income for the three months ended March 31, 2021 and March 31, 2020 are immaterial. As of March 31, 2021 and December 31, 2020, the following amounts were recorded in the consolidated statement of condition related to cumulative basis adjustments for fair value hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ ​ ​ ​ ​ ​ ​ Cumulative Amount of Fair Value ​ ​ Carrying Amount of the Hedged ​ Hedging Adjustment Included in the Line Item in the Consolidated ​ Assets ​ Carrying Amount of the Hedged Assets Statement of Condition in Which ​ March 31, ​ December 31, ​ March 31, ​ December 31, the Hedged Item Is Included 2021 2020 2021 2020 Loans $ 5,854 $ 5,675 $ (319) $ (498) ​ Fair values of derivative instruments as of March 31, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ March 31, 2021 ​ ​ Derivative Assets ​ Derivative Liabilities ​ ​ Consolidated Statement ​ Fair ​ Consolidated Statement of ​ Fair ​ of Condition Location Value Condition Location Value Derivatives designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ $ 319 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ ​ Interest rate swaps Other assets ​ 388 Accrued interest and other liabilities ​ $ 388 Commitments to originate real estate loans for sale Other assets ​ 34 ​ ​ Forward sales commitments Other assets ​ 50 ​ ​ Total derivatives ​ $ 791 ​ $ 388 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ December 31, 2020 ​ ​ Derivative Assets ​ Derivative Liabilities ​ ​ Consolidated Statement ​ Fair ​ Consolidated Statement of ​ Fair ​ of Condition Location Value Condition Location Value Derivatives designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ $ 498 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ ​ ​ Interest rate swaps Other assets ​ 1,074 Accrued interest and other liabilities ​ $ 1,074 Commitments to originate real estate loans for sale ​ Other assets ​ ​ 14 ​ ​ ​ ​ ​ Forward sales commitments ​ Other assets ​ ​ 2 ​ ​ ​ ​ ​ Total derivatives ​ ​ $ 1,588 ​ $ 1,074 ​ The Company assessed its counterparty risk at March 31, 2021 and December 31, 2020 and determined any credit risk inherent in our derivative contracts was not material. Further information about the fair value of derivative financial instruments can be found in Note K to these consolidated financial statements.

SEGMENT INFORMATION

SEGMENT INFORMATION	3 Months Ended
	Mar. 31, 2021
SEGMENT INFORMATION
SEGMENT INFORMATION	NOTE M: SEGMENT INFORMATION Operating segments are components of an enterprise, which are evaluated regularly by the “chief operating decision maker” in deciding how to allocate resources and assess performance. The Company’s chief operating decision maker is the President and Chief Executive Officer of the Company. The Company has identified Banking, Employee Benefit Services and All Other as its reportable operating business segments. Community Bank, N.A. (the “Bank” or “CBNA”) operates the Banking segment that provides full-service banking to consumers, businesses, and governmental units in Upstate New York as well as Northeastern Pennsylvania, Vermont and Western Massachusetts. Employee Benefit Services, which includes the operating subsidiaries Benefit Plans Administrative Services, LLC, BPAS Actuarial and Pension Services, LLC, BPAS Trust Company of Puerto Rico, Northeast Retirement Services, LLC (“NRS”), Global Trust Company, Inc. (“GTC”), and Hand Benefits & Trust Company, provides employee benefit trust, collective investment fund, retirement plan administration, fund administration, transfer agency, actuarial, VEBA/HRA, and health and welfare consulting services. The All Other segment is comprised of: (a) wealth management services including trust services provided by the personal trust unit within the Bank, broker-dealer and investment advisory services provided by Community Investment Services, Inc., The Carta Group, Inc. and OneGroup Wealth Partners, Inc. as well as asset management provided by Nottingham Advisors, Inc., and (b) full-service insurance, risk management and employee benefit services provided by OneGroup NY, Inc. The accounting policies used in the disclosure of business segments are the same as those described in the summary of significant accounting policies (See Note A, Summary of Significant Accounting Policies Information about reportable segments and reconciliation of the information to the consolidated financial statements follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee ​ ​ ​ ​ ​ ​ ​ Consolidated (000's omitted) Banking Benefit Services All Other Eliminations Total Three Months Ended March 31, 2021 ​ ​ ​ ​ ​ Net interest income ​ $ 93,839 ​ $ 94 ​ $ 21 ​ $ 0 ​ $ 93,954 Provision for credit losses ​ (5,719) ​ 0 ​ 0 ​ 0 ​ (5,719) Noninterest revenues ​ 16,454 ​ 27,149 ​ 16,817 ​ (1,889) ​ 58,531 Amortization of intangible assets ​ 1,324 ​ 1,354 ​ 673 ​ 0 ​ 3,351 Acquisition expenses ​ 27 ​ 0 ​ 0 ​ 0 ​ 27 Other operating expenses ​ 65,007 ​ 15,005 ​ 11,745 ​ (1,889) ​ 89,868 Income before income taxes ​ $ 49,654 ​ $ 10,884 ​ $ 4,420 ​ $ 0 ​ $ 64,958 Assets ​ $ 14,427,834 ​ $ 210,297 ​ $ 82,074 ​ $ (100,024) ​ $ 14,620,181 Goodwill ​ $ 689,869 ​ $ 83,275 ​ $ 20,312 ​ $ 0 ​ $ 793,456 Core deposit intangibles & Other intangibles ​ $ 12,507 ​ $ 30,697 ​ $ 6,385 ​ $ 0 ​ $ 49,589 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net interest income ​ $ 89,763 ​ $ 240 ​ $ 51 ​ $ 0 ​ $ 90,054 Provision for credit losses ​ 5,594 ​ 0 ​ 0 ​ 0 ​ 5,594 Noninterest revenues ​ 18,680 ​ 25,925 ​ 15,536 ​ (1,519) ​ 58,622 Amortization of intangible assets ​ 1,417 ​ 1,494 ​ 756 ​ 0 ​ 3,667 Acquisition expenses ​ 369 ​ 0 ​ 0 ​ 0 ​ 369 Other operating expenses ​ 64,200 ​ 15,130 ​ 11,816 ​ (1,519) ​ 89,627 Income before income taxes ​ $ 36,863 ​ $ 9,541 ​ $ 3,015 ​ $ 0 ​ $ 49,419 Assets ​ $ 11,633,330 ​ $ 213,768 ​ $ 76,525 ​ $ (114,640) ​ $ 11,808,983 Goodwill ​ $ 669,886 ​ $ 83,275 ​ $ 20,312 ​ $ 0 ​ $ 773,473 Core deposit intangibles & Other intangibles ​ $ 15,001 ​ $ 36,281 ​ $ 8,164 ​ $ 0 ​ $ 59,446 ​

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2021
ACCOUNTING POLICIES
Contract Balances	Contract Balances A contract asset balance occurs when an entity performs a service for a customer before the customer pays consideration (resulting in a contract receivable) or before payment is due (resulting in a contract asset). A contract liability balance is an entity’s obligation to transfer a service to a customer for which the entity has already received payment (or payment is due) from the customer. The Company’s noninterest revenue streams are largely based on transactional activity, or standard month-end revenue accruals such as asset management fees based on month-end market values. Consideration is often received immediately or shortly after the Company satisfies its performance obligation and revenue is recognized. The Company does not typically enter into long-term revenue contracts with customers, and therefore, does not experience significant contract balances. As of March 31, 2021, $26.8 million of accounts receivable, including $8.7 million of unbilled fee revenue, and $4.0 million of unearned revenue was recorded in the consolidated statements of condition. As of December 31, 2020, $30.3 million of accounts receivable, including $7.7 million of unbilled fee revenue, and $1.4 million of unearned revenue was recorded in the consolidated statements of condition.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In August 2018, the FASB issued ASU No. 2018-14, Disclosure Framework - Changes to the Disclosure Requirements for Defined Benefit Plans (Subtopic 715-20) . The updated guidance removed the requirements to identify amounts that are expected to be reclassified out of accumulated other comprehensive income and recognized as components of net periodic benefit cost in the next fiscal year, as well as the effects of a one-percentage-point change in assumed health care cost trend rates on service and interest cost and on the postretirement benefit obligation. The updated guidance added disclosure requirements for the weighted-average interest crediting rates for cash balance plans and other plans with interest crediting rates, and explanations for significant gains and losses related to changes in the benefit obligation for the period. This new guidance is effective retrospectively for fiscal years beginning after December 15, 2020 with early adoption permitted. The Company adopted this guidance on January 1, 2021 and determined the adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (Topic 740) . The updated guidance simplifies the accounting for income taxes by removing certain exceptions to the general principles in Topic 740, and clarifying and amending existing guidance to improve consistent application. This new guidance is effective for fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. Early adoption is permitted in any interim periods for which financial statements have not been issued. The Company adopted this guidance on January 1, 2021 and determined the adoption of this guidance did not have a material impact on the Company’s consolidated financial statements.
New Accounting Pronouncements	New Accounting Pronouncements In March 2020, the FASB issued ASU No. 2020-04, Facilitation of the Effects of Reference Rate Reform on Financial Reporting (Topic 848)

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	3 Months Ended
	Mar. 31, 2021
ACQUISITIONS
Schedule of estimated fair value of assets acquired and liabilities assumed	The following table summarizes the estimated fair value of the assets acquired and liabilities assumed after considering the measurement period adjustments described above: ​ ​ ​ ​ ​ ​ ​ 2020 (000s omitted) ​ Steuben Consideration paid : ​ ​ 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: ​ 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 ​ 2,701 Other assets ​ 17,675 Core deposit intangibles ​ 2,928 Other intangibles ​ 1,196 Deposits ​ (516,274) Other liabilities ​ (4,843) Other Federal Home Loan Bank borrowings ​ (6,000) Subordinated debt held by unconsolidated subsidiary trusts ​ (2,062) Total identifiable assets, net ​ 78,572 Goodwill ​ $ 19,983 ​
Schedule of loans acquired	​ ​ ​ ​ ​ (000s omitted) PCD Loans Par value of PCD loans at acquisition ​ $ 35,906 Allowance for credit losses at acquisition ​ (668) Non-credit premium at acquisition ​ 103 Fair value of PCD loans at acquisition ​ $ 35,341 ​ ​ ​ ​ ​ (000s omitted) Non-PCD Loans Contractually required principal and interest at acquisition ​ $ 400,738 Contractual cash flows not expected to be collected ​ (2,994) Expected cash flows at acquisition ​ 397,744 Interest component of expected cash flows ​ (94,068) Fair value of non-PCD loans at acquisition ​ $ 303,676

INVESTMENT SECURITIES (Tables)

INVESTMENT SECURITIES (Tables)	3 Months Ended
	Mar. 31, 2021
INVESTMENT SECURITIES
Schedule of amortized cost and estimated fair value of investment securities	The amortized cost and estimated fair value of investment securities as of March 31, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ December 31, 2020 ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ ​ ​ Gross ​ Gross ​ ​ ​ ​ ​ ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ Amortized ​ Unrealized ​ Unrealized ​ Fair ​ (000's omitted) Cost Gains Losses Value Cost Gains Losses Value Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 2,892,001 ​ $ 38,711 ​ $ 174,454 ​ $ 2,756,258 ​ $ 2,423,236 ​ $ 94,741 ​ $ 16,595 ​ $ 2,501,382 ​ Obligations of state and political subdivisions ​ 430,447 ​ 19,733 ​ 9 ​ 450,171 ​ 451,028 ​ 24,632 ​ 0 ​ 475,660 ​ Government agency mortgage-backed securities ​ 537,317 ​ 12,638 ​ 4,969 ​ 544,986 ​ 506,540 ​ 16,280 ​ 182 ​ 522,638 ​ Corporate debt securities ​ 3,000 ​ 82 ​ 0 ​ 3,082 ​ 4,499 ​ 137 ​ 1 ​ 4,635 ​ Government agency collateralized mortgage obligations ​ 35,939 ​ 962 ​ 7 ​ 36,894 ​ 42,476 ​ 1,111 ​ 10 ​ 43,577 ​ Total available-for-sale portfolio ​ $ 3,898,704 ​ $ 72,126 ​ $ 179,439 ​ $ 3,791,391 ​ $ 3,427,779 ​ $ 136,901 ​ $ 16,788 ​ $ 3,547,892 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity and other Securities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Equity securities, at fair value ​ $ 251 ​ $ 218 ​ $ 0 ​ $ 469 ​ $ 251 ​ $ 194 ​ $ 0 ​ $ 445 ​ Federal Home Loan Bank common stock ​ 7,410 ​ 0 ​ 0 ​ 7,410 ​ 7,468 ​ 0 ​ 0 ​ 7,468 ​ Federal Reserve Bank common stock ​ 33,916 ​ 0 ​ 0 ​ 33,916 ​ 33,916 ​ 0 ​ 0 ​ 33,916 ​ Other equity securities, at adjusted cost ​ 2,561 ​ 750 ​ 0 ​ 3,311 ​ 4,876 ​ 750 ​ 0 ​ 5,626 ​ Total equity and other securities ​ $ 44,138 ​ $ 968 ​ $ 0 ​ $ 45,106 ​ $ 46,511 ​ $ 944 ​ $ 0 ​ $ 47,455 ​
Schedule of investment securities that have been in a continuous unrealized loss position for less than or greater than twelve months	A summary of investment securities that have been in a continuous unrealized loss position is as follows: As of March 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 Months 12 Months or Longer Total ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized (000's omitted) # Value Losses # Value Losses # Value Losses ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ 31 ​ $ 1,440,822 ​ $ 174,454 ​ 0 ​ $ 0 ​ $ 0 ​ 31 ​ $ 1,440,822 ​ $ 174,454 Obligations of state and political subdivisions ​ 17 ​ 7,028 ​ 9 ​ 0 ​ 0 ​ 0 ​ 17 ​ 7,028 ​ 9 Government agency mortgage-backed securities ​ 162 ​ 184,325 ​ 4,969 ​ 2 ​ 13 ​ 0 ​ 164 ​ 184,338 ​ 4,969 Government agency collateralized mortgage obligations ​ 8 ​ 2,720 ​ 7 ​ 1 ​ 0 ​ 0 ​ 9 ​ 2,720 ​ 7 Total available-for-sale investment portfolio ​ 218 ​ $ 1,634,895 ​ $ 179,439 ​ 3 ​ $ 13 ​ $ 0 ​ 221 ​ $ 1,634,908 ​ $ 179,439 ​ As of December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Less than 12 Months 12 Months or Longer Total ​ ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ Gross ​ ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized ​ ​ ​ Fair ​ Unrealized (000's omitted) # Value Losses # Value Losses # Value Losses ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale Portfolio: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ U.S. Treasury and agency securities ​ 13 ​ $ 831,015 ​ $ 16,595 ​ 0 ​ $ 0 ​ $ 0 ​ 13 ​ $ 831,015 ​ $ 16,595 Obligations of state and political subdivisions ​ 1 ​ 358 ​ 0 ​ 0 ​ 0 ​ 0 ​ 1 ​ 358 ​ 0 Government agency mortgage-backed securities ​ 89 ​ 75,992 ​ 182 ​ 2 ​ 14 ​ 0 ​ 91 ​ 76,006 ​ 182 Corporate debt securities ​ 1 ​ ​ 1,001 ​ ​ 1 ​ 0 ​ ​ 0 ​ ​ 0 ​ 1 ​ ​ 1,001 ​ ​ 1 Government agency collateralized mortgage obligations ​ 13 ​ 5,246 ​ 10 ​ 1 ​ 0 ​ 0 ​ 14 ​ 5,246 ​ 10 Total available-for-sale investment portfolio ​ 117 ​ $ 913,612 ​ $ 16,788 ​ 3 ​ $ 14 ​ $ 0 ​ 120 ​ $ 913,626 ​ $ 16,788 ​
Schedule of amortized cost and estimated fair value of debt securities by contractual maturity	The amortized cost and estimated fair value of debt securities at March 31, 2021, by contractual maturity, are shown below. Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. Securities not due at a single maturity date are shown separately. ​ ​ ​ ​ ​ ​ ​ ​ ​ Available-for-Sale ​ ​ Amortized ​ Fair (000's omitted) Cost Value Due in one year or less ​ $ 201,210 ​ $ 202,974 Due after one through five years ​ 727,189 ​ 758,445 Due after five years through ten years ​ 954,210 ​ 952,781 Due after ten years ​ 1,442,839 ​ 1,295,311 Subtotal ​ 3,325,448 ​ 3,209,511 Government agency mortgage-backed securities ​ 537,317 ​ 544,986 Government agency collateralized mortgage obligations ​ 35,939 ​ 36,894 Total ​ $ 3,898,704 ​ $ 3,791,391

LOANS (Tables)

LOANS (Tables)	3 Months Ended
	Mar. 31, 2021
Loans and Leases Receivable Disclosure [Line Items]
Schedule of loans receivable, net	The segments of the Company’s loan portfolio are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, ​ December 31, ​ (000’s omitted) ​ 2021 2020 ​ Business lending ​ $ 3,391,786 ​ $ 3,440,077 ​ Consumer mortgage ​ 2,409,373 ​ 2,401,499 ​ Consumer indirect ​ 1,029,335 ​ 1,021,885 ​ Consumer direct ​ 142,425 ​ 152,657 ​ Home equity ​ 395,408 ​ 399,834 ​ Gross loans, including deferred origination costs ​ 7,368,327 ​ 7,415,952 ​ Allowance for credit losses ​ (55,069) ​ (60,869) ​ Loans, net of allowance for credit losses ​ $ 7,313,258 ​ $ 7,355,083 ​ ​
Schedule of aged analysis of past due loans by class	The following table presents the aging of the amortized cost basis of the Company’s past due loans, including PCD loans, by segment as of March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Current Total Loans Business lending ​ $ 3,681 ​ $ 88 ​ $ 54,930 ​ $ 58,699 ​ $ 3,333,087 ​ $ 3,391,786 Consumer mortgage ​ 8,022 ​ 1,688 ​ 15,836 ​ 25,546 ​ 2,383,827 ​ 2,409,373 Consumer indirect ​ 6,431 ​ 115 ​ 0 ​ 6,546 ​ 1,022,789 ​ 1,029,335 Consumer direct ​ 559 ​ 16 ​ 2 ​ 577 ​ 141,848 ​ 142,425 Home equity ​ 958 ​ 245 ​ 2,542 ​ 3,745 ​ 391,663 ​ 395,408 Total ​ $ 19,651 ​ $ 2,152 ​ $ 73,310 ​ $ 95,113 ​ $ 7,273,214 ​ $ 7,368,327 ​ The following table presents the aging of the amortized cost basis of the Company’s past due loans, including PCD loans, by segment as of December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Past Due ​ 90+ Days Past ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 30 – 89 ​ Due and ​ ​ ​ ​ Total ​ ​ ​ ​ ​ ​ (000’s omitted) Days Still Accruing Nonaccrual Past Due Current Total Loans Business lending ​ $ 4,896 ​ $ 59 ​ $ 55,709 ​ $ 60,664 ​ $ 3,379,413 ​ $ 3,440,077 Consumer mortgage ​ 13,236 ​ 3,051 ​ 14,970 ​ 31,257 ​ 2,370,242 ​ 2,401,499 Consumer indirect ​ 13,161 ​ 219 ​ 1 ​ 13,381 ​ 1,008,504 ​ 1,021,885 Consumer direct ​ 1,170 ​ 28 ​ 3 ​ 1,201 ​ 151,456 ​ 152,657 Home equity ​ 2,296 ​ 565 ​ 2,246 ​ 5,107 ​ 394,727 ​ 399,834 Total ​ $ 34,759 ​ $ 3,922 ​ $ 72,929 ​ $ 111,610 ​ $ 7,304,342 ​ $ 7,415,952 ​
Schedule of non-business impaired loans	All loan classes are collectively evaluated for impairment except business lending. A summary of individually evaluated impaired business loans as of March 31, 2021 and December 31, 2020 follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, (000’s omitted) 2021 2020 Loans with allowance allocation ​ $ 26,670 ​ $ 27,437 Loans without allowance allocation ​ 8,028 ​ 8,138 Carrying balance ​ 34,698 ​ 35,575 Contractual balance ​ 37,745 ​ 38,362 Specifically allocated allowance ​ 3,560 ​ 3,874 ​
Schedule of troubled debt restructurings on financing receivables	Information regarding TDRs as of March 31, 2021 and December 31, 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 (000’s omitted) ​ Nonaccrual ​ Accruing ​ Total ​ Nonaccrual ​ Accruing ​ Total ​ # Amount # Amount # Amount # Amount # Amount # Amount Business lending ​ 6 ​ $ 505 4 ​ $ 185 10 ​ $ 690 6 ​ $ 529 4 ​ $ 191 10 ​ $ 720 Consumer mortgage ​ 55 ​ 2,389 44 ​ 2,174 99 ​ 4,563 56 ​ 2,413 48 ​ 2,266 104 ​ 4,679 Consumer indirect ​ 0 ​ 0 78 ​ 882 78 ​ 882 0 ​ 0 86 ​ 951 86 ​ 951 Consumer direct ​ 0 ​ 0 20 ​ 31 20 ​ 31 0 ​ 0 23 ​ 85 23 ​ 85 Home equity ​ 10 ​ 261 12 ​ 257 22 ​ 518 11 ​ 285 13 ​ 264 24 ​ 549 Total ​ 71 ​ $ 3,155 158 ​ $ 3,529 229 ​ $ 6,684 73 ​ $ 3,227 174 ​ $ 3,757 247 ​ $ 6,984 ​ The following table presents information related to loans modified in a TDR during the three months ended March 31, 2021 and 2020. Of the loans noted in the table below, all consumer mortgage loans for the three months ended March 31, 2021 and 2020 were modified due to a Chapter 7 bankruptcy as described previously. The financial effects of these restructurings were immaterial. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Three Months Ended ​ ​ March 31, 2021 ​ March 31, 2020 ​ ​ Number of ​ Outstanding ​ Number of ​ Outstanding (000’s omitted) loans modified Balance loans modified Balance Business lending 0 ​ $ 0 0 ​ $ 0 Consumer mortgage 3 ​ 110 7 ​ 617 Consumer indirect 6 ​ 66 14 ​ 127 Consumer direct 1 ​ 7 1 ​ 12 Home equity 0 ​ 0 0 ​ 0 Total 10 ​ $ 183 22 ​ $ 756 ​
Schedule of allowance for loan losses by class	The following presents by segment the activity in the allowance for credit losses during the three months ended March 31, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, 2021 ​ ​ Beginning ​ Charge- ​ ​ ​ ​ ​ ​ ​ Ending (000’s omitted) balance offs Recoveries Provision balance Business lending ​ $ 28,190 ​ $ (51) ​ $ 67 ​ $ (1,164) ​ $ 27,042 Consumer mortgage ​ 10,672 ​ (100) ​ 10 ​ (896) ​ 9,686 Consumer indirect ​ 13,696 ​ (1,399) ​ 1,246 ​ (2,423) ​ 11,120 Consumer direct ​ 3,207 ​ (318) ​ 231 ​ (438) ​ 2,682 Home equity ​ 2,222 ​ (98) ​ 4 ​ (585) ​ 1,543 Unallocated ​ 1,000 ​ 0 ​ 0 ​ 0 ​ 1,000 Purchased credit deteriorated ​ 1,882 ​ 0 ​ 27 ​ 87 ​ 1,996 Allowance for credit losses – loans ​ 60,869 ​ (1,966) ​ 1,585 ​ (5,419) ​ 55,069 Liabilities for off-balance-sheet credit exposures ​ 1,489 ​ 0 ​ 0 ​ (300) ​ 1,189 Total allowance for credit losses ​ $ 62,358 ​ $ (1,966) ​ $ 1,585 ​ $ (5,719) ​ $ 56,258 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, 2020 ​ ​ Beginning ​ ​ ​ ​ Beginning ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ balance, ​ ​ ​ ​ balance, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ prior to the ​ ​ ​ ​ after ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ adoption of ​ Impact of ​ adoption of ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Ending (000’s omitted) ASC 326 ASC 326 ASC 326 Charge-offs Recoveries Provision balance Business lending ​ $ 19,426 ​ $ 288 ​ $ 19,714 ​ $ (176) ​ $ 138 ​ $ (187) ​ $ 19,489 Consumer mortgage ​ 10,269 ​ (1,051) ​ 9,218 ​ (186) ​ 8 ​ 3,390 ​ 12,430 Consumer indirect ​ 13,712 ​ (997) ​ 12,715 ​ (2,079) ​ 1,163 ​ 1,895 ​ 13,694 Consumer direct ​ 3,255 ​ (643) ​ 2,612 ​ (533) ​ 182 ​ 1,476 ​ 3,737 Home equity ​ 2,129 ​ 808 ​ 2,937 ​ (73) ​ 6 ​ (386) ​ 2,484 Unallocated ​ 957 ​ 43 ​ 1,000 ​ 0 ​ 0 ​ (228) ​ 772 Purchased credit deteriorated ​ 0 ​ 3,072 ​ 3,072 ​ 0 ​ 0 ​ (26) ​ 3,046 Purchased credit impaired ​ 163 ​ (163) ​ 0 ​ 0 ​ 0 ​ 0 ​ 0 Allowance for credit losses – loans ​ 49,911 ​ 1,357 ​ 51,268 ​ (3,047) ​ 1,497 ​ 5,934 ​ 55,652 Liabilities for off-balance-sheet credit exposures ​ 0 ​ 1,185 ​ 1,185 ​ 0 ​ 0 ​ (340) ​ 845 Total allowance for credit losses ​ $ 49,911 ​ $ 2,542 ​ $ 52,453 ​ $ (3,047) ​ $ 1,497 ​ $ 5,594 ​ $ 56,497 ​
Schedule of financing receivables purchased and Sold	The following table presents the carrying amounts of loans purchased and sold during the three months ended March 31, 2021 by portfolio segment: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Business ​ Consumer ​ Consumer ​ Consumer ​ Home ​ ​ ​ (000’s omitted) lending mortgage indirect direct equity Total Purchases ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 ​ $ 0 Sales ​ ​ 0 ​ ​ 8,284 ​ ​ 0 ​ ​ 0 ​ ​ 0 ​ ​ 8,284
Business Lending [Member]
Loans and Leases Receivable Disclosure [Line Items]
Schedule of loans by credit quality indicator	The following tables show the amount of business lending loans by credit quality category at March 31, 2021 and December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ March 31, 2021 2021 2020 2019 2018 2017 Prior Cost Basis Total Business lending: ​ ​ ​ ​ ​ ​ ​ ​ Risk rating ​ ​ ​ ​ ​ ​ ​ ​ Pass ​ $ 289,320 ​ $ 599,626 ​ $ 344,078 ​ $ 296,523 ​ $ 202,536 ​ $ 715,334 ​ $ 491,420 ​ $ 2,938,837 Special mention ​ 1,187 ​ 13,585 ​ 16,348 ​ 24,560 ​ 25,583 ​ 76,596 ​ 44,936 ​ 202,795 Classified ​ 63 ​ 4,493 ​ 22,684 ​ 38,881 ​ 25,884 ​ 93,255 ​ 61,343 ​ 246,603 Doubtful ​ 0 ​ 0 ​ 17 ​ 88 ​ 0 ​ 71 ​ 3,375 ​ 3,551 Total business lending ​ $ 290,570 ​ $ 617,704 ​ $ 383,127 ​ $ 360,052 ​ $ 254,003 ​ $ 885,256 ​ $ 601,074 ​ $ 3,391,786 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ December 31, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Business lending: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Risk rating ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pass ​ $ 860,178 ​ $ 351,350 ​ $ 312,087 ​ $ 217,138 ​ $ 231,453 ​ $ 543,999 ​ $ 483,018 ​ $ 2,999,223 Special mention ​ 14,687 ​ 36,041 ​ 28,410 ​ 21,875 ​ 29,386 ​ 51,657 ​ 52,732 ​ 234,788 Classified ​ 6,336 ​ 4,560 ​ 30,422 ​ 24,807 ​ 14,891 ​ 65,157 ​ 56,000 ​ 202,173 Doubtful ​ 0 ​ 18 ​ 2,888 ​ 0 ​ 0 ​ 108 ​ 879 ​ 3,893 Total business lending ​ $ 881,201 ​ $ 391,969 ​ $ 373,807 ​ $ 263,820 ​ $ 275,730 ​ $ 660,921 ​ $ 592,629 ​ $ 3,440,077
All Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Schedule of loans by credit quality indicator	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ March 31, 2021 2021 2020 2019 2018 2017 Prior Cost Basis Total Consumer mortgage: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ FICO AB ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 106,415 ​ $ 254,218 ​ $ 213,877 ​ $ 152,748 ​ $ 149,072 ​ $ 715,345 ​ $ 95 ​ $ 1,591,770 Nonperforming ​ 0 ​ 0 ​ 0 ​ 268 ​ 649 ​ 2,880 ​ 0 ​ 3,797 Total FICO AB ​ 106,415 ​ 254,218 ​ 213,877 ​ 153,016 ​ 149,721 ​ 718,225 ​ 95 ​ 1,595,567 FICO CDE ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ 28,736 ​ 132,230 ​ 98,451 ​ 77,047 ​ 69,565 ​ 373,604 ​ 20,446 ​ 800,079 Nonperforming ​ 0 ​ 130 ​ 908 ​ 799 ​ 751 ​ 11,139 ​ 0 ​ 13,727 Total FICO CDE ​ 28,736 ​ 132,360 ​ 99,359 ​ 77,846 ​ 70,316 ​ 384,743 ​ 20,446 ​ 813,806 Total consumer mortgage ​ $ 135,151 ​ $ 386,578 ​ $ 313,236 ​ $ 230,862 ​ $ 220,037 ​ $ 1,102,968 ​ $ 20,541 ​ $ 2,409,373 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer indirect: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 119,208 ​ $ 282,934 ​ $ 273,903 ​ $ 175,721 ​ $ 72,517 ​ $ 104,937 ​ $ 0 ​ $ 1,029,220 Nonperforming ​ 0 ​ 40 ​ 17 ​ 41 ​ 11 ​ 6 ​ 0 ​ 115 Total consumer indirect ​ $ 119,208 ​ $ 282,974 ​ $ 273,920 ​ $ 175,762 ​ $ 72,528 ​ $ 104,943 ​ 0 ​ $ 1,029,335 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer direct: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 13,121 ​ $ 42,530 ​ $ 40,319 ​ $ 22,983 ​ $ 9,781 ​ $ 7,493 ​ $ 6,180 ​ $ 142,407 Nonperforming ​ 0 ​ 0 ​ 10 ​ 2 ​ 0 ​ 6 ​ 0 ​ 18 Total consumer direct ​ $ 13,121 ​ $ 42,530 ​ $ 40,329 ​ $ 22,985 ​ $ 9,781 ​ $ 7,499 ​ $ 6,180 ​ $ 142,425 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Home equity: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 17,564 ​ $ 49,686 ​ $ 45,846 ​ $ 25,565 ​ $ 21,395 ​ $ 48,214 ​ $ 184,351 ​ $ 392,621 Nonperforming ​ 0 ​ 0 ​ 22 ​ 111 ​ 97 ​ 701 ​ 1,856 ​ 2,787 Total home equity ​ $ 17,564 ​ $ 49,686 ​ $ 45,868 ​ $ 25,676 ​ $ 21,492 ​ $ 48,915 ​ $ 186,207 ​ $ 395,408 ​ The following table details the balances in all other loan categories at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Revolving ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Loans ​ ​ ​ (000’s omitted) ​ Term Loans Amortized Cost Basis by Origination Year ​ Amortized ​ ​ ​ December 31, 2020 2020 2019 2018 2017 2016 Prior Cost Basis Total Consumer mortgage: ​ ​ ​ ​ ​ ​ ​ ​ FICO AB ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 260,588 ​ $ 227,027 ​ $ 166,638 ​ $ 163,653 ​ $ 160,911 ​ $ 614,976 ​ $ 321 ​ $ 1,594,114 Nonperforming ​ 0 ​ 0 ​ 275 ​ 398 ​ 345 ​ 2,709 ​ 0 ​ 3,727 Total FICO AB ​ 260,588 ​ 227,027 ​ 166,913 ​ 164,051 ​ 161,256 ​ 617,685 ​ 321 ​ 1,597,841 FICO CDE ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ 115,049 ​ 102,788 ​ 80,973 ​ 75,289 ​ 83,214 ​ 314,668 ​ 17,382 ​ 789,363 Nonperforming ​ 0 ​ 1,010 ​ 582 ​ 877 ​ 1,786 ​ 10,040 ​ 0 ​ 14,295 Total FICO CDE ​ 115,049 ​ 103,798 ​ 81,555 ​ 76,166 ​ 85,000 ​ 324,708 ​ 17,382 ​ 803,658 Total consumer mortgage ​ $ 375,637 ​ $ 330,825 ​ $ 248,468 ​ $ 240,217 ​ $ 246,256 ​ $ 942,393 ​ $ 17,703 ​ $ 2,401,499 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer indirect: ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 303,471 ​ $ 305,901 ​ $ 202,373 ​ $ 86,497 ​ $ 61,449 ​ $ 61,975 ​ $ 0 ​ $ 1,021,666 Nonperforming ​ 51 ​ 52 ​ 82 ​ 17 ​ 16 ​ 1 ​ 0 ​ 219 Total consumer indirect ​ $ 303,522 ​ $ 305,953 ​ $ 202,455 ​ $ 86,514 ​ $ 61,465 ​ $ 61,976 ​ ​ 0 ​ $ 1,021,885 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Consumer direct: ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 49,181 ​ $ 46,992 ​ $ 27,872 ​ $ 12,326 ​ $ 5,232 ​ $ 4,146 ​ $ 6,878 ​ $ 152,627 Nonperforming ​ 1 ​ 19 ​ 2 ​ 5 ​ 0 ​ 3 ​ 0 ​ 30 Total consumer direct ​ $ 49,182 ​ $ 47,011 ​ $ 27,874 ​ $ 12,331 ​ $ 5,232 ​ $ 4,149 ​ $ 6,878 ​ $ 152,657 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Home equity: ​ ​ ​ ​ ​ ​ ​ ​ Performing ​ $ 48,145 ​ $ 48,780 ​ $ 28,074 ​ $ 23,524 ​ $ 17,828 ​ $ 35,900 ​ $ 194,773 ​ $ 397,024 Nonperforming ​ 0 ​ 24 ​ 73 ​ 104 ​ 183 ​ 490 ​ 1,936 ​ 2,810 Total home equity ​ $ 48,145 ​ $ 48,804 ​ $ 28,147 ​ $ 23,628 ​ $ 18,011 ​ $ 36,390 ​ $ 196,709 ​ $ 399,834 ​

GOODWILL AND IDENTIFIABLE INT_2

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Tables)	3 Months Ended
	Mar. 31, 2021
GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS
Schedule of gross carrying amount and accumulated amortization for each type of identifiable intangible asset	The gross carrying amount and accumulated amortization for each type of identifiable intangible asset are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 December 31, 2020 ​ ​ Gross ​ ​ ​ ​ Net ​ Gross ​ ​ ​ ​ Net ​ ​ Carrying Accumulated Carrying Carrying Accumulated Carrying (000’s omitted) ​ Amount Amortization Amount Amount Amortization Amount Amortizing intangible assets: ​ ​ ​ ​ ​ ​ ​ Core deposit intangibles ​ $ 69,403 ​ $ (56,896) ​ $ 12,507 ​ $ 69,403 ​ $ (55,572) ​ $ 13,831 Other intangibles ​ 90,462 ​ (53,380) ​ 37,082 ​ 90,462 ​ (51,353) ​ 39,109 Total amortizing intangibles ​ $ 159,865 ​ $ (110,276) ​ $ 49,589 ​ $ 159,865 ​ $ (106,925) ​ $ 52,940
Schedule of estimated aggregate amortization expense for each of five succeeding fiscal years	The estimated aggregate amortization expense for each of the five succeeding fiscal years ended December 31 is as follows: ​ ​ ​ ​ ​ ​ (000's omitted) Apr - Dec 2021 $ 9,289 2022 ​ 10,844 2023 ​ 9,082 2024 ​ 7,551 2025 ​ 6,374 Thereafter ​ 6,449 Total ​ $ 49,589
Schedule of components of goodwill	Shown below are the components of the Company’s goodwill at December 31, 2020 and March 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) December 31, 2020 Activity March 31, 2021 Goodwill, net ​ $ 793,708 ​ $ (252) ​ $ 793,456 ​

BENEFIT PLANS (Tables)

BENEFIT PLANS (Tables)	3 Months Ended
	Mar. 31, 2021
BENEFIT PLANS
Schedule of net periodic benefit cost	The net periodic benefit cost for the three months ended March 31, 2021 and 2020 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Pension Benefits ​ Post-retirement Benefits ​ ​ ​ Three Months Ended ​ Three Months Ended ​ ​ ​ March 31, ​ March 31, ​ (000’s omitted) ​ 2021 2020 2021 ​ 2020 Service cost ​ $ 1,480 ​ $ 1,438 ​ $ 0 ​ $ 0 ​ Interest cost ​ 1,259 1,356 11 ​ 14 Expected return on plan assets ​ (4,696) ​ (3,932) ​ 0 ​ 0 ​ Amortization of unrecognized net loss ​ 900 ​ 810 ​ 11 ​ 10 ​ Amortization of prior service cost ​ 95 ​ 60 ​ (45) ​ (45) ​ Net periodic benefit ​ $ (962) ​ $ (268) ​ $ (23) ​ $ (21) ​

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2021
EARNINGS PER SHARE
Schedule of reconciliation of basic to diluted earnings per share	The following is a reconciliation of basic to diluted earnings per share for the three months ended March 31, 2021 and 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ ​ ​ March 31, ​ (000’s omitted, except per share data) ​ 2021 2020 Net income ​ $ 52,850 ​ $ 40,134 ​ Income attributable to unvested stock-based compensation awards ​ (130) ​ (146) ​ Income available to common shareholders ​ $ 52,720 ​ $ 39,988 ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 53,845 ​ 52,036 ​ Basic earnings per share ​ $ 0.98 ​ $ 0.77 ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income ​ $ 52,850 ​ $ 40,134 ​ Income attributable to unvested stock-based compensation awards ​ (130) ​ (146) ​ Income available to common shareholders ​ $ 52,720 ​ $ 39,988 ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average common shares outstanding – basic ​ 53,845 ​ 52,036 ​ Assumed exercise of stock options ​ 438 ​ 420 ​ Weighted-average common shares outstanding – diluted ​ 54,283 ​ 52,456 ​ Diluted earnings per share ​ $ 0.97 ​ $ 0.76 ​

COMMITMENTS, CONTINGENT LIABI_2

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS (Tables)	3 Months Ended
	Mar. 31, 2021
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS
Schedule of The contract amounts of commitments and contingencies	The contract amounts of commitments and contingencies are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, December 31, (000’s omitted) ​ 2021 ​ 2020 Commitments to extend credit ​ $ 1,277,853 ​ $ 1,313,568 ​ Standby letters of credit ​ 37,638 ​ 39,213 ​ Total ​ $ 1,315,491 ​ $ 1,352,781 ​

FAIR VALUE (Tables)

FAIR VALUE (Tables)	3 Months Ended
	Mar. 31, 2021
FAIR VALUE
Fair Value Measured on a Recurring Basis	A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The following tables set forth the Company’s financial assets and liabilities that were accounted for at fair value on a recurring basis. There were no transfers between any of the levels for the periods presented. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair (000’s omitted) Level 1 Level 2 Level 3 Value Available-for-sale investment securities: ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 2,632,967 ​ $ 123,291 ​ $ 0 ​ $ 2,756,258 Obligations of state and political subdivisions ​ 0 ​ 450,171 ​ 0 ​ 450,171 Government agency mortgage-backed securities ​ 0 ​ 544,986 ​ 0 ​ 544,986 Corporate debt securities ​ 0 ​ 3,082 ​ 0 ​ 3,082 Government agency collateralized mortgage obligations ​ 0 ​ 36,894 ​ 0 ​ 36,894 Total available-for-sale investment securities ​ 2,632,967 ​ 1,158,424 ​ 0 ​ 3,791,391 Equity securities ​ 469 ​ 0 ​ 0 ​ 469 Mortgage loans held for sale ​ ​ 0 ​ ​ 292 ​ ​ 0 ​ ​ 292 Commitments to originate real estate loans for sale ​ ​ 0 ​ ​ 0 ​ ​ 34 ​ ​ 34 Forward sales commitments ​ ​ 0 ​ ​ 50 ​ ​ 0 ​ ​ 50 Interest rate swap agreements asset ​ 0 ​ 707 ​ 0 ​ 707 Interest rate swap agreements liability ​ 0 ​ (388) ​ 0 ​ (388) Total ​ $ 2,633,436 ​ $ 1,159,085 ​ $ 34 ​ $ 3,792,555 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total Fair (000’s omitted) Level 1 Level 2 Level 3 Value Available-for-sale investment securities: ​ ​ ​ ​ U.S. Treasury and agency securities ​ $ 2,359,912 ​ $ 141,470 ​ $ 0 ​ $ 2,501,382 Obligations of state and political subdivisions ​ 0 ​ 475,660 ​ 0 ​ 475,660 Government agency mortgage-backed securities ​ 0 ​ 522,638 ​ 0 ​ 522,638 Corporate debt securities ​ 0 ​ 4,635 ​ 0 ​ 4,635 Government agency collateralized mortgage obligations ​ 0 ​ 43,577 ​ 0 ​ 43,577 Total available-for-sale investment securities ​ 2,359,912 ​ 1,187,980 ​ 0 ​ 3,547,892 Equity securities ​ 445 ​ 0 ​ 0 ​ 445 Mortgage loans held for sale ​ 0 ​ 1,622 ​ 0 ​ 1,622 Commitments to originate real estate loans for sale ​ ​ 0 ​ ​ 0 ​ ​ 14 ​ ​ 14 Forward sales commitments ​ ​ 0 ​ ​ 2 ​ ​ 0 ​ ​ 2 Interest rate swap agreements asset ​ 0 ​ 1,572 ​ 0 ​ 1,572 Interest rate swap agreements liability ​ 0 ​ (1,074) ​ ​ 0 ​ (1,074) Total ​ $ 2,360,357 ​ $ 1,190,102 ​ $ 14 ​ $ 3,550,473
Assets and Liabilities Measured on a Non-Recurring Basis	The fair value information of assets and liabilities measured on a non-recurring basis presented below is not as of the period-end, but rather as of the date the fair value adjustment was recorded closest to the date presented. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ December 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ Total Fair ​ ​ ​ ​ ​ ​ Total Fair (000’s omitted) ​ Level 1 ​ Level 2 ​ Level 3 ​ Value ​ Level 1 ​ Level 2 ​ Level 3 ​ Value Impaired loans ​ $ 0 ​ $ 0 ​ $ 21,647 $ 21,647 ​ $ 0 ​ $ 0 ​ $ 25,063 $ 25,063 Business loans held for sale ​ 0 ​ 0 ​ 848 848 ​ 0 ​ 0 ​ 0 0 Other real estate owned ​ 0 ​ 0 ​ 824 824 ​ 0 ​ 0 ​ 883 883 Mortgage servicing rights ​ 0 ​ 0 ​ 807 807 ​ 0 ​ 0 ​ 682 682 Total ​ $ 0 ​ $ 0 ​ $ 24,126 $ 24,126 ​ $ 0 ​ $ 0 ​ $ 26,628 $ 26,628
Significant Unobservable Inputs, Fair Value Valuation Techniques	The Company determines fair values based on quoted market values, where available, estimates of present values, or other valuation techniques. Those techniques are significantly affected by the assumptions used, including, but not limited to, the discount rate and estimates of future cash flows. In that regard, the derived fair value estimates cannot be substantiated by comparison to independent markets and, in many cases, may not be realized in immediate settlement of the instrument. The significant unobservable inputs used in the determination of fair value of assets classified as Level 3 on a recurring or non-recurring basis are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ ​ ​ ​ Unobservable Input ​ ​ Fair Value at ​ ​ ​ ​ ​ Range ​ (000's omitted, except per loan data) ​ March 31, 2021 ​ Valuation Technique ​ Significant Unobservable Inputs (Weighted Average) ​ Impaired loans ​ $ 21,647 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 78.7% (54.3%) ​ Business loans held for sale ​ 848 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 35.0% (27.9%) ​ Other real estate owned ​ 824 Fair value of collateral Estimated cost of disposal/market adjustment ​ 31.8% - 97.5% (42.0%) ​ Commitments to originate real estate loans for sale ​ 34 Discounted cash flow Embedded servicing value ​ 1 % Mortgage servicing rights ​ 807 Discounted cash flow Weighted average constant prepayment rate ​ 13.7% - 27.0% (15.7%) ​ ​ ​ ​ ​ ​ ​ ​ Weighted average discount rate ​ ​ 2.49% - 3.06% (2.97%) ​ ​ ​ ​ ​ ​ ​ ​ Adequate compensation ​ $ 7/loan ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Significant ​ ​ ​ ​ ​ ​ ​ ​ ​ Unobservable Input ​ ​ ​ Fair Value at ​ ​ ​ ​ ​ Range ​ (000's omitted, except per loan data) ​ December 31, 2020 ​ Valuation Technique ​ Significant Unobservable Inputs ​ (Weighted Average) Impaired loans ​ $ 25,063 Fair value of collateral Estimated cost of disposal/market adjustment ​ 9.0% - 78.4% (52.7%) ​ Other real estate owned ​ 883 Fair value of collateral Estimated cost of disposal/market adjustment ​ 11.3% - 52.9% (34.0%) ​ Commitments to originate real estate loans for sale ​ ​ 14 ​ Discounted cash flow ​ Embedded servicing value ​ ​ 1.0 % Mortgage servicing rights ​ 682 Discounted cash flow Weighted average constant prepayment rate ​ 9.8% - 18.8% (17.6%) ​ ​ ​ Weighted average discount rate ​ 1.7% - 2.2% (2.1%) ​ ​ ​ ​ ​ ​ ​ Adequate compensation ​ $ 7/loan ​
Carrying Amounts and Estimated Fair Values of Other Financial Instruments	Certain financial instruments and all nonfinancial instruments are excluded from fair value disclosure requirements. Accordingly, the aggregate fair value amounts presented do not represent the underlying value of the Company. The carrying amounts and estimated fair values of the Company’s other financial instruments that are not accounted for at fair value at March 31, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ March 31, 2021 ​ December 31, 2020 ​ Carrying Fair Carrying Fair (000’s omitted) ​ Value ​ Value ​ Value ​ Value Financial assets: ​ ​ ​ ​ Net loans ​ $ 7,313,258 ​ $ 7,565,204 ​ $ 7,355,083 ​ $ 7,655,044 Financial liabilities: ​ ​ ​ ​ ​ ​ ​ ​ Deposits ​ 12,204,237 ​ 12,215,473 ​ 11,224,974 ​ 11,239,628 Securities sold under agreement to repurchase, short-term ​ 257,767 ​ 257,767 ​ 284,008 ​ 284,008 Other Federal Home Loan Bank borrowings ​ 5,959 ​ 6,031 ​ 6,658 ​ 6,758 Subordinated notes payable ​ 3,297 ​ 3,297 ​ 3,303 ​ 3,303 Subordinated debt held by unconsolidated subsidiary trusts ​ 0 ​ 0 ​ 77,320 ​ 77,320 ​

DERIVATIVE INSTRUMENTS (Tables)

DERIVATIVE INSTRUMENTS (Tables)	3 Months Ended
	Mar. 31, 2021
DERIVATIVE INSTRUMENTS
Amounts Related to Cumulative Basis Adjustments for Fair Value Hedges	As of March 31, 2021 and December 31, 2020, the following amounts were recorded in the consolidated statement of condition related to cumulative basis adjustments for fair value hedges: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ ​ ​ ​ ​ ​ ​ Cumulative Amount of Fair Value ​ ​ Carrying Amount of the Hedged ​ Hedging Adjustment Included in the Line Item in the Consolidated ​ Assets ​ Carrying Amount of the Hedged Assets Statement of Condition in Which ​ March 31, ​ December 31, ​ March 31, ​ December 31, the Hedged Item Is Included 2021 2020 2021 2020 Loans $ 5,854 $ 5,675 $ (319) $ (498)
Fair Value of Derivative Instruments	Fair values of derivative instruments as of March 31, 2021 and December 31, 2020 are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ March 31, 2021 ​ ​ Derivative Assets ​ Derivative Liabilities ​ ​ Consolidated Statement ​ Fair ​ Consolidated Statement of ​ Fair ​ of Condition Location Value Condition Location Value Derivatives designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ $ 319 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ ​ Interest rate swaps Other assets ​ 388 Accrued interest and other liabilities ​ $ 388 Commitments to originate real estate loans for sale Other assets ​ 34 ​ ​ Forward sales commitments Other assets ​ 50 ​ ​ Total derivatives ​ $ 791 ​ $ 388 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ (000’s omitted) ​ December 31, 2020 ​ ​ Derivative Assets ​ Derivative Liabilities ​ ​ Consolidated Statement ​ Fair ​ Consolidated Statement of ​ Fair ​ of Condition Location Value Condition Location Value Derivatives designated as hedging instruments under Subtopic 815-20 ​ ​ Interest rate swaps Other assets ​ $ 498 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives not designated as hedging instruments under Subtopic 815-20 ​ ​ ​ ​ Interest rate swaps Other assets ​ 1,074 Accrued interest and other liabilities ​ $ 1,074 Commitments to originate real estate loans for sale ​ Other assets ​ ​ 14 ​ ​ ​ ​ ​ Forward sales commitments ​ Other assets ​ ​ 2 ​ ​ ​ ​ ​ Total derivatives ​ ​ $ 1,588 ​ $ 1,074 ​

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	3 Months Ended
	Mar. 31, 2021
SEGMENT INFORMATION
Schedule of Segment Reporting Information by Segment	Information about reportable segments and reconciliation of the information to the consolidated financial statements follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Employee ​ ​ ​ ​ ​ ​ ​ Consolidated (000's omitted) Banking Benefit Services All Other Eliminations Total Three Months Ended March 31, 2021 ​ ​ ​ ​ ​ Net interest income ​ $ 93,839 ​ $ 94 ​ $ 21 ​ $ 0 ​ $ 93,954 Provision for credit losses ​ (5,719) ​ 0 ​ 0 ​ 0 ​ (5,719) Noninterest revenues ​ 16,454 ​ 27,149 ​ 16,817 ​ (1,889) ​ 58,531 Amortization of intangible assets ​ 1,324 ​ 1,354 ​ 673 ​ 0 ​ 3,351 Acquisition expenses ​ 27 ​ 0 ​ 0 ​ 0 ​ 27 Other operating expenses ​ 65,007 ​ 15,005 ​ 11,745 ​ (1,889) ​ 89,868 Income before income taxes ​ $ 49,654 ​ $ 10,884 ​ $ 4,420 ​ $ 0 ​ $ 64,958 Assets ​ $ 14,427,834 ​ $ 210,297 ​ $ 82,074 ​ $ (100,024) ​ $ 14,620,181 Goodwill ​ $ 689,869 ​ $ 83,275 ​ $ 20,312 ​ $ 0 ​ $ 793,456 Core deposit intangibles & Other intangibles ​ $ 12,507 ​ $ 30,697 ​ $ 6,385 ​ $ 0 ​ $ 49,589 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended March 31, 2020 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net interest income ​ $ 89,763 ​ $ 240 ​ $ 51 ​ $ 0 ​ $ 90,054 Provision for credit losses ​ 5,594 ​ 0 ​ 0 ​ 0 ​ 5,594 Noninterest revenues ​ 18,680 ​ 25,925 ​ 15,536 ​ (1,519) ​ 58,622 Amortization of intangible assets ​ 1,417 ​ 1,494 ​ 756 ​ 0 ​ 3,667 Acquisition expenses ​ 369 ​ 0 ​ 0 ​ 0 ​ 369 Other operating expenses ​ 64,200 ​ 15,130 ​ 11,816 ​ (1,519) ​ 89,627 Income before income taxes ​ $ 36,863 ​ $ 9,541 ​ $ 3,015 ​ $ 0 ​ $ 49,419 Assets ​ $ 11,633,330 ​ $ 213,768 ​ $ 76,525 ​ $ (114,640) ​ $ 11,808,983 Goodwill ​ $ 669,886 ​ $ 83,275 ​ $ 20,312 ​ $ 0 ​ $ 773,473 Core deposit intangibles & Other intangibles ​ $ 15,001 ​ $ 36,281 ​ $ 8,164 ​ $ 0 ​ $ 59,446

ACQUISITIONS (Narrative) (Detai

ACQUISITIONS (Narrative) (Details) shares in Thousands, $ in Thousands	Jun. 12, 2020USD ($)countryOfficeshares	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Mar. 31, 2020USD ($)
Acquisitions [Abstract]
Goodwill		$ 793,456	$ 793,708	$ 773,473
Steuben Trust Corporation [Member]
Acquisitions [Abstract]
Cash	$ 21,600		21,613
Issuance of common shares (in shares) | shares	1,360
Purchase price of acquisition	$ 98,600		98,555
Deposits	516,300		516,274
Goodwill	20,000		19,983
Assets acquired	607,800
Loans	339,700		339,017
Investment securities	$ 180,500		$ 180,497
Revenue earned		1,300
Direct expenses		3,200
Increase (decrease) in other liabilities as a result of reclassification and adjustment		300
Increase (decrease) in goodwill as a result of fair value adjustment		$ 300
Steuben Trust Corporation [Member] | Western New York State [Member]
Acquisitions [Abstract]
Number of counties where the bank has facilities | country	4
Number of new counties where the bank has extended footprints | country	2
Number of branch locations | Office	11

ACQUISITIONS - Estimated Fair V

ACQUISITIONS - Estimated Fair Value of Assets Acquired and Liabilities assumed (Details) - USD ($) $ in Thousands	Jun. 12, 2020	Dec. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Goodwill		$ 793,708	$ 793,456	$ 773,473
Steuben Trust Corporation [Member]
Consideration paid [Abstract]
Cash	$ 21,600	21,613
Community Bank System, Inc. common stock		76,942
Total net consideration paid	98,600	98,555
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents		55,973
Investment securities	180,500	180,497
Loans, net of allowance for credit losses on PCD loans	339,700	339,017
Premises and equipment, net		7,764
Accrued interest and fees receivable		2,701
Other assets		17,675
Deposits	(516,300)	(516,274)
Other liabilities		(4,843)
Other Federal Home Loan Bank borrowings		(6,000)
Subordinated debt held by unconsolidated subsidiary trusts		(2,062)
Total identifiable assets, net		78,572
Goodwill	$ 20,000	19,983
Steuben Trust Corporation [Member] | Core deposit intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles		2,928
Steuben Trust Corporation [Member] | Other intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles		$ 1,196

ACQUISITIONS - Summary of Loans

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

ACQUISITIONS - Intangible Asset

ACQUISITIONS - Intangible Asset, Goodwill and Acquisition-related Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Summary of loans acquired [Abstract]
Merger and acquisition integration related (recoveries) expenses	$ 27	$ 369
Steuben Trust Corporation [Member] | Core deposit intangibles [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Intangible asset useful life (amortization period)	8 years
Steuben Trust Corporation [Member] | Other intangibles [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Intangible asset useful life (amortization period)	8 years

ACCOUNTING POLICIES (Details)

ACCOUNTING POLICIES (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Contract Balances
Accounts receivable	$ 26.8	$ 30.3
Unbilled fee revenue	8.7	7.7
Unearned revenue	$ 4	$ 1.4

INVESTMENT SECURITIES, Availabl

INVESTMENT SECURITIES, Available-for-Sale Portfolio (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Available-for-Sale Portfolio [Abstract]
Amortized cost	$ 3,898,704	$ 3,427,779
Gross unrealized gains	72,126	136,901
Gross unrealized losses	179,439	16,788
Fair value	3,791,391	3,547,892
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	3,898,704
Fair value	3,791,391
U.S. Treasury and agency securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	2,892,001	2,423,236
Gross unrealized gains	38,711	94,741
Gross unrealized losses	174,454	16,595
Fair value	2,756,258	2,501,382
Obligations of state and political subdivisions
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	430,447	451,028
Gross unrealized gains	19,733	24,632
Gross unrealized losses	9	0
Fair value	450,171	475,660
Government agency mortgage-backed securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	537,317	506,540
Gross unrealized gains	12,638	16,280
Gross unrealized losses	4,969	182
Fair value	544,986	522,638
Corporate debt securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	3,000	4,499
Gross unrealized gains	82	137
Gross unrealized losses	0	1
Fair value	3,082	4,635
Government agency collateralized mortgage obligations
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	35,939	42,476
Gross unrealized gains	962	1,111
Gross unrealized losses	7	10
Fair value	$ 36,894	$ 43,577

INVESTMENT SECURITIES, Equity a

INVESTMENT SECURITIES, Equity and Other Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Equity and Other Securities [Abstract]
Amortized cost	$ 44,138	$ 46,511
Gross unrealized gains	968	944
Gross unrealized losses	0	0
Equity and other securities (cost of $44,138 and $46,511, respectively)	45,106	47,455
Equity Securities, at Fair Value [Abstract]
Amortized cost	251	251
Gross unrealized gains	218	194
Gross unrealized losses	0	0
Fair value	469	445
Federal Home Loan Bank Common Stock [Member]
Other Equity Securities, at Adjusted Cost [Abstract]
Amortized cost	7,410	7,468
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	7,410	7,468
Federal Reserve Bank Stock [Member]
Other Equity Securities, at Adjusted Cost [Abstract]
Amortized cost	33,916	33,916
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	33,916	33,916
Other Equity Securities [Member]
Other Equity Securities, at Adjusted Cost [Abstract]
Amortized cost	2,561	4,876
Gross unrealized gains	750	750
Gross unrealized losses	0	0
Fair value	$ 3,311	$ 5,626

INVESTMENT SECURITIES, Investme

INVESTMENT SECURITIES, Investment Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months	218	117
12 months or longer	3	3
Total	221	120
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 1,634,895	$ 913,612
12 months or longer	13	14
Total	1,634,908	913,626
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	179,439	16,788
12 months or longer	0	0
Total	179,439	$ 16,788
Available-for-sale, allowance for credit losses	0
Accrued interest and fees receivable	20,900
Available-for-sale Securities [Member]
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Accrued interest and fees receivable	$ 12,000
U.S. Treasury and agency securities
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months	31	13
12 months or longer	0	0
Total	31	13
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 1,440,822	$ 831,015
12 months or longer	0	0
Total	1,440,822	831,015
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	174,454	16,595
12 months or longer	0	0
Total	$ 174,454	$ 16,595
Obligations of state and political subdivisions
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months	17	1
12 months or longer	0	0
Total	17	1
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 7,028	$ 358
12 months or longer	0	0
Total	7,028	358
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	9	0
12 months or longer	0	0
Total	$ 9	$ 0
Government agency mortgage-backed securities
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months	162	89
12 months or longer	2	2
Total	164	91
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 184,325	$ 75,992
12 months or longer	13	14
Total	184,338	76,006
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	4,969	182
12 months or longer	0	0
Total	$ 4,969	$ 182
Corporate debt securities
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months		1
12 months or longer		0
Total		1
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months		$ 1,001
12 months or longer		0
Total		1,001
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months		1
12 months or longer		0
Total		$ 1
Government agency collateralized mortgage obligations
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months	8	13
12 months or longer	1	1
Total	9	14
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 2,720	$ 5,246
12 months or longer	0	0
Total	2,720	5,246
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	7	10
12 months or longer	0	0
Total	$ 7	$ 10

INVESTMENT SECURITIES, Amortize

INVESTMENT SECURITIES, Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Due in one year or less	$ 201,210
Due after one through five years	727,189
Due after five years through ten years	954,210
Due after ten years	1,442,839
Subtotal	3,325,448
Amortized cost	3,898,704
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Due in one year or less	202,974
Due after one through five years	758,445
Due after five years through ten years	952,781
Due after ten years	1,295,311
Subtotal	3,209,511
Fair value	3,791,391
Government agency mortgage-backed securities
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Without single maturity date	537,317
Amortized cost	537,317	$ 506,540
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Without single maturity date	544,986
Fair value	544,986	522,638
Government agency collateralized mortgage obligations
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Without single maturity date	35,939
Amortized cost	35,939	42,476
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Without single maturity date	36,894
Fair value	$ 36,894	$ 43,577

INVESTMENT SECURITIES, Invest_2

INVESTMENT SECURITIES, Investment Securities Pledged as Collateral (Details) $ in Millions	Mar. 31, 2021USD ($)
U.S. Treasury and agency securities | Securities Sold under Agreements to Repurchase [Member]
Investment Securities Pledged as Collateral
Investment securities pledged to collateralize certain deposits and borrowings	$ 271.3

LOANS, Loan Summary (Details)

LOANS, Loan Summary (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Loans receivable, net
Gross loans, including deferred origination costs	$ 7,368,327	$ 7,415,952
Allowance for credit losses	(55,069)	(60,869)	$ (49,911)
Net loans	7,313,258	7,355,083
Commercial Portfolio Segment [Member] | Business Lending [Member]
Loans receivable, net
Gross loans, including deferred origination costs	3,391,786	3,440,077
Allowance for credit losses	(27,042)	(28,190)	(19,426)
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Loans receivable, net
Gross loans, including deferred origination costs	2,409,373
Allowance for credit losses	(9,686)	(10,672)	(10,269)
Consumer Portfolio Segment [Member] | Consumer Mortgage [Member]
Loans receivable, net
Gross loans, including deferred origination costs	2,409,373	2,401,499
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Loans receivable, net
Gross loans, including deferred origination costs	1,029,335	1,021,885
Allowance for credit losses	(11,120)	(13,696)	(13,712)
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Loans receivable, net
Gross loans, including deferred origination costs	142,425	152,657
Allowance for credit losses	(2,682)	(3,207)	(3,255)
Consumer Portfolio Segment [Member] | Home Equity [Member]
Loans receivable, net
Gross loans, including deferred origination costs	395,408	399,834
Allowance for credit losses	$ (1,543)	$ (2,222)	$ (2,129)

LOANS, Credit Quality By Past D

LOANS, Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Aged analysis of the company's loans
Total loans	$ 7,368,327	$ 7,415,952
Interest income on nonaccrual loans	0
Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		3,922
Nonaccrual		72,929
Total past due		111,610
Current		7,304,342
Total loans		7,415,952
Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		34,759
Acquired Loans [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	2,152
Nonaccrual	73,310
Total past due	95,113
Current	7,273,214
Total loans	7,368,327
Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	19,651
Commercial Portfolio Segment [Member] | Business Lending [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	88
Nonaccrual	54,930
Total past due	58,699
Current	3,333,087
Total loans	3,391,786	3,440,077
Commercial Portfolio Segment [Member] | Business Lending [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	3,681
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		59
Nonaccrual		55,709
Total past due		60,664
Current		3,379,413
Total loans		3,440,077
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		4,896
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	1,688
Nonaccrual	15,836
Total past due	25,546
Current	2,383,827
Total loans	2,409,373
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	8,022
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		3,051
Nonaccrual		14,970
Total past due		31,257
Current		2,370,242
Total loans		2,401,499
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		13,236
Consumer Portfolio Segment [Member] | Consumer Mortgage [Member]
Aged analysis of the company's loans
Total loans	2,409,373	2,401,499
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	115
Nonaccrual	0
Total past due	6,546
Current	1,022,789
Total loans	1,029,335	1,021,885
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	6,431
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		219
Nonaccrual		1
Total past due		13,381
Current		1,008,504
Total loans		1,021,885
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		13,161
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	16
Nonaccrual	2
Total past due	577
Current	141,848
Total loans	142,425	152,657
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	559
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		28
Nonaccrual		3
Total past due		1,201
Current		151,456
Total loans		152,657
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		1,170
Consumer Portfolio Segment [Member] | Home Equity [Member]
Aged analysis of the company's loans
90 + days past due and still accruing	245
Nonaccrual	2,542
Total past due	3,745
Current	391,663
Total loans	395,408	399,834
Consumer Portfolio Segment [Member] | Home Equity [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due	$ 958
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loan [Member]
Aged analysis of the company's loans
90 + days past due and still accruing		565
Nonaccrual		2,246
Total past due		5,107
Current		394,727
Total loans		399,834
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans
Total past due		$ 2,296

LOANS - Amount of Business Lend

LOANS - Amount of Business Lending Loans by Credit Quality Categories (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Business Lending [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	$ 290,570
2020	617,704	$ 881,201
2019	383,127	391,969
2018	360,052	373,807
2017	254,003	263,820
2016		275,730
Prior	885,256	660,921
Revolving loans amortized cost basis	601,074	592,629
Total	3,391,786	3,440,077
Business Lending [Member] | Pass [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	289,320
2020	599,626	860,178
2019	344,078	351,350
2018	296,523	312,087
2017	202,536	217,138
2016		231,453
Prior	715,334	543,999
Revolving loans amortized cost basis	491,420	483,018
Total	2,938,837	2,999,223
Business Lending [Member] | Special Mention [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	1,187
2020	13,585	14,687
2019	16,348	36,041
2018	24,560	28,410
2017	25,583	21,875
2016		29,386
Prior	76,596	51,657
Revolving loans amortized cost basis	44,936	52,732
Total	202,795	234,788
Business Lending [Member] | Classified [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	63
2020	4,493	6,336
2019	22,684	4,560
2018	38,881	30,422
2017	25,884	24,807
2016		14,891
Prior	93,255	65,157
Revolving loans amortized cost basis	61,343	56,000
Total	246,603	202,173
Business Lending [Member] | Doubtful [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	0	0
2019	17	18
2018	88	2,888
2017	0	0
2016		0
Prior	71	108
Revolving loans amortized cost basis	3,375	879
Total	3,551	3,893
Consumer Mortgage [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	135,151
2020	386,578	375,637
2019	313,236	330,825
2018	230,862	248,468
2017	220,037	240,217
2016		246,256
Prior	1,102,968	942,393
Revolving loans amortized cost basis	20,541	17,703
Total	2,409,373	2,401,499
Consumer Mortgage [Member] | FICO AB [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	106,415
2020	254,218	260,588
2019	213,877	227,027
2018	153,016	166,913
2017	149,721	164,051
2016		161,256
Prior	718,225	617,685
Revolving loans amortized cost basis	95	321
Total	1,595,567	1,597,841
Consumer Mortgage [Member] | FICO AB [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	106,415
2020	254,218	260,588
2019	213,877	227,027
2018	152,748	166,638
2017	149,072	163,653
2016		160,911
Prior	715,345	614,976
Revolving loans amortized cost basis	95	321
Total	1,591,770	1,594,114
Consumer Mortgage [Member] | FICO AB [Member] | Nonperforming Financial Instruments [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	0	0
2019	0	0
2018	268	275
2017	649	398
2016		345
Prior	2,880	2,709
Revolving loans amortized cost basis	0	0
Total	3,797	3,727
Consumer Mortgage [Member] | FICO CDE [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	28,736
2020	132,360	115,049
2019	99,359	103,798
2018	77,846	81,555
2017	70,316	76,166
2016		85,000
Prior	384,743	324,708
Revolving loans amortized cost basis	20,446	17,382
Total	813,806	803,658
Consumer Mortgage [Member] | FICO CDE [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	28,736
2020	132,230	115,049
2019	98,451	102,788
2018	77,047	80,973
2017	69,565	75,289
2016		83,214
Prior	373,604	314,668
Revolving loans amortized cost basis	20,446	17,382
Total	800,079	789,363
Consumer Mortgage [Member] | FICO CDE [Member] | Nonperforming Financial Instruments [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	130	0
2019	908	1,010
2018	799	582
2017	751	877
2016		1,786
Prior	11,139	10,040
Revolving loans amortized cost basis	0	0
Total	13,727	14,295
Consumer Indirect [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	119,208
2020	282,974	303,522
2019	273,920	305,953
2018	175,762	202,455
2017	72,528	86,514
2016		61,465
Prior	104,943	61,976
Revolving loans amortized cost basis	0	0
Total	1,029,335	1,021,885
Consumer Indirect [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	119,208
2020	282,934	303,471
2019	273,903	305,901
2018	175,721	202,373
2017	72,517	86,497
2016		61,449
Prior	104,937	61,975
Revolving loans amortized cost basis	0	0
Total	1,029,220	1,021,666
Consumer Indirect [Member] | Nonperforming Financial Instruments [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	40	51
2019	17	52
2018	41	82
2017	11	17
2016		16
Prior	6	1
Revolving loans amortized cost basis	0	0
Total	115	219
Consumer Direct [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	13,121
2020	42,530	49,182
2019	40,329	47,011
2018	22,985	27,874
2017	9,781	12,331
2016		5,232
Prior	7,499	4,149
Revolving loans amortized cost basis	6,180	6,878
Total	142,425	152,657
Consumer Direct [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	13,121
2020	42,530	49,181
2019	40,319	46,992
2018	22,983	27,872
2017	9,781	12,326
2016		5,232
Prior	7,493	4,146
Revolving loans amortized cost basis	6,180	6,878
Total	142,407	152,627
Consumer Direct [Member] | Nonperforming Financial Instruments [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	0	1
2019	10	19
2018	2	2
2017	0	5
2016		0
Prior	6	3
Revolving loans amortized cost basis	0	0
Total	18	30
Home Equity [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	17,564
2020	49,686	48,145
2019	45,868	48,804
2018	25,676	28,147
2017	21,492	23,628
2016		18,011
Prior	48,915	36,390
Revolving loans amortized cost basis	186,207	196,709
Total	395,408	399,834
Home Equity [Member] | Performing [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	17,564
2020	49,686	48,145
2019	45,846	48,780
2018	25,565	28,074
2017	21,395	23,524
2016		17,828
Prior	48,214	35,900
Revolving loans amortized cost basis	184,351	194,773
Total	392,621	397,024
Home Equity [Member] | Nonperforming Financial Instruments [Member]
Term Loans Amortized Cost Basis by Origination Year
2021	0
2020	0	0
2019	22	24
2018	111	73
2017	97	104
2016		183
Prior	701	490
Revolving loans amortized cost basis	1,856	1,936
Total	$ 2,787	$ 2,810

LOANS, Summary of Impaired Loan

LOANS, Summary of Impaired Loans, Excluding Purchased Impaired (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Impaired loans
Loans with allowance allocation	$ 26,670		$ 27,437
Loans without allowance allocation	8,028		8,138
Carrying balance	34,698		35,575
Contractual balance	37,745		38,362
Specifically allocated allowance	3,560		$ 3,874
Average carrying balance of individually evaluated impaired loans	34,900	$ 2,200
Interest income on individually evaluated impaired loans	$ 0	$ 0

LOANS, Troubled Debt Restructur

LOANS, Troubled Debt Restructurings (TDRs) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021USD ($)loanborrower	Mar. 31, 2020USD ($)loan	Dec. 31, 2020USD ($)loanborrower
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	229		247
TDRs, amount	$ 6,684		$ 6,984
Loans modified in TDR during the year, number | loan	10	22
Loans modified in TDR during the year, amount	$ 183	$ 756
Number of borrowers representing $75.6 million in outstanding loan balances | borrower	47
Outstanding loan balances of 47 number of borrowers	$ 75,600
Percentage of total loan outstanding	1.00%		0.90%
Number of business borrowers representing $75.1 million in outstanding loan balances | borrower	42
Outstanding loan balances of 42 number of business borrowers	$ 75,100
Number of consumer borrowers representing $0.5 million in outstanding loan balances | borrower	5
Outstanding loan balances of 5 number of consumer borrowers	$ 500
Number of borrowers representing $66.5 million in outstanding loan balances | borrower			74
Outstanding loan balances of 74 number of borrowers			$ 66,500
Number of borrowers representing $65.7 million in outstanding loan balances | borrower			63
Outstanding loan balances of 63 number of borrowers			$ 65,700
Number of borrowers representing $0.8 million in outstanding loan balances | borrower			11
Outstanding loan balances of 11 number of borrowers			$ 800
Minimum [Member]
Troubled Debt Restructurings (TDRs)
Threshold balance of loan individually evaluated for impairment	500
Maximum [Member]
Troubled Debt Restructurings (TDRs)
Threshold balance of TDR loans collectively included in general loan loss allocation and qualitative review	$ 500
Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	71		73
TDRs, amount	$ 3,155		$ 3,227
Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	158		174
TDRs, amount	$ 3,529		$ 3,757
Commercial Portfolio Segment [Member] | Business Lending [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	10		10
TDRs, amount	$ 690		$ 720
Loans modified in TDR during the year, number | loan	0	0
Loans modified in TDR during the year, amount	$ 0	$ 0
Commercial Portfolio Segment [Member] | Business Lending [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	6		6
TDRs, amount	$ 505		$ 529
Commercial Portfolio Segment [Member] | Business Lending [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	4		4
TDRs, amount	$ 185		$ 191
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	99		104
TDRs, amount	$ 4,563		$ 4,679
Loans modified in TDR during the year, number | loan	3	7
Loans modified in TDR during the year, amount	$ 110	$ 617
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	55		56
TDRs, amount	$ 2,389		$ 2,413
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	44		48
TDRs, amount	$ 2,174		$ 2,266
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	78		86
TDRs, amount	$ 882		$ 951
Loans modified in TDR during the year, number | loan	6	14
Loans modified in TDR during the year, amount	$ 66	$ 127
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	0		0
TDRs, amount	$ 0		$ 0
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	78		86
TDRs, amount	$ 882		$ 951
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	20		23
TDRs, amount	$ 31		$ 85
Loans modified in TDR during the year, number | loan	1	1
Loans modified in TDR during the year, amount	$ 7	$ 12
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	0		0
TDRs, amount	$ 0		$ 0
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	20		23
TDRs, amount	$ 31		$ 85
Consumer Portfolio Segment [Member] | Home Equity [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	22		24
TDRs, amount	$ 518		$ 549
Loans modified in TDR during the year, number | loan	0	0
Loans modified in TDR during the year, amount	$ 0	$ 0
Consumer Portfolio Segment [Member] | Home Equity [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	10		11
TDRs, amount	$ 261		$ 285
Consumer Portfolio Segment [Member] | Home Equity [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs)
TDRs, number | loan	12		13
TDRs, amount	$ 257		$ 264

LOANS - Allowance for Credit Lo

LOANS - Allowance for Credit Losses (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)	Dec. 31, 2020USD ($)
Allowance for loan losses [Roll Forward]
Balance, beginning of period	$ 60,869	$ 49,911	$ 49,911
Charge-offs	(1,966)
Recoveries	1,585
Provision	(5,419)
Balance, end of period	55,069		60,869
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance	1,489	0	0
Charge-offs	0
Recoveries	0
Provision	(300)
Ending balance	1,189		1,489
Total allowance for credit losses [Roll Forward]
Beginning balance	62,358	49,911	49,911
Charge-offs	(1,966)
Recoveries	1,585
Provision	(5,719)
Ending balance	$ 56,258		$ 62,358
Allowance for Credit Losses
Allowance for credit losses to total loans ratio	0.75
Basis points lower level	0.06		0.07
Accrued interest and fees receivable	$ 20,900
Minimum [Member] | COVID-19 [Member]
Allowance for Credit Losses
Percentage of peak unemployment	3.00%
Maximum [Member] | COVID-19 [Member]
Allowance for Credit Losses
Percentage of peak unemployment	8.00%
ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		51,268	$ 51,268
Charge-offs		(3,047)
Recoveries		1,497
Provision		5,934
Balance, end of period		55,652
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance		1,185	1,185
Charge-offs		0
Recoveries		0
Provision		(340)
Ending balance		845
Total allowance for credit losses [Roll Forward]
Beginning balance		52,453	52,453
Charge-offs		(3,047)
Recoveries		1,497
Provision		5,594
Ending balance		56,497
ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		1,357	1,357
Liabilities for off-balance-sheet credit exposures [Roll Forward]
Beginning balance		1,185	1,185
Total allowance for credit losses [Roll Forward]
Beginning balance		2,542	2,542
Acquired Impaired Loans [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		163	163
Acquired Impaired Loans [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		0	0
Charge-offs		0
Recoveries		0
Provision		0
Balance, end of period		0
Acquired Impaired Loans [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		(163)	(163)
Acquired Deteriorated
Allowance for loan losses [Roll Forward]
Balance, beginning of period	$ 1,882	0	0
Charge-offs	0
Recoveries	27
Provision	87
Balance, end of period	1,996		1,882
Acquired Deteriorated | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		3,072	3,072
Charge-offs		0
Recoveries		0
Provision		(26)
Balance, end of period		3,046
Acquired Deteriorated | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		3,072	3,072
Commercial Portfolio Segment [Member] | Business Lending [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	28,190	19,426	19,426
Charge-offs	(51)
Recoveries	67
Provision	(1,164)
Balance, end of period	27,042		28,190
Commercial Portfolio Segment [Member] | Business Lending [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		19,714	19,714
Charge-offs		(176)
Recoveries		138
Provision		(187)
Balance, end of period		19,489
Commercial Portfolio Segment [Member] | Business Lending [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		288	288
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	10,672	10,269	10,269
Charge-offs	(100)
Recoveries	10
Provision	(896)
Balance, end of period	9,686		10,672
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		9,218	9,218
Charge-offs		(186)
Recoveries		8
Provision		3,390
Balance, end of period		12,430
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		(1,051)	(1,051)
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	13,696	13,712	13,712
Charge-offs	(1,399)
Recoveries	1,246
Provision	(2,423)
Balance, end of period	11,120		13,696
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		12,715	12,715
Charge-offs		(2,079)
Recoveries		1,163
Provision		1,895
Balance, end of period		13,694
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		(997)	(997)
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	3,207	3,255	3,255
Charge-offs	(318)
Recoveries	231
Provision	(438)
Balance, end of period	2,682		3,207
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		2,612	2,612
Charge-offs		(533)
Recoveries		182
Provision		1,476
Balance, end of period		3,737
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		(643)	(643)
Consumer Portfolio Segment [Member] | Home Equity [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	2,222	2,129	2,129
Charge-offs	(98)
Recoveries	4
Provision	(585)
Balance, end of period	1,543		2,222
Consumer Portfolio Segment [Member] | Home Equity [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		2,937	2,937
Charge-offs		(73)
Recoveries		6
Provision		(386)
Balance, end of period		2,484
Consumer Portfolio Segment [Member] | Home Equity [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		808	808
Unallocated Financing Receivables [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	1,000	957	957
Charge-offs	0
Recoveries	0
Provision	0
Balance, end of period	$ 1,000		1,000
Unallocated Financing Receivables [Member] | ASU 2016-13 [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		1,000	1,000
Charge-offs		0
Recoveries		0
Provision		(228)
Balance, end of period		772
Unallocated Financing Receivables [Member] | ASU 2016-13 [Member] | Cumulative Effect Adjustment [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period		$ 43	$ 43

LOANS - Carrying Amounts of Loa

LOANS - Carrying Amounts of Loans Purchased and Sold (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Carrying Amounts of Loans Purchased and Sold
Purchases	$ 0
Sales	8,284
Commercial Portfolio Segment [Member] | Business Lending [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	0
Sales	0
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	0
Sales	8,284
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	0
Sales	0
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	0
Sales	0
Consumer Portfolio Segment [Member] | Home Equity [Member]
Carrying Amounts of Loans Purchased and Sold
Purchases	0
Sales	$ 0

GOODWILL AND IDENTIFIABLE INT_3

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Identifiable Intangible Assets [Abstract]
Gross Carrying Amount	$ 159,865	$ 159,865
Accumulated Amortization	(110,276)	(106,925)
Net Carrying Amount	49,589	52,940
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Apr - Dec 2021	9,289
2022	10,844
2023	9,082
2024	7,551
2025	6,374
Thereafter	6,449
Net Carrying Amount	49,589	52,940
Components of goodwill [Abstract]
Goodwill, net, beginning of period	793,708
Goodwill, net, activity	(252)
Goodwill, net, end of period	793,456
Core deposit intangibles [Member]
Identifiable Intangible Assets [Abstract]
Gross Carrying Amount	69,403	69,403
Accumulated Amortization	(56,896)	(55,572)
Net Carrying Amount	12,507	13,831
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Net Carrying Amount	12,507	13,831
Other intangibles [Member]
Identifiable Intangible Assets [Abstract]
Gross Carrying Amount	90,462	90,462
Accumulated Amortization	(53,380)	(51,353)
Net Carrying Amount	37,082	39,109
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Net Carrying Amount	$ 37,082	$ 39,109

MANDATORILY REDEEMABLE PREFER_2

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

BENEFIT PLANS (Details) (Import

BENEFIT PLANS (Details) (Imported) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Pension Benefits [Member]
Pension Plans [Abstract]
Contribution made to defined benefit pension plan by employer	$ 2,800
Net periodic benefit cost [Abstract]
Service cost	1,480	$ 1,438
Interest cost	1,259	1,356
Expected return on plan assets	(4,696)	(3,932)
Amortization of unrecognized net loss	900	810
Amortization of prior service cost	95	60
Net periodic benefit	(962)	(268)
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0	0
Interest cost	11	14
Expected return on plan assets	0	0
Amortization of unrecognized net loss	11	10
Amortization of prior service cost	(45)	(45)
Net periodic benefit	(23)	$ (21)
Steuben Trust Company Pension Plan
Pension Plans [Abstract]
Contribution made to defined benefit pension plan by employer	$ 90

EARNINGS PER SHARE (Details)-1

EARNINGS PER SHARE (Details)-1 - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
EARNINGS PER SHARE
Weighted-average anti-dilutive stock options outstanding (in shares)	30,000	200,000
Basic earnings per share [Abstract]
Net income	$ 52,850	$ 40,134
Income attributable to unvested stock-based compensation awards	(130)	(146)
Income available to common shareholders	$ 52,720	$ 39,988
Weighted-average common shares outstanding - basic (in shares)	53,845,000	52,036,000
Basic earnings per share (in dollars per share)	$ 0.98	$ 0.77
Diluted earnings per share [Abstract]
Net income	$ 52,850	$ 40,134
Income attributable to unvested stock-based compensation awards	(130)	(146)
Income available to common shareholders	$ 52,720	$ 39,988
Weighted-average common shares outstanding - basic (in shares)	53,845,000	52,036,000
Assumed exercise of stock options (in shares)	438,000	420,000
Weighted-average common shares outstanding - diluted (in shares)	54,283,000	52,456,000
Diluted earnings per share (in dollars per share)	$ 0.97	$ 0.76
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)			2,680,000	2,600,000
Number of common shares repurchased (in shares)	0	0

COMMITMENTS, CONTINGENT LIABI_3

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Mar. 31, 2021
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	$ 1,352,781	$ 1,315,491
Expense recorded for litigation accrual	3,000
Minimum [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Range of reasonably possible losses for such matters in the aggregate, beyond the existing recorded liability		0
Maximum [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Range of reasonably possible losses for such matters in the aggregate, beyond the existing recorded liability		1,000
Commitments to Extend Credit [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	1,313,568	1,277,853
Standby Letters of Credit [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	$ 39,213	$ 37,638

FAIR VALUE - Financial Assets a

FAIR VALUE - Financial Assets and Liabilities Accounted for at Fair Value On a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	$ 3,791,391
Equity securities	469	$ 445
U.S. Treasury and agency securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,756,258	2,501,382
Obligations of state and political subdivisions
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	450,171	475,660
Government agency mortgage-backed securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	544,986	522,638
Corporate debt securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,082	4,635
Government agency collateralized mortgage obligations
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	36,894	43,577
Significant Unobservable Inputs, Level 3 [Member] | Commitments to originate real estate loans for sale
Available-for-sale investment securities [Abstract]
Derivative asset	34	14
Recurring [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,791,391	3,547,892
Equity securities	469	445
Mortgage loans held for sale	292	1,622
Total	3,792,555	3,550,473
Recurring [Member] | Commitments to originate real estate loans for sale
Available-for-sale investment securities [Abstract]
Derivative asset	34	14
Recurring [Member] | Forward sales commitments
Available-for-sale investment securities [Abstract]
Derivative asset	50
Derivative liability		2
Recurring [Member] | Interest rate swap agreements
Available-for-sale investment securities [Abstract]
Derivative asset	707	1,572
Derivative liability	(388)	(1,074)
Recurring [Member] | U.S. Treasury and agency securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,756,258	2,501,382
Recurring [Member] | Obligations of state and political subdivisions
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	450,171	475,660
Recurring [Member] | Government agency mortgage-backed securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	544,986	522,638
Recurring [Member] | Corporate debt securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,082	4,635
Recurring [Member] | Government agency collateralized mortgage obligations
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	36,894	43,577
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,632,967	2,359,912
Equity securities	469	445
Mortgage loans held for sale	0	0
Total	2,633,436	2,360,357
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Commitments to originate real estate loans for sale
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Forward sales commitments
Available-for-sale investment securities [Abstract]
Derivative asset	0
Derivative liability		0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Interest rate swap agreements
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Derivative liability	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | U.S. Treasury and agency securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,632,967	2,359,912
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Obligations of state and political subdivisions
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Government agency mortgage-backed securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Corporate debt securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member] | Government agency collateralized mortgage obligations
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Significant Observable Inputs, Level 2 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,158,424	1,187,980
Equity securities	0	0
Mortgage loans held for sale	292	1,622
Total	1,159,085	1,190,102
Mortgage loans held for sale	300	1,600
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Commitments to originate real estate loans for sale
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Forward sales commitments
Available-for-sale investment securities [Abstract]
Derivative asset	50
Derivative liability		2
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Interest rate swap agreements
Available-for-sale investment securities [Abstract]
Derivative asset	707	1,572
Derivative liability	(388)	(1,074)
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | U.S. Treasury and agency securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	123,291	141,470
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Obligations of state and political subdivisions
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	450,171	475,660
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Government agency mortgage-backed securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	544,986	522,638
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Corporate debt securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,082	4,635
Recurring [Member] | Significant Observable Inputs, Level 2 [Member] | Government agency collateralized mortgage obligations
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	36,894	43,577
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Equity securities	0	0
Mortgage loans held for sale	0	0
Total	34	14
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Commitments to originate real estate loans for sale
Available-for-sale investment securities [Abstract]
Derivative asset	34	14
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Forward sales commitments
Available-for-sale investment securities [Abstract]
Derivative asset	0
Derivative liability		0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Interest rate swap agreements
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Derivative liability	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | U.S. Treasury and agency securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Obligations of state and political subdivisions
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Government agency mortgage-backed securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Corporate debt securities
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Significant Unobservable Inputs, Level 3 [Member] | Government agency collateralized mortgage obligations
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	$ 0	$ 0

FAIR VALUE - Assets and Liabili

FAIR VALUE - Assets and Liabilities Measured on Nonrecurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Unpaid principal value of business lending loans held for sale	$ 800
Valuation allowance	3,560	$ 3,874
Mortgage Servicing Rights [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Valuation allowance	100	200
Significant Unobservable Inputs, Level 3 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	21,647	25,063
Business loans held for sale	848
Other real estate owned	824	883
Mortgage servicing rights	807	682
Non-recurring [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	21,647	25,063
Business loans held for sale	848	0
Other real estate owned	824	883
Mortgage servicing rights	807	682
Total	24,126	26,628
Non-recurring [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	0	0
Business loans held for sale	0	0
Other real estate owned	0	0
Mortgage servicing rights	0	0
Total	0	0
Non-recurring [Member] | Significant Observable Inputs, Level 2 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	0	0
Business loans held for sale	0	0
Other real estate owned	0	0
Mortgage servicing rights	0	0
Total	0	0
Non-recurring [Member] | Significant Unobservable Inputs, Level 3 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	21,647	25,063
Business loans held for sale	848	0
Other real estate owned	824	883
Mortgage servicing rights	807	682
Total	$ 24,126	$ 26,628

FAIR VALUE, Significant Unobser

FAIR VALUE, Significant Unobservable Inputs (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Minimum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Other real estate owned, measurement input	31.8
Maximum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Other real estate owned, measurement input	97.5
Significant Unobservable Inputs, Level 3 [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans	$ 21,647	$ 25,063
Business loans held for sale	848
Other real estate owned	824	883
Fair value of MSRs at end of period	$ 807	$ 682
Significant Unobservable Inputs, Level 3 [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans, Valuation Technique [Extensible List]	Fair Value of Collateral [Member]	Fair Value of Collateral [Member]
Impaired loans, Measurement Input [Extensible List]	us-gaap:MeasurementInputCostToSellMember	us-gaap:MeasurementInputCostToSellMember
Other real estate owned, Valuation Technique [Extensible List]	Fair Value of Collateral [Member]	Fair Value of Collateral [Member]
Other real estate owned, Measurement Input [Extensible List]	us-gaap:MeasurementInputCostToSellMember	us-gaap:MeasurementInputCostToSellMember
Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, Valuation Technique [Extensible List]	Discounted Cash Flow [Member]	Discounted Cash Flow [Member]
Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, Measurement Input [Extensible List]	Weighted Average Constant Prepayment Rate [Member]	Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, Measurement Input [Extensible List]	Weighted Average Discount Rate [Member]	Weighted Average Discount Rate [Member]
Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member] | Adequate Compensation [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	7
Mortgage servicing rights, measurement input		7
Mortgage servicing rights, Measurement Input [Extensible List]	Adequate Compensation [Member]	Adequate Compensation [Member]
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans, measurement input	9	9
Business loans held for sale, measurement input	9
Other real estate owned, measurement input	31.8	11.3
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	13.7	9.8
Significant Unobservable Inputs, Level 3 [Member] | Minimum [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	2.49	1.7
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans, measurement input	78.7	78.4
Business loans held for sale, measurement input	35
Other real estate owned, measurement input	97.5	52.9
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	27	18.8
Significant Unobservable Inputs, Level 3 [Member] | Maximum [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input	3.06	2.2
Significant Unobservable Inputs, Level 3 [Member] | Weighted Average [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans, measurement input	54.3	52.7
Business loans held for sale, measurement input	27.9
Other real estate owned, measurement input	42	34
Significant Unobservable Inputs, Level 3 [Member] | Weighted Average [Member] | Discounted Cash Flow [Member] | Weighted Average Constant Prepayment Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input		17.6
Mortgage servicing rights, measurement input	15.7
Significant Unobservable Inputs, Level 3 [Member] | Weighted Average [Member] | Discounted Cash Flow [Member] | Weighted Average Discount Rate [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Mortgage servicing rights, measurement input		2.1
Mortgage servicing rights, measurement input	2.97
Commitments to originate real estate loans for sale | Significant Unobservable Inputs, Level 3 [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Commitments to originate real estate loans for sale	$ 34	$ 14
Commitments to originate real estate loans for sale, measurement input	1	1
Commitments to originate real estate loans for sale | Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Commitments to originate real estate loans for sale, Valuation Technique [Extensible List]	Discounted Cash Flow [Member]	Discounted Cash Flow [Member]
Commitments to originate real estate loans for sale | Significant Unobservable Inputs, Level 3 [Member] | Discounted Cash Flow [Member] | Embedded Servicing Value [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Commitments to originate real estate loans for sale, Measurement Input [Extensible List]	Embedded Servicing Value [Member]	Embedded Servicing Value [Member]
Business loans held for sale | Significant Unobservable Inputs, Level 3 [Member] | Fair Value of Collateral [Member] | Estimated Cost of Disposal/Market Adjustment [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Impaired loans, Valuation Technique [Extensible List]	Fair Value of Collateral [Member]
Impaired loans, Measurement Input [Extensible List]	us-gaap:MeasurementInputCostToSellMember

FAIR VALUE - Carrying Amounts a

FAIR VALUE - Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Carrying Value [Member]
Financial assets:
Net loans	$ 7,313,258	$ 7,355,083
Financial liabilities:
Deposits	12,204,237	11,224,974
Securities sold under agreement to repurchase, short-term	257,767	284,008
Other Federal Home Loan Bank borrowings	5,959	6,658
Subordinated notes payable	3,297	3,303
Subordinated debt held by unconsolidated subsidiary trusts	0	77,320
Fair Value [Member]
Financial assets:
Net loans	7,565,204	7,655,044
Financial liabilities:
Deposits	12,215,473	11,239,628
Securities sold under agreement to repurchase, short-term	257,767	284,008
Other Federal Home Loan Bank borrowings	6,031	6,758
Subordinated notes payable	3,297	3,303
Subordinated debt held by unconsolidated subsidiary trusts	$ 0	$ 77,320

DERIVATIVE INSTRUMENTS (Details

DERIVATIVE INSTRUMENTS (Details) - Interest rate swap agreements - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Derivative Instruments [Abstract]
Derivative, notional amount	$ 7.5	$ 14.4
Derivative weighted average receive rate	2.14%	2.10%
Derivative weighted average pay rate	4.44%	4.44%
Weighted average maturity period	2 years 8 months 12 days	5 years 2 months 12 days
Designated As Hedging Instrument | Fair Value Hedging [Member]
Derivative Instruments [Abstract]
Derivative, notional amount	$ 5.7	$ 5.7
Derivative weighted average receive rate	1.40%	1.42%
Derivative weighted average pay rate	3.11%	3.11%
Weighted average maturity period	12 years 3 months 18 days	12 years 6 months

DERIVATIVE INSTRUMENTS - Cumula

DERIVATIVE INSTRUMENTS - Cumulative Basis Adjustments for Fair Value Hedges (Details) - Loans [Member] - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cumulative Basis Adjustments for Fair Value Hedges [Abstract]
Carrying amount of the hedged assets	$ 5,854	$ 5,675
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets	$ (319)	$ (498)

DERIVATIVE INSTRUMENTS - Fair V

DERIVATIVE INSTRUMENTS - Fair Values of Derivative Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Values of Derivative Instruments
Derivative assets	$ 791	$ 1,588
Derivative liabilities	388	1,074
Interest rate swap agreements | Designated As Hedging Instrument | Other Assets
Fair Values of Derivative Instruments
Derivative assets	319	498
Interest rate swap agreements | Not Designated as Hedging Instrument | Other Assets
Fair Values of Derivative Instruments
Derivative assets	388	1,074
Interest rate swap agreements | Not Designated as Hedging Instrument | Accrued Interest and Other Liabilities
Fair Values of Derivative Instruments
Derivative liabilities	388	1,074
Commitments to originate real estate loans for sale | Not Designated as Hedging Instrument | Other Assets
Fair Values of Derivative Instruments
Derivative assets	34	14
Forward sales commitments | Not Designated as Hedging Instrument | Other Assets
Fair Values of Derivative Instruments
Derivative assets	$ 50	$ 2

SEGMENT INFORMATION (Details)

SEGMENT INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Segment Reporting Information, Additional Information [Abstract]
Net interest income	$ 93,954	$ 90,054
Provision for credit losses	(5,719)	5,594
Noninterest revenues	58,531	58,622
Amortization of intangible assets	3,351	3,667
Acquisition expenses	27	369
Other operating expenses	89,868	89,627
Income before income taxes	64,958	49,419
Assets	14,620,181	11,808,983	$ 13,931,094
Goodwill	793,456	773,473	$ 793,708
Core deposit intangibles & Other intangibles	49,589	59,446
Eliminations [Member]
Segment Reporting Information, Additional Information [Abstract]
Net interest income	0	0
Provision for credit losses	0	0
Noninterest revenues	(1,889)	(1,519)
Amortization of intangible assets	0	0
Acquisition expenses	0	0
Other operating expenses	(1,889)	(1,519)
Income before income taxes	0	0
Assets	(100,024)	(114,640)
Goodwill	0	0
Core deposit intangibles & Other intangibles	0	0
Banking [Member] | Operating Segments [Member]
Segment Reporting Information, Additional Information [Abstract]
Net interest income	93,839	89,763
Provision for credit losses	(5,719)	5,594
Noninterest revenues	16,454	18,680
Amortization of intangible assets	1,324	1,417
Acquisition expenses	27	369
Other operating expenses	65,007	64,200
Income before income taxes	49,654	36,863
Assets	14,427,834	11,633,330
Goodwill	689,869	669,886
Core deposit intangibles & Other intangibles	12,507	15,001
Employee Benefit Services [Member] | Operating Segments [Member]
Segment Reporting Information, Additional Information [Abstract]
Net interest income	94	240
Provision for credit losses	0	0
Noninterest revenues	27,149	25,925
Amortization of intangible assets	1,354	1,494
Acquisition expenses	0	0
Other operating expenses	15,005	15,130
Income before income taxes	10,884	9,541
Assets	210,297	213,768
Goodwill	83,275	83,275
Core deposit intangibles & Other intangibles	30,697	36,281
All Other [Member] | Operating Segments [Member]
Segment Reporting Information, Additional Information [Abstract]
Net interest income	21	51
Provision for credit losses	0	0
Noninterest revenues	16,817	15,536
Amortization of intangible assets	673	756
Acquisition expenses	0	0
Other operating expenses	11,745	11,816
Income before income taxes	4,420	3,015
Assets	82,074	76,525
Goodwill	20,312	20,312
Core deposit intangibles & Other intangibles	$ 6,385	$ 8,164