Community Bank System (CBU) 10-K 1 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	COMMUNITY BANK SYSTEM, INC.
Entity Central Index Key	723,188
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 2,750,913,268
Entity Common Stock, Shares Outstanding		50,796,090
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017

CONSOLIDATED STATEMENTS OF COND

CONSOLIDATED STATEMENTS OF CONDITION - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Cash and cash equivalents	$ 221,038	$ 173,857
Available-for-sale investment securities (cost of $3,007,148 and $2,706,863, respectively)	3,031,088	2,748,656
Other securities, at cost	50,291	35,736
Loans held for sale, at fair value	461	2,416
Loans	6,256,757	4,948,562
Allowance for loan losses	(47,583)	(47,233)
Net loans	6,209,174	4,901,329
Goodwill	734,430	465,142
Core deposit intangibles, net	25,025	7,107
Other intangibles, net	65,633	8,595
Intangible assets, net	825,088	480,844
Premises and equipment, net	123,393	112,318
Accrued interest and fees receivable	36,177	31,093
Other assets	249,488	180,188
Total assets	10,746,198	8,666,437
Liabilities:
Noninterest-bearing deposits	2,293,057	1,646,039
Interest-bearing deposits	6,151,363	5,429,915
Total deposits	8,444,420	7,075,954
Short-term borrowings	24,000	146,200
Securities sold under agreement to repurchase, short-term	337,011	0
Other long-term debt	2,071	0
Subordinated debt held by unconsolidated subsidiary trusts	122,814	102,170
Accrued interest and other liabilities	180,567	144,013
Total liabilities	9,110,883	7,468,337
Commitments and contingencies (See Note N)
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; 51,263,841 and 44,950,352 shares issued, respectively	51,264	44,950
Additional paid-in capital	894,879	545,775
Retained earnings	700,557	614,692
Accumulated other comprehensive (loss)/income	(3,699)	7,843
Treasury stock, at cost (567,764 shares including 237,494 shares held by deferred compensation arrangements at December 31, 2017, and 512,937 shares at December 31, 2016)	(21,014)	(15,160)
Deferred compensation arrangements (237,494 shares at December 31, 2017)	13,328	0
Total shareholders' equity	1,635,315	1,198,100
Total liabilities and shareholders' equity	$ 10,746,198	$ 8,666,437

CONSOLIDATED STATEMENTS OF CON3

CONSOLIDATED STATEMENTS OF CONDITION (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Available-for-sale investment securities, cost	$ 3,007,148	$ 2,706,863
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)	51,263,841	44,950,352
Treasury stock, at cost (in shares)	567,764	512,937
Shares held by deferred compensation arrangements (in shares)	237,494

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income:
Interest and fees on loans	$ 253,949	$ 211,467	$ 187,743
Interest and dividends on taxable investments	60,159	56,201	52,871
Interest and dividends on nontaxable investments	15,347	17,519	19,008
Total interest income	329,455	285,187	259,622
Interest expense:
Interest on deposits	8,031	7,325	6,971
Interest on borrowings	1,845	1,017	1,694
Interest on subordinated debt held by unconsolidated subsidiary trusts	3,904	2,949	2,537
Total interest expense	13,780	11,291	11,202
Net interest income	315,675	273,896	248,420
Provision for loan losses	10,984	8,076	6,447
Net interest income after provision for loan losses	304,691	265,820	241,973
Noninterest revenues:
Deposit service fees	67,896	58,595	52,747
Other banking revenues	5,466	7,477	4,960
Employee benefit services	80,830	46,628	45,388
Insurance services	26,150	23,149	3,352
Wealth management services	22,079	19,776	16,856
Gain/(loss) on sales of investment securities, net	2	0	(4)
Total noninterest revenues	202,423	155,625	123,299
Noninterest expenses:
Salaries and employee benefits	179,993	151,647	126,356
Occupancy and equipment	35,561	30,078	27,593
Data processing and communications	37,579	34,501	30,430
Amortization of intangible assets	16,941	5,479	3,663
Legal and professional fees	11,576	8,455	6,813
Office supplies and postage	7,506	7,274	6,476
Business development and marketing	9,994	7,484	7,204
FDIC insurance premiums	3,473	3,671	3,962
Acquisition expenses	25,986	1,706	7,037
Other expenses	18,540	16,553	13,521
Total noninterest expenses	347,149	266,848	233,055
Income before income taxes	159,965	154,597	132,217
Income taxes	9,248	50,785	40,987
Net income	$ 150,717	$ 103,812	$ 91,230
Basic earnings per share (in dollars per share)	$ 3.07	$ 2.34	$ 2.21
Diluted earnings per share (in dollars per share)	3.03	2.32	2.19
Cash dividends declared per share (in dollars per share)	$ 1.32	$ 1.26	$ 1.22

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension and other post retirement obligations:
Amortization of actuarial (gains)/losses included in net periodic pension cost, gross	$ (707)	$ 5,514	$ (7,236)
Tax effect	263	(2,108)	2,774
Amortization of actuarial (gains)/losses included in net periodic pension cost, net	(444)	3,406	(4,462)
Amortization of prior service cost included in net periodic pension cost, gross	(859)	(136)	(170)
Tax effect	324	52	65
Amortization of prior service cost included in net periodic pension cost, net	(535)	(84)	(105)
Unamortized actuarial gain due to plan merger, gross	1,858	0	0
Tax effect	(711)	0	0
Unamortized actuarial gain due to plan merger, net	1,147	0	0
Other comprehensive income/(loss) related to pension and other post retirement obligations, net of taxes	168	3,322	(4,567)
Unrealized (losses)/gains on securities:
Net unrealized holding losses arising during period, gross	(17,851)	(24,042)	(9,209)
Tax effect	6,787	9,328	2,289
Net unrealized holding losses arising during period, net	(11,064)	(14,714)	(6,920)
Reclassification adjustment for net (gains)/losses included in net income, gross	(2)	0	4
Tax effect	1	0	(2)
Reclassification adjustment for net gains/losses included in net income, net	(1)	0	2
Other comprehensive (loss) related to unrealized (losses)/gains on available-for-sale securities, net of taxes	(11,065)	(14,714)	(6,918)
Other comprehensive (loss), net of tax	(10,897)	(11,392)	(11,485)
Net income	150,717	103,812	91,230
Comprehensive income	139,820	92,420	79,745
Accumulated Other Comprehensive Income/(Loss) By Component:
Unrealized loss for pension and other postretirement obligations	(28,677)	(28,969)	(34,347)
Tax effect	7,044	11,008	13,064
Net unrealized loss for pension and other postretirement obligations	(21,633)	(17,961)	(21,283)
Unrealized gain on available-for-sale securities	23,940	41,793	65,835
Tax effect	(6,006)	(15,989)	(25,317)
Net unrealized gain on available-for-sale securities	17,934	25,804	40,518
Accumulated other comprehensive (loss)/income	$ (3,699)	$ 7,843	$ 19,235

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [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, 2014	$ 41,606	$ 409,984	$ 525,985	$ 30,720	$ (20,391)	$ 0	$ 987,904
Balance (in shares) at Dec. 31, 2014	40,747,721
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			91,230				91,230
Other comprehensive income (loss), net of tax				(11,485)			(11,485)
Dividends declared:
Common			(50,624)				(50,624)
Common stock issued under employee stock plan	$ 459	9,315					9,774
Common stock issued under employee stock plan (in shares)	458,817
Stock-based compensation		4,201					4,201
Stock issued for acquisitions	$ 2,378	99,824					102,202
Stock issued for acquisitions (in shares)	2,377,329
Treasury stock purchased					(9,126)		$ (9,126)
Treasury stock purchased (in shares)	(265,230)						(300,000)
Treasury stock issued to benefit plan		4,691			11,880		$ 16,571
Treasury stock issued to benefit plan (in shares)	456,223
Balance at Dec. 31, 2015	$ 44,443	528,015	566,591	19,235	(17,637)	0	1,140,647
Balance (in shares) at Dec. 31, 2015	43,774,860
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			103,812				103,812
Other comprehensive income (loss), net of tax				(11,392)			(11,392)
Dividends declared:
Common			(55,711)				(55,711)
Common stock issued under employee stock plan	$ 507	10,036					10,543
Common stock issued under employee stock plan (in shares)	507,784
Stock-based compensation		4,783					4,783
Treasury stock purchased					(3,470)		$ (3,470)
Treasury stock purchased (in shares)	(67,826)						0
Treasury stock issued to benefit plan		2,941			5,947		$ 8,888
Treasury stock issued to benefit plan (in shares)	222,597
Balance at Dec. 31, 2016	$ 44,950	545,775	614,692	7,843	(15,160)	0	1,198,100
Balance (in shares) at Dec. 31, 2016	44,437,415
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			150,717				150,717
Other comprehensive income (loss), net of tax				(10,897)			(10,897)
Reclassification related to tax effect of Tax Cuts and Jobs Act			645	(645)			0
Dividends declared:
Common			(65,497)				(65,497)
Common stock issued under employee stock plan	$ 265	4,298					4,563
Common stock issued under employee stock plan (in shares)	264,640
Stock-based compensation		5,137					5,137
Stock issued for acquisitions	$ 6,049	337,083					343,132
Stock issued for acquisitions (in shares)	6,048,849
Deferred compensation arrangements acquired					(10,022)	10,022	0
Deferred compensation arrangements acquired (in shares)	(179,003)
Treasury stock purchased					(3,306)	3,306	$ 0
Treasury stock purchased (in shares)	(58,491)						0
Treasury stock issued to benefit plan		2,586			7,474	0	$ 10,060
Treasury stock issued to benefit plan (in shares)	182,667
Balance at Dec. 31, 2017	$ 51,264	$ 894,879	$ 700,557	$ (3,699)	$ (21,014)	$ 13,328	$ 1,635,315
Balance (in shares) at Dec. 31, 2017	50,696,077

CONSOLIDATED STATEMENTS OF CHA7

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash dividends declared:
Dividends declared per common share (in dollars per share)	$ 1.32	$ 1.26	$ 1.22
Common stock issued under employee stock plan, tax benefits		$ 3,091	$ 2,297

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 150,717	$ 103,812	$ 91,230
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	16,024	14,398	13,132
Amortization of intangible assets	16,941	5,479	3,663
Net accretion on securities, loans and borrowings	(6,619)	(4,405)	(3,289)
Stock-based compensation	5,137	4,783	4,201
(Benefit)/provision for loan losses	10,984	8,076	6,447
Provision for deferred income taxes	(28,692)	13,066	10,716
Amortization of mortgage servicing rights	499	518	409
Income from bank-owned life insurance policies	(1,586)	(1,505)	(1,086)
(Gain)/loss on sales of investment securities, net	(2)	0	4
Net loss/(gain) on sale of loans and other assets	181	(837)	(180)
Change in other assets and liabilities	26,090	(7,614)	(5,681)
Net cash provided by operating activities	189,674	135,771	119,566
Investing activities:
Proceeds from sales of available-for-sale investment securities	0	0	221,136
Proceeds from maturities of available-for-sale investment securities	157,278	109,638	169,562
Proceeds from maturities of other securities	30,116	8,703	1,790
Purchases of available-for-sale investment securities	(90,380)	(65,966)	(503,000)
Purchases of other securities	(13,302)	(4,612)	0
Net change in loans	164,846	(159,871)	(176,754)
Cash (paid)/received for acquisition, net of cash acquired of $52,132, $0, and $81,772, respectively	(107,414)	(575)	25,505
Settlement of bank owned life insurance policies	1,779	3,127	0
Purchases of premises and equipment, net	(10,819)	(12,442)	(12,400)
Real estate limited partnership investments	(733)	0	0
Net cash provided by/(used in) investing activities	131,371	(121,998)	(274,161)
Financing activities:
Net change in deposits	(79,940)	202,480	238,969
Net change in borrowings, net of payments of $81,544, $0 and $0	(144,809)	(155,100)	(36,700)
Issuance of common stock	4,563	10,543	9,774
Purchase of treasury stock	(3,306)	(3,470)	(9,126)
Sale of treasury stock	10,060	8,888	16,571
Increase in deferred compensation arrangements	3,306	0	0
Cash dividends paid	(62,305)	(55,048)	(49,273)
Withholding taxes paid on share-based compensation	(1,433)	(1,419)	(806)
Net cash (used in)/provided by financing activities	(273,864)	6,874	169,409
Change in cash and cash equivalents	47,181	20,647	14,814
Cash and cash equivalents at beginning of year	173,857	153,210	138,396
Cash and cash equivalents at end of year	221,038	173,857	153,210
Supplemental disclosures of cash flow information:
Cash paid for interest	13,705	11,268	11,252
Cash paid for income taxes	41,231	32,239	28,891
Supplemental disclosures of noncash financing and investing activities:
Dividends declared and unpaid	17,460	14,268	13,605
Transfers from loans to other real estate	3,518	2,612	3,943
Acquisitions:
Common stock issued	343,132	0	102,202
Fair value of assets acquired, excluding acquired cash and intangibles	1,961,246	0	675,025
Fair value of liabilities assumed	$ 1,871,685	$ 0	$ 700,574

CONSOLIDATED STATEMENTS OF CAS9

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investing activities:
Cash acquired related to acquisition	$ 52,132	$ 0	$ 81,772
Financing activities:
Payment made on borrowings	$ 81,544	$ 0	$ 0

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2017
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE A: SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Nature of Operations Community Bank System, Inc. (the “Company”) is a registered financial holding company which wholly-owns two significant consolidated subsidiaries: Community Bank, N.A. (the “Bank” or “CBNA”), and Benefit Plans Administrative Services, Inc. (“BPAS”). As of December 31, 2017, BPAS owns five subsidiaries: Benefit Plans Administrative Services, LLC (“BPA”), a provider of defined benefit contribution plan administration services; Northeast Retirement Services, LLC (“NRS”), a provider of institutional transfer agency, master recordkeeping services, fund administration, trust and retirement plan services; BPAS Actuarial & Pension Services, LLC (“BPAS-APS”), a provider of actuarial and benefit consulting services; BPAS Trust Company of Puerto Rico, a Puerto Rican trust company; and Hand Benefits & Trust Company (“HB&T”), a provider of collective investment fund administration and institutional trust services. NRS owns one subsidiary, Global Trust Company, Inc. (“GTC”), a non-depository trust company which provides fiduciary services for collective investment trusts and other products. HB&T owns one subsidiary, Hand Securities Inc. (“HSI”), an introducing broker-dealer. The Company also wholly-owns three unconsolidated subsidiary business trusts formed for the purpose of issuing mandatorily-redeemable preferred securities which are considered Tier I capital under regulatory capital adequacy guidelines (see Note P). As of December 31, 2017, the Bank operated 225 full service branches operating as Community Bank, N.A. throughout 35 counties of Upstate New York, six counties of Northeastern Pennsylvania, 12 counties of Vermont and one county of Western Massachusetts, offering a range of commercial and retail banking services. The Bank owns the following operating subsidiaries: The Carta Group, Inc. (“Carta Group”), CBNA Preferred Funding Corporation (“PFC”), CBNA Treasury Management Corporation (“TMC”), Community Investment Services, Inc. (“CISI”), NOTCH Investment Fund, LLC (“NOTCH”), Nottingham Advisors, Inc. (“Nottingham”), OneGroup NY, Inc. (“OneGroup”), and Oneida Preferred Funding II LLC (“OPFC II”). OneGroup is a full-service insurance agency offering personal and commercial property insurance and other risk management products and services. NOTCH, PFC and OPFC II primarily act as investors in residential and commercial real estate activities. TMC provides cash management, investment, and treasury services to the Bank. CISI and Carta Group provide broker-dealer and investment advisory services. Nottingham provides asset management services to individuals, corporations, corporate pension and profit sharing plans, and foundations. Principles of Consolidation The consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. Variable Interest Entities (“VIE”) are legal entities in which equity investors do not have the characteristics of a controlling financial interest or do not have sufficient equity at risk for the legal entities to finance its activities without additional subordinated financial support. VIEs may be required to be consolidated by a company if it is determined the company is the primary beneficiary of a VIE. The primary beneficiary of a VIE is the enterprise that has: (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance, and (2) the obligation to absorb losses of the VIE that could potentially be significant to the VIE or the right to receive benefits of the VIE that could potentially be significant to the VIE. The Company’s VIE’s are described in more detail in Note T to the consolidated financial statements. Critical Accounting Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Critical accounting estimates include the allowance for loan losses, actuarial assumptions associated with the pension, post-retirement and other employee benefit plans, the provision for income taxes, investment valuation and other-than-temporary impairment, the carrying value of goodwill and other intangible assets, and acquired loan valuations. Risk and Uncertainties In the normal course of its business, the Company encounters economic and regulatory risks. There are three main components of economic risk: interest rate risk, credit risk and market risk. The Company is subject to interest rate risk to the degree that its interest-bearing liabilities mature or reprice at different speeds, or on different basis, from its interest-earning assets. The Company’s primary credit risk is the risk of default on the Company’s loan portfolio that results from the borrowers’ inability or unwillingness to make contractually required payments. Market risk reflects potential changes in the value of collateral underlying loans, the fair value of investment securities, and loans held for sale. The Company is subject to regulations of various governmental agencies. These regulations can change significantly from period to period. The Company also undergoes periodic examinations by the regulatory agencies which may subject it to further changes with respect to asset valuations, amounts of required loan loss allowances, and operating restrictions resulting from the regulators’ judgments based on information available to them at the time of their examinations. Revenue Recognition The Company recognizes income on an accrual basis. CISI and Carta Group recognize fee income when investment and insurance products are sold to customers. Nottingham provides asset management services to brokerage firms and clients and recognizes income ratably over the contract period during which service is performed. Revenue from BPA’s administration and recordkeeping services is recognized ratably over the service contract period. Revenue from consulting and actuarial services is recognized when services are rendered. OneGroup recognizes commission revenue at the later of All intercompany revenue and expense among related entities are eliminated in consolidation. Cash and Cash Equivalents For purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks, and highly liquid investments with original maturities of less than 90 days. The carrying amounts reported in the consolidated statements of condition for cash and cash equivalents approximate those assets’ fair values. Investment Securities The Company can classify its investments in debt and equity securities as trading, held-to-maturity, or available-for-sale. Held-to-maturity securities are those for which the Company has the positive intent and ability to hold until maturity, and are reported at amortized cost. The Company did not use the held-to-maturity classification in 2016 or 2017. Securities classified as available-for-sale are reported at fair value with net unrealized gains and losses reflected as a separate component of shareholders' equity, net of applicable income taxes. None of the Company's investment securities have been classified as trading securities at December 31, 2017. Certain equity securities are stated at cost and include restricted stock of the Federal Reserve Bank of New York (“Federal Reserve”) and the Federal Home Loan Bank of New York and the Federal Home Loan Bank of Boston (collectively referred to as “FHLB”). Fair values for investment securities are based upon quoted market prices, where available. If quoted market prices are not available, fair values are based upon quoted market prices of comparable instruments, or a discounted cash flow model using market estimates of interest rates and volatility. The Company conducts an assessment of all securities in an unrealized loss An OTTI loss must be recognized for a debt security in an unrealized loss position if there is intent to sell the security or it is more likely than not the Company will be required to sell the security prior to recovery of its amortized cost basis. In this situation, the amount of loss recognized in income is equal to the difference between the fair value and the amortized cost basis of the security. Even if management does not have the intent, and it is not more likely than not that the Company will be required to sell the securities, an evaluation of the expected cash flows to be received is performed to determine if a credit loss has occurred. For debt securities, a critical component of the evaluation for OTTI is the identification of credit-impaired securities, where the Company does not expect to receive cash flows sufficient to recover the entire amortized cost basis of the security. In the event of a credit loss, only the amount of impairment associated with the credit loss would be recognized in income. The portion of the unrealized loss relating to other factors, such as liquidity conditions in the market or changes in market interest rates, is recorded in accumulated other comprehensive loss. Equity securities are also evaluated to determine whether the unrealized loss is expected to be recoverable based on whether evidence exists to support a realizable value equal to or greater than the amortized cost basis. If it is probable that the amortized cost basis will not be recovered, taking into consideration the estimated recovery period and the ability to hold the equity security until recovery, OTTI is recognized in earnings equal to the difference between the fair value and the amortized cost basis of the security. The specific identification method is used in determining the realized gains and losses on sales of investment securities and OTTI charges. Premiums and discounts on securities are amortized and accreted, respectively, on the interest method basis over the period to maturity or estimated life of the related security. Purchases and sales of securities are recognized on a trade date basis. Loans Loans are stated at unpaid principal balances, net of unearned income. Mortgage loans held for sale are carried at fair value and are included in loans held for sale on the consolidated statements of condition. Fair values for variable rate loans that reprice frequently are based on carrying values. Fair values for fixed rate loans are estimated using discounted cash flows and interest rates currently being offered for loans with similar terms to borrowers of similar credit quality. The carrying amount of accrued interest approximates its fair value. Interest on loans is accrued and credited to operations based upon the principal amount outstanding. Nonrefundable loan fees and related direct costs are deferred and included in the loan balances where they are amortized over the life of the loan as an adjustment to loan yield using the effective yield method. Premiums and discounts on purchased loans are amortized using the effective yield method over the life of the loans. Acquired loans Acquired loans are initially recorded at their acquisition date fair values. The carryover of allowance for loan losses is prohibited as any credit losses in the loans are included in the determination of the fair value of the loans at the acquisition date. Fair values for acquired loans are based on a discounted cash flow methodology that involves assumptions and judgments as to credit risk, prepayment risk, liquidity risk, default rates, loss severity, payment speeds, collateral values and discount rate. Acquired impaired loans Acquired loans that have evidence of deterioration in credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all contractually required payments are accounted for as impaired loans under ASC 310-30. The excess of undiscounted cash flows expected at acquisition over the estimated fair value is referred to as the accretable discount and is recognized into interest income over the remaining life of the loans using the interest method. The difference between contractually required payments at acquisition and the undiscounted cash flows expected to be collected at acquisition is referred to as the non-accretable discount. The non-accretable discount represents estimated future credit losses and other contractually required payments that the Company does not expect to collect. Subsequent decreases in expected cash flows are recognized as impairments through a charge to the provision for loan losses resulting in an increase in the allowance for loan losses. Subsequent improvements in expected cash flows result in a recovery of previously recorded allowance for loan losses or a reversal of a corresponding amount of the non-accretable discount, which the Company then reclassifies as an accretable discount that is recognized into interest income over the remaining life of the loans using the interest method. Acquired loans that met the criteria for non-accrual of interest prior to acquisition may be considered performing upon acquisition, regardless of whether the customer is contractually delinquent, if the Company can reasonably estimate the timing and amount of the expected cash flows on such loans and if the Company expects to fully collect the new carrying value of the loans. As such, the Company may no longer consider the loan to be non-accrual or non-performing and may accrue interest on these loans, including the impact of any accretable discount. Acquired non-impaired loans Acquired loans that do not meet the requirements under ASC 310-30 are considered acquired non-impaired loans. The difference between the acquisition date fair value and the outstanding balance represents the fair value adjustment for a loan and 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 in accordance with ASC 310-20. 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. Subsequent to the purchase date, the methods used to estimate the allowance for loan losses for the acquired non-impaired loans is consistent with the policy described below. However, the Company compares the net realizable value of the loans to the carrying value, for loans collectively evaluated for impairment. The carrying value represents the net of the loan’s unpaid principal balance and the remaining purchase discount (or premium) that has yet to be accreted (or amortized) into interest income (or interest expense). When the carrying value exceeds the net realizable value, an allowance for loan losses is recognized. Impaired and Other Nonaccrual Loans The Company places a loan on nonaccrual status when the loan becomes 90 days past due (or sooner, if management concludes collection is doubtful), except when, in the opinion of management, it is well-collateralized and in the process of collection. A loan may be placed on nonaccrual status earlier than ninety days past due if there is deterioration in the financial position of the borrower or if other conditions of the loan so warrant. When a loan is placed on nonaccrual status, uncollected accrued interest is reversed against interest income and the amortization of nonrefundable loan fees and related direct costs is discontinued. Interest income during the period the loan is on nonaccrual status is recorded on a cash basis after recovery of principal is reasonably assured. Nonaccrual loans are returned to accrual status when management determines that the borrower’s performance has improved and that both principal and interest are collectible. This generally requires a sustained period of timely principal and interest payments and a well-documented credit evaluation of the borrower’s financial condition. A loan is considered modified in a troubled debt restructuring (“TDR”) when, due to a borrower’s financial difficulties, the Company makes a concession(s) to the borrower that it would not otherwise consider. These modifications may include, among others, an extension for the term of the loan, or granting a period when interest–only payments can be made with the principal payments and interest caught up over the remaining term of the loan or at maturity. Generally, a nonaccrual loan that has been modified in a TDR remains on nonaccrual status for a period of 12 months to demonstrate that the borrower is able to meet the terms of the modified loan. If the borrower’s ability to meet the revised payment schedule is uncertain, the loan remains on nonaccrual status. Regulatory guidance issued by the OCC requires certain loans that have been discharged in Chapter 7 bankruptcy to be reported as TDRs. In accordance with this guidance, 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 and 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. Commercial loans greater than $0.5 million are evaluated individually for impairment. A loan is considered impaired, based on current information and events, if it is probable that the Company will be unable to collect the scheduled payments of principal or interest when due according to the contractual terms of the loan agreement. The measurement of impaired loans is generally based upon the present value of expected future cash flows or the fair value of the collateral, if the loan is collateral-dependent. The Company’s charge-off policy by loan type is as follows: · Business lending loans are generally charged-off to the extent outstanding principal exceeds the fair value of estimated proceeds from collection efforts, including liquidation of collateral. The charge-off is recognized when the loss becomes reasonably quantifiable. · Consumer installment loans are generally charged-off to the extent outstanding principal exceeds the fair value of collateral, and are recognized by the end of the month in which the loan becomes 90 days past due. · Consumer mortgage and home equity loans are generally charged-off to the extent outstanding principal exceeds the fair value of the property, less estimated costs to sell, and are recognized when the loan becomes 180 days past due. Allowance for Loan Losses Management continually evaluates the credit quality of the Company’s loan portfolio, and performs a formal review of the adequacy of the allowance for loan losses on a quarterly basis. The allowance reflects management’s best estimate of probable losses inherent in the loan portfolio. Determination of the allowance is subjective in nature and requires significant estimates. The Company’s allowance methodology consists of two broad components - general and specific loan loss allocations. The general loan loss allocation is composed of two calculations that are computed on five main loan segments: business lending, consumer direct, consumer indirect, home equity and consumer mortgage. The first calculation is quantitative and determines an allowance level based on the latest 36 months of historical net charge-off data for each loan class (commercial loans exclude balances with specific loan loss allocations). The second calculation is qualitative and takes into consideration eight qualitative environmental factors: levels and trends in delinquencies and impaired loans; levels of and trends in charge-offs and recoveries; trends in volume and terms of loans; effects of any changes in risk selection and underwriting standards, and other changes in lending policies, procedures, and practices; experience, ability, and depth of lending management and other relevant staff; national and local economic trends and conditions; industry conditions; and effects of changes in credit concentrations. A component of the qualitative calculation is the unallocated allowance for loan loss. The qualitative and quantitative calculations are added together to determine the general loan loss allocation. The specific loan loss allocation relates to individual commercial loans that are both greater than $0.5 million and in a nonaccruing status with respect to interest. Specific loan losses are based on discounted estimated cash flows, including any cash flows resulting from the conversion of collateral or collateral shortfalls. The allowance levels computed from the specific and general loan loss allocation methods are combined with unallocated allowances and allowances needed for acquired loans to derive the total required allowance for loan losses to be reflected on the Consolidated Statement of Condition. Loan losses are charged off against the allowance, while recoveries of amounts previously charged off are credited to the allowance. A provision for loan losses is charged to operations based on management’s periodic evaluation of factors previously mentioned. Intangible Assets Intangible assets include core deposit intangibles, customer relationship intangibles and goodwill arising from acquisitions. Core deposit intangibles and customer relationship intangibles are amortized on either an accelerated or straight-line basis over periods ranging from seven to 20 years. The initial and ongoing carrying value of goodwill and other intangible assets is based upon discounted cash flow modeling techniques that require management to make estimates regarding the amount and timing of expected future cash flows. It also requires use of a discount rate that reflects the current return requirements of the market in relation to present risk-free interest rates, required equity market premiums, peer volatility indicators, and company-specific risk indicators. The Company evaluates goodwill for impairment on an annual basis, or more often if events or circumstances indicate there may be impairment. The implied fair value of a reporting unit’s goodwill is compared to its carrying amount and the impairment loss is measured by the excess of the carrying value over fair value. The fair value of each reporting unit is compared to the carrying amount of that reporting unit in order to determine if impairment is indicated. Premises and Equipment Premises and equipment are stated at cost less accumulated depreciation. Computer software costs that are capitalized only include external direct costs of obtaining and installing the software. The Company has not developed any internal use software. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets. Useful lives range from three to 10 years for equipment; three to seven years for software and hardware; and 10 to 40 years for building and building improvements. Land improvements are depreciated over 20 years and leasehold improvements are amortized over the shorter of the term of the respective lease plus any optional renewal periods that are reasonably assured or life of the asset. Maintenance and repairs are charged to expense as incurred. Other Real Estate Other real estate owned is comprised of properties acquired through foreclosure, or by deed in lieu of foreclosure. These assets are carried at fair value less estimated costs of disposal. At foreclosure, if the fair value, less estimated costs to sell, of the real estate acquired is less than the Company’s recorded investment in the related loan, a write-down is recognized through a charge to the allowance for loan losses. Any subsequent reduction in value is recognized by a charge to income. Operating costs associated with the properties are charged to expense as incurred. At December 31, 2017 and 2016, other real estate amounted to $1.9 million and $2.0 million, respectively, and is included in other assets. Mortgage Servicing Rights 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 period of estimated net servicing income or loss. The Company uses a valuation model that calculates the present value of future cash flows to determine the fair value of servicing rights. In using this valuation method, the Company incorporates assumptions that market participants would use in estimating future net servicing income, which includes estimates of the servicing cost per loan, the discount rate, and prepayment speeds. The carrying value of the originated mortgage servicing rights is included in other assets and is evaluated quarterly for impairment using these same market assumptions. The amount of impairment recognized is the amount by which the carrying value of the capitalized servicing rights for a stratum exceeds estimated fair value. Impairment is recognized through a valuation allowance. Treasury Stock Repurchases of shares of the Company’s common stock are recorded at cost as a reduction of shareholders’ equity. Reissuance of shares of treasury stock is recorded at average cost. Income Taxes The Company and its subsidiaries file a consolidated federal income tax return. Provisions for income taxes are based on taxes currently payable or refundable as well as deferred taxes that are based on temporary differences between the tax basis of assets and liabilities and their reported amounts in the consolidated financial statements. Deferred tax assets and liabilities are reported in the consolidated financial statements at currently enacted income tax rates applicable to the period in which the deferred tax assets and liabilities are expected to be realized or settled. Benefits from tax positions should be recognized in the financial statements only when it is more likely than not that the tax position will be sustained upon examination by the appropriate taxing authority having full knowledge of all relevant information. A tax position meeting the more-likely-than-not recognition threshold should be measured at the largest amount of benefit for which the likelihood of realization upon ultimate settlement exceeds 50 percent. Investments in Real Estate Limited Partnerships The Company has investments in various real estate limited partnerships that acquire, develop, own and operate low and moderate-income housing. The Company’s ownership interest in these limited partnerships ranges from 5.00% to 99.99% as of December 31, 2017. These investments are made directly in Low Income Housing Tax Credit, or LIHTC, partnerships formed by third parties. As a limited partner in these operating partnerships, we receive tax credits and tax deductions for losses incurred by the underlying properties. The Company accounts for its ownership interest in LIHTC partnerships in accordance with Accounting Standards Update (“ASU”) 2014-01, Investments – Equity Method and Joint Ventures (Topic 323): Accounting for Investments in Qualified Affordable Housing Projects Repurchase Agreements The Company sells certain securities under agreements to repurchase. These agreements are treated as collateralized financing transactions. These secured borrowings are reflected as liabilities in the accompanying consolidated statements of condition and are recorded at the amount of cash received in connection with the transaction. Short-term securities sold under agreements to repurchase generally mature within one day from the transaction date. Securities, generally U.S. government and federal agency securities, pledged as collateral under these financing arrangements can be repledged by the secured party. Additional collateral may be required based on the fair value of the underlying securities. Retirement Benefits The Company provides defined benefit pension benefits to eligible employees and post-retirement health and life insurance benefits to certain eligible retirees. The Company also provides deferred compensation and supplemental executive retirement plans for selected current and former employees, officers, and directors. Expense under these plans is charged to current operations and consists of several components of net periodic benefit cost based on various actuarial assumptions regarding future experience under the plans, including discount rate, rate of future compensation increases and expected return on plan assets. Derivative Financial Instruments and Hedging Activities The Company accounts for derivative financial instruments at fair value. If certain conditions are met, a derivative may be specifically designated as (1) a hedge of the exposure to changes in the fair value of a recognized asset or liability or an unrecognized firm commitment (“fair value hedge”), (2) a hedge of the exposure to variable cash flows of a forecasted transaction or the variability of cash flows to be received or paid related to a recognized asset or liability (“cash flow hedge”), or (3) an instrument with no hedging designation (“stand-alone derivative”). For a fair value hedge, the gain or loss on the derivative, as well as the offsetting loss or gain on the hedged item, are recognized in current earnings as fair values change. For a cash flow hedge, the gain or loss on the derivative is reported in other comprehensive income and is reclassified into earnings in the same periods during which the hedged transaction affects earnings. For both types of hedges, changes in the fair value of derivatives that are not highly effective in hedging the changes in fair value or expected cash flows of the hedged item are recognized immediately in current earnings. Changes in the fair value of derivatives that do not qualify for hedge accounting are reported currently in earnings, as noninterest income. Net cash settlements on derivatives that qualify for hedge accounting are recorded in interest income or interest expense, based on the item being hedged. Net cash settlements on derivatives that do not qualify for hedge accounting are reported in noninterest income. Cash flows on hedges are classified in the consolidated statement of cash flow statement the same as the cash flows of the items being hedged. The Company formally documents the relationship between derivatives and hedged items, as well as the risk-management objective and strategy for undertaking hedge transactions at the inception of the hedging relationship. This documentation includes linking the fair value or cash flow hedges to specific assets and liabilities on the statement of condition or to specific commitments or forecasted transactions. The Company also formally assesses, both at the hedge’s inception and on an ongoing basis, whether the derivative instruments that are used are highly effective in offsetting changes in fair values or cash flows of the hedged items. When hedge accounting is discontinued, subsequent changes in fair value of the derivative are recorded in noninterest income. When a fair value hedge is discontinued, the hedged asset or liability is no longer adjusted for changes in fair value and the existing basis adjustment is amortized or accreted over the remaining life of the asset or liability. When a cash flow hedge is discontinued, but the hedged cash flows or forecasted transactions are still expected to occur, gains or losses that were accumulated in other comprehensive income are amortized into earnings over the same periods which the hedged transactions will affect earnings. Assets Under Management or Administration Assets held in fiduciary or agency capacities for customers are not included in the accompanying consolidated statements of condition as they are not assets of the Company. All fees associated with providing asset management services are recorded on an accrual basis of accounting and are included in noninterest income. Advertising Advertising costs amounting to approximately $5.7 million, $3.9 million and $3.6 million for the years ending December 31, 2017, 2016 and 2015, respectively, are nondirect response in nature and expensed as inc

ACQUISITIONS

ACQUISITIONS	12 Months Ended
	Dec. 31, 2017
ACQUISITIONS [Abstract]
ACQUISITIONS	NOTE B: ACQUISITIONS On December 4, 2017, the Company, through its subsidiary, OneGroup, completed its acquisition of Gordon B. Roberts Agency, Inc. (“GBR”), an insurance agency headquartered in Oneonta, New York for $3.7 million in Company stock and cash, comprised of $1.35 million in cash and the issuance of 0.04 million shares of common stock. The transaction resulted in the acquisition of $0.6 million of assets, $0.7 million of other liabilities, goodwill in the amount of $2.2 million and other intangible assets of $1.6 million. The effects of the acquired assets and liabilities have been included in the consolidated financial statements since that date. On November 17, 2017, the Company, through its subsidiary, CISI, completed its acquisition of certain assets of Northeast Capital Management, Inc. (“NECM”), a financial services business headquartered in Wilkes Barre, Pennsylvania. The Company agreed to pay $1.2 million in cash, including a $0.2 million contingent payment based on certain customer retention objectives, to acquire a customer list from NECM, and recorded a $1.2 million customer list intangible asset in conjunction with the acquisition. The effects of the acquired assets have been included in the consolidated financial statements since that date. On May 12, 2017, the Company completed its acquisition of Merchants Bancshares, Inc. (“Merchants”), parent company of Merchants Bank, headquartered in South Burlington, Vermont, for $345.2 million in Company stock and cash, comprised of $82.9 million in cash and the issuance of 4.68 million shares of common stock. The acquisition extends the Company’s footprint into the Vermont and Western Massachusetts markets with the addition of 31 branch locations in Vermont and one location in Massachusetts. This transaction resulted in the acquisition of $2.0 billion of assets, including $1.49 billion of loans and $370.6 million of investment securities, as well as $1.45 billion of deposits and $189.0 million in goodwill. The effects of the acquired assets and liabilities have been included in the consolidated financial statements since that date. Revenues of approximately $42.6 million and direct expenses, which may not include certain shared expenses, of approximately $19.9 million from Merchants were included in the consolidated income statement for the year ended December 31, 2017. On March 1, 2017, the Company, through its subsidiary, OneGroup, completed its acquisition of certain assets of Dryfoos Insurance Agency, Inc. (“Dryfoos”), an insurance agency headquartered in Hazleton, Pennsylvania. The Company paid $3.0 million in cash to acquire the assets of Dryfoos, and recorded goodwill in the amount of $1.7 million and other intangible assets of $1.7 million in conjunction with the acquisition. The effects of the acquired assets and liabilities have been included in the consolidated financial statements since that date. On February 3, 2017, the Company completed its acquisition of NRS and its subsidiary GTC, headquartered in Woburn, Massachusetts, for $148.6 million in Company stock and cash. NRS was a privately held corporation focused on providing institutional transfer agency, master recordkeeping services, custom target date fund administration, trust product administration and customized reporting services to institutional clients. Its wholly-owned subsidiary, GTC, is chartered in the State of Maine as a non-depository trust company and provides fiduciary services for collective investment trusts and other products. The acquisition of NRS and GTC, hereafter referred to collectively as NRS, will strengthen and complement the Company’s existing employee benefit services businesses. Upon the completion of the merger, NRS became a wholly-owned subsidiary of BPAS and operates as Northeast Retirement Services, LLC, a Delaware limited liability company. This transaction resulted in the acquisition of $36.1 million in net tangible assets, principally cash and certificates of deposit, $60.2 million in customer list intangibles that will be amortized using the 150% declining balance method over 10 years, a $24.2 million deferred tax liability associated with the customer list intangible, and $76.4 million in goodwill. The effects of the acquired assets and liabilities have been included in the consolidated financial statements since that date. Revenues of $31.5 million and expenses of $21.5 million from NRS were included in the consolidated statement of income for the year ended December 31, 2017. On January 1, 2017, the Company, through its subsidiary, OneGroup, acquired certain assets of Benefits Advisory Service, Inc. (“BAS”), a benefits consulting group headquartered in Forest Hills, New York. The Company paid $1.2 million in cash to acquire the assets of BAS and recorded intangible assets of $1.2 million in conjunction with the acquisition. The effects of the acquired assets and liabilities have been included in the consolidated financial statements since that date. On January 4, 2016, the Company, through its subsidiary, CBNA Insurance Agency, Inc. (“CBNA Insurance”), completed its acquisition of WJL Agencies Inc. doing business as The Clark Insurance Agencies (“WJL”), an insurance agency operating in Canton, New York. The Company paid $0.6 million in cash for the intangible assets of the company. Goodwill in the amount of $0.3 million and intangible assets in the amount of $0.3 million were recorded in conjunction with the acquisition. The effects of the acquired assets and liabilities have been included in the consolidated financial statements since that date. On August 19, 2016, the Company merged together its insurance subsidiaries and as of that date, the activities of CBNA Insurance were merged into OneGroup. On December 4, 2015, the Company completed its acquisition of Oneida Financial Corp. (“Oneida”), parent company of Oneida Savings Bank, headquartered in Oneida, New York for $158.5 million in Company stock and cash, comprised of $56.3 million of cash and the issuance of 2.38 million common shares. Upon the completion of the merger, the Bank added 12 branch locations in Oneida and Madison counties and approximately $769.4 million of assets, including approximately $399.4 million of loans and $225.7 million of investment securities, along with $699.2 million of deposits. Through the acquisition of Oneida, the Company acquired OneGroup and Oneida Wealth Management, Inc. (“OWM”) as wholly-owned subsidiaries primarily engaged in offering insurance and investment advisory services. These subsidiaries complement the Company’s other non-banking financial services businesses. The effects of the acquired assets and liabilities have been included in the consolidated financial statements since that date. On April 22, 2016, the activities of OWM were merged into CISI. 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 acquisition, and were subject to adjustment based on updated information not available at the time of acquisition. During the second quarter of 2017, the carrying amount of other assets decreased by $2.7 million and other liabilities decreased by $2.4 million as a result of a reclassification of amounts from other assets into other liabilities, and an adjustment to other liabilities as a result of updated information not available at the time of acquisition. Goodwill associated with the NRS acquisition increased $0.3 million during the second quarter as a result of these changes in fair value. During the third quarter of 2017, the carrying amount of investments increased by $0.2 million as a result of updated information not available at the time of acquisition, the carrying amount of loans decreased $0.6 million as a result of an adjustment to the valuation of acquired impaired loans, the carrying amount of premises and equipment increased $3.6 million as a result of updated appraisal information not available at the time of acquisition, and the value of other assets and other liabilities increased $5.5 million and $6.6 million, respectively, as a result of adjustments to accrued income taxes, deferred taxes and certain tax credit arrangements that were recorded on a provisional basis. Goodwill associated with the NRS and Merchants acquisitions decreased $0.1 million and $2.0 million during the third quarter, respectively, as a result of these changes in fair value estimates. During the fourth quarter of 2017, the carrying amount of loans decreased $0.5 million as a result of an adjustment to the valuation of acquired impaired loans and the value of other assets and other liabilities decreased $0.3 million and $0.02 million, respectively, as a result of adjustments to deferred taxes and certain tax credit arrangements. Goodwill associated with the Merchants acquisition increased $0.8 million during the fourth quarter as a result of these changes in fair value estimates. The above referenced acquisitions expanded the Company’s geographical presence in New York, Pennsylvania, Vermont, and Western Massachusetts 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: 2017 2016 2015 (000s omitted) NRS Merchants Other (1) Total WJL Oneida Consideration paid : Cash (2) $ 70,073 $ 82,898 $ 6,775 $ 159,746 $ 575 $ 56,266 Community Bank System, Inc. common stock 78,483 262,254 2,395 343,132 0 102,202 Total net consideration paid 148,556 345,152 9,170 502,878 575 158,468 Recognized amounts of identifiable assets acquired and liabilities assumed: Cash and cash equivalents 11,063 40,730 339 52,132 0 81,772 Investment securities 20,294 370,648 0 390,942 0 225,729 Loans 0 1,488,157 0 1,488,157 0 399,422 Premises and equipment 411 16,608 27 17,046 0 22,212 Accrued interest receivable 72 4,773 0 4,845 0 1,133 Other assets 8,088 51,585 583 60,256 0 26,529 Core deposit intangibles 0 23,214 0 23,214 0 2,570 Other intangibles 60,200 2,857 5,626 68,683 288 9,994 Deposits 0 (1,448,406 ) 0 (1,448,406 ) 0 (699,241 ) Other liabilities (28,002 ) (11,750 ) (1,217 ) (40,969 ) 0 (1,333 ) Short-term advances 0 (80,000 ) 0 (80,000 ) 0 0 Securities sold under agreement to repurchase, short-term 0 (278,076 ) 0 (278,076 ) 0 0 Long-term debt 0 (3,615 ) 0 (3,615 ) 0 0 Subordinated debt held by unconsolidated subsidiary trusts 0 (20,619 ) 0 (20,619 ) 0 0 Total identifiable assets, net 72,126 156,106 5,358 233,590 288 68,787 Goodwill $ 76,430 $ 189,046 $ 3,812 $ 269,288 $ 287 $ 89,681 (1) (2) Includes NECM $0.2 million contingent cash payment consideration. Acquired loans that have evidence of deterioration in credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all contractually required payments were aggregated by comparable characteristics and recorded at fair value without a carryover of the related allowance for loan losses. Cash flows for each loan were determined using an estimate of credit losses and rate of prepayments. Projected monthly cash flows were then discounted to present value using a market-based discount rate. The excess of the undiscounted expected cash flows over the estimated fair value is referred to as the “accretable yield” and is recognized into interest income over the remaining lives of the acquired loans. The following is a summary of the loans acquired from Merchants at the date of acquisition: (000s omitted) Acquired Impaired Loans Acquired Non-impaired Loans Total Acquired Loans Contractually required principal and interest at acquisition $ 15,454 $ 1,872,574 $ 1,888,028 Contractual cash flows not expected to be collected (5,385 ) (14,753 ) (20,138 ) Expected cash flows at acquisition 10,069 1,857,821 1,867,890 Interest component of expected cash flows (793 ) (378,940 ) (379,733 ) Fair value of acquired loans $ 9,276 $ 1,478,881 $ 1,488,157 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 Merchants, Dryfoos, BAS, WJL and Oneida acquisitions are being amortized using an accelerated method over their estimated useful life of eight years. The goodwill, which is not amortized for book purposes, was assigned to the Banking segment for the Merchants and Oneida acquisitions, the Employee Benefit Services segment for NRS, and All Other segments for the Dryfoos, BAS, and WJL acquisitions. Goodwill arising from the Merchants, NRS, GBR and Oneida acquisitions is not deductible for tax purposes. Goodwill arising from the Dryfoos, BAS and WJL acquisitions is deductible for tax purposes. Direct costs related to the acquisitions were expensed as incurred. Merger and acquisition integration-related expenses amount to $26.0 million, $1.7 million and $7.0 million during 2017, 2016 and 2015, respectively, and have been separately stated in the consolidated statements of income. Supplemental Pro Forma Financial Information The following unaudited condensed pro forma information assumes the Merchants and NRS acquisitions had been completed as of January 1, 2016 for the year ended December 31, 2017 and December 31, 2016. The pro forma information does not include amounts related to BAS, Dryfoos, NECM and GBR as the amounts were immaterial. The table below has been prepared for comparative purposes only and is not necessarily indicative of the actual results that would have been attained had the acquisitions occurred as of the beginning of the year presented, nor is it indicative of the Company’s future results. Furthermore, the unaudited pro forma information does not reflect management’s estimate of any revenue-enhancing opportunities nor anticipated cost savings that may have occurred as a result of the integration and consolidation of the acquisitions. The pro forma information set forth below reflects the historical results of Merchants and NRS combined with the Company’s consolidated statement of income with adjustments related to (a) certain purchase accounting fair value adjustments and (b) amortization of customer lists and core deposit intangibles. Acquisition expenses related to the Merchants and NRS transactions totaling $25.7 million for the year ended December 31, 2017 were included in the pro forma information as if they were incurred in 2016. Pro Forma (Unaudited) Year Ended December 31, (000’s omitted) 2017 2016 Total revenue, net of interest expense $ 546,977 $ 536,183 Net income 176,257 109,186

INVESTMENT SECURITIES

INVESTMENT SECURITIES	12 Months Ended
	Dec. 31, 2017
INVESTMENT SECURITIES [Abstract]
INVESTMENT SECURITIES	NOTE C: INVESTMENT SECURITIES The amortized cost and estimated fair value of investment securities as of December 31 are as follows: 2017 2016 (000's omitted) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Available-for-Sale Portfolio: U.S. Treasury and agency securities $ 2,043,023 $ 15,886 $ 4,838 $ 2,054,071 $ 1,876,358 $ 28,522 $ 2,118 $ 1,902,762 Obligations of state and political subdivisions 514,949 14,064 57 528,956 582,655 13,389 1,054 594,990 Government agency mortgage-backed securities 358,180 3,121 3,763 357,538 232,657 5,040 2,467 235,230 Corporate debt securities 2,648 0 25 2,623 5,716 2 31 5,687 Government agency collateralized mortgage obligations 88,097 155 878 87,374 9,225 310 0 9,535 Marketable equity securities 251 275 0 526 252 200 0 452 Total available-for-sale portfolio $ 3,007,148 $ 33,501 $ 9,561 $ 3,031,088 $ 2,706,863 $ 47,463 $ 5,670 $ 2,748,656 Other Securities: Federal Home Loan Bank common stock $ 9,896 $ 9,896 $ 12,191 $ 12,191 Federal Reserve Bank common stock 30,690 30,690 19,781 19,781 Certificates of deposit 3,865 3,865 0 0 Other equity securities 5,840 5,840 3,764 3,764 Total other securities $ 50,291 $ 50,291 $ 35,736 $ 35,736 A summary of investment securities that have been in a continuous unrealized loss position for less than or greater than twelve months is as follows: As of December 31, 2017 Less than 12 Months 12 Months or Longer Total (000's omitted) # Fair Value Gross Unrealized Losses # Fair Value Gross Unrealized Losses # Fair Value Gross Unrealized Losses Available-for-Sale Portfolio: U.S. Treasury and agency securities 44 $ 699,709 $ 4,838 0 $ 0 $ 0 44 $ 699,709 $ 4,838 Obligations of state and political subdivisions 45 23,432 57 0 0 0 45 23,432 57 Government agency mortgage-backed securities 120 185,716 1,433 55 75,712 2,330 175 261,428 3,763 Corporate debt securities 1 2,623 25 0 0 0 1 2,623 25 Government agency collateralized mortgage obligations 39 80,041 878 1 1 0 40 80,042 878 Total available-for-sale investment portfolio 249 $ 991,521 $ 7,231 56 $ 75,713 $ 2,330 305 $ 1,067,234 $ 9,561 As of December 31, 2016 Less than 12 Months 12 Months or Longer Total (000's omitted) # Fair Value Gross Unrealized Losses # Fair Value Gross Unrealized Losses # Fair Value Gross Unrealized Losses Available-for-Sale Portfolio: U.S. Treasury and agency securities 13 $ 449,242 $ 2,118 0 $ 0 $ 0 13 $ 449,242 $ 2,118 Obligations of state and political subdivisions 197 102,106 1,054 0 0 0 197 102,106 1,054 Government agency mortgage-backed securities 57 83,862 1,637 15 21,788 830 72 105,650 2,467 Corporate debt securities 1 2,677 31 0 0 0 1 2,677 31 Government agency collateralized mortgage obligations 0 0 0 2 2 0 2 2 0 Total available-for-sale investment portfolio 268 $ 637,887 $ 4,84 0 17 $ 21,790 $ 830 285 $ 659,677 $ 5,67 0 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. 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 December 31, 2017 represents OTTI. The amortized cost and estimated fair value of debt securities at December 31, 2017, 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 (000's omitted) Amortized Cost Fair Value Due in one year or less $ 45,966 $ 46,042 Due after one through five years 1,565,423 1,572,634 Due after five years through ten years 758,742 769,828 Due after ten years 190,489 197,146 Subtotal 2,560,620 2,585,650 Government agency mortgage-backed securities 358,180 357,538 Government agency collateralized mortgage obligations 88,097 87,374 Total $ 3,006,897 $ 3,030,562 Investment securities with a carrying value of $1.530 billion and $1.865 billion at December 31, 2017 and 2016, respectively, were pledged to collateralize certain deposits and borrowings. As of December 31, 2017, securities pledged to collateralize certain deposits and borrowings included $473.2 million of U.S. Treasury securities that were pledged as collateral for securities sold under agreement to repurchase. All securities sold under agreement to repurchase as of December 31, 2017 have an overnight and continuous maturity.

LOANS

LOANS	12 Months Ended
	Dec. 31, 2017
LOANS [Abstract]
LOANS	NOTE D: LOANS The segments of the Company’s loan portfolio are disaggregated into the following classes that allow management to monitor risk and performance: · Consumer mortgages consist primarily of fixed rate residential instruments, typically 10 – 30 years in contractual term, secured by first liens on real property. · Business lending is comprised of general purpose commercial and industrial loans including, but not limited to agricultural-related and dealer floor plans, as well as mortgages on commercial property. · Consumer indirect consists primarily of installment loans originated through selected dealerships and are secured by automobiles, marine and other recreational vehicles. · Consumer direct consists of all other loans to consumers such as personal installment loans and lines of credit. · Home equity products are consumer purpose installment loans or lines of credit most often secured by a first or second lien position on residential real estate with terms up to 30 years. The balances of these classes at December 31 are summarized as follows: (000's omitted) 2017 2016 Consumer mortgage $ 2,220,298 $ 1,819,701 Business lending 2,424,223 1,490,076 Consumer indirect 1,011,978 1,044,972 Consumer direct 179,929 191,815 Home equity 420,329 401,998 Gross loans, including deferred origination costs 6,256,757 4,948,562 Allowance for loan losses (47,583 ) (47,233 ) Loans, net of allowance for loan losses $ 6,209,174 $ 4,901,329 The Company had approximately $25.3 million and $22.8 million of net deferred loan origination costs included in gross loans as of December 31, 2017 and 2016, respectively. Certain directors and executive officers of the Company, as well as associates of such persons, are loan customers. Loans to these individuals were made in the ordinary course of business under normal credit terms and do not have more than a normal risk of collection. Following is a summary of the aggregate amount of such loans during 2017 and 2016. (000's omitted) 2017 2016 Balance at beginning of year $ 10,950 $ 11,337 New loans 16,617 4,959 Payments (5,223 ) (5,346 ) Balance at end of year $ 22,344 $ 10,950 Acquired loans Acquired loans are recorded at fair value as of the date of purchase with no allowance for loan loss. The outstanding principal balance and the related carrying amount of acquired loans included in the Consolidated Statement of Condition at December 31 are as follows: (000's omitted) 2017 2016 Credit impaired acquired loans: Outstanding principal balance $ 13,242 $ 6,354 Carrying amount 10,115 5,553 Non-impaired acquired loans: Outstanding principal balance 1,658,780 497,308 Carrying amount 1,626,979 489,807 Total acquired loans: Outstanding principal balance 1,672,022 503,662 Carrying amount 1,637,094 495,360 The outstanding balance related to credit impaired acquired loans was $13.4 million and $6.6 million at December 31, 2017 and 2016, respectively. The changes in the accretable discount related to the credit impaired acquired loans are as follows: (000's omitted) 2017 2016 Balance at beginning of year $ 498 $ 810 Merchants acquisition 793 0 Accretion recognized (905 ) (455 ) Net reclassification to accretable from nonaccretable 590 143 Balance at end of year $ 976 $ 498 Credit Quality Management monitors the credit quality of its loan portfolio on an ongoing basis. Measurement of delinquency and past due status are based on the contractual terms of each loan. Past due loans are reviewed on a monthly basis to identify loans for non-accrual status. The following is an aged analysis of the Company’s past due loans by class as of December 31, 2017: Legacy Loans (000’s omitted) Past Due 30 - 89 days 90+ Days Past Due and Still Accruing Nonaccrual Total Past Due Current Total Loans Consumer mortgage $ 13,564 $ 1,500 $ 10,722 $ 25,786 $ 1,728,823 $ 1,754,609 Business lending 2,283 571 3,944 6,798 1,369,801 1,376,599 Consumer indirect 14,197 295 0 14,492 977,344 991,836 Consumer direct 1,875 48 0 1,923 172,556 174,479 Home equity 1,116 94 1,354 2,564 319,576 322,140 Total $ 33,035 $ 2,508 $ 16,020 $ 51,563 $ 4,568,100 $ 4,619,663 Acquired Loans (000’s omitted) Past Due 30 - 89 days 90+ Days Past Due and Still Accruing Nonaccrual Total Past Due Acquired Impaired (1) Current Total Loans Consumer mortgage $ 2,603 $ 26 $ 3,066 $ 5,695 $ 0 $ 459,994 $ 465,689 Business lending 4,661 0 4,328 8,989 10,115 1,028,520 1,047,624 Consumer indirect 245 8 0 253 0 19,889 20,142 Consumer direct 100 0 0 100 0 5,350 5,450 Home equity 634 170 1,326 2,130 0 96,059 98,189 Total $ 8,243 $ 204 $ 8,720 $ 17,167 $ 10,115 $ 1,609,812 $ 1,637,094 (1) Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performing under ASC 310-30. As a result interest income, through the accretion of the difference between the carrying amount of the loans and the expected cashflows, is being recognized on all acquired impaired loans. The following is an aged analysis of the Company’s past due loans by class as of December 31, 2016: Legacy Loans (000’s omitted) Past Due 30 - 89 days 90+ Days Past Due and Still Accruing Nonaccrual Total Past Due Current Total Loans Consumer mortgage $ 11,379 $ 1,180 $ 11,352 $ 23,911 $ 1,635,849 $ 1,659,760 Business lending 3,921 145 3,811 7,877 1,269,789 1,277,666 Consumer indirect 13,883 166 0 14,049 1,000,776 1,014,825 Consumer direct 1,549 58 0 1,607 180,315 181,922 Home equity 1,250 414 1,437 3,101 315,928 319,029 Total $ 31,982 $ 1,963 $ 16,600 $ 50,545 $ 4,402,657 $ 4,453,202 Acquired Loans (000’s omitted) Past Due 30 - 89 days 90+ Days Past Due and Still Accruing Nonaccrual Total Past Due Acquired Impaired (1) Current Total Loans Consumer mortgage $ 1,539 $ 205 $ 2,332 $ 4,076 $ 0 $ 155,865 $ 159,941 Business lending 528 0 1,252 1,780 5,553 205,077 212,410 Consumer indirect 231 3 0 234 0 29,913 30,147 Consumer direct 231 0 0 231 0 9,662 9,893 Home equity 778 905 435 2,118 0 80,851 82,969 Total $ 3,307 $ 1,113 $ 4,019 $ 8,439 $ 5,553 $ 481,368 $ 495,360 (1) Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performing under ASC 310-30. As a result interest income, through the accretion of the difference between the carrying amount of the loans and the expected cashflows, is being recognized on all acquired impaired loans. The 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. 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. Classified The condition of the borrower has significantly deteriorated and the performance of the loan could further deteriorate 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. The following table shows the amount of business lending loans by credit quality category: December 31, 2017 December 31, 2016 (000’s omitted) Legacy Acquired Total Legacy Acquired Total Pass $ 1,170,156 $ 963,981 $ 2,134,137 $ 1,051,005 $ 162,165 $ 1,213,170 Special mention 129,076 37,321 166,397 135,602 29,690 165,292 Classified 77,367 34,628 111,995 90,585 15,002 105,587 Doubtful 0 1,579 1,579 474 0 474 Acquired impaired 0 10,115 10,115 0 5,553 5,553 Total $ 1,376,599 $ 1,047,624 $ 2,424,223 $ 1,277,666 $ 212,410 $ 1,490,076 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 current, 30 – 89 days past due and acquired impaired loans. Nonperforming loans include 90+ days past due and still accruing and nonaccrual loans. The following tables detail the balances in all loan categories except for business lending at December 31, 2017: Legacy loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 1,742,387 $ 991,541 $ 174,431 $ 320,692 $ 3,229,051 Nonperforming 12,222 295 48 1,448 14,013 Total $ 1,754,609 $ 991,836 $ 174,479 $ 322,140 $ 3,243,064 Acquired loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 462,597 $ 20,134 $ 5,450 $ 96,693 $ 584,874 Nonperforming 3,092 8 0 1,496 4,596 Total $ 465,689 $ 20,142 $ 5,450 $ 98,189 $ 589,470 The following table details the balances in all other loan categories at December 31, 2016: Legacy loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 1,647,228 $ 1,014,659 $ 181,864 $ 317,178 $ 3,160,929 Nonperforming 12,532 166 58 1,851 14,607 Total $ 1,659,760 $ 1,014,825 $ 181,922 $ 319,029 $ 3,175,536 Acquired loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 157,404 $ 30,144 $ 9,893 $ 81,629 $ 279,070 Nonperforming 2,537 3 0 1,340 3,880 Total $ 159,941 $ 30,147 $ 9,893 $ 82,969 $ 282,950 All loan classes are collectively evaluated for impairment except business lending, as described in Note A. A summary of individually evaluated impaired loans as of December 31, 2017 and 2016 is as follows: (000’s omitted) 2017 2016 Loans with allowance allocation $ 5,125 $ 1,109 Loans without allowance allocation 884 556 Carrying balance 6,009 1,665 Contractual balance 9,165 3,340 Specifically allocated allowance 804 477 Average impaired loans 9,517 4,683 Interest income recognized 0 0 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. With regard to determination of the amount of the allowance for loan losses, troubled debt restructured loans are considered to be impaired. As a result, the determination of the amount of allowance for loan losses related to impaired loans for each portfolio segment within TDRs is the same as detailed previously. In accordance with clarified guidance issued by the 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 2017, 2016 and 2015 was immaterial. TDRs less than $0.5 million are collectively included in the general loan loss allocation and the qualitative review, if necessary. Commercial loans greater than $0.5 million are individually evaluated for impairment, and if necessary, a specific allocation of the allowance for loan losses is provided. Information regarding TDRs as of December 31, 2017 and December 31, 2016 is as follows December 31, 2017 December 31, 2016 (000’s omitted) Nonaccrual Accruing Total Nonaccrual Accruing Total # Amount # Amount # Amount # Amount # Amount # Amount Consumer mortgage 51 $ 2,265 44 $ 1,750 95 $ 4,015 36 $ 1,520 45 $ 1,956 81 $ 3,476 Business lending 8 218 7 501 15 719 6 91 5 690 11 781 Consumer indirect 0 0 71 883 71 883 0 0 78 771 78 771 Consumer direct 0 0 25 69 25 69 0 0 23 65 23 65 Home equity 13 245 7 204 20 449 14 221 7 216 21 437 Total 72 $ 2,728 154 $ 3,407 226 $ 6,135 56 $ 1,832 158 $ 3,698 214 $ 5,530 The following table presents information related to loans modified in a TDR during the years ended December 31, 2017 and 2016. Of the loans noted in the table below, all loans for the years ended December 31, 2017 and December 31, 2016, were modified due to a Chapter 7 bankruptcy as described previously. The financial effects of these restructurings were immaterial. December 31, 2017 December 31, 2016 (000’s omitted) # Amount # Amount Consumer mortgage 23 $ 1,254 9 $ 597 Business lending 8 412 0 0 Consumer indirect 33 490 33 459 Consumer direct 6 17 3 51 Home equity 4 95 3 50 Total 74 $ 2,268 48 $ 1,157 Allowance for Loan Losses The allowance for loan losses is general in nature and is available to absorb losses from any loan type despite the analysis below. The following presents by class the activity in the allowance for loan losses: (000’s omitted) Consumer Mortgage Business Lending Consumer Indirect Consumer Direct Home Equity Unallocated Acquired Impaired Total Balance at December 31, 2014 $ 10,286 $ 15,787 $ 11,544 $ 3,083 $ 2,701 $ 1,767 $ 173 $ 45,341 Charge-offs (1,374 ) (2,146 ) (6,714 ) (1,490 ) (244 ) 0 (103 ) (12,071 ) Recoveries 80 877 3,943 722 62 0 0 5,684 Provision 1,206 1,231 3,649 682 147 (566 ) 98 6,447 Balance at December 31, 2015 10,198 15,749 12,422 2,997 2,666 1,201 168 45,401 Charge-offs (647 ) (1,872 ) (7,643 ) (1,706 ) (218 ) 0 (97 ) (12,183 ) Recoveries 115 616 4,168 901 139 0 0 5,939 Provision 428 2,727 4,835 787 (188 ) (550 ) 37 8,076 Balance at December 31, 2016 10,094 17,220 13,782 2,979 2,399 651 108 47,233 Charge-offs (707 ) (4,959 ) (8,456 ) (2,081 ) (284 ) 0 (270 ) (16,757 ) Recoveries 50 656 4,516 849 52 0 0 6,123 Provision 1,028 4,340 3,626 1,292 (60 ) 449 309 10,984 Balance at December 31, 2017 $ 10,465 $ 17,257 $ 13,468 $ 3,039 $ 2,107 $ 1,100 $ 147 $ 47,583

PREMISES AND EQUIPMENT

PREMISES AND EQUIPMENT	12 Months Ended
	Dec. 31, 2017
PREMISES AND EQUIPMENT [Abstract]
PREMISES AND EQUIPMENT	NOTE E: PREMISES AND EQUIPMENT Premises and equipment consist of the following at December 31: (000's omitted) 2017 2016 Land and land improvements $ 23,869 $ 22,585 Bank premises 131,647 116,663 Equipment and construction in progress 86,059 80,527 Premises and equipment, gross 241,575 219,775 Accumulated depreciation (118,182 ) (107,457 ) Premises and equipment, net $ 123,393 $ 112,318

GOODWILL AND IDENTIFIABLE INTAN

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS	12 Months Ended
	Dec. 31, 2017
GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS [Abstract]
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: December 31, 2017 December 31, 2016 (000's omitted) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Amortizing intangible assets: Core deposit intangibles $ 62,902 $ (37,877 ) $ 25,025 $ 39,688 $ (32,581 ) $ 7,107 Other intangibles 86,535 (20,902 ) 65,633 17,853 (9,258 ) 8,595 Total amortizing intangibles $ 149,437 $ (58,779 ) $ 90,658 $ 57,541 $ (41,839 ) $ 15,702 The estimated aggregate amortization expense for each of the five succeeding fiscal years ended December 31 is as follows: 2018 $ 17 , 2019 15,033 2020 12,497 2021 10,665 2022 9,165 Thereafter 25,426 Total $ 90,658 Shown below are the components of the Company’s goodwill at December 31, 2017 and 2016: (000’s omitted) Year Ended December 31, 2015 Activity Year Ended December 31, 2016 Activity Year Ended December 31, 2017 Goodwill $ 468,076 $ 1,890 $ 469,966 $ 269,288 $ 739,254 Accumulated impairment (4,824 ) 0 (4,824 ) 0 (4,824 ) Goodwill, net $ 463,252 $ 1,890 $ 465,142 $ 269,288 $ 734,430 During the first quarter of 2017, the Company performed its annual internal valuation of goodwill and impairment analysis by comparing the fair value of each reporting unit to its carrying value. Results of the valuations indicate there was no goodwill impairment. Mortgage Servicing Rights Under certain circumstances, the Company sells consumer residential mortgage loans in the secondary market and typically retains the right to service the loans sold. Generally, the Company’s residential mortgage loans sold to third parties are sold on a non-recourse basis. Upon sale, a mortgage servicing right (“MSR”) is established, which represents the current fair value of future net cash flows expected to be realized for performing the servicing activities. The Company stratifies these assets based on predominant risk characteristics, namely expected term of the underlying financial instruments, and uses a valuation model that calculates the present value of future cash flows to determine the fair value of servicing rights. MSRs are recorded in other assets at the lower of the initial capitalized amount, net of accumulated amortization or fair value. Mortgage loans serviced for others are not included in the accompanying consolidated statements of condition. The following table summarizes the changes in carrying value of MSRs and the associated valuation allowance: (000’s omitted) 2017 2016 Carrying value before valuation allowance at beginning of period $ 1,435 $ 1,472 Additions 358 481 Merchants acquisition 64 0 Amortization (499 ) (518 ) Carrying value before valuation allowance at end of period 1,358 1,435 Valuation allowance balance at beginning of period 0 0 Impairment charges 0 (226 ) Impairment recoveries 0 226 Valuation allowance balance at end of period 0 0 Net carrying value at end of period $ 1,358 $ 1,435 Fair value of MSRs at end of period $ 2,473 $ 1,928 Principal balance of loans sold during the year $ 32,937 $ 45,852 Principal balance of loans serviced for others $ 358,518 $ 365,374 Custodial escrow balances maintained in connection with loans serviced for others $ 5,363 $ 5,603 The following table summarizes the key economic assumptions used to estimate the value of the MSRs at December 31: 2017 2016 Weighted-average contractual life (in years) 21.3 20.8 Weighted-average constant prepayment rate (CPR) 11.1 % 15.1 % Weighted-average discount rate 3.3 % 3.5 %

DEPOSITS

DEPOSITS	12 Months Ended
	Dec. 31, 2017
DEPOSITS [Abstract]
DEPOSITS	NOTE G: DEPOSITS Deposits consist of the following at December 31: (000's omitted) 2017 2016 Noninterest checking $ 2,293,057 $ 1,646,039 Interest checking 1,830,914 1,644,029 Savings 1,421,512 1,303,851 Money market 2,124,633 1,778,907 Time 774,304 703,128 Total deposits $ 8,444,420 $ 7,075,954 The approximate maturities of time deposits at December 31, 2017 are as follows: (000's omitted) All Accounts Accounts $250,000 or Greater 2018 $ 545,389 $ 51,875 2019 100,833 5,958 2020 59,849 7,445 2021 34,582 1,807 2022 33,400 601 Thereafter 251 0 Total $ 774,304 $ 67,686

BORROWINGS

BORROWINGS	12 Months Ended
	Dec. 31, 2017
BORROWINGS [Abstract]
BORROWINGS	NOTE H: BORROWINGS Outstanding borrowings at December 31 are as follows: (000's omitted) 2017 2016 FHLB overnight advance $ 24,000 $ 146,200 Subordinated debt held by unconsolidated subsidiary trusts, net of discount of $332 and $357, respectively 122,814 102,170 Securities sold under agreement to repurchase, short term 337,011 0 FHLB Long term advances 2,071 0 Total borrowings $ 485,896 $ 248,370 FHLB advances are collateralized by a blanket lien on the Company's residential real estate loan portfolio and various investment securities. Borrowings at December 31, 2017 have contractual maturity dates as follows: (000's omitted, except rate) Carrying Value Weighted-average Rate at December 31, 2017 January 2, 2018 $ 361,011 0.54 % July 3, 2023 601 2.25 % October 23, 2023 515 1.50 % October 1, 2025 329 1.50 % March 1, 2029 626 2.50 % July 31, 2031 24,875 4.96 % December 15, 2034 20,619 3.54 % December 15, 2036 77,320 3.24 % Total $ 485,896 1.34 % The weighted-average interest rate on borrowings for the years ended December 31, 2017 and 2016 was 1.51% and 1.46%, respectively. The Company sponsors three business trusts, Community Statutory Trust III (“CST III”), Community Capital Trust IV (“CCT IV”) and MBVT Statutory Trust I (“MBVT I”), of which 100% of the common stock is owned by the Company. The common stock of MBVT Statutory Trust I was acquired in the Merchants acquisition. The trusts were formed for the purpose of issuing company-obligated mandatorily redeemable preferred securities to third-party investors and investing the proceeds from the sale of such preferred securities solely in junior subordinated debt securities of the Company. The debentures held by each trust are the sole assets of such trust. Distributions on the preferred securities issued by each trust are payable quarterly at a rate per annum equal to the interest rate being earned by the trust on the debentures held by that trust and are recorded as interest expense in the consolidated financial statements. The preferred securities are subject to mandatory redemption, in whole or in part, upon repayment of the debentures. The Company has entered into agreements which, taken collectively, fully and unconditionally guarantee the preferred securities subject to the terms of each of the guarantees. The terms of the preferred securities of each trust are as follows: Trust Issuance Date Par Amount Interest Rate Maturity Date Call Price CST III 7/31/2001 $24.5 million 3 month LIBOR plus 3.58% (4.96%) 7/31/2031 Par CCT IV 12/8/2006 $75.0 million 3 month LIBOR plus 1.65% (3.24%) 12/15/2036 Par MBVT I 12/15/2004 $20.6 million 3 month LIBOR plus 1.95% (3.54%) 12/15/2034 Par

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2017
INCOME TAXES [Abstract]
INCOME TAXES	NOTE I: INCOME TAXES The provision for income taxes for the years ended December 31 is as follows: (000's omitted) 2017 2016 2015 Current: Federal $ 31,152 $ 32,829 $ 27,663 State and other 6,788 4,890 2,608 Deferred: Federal (28,146 ) 11,444 9,604 State and other (546 ) 1,622 1,112 Provision for income taxes $ 9,248 $ 50,785 $ 40,987 Components of the net deferred tax liability, included in other liabilities, as of December 31 are as follows: (000's omitted) 2017 2016 Allowance for loan losses $ 11,675 $ 18,366 Employee benefits 4,216 6,311 Debt extinguishment 0 299 Other, net 0 5,202 Deferred tax asset 15,891 30,178 Investment securities 22,690 32,839 Tax-deductible goodwill 39,154 43,504 Loan origination costs 6,109 8,228 Depreciation 2,372 71 Mortgage servicing rights 330 548 Pension 13,228 18,194 Other, net 542 0 Deferred tax liability 84,425 103,384 Net deferred tax liability $ (68,534 ) $ (73,206 ) The Company has determined that no valuation allowance is necessary as it is more likely than not that the gross deferred tax assets will be realized through carryback of future deductions to taxable income in prior years, future reversals of existing temporary differences, and through future taxable income. A reconciliation of the differences between the federal statutory income tax rate and the effective tax rate for the years ended December 31 is shown in the following table: 2017 2016 2015 Federal statutory income tax rate 35.0 % 35.0 % 35.0 % Increase (reduction) in taxes resulting from: Tax-exempt interest (3.8 ) (4.0 ) (5.0 ) State income taxes, net of federal benefit 2.5 2.7 1.8 Stock-based compensation (2.0 ) 0 0 Federal deferred tax revaluation adjustment (23.7 ) 0 0 Other, net (2.2 ) (0.9 ) (0.8 ) Effective income tax rate 5.8 % 32.8 % 31.0 % A reconciliation of the unrecognized tax benefits for the years ended December 31 is shown in the following table: (000’s omitted) 2017 2016 2015 Unrecognized tax benefits at beginning of year $ 92 $ 127 $ 162 Changes related to: Lapse of statutes of limitations (68 ) (35 ) (35 ) Unrecognized tax benefits at end of year $ 24 $ 92 $ 127 As of December 31, 2017, the total amount of unrecognized tax benefits that would impact the Company’s effective tax rate if recognized is $0.02 million. It is reasonably possible that the amount of unrecognized tax benefits could change in the next twelve months as a result of various examinations and expiration of statutes of limitations on prior tax returns. The Company’s policy is to recognize interest and penalties related to unrecognized tax benefits as part of income taxes in the consolidated statement of income. The accrued interest related to tax positions was immaterial. The Company’s federal and state income tax returns are routinely subject to examination from various governmental taxing authorities. Such examinations may result in challenges to the tax return treatment applied by the Company to specific transactions. Management believes that the assumptions and judgment used to record tax-related assets or liabilities have been appropriate. Future examinations by taxing authorities of the Company’s federal or state tax returns could have a material impact on the Company’s results of operations. The Company’s federal income tax returns for years after 2013 may still be examined by the Internal Revenue Service. New York State income tax returns for years after 2012 may still be examined by the New York Department of Taxation and Finance. It is not possible to estimate, if and when those examinations may be completed. On December 22, 2017, H.R.1, referred to as the “Tax Cuts and Jobs Act,” was signed into law. Among other things, the Tax Cuts and Jobs Act permanently lowers the corporate tax rate to 21% from the existing maximum rate of 35%, effective for tax years including or commencing January 1, 2018. ASC 740, Income Taxes On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”), which provided guidance on reporting accounting impacts of the recently enacted tax reform legislation. In SAB 118, it is noted that reporting companies may be unable to complete the accounting for certain income tax effects of the Tax Cuts and Jobs Act by the time financial statements are issued for the reporting period in which the Tax Cuts and Jobs Act was enacted (the “Enactment Period”). SAB 118 provides guidance for the scenarios in which a company does not have the necessary information available, prepared or analyzed to complete the accounting for certain income tax effects when it issues financial statements covering the Enactment Period. In those cases, SAB 118 would permit the company to provide “reasonable estimates” for the income tax effects of the Tax Cuts and Jobs Act and to report those effects as “provisional amounts” in its financial statements during a limited “measurement period.” Based on the review of its deferred tax assets and liabilities, the Company notes that the accounting for the enactment of the Tax Cuts and Jobs Act is complete and the effects have been appropriately reflected in the consolidated statement of condition as of December 31, 2017 and the consolidated statement of income for the year ended December 31, 2017.

LIMITS ON DIVIDENDS AND OTHER R

LIMITS ON DIVIDENDS AND OTHER REVENUE SOURCES	12 Months Ended
	Dec. 31, 2017
LIMITS ON DIVIDENDS AND OTHER REVENUE SOURCES [Abstract]
LIMITS ON DIVIDENDS AND OTHER REVENUE SOURCES	NOTE J: LIMITS ON DIVIDENDS AND OTHER REVENUE SOURCES The Company’s ability to pay dividends to its shareholders is largely dependent on the Bank’s ability to pay dividends to the Company. In addition to the capital requirements discussed below, the circumstances under which the Bank may pay dividends are limited by federal statutes, regulations, and policies. For example, as a national bank, the Bank must obtain the approval of the Office of the Comptroller of the Currency (“OCC”) for payments of dividends if the total of all dividends declared in any calendar year would exceed the total of the Bank’s net profits, as defined by applicable regulations, for that year, combined with its retained net profits for the preceding two years. Furthermore, the Bank may not pay a dividend in an amount greater than its undivided profits then on hand after deducting its losses and bad debts, as defined by applicable regulations. At December 31, 2017, the Bank had approximately $69.0 million in undivided profits legally available for the payment of dividends. In addition, the Board of Governors of the Federal Reserve System (“FRB”) and the OCC are authorized to determine under certain circumstances that the payment of dividends would be an unsafe or unsound practice and to prohibit payment of such dividends. The FRB has indicated that banking organizations should generally pay dividends only out of current operating earnings. There are also statutory limits on the transfer of funds to the Company by its banking subsidiary, whether in the form of loans or other extensions of credit, investments or assets purchases. Such transfer by the Bank to the Company generally is limited in amount to 10% of the Bank’s capital and surplus, or 20% in the aggregate. Furthermore, such loans and extensions of credit are required to be collateralized in specific amounts.

BENEFIT PLANS

BENEFIT PLANS	12 Months Ended
	Dec. 31, 2017
BENEFIT PLANS [Abstract]
BENEFIT PLANS	NOTE K: BENEFIT PLANS Pension and post-retirement 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. Using a measurement date of December 31, the following table shows the funded status of the Company's plans reconciled with amounts reported in the Company's consolidated statements of condition: Pension Benefits Post-retirement Benefits (000's omitted) 2017 2016 2017 2016 Change in benefit obligation: Benefit obligation at the beginning of year $ 127,084 $ 127,134 $ 1,806 $ 1,918 Service cost 4,181 4,106 0 0 Interest cost 5,717 5,624 76 82 Plan amendment / acquisition 11,646 22 0 0 Participant contributions 0 0 467 516 Deferred actuarial loss/(gain) 8,978 (1,628 ) 245 174 Benefits paid (10,156 ) (8,174 ) (809 ) (884 ) Benefit obligation at end of year 147,450 127,084 1,785 1,806 Change in plan assets: Fair value of plan assets at beginning of year 180,400 172,026 0 0 Actual return of plan assets 22,954 14,402 0 0 Participant contributions 0 0 467 516 Employer contributions 9,839 2,146 342 368 Plan acquisition 14,070 0 0 0 Benefits paid (10,156 ) (8,174 ) (809 ) (884 ) Fair value of plan assets at end of year 217,107 180,400 0 0 Over/(Under) funded status at year end $ 69,657 $ 53,316 $ (1,785 ) $ (1,806 ) Amounts recognized in the consolidated statement of condition were: Other assets $ 81,000 $ 64,709 $ 0 $ 0 Other liabilities (11,343 ) (11,393 ) (1,785 ) (1,806 ) Amounts recognized in accumulated other comprehensive income (loss) (“AOCI”) were: Net loss $ 26,935 $ 28,323 $ 420 $ 183 Net prior service cost (credit) 2,944 2,264 (1,622 ) (1,801 ) Pre-tax AOCI 29,879 30,587 (1,202 ) (1,618 ) Taxes (7,340 ) (11,622 ) 296 614 AOCI at year end $ 22,539 $ 18,965 $ (906 ) $ (1,004 ) The benefit obligation for the defined benefit pension plan was $136.1 million and $115.7 million as of December 31, 2017 and 2016, respectively, and the fair value of plan assets as of December 31, 2017 and 2016 was $217.1 million and $180.4 million, respectively. Effective May 12, 2017, the Merchants Bank Pension Plan was merged into the Community Bank System, Inc. Pension Plan and the combined plan was revalued resulting in an additional unamortized actuarial gain of approximately $1.9 million, due primarily to a gain on plan assets that was partially offset by a decrease in the discount rate from 4.50% to 4.40% as of the valuation date. The Company has unfunded supplemental pension plans for certain key active and retired executives. The projected benefit obligation for the unfunded supplemental pension plan for certain key executives was $11.3 million for 2017 and 2016. The Company also has an unfunded stock balance plan for certain of its nonemployee directors. The projected benefit obligation for the unfunded stock balance plan was $0.1 million for 2017 and 2016. The plan was frozen effective December 31, 2009. Effective December 31, 2009, the Company terminated its post-retirement medical program for current and future employees. Remaining plan participants will include only existing retirees as of December 31, 2010. This change was accounted for as a negative plan amendment and a $3.5 million, net of income taxes, benefit for prior service was recognized in AOCI in 2009. This negative plan amendment is being amortized over the expected benefit utilization period of remaining plan participants. Amounts recognized in accumulated other comprehensive income, net of tax, for the year ended December 31, are as follows: Pension Benefits Post-retirement Benefits (000's omitted) 2017 2016 2017 2016 Prior service cost/(credit) $ 424 $ (26 ) $ 111 $ 110 Net (gain) loss (851 ) (3,517 ) 148 111 Total $ (427 ) $ (3,543 ) $ 259 $ 221 The estimated costs, net of tax, that will be amortized from accumulated other comprehensive (income) loss into net periodic (income) cost over the next fiscal year are as follows: (000's omitted) Pension Benefits Post-retirement Benefits Prior service credit $ (330 ) $ (179 ) Net loss 1,054 18 Total $ 724 $ (161 ) The weighted-average assumptions used to determine the benefit obligations as of December 31 are as follows: Pension Benefits Post-retirement Benefits 2017 2016 2017 2016 Discount rate 4.00 % 4.50 % 4.00 % 4.40 % Expected return on plan assets 7.00 % 7.00 % N/A N/A Rate of compensation increase 3.50 % 3.50 % N/A N/A The net periodic benefit cost as of December 31 is as follows: Pension Benefits Post-retirement Benefits (000's omitted) 2017 2016 2015 2017 2016 2015 Service cost $ 4,181 $ 4,106 $ 3,324 $ 0 $ 0 $ 0 Interest cost 5,717 5,624 5,506 76 82 87 Expected return on plan assets (13,354 ) (11,842 ) (12,169 ) 0 0 0 Plan amendment 0 20 0 0 0 0 Amortization of unrecognized net loss/(gain) 767 1,508 1,466 8 (5 ) (13 ) Amortization of prior service cost 55 43 8 (179 ) (179 ) (179 ) Net periodic (benefit) $ (2,634 ) $ (541 ) $ (1,865 ) $ (95 ) $ (102 ) $ (105 ) Prior service costs in which all or almost all of the plan’s participants are fully eligible for benefits under the plan are amortized on a straight-line basis over the expected future working years of all active plan participants. Unrecognized gains or losses are amortized using the “corridor approach”, which is the minimum amortization required. Under the corridor approach, the net gain or loss in excess of 10 percent of the greater of the projected benefit obligation or the market-related value of the assets is amortized on a straight-line basis over the expected future working years of all active plan participants. The weighted-average assumptions used to determine the net periodic pension cost for the years ended December 31 are as follows: Pension Benefits Post-retirement Benefits 2017 2016 2015 2017 2016 2015 Discount rate 4.40 % 4.70 % 4.50 % 4.40 % 4.70 % 4.50 % Expected return on plan assets 7.00 % 7.00 % 7.00 % N/A N/A N/A Rate of compensation increase 3.50 % 3.50 % 3.50 % N/A N/A N/A The amount of benefit payments that are expected to be paid over the next ten years are as follows: (000's omitted) Pension Benefits Post-retirement Benefits 2018 $ 8,702 $ 145 2019 9,163 142 2020 9,404 139 2021 9,943 136 2022 10,378 133 2023-2027 56,064 618 The payments reflect future service and are based on various assumptions including retirement age and form of payment (lump-sum versus annuity). Actual results may differ from these estimates. The assumed discount rate is used to reflect the time value of future benefit obligations. The discount rate was determined based upon the yield on high-quality fixed income investments expected to be available during the period to maturity of the pension benefits. This rate is sensitive to changes in interest rates. A decrease in the discount rate would increase the Company’s obligation and future expense while an increase would have the opposite effect. The expected long-term rate of return was estimated by taking into consideration asset allocation, reviewing historical returns on the type of assets held and current economic factors. Based on the Company’s anticipation of future experience under the defined benefit pension plan, the mortality tables used to determine future benefit obligations under the plan were updated as of December 31, 2017 to the RP-2014 Mortality Table for annuitants and non-annuitants, adjusted backward to 2006 with Scale MP-2014, and then adjusted for mortality improvements with the Scale MP-2016 mortality improvement scale on a fully generational basis. The appropriateness of the assumptions is reviewed annually. Plan Assets The investment objective for the defined benefit pension plan is to achieve an average annual total return over a five-year period equal to the assumed rate of return used in the actuarial calculations. At a minimum performance level, the portfolio should earn the return obtainable on high quality intermediate-term bonds. The Company’s perspective regarding portfolio assets combines both preservation of capital and moderate risk-taking. Asset allocation favors equities, with a target allocation of approximately 60% equity securities and 40% fixed income securities and money market funds. Due to the volatility in the market, the target allocation is not always desirable and asset allocations will fluctuate between acceptable ranges. Prohibited transactions include purchase of securities on margin, uncovered call options, and short sale transactions. The fair values of the Company’s defined benefit pension plan assets at December 31, 2017 by asset category are as follows: Asset category (000’s omitted) Quoted Prices in Active Markets for Identical Assets Level 1 Significant Observable Inputs Level 2 Significant Unobservable Inputs Level 3 Total Money Market Accounts $ 0 $ 10,381 $ 0 $ 10,381 Equity securities: U.S. large-cap 53,154 0 0 53,154 U.S mid/small cap 26,309 0 0 26,309 CBU stock 8,344 0 0 8,344 International 47,723 0 0 47,723 135,530 0 0 135,530 Fixed income securities: Government securities 13,929 9,686 0 23,615 Investment grade bonds 19,278 0 0 19,278 High yield (a) 16,297 0 0 16,297 49,504 9,686 0 59,190 Other investments (b) 11,302 73 0 11,375 Total (c) $ 196,336 $ 20,140 $ 0 $ 216,476 The fair values of the Company’s defined benefit pension plan assets at December 31, 2016 by asset category are as follows: Asset category (000’s omitted) Quoted Prices in Active Markets for Identical Assets Level 1 Significant Observable Inputs Level 2 Significant Unobservable Inputs Level 3 Total Money Market Accounts $ 103 $ 8,048 $ 0 $ 8,151 Equity securities: U.S. large-cap 43,235 0 0 43,235 U.S mid/small cap 19,032 0 0 19,032 CBU stock 7,417 0 0 7,417 International 27,064 0 0 27,064 96,748 0 0 96,748 Fixed income securities: Government securities 25,375 5,863 0 31,238 Investment grade bonds 15,253 0 0 15,253 High yield (a) 16,615 0 0 16,615 57,243 5,863 0 63,106 Other investments (b) 12,023 58 0 12,081 Total (c) $ 166,117 $ 13,969 $ 0 $ 180,086 (a) This category is exchange-traded funds representing a diversified index of high yield corporate bonds. (b) This category is comprised of exchange-traded funds and mutual funds holding non-traditional investment classes including private equity funds and alternative exchange funds. (c) Excludes dividends and interest receivable totaling $0.6 million and $0.3 million at December 31, 2017 and 2016, respectively. The valuation techniques used to measure fair value for the items in the table above are as follows: · Money market funds - Managed portfolios, including commercial paper and other fixed income securities issued by U.S. and foreign corporations, asset-backed commercial paper, U.S. government securities, obligations of foreign governments and U.S. and foreign banks, which are valued at the closing price reported on the market on which the underlying securities are traded. · Equity securities and other investments – Mutual funds, equity securities and common stock of the Company which are valued at the quoted market price of shares held at year-end. · Fixed income securities - U.S. Treasuries, municipal bonds and notes, government sponsored entities, and corporate debt valued at the closing price reported on the active market on which the individual securities are traded or for municipal bonds and notes based on quoted prices for similar assets in the active market. The Company makes contributions to its funded qualified pension plan as required by government regulation or as deemed appropriate by management after considering the fair value of plan assets, expected return on such assets, and the value of the accumulated benefit obligation. The Company made a $2.0 million contribution to the Merchants Bank Pension Plan in 2017. The Company made a $7.2 million contribution to its defined benefit pension plan in 2017. The Company funds the payment of benefit obligations for the supplemental pension and post-retirement plans because such plans do not hold assets for investment. Tupper Lake National Bank (“TLNB”), acquired in 2007, participated in the Pentegra Defined Benefit Plan for Financial Institutions (“Pentegra DB Plan”), a multi-employer tax qualified defined benefit pension plan. The identification number and plan number of the Pentegra DB Plan are 13-5645888 and 333, respectively. All employees of TLNB who met minimum service requirements participated in the plan. As of June 30, 2016, the Pentegra DB Plan had total assets of $3.3 billion, actuarial present value of accumulated benefits of $4.8 billion and was at least 80 percent funded. The assets of the multi-employer plan may be used to satisfy obligations of any of the employers participating in the plan. As a result, contributions made by the Company may be used to provide benefits to participants of other participating employers. Contributions for 2017, 2016 and 2015 were approximately $0.1 million, $0.05 million, and $0.03 million, respectively. Contributions made by the Company to the Pentegra DB Plan do not represent more than 5% of contributions made to the Pentegra DB Plan. The assumed health care cost trend rate used in the post-retirement health plan at December 31, 2017 was 7.25% for the pre-65 participants and 5.00% for the post-65 participants for medical costs and 10.5% for prescription drugs. The rate to which the cost trend rate is assumed to decline (the ultimate trend rate) and the year that the rate reaches the ultimate trend rate is 3.89% and 2075, respectively. Assumed health care cost trend rates impact the amounts reported for the health care plan. A one-percentage-point increase or decrease in the trend rate would increase the service and interest cost components by nominal amounts. 401(k) Employee Stock Ownership Plan The Company has a 401(k) Employee Stock Ownership Plan in which employees can contribute from 1% to 90% of eligible compensation, with the first 3% being eligible for a 100% matching contribution in the form of Company common stock and the next 3% being eligible for a 50% matching contributions in the form of Company common stock. The expense recognized under this plan for the years ended December 31, 2017, 2016 and 2015 was $5.3 million, $4.3 million, and $3.6 million, respectively. Effective January 1, 2010, the defined benefit pension plan was modified to a new plan design that includes an interest credit contribution to be made to the 401(k) plan. The expense recognized for this interest credit contribution for the years ended December 31, 2017, 2016, and 2015 was $0.8 million, $0.7 million, and $1.1 million, respectively. The Company acquired The Merchants Bank 401(k) ESOP Plan with the Merchants acquisition and The Gordon B. Roberts 401(k) Plan with the GBR acquisition. Effective January 1, 2018, The Merchants Bank 401(k) ESOP Plan and The Gordon B. Roberts 401(k) Plan were merged into and became part of the Community Bank System, Inc. 401(k) Employee Stock Ownership Plan. Other Deferred Compensation Arrangements In addition to the supplemental pension plans for certain executives, the Company has nonqualified deferred compensation arrangements for several former directors, officers and key employees. All benefits provided under these plans are unfunded and payments to plan participants are made by the Company. At December 31, 2017 and 2016, the Company has recorded a liability of $3.1 million and $3.2 million, respectively. The expense recognized under these plans for the years ended December 31, 2017, 2016, and 2015 was approximately $0.3 million, $0.03 million, and $0.1 million, respectively. Deferred Compensation Plans for Directors Directors of the Company may defer all or a portion of their director fees under the Deferred Compensation Plan for Directors. Under this plan, there is a separate account for each participating director which is credited with the amount of shares that could have been purchased with the director’s fees as well as any dividends on such shares. On the distribution date, the director will receive common stock equal to the accumulated share balance in their account. As of December 31, 2017 and 2016, there were 150,110 and 154,013 shares credited to the participants’ accounts, for which a liability of $4.2 million and $4.0 million was accrued, respectively. The expense recognized under the plan for the years ended December 31, 2017, 2016 and 2015, was $0.2 million, $0.2 million, and $0.2 million, respectively. The Company acquired deferred compensation plans for certain non-employee directors and trustees of Merchants. Under the terms of these acquired deferred compensation plans,

STOCK-BASED COMPENSATION PLANS

STOCK-BASED COMPENSATION PLANS	12 Months Ended
	Dec. 31, 2017
STOCK-BASED COMPENSATION PLANS [Abstract]
STOCK-BASED COMPENSATION PLANS	NOTE L: STOCK-BASED COMPENSATION PLANS The Company has a long-term incentive program for directors, officers and employees. Under this program, the Company initially authorized four million shares of Company common stock for the grant of incentive stock options, nonqualified stock options, restricted stock awards, and retroactive stock appreciation rights. The long-term incentive program was amended effective May 25, 2011, May 14, 2014 and May 17, 2017 to authorize an additional 900,000 shares, 1,000,000 shares and 1,000,000 shares of Company common stock, respectively, for the grant of incentive stock options, nonqualified stock options, restricted stock awards, and retroactive stock appreciation rights. As of December 31, 2017, the Company has authorization to grant up to approximately 1.7 million additional shares of Company common stock for these instruments. The nonqualified (offset) stock options in its Director’s Stock Balance Plan vest and become exercisable immediately and expire one year after the date the director retires or two years in the event of death. The remaining options have a ten-year term, and vest and become exercisable on a grant-by-grant basis, ranging from immediate vesting to ratably over a five-year period. Activity in this long-term incentive program is as follows: Stock Options Outstanding Weighted- average Exercise Price of Shares Outstanding at December 31, 2015 1,969,301 $ 28.15 Granted 330,383 38.02 Exercised (525,298 ) 25.12 Forfeited (18,394 ) 34.47 Outstanding at December 31, 2016 1,755,992 30.85 Granted 197,943 57.02 Exercised (238,499 ) 25.72 Forfeited (7,140 ) 37.47 Outstanding at December 31, 2017 1,708,296 34.57 Exercisable at December 31, 2017 1,015,823 $ 29.57 The following table summarizes the information about stock options outstanding under the Company’s stock option plan at December 31, 2017: Options outstanding Options exercisable Range of Exercise Price Shares Weighted- average Exercise Price Weighted- average Remaining Life (years) Shares Weighted average Exercise Price $ 0.00 – $18.00 24,736 $ 17.82 1.31 24,736 $ 17.82 $ 18.001 – $28.00 314,511 22.23 2.93 314,511 22.23 $ 28.001 – $29.00 171,083 28.78 4.22 171,083 28.78 $ 29.001 – $30.00 228,668 29.79 5.20 176,843 29.79 $ 30.001 – $40.00 771,781 37.09 7.28 317,005 37.06 $ 40.001 – $60.00 197,517 57.02 9.14 11,645 57.12 TOTAL 1,708,296 $ 34.57 6.02 1,015,823 $ 29.57 The weighted-average remaining contractual term of outstanding and exercisable stock options at December 31, 2017 is 6.02 years and 4.85 years, respectively. The aggregate intrinsic value of outstanding and exercisable stock options at December 31, 2017 is $33.4 million and $24.6 million, respectively. The Company recognized stock-based compensation expense related to non-qualified stock options of $2.2 million, $2.2 million and $1.8 million for the years ended December 31, 2017, 2016 and 2015, respectively. A related income tax benefit was recognized of $0.8 million, $0.8 million and $0.7 million for the 2017, 2016 and 2015 years, respectively. Compensation expense related to restricted stock vesting recognized in the income statement for 2017, 2016 and 2015 was approximately $2.7 million, $2.4 million and $2.2 million, respectively. Management estimated the fair value of options granted using the Black-Scholes option-pricing model. This model was originally developed to estimate the fair value of exchange-traded equity options, which (unlike employee stock options) have no vesting period or transferability restrictions. As a result, the Black-Scholes model is not necessarily a precise indicator of the value of an option, but it is commonly used for this purpose. The Black-Scholes model requires several assumptions, which management developed based on historical trends and current market observations. 2017 2016 2015 Weighted-average Fair Value of Options Granted $ 12.78 $ 7.90 $ 7.48 Assumptions: Weighted-average expected life (in years) 6.50 6.50 6.50 Future dividend yield 3.19 % 3.43 % 3.40 % Share price volatility 29.71 % 30.00 % 30.34 % Weighted-average risk-free interest rate 2.31 % 1.72 % 1.73 % Unrecognized stock-based compensation expense related to non-vested stock options totaled $4.6 million at December 31, 2017. The weighted-average period over which this unrecognized expense would be recognized is 3.2 years. The total fair value of stock options vested during 2017, 2016, and 2015 were $2.2 million, $2.1 million and $1.9 million, respectively. During the 12 months ended December 31, 2017 and 2016, proceeds from stock option exercises totaled $7.7 million and $12.0 million, respectively, and the related tax benefits from exercise were approximately $2.3 million and $2.7 million, respectively. During the twelve months ended December 31, 2017 and 2016, approximately 0.2 million and 0.4 million shares, respectively, were issued in connection with stock option exercises each year. The total intrinsic value of options exercised during 2017, 2016 and 2015 were $7.6 million, $10.3 million and $7.6 million, respectively. A summary of the status of the Company’s unvested restricted stock awards as of December 31, 2017, and changes during the twelve months ended December 31, 2017 and 2016, is presented below: Restricted Shares Weighted-average grant date fair value Unvested at December 31, 2015 246,311 $ 27.85 Awards 148,240 27.04 Forfeitures (42,394 ) 17.49 Vestings (98,327 ) 25.64 Unvested at December 31, 2016 253,830 29.98 Awards 46,428 57.02 Forfeitures (4,863 ) 24.78 Vestings (64,522 ) 33.69 Unvested at December 31, 2017 230,873 $ 34.06 Unrecognized stock-based compensation expense related to unvested restricted stock totaled $5.7 million at December 31, 2017, which will be recognized as expense over the next five years. The weighted-average period over which this unrecognized expense would be recognized is 4.3 years. The total fair value of restricted stock vested during 2017, 2016, and 2015 were $2.2 million, $2.5 million and $1.7 million, respectively.

EARNINGS PER SHARE

EARNINGS PER SHARE	12 Months Ended
	Dec. 31, 2017
EARNINGS PER SHARE [Abstract]
EARNINGS PER SHARE	NOTE M: 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 December 31, 2017. Basic earnings per share are computed based on the weighted-average of the common shares outstanding for the period. Diluted earnings per share are based on the weighted-average of the shares outstanding and the assumed exercise of stock options during the year. The dilutive effect of options is calculated using the treasury stock method of accounting. The treasury stock method determines the number of common shares that would be outstanding if all the dilutive options (those where the average market price is greater than the exercise price) were exercised and the proceeds were used to repurchase common shares in the open market at the average market price for the applicable time period. There were approximately 0.2 million, 0.3 million and 0.3 million weighted-average anti-dilutive stock options outstanding at December 31, 2017, 2016 and 2015, respectively, which were not included in the computation below. The following is a reconciliation of basic to diluted earnings per share for the years ended December 31, 2017, 2016 and 2015. (000's omitted, except per share data) 2017 2016 2015 Net income $ 150,717 $ 103,812 $ 91,230 Income attributable to unvested stock-based compensation awards (597 ) (550 ) (453 ) Income available to common shareholders $ 15 0, 0 $ 103,262 $ 90,777 Weighted-average common shares outstanding - basic 48 , 44,091 40,996 Basic earnings per share $ 3 . $ 2.34 $ 2.21 Net income $ 150,717 $ 103,812 $ 91,230 Income attributable to unvested stock-based compensation awards (597 ) (550 ) (453 ) Income available to common shareholders $ 150,12 0 $ 103,262 $ 90,777 Weighted-average common shares outstanding 48 , 44,091 40,996 Assumed exercise of stock options 627 394 405 Weighted-average common shares outstanding – diluted 49,470 44,485 41,401 Diluted earnings per share $ 3.03 $ 2.32 $ 2.19 Cash dividends declared per share $ 1.32 $ 1.26 $ 1.22 Stock Repurchase Program At its December 2016 meeting, the Board approved a stock repurchase program authorizing the repurchase of up to 2.2 million shares of the Company’s common stock, in accordance with securities laws and regulations, through December 31, 2017. At its December 2017 meeting, the Board approved a similar program for 2018, authorizing the repurchase of up to 2.5 million shares of the Company’s common stock through December 31, 2018. 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. There were no stock repurchases pursuant to the announced plans in 2017 or 2016. During 2015, the Company repurchased approximately 0.3 million shares of its common stock in open market transactions.

COMMITMENTS, CONTINGENT LIABILI

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS	12 Months Ended
	Dec. 31, 2017
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS [Abstract]
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS	NOTE N: 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 at December 31: (000's omitted) 2017 2016 Commitments to extend credit $ 1,080,004 $ 773,442 Standby letters of credit 23,782 22,656 Total $ 1,103,786 $ 796,098 The Bank has unused lines of credit of $25.0 million at December 31, 2017. The Bank has unused borrowing capacity of approximately $1.68 billion through collateralized transactions with the FHLB and $22.9 million through collateralized transactions with the Federal Reserve. The Company is required to maintain a reserve balance, as established by the Federal Reserve. The required average total reserve for the 14-day maintenance period of December 21, 2017 through January 3, 2018 was with $73.2 million represented by cash on hand and the remaining $11.6 million was required to be on deposit with the Federal Reserve. 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 December 31, 2017, 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 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.

LEASES

LEASES	12 Months Ended
	Dec. 31, 2017
LEASES [Abstract]
LEASES	NOTE O: LEASES The Company leases buildings, office space, and equipment under agreements that expire in various years. Rental expense included in operating expenses amounted to $7.3 million, $5.8 million and $5.4 million in 2017, 2016 and 2015, respectively. The future minimum rental commitments as of December 31, 2017 for all non-cancelable operating leases are as follows: 2018 $ 9,189 2019 8,194 2020 6,603 2021 5,164 2022 4,101 Thereafter 8,623 Total $ 41,874

REGULATORY MATTERS

REGULATORY MATTERS	12 Months Ended
	Dec. 31, 2017
REGULATORY MATTERS [Abstract]
REGULATORY MATTERS	NOTE P: REGULATORY MATTERS The Company and the Bank are subject to various regulatory capital requirements administered by federal banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company’s financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company and the Bank must meet specific capital guidelines that involve quantitative measures of the Company’s and the Bank’s assets, liabilities, and certain off-balance sheet items as calculated under regulatory accounting practices. The Company’s and the Bank's capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors. Management believes, as of December 31, 2017, that the Company and Bank meet all applicable capital adequacy requirements. Basel III Transitional rules became effective for the Company on January 1, 2015 with all of the requirements being phased in over a multi-year schedule, and fully phased in by January 1, 2019. Beginning in 2016, the Company and the Bank are required to maintain a “capital conservation buffer,” composed entirely of common equity Tier 1 capital, in addition to minimum risk-based capital ratios. The required capital conservation buffer is 1.25% for 2017 and 0.625% for 2016. As of December 31, 2017 and 2016, the amounts, ratios and requirements for the Company are presented below calculated under the Basel III Standardized Transitional Approach. As of December 31, 2017, the OCC categorized the Company and Bank as “well capitalized” under the regulatory framework for prompt corrective action. Actual For capital adequacy purposes For capital adequacy purposes plus Capital Conservation Buffer To be well-capitalized under prompt corrective action (000’s omitted) Amount Ratio Amount Ratio Amount Ratio Amount Ratio Community Bank System, Inc.: 2017 Tier 1 Leverage ratio $ 995,860 10.00 % $ 398,183 4.00 % $ 497,729 5.00 % Tier 1 risk-based capital 995,860 16.64 % 358,988 6.00 % $ 433,777 7.25 % 478,651 8.00 % Total risk-based capital 1,043,910 17.45 % 478,651 8.00 % 553,440 9.25 % 598,314 10.00 % Common equity tier 1 capital 876,685 14.65 % 269,241 4.50 % 344,030 5.75 % 388,904 6.50 % 2016 Tier 1 Leverage ratio $ 858,347 10.55 % $ 325,438 4.00 % $ 406,798 5.00 % Tier 1 risk-based capital 858,347 18.10 % 284,583 6.00 % $ 314,228 6.625 % 379,445 8.00 % Total risk-based capital 905,996 19.10 % 379,445 8.00 % 409,089 8.625 % 474,306 10.00 % Common equity tier 1 capital 759,199 16.01 % 213,438 4.50 % 243,082 5.125 % 308,299 6.50 % Community Bank, N.A.: 2017 Tier 1 Leverage ratio $ 859,538 8.71 % $ 394,981 4.00 % $ 493,726 5.00 % Tier 1 risk-based capital 859,538 14.50 % 355,641 6.00 % $ 429,733 7.25 % 474,188 8.00 % Total risk-based capital 907,588 15.31 % 474,188 8.00 % 548,280 9.25 % 592,736 10.00 % Common equity tier 1 capital 859,483 14.50 % 266,731 4.50 % 340,823 5.75 % 385,278 6.50 % 2016 Tier 1 Leverage ratio $ 672,633 8.30 % $ 324,080 4.00 % $ 405,099 5.00 % Tier 1 risk-based capital 672,633 14.28 % 282,662 6.00 % $ 312,106 6.625 % 376,883 8.00 % Total risk-based capital 720,282 15.29 % 376,883 8.00 % 406,327 8.625 % 471,104 10.00 % Common equity tier 1 capital 672,578 14.28 % 211,997 4.50 % 241,441 5.125 % 306,217 6.50 %

PARENT COMPANY STATEMENTS

PARENT COMPANY STATEMENTS	12 Months Ended
	Dec. 31, 2017
PARENT COMPANY STATEMENTS [Abstract]
PARENT COMPANY STATEMENTS	NOTE Q: PARENT COMPANY STATEMENTS The condensed statements of condition of the parent company at December 31 are as follows: (000's omitted) 2017 2016 Assets: Cash and cash equivalents $ 84,460 $ 151,127 Investment securities 4,322 3,628 Investment in and advances to: Bank subsidiary 1,511,780 1,116,554 Non-bank subsidiaries 169,341 35,566 Other assets 9,150 10,345 Total assets $ 1,779,053 $ 1,317,220 Liabilities and shareholders' equity: Accrued interest and other liabilities $ 20,924 $ 16,950 Borrowings 122,814 102,170 Shareholders' equity 1,635,315 1,198,100 Total liabilities and shareholders' equity $ 1,779,053 $ 1,317,220 The condensed statements of income of the parent company for the years ended December 31 is as follows: (000's omitted) 2017 2016 2015 Revenues: Dividends from subsidiaries: Bank subsidiary $ 91,000 $ 89,000 $ 70,000 Non-bank subsidiaries 35,500 1,750 6,000 Interest and dividends on investments 133 102 94 Total revenues 126,633 90,852 76,094 Expenses: Interest on borrowings 3,904 2,949 2,537 Acquisition expenses 91 429 0 Other expenses 26 11 19 Total expenses 4,021 3,389 2,556 Income before tax benefit and equity in undistributed net income of subsidiaries 122,612 87,463 73,538 Income tax benefit/(expense) 1,930 866 (572 ) Income before equity in undistributed net income of subsidiaries 124,542 88,329 72,966 Equity in undistributed net income of subsidiaries 26,175 15,483 18,264 Net income $ 150,717 $ 103,812 $ 91,230 Other comprehensive (loss), net of tax: Changes in other comprehensive income/(loss) related to pension and other post retirement obligations 168 3,322 (4,567 ) Changes in other comprehensive loss related to unrealized losses on available-for-sale securities (11,065 ) (14,714 ) (6,918 ) Other comprehensive loss (10,897 ) (11,392 ) (11,485 ) Comprehensive income $ 139,820 $ 92,420 $ 79,745 The statements of cash flows of the parent company for the years ended December 31 is as follows: (000's omitted) 2017 2016 2015 Operating activities: Net income $ 150,717 $ 103,812 $ 91,230 Adjustments to reconcile net income to net cash provided by operating activities Equity in undistributed net income of subsidiaries (26,175 ) (15,483 ) (18,264 ) Net change in other assets and other liabilities 1,870 (215 ) (27 ) Net cash provided by operating activities 126,412 88,114 72,939 Investing activities: Proceeds from sale of investment securities 0 0 0 Cash (paid)/received for acquisitions, net of cash acquired of $150,534, $0, and $81,772, respectively (139,471 ) 0 25,505 Capital contributions to subsidiaries (11,063 ) 0 (80,231 ) Net cash used in investing activities (150,534 ) 0 (54,726 ) Financing activities: Issuance of common stock 9,700 15,326 13,975 Purchase of treasury stock (3,306 ) (3,470 ) (9,126 ) Sale of treasury stock 10,060 8,888 16,571 Increase in deferred compensation arrangements 3,306 0 0 Cash dividends paid (62,305 ) (55,048 ) (49,273 ) Net cash used in financing activities (42,545 ) (34,304 ) (27,853 ) Change in cash and cash equivalents (66,667 ) 53,81 0 (9,640 ) Cash and cash equivalents at beginning of year 151,127 97,317 106,957 Cash and cash equivalents at end of year $ 84,460 $ 151,127 $ 97,317 Supplemental disclosures of cash flow information: Cash paid for interest $ 3,826 $ 2,909 $ 2,523 Supplemental disclosures of noncash financing activities Dividends declared and unpaid $ 17,460 $ 14,268 $ 13,605 Capital contributions to subsidiaries 513,769 0 76,461 Common stock issued for acquisition 343,132 0 102,202

FAIR VALUE

FAIR VALUE	12 Months Ended
	Dec. 31, 2017
FAIR VALUE [Abstract]
FAIR VALUE	NOTE R: FAIR VALUE Accounting standards allow entities an irrevocable option to measure certain financial assets and financial liabilities at fair value. Unrealized gains and losses on items for which the fair value option has been elected are reported in earnings. The Company has elected to value mortgage loans held for sale at fair value in order to more closely match the gains and losses associated with loans held for sale with the gains and losses on forward sales contracts. Accordingly, the impact on the valuation will be recognized in the Company’s consolidated statement of income. All mortgage loans held for sale are current and in performing status. 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: ● Level 1 – Quoted prices in active markets for identical assets or liabilities. · Level 2 – 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. · Level 3 – 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. December 31, 2017 (000's omitted) Level 1 Level 2 Level 3 Total Fair Value Available-for-sale investment securities: U.S. Treasury and agency securities $ 1,909,290 $ 144,781 $ 0 $ 2,054,071 Obligations of state and political subdivisions 0 528,956 0 528,956 Government agency mortgage-backed securities 0 357,538 0 357,538 Corporate debt securities 0 2,623 0 2,623 Government agency collateralized mortgage obligations 0 87,374 0 87,374 Marketable equity securities 526 0 0 526 Total available-for-sale investment securities 1,909,816 1,121,272 0 3,031,088 Mortgage loans held for sale 0 461 0 461 Commitments to originate real estate loans for sale 0 0 89 89 Forward sales commitments 0 4 0 4 Interest rate swap agreements asset 0 1,064 0 1,064 Interest rate swap agreements liability 0 (904 ) 0 (904 ) Total $ 1,909,816 $ 1,121,897 $ 89 $ 3,031,802 December 31, 2016 (000's omitted) Level 1 Level 2 Level 3 Total Fair Value Available-for-sale investment securities: U.S. Treasury and agency securities $ 1,902,762 $ 0 $ 0 $ 1,902,762 Obligations of state and political subdivisions 0 594,990 0 594,990 Government agency mortgage-backed securities 0 235,230 0 235,230 Corporate debt securities 0 5,687 0 5,687 Government agency collateralized mortgage obligations 0 9,535 0 9,535 Marketable equity securities 452 0 0 452 Total available-for-sale investment securities 1,903,214 845,442 0 2,748,656 Mortgage loans held for sale 0 2,416 0 2,416 Commitments to originate real estate loans for sale 0 0 54 54 Forward sales commitments 0 3 0 3 Total $ 1,903,214 $ 847,861 $ 54 $ 2,751,129 The valuation techniques used to measure fair value for the items in the table above are as follows: · Available for sale investment securities – The fair value of available-for-sale investment securities is 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 C for further disclosure of the fair value of investment securities. · Mortgage loans held for sale – Mortgage loans held for sale are carried at fair value, which is determined using quoted secondary-market prices of loans with similar characteristics and, as such, have been classified as a Level 2 valuation. The unpaid principal value of mortgage loans held for sale at December 31, 2017 is approximately $0.5 million. The unrealized gain on mortgage loans held for sale of approximately $13,000 was recognized in other banking services in the Consolidated Statement of Income for the year ended December 31, 2017. · 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 swap agreements – The interest rate swaps are reported at their fair value utilizing Level 2 inputs from third parties. The fair value of our 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. Assets and liabilities measured on a non-recurring basis: December 31, 2017 December 31, 2016 (000's omitted) Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Impaired loans $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 633 $ 633 Other real estate owned 0 0 1,915 1,915 0 0 1,966 1,966 Total $ 0 $ 0 $ 1,915 $ 1,915 $ 0 $ 0 $ 2,599 $ 2,599 Loans are generally not recorded at fair value on a recurring basis. Periodically, the Company records nonrecurring adjustments to the carrying value of loans based on fair value measurements for partial charge-offs of the uncollectible portions of those loans. Nonrecurring adjustments also include certain impairment amounts for collateral-dependent loans calculated when establishing the allowance for credit losses. Such amounts are generally based on the fair value of the underlying collateral supporting the loan and, as a result, the carrying value of the loan less the calculated valuation amount does not necessarily represent the fair value of the loan. Real estate collateral is typically valued using independent appraisals or other indications of value based on recent comparable sales of similar properties or assumptions generally observable in the marketplace, adjusted for non-observable inputs. Thus, the resulting nonrecurring fair value measurements are generally classified as Level 3. Estimates of fair value used for other collateral supporting commercial loans generally are based on assumptions not observable in the marketplace and, therefore, such valuations classify as Level 3. Other real estate owned (“OREO”) is valued at the time the loan is foreclosed upon and the asset is transferred to OREO. The value is based primarily on third party appraisals, less estimated costs to sell. The appraisals are sometimes further discounted based on management’s historical knowledge, changes in market conditions from the time of valuation, and/or management’s expertise and knowledge of the customer and customer’s business. Such discounts are significant, ranging from 9% to 99% at December 31, 2017, 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 no valuation allowance at December 31, 2017 as the fair value of mortgage servicing rights of approximately $2.5 million exceeded the carrying value of approximately $1.4 million. The Company evaluates goodwill for impairment on an annual basis, or more often if events or circumstances indicate there may be impairment. The fair value of each reporting unit is compared to the carrying amount of that reporting unit in order to determine if impairment is indicated. If so, the implied fair value of the reporting unit’s goodwill is compared to its carrying amount and the impairment loss is measured by the excess of the carrying value of the goodwill over fair value of the goodwill. In such situations, the Company performs a discounted cash flow modeling technique that requires management to make estimates regarding the amount and timing of expected future cash flows of the assets and liabilities of the reporting unit that enable the Company to calculate the implied fair value of the goodwill. It also requires use of a discount rate that reflects the current return expectation of the market in relation to present risk-free interest rates, expected equity market premiums, peer volatility indicators and company-specific risk indicators. The Company did not recognize an impairment charge during 2017 or 2016. The significant unobservable inputs used in the determination of fair value of assets classified as Level 3 on a recurring or non-recurring basis as of December 31, 2017 are as follows: (000's omitted) Fair Value Valuation Technique Significant Unobservable Inputs Significant Unobservable Input Range (Weighted Average) Other real estate owned $ 1,915 Fair value of collateral Estimated cost of disposal/market adjustment 9.0% - 99.0% (38.5 %) Commitments to originate real estate loans for sale 89 Discounted cash flow Embedded servicing value 1 % The significant unobservable inputs used in the determination of fair value of assets classified as Level 3 on a recurring or non-recurring basis as of December 31, 2016 are as follows: (000's omitted) Fair Value Valuation Technique Significant Unobservable Inputs Significant Unobservable Input Range (Weighted Average) Other real estate owned $ 1,966 Fair value of collateral Estimated cost of disposal/market adjustment 9.0% - 97.0% (29.6 %) Impaired loans 633 Fair value of collateral Estimated cost of disposal/market adjustment 15.0% - 50.0% (36.5 %) Commitments to originate real estate loans for sale 54 Discounted cash flow Embedded servicing value 1 % 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. 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 December 31, 2017 and 2016 are as follows: December 31, 2017 December 31, 2016 (000's omitted) Carrying Value Fair Value Carrying Value Fair Value Financial assets: Net loans $ 6,209,174 $ 6,244,941 $ 4,901,329 4,935,140 Financial liabilities: Deposits 8,444,420 8,431,481 7,075,954 7,071,191 Short-term borrowings 24,000 24,000 146,200 146,200 Securities sold under agreement to repurchase, short-term 337,011 337,011 0 0 Other long-term debt 2,071 2,021 0 0 Subordinated debt held by unconsolidated subsidiary trusts 122,814 122,814 102,170 90,144 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 FHLB overnight advances and securities sold under agreement to repurchase, short-term, is the amount payable on demand at the reporting date. Fair values for long-term borrowings 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	12 Months Ended
	Dec. 31, 2017
DERIVATIVE INSTRUMENTS [Abstract]
DERIVATIVE INSTRUMENTS	NOTE S: 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 December 31, 2017. The effect of the changes to these derivatives for the year then ended was also immaterial. The Company acquired interest rate swaps from the Merchants acquisition with notional amounts with certain commercial customers which totaled $38.9 million at December 31, 2017. 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 $38.9 million. The weighted average receive rate of these interest rate swaps was 3.38%, the weighted average pay rate was 3.84% and the weighted average maturity was 6.5 years. The fair values of $0.9 million and $0.9 million were reflected in other assets and other liabilities, respectively, in the accompanying consolidated statement of condition at December 31, 2017. Hedge accounting has not been applied for these derivatives. Since the terms of the swaps with our customer and the other financial institution offset each other, with the only difference being counterparty credit risk, changes in the fair value of the underlying derivative contracts are not materially different and do not significantly impact our results of operations. The Company also acquired interest rate swaps from the Merchants acquisition with notional amounts totaling $7.0 million at December 31, 2017 that were designated as fair value hedges of certain fixed rate loans with municipalities. At December 31, 2017, the weighted average receive rate of these interest rate swaps was 2.30%, the weighted average pay rate was 3.11% and the weighted average maturity was 15.5 years. The fair value of $0.2 million at December 31, 2017, was reflected as a reduction to loans and an increase to other assets. The ineffective portion of the interest swaps was immaterial and as such, amounts are not recognized in earnings. The Company assessed its counterparty risk at December 31, 2017 and determined any credit risk inherent in our derivative contracts was not material. Information about the fair value of derivative financial instruments can be found in Note R to these consolidated financial statements.

VARIABLE INTEREST ENTITIES

VARIABLE INTEREST ENTITIES	12 Months Ended
	Dec. 31, 2017
VARIABLE INTEREST ENTITIES [Abstract]
VARIABLE INTEREST ENTITIES	NOTE T: VARIABLE INTEREST ENTITIES The Company’s wholly-owned subsidiaries, Community Statutory Trust III, Community Capital Trust IV and MBVT Statutory Trust I, are VIEs for which the Company is not the primary beneficiary. Accordingly, the accounts of these entities are not included in the Company’s consolidated financial statements. See further information regarding Community Statutory Trust III, Community Capital Trust IV and MBVT Statutory Trust I in Note H: Borrowings. In connection with the Company’s acquisition of Oneida, the Company acquired OPFC II which holds a 50% membership interest in 706 North Clinton, LLC (“706 North Clinton”), an entity formed for the purpose of acquiring and rehabilitating real property. The real property held by 706 North Clinton is principally occupied by subsidiaries of the Company. The Company analyzed the operating agreement and capital structure of 706 North Clinton and determined that it was the primary beneficiary and therefore should consolidate 706 North Clinton in its financial statements. This conclusion was based on the determination that the Company has a de facto agency relationship because of the financing arrangement between the other member of 706 North Clinton and the Bank which provides OPFC II with both the power to direct the activities of 706 North Clinton and the obligation to absorb any losses of 706 North Clinton. The carrying amount of the assets and liabilities of 706 North Clinton and the classification of these assets and liabilities in the Company’s consolidated statements of condition at December 31 is as follows: (000's omitted) 2017 2016 Cash and cash equivalents $ 74 $ 30 Premises and equipment, net 6,266 6,429 Other assets 5 0 Total assets $ 6,345 $ 6,459 Accrued interest and other liabilities / Total liabilities $ 0 $ 1 In addition to the assets and liabilities of 706 North Clinton, the minority interest in 706 North Clinton of $3.2 million at December 31, 2017 is included in the Company’s consolidated statement of condition. The creditors of 706 North Clinton do not have a claim on the general assets of the Company. The Company’s maximum loss exposure net of minority interest in 706 North Clinton is approximately $4.7 million as of December 31, 2017, including a $1.5 million loss exposure related to the financing agreement between the other member of 706 North Clinton and the Bank.

SEGMENT INFORMATION

SEGMENT INFORMATION	12 Months Ended
	Dec. 31, 2017
SEGMENT INFORMATION [Abstract]
SEGMENT INFORMATION	NOTE U: 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. 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 operating subsidiaries of BPAS, BPAS-APS, BPAS Trust Company of Puerto Rico, NRS and HB&T, management services including trust services provided by the personal trust unit within the Bank, broker-dealer and investment advisory services provided by CISI and The Carta Group, and asset management provided by Nottingham, and (b) full-service insurance, risk management and employee benefit services provided by OneGroup. The accounting policies used in the disclosure of business segments are the same as those described in the summary of significant accounting policies (See Note A). Information about reportable segments and reconciliation of the information to the consolidated financial statements follows: (000's omitted) Banking Employee Benefit Services All Other Eliminations Consolidated Total 2017 Net interest income $ 315,025 $ 396 $ 254 $ 0 $ 315,675 Provision for loan losses 10,984 0 0 0 10,984 Noninterest income 73,337 82,743 49,201 (2,858 ) 202,423 Amortization of intangible assets 5,296 8,578 3,067 0 16,941 Acquisition expenses 24,549 1,194 243 0 25,986 Other operating expenses 218,608 51,138 37,334 (2,858 ) 304,222 Income before income taxes $ 128,925 $ 22,229 $ 8,811 $ 0 $ 159,965 Assets $ 10,505,919 $ 203,369 $ 66,548 $ (29,638 ) $ 10,746,198 Goodwill $ 629,916 $ 84,449 $ 20,065 $ 0 $ 734,430 2016 Net interest income $ 273,542 $ 162 $ 192 $ 0 $ 273,896 Provision for loan losses 8,076 0 0 0 8,076 Noninterest income 66,059 48,261 43,747 (2,442 ) 155,625 Amortization of intangible assets 2,682 420 2,377 0 5,479 Acquisition expenses 1,005 445 256 0 1,706 Other operating expenses 190,263 36,892 34,950 (2,442 ) 259,663 Income before income taxes $ 137,575 $ 10,666 $ 6,356 $ 0 $ 154,597 Assets $ 8,598,057 $ 38,742 $ 71,428 $ (41,790 ) $ 8,666,437 Goodwill $ 440,870 $ 8,019 $ 16,253 $ 0 $ 465,142 2015 Net interest income $ 248,167 $ 132 $ 121 $ 0 $ 248,420 Provision for loan losses 6,447 0 0 0 6,447 Noninterest income 57,704 46,784 20,967 (2,156 ) 123,299 Amortization of intangible assets 2,803 515 345 0 3,663 Acquisition expenses 6,947 21 69 0 7,037 Other operating expenses 174,918 35,197 14,396 (2,156 ) 222,355 Income before income taxes $ 114,756 $ 11,183 $ 6,278 $ 0 $ 132,217 Assets $ 8,513,228 $ 35,011 $ 70,067 $ (65,637 ) $ 8,552,669 Goodwill $ 439,052 $ 8,019 $ 16,181 $ 0 $ 463,252

SUMMARY OF SIGNIFICANT ACCOUN31

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2017
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Nature of Operations	Nature of Operations Community Bank System, Inc. (the “Company”) is a registered financial holding company which wholly-owns two significant consolidated subsidiaries: Community Bank, N.A. (the “Bank” or “CBNA”), and Benefit Plans Administrative Services, Inc. (“BPAS”). As of December 31, 2017, BPAS owns five subsidiaries: Benefit Plans Administrative Services, LLC (“BPA”), a provider of defined benefit contribution plan administration services; Northeast Retirement Services, LLC (“NRS”), a provider of institutional transfer agency, master recordkeeping services, fund administration, trust and retirement plan services; BPAS Actuarial & Pension Services, LLC (“BPAS-APS”), a provider of actuarial and benefit consulting services; BPAS Trust Company of Puerto Rico, a Puerto Rican trust company; and Hand Benefits & Trust Company (“HB&T”), a provider of collective investment fund administration and institutional trust services. NRS owns one subsidiary, Global Trust Company, Inc. (“GTC”), a non-depository trust company which provides fiduciary services for collective investment trusts and other products. HB&T owns one subsidiary, Hand Securities Inc. (“HSI”), an introducing broker-dealer. The Company also wholly-owns three unconsolidated subsidiary business trusts formed for the purpose of issuing mandatorily-redeemable preferred securities which are considered Tier I capital under regulatory capital adequacy guidelines (see Note P). As of December 31, 2017, the Bank operated 225 full service branches operating as Community Bank, N.A. throughout 35 counties of Upstate New York, six counties of Northeastern Pennsylvania, 12 counties of Vermont and one county of Western Massachusetts, offering a range of commercial and retail banking services. The Bank owns the following operating subsidiaries: The Carta Group, Inc. (“Carta Group”), CBNA Preferred Funding Corporation (“PFC”), CBNA Treasury Management Corporation (“TMC”), Community Investment Services, Inc. (“CISI”), NOTCH Investment Fund, LLC (“NOTCH”), Nottingham Advisors, Inc. (“Nottingham”), OneGroup NY, Inc. (“OneGroup”), and Oneida Preferred Funding II LLC (“OPFC II”). OneGroup is a full-service insurance agency offering personal and commercial property insurance and other risk management products and services. NOTCH, PFC and OPFC II primarily act as investors in residential and commercial real estate activities. TMC provides cash management, investment, and treasury services to the Bank. CISI and Carta Group provide broker-dealer and investment advisory services. Nottingham provides asset management services to individuals, corporations, corporate pension and profit sharing plans, and foundations.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. Variable Interest Entities (“VIE”) are legal entities in which equity investors do not have the characteristics of a controlling financial interest or do not have sufficient equity at risk for the legal entities to finance its activities without additional subordinated financial support. VIEs may be required to be consolidated by a company if it is determined the company is the primary beneficiary of a VIE. The primary beneficiary of a VIE is the enterprise that has: (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance, and (2) the obligation to absorb losses of the VIE that could potentially be significant to the VIE or the right to receive benefits of the VIE that could potentially be significant to the VIE. The Company’s VIE’s are described in more detail in Note T to the consolidated financial statements.
Critical Accounting Estimates in the Preparation of Financial Statements	Critical Accounting Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Critical accounting estimates include the allowance for loan losses, actuarial assumptions associated with the pension, post-retirement and other employee benefit plans, the provision for income taxes, investment valuation and other-than-temporary impairment, the carrying value of goodwill and other intangible assets, and acquired loan valuations.
Risk and Uncertainties	Risk and Uncertainties In the normal course of its business, the Company encounters economic and regulatory risks. There are three main components of economic risk: interest rate risk, credit risk and market risk. The Company is subject to interest rate risk to the degree that its interest-bearing liabilities mature or reprice at different speeds, or on different basis, from its interest-earning assets. The Company’s primary credit risk is the risk of default on the Company’s loan portfolio that results from the borrowers’ inability or unwillingness to make contractually required payments. Market risk reflects potential changes in the value of collateral underlying loans, the fair value of investment securities, and loans held for sale. The Company is subject to regulations of various governmental agencies. These regulations can change significantly from period to period. The Company also undergoes periodic examinations by the regulatory agencies which may subject it to further changes with respect to asset valuations, amounts of required loan loss allowances, and operating restrictions resulting from the regulators’ judgments based on information available to them at the time of their examinations.
Revenue Recognition	Revenue Recognition The Company recognizes income on an accrual basis. CISI and Carta Group recognize fee income when investment and insurance products are sold to customers. Nottingham provides asset management services to brokerage firms and clients and recognizes income ratably over the contract period during which service is performed. Revenue from BPA’s administration and recordkeeping services is recognized ratably over the service contract period. Revenue from consulting and actuarial services is recognized when services are rendered. OneGroup recognizes commission revenue at the later of All intercompany revenue and expense among related entities are eliminated in consolidation.
Cash and Cash Equivalents	Cash and Cash Equivalents For purposes of reporting cash flows, cash and cash equivalents include cash on hand, amounts due from banks, and highly liquid investments with original maturities of less than 90 days. The carrying amounts reported in the consolidated statements of condition for cash and cash equivalents approximate those assets’ fair values.
Investment Securities	Investment Securities The Company can classify its investments in debt and equity securities as trading, held-to-maturity, or available-for-sale. Held-to-maturity securities are those for which the Company has the positive intent and ability to hold until maturity, and are reported at amortized cost. The Company did not use the held-to-maturity classification in 2016 or 2017. Securities classified as available-for-sale are reported at fair value with net unrealized gains and losses reflected as a separate component of shareholders' equity, net of applicable income taxes. None of the Company's investment securities have been classified as trading securities at December 31, 2017. Certain equity securities are stated at cost and include restricted stock of the Federal Reserve Bank of New York (“Federal Reserve”) and the Federal Home Loan Bank of New York and the Federal Home Loan Bank of Boston (collectively referred to as “FHLB”). Fair values for investment securities are based upon quoted market prices, where available. If quoted market prices are not available, fair values are based upon quoted market prices of comparable instruments, or a discounted cash flow model using market estimates of interest rates and volatility. The Company conducts an assessment of all securities in an unrealized loss An OTTI loss must be recognized for a debt security in an unrealized loss position if there is intent to sell the security or it is more likely than not the Company will be required to sell the security prior to recovery of its amortized cost basis. In this situation, the amount of loss recognized in income is equal to the difference between the fair value and the amortized cost basis of the security. Even if management does not have the intent, and it is not more likely than not that the Company will be required to sell the securities, an evaluation of the expected cash flows to be received is performed to determine if a credit loss has occurred. For debt securities, a critical component of the evaluation for OTTI is the identification of credit-impaired securities, where the Company does not expect to receive cash flows sufficient to recover the entire amortized cost basis of the security. In the event of a credit loss, only the amount of impairment associated with the credit loss would be recognized in income. The portion of the unrealized loss relating to other factors, such as liquidity conditions in the market or changes in market interest rates, is recorded in accumulated other comprehensive loss. Equity securities are also evaluated to determine whether the unrealized loss is expected to be recoverable based on whether evidence exists to support a realizable value equal to or greater than the amortized cost basis. If it is probable that the amortized cost basis will not be recovered, taking into consideration the estimated recovery period and the ability to hold the equity security until recovery, OTTI is recognized in earnings equal to the difference between the fair value and the amortized cost basis of the security. The specific identification method is used in determining the realized gains and losses on sales of investment securities and OTTI charges. Premiums and discounts on securities are amortized and accreted, respectively, on the interest method basis over the period to maturity or estimated life of the related security. Purchases and sales of securities are recognized on a trade date basis.
Loans	Loans Loans are stated at unpaid principal balances, net of unearned income. Mortgage loans held for sale are carried at fair value and are included in loans held for sale on the consolidated statements of condition. Fair values for variable rate loans that reprice frequently are based on carrying values. Fair values for fixed rate loans are estimated using discounted cash flows and interest rates currently being offered for loans with similar terms to borrowers of similar credit quality. The carrying amount of accrued interest approximates its fair value. Interest on loans is accrued and credited to operations based upon the principal amount outstanding. Nonrefundable loan fees and related direct costs are deferred and included in the loan balances where they are amortized over the life of the loan as an adjustment to loan yield using the effective yield method. Premiums and discounts on purchased loans are amortized using the effective yield method over the life of the loans.
Acquired Loans	Acquired loans Acquired loans are initially recorded at their acquisition date fair values. The carryover of allowance for loan losses is prohibited as any credit losses in the loans are included in the determination of the fair value of the loans at the acquisition date. Fair values for acquired loans are based on a discounted cash flow methodology that involves assumptions and judgments as to credit risk, prepayment risk, liquidity risk, default rates, loss severity, payment speeds, collateral values and discount rate. Acquired impaired loans Acquired loans that have evidence of deterioration in credit quality since origination and for which it is probable, at acquisition, that the Company will be unable to collect all contractually required payments are accounted for as impaired loans under ASC 310-30. The excess of undiscounted cash flows expected at acquisition over the estimated fair value is referred to as the accretable discount and is recognized into interest income over the remaining life of the loans using the interest method. The difference between contractually required payments at acquisition and the undiscounted cash flows expected to be collected at acquisition is referred to as the non-accretable discount. The non-accretable discount represents estimated future credit losses and other contractually required payments that the Company does not expect to collect. Subsequent decreases in expected cash flows are recognized as impairments through a charge to the provision for loan losses resulting in an increase in the allowance for loan losses. Subsequent improvements in expected cash flows result in a recovery of previously recorded allowance for loan losses or a reversal of a corresponding amount of the non-accretable discount, which the Company then reclassifies as an accretable discount that is recognized into interest income over the remaining life of the loans using the interest method. Acquired loans that met the criteria for non-accrual of interest prior to acquisition may be considered performing upon acquisition, regardless of whether the customer is contractually delinquent, if the Company can reasonably estimate the timing and amount of the expected cash flows on such loans and if the Company expects to fully collect the new carrying value of the loans. As such, the Company may no longer consider the loan to be non-accrual or non-performing and may accrue interest on these loans, including the impact of any accretable discount. Acquired non-impaired loans Acquired loans that do not meet the requirements under ASC 310-30 are considered acquired non-impaired loans. The difference between the acquisition date fair value and the outstanding balance represents the fair value adjustment for a loan and 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 in accordance with ASC 310-20. 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. Subsequent to the purchase date, the methods used to estimate the allowance for loan losses for the acquired non-impaired loans is consistent with the policy described below. However, the Company compares the net realizable value of the loans to the carrying value, for loans collectively evaluated for impairment. The carrying value represents the net of the loan’s unpaid principal balance and the remaining purchase discount (or premium) that has yet to be accreted (or amortized) into interest income (or interest expense). When the carrying value exceeds the net realizable value, an allowance for loan losses is recognized.
Impaired and Other Nonaccrual Loans	Impaired and Other Nonaccrual Loans The Company places a loan on nonaccrual status when the loan becomes 90 days past due (or sooner, if management concludes collection is doubtful), except when, in the opinion of management, it is well-collateralized and in the process of collection. A loan may be placed on nonaccrual status earlier than ninety days past due if there is deterioration in the financial position of the borrower or if other conditions of the loan so warrant. When a loan is placed on nonaccrual status, uncollected accrued interest is reversed against interest income and the amortization of nonrefundable loan fees and related direct costs is discontinued. Interest income during the period the loan is on nonaccrual status is recorded on a cash basis after recovery of principal is reasonably assured. Nonaccrual loans are returned to accrual status when management determines that the borrower’s performance has improved and that both principal and interest are collectible. This generally requires a sustained period of timely principal and interest payments and a well-documented credit evaluation of the borrower’s financial condition. A loan is considered modified in a troubled debt restructuring (“TDR”) when, due to a borrower’s financial difficulties, the Company makes a concession(s) to the borrower that it would not otherwise consider. These modifications may include, among others, an extension for the term of the loan, or granting a period when interest–only payments can be made with the principal payments and interest caught up over the remaining term of the loan or at maturity. Generally, a nonaccrual loan that has been modified in a TDR remains on nonaccrual status for a period of 12 months to demonstrate that the borrower is able to meet the terms of the modified loan. If the borrower’s ability to meet the revised payment schedule is uncertain, the loan remains on nonaccrual status. Regulatory guidance issued by the OCC requires certain loans that have been discharged in Chapter 7 bankruptcy to be reported as TDRs. In accordance with this guidance, 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 and 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. Commercial loans greater than $0.5 million are evaluated individually for impairment. A loan is considered impaired, based on current information and events, if it is probable that the Company will be unable to collect the scheduled payments of principal or interest when due according to the contractual terms of the loan agreement. The measurement of impaired loans is generally based upon the present value of expected future cash flows or the fair value of the collateral, if the loan is collateral-dependent. The Company’s charge-off policy by loan type is as follows: · Business lending loans are generally charged-off to the extent outstanding principal exceeds the fair value of estimated proceeds from collection efforts, including liquidation of collateral. The charge-off is recognized when the loss becomes reasonably quantifiable. · Consumer installment loans are generally charged-off to the extent outstanding principal exceeds the fair value of collateral, and are recognized by the end of the month in which the loan becomes 90 days past due. · Consumer mortgage and home equity loans are generally charged-off to the extent outstanding principal exceeds the fair value of the property, less estimated costs to sell, and are recognized when the loan becomes 180 days past due.
Allowance for Loan Losses	Allowance for Loan Losses Management continually evaluates the credit quality of the Company’s loan portfolio, and performs a formal review of the adequacy of the allowance for loan losses on a quarterly basis. The allowance reflects management’s best estimate of probable losses inherent in the loan portfolio. Determination of the allowance is subjective in nature and requires significant estimates. The Company’s allowance methodology consists of two broad components - general and specific loan loss allocations. The general loan loss allocation is composed of two calculations that are computed on five main loan segments: business lending, consumer direct, consumer indirect, home equity and consumer mortgage. The first calculation is quantitative and determines an allowance level based on the latest 36 months of historical net charge-off data for each loan class (commercial loans exclude balances with specific loan loss allocations). The second calculation is qualitative and takes into consideration eight qualitative environmental factors: levels and trends in delinquencies and impaired loans; levels of and trends in charge-offs and recoveries; trends in volume and terms of loans; effects of any changes in risk selection and underwriting standards, and other changes in lending policies, procedures, and practices; experience, ability, and depth of lending management and other relevant staff; national and local economic trends and conditions; industry conditions; and effects of changes in credit concentrations. A component of the qualitative calculation is the unallocated allowance for loan loss. The qualitative and quantitative calculations are added together to determine the general loan loss allocation. The specific loan loss allocation relates to individual commercial loans that are both greater than $0.5 million and in a nonaccruing status with respect to interest. Specific loan losses are based on discounted estimated cash flows, including any cash flows resulting from the conversion of collateral or collateral shortfalls. The allowance levels computed from the specific and general loan loss allocation methods are combined with unallocated allowances and allowances needed for acquired loans to derive the total required allowance for loan losses to be reflected on the Consolidated Statement of Condition. Loan losses are charged off against the allowance, while recoveries of amounts previously charged off are credited to the allowance. A provision for loan losses is charged to operations based on management’s periodic evaluation of factors previously mentioned.
Intangible Assets	Intangible Assets Intangible assets include core deposit intangibles, customer relationship intangibles and goodwill arising from acquisitions. Core deposit intangibles and customer relationship intangibles are amortized on either an accelerated or straight-line basis over periods ranging from seven to 20 years. The initial and ongoing carrying value of goodwill and other intangible assets is based upon discounted cash flow modeling techniques that require management to make estimates regarding the amount and timing of expected future cash flows. It also requires use of a discount rate that reflects the current return requirements of the market in relation to present risk-free interest rates, required equity market premiums, peer volatility indicators, and company-specific risk indicators. The Company evaluates goodwill for impairment on an annual basis, or more often if events or circumstances indicate there may be impairment. The implied fair value of a reporting unit’s goodwill is compared to its carrying amount and the impairment loss is measured by the excess of the carrying value over fair value. The fair value of each reporting unit is compared to the carrying amount of that reporting unit in order to determine if impairment is indicated.
Premises and Equipment	Premises and Equipment Premises and equipment are stated at cost less accumulated depreciation. Computer software costs that are capitalized only include external direct costs of obtaining and installing the software. The Company has not developed any internal use software. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets. Useful lives range from three to 10 years for equipment; three to seven years for software and hardware; and 10 to 40 years for building and building improvements. Land improvements are depreciated over 20 years and leasehold improvements are amortized over the shorter of the term of the respective lease plus any optional renewal periods that are reasonably assured or life of the asset. Maintenance and repairs are charged to expense as incurred.
Other Real Estate	Other Real Estate Other real estate owned is comprised of properties acquired through foreclosure, or by deed in lieu of foreclosure. These assets are carried at fair value less estimated costs of disposal. At foreclosure, if the fair value, less estimated costs to sell, of the real estate acquired is less than the Company’s recorded investment in the related loan, a write-down is recognized through a charge to the allowance for loan losses. Any subsequent reduction in value is recognized by a charge to income. Operating costs associated with the properties are charged to expense as incurred. At December 31, 2017 and 2016, other real estate amounted to $1.9 million and $2.0 million, respectively, and is included in other assets.
Mortgage Servicing Rights	Mortgage Servicing Rights 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 period of estimated net servicing income or loss. The Company uses a valuation model that calculates the present value of future cash flows to determine the fair value of servicing rights. In using this valuation method, the Company incorporates assumptions that market participants would use in estimating future net servicing income, which includes estimates of the servicing cost per loan, the discount rate, and prepayment speeds. The carrying value of the originated mortgage servicing rights is included in other assets and is evaluated quarterly for impairment using these same market assumptions. The amount of impairment recognized is the amount by which the carrying value of the capitalized servicing rights for a stratum exceeds estimated fair value. Impairment is recognized through a valuation allowance.
Treasury Stock	Treasury Stock Repurchases of shares of the Company’s common stock are recorded at cost as a reduction of shareholders’ equity. Reissuance of shares of treasury stock is recorded at average cost.
Income Taxes	Income Taxes The Company and its subsidiaries file a consolidated federal income tax return. Provisions for income taxes are based on taxes currently payable or refundable as well as deferred taxes that are based on temporary differences between the tax basis of assets and liabilities and their reported amounts in the consolidated financial statements. Deferred tax assets and liabilities are reported in the consolidated financial statements at currently enacted income tax rates applicable to the period in which the deferred tax assets and liabilities are expected to be realized or settled. Benefits from tax positions should be recognized in the financial statements only when it is more likely than not that the tax position will be sustained upon examination by the appropriate taxing authority having full knowledge of all relevant information. A tax position meeting the more-likely-than-not recognition threshold should be measured at the largest amount of benefit for which the likelihood of realization upon ultimate settlement exceeds 50 percent.
Investments in Real Estate Limited Partnerships	Investments in Real Estate Limited Partnerships The Company has investments in various real estate limited partnerships that acquire, develop, own and operate low and moderate-income housing. The Company’s ownership interest in these limited partnerships ranges from 5.00% to 99.99% as of December 31, 2017. These investments are made directly in Low Income Housing Tax Credit, or LIHTC, partnerships formed by third parties. As a limited partner in these operating partnerships, we receive tax credits and tax deductions for losses incurred by the underlying properties. The Company accounts for its ownership interest in LIHTC partnerships in accordance with Accounting Standards Update (“ASU”) 2014-01, Investments – Equity Method and Joint Ventures (Topic 323): Accounting for Investments in Qualified Affordable Housing Projects
Repurchase Agreements	Repurchase Agreements The Company sells certain securities under agreements to repurchase. These agreements are treated as collateralized financing transactions. These secured borrowings are reflected as liabilities in the accompanying consolidated statements of condition and are recorded at the amount of cash received in connection with the transaction. Short-term securities sold under agreements to repurchase generally mature within one day from the transaction date. Securities, generally U.S. government and federal agency securities, pledged as collateral under these financing arrangements can be repledged by the secured party. Additional collateral may be required based on the fair value of the underlying securities.
Retirement Benefits	Retirement Benefits The Company provides defined benefit pension benefits to eligible employees and post-retirement health and life insurance benefits to certain eligible retirees. The Company also provides deferred compensation and supplemental executive retirement plans for selected current and former employees, officers, and directors. Expense under these plans is charged to current operations and consists of several components of net periodic benefit cost based on various actuarial assumptions regarding future experience under the plans, including discount rate, rate of future compensation increases and expected return on plan assets.
Derivative Financial Instruments and Hedging Activities	Derivative Financial Instruments and Hedging Activities The Company accounts for derivative financial instruments at fair value. If certain conditions are met, a derivative may be specifically designated as (1) a hedge of the exposure to changes in the fair value of a recognized asset or liability or an unrecognized firm commitment (“fair value hedge”), (2) a hedge of the exposure to variable cash flows of a forecasted transaction or the variability of cash flows to be received or paid related to a recognized asset or liability (“cash flow hedge”), or (3) an instrument with no hedging designation (“stand-alone derivative”). For a fair value hedge, the gain or loss on the derivative, as well as the offsetting loss or gain on the hedged item, are recognized in current earnings as fair values change. For a cash flow hedge, the gain or loss on the derivative is reported in other comprehensive income and is reclassified into earnings in the same periods during which the hedged transaction affects earnings. For both types of hedges, changes in the fair value of derivatives that are not highly effective in hedging the changes in fair value or expected cash flows of the hedged item are recognized immediately in current earnings. Changes in the fair value of derivatives that do not qualify for hedge accounting are reported currently in earnings, as noninterest income. Net cash settlements on derivatives that qualify for hedge accounting are recorded in interest income or interest expense, based on the item being hedged. Net cash settlements on derivatives that do not qualify for hedge accounting are reported in noninterest income. Cash flows on hedges are classified in the consolidated statement of cash flow statement the same as the cash flows of the items being hedged. The Company formally documents the relationship between derivatives and hedged items, as well as the risk-management objective and strategy for undertaking hedge transactions at the inception of the hedging relationship. This documentation includes linking the fair value or cash flow hedges to specific assets and liabilities on the statement of condition or to specific commitments or forecasted transactions. The Company also formally assesses, both at the hedge’s inception and on an ongoing basis, whether the derivative instruments that are used are highly effective in offsetting changes in fair values or cash flows of the hedged items. When hedge accounting is discontinued, subsequent changes in fair value of the derivative are recorded in noninterest income. When a fair value hedge is discontinued, the hedged asset or liability is no longer adjusted for changes in fair value and the existing basis adjustment is amortized or accreted over the remaining life of the asset or liability. When a cash flow hedge is discontinued, but the hedged cash flows or forecasted transactions are still expected to occur, gains or losses that were accumulated in other comprehensive income are amortized into earnings over the same periods which the hedged transactions will affect earnings.
Assets Under Management or Administration	Assets Under Management or Administration Assets held in fiduciary or agency capacities for customers are not included in the accompanying consolidated statements of condition as they are not assets of the Company. All fees associated with providing asset management services are recorded on an accrual basis of accounting and are included in noninterest income.
Advertising	Advertising Advertising costs amounting to approximately $5.7 million, $3.9 million and $3.6 million for the years ending December 31, 2017, 2016 and 2015, respectively, are nondirect response in nature and expensed as incurred.
Bank Owned Life Insurance	Bank Owned Life Insurance The Company owns life insurance policies on certain current and former employees and directors where the Bank is the beneficiary. Bank owned life insurance is recorded at the amount that can be realized under the insurance contract at the balance sheet date, which is the cash surrender value (“CSV”) adjusted for other charges or other amounts due that are probable at settlement. Increases in the CSV of the policies, as well as the death benefits received, net of any CSV, are recorded in noninterest income, and are not subject to income taxes.
Earnings Per Share	Earnings Per Share Using the two-class method, basic earnings per common share is computed based upon net income available to common shareholders divided by the weighted average number of common shares outstanding during each period, which excludes the outstanding unvested restricted stock. Diluted earnings per share is computed using the weighted average number of common shares determined for the basic earnings per common share computation plus the dilutive effect of stock options using the treasury stock method. Stock options where the exercise price is greater than the average market price of common shares were not included in the computation of earnings per diluted share as they would have been anti-dilutive. Shares held in rabbi trusts related to deferred compensation plans are considered outstanding for purposes of computing earnings per share.
Stock-based Compensation	Stock-based Compensation Companies are required to measure and record compensation expense for stock options and other share-based payments on the instruments’ fair value on the date of grant. Stock-based compensation expense is recognized ratably over the requisite service period for all awards (see Note L).
Fair Values of Financial Instruments	Fair Values of Financial Instruments The Company determines fair values based on quoted market values where available or on estimates using present values or other valuation techniques. Those techniques are significantly affected by the assumptions used, including 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, could not be realized in immediate settlement of the instrument. Certain financial instruments and all nonfinancial instruments are excluded from this disclosure requirement. Accordingly, the aggregate fair value amounts presented do not represent the underlying value of the Company. The fair values of investment securities, loans, deposits, and borrowings have been disclosed in Note R.
Reclassifications	Reclassifications Certain reclassifications have been made to prior years’ balances to conform to the current year presentation.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In March 2016, the FASB issued ASU 2016-09, Compensation – Stock Compensation (Topic 718) In February 2018, the FASB issued ASU 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.
New Accounting Pronouncements	New Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) ASC 605, Revenue Recognition In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The Company has completed its evaluation of adoption of the new guidance on the Company’s consolidated financial statements and the impact was considered immaterial. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) Topic 840, Leases In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) In January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350) In March 2017, the FASB issued ASU No. 2017-07, Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities.

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	12 Months Ended
	Dec. 31, 2017
ACQUISITIONS [Abstract]
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: 2017 2016 2015 (000s omitted) NRS Merchants Other (1) Total WJL Oneida Consideration paid : Cash (2) $ 70,073 $ 82,898 $ 6,775 $ 159,746 $ 575 $ 56,266 Community Bank System, Inc. common stock 78,483 262,254 2,395 343,132 0 102,202 Total net consideration paid 148,556 345,152 9,170 502,878 575 158,468 Recognized amounts of identifiable assets acquired and liabilities assumed: Cash and cash equivalents 11,063 40,730 339 52,132 0 81,772 Investment securities 20,294 370,648 0 390,942 0 225,729 Loans 0 1,488,157 0 1,488,157 0 399,422 Premises and equipment 411 16,608 27 17,046 0 22,212 Accrued interest receivable 72 4,773 0 4,845 0 1,133 Other assets 8,088 51,585 583 60,256 0 26,529 Core deposit intangibles 0 23,214 0 23,214 0 2,570 Other intangibles 60,200 2,857 5,626 68,683 288 9,994 Deposits 0 (1,448,406 ) 0 (1,448,406 ) 0 (699,241 ) Other liabilities (28,002 ) (11,750 ) (1,217 ) (40,969 ) 0 (1,333 ) Short-term advances 0 (80,000 ) 0 (80,000 ) 0 0 Securities sold under agreement to repurchase, short-term 0 (278,076 ) 0 (278,076 ) 0 0 Long-term debt 0 (3,615 ) 0 (3,615 ) 0 0 Subordinated debt held by unconsolidated subsidiary trusts 0 (20,619 ) 0 (20,619 ) 0 0 Total identifiable assets, net 72,126 156,106 5,358 233,590 288 68,787 Goodwill $ 76,430 $ 189,046 $ 3,812 $ 269,288 $ 287 $ 89,681 (1) (2) Includes NECM $0.2 million contingent cash payment consideration.
Summary of Loans Acquired	The following is a summary of the loans acquired from Merchants at the date of acquisition: (000s omitted) Acquired Impaired Loans Acquired Non-impaired Loans Total Acquired Loans Contractually required principal and interest at acquisition $ 15,454 $ 1,872,574 $ 1,888,028 Contractual cash flows not expected to be collected (5,385 ) (14,753 ) (20,138 ) Expected cash flows at acquisition 10,069 1,857,821 1,867,890 Interest component of expected cash flows (793 ) (378,940 ) (379,733 ) Fair value of acquired loans $ 9,276 $ 1,478,881 $ 1,488,157
Pro Forma Financial Information	The pro forma information set forth below reflects the historical results of Merchants and NRS combined with the Company’s consolidated statement of income with adjustments related to (a) certain purchase accounting fair value adjustments and (b) amortization of customer lists and core deposit intangibles. Acquisition expenses related to the Merchants and NRS transactions totaling $25.7 million for the year ended December 31, 2017 were included in the pro forma information as if they were incurred in 2016. Pro Forma (Unaudited) Year Ended December 31, (000’s omitted) 2017 2016 Total revenue, net of interest expense $ 546,977 $ 536,183 Net income 176,257 109,186

INVESTMENT SECURITIES (Tables)

INVESTMENT SECURITIES (Tables)	12 Months Ended
	Dec. 31, 2017
INVESTMENT SECURITIES [Abstract]
Amortized Cost and Estimated Fair Value of Investment Securities	The amortized cost and estimated fair value of investment securities as of December 31 are as follows: 2017 2016 (000's omitted) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Available-for-Sale Portfolio: U.S. Treasury and agency securities $ 2,043,023 $ 15,886 $ 4,838 $ 2,054,071 $ 1,876,358 $ 28,522 $ 2,118 $ 1,902,762 Obligations of state and political subdivisions 514,949 14,064 57 528,956 582,655 13,389 1,054 594,990 Government agency mortgage-backed securities 358,180 3,121 3,763 357,538 232,657 5,040 2,467 235,230 Corporate debt securities 2,648 0 25 2,623 5,716 2 31 5,687 Government agency collateralized mortgage obligations 88,097 155 878 87,374 9,225 310 0 9,535 Marketable equity securities 251 275 0 526 252 200 0 452 Total available-for-sale portfolio $ 3,007,148 $ 33,501 $ 9,561 $ 3,031,088 $ 2,706,863 $ 47,463 $ 5,670 $ 2,748,656 Other Securities: Federal Home Loan Bank common stock $ 9,896 $ 9,896 $ 12,191 $ 12,191 Federal Reserve Bank common stock 30,690 30,690 19,781 19,781 Certificates of deposit 3,865 3,865 0 0 Other equity securities 5,840 5,840 3,764 3,764 Total other securities $ 50,291 $ 50,291 $ 35,736 $ 35,736
Summary of Investment Securities That Have Been in a Continuous Unrealized Loss Position for Less Than or Greater Than Twelve Months	A summary of investment securities that have been in a continuous unrealized loss position for less than or greater than twelve months is as follows: As of December 31, 2017 Less than 12 Months 12 Months or Longer Total (000's omitted) # Fair Value Gross Unrealized Losses # Fair Value Gross Unrealized Losses # Fair Value Gross Unrealized Losses Available-for-Sale Portfolio: U.S. Treasury and agency securities 44 $ 699,709 $ 4,838 0 $ 0 $ 0 44 $ 699,709 $ 4,838 Obligations of state and political subdivisions 45 23,432 57 0 0 0 45 23,432 57 Government agency mortgage-backed securities 120 185,716 1,433 55 75,712 2,330 175 261,428 3,763 Corporate debt securities 1 2,623 25 0 0 0 1 2,623 25 Government agency collateralized mortgage obligations 39 80,041 878 1 1 0 40 80,042 878 Total available-for-sale investment portfolio 249 $ 991,521 $ 7,231 56 $ 75,713 $ 2,330 305 $ 1,067,234 $ 9,561 As of December 31, 2016 Less than 12 Months 12 Months or Longer Total (000's omitted) # Fair Value Gross Unrealized Losses # Fair Value Gross Unrealized Losses # Fair Value Gross Unrealized Losses Available-for-Sale Portfolio: U.S. Treasury and agency securities 13 $ 449,242 $ 2,118 0 $ 0 $ 0 13 $ 449,242 $ 2,118 Obligations of state and political subdivisions 197 102,106 1,054 0 0 0 197 102,106 1,054 Government agency mortgage-backed securities 57 83,862 1,637 15 21,788 830 72 105,650 2,467 Corporate debt securities 1 2,677 31 0 0 0 1 2,677 31 Government agency collateralized mortgage obligations 0 0 0 2 2 0 2 2 0 Total available-for-sale investment portfolio 268 $ 637,887 $ 4,84 0 17 $ 21,790 $ 830 285 $ 659,677 $ 5,67 0
Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity	The amortized cost and estimated fair value of debt securities at December 31, 2017, 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 (000's omitted) Amortized Cost Fair Value Due in one year or less $ 45,966 $ 46,042 Due after one through five years 1,565,423 1,572,634 Due after five years through ten years 758,742 769,828 Due after ten years 190,489 197,146 Subtotal 2,560,620 2,585,650 Government agency mortgage-backed securities 358,180 357,538 Government agency collateralized mortgage obligations 88,097 87,374 Total $ 3,006,897 $ 3,030,562

LOANS (Tables)

LOANS (Tables)	12 Months Ended
	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Schedule of Loans Receivable, Net	The balances of these classes at December 31 are summarized as follows: (000's omitted) 2017 2016 Consumer mortgage $ 2,220,298 $ 1,819,701 Business lending 2,424,223 1,490,076 Consumer indirect 1,011,978 1,044,972 Consumer direct 179,929 191,815 Home equity 420,329 401,998 Gross loans, including deferred origination costs 6,256,757 4,948,562 Allowance for loan losses (47,583 ) (47,233 ) Loans, net of allowance for loan losses $ 6,209,174 $ 4,901,329
Summary of Aggregate Amounts Loaned to Related Parties	Following is a summary of the aggregate amount of such loans during 2017 and 2016. (000's omitted) 2017 2016 Balance at beginning of year $ 10,950 $ 11,337 New loans 16,617 4,959 Payments (5,223 ) (5,346 ) Balance at end of year $ 22,344 $ 10,950
Outstanding Principal Balance and Related Carrying Amount of Acquired Loans	The outstanding principal balance and the related carrying amount of acquired loans included in the Consolidated Statement of Condition at December 31 are as follows: (000's omitted) 2017 2016 Credit impaired acquired loans: Outstanding principal balance $ 13,242 $ 6,354 Carrying amount 10,115 5,553 Non-impaired acquired loans: Outstanding principal balance 1,658,780 497,308 Carrying amount 1,626,979 489,807 Total acquired loans: Outstanding principal balance 1,672,022 503,662 Carrying amount 1,637,094 495,360
Schedule of Accretable Discount Related to Credit Impaired Acquired Loans	The changes in the accretable discount related to the credit impaired acquired loans are as follows: (000's omitted) 2017 2016 Balance at beginning of year $ 498 $ 810 Merchants acquisition 793 0 Accretion recognized (905 ) (455 ) Net reclassification to accretable from nonaccretable 590 143 Balance at end of year $ 976 $ 498
Aged Analysis of Past Due Loans by Class	The following is an aged analysis of the Company’s past due loans by class as of December 31, 2017: Legacy Loans (000’s omitted) Past Due 30 - 89 days 90+ Days Past Due and Still Accruing Nonaccrual Total Past Due Current Total Loans Consumer mortgage $ 13,564 $ 1,500 $ 10,722 $ 25,786 $ 1,728,823 $ 1,754,609 Business lending 2,283 571 3,944 6,798 1,369,801 1,376,599 Consumer indirect 14,197 295 0 14,492 977,344 991,836 Consumer direct 1,875 48 0 1,923 172,556 174,479 Home equity 1,116 94 1,354 2,564 319,576 322,140 Total $ 33,035 $ 2,508 $ 16,020 $ 51,563 $ 4,568,100 $ 4,619,663 Acquired Loans (000’s omitted) Past Due 30 - 89 days 90+ Days Past Due and Still Accruing Nonaccrual Total Past Due Acquired Impaired (1) Current Total Loans Consumer mortgage $ 2,603 $ 26 $ 3,066 $ 5,695 $ 0 $ 459,994 $ 465,689 Business lending 4,661 0 4,328 8,989 10,115 1,028,520 1,047,624 Consumer indirect 245 8 0 253 0 19,889 20,142 Consumer direct 100 0 0 100 0 5,350 5,450 Home equity 634 170 1,326 2,130 0 96,059 98,189 Total $ 8,243 $ 204 $ 8,720 $ 17,167 $ 10,115 $ 1,609,812 $ 1,637,094 (1) Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performing under ASC 310-30. As a result interest income, through the accretion of the difference between the carrying amount of the loans and the expected cashflows, is being recognized on all acquired impaired loans. The following is an aged analysis of the Company’s past due loans by class as of December 31, 2016: Legacy Loans (000’s omitted) Past Due 30 - 89 days 90+ Days Past Due and Still Accruing Nonaccrual Total Past Due Current Total Loans Consumer mortgage $ 11,379 $ 1,180 $ 11,352 $ 23,911 $ 1,635,849 $ 1,659,760 Business lending 3,921 145 3,811 7,877 1,269,789 1,277,666 Consumer indirect 13,883 166 0 14,049 1,000,776 1,014,825 Consumer direct 1,549 58 0 1,607 180,315 181,922 Home equity 1,250 414 1,437 3,101 315,928 319,029 Total $ 31,982 $ 1,963 $ 16,600 $ 50,545 $ 4,402,657 $ 4,453,202 Acquired Loans (000’s omitted) Past Due 30 - 89 days 90+ Days Past Due and Still Accruing Nonaccrual Total Past Due Acquired Impaired (1) Current Total Loans Consumer mortgage $ 1,539 $ 205 $ 2,332 $ 4,076 $ 0 $ 155,865 $ 159,941 Business lending 528 0 1,252 1,780 5,553 205,077 212,410 Consumer indirect 231 3 0 234 0 29,913 30,147 Consumer direct 231 0 0 231 0 9,662 9,893 Home equity 778 905 435 2,118 0 80,851 82,969 Total $ 3,307 $ 1,113 $ 4,019 $ 8,439 $ 5,553 $ 481,368 $ 495,360 (1) Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performing under ASC 310-30. As a result interest income, through the accretion of the difference between the carrying amount of the loans and the expected cashflows, is being recognized on all acquired impaired loans.
Summary of Non-Business Impaired Loans	A summary of individually evaluated impaired loans as of December 31, 2017 and 2016 is as follows: (000’s omitted) 2017 2016 Loans with allowance allocation $ 5,125 $ 1,109 Loans without allowance allocation 884 556 Carrying balance 6,009 1,665 Contractual balance 9,165 3,340 Specifically allocated allowance 804 477 Average impaired loans 9,517 4,683 Interest income recognized 0 0
Troubled Debt Restructurings on Financing Receivables	Information regarding TDRs as of December 31, 2017 and December 31, 2016 is as follows December 31, 2017 December 31, 2016 (000’s omitted) Nonaccrual Accruing Total Nonaccrual Accruing Total # Amount # Amount # Amount # Amount # Amount # Amount Consumer mortgage 51 $ 2,265 44 $ 1,750 95 $ 4,015 36 $ 1,520 45 $ 1,956 81 $ 3,476 Business lending 8 218 7 501 15 719 6 91 5 690 11 781 Consumer indirect 0 0 71 883 71 883 0 0 78 771 78 771 Consumer direct 0 0 25 69 25 69 0 0 23 65 23 65 Home equity 13 245 7 204 20 449 14 221 7 216 21 437 Total 72 $ 2,728 154 $ 3,407 226 $ 6,135 56 $ 1,832 158 $ 3,698 214 $ 5,530 The following table presents information related to loans modified in a TDR during the years ended December 31, 2017 and 2016. Of the loans noted in the table below, all loans for the years ended December 31, 2017 and December 31, 2016, were modified due to a Chapter 7 bankruptcy as described previously. The financial effects of these restructurings were immaterial. December 31, 2017 December 31, 2016 (000’s omitted) # Amount # Amount Consumer mortgage 23 $ 1,254 9 $ 597 Business lending 8 412 0 0 Consumer indirect 33 490 33 459 Consumer direct 6 17 3 51 Home equity 4 95 3 50 Total 74 $ 2,268 48 $ 1,157
Schedule of Allowance for Loan Losses by Class	The following presents by class the activity in the allowance for loan losses: (000’s omitted) Consumer Mortgage Business Lending Consumer Indirect Consumer Direct Home Equity Unallocated Acquired Impaired Total Balance at December 31, 2014 $ 10,286 $ 15,787 $ 11,544 $ 3,083 $ 2,701 $ 1,767 $ 173 $ 45,341 Charge-offs (1,374 ) (2,146 ) (6,714 ) (1,490 ) (244 ) 0 (103 ) (12,071 ) Recoveries 80 877 3,943 722 62 0 0 5,684 Provision 1,206 1,231 3,649 682 147 (566 ) 98 6,447 Balance at December 31, 2015 10,198 15,749 12,422 2,997 2,666 1,201 168 45,401 Charge-offs (647 ) (1,872 ) (7,643 ) (1,706 ) (218 ) 0 (97 ) (12,183 ) Recoveries 115 616 4,168 901 139 0 0 5,939 Provision 428 2,727 4,835 787 (188 ) (550 ) 37 8,076 Balance at December 31, 2016 10,094 17,220 13,782 2,979 2,399 651 108 47,233 Charge-offs (707 ) (4,959 ) (8,456 ) (2,081 ) (284 ) 0 (270 ) (16,757 ) Recoveries 50 656 4,516 849 52 0 0 6,123 Provision 1,028 4,340 3,626 1,292 (60 ) 449 309 10,984 Balance at December 31, 2017 $ 10,465 $ 17,257 $ 13,468 $ 3,039 $ 2,107 $ 1,100 $ 147 $ 47,583
Business Lending [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Schedule of Loans by Credit Quality Indicator	The following table shows the amount of business lending loans by credit quality category: December 31, 2017 December 31, 2016 (000’s omitted) Legacy Acquired Total Legacy Acquired Total Pass $ 1,170,156 $ 963,981 $ 2,134,137 $ 1,051,005 $ 162,165 $ 1,213,170 Special mention 129,076 37,321 166,397 135,602 29,690 165,292 Classified 77,367 34,628 111,995 90,585 15,002 105,587 Doubtful 0 1,579 1,579 474 0 474 Acquired impaired 0 10,115 10,115 0 5,553 5,553 Total $ 1,376,599 $ 1,047,624 $ 2,424,223 $ 1,277,666 $ 212,410 $ 1,490,076
All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Schedule of Loans by Credit Quality Indicator	The following tables detail the balances in all loan categories except for business lending at December 31, 2017: Legacy loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 1,742,387 $ 991,541 $ 174,431 $ 320,692 $ 3,229,051 Nonperforming 12,222 295 48 1,448 14,013 Total $ 1,754,609 $ 991,836 $ 174,479 $ 322,140 $ 3,243,064 Acquired loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 462,597 $ 20,134 $ 5,450 $ 96,693 $ 584,874 Nonperforming 3,092 8 0 1,496 4,596 Total $ 465,689 $ 20,142 $ 5,450 $ 98,189 $ 589,470 The following table details the balances in all other loan categories at December 31, 2016: Legacy loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 1,647,228 $ 1,014,659 $ 181,864 $ 317,178 $ 3,160,929 Nonperforming 12,532 166 58 1,851 14,607 Total $ 1,659,760 $ 1,014,825 $ 181,922 $ 319,029 $ 3,175,536 Acquired loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 157,404 $ 30,144 $ 9,893 $ 81,629 $ 279,070 Nonperforming 2,537 3 0 1,340 3,880 Total $ 159,941 $ 30,147 $ 9,893 $ 82,969 $ 282,950

PREMISES AND EQUIPMENT (Tables)

PREMISES AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2017
PREMISES AND EQUIPMENT [Abstract]
Components of Premises and Equipment	Premises and equipment consist of the following at December 31: (000's omitted) 2017 2016 Land and land improvements $ 23,869 $ 22,585 Bank premises 131,647 116,663 Equipment and construction in progress 86,059 80,527 Premises and equipment, gross 241,575 219,775 Accumulated depreciation (118,182 ) (107,457 ) Premises and equipment, net $ 123,393 $ 112,318

GOODWILL AND IDENTIFIABLE INT36

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2017
GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS [Abstract]
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: December 31, 2017 December 31, 2016 (000's omitted) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Amortizing intangible assets: Core deposit intangibles $ 62,902 $ (37,877 ) $ 25,025 $ 39,688 $ (32,581 ) $ 7,107 Other intangibles 86,535 (20,902 ) 65,633 17,853 (9,258 ) 8,595 Total amortizing intangibles $ 149,437 $ (58,779 ) $ 90,658 $ 57,541 $ (41,839 ) $ 15,702
Estimated Aggregate Amortization Expense	The estimated aggregate amortization expense for each of the five succeeding fiscal years ended December 31 is as follows: 2018 $ 17 , 2019 15,033 2020 12,497 2021 10,665 2022 9,165 Thereafter 25,426 Total $ 90,658
Components of Goodwill	Shown below are the components of the Company’s goodwill at December 31, 2017 and 2016: (000’s omitted) Year Ended December 31, 2015 Activity Year Ended December 31, 2016 Activity Year Ended December 31, 2017 Goodwill $ 468,076 $ 1,890 $ 469,966 $ 269,288 $ 739,254 Accumulated impairment (4,824 ) 0 (4,824 ) 0 (4,824 ) Goodwill, net $ 463,252 $ 1,890 $ 465,142 $ 269,288 $ 734,430
Changes in Carrying Value of MSRs and Associated Valuation Allowance	The following table summarizes the changes in carrying value of MSRs and the associated valuation allowance: (000’s omitted) 2017 2016 Carrying value before valuation allowance at beginning of period $ 1,435 $ 1,472 Additions 358 481 Merchants acquisition 64 0 Amortization (499 ) (518 ) Carrying value before valuation allowance at end of period 1,358 1,435 Valuation allowance balance at beginning of period 0 0 Impairment charges 0 (226 ) Impairment recoveries 0 226 Valuation allowance balance at end of period 0 0 Net carrying value at end of period $ 1,358 $ 1,435 Fair value of MSRs at end of period $ 2,473 $ 1,928 Principal balance of loans sold during the year $ 32,937 $ 45,852 Principal balance of loans serviced for others $ 358,518 $ 365,374 Custodial escrow balances maintained in connection with loans serviced for others $ 5,363 $ 5,603
Summary of Key Economic Assumptions Used to Estimate Value of MSRs	The following table summarizes the key economic assumptions used to estimate the value of the MSRs at December 31: 2017 2016 Weighted-average contractual life (in years) 21.3 20.8 Weighted-average constant prepayment rate (CPR) 11.1 % 15.1 % Weighted-average discount rate 3.3 % 3.5 %

DEPOSITS (Tables)

DEPOSITS (Tables)	12 Months Ended
	Dec. 31, 2017
DEPOSITS [Abstract]
Components of Deposits	Deposits consist of the following at December 31: (000's omitted) 2017 2016 Noninterest checking $ 2,293,057 $ 1,646,039 Interest checking 1,830,914 1,644,029 Savings 1,421,512 1,303,851 Money market 2,124,633 1,778,907 Time 774,304 703,128 Total deposits $ 8,444,420 $ 7,075,954
Maturities of Time Deposits	The approximate maturities of time deposits at December 31, 2017 are as follows: (000's omitted) All Accounts Accounts $250,000 or Greater 2018 $ 545,389 $ 51,875 2019 100,833 5,958 2020 59,849 7,445 2021 34,582 1,807 2022 33,400 601 Thereafter 251 0 Total $ 774,304 $ 67,686

BORROWINGS (Tables)

BORROWINGS (Tables)	12 Months Ended
	Dec. 31, 2017
BORROWINGS [Abstract]
Outstanding Borrowings	Outstanding borrowings at December 31 are as follows: (000's omitted) 2017 2016 FHLB overnight advance $ 24,000 $ 146,200 Subordinated debt held by unconsolidated subsidiary trusts, net of discount of $332 and $357, respectively 122,814 102,170 Securities sold under agreement to repurchase, short term 337,011 0 FHLB Long term advances 2,071 0 Total borrowings $ 485,896 $ 248,370
Borrowings by Contractual Maturity Dates	Borrowings at December 31, 2017 have contractual maturity dates as follows: (000's omitted, except rate) Carrying Value Weighted-average Rate at December 31, 2017 January 2, 2018 $ 361,011 0.54 % July 3, 2023 601 2.25 % October 23, 2023 515 1.50 % October 1, 2025 329 1.50 % March 1, 2029 626 2.50 % July 31, 2031 24,875 4.96 % December 15, 2034 20,619 3.54 % December 15, 2036 77,320 3.24 % Total $ 485,896 1.34 %
Terms of Preferred Securities	The terms of the preferred securities of each trust are as follows: Trust Issuance Date Par Amount Interest Rate Maturity Date Call Price CST III 7/31/2001 $24.5 million 3 month LIBOR plus 3.58% (4.96%) 7/31/2031 Par CCT IV 12/8/2006 $75.0 million 3 month LIBOR plus 1.65% (3.24%) 12/15/2036 Par MBVT I 12/15/2004 $20.6 million 3 month LIBOR plus 1.95% (3.54%) 12/15/2034 Par

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2017
INCOME TAXES [Abstract]
Provision for Income Taxes	The provision for income taxes for the years ended December 31 is as follows: (000's omitted) 2017 2016 2015 Current: Federal $ 31,152 $ 32,829 $ 27,663 State and other 6,788 4,890 2,608 Deferred: Federal (28,146 ) 11,444 9,604 State and other (546 ) 1,622 1,112 Provision for income taxes $ 9,248 $ 50,785 $ 40,987
Components of Net Deferred Tax Liability	Components of the net deferred tax liability, included in other liabilities, as of December 31 are as follows: (000's omitted) 2017 2016 Allowance for loan losses $ 11,675 $ 18,366 Employee benefits 4,216 6,311 Debt extinguishment 0 299 Other, net 0 5,202 Deferred tax asset 15,891 30,178 Investment securities 22,690 32,839 Tax-deductible goodwill 39,154 43,504 Loan origination costs 6,109 8,228 Depreciation 2,372 71 Mortgage servicing rights 330 548 Pension 13,228 18,194 Other, net 542 0 Deferred tax liability 84,425 103,384 Net deferred tax liability $ (68,534 ) $ (73,206 )
Reconciliation of Differences between Federal Statutory Income Tax Rate and Effective Tax Rate	A reconciliation of the differences between the federal statutory income tax rate and the effective tax rate for the years ended December 31 is shown in the following table: 2017 2016 2015 Federal statutory income tax rate 35.0 % 35.0 % 35.0 % Increase (reduction) in taxes resulting from: Tax-exempt interest (3.8 ) (4.0 ) (5.0 ) State income taxes, net of federal benefit 2.5 2.7 1.8 Stock-based compensation (2.0 ) 0 0 Federal deferred tax revaluation adjustment (23.7 ) 0 0 Other, net (2.2 ) (0.9 ) (0.8 ) Effective income tax rate 5.8 % 32.8 % 31.0 %
Reconciliation of Unrecognized Tax Benefits	A reconciliation of the unrecognized tax benefits for the years ended December 31 is shown in the following table: (000’s omitted) 2017 2016 2015 Unrecognized tax benefits at beginning of year $ 92 $ 127 $ 162 Changes related to: Lapse of statutes of limitations (68 ) (35 ) (35 ) Unrecognized tax benefits at end of year $ 24 $ 92 $ 127

BENEFIT PLANS (Tables)

BENEFIT PLANS (Tables)	12 Months Ended
	Dec. 31, 2017
BENEFIT PLANS [Abstract]
Funded Status of Plans Reconciled with Amounts Reported in Consolidated Statements of Condition	Using a measurement date of December 31, the following table shows the funded status of the Company's plans reconciled with amounts reported in the Company's consolidated statements of condition: Pension Benefits Post-retirement Benefits (000's omitted) 2017 2016 2017 2016 Change in benefit obligation: Benefit obligation at the beginning of year $ 127,084 $ 127,134 $ 1,806 $ 1,918 Service cost 4,181 4,106 0 0 Interest cost 5,717 5,624 76 82 Plan amendment / acquisition 11,646 22 0 0 Participant contributions 0 0 467 516 Deferred actuarial loss/(gain) 8,978 (1,628 ) 245 174 Benefits paid (10,156 ) (8,174 ) (809 ) (884 ) Benefit obligation at end of year 147,450 127,084 1,785 1,806 Change in plan assets: Fair value of plan assets at beginning of year 180,400 172,026 0 0 Actual return of plan assets 22,954 14,402 0 0 Participant contributions 0 0 467 516 Employer contributions 9,839 2,146 342 368 Plan acquisition 14,070 0 0 0 Benefits paid (10,156 ) (8,174 ) (809 ) (884 ) Fair value of plan assets at end of year 217,107 180,400 0 0 Over/(Under) funded status at year end $ 69,657 $ 53,316 $ (1,785 ) $ (1,806 ) Amounts recognized in the consolidated statement of condition were: Other assets $ 81,000 $ 64,709 $ 0 $ 0 Other liabilities (11,343 ) (11,393 ) (1,785 ) (1,806 ) Amounts recognized in accumulated other comprehensive income (loss) (“AOCI”) were: Net loss $ 26,935 $ 28,323 $ 420 $ 183 Net prior service cost (credit) 2,944 2,264 (1,622 ) (1,801 ) Pre-tax AOCI 29,879 30,587 (1,202 ) (1,618 ) Taxes (7,340 ) (11,622 ) 296 614 AOCI at year end $ 22,539 $ 18,965 $ (906 ) $ (1,004 )
Amounts Recognized in Accumulated Other Comprehensive Income, Net of Tax	Amounts recognized in accumulated other comprehensive income, net of tax, for the year ended December 31, are as follows: Pension Benefits Post-retirement Benefits (000's omitted) 2017 2016 2017 2016 Prior service cost/(credit) $ 424 $ (26 ) $ 111 $ 110 Net (gain) loss (851 ) (3,517 ) 148 111 Total $ (427 ) $ (3,543 ) $ 259 $ 221
Estimated Costs, Net of Tax, That Will Be Amortized from Accumulated Other Comprehensive (Income) Loss into Net Periodic (Income) Cost over Next Fiscal Year	The estimated costs, net of tax, that will be amortized from accumulated other comprehensive (income) loss into net periodic (income) cost over the next fiscal year are as follows: (000's omitted) Pension Benefits Post-retirement Benefits Prior service credit $ (330 ) $ (179 ) Net loss 1,054 18 Total $ 724 $ (161 )
Weighted Average Assumptions Used To Determine Benefit Obligations	The weighted-average assumptions used to determine the benefit obligations as of December 31 are as follows: Pension Benefits Post-retirement Benefits 2017 2016 2017 2016 Discount rate 4.00 % 4.50 % 4.00 % 4.40 % Expected return on plan assets 7.00 % 7.00 % N/A N/A Rate of compensation increase 3.50 % 3.50 % N/A N/A
Net Periodic Benefit Cost	The net periodic benefit cost as of December 31 is as follows: Pension Benefits Post-retirement Benefits (000's omitted) 2017 2016 2015 2017 2016 2015 Service cost $ 4,181 $ 4,106 $ 3,324 $ 0 $ 0 $ 0 Interest cost 5,717 5,624 5,506 76 82 87 Expected return on plan assets (13,354 ) (11,842 ) (12,169 ) 0 0 0 Plan amendment 0 20 0 0 0 0 Amortization of unrecognized net loss/(gain) 767 1,508 1,466 8 (5 ) (13 ) Amortization of prior service cost 55 43 8 (179 ) (179 ) (179 ) Net periodic (benefit) $ (2,634 ) $ (541 ) $ (1,865 ) $ (95 ) $ (102 ) $ (105 )
Weighted-Average Assumptions Used to Determine Benefit Obligations and Net Periodic Pension Cost	The weighted-average assumptions used to determine the net periodic pension cost for the years ended December 31 are as follows: Pension Benefits Post-retirement Benefits 2017 2016 2015 2017 2016 2015 Discount rate 4.40 % 4.70 % 4.50 % 4.40 % 4.70 % 4.50 % Expected return on plan assets 7.00 % 7.00 % 7.00 % N/A N/A N/A Rate of compensation increase 3.50 % 3.50 % 3.50 % N/A N/A N/A
Amount of Expected Benefit Payments	The amount of benefit payments that are expected to be paid over the next ten years are as follows: (000's omitted) Pension Benefits Post-retirement Benefits 2018 $ 8,702 $ 145 2019 9,163 142 2020 9,404 139 2021 9,943 136 2022 10,378 133 2023-2027 56,064 618
Fair Value of Defined Benefit Plan Assets by Asset Category	The fair values of the Company’s defined benefit pension plan assets at December 31, 2017 by asset category are as follows: Asset category (000’s omitted) Quoted Prices in Active Markets for Identical Assets Level 1 Significant Observable Inputs Level 2 Significant Unobservable Inputs Level 3 Total Money Market Accounts $ 0 $ 10,381 $ 0 $ 10,381 Equity securities: U.S. large-cap 53,154 0 0 53,154 U.S mid/small cap 26,309 0 0 26,309 CBU stock 8,344 0 0 8,344 International 47,723 0 0 47,723 135,530 0 0 135,530 Fixed income securities: Government securities 13,929 9,686 0 23,615 Investment grade bonds 19,278 0 0 19,278 High yield (a) 16,297 0 0 16,297 49,504 9,686 0 59,190 Other investments (b) 11,302 73 0 11,375 Total (c) $ 196,336 $ 20,140 $ 0 $ 216,476 The fair values of the Company’s defined benefit pension plan assets at December 31, 2016 by asset category are as follows: Asset category (000’s omitted) Quoted Prices in Active Markets for Identical Assets Level 1 Significant Observable Inputs Level 2 Significant Unobservable Inputs Level 3 Total Money Market Accounts $ 103 $ 8,048 $ 0 $ 8,151 Equity securities: U.S. large-cap 43,235 0 0 43,235 U.S mid/small cap 19,032 0 0 19,032 CBU stock 7,417 0 0 7,417 International 27,064 0 0 27,064 96,748 0 0 96,748 Fixed income securities: Government securities 25,375 5,863 0 31,238 Investment grade bonds 15,253 0 0 15,253 High yield (a) 16,615 0 0 16,615 57,243 5,863 0 63,106 Other investments (b) 12,023 58 0 12,081 Total (c) $ 166,117 $ 13,969 $ 0 $ 180,086 (a) This category is exchange-traded funds representing a diversified index of high yield corporate bonds. (b) This category is comprised of exchange-traded funds and mutual funds holding non-traditional investment classes including private equity funds and alternative exchange funds. (c) Excludes dividends and interest receivable totaling $0.6 million and $0.3 million at December 31, 2017 and 2016, respectively.

STOCK-BASED COMPENSATION PLANS

STOCK-BASED COMPENSATION PLANS (Tables)	12 Months Ended
	Dec. 31, 2017
STOCK-BASED COMPENSATION PLANS [Abstract]
Activity in Long-Term Incentive Program	Activity in this long-term incentive program is as follows: Stock Options Outstanding Weighted- average Exercise Price of Shares Outstanding at December 31, 2015 1,969,301 $ 28.15 Granted 330,383 38.02 Exercised (525,298 ) 25.12 Forfeited (18,394 ) 34.47 Outstanding at December 31, 2016 1,755,992 30.85 Granted 197,943 57.02 Exercised (238,499 ) 25.72 Forfeited (7,140 ) 37.47 Outstanding at December 31, 2017 1,708,296 34.57 Exercisable at December 31, 2017 1,015,823 $ 29.57
Summary of Information about Stock Options Outstanding under Stock Option Plan	The following table summarizes the information about stock options outstanding under the Company’s stock option plan at December 31, 2017: Options outstanding Options exercisable Range of Exercise Price Shares Weighted- average Exercise Price Weighted- average Remaining Life (years) Shares Weighted average Exercise Price $ 0.00 – $18.00 24,736 $ 17.82 1.31 24,736 $ 17.82 $ 18.001 – $28.00 314,511 22.23 2.93 314,511 22.23 $ 28.001 – $29.00 171,083 28.78 4.22 171,083 28.78 $ 29.001 – $30.00 228,668 29.79 5.20 176,843 29.79 $ 30.001 – $40.00 771,781 37.09 7.28 317,005 37.06 $ 40.001 – $60.00 197,517 57.02 9.14 11,645 57.12 TOTAL 1,708,296 $ 34.57 6.02 1,015,823 $ 29.57
Summary of Valuation Assumptions Used to Estimate Value of Stock Options	The Black-Scholes model requires several assumptions, which management developed based on historical trends and current market observations. 2017 2016 2015 Weighted-average Fair Value of Options Granted $ 12.78 $ 7.90 $ 7.48 Assumptions: Weighted-average expected life (in years) 6.50 6.50 6.50 Future dividend yield 3.19 % 3.43 % 3.40 % Share price volatility 29.71 % 30.00 % 30.34 % Weighted-average risk-free interest rate 2.31 % 1.72 % 1.73 %
Activity of Unvested Restricted Stock Awards	A summary of the status of the Company’s unvested restricted stock awards as of December 31, 2017, and changes during the twelve months ended December 31, 2017 and 2016, is presented below: Restricted Shares Weighted-average grant date fair value Unvested at December 31, 2015 246,311 $ 27.85 Awards 148,240 27.04 Forfeitures (42,394 ) 17.49 Vestings (98,327 ) 25.64 Unvested at December 31, 2016 253,830 29.98 Awards 46,428 57.02 Forfeitures (4,863 ) 24.78 Vestings (64,522 ) 33.69 Unvested at December 31, 2017 230,873 $ 34.06

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2017
EARNINGS PER SHARE [Abstract]
Reconciliation of Basic to Diluted Earnings per Share	The following is a reconciliation of basic to diluted earnings per share for the years ended December 31, 2017, 2016 and 2015. (000's omitted, except per share data) 2017 2016 2015 Net income $ 150,717 $ 103,812 $ 91,230 Income attributable to unvested stock-based compensation awards (597 ) (550 ) (453 ) Income available to common shareholders $ 15 0, 0 $ 103,262 $ 90,777 Weighted-average common shares outstanding - basic 48 , 44,091 40,996 Basic earnings per share $ 3 . $ 2.34 $ 2.21 Net income $ 150,717 $ 103,812 $ 91,230 Income attributable to unvested stock-based compensation awards (597 ) (550 ) (453 ) Income available to common shareholders $ 150,12 0 $ 103,262 $ 90,777 Weighted-average common shares outstanding 48 , 44,091 40,996 Assumed exercise of stock options 627 394 405 Weighted-average common shares outstanding – diluted 49,470 44,485 41,401 Diluted earnings per share $ 3.03 $ 2.32 $ 2.19 Cash dividends declared per share $ 1.32 $ 1.26 $ 1.22

COMMITMENTS, CONTINGENT LIABI43

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS (Tables)	12 Months Ended
	Dec. 31, 2017
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS [Abstract]
Off Balance Sheet Financial Instruments Contract Amounts	The contract amounts of commitments and contingencies are as follows at December 31: (000's omitted) 2017 2016 Commitments to extend credit $ 1,080,004 $ 773,442 Standby letters of credit 23,782 22,656 Total $ 1,103,786 $ 796,098

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2017
LEASES [Abstract]
Future Minimum Rental Commitments	The future minimum rental commitments as of December 31, 2017 for all non-cancelable operating leases are as follows: 2018 $ 9,189 2019 8,194 2020 6,603 2021 5,164 2022 4,101 Thereafter 8,623 Total $ 41,874

REGULATORY MATTERS (Tables)

REGULATORY MATTERS (Tables)	12 Months Ended
	Dec. 31, 2017
REGULATORY MATTERS [Abstract]
Capital Ratios and Amounts	As of December 31, 2017, the OCC categorized the Company and Bank as “well capitalized” under the regulatory framework for prompt corrective action. Actual For capital adequacy purposes For capital adequacy purposes plus Capital Conservation Buffer To be well-capitalized under prompt corrective action (000’s omitted) Amount Ratio Amount Ratio Amount Ratio Amount Ratio Community Bank System, Inc.: 2017 Tier 1 Leverage ratio $ 995,860 10.00 % $ 398,183 4.00 % $ 497,729 5.00 % Tier 1 risk-based capital 995,860 16.64 % 358,988 6.00 % $ 433,777 7.25 % 478,651 8.00 % Total risk-based capital 1,043,910 17.45 % 478,651 8.00 % 553,440 9.25 % 598,314 10.00 % Common equity tier 1 capital 876,685 14.65 % 269,241 4.50 % 344,030 5.75 % 388,904 6.50 % 2016 Tier 1 Leverage ratio $ 858,347 10.55 % $ 325,438 4.00 % $ 406,798 5.00 % Tier 1 risk-based capital 858,347 18.10 % 284,583 6.00 % $ 314,228 6.625 % 379,445 8.00 % Total risk-based capital 905,996 19.10 % 379,445 8.00 % 409,089 8.625 % 474,306 10.00 % Common equity tier 1 capital 759,199 16.01 % 213,438 4.50 % 243,082 5.125 % 308,299 6.50 % Community Bank, N.A.: 2017 Tier 1 Leverage ratio $ 859,538 8.71 % $ 394,981 4.00 % $ 493,726 5.00 % Tier 1 risk-based capital 859,538 14.50 % 355,641 6.00 % $ 429,733 7.25 % 474,188 8.00 % Total risk-based capital 907,588 15.31 % 474,188 8.00 % 548,280 9.25 % 592,736 10.00 % Common equity tier 1 capital 859,483 14.50 % 266,731 4.50 % 340,823 5.75 % 385,278 6.50 % 2016 Tier 1 Leverage ratio $ 672,633 8.30 % $ 324,080 4.00 % $ 405,099 5.00 % Tier 1 risk-based capital 672,633 14.28 % 282,662 6.00 % $ 312,106 6.625 % 376,883 8.00 % Total risk-based capital 720,282 15.29 % 376,883 8.00 % 406,327 8.625 % 471,104 10.00 % Common equity tier 1 capital 672,578 14.28 % 211,997 4.50 % 241,441 5.125 % 306,217 6.50 %

PARENT COMPANY STATEMENTS (Tabl

PARENT COMPANY STATEMENTS (Tables)	12 Months Ended
	Dec. 31, 2017
PARENT COMPANY STATEMENTS [Abstract]
Condensed Statements of Condition of Parent Company	The condensed statements of condition of the parent company at December 31 are as follows: (000's omitted) 2017 2016 Assets: Cash and cash equivalents $ 84,460 $ 151,127 Investment securities 4,322 3,628 Investment in and advances to: Bank subsidiary 1,511,780 1,116,554 Non-bank subsidiaries 169,341 35,566 Other assets 9,150 10,345 Total assets $ 1,779,053 $ 1,317,220 Liabilities and shareholders' equity: Accrued interest and other liabilities $ 20,924 $ 16,950 Borrowings 122,814 102,170 Shareholders' equity 1,635,315 1,198,100 Total liabilities and shareholders' equity $ 1,779,053 $ 1,317,220
Condensed Statements of Income of Parent Company	The condensed statements of income of the parent company for the years ended December 31 is as follows: (000's omitted) 2017 2016 2015 Revenues: Dividends from subsidiaries: Bank subsidiary $ 91,000 $ 89,000 $ 70,000 Non-bank subsidiaries 35,500 1,750 6,000 Interest and dividends on investments 133 102 94 Total revenues 126,633 90,852 76,094 Expenses: Interest on borrowings 3,904 2,949 2,537 Acquisition expenses 91 429 0 Other expenses 26 11 19 Total expenses 4,021 3,389 2,556 Income before tax benefit and equity in undistributed net income of subsidiaries 122,612 87,463 73,538 Income tax benefit/(expense) 1,930 866 (572 ) Income before equity in undistributed net income of subsidiaries 124,542 88,329 72,966 Equity in undistributed net income of subsidiaries 26,175 15,483 18,264 Net income $ 150,717 $ 103,812 $ 91,230 Other comprehensive (loss), net of tax: Changes in other comprehensive income/(loss) related to pension and other post retirement obligations 168 3,322 (4,567 ) Changes in other comprehensive loss related to unrealized losses on available-for-sale securities (11,065 ) (14,714 ) (6,918 ) Other comprehensive loss (10,897 ) (11,392 ) (11,485 ) Comprehensive income $ 139,820 $ 92,420 $ 79,745
Statements of Cash Flows of Parent Company	The statements of cash flows of the parent company for the years ended December 31 is as follows: (000's omitted) 2017 2016 2015 Operating activities: Net income $ 150,717 $ 103,812 $ 91,230 Adjustments to reconcile net income to net cash provided by operating activities Equity in undistributed net income of subsidiaries (26,175 ) (15,483 ) (18,264 ) Net change in other assets and other liabilities 1,870 (215 ) (27 ) Net cash provided by operating activities 126,412 88,114 72,939 Investing activities: Proceeds from sale of investment securities 0 0 0 Cash (paid)/received for acquisitions, net of cash acquired of $150,534, $0, and $81,772, respectively (139,471 ) 0 25,505 Capital contributions to subsidiaries (11,063 ) 0 (80,231 ) Net cash used in investing activities (150,534 ) 0 (54,726 ) Financing activities: Issuance of common stock 9,700 15,326 13,975 Purchase of treasury stock (3,306 ) (3,470 ) (9,126 ) Sale of treasury stock 10,060 8,888 16,571 Increase in deferred compensation arrangements 3,306 0 0 Cash dividends paid (62,305 ) (55,048 ) (49,273 ) Net cash used in financing activities (42,545 ) (34,304 ) (27,853 ) Change in cash and cash equivalents (66,667 ) 53,81 0 (9,640 ) Cash and cash equivalents at beginning of year 151,127 97,317 106,957 Cash and cash equivalents at end of year $ 84,460 $ 151,127 $ 97,317 Supplemental disclosures of cash flow information: Cash paid for interest $ 3,826 $ 2,909 $ 2,523 Supplemental disclosures of noncash financing activities Dividends declared and unpaid $ 17,460 $ 14,268 $ 13,605 Capital contributions to subsidiaries 513,769 0 76,461 Common stock issued for acquisition 343,132 0 102,202

FAIR VALUE (Tables)

FAIR VALUE (Tables)	12 Months Ended
	Dec. 31, 2017
FAIR VALUE [Abstract]
Summary of Fair Value Measured on a Recurring Basis	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. December 31, 2017 (000's omitted) Level 1 Level 2 Level 3 Total Fair Value Available-for-sale investment securities: U.S. Treasury and agency securities $ 1,909,290 $ 144,781 $ 0 $ 2,054,071 Obligations of state and political subdivisions 0 528,956 0 528,956 Government agency mortgage-backed securities 0 357,538 0 357,538 Corporate debt securities 0 2,623 0 2,623 Government agency collateralized mortgage obligations 0 87,374 0 87,374 Marketable equity securities 526 0 0 526 Total available-for-sale investment securities 1,909,816 1,121,272 0 3,031,088 Mortgage loans held for sale 0 461 0 461 Commitments to originate real estate loans for sale 0 0 89 89 Forward sales commitments 0 4 0 4 Interest rate swap agreements asset 0 1,064 0 1,064 Interest rate swap agreements liability 0 (904 ) 0 (904 ) Total $ 1,909,816 $ 1,121,897 $ 89 $ 3,031,802 December 31, 2016 (000's omitted) Level 1 Level 2 Level 3 Total Fair Value Available-for-sale investment securities: U.S. Treasury and agency securities $ 1,902,762 $ 0 $ 0 $ 1,902,762 Obligations of state and political subdivisions 0 594,990 0 594,990 Government agency mortgage-backed securities 0 235,230 0 235,230 Corporate debt securities 0 5,687 0 5,687 Government agency collateralized mortgage obligations 0 9,535 0 9,535 Marketable equity securities 452 0 0 452 Total available-for-sale investment securities 1,903,214 845,442 0 2,748,656 Mortgage loans held for sale 0 2,416 0 2,416 Commitments to originate real estate loans for sale 0 0 54 54 Forward sales commitments 0 3 0 3 Total $ 1,903,214 $ 847,861 $ 54 $ 2,751,129
Assets and Liabilities Measured on a Non-Recurring Basis	Assets and liabilities measured on a non-recurring basis: December 31, 2017 December 31, 2016 (000's omitted) Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Impaired loans $ 0 $ 0 $ 0 $ 0 $ 0 $ 0 $ 633 $ 633 Other real estate owned 0 0 1,915 1,915 0 0 1,966 1,966 Total $ 0 $ 0 $ 1,915 $ 1,915 $ 0 $ 0 $ 2,599 $ 2,599
Significant Unobservable Inputs, Fair Value Valuation Techniques	The significant unobservable inputs used in the determination of fair value of assets classified as Level 3 on a recurring or non-recurring basis as of December 31, 2017 are as follows: (000's omitted) Fair Value Valuation Technique Significant Unobservable Inputs Significant Unobservable Input Range (Weighted Average) Other real estate owned $ 1,915 Fair value of collateral Estimated cost of disposal/market adjustment 9.0% - 99.0% (38.5 %) Commitments to originate real estate loans for sale 89 Discounted cash flow Embedded servicing value 1 % The significant unobservable inputs used in the determination of fair value of assets classified as Level 3 on a recurring or non-recurring basis as of December 31, 2016 are as follows: (000's omitted) Fair Value Valuation Technique Significant Unobservable Inputs Significant Unobservable Input Range (Weighted Average) Other real estate owned $ 1,966 Fair value of collateral Estimated cost of disposal/market adjustment 9.0% - 97.0% (29.6 %) Impaired loans 633 Fair value of collateral Estimated cost of disposal/market adjustment 15.0% - 50.0% (36.5 %) Commitments to originate real estate loans for sale 54 Discounted cash flow Embedded servicing value 1 %
Carrying Amounts and Estimated Fair Values of Other Financial Instruments	The carrying amounts and estimated fair values of the Company’s other financial instruments that are not accounted for at fair value at December 31, 2017 and 2016 are as follows: December 31, 2017 December 31, 2016 (000's omitted) Carrying Value Fair Value Carrying Value Fair Value Financial assets: Net loans $ 6,209,174 $ 6,244,941 $ 4,901,329 4,935,140 Financial liabilities: Deposits 8,444,420 8,431,481 7,075,954 7,071,191 Short-term borrowings 24,000 24,000 146,200 146,200 Securities sold under agreement to repurchase, short-term 337,011 337,011 0 0 Other long-term debt 2,071 2,021 0 0 Subordinated debt held by unconsolidated subsidiary trusts 122,814 122,814 102,170 90,144

VARIABLE INTEREST ENTITIES (Tab

VARIABLE INTEREST ENTITIES (Tables)	12 Months Ended
	Dec. 31, 2017
VARIABLE INTEREST ENTITIES [Abstract]
Carrying Amount and Classification of Assets and Liabilities of 706 North Clinton	The carrying amount of the assets and liabilities of 706 North Clinton and the classification of these assets and liabilities in the Company’s consolidated statements of condition at December 31 is as follows: (000's omitted) 2017 2016 Cash and cash equivalents $ 74 $ 30 Premises and equipment, net 6,266 6,429 Other assets 5 0 Total assets $ 6,345 $ 6,459 Accrued interest and other liabilities / Total liabilities $ 0 $ 1

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2017
SEGMENT INFORMATION [Abstract]
Schedule of Segment Reporting Information by Segment	Information about reportable segments and reconciliation of the information to the consolidated financial statements follows: (000's omitted) Banking Employee Benefit Services All Other Eliminations Consolidated Total 2017 Net interest income $ 315,025 $ 396 $ 254 $ 0 $ 315,675 Provision for loan losses 10,984 0 0 0 10,984 Noninterest income 73,337 82,743 49,201 (2,858 ) 202,423 Amortization of intangible assets 5,296 8,578 3,067 0 16,941 Acquisition expenses 24,549 1,194 243 0 25,986 Other operating expenses 218,608 51,138 37,334 (2,858 ) 304,222 Income before income taxes $ 128,925 $ 22,229 $ 8,811 $ 0 $ 159,965 Assets $ 10,505,919 $ 203,369 $ 66,548 $ (29,638 ) $ 10,746,198 Goodwill $ 629,916 $ 84,449 $ 20,065 $ 0 $ 734,430 2016 Net interest income $ 273,542 $ 162 $ 192 $ 0 $ 273,896 Provision for loan losses 8,076 0 0 0 8,076 Noninterest income 66,059 48,261 43,747 (2,442 ) 155,625 Amortization of intangible assets 2,682 420 2,377 0 5,479 Acquisition expenses 1,005 445 256 0 1,706 Other operating expenses 190,263 36,892 34,950 (2,442 ) 259,663 Income before income taxes $ 137,575 $ 10,666 $ 6,356 $ 0 $ 154,597 Assets $ 8,598,057 $ 38,742 $ 71,428 $ (41,790 ) $ 8,666,437 Goodwill $ 440,870 $ 8,019 $ 16,253 $ 0 $ 465,142 2015 Net interest income $ 248,167 $ 132 $ 121 $ 0 $ 248,420 Provision for loan losses 6,447 0 0 0 6,447 Noninterest income 57,704 46,784 20,967 (2,156 ) 123,299 Amortization of intangible assets 2,803 515 345 0 3,663 Acquisition expenses 6,947 21 69 0 7,037 Other operating expenses 174,918 35,197 14,396 (2,156 ) 222,355 Income before income taxes $ 114,756 $ 11,183 $ 6,278 $ 0 $ 132,217 Assets $ 8,513,228 $ 35,011 $ 70,067 $ (65,637 ) $ 8,552,669 Goodwill $ 439,052 $ 8,019 $ 16,181 $ 0 $ 463,252

SUMMARY OF SIGNIFICANT ACCOUN50

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017USD ($)SubsidiaryTrustBranchCountyComponentCalculationSegmentFactorType$ / shares	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Subsidiary, Sale of Stock [Line Items]
Number of significant consolidated subsidiaries owned | Subsidiary		2
Number of unconsolidated subsidiary business trusts owned | Trust		3
Number of bank branches | Branch		225
Risks and Uncertainties [Abstract]
Number of main components of economic risk | Component		3
Financing Receivable, Recorded Investment, Past Due [Line Items]
Period for which a nonaccrual TDR loan remains on nonaccrual status		12 months
Number of days past due for loans to be placed on nonaccrual status		90 days
Allowance for Loan Losses [Abstract]
Number of broad components used in allowance methodology | Component		2
Number of calculations used for general loan loss allocations | Calculation		2
Number of main loan segments | Segment		5
Period of historical net charge-off data for each loan class used in determining allowance level		36 months
Number of qualitative environmental factors used in qualitative calculation for general loan loss allocations | Factor		8
Other Real Estate [Abstract]
Other real estate		$ 1,900	$ 2,000
Derivative Financial Instruments and Hedging Activities [Abstract]
Number of types of derivative financial instruments | Type		3
Advertising [Abstract]
Advertising costs		$ 5,700	$ 3,900	$ 3,600
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Corporate income tax rate		35.00%	35.00%	35.00%
Reclassification related to tax effect of Tax Cuts and Jobs Act		$ 0
Minimum [Member]
Investments in Real Estate Limited Partnerships [Abstract]
Company's ownership interest in limited partnerships		5.00%
Maximum [Member]
Investments in Real Estate Limited Partnerships [Abstract]
Company's ownership interest in limited partnerships		99.99%
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification related to tax effect of Tax Cuts and Jobs Act		$ 645
Accumulated Other Comprehensive Income/(Loss) [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification related to tax effect of Tax Cuts and Jobs Act		(645)
ASU 2014-01 [Member]
Investments in Real Estate Limited Partnerships [Abstract]
Unfunded commitments		3,200
Impairment losses related to real estate partnerships		0
ASU 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effect of change on net income from excess tax benefits		$ 3,100
Effect of change on net income from excess tax benefits per diluted common share (in dollars per share) | $ / shares		$ 0.06
ASU 2018-02 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification related to tax effect of Tax Cuts and Jobs Act		$ 645
ASU 2018-02 [Member] | Accumulated Other Comprehensive Income/(Loss) [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification related to tax effect of Tax Cuts and Jobs Act		$ (645)
Plan [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Corporate income tax rate	21.00%
Plan [Member] | ASU 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Corporate income tax rate	21.00%
Upstate New York [Member]
Subsidiary, Sale of Stock [Line Items]
Number of counties where the bank has facilities | County		35
Northeastern Pennsylvania [Member]
Subsidiary, Sale of Stock [Line Items]
Number of counties where the bank has facilities | County		6
Vermont [Member]
Subsidiary, Sale of Stock [Line Items]
Number of counties where the bank has facilities | County		12
Western Massachusetts [Member]
Subsidiary, Sale of Stock [Line Items]
Number of counties where the bank has facilities | County		1
Consumer Installment Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of days past due after which loans are charged off to the extent outstanding principal balance exceeds fair value of collateral/property		90 days
Consumer Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of days past due after which loans are charged off to the extent outstanding principal balance exceeds fair value of collateral/property		180 days
Home Equity Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of days past due after which loans are charged off to the extent outstanding principal balance exceeds fair value of collateral/property		180 days
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life		3 years
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life		10 years
Software [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life		3 years
Software [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life		7 years
Hardware [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life		3 years
Hardware [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life		7 years
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life		10 years
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life		40 years
Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life		20 years
BPAS [Member]
Subsidiary, Sale of Stock [Line Items]
Number of significant consolidated subsidiaries owned | Subsidiary		5
Hand Benefits & Trust [Member]
Subsidiary, Sale of Stock [Line Items]
Number of significant consolidated subsidiaries owned | Subsidiary		1
NRS [Member]
Subsidiary, Sale of Stock [Line Items]
Number of significant consolidated subsidiaries owned | Subsidiary		1
Core Deposits [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (amortization period)		7 years
Core Deposits [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (amortization period)		20 years
Customer Relationships [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (amortization period)		7 years
Customer Relationships [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset useful life (amortization period)		20 years
Commercial Portfolio Segment [Member] | Minimum [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Threshold balance of loans individually evaluated for impairment		$ 500

ACQUISITIONS (Details)

ACQUISITIONS (Details) shares in Thousands, $ in Thousands

Dec. 04, 2017USD ($)shares

Nov. 17, 2017USD ($)

May 12, 2017USD ($)Branchshares

Mar. 01, 2017USD ($)

Feb. 03, 2017USD ($)

Jan. 02, 2017USD ($)

Dec. 04, 2015USD ($)Branchshares

Dec. 31, 2017USD ($)

Sep. 30, 2017USD ($)

Jun. 30, 2017USD ($)

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Business Acquisition [Line Items]

Cash

$ 107,414

$ 575

$ (25,505)

Goodwill

$ 734,430

734,430

$ 465,142

$ 463,252

Increase (decrease) in other assets as a result of reclassification and adjustment

(300)

$ 5,500

$ (2,700)

Increase (decrease) in other liabilities as a result of reclassification and adjustment

(20)

6,600

(2,400)

Increase in investments as a result of updated information not available at the time of acquisition

200

Decrease in loans as a result of an adjustment to the valuation of acquired impaired loans

(500)

(600)

Increase in premises and equipment as a result of updated appraisal information not available at the time of acquisition

3,600

Gordon B. Roberts Agency, Inc [Member]

Business Acquisition [Line Items]

Cash

$ 1,350

Purchase price of acquisition

$ 3,700

Issuance of common shares (in shares) | shares

40

Assets acquired

$ 600

Other liabilities

700

Goodwill

2,200

Gordon B. Roberts Agency, Inc [Member] | Other Intangibles [Member]

Business Acquisition [Line Items]

Intangibles

$ 1,600

Northeast Capital Management, Inc [Member]

Business Acquisition [Line Items]

Cash

$ 1,200

Contingent payment

200

Northeast Capital Management, Inc [Member] | Other Intangibles [Member]

Business Acquisition [Line Items]

Intangibles

$ 1,200

Dryfoos [Member]

Business Acquisition [Line Items]

Cash

$ 3,000

Goodwill

1,700

Dryfoos [Member] | Other Intangibles [Member]

Business Acquisition [Line Items]

Intangibles

$ 1,700

BAS [Member]

Business Acquisition [Line Items]

Cash

$ 1,200

BAS [Member] | Other Intangibles [Member]

Business Acquisition [Line Items]

Intangibles

$ 1,200

Merchants Bancshares, Inc. [Member]

Business Acquisition [Line Items]

Cash

[1]

$ 82,898

Purchase price of acquisition

$ 345,152

Issuance of common shares (in shares) | shares

4,680

Assets acquired

$ 2,000,000

Other liabilities

11,750

Goodwill

189,046

Revenue earned

42,600

Expenses incurred

$ 19,900

Increase (decrease) in goodwill as a result of fair value adjustment

$ 800

(2,000)

Merchants Bancshares, Inc. [Member] | Other Intangibles [Member]

Business Acquisition [Line Items]

Intangibles

$ 2,857

Merchants Bancshares, Inc. [Member] | Vermont [Member]

Business Acquisition [Line Items]

Number of branch locations added upon merger | Branch

31

Merchants Bancshares, Inc. [Member] | Massachusetts [Member]

Business Acquisition [Line Items]

Number of branch locations added upon merger | Branch

1

Oneida Financial Corp [Member]

Business Acquisition [Line Items]

Cash

[1]

$ 56,266

Purchase price of acquisition

$ 158,468

Issuance of common shares (in shares) | shares

2,380

Number of new branch locations included in acquisition or purchase agreement | Branch

12

Assets acquired

$ 769,400

Other liabilities

1,333

Goodwill

89,681

Oneida Financial Corp [Member] | Other Intangibles [Member]

Business Acquisition [Line Items]

Intangibles

$ 9,994

Northeast Retirement Services, Inc. [Member]

Business Acquisition [Line Items]

Cash

[1]

$ 70,073

Purchase price of acquisition

148,556

Tangible assets, net

$ 36,100

Factor of straight-line rate of depreciation used in declining balance depreciation method

150.00%

Period of amortization

10 years

Deferred tax liability

$ 24,200

Other liabilities

28,002

Goodwill

76,430

Revenue earned

$ 31,500

Expenses incurred

$ 21,500

Increase (decrease) in goodwill as a result of fair value adjustment

$ (100)

$ 300

Northeast Retirement Services, Inc. [Member] | Other Intangibles [Member]

Business Acquisition [Line Items]

Intangibles

$ 60,200

[1]

Includes NECM $0.2 million contingent cash payment consideration.

ACQUISITIONS, Estimated Fair Va

ACQUISITIONS, Estimated Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands		May 12, 2017	Feb. 03, 2017	Jan. 04, 2016	Dec. 04, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consideration paid [Abstract]
Cash						$ 107,414	$ 575	$ (25,505)
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Goodwill						734,430	$ 465,142	$ 463,252
NRS [Member]
Consideration paid [Abstract]
Cash	[1]		$ 70,073
Community Bank System, Inc. common stock			78,483
Total net consideration paid			148,556
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents			11,063
Investment securities			20,294
Loans			0
Premises and equipment			411
Accrued interest receivable			72
Other assets			8,088
Deposits			0
Other liabilities			(28,002)
Short-term advances			0
Securities sold under agreement to repurchase, short-term			0
Long-term debt			0
Subordinated debt held by unconsolidated subsidiary trusts			0
Total identifiable assets, net			72,126
Goodwill			76,430
NRS [Member] | Core Deposits [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles			0
NRS [Member] | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles			$ 60,200
Merchants Bancshares, Inc. [Member]
Consideration paid [Abstract]
Cash	[1]	$ 82,898
Community Bank System, Inc. common stock		262,254
Total net consideration paid		345,152
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents		40,730
Investment securities		370,648
Loans		1,488,157
Premises and equipment		16,608
Accrued interest receivable		4,773
Other assets		51,585
Deposits		(1,448,406)
Other liabilities		(11,750)
Short-term advances		(80,000)
Securities sold under agreement to repurchase, short-term		(278,076)
Long-term debt		(3,615)
Subordinated debt held by unconsolidated subsidiary trusts		(20,619)
Total identifiable assets, net		156,106
Goodwill		189,046
Merchants Bancshares, Inc. [Member] | Core Deposits [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles		23,214
Merchants Bancshares, Inc. [Member] | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles		$ 2,857
WJL Agencies Inc [Member]
Consideration paid [Abstract]
Cash	[1]			$ 575
Community Bank System, Inc. common stock				0
Total net consideration paid				575
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents				0
Investment securities				0
Loans				0
Premises and equipment				0
Accrued interest receivable				0
Other assets				0
Deposits				0
Other liabilities				0
Short-term advances				0
Securities sold under agreement to repurchase, short-term				0
Long-term debt				0
Subordinated debt held by unconsolidated subsidiary trusts				0
Total identifiable assets, net				288
Goodwill				287
WJL Agencies Inc [Member] | Core Deposits [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles				0
WJL Agencies Inc [Member] | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles				$ 288
Other [Member]
Consideration paid [Abstract]
Cash	[1],[2]					6,775
Community Bank System, Inc. common stock	[2]					2,395
Total net consideration paid	[2]					9,170
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents	[2]					339
Investment securities	[2]					0
Loans	[2]					0
Premises and equipment	[2]					27
Accrued interest receivable	[2]					0
Other assets	[2]					583
Deposits	[2]					0
Other liabilities	[2]					(1,217)
Short-term advances	[2]					0
Securities sold under agreement to repurchase, short-term	[2]					0
Long-term debt	[2]					0
Subordinated debt held by unconsolidated subsidiary trusts	[2]					0
Total identifiable assets, net	[2]					5,358
Goodwill	[2]					3,812
Other [Member] | Core Deposits [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles	[2]					0
Other [Member] | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles	[2]					5,626
Total [Member]
Consideration paid [Abstract]
Cash	[1]					159,746
Community Bank System, Inc. common stock						343,132
Total net consideration paid						502,878
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents						52,132
Investment securities						390,942
Loans						1,488,157
Premises and equipment						17,046
Accrued interest receivable						4,845
Other assets						60,256
Deposits						(1,448,406)
Other liabilities						(40,969)
Short-term advances						(80,000)
Securities sold under agreement to repurchase, short-term						(278,076)
Long-term debt						(3,615)
Subordinated debt held by unconsolidated subsidiary trusts						(20,619)
Total identifiable assets, net						233,590
Goodwill						269,288
Total [Member] | Core Deposits [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles						23,214
Total [Member] | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles						$ 68,683
Oneida Financial Corp [Member]
Consideration paid [Abstract]
Cash	[1]				$ 56,266
Community Bank System, Inc. common stock					102,202
Total net consideration paid					158,468
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents					81,772
Investment securities					225,729
Loans					399,422
Premises and equipment					22,212
Accrued interest receivable					1,133
Other assets					26,529
Deposits					(699,241)
Other liabilities					(1,333)
Short-term advances					0
Securities sold under agreement to repurchase, short-term					0
Long-term debt					0
Subordinated debt held by unconsolidated subsidiary trusts					0
Total identifiable assets, net					68,787
Goodwill					89,681
Oneida Financial Corp [Member] | Core Deposits [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles					2,570
Oneida Financial Corp [Member] | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles					$ 9,994
[1]	Includes NECM $0.2 million contingent cash payment consideration.
[2]	Includes amounts related to the BAS, Dryfoos, NECM and GBR acquisitions.

ACQUISITIONS, Summary of Loans

ACQUISITIONS, Summary of Loans Acquired (Details) - Merchants Bancshares, Inc. [Member] $ in Thousands	May 12, 2017USD ($)
Summary of loans acquired [Abstract]
Contractually required principal and interest at acquisition	$ 1,888,028
Contractual cash flows not expected to be collected	(20,138)
Expected cash flows at acquisition	1,867,890
Interest component of expected cash flows	(379,733)
Fair value of acquired loans	1,488,157
Acquired Impaired Loans [Member]
Summary of loans acquired [Abstract]
Contractually required principal and interest at acquisition	15,454
Contractual cash flows not expected to be collected	(5,385)
Expected cash flows at acquisition	10,069
Interest component of expected cash flows	(793)
Fair value of acquired loans	9,276
Acquired Non Impaired Loans [Member]
Summary of loans acquired [Abstract]
Contractually required principal and interest at acquisition	1,872,574
Contractual cash flows not expected to be collected	(14,753)
Expected cash flows at acquisition	1,857,821
Interest component of expected cash flows	(378,940)
Fair value of acquired loans	$ 1,478,881

ACQUISITIONS, Intangible Asset,

ACQUISITIONS, Intangible Asset, Goodwill and Acquisition-related Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of loans acquired [Abstract]
Merger and acquisition integration-related expenses	$ 25,986	$ 1,706	$ 7,037
Merchants Bancshares, Inc. [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
Merchants Bancshares, Inc. [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
Dryfoos [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
Dryfoos [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
BAS [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
BAS [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
WJL Agencies Inc [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
WJL Agencies Inc [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
Oneida Financial Corp [Member] | Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years
Oneida Financial Corp [Member] | Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Estimated useful life	8 years

ACQUISITIONS, Supplemental Pro

ACQUISITIONS, Supplemental Pro Forma Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Supplemental Pro Forma Financial Information [Abstract]
Acquisitions-related expenses	$ 25,700
Total revenue, net of interest expense, pro forma	546,977	$ 536,183
Net income, pro forma	$ 176,257	$ 109,186

INVESTMENT SECURITIES (Details)

INVESTMENT SECURITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-Sale Portfolio [Abstract]
Amortized cost	$ 3,007,148	$ 2,706,863
Gross unrealized gains	33,501	47,463
Gross unrealized losses	9,561	5,670
Fair value	3,031,088	2,748,656
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	3,006,897
Estimated fair value	3,030,562
Other Securities [Abstract]
Amortized cost	50,291	35,736
Estimated fair value	50,291	35,736
U.S. Treasury and Agency Securities [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	2,043,023	1,876,358
Gross unrealized gains	15,886	28,522
Gross unrealized losses	4,838	2,118
Estimated fair value	2,054,071	1,902,762
Obligations of State and Political Subdivisions [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	514,949	582,655
Gross unrealized gains	14,064	13,389
Gross unrealized losses	57	1,054
Estimated fair value	528,956	594,990
Government Agency Mortgage-Backed Securities [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	358,180	232,657
Gross unrealized gains	3,121	5,040
Gross unrealized losses	3,763	2,467
Estimated fair value	357,538	235,230
Corporate Debt Securities [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	2,648	5,716
Gross unrealized gains	0	2
Gross unrealized losses	25	31
Estimated fair value	2,623	5,687
Government Agency Collateralized Mortgage Obligations [Member]
Available For Sale Debt Securities Amortized Cost Basis [Abstract]
Amortized cost	88,097	9,225
Gross unrealized gains	155	310
Gross unrealized losses	878	0
Estimated fair value	87,374	9,535
Marketable Equity Security [Member]
Available For Sale Equity Securities Amortized Cost Basis [Abstract]
Amortized cost	251	252
Gross unrealized gains	275	200
Gross unrealized losses	0	0
Estimated fair value	526	452
Federal Home Loan Bank Common Stock [Member]
Other Securities [Abstract]
Amortized cost	9,896	12,191
Estimated fair value	9,896	12,191
Federal Reserve Bank Common Stock [Member]
Other Securities [Abstract]
Amortized cost	30,690	19,781
Estimated fair value	30,690	19,781
Certificates of Deposit [Member]
Other Securities [Abstract]
Amortized cost	3,865	0
Estimated fair value	3,865	0
Other Equity Securities [Member]
Other Securities [Abstract]
Amortized cost	5,840	3,764
Estimated fair value	$ 5,840	$ 3,764

INVESTMENT SECURITIES, Investme

INVESTMENT SECURITIES, Investment Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2017USD ($)Position	Dec. 31, 2016USD ($)Position
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	249	268
12 months or longer | Position	56	17
Total | Position	305	285
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 991,521	$ 637,887
12 months or longer	75,713	21,790
Total	1,067,234	659,677
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	7,231	4,840
12 months or longer	2,330	830
Total	$ 9,561	$ 5,670
U.S. Treasury and Agency Securities [Member]
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	44	13
12 months or longer | Position	0	0
Total | Position	44	13
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 699,709	$ 449,242
12 months or longer	0	0
Total	699,709	449,242
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	4,838	2,118
12 months or longer	0	0
Total	$ 4,838	$ 2,118
Obligations of State and Political Subdivisions [Member]
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	45	197
12 months or longer | Position	0	0
Total | Position	45	197
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 23,432	$ 102,106
12 months or longer	0	0
Total	23,432	102,106
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	57	1,054
12 months or longer	0	0
Total	$ 57	$ 1,054
Government Agency Mortgage-Backed Securities [Member]
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	120	57
12 months or longer | Position	55	15
Total | Position	175	72
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 185,716	$ 83,862
12 months or longer	75,712	21,788
Total	261,428	105,650
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	1,433	1,637
12 months or longer	2,330	830
Total	$ 3,763	$ 2,467
Corporate Debt Securities [Member]
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	1	1
12 months or longer | Position	0	0
Total | Position	1	1
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 2,623	$ 2,677
12 months or longer	0	0
Total	2,623	2,677
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	25	31
12 months or longer	0	0
Total	$ 25	$ 31
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	39	0
12 months or longer | Position	1	2
Total | Position	40	2
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 80,041	$ 0
12 months or longer	1	2
Total	80,042	2
Available-for-Sale Securities, in Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	878	0
12 months or longer	0	0
Total	$ 878	$ 0

INVESTMENT SECURITIES, Amortize

INVESTMENT SECURITIES, Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Due in one year or less	$ 45,966
Due after one through five years	1,565,423
Due after five years through ten years	758,742
Due after ten years	190,489
Subtotal	2,560,620
Amortized cost	3,006,897
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Due in one year or less	46,042
Due after one through five years	1,572,634
Due after five years through ten years	769,828
Due after ten years	197,146
Subtotal	2,585,650
Fair value	3,030,562
Government Agency Mortgage-Backed Securities [Member]
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Without single maturity date	358,180
Amortized cost	358,180	$ 232,657
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Without single maturity date	357,538
Fair value	357,538	235,230
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Without single maturity date	88,097
Amortized cost	88,097	9,225
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Without single maturity date	87,374
Fair value	87,374	9,535
U.S. Treasury Securities [Member]
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Amortized cost	2,043,023	1,876,358
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Fair value	$ 2,054,071	$ 1,902,762

INVESTMENT SECURITIES, Invest59

INVESTMENT SECURITIES, Investment Securities Pledged as Collateral (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Investment securities pledged to collateralize certain deposits and borrowings	$ 1,530	$ 1,865
U.S. Treasury Securities [Member] | Securities Sold under Agreements to Repurchase [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment securities pledged to collateralize certain deposits and borrowings	$ 473.2

LOANS, Loan Summary (Details)

LOANS, Loan Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 6,256,757	$ 4,948,562
Allowance for loan losses	(47,583)	(47,233)	$ (45,401)	$ (45,341)
Net loans	6,209,174	4,901,329
Net deferred loan origination costs	25,300	22,800
Loans receivable, related parties [Roll Forward]
Balance at beginning of year	10,950	11,337
New loans	16,617	4,959
Payments	(5,223)	(5,346)
Balance at end of year	$ 22,344	10,950
Consumer Mortgage [Member] | Minimum [Member]
Loans receivable, net [Abstract]
Typical contract term	10 years
Consumer Mortgage [Member] | Maximum [Member]
Loans receivable, net [Abstract]
Typical contract term	30 years
Business Lending [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 2,424,223	1,490,076
Home Equity [Member] | Maximum [Member]
Loans receivable, net [Abstract]
Typical contract term	30 years
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 2,220,298	1,819,701
Allowance for loan losses	(10,465)	(10,094)	(10,198)	(10,286)
Commercial Portfolio Segment [Member] | Business Lending [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	2,424,223	1,490,076
Allowance for loan losses	(17,257)	(17,220)	(15,749)	(15,787)
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	1,011,978	1,044,972
Allowance for loan losses	(13,468)	(13,782)	(12,422)	(11,544)
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	179,929	191,815
Allowance for loan losses	(3,039)	(2,979)	(2,997)	(3,083)
Consumer Portfolio Segment [Member] | Home Equity [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	420,329	401,998
Allowance for loan losses	$ (2,107)	$ (2,399)	$ (2,666)	$ (2,701)

LOANS, Acquired Loans (Details)

LOANS, Acquired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Credit impaired acquired loans [Abstract]
Outstanding principal balance	$ 13,242	$ 6,354
Carrying amount	10,115	5,553
Credit impaired acquired loans, total balance due	13,400	6,600
Non-impaired acquired loans [Abstract]
Outstanding principal balance	1,658,780	497,308
Carrying amount	1,626,979	489,807
Total acquired loans [Abstract]
Outstanding principal balance	1,672,022	503,662
Carrying amount	1,637,094	495,360
Accretable discount related to acquired loans [Roll forward]
Balance at beginning of year	498	810
Merchants acquisition	793	0
Accretion recognized	(905)	(455)
Net reclassification to accretable from nonaccretable	590	143
Balance at end of year	$ 976	$ 498

LOANS, Credit Quality By Past D

LOANS, Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Aged analysis of the company's loans [Abstract]
Total loans		$ 6,256,757	$ 4,948,562
Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		2,508	1,963
Nonaccrual		16,020	16,600
Total past due		51,563	50,545
Current		4,568,100	4,402,657
Total loans		4,619,663	4,453,202
Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		33,035	31,982
Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		204	1,113
Nonaccrual		8,720	4,019
Total past due		17,167	8,439
Acquired impaired	[1]	10,115	5,553
Current		1,609,812	481,368
Total loans		1,637,094	495,360
Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		8,243	3,307
Consumer Mortgage [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,754,609	1,659,760
Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		465,689	159,941
Business Lending [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,424,223	1,490,076
Business Lending [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,376,599	1,277,666
Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,047,624	212,410
Consumer Indirect [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Total loans		991,836	1,014,825
Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		20,142	30,147
Consumer Direct [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Total loans		174,479	181,922
Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		5,450	9,893
Home Equity [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Total loans		322,140	319,029
Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		98,189	82,969
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,220,298	1,819,701
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		1,500	1,180
Nonaccrual		10,722	11,352
Total past due		25,786	23,911
Current		1,728,823	1,635,849
Total loans		1,754,609	1,659,760
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		13,564	11,379
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		26	205
Nonaccrual		3,066	2,332
Total past due		5,695	4,076
Acquired impaired	[1]	0	0
Current		459,994	155,865
Total loans		465,689	159,941
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		2,603	1,539
Commercial Portfolio Segment [Member] | Business Lending [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,424,223	1,490,076
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		571	145
Nonaccrual		3,944	3,811
Total past due		6,798	7,877
Current		1,369,801	1,269,789
Total loans		1,376,599	1,277,666
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		2,283	3,921
Commercial Portfolio Segment [Member] | Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		0	0
Nonaccrual		4,328	1,252
Total past due		8,989	1,780
Acquired impaired	[1]	10,115	5,553
Current		1,028,520	205,077
Total loans		1,047,624	212,410
Commercial Portfolio Segment [Member] | Business Lending [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		4,661	528
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,011,978	1,044,972
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		295	166
Nonaccrual		0	0
Total past due		14,492	14,049
Current		977,344	1,000,776
Total loans		991,836	1,014,825
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		14,197	13,883
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		8	3
Nonaccrual		0	0
Total past due		253	234
Acquired impaired	[1]	0	0
Current		19,889	29,913
Total loans		20,142	30,147
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		245	231
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Aged analysis of the company's loans [Abstract]
Total loans		179,929	191,815
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		48	58
Nonaccrual		0	0
Total past due		1,923	1,607
Current		172,556	180,315
Total loans		174,479	181,922
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,875	1,549
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		0	0
Nonaccrual		0	0
Total past due		100	231
Acquired impaired	[1]	0	0
Current		5,350	9,662
Total loans		5,450	9,893
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		100	231
Consumer Portfolio Segment [Member] | Home Equity [Member]
Aged analysis of the company's loans [Abstract]
Total loans		420,329	401,998
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		94	414
Nonaccrual		1,354	1,437
Total past due		2,564	3,101
Current		319,576	315,928
Total loans		322,140	319,029
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loan [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,116	1,250
Consumer Portfolio Segment [Member] | Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		170	905
Nonaccrual		1,326	435
Total past due		2,130	2,118
Acquired impaired	[1]	0	0
Current		96,059	80,851
Total loans		98,189	82,969
Consumer Portfolio Segment [Member] | Home Equity [Member] | Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		$ 634	$ 778
[1]	Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performing under ASC 310-30. As a result interest income, through the accretion of the difference between the carrying amount of the loans and the expected cashflows, is being recognized on all acquired impaired loans.

LOANS, Amount of Business Lendi

LOANS, Amount of Business Lending Loans by Credit Quality Category (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 6,256,757	$ 4,948,562
Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	4,619,663	4,453,202
Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,637,094	495,360
Business Lending [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,424,223	1,490,076
Business Lending [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,376,599	1,277,666
Business Lending [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,047,624	212,410
Business Lending [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	2,134,137	1,213,170
Business Lending [Member] | Pass [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,170,156	1,051,005
Business Lending [Member] | Pass [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	963,981	162,165
Business Lending [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	166,397	165,292
Business Lending [Member] | Special Mention [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	129,076	135,602
Business Lending [Member] | Special Mention [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	37,321	29,690
Business Lending [Member] | Classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	111,995	105,587
Business Lending [Member] | Classified [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	77,367	90,585
Business Lending [Member] | Classified [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	34,628	15,002
Business Lending [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,579	474
Business Lending [Member] | Doubtful [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	0	474
Business Lending [Member] | Doubtful [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,579	0
Business Lending [Member] | Acquired Impaired [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	10,115	5,553
Business Lending [Member] | Acquired Impaired [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	0	0
Business Lending [Member] | Acquired Impaired [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	10,115	5,553
All Other Loans [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	3,243,064	3,175,536
All Other Loans [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	589,470	282,950
All Other Loans [Member] | Performing [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	3,229,051	3,160,929
All Other Loans [Member] | Performing [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	584,874	279,070
All Other Loans [Member] | Nonperforming [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	14,013	14,607
All Other Loans [Member] | Nonperforming [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	4,596	3,880
Consumer Mortgage [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,754,609	1,659,760
Consumer Mortgage [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	465,689	159,941
Consumer Mortgage [Member] | Performing [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,742,387	1,647,228
Consumer Mortgage [Member] | Performing [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	462,597	157,404
Consumer Mortgage [Member] | Nonperforming [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	12,222	12,532
Consumer Mortgage [Member] | Nonperforming [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	3,092	2,537
Consumer Indirect [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	991,836	1,014,825
Consumer Indirect [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	20,142	30,147
Consumer Indirect [Member] | Performing [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	991,541	1,014,659
Consumer Indirect [Member] | Performing [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	20,134	30,144
Consumer Indirect [Member] | Nonperforming [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	295	166
Consumer Indirect [Member] | Nonperforming [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	8	3
Consumer Direct [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	174,479	181,922
Consumer Direct [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,450	9,893
Consumer Direct [Member] | Performing [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	174,431	181,864
Consumer Direct [Member] | Performing [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	5,450	9,893
Consumer Direct [Member] | Nonperforming [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	48	58
Consumer Direct [Member] | Nonperforming [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	0	0
Home Equity [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	322,140	319,029
Home Equity [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	98,189	82,969
Home Equity [Member] | Performing [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	320,692	317,178
Home Equity [Member] | Performing [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	96,693	81,629
Home Equity [Member] | Nonperforming [Member] | Legacy Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	1,448	1,851
Home Equity [Member] | Nonperforming [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans	$ 1,496	$ 1,340

LOANS, Summary of Impaired Loan

LOANS, Summary of Impaired Loans, Excluding Purchased Impaired (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Impaired loans [Abstract]
Loans with allowance allocation	$ 5,125	$ 1,109
Loans without allowance allocation	884	556
Carrying balance	6,009	1,665
Contractual balance	9,165	3,340
Specifically allocated allowance	804	477
Average impaired loans	9,517	4,683
Interest income recognized	$ 0	$ 0

LOANS, Troubled Debt Restructur

LOANS, Troubled Debt Restructuring (TDR) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)Loan	Dec. 31, 2016USD ($)Loan
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	226	214
TDRs, amount	$ 6,135	$ 5,530
Loans modified in TDR during the year, number | Loan	74	48
Loans modified in TDR during the year, amount	$ 2,268	$ 1,157
Maximum [Member]
Financing Receivable, Modifications [Line Items]
Threshold balance of TDR loans collectively included in general loan loss allocation and qualitative review	$ 500
Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	72	56
TDRs, amount	$ 2,728	$ 1,832
Accruing [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	154	158
TDRs, amount	$ 3,407	$ 3,698
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	95	81
TDRs, amount	$ 4,015	$ 3,476
Loans modified in TDR during the year, number | Loan	23	9
Loans modified in TDR during the year, amount	$ 1,254	$ 597
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	51	36
TDRs, amount	$ 2,265	$ 1,520
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Accruing [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	44	45
TDRs, amount	$ 1,750	$ 1,956
Commercial Portfolio Segment [Member] | Minimum [Member]
Financing Receivable, Modifications [Line Items]
Threshold balance of loan individually evaluated for impairment	$ 500
Commercial Portfolio Segment [Member] | Business Lending [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	15	11
TDRs, amount	$ 719	$ 781
Loans modified in TDR during the year, number | Loan	8	0
Loans modified in TDR during the year, amount	$ 412	$ 0
Commercial Portfolio Segment [Member] | Business Lending [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	8	6
TDRs, amount	$ 218	$ 91
Commercial Portfolio Segment [Member] | Business Lending [Member] | Accruing [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	7	5
TDRs, amount	$ 501	$ 690
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	71	78
TDRs, amount	$ 883	$ 771
Loans modified in TDR during the year, number | Loan	33	33
Loans modified in TDR during the year, amount	$ 490	$ 459
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	0	0
TDRs, amount	$ 0	$ 0
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Accruing [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	71	78
TDRs, amount	$ 883	$ 771
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	25	23
TDRs, amount	$ 69	$ 65
Loans modified in TDR during the year, number | Loan	6	3
Loans modified in TDR during the year, amount	$ 17	$ 51
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	0	0
TDRs, amount	$ 0	$ 0
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Accruing [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	25	23
TDRs, amount	$ 69	$ 65
Consumer Portfolio Segment [Member] | Home Equity [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	20	21
TDRs, amount	$ 449	$ 437
Loans modified in TDR during the year, number | Loan	4	3
Loans modified in TDR during the year, amount	$ 95	$ 50
Consumer Portfolio Segment [Member] | Home Equity [Member] | Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	13	14
TDRs, amount	$ 245	$ 221
Consumer Portfolio Segment [Member] | Home Equity [Member] | Accruing [Member]
Financing Receivable, Modifications [Line Items]
TDRs, number | Loan	7	7
TDRs, amount	$ 204	$ 216

LOANS, Allowance for Loan Losse

LOANS, Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for loan losses [Roll Forward]
Balance, beginning of period	$ 47,233	$ 45,401	$ 45,341
Charge-offs	(16,757)	(12,183)	(12,071)
Recoveries	6,123	5,939	5,684
Provision	10,984	8,076	6,447
Balance, end of period	47,583	47,233	45,401
Acquired Impaired [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	108	168	173
Charge-offs	(270)	(97)	(103)
Recoveries	0	0	0
Provision	309	37	98
Balance, end of period	147	108	168
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	10,094	10,198	10,286
Charge-offs	(707)	(647)	(1,374)
Recoveries	50	115	80
Provision	1,028	428	1,206
Balance, end of period	10,465	10,094	10,198
Commercial Portfolio Segment [Member] | Business Lending [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	17,220	15,749	15,787
Charge-offs	(4,959)	(1,872)	(2,146)
Recoveries	656	616	877
Provision	4,340	2,727	1,231
Balance, end of period	17,257	17,220	15,749
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	13,782	12,422	11,544
Charge-offs	(8,456)	(7,643)	(6,714)
Recoveries	4,516	4,168	3,943
Provision	3,626	4,835	3,649
Balance, end of period	13,468	13,782	12,422
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	2,979	2,997	3,083
Charge-offs	(2,081)	(1,706)	(1,490)
Recoveries	849	901	722
Provision	1,292	787	682
Balance, end of period	3,039	2,979	2,997
Consumer Portfolio Segment [Member] | Home Equity [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	2,399	2,666	2,701
Charge-offs	(284)	(218)	(244)
Recoveries	52	139	62
Provision	(60)	(188)	147
Balance, end of period	2,107	2,399	2,666
Unallocated Financing Receivables [Member]
Allowance for loan losses [Roll Forward]
Balance, beginning of period	651	1,201	1,767
Charge-offs	0	0	0
Recoveries	0	0	0
Provision	449	(550)	(566)
Balance, end of period	$ 1,100	$ 651	$ 1,201

PREMISES AND EQUIPMENT (Details

PREMISES AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 241,575	$ 219,775
Accumulated depreciation	(118,182)	(107,457)
Premises and equipment, net	123,393	112,318
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	23,869	22,585
Bank Premises [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	131,647	116,663
Equipment and Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 86,059	$ 80,527

GOODWILL AND IDENTIFIABLE INT68

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 149,437	$ 57,541
Accumulated amortization	(58,779)	(41,839)
Net carrying amount	90,658	15,702
Finite-lived intangible assets, future amortization expense [Abstract]
2,018	17,872
2,019	15,033
2,020	12,497
2,021	10,665
2,022	9,165
Thereafter	25,426
Net carrying amount	90,658	15,702
Components of goodwill [Abstract]
Goodwill	739,254	469,966	$ 468,076
Goodwill, activity	269,288	1,890
Accumulated impairment	(4,824)	(4,824)	(4,824)
Accumulated impairment, activity	0	0
Goodwill, net	734,430	465,142	$ 463,252
Goodwill, net, activity	269,288	1,890
Servicing Asset at Fair Value, Amount [Roll Forward]
Carrying value before valuation allowance at beginning of period	1,435	1,472
Additions	358	481
Merchants acquisition	64	0
Amortization	(499)	(518)
Carrying value before valuation allowance at end of period	1,358	1,435
Valuation allowance balance at beginning of period	0	0
Impairment charges	0	(226)
Impairment recoveries	0	226
Valuation allowance balance at end of period	0	0
Net carrying value at end of period	1,358	1,435
Fair value of MSRs at end of period	2,473	1,928
Principal balance of loans sold during the year	32,937	45,852
Principal balance of loans serviced for others	358,518	365,374
Custodial escrow balances maintained in connection with loans serviced for others	$ 5,363	$ 5,603
Key economic assumptions used to estimate the value of the MSRs [Abstract]
Weighted-average contractual life	21 years 3 months 18 days	20 years 9 months 18 days
Weighted-average constant prepayment rate (CPR)	11.10%	15.10%
Weighted-average discount rate	3.30%	3.50%
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 62,902	$ 39,688
Accumulated amortization	(37,877)	(32,581)
Net carrying amount	25,025	7,107
Finite-lived intangible assets, future amortization expense [Abstract]
Net carrying amount	25,025	7,107
Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	86,535	17,853
Accumulated amortization	(20,902)	(9,258)
Net carrying amount	65,633	8,595
Finite-lived intangible assets, future amortization expense [Abstract]
Net carrying amount	$ 65,633	$ 8,595

DEPOSITS (Details)

DEPOSITS (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
DEPOSITS [Abstract]
Noninterest checking	$ 2,293,057	$ 1,646,039
Interest checking	1,830,914	1,644,029
Savings	1,421,512	1,303,851
Money market	2,124,633	1,778,907
Time	774,304	703,128
Total deposits	8,444,420	7,075,954
Maturities of time deposits [Abstract]
2,018	545,389
2,019	100,833
2,020	59,849
2,021	34,582
2,022	33,400
Thereafter	251
Total	774,304	$ 703,128
Maturities of time deposits, accounts $250,000 or greater [Abstract]
2,018	51,875
2,019	5,958
2,020	7,445
2,021	1,807
2,022	601
Thereafter	0
Total	$ 67,686

BORROWINGS, Outstanding Borrowi

BORROWINGS, Outstanding Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
BORROWINGS [Abstract]
FHLB overnight advance	$ 24,000	$ 146,200
Subordinated debt held by unconsolidated subsidiary trusts, net of discount of $332 and $357, respectively	122,814	102,170
Securities sold under agreement to repurchase, short term	337,011	0
FHLB Long term advances	2,071	0
Total borrowings	485,896	248,370
Subordinated debt held by unconsolidated subsidiary trust, discount	$ 332	$ 357

BORROWINGS, Contractual Maturit

BORROWINGS, Contractual Maturity on Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Carrying value	$ 485,896	$ 248,370
Weighted-average rate at period end	1.34%
Weighted-average interest rate on borrowings during period	1.51%	1.46%
January 2, 2018 [Member]
Debt Instrument [Line Items]
Carrying value	$ 361,011
Weighted-average rate at period end	0.54%
July 3, 2023 [Member]
Debt Instrument [Line Items]
Carrying value	$ 601
Weighted-average rate at period end	2.25%
October 23, 2023 [Member]
Debt Instrument [Line Items]
Carrying value	$ 515
Weighted-average rate at period end	1.50%
October 1, 2025 [Member]
Debt Instrument [Line Items]
Carrying value	$ 329
Weighted-average rate at period end	1.50%
March 1, 2029 [Member]
Debt Instrument [Line Items]
Carrying value	$ 626
Weighted-average rate at period end	2.50%
July 31, 2031 [Member]
Debt Instrument [Line Items]
Carrying value	$ 24,875
Weighted-average rate at period end	4.96%
December 15, 2034 [Member]
Debt Instrument [Line Items]
Carrying value	$ 20,619
Weighted-average rate at period end	3.54%
December 15, 2036 [Member]
Debt Instrument [Line Items]
Carrying value	$ 77,320
Weighted-average rate at period end	3.24%

BORROWINGS, Preferred Securitie

BORROWINGS, Preferred Securities (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)Trust
Debt Instrument [Line Items]
Number of unconsolidated subsidiary business trusts owned | Trust	3
Percent ownership of unconsolidated subsidiary trusts	100.00%
Preferred Debt [Member] | Community Statutory Trust III [Member]
Terms of preferred securities for each trust [Abstract]
Issuance date	Jul. 31, 2001
Par amount	$ 24.5
Variable interest rate basis	3 month LIBOR
Effective interest rate	4.96%
Maturity date	Jul. 31, 2031
Call price	Par
Preferred Debt [Member] | Community Statutory Trust III [Member] | LIBOR [Member]
Terms of preferred securities for each trust [Abstract]
Term of variable rate	3 months
Variable interest rate, basis spread	3.58%
Preferred Debt [Member] | Community Capital Trust IV [Member]
Terms of preferred securities for each trust [Abstract]
Issuance date	Dec. 8, 2006
Par amount	$ 75
Variable interest rate basis	3 month LIBOR
Effective interest rate	3.24%
Maturity date	Dec. 15, 2036
Call price	Par
Preferred Debt [Member] | Community Capital Trust IV [Member] | LIBOR [Member]
Terms of preferred securities for each trust [Abstract]
Term of variable rate	3 months
Variable interest rate, basis spread	1.65%
Preferred Debt [Member] | MBVT Statutory Trust I [Member]
Terms of preferred securities for each trust [Abstract]
Issuance date	Dec. 15, 2004
Par amount	$ 20.6
Variable interest rate basis	3 month LIBOR
Effective interest rate	3.54%
Maturity date	Dec. 15, 2034
Call price	Par
Preferred Debt [Member] | MBVT Statutory Trust I [Member] | LIBOR [Member]
Terms of preferred securities for each trust [Abstract]
Term of variable rate	3 months
Variable interest rate, basis spread	1.95%

INCOME TAXES, Provision for Inc

INCOME TAXES, Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current [Abstract]
Federal	$ 31,152	$ 32,829	$ 27,663
State and other	6,788	4,890	2,608
Deferred [Abstract]
Federal	(28,146)	11,444	9,604
State and other	(546)	1,622	1,112
Provision for income taxes	$ 9,248	$ 50,785	$ 40,987

INCOME TAXES, Components of Net

INCOME TAXES, Components of Net Deferred Tax Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Components of net deferred tax liability [Abstract]
Allowance for loan losses	$ 11,675	$ 18,366
Employee benefits	4,216	6,311
Debt extinguishment	0	299
Other, net	0	5,202
Deferred tax asset	15,891	30,178
Investment securities	22,690	32,839
Tax-deductible goodwill	39,154	43,504
Loan origination costs	6,109	8,228
Depreciation	2,372	71
Mortgage servicing rights	330	548
Pension	13,228	18,194
Other, net	542	0
Deferred tax liability	84,425	103,384
Net deferred tax liability	$ (68,534)	$ (73,206)

INCOME TAXES, Effective Tax Rat

INCOME TAXES, Effective Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective tax rate reconciliation [Abstract]
Federal statutory income tax rate	35.00%	35.00%	35.00%
Increase (reduction) in taxes resulting from [Abstract]
Tax-exempt interest	(3.80%)	(4.00%)	(5.00%)
State income taxes, net of federal benefit	2.50%	2.70%	1.80%
Stock-based compensation	(2.00%)	0.00%	0.00%
Federal deferred tax revaluation adjustment	(23.70%)	0.00%	0.00%
Other, net	(2.20%)	(0.90%)	(0.80%)
Effective income tax rate	5.80%	32.80%	31.00%

INCOME TAXES, Unrecognized Tax

INCOME TAXES, Unrecognized Tax Benefits and Tax Cuts and Jobs Act (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unrecognized tax benefits [Roll forward]
Unrecognized tax benefits at beginning of year	$ 24	$ 92	$ 127	$ 162
Changes related to [Abstract]
Lapse of statutes of limitation		(68)	(35)	(35)
Unrecognized tax benefits at end of year		24	$ 92	$ 127
Unrecognized tax benefits that would impact effective tax rate, if recognized		$ 20
Income Tax Disclosure [Line Items]
Federal corporate tax rate		35.00%	35.00%	35.00%
Marginal tax rate		37.70%
Deferred tax benefit from write-down of net deferred tax liabilities		$ (38,000)
Plan [Member]
Income Tax Disclosure [Line Items]
Federal corporate tax rate	21.00%
Marginal tax rate	24.29%

LIMITS ON DIVIDENDS AND OTHER77

LIMITS ON DIVIDENDS AND OTHER REVENUE SOURCES (Details) $ in Millions	Dec. 31, 2017USD ($)
LIMITS ON DIVIDENDS AND OTHER REVENUE SOURCES [Abstract]
Undivided profits legally available for the payments of dividends	$ 69
Percentage of Bank's capital and surplus that can be transferred to Company, maximum	10.00%
Aggregate percentage of Bank's capital and surplus that can be transferred to Company, maximum	20.00%

BENEFIT PLANS, Funded Status an

BENEFIT PLANS, Funded Status and Amounts Recognized in Balance Sheets and AOCI (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2009	May 12, 2017
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	[1]	$ 180,086
Fair value of plan assets at end of year	[1]	216,476	$ 180,086
Amounts recognized in accumulated other comprehensive income (loss) ("AOCI") [Abstract]
AOCI at year end		$ 21,633	17,961	$ 21,283
Accumulated other comprehensive income (loss), negative postretirement medical plan amendment, arising during period, net of tax					$ 3,500
Stock Balance Plan [Member] | Nonemployee Directors [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funding Status [Extensible List]		us-gaap:UnfundedPlanMember
Change in benefit obligation [Roll Forward]
Benefit obligation at the beginning of year		$ 100
Benefit obligation at end of year		100	100
Pension Benefits [Member]
Change in benefit obligation [Roll Forward]
Benefit obligation at the beginning of year		127,084	127,134
Service cost		4,181	4,106	3,324
Interest cost		5,717	5,624	5,506
Plan amendment / acquisition		11,646	22
Participant contributions		0	0
Deferred actuarial loss/(gain)		8,978	(1,628)
Benefits paid		(10,156)	(8,174)
Benefit obligation at end of year		147,450	127,084	127,134
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year		180,400	172,026
Actual return of plan assets		22,954	14,402
Participant contributions		0	0
Employer contributions		9,839	2,146
Plan acquisition		14,070	0
Benefits paid		(10,156)	(8,174)
Fair value of plan assets at end of year		217,107	180,400	172,026
Over/(Under) funded status at year end		69,657	53,316
Amounts recognized in the consolidated statement of condition [Abstract]
Other assets		81,000	64,709
Other liabilities		(11,343)	(11,393)
Amounts recognized in accumulated other comprehensive income (loss) ("AOCI") [Abstract]
Net loss		26,935	28,323
Net prior service cost (credit)		2,944	2,264
Pre-tax AOCI		29,879	30,587
Taxes		(7,340)	(11,622)
AOCI at year end		$ 22,539	$ 18,965
Unamortized actuarial gain						$ 1,900
Discount rate		4.00%	4.50%			4.40%
Post-retirement Benefits [Member]
Change in benefit obligation [Roll Forward]
Benefit obligation at the beginning of year		$ 1,806	$ 1,918
Service cost		0	0	0
Interest cost		76	82	87
Plan amendment / acquisition		0	0
Participant contributions		467	516
Deferred actuarial loss/(gain)		245	174
Benefits paid		(809)	(884)
Benefit obligation at end of year		1,785	1,806	1,918
Change in plan assets [Roll Forward]
Fair value of plan assets at beginning of year		0	0
Actual return of plan assets		0	0
Participant contributions		467	516
Employer contributions		342	368
Plan acquisition		0	0
Benefits paid		(809)	(884)
Fair value of plan assets at end of year		0	0	$ 0
Over/(Under) funded status at year end		(1,785)	(1,806)
Amounts recognized in the consolidated statement of condition [Abstract]
Other assets		0	0
Other liabilities		(1,785)	(1,806)
Amounts recognized in accumulated other comprehensive income (loss) ("AOCI") [Abstract]
Net loss		420	183
Net prior service cost (credit)		(1,622)	(1,801)
Pre-tax AOCI		(1,202)	(1,618)
Taxes		296	614
AOCI at year end		$ (906)	$ (1,004)
Discount rate		4.00%	4.40%
Supplemental Pension Plans [Member] | Key Executives [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Funding Status [Extensible List]		us-gaap:UnfundedPlanMember
Change in benefit obligation [Roll Forward]
Benefit obligation at the beginning of year		$ 11,300
Benefit obligation at end of year		11,300	$ 11,300
Amounts recognized in accumulated other comprehensive income (loss) ("AOCI") [Abstract]
Benefit obligation for defined benefit pension plan prior to plan revaluation		$ 136,100	$ 115,700
[1]	Excludes dividends and interest receivable totaling $0.6 million and $0.3 million at December 31, 2017 and 2016, respectively.

BENEFIT PLANS, Amounts Recogniz

BENEFIT PLANS, Amounts Recognized in AOCI, Net of Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amounts recognized in AOCI, net of tax [Abstract]
Net (gain) loss	$ (1,147)	$ 0	$ 0
Total	(168)	(3,322)	$ 4,567
Pension Benefits [Member]
Amounts recognized in AOCI, net of tax [Abstract]
Prior service cost/(credit)	424	(26)
Net (gain) loss	(851)	(3,517)
Total	(427)	(3,543)
Post-retirement Benefits [Member]
Amounts recognized in AOCI, net of tax [Abstract]
Prior service cost/(credit)	111	110
Net (gain) loss	148	111
Total	$ 259	$ 221

BENEFIT PLANS, Costs That Will

BENEFIT PLANS, Costs That Will Be Amortized from AOCI in Next Fiscal Year (Details) $ in Thousands	Dec. 31, 2017USD ($)
Pension Benefits [Member]
Costs that will be amortized from accumulated other comprehensive (income) loss in net periodic (income) cost in next fiscal year [Abstract]
Prior service credit	$ (330)
Net loss	1,054
Total	724
Post-retirement Benefits [Member]
Costs that will be amortized from accumulated other comprehensive (income) loss in net periodic (income) cost in next fiscal year [Abstract]
Prior service credit	(179)
Net loss	18
Total	$ (161)

BENEFIT PLANS, Weighted-average

BENEFIT PLANS, Weighted-average Assumptions Used to Determine Benefit Obligations (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	May 12, 2017
Pension Benefits [Member]
Weighed average assumption used in calculating benefit obligations [Abstract]
Discount rate	4.00%	4.50%	4.40%
Expected return on plan assets	7.00%	7.00%
Rate of compensation increase	3.50%	3.50%
Post-retirement Benefits [Member]
Weighed average assumption used in calculating benefit obligations [Abstract]
Discount rate	4.00%	4.40%

BENEFIT PLANS, Net Periodic Ben

BENEFIT PLANS, Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Prior service costs [Abstract]
Maximum percentage of net gain or loss over the greater of the projected benefit obligation or the market-related value of assets without requiring amortization	10.00%
Pension Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	$ 4,181	$ 4,106	$ 3,324
Interest cost	5,717	5,624	5,506
Expected return on plan assets	(13,354)	(11,842)	(12,169)
Plan amendment	0	20	0
Amortization of unrecognized net loss/(gain)	767	1,508	1,466
Amortization of prior service cost	55	43	8
Net periodic (benefit)	(2,634)	(541)	(1,865)
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0	0	0
Interest cost	76	82	87
Expected return on plan assets	0	0	0
Plan amendment	0	0	0
Amortization of unrecognized net loss/(gain)	8	(5)	(13)
Amortization of prior service cost	(179)	(179)	(179)
Net periodic (benefit)	$ (95)	$ (102)	$ (105)

BENEFIT PLANS, Weighted-avera83

BENEFIT PLANS, Weighted-average Assumptions Used to Determine Net Periodic Benefit Cost (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension Benefits [Member]
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.40%	4.70%	4.50%
Expected return on plan assets	7.00%	7.00%	7.00%
Rate of compensation increase	3.50%	3.50%	3.50%
Post-retirement Benefits [Member]
Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.40%	4.70%	4.50%

BENEFIT PLANS, Estimated Future

BENEFIT PLANS, Estimated Future Benefit Payments (Details) $ in Thousands	Dec. 31, 2017USD ($)
Pension Benefits [Member]
Estimated Future Benefit Payments [Abstract]
2,018	$ 8,702
2,019	9,163
2,020	9,404
2,021	9,943
2,022	10,378
2023-2027	56,064
Post-retirement Benefits [Member]
Estimated Future Benefit Payments [Abstract]
2,018	145
2,019	142
2,020	139
2,021	136
2,022	133
2023-2027	$ 618

BENEFIT PLANS, Target Plan Asse

BENEFIT PLANS, Target Plan Assets Allocation (Details)	Dec. 31, 2017
Equity Securities [Member]
Plan Assets [Abstract]
Target allocation percentage of assets	60.00%
Fixed Income Securities [Member]
Plan Assets [Abstract]
Target allocation percentage of assets	40.00%

BENEFIT PLANS, Fair Value of Pl

BENEFIT PLANS, Fair Value of Plan Assets by Assets Category (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	$ 216,476	$ 180,086
Total dividends and interest receivable excluded from plan assets		600	300
Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	196,336	166,117
Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	20,140	13,969
Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	0	0
Money Market Accounts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		10,381	8,151
Money Market Accounts [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	103
Money Market Accounts [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		10,381	8,048
Money Market Accounts [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		135,530	96,748
Equity Securities [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		135,530	96,748
Equity Securities [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity Securities [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
U.S. Large-Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		53,154	43,235
U.S. Large-Cap [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		53,154	43,235
U.S. Large-Cap [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
U.S. Large-Cap [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
U.S Mid/Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		26,309	19,032
U.S Mid/Small Cap [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		26,309	19,032
U.S Mid/Small Cap [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
U.S Mid/Small Cap [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
CBU Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		8,344	7,417
CBU Stock [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		8,344	7,417
CBU Stock [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
CBU Stock [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
International [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		47,723	27,064
International [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		47,723	27,064
International [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
International [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		59,190	63,106
Fixed Income Securities [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		49,504	57,243
Fixed Income Securities [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		9,686	5,863
Fixed Income Securities [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Government Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		23,615	31,238
Government Securities [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		13,929	25,375
Government Securities [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		9,686	5,863
Government Securities [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Investment Grade Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		19,278	15,253
Investment Grade Bonds [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		19,278	15,253
Investment Grade Bonds [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Investment Grade Bonds [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
High Yield [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	16,297	16,615
High Yield [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	16,297	16,615
High Yield [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0	0
High Yield [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	0	0
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	11,375	12,081
Other Investments [Member] | Quoted Prices in Active Markets For Identical Assets, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	11,302	12,023
Other Investments [Member] | Significant Observable Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	73	58
Other Investments [Member] | Significant Unobservable Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	0	0
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		217,107	180,400	$ 172,026
Employer contributions		9,839	$ 2,146
Pension Benefits [Member] | Merchants Bank Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		2,000
Pension Benefits [Member] | Defined Benefit Pension Plan Excluding Merchant Bank Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions		$ 7,200
[1]	Excludes dividends and interest receivable totaling $0.6 million and $0.3 million at December 31, 2017 and 2016, respectively.
[2]	This category is exchange-traded funds representing a diversified index of high yield corporate bonds.
[3]	This category is comprised of exchange-traded funds and mutual funds holding non-traditional investment classes including private equity funds and alternative exchange funds.

BENEFIT PLANS, Multi-employer D

BENEFIT PLANS, Multi-employer Defined Benefit Plan (Details) - Multiemployer Plans, Pension [Member] - Pentegra DB Plan [Member] - Tupper Lake National Bank [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2016
Multiemployer Plans [Line Items]
Identification number	135,645,888
Plan number	333
Fair value of plan assets				$ 3,300,000
Projected benefit obligation				$ 4,800,000
Funded status	At least 80 percent
Period contributions	$ 100	$ 50	$ 30
Significance of employer contributions	false

BENEFIT PLANS, Assumed Health C

BENEFIT PLANS, Assumed Health Care Cost Trend Rate (Details)	12 Months Ended
	Dec. 31, 2017
Assumed Health Care Cost Trend Rates [Abstract]
Assumed health care cost trend rate for medical costs for participants younger than 65	7.25%
Assumed health care cost trend rate for medical cost for participants older than 65	5.00%
Assumed health care cost trend rate for prescription drugs	10.50%
Ultimate health care cost trend rate	3.89%
Year that rate reaches ultimate trend rate	2,075

BENEFIT PLANS, 401(K) Employee

BENEFIT PLANS, 401(K) Employee Stock Ownership Plan (Details) - 401(k) Employee Stock Ownership Plan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Percentage of first eligible compensation fully matched by employer	3.00%
Percentage of matching contribution in the form of common stock	100.00%
Percentage of the next eligible compensation matched at 50% by employer	3.00%
Percentage of matching contributions for the next eligible compensation in the form of company stock	50.00%
(Income)/expense recognized under plan	$ 5.3	$ 4.3	$ 3.6
Interest credit contribution expense recognized for 401(k) plan	$ 0.8	$ 0.7	$ 1.1
Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Contribution from eligible compensation	1.00%
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Contribution from eligible compensation	90.00%

BENEFIT PLANS, Other Deferred C

BENEFIT PLANS, Other Deferred Compensation Arrangements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Liability recorded for compensation plan	$ 13,328	$ 0
Other Deferred Compensation Arrangements [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Liability recorded for compensation plan	3,100	3,200
Expense recognized under plan	$ 300	$ 30	$ 100

BENEFIT PLANS, Deferred Compens

BENEFIT PLANS, Deferred Compensation Plans for Directors (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Liability accrued for compensation plan	$ 13,328	$ 0
Deferred Compensation Plans for Directors [Member] | Directors [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Deferred compensation arrangement with individual, shares credited (in shares)	150,110	154,013
Liability accrued for compensation plan	$ 4,200	$ 4,000
Expense recognized under plan	$ 200	$ 200	$ 200

STOCK-BASED COMPENSATION PLANS,

STOCK-BASED COMPENSATION PLANS, Long-Term Incentive Program (Details) - shares	May 17, 2017	May 14, 2014	May 25, 2011	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock authorized for stock-based compensation plan (in shares)				4,000,000
Additional shares of common stock authorized for stock-based compensation plan (in shares)	1,000,000	1,000,000	900,000
Number of shares available for grant (in shares)				1,700,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of options				10 years
Award vesting period				5 years

STOCK-BASED COMPENSATION PLAN93

STOCK-BASED COMPENSATION PLANS, Activity in Long-Term Incentive Program (Details) - Stock Options [Member] - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Options, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	1,755,992	1,969,301
Granted (in shares)	197,943	330,383
Exercised (in shares)	(238,499)	(525,298)
Forfeited (in shares)	(7,140)	(18,394)
Outstanding, end of period (in shares)	1,708,296	1,755,992
Exercisable, end of period (in shares)	1,015,823
Weighted-average exercise price of shares [Abstract]
Outstanding, beginning of period (in dollars per share)	$ 30.85	$ 28.15
Granted (in dollars per share)	57.02	38.02
Exercised (in dollars per share)	25.72	25.12
Forfeited (in dollars per share)	37.47	34.47
Outstanding, end of period (in dollars per share)	34.57	$ 30.85
Exercisable, end of period (in dollars per share)	$ 29.57

STOCK-BASED COMPENSATION PLAN94

STOCK-BASED COMPENSATION PLANS, Summary of Stock Options Outstanding (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Options [Abstract]
Options outstanding, shares (in shares) | shares	1,708,296
Options outstanding, weighted-average exercise price (in dollars per share)	$ 34.57
Options outstanding, weighted-average remaining life	6 years 7 days
Options exercisable, shares (in shares) | shares	1,015,823
Options exercisable, weighted-average exercise price (in dollars per share)	$ 29.57
Weighted-average remaining contractual term of outstanding stock options	6 years 7 days
Weighted-average remaining contractual term of outstanding and exercisable stock options	4 years 10 months 6 days
Aggregate intrinsic value of outstanding stock options | $	$ 33.4
Aggregate intrinsic value of exercisable stock options | $	$ 24.6
$0.00 - $18.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	$ 0
Exercise price range, upper range limit (in dollars per share)	$ 18
Options [Abstract]
Options outstanding, shares (in shares) | shares	24,736
Options outstanding, weighted-average exercise price (in dollars per share)	$ 17.82
Options outstanding, weighted-average remaining life	1 year 3 months 22 days
Options exercisable, shares (in shares) | shares	24,736
Options exercisable, weighted-average exercise price (in dollars per share)	$ 17.82
$18.001 - $28.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	18.001
Exercise price range, upper range limit (in dollars per share)	$ 28
Options [Abstract]
Options outstanding, shares (in shares) | shares	314,511
Options outstanding, weighted-average exercise price (in dollars per share)	$ 22.23
Options outstanding, weighted-average remaining life	2 years 11 months 5 days
Options exercisable, shares (in shares) | shares	314,511
Options exercisable, weighted-average exercise price (in dollars per share)	$ 22.23
$28.001 - $29.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	28.001
Exercise price range, upper range limit (in dollars per share)	$ 29
Options [Abstract]
Options outstanding, shares (in shares) | shares	171,083
Options outstanding, weighted-average exercise price (in dollars per share)	$ 28.78
Options outstanding, weighted-average remaining life	4 years 2 months 19 days
Options exercisable, shares (in shares) | shares	171,083
Options exercisable, weighted-average exercise price (in dollars per share)	$ 28.78
$29.001 - $30.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	29.001
Exercise price range, upper range limit (in dollars per share)	$ 30
Options [Abstract]
Options outstanding, shares (in shares) | shares	228,668
Options outstanding, weighted-average exercise price (in dollars per share)	$ 29.79
Options outstanding, weighted-average remaining life	5 years 2 months 12 days
Options exercisable, shares (in shares) | shares	176,843
Options exercisable, weighted-average exercise price (in dollars per share)	$ 29.79
$30.001 - $40.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	30.001
Exercise price range, upper range limit (in dollars per share)	$ 40
Options [Abstract]
Options outstanding, shares (in shares) | shares	771,781
Options outstanding, weighted-average exercise price (in dollars per share)	$ 37.09
Options outstanding, weighted-average remaining life	7 years 3 months 11 days
Options exercisable, shares (in shares) | shares	317,005
Options exercisable, weighted-average exercise price (in dollars per share)	$ 37.06
$40.001 - $60.00 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price range, lower range limit (in dollars per share)	40.001
Exercise price range, upper range limit (in dollars per share)	$ 60
Options [Abstract]
Options outstanding, shares (in shares) | shares	197,517
Options outstanding, weighted-average exercise price (in dollars per share)	$ 57.02
Options outstanding, weighted-average remaining life	9 years 1 month 20 days
Options exercisable, shares (in shares) | shares	11,645
Options exercisable, weighted-average exercise price (in dollars per share)	$ 57.12

STOCK-BASED COMPENSATION PLAN95

STOCK-BASED COMPENSATION PLANS, Stock-Based Compensation Expense Recognized (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense related to incentive and non-qualified stock options recognized	$ 2.2	$ 2.2	$ 1.8
Income tax benefit recognized	0.8	0.8	0.7
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense related to incentive and non-qualified stock options recognized	$ 2.7	$ 2.4	$ 2.2

STOCK-BASED COMPENSATION PLAN96

STOCK-BASED COMPENSATION PLANS, Assumptions Used to Estimate Value of Stock Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
STOCK-BASED COMPENSATION PLANS [Abstract]
Fair value assumptions, method used	Black-Scholes model	Black-Scholes model	Black-Scholes model
Weighted-average Fair Value of Options Granted (in dollars per share)	$ 12.78	$ 7.90	$ 7.48
Assumptions [Abstract]
Weighted-average expected life	6 years 6 months	6 years 6 months	6 years 6 months
Future dividend yield	3.19%	3.43%	3.40%
Share price volatility	29.71%	30.00%	30.34%
Weighted-average risk-free interest rate	2.31%	1.72%	1.73%

STOCK-BASED COMPENSATION PLAN97

STOCK-BASED COMPENSATION PLANS, Unrecognized Stock-Based Compensation Expense and Stock Option Exercises (Details) - Stock Options [Member] - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense related to non-vested stock options	$ 4.6
Weighted average period for recognition of unrecognized compensation cost	3 years 2 months 12 days
Total fair value of stock options vested	$ 2.2	$ 2.1	$ 1.9
Proceeds from stock option exercises	7.7	12
Related tax benefits from stock option exercises	$ 2.3	$ 2.7
Shares issued in connection with stock option exercise (in shares)	0.2	0.4
Total intrinsic value of options exercised	$ 7.6	$ 10.3	$ 7.6

STOCK-BASED COMPENSATION PLAN98

STOCK-BASED COMPENSATION PLANS, Activity of Unvested Restricted Stock Awards (Details) - Restricted Stock [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Shares [Roll Forward]
Unvested, beginning of period (in shares)	253,830	246,311
Awards (in shares)	46,428	148,240
Forfeitures (in shares)	(4,863)	(42,394)
Vestings (in shares)	(64,522)	(98,327)
Unvested, end of period (in shares)	230,873	253,830	246,311
Weighted-average grant date fair value [Abstract]
Unvested, beginning of period (in dollars per share)	$ 29.98	$ 27.85
Awards (in dollars per share)	57.02	27.04
Forfeitures (in dollars per share)	24.78	17.49
Vestings (in dollars per share)	33.69	25.64
Unvested, end of period (in dollars per share)	$ 34.06	$ 29.98	$ 27.85
Unrecognized stock-based compensation expense	$ 5.7
Award vesting period	5 years
Weighted-average period for recognition of unrecognized compensation cost	4 years 3 months 18 days
Total fair value of restricted stock vested	$ 2.2	$ 2.5	$ 1.7

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)	200	300	300
Basic earnings per share [Abstract]
Net income	$ 150,717	$ 103,812	$ 91,230
Income attributable to unvested stock-based compensation awards	(597)	(550)	(453)
Income available to common shareholders	$ 150,120	$ 103,262	$ 90,777
Weighted-average common shares outstanding - basic (in shares)	48,843	44,091	40,996
Basic earnings per share (in dollars per share)	$ 3.07	$ 2.34	$ 2.21
Diluted earnings per share [Abstract]
Net income	$ 150,717	$ 103,812	$ 91,230
Income attributable to unvested stock-based compensation awards	(597)	(550)	(453)
Income available to common shareholders	$ 150,120	$ 103,262	$ 90,777
Weighted-average common shares outstanding (in shares)	48,843	44,091	40,996
Assumed exercise of stock options (in shares)	627	394	405
Weighted-average common shares outstanding - diluted (in shares)	49,470	44,485	41,401
Diluted earnings per share (in dollars per share)	$ 3.03	$ 2.32	$ 2.19
Cash dividends declared per share (in dollars per share)	$ 1.32	$ 1.26	$ 1.22
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)	2,500	2,200
Number of common shares repurchased (in shares)	0	0	300

COMMITMENTS, CONTINGENT LIAB100

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount of commitments and contingencies	$ 1,103,786	$ 796,098
Unused lines of credit	25,000
Federal Home Loan Bank unused borrowing capacity	1,680,000
Federal Reserve unused borrowing capacity	22,900
Federal Reserve required average total reserve	84,800
Federal Reserve requirement represented by cash on hand	73,200
Required deposit with Federal Reserve	11,600
Minimum [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Range of reasonably possible losses for such matters in the aggregate, beyond the existing recorded liability	0
Maximum [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Range of reasonably possible losses for such matters in the aggregate, beyond the existing recorded liability	1,000
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount of commitments and contingencies	1,080,004	773,442
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Contract amount of commitments and contingencies	$ 23,782	$ 22,656

LEASES (Details)

LEASES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
LEASES [Abstract]
Rental expense	$ 7,300	$ 5,800	$ 5,400
Future minimum rental commitments [Abstract]
2,018	9,189
2,019	8,194
2,020	6,603
2,021	5,164
2,022	4,101
Thereafter	8,623
Total	$ 41,874

REGULATORY MATTERS (Details)

REGULATORY MATTERS (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Tier 1 Leverage ratio [Abstract]
Tier 1 Leverage ratio, actual amount	$ 995,860	$ 858,347
Tier 1 Leverage ratio, actual ratio	10.00%	10.55%
Tier 1 leverage ratio for capital adequacy purposes, amount	$ 398,183	$ 325,438
Tier 1 leverage ratio for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage capital to be well-capitalized under prompt corrective action, amount	$ 497,729	$ 406,798
Tier 1 leverage capital to be well-capitalized under prompt corrective action, ratio	5.00%	5.00%
Tier 1 risk-based capital [Abstract]
Tier 1 risk-based capital, actual amount	$ 995,860	$ 858,347
Tier 1 risk-based capital, actual ratio	16.64%	18.10%
Tier 1 risk-based capital for capital adequacy purposes, amount	$ 358,988	$ 284,583
Tier 1 risk-based capital for capital adequacy purposes, ratio	6.00%	6.00%
Tier 1 risk-based capital for capital adequacy purposes plus capital conservation buffer, amount	$ 433,777	$ 314,228
Tier 1 risk-based capital for capital adequacy purposes plus capital conservation buffer, ratio	7.25%	6.625%
Tier 1 risk based capital to be well-capitalized under prompt corrective action, amount	$ 478,651	$ 379,445
Tier 1 risk-based capital to be well-capitalized under prompt corrective action, ratio	8.00%	8.00%
Total risk-based capital [Abstract]
Total risk-based capital, actual amount	$ 1,043,910	$ 905,996
Total risk-based capital, actual ratio	17.45%	19.10%
Total risk-based capital for capital adequacy purposes, amount	$ 478,651	$ 379,445
Total risk-based capita for capital adequacy purposes, ratio	8.00%	8.00%
Total risk-based capital for capital adequacy purposes plus capital conservation buffer, amount	$ 553,440	$ 409,089
Total risk-based capita for capital adequacy purposes plus capital conservation buffer, ratio	9.25%	8.625%
Total risk based capital to be well-capitalized under prompt corrective action, amount	$ 598,314	$ 474,306
Total risk based capital to be well-capitalized under prompt corrective action, ratio	10.00%	10.00%
Common equity Tier 1 capital [Abstract]
Common equity Tier 1 capital, actual amount	$ 876,685	$ 759,199
Common equity Tier 1 capital, actual ratio	14.65%	16.01%
Common equity Tier 1 capital for capital adequacy purposes, amount	$ 269,241	$ 213,438
Common equity Tier 1 capital for capital adequacy purposes, ratio	4.50%	4.50%
Common equity Tier 1 capital for capital adequacy purposes plus capital conservation buffer, amount	$ 344,030	$ 243,082
Common equity Tier 1 capital for capital adequacy purposes plus capital conservation buffer, ratio	5.75%	5.125%
Common equity Tier 1 capital to be well-capitalized under prompt corrective action, amount	$ 388,904	$ 308,299
Common equity Tier 1 capital to be well-capitalized under prompt corrective action, ratio	6.50%	6.50%
Community Bank, N.A. [Member]
Tier 1 Leverage ratio [Abstract]
Tier 1 Leverage ratio, actual amount	$ 859,538	$ 672,633
Tier 1 Leverage ratio, actual ratio	8.71%	8.30%
Tier 1 leverage ratio for capital adequacy purposes, amount	$ 394,981	$ 324,080
Tier 1 leverage ratio for capital adequacy purposes, ratio	4.00%	4.00%
Tier 1 leverage capital to be well-capitalized under prompt corrective action, amount	$ 493,726	$ 405,099
Tier 1 leverage capital to be well-capitalized under prompt corrective action, ratio	5.00%	5.00%
Tier 1 risk-based capital [Abstract]
Tier 1 risk-based capital, actual amount	$ 859,538	$ 672,633
Tier 1 risk-based capital, actual ratio	14.50%	14.28%
Tier 1 risk-based capital for capital adequacy purposes, amount	$ 355,641	$ 282,662
Tier 1 risk-based capital for capital adequacy purposes, ratio	6.00%	6.00%
Tier 1 risk-based capital for capital adequacy purposes plus capital conservation buffer, amount	$ 429,733	$ 312,106
Tier 1 risk-based capital for capital adequacy purposes plus capital conservation buffer, ratio	7.25%	6.625%
Tier 1 risk based capital to be well-capitalized under prompt corrective action, amount	$ 474,188	$ 376,883
Tier 1 risk-based capital to be well-capitalized under prompt corrective action, ratio	8.00%	8.00%
Total risk-based capital [Abstract]
Total risk-based capital, actual amount	$ 907,588	$ 720,282
Total risk-based capital, actual ratio	15.31%	15.29%
Total risk-based capital for capital adequacy purposes, amount	$ 474,188	$ 376,883
Total risk-based capita for capital adequacy purposes, ratio	8.00%	8.00%
Total risk-based capital for capital adequacy purposes plus capital conservation buffer, amount	$ 548,280	$ 406,327
Total risk-based capita for capital adequacy purposes plus capital conservation buffer, ratio	9.25%	8.625%
Total risk based capital to be well-capitalized under prompt corrective action, amount	$ 592,736	$ 471,104
Total risk based capital to be well-capitalized under prompt corrective action, ratio	10.00%	10.00%
Common equity Tier 1 capital [Abstract]
Common equity Tier 1 capital, actual amount	$ 859,483	$ 672,578
Common equity Tier 1 capital, actual ratio	14.50%	14.28%
Common equity Tier 1 capital for capital adequacy purposes, amount	$ 266,731	$ 211,997
Common equity Tier 1 capital for capital adequacy purposes, ratio	4.50%	4.50%
Common equity Tier 1 capital for capital adequacy purposes plus capital conservation buffer, amount	$ 340,823	$ 241,441
Common equity Tier 1 capital for capital adequacy purposes plus capital conservation buffer, ratio	5.75%	5.125%
Common equity Tier 1 capital to be well-capitalized under prompt corrective action, amount	$ 385,278	$ 306,217
Common equity Tier 1 capital to be well-capitalized under prompt corrective action, ratio	6.50%	6.50%

PARENT COMPANY STATEMENTS, Cond

PARENT COMPANY STATEMENTS, Condensed Statements of Condition (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets [Abstract]
Cash and cash equivalents	$ 221,038	$ 173,857	$ 153,210	$ 138,396
Investment in and advances to [Abstract]
Other assets	249,488	180,188
Total assets	10,746,198	8,666,437	8,552,669
Liabilities and shareholders' equity [Abstract]
Accrued interest and other liabilities	180,567	144,013
Borrowings	122,814	102,170
Shareholders' equity	1,635,315	1,198,100	1,140,647	987,904
Total liabilities and shareholders' equity	10,746,198	8,666,437
Parent Company [Member]
Assets [Abstract]
Cash and cash equivalents	84,460	151,127	$ 97,317	$ 106,957
Investment securities	4,322	3,628
Investment in and advances to [Abstract]
Bank subsidiary	1,511,780	1,116,554
Non-bank subsidiaries	169,341	35,566
Other assets	9,150	10,345
Total assets	1,779,053	1,317,220
Liabilities and shareholders' equity [Abstract]
Accrued interest and other liabilities	20,924	16,950
Borrowings	122,814	102,170
Shareholders' equity	1,635,315	1,198,100
Total liabilities and shareholders' equity	$ 1,779,053	$ 1,317,220

PARENT COMPANY STATEMENTS, C104

PARENT COMPANY STATEMENTS, Condensed Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Expenses [Abstract]
Interest on borrowings	$ 3,904	$ 2,949	$ 2,537
Acquisition expenses	25,986	1,706	7,037
Other expenses	18,540	16,553	13,521
Income before tax benefit and equity in undistributed net income of subsidiaries	159,965	154,597	132,217
Income tax benefit/(expense)	(9,248)	(50,785)	(40,987)
Net income	150,717	103,812	91,230
Other comprehensive (loss), net of tax [Abstract]
Changes in other comprehensive income/(loss) related to pension and other post retirement obligations	168	3,322	(4,567)
Changes in other comprehensive loss related to unrealized losses on available-for-sale securities	(11,065)	(14,714)	(6,918)
Other comprehensive (loss), net of tax	(10,897)	(11,392)	(11,485)
Comprehensive income	139,820	92,420	79,745
Parent Company [Member]
Dividends from subsidiaries [Abstract]
Bank subsidiary	91,000	89,000	70,000
Non-bank subsidiaries	35,500	1,750	6,000
Interest and dividends on investments	133	102	94
Total revenues	126,633	90,852	76,094
Expenses [Abstract]
Interest on borrowings	3,904	2,949	2,537
Acquisition expenses	91	429	0
Other expenses	26	11	19
Total expenses	4,021	3,389	2,556
Income before tax benefit and equity in undistributed net income of subsidiaries	122,612	87,463	73,538
Income tax benefit/(expense)	1,930	866	(572)
Income before equity in undistributed net income of subsidiaries	124,542	88,329	72,966
Equity in undistributed net income of subsidiaries	26,175	15,483	18,264
Net income	150,717	103,812	91,230
Other comprehensive (loss), net of tax [Abstract]
Changes in other comprehensive income/(loss) related to pension and other post retirement obligations	168	3,322	(4,567)
Changes in other comprehensive loss related to unrealized losses on available-for-sale securities	(11,065)	(14,714)	(6,918)
Other comprehensive (loss), net of tax	(10,897)	(11,392)	(11,485)
Comprehensive income	$ 139,820	$ 92,420	$ 79,745

PARENT COMPANY STATEMENTS, C105

PARENT COMPANY STATEMENTS, Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities [Abstract]
Net income	$ 150,717	$ 103,812	$ 91,230
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Net change in other assets and other liabilities	26,090	(7,614)	(5,681)
Net cash provided by operating activities	189,674	135,771	119,566
Investing activities [Abstract]
Cash (paid)/received for acquisitions, net of cash acquired of $150,534, $0, and $81,772, respectively	(107,414)	(575)	25,505
Net cash provided by/(used in) investing activities	131,371	(121,998)	(274,161)
Financing activities [Abstract]
Issuance of common stock	4,563	10,543	9,774
Purchase of treasury stock	(3,306)	(3,470)	(9,126)
Sale of treasury stock	10,060	8,888	16,571
Increase in deferred compensation arrangements	3,306	0	0
Net cash (used in)/provided by financing activities	(273,864)	6,874	169,409
Change in cash and cash equivalents	47,181	20,647	14,814
Cash and cash equivalents at beginning of year	173,857	153,210	138,396
Cash and cash equivalents at end of year	221,038	173,857	153,210
Supplemental disclosures of cash flow information [Abstract]
Cash paid for interest	13,705	11,268	11,252
Supplemental disclosures of noncash financing activities [Abstract]
Dividends declared and unpaid	17,460	14,268	13,605
Common stock issued for acquisition	343,132	0	102,202
Cash acquired related to acquisition	52,132	0	81,772
Parent Company [Member]
Operating activities [Abstract]
Net income	150,717	103,812	91,230
Adjustments to reconcile net income to net cash provided by operating activities [Abstract]
Equity in undistributed net income of subsidiaries	(26,175)	(15,483)	(18,264)
Net change in other assets and other liabilities	1,870	(215)	(27)
Net cash provided by operating activities	126,412	88,114	72,939
Investing activities [Abstract]
Proceeds from sale of investment securities	0	0	0
Cash (paid)/received for acquisitions, net of cash acquired of $150,534, $0, and $81,772, respectively	(139,471)	0	25,505
Capital contributions to subsidiaries	(11,063)	0	(80,231)
Net cash provided by/(used in) investing activities	(150,534)	0	(54,726)
Financing activities [Abstract]
Issuance of common stock	9,700	15,326	13,975
Purchase of treasury stock	(3,306)	(3,470)	(9,126)
Sale of treasury stock	10,060	8,888	16,571
Increase in deferred compensation arrangements	3,306	0	0
Cash dividends paid	(62,305)	(55,048)	(49,273)
Net cash (used in)/provided by financing activities	(42,545)	(34,304)	(27,853)
Change in cash and cash equivalents	(66,667)	53,810	(9,640)
Cash and cash equivalents at beginning of year	151,127	97,317	106,957
Cash and cash equivalents at end of year	84,460	151,127	97,317
Supplemental disclosures of cash flow information [Abstract]
Cash paid for interest	3,826	2,909	2,523
Supplemental disclosures of noncash financing activities [Abstract]
Dividends declared and unpaid	17,460	14,268	13,605
Capital contributions to subsidiaries	513,769	0	76,461
Common stock issued for acquisition	343,132	0	102,202
Cash acquired related to acquisition	$ 150,534	$ 0	$ 81,772

FAIR VALUE, Financial Assets an

FAIR VALUE, Financial Assets and Liabilities Accounted for at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	$ 3,031,088	$ 2,748,656
Recurring [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	3,031,088	2,748,656
Mortgage loans held for sale	461	2,416
Total	3,031,802	2,751,129
Recurring [Member] | Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	89	54
Recurring [Member] | Forward Sales Commitments [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	4	3
Recurring [Member] | Interest Rate Swap Agreements [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	1,064
Derivative liability	(904)
Recurring [Member] | U.S. Treasury and Agency Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,054,071	1,902,762
Recurring [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	528,956	594,990
Recurring [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	357,538	235,230
Recurring [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,623	5,687
Recurring [Member] | Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	87,374	9,535
Recurring [Member] | Marketable Equity Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	526	452
Recurring [Member] | Level 1 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,909,816	1,903,214
Mortgage loans held for sale	0	0
Total	1,909,816	1,903,214
Recurring [Member] | Level 1 [Member] | Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Recurring [Member] | Level 1 [Member] | Forward Sales Commitments [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Recurring [Member] | Level 1 [Member] | Interest Rate Swap Agreements [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0
Derivative liability	0
Recurring [Member] | Level 1 [Member] | U.S. Treasury and Agency Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,909,290	1,902,762
Recurring [Member] | Level 1 [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 1 [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 1 [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 1 [Member] | Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 1 [Member] | Marketable Equity Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	526	452
Recurring [Member] | Level 2 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,121,272	845,442
Mortgage loans held for sale	461	2,416
Total	1,121,897	847,861
Mortgage loans held for sale, at principal value	500
Mortgage loans held for sale, gross unrealized gain (Loss)	13
Recurring [Member] | Level 2 [Member] | Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Recurring [Member] | Level 2 [Member] | Forward Sales Commitments [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	4	3
Recurring [Member] | Level 2 [Member] | Interest Rate Swap Agreements [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	1,064
Derivative liability	(904)
Recurring [Member] | Level 2 [Member] | U.S. Treasury and Agency Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	144,781	0
Recurring [Member] | Level 2 [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	528,956	594,990
Recurring [Member] | Level 2 [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	357,538	235,230
Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,623	5,687
Recurring [Member] | Level 2 [Member] | Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	87,374	9,535
Recurring [Member] | Level 2 [Member] | Marketable Equity Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 3 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Mortgage loans held for sale	0	0
Total	89	54
Recurring [Member] | Level 3 [Member] | Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	89	54
Recurring [Member] | Level 3 [Member] | Forward Sales Commitments [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0	0
Recurring [Member] | Level 3 [Member] | Interest Rate Swap Agreements [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	0
Derivative liability	0
Recurring [Member] | Level 3 [Member] | U.S. Treasury and Agency Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 3 [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 3 [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 3 [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 3 [Member] | Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 3 [Member] | Marketable Equity Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	$ 0	$ 0

FAIR VALUE, Assets and Liabilit

FAIR VALUE, Assets and Liabilities Measured on Nonrecurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of MSRs at end of period	$ 2,473	$ 1,928
Valuation allowance	804	477
Carrying value before valuation allowance at end of period	1,358	1,435	$ 1,472
Mortgage Servicing Rights [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of MSRs at end of period	2,500
Valuation allowance	0
Carrying value before valuation allowance at end of period	1,400
Other Real Estate Owned [Member] | Market Approach Valuation Technique [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 1,915	$ 1,966
Other Real Estate Owned [Member] | Market Approach Valuation Technique [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	9.00%	9.00%
Other Real Estate Owned [Member] | Market Approach Valuation Technique [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	99.00%	97.00%
Level 3 [Member] | Other Real Estate Owned [Member] | Market Approach Valuation Technique [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	9.00%
Level 3 [Member] | Other Real Estate Owned [Member] | Market Approach Valuation Technique [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate	99.00%
Non-recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	$ 0	$ 633
Other real estate owned	1,915	1,966
Total	1,915	2,599
Non-recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0	0
Other real estate owned	0	0
Total	0	0
Non-recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0	0
Other real estate owned	0	0
Total	0	0
Non-recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	0	633
Other real estate owned	1,915	1,966
Total	$ 1,915	$ 2,599

FAIR VALUE, Significant Unobser

FAIR VALUE, Significant Unobservable Inputs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Other Real Estate Owned [Member] | Fair Value of Collateral [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 1,915	$ 1,966
Other Real Estate Owned [Member] | Fair Value of Collateral [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Estimated cost of disposal/market adjustment	9.00%	9.00%
Other Real Estate Owned [Member] | Fair Value of Collateral [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Estimated cost of disposal/market adjustment	99.00%	97.00%
Other Real Estate Owned [Member] | Fair Value of Collateral [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Estimated cost of disposal/market adjustment	38.50%	29.60%
Impaired Loans [Member] | Fair Value of Collateral [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value		$ 633
Impaired Loans [Member] | Fair Value of Collateral [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Estimated cost of disposal/market adjustment		15.00%
Impaired Loans [Member] | Fair Value of Collateral [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Estimated cost of disposal/market adjustment		50.00%
Impaired Loans [Member] | Fair Value of Collateral [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Estimated cost of disposal/market adjustment		36.50%
Commitments to Originate Real Estate Loans for Sale [Member] | Discounted Cash Flow [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 89	$ 54
Embedded servicing value	1.00%	1.00%

FAIR VALUE, Carrying Amounts an

FAIR VALUE, Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Carrying Value [Member]
Financial assets [Abstract]
Net loans	$ 6,209,174	$ 4,901,329
Financial liabilities [Abstract]
Deposits	8,444,420	7,075,954
Short-term borrowings	24,000	146,200
Securities sold under agreement to repurchase, short-term	337,011	0
Other long-term debt	2,071	0
Subordinated debt held by unconsolidated subsidiary trusts	122,814	102,170
Fair Value [Member]
Financial assets [Abstract]
Net loans	6,244,941	4,935,140
Financial liabilities [Abstract]
Deposits	8,431,481	7,071,191
Short-term borrowings	24,000	146,200
Securities sold under agreement to repurchase, short-term	337,011	0
Other long-term debt	2,021	0
Subordinated debt held by unconsolidated subsidiary trusts	$ 122,814	$ 90,144

DERIVATIVE INSTRUMENTS (Details

DERIVATIVE INSTRUMENTS (Details) - Interest Rate Swap [Member] $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)
Derivative [Line Items]
Derivative, notional amount	$ 38.9
Derivative weighted average receive rate	3.38%
Derivative weighted average pay rate	3.84%
Weighted average maturity period	6 years 6 months
Other Assets [Member]
Derivative [Line Items]
Fair value of derivate assets	$ 0.9
Other Liabilities [Member]
Derivative [Line Items]
Fair value of derivate liability	0.9
Designated as Hedging Instrument [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative, notional amount	$ 7
Derivative weighted average receive rate	2.30%
Derivative weighted average pay rate	3.11%
Weighted average maturity period	15 years 6 months
Designated as Hedging Instrument [Member] | Fair Value Hedging [Member] | Other Assets [Member]
Derivative [Line Items]
Fair value of derivate assets	$ 0.2

VARIABLE INTEREST ENTITIES (Det

VARIABLE INTEREST ENTITIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Cash and cash equivalents	$ 221,038	$ 173,857	$ 153,210	$ 138,396
Premises and equipment, net	123,393	112,318
Other assets	249,488	180,188
Variable Interest Entity, Primary Beneficiary [Member] | 706 North Clinton [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents	74	30
Premises and equipment, net	6,266	6,429
Other assets	5	0
Total assets	6,345	6,459
Accrued interest and other liabilities / Total liabilities	0	$ 1
Minority interest	3,200
Loss of minority interest	4,700
Minority interest loss exposure related to financing agreement	$ 1,500
Variable Interest Entity, Primary Beneficiary [Member] | 706 North Clinton [Member] | Oneida Preferred Funding II LLC [Member]
Variable Interest Entity [Line Items]
Percentage of membership interest	50.00%

SEGMENT INFORMATION (Details)

SEGMENT INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Information about reportable segments [Abstract]
Net interest income	$ 315,675	$ 273,896	$ 248,420
(Benefit)/provision for loan losses	10,984	8,076	6,447
Noninterest income	202,423	155,625	123,299
Amortization of intangible assets	16,941	5,479	3,663
Acquisition expenses	25,986	1,706	7,037
Other operating expenses	304,222	259,663	222,355
Income before income taxes	159,965	154,597	132,217
Assets	10,746,198	8,666,437	8,552,669
Goodwill	734,430	465,142	463,252
Eliminations [Member]
Information about reportable segments [Abstract]
Net interest income	0	0	0
(Benefit)/provision for loan losses	0	0	0
Noninterest income	(2,858)	(2,442)	(2,156)
Amortization of intangible assets	0	0	0
Acquisition expenses	0	0	0
Other operating expenses	(2,858)	(2,442)	(2,156)
Income before income taxes	0	0	0
Assets	(29,638)	(41,790)	(65,637)
Goodwill	0	0	0
Banking [Member] | Operating Segments [Member]
Information about reportable segments [Abstract]
Net interest income	315,025	273,542	248,167
(Benefit)/provision for loan losses	10,984	8,076	6,447
Noninterest income	73,337	66,059	57,704
Amortization of intangible assets	5,296	2,682	2,803
Acquisition expenses	24,549	1,005	6,947
Other operating expenses	218,608	190,263	174,918
Income before income taxes	128,925	137,575	114,756
Assets	10,505,919	8,598,057	8,513,228
Goodwill	629,916	440,870	439,052
Employee Benefit Services [Member] | Operating Segments [Member]
Information about reportable segments [Abstract]
Net interest income	396	162	132
(Benefit)/provision for loan losses	0	0	0
Noninterest income	82,743	48,261	46,784
Amortization of intangible assets	8,578	420	515
Acquisition expenses	1,194	445	21
Other operating expenses	51,138	36,892	35,197
Income before income taxes	22,229	10,666	11,183
Assets	203,369	38,742	35,011
Goodwill	84,449	8,019	8,019
All Other [Member] | Operating Segments [Member]
Information about reportable segments [Abstract]
Net interest income	254	192	121
(Benefit)/provision for loan losses	0	0	0
Noninterest income	49,201	43,747	20,967
Amortization of intangible assets	3,067	2,377	345
Acquisition expenses	243	256	69
Other operating expenses	37,334	34,950	14,396
Income before income taxes	8,811	6,356	6,278
Assets	66,548	71,428	70,067
Goodwill	$ 20,065	$ 16,253	$ 16,181