Community Bank System (CBU) 10-Q 9 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Jul. 31, 2018
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 Common Stock, Shares Outstanding		51,107,725
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018

CONSOLIDATED STATEMENTS OF COND

CONSOLIDATED STATEMENTS OF CONDITION (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets:
Cash and cash equivalents	$ 250,154	$ 221,038
Available-for-sale investment securities (cost of $2,972,889 and $3,007,148, respectively)	2,939,944	3,031,088
Equity and other securities (cost of $43,155 and $50,291, respectively)	43,408	50,291
Loans held for sale, at fair value	1,281	461
Loans	6,238,009	6,256,757
Allowance for loan losses	(49,618)	(47,583)
Net loans	6,188,391	6,209,174
Goodwill, net	733,479	734,430
Core deposit intangibles, net	21,646	25,025
Other intangibles, net	61,002	65,633
Intangible assets, net	816,127	825,088
Premises and equipment, net	120,715	123,393
Accrued interest and fees receivable	34,921	36,177
Other assets	238,153	249,488
Total assets	10,633,094	10,746,198
Liabilities:
Noninterest-bearing deposits	2,332,745	2,293,057
Interest-bearing deposits	6,181,248	6,151,363
Total deposits	8,513,993	8,444,420
Short-term borrowings	0	24,000
Securities sold under agreement to repurchase, short-term	181,765	337,011
Other long-term debt	2,020	2,071
Subordinated debt held by unconsolidated subsidiary trusts	122,826	122,814
Accrued interest and other liabilities	155,531	180,567
Total liabilities	8,976,135	9,110,883
Commitments and contingencies (See Note J)
Shareholders' equity:
Preferred stock, $1.00 par value, 500,000 shares authorized, 0 shares issued	0	0
Common stock, $1.00 par value, 75,000,000 shares authorized; 51,511,992 and 51,263,841 shares issued, respectively	51,512	51,264
Additional paid-in capital	904,913	894,879
Retained earnings	750,779	700,557
Accumulated other comprehensive loss	(46,491)	(3,699)
Treasury stock, at cost (426,118 shares, including 205,017 shares held by deferred compensation arrangements at June 30, 2018 and 567,764 shares including 237,494 shares held by deferred compensation arrangements at December 31, 2017, respectively)	(15,334)	(21,014)
Deferred compensation arrangements (205,017 and 237,494 shares, respectively)	11,580	13,328
Total shareholders' equity	1,656,959	1,635,315
Total liabilities and shareholders' equity	$ 10,633,094	$ 10,746,198

CONSOLIDATED STATEMENTS OF CON3

CONSOLIDATED STATEMENTS OF CONDITION (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets:
Available-for-sale investment securities, cost	$ 2,972,889	$ 3,007,148
Equity and other securities, cost	$ 43,155	$ 50,291
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)	51,511,992	51,263,841
Treasury stock, shares at cost (in shares)	426,118	567,764
Shares held by deferred compensation arrangements (in shares)	205,017	237,494

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Interest income:
Interest and fees on loans	$ 71,152	$ 62,351	$ 140,593	$ 114,735
Interest and dividends on taxable investments	16,517	15,175	32,041	28,741
Interest on nontaxable investments	3,336	3,896	6,775	7,904
Total interest income	91,005	81,422	179,409	151,380
Interest expense:
Interest on deposits	2,381	2,065	4,513	3,795
Interest on borrowings	446	392	926	541
Interest on subordinated debt held by unconsolidated subsidiary trusts	1,332	936	2,500	1,741
Total interest expense	4,159	3,393	7,939	6,077
Net interest income	86,846	78,029	171,470	145,303
Provision for loan losses	2,448	1,461	6,127	3,289
Net interest income after provision for loan losses	84,398	76,568	165,343	142,014
Noninterest revenues:
Deposit service fees	18,964	16,655	38,141	31,362
Other banking services	1,163	1,407	2,406	2,566
Employee benefit services	22,542	20,662	45,548	37,851
Insurance services	7,415	6,965	14,774	13,365
Wealth management services	6,496	5,537	13,202	10,398
Unrealized loss on equity securities	(21)	0	(21)	0
Gain on sales of investment securities	0	0	0	2
Total noninterest revenues	56,559	51,226	114,050	95,544
Noninterest expenses:
Salaries and employee benefits	52,402	46,564	104,261	89,471
Occupancy and equipment	9,437	8,637	19,968	16,833
Data processing and communications	10,212	10,395	18,954	18,916
Amortization of intangible assets	4,555	4,263	9,353	7,031
Legal and professional fees	2,745	2,619	5,525	5,033
Business development and marketing	2,654	2,451	4,714	4,532
Acquisition expenses	71	22,896	63	24,612
Other expenses	4,036	5,054	9,605	10,026
Total noninterest expenses	86,112	102,879	172,443	176,454
Income before income taxes	54,845	24,915	106,950	61,104
Income taxes	10,239	7,724	22,238	17,656
Net income	$ 44,606	$ 17,191	$ 84,712	$ 43,448
Basic earnings per share (in dollars per share)	$ 0.87	$ 0.35	$ 1.65	$ 0.92
Diluted earnings per share (in dollars per share)	0.86	0.35	1.63	0.91
Cash dividends declared per share (in dollars per share)	$ 0.34	$ 0.32	$ 0.68	$ 0.64

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Pension and other post retirement obligations:
Amortization of actuarial losses included in net periodic pension cost, gross	$ 303	$ 211	$ 606	$ 476
Tax effect	(74)	(80)	(147)	(182)
Amortization of actuarial losses included in net periodic pension cost, net	229	131	459	294
Amortization of prior service cost included in net periodic pension cost, gross	(127)	(28)	(254)	(59)
Tax effect	31	10	62	22
Amortization of prior service cost included in net periodic pension cost, net	(96)	(18)	(192)	(37)
Unamortized actuarial gain due to plan merger, gross (See Note H)	0	1,857	0	1,857
Tax effect	0	(710)	0	(710)
Unamortized actuarial gain due to plan merger, net	0	1,147	0	1,147
Other comprehensive income related to pension and other post retirement obligations, net of taxes	133	1,260	267	1,404
Unrealized (losses) gains on available-for-sale securities:
Net unrealized holding (losses)/gains arising during period, gross	(14,816)	9,760	(56,632)	13,653
Tax effect	3,625	(3,732)	13,781	(5,258)
Net unrealized holding (losses)/gains arising during period, net	(11,191)	6,028	(42,851)	8,395
Reclassification of other comprehensive income due to change in accounting principle - equity securities	(208)	0	(208)	0
Other comprehensive (loss)/income related to unrealized (losses)/gains on available-for-sale securities, net of taxes	(11,399)	6,028	(43,059)	8,395
Other comprehensive (loss)/income, net of tax	(11,266)	7,288	(42,792)	9,799
Net income	44,606	17,191	84,712	43,448
Comprehensive income	33,340	$ 24,479	41,920	$ 53,247
Accumulated Other Comprehensive Income By Component:
Unrealized loss for pension and other post-retirement obligations	(28,325)		(28,325)		$ (28,677)
Tax effect	6,959		6,959		7,044
Net unrealized loss for pension and other postretirement obligations	(21,366)		(21,366)		(21,633)
Unrealized (loss) gain on available-for-sale securities	(32,692)		(32,692)		23,940
Tax effect	7,775		7,775		(6,006)
Reclassification of other comprehensive income due to change in accounting principle - equity securities	(208)		(208)		0
Net unrealized (loss) gain on available-for-sale securities	(25,125)		(25,125)		17,934
Accumulated other comprehensive loss	$ (46,491)		$ (46,491)		$ (3,699)

CONSOLIDATED STATEMENT OF CHANG

CONSOLIDATED STATEMENT OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) - 6 months ended Jun. 30, 2018 - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Treasury Stock [Member]	Deferred Compensation Arrangements [Member]	Total
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income			84,712				84,712
Other comprehensive loss, net of tax				(42,584)			(42,584)
Cash dividends declared:
Common, $0.68 per share			(34,698)				(34,698)
Common stock issued under employee stock ownership plan	$ 248	4,396					4,644
Common stock issued under employee stock ownership plan (in shares)	248,151
Stock-based compensation		3,396					3,396
Distribution of stock under deferred compensation arrangements					1,898	(1,898)	0
Distribution of stock under deferred compensation arrangements (in shares)	35,233
Treasury stock issued to benefit plans, net		2,242			3,782	150	6,174
Treasury stock issued to benefit plans, net (in shares)	106,413
Balance at Jun. 30, 2018	$ 51,512	$ 904,913	750,779	(46,491)	$ (15,334)	$ 11,580	1,656,959
Balance (in shares) at Jun. 30, 2018	51,085,874
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle - equity securities			$ 208	$ (208)			$ 0

CONSOLIDATED STATEMENT OF CHAN7

CONSOLIDATED STATEMENT OF CHANGES IN SHAREHOLDERS' EQUITY (Unaudited) (Parenthetical) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Cash dividends declared:
Dividends declared per common share (in dollars per share)	$ 0.34	$ 0.32	$ 0.68	$ 0.64

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating activities:
Net income	$ 84,712	$ 43,448
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	7,959	7,775
Amortization of intangible assets	9,353	7,031
Net accretion on securities, loans and borrowings	(4,784)	(2,345)
Stock-based compensation	3,396	2,730
Provision for loan losses	6,127	3,289
Amortization of mortgage servicing rights	229	248
Income from bank-owned life insurance policies	(784)	(746)
Net (gain) loss on sale of loans and other assets	(146)	257
Change in other assets and other liabilities	5,558	30,397
Net cash provided by operating activities	111,620	92,084
Investing activities:
Proceeds from maturities of available-for-sale investment securities	69,637	73,770
Proceeds from maturities of other investment securities	7,408	10,006
Purchases of available-for-sale investment securities	(31,669)	(34,842)
Purchases of other securities	(21)	(1,447)
Net change in loans	13,647	70,094
Cash paid for acquisitions, net of cash acquired of $16 and $51,793, respectively	(1,737)	(105,402)
Settlement of bank-owned life insurance policies	0	1,779
Purchases of premises and equipment, net	(5,298)	(5,390)
Net cash provided by investing activities	51,967	8,568
Financing activities:
Net increase in deposits	69,573	101,243
Net change in borrowings	(179,297)	(134,838)
Issuance of common stock	4,644	2,829
Purchases of treasury stock	(150)	(3,078)
Sales of treasury stock	6,174	6,169
Increase in deferred compensation arrangements	150	3,078
Cash dividends paid	(34,611)	(28,849)
Withholding taxes paid on share-based compensation	(954)	(1,368)
Net cash used in financing activities	(134,471)	(54,814)
Change in cash and cash equivalents	29,116	45,838
Cash and cash equivalents at beginning of period	221,038	173,857
Cash and cash equivalents at end of period	250,154	219,695
Supplemental disclosures of cash flow information:
Cash paid for interest	7,896	6,010
Cash paid for income taxes	12,681	20,154
Supplemental disclosures of noncash financing and investing activities:
Dividends declared and unpaid	17,547	16,331
Transfers from loans to other real estate	1,845	2,048
Acquisitions:
Common stock issued	0	340,737
Fair value of assets acquired, excluding acquired cash and intangibles	115	1,960,935
Fair value of liabilities assumed	$ 31	$ 1,869,876

CONSOLIDATED STATEMENTS OF CAS9

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Investing activities:
Cash acquired from acquisition	$ 16	$ 51,793

BASIS OF PRESENTATION

BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2018
BASIS OF PRESENTATION [Abstract]
BASIS OF PRESENTATION	NOTE A: BASIS OF PRESENTATION The interim financial data as of and for the three and six months ended June 30, 2018 is unaudited; however, in the opinion of Community Bank System, Inc. (the “Company”), the interim data includes all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement of the results for the interim periods in conformity with generally accepted accounting principles (“GAAP”). The results of operations for the interim periods are not necessarily indicative of the results that may be expected for the full year or any other interim period.

ACQUISITIONS

ACQUISITIONS	6 Months Ended
	Jun. 30, 2018
ACQUISITIONS [Abstract]
ACQUISITIONS	NOTE B: ACQUISITIONS On April 2, 2018, the Company, through its subsidiary, Benefit Plans Administrative Services, Inc. (“BPAS”), acquired certain assets of HR Consultants (SA), LLC (“HR Consultants”), a benefits consulting group headquartered in Puerto Rico. The Company paid $0.3 million in cash to acquire the assets of HR Consultants and recorded intangible assets of $0.3 million in conjunction with the acquisition. The effects of the acquired assets have been included in the consolidated financial statements since that date. On January 2, 2018, the Company, through its subsidiary, OneGroup NY, Inc. (“OneGroup”), completed its acquisition of certain assets of Penna & Associates Agency, Inc. (“Penna”), an insurance agency headquartered in Johnson City, New York. The Company paid $0.8 million in cash to acquire the assets of Penna, and recorded goodwill in the amount of $0.3 million and a customer list intangible asset of $0.3 million in conjunction with the acquisition. The effects of the acquired assets have been included in the consolidated financial statements since that date. On January 2, 2018, the Company, through its subsidiary, Community Investment Services, Inc. (“CISI”), completed its acquisition of certain assets of Styles Bridges Associates (“Styles Bridges”), a financial services business headquartered in Canton, New York. The Company paid $0.7 million in cash to acquire a customer list from Styles Bridges, and recorded a $0.7 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 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, $0.6 million of other liabilities, goodwill in the amount of $2.1 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 paid $1.2 million in cash 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 $16.1 million and $32.2 million from Merchants were included in the consolidated income statement for the three and six months ended June 30, 2018, respectively. Direct expenses, which may not include certain shared expenses, of approximately $7.6 million and $15.4 million from Merchants were included in the consolidated income statement for the three and six months ended June 30, 2018, respectively. Revenues of approximately $8.9 million and direct expenses, which may not include certain shared expenses, of approximately $4.0 million from Merchants were included in the consolidated income statement for the three and six months ended June 30, 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 Northeast Retirement Services, Inc. (“NRS”) and its subsidiary Global Trust Company (“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 $23.0 million deferred tax liability associated with the customer list intangible, and $75.3 million in goodwill. The effects of the acquired assets and liabilities have been included in the consolidated financial statements since that date. Revenues of $9.7 million and $19.8 million from NRS were included in the consolidated statement of income for the three and six months ended June 30, 2018, respectively. Expenses of $6.0 million and $12.0 million from NRS were included in the consolidated statement of income for the three and six months ended June 30, 2018, respectively. Revenues of $8.4 million and $13.4 million from NRS were included in the consolidated income statement for the three and six months ended June 30, 2017, respectively. Expenses of $5.7 million and $9.3 million from NRS were included in the consolidated income statement for the three and six months ended June 30, 2017, respectively. 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 have been included in the consolidated financial statements since that date. The assets and liabilities assumed in the acquisitions were recorded at their estimated fair values based on management’s best estimates using information available at the dates of the acquisition, and were subject to adjustment based on updated information not available at the time of acquisition. During the first quarter of 2018, the carrying amount of other liabilities associated with the NRS acquisition decreased by $1.2 million as a result of an adjustment to deferred taxes. Goodwill associated with the NRS acquisition decreased $1.2 million as a result of this adjustment. During the second quarter of 2018, the carrying amount of other liabilities associated with the GBR acquisition decreased by $0.09 million as a result of updated information not available at the time of acquisition. Goodwill associated with the GBR acquisition decreased $0.09 million as a result of this adjustment. 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: 2018 2017 (000s omitted) Other (1) NRS Merchants Other (2) Total Consideration paid : Cash $ 1,753 $ 70,073 $ 82,898 $ 6,775 $ 159,746 Community Bank System, Inc. common stock 0 78,483 262,254 2,395 343,132 Total net consideration paid 1,753 148,556 345,152 9,170 502,878 Recognized amounts of identifiable assets acquired and liabilities assumed: Cash and cash equivalents 16 11,063 40,730 339 52,132 Investment securities 0 20,294 370,648 0 390,942 Loans 0 0 1,488,157 0 1,488,157 Premises and equipment 10 411 16,608 27 17,046 Accrued interest receivable 0 72 4,773 0 4,845 Other assets 105 8,088 51,585 583 60,256 Core deposit intangibles 0 0 23,214 0 23,214 Other intangibles 1,343 60,200 2,857 5,626 68,683 Deposits 0 0 (1,448,406 ) 0 (1,448,406 ) Other liabilities (31 ) (26,828 ) (11,750 ) (1,131 ) (39,709 ) Short-term advances 0 0 (80,000 ) 0 (80,000 ) Securities sold under agreement to repurchase, short-term 0 0 (278,076 ) 0 (278,076 ) Long-term debt 0 0 (3,615 ) 0 (3,615 ) Subordinated debt held by unconsolidated subsidiary trusts 0 0 (20,619 ) 0 (20,619 ) Total identifiable assets, net 1,443 73,300 156,106 5,444 234,850 Goodwill $ 310 $ 75,256 $ 189,046 $ 3,726 $ 268,028 (1) (2) 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 HR Consultants, Penna, Styles Bridges, GBR, NECM, Merchants, Dryfoos, and BAS 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 acquisition, the Employee Benefit Services segment for NRS, and All Other segments for the Penna, GBR, and Dryfoos acquisitions. Goodwill arising from the Merchants, NRS and GBR acquisitions is not deductible for tax purposes. Goodwill arising from the Penna and Dryfoos acquisitions is deductible for tax purposes. Direct costs related to the acquisitions were expensed as incurred. Merger and acquisition integration-related expenses amount to $22.9 million and $24.6 million during the three and six months ended June 30, 2017 and have been separately stated in the Consolidated Statements of Income. Merger and acquisition integration-related expenses for the three and six months ended June 30, 2018 were immaterial.

ACCOUNTING POLICIES

ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2018
ACCOUNTING POLICIES [Abstract]
ACCOUNTING POLICIES	NOTE C: ACCOUNTING POLICIES The accounting policies of the Company, as applied in the consolidated interim financial statements presented herein, are substantially the same as those followed on an annual basis as presented on pages 63 through 71 of the Annual Report on Form 10-K for the year ended December 31, 2017 filed with the Securities and Exchange Commission (“SEC”) on March 1, 2018. Investment Securities The Company can classify its investments in debt securities as held-to-maturity, available-for-sale, or trading. Held-to-maturity securities are those for which the Company has the positive intent and ability to hold until maturity, and are reported at cost, which is adjusted for amortization of premiums and accretion of discounts. Available-for-sale debt securities are reported at fair value with net unrealized gains and losses reflected as a separate component of shareholders’ equity, net of applicable income taxes. Equity securities with a readily determinable fair value are reported at fair value with net unrealized gains and losses recognized in the consolidated statement of income. None of the Company’s investment securities have been classified as trading securities at June 30, 2018. Certain equity securities are stated at cost and include restricted stock of the Federal Reserve Bank of New York (“Federal Reserve”), 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. 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. Revenue Recognition On January 1, 2018, the Company adopted ASU No. 2014-09 Revenue from Contracts with Customers (Topic 606) Topic 606 does not apply to revenue associated with financial instruments, including revenue from loans and securities. In addition, certain noninterest income streams such as fees associated with mortgage servicing rights, financial guarantees, derivatives, and certain credit card fees are also not in scope of the newly adopted guidance. Topic 606 is applicable to the Company’s noninterest revenue streams including its deposit related fees, electronic payment interchange fees, merchant income, trust, asset management and other wealth management revenues, insurance commissions and benefit plan services income. However, the recognition of these revenue streams did not change significantly upon adoption of Topic 606. Noninterest revenue streams in-scope of Topic 606 are discussed below. Deposit Service Fees Deposit service fees consist of account activity fees, monthly service fees, check orders, debit and credit card income, ATM fees, Merchant services income and other revenues from processing wire transfers, bill pay service, cashier’s checks and foreign exchange. Debit and credit card income is primarily comprised of interchange fees earned at the time the Company’s debit and credit cards are processed through card payment networks such as Visa. ATM fees are primarily generated when a Company cardholder uses a non-Company ATM or a non-Company cardholder uses a Company ATM. Merchant services income mainly represents fees charged to merchants to process their debit and credit card transactions, in addition to account management fees. The Company’s performance obligation for deposit service fees is generally satisfied, and the related revenue recognized, when the services are rendered or the transaction has been completed. Payment for deposit service fees is typically received at the time it is assessed through a direct charge to customers’ accounts or on a monthly basis. Deposit service fees revenue primarily relates to the Company’s Banking operating segment. Other Banking Services Other banking services consists of other recurring revenue streams such as commissions from sales of credit life insurance, safe deposit box rental fees, mortgage banking income, bank owned life insurance income and other miscellaneous revenue streams. Commissions from the sale of credit life insurance are recognized at the time of sale of the policies. Safe deposit box rental fees are charged to the customer on an annual basis and recognized upon receipt of payment. The Company determined that since rentals and renewals occur fairly consistently over time, revenue is recognized on a basis consistent with the duration of the performance obligation. Mortgage banking income and bank owned life insurance income are not within the scope of Topic 606. Other banking services revenue primarily relates to the Company’s Banking operating segment. Employee Benefit Services Employee benefit services income consists of revenue received from retirement plan services, collective investment fund services, fund administration, transfer agency, consulting and actuarial services. The Company’s performance obligation that relates to plan services are satisfied over time and the resulting fees are recognized monthly or quarterly, based upon the market value of the assets under management and the applicable fee rate or on a time expended basis. Payment is generally received a few days after month end or quarter end. The Company does not earn performance-based incentives. Transactional services such as consulting services, mailings, or other adhoc services are provided to existing trust and asset management customers. The Company’s performance obligation for these transactional-based services is generally satisfied, and related revenue recognized, at a point in time (i.e., as incurred). Payment is received shortly after services are rendered. Employee benefit services revenue primarily relates to the Company’s Employee Benefit Services operating segment. Insurance Services Insurance services primarily consists of commissions received on insurance product sales and consulting services. The Company acts in the capacity of a broker or agent between the Company’s customer and the insurance carrier. The Company’s performance obligation related to insurance sales for both property and casualty insurance and employee benefit plans is generally satisfied upon the later of the issuance or effective date of the policy. The Company’s performance obligation related to consulting services is considered transactional in nature and is generally satisfied when the services have been completed and related revenue recognized at a point in time. Payment is received at the time services are rendered. The Company earns performance based incentives, commonly known as contingency payments, which usually are based on certain criteria established by the insurance carrier such as premium volume, growth and insured loss ratios. Contingent payments are accrued for based upon management’s expectations for the year. Commission expense associated with sales of insurance products is expensed as incurred. Insurance services revenue primarily relates to the Company’s All Other operating segment. Wealth Management Services Wealth management services income is primarily comprised of fees earned from the management and administration of trusts and other customer assets. The Company generally has two types of performance obligations related to these services. The Company’s performance obligation that relates to advisory and administration services are satisfied over time and the resulting fees are recognized monthly, based upon the market value of the assets under management and the applicable fee rate. Payment is generally received soon after month end or quarter end through a direct charge to customers’ accounts. The Company does not earn performance-based incentives. Transactional services such as tax return preparation services, purchases and sales of investments and insurance products are also available to existing trust and asset management customers. The Company’s performance obligation for these transactional-based services is generally satisfied, and related revenue recognized, at a point in time (i.e. as incurred). Payment is generally received on a monthly basis. Wealth management services revenue primarily relates to the Company’s All Other operating segment. Contract Balances A contract asset balance occurs when an entity performs a service for a customer before the customer pays consideration (resulting in a contract receivable) or before payment is due (resulting in a contract asset). A contract liability balance is an entity’s obligation to transfer a service to a customer for which the entity has already received payment (or payment is due) from the customer. The Company’s noninterest revenue streams are largely based on transactional activity, or standard month-end revenue accruals such as asset management fees based on month-end market values. Consideration is often received immediately or shortly after the Company satisfies its performance obligation and revenue is recognized. The Company does not typically enter into long-term revenue contracts with customers, and therefore, does not experience significant contract balances. As of June 30, 2018, $25.7 million of accounts receivable, including $7.4 million of unbilled fee revenue, and $3.0 million of unearned revenue was recorded in the Consolidated Statements of Condition. As of December 31, 2017, $29.8 million of accounts receivable, including $6.5 million of unbilled fee revenue, and $3.9 million of unearned revenue was recorded in the Consolidated Statements of Condition. Contract Acquisition Costs In connection with the adoption of Topic 606, an entity is required to capitalize, and subsequently amortize into expense, certain incremental costs of obtaining a contract with a customer if these costs are expected to be recovered. The incremental costs of obtaining a contract are those costs that an entity incurs to obtain a contract with a customer that it would not have incurred if the contract had not been obtained (for example, sales commission). The Company utilizes the practical expedient method which allows entities to immediately expense contract acquisition costs when the asset that would have resulted from capitalizing these costs would have been amortized in one year or less. Upon adoption of Topic 606, the Company did not capitalize any contract acquisition costs. Recently Adopted Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) 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 adopted this guidance on January 1, 2018. The impact of the adoption of this guidance resulted in the reclassification of $0.2 million of other comprehensive income to retained earnings. See the Consolidated Statements of Comprehensive Income and Consolidated Statement of Changes in Shareholders’ Equity. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) 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. New Accounting Pronouncements 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 January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350) In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. Subsequent Event On July 31, 2018, the Company exercised its right to redeem all of the Community Statutory Trust III (“CST III”) debentures and associated preferred securities for a total of $25.2 million. See note G.

INVESTMENT SECURITIES

INVESTMENT SECURITIES	6 Months Ended
	Jun. 30, 2018
INVESTMENT SECURITIES [Abstract]
INVESTMENT SECURITIES	NOTE D: INVESTMENT SECURITIES The amortized cost and estimated fair value of investment securities as of June 30, 2018 and December 31, 2017 are as follows: June 30, 2018 December 31, 2017 (000’s omitted) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-Sale Portfolio: U.S. Treasury and agency securities $ 2,042,116 $ 477 $ 28,631 $ 2,013,962 $ 2,043,023 $ 15,886 $ 4,838 $ 2,054,071 Obligations of state and political subdivisions 485,099 7,825 1,440 491,484 514,949 14,064 57 528,956 Government agency mortgage-backed securities 364,919 1,724 10,746 355,897 358,180 3,121 3,763 357,538 Corporate debt securities 2,618 0 55 2,563 2,648 0 25 2,623 Government agency collateralized mortgage obligations 78,137 52 2,151 76,038 88,097 155 878 87,374 Marketable equity securities 0 0 0 0 251 275 0 526 Total available-for-sale portfolio $ 2,972,889 $ 10,078 $ 43,023 $ 2,939,944 $ 3,007,148 $ 33,501 $ 9,561 $ 3,031,088 Equity and other Securities: Equity securities, at fair value $ 251 $ 253 $ 0 $ 504 $ 0 $ 0 $ 0 $ 0 Federal Home Loan Bank common stock 6,371 0 0 6,371 9,896 0 0 9,896 Federal Reserve Bank common stock 30,690 0 0 30,690 30,690 0 0 30,690 Certificates of deposit 0 0 0 0 3,865 0 0 3,865 Other equity securities, at cost 5,843 0 0 5,843 5,840 0 0 5,840 Total equity and other securities $ 43,155 $ 253 $ 0 $ 43,408 $ 50,291 $ 0 $ 0 $ 50,291 A summary of investment securities that have been in a continuous unrealized loss position is as follows: As of June 30, 2018 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 77 $ 1,924,896 $ 28,567 3 $ 14,945 $ 64 80 $ 1,939,841 $ 28,631 Obligations of state and political subdivisions 224 111,946 1,440 0 0 0 224 111,946 1,440 Government agency mortgage-backed securities 135 213,903 5,885 77 85,735 4,861 212 299,638 10,746 Corporate debt securities 1 2,563 55 0 0 0 1 2,563 55 Government agency collateralized mortgage obligations 32 58,808 1,868 9 11,419 283 41 70,227 2,151 Total available-for-sale investment portfolio 469 $ 2,312,116 $ 37,815 89 $ 112,099 $ 5,208 558 $ 2,424,215 $ 43,023 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 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 June 30, 2018 represents OTTI. The amortized cost and estimated fair value of debt securities at June 30, 2018, 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 $ 63,241 $ 63,194 Due after one through five years 1,884,323 1,861,933 Due after five years through ten years 414,137 412,375 Due after ten years 168,132 170,507 Subtotal 2,529,833 2,508,009 Government agency mortgage-backed securities 364,919 355,897 Government agency collateralized mortgage obligations 78,137 76,038 Total $ 2,972,889 $ 2,939,944 As of June 30, 2018, $181.8 million of U.S. Treasury securities were pledged as collateral for securities sold under agreement to repurchase. All securities sold under agreement to repurchase as of June 30, 2018 have an overnight and continuous maturity.

LOANS

LOANS	6 Months Ended
	Jun. 30, 2018
LOANS [Abstract]
LOANS	NOTE E: 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, municipal lending, agricultural-related and dealer floor plans, as well as mortgages on commercial properties. · 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 are summarized as follows: (000’s omitted) June 30, 2018 December 31, 2017 Business lending $ 2,384,629 $ 2,424,223 Consumer mortgage 2,210,051 2,220,298 Consumer indirect 1,063,679 1,011,978 Consumer direct 181,217 179,929 Home equity 398,433 420,329 Gross loans, including deferred origination costs 6,238,009 6,256,757 Allowance for loan losses (49,618 ) (47,583 ) Loans, net of allowance for loan losses $ 6,188,391 $ 6,209,174 The outstanding balance related to credit impaired acquired loans was $7.9 million and $13.4 million at June 30, 2018 and December 31, 2017, respectively. The changes in the accretable discount related to the credit impaired acquired loans are as follows: (000’s omitted) Balance at December 31, 2017 $ 976 Accretion recognized, year-to-date (688 ) Net reclassification between accretable and non-accretable 326 Balance at June 30, 2018 $ 614 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 June 30, 2018: Legacy Loans (000’s omitted) Past Due 30 – 89 Days 90+ Days Past Due and Still Accruing Nonaccrual Total Past Due Current Total Loans Business lending $ 1,185 $ 3,789 $ 3,830 $ 8,804 $ 1,483,884 $ 1,492,688 Consumer mortgage 9,066 1,992 9,526 20,584 1,762,980 1,783,564 Consumer indirect 10,254 124 5 10,383 1,038,385 1,048,768 Consumer direct 1,297 20 0 1,317 175,977 177,294 Home equity 1,156 318 1,283 2,757 311,071 313,828 Total $ 22,958 $ 6,243 $ 14,644 $ 43,845 $ 4,772,297 $ 4,816,142 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 Business lending $ 784 $ 0 $ 3,821 $ 4,605 $ 6,004 $ 881,332 $ 891,941 Consumer mortgage 1,444 110 3,069 4,623 0 421,864 426,487 Consumer indirect 94 35 0 129 0 14,782 14,911 Consumer direct 80 0 0 80 0 3,843 3,923 Home equity 580 144 1,273 1,997 0 82,608 84,605 Total $ 2,982 $ 289 $ 8,163 $ 11,434 $ 6,004 $ 1,404,429 $ 1,421,867 (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, 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 Business lending $ 2,283 $ 571 $ 3,944 $ 6,798 $ 1,369,801 $ 1,376,599 Consumer mortgage 13,564 1,500 10,722 25,786 1,728,823 1,754,609 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 Business lending $ 4,661 $ 0 $ 4,328 $ 8,989 $ 10,115 $ 1,028,520 $ 1,047,624 Consumer mortgage 2,603 26 3,066 5,695 0 459,994 465,689 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 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: June 30, 2018 December 31, 2017 (000’s omitted) Legacy Acquired Total Legacy Acquired Total Pass $ 1,302,009 $ 805,098 $ 2,107,107 $ 1,170,156 $ 963,981 $ 2,134,137 Special mention 114,305 47,412 161,717 129,076 37,321 166,397 Classified 76,147 31,829 107,976 77,367 34,628 111,995 Doubtful 227 1,598 1,825 0 1,579 1,579 Acquired impaired 0 6,004 6,004 0 10,115 10,115 Total $ 1,492,688 $ 891,941 $ 2,384,629 $ 1,376,599 $ 1,047,624 $ 2,424,223 All other loans are underwritten and structured using standardized criteria and characteristics, primarily payment performance, and are normally risk rated and monitored collectively on a monthly basis. These are typically loans to individuals in the consumer categories and are delineated as either performing or nonperforming. Performing loans include loans classified as current as well as those classified as 30 - 89 days past due. Nonperforming loans include 90+ days past due and still accruing and nonaccrual loans. The following table details the balances in all other loan categories at June 30, 2018: Legacy Loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 1,772,046 $ 1,048,639 $ 177,274 $ 312,227 $ 3,310,186 Nonperforming 11,518 129 20 1,601 13,268 Total $ 1,783,564 $ 1,048,768 $ 177,294 $ 313,828 $ 3,323,454 Acquired Loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 423,308 $ 14,876 $ 3,923 $ 83,188 $ 525,295 Nonperforming 3,179 35 0 1,417 4,631 Total $ 426,487 $ 14,911 $ 3,923 $ 84,605 $ 529,926 The following table details the balances in all other loan categories 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 All loan classes are collectively evaluated for impairment except business lending. A summary of individually evaluated impaired loans as of June 30, 2018 and December 31, 2017 follows: (000’s omitted) June 30, 2018 December 31, 2017 Loans with allowance allocation $ 4,496 $ 5,125 Loans without allowance allocation 1,173 884 Carrying balance 5,669 6,009 Contractual balance 10,225 9,165 Specifically allocated allowance 1,094 804 In the course of working with borrowers, the Company may choose to restructure the contractual terms of certain loans. In this scenario, the Company attempts to work-out an alternative payment schedule with the borrower in order to optimize collectability of the loan. Any loans that are modified are reviewed by the Company to identify if a troubled debt restructuring (“TDR”) has occurred, which is when, for economic or legal reasons related to a borrower’s financial difficulties, the Company grants a concession to the borrower that it would not otherwise consider. Terms may be modified to fit the ability of the borrower to repay in line with its current financial standing and the restructuring of the loan may include the transfer of assets from the borrower to satisfy the debt, a modification of loan terms, or a combination of the two. In accordance with the clarified guidance issued by the Office of the Comptroller of the Currency (“OCC”), loans that have been discharged in Chapter 7 bankruptcy but not reaffirmed by the borrower, are classified as TDRs, irrespective of payment history or delinquency status, even if the repayment terms for the loan have not been otherwise modified. The Company’s lien position against the underlying collateral remains unchanged. Pursuant to that guidance, the Company records a charge-off equal to any portion of the carrying value that exceeds the net realizable value of the collateral. The amount of loss incurred in the three and six months ended June 30, 2018 and 2017 was immaterial. TDRs that are less than $0.5 million are collectively included in the general loan loss allocation and the qualitative review. TDRs that are commercial loans and greater than $0.5 million are individually evaluated for impairment, and if necessary, a specific allocation of the allowance for loan losses is provided. As a result, the determination of the amount of allowance for loan losses related to TDRs is the same as detailed in the critical accounting policies. Information regarding TDRs as of June 30, 2018 and December 31, 2017 is as follows: June 30, 2018 December 31, 2017 (000’s omitted) Nonaccrual Accruing Total Nonaccrual Accruing Total # Amount # Amount # Amount # Amount # Amount # Amount Business lending 5 $ 210 4 $ 346 9 $ 556 8 $ 218 7 $ 501 15 $ 719 Consumer mortgage 47 2,264 43 1,689 90 3,953 51 2,265 44 1,750 95 4,015 Consumer indirect 0 0 70 796 70 796 0 0 71 883 71 883 Consumer direct 0 0 26 73 26 73 0 0 25 69 25 69 Home equity 11 226 8 284 19 510 13 245 7 204 20 449 Total 63 $ 2,700 151 $ 3,188 214 $ 5,888 72 $ 2,728 154 $ 3,407 226 $ 6,135 The following table presents information related to loans modified in a TDR during the three months and six months ended June 30, 2018 and 2017. Of the loans noted in the table below, all loans for the three months and six months ended June 30, 2018 and 2017 were modified due to a Chapter 7 bankruptcy as described previously. The financial effects of these restructurings were immaterial. Three Months Ended June 30, 2018 Three Months Ended June 30, 2017 (000’s omitted) Number of loans modified Outstanding Balance Number of loans modified Outstanding Balance Business lending 0 $ 0 3 $ 363 Consumer mortgage 4 452 1 43 Consumer indirect 8 70 8 80 Consumer direct 3 12 1 0 Home equity 1 86 0 0 Total 16 $ 620 13 $ 486 Six Months Ended June 30, 2018 Six Months Ended June 30, 2017 (000’s omitted) Number of loans modified Outstanding Balance Number of loans modified Outstanding Balance Business lending 1 $ 93 3 $ 363 Consumer mortgage 4 452 8 545 Consumer indirect 11 92 14 156 Consumer direct 5 14 4 14 Home equity 1 86 2 98 Total 22 $ 737 31 $ 1,176 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: Three Months Ended (000’s omitted) Business Lending Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Unallocated Acquired Impaired Total Beginning balance $ 17,607 $ 10,382 $ 13,698 $ 2,984 $ 2,040 $ 1,084 $ 308 $ 48,103 Charge-offs (260 ) (245 ) (1,383 ) (364 ) (47 ) 0 (323 ) (2,622 ) Recoveries 114 54 1,347 167 7 0 0 1,689 Provision 978 282 762 377 15 (14 ) 48 2,448 Ending balance $ 18,439 $ 10,473 $ 14,424 $ 3,164 $ 2,015 $ 1,070 $ 33 $ 49,618 Three Months Ended (000’s omitted) Business Lending Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Unallocated Acquired Impaired Total Beginning balance $ 16,857 $ 10,149 $ 13,996 $ 2,852 $ 2,359 $ 773 $ 110 $ 47,096 Charge-offs (245 ) (258 ) (1,695 ) (470 ) (190 ) 0 (183 ) (3,041 ) Recoveries 283 11 1,452 182 7 0 0 1,935 Provision 335 295 165 381 66 83 136 1,461 Ending balance $ 17,230 $ 10,197 $ 13,918 $ 2,945 $ 2,242 $ 856 $ 63 $ 47,451 Six Months Ended (000’s omitted) Business Lending Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Unallocated Acquired Impaired Total Beginning balance $ 17,257 $ 10,465 $ 13,468 $ 3,039 $ 2,107 $ 1,100 $ 147 $ 47,583 Charge-offs (1,928 ) (444 ) (3,667 ) (860 ) (103 ) 0 (367 ) (7,369 ) Recoveries 312 62 2,498 389 16 0 0 3,277 Provision 2,798 390 2,125 596 (5 ) (30 ) 253 6,127 Ending balance $ 18,439 $ 10,473 $ 14,424 $ 3,164 $ 2,015 $ 1,070 $ 33 $ 49,618 Six Months Ended (000’s omitted) Business Lending Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Unallocated Acquired Impaired Total Beginning balance $ 17,220 $ 10,094 $ 13,782 $ 2,979 $ 2,399 $ 651 $ 108 $ 47,233 Charge-offs (938 ) (343 ) (3,642 ) (888 ) (228 ) 0 (184 ) (6,223 ) Recoveries 354 18 2,321 427 32 0 0 3,152 Provision 594 428 1,457 427 39 205 139 3,289 Ending balance $ 17,230 $ 10,197 $ 13,918 $ 2,945 $ 2,242 $ 856 $ 63 $ 47,451

GOODWILL AND IDENTIFIABLE INTAN

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS	6 Months Ended
	Jun. 30, 2018
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: June 30, 2018 December 31, 2017 (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 $ (41,256 ) $ 21,646 $ 62,902 $ (37,877 ) $ 25,025 Other intangibles 87,616 (26,614 ) 61,002 86,535 (20,902 ) 65,633 Total amortizing intangibles $ 150,518 $ (67,870 ) $ 82,648 $ 149,437 $ (58,779 ) $ 90,658 The estimated aggregate amortization expense for each of the five succeeding fiscal years ended December 31 is as follows: (000’s omitted) Jul - Dec 2018 $ 8,802 2019 15,296 2020 12,722 2021 10,853 2022 9,317 Thereafter 25,658 Total $ 82,648 Shown below are the components of the Company’s goodwill at December 31, 2017 and June 30, 2018: (000’s omitted) December 31, 2017 Activity June 30, 2018 Goodwill $ 739,254 $ (951 ) $ 738,303 Accumulated impairment (4,824 ) 0 (4,824 ) Goodwill, net $ 734,430 $ (951 ) $ 733,479

MANDATORILY REDEEMABLE PREFERRE

MANDATORILY REDEEMABLE PREFERRED SECURITIES	6 Months Ended
	Jun. 30, 2018
MANDATORILY REDEEMABLE PREFERRED SECURITIES [Abstract]
MANDATORILY REDEEMABLE PREFERRED SECURITIES	NOTE G: MANDATORILY REDEEMABLE PREFERRED SECURITIES 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% (5.94%) 7/31/2031 Par CCT IV 12/8/2006 $75.0 million 3 month LIBOR plus 1.65% (3.99%) 12/15/2036 Par MBVT I 12/15/2004 $20.6 million 3 month LIBOR plus 1.95% (4.29%) 12/31/2034 Par On July 31, 2018, the Company exercised its right to redeem all of the CST III debentures and associated preferred securities for a total of $25.2 million.

BENEFIT PLANS

BENEFIT PLANS	6 Months Ended
	Jun. 30, 2018
BENEFIT PLANS [Abstract]
BENEFIT PLANS	NOTE H: BENEFIT PLANS The Company provides a qualified defined benefit pension to eligible employees and retirees, other post-retirement health and life insurance benefits to certain retirees, an unfunded supplemental pension plan for certain key executives, and an unfunded stock balance plan for certain of its nonemployee directors. The Company accrues for the estimated cost of these benefits through charges to expense during the years that employees earn these benefits. 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 net periodic benefit cost for the three and six months ended June 30, 2018 and 2017 is as follows: Pension Benefits Post-retirement Benefits Three Months Ended June 30, Six Months Ended June 30, Three Months Ended June 30, Six Months Ended June 30, (000’s omitted) 2018 2017 2018 2017 2018 2017 2018 2017 Service cost $ 1,121 $ 1,067 $ 2,242 $ 2,106 $ 0 $ 0 $ 0 $ 0 Interest cost 1,415 1,449 2,829 2,812 17 19 34 38 Expected return on plan assets (3,705 ) (3,407 ) (7,410 ) (6,529 ) 0 0 0 0 Amortization of unrecognized net loss 298 209 596 472 5 2 10 4 Amortization of prior service cost (83 ) 17 (165 ) 30 (44 ) (45 ) (89 ) (89 ) Net periodic benefit cost (income) $ (954 ) $ (665 ) $ (1,908 ) $ (1,109 ) $ (22 ) $ (24 ) $ (45 ) $ (47 )

EARNINGS PER SHARE

EARNINGS PER SHARE	6 Months Ended
	Jun. 30, 2018
EARNINGS PER SHARE [Abstract]
EARNINGS PER SHARE	NOTE I: EARNINGS PER SHARE The two class method is used in the calculations of basic and diluted earnings per share. Under the two class method, earnings available to common shareholders for the period are allocated between common shareholders and participating securities according to dividends declared and participation rights in undistributed earnings. The Company has determined that all of its outstanding non-vested stock awards are participating securities as of June 30, 2018. 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 0.4 million weighted-average anti-dilutive stock options outstanding for the three months and six months ended June 30, 2018, compared to 0.2 million weighted-average anti-dilutive stock options outstanding for the three months and six months ended June 30, 2017 that were not included in the computation below. The following is a reconciliation of basic to diluted earnings per share for the three and six months ended June 30, 2018 and 2017: Three Months Ended June 30, Six Months Ended June 30, (000’s omitted, except per share data) 2018 2017 2018 2017 Net income $ 44,606 $ 17,191 $ 84,712 $ 43,448 Income attributable to unvested stock-based compensation awards (188 ) (83 ) (353 ) (219 ) Income available to common shareholders $ 44,418 $ 17,108 $ 84,359 $ 43,229 Weighted-average common shares outstanding – basic 51,140 48,525 51,037 46,913 Basic earnings per share $ 0.87 $ 0.35 $ 1.65 $ 0.92 Net income $ 44,606 $ 17,191 $ 84,712 $ 43,448 Income attributable to unvested stock-based compensation awards (188 ) (83 ) (353 ) (219 ) Income available to common shareholders $ 44,418 $ 17,108 $ 84,359 $ 43,229 Weighted-average common shares outstanding – basic 51,140 48,525 51,037 46,913 Assumed exercise of stock options 583 626 576 665 Weighted-average common shares outstanding – diluted 51,723 49,151 51,613 47,578 Diluted earnings per share $ 0.86 $ 0.35 $ 1.63 $ 0.91 Stock Repurchase Program At its December 2017 meeting, the Company’s Board of Directors (the “Board”) approved a stock repurchase program authorizing the repurchase of up to 2.5 million shares of the Company’s common stock in accordance with securities laws and regulations, through December 31, 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. The Company did not repurchase any shares under the authorized plan during the first six months of 2018.

COMMITMENTS, CONTINGENT LIABILI

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS	6 Months Ended
	Jun. 30, 2018
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS [Abstract]
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS	NOTE J: COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS The Company is a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments consist primarily of commitments to extend credit and standby letters of credit. Commitments to extend credit are agreements to lend to customers, generally having fixed expiration dates or other termination clauses that may require payment of a fee. These commitments consist principally of unused commercial and consumer credit lines. Standby letters of credit generally are contingent upon the failure of the customer to perform according to the terms of an underlying contract with a third party. The credit risks associated with commitments to extend credit and standby letters of credit are essentially the same as that involved with extending loans to customers and are subject to the Company’s normal credit policies. Collateral may be obtained based on management’s assessment of the customer’s creditworthiness. The fair value of the standby letters of credit is immaterial for disclosure. The contract amounts of commitments and contingencies are as follows: (000’s omitted) June 30, 2018 December 31, 2017 Commitments to extend credit $ 1,072,858 $ 1,080,004 Standby letters of credit 33,636 23,782 Total $ 1,106,494 $ 1,103,786 The Company and its subsidiaries are subject in the normal course of business to various pending and threatened legal proceedings in which claims for monetary damages are asserted. As of June 30, 2018, 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.

FAIR VALUE

FAIR VALUE	6 Months Ended
	Jun. 30, 2018
FAIR VALUE [Abstract]
FAIR VALUE	NOTE K: FAIR VALUE Accounting standards establish a framework for measuring fair value and require certain disclosures about such fair value instruments. It defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (i.e. exit price). Inputs used to measure fair value are classified into the following hierarchy: · 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. June 30, 2018 (000’s omitted) Level 1 Level 2 Level 3 Total Fair Value Available-for-sale investment securities: U.S. Treasury and agency securities $ 1,876,745 $ 137,217 $ 0 $ 2,013,962 Obligations of state and political subdivisions 0 491,484 0 491,484 Government agency mortgage-backed securities 0 355,897 0 355,897 Corporate debt securities 0 2,563 0 2,563 Government agency collateralized mortgage obligations 0 76,038 0 76,038 Total available-for-sale investment securities 1,876,745 1,063,199 0 2,939,944 Equity securities 504 0 0 504 Mortgage loans held for sale 0 1,281 0 1,281 Commitments to originate real estate loans for sale 0 0 128 128 Forward sales commitments 0 64 0 64 Interest rate swap agreements asset 0 1,107 0 1,107 Interest rate swap agreements liability 0 (1,113 ) 0 (1,113 ) Total $ 1,877,249 $ 1,064,538 $ 128 $ 2,941,915 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 The valuation techniques used to measure fair value for the items in the table above are as follows: · Available-for-sale investment securities and equity securities – The fair values of available-for-sale investment securities and equity securities are based upon quoted prices, if available. If quoted prices are not available, fair values are measured using quoted market prices for similar securities or model-based valuation techniques. Level 1 securities include U.S. Treasury obligations and equity securities that are traded by dealers or brokers in active over-the-counter markets. Level 2 securities include U.S. agency securities, mortgage-backed securities issued by government-sponsored entities, municipal securities and corporate debt securities that are valued by reference to prices for similar securities or through model-based techniques in which all significant inputs, such as reported trades, trade execution data, LIBOR swap yield curve, market prepayment speeds, credit information, market spreads, and security’s terms and conditions, are observable. See Note D for further disclosure of the fair value of investment securities. · Mortgage loans held for sale –The Company has elected to value loans held for sale at fair value in order to more closely match the gains and losses associated with loans held for sale with the gains and losses on forward sales contracts. Accordingly, the impact on the valuation will be recognized in the Company’s consolidated statement of income. All mortgage loans held for sale are current and in performing status. The fair value of mortgage loans held for sale is determined using quoted secondary-market prices of loans with similar characteristics and, as such, has been classified as a Level 2 valuation. The unpaid principal value of mortgage loans held for sale at June 30, 2018 was approximately $1.3 million. The unrealized gain on mortgage loans held for sale was recognized in mortgage banking and other income in the consolidated statement and is immaterial. · Forward sales commitments – The Company enters into forward sales commitments to sell certain residential real estate loans. Such commitments are considered to be derivative financial instruments and, therefore, are carried at estimated fair value in the other asset or other liability section of the consolidated statement of condition. The fair value of these forward sales commitments is primarily measured by obtaining pricing from certain government-sponsored entities and reflects the underlying price the entity would pay the Company for an immediate sale on these mortgages. As such, these instruments are classified as Level 2 in the fair value hierarchy. · Commitments to originate real estate loans for sale – The Company enters into various commitments to originate residential real estate loans for sale. Such commitments are considered to be derivative financial instruments and, therefore, are carried at estimated fair value in the other asset or other liability section of the consolidated statement of condition. The estimated fair value of these commitments is determined using quoted secondary market prices obtained from certain government-sponsored entities. Additionally, accounting guidance requires the expected net future cash flows related to the associated servicing of the loan to be included in the fair value measurement of the derivative. The expected net future cash flows are based on a valuation model that calculates the present value of estimated net servicing income. The valuation model incorporates assumptions that market participants would use in estimating future net servicing income. Such assumptions include estimates of the cost of servicing loans, appropriate discount rate and prepayment speeds. The determination of expected net cash flows is considered a significant unobservable input contributing to the Level 3 classification of commitments to originate real estate loans for sale. · Interest rate swaps – The interest rate swaps are reported at their fair value utilizing Level 2 inputs from third parties. The fair value of the interest rate swaps are determined using prices obtained from a third party advisor. The fair value measurement of the interest rate swap is determined by netting the discounted future fixed cash payments and the discounted expected variable cash receipts. The variable cash receipts are based on the expectation of future interest rates derived from observed market interest rate curves. The changes in Level 3 assets measured at fair value on a recurring basis are immaterial. The fair value information of assets and liabilities measured on a non-recurring basis presented below is not as of the period-end, but rather as of the date the fair value adjustment was recorded closest to the date presented. June 30, 2018 December 31, 2017 (000’s omitted) Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Other real estate owned $ 0 $ 0 $ 1,310 $ 1,310 $ 0 $ 0 $ 1,915 $ 1,915 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 loan losses. Such amounts are generally based on the fair value of the underlying collateral supporting the loan and, as a result, the carrying value of the loan less the calculated valuation amount does not necessarily represent the fair value of the loan. Real estate collateral is typically valued using independent appraisals or other indications of value based on recent comparable sales of similar properties or assumptions generally observable in the marketplace, adjusted for non-observable inputs. Thus, the resulting nonrecurring fair value measurements are generally classified as Level 3. Estimates of fair value used for other collateral supporting commercial loans generally are based on assumptions not observable in the marketplace and, therefore, such valuations classify as Level 3. Other real estate owned (“OREO”) is valued at the time the loan is foreclosed upon and the asset is transferred to OREO. The value is based primarily on third party appraisals, less costs to sell. The appraisals are sometimes further discounted based on management’s historical knowledge, changes in market conditions from the time of valuation, and/or management’s expertise and knowledge of the customer and customer’s business. Such discounts are significant, ranging from 9% to 60.0% at June 30, 2018 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 June 30, 2018. The Company determines fair values based on quoted market values, where available, estimates of present values, or other valuation techniques. Those techniques are significantly affected by the assumptions used, including, but not limited to, the discount rate and estimates of future cash flows. In that regard, the derived fair value estimates cannot be substantiated by comparison to independent markets and, in many cases, may not be realized in immediate settlement of the instrument. The significant unobservable inputs used in the determination of fair value of assets classified as Level 3 on a recurring or non-recurring basis are as follows: (000’s omitted) Fair Value at June 30, 2018 Valuation Technique Significant Unobservable Inputs Significant Unobservable Input Range (Weighted Average) Other real estate owned $ 1,310 Fair Value of Collateral Estimated cost of disposal/market adjustment 9.0% - 60.0% (25.1 %) Commitments to originate real estate loans for sale 128 Discounted cash flow Embedded servicing value 1 % (000’s omitted) Fair Value at December 31, 2017 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 % Certain financial instruments and all nonfinancial instruments are excluded from fair value disclosure requirements. Accordingly, the aggregate fair value amounts presented do not represent the underlying value of the Company. The carrying amounts and estimated fair values of the Company’s other financial instruments that are not accounted for at fair value at June 30, 2018 and December 31, 2017 are as follows: June 30, 2018 December 31, 2017 (000’s omitted) Carrying Value Fair Value Carrying Value Fair Value Financial assets: Net loans $ 6,188,391 $ 6,149,955 $ 6,209,174 $ 6,244,941 Financial liabilities: Deposits 8,513,993 8,494,971 8,444,420 8,431,481 Short-term borrowings 0 0 24,000 24,000 Securities sold under agreement to repurchase, short-term 181,765 181,765 337,011 337,011 Other long-term debt 2,020 1,948 2,071 2,021 Subordinated debt held by unconsolidated subsidiary trusts 122,826 122,826 122,814 122,814 The following is a further description of the principal valuation methods used by the Company to estimate the fair values of its financial instruments. Loans have been classified as a Level 3 valuation. Fair values for variable rate loans that reprice frequently are based on carrying values. Fair values for fixed rate loans are estimated using discounted cash flows and interest rates currently being offered for loans with similar terms to borrowers of similar credit quality. Deposits have been classified as a Level 2 valuation. The fair value of demand deposits, interest-bearing checking deposits, savings accounts, and money market deposits is the amount payable on demand at the reporting date. The fair value of time deposit obligations are based on current market rates for similar products. Borrowings and subordinated debt held by unconsolidated subsidiary trusts have been classified as a Level 2 valuation. The fair value of short-term borrowings and securities sold under agreement to repurchase, short-term, is the amount payable on demand at the reporting date. Fair values for long-term debt and subordinated debt held by unconsolidated subsidiary trusts are estimated using discounted cash flows and interest rates currently being offered on similar securities. The difference between the carrying values of long-term borrowings and subordinated debt held by unconsolidated subsidiary trusts, and their fair values, are not material as of the reporting dates. Other financial assets and liabilities – Cash and cash equivalents have been classified as a Level 1 valuation, while accrued interest receivable and accrued interest payable have been classified as a Level 2 valuation. The fair values of each approximate the respective carrying values because the instruments are payable on demand or have short-term maturities and present relatively low credit risk and interest rate risk.

DERIVATIVE INSTRUMENTS

DERIVATIVE INSTRUMENTS	6 Months Ended
	Jun. 30, 2018
DERIVATIVE INSTRUMENTS [Abstract]
DERIVATIVE INSTRUMENTS	NOTE L: DERIVATIVE INSTRUMENTS The Company is party to derivative financial instruments in the normal course of its business to meet the financing needs of its customers and to manage its own exposure to fluctuations in interest rates. These financial instruments have been limited to interest rate swap agreements, commitments to originate real estate loans held for sale and forward sales commitments. The Company does not hold or issue derivative financial instruments for trading or other speculative purposes. The Company enters into forward sales commitments for the future delivery of residential mortgage loans, and interest rate lock commitments to fund loans at a specified interest rate. The forward sales commitments are utilized to reduce interest rate risk associated with interest rate lock commitments and loans held for sale. Changes in the estimated fair value of the forward sales commitments and interest rate lock commitments subsequent to inception are based on changes in the fair value of the underlying loan resulting from the fulfillment of the commitment and changes in the probability that the loan will fund within the terms of the commitment, which is affected primarily by changes in interest rates and the passage of time. At inception and during the life of the interest rate lock commitment, the Company includes the expected net future cash flows related to the associated servicing of the loan as part of the fair value measurement of the interest rate lock commitments. These derivatives are recorded at fair value, which were immaterial at June 30, 2018. The effect of the changes to these derivatives for the three and six months then ended was also immaterial. The Company acquired interest rate swaps from the Merchants acquisition with notional amounts with certain commercial customers which totaled $38.0 million at June 30, 2018. 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 $38.0 million. The weighted average receive rate of these interest rate swaps was 3.95%, the weighted average pay rate was 3.84% and the weighted average maturity was 6.0 years. The fair values of $1.1 million and $1.1 million were reflected in other assets and other liabilities, respectively, in the accompanying consolidated statement of condition at June 30, 2018. Hedge accounting has not been applied for these derivatives. Since the terms of the swaps with the customer and the other financial institution offset each other, with the only difference being counterparty credit risk, changes in the fair value of the underlying derivative contracts are not materially different and do not significantly impact our results of operations. The Company also acquired interest rate swaps from the Merchants acquisition with notional amounts totaling $6.7 million at June 30, 2018 that were designated as fair value hedges of certain fixed rate loans with municipalities. At June 30, 2018, the weighted average receive rate of these interest rate swaps was 2.67%, the weighted average pay rate was 3.11% and the weighted average maturity was 15.0 years. The fair value of $0.01 million at June 30, 2018, was reflected as an increase to loans and an increase to other liabilities. The ineffective portion of the interest swaps was immaterial and is not recorded in earnings. The Company assessed its counterparty risk at June 30, 2018 and determined any credit risk inherent in our derivative contracts was not material. Information about the fair value of derivative financial instruments can be found in Note K to these consolidated financial statements.

SEGMENT INFORMATION

SEGMENT INFORMATION	6 Months Ended
	Jun. 30, 2018
SEGMENT INFORMATION [Abstract]
SEGMENT INFORMATION	NOTE M: SEGMENT INFORMATION Operating segments are components of an enterprise, which are evaluated regularly by the “chief operating decision maker” in deciding how to allocate resources and assess performance. The Company’s chief operating decision maker is the President and Chief Executive Officer of the Company. The Company has identified Banking, Employee Benefit Services and All Other as its reportable operating business segments. Community Bank, N.A. (the “Bank” or “CBNA”) operates the Banking segment that provides full-service banking to consumers, businesses, and governmental units in Upstate New York as well as Northeastern Pennsylvania, Vermont and Western Massachusetts. Employee Benefit Services, which includes the operating subsidiaries Benefit Plans Administrative Services, LLC, BPAS Actuarial and Pension Services, LLC, BPAS Trust Company of Puerto Rico, NRS, GTC, and Hand Benefits & Trust Company, provides employee benefit trust, collective investment fund, retirement plan administration, fund administration, transfer agency, actuarial, VEBA/HRA, and health and welfare consulting services. The All Other segment is comprised of: (a) wealth management services including trust services provided by the personal trust unit within the Bank, broker-dealer and investment advisory services provided by CISI and The Carta Group, Inc., as well as asset management provided by Nottingham Advisors, Inc., and (b) full-service insurance, risk management and employee benefit services provided by OneGroup. The accounting policies used in the disclosure of business segments are the same as those described in the summary of significant accounting policies (See Note A: Summary of Significant Accounting Policies Information about reportable segments and reconciliation of the information to the consolidated financial statements follows: (000’s omitted) Banking Employee Benefit Services All Other Eliminations Consolidated Total Three Months Ended June 30, 2018 Net interest income $ 86,723 $ 93 $ 30 $ 0 $ 86,846 Provision for loan losses 2,448 0 0 0 2,448 Noninterest revenues 20,040 23,051 14,168 (700 ) 56,559 Amortization of intangible assets 1,635 1,989 931 0 4,555 Acquisition expenses 65 0 6 0 71 Other operating expenses 57,464 14,204 10,518 (700 ) 81,486 Income before income taxes $ 45,151 $ 6,951 $ 2,743 $ 0 $ 54,845 Assets $ 10,415,083 $ 207,114 $ 64,560 $ (53,663 ) $ 10,633,094 Goodwill $ 629,916 $ 83,275 $ 20,288 $ 0 $ 733,479 Three Months Ended June 30, 2017 Net interest income $ 77,872 $ 94 $ 63 $ 0 $ 78,029 Provision for loan losses 1,461 0 0 0 1,461 Noninterest revenues 18,062 21,118 12,733 (687 ) 51,226 Amortization of intangible assets 1,170 2,343 750 0 4,263 Acquisition expenses 22,729 117 50 0 22,896 Other operating expenses 53,890 13,068 9,449 (687 ) 75,720 Income before income taxes $ 16,684 $ 5,684 $ 2,547 $ 0 $ 24,915 Assets $ 10,635,177 $ 217,020 $ 75,382 $ (43,533 ) $ 10,884,046 Goodwill $ 631,148 $ 84,552 $ 17,904 $ 0 $ 733,604 (000’s omitted) Banking Employee Benefit Services All Other Eliminations Consolidated Total Six Months Ended June 30, 2018 Net interest income $ 171,253 $ 163 $ 54 $ 0 $ 171,470 Provision for loan losses 6,127 0 0 0 6,127 Noninterest revenues 40,397 46,500 28,548 (1,395 ) 114,050 Amortization of intangible assets 3,379 4,077 1,897 0 9,353 Acquisition expenses 50 7 6 0 63 Other operating expenses 114,418 27,914 22,090 (1,395 ) 163,027 Income before income taxes $ 87,676 $ 14,665 $ 4,609 $ 0 $ 106,950 Six Months Ended June 30, 2017 Net interest income $ 145,006 $ 172 $ 125 $ 0 $ 145,303 Provision for loan losses 3,289 0 0 0 3,289 Noninterest revenues 33,929 38,754 24,212 (1,351 ) 95,544 Amortization of intangible assets 1,724 3,933 1,374 0 7,031 Acquisition expenses 23,250 1,179 183 0 24,612 Other operating expenses 103,383 24,438 18,341 (1,351 ) 144,811 Income before income taxes $ 47,289 $ 9,376 $ 4,439 $ 0 $ 61,104

BASIS OF PRESENTATION (Policies

BASIS OF PRESENTATION (Policies)	6 Months Ended
	Jun. 30, 2018
BASIS OF PRESENTATION [Abstract]
Basis of Presentation	The interim financial data as of and for the three and six months ended June 30, 2018 is unaudited; however, in the opinion of Community Bank System, Inc. (the “Company”), the interim data includes all adjustments, consisting only of normal recurring adjustments, necessary for a fair statement of the results for the interim periods in conformity with generally accepted accounting principles (“GAAP”). The results of operations for the interim periods are not necessarily indicative of the results that may be expected for the full year or any other interim period.

ACCOUNTING POLICIES (Policies)

ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2018
ACCOUNTING POLICIES [Abstract]
Investment Securities	Investment Securities The Company can classify its investments in debt securities as held-to-maturity, available-for-sale, or trading. Held-to-maturity securities are those for which the Company has the positive intent and ability to hold until maturity, and are reported at cost, which is adjusted for amortization of premiums and accretion of discounts. Available-for-sale debt securities are reported at fair value with net unrealized gains and losses reflected as a separate component of shareholders’ equity, net of applicable income taxes. Equity securities with a readily determinable fair value are reported at fair value with net unrealized gains and losses recognized in the consolidated statement of income. None of the Company’s investment securities have been classified as trading securities at June 30, 2018. Certain equity securities are stated at cost and include restricted stock of the Federal Reserve Bank of New York (“Federal Reserve”), 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. 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.
Revenue Recognition	Revenue Recognition On January 1, 2018, the Company adopted ASU No. 2014-09 Revenue from Contracts with Customers (Topic 606) Topic 606 does not apply to revenue associated with financial instruments, including revenue from loans and securities. In addition, certain noninterest income streams such as fees associated with mortgage servicing rights, financial guarantees, derivatives, and certain credit card fees are also not in scope of the newly adopted guidance. Topic 606 is applicable to the Company’s noninterest revenue streams including its deposit related fees, electronic payment interchange fees, merchant income, trust, asset management and other wealth management revenues, insurance commissions and benefit plan services income. However, the recognition of these revenue streams did not change significantly upon adoption of Topic 606. Noninterest revenue streams in-scope of Topic 606 are discussed below. Deposit Service Fees Deposit service fees consist of account activity fees, monthly service fees, check orders, debit and credit card income, ATM fees, Merchant services income and other revenues from processing wire transfers, bill pay service, cashier’s checks and foreign exchange. Debit and credit card income is primarily comprised of interchange fees earned at the time the Company’s debit and credit cards are processed through card payment networks such as Visa. ATM fees are primarily generated when a Company cardholder uses a non-Company ATM or a non-Company cardholder uses a Company ATM. Merchant services income mainly represents fees charged to merchants to process their debit and credit card transactions, in addition to account management fees. The Company’s performance obligation for deposit service fees is generally satisfied, and the related revenue recognized, when the services are rendered or the transaction has been completed. Payment for deposit service fees is typically received at the time it is assessed through a direct charge to customers’ accounts or on a monthly basis. Deposit service fees revenue primarily relates to the Company’s Banking operating segment. Other Banking Services Other banking services consists of other recurring revenue streams such as commissions from sales of credit life insurance, safe deposit box rental fees, mortgage banking income, bank owned life insurance income and other miscellaneous revenue streams. Commissions from the sale of credit life insurance are recognized at the time of sale of the policies. Safe deposit box rental fees are charged to the customer on an annual basis and recognized upon receipt of payment. The Company determined that since rentals and renewals occur fairly consistently over time, revenue is recognized on a basis consistent with the duration of the performance obligation. Mortgage banking income and bank owned life insurance income are not within the scope of Topic 606. Other banking services revenue primarily relates to the Company’s Banking operating segment. Employee Benefit Services Employee benefit services income consists of revenue received from retirement plan services, collective investment fund services, fund administration, transfer agency, consulting and actuarial services. The Company’s performance obligation that relates to plan services are satisfied over time and the resulting fees are recognized monthly or quarterly, based upon the market value of the assets under management and the applicable fee rate or on a time expended basis. Payment is generally received a few days after month end or quarter end. The Company does not earn performance-based incentives. Transactional services such as consulting services, mailings, or other adhoc services are provided to existing trust and asset management customers. The Company’s performance obligation for these transactional-based services is generally satisfied, and related revenue recognized, at a point in time (i.e., as incurred). Payment is received shortly after services are rendered. Employee benefit services revenue primarily relates to the Company’s Employee Benefit Services operating segment. Insurance Services Insurance services primarily consists of commissions received on insurance product sales and consulting services. The Company acts in the capacity of a broker or agent between the Company’s customer and the insurance carrier. The Company’s performance obligation related to insurance sales for both property and casualty insurance and employee benefit plans is generally satisfied upon the later of the issuance or effective date of the policy. The Company’s performance obligation related to consulting services is considered transactional in nature and is generally satisfied when the services have been completed and related revenue recognized at a point in time. Payment is received at the time services are rendered. The Company earns performance based incentives, commonly known as contingency payments, which usually are based on certain criteria established by the insurance carrier such as premium volume, growth and insured loss ratios. Contingent payments are accrued for based upon management’s expectations for the year. Commission expense associated with sales of insurance products is expensed as incurred. Insurance services revenue primarily relates to the Company’s All Other operating segment. Wealth Management Services Wealth management services income is primarily comprised of fees earned from the management and administration of trusts and other customer assets. The Company generally has two types of performance obligations related to these services. The Company’s performance obligation that relates to advisory and administration services are satisfied over time and the resulting fees are recognized monthly, based upon the market value of the assets under management and the applicable fee rate. Payment is generally received soon after month end or quarter end through a direct charge to customers’ accounts. The Company does not earn performance-based incentives. Transactional services such as tax return preparation services, purchases and sales of investments and insurance products are also available to existing trust and asset management customers. The Company’s performance obligation for these transactional-based services is generally satisfied, and related revenue recognized, at a point in time (i.e. as incurred). Payment is generally received on a monthly basis. Wealth management services revenue primarily relates to the Company’s All Other operating segment. Contract Balances A contract asset balance occurs when an entity performs a service for a customer before the customer pays consideration (resulting in a contract receivable) or before payment is due (resulting in a contract asset). A contract liability balance is an entity’s obligation to transfer a service to a customer for which the entity has already received payment (or payment is due) from the customer. The Company’s noninterest revenue streams are largely based on transactional activity, or standard month-end revenue accruals such as asset management fees based on month-end market values. Consideration is often received immediately or shortly after the Company satisfies its performance obligation and revenue is recognized. The Company does not typically enter into long-term revenue contracts with customers, and therefore, does not experience significant contract balances. As of June 30, 2018, $25.7 million of accounts receivable, including $7.4 million of unbilled fee revenue, and $3.0 million of unearned revenue was recorded in the Consolidated Statements of Condition. As of December 31, 2017, $29.8 million of accounts receivable, including $6.5 million of unbilled fee revenue, and $3.9 million of unearned revenue was recorded in the Consolidated Statements of Condition. Contract Acquisition Costs In connection with the adoption of Topic 606, an entity is required to capitalize, and subsequently amortize into expense, certain incremental costs of obtaining a contract with a customer if these costs are expected to be recovered. The incremental costs of obtaining a contract are those costs that an entity incurs to obtain a contract with a customer that it would not have incurred if the contract had not been obtained (for example, sales commission). The Company utilizes the practical expedient method which allows entities to immediately expense contract acquisition costs when the asset that would have resulted from capitalizing these costs would have been amortized in one year or less. Upon adoption of Topic 606, the Company did not capitalize any contract acquisition costs.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) 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 adopted this guidance on January 1, 2018. The impact of the adoption of this guidance resulted in the reclassification of $0.2 million of other comprehensive income to retained earnings. See the Consolidated Statements of Comprehensive Income and Consolidated Statement of Changes in Shareholders’ Equity. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) 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.
New Accounting Pronouncements	New Accounting Pronouncements 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 January 2017, the FASB issued ASU No. 2017-04, Intangibles-Goodwill and Other (Topic 350) In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities.
Subsequent Event	Subsequent Event On July 31, 2018, the Company exercised its right to redeem all of the Community Statutory Trust III (“CST III”) debentures and associated preferred securities for a total of $25.2 million. See note G.

ACQUISITIONS (Tables)

ACQUISITIONS (Tables)	6 Months Ended
	Jun. 30, 2018
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: 2018 2017 (000s omitted) Other (1) NRS Merchants Other (2) Total Consideration paid : Cash $ 1,753 $ 70,073 $ 82,898 $ 6,775 $ 159,746 Community Bank System, Inc. common stock 0 78,483 262,254 2,395 343,132 Total net consideration paid 1,753 148,556 345,152 9,170 502,878 Recognized amounts of identifiable assets acquired and liabilities assumed: Cash and cash equivalents 16 11,063 40,730 339 52,132 Investment securities 0 20,294 370,648 0 390,942 Loans 0 0 1,488,157 0 1,488,157 Premises and equipment 10 411 16,608 27 17,046 Accrued interest receivable 0 72 4,773 0 4,845 Other assets 105 8,088 51,585 583 60,256 Core deposit intangibles 0 0 23,214 0 23,214 Other intangibles 1,343 60,200 2,857 5,626 68,683 Deposits 0 0 (1,448,406 ) 0 (1,448,406 ) Other liabilities (31 ) (26,828 ) (11,750 ) (1,131 ) (39,709 ) Short-term advances 0 0 (80,000 ) 0 (80,000 ) Securities sold under agreement to repurchase, short-term 0 0 (278,076 ) 0 (278,076 ) Long-term debt 0 0 (3,615 ) 0 (3,615 ) Subordinated debt held by unconsolidated subsidiary trusts 0 0 (20,619 ) 0 (20,619 ) Total identifiable assets, net 1,443 73,300 156,106 5,444 234,850 Goodwill $ 310 $ 75,256 $ 189,046 $ 3,726 $ 268,028 (1) (2)
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

INVESTMENT SECURITIES (Tables)

INVESTMENT SECURITIES (Tables)	6 Months Ended
	Jun. 30, 2018
INVESTMENT SECURITIES [Abstract]
Amortized Cost and Estimated Fair Value of Investment Securities	The amortized cost and estimated fair value of investment securities as of June 30, 2018 and December 31, 2017 are as follows: June 30, 2018 December 31, 2017 (000’s omitted) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Available-for-Sale Portfolio: U.S. Treasury and agency securities $ 2,042,116 $ 477 $ 28,631 $ 2,013,962 $ 2,043,023 $ 15,886 $ 4,838 $ 2,054,071 Obligations of state and political subdivisions 485,099 7,825 1,440 491,484 514,949 14,064 57 528,956 Government agency mortgage-backed securities 364,919 1,724 10,746 355,897 358,180 3,121 3,763 357,538 Corporate debt securities 2,618 0 55 2,563 2,648 0 25 2,623 Government agency collateralized mortgage obligations 78,137 52 2,151 76,038 88,097 155 878 87,374 Marketable equity securities 0 0 0 0 251 275 0 526 Total available-for-sale portfolio $ 2,972,889 $ 10,078 $ 43,023 $ 2,939,944 $ 3,007,148 $ 33,501 $ 9,561 $ 3,031,088 Equity and other Securities: Equity securities, at fair value $ 251 $ 253 $ 0 $ 504 $ 0 $ 0 $ 0 $ 0 Federal Home Loan Bank common stock 6,371 0 0 6,371 9,896 0 0 9,896 Federal Reserve Bank common stock 30,690 0 0 30,690 30,690 0 0 30,690 Certificates of deposit 0 0 0 0 3,865 0 0 3,865 Other equity securities, at cost 5,843 0 0 5,843 5,840 0 0 5,840 Total equity and other securities $ 43,155 $ 253 $ 0 $ 43,408 $ 50,291 $ 0 $ 0 $ 50,291
Summary of Investment Securities That Have Been in a Continuous Unrealized Loss Position for Less Than or Greater Than Twelve Months	A summary of investment securities that have been in a continuous unrealized loss position is as follows: As of June 30, 2018 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 77 $ 1,924,896 $ 28,567 3 $ 14,945 $ 64 80 $ 1,939,841 $ 28,631 Obligations of state and political subdivisions 224 111,946 1,440 0 0 0 224 111,946 1,440 Government agency mortgage-backed securities 135 213,903 5,885 77 85,735 4,861 212 299,638 10,746 Corporate debt securities 1 2,563 55 0 0 0 1 2,563 55 Government agency collateralized mortgage obligations 32 58,808 1,868 9 11,419 283 41 70,227 2,151 Total available-for-sale investment portfolio 469 $ 2,312,116 $ 37,815 89 $ 112,099 $ 5,208 558 $ 2,424,215 $ 43,023 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
Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity	The amortized cost and estimated fair value of debt securities at June 30, 2018, 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 $ 63,241 $ 63,194 Due after one through five years 1,884,323 1,861,933 Due after five years through ten years 414,137 412,375 Due after ten years 168,132 170,507 Subtotal 2,529,833 2,508,009 Government agency mortgage-backed securities 364,919 355,897 Government agency collateralized mortgage obligations 78,137 76,038 Total $ 2,972,889 $ 2,939,944

LOANS (Tables)

LOANS (Tables)	6 Months Ended
	Jun. 30, 2018
Loans and Leases Receivable Disclosure [Line Items]
Loans Receivable, Net	The balances of these classes are summarized as follows: (000’s omitted) June 30, 2018 December 31, 2017 Business lending $ 2,384,629 $ 2,424,223 Consumer mortgage 2,210,051 2,220,298 Consumer indirect 1,063,679 1,011,978 Consumer direct 181,217 179,929 Home equity 398,433 420,329 Gross loans, including deferred origination costs 6,238,009 6,256,757 Allowance for loan losses (49,618 ) (47,583 ) Loans, net of allowance for loan losses $ 6,188,391 $ 6,209,174
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) Balance at December 31, 2017 $ 976 Accretion recognized, year-to-date (688 ) Net reclassification between accretable and non-accretable 326 Balance at June 30, 2018 $ 614
Aged Analysis of Past Due Loans by Class	Legacy Loans (000’s omitted) Past Due 30 – 89 Days 90+ Days Past Due and Still Accruing Nonaccrual Total Past Due Current Total Loans Business lending $ 1,185 $ 3,789 $ 3,830 $ 8,804 $ 1,483,884 $ 1,492,688 Consumer mortgage 9,066 1,992 9,526 20,584 1,762,980 1,783,564 Consumer indirect 10,254 124 5 10,383 1,038,385 1,048,768 Consumer direct 1,297 20 0 1,317 175,977 177,294 Home equity 1,156 318 1,283 2,757 311,071 313,828 Total $ 22,958 $ 6,243 $ 14,644 $ 43,845 $ 4,772,297 $ 4,816,142 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 Business lending $ 784 $ 0 $ 3,821 $ 4,605 $ 6,004 $ 881,332 $ 891,941 Consumer mortgage 1,444 110 3,069 4,623 0 421,864 426,487 Consumer indirect 94 35 0 129 0 14,782 14,911 Consumer direct 80 0 0 80 0 3,843 3,923 Home equity 580 144 1,273 1,997 0 82,608 84,605 Total $ 2,982 $ 289 $ 8,163 $ 11,434 $ 6,004 $ 1,404,429 $ 1,421,867 (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, 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 Business lending $ 2,283 $ 571 $ 3,944 $ 6,798 $ 1,369,801 $ 1,376,599 Consumer mortgage 13,564 1,500 10,722 25,786 1,728,823 1,754,609 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 Business lending $ 4,661 $ 0 $ 4,328 $ 8,989 $ 10,115 $ 1,028,520 $ 1,047,624 Consumer mortgage 2,603 26 3,066 5,695 0 459,994 465,689 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.
Summary of Non-Business Impaired Loans	A summary of individually evaluated impaired loans as of June 30, 2018 and December 31, 2017 follows: (000’s omitted) June 30, 2018 December 31, 2017 Loans with allowance allocation $ 4,496 $ 5,125 Loans without allowance allocation 1,173 884 Carrying balance 5,669 6,009 Contractual balance 10,225 9,165 Specifically allocated allowance 1,094 804
Troubled Debt Restructurings on Financing Receivables	Information regarding TDRs as of June 30, 2018 and December 31, 2017 is as follows: June 30, 2018 December 31, 2017 (000’s omitted) Nonaccrual Accruing Total Nonaccrual Accruing Total # Amount # Amount # Amount # Amount # Amount # Amount Business lending 5 $ 210 4 $ 346 9 $ 556 8 $ 218 7 $ 501 15 $ 719 Consumer mortgage 47 2,264 43 1,689 90 3,953 51 2,265 44 1,750 95 4,015 Consumer indirect 0 0 70 796 70 796 0 0 71 883 71 883 Consumer direct 0 0 26 73 26 73 0 0 25 69 25 69 Home equity 11 226 8 284 19 510 13 245 7 204 20 449 Total 63 $ 2,700 151 $ 3,188 214 $ 5,888 72 $ 2,728 154 $ 3,407 226 $ 6,135 The following table presents information related to loans modified in a TDR during the three months and six months ended June 30, 2018 and 2017. Of the loans noted in the table below, all loans for the three months and six months ended June 30, 2018 and 2017 were modified due to a Chapter 7 bankruptcy as described previously. The financial effects of these restructurings were immaterial. Three Months Ended June 30, 2018 Three Months Ended June 30, 2017 (000’s omitted) Number of loans modified Outstanding Balance Number of loans modified Outstanding Balance Business lending 0 $ 0 3 $ 363 Consumer mortgage 4 452 1 43 Consumer indirect 8 70 8 80 Consumer direct 3 12 1 0 Home equity 1 86 0 0 Total 16 $ 620 13 $ 486 Six Months Ended June 30, 2018 Six Months Ended June 30, 2017 (000’s omitted) Number of loans modified Outstanding Balance Number of loans modified Outstanding Balance Business lending 1 $ 93 3 $ 363 Consumer mortgage 4 452 8 545 Consumer indirect 11 92 14 156 Consumer direct 5 14 4 14 Home equity 1 86 2 98 Total 22 $ 737 31 $ 1,176
Allowance for Loan Losses by Class	The following presents by class the activity in the allowance for loan losses: Three Months Ended (000’s omitted) Business Lending Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Unallocated Acquired Impaired Total Beginning balance $ 17,607 $ 10,382 $ 13,698 $ 2,984 $ 2,040 $ 1,084 $ 308 $ 48,103 Charge-offs (260 ) (245 ) (1,383 ) (364 ) (47 ) 0 (323 ) (2,622 ) Recoveries 114 54 1,347 167 7 0 0 1,689 Provision 978 282 762 377 15 (14 ) 48 2,448 Ending balance $ 18,439 $ 10,473 $ 14,424 $ 3,164 $ 2,015 $ 1,070 $ 33 $ 49,618 Three Months Ended (000’s omitted) Business Lending Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Unallocated Acquired Impaired Total Beginning balance $ 16,857 $ 10,149 $ 13,996 $ 2,852 $ 2,359 $ 773 $ 110 $ 47,096 Charge-offs (245 ) (258 ) (1,695 ) (470 ) (190 ) 0 (183 ) (3,041 ) Recoveries 283 11 1,452 182 7 0 0 1,935 Provision 335 295 165 381 66 83 136 1,461 Ending balance $ 17,230 $ 10,197 $ 13,918 $ 2,945 $ 2,242 $ 856 $ 63 $ 47,451 Six Months Ended (000’s omitted) Business Lending Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Unallocated Acquired Impaired Total Beginning balance $ 17,257 $ 10,465 $ 13,468 $ 3,039 $ 2,107 $ 1,100 $ 147 $ 47,583 Charge-offs (1,928 ) (444 ) (3,667 ) (860 ) (103 ) 0 (367 ) (7,369 ) Recoveries 312 62 2,498 389 16 0 0 3,277 Provision 2,798 390 2,125 596 (5 ) (30 ) 253 6,127 Ending balance $ 18,439 $ 10,473 $ 14,424 $ 3,164 $ 2,015 $ 1,070 $ 33 $ 49,618 Six Months Ended (000’s omitted) Business Lending Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Unallocated Acquired Impaired Total Beginning balance $ 17,220 $ 10,094 $ 13,782 $ 2,979 $ 2,399 $ 651 $ 108 $ 47,233 Charge-offs (938 ) (343 ) (3,642 ) (888 ) (228 ) 0 (184 ) (6,223 ) Recoveries 354 18 2,321 427 32 0 0 3,152 Provision 594 428 1,457 427 39 205 139 3,289 Ending balance $ 17,230 $ 10,197 $ 13,918 $ 2,945 $ 2,242 $ 856 $ 63 $ 47,451
Business Lending [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans by Credit Quality Indicator	The following table shows the amount of business lending loans by credit quality category: June 30, 2018 December 31, 2017 (000’s omitted) Legacy Acquired Total Legacy Acquired Total Pass $ 1,302,009 $ 805,098 $ 2,107,107 $ 1,170,156 $ 963,981 $ 2,134,137 Special mention 114,305 47,412 161,717 129,076 37,321 166,397 Classified 76,147 31,829 107,976 77,367 34,628 111,995 Doubtful 227 1,598 1,825 0 1,579 1,579 Acquired impaired 0 6,004 6,004 0 10,115 10,115 Total $ 1,492,688 $ 891,941 $ 2,384,629 $ 1,376,599 $ 1,047,624 $ 2,424,223
All Other Loans [Member]
Loans and Leases Receivable Disclosure [Line Items]
Loans by Credit Quality Indicator	The following table details the balances in all other loan categories at June 30, 2018: Legacy Loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 1,772,046 $ 1,048,639 $ 177,274 $ 312,227 $ 3,310,186 Nonperforming 11,518 129 20 1,601 13,268 Total $ 1,783,564 $ 1,048,768 $ 177,294 $ 313,828 $ 3,323,454 Acquired Loans (000’s omitted) Consumer Mortgage Consumer Indirect Consumer Direct Home Equity Total Performing $ 423,308 $ 14,876 $ 3,923 $ 83,188 $ 525,295 Nonperforming 3,179 35 0 1,417 4,631 Total $ 426,487 $ 14,911 $ 3,923 $ 84,605 $ 529,926 The following table details the balances in all other loan categories 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

GOODWILL AND IDENTIFIABLE INT28

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Tables)	6 Months Ended
	Jun. 30, 2018
GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS [Abstract]
Gross Carrying Amount and Accumulated Amortization of Identifiable Intangible Assets	The gross carrying amount and accumulated amortization for each type of identifiable intangible asset are as follows: June 30, 2018 December 31, 2017 (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 $ (41,256 ) $ 21,646 $ 62,902 $ (37,877 ) $ 25,025 Other intangibles 87,616 (26,614 ) 61,002 86,535 (20,902 ) 65,633 Total amortizing intangibles $ 150,518 $ (67,870 ) $ 82,648 $ 149,437 $ (58,779 ) $ 90,658
Estimated Aggregate Amortization Expense for Each of Five Succeeding Fiscal Years	The estimated aggregate amortization expense for each of the five succeeding fiscal years ended December 31 is as follows: (000’s omitted) Jul - Dec 2018 $ 8,802 2019 15,296 2020 12,722 2021 10,853 2022 9,317 Thereafter 25,658 Total $ 82,648
Components of Goodwill	Shown below are the components of the Company’s goodwill at December 31, 2017 and June 30, 2018: (000’s omitted) December 31, 2017 Activity June 30, 2018 Goodwill $ 739,254 $ (951 ) $ 738,303 Accumulated impairment (4,824 ) 0 (4,824 ) Goodwill, net $ 734,430 $ (951 ) $ 733,479

MANDATORILY REDEEMABLE PREFER29

MANDATORILY REDEEMABLE PREFERRED SECURITIES (Tables)	6 Months Ended
	Jun. 30, 2018
MANDATORILY REDEEMABLE PREFERRED SECURITIES [Abstract]
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% (5.94%) 7/31/2031 Par CCT IV 12/8/2006 $75.0 million 3 month LIBOR plus 1.65% (3.99%) 12/15/2036 Par MBVT I 12/15/2004 $20.6 million 3 month LIBOR plus 1.95% (4.29%) 12/31/2034 Par

BENEFIT PLANS (Tables)

BENEFIT PLANS (Tables)	6 Months Ended
	Jun. 30, 2018
BENEFIT PLANS [Abstract]
Net Periodic Benefit Cost	The net periodic benefit cost for the three and six months ended June 30, 2018 and 2017 is as follows: Pension Benefits Post-retirement Benefits Three Months Ended June 30, Six Months Ended June 30, Three Months Ended June 30, Six Months Ended June 30, (000’s omitted) 2018 2017 2018 2017 2018 2017 2018 2017 Service cost $ 1,121 $ 1,067 $ 2,242 $ 2,106 $ 0 $ 0 $ 0 $ 0 Interest cost 1,415 1,449 2,829 2,812 17 19 34 38 Expected return on plan assets (3,705 ) (3,407 ) (7,410 ) (6,529 ) 0 0 0 0 Amortization of unrecognized net loss 298 209 596 472 5 2 10 4 Amortization of prior service cost (83 ) 17 (165 ) 30 (44 ) (45 ) (89 ) (89 ) Net periodic benefit cost (income) $ (954 ) $ (665 ) $ (1,908 ) $ (1,109 ) $ (22 ) $ (24 ) $ (45 ) $ (47 )

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2018
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 three and six months ended June 30, 2018 and 2017: Three Months Ended June 30, Six Months Ended June 30, (000’s omitted, except per share data) 2018 2017 2018 2017 Net income $ 44,606 $ 17,191 $ 84,712 $ 43,448 Income attributable to unvested stock-based compensation awards (188 ) (83 ) (353 ) (219 ) Income available to common shareholders $ 44,418 $ 17,108 $ 84,359 $ 43,229 Weighted-average common shares outstanding – basic 51,140 48,525 51,037 46,913 Basic earnings per share $ 0.87 $ 0.35 $ 1.65 $ 0.92 Net income $ 44,606 $ 17,191 $ 84,712 $ 43,448 Income attributable to unvested stock-based compensation awards (188 ) (83 ) (353 ) (219 ) Income available to common shareholders $ 44,418 $ 17,108 $ 84,359 $ 43,229 Weighted-average common shares outstanding – basic 51,140 48,525 51,037 46,913 Assumed exercise of stock options 583 626 576 665 Weighted-average common shares outstanding – diluted 51,723 49,151 51,613 47,578 Diluted earnings per share $ 0.86 $ 0.35 $ 1.63 $ 0.91

COMMITMENTS, CONTINGENT LIABI32

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS (Tables)	6 Months Ended
	Jun. 30, 2018
COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS [Abstract]
Off Balance Sheet Financial Instruments Contract Amounts	The contract amounts of commitments and contingencies are as follows: (000’s omitted) June 30, 2018 December 31, 2017 Commitments to extend credit $ 1,072,858 $ 1,080,004 Standby letters of credit 33,636 23,782 Total $ 1,106,494 $ 1,103,786

FAIR VALUE (Tables)

FAIR VALUE (Tables)	6 Months Ended
	Jun. 30, 2018
FAIR VALUE [Abstract]
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. June 30, 2018 (000’s omitted) Level 1 Level 2 Level 3 Total Fair Value Available-for-sale investment securities: U.S. Treasury and agency securities $ 1,876,745 $ 137,217 $ 0 $ 2,013,962 Obligations of state and political subdivisions 0 491,484 0 491,484 Government agency mortgage-backed securities 0 355,897 0 355,897 Corporate debt securities 0 2,563 0 2,563 Government agency collateralized mortgage obligations 0 76,038 0 76,038 Total available-for-sale investment securities 1,876,745 1,063,199 0 2,939,944 Equity securities 504 0 0 504 Mortgage loans held for sale 0 1,281 0 1,281 Commitments to originate real estate loans for sale 0 0 128 128 Forward sales commitments 0 64 0 64 Interest rate swap agreements asset 0 1,107 0 1,107 Interest rate swap agreements liability 0 (1,113 ) 0 (1,113 ) Total $ 1,877,249 $ 1,064,538 $ 128 $ 2,941,915 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
Assets and Liabilities Measured on a Non-Recurring Basis	The fair value information of assets and liabilities measured on a non-recurring basis presented below is not as of the period-end, but rather as of the date the fair value adjustment was recorded closest to the date presented. June 30, 2018 December 31, 2017 (000’s omitted) Level 1 Level 2 Level 3 Total Fair Value Level 1 Level 2 Level 3 Total Fair Value Other real estate owned $ 0 $ 0 $ 1,310 $ 1,310 $ 0 $ 0 $ 1,915 $ 1,915
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 are as follows: (000’s omitted) Fair Value at June 30, 2018 Valuation Technique Significant Unobservable Inputs Significant Unobservable Input Range (Weighted Average) Other real estate owned $ 1,310 Fair Value of Collateral Estimated cost of disposal/market adjustment 9.0% - 60.0% (25.1 %) Commitments to originate real estate loans for sale 128 Discounted cash flow Embedded servicing value 1 % (000’s omitted) Fair Value at December 31, 2017 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 %
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 June 30, 2018 and December 31, 2017 are as follows: June 30, 2018 December 31, 2017 (000’s omitted) Carrying Value Fair Value Carrying Value Fair Value Financial assets: Net loans $ 6,188,391 $ 6,149,955 $ 6,209,174 $ 6,244,941 Financial liabilities: Deposits 8,513,993 8,494,971 8,444,420 8,431,481 Short-term borrowings 0 0 24,000 24,000 Securities sold under agreement to repurchase, short-term 181,765 181,765 337,011 337,011 Other long-term debt 2,020 1,948 2,071 2,021 Subordinated debt held by unconsolidated subsidiary trusts 122,826 122,826 122,814 122,814

SEGMENT INFORMATION (Tables)

SEGMENT INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2018
SEGMENT INFORMATION [Abstract]
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 Three Months Ended June 30, 2018 Net interest income $ 86,723 $ 93 $ 30 $ 0 $ 86,846 Provision for loan losses 2,448 0 0 0 2,448 Noninterest revenues 20,040 23,051 14,168 (700 ) 56,559 Amortization of intangible assets 1,635 1,989 931 0 4,555 Acquisition expenses 65 0 6 0 71 Other operating expenses 57,464 14,204 10,518 (700 ) 81,486 Income before income taxes $ 45,151 $ 6,951 $ 2,743 $ 0 $ 54,845 Assets $ 10,415,083 $ 207,114 $ 64,560 $ (53,663 ) $ 10,633,094 Goodwill $ 629,916 $ 83,275 $ 20,288 $ 0 $ 733,479 Three Months Ended June 30, 2017 Net interest income $ 77,872 $ 94 $ 63 $ 0 $ 78,029 Provision for loan losses 1,461 0 0 0 1,461 Noninterest revenues 18,062 21,118 12,733 (687 ) 51,226 Amortization of intangible assets 1,170 2,343 750 0 4,263 Acquisition expenses 22,729 117 50 0 22,896 Other operating expenses 53,890 13,068 9,449 (687 ) 75,720 Income before income taxes $ 16,684 $ 5,684 $ 2,547 $ 0 $ 24,915 Assets $ 10,635,177 $ 217,020 $ 75,382 $ (43,533 ) $ 10,884,046 Goodwill $ 631,148 $ 84,552 $ 17,904 $ 0 $ 733,604 (000’s omitted) Banking Employee Benefit Services All Other Eliminations Consolidated Total Six Months Ended June 30, 2018 Net interest income $ 171,253 $ 163 $ 54 $ 0 $ 171,470 Provision for loan losses 6,127 0 0 0 6,127 Noninterest revenues 40,397 46,500 28,548 (1,395 ) 114,050 Amortization of intangible assets 3,379 4,077 1,897 0 9,353 Acquisition expenses 50 7 6 0 63 Other operating expenses 114,418 27,914 22,090 (1,395 ) 163,027 Income before income taxes $ 87,676 $ 14,665 $ 4,609 $ 0 $ 106,950 Six Months Ended June 30, 2017 Net interest income $ 145,006 $ 172 $ 125 $ 0 $ 145,303 Provision for loan losses 3,289 0 0 0 3,289 Noninterest revenues 33,929 38,754 24,212 (1,351 ) 95,544 Amortization of intangible assets 1,724 3,933 1,374 0 7,031 Acquisition expenses 23,250 1,179 183 0 24,612 Other operating expenses 103,383 24,438 18,341 (1,351 ) 144,811 Income before income taxes $ 47,289 $ 9,376 $ 4,439 $ 0 $ 61,104

ACQUISITIONS (Details)

ACQUISITIONS (Details) shares in Thousands, $ in Thousands

Apr. 02, 2018USD ($)

Jan. 02, 2018USD ($)

Dec. 04, 2017USD ($)shares

Nov. 17, 2017USD ($)

May 12, 2017USD ($)BranchLocationshares

Mar. 01, 2017USD ($)

Feb. 03, 2017USD ($)

Jan. 01, 2017USD ($)

Jun. 30, 2018USD ($)

Mar. 31, 2018USD ($)

Jun. 30, 2017USD ($)

Jun. 30, 2018USD ($)

Jun. 30, 2017USD ($)

Dec. 31, 2017USD ($)

Jan. 02, 2017USD ($)

Acquisitions [Abstract]

Cash

$ 1,737

$ 105,402

Goodwill

$ 733,479

$ 733,604

733,479

733,604

$ 734,430

HR Consultants (SA), LLC [Member]

Acquisitions [Abstract]

Cash

$ 300

HR Consultants (SA), LLC [Member] | Customer Lists [Member]

Acquisitions [Abstract]

Intangibles

$ 300

Penna & Associates Agency, Inc. [Member]

Acquisitions [Abstract]

Cash

$ 800

Goodwill

300

Penna & Associates Agency, Inc. [Member] | Customer Lists [Member]

Acquisitions [Abstract]

Intangibles

300

Styles Bridges Associates [Member]

Acquisitions [Abstract]

Cash

700

Styles Bridges Associates [Member] | Customer Lists [Member]

Acquisitions [Abstract]

Intangibles

$ 700

Gordon B. Roberts Agency, Inc [Member]

Acquisitions [Abstract]

Purchase price of acquisition

$ 3,700

Cash

$ 1,350

Issuance of common shares (in shares) | shares

40

Other liabilities

$ 600

Goodwill

2,100

Assets acquired

600

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

(90)

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

(90)

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

Acquisitions [Abstract]

Intangibles

$ 1,600

Northeast Capital Management, Inc [Member]

Acquisitions [Abstract]

Cash

$ 1,200

Northeast Capital Management, Inc [Member] | Customer Lists [Member]

Acquisitions [Abstract]

Intangibles

$ 1,200

Merchants Bancshares, Inc. [Member]

Acquisitions [Abstract]

Purchase price of acquisition

$ 345,152

Cash

$ 82,898

Issuance of common shares (in shares) | shares

4,680

Other liabilities

$ 11,750

Goodwill

189,046

Assets acquired

$ 2,000,000

Revenues earned

16,100

8,900

32,200

8,900

Expenses incurred

7,600

4,000

15,400

4,000

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

Acquisitions [Abstract]

Number of branch locations added upon merger | Branch

31

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

Acquisitions [Abstract]

Number of branch locations added upon merger | Location

1

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

Acquisitions [Abstract]

Intangibles

$ 2,857

Dryfoos [Member]

Acquisitions [Abstract]

Cash

$ 3,000

Goodwill

1,700

Dryfoos [Member] | Other Intangibles [Member]

Acquisitions [Abstract]

Intangibles

$ 1,700

BAS [Member]

Acquisitions [Abstract]

Cash

$ 1,200

BAS [Member] | Other Intangibles [Member]

Acquisitions [Abstract]

Intangibles

$ 1,200

Northeast Retirement Services, Inc. [Member]

Acquisitions [Abstract]

Purchase price of acquisition

$ 148,556

Cash

70,073

Other liabilities

26,828

Goodwill

75,256

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

$ 23,000

Revenues earned

9,700

8,400

19,800

13,400

Expenses incurred

$ 6,000

$ 5,700

$ 12,000

$ 9,300

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

$ (1,200)

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

$ (1,200)

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

Acquisitions [Abstract]

Intangibles

$ 60,200

ACQUISITIONS, Estimated Fair Va

ACQUISITIONS, Estimated Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands		Apr. 02, 2018	May 12, 2017	Feb. 03, 2017	Jan. 01, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Jan. 02, 2017
Consideration paid [Abstract]
Cash						$ 1,737	$ 105,402
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Goodwill						733,479	$ 733,604	$ 734,430
Other [Member]
Consideration paid [Abstract]
Cash	[1]	$ 1,753
Community Bank System, Inc. common stock	[1]	0
Total net consideration paid	[1]	1,753
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Cash and cash equivalents	[1]	16
Investment securities	[1]	0
Loans	[1]	0
Premises and equipment	[1]	10
Accrued interest receivable	[1]	0
Other assets	[1]	105
Deposits	[1]	0
Other liabilities	[1]	(31)
Short-term advances	[1]	0
Securities sold under agreement to repurchase, short-term	[1]	0
Long-term debt	[1]	0
Subordinated debt held by unconsolidated subsidiary trusts	[1]	0
Total identifiable assets, net	[1]	1,443
Goodwill	[1]	310
Other [Member] | Core Deposits [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles	[1]	0
Other [Member] | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles	[1]	$ 1,343
BAS [Member]
Consideration paid [Abstract]
Cash					$ 1,200
BAS [Member] | Other Intangibles [Member]
Recognized amounts of identifiable assets acquired and liabilities assumed [Abstract]
Intangibles									$ 1,200
NRS [Member]
Consideration paid [Abstract]
Cash				$ 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				(26,828)
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				73,300
Goodwill				75,256
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			$ 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
Other [Member]
Consideration paid [Abstract]
Cash	[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]					(1,131)
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]					5,444
Goodwill	[2]					3,726
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						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						(39,709)
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						234,850
Goodwill						268,028
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
[1]	Includes amounts related to the Penna, Styles Bridges and HR Consultants acquisitions.
[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	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Summary of loans acquired [Abstract]
Merger and acquisition integration-related expenses	$ 71	$ 22,896	$ 63	$ 24,612
HR Consultants (SA), LLC [Member] | Core Deposits [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
HR Consultants (SA), LLC [Member] | Other Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Penna & Associates Agency, Inc. [Member] | Core Deposits [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Penna & Associates Agency, Inc. [Member] | Other Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Styles Bridges Associates [Member] | Core Deposits [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Styles Bridges Associates [Member] | Other Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Gordon B. Roberts Agency, Inc [Member] | Core Deposits [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Gordon B. Roberts Agency, Inc [Member] | Other Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Northeast Capital Management, Inc [Member] | Core Deposits [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Northeast Capital Management, Inc [Member] | Other Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Merchants Bancshares, Inc. [Member] | Core Deposits [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Merchants Bancshares, Inc. [Member] | Other Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Dryfoos Insurance Agency, Inc [Member] | Core Deposits [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Dryfoos Insurance Agency, Inc [Member] | Other Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Benefits Advisory Service, Inc [Member] | Core Deposits [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years
Benefits Advisory Service, Inc [Member] | Other Intangibles [Member]
Intangible Assets [Abstract]
Estimated useful life			8 years

ACCOUNTING POLICIES (Details)

ACCOUNTING POLICIES (Details) $ in Thousands	Jul. 31, 2018USD ($)	Jun. 30, 2018USD ($)Type	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)Type	Jun. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Wealth Management Services [Abstract]
Number of types of performance obligations | Type		2		2
Contract Balances [Abstract]
Accounts receivable		$ 25,700		$ 25,700		$ 29,800
Unbilled fee revenue		7,400		7,400		6,500
Unearned revenue		3,000		3,000		$ 3,900
Recently Adopted Accounting Pronouncements [Abstract]
Reclassification of other comprehensive income to retained earnings		0		0
Salaries and employee benefits		52,402	$ 46,564	104,261	$ 89,471
Other expenses		4,036	5,054	9,605	10,026
Retained Earnings [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Reclassification of other comprehensive income to retained earnings		208		208
Accumulated Other Comprehensive Loss [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Reclassification of other comprehensive income to retained earnings		(208)		(208)
Subsequent Event [Member] | Community Statutory Trust III [Member]
Subsequent Event [Abstract]
Redemption of debentures and associated preferred securities	$ 25,200
ASU 2017-07 [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Salaries and employee benefits			(1,800)		(3,300)
Other expenses			$ 1,800		$ 3,300
ASU 2016-01 [Member] | Retained Earnings [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Reclassification of other comprehensive income to retained earnings		208		208
ASU 2016-01 [Member] | Accumulated Other Comprehensive Loss [Member]
Recently Adopted Accounting Pronouncements [Abstract]
Reclassification of other comprehensive income to retained earnings		$ (208)		$ (208)

INVESTMENT SECURITIES, Availabl

INVESTMENT SECURITIES, Available-for-Sale Portfolio (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Available-for-Sale Portfolio [Abstract]
Amortized cost	$ 2,972,889	$ 3,007,148
Gross unrealized gains	10,078	33,501
Gross unrealized losses	43,023	9,561
Fair value	2,939,944	3,031,088
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	2,972,889
Fair value	2,939,944
Marketable Equity Securities [Abstract]
Amortized cost		251
Gross unrealized gains		275
Gross unrealized losses		0
Fair value		526
U.S. Treasury and Agency Securities [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	2,042,116	2,043,023
Gross unrealized gains	477	15,886
Gross unrealized losses	28,631	4,838
Fair value	2,013,962	2,054,071
Obligations of State and Political Subdivisions [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	485,099	514,949
Gross unrealized gains	7,825	14,064
Gross unrealized losses	1,440	57
Fair value	491,484	528,956
Government Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	364,919	358,180
Gross unrealized gains	1,724	3,121
Gross unrealized losses	10,746	3,763
Fair value	355,897	357,538
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	2,618	2,648
Gross unrealized gains	0	0
Gross unrealized losses	55	25
Fair value	2,563	2,623
Government Agency Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Amortized cost	78,137	88,097
Gross unrealized gains	52	155
Gross unrealized losses	2,151	878
Fair value	$ 76,038	$ 87,374

INVESTMENT SECURITIES, Equity a

INVESTMENT SECURITIES, Equity and Other Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Equity and Other Securities [Abstract]
Amortized cost	$ 43,155	$ 50,291
Gross unrealized gains	253	0
Gross unrealized losses	0	0
Fair value	43,408	50,291
Equity Securities, at Fair Value [Abstract]
Amortized cost	251	0
Gross unrealized gains	253	0
Gross unrealized losses	0	0
Fair value	504	0
Federal Home Loan Bank Common Stock [Member]
Other Securities [Abstract]
Amortized cost	6,371	9,896
Fair value	6,371	9,896
Federal Reserve Bank Common Stock [Member]
Other Securities [Abstract]
Amortized cost	30,690	30,690
Fair value	30,690	30,690
Certificates of Deposit [Member]
Other Securities [Abstract]
Amortized cost	0	3,865
Fair value	0	3,865
Other Equity Securities [Member]
Other Securities [Abstract]
Amortized cost	5,843	5,840
Fair value	$ 5,843	$ 5,840

INVESTMENT SECURITIES, Investme

INVESTMENT SECURITIES, Investment Securities in a Continuous Unrealized Loss Position (Details) $ in Thousands	Jun. 30, 2018USD ($)Position	Dec. 31, 2017USD ($)Position
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	469	249
12 months or longer | Position	89	56
Total | Position	558	305
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 2,312,116	$ 991,521
12 months or longer	112,099	75,713
Total	2,424,215	1,067,234
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	37,815	7,231
12 months or longer	5,208	2,330
Total	$ 43,023	$ 9,561
U.S. Treasury and Agency Securities [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	77	44
12 months or longer | Position	3	0
Total | Position	80	44
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 1,924,896	$ 699,709
12 months or longer	14,945	0
Total	1,939,841	699,709
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	28,567	4,838
12 months or longer	64	0
Total	$ 28,631	$ 4,838
Obligations of State and Political Subdivisions [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	224	45
12 months or longer | Position	0	0
Total | Position	224	45
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 111,946	$ 23,432
12 months or longer	0	0
Total	111,946	23,432
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	1,440	57
12 months or longer	0	0
Total	$ 1,440	$ 57
Government Agency Mortgage-Backed Securities [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	135	120
12 months or longer | Position	77	55
Total | Position	212	175
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 213,903	$ 185,716
12 months or longer	85,735	75,712
Total	299,638	261,428
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	5,885	1,433
12 months or longer	4,861	2,330
Total	$ 10,746	$ 3,763
Corporate Debt Securities [Member]
Available-for-Sale Portfolio 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	$ 2,563	$ 2,623
12 months or longer	0	0
Total	2,563	2,623
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	55	25
12 months or longer	0	0
Total	$ 55	$ 25
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	32	39
12 months or longer | Position	9	1
Total | Position	41	40
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 58,808	$ 80,041
12 months or longer	11,419	1
Total	70,227	80,042
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	1,868	878
12 months or longer	283	0
Total	$ 2,151	$ 878

INVESTMENT SECURITIES, Amortize

INVESTMENT SECURITIES, Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Due in one year or less	$ 63,241
Due after one through five years	1,884,323
Due after five years through ten years	414,137
Due after ten years	168,132
Subtotal	2,529,833
Amortized cost	2,972,889
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Due in one year or less	63,194
Due after one through five years	1,861,933
Due after five years through ten years	412,375
Due after ten years	170,507
Subtotal	2,508,009
Fair value	2,939,944
Government Agency Mortgage-Backed Securities [Member]
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Without single maturity date	364,919
Amortized cost	364,919	$ 358,180
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Without single maturity date	355,897
Fair value	355,897	357,538
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Without single maturity date	78,137
Amortized cost	78,137	88,097
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Without single maturity date	76,038
Fair value	76,038	87,374
U.S. Treasury Securities [Member]
Available-for-Sale, Debt Maturities, Amortized Cost [Abstract]
Amortized cost	2,042,116	2,043,023
Available-for-Sale, Debt Maturities, Fair Value [Abstract]
Fair value	2,013,962	$ 2,054,071
Securities pledged as collateral for securities sold under agreement to repurchase	$ 181,800

LOANS, Loan Summary (Details)

LOANS, Loan Summary (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 6,238,009		$ 6,256,757
Allowance for loan losses	(49,618)	$ (48,103)	(47,583)	$ (47,451)	$ (47,096)	$ (47,233)
Net loans	6,188,391		6,209,174
Credit impaired acquired loans, total balance due	7,900		13,400
Accretable discount related to credit impaired acquired loans [Roll forward]
Beginning Balance	976
Accretion recognized, year-to-date	(688)
Net reclassification between accretable and non-accretable	326
Ending Balance	614
Business Lending [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 2,384,629		2,424,223
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
Home Equity [Member] | Maximum [Member]
Loans receivable, net [Abstract]
Typical contract term	30 years
Commercial Portfolio Segment [Member] | Business Lending [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	$ 2,384,629		2,424,223
Allowance for loan losses	(10,473)		(10,465)	(10,197)		(10,094)
Commercial Portfolio Segment [Member] | Consumer Mortgage [Member]
Loans receivable, net [Abstract]
Allowance for loan losses	(10,473)	(10,382)		(10,197)	(10,149)
Residential Portfolio Segment [Member] | Business Lending [Member]
Loans receivable, net [Abstract]
Allowance for loan losses	(18,439)	(17,607)		(17,230)	(16,857)
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	2,210,051		2,220,298
Allowance for loan losses	(18,439)		(17,257)	(17,230)		(17,220)
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	1,063,679		1,011,978
Allowance for loan losses	(14,424)	(13,698)	(13,468)	(13,918)	(13,996)	(13,782)
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	181,217		179,929
Allowance for loan losses	(3,164)	(2,984)	(3,039)	(2,945)	(2,852)	(2,979)
Consumer Portfolio Segment [Member] | Home Equity [Member]
Loans receivable, net [Abstract]
Gross loans, including deferred origination costs	398,433		420,329
Allowance for loan losses	$ (2,015)	$ (2,040)	$ (2,107)	$ (2,242)	$ (2,359)	$ (2,399)

LOANS, Credit Quality By Past D

LOANS, Credit Quality By Past Due Status (Details) - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017
Aged analysis of the company's loans [Abstract]
Total loans		$ 6,238,009	$ 6,256,757
Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		6,243	2,508
Nonaccrual		14,644	16,020
Total past due		43,845	51,563
Current		4,772,297	4,568,100
Total loans		4,816,142	4,619,663
Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		22,958	33,035
Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		289	204
Nonaccrual		8,163	8,720
Total past due		11,434	17,167
Acquired impaired	[1]	6,004	10,115
Current		1,404,429	1,609,812
Total loans		1,421,867	1,637,094
Acquired Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		2,982	8,243
Business Lending [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,384,629	2,424,223
Business Lending [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,492,688	1,376,599
Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		891,941	1,047,624
Consumer Mortgage [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,783,564	1,754,609
Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		426,487	465,689
Consumer Indirect [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,048,768	991,836
Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		14,911	20,142
Consumer Direct [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		177,294	174,479
Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		3,923	5,450
Home Equity [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		313,828	322,140
Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Total loans		84,605	98,189
Commercial Portfolio Segment [Member] | Business Lending [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,384,629	2,424,223
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		3,789	571
Nonaccrual		3,830	3,944
Total past due		8,804	6,798
Current		1,483,884	1,369,801
Total loans		1,492,688	1,376,599
Commercial Portfolio Segment [Member] | Business Lending [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,185	2,283
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		3,821	4,328
Total past due		4,605	8,989
Acquired impaired	[1]	6,004	10,115
Current		881,332	1,028,520
Total loans		891,941	1,047,624
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		784	4,661
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Aged analysis of the company's loans [Abstract]
Total loans		2,210,051	2,220,298
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		1,992	1,500
Nonaccrual		9,526	10,722
Total past due		20,584	25,786
Current		1,762,980	1,728,823
Total loans		1,783,564	1,754,609
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		9,066	13,564
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		110	26
Nonaccrual		3,069	3,066
Total past due		4,623	5,695
Acquired impaired	[1]	0	0
Current		421,864	459,994
Total loans		426,487	465,689
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		1,444	2,603
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Aged analysis of the company's loans [Abstract]
Total loans		1,063,679	1,011,978
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		124	295
Nonaccrual		5	0
Total past due		10,383	14,492
Current		1,038,385	977,344
Total loans		1,048,768	991,836
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		10,254	14,197
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		35	8
Nonaccrual		0	0
Total past due		129	253
Acquired impaired	[1]	0	0
Current		14,782	19,889
Total loans		14,911	20,142
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		94	245
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Aged analysis of the company's loans [Abstract]
Total loans		181,217	179,929
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		20	48
Nonaccrual		0	0
Total past due		1,317	1,923
Current		175,977	172,556
Total loans		177,294	174,479
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,297	1,875
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		80	100
Acquired impaired	[1]	0	0
Current		3,843	5,350
Total loans		3,923	5,450
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		80	100
Consumer Portfolio Segment [Member] | Home Equity [Member]
Aged analysis of the company's loans [Abstract]
Total loans		398,433	420,329
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loans [Member]
Aged analysis of the company's loans [Abstract]
90 + days past due and still accruing		318	94
Nonaccrual		1,283	1,354
Total past due		2,757	2,564
Current		311,071	319,576
Total loans		313,828	322,140
Consumer Portfolio Segment [Member] | Home Equity [Member] | Legacy Loans [Member] | Past Due 30 - 89 Days [Member]
Aged analysis of the company's loans [Abstract]
Total past due		1,156	1,116
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		144	170
Nonaccrual		1,273	1,326
Total past due		1,997	2,130
Acquired impaired	[1]	0	0
Current		82,608	96,059
Total loans		84,605	98,189
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		$ 580	$ 634
[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	Jun. 30, 2018	Dec. 31, 2017
Business Lending Loans by Credit Quality Category [Abstract]
Loans	$ 6,238,009	$ 6,256,757
Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	4,816,142	4,619,663
Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,421,867	1,637,094
Business Lending [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,384,629	2,424,223
Business Lending [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,492,688	1,376,599
Business Lending [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	891,941	1,047,624
Business Lending [Member] | Pass [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	2,107,107	2,134,137
Business Lending [Member] | Pass [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,302,009	1,170,156
Business Lending [Member] | Pass [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	805,098	963,981
Business Lending [Member] | Special Mention [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	161,717	166,397
Business Lending [Member] | Special Mention [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	114,305	129,076
Business Lending [Member] | Special Mention [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	47,412	37,321
Business Lending [Member] | Classified [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	107,976	111,995
Business Lending [Member] | Classified [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	76,147	77,367
Business Lending [Member] | Classified [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	31,829	34,628
Business Lending [Member] | Doubtful [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,825	1,579
Business Lending [Member] | Doubtful [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	227	0
Business Lending [Member] | Doubtful [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,598	1,579
Business Lending [Member] | Acquired Impaired [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	6,004	10,115
Business Lending [Member] | Acquired Impaired [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	0	0
Business Lending [Member] | Acquired Impaired [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	6,004	10,115
All Other Loans [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,323,454	3,243,064
All Other Loans [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	529,926	589,470
All Other Loans [Member] | Performing [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,310,186	3,229,051
All Other Loans [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	525,295	584,874
All Other Loans [Member] | Nonperforming [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	13,268	14,013
All Other Loans [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	4,631	4,596
Consumer Mortgage [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,783,564	1,754,609
Consumer Mortgage [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	426,487	465,689
Consumer Mortgage [Member] | Performing [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,772,046	1,742,387
Consumer Mortgage [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	423,308	462,597
Consumer Mortgage [Member] | Nonperforming [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	11,518	12,222
Consumer Mortgage [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,179	3,092
Consumer Indirect [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,048,768	991,836
Consumer Indirect [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	14,911	20,142
Consumer Indirect [Member] | Performing [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,048,639	991,541
Consumer Indirect [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	14,876	20,134
Consumer Indirect [Member] | Nonperforming [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	129	295
Consumer Indirect [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	35	8
Consumer Direct [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	177,294	174,479
Consumer Direct [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,923	5,450
Consumer Direct [Member] | Performing [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	177,274	174,431
Consumer Direct [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	3,923	5,450
Consumer Direct [Member] | Nonperforming [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	20	48
Consumer Direct [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	0	0
Home Equity [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	313,828	322,140
Home Equity [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	84,605	98,189
Home Equity [Member] | Performing [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	312,227	320,692
Home Equity [Member] | Performing [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	83,188	96,693
Home Equity [Member] | Nonperforming [Member] | Legacy Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	1,601	1,448
Home Equity [Member] | Nonperforming [Member] | Acquired Loans [Member]
Business Lending Loans by Credit Quality Category [Abstract]
Loans	$ 1,417	$ 1,496

LOANS, Summary of Impaired Loan

LOANS, Summary of Impaired Loans, Excluding Purchased Impaired (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Impaired loans [Abstract]
Loans with allowance allocation	$ 4,496	$ 5,125
Loans without allowance allocation	1,173	884
Carrying balance	5,669	6,009
Contractual balance	10,225	9,165
Specifically allocated allowance	$ 1,094	$ 804

LOANS, Troubled Debt Restructur

LOANS, Troubled Debt Restructurings (TDRs) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018USD ($)Loan	Jun. 30, 2017USD ($)Loan	Jun. 30, 2018USD ($)Loan	Jun. 30, 2017USD ($)Loan	Dec. 31, 2017USD ($)Loan
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	214		214		226
TDRs, amount	$ 5,888		$ 5,888		$ 6,135
Loans modified in TDR during the year, number | Loan	16	13	22	31
Loans modified in TDR during the year, amount	$ 620	$ 486	$ 737	$ 1,176
Maximum [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
Threshold balance of TDR loans collectively included in general loan loss allocation and qualitative review	$ 500		$ 500
Nonaccrual [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	63		63		72
TDRs, amount	$ 2,700		$ 2,700		$ 2,728
Accruing [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	151		151		154
TDRs, amount	$ 3,188		$ 3,188		$ 3,407
Commercial Portfolio Segment [Member] | Minimum [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
Threshold balance of loans individually evaluated for impairment	$ 500		$ 500
Commercial Portfolio Segment [Member] | Business Lending [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	9		9		15
TDRs, amount	$ 556		$ 556		$ 719
Loans modified in TDR during the year, number | Loan	0	3	1	3
Loans modified in TDR during the year, amount	$ 0	$ 363	$ 93	$ 363
Commercial Portfolio Segment [Member] | Business Lending [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	5		5		8
TDRs, amount	$ 210		$ 210		$ 218
Commercial Portfolio Segment [Member] | Business Lending [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	4		4		7
TDRs, amount	$ 346		$ 346		$ 501
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	90		90		95
TDRs, amount	$ 3,953		$ 3,953		$ 4,015
Loans modified in TDR during the year, number | Loan	4	1	4	8
Loans modified in TDR during the year, amount	$ 452	$ 43	$ 452	$ 545
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	47		47		51
TDRs, amount	$ 2,264		$ 2,264		$ 2,265
Residential Portfolio Segment [Member] | Consumer Mortgage [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	43		43		44
TDRs, amount	$ 1,689		$ 1,689		$ 1,750
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	70		70		71
TDRs, amount	$ 796		$ 796		$ 883
Loans modified in TDR during the year, number | Loan	8	8	11	14
Loans modified in TDR during the year, amount	$ 70	$ 80	$ 92	$ 156
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	0		0		0
TDRs, amount	$ 0		$ 0		$ 0
Consumer Portfolio Segment [Member] | Consumer Indirect [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	70		70		71
TDRs, amount	$ 796		$ 796		$ 883
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	26		26		25
TDRs, amount	$ 73		$ 73		$ 69
Loans modified in TDR during the year, number | Loan	3	1	5	4
Loans modified in TDR during the year, amount	$ 12	$ 0	$ 14	$ 14
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	0		0		0
TDRs, amount	$ 0		$ 0		$ 0
Consumer Portfolio Segment [Member] | Consumer Direct [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	26		26		25
TDRs, amount	$ 73		$ 73		$ 69
Consumer Portfolio Segment [Member] | Home Equity [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	19		19		20
TDRs, amount	$ 510		$ 510		$ 449
Loans modified in TDR during the year, number | Loan	1	0	1	2
Loans modified in TDR during the year, amount	$ 86	$ 0	$ 86	$ 98
Consumer Portfolio Segment [Member] | Home Equity [Member] | Nonaccrual [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	11		11		13
TDRs, amount	$ 226		$ 226		$ 245
Consumer Portfolio Segment [Member] | Home Equity [Member] | Accruing [Member]
Troubled Debt Restructurings (TDRs) [Abstract]
TDRs, number | Loan	8		8		7
TDRs, amount	$ 284		$ 284		$ 204

LOANS, Allowance for Loan Losse

LOANS, Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Allowance for loan losses [Roll Forward]
Beginning balance	$ 48,103	$ 47,096	$ 47,583	$ 47,233
Charge-offs	(2,622)	(3,041)	(7,369)	(6,223)
Recoveries	1,689	1,935	3,277	3,152
Provision	2,448	1,461	6,127	3,289
Ending balance	49,618	47,451	49,618	47,451
Acquired Impaired [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	308	110	147	108
Charge-offs	(323)	(183)	(367)	(184)
Recoveries	0	0	0	0
Provision	48	136	253	139
Ending balance	33	63	33	63
Residential Portfolio Segment [Member] | Business Lending [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	17,607	16,857
Charge-offs	(260)	(245)
Recoveries	114	283
Provision	978	335
Ending balance	18,439	17,230	18,439	17,230
Residential Portfolio Segment [Member] | Consumer Mortgage [Member]
Allowance for loan losses [Roll Forward]
Beginning balance			17,257	17,220
Charge-offs			(1,928)	(938)
Recoveries			312	354
Provision			2,798	594
Ending balance	18,439	17,230	18,439	17,230
Commercial Portfolio Segment [Member] | Business Lending [Member]
Allowance for loan losses [Roll Forward]
Beginning balance			10,465	10,094
Charge-offs			(444)	(343)
Recoveries			62	18
Provision			390	428
Ending balance	10,473	10,197	10,473	10,197
Commercial Portfolio Segment [Member] | Consumer Mortgage [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	10,382	10,149
Charge-offs	(245)	(258)
Recoveries	54	11
Provision	282	295
Ending balance	10,473	10,197	10,473	10,197
Consumer Portfolio Segment [Member] | Consumer Indirect [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	13,698	13,996	13,468	13,782
Charge-offs	(1,383)	(1,695)	(3,667)	(3,642)
Recoveries	1,347	1,452	2,498	2,321
Provision	762	165	2,125	1,457
Ending balance	14,424	13,918	14,424	13,918
Consumer Portfolio Segment [Member] | Consumer Direct [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	2,984	2,852	3,039	2,979
Charge-offs	(364)	(470)	(860)	(888)
Recoveries	167	182	389	427
Provision	377	381	596	427
Ending balance	3,164	2,945	3,164	2,945
Consumer Portfolio Segment [Member] | Home Equity [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	2,040	2,359	2,107	2,399
Charge-offs	(47)	(190)	(103)	(228)
Recoveries	7	7	16	32
Provision	15	66	(5)	39
Ending balance	2,015	2,242	2,015	2,242
Unallocated Financing Receivables [Member]
Allowance for loan losses [Roll Forward]
Beginning balance	1,084	773	1,100	651
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	(14)	83	(30)	205
Ending balance	$ 1,070	$ 856	$ 1,070	$ 856

GOODWILL AND IDENTIFIABLE INT50

GOODWILL AND IDENTIFIABLE INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Identifiable Intangible Assets [Abstract]
Gross carrying amount	$ 150,518	$ 149,437
Accumulated amortization	(67,870)	(58,779)
Net carrying amount	82,648	90,658
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Jul - Dec 2018	8,802
2,019	15,296
2,020	12,722
2,021	10,853
2,022	9,317
Thereafter	25,658
Net carrying amount	82,648	90,658
Components of goodwill [Abstract]
Goodwill, beginning of period	739,254
Goodwill, activity	(951)
Goodwill, end of period	738,303
Accumulated impairment, beginning of period	(4,824)
Accumulated impairment, activity	0
Accumulated impairment, end of period	(4,824)
Goodwill, net, beginning of period	734,430
Goodwill, net, activity	(951)
Goodwill, net, end of period	733,479
Core Deposit Intangibles [Member]
Identifiable Intangible Assets [Abstract]
Gross carrying amount	62,902	62,902
Accumulated amortization	(41,256)	(37,877)
Net carrying amount	21,646	25,025
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Net carrying amount	21,646	25,025
Other Intangibles [Member]
Identifiable Intangible Assets [Abstract]
Gross carrying amount	87,616	86,535
Accumulated amortization	(26,614)	(20,902)
Net carrying amount	61,002	65,633
Estimated aggregate amortization expense for each of five succeeding fiscal years [Abstract]
Net carrying amount	$ 61,002	$ 65,633

MANDATORILY REDEEMABLE PREFER51

MANDATORILY REDEEMABLE PREFERRED SECURITIES (Details) $ in Millions	Jul. 31, 2018USD ($)	Jun. 30, 2018USD ($)Trust
Mandatorily Redeemable Preferred Securities [Abstract]
Number of unconsolidated subsidiary business trusts owned | Trust		3
Percent ownership of unconsolidated subsidiary trusts		100.00%
Community Statutory Trust III [Member] | Subsequent Event [Member]
Mandatorily Redeemable Preferred Securities [Abstract]
Redemption of debentures and associated preferred securities	$ 25.2
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		5.94%
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		3.99%
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		4.29%
Maturity date		Dec. 31, 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%

BENEFIT PLANS (Details)

BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	May 12, 2017	Dec. 31, 2016
Pension Benefits [Member]
Pension Plans [Abstract]
Defined Benefit Plan, Tax Status [Extensible List]	us-gaap:QualifiedPlanMember		us-gaap:QualifiedPlanMember
Unamortized actuarial gain					$ 1,900
Discount rate					4.40%	4.50%
Net periodic benefit cost [Abstract]
Service cost	$ 1,121	$ 1,067	$ 2,242	$ 2,106
Interest cost	1,415	1,449	2,829	2,812
Expected return on plan assets	(3,705)	(3,407)	(7,410)	(6,529)
Amortization of unrecognized net loss	298	209	596	472
Amortization of prior service cost	(83)	17	(165)	30
Net periodic benefit cost (income)	(954)	(665)	(1,908)	(1,109)
Post-retirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost	0	0	0	0
Interest cost	17	19	34	38
Expected return on plan assets	0	0	0	0
Amortization of unrecognized net loss	5	2	10	4
Amortization of prior service cost	(44)	(45)	(89)	(89)
Net periodic benefit cost (income)	$ (22)	$ (24)	$ (45)	$ (47)

EARNINGS PER SHARE (Details)

EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
EARNINGS PER SHARE [Abstract]
Weighted-average anti-dilutive stock options outstanding (in shares)	400,000	200,000	400,000	200,000
Basic earnings per share [Abstract]
Net income	$ 44,606	$ 17,191	$ 84,712	$ 43,448
Income attributable to unvested stock-based compensation awards	(188)	(83)	(353)	(219)
Income available to common shareholders	$ 44,418	$ 17,108	$ 84,359	$ 43,229
Weighted-average common shares outstanding - basic (in shares)	51,140,000	48,525,000	51,037,000	46,913,000
Basic earnings per share (in dollars per share)	$ 0.87	$ 0.35	$ 1.65	$ 0.92
Diluted earnings per share [Abstract]
Net income	$ 44,606	$ 17,191	$ 84,712	$ 43,448
Income attributable to unvested stock-based compensation awards	(188)	(83)	(353)	(219)
Income available to common shareholders	$ 44,418	$ 17,108	$ 84,359	$ 43,229
Weighted-average common shares outstanding - basic (in shares)	51,140,000	48,525,000	51,037,000	46,913,000
Assumed exercise of stock options (in shares)	583,000	626,000	576,000	665,000
Weighted-average common shares outstanding - diluted (in shares)	51,723,000	49,151,000	51,613,000	47,578,000
Diluted earnings per share (in dollars per share)	$ 0.86	$ 0.35	$ 1.63	$ 0.91
Stock Repurchase Program [Abstract]
Number of common shares authorized to be repurchased (in shares)					2,500,000
Number of common shares repurchased (in shares)			0

COMMITMENTS, CONTINGENT LIABI54

COMMITMENTS, CONTINGENT LIABILITIES AND RESTRICTIONS (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	$ 1,106,494	$ 1,103,786
Minimum [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Range of reasonably possible losses for such matters in the aggregate, beyond the existing recorded liability	0
Maximum [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Range of reasonably possible losses for such matters in the aggregate, beyond the existing recorded liability	1,000
Commitments to Extend Credit [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	1,072,858	1,080,004
Standby Letters of Credit [Member]
Commitments, Contingent Liabilities and Restrictions [Abstract]
Contract amount of commitments and contingencies	$ 33,636	$ 23,782

FAIR VALUE, Financial Assets an

FAIR VALUE, Financial Assets and Liabilities Accounted for at Fair Value On a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	$ 2,939,944
Equity securities	504	$ 0
Marketable equity securities		526
Available-for-sale investment securities	2,939,944	3,031,088
Derivative asset	128	89
U.S. Treasury and Agency Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,013,962	2,054,071
Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	491,484	528,956
Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	355,897	357,538
Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,563	2,623
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	76,038	87,374
Recurring [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,939,944
Equity securities	504
Marketable equity securities		526
Available-for-sale investment securities		3,031,088
Mortgage loans held for sale	1,281	461
Total	2,941,915	3,031,802
Recurring [Member] | Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	128	89
Recurring [Member] | Forward Sales Commitments [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	64	4
Recurring [Member] | Interest Rate Swap Agreements [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	1,107	1,064
Derivative liability	(1,113)	(904)
Recurring [Member] | U.S. Treasury and Agency Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,013,962	2,054,071
Recurring [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	491,484	528,956
Recurring [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	355,897	357,538
Recurring [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,563	2,623
Recurring [Member] | Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	76,038	87,374
Recurring [Member] | Level 1 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,876,745
Equity securities	504
Marketable equity securities		526
Available-for-sale investment securities		1,909,816
Mortgage loans held for sale	0	0
Total	1,877,249	1,909,816
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	0
Derivative liability	0	0
Recurring [Member] | Level 1 [Member] | U.S. Treasury and Agency Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,876,745	1,909,290
Recurring [Member] | Level 1 [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 1 [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 1 [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 1 [Member] | Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0	0
Recurring [Member] | Level 2 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	1,063,199
Equity securities	0
Marketable equity securities		0
Available-for-sale investment securities		1,121,272
Mortgage loans held for sale	1,281	461
Total	1,064,538	1,121,897
Mortgage loans held for sale, at principal value	1,300
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	64	4
Recurring [Member] | Level 2 [Member] | Interest Rate Swap Agreements [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	1,107	1,064
Derivative liability	(1,113)	(904)
Recurring [Member] | Level 2 [Member] | U.S. Treasury and Agency Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	137,217	144,781
Recurring [Member] | Level 2 [Member] | Obligations of State and Political Subdivisions [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	491,484	528,956
Recurring [Member] | Level 2 [Member] | Government Agency Mortgage-Backed Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	355,897	357,538
Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	2,563	2,623
Recurring [Member] | Level 2 [Member] | Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	76,038	87,374
Recurring [Member] | Level 3 [Member]
Available-for-sale investment securities [Abstract]
Available-for-sale investment securities	0
Equity securities	0
Marketable equity securities		0
Available-for-sale investment securities		0
Mortgage loans held for sale	0	0
Total	128	89
Recurring [Member] | Level 3 [Member] | Commitments to Originate Real Estate Loans for Sale [Member]
Available-for-sale investment securities [Abstract]
Derivative asset	128	89
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	0
Derivative liability	0	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

FAIR VALUE, Assets and Liabilit

FAIR VALUE, Assets and Liabilities Measured on Nonrecurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Other real estate owned	$ 1,310	$ 1,915
Valuation allowance	1,094	804
Mortgage Servicing Rights [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Valuation allowance	0
Non-recurring [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Other real estate owned	1,310	1,915
Non-recurring [Member] | Level 1 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Other real estate owned	0	0
Non-recurring [Member] | Level 2 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Other real estate owned	0	0
Non-recurring [Member] | Level 3 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Other real estate owned	$ 1,310	$ 1,915

FAIR VALUE, Significant Unobser

FAIR VALUE, Significant Unobservable Inputs (Details) $ in Thousands	Jun. 30, 2018USD ($)	Dec. 31, 2017USD ($)
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Other real estate owned	$ 1,310	$ 1,915
Other real estate owned, Valuation Technique [Extensible List]	us-gaap:MarketApproachValuationTechniqueMember	us-gaap:MarketApproachValuationTechniqueMember
Other real estate owned, Measurement Input [Extensible List]	us-gaap:MeasurementInputCostToSellMember	us-gaap:MeasurementInputCostToSellMember
Commitments to originate real estate loans for sale	$ 128	$ 89
Commitments to originate real estate loans for sale, Valuation Technique [Extensible List]	us-gaap:ValuationTechniqueDiscountedCashFlowMember	us-gaap:ValuationTechniqueDiscountedCashFlowMember
Commitments to originate real estate loans for sale, Measurement Input [Extensible List]	cbu:MeasurementInputEmbeddedServicingValueMember	cbu:MeasurementInputEmbeddedServicingValueMember
Commitments to originate real estate loans for sale, measurement input	0.01	0.01
Minimum [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Other real estate owned, measurement input	0.090	0.090
Maximum [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Other real estate owned, measurement input	0.600	0.990
Weighted Average [Member]
Significant Unobservable Inputs used in determination of Fair Value of Assets Classified as Level 3 [Abstract]
Other real estate owned, measurement input	0.251	0.385

FAIR VALUE, Carrying Amounts an

FAIR VALUE, Carrying Amounts and Estimated Fair Values of Other Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Carrying Value [Member]
Financial assets [Abstract]
Net loans	$ 6,188,391	$ 6,209,174
Financial liabilities [Abstract]
Deposits	8,513,993	8,444,420
Short-term borrowings	0	24,000
Securities sold under agreement to repurchase, short-term	181,765	337,011
Other long-term debt	2,020	2,071
Subordinated debt held by unconsolidated subsidiary trusts	122,826	122,814
Fair Value [Member]
Financial assets [Abstract]
Net loans	6,149,955	6,244,941
Financial liabilities [Abstract]
Deposits	8,494,971	8,431,481
Short-term borrowings	0	24,000
Securities sold under agreement to repurchase, short-term	181,765	337,011
Other long-term debt	1,948	2,021
Subordinated debt held by unconsolidated subsidiary trusts	$ 122,826	$ 122,814

DERIVATIVE INSTRUMENTS (Details

DERIVATIVE INSTRUMENTS (Details) - Interest Rate Swap [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Derivative Instruments [Abstract]
Derivative, notional amount	$ 38,000
Derivative weighted average receive rate	3.95%
Derivative weighted average pay rate	3.84%
Weighted average maturity period	6 years
Other Assets [Member]
Derivative Instruments [Abstract]
Fair value of derivate assets	$ 1,100
Other Liabilities [Member]
Derivative Instruments [Abstract]
Fair value of derivate liability	1,100
Designated as Hedging Instrument [Member] | Fair Value Hedging [Member]
Derivative Instruments [Abstract]
Derivative, notional amount	$ 6,700
Derivative weighted average receive rate	2.67%
Derivative weighted average pay rate	3.11%
Weighted average maturity period	15 years
Designated as Hedging Instrument [Member] | Fair Value Hedging [Member] | Other Liabilities [Member]
Derivative Instruments [Abstract]
Fair value of derivate liability	$ 10

SEGMENT INFORMATION (Details)

SEGMENT INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Information about reportable segments [Abstract]
Net interest income	$ 86,846	$ 78,029	$ 171,470	$ 145,303
Provision for loan losses	2,448	1,461	6,127	3,289
Noninterest revenues	56,559	51,226	114,050	95,544
Amortization of intangible assets	4,555	4,263	9,353	7,031
Acquisition expenses	71	22,896	63	24,612
Other operating expenses	81,486	75,720	163,027	144,811
Income before income taxes	54,845	24,915	106,950	61,104
Assets	10,633,094	10,884,046	10,633,094	10,884,046	$ 10,746,198
Goodwill	733,479	733,604	733,479	733,604	$ 734,430
Eliminations [Member]
Information about reportable segments [Abstract]
Net interest income	0	0	0	0
Provision for loan losses	0	0	0	0
Noninterest revenues	(700)	(687)	(1,395)	(1,351)
Amortization of intangible assets	0	0	0	0
Acquisition expenses	0	0	0	0
Other operating expenses	(700)	(687)	(1,395)	(1,351)
Income before income taxes	0	0	0	0
Assets	(53,663)	(43,533)	(53,663)	(43,533)
Goodwill	0	0	0	0
Banking [Member] | Operating Segments [Member]
Information about reportable segments [Abstract]
Net interest income	86,723	77,872	171,253	145,006
Provision for loan losses	2,448	1,461	6,127	3,289
Noninterest revenues	20,040	18,062	40,397	33,929
Amortization of intangible assets	1,635	1,170	3,379	1,724
Acquisition expenses	65	22,729	50	23,250
Other operating expenses	57,464	53,890	114,418	103,383
Income before income taxes	45,151	16,684	87,676	47,289
Assets	10,415,083	10,635,177	10,415,083	10,635,177
Goodwill	629,916	631,148	629,916	631,148
Employee Benefit Services [Member] | Operating Segments [Member]
Information about reportable segments [Abstract]
Net interest income	93	94	163	172
Provision for loan losses	0	0	0	0
Noninterest revenues	23,051	21,118	46,500	38,754
Amortization of intangible assets	1,989	2,343	4,077	3,933
Acquisition expenses	0	117	7	1,179
Other operating expenses	14,204	13,068	27,914	24,438
Income before income taxes	6,951	5,684	14,665	9,376
Assets	207,114	217,020	207,114	217,020
Goodwill	83,275	84,552	83,275	84,552
All Other [Member] | Operating Segments [Member]
Information about reportable segments [Abstract]
Net interest income	30	63	54	125
Provision for loan losses	0	0	0	0
Noninterest revenues	14,168	12,733	28,548	24,212
Amortization of intangible assets	931	750	1,897	1,374
Acquisition expenses	6	50	6	183
Other operating expenses	10,518	9,449	22,090	18,341
Income before income taxes	2,743	2,547	4,609	4,439
Assets	64,560	75,382	64,560	75,382
Goodwill	$ 20,288	$ 17,904	$ 20,288	$ 17,904