PARENT COMPANY FINANCIAL INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets:
Cash on deposit with subsidiary bank	$ 27,966	$ 28,205
Securities available for sale, at estimated fair value	293,627	303,402
Total assets	1,707,620	1,657,179	$ 1,619,964
Liabilities and shareholders' equity:
Dividends payable	1,233	1,225	1,214
Total liabilities	1,557,807	1,513,431
Shareholders' equity:
Total shareholders' equity	149,813	143,748	137,242	$ 133,628
Total liabilities and shareholders' equity	1,707,620	1,657,179
STATEMENTS OF INCOME [Abstract]
Income before income tax expense	14,692	14,431	14,091
Income tax benefit	7,262	4,404	4,658
Net income	7,430	10,027	9,433
Cash flows from operating activities:
Net income	7,430	10,027	9,433
Adjustments to reconcile net income to net cash provided by operating activities:
Change in other assets	636	(165)	4,931
Change in other liabilities	(3,664)	5,427	(9,421)
Net cash provided by operating activities	23,645	22,141	14,123
Cash flow from financing activities:
Cash dividends paid	(4,917)	(4,878)	(4,833)
Sale of treasury stock	582	438	438
Net cash provided by financing activities	39,564	26,565	97,547
Net increase (decrease) in cash and cash equivalents	(43,433)	47,977	(2,978)
Cash and cash equivalents, beginning of period	74,162	26,185	29,163
Cash and cash equivalents, end of period	30,729	74,162	26,185
Parent Company
Assets:
Cash on deposit with subsidiary bank	3,017	2,336
Dividends receivable from subsidiary bank	1,233	1,225
Securities available for sale, at estimated fair value	420	386
Other assets	1,039	825
Total assets	151,121	145,020
Liabilities and shareholders' equity:
Dividends payable	1,233	1,225
Other liabilities	75	47
Total liabilities	1,308	1,272
Shareholders' equity:
Total shareholders' equity	149,813	143,748
Total liabilities and shareholders' equity	151,121	145,020
STATEMENTS OF INCOME [Abstract]
Dividends from subsidiary bank	4,926	4,889	2,424
Interest and dividend income	10	9	9
Non-interest income	22	0	0
Non-interest expenses	433	526	270
Income before income tax expense	4,525	4,372	2,163
Income before income tax	7,213	9,763	9,264
Income tax benefit	(217)	(264)	(169)
Net income	7,430	10,027	9,433
Cash flows from operating activities:
Net income	7,430	10,027	9,433
Adjustments to reconcile net income to net cash provided by operating activities:
Change in dividend receivable	(8)	(11)	(10)
Change in other assets	(214)	82	222
Change in other liabilities	51	(203)	(23)
Expense related to employee stock compensation	200	210	93
Expense related to restricted stock units for directors' deferred compensation plan	98	97	95
Expense to employee restricted stock awards	210	192	314
Net cash provided by operating activities	5,079	5,003	3,023
Cash flow from financing activities:
Cash dividends paid	(4,919)	(4,878)	(4,833)
Purchase of treasury stock	(61)	(22)	(33)
Sale of treasury stock	582	438	438
Net cash provided by financing activities	(4,398)	(4,462)	(4,428)
Net increase (decrease) in cash and cash equivalents	681	541	(1,405)
Cash and cash equivalents, beginning of period	2,336	1,795	3,200
Cash and cash equivalents, end of period	3,017	2,336	1,795
Parent Company | Chemung Canal Trust Company
Assets:
Investment in subsidiary	142,884	138,469
STATEMENTS OF INCOME [Abstract]
Income (loss) from equity method investments	1,939	4,856	7,015
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings	(1,939)	(4,856)	(7,015)
Parent Company | CFS Group Inc.
Assets:
Investment in subsidiary	904	946
STATEMENTS OF INCOME [Abstract]
Income (loss) from equity method investments	(42)	(48)	86
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings	42	48	(86)
Parent Company | Chemung Risk Management
Assets:
Investment in subsidiary	1,624	833
STATEMENTS OF INCOME [Abstract]
Income (loss) from equity method investments	791	583	0
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings	$ (791)	$ (583)	$ 0