PARENT COMPANY FINANCIAL INFORMATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets:
Cash on deposit with subsidiary bank	$ 25,203	$ 33,040
Securities available for sale, at estimated fair value	284,090	242,258
Total assets	1,787,827	1,755,343	$ 1,707,620
Liabilities and shareholders' equity:
Dividends payable	1,263	1,254	1,233
Total liabilities	1,605,200	1,590,314
Shareholders' equity:
Total shareholders' equity	182,627	165,029	149,813	$ 143,748
Total liabilities and shareholders' equity	1,787,827	1,755,343
STATEMENTS OF INCOME [Abstract]
Income before income tax expense	19,043	23,635	14,692
Income tax benefit	3,434	4,009	7,262
Net of tax	15,609	19,626	7,430
Cash flows from operating activities:
Net income	15,609	19,626	7,430
Adjustments to reconcile net income to net cash provided by operating activities:
Change in other assets	(1,945)	(2,651)	579
Change in other liabilities	3,333	(654)	(3,664)
Net cash provided by operating activities	26,405	27,772	23,645
Cash flow from financing activities:
Cash dividends paid	(5,029)	(4,969)	(4,917)
Sale of treasury stock	585	643	582
Net cash (used in) provided by financing activities	(1,762)	27,552	39,564
Cash and cash equivalents, beginning of period	129,972
Cash and cash equivalents, end of period	121,904	129,972
Parent Company
Assets:
Cash on deposit with subsidiary bank	3,938	3,978
Dividends receivable from subsidiary bank	0	0
Securities available for sale, at estimated fair value	492	554
Other assets	1,266	1,071
Total assets	183,988	166,390
Liabilities and shareholders' equity:
Dividends payable	1,263	1,254
Other liabilities	98	107
Total liabilities	1,361	1,361
Shareholders' equity:
Total shareholders' equity	182,627	165,029
Total liabilities and shareholders' equity	183,988	166,390
STATEMENTS OF INCOME [Abstract]
Dividends from subsidiary bank and non-bank	4,516	3,187	4,926
Interest and dividend income	9	10	10
Non-interest income	(62)	(20)	22
Non-interest expenses	439	477	433
Income before impact of subsidiaries' undistributed earnings	4,024	2,700	4,525
Income before income tax expense	15,445	19,462	7,213
Income tax benefit	(164)	(164)	(217)
Net of tax	15,609	19,626	7,430
Cash flows from operating activities:
Net income	15,609	19,626	7,430
Adjustments to reconcile net income to net cash provided by operating activities:
Change in dividend receivable	0	1,233	(8)
Change in other assets	(196)	(32)	(214)
Change in other liabilities	(48)	773	51
Expense related to employee stock compensation	100	89	200
Expense related to restricted stock units for directors' deferred compensation plan	42	67	98
Expense to employee restricted stock awards	503	405	210
Net cash provided by operating activities	4,589	5,399	5,079
Cash flow from financing activities:
Cash dividends paid	(5,029)	(4,969)	(4,919)
Purchase of treasury stock	(185)	(112)	(61)
Sale of treasury stock	585	643	582
Net cash (used in) provided by financing activities	(4,629)	(4,438)	(4,398)
Net increase (decrease) in cash and cash equivalents	(40)	961	681
Cash and cash equivalents, beginning of period	3,978	3,017	2,336
Cash and cash equivalents, end of period	3,938	3,978	3,017
Parent Company | Chemung Canal Trust Company
Assets:
Investment in subsidiary	175,470	158,166
STATEMENTS OF INCOME [Abstract]
Income (loss) from equity method investments	11,220	16,670	1,939
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings	(11,220)	(16,670)	(1,939)
Parent Company | CFS Group Inc.
Assets:
Investment in subsidiary	868	873
STATEMENTS OF INCOME [Abstract]
Income (loss) from equity method investments	(4)	(32)	(42)
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings	4	32	42
Parent Company | Chemung Risk Management
Assets:
Investment in subsidiary	1,954	1,748
STATEMENTS OF INCOME [Abstract]
Income (loss) from equity method investments	205	124	791
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings	$ (205)	$ (124)	$ (791)