SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Period of delinquency after which a loan is placed on non-accrual status (days)	90 days
Number of consecutive months for which loans remain current before non-accrual loans are returned to accrual status	6 months
Rolling historical period of net losses used in evaluating general component of valuation allowance for loans not impaired but classified as substandard and special mention (years)	5 years
Number of most recent years of actual loss history used in determining historical loss experience for all other unclassified loans (years)	2 years
Assets under management	$ 2,053.0	$ 2,325.0
Chemung Financial Corporation
Property, Plant and Equipment [Line Items]
Assets under management	$ 346.5	$ 344.2
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	15 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	50 years
Equipment and Furniture | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	3 years
Equipment and Furniture | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives (years)	10 years