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PENSION PLAN AND OTHER BENEFIT PLANS - Additional Information (Details) - USD ($) |  |  | 12 Months Ended
--- | --- | --- | ---
Jan. 01, 2017 | Oct. 20, 2016 | Dec. 31, 2023 | Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Period of employment multiplier |  |  | 5 years |
Actuarial gain (loss), decrease due to change in mortality losses |  |  | $ 200,000 |
Average total life expectancy of participants (years) |  |  | 10 years 2 months 12 days |
Hours requirement to be eligible |  | 1000 hours |  |
Percentage increase (decrease) in unrecognized net loss of the projected benefit obligation |  |  | (0.16) |
All other sources gain (loss) (less than) |  |  | $ 1,000 |
Defined Contribution Profit Sharing, Savings and Investment Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined contribution plan, employer non-discretionary contribution amount | 3.00% |  | 3.00% |
Contribution cost percentage | 50.00% |  | 50.00% |
Defined contribution plan, employer matching contribution, percent of employees' gross pay | 6.00% |  | 6.00% |
Total expense |  |  | $ 1,400,000 |
Chemung common stock included in defined contribution plan assets (in shares) |  |  | 124,214 | 121,847
Defined Contribution Supplemental Executive Retirement Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Total expense |  |  | $ 600,000 | $ 500,000
Balance in the plan |  |  | 3,400,000 | 2,900,000
Pension Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Accumulated benefit obligation |  |  | 31,000,000 | 30,500,000
Actuarial gain (loss), increase due to change in discount rate |  |  | $ 1,000,000 |
Percentage of combined loss of expected year end obligations (less than) |  |  | 0.01 |
Other comprehensive income, defined benefit plans, decrease in net unamortized gain loss arising during period net of tax |  |  | $ 1,000,000 |
Other comprehensive income, defined benefit plans, increase (decrease) in net unamortized gain loss arising during period net of tax, due to variance of actual and expected return on plan assets |  |  | $ 2,100,000 |
Total unrecognized net loss increased percentage of obligation amortization threshold |  |  | 10.00% |
Total unrecognized net loss increased (decreased) percentage of plan assets threshold |  |  | 10.00% |
Pension Plan | Minimum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Evaluation period of expected long-term return on plan assets |  |  | 3 years |
Pension Plan | Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Evaluation period of expected long-term return on plan assets |  |  | 5 years |
Other Postretirement Benefit Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Other comprehensive income, defined benefit plans, decrease in net unamortized gain loss arising during period net of tax |  |  | $ 16,000 |
Contribution cost percentage |  |  | 50.00% |
Decrease in accumulated benefit obligation due to change in discount rate |  |  | $ 1,000 |
Increase in accumulated benefit obligation due to discount rate, claims and date experience |  |  | $ 6,000 |
Average future working lifetime of active participants |  |  | 6 years |
Estimated employer contributions in next fiscal year |  |  | $ 12,000 |
Executive Supplemental Pension Plan |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Accumulated benefit obligation |  |  | 900,000 | $ 900,000
Actuarial gain (loss), increase due to change in discount rate |  |  | 20,000 |
Actuarial gain (loss), decrease due to change in mortality losses |  |  | $ 8,000 |
Total unrecognized net loss increased percentage of obligation amortization threshold |  |  | 10.00% |
Total unrecognized net loss increased (decreased) percentage of plan assets threshold |  |  | 10.00% |
Average total life expectancy of participants (years) |  |  | 10 years 2 months 1 day |
Decrease in accumulated benefit obligation due to discount rate, health care trend rates |  |  | $ 4,000 |
Percentage increase (decrease) in unrecognized net loss of the projected benefit obligation |  |  | 0.032 |
Estimated employer contributions in next fiscal year |  |  | $ 110,000 |
Actuarial gain (loss), increase (decrease) due to change in mortality longevity |  |  | 25,000 |
Defined benefit plan, increase in total unrecognized net loss |  |  | 30,000 |
All other sources gain (loss) (less than) |  |  | $ 0 |

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