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EMPLOYEE BENEFITS - Narrative (Details) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items] |  |  |
Employee stock ownership plan, maximum employer contribution as a percentage of participant's qualified compensation | 5.00% |  |
Employee stock ownership plan, total contributions accrued or paid | $ 1,031 | $ 973 |
Employee stock ownership plan, shares held under plan (in shares) | 1,253,010 |  | 1,224,697
Employee stock ownership plan, unallocated shares (in shares) | 0 |  | 0
Cash surrender value of life insurance | $ 35,304 |  | $ 34,495
Bonus expense | 1,610 | 2,304 |
Executive Incentive Retirement Plan | Postretirement Life Insurance | Nonqualified Plan | Unfunded Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash surrender value of life insurance | 35,304 |  | 34,495
Plan cost | 500 | $ 504 | 602
Plan obligation | $ 4,424 |  | $ 4,081

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