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EMPLOYEE BENEFITS - Narrative (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
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 | $ 1,125 | $ 965 | $ 935
Employee stock ownership plan, shares held under plan (in shares) | 1,333,504 | 1,314,277 |
Employee stock ownership plan, unallocated shares (in shares) | 0 | 0 |
Cash surrender value of life insurance | $ 26,301 | $ 19,117 |
Bonus expense | 2,943 | 2,316 | 2,069
Unfunded Plan | Nonqualified Plan | Executive Incentive Retirement Plan | Postretirement Life Insurance |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash surrender value of life insurance | 26,301 | 19,117 |
Plan cost | 502 | 447 | $ 390
Plan obligation | $ 3,667 | $ 2,420 |

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