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EMPLOYEE BENEFITS - Narrative (Details) - USD ($) $ in Thousands | 9 Months Ended |
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016
Retirement Benefits [Abstract] |  |  |
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 | $ 739 | $ 727 |
Employee stock ownership plan, fair value of shares subject to repurchase obligation |  |  | $ 31,661
Employee stock ownership plan, shares held under plan (in shares) | 1,314,277 |  | 1,319,225
Employee stock ownership plan, unallocated shares (in shares) | 0 |  | 50,000
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash surrender value of life insurance | $ 18,376 |  | $ 17,804
Bonus expense | 1,718 | 1,451 |
Unfunded Plan | Nonqualified Plan | Executive Incentive Retirement Plan | Postretirement Life Insurance |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Cash surrender value of life insurance | 18,376 |  | 17,804
Plan cost | 381 | $ 329 |
Plan obligation | $ 2,361 |  | $ 2,002

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