EMPLOYEE BENEFITS - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
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	$ 856	$ 739
Employee stock ownership plan, fair value of shares subject to repurchase obligation		34,300
Employee stock ownership plan, shares held under plan (in shares)	1,320,876		1,314,277
Employee stock ownership plan, unallocated shares (in shares)	0		0
Cash surrender value of life insurance	$ 25,747		$ 19,117
Bonus expense	2,170	1,718
Unfunded Plan | Nonqualified Plan | Executive Incentive Retirement Plan | Postretirement Life Insurance
Defined Benefit Plan Disclosure [Line Items]
Cash surrender value of life insurance	25,747		19,117
Plan cost	419	$ 381
Plan obligation	$ 3,678		$ 2,420