INCOME TAXES - Summary of Net Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets
Allowance for loan losses	$ 5,673	$ 4,364
Unrealized losses on securities available for sale	7,926	4,285
Fair value adjustment on loans	1,894	2,607
Alternative minimum tax credit		6,943
Unfunded status of defined benefit plan	6,979	7,018
State business tax credit	483	544
Stock-based compensation	797	642
Gross deferred tax assets	23,752	26,403
Liabilities
Retirement and other benefit plans	(2,519)	(2,102)
Premises and equipment	(6,360)	(5,716)
Core deposit intangible	(2,748)	(3,660)
Effective hedging derivatives	(1,761)	(1,701)
Fair value adjustment on time deposits	(6)	(54)
Other	(582)	(966)
Gross deferred tax liabilities	(13,976)	(14,199)
Net deferred tax asset at year-end	$ 9,776	$ 12,204