COMPREHENSIVE INCOME - Reconciliation of changes in components of other comprehensive loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other comprehensive loss
Net unrealized losses on securities available-for-sale	$ (318)	$ (399)	$ (1,297)
Unrealized losses on securities available-for-sale	(496)	(983)	(1,489)
Other comprehensive (loss) income, net of tax	(298)	(648)	(983)
Statements of Comprehensive Income (Loss)
Other comprehensive loss
Net unrealized losses on securities available-for-sale	(318)	(399)	(1,297)
Reclassification of net realized gains in net income	(178)	(584)	(192)
Unrealized losses on securities available-for-sale	(496)	(983)	(1,489)
Income tax benefit (expense)	198	335	506
Unrealized (losses) gains on securities available-for-sale, net of tax	(298)	(648)	(983)
Other comprehensive (loss) income, net of tax	$ (298)	$ (648)	$ (983)