INCOME TAXES - Schedule of Components of Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Provision or benefit for income taxes
Currently payable									$ 5,690	$ 3,054	$ 3,527
Deferred benefit									(955)	1,543	209
Change in corporate tax rate									2,724	0	0
Total provision	$ 3,968	$ 1,282	$ 1,223	$ 986	$ 1,290	$ 1,273	$ 1,152	$ 882	$ 7,459	$ 4,597	$ 3,736