INCOME TAXES (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
Current income tax provision:
Federal									$ 13,175	$ 11,717	$ 7,264
State									690	1,321	611
Total									13,865	13,038	7,875
Deferred income tax provision/(benefit):
Federal									4,065	(8,387)	(1,468)
State									(556)	(658)	(409)
Total									3,509	(9,045)	(1,877)
Change in valuation allowance									51	134	0
Excess tax benefit from stock-based compensation awards									0	617	360
Total provision for income taxes	$ (13,979)	$ (1,654)	$ (1,269)	$ (523)	$ 524	$ (2,501)	$ (1,227)	$ (1,540)	$ 17,425	$ 4,744	$ 6,358