INCOME TAXES - Provision for income taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current income tax provision:
Federal									$ 4,985	$ 7,985	$ 13,175
State									1,212	1,751	690
Total									6,197	9,736	13,865
Deferred income tax (benefit)/provision:
Federal									(6,274)	(4,630)	4,065
State									(2,027)	(556)	(556)
Foreign									1,000	(214)	0
Total									(7,301)	(5,400)	3,509
Change in valuation allowance									(1,833)	221	51
Total (benefit)/provision for income taxes	$ (2,817)	$ 64	$ (653)	$ 469	$ 1,910	$ 1,329	$ 726	$ 592	$ (2,937)	$ 4,557	$ 17,425