INCOME TAXES - Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ 5,510	$ (28,392)	$ (24,935)
State taxes, net of federal benefit	176	(216)	(885)
Permanent differences	1,582	498	579
Stock-based compensation	(655)	0	0
Valuation allowance	273	879	0
Effect of change in enacted Tax Act	(3,448)	0	0
Other	(310)	(741)	(147)
Income tax expense (benefit)	$ 3,128	$ (27,972)	$ (25,388)