INCOME TAXES - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ 0	$ 0	$ 0
State	0	0	0
Foreign	0	0	0
Total current	0	0	0
Deferred:
Federal	6,896	(28,331)	22,449
State	1,264	2,345	1,796
Foreign	916	85	864
Change in uncertain tax positions	(105)	(120)	(117)
Change in valuation allowance	(8,971)	26,021	(24,992)
Total deferred	0	0	0
Income tax benefit	$ 0	$ 0	$ 0