INCOME TAXES - Benefit from Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 0	$ 0	$ 0
State	163	106	166
Foreign	20	(8)	26
Deferred:
Federal	808	(6,572)	(10,179)
State	(4,039)	(772)	(963)
Foreign	(2,034)	(1,273)	(536)
Change in valuation allowance	3,608	8,593	11,678
Income taxes (benefit) expense	$ (1,474)	$ 74	$ 192