STOCKHOLDERS' DEFICIT - Carrying Value of Preferred Stock Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Series A Preferred Stock
Class of Warrant or Right [Line Items]
Dividend accrual rate	11.50%
Convertible preferred stock series, liquidation preference	$ 3,084	$ 2,916
Series C Preferred Stock
Class of Warrant or Right [Line Items]
Dividend accrual rate	11.50%
Convertible preferred stock series, liquidation preference	$ 89,445	$ 84,555