STOCKHOLDERS' DEFICIT - First Quarter 2017 Private Placement (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Jun. 29, 2017	Mar. 01, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Proceeds from equity offering			$ 20,777	$ 83,267	$ 0
Private Placement | Common Stock
Class of Stock [Line Items]
Shares issued (in shares)	6,359,350	3,300,000.0
Proceeds from equity offering	$ 15,900	$ 5,100
Stock offering price (in USD per share)	$ 2.50	$ 1.5366