STOCKHOLDERS' EQUITY - Warrants (Details) - USD ($) $ in Thousands	12 Months Ended			18 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Apr. 22, 2016
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)			0
Net proceeds from issuance of Series A Preferred Warrants	$ 127	$ 5	$ 0	$ 131
Registration statement
Class of Stock [Line Items]
Premium of the exercise price of the warrant as a percent to net asset value of common stock					15.00%