STOCKHOLDERS' EQUITY - Warrants (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Apr. 22, 2016
Class of Stock [Line Items]
Net proceeds from issuance of Series A Preferred Warrants	$ 73	$ 127	$ 5
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%
Series A Preferred Unit
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)	2,853,555
Net proceeds from issuance of Series A Preferred Warrants	$ 204