STOCKHOLDERS' EQUITY - Warrants Narrative (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Jun. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Class of Warrant or Right [Line Items]
Proceeds from exercises of common stock warrants					$ 3,434	$ 7,315
Exercises of common stock warrants (in shares)					3,361,000
Common Stock
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)	3,361,115	50,000	8,294,718	420,778	3,400,000	8,700,000