STOCKHOLDERS' (DEFICIT) EQUITY - Warrants Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Oct. 28, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Oct. 31, 2019	Oct. 27, 2019	Jun. 30, 2019	Mar. 31, 2018	Nov. 01, 2017
Class of Warrant or Right [Line Items]
Proceeds from exercises of common stock warrants		$ 5,481	$ 7,315	$ 45
Exercises of common stock warrants (in shares)		6,773,000
Exercise price per warrant (in dollars per share)							$ 1.47	$ 1.20	$ 0.80
Increase in warrant value		$ 1,100
Common Stock
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)		6,772,928	8,765,496	4,475,000
2018 Warrants [Member] | Common Stock
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)			5,300,000
2017 Warrants [Member] | Common Stock
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)				1,500,000
Warrants, Expiring March 2023
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)		5,268,000
Exercise price per warrant (in dollars per share)		$ 0.95
Warrants, Expiring March 2023 | Common Stock
Class of Warrant or Right [Line Items]
Proceeds from exercises of common stock warrants	$ 2,000
Exercises of common stock warrants (in shares)	3,400,000
Exercise price per warrant (in dollars per share)	$ 0.60				$ 0.95	$ 1.20
2018 Warrant Amendment, Amendment to Securities Purchase Agreement
Class of Warrant or Right [Line Items]
Minimum percentage of securities issued	50.10%
Warrants, Expiring November 2022
Class of Warrant or Right [Line Items]
Exercises of common stock warrants (in shares)		1,505,000
Exercise price per warrant (in dollars per share)		$ 0.55
Warrants, Expiring November 2022 | Common Stock
Class of Warrant or Right [Line Items]
Exercise price per warrant (in dollars per share)	$ 0.55				$ 0.55	$ 0.80