CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY - Common Stock (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Nov. 30, 2017	Jul. 31, 2017	Apr. 30, 2017
Beneficial ownership interest if common stock issued (as a percentage)	9.99%
Minimum
Beneficial ownership interest if common stock issued (as a percentage)	4.99%
Common Stock
Issuance of stock (in shares)	45,275,000
Warrant
Net proceeds from issuance of common stock and warrants	$ 9.7
Prefunded warrants
Warrants exercise price (in dollars per share)	$ 0.001
Prefunded warrants | Warrant
Number of shares of common stock subject to warrant (in shares)	28,225,000
Series A Warrants | Warrant
Number of shares of common stock subject to warrant (in shares)	73,500,000
Warrants exercise price (in dollars per share)	$ 0.20
Warrants, expiration term	5 years
Series B Warrants | Warrant
Number of shares of common stock subject to warrant (in shares)	73,500,000
Warrants exercise price (in dollars per share)	$ 0.25
Warrants exercisable after number of trading days from a press release	20 days
Warrants exercisable after number of months from issuance	18 months
Prefunded warrants and series A | Common Stock
Number of common shares called by each warrant (in shares)	1
Prefunded warrants and series B | Common Stock
Number of common shares called by each warrant (in shares)	1
Prefunded warrants, series A and series B | Warrant
Warrants exercise price (in dollars per share)	$ 0.1490
Series A and series B | Common Stock
Warrants exercise price (in dollars per share)	$ 0.15
Private placement
Issuance of stock (in shares)		5,500,000	6,410,258
Net proceeds from the sale of common stock		$ 1.9	$ 4.4
Share price (in dollars per share)		$ 0.36	$ 0.78
Number of shares of common stock subject to warrant (in shares)			3,365,385
Warrants exercise price (in dollars per share)			$ 0.90