STOCKHOLDERS' EQUITY (Details)	Dec. 31, 2018 shares
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	17,550,173
Warrants to purchase common stock
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	11,817,912
Stock Option Plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	5,574,901
Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	157,360