STOCKHOLDERS' EQUITY (Details)	Dec. 31, 2017 shares
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	17,881,994
Warrants to purchase common stock
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	11,396,262
Stock Option Plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	6,306,836
Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	178,896