v3.8.0.1
STOCKHOLDERS' EQUITY - Common Stock Reserved for Future Issuance (Details) - shares
Sep. 30, 2017
Dec. 31, 2016
Class of Stock [Line Items]    
Total reserved shares of common stock for future issuance 18,740,132  
Employee Stock Options and Restricted Stock Units    
Class of Stock [Line Items]    
Options and Restricted Stock Units issued and outstanding 9,254,272  
2014 Equity Incentive Plan    
Class of Stock [Line Items]    
Shares reserved for issuance under share-based compensation plan 7,473,429 5,116,753
Employee Stock Purchase Plan    
Class of Stock [Line Items]    
Shares reserved for issuance under share-based compensation plan 2,012,431