v3.7.0.1
NET LOSS PER SHARE - Antidilutive Securities (Details) - shares
6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Shares excluded from the diluted per share calculation 10,492,870 12,496,935
Shares of common stock issuable under the Equity Incentive Plan    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Shares excluded from the diluted per share calculation 10,396,671 12,397,881
Employee Stock Purchase Plan    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Shares excluded from the diluted per share calculation 96,199 99,054