v3.7.0.1
NET LOSS PER SHARE - Antidilutive Securities (Details) - shares
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Shares excluded from the diluted per share calculation 9,935,374 10,417,716
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 9,465,157 9,893,775
Employee Stock Purchase Plan    
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]    
Shares excluded from the diluted per share calculation 470,217 523,941