v3.6.0.2
NET LOSS PER SHARE - Antidilutive Securities (Details) - shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Shares excluded from the diluted per share calculation 10,685,124 10,796,264 10,017,184
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 10,585,444 10,589,268 9,776,124
Common stock subject to repurchase      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Shares excluded from the diluted per share calculation 0 0 27,000
Common stock issuable upon exercise of warrants      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Shares excluded from the diluted per share calculation 0 73,883 107,876
Employee Stock Purchase Plan      
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]      
Shares excluded from the diluted per share calculation 99,680 133,113 106,184