Quarterly report pursuant to Section 13 or 15(d)

Net Loss per Common Share - Antidilutive Securities Excluded From Computation of Diluted Net Loss per Common Share (Detail)

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Net Loss per Common Share - Antidilutive Securities Excluded From Computation of Diluted Net Loss per Common Share (Detail) - shares
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of earnings per share 7,426,647 5,621,741
Unvested RSUs    
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of earnings per share 1,899,505 1,818,315
Vested and Unvested Options    
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of earnings per share 5,466,825 3,775,661
ESPP Share Purchase Rights    
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]    
Antidilutive securities excluded from computation of earnings per share 60,317 27,765