Net Loss Per Share - Summary of Potentially Dilutive Securities that are not Included in Diluted Per Share (Detail) - shares	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount (shares)	13,868,349	12,897,803
Employee Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount (shares)	206,986	0
Common stock subject to repurchase [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount (shares)	0	41,344
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount (shares)	7,934,530	7,521,078
Restricted stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount (shares)	5,726,833	5,335,381