Net Loss per Common Share - Antidilutive Securities Excluded From Computation of Diluted Net Loss per Common Share (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	14,480,922	10,727,142	8,865,464
Unvested RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	5,253,347	2,868,407	1,910,764
Vested and Unvested Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	9,200,337	7,832,386	6,934,262
ESPP Share Purchase Rights
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	27,238	26,349	20,438