Stockholders' Equity - Outstanding and Reserved Shares of Common Stock for Future Issuance (Detail) - shares	9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Stock plans:
Options outstanding (in shares)	386,000	484,000	454,000	522,000
Total shares of common stock reserved for future issuance (in shares)	26,009,000
2021 Equity Incentive Plan
Stock plans:
Total shares of common stock reserved for future issuance (in shares)	9,707,000
Amended and Restated 2012 Employee Stock Purchase Plan
Stock plans:
Total shares of common stock reserved for future issuance (in shares)	9,389,000
Options outstanding
Stock plans:
Options outstanding (in shares)	386,000
RSUs
Stock plans:
RSUs (in shares)	6,527,000	7,305,000	8,047,000	7,362,000
Performance-based RSUs
Stock plans:
Number of shares eligible to vest (percent)	100.00%