Capitalization - Schedule of Reserved Shares of Common Stock for Future Issuance (Detail) - shares shares in Thousands	Dec. 31, 2020	Dec. 31, 2019
Schedule of Capitalization [Line Items]
Reserved common shares	9,107	7,741
Equity Incentive Plans [Member]
Schedule of Capitalization [Line Items]
Reserved common shares	8,659	7,607
Employee Stock Purchase Plan [Member]
Schedule of Capitalization [Line Items]
Reserved common shares	448	134