Net Loss Per Share - Potentially Dilutive Securities Excluded from Diluted Net Loss Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from diluted net loss per share attributable to common stockholders (in shares)	3,802,675	5,009,115	3,802,675	5,009,115
Shares of common stock subject to outstanding options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from diluted net loss per share attributable to common stockholders (in shares)	1,989,286	3,082,273	1,989,286	3,082,273
Shares of common stock subject to outstanding common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from diluted net loss per share attributable to common stockholders (in shares)	3,132	14,445	3,132	14,445
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from diluted net loss per share attributable to common stockholders (in shares)	1,810,257	1,912,397	1,810,257	1,912,397