Summary of Significant Accounting Policies - Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share (Detail) - shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents	9,806,381	8,417,102
Stock Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents	9,802,633	8,258,031
Unvested Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents		145,900
Shares Issuable under ESPP [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents	3,748	13,171