Net Loss Per Share - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted-Average Shares Outstanding (Details) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of securities excluded from computation of diluted weighted-average shares outstanding (in shares)	6,414,337	5,787,711
Unvested common stock from early exercise of options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of securities excluded from computation of diluted weighted-average shares outstanding (in shares)	48,263	102,436
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of securities excluded from computation of diluted weighted-average shares outstanding (in shares)	6,352,031	5,685,275
Common stock offering from ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total number of securities excluded from computation of diluted weighted-average shares outstanding (in shares)	14,043	0