Net Loss Per Share - Schedule of Dilutive Securities Not Included in Diluted Per Share Calculations (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	15,950,786	12,818,053	15,950,786	12,818,053
Options issued and outstanding and ESPP shares issuable
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	13,680,889	11,981,119	13,680,889	11,981,119
Restricted shares subject to future vesting
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	2,269,897	826,511	2,269,897	826,511
Early exercised common stock subject to future vesting
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	0	10,423	0	10,423