Net Loss Per Share - Schedule of Potentially Dilutive Securities Not Included in Diluted Per Share Calculations (Details) - shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	9,742,646	97,364,888
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)		88,112,733
Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	9,459,015	6,316,944
Restricted Shares Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)	283,631	2,690,767
Warrants to Purchase Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation of diluted net loss per share (in shares)		244,444