Common Stock - Schedule of Common Stock Shares Reserved for Future Issuance (Details) - 2020 Plan and 2014 Plan - shares	Sep. 30, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Reserved common stock for future issuances	9,934,318	24,681,737
Options Issued and Outstanding
Class Of Stock [Line Items]
Reserved common stock for future issuances	5,094,669	3,364,568
Shares Available for Future Stock Option Grants
Class Of Stock [Line Items]
Reserved common stock for future issuances	4,839,649	835,941
Conversion of Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Reserved common stock for future issuances		20,390,095
Redeemable Convertible Preferred Stock Warrant
Class Of Stock [Line Items]
Reserved common stock for future issuances		59,276
Common Stock Warrant
Class Of Stock [Line Items]
Reserved common stock for future issuances		31,857