Convertible Preferred Stock - Schedule of Preferred Stock (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019
Class Of Stock [Line Items]
Preferred Stock Authorized				79,398,350
Preferred Stock Issued				59,398,350
Preferred Stock Outstanding				59,398,350
Carrying Value				$ 173,127
Liquidation Value				$ 188,034
Common Stock Issuable Upon Conversion				39,859,139
Series A1 Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized				20,000,000
Series A2 Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized				20,000,000
Preferred Stock Issued				20,000,000
Preferred Stock Outstanding				20,000,000
Carrying Value				$ 29,775
Liquidation Value				$ 30,000
Common Stock Issuable Upon Conversion				13,420,970
Series A3 Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized				22,453,987
Preferred Stock Issued				22,453,987
Preferred Stock Outstanding				22,453,987
Carrying Value				$ 19,364
Liquidation Value				$ 33,681
Common Stock Issuable Upon Conversion				15,067,706
Series A4 Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized				2,066,666
Preferred Stock Issued				2,066,666
Preferred Stock Outstanding				2,066,666
Carrying Value				$ 3,065
Liquidation Value				$ 3,100
Common Stock Issuable Upon Conversion				1,386,831
Series B Preferred Stock
Class Of Stock [Line Items]
Preferred Stock Authorized	0			14,877,697
Preferred Stock Issued	0			14,877,697
Preferred Stock Outstanding	0	14,877,697	14,877,697	14,877,697	14,877,697	14,877,697
Carrying Value		$ 120,923	$ 120,923	$ 120,923	$ 120,923	$ 120,923
Liquidation Value				$ 121,253
Common Stock Issuable Upon Conversion				9,983,632