Convertible Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended	9 Months Ended
	Aug. 21, 2020	Mar. 31, 2020	Jan. 31, 2020	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Aug. 20, 2020	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Temporary Equity [Line Items]
Stock issuance costs				$ 17,003	$ 17,003
Deemed dividend from exchange of convertible preferred stock					$ 9,050
Common Stock
Temporary Equity [Line Items]
Conversion of stock, shares issued and outstanding	50,439,595
Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, authorized							52,483,788
Convertible Preferred Stock, par or stated value per share							$ 0.0001
Convertible Preferred Stock, issued				0	0
Number of preferred Stock converted to common stock	31,625,534
Convertible Preferred Stock, outstanding				0	0
Series Seed Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, authorized				0	0		3,000,000		3,000,000
Convertible Preferred Stock, par or stated value per share				$ 0.0001	$ 0.0001				$ 0.0001
Convertible Preferred Stock, issued				0	0				3,000,000
Convertible Preferred Stock, outstanding				0	0	3,000,000		3,000,000	3,000,000	3,000,000	3,000,000
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, authorized				0	0		14,886,305		14,886,305
Convertible Preferred Stock, par or stated value per share				$ 0.0001	$ 0.0001				$ 0.0001
Convertible Preferred Stock, issued				0	0				14,886,305
Convertible Preferred Stock, outstanding				0	0	14,664,730		12,842,112	14,720,126	14,609,335	14,498,547
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, authorized				0	0		16,009,845		16,009,848
Convertible Preferred Stock, par or stated value per share			$ 4.06	$ 0.0001	$ 0.0001				$ 0.0001
Convertible Preferred Stock, issued			1,182,265	0	0				14,827,580
Proceeds from issuance of convertible preferred stock			$ 4,800
Stock issuance costs					$ 0
Convertible Preferred Stock, outstanding				0	0	9,605,905		16,009,845	14,827,580	9,605,905	9,605,905
Series B-1 Convertible Preferred
Temporary Equity [Line Items]
Convertible Preferred Stock, authorized				0	0		3,059,695		3,059,695
Convertible Preferred Stock, par or stated value per share				$ 0.0001	$ 0.0001				$ 0.0001
Convertible Preferred Stock, issued				0	0				3,059,695
Proceeds from issuance of convertible preferred stock					$ 4,800	$ 14,025
Stock issuance costs						$ 49
Convertible Preferred Stock, outstanding				0	0	3,059,695		3,059,695	3,059,695	3,059,695
Series C Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible Preferred Stock, authorized							15,527,943
Convertible Preferred Stock, issued		15,527,943
Proceeds from issuance of convertible preferred stock					$ 88,181
Stock issuance costs					320
Shares issued upon exchange of Series A convertible preferred stock		1,988,802
Deemed dividend from exchange of convertible preferred stock					9,100
Reduction of additional paid-in-capital related to temporary equity deemed dividend					2,300
Increase in accumulated deficit related to temporary equity deemed dividend					$ 6,700
Convertible Preferred Stock, outstanding								15,527,943
Series C Convertible Preferred Stock | Series C SPA
Temporary Equity [Line Items]
Convertible Preferred Stock, par or stated value per share		$ 6.5366
Convertible Preferred Stock, issued		13,539,141
Proceeds from issuance of convertible preferred stock		$ 88,200
Stock issuance costs		$ 300