Stockholder's Equity - Schedule of Preferred Stock (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jul. 31, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
PREFERRED STOCK AUTHORIZED	264,000,000			146,760,000
PREFERRED STOCK ISSUED	256,003,042			113,145,900
PREFERRED STOCK OUTSTANDING	256,003,042			113,145,900
CARRYING VALUE	$ 256,520			$ 110,995
LIQUIDATION VALUE	$ 256,520			$ 110,995
COMMON STOCK ISSUABLE UPON CONVERSION	30,355,379			13,416,155
Series Seed Preferred Stock
Class Of Stock [Line Items]
PREFERRED STOCK AUTHORIZED	4,000,000			4,000,000
PREFERRED STOCK ISSUED	4,000,000			4,000,000
PREFERRED STOCK OUTSTANDING	4,000,000		4,000,000	4,000,000	4,000,000	4,000,000	4,000,000
CARRYING VALUE	$ 1,000		$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 1,000
LIQUIDATION VALUE	$ 1,000			$ 1,000
COMMON STOCK ISSUABLE UPON CONVERSION	474,298			474,298
Series A Preferred Stock
Class Of Stock [Line Items]
PREFERRED STOCK AUTHORIZED	110,000,000			110,000,000
PREFERRED STOCK ISSUED	109,145,900			109,145,900
PREFERRED STOCK OUTSTANDING	109,145,900		109,145,900	109,145,900	109,145,900	109,145,900	109,145,900
CARRYING VALUE	$ 109,995		$ 109,995	$ 109,995	$ 109,995	$ 109,995	$ 109,995
LIQUIDATION VALUE	$ 109,995			$ 109,995
COMMON STOCK ISSUABLE UPON CONVERSION	12,941,857			12,941,857
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
PREFERRED STOCK AUTHORIZED	150,000,000			0
PREFERRED STOCK ISSUED	142,857,142	4,285,714	138,571,428	0
PREFERRED STOCK OUTSTANDING	142,857,142		138,571,428	0
CARRYING VALUE	$ 145,525		$ 141,026
LIQUIDATION VALUE	$ 145,525			$ 0
COMMON STOCK ISSUABLE UPON CONVERSION	16,939,224
FF Preferred Stock
Class Of Stock [Line Items]
PREFERRED STOCK AUTHORIZED				32,760,000