Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	IPO	Convertible Preferred Stock	Common Stock	Common Stock IPO	Additional Paid-in Capital	Additional Paid-in Capital IPO	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ (142,542)			$ 1		$ 1,558		$ 26	$ (144,127)
Beginning balance (in shares) at Dec. 31, 2019			106,890,000
Beginning balance at Dec. 31, 2019			$ 417,359
Beginning balance (in shares) at Dec. 31, 2019				10,003,000
Issuance of Series B convertible preferred stock, net of issuance costs			$ 435,543
Issuance of Series B convertible preferred stock, net of issuance costs, (in shares)			27,223,000
Issuance of common stock in connection with license agreement	388					388
Issuance of common stock in connection with license agreement (in shares)				63,000
Vesting of restricted stock (in shares)				2,809,000
Exercise of stock options	37					37
Exercise of stock options (in shares)				26,000
Stock-based compensation expense	1,871					1,871
Unrealized loss on marketable securities, net	(3)							(3)
Net income (loss)	(120,683)								(120,683)
Ending balance at Jun. 30, 2020	(260,932)			$ 1		3,854		23	(264,810)
Ending balance (in shares) at Jun. 30, 2020			134,113,000
Ending balance at Jun. 30, 2020			$ 852,902
Ending balance (in shares) at Jun. 30, 2020				12,901,000
Beginning balance at Dec. 31, 2020	$ (421,184)			$ 2		8,216		30	(429,432)
Beginning balance (in shares) at Dec. 31, 2020	134,113,000		134,113,000
Beginning balance at Dec. 31, 2020	$ 852,897		$ 852,897
Beginning balance (in shares) at Dec. 31, 2020	16,170,000			16,170,000
Conversion of convertible preferred stock into common stock upon initial public offering	$ 852,897			$ 13		852,884
'Conversion of convertible preferred stock into common stock, upon initial public offering (in shares)			(134,113,000)
Conversion of convertible preferred stock into common stock, upon initial public offering			$ (852,897)
Conversion of convertible preferred stock into common stock, upon initial public offering (in shares)				134,113,000
Issuance of common stock in initial public offering, net of offering costs		$ 626,405			$ 3		$ 626,402
Issuance of common stock in initial public offering, net of offering costs (in shares)					27,025,000
Vesting of restricted stock (in shares)				2,851,000
Exercise of stock options	$ 631					631
Exercise of stock options (in shares)	417,000			417,000
Stock-based compensation expense	$ 9,099					9,099
Unrealized loss on marketable securities, net	(17)							(17)
Net income (loss)	(161,934)								(161,934)
Ending balance at Jun. 30, 2021	$ 905,897			$ 18		$ 1,497,232		$ 13	$ (591,366)
Ending balance (in shares) at Jun. 30, 2021	0		0
Ending balance (in shares) at Jun. 30, 2021	180,576,000			180,576,000