Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Total	IPO	ATM offering	Series A Convertible Preferred Stock	Series A Convertible Preferred Stock Series A1 Convertible Preferred Shares	Subscriptions Receivables from Preferred Stockholders	Common Stock	Common Stock IPO	Common Stock ATM offering	Notes Receivable from Common Stockholders	Additional Paid-in Capital	Additional Paid-in Capital IPO	Additional Paid-in Capital ATM offering	Accumulated Deficit	Accumulated Other Comprehensive Income
Balance (in shares) at Dec. 31, 2017				0			26,249,993
Balance at Dec. 31, 2017	$ (2)			$ 0		$ 0	$ 26			$ (5)	$ 0			$ (23)	$ 0
Issuance of Series A convertible preferred shares at $35.06 per share, net of issuance costs of $635 and $84 (in shares)				7,557,990	998,225
Issuance of Series A convertible preferred shares at $35.06 per share, net of issuance costs of $635 and $84				$ 264,365	$ 34,917
Issuance of Series A-1 convertible preferred shares at $35.06 per share in connection with asset acquisition (in shares)					3,187,772
Issuance of Series A-1 convertible preferred shares at $35.06 per share in connection with asset acquisition					$ 111,770
Proceeds received from common stockholders for issuance of founders' stock at inception	5									5
Subscriptions receivable from preferred stockholders	(150,000)					(150,000)
Proceeds received from preferred stockholders	150,000					150,000
Issuance of common stock for exercise of stock options (in shares)							5,020,580
Issuance of common stock for early exercise of stock options	5						$ 5
Issuance of common stock, net of issuance costs (in shares)								20,700,000
Issuance of common stock, net of issuance costs		$ 343,329						$ 21				$ 343,308
Conversion of Series A convertible preferred stock (in shares)				(11,743,987)			61,655,922
Conversion of Series A convertible preferred stock	411,052			$ (411,052)			$ 62				410,990
Issuance of common stock upon conversion of convertible stock (in shares)							7,856,176
Issuance of common stock upon conversion of convertible notes	141,410						$ 7				141,403
Adjustment for fractional shares from forward stock split	(2)										(2)
Stock-based compensation	18,566										18,566
Net loss	(211,505)													(211,505)
Net unrealized loss on available-for-sale investments	306														306
Balance (in shares) at Dec. 31, 2018				0			121,482,671
Balance at Dec. 31, 2018	703,164			$ 0		$ 0	$ 121			$ 0	914,265			(211,528)	306
Issuance of common stock for exercise of stock options (in shares)							711,623
Issuance of common stock for early exercise of stock options	2,959						$ 1				2,958
Employee stock purchase plan (in shares)							107,982
Employee stock purchase plan	1,783										1,783
Issuance of common stock, net of issuance costs (in shares)							1,965,082
Issuance of common stock, net of issuance costs	54,219						$ 2				54,217
Vesting of early exercised common stock	4,590										4,590
Stock-based compensation	46,063										46,063
Net loss	(184,594)													(184,594)
Net unrealized loss on available-for-sale investments	$ 839														839
Balance (in shares) at Dec. 31, 2019	124,267,358						124,267,358
Balance at Dec. 31, 2019	$ 629,023						$ 124				1,023,876			(396,122)	1,145
Issuance of common stock for exercise of stock options (in shares)							1,725,695
Issuance of common stock for early exercise of stock options	8,815						$ 2				8,813
Employee stock purchase plan (in shares)							175,142
Employee stock purchase plan	2,843										2,843
Issuance of common stock, net of issuance costs (in shares)			848,663				13,457,447		848,663
Issuance of common stock, net of issuance costs	595,730		$ 26,203				$ 13		$ 1		595,717		$ 26,202
Vesting of early exercised common stock	2,840										2,840
Stock-based compensation	65,261										65,261
Net loss	(250,221)													(250,221)
Net unrealized loss on available-for-sale investments	$ (877)														(877)
Balance (in shares) at Dec. 31, 2020	140,474,305						140,474,305
Balance at Dec. 31, 2020	$ 1,079,617						$ 140				$ 1,725,552			$ (646,343)	$ 268