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Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Related Party Transaction [Line Items]
Redeemable convertible preferred stock	0		0		0
Revenue—related party	$ 3,429	$ 3,028	$ 4,262	$ 12,493
Regeneron Pharmaceuticals, Inc.
Related Party Transaction [Line Items]
Revenue—related party	3,400	$ 3,000	4,300
Deferred revenue	$ 10,100		$ 10,100
Regeneron Pharmaceuticals, Inc. \| Series B Convertible Preferred Stock [ Member ]
Related Party Transaction [Line Items]
Redeemable convertible preferred stock	883,568		883,568		883,568