Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Follow On Public Offering	At The Market Offerings	Regeneron Pharmaceuticals Inc. [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Follow-on Offering [Member]	Follow-on Offering [Member] Follow On Public Offering	Follow-on Offering [Member] At The Market Offerings	Follow-on Offering [Member] Regeneron Pharmaceuticals Inc. [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Follow On Public Offering	Additional Paid-In Capital [Member] At The Market Offerings	Additional Paid-In Capital [Member] Regeneron Pharmaceuticals Inc. [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]
Beginning balance at Dec. 31, 2018	$ 277,920					$ 5				$ 478,968				$ (28)	$ (201,025)
Beginning balance (ASC 842 [Member]) at Dec. 31, 2018					$ (320)											$ (320)
Beginning balance, shares at Dec. 31, 2018						45,224,480
Issuance of common stock			$ 72,256									$ 72,256
Issuance of common stock, shares								4,518,579
Exercise of stock options	3,086									3,086
Exercise of stock options, shares						364,404
Issuance of shares under employee stock purchase plan	1,092									1,092
Issuance of shares under employee stock purchase plan, shares						90,581
Equity-based compensation	15,091									15,091
Equity-based compensation, shares						0
Other comprehensive income - unrealized gain (loss) on marketable securities	289													289
Net loss	(99,533)														(99,533)
Ending balance at Dec. 31, 2019	269,881					$ 5				570,493				261	(300,878)
Ending balance, shares at Dec. 31, 2019						50,198,044
Issuance of common stock		$ 296,607	49,461	$ 12,580			$ 2				$ 296,605	49,461	$ 12,580
Issuance of common stock, shares							11,815,069	2,270,161	925,218
Exercise of stock options	11,574									11,574
Exercise of stock options, shares						840,824
Vesting of restricted stock units, shares						82,829
Issuance of shares under employee stock purchase plan	1,557									1,557
Issuance of shares under employee stock purchase plan, shares						101,911
Equity-based compensation	19,903									19,903
Other comprehensive income - unrealized gain (loss) on marketable securities	(260)													(260)
Net loss	(134,231)														(134,231)
Ending balance at Dec. 31, 2020	$ 527,072					$ 7				962,173				1	(435,109)
Ending balance, shares at Dec. 31, 2020	66,234,056					66,234,056
Issuance of common stock		$ 648,315	$ 45,255								$ 648,315	$ 45,255
Issuance of common stock, shares							4,758,620	641,709
Exercise of stock options	$ 41,094									41,094
Exercise of stock options, shares	2,700,886					2,700,886
Vesting of restricted stock units, shares						119,715
Issuance of shares under employee stock purchase plan	$ 2,024									2,024
Issuance of shares under employee stock purchase plan, shares						30,897
Equity-based compensation	47,009									47,009
Other comprehensive income - unrealized gain (loss) on marketable securities	(2,126)													(2,126)
Other comprehensive loss - equity method investment	(507)													(507)
Net loss	(267,892)
Ending balance at Dec. 31, 2021	$ 1,040,244					$ 7				$ 1,745,870				$ (2,632)	$ (703,001)
Ending balance, shares at Dec. 31, 2021	74,485,883					74,485,883