Liability Related to Sale of Future Royalties - Schedule of Activity Within Liability Related to Sale of Future Royalties (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Liability Related To Sale Of Future Royalties [Abstract]
Liability related to sale of future royalties, Balance at December 31, 2020	$ 316,305
Non-cash interest expense recognized	34,263
Liability related to sale of future royalties, Balance at September 30, 2021	350,568
Less: Unamortized transaction cost	(802)
Liability related to sale of future royalties, Carrying value at September 30, 2021	$ 349,766