Liability Related to Sale of Future Royalties - Schedule of Activity Within Liability Related to Sale of Future Royalties (Details) $ in Thousands	3 Months Ended
	Mar. 31, 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, net of transaction cost amortization	10,909
Liability related to sale of future royalties, Balance at March 31, 2021	327,214
Less: Unamortized transaction cost	(835)
Liability related to sale of future royalties, Carrying value at March 31, 2021	$ 326,379