Liability Related to Sale of Future Royalties - Estimates of Annual Interest Rate (Details)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
2012 Purchase and Sale Agreement
Liability Related to Sale of Future Royalties [Line Items]
Implicit interest rate over the life of the agreement	20.20%	19.50%
Prospective effective interest rate	48.00%	38.00%
2020 Purchase and Sale Agreement
Liability Related to Sale of Future Royalties [Line Items]
Implicit interest rate over the life of the agreement	16.00%
Prospective effective interest rate	16.00%