Summary of Significant Accounting Principles - Concentration of Credit Risk (Details)	3 Months Ended
	Mar. 31, 2021 agreement item	Mar. 31, 2020 item
Concentration of Credit Risk
Number of license agreements | agreement	10
Revenue | Product concentration risk | Royalty
Concentration of Credit Risk
Number of license agreements	2	4
Concentration risk percentage	0.00%	0.00%
Revenue | Product concentration risk | Royalty | Licensees Two
Concentration of Credit Risk
Concentration risk percentage	100.00%
Revenue | Product concentration risk | Royalty | Licensees Four
Concentration of Credit Risk
Concentration risk percentage		99.00%
Revenue | Product concentration risk | Minimum | Royalty | Licensees Two
Concentration of Credit Risk
Concentration risk percentage	41.00%
Revenue | Product concentration risk | Minimum | Royalty | Licensees Four
Concentration of Credit Risk
Concentration risk percentage		11.00%
Revenue | Product concentration risk | Maximum | Royalty | Licensees Two
Concentration of Credit Risk
Concentration risk percentage	59.00%
Revenue | Product concentration risk | Maximum | Royalty | Licensees Four
Concentration of Credit Risk
Concentration risk percentage		43.00%
Accounts receivable | Credit concentration risk | Royalty
Concentration of Credit Risk
Number of license agreements	1	1
Concentration risk percentage	0.00%	0.00%
Accounts receivable | Credit concentration risk | Royalty | one receivable
Concentration of Credit Risk
Concentration risk percentage	100.00%	100.00%