Revenue from Contracts with Customers (Summary of Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation Of Revenue [Line Items]
Revenue	$ 252,954	$ 14,832	$ 275,404	$ 56,906
License Fees And Milestones [Member]
Disaggregation Of Revenue [Line Items]
Revenue	220,000		220,000
Clinical Product Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	587		587
License Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue				13,857
Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,375	1,489	4,201	2,511
Recognition of deferred revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	18,189	4,221	20,613	10,026
Non-Cash Royalty Revenue Related to the Sale of Future Royalties [Member]
Disaggregation Of Revenue [Line Items]
Revenue	12,593	8,947	28,903	29,950
Recognition of deferred grant revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue			35	52
Non-cash royalty revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue		8,947	28,903	29,950
Research and Development Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	210	175	1,065	510
United States [Member]
Disaggregation Of Revenue [Line Items]
Revenue	251,579	13,233	271,203	54,241
United States [Member] | License Fees And Milestones [Member]
Disaggregation Of Revenue [Line Items]
Revenue	220,000		220,000
United States [Member] | Clinical Product Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	587		587
United States [Member] | License Fee Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue				13,857
United States [Member] | Recognition of deferred revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	18,189	4,111	20,613	9,916
United States [Member] | Non-Cash Royalty Revenue Related to the Sale of Future Royalties [Member]
Disaggregation Of Revenue [Line Items]
Revenue	12,593
United States [Member] | Recognition of deferred grant revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue			35	8
United States [Member] | Non-cash royalty revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue		8,947	28,903	29,950
United States [Member] | Research and Development Revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue	210	175	1,065	510
Rest of World [Member]
Disaggregation Of Revenue [Line Items]
Revenue	1,375	1,599	4,201	2,665
Rest of World [Member] | Other [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 1,375	1,489	$ 4,201	2,511
Rest of World [Member] | Recognition of deferred revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue		$ 110		110
Rest of World [Member] | Recognition of deferred grant revenue [Member]
Disaggregation Of Revenue [Line Items]
Revenue				$ 44