License, Collaboration and Other Significant Agreements - Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Contract liabilities:
Balance at End of Period	$ 43,657
Accounts receivable
Contract assets:
Balance at Beginning of Period	3,045	$ 15,822
Additions	38,795	143,148
Deductions	(20,427)	(156,209)
Balance at End of Period	21,413	2,761
Prepaid expenses and other current assets
Contract assets:
Balance at Beginning of Period	1,722	0
Additions	1,725	1,248
Deductions	(5)	0
Balance at End of Period	3,442	1,248
Deferred revenue
Contract liabilities:
Balance at Beginning of Period	40,559	72,950
Additions	65,890	110,295
Deductions	(62,792)	(131,551)
Balance at End of Period	43,657	51,694
Accounts payable
Contract liabilities:
Balance at Beginning of Period	7,227	0
Additions	0	10,097
Deductions	(7,227)	(5,651)
Balance at End of Period	0	4,446
Accrued expenses and other current liabilities
Contract liabilities:
Balance at Beginning of Period	10,000	0
Additions	0	615
Deductions	0	(615)
Balance at End of Period	$ 10,000	$ 0