Collaborative Arrangements and Licensing Agreements, Dynacure, SAS (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Collaborative Arrangement and Licensing Agreement [Abstract]
Revenue earned	$ 172,299	$ 120,911	$ 104,152	$ 110,304	$ 160,349	$ 110,927	$ 38,470	$ 36,874	$ 507,666	$ 346,620	$ 283,703
Dynacure, SAS [Member]
Collaborative Arrangement and Licensing Agreement [Abstract]
Ownership interest percentage	15.00%								15.00%
Maximum amount of payments receivable for license fees and substantive milestones	$ 210,000								$ 210,000
Maximum amount of payments receivable for development milestones	34,500								34,500
Maximum amount of payments receivable for regulatory milestones	111,000								111,000
Maximum amount of payments receivable for commercialization milestones	$ 60,000								60,000
Revenue earned									$ 0	$ 0