Collaborative Arrangements - Janssen Pharmaceutica NV (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty revenues	$ 6,331	$ 5,759	$ 5,077	$ 6,792	$ 8,785	$ 8,386	$ 13,015	$ 10,733	$ 23,959	$ 40,919	$ 156,592
Collaborative revenues:
Total collaborative revenues attributable to the Janssen HCV collaboration	5,054	1,546	611	842	10,829	33,502	3,087	4,257	8,053	51,675	217,738
Total revenues	$ 417,935	$ 309,816	$ 166,076	$ 138,509	$ 144,556	$ 178,987	$ 138,421	$ 118,451	1,032,336	580,415	1,211,975
Janssen
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty revenues									1,518	13,481	130,724
Collaborative revenues:
Up-front and amendment payments revenues									0	0	190,345
Net reimbursement for telaprevir development costs									1,946	7,104	2,793
Reimbursement for manufacturing services									0	0	10,299
Total collaborative revenues attributable to the Janssen HCV collaboration									1,946	7,104	203,437
Total revenues									$ 3,464	$ 20,585	$ 334,161