Investments in Variable Interest Entities (Details) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended		1 Months Ended		1 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 Neurimmune	Jun. 30, 2013 Neurimmune	Jun. 30, 2014 Neurimmune	Jun. 30, 2013 Neurimmune	Feb. 28, 2014 Ataxion	Feb. 28, 2014 Commitments to invest Ataxion	Feb. 28, 2014 Minority interest Ataxion
Investment in Variable Interest Entities (Textual) [Abstract]
Remaining potential development milestone payments and royalties on commercial sales under the terms of collaboration agreement								$ 335,000,000
Research and development	447,273,000	327,463,000	976,157,000	611,803,000		10,600,000	5,700,000	21,700,000	10,700,000
Milestone payments made during period								10,000,000
Payments to acquire interest in preferred stock of affiliate										1,600,000
Term for right to purchase outstanding shares										30 days
Additional investments committed to if certain milestones are met											6,200,000
In-process research and development												3,500,000
Investment in biotechnology companies that are determined to be unconsolidated variable interest entities	$ 11,400,000		$ 11,400,000		$ 5,500,000