Investments in Variable Interest Entities (Details Textual) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investment in Variable Interest Entities (Textual)
Percentage of operations of joint venture investments on financial statements			100.00%
Percentage of net income (loss) attributable to noncontrolling interests			50.00%
Research and development expense		$ 1,334,919,000	$ 1,219,602,000	$ 1,248,604,000
Investment in biotechnology companies that are determined to be unconsolidated variable interest entities	9,400,000	9,400,000	14,600,000
Knopp
Investment in Variable Interest Entities (Textual)
Total upfront and reimbursement payment made to collaborative partner		0	0	26,400,000
Purchase consideration for variable interest entities				60,000,000
Research and development expense	12,300,000			205,000,000
IPR&D charge allocated to noncontrolling interest				145,000,000
Milestone payments made during period		0	10,000,000	0
Neurimmune
Investment in Variable Interest Entities (Textual)
Milestone payments made during period		0	15,000,000	0
Remaining potential development milestone payments and royalties on commercial sales under the terms of collaboration agreement		$ 345,000,000
Percentage of funding for R&D cost required in support of the collaboration agreement		100.00%
Common Class B | Knopp
Investment in Variable Interest Entities (Textual)
Purchase of common shares in variable interest entities				30.00%