Acquisitions (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended					3 Months Ended
	Jun. 30, 2011	Jun. 30, 2011	Jun. 30, 2011 Accrued expenses and other [Member] Panima Pharmaceuticals AG [Member]	Jun. 30, 2011 Other long-term liabilities [Member] Panima Pharmaceuticals AG [Member]	Jun. 30, 2011 Panima Pharmaceuticals AG [Member]	Dec. 17, 2010 Panima Pharmaceuticals AG [Member]	Mar. 31, 2011 Biogen Idec Hemophilia [Member]
Acquisitions (Textuals) [Abstract]
Stock acquired in acquisition						100.00%
Cash portion of consideration						$ 32.5
Maximum contingent cash payments						395.0
Contingent consideration			4.9	79.7	84.6	81.2
Payment to former shareholders of Syntonix Pharmaceuticals							40.0
Contingent consideration expense	$ 2.2	$ 3.4