Collaborative and Other Relationships Collaborative and Other Relationships - Equity Method Investments (Details)	3 Months Ended			1 Months Ended		3 Months Ended			12 Months Ended
	Mar. 31, 2013 USD ($)	Mar. 31, 2012 USD ($)	Dec. 31, 2012 USD ($)	Feb. 29, 2012 Samsung Biosimilar Agreement [Member] USD ($)	Feb. 29, 2012 Samsung Biosimilar Agreement [Member] KRW	Mar. 31, 2013 Samsung Biosimilar Agreement [Member] USD ($)	Mar. 31, 2013 Samsung Biosimilar Agreement [Member] KRW	Mar. 31, 2012 Samsung Biosimilar Agreement [Member] USD ($)	Dec. 31, 2012 Samsung Biosimilar Agreement [Member] USD ($)	Dec. 31, 2012 Samsung Biosimilar Agreement [Member] KRW
Schedule of Equity Method Investments [Line Items]
Contribution from Samsung to develop, manufacture and market bio-similar pharmaceuticals				$ 250,000,000	280,500,000,000
Variable interest entity, qualitative or quantitative information, ownership percentage				85.00%	85.00%
Contribution from Biogen Idec to develop, manufacture and market biosimilar pharmaceuticals				45,000,000	49,500,000,000	31,400,000	35,000,000,000		27,800,000	29,700,000,000
Percentage of stake in entity minimum				15.00%	15.00%
Percentage of stake in entity maximum				49.90%	49.90%
Payments to Acquire Equity Method Investments						38,600,000	43,000,000,000		32,100,000	36,000,000,000
Remaining obligation of financing arrangements						5,800,000	6,500,000,000
Recognized loss	(3,811,000)	0				(3,811,000)
Revenue related to technical development and technology transfer services						6,800,000		1,000,000
Deferred revenue	$ 157,100,000		$ 148,000,000			$ 26,100,000