Collaborative and Other Relationships (Details 4) (AbbVie, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of activity related to collaboration with Facet Biotech
Total expense incurred by collaboration	$ 128.0	$ 105.2	$ 74.8
Total expense reflected within our consolidated statements of income	65.6	54.2	37.4
Summary of activity related to collaboration, along with an estimate of additional future development expense
Total upfront and milestone payments made to Collaborative Partner	80.0		30.0
Total expense incurred by Biogen Idec, excluding upfront and milestone payments	279.7
Daclizumab And Volociximab [Member]
Summary of activity related to collaboration, along with an estimate of additional future development expense
Estimate of additional amounts to be incurred by us in Product development	$ 222.1