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Investments in Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011
Neurimmune |  |  |
Summary of activity related to collaboration |  |  |
Milestone payments made during period | $ 0 | $ 0 | $ 15.0
Biogen Idec's share of expense reflected within our consolidation statements of income | 27.2 | 13.3 | 24.2
Collaboration expense attributed to noncontrolling interests, net of tax | 0 | 0 | 14.7
Total expense incurred by Biogen Idec | 115.7 |  |
Estimate of additional amounts to be incurred by us in development of the lead compound | 800.9 |  |
Knopp |  |  |
Summary of activity related to collaboration |  |  |
Milestone payments made during period | 0 | 0 | 10.0
Biogen Idec's share of expense reflected within our consolidation statements of income | 0 | 113.0 | 54.8
Collaboration expense attributed to noncontrolling interests, net of tax | $ 0 | $ 0 | $ 8.6

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