Collaborative and Other Relationships (Details 2) - AbbVie - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaborative arrangements and non-collaborative arrangement transactions
Total expense incurred by collaboration	$ 113.8	$ 117.8	$ 133.4
Biogen's share of expense reflected within our consolidation statements of income	$ 60.8	$ 67.4	$ 71.0

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