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Intangible Assets and Goodwill (Details 1) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Feb. 01, 2017
Goodwill [Line Items]
Increase to goodwill			$ 508.9
Income tax benefit (expense)	$ 269.6	$ 353.6	508.8	$ 710.0
Summary of roll forward of the changes in goodwill
Goodwill, beginning of period			3,669.3
Other			6.3
Goodwill, end of period	$ 3,870.4		3,870.4
TECFIDERA \| Fumapharm AG
Goodwill [Line Items]
Increase to goodwill			600.0
Income tax benefit (expense)			$ 91.1
Bioverativ
Goodwill [Line Items]
Elimination of goodwill allocated to our hemophilia business					$ (314.1)