Intangible Assets and Goodwill (Details 1) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Goodwill [Line Items]
Income tax benefit (expense)	$ 337.0	$ 330.1	$ 1,047.0	$ 904.5
Increase to goodwill			771.3
Summary of roll forward of the changes in goodwill
Goodwill, beginning of period			2,663.8
Other			(15.4)
Goodwill, end of period	$ 3,419.7		3,419.7
TECFIDERA | Fumapharm AG
Goodwill [Line Items]
Income tax benefit (expense)			128.7
Increase to goodwill			$ 900.0