Intangible Assets and Goodwill (Details 1) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Goodwill [Line Items]
Income tax benefit (expense)	$ 356.4	$ 281.9
Increase to goodwill	257.8
Summary of roll forward of the changes in goodwill
Goodwill, beginning of period	2,663.8
Other	(3.7)
Goodwill, end of period	2,917.9
TECFIDERA | Fumapharm AG
Goodwill [Line Items]
Income tax benefit (expense)	42.2
Increase to goodwill	$ 300.0