Intangible Assets and Goodwill (Details 1) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Line Items]
Income tax expense	$ 989,942,000	$ 601,014,000	$ 470,554,000
Accumulated impairment losses related to goodwill	0
Summary of roll forward of the changes in goodwill
Goodwill, beginning of period	1,232,916,000	1,201,300,000
Increase to goodwill	527,300,000	35,700,000
Other goodwill adjustments	0
Goodwill, end of period	1,760,249,000	1,232,916,000	1,201,300,000
Fumapharm AG | TECFIDERA
Goodwill [Line Items]
Income tax expense	72,700,000
Summary of roll forward of the changes in goodwill
Increase to goodwill	$ 600,000,000