Intangible Assets and Goodwill (Details 1) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Goodwill [Line Items]
Income tax expense	$ 186,105,000	$ 131,044,000	$ 410,753,000	$ 334,213,000
Goodwill acquired during the period			13,500,000		48,200,000
Summary of roll forward of the changes in goodwill
Goodwill, beginning of period			1,201,296,000	1,146,300,000	1,146,300,000
Goodwill acquired during the period			13,500,000		48,200,000
Other Goodwill Adjustments			(4,100,000)		6,800,000
Goodwill, end of period	1,210,718,000		1,210,718,000		1,201,296,000
TECFIDERA [Member]
Goodwill [Line Items]
Income tax expense			1,500,000
Goodwill acquired during the period			15,000,000
Summary of roll forward of the changes in goodwill
Goodwill acquired during the period			$ 15,000,000