Commitments and Contingences (Details Textual) (USD $)	9 Months Ended		12 Months Ended	9 Months Ended			9 Months Ended			9 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Fumapharm AG TECFIDERA	Sep. 30, 2014 One billion Fumapharm AG	Dec. 31, 2013 One billion Fumapharm AG	Sep. 30, 2014 One billion Fumapharm AG TECFIDERA	Sep. 30, 2014 Two billion Fumapharm AG	Jun. 30, 2014 Two billion Fumapharm AG	Sep. 30, 2014 Two billion Fumapharm AG TECFIDERA	Sep. 30, 2014 Three billion Fumapharm AG	Sep. 30, 2014 Three billion Fumapharm AG TECFIDERA
Business Acquisition, Contingent Consideration [Line Items]
Payment of contingent payment for acquisition	$ 175,000,000	$ 0					$ 25,000,000
Payment of contingent payment for acquisition	308,300,000		35,700,000	350,000,000						150,000,000		200,000,000
Cumulative sales level					$ 1,000,000,000.0	$ 1,000,000,000		$ 2,000,000,000	$ 2,000,000,000		$ 3,000,000,000