Commitments and Contingences (Details Textual) (USD $)	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Fumapharm AG [Member] TECFIDERA [Member]	Mar. 31, 2014 One billion [Member] Fumapharm AG [Member]	Dec. 31, 2013 One billion [Member] Fumapharm AG [Member]
Business Acquisition, Contingent Consideration [Line Items]
Payment of contingent payment for acquisition	$ 25,000,000	$ 0	$ 25,000,000
Cumulative sales level				$ 1,000,000,000.0	$ 1,000,000,000

The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration