Litigation	6 Months Ended
Jun. 30, 2014
Loss Contingency, Information about Litigation Matters [Abstract]
Litigation	Litigation ’755 Patent Litigation On May 27, 2010, Bayer Healthcare Pharmaceuticals Inc. (Bayer) filed a lawsuit against us in the U.S. District Court for the District of New Jersey seeking a declaratory judgment that they do not infringe our U.S. Patent No. 7,588,755 ('755 Patent), which claims the use of interferon beta for immunomodulation or treating a viral condition, viral disease, cancers or tumors, and that the patent is invalid and seeking monetary relief in the form of attorneys' fees, costs and expenses. On May 28, 2010, Biogen Idec MA Inc. (BIMA) filed a lawsuit in the U.S. District Court for the District of New Jersey alleging infringement of the ’755 Patent by EMD Serono, Inc. (manufacturer, marketer and seller of REBIF), Pfizer, Inc. (co-marketer of REBIF), Bayer (manufacturer, marketer and seller of BETASERON and manufacturer of EXTAVIA), and Novartis Pharmaceuticals Corp. (marketer and seller of EXTAVIA) and seeking monetary damages, including lost profits and royalties. The court has consolidated the two lawsuits, and we refer to the two actions as the “Consolidated ’755 Patent Actions”. Bayer, Pfizer, Novartis and EMD Serono have all filed counterclaims in the Consolidated ’755 Patent Actions seeking declaratory judgments of patent invalidity and non-infringement, and seeking monetary relief in the form of costs and attorneys' fees, and EMD Serono and Bayer have each filed a counterclaim seeking a declaratory judgment that the ’755 Patent is unenforceable based on alleged inequitable conduct. Bayer has also amended its complaint to seek such a declaration. No trial date has been set. Italian National Medicines Agency In the fourth quarter of 2011, Biogen Idec Italia SRL received notice from the Italian National Medicines Agency (Agenzia Italiana del Farmaco or AIFA) that sales of TYSABRI after mid-February 2009 exceeded a reimbursement limit established pursuant to a Price Determination Resolution (Price Resolution) granted by AIFA in December 2006. The Price Resolution set the initial price for the sale of TYSABRI in Italy and limited the amount of government reimbursement “for the first 24 months” of TYSABRI sales. As the basis for the claim, the AIFA notice referred to a 2001 Decree that provides for an automatic 24-month renewal of the terms of all Price Resolutions that are not renegotiated prior to the expiration of their term. On December 23, 2011, we filed an appeal in the Regional Administrative Tribunal of Lazio (Il Tribunale Amministrativo Regionale per il Lazio) in Rome against AIFA, seeking a ruling that the reimbursement limit in the Price Resolution should apply as written to only "the first 24 months" of TYSABRI sales, which ended in February 2009. The final determination of the appeal is still pending and AIFA and Biogen Idec Italia SRL are in discussions about a resolution of the period from mid-February 2009 through January 2013. On November 21, 2012, the tribunal ruled that the reimbursement limit would not automatically renew. On June 10, 2014, AIFA approved a resolution, effective for a 24-month term beginning on June 19, 2014, setting the price for TYSABRI in Italy for this 24-month term. The resolution also eliminates the reimbursement limit from February 2013 going forward. Average Manufacturer Price Litigation On September 6, 2011, we and several other pharmaceutical companies were served with a complaint originally filed under seal on October 28, 2008 in the United States District Court for the Eastern District of Pennsylvania by Ronald Streck (the relator) on behalf of himself and the United States, and the states of New Jersey, California, Rhode Island, Michigan, Montana, Wisconsin, Massachusetts, Tennessee, Oklahoma, Texas, Indiana, New Hampshire, North Carolina, Florida, Georgia, New Mexico, Illinois, New York, Virginia, Delaware, Hawaii, Louisiana, Connecticut, and Nevada (collectively, the States), and the District of Columbia, alleging violations of the False Claims Act, 31 U.S.C. § 3729 et seq. and state and District of Columbia statutory counterparts. The United States and the States have declined to intervene, and the District of Columbia has not intervened. The complaint as amended alleges that Biogen Idec and other defendants underreport Average Manufacturer Price (AMP) information to the Centers for Medicare and Medicaid Services, thereby causing Biogen Idec and the other defendants to underpay rebates under the Medicaid Drug Rebate Program. The relator alleges that the underreporting has occurred because Biogen Idec and other defendants improperly consider various payments that they make to drug wholesalers to be discounts under applicable federal law. The court has dismissed certain claims and a trial has been set for May 2015 on the remaining claims. We have not formed an opinion that an unfavorable outcome under the remaining claims is either “probable” or “remote,” and are unable at this stage of the litigation to form an opinion as to the magnitude or range of any potential loss. We believe that we have good and valid defenses and intend to vigorously defend against the allegations. Government Matters We have learned that state and federal governmental authorities are investigating our sales and promotional practices and have received related subpoenas. We have also received a subpoena from the federal government for documents relating to our relationship with certain pharmacy benefit managers. We are cooperating with the government in these matters. Qui Tam Litigation In August, 2012, we learned that a relator, on behalf of the United States and certain states, filed a suit under seal on February 17, 2011 against us, Elan Corporation, plc, and Elan Pharmaceuticals, Inc. in the United States District Court for the Western District of Virginia. We have neither seen nor been served with the complaint, but understand that it was filed under the Federal False Claims Act. Product Liability and Other Legal Proceedings We are also involved in product liability claims and other legal proceedings generally incidental to our normal business activities. While the outcome of any of these proceedings cannot be accurately predicted, we do not believe the ultimate resolution of any of these existing matters would have a material adverse effect on our business or financial condition.

Litigation

’755 Patent Litigation

On May 27, 2010, Bayer Healthcare Pharmaceuticals Inc. (Bayer) filed a lawsuit against us in the U.S. District Court for the District of New Jersey seeking a declaratory judgment that they do not infringe our U.S. Patent No. 7,588,755 ('755 Patent), which claims the use of interferon beta for immunomodulation or treating a viral condition, viral disease, cancers or tumors, and that the patent is invalid and seeking monetary relief in the form of attorneys' fees, costs and expenses. On May 28, 2010, Biogen Idec MA Inc. (BIMA) filed a lawsuit in the U.S. District Court for the District of New Jersey alleging infringement of the ’755 Patent by EMD Serono, Inc. (manufacturer, marketer and seller of REBIF), Pfizer, Inc. (co-marketer of REBIF), Bayer (manufacturer, marketer and seller of BETASERON and manufacturer of EXTAVIA), and Novartis Pharmaceuticals Corp. (marketer and seller of EXTAVIA) and seeking monetary damages, including lost profits and royalties. The court has consolidated the two lawsuits, and we refer to the two actions as the “Consolidated ’755 Patent Actions”.

Bayer, Pfizer, Novartis and EMD Serono have all filed counterclaims in the Consolidated ’755 Patent Actions seeking declaratory judgments of patent invalidity and non-infringement, and seeking monetary relief in the form of costs and attorneys' fees, and EMD Serono and Bayer have each filed a counterclaim seeking a declaratory judgment that the ’755 Patent is unenforceable based on alleged inequitable conduct. Bayer has also amended its complaint to seek such a declaration. No trial date has been set.

Italian National Medicines Agency

In the fourth quarter of 2011, Biogen Idec Italia SRL received notice from the Italian National Medicines Agency (Agenzia Italiana del Farmaco or AIFA) that sales of TYSABRI after mid-February 2009 exceeded a reimbursement limit established pursuant to a Price Determination Resolution (Price Resolution) granted by AIFA in December 2006. The Price Resolution set the initial price for the sale of TYSABRI in Italy and limited the amount of government reimbursement “for the first 24 months” of TYSABRI sales. As the basis for the claim, the AIFA notice referred to a 2001 Decree that provides for an automatic 24-month renewal of the terms of all Price Resolutions that are not renegotiated prior to the expiration of their term.

On December 23, 2011, we filed an appeal in the Regional Administrative Tribunal of Lazio (Il Tribunale Amministrativo Regionale per il Lazio) in Rome against AIFA, seeking a ruling that the reimbursement limit in the Price Resolution should apply as written to only "the first 24 months" of TYSABRI sales, which ended in February 2009. The final determination of the appeal is still pending and AIFA and Biogen Idec Italia SRL are in discussions about a resolution of the period from mid-February 2009 through January 2013. On November 21, 2012, the tribunal ruled that the reimbursement limit would not automatically renew.

On June 10, 2014, AIFA approved a resolution, effective for a 24-month term beginning on June 19, 2014, setting the price for TYSABRI in Italy for this 24-month term. The resolution also eliminates the reimbursement limit from February 2013 going forward.

Average Manufacturer Price Litigation

On September 6, 2011, we and several other pharmaceutical companies were served with a complaint originally filed under seal on October 28, 2008 in the United States District Court for the Eastern District of Pennsylvania by Ronald Streck (the relator) on behalf of himself and the United States, and the states of New Jersey, California, Rhode Island, Michigan, Montana, Wisconsin, Massachusetts, Tennessee, Oklahoma, Texas, Indiana, New Hampshire, North Carolina, Florida, Georgia, New Mexico, Illinois, New York, Virginia, Delaware, Hawaii, Louisiana, Connecticut, and Nevada (collectively, the States), and the District of Columbia, alleging violations of the False Claims Act, 31 U.S.C. § 3729 et seq. and state and District of Columbia statutory counterparts. The United States and the States have declined to intervene, and the District of Columbia has not intervened. The complaint as amended alleges that Biogen Idec and other defendants underreport Average Manufacturer Price (AMP) information to the Centers for Medicare and Medicaid Services, thereby causing Biogen Idec and the other defendants to underpay rebates under the Medicaid Drug Rebate Program. The relator alleges that the underreporting has occurred because Biogen Idec and other defendants improperly consider various payments that they make to drug wholesalers to be discounts under applicable federal law. The court has dismissed certain claims and a trial has been set for May 2015 on the remaining claims. We have not formed an opinion that an unfavorable outcome under the remaining claims is either “probable” or “remote,” and are unable at this stage of the litigation to form an opinion as to the magnitude or range of any potential loss. We believe that we have good and valid defenses and intend to vigorously defend against the allegations.

Government Matters

We have learned that state and federal governmental authorities are investigating our sales and promotional practices and have received related subpoenas. We have also received a subpoena from the federal government for documents relating to our relationship with certain pharmacy benefit managers. We are cooperating with the government in these matters.

Qui Tam Litigation

In August, 2012, we learned that a relator, on behalf of the United States and certain states, filed a suit under seal on February 17, 2011 against us, Elan Corporation, plc, and Elan Pharmaceuticals, Inc. in the United States District Court for the Western District of Virginia. We have neither seen nor been served with the complaint, but understand that it was filed under the Federal False Claims Act.

Product Liability and Other Legal Proceedings

We are also involved in product liability claims and other legal proceedings generally incidental to our normal business activities. While the outcome of any of these proceedings cannot be accurately predicted, we do not believe the ultimate resolution of any of these existing matters would have a material adverse effect on our business or financial condition.