10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K

þ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2011

or

¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

Commission file number: 0-19311

BIOGEN IDEC INC.

(Exact name of registrant as specified in its charter)

Delaware	33-0112644
(State or other jurisdiction of incorporation or organization)	(I.R.S. Employer Identification No.)

133 Boston Post Road, Weston, Massachusetts 02493

(781) 464-2000

(Address, including zip code, and telephone number, including area code, of Registrant’s principal executive offices)

Securities registered pursuant to Section 12(b) of the Act:

Title of Each Class	Name of Each Exchange on Which Registered
Common Stock, $0.0005 par value	The Nasdaq Global Select Market

Securities registered pursuant to Section 12(g) of the Act:

None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    Yes þ        No ¨

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act.    Yes ¨        No þ

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes þ        No ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files):    Yes þ        No ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of the registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.    ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer þ	Accelerated filer ¨	Non-accelerated filer ¨	Smaller reporting company	¨
		(Do not check if a smaller reporting company)

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act).    Yes ¨        No þ

The aggregate market value of the registrant’s common stock held by non-affiliates of the registrant (without admitting that any person whose shares are not included in such calculation is an affiliate) computed by reference to the price at which the common stock was last sold as of the last business day of the registrant’s most recently completed second fiscal quarter was $25,908,506,479.

As of January 31, 2012, the registrant had 238,725,065 shares of common stock, $0.0005 par value, outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the definitive proxy statement for our 2012 Annual Meeting of Stockholders are incorporated by reference into Part III of this report.

BIOGEN IDEC INC.

ANNUAL REPORT ON FORM 10-K

For the Year Ended December 31, 2011

TABLE OF CONTENTS

		Page
PART I
Item 1.	Business		1
Item 1A.	Risk Factors		21
Item 1B.	Unresolved Staff Comments		31
Item 2.	Properties		31
Item 3.	Legal Proceedings		33
Item 4.	Mine Safety Disclosures		33
PART II
Item 5.	Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities		34
Item 6.	Selected Consolidated Financial Data		36
Item 7.	Management’s Discussion and Analysis of Financial Condition and Results of Operations		38
Item 7A.	Quantitative and Qualitative Disclosures About Market Risk		75
Item 8.	Consolidated Financial Statements and Supplementary Data		75
Item 9.	Changes in and Disagreements with Accountants on Accounting and Financial Disclosure		75
Item 9A.	Controls and Procedures		75
Item 9B.	Other Information		76
PART III
Item 10.	Directors, Executive Officers and Corporate Governance		77
Item 11.	Executive Compensation		77
Item 12.	Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters		77
Item 13.	Certain Relationships and Related Transactions, and Director Independence		77
Item 14.	Principal Accountant Fees and Services		77
PART IV
Item 15.	Exhibits, Financial Statement Schedules		78
Signatures			79
Consolidated Financial Statements			F-1
Exhibit Index			A-1

NOTE REGARDING FORWARD-LOOKING STATEMENTS

This report contains forward-looking statements that are based on our current beliefs and expectations. These forward-looking statements may be accompanied by such words as “anticipate,” “believe,” “estimate,” “expect,” “forecast,” “intend,” “may,” “plan,” “project,” “target,” “will” and other words and terms of similar meaning. Reference is made in particular to forward-looking statements regarding:

• the anticipated amount, timing and accounting of product revenues, joint business revenues, royalty revenues, milestone and other payments under licensing, collaboration or acquisition agreements, tax positions and contingencies, effective tax rate, doubtful accounts, cost of sales, expenses, and amortization of intangible assets;

• our plans to develop further risk stratification protocols for TYSABRI and the impact of such protocols;

• product pricing and pricing pressures;

• the expected lifetime revenue of AVONEX and amortization recorded in relation to its core technology;

• the anticipated regulatory submissions for and launch of BG-12 as well as the data and market exclusivity rights associated with the commercialization of BG-12;

• additional planned launches of FAMPYRA;

• the incidence, timing, outcome and impact of proceedings related to: patents and other intellectual property rights; tax audits, assessments and settlements; product liability claims; and other legal proceedings;

• the impact of accounting standards;

• the costs and scope of, timing of enrollment and data readouts for, and regulatory actions related to, the development and commercialization of our pipeline products and services;

• the timing and financial impact of U.S. healthcare reform, including the annual fee on prescription drug manufacturers, and other measures worldwide designed to reduce healthcare costs;

• the impact that the deterioration of the credit and economic conditions in certain countries in Europe may have on the collection of outstanding receivables in such countries;

• our ability to finance our operations and business initiatives and obtain funding for such activities;

• our reliance on third parties for certain aspects of our business;

• share repurchase activity, dividends, and availability of our unrepatriated foreign earnings;

• the financial and operational impact of our restructuring initiatives;

• patent terms, patent term extensions and patent office actions;

• manufacturing capacity and contract manufacturing activity;

• the operation and development of our biosimilar arrangement with Samsung BioLogics Co. Ltd.;

• the expected financial impact of vacating our facility in Weston, MA;

• the location of, plans for, and financial impact of our manufacturing facilities, corporate headquarters and other properties; and

• the drivers for growing our business, including our plans to pursue business development and research opportunities, and competitive conditions.

These forward-looking statements involve risks and uncertainties that could cause actual results to differ materially from those reflected in such statements, including those that are described in the “Risk Factors” section of this report and elsewhere within this report. You should not place undue reliance on these statements. Forward-looking statements speak only as of the date of this report. We do not undertake any obligation to publicly update any forward-looking statements.

NOTE REGARDING COMPANY AND PRODUCT REFERENCES

Throughout this report, “Biogen Idec,” the “Company,” “we,” “us” and “our” refer to Biogen Idec Inc. and its consolidated subsidiaries. References to “RITUXAN” refer to both RITUXAN (the trade name for rituximab in the U.S., Canada and Japan) and MabThera (the trade name for rituximab outside the U.S., Canada and Japan), and “ANGIOMAX” refers to both ANGIOMAX (the trade name for bivalirudin in the U.S., Canada and Latin America) and ANGIOX (the trade name for bivalirudin in Europe).

NOTE REGARDING TRADEMARKS

AVONEX^®, AVONEX PEN^® and RITUXAN^® are registered trademarks of Biogen Idec. FUMADERM^™ is a trademark of Biogen Idec. TYSABRI^® and TOUCH^® are registered trademarks of Elan Pharmaceuticals, Inc. The following are trademarks of the respective companies listed: ACTEMRA^® — Chugai Seiyaku Kabushiki Kaisha; AMPYRA^® and FAMPYRA^® — Acorda Therapeutics, Inc.; ANGIOMAX^® and ANGIOX^® — The Medicines Company; ARZERRA^® — Glaxo Group Limited; BETASERON^® and BETAFERON^® — Bayer Schering Pharma AG; CAMPATH^® and LEMTRADA^® — Genzyme Corporation; CIMZIA^® — UCB Pharma, S.A.; COPAXONE^® — Teva Pharmaceutical Industries Limited; ENBREL^® — Immunex Corporation; EXTAVIA^® and GILENYA^® — Novartis AG; HUMIRA^® — Abbott Biotechnology Ltd.; ORENCIA^® — Bristol-Myers Squibb Company; REBIF^® — Ares Trading S.A.; REMICADE^® — Centocor Ortho Biotech Inc.; SIMPONI^® — Johnson & Johnson; and TREANDA^® — Cephalon, Inc.

PART I

Item 1. Business

Overview

Biogen Idec is a global biotechnology company that discovers, develops, manufactures and markets therapies for the treatment of neurodegenerative diseases, hemophilia and autoimmune disorders. Patients worldwide benefit from our leading multiple sclerosis therapies, and the company generates $5 billion in annual revenues.

			Product Revenues to Biogen Idec (in millions)
Product	Indications	Development or Marketing Collaborator	2011		2010		2009
AVONEX (1)	Multiple sclerosis	None	$	2,686.6	$	2,518.4	$	2,322.9
TYSABRI (2)	Multiple sclerosis Crohn’s disease	Elan Pharmaceuticals	$	1,079.5	$	900.2	$	776.0
FAMPYRA (3)	Multiple sclerosis (walking ability)	Acorda Therapeutics	$	13.6	$	—	$	—
FUMADERM (4)	Psoriasis	None	$	54.7	$	51.2	$	49.6
			Unconsolidated Joint Business Revenues to Biogen Idec (in millions)
Product	Indications	Development or Marketing Collaborator	2011		2010		2009
RITUXAN (5)	Non-Hodgkin’s lymphoma Rheumatoid arthritis Chronic lymphocytic leukemia ANCA-associated vasculitis	Genentech (Roche Group)	$	996.6	$	1,077.2	$	1,094.9

(1) AVONEX (interferon beta-1a) is indicated for the treatment of patients with relapsing forms of MS to slow the accumulation of physical disability and decrease the frequency of clinical exacerbations.

(2) TYSABRI (natalizumab) is indicated for the treatment of (1) relapsing forms of MS as a monotherapy to delay the accumulation of physical disability and reduce the frequency of clinical exacerbations and (2) in the U.S., moderately to severely active Crohn’s disease with evidence of inflammation in adult patients who have had an inadequate response to or inability to tolerate conventional Crohn’s disease therapies and TNF inhibitors.

(3) FAMPYRA (prolonged-release fampridine tablets) is indicated for the improvement of walking in adult patients with MS with walking disability (EDSS 4-7).

(4) FUMADERM (dimethylfumarate and monoethylfumarate salts) is only approved in Germany and is indicated for the treatment of adult patients with moderate to severe plaque psoriasis for whom topical therapy is ineffective.

(5) RITUXAN (rituximab) is indicated for the treatment of (1)(a) relapsed or refractory, low-grade or follicular, CD20-positive, B-cell Non-Hodgkin’s lymphoma (NHL) as a single agent, (b) previously untreated follicular, CD20-positive, B-cell NHL in combination with first line chemotherapy and, in patients achieving a complete or partial response to RITUXAN in combination with chemotherapy, as a single-agent maintenance therapy, (c) non-progressing (including stable disease), low-grade, CD20-positive, B-cell NHL, as a single agent, after first-line CVP chemotherapy, and (d) previously untreated diffuse large B-cell, CD20-positive NHL in combination with CHOP or other anthracycline-based chemotherapy regimens, (2) CD20-positive chronic lymphocytic leukemia in combination with fludarabine and cyclophosphamide,

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(3) moderately- to severely-active rheumatoid arthritis, in combination with methotrexate, in adult patients who have had an inadequate response to one or more TNF antagonist therapies, and (4) Wegener’s Granulomatosis and Microscopic Polyangiitis, in combination with glucocorticoids, in adult patients.

Additional financial information about our product revenues, other revenues and geographic areas in which we operate is set forth in our consolidated financial statements, Note 25, Segment Information to our consolidated financial statements, and Item 6. Selected Consolidated Financial Data included in this report. A discussion of the risks attendant to our international operations is set forth in the “Risk Factors” section of this report.

We devote significant resources to research and development programs and external business development opportunities, as summarized in the table below:

(In millions)	2011		2010			2009
Research and development costs	$	1,219.6	$	1,248.6		$	1,283.1
Acquired in process research and development	$	—	$	245.0	*	$	—

* $145.0 million attributed to noncontrolling interests, net of tax.

Additional information about our research and development programs and business development activity during 2011 is set forth below under the subsections entitled “Research and Development Programs” and “Business Development.”

We were formed as a California corporation in 1985 and became a Delaware corporation in 1997. In 2003, we acquired Biogen, Inc. and changed our corporate name from IDEC Pharmaceuticals Corporation to Biogen Idec Inc. Our principal executive offices are located at 133 Boston Post Road, Weston, MA 02493 and our telephone number is (781) 464-2000. Our website address is www.biogenidec.com. We make available free of charge through the Investors section of our website our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and all amendments to those reports as soon as reasonably practicable after such material is electronically filed with or furnished to the Securities and Exchange Commission (SEC). We include our website address in this report only as an inactive textual reference and do not intend it to be an active link to our website. The contents of our website are not incorporated into this filing.

Marketed Products

AVONEX

AVONEX is one of the most prescribed treatments in the world for relapsing forms of MS. MS is a progressive neurological disease in which the body loses the ability to transmit messages along nerve cells, leading to a loss of muscle control, paralysis and, in some cases, death. Patients with active relapsing MS experience an uneven pattern of disease progression characterized by periods of stability that are interrupted by flare-ups of the disease after which the patient returns to a new baseline of functioning. AVONEX is a recombinant form of the interferon beta protein produced in the body in response to viral infection.

2011 Developments

• We began making AVONEX PEN available in the E.U. and Canada following marketing approval during the first half of 2011, and we filed for marketing approval of AVONEX PEN in the U.S. AVONEX PEN is the first single-use intramuscular autoinjector designed to improve the convenience of once-weekly AVONEX administration in patients with relapsing MS.

• In June 2011, we announced clinical trial data showing that titrating AVONEX at the initiation of treatment reduced the severity of flu-like symptoms. The European Commission has approved the AVONEX titration kit, which is designed to help mitigate flu-like symptoms at the start of therapy, and we filed for marketing approval of the AVONEX titration kit in the U.S.

TYSABRI

TYSABRI has advanced the treatment of MS patients with its established efficacy. TYSABRI is a monoclonal antibody approved in numerous countries as a monotherapy treatment for relapsing MS and also approved in the U.S. to treat Crohn’s disease, an inflammatory disease of the intestines.

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TYSABRI increases the risk of progressive multifocal leukoencephalopathy (PML), an opportunistic infection of the brain by the JC virus that often leads to death or severe disability. Factors that increase the risk of PML are presence of anti-JCV antibodies, prior immunosuppressant use, and longer TYSABRI treatment duration. Patients who have all three risk factors have the highest risk of developing PML. Reports of cases of PML in patients treated with TYSABRI in clinical studies led us to voluntarily suspend the marketing and commercial distribution of TYSABRI in February 2005 until its reintroduction to the market in July 2006. Because of the risk of PML, TYSABRI has a boxed warning and is marketed under risk management or minimization plans approved by regulatory authorities. In the U.S., for example, TYSABRI is marketed under the TOUCH Prescribing Program, a restricted distribution program designed to assess and minimize the risk of PML, minimize death and disability due to PML, and promote informed risk-benefit decisions regarding TYSABRI use.

U.S. and E.U. regulators continue to monitor and assess on an ongoing basis the criteria for confirming PML diagnosis, the number of PML cases, the incidence of PML in TYSABRI patients, the risk factors for PML, and TYSABRI’s benefit-risk profile, which could result in modifications to the approved labels or other restrictions on TYSABRI treatment. We continue to research and develop protocols and therapies that may reduce risk and improve outcomes of PML in patients. For example, we are conducting two clinical studies in the U.S., known as STRATIFY-1 and STRATIFY-2, that collectively are intended to define the prevalence of serum JC virus antibody in patients with relapsing MS receiving or considering treatment with TYSABRI and to stratify patients into lower or higher risk for developing PML based on antibody status.

We collaborate with Elan on the development and commercialization of TYSABRI. For information about this collaboration, please read Note 20, Collaborations to our consolidated financial statements included in this report.

2011-2012 Developments

• In January 2012, the FDA approved the inclusion of anti-JCV antibody status as an additional factor in stratifying patients for developing PML in the U.S. product label for TYSABRI. The FDA also approved the inclusion of a table summarizing the estimated incidence of PML according to the duration of TYSABRI treatment, prior immunosuppressant use and anti-JCV antibody status. In addition, the FDA granted Quest Diagnostics a de novo classification petition for the STRATIFY JCV Antibody ELISA testing service, which allows neurologists to determine their MS patients’ anti-JCV antibody status.

• In August 2011, our JC virus assay became commercially available broadly in the U.S. The assay was developed to detect the presence of anti-JC virus antibodies in human serum and plasma. The assay became commercially available broadly in the E.U. in May 2011. The cost of the assay is currently shared by us and Elan.

• In June 2011, the European Commission approved the inclusion of anti-JC virus antibody status as an additional factor in stratifying patients for developing PML in the E.U. product label for TYSABRI.

• In June 2011, as part of a standard review process, the European Commission concluded that the quality, safety and efficacy of TYSABRI continue to be adequately demonstrated and renewed the E.U. five-year marketing authorization for TYSABRI. TYSABRI will undergo a second renewal process in another five years.

RITUXAN

RITUXAN is a widely prescribed monoclonal antibody therapeutic used to treat non-Hodgkin’s lymphoma, rheumatoid arthritis, chronic lymphocytic leukemia and two forms of ANCA-associated vasculitis. Non-Hodgkin’s lymphoma and chronic lymphocytic leukemia are cancers that affect lymphocytes, which are a type of white blood cell that help to fight infection. Rheumatoid arthritis is a chronic disease that occurs when the immune system mistakenly attacks the body’s joints, resulting in inflammation, pain and joint damage. ANCA-associated vasculitis is a rare autoimmune disease that largely affects the small blood vessels of the kidneys, lungs, sinuses, and a variety of other organs.

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We collaborate with Genentech on the development and commercialization of RITUXAN. For information about this collaboration, please read Note 20, Collaborations to our consolidated financial statements included in this report.

2011 Developments

• In April 2011, the FDA approved RITUXAN, in combination with corticosteroids, as a treatment for adults with Wegener’s granulomatosis and microscopic polyangiitis, two forms of ANCA-associated vasculitis.

• In January 2011, the FDA approved RITUXAN as a maintenance treatment for patients with advanced follicular lymphoma who responded to initial treatment with RITUXAN plus chemotherapy (induction treatment). The European Commission approved RITUXAN for this indication in October 2010.

FAMPYRA

FAMPYRA is the first treatment that addresses the unmet medical need of walking improvement in adult patients with MS who have walking disability. FAMPYRA is a prolonged-release tablet formulation of the drug fampridine. We launched FAMPYRA in Australia, Denmark, Germany, Norway and the U.K. in 2011 and plan to launch in additional markets during 2012. We have a license from Acorda Therapeutics, Inc. to develop and commercialize FAMPYRA in all markets outside the U.S. For information about this relationship, please read Note 20, Collaborations to our consolidated financial statements included in this report.

2011 Developments

• In July 2011, the European Commission granted a conditional marketing authorization for FAMPYRA in the E.U. To meet the conditions of this marketing authorization, we will provide additional data from on-going clinical studies regarding FAMPYRA’s benefits and safety in the long term. A conditional marketing authorization is renewable annually and is granted to a medicinal product with a positive benefit/risk assessment that fulfills an unmet medical need when the benefit to public health of immediate availability outweighs the risk inherent in the fact that additional data are still required.

• In May 2011, the Australian Therapeutics Goods Administration granted marketing approval for FAMPRYA in Australia.

FUMADERM

FUMADERM is approved for the treatment of severe psoriasis in Germany. Psoriasis is a skin disease in which cells build up on the skin surface and form scales and red patches.

Other Sources of Revenue

Our primary source of other revenue is derived from royalties received on sales by our licensees of other products covered under patents that we own. Our royalty revenues are dependent upon our licensees’ sales of licensed products which could vary significantly due to competition, manufacturing, regulatory, safety or efficacy issues or other factors that are outside our control. In addition, the expiration or invalidation of any underlying patents could reduce or eliminate the royalty revenues derived from such patents. Royalties on sales of ANGIOMAX by The Medicines Company (TMC) represent our most significant source of other revenue. TMC markets ANGIOMAX primarily in the U.S. and the E.U. for use as an anticoagulant in patients undergoing percutaneous coronary intervention. For a description of this royalty arrangement and factors that could adversely affect this portion of our revenues, please read the subsection entitled “Other Revenues — Royalty Revenues” in the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” section of this report.

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We have also sold or exclusively licensed to third parties rights to certain products previously included within our product line. Supply agreement revenues received based upon those products are recorded as corporate partner revenues within our consolidated statements of income. Amounts recorded as corporate partner revenue also include amounts earned upon delivery of product under contract manufacturing agreements.

(In millions)	2011		2010		2009
Royalty revenues	$	158.5	$	137.4	$	124.4
Corporate partner revenues	$	57.4	$	31.7	$	5.1

2011 Developments

• The principal U.S. patent that covers ANGIOMAX (’404 Patent) was due to expire in March 2010 and TMC applied for an extension of the term of this patent. Initially, the U.S. Patent and Trademark Office (PTO) rejected TMC’s application because in its view the application was not timely filed. TMC sued the PTO in federal district court seeking to extend the term of the ’404 patent to December 2014. On August 3, 2010, the federal district court ordered the PTO to deem the application as timely filed. The PTO has granted an interim extension of the patent term until August 13, 2012 pending completion of its review of TMC’s application. A generic manufacturer challenged the federal district court’s order in an appellate proceeding, but on January 23, 2012 the manufacturer filed a motion to dismiss its appeal. The PTO has granted an interim extension of the patent term until August 23, 2012 pending completion of its review of TMC’s application for extension to December 2014. For more information about our royalty revenues derived from sales of ANGIOMAX, please read the subsection entitled “Other Revenues - Royalty Revenues” in the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” section of this report.

Research and Development Programs

A commitment to research is fundamental to our mission at Biogen Idec. Our research and development strategy is to discover and develop first-in-class molecules or best-in-class molecules that improve safety or efficacy for unmet medical needs. By applying our expertise in biologics and our growing capabilities in small-molecule drug discovery and development, we target specific medical needs where new or better treatments are needed.

We intend to continue committing significant resources to research and development opportunities and business development activity. As part of our ongoing research and development efforts, we have devoted significant resources to conducting clinical studies to advance the development of new pharmaceutical products and to explore the utility of our existing products in treating disorders beyond those currently approved in their labels. The table below highlights our current research and development programs. Drug development involves a high degree of risk and investment, and the status, timing and scope of our development programs are subject to change. Important factors that could adversely affect our drug development efforts are discussed in the “Risk Factors” section of this report.

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Therapeutic Area	Product Candidate	Targeted Indications	Status
Neurology	BG-12	MS (monotherapy)	Plan to file for marketing approval
	Daclizumab	MS	Phase 3
	Dexpramipexole	Amyotrophic lateral sclerosis	Phase 3
	PEGylated interferon beta 1a	MS	Phase 3
	TYSABRI	Secondary-progressive MS	Phase 3
	BG-12	MS (combination therapy)	Phase 2
	Anti-LINGO	MS	Phase 2
	BIIB037	Alzheimer’s disease	Phase 1
	ISIS – SMNRx	Spinal muscular atrophy	Phase 1
	Neublastin	Neuropathic pain	Phase 1
	BIIB053	MS	Preclinical
	BIIB054	Parkinson’s disease	Preclinical
Hemophilia	Factor VIII Fc	Hemophilia A	Phase 3
	Factor IX Fc	Hemophilia B	Phase 3
Immunology	Anti-TWEAK	Lupus nephritis	Phase 2
	Anti-CD40 Ligand	General lupus	Phase 1
	Syk inhibitor	Rheumatoid arthritis and systemic lupus erythematosus	Phase 1
Other	GA101	Chronic lymphocytic leukemia	Phase 3
	GA101	Non-Hodgkin’s lymphoma	Phase 3

Late Stage Product Candidates

Additional information about our late stage product candidates is set forth below.

BG-12

In April 2011, we announced positive top-line results from DEFINE, the first of two pivotal Phase 3 clinical trials designed to evaluate our investigational oral compound BG-12 (dimethyl fumarate) as a monotherapy in relapsing MS. Results showed that 240 mg of BG-12, administered either twice or three times a day, met the primary and secondary study endpoints with a favorable safety and tolerability profile. In October 2011, we announced positive top-line results from CONFIRM, the second of such pivotal Phase 3 clinical trials. Results showed that 240 mg of BG-12, administered either twice a day or three times a day, demonstrated significant efficacy and favorable safety and tolerability profiles. We are preparing regulatory submissions for BG-12 based on the positive results from these two trials.

We acquired BG-12 as part of our acquisition of Fumapharm AG in 2006. For more information about this acquisition and associated milestone obligations, please read the subsection entitled “Contractual Obligations and Off-Balance Sheet Arrangements—Contingent Consideration” in the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” section of this report.

Daclizumab

Daclizumab is a monoclonal antibody that is being tested in relapsing MS. In May 2010, we began patient enrollment in a Phase 3 study of daclizumab in relapsing MS, known as DECIDE, evaluating the efficacy and safety of daclizumab compared to interferon beta-1a (AVONEX). The DECIDE trial is designed to have a two year endpoint and is expected to involve approximately 1,800 patients.

In August 2011, we announced positive results from SELECT, a global, registrational Phase 2b clinical trial designed to evaluate daclizumab in relapsing MS over one year. Results showed that daclizumab, administered subcutaneously once every four weeks, met primary and key secondary study endpoints, compared to placebo.

We collaborate with Abbott Biotherapeutics Corporation (Abbott) on the development and commercialization of daclizumab. For information about this collaboration, please read Note 20, Collaborations to our consolidated financial statements included in this report.

Dexpramipexole

Dexpramipexole is an orally administered small molecule in clinical development for the treatment of amyotrophic lateral sclerosis (ALS). ALS, also known as Lou Gehrig’s disease and motor neuron disease, is a rapidly fatal, neurodegenerative disorder characterized by progressive muscle weakness and wasting. In the

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fourth quarter of 2011, we completed enrollment in a Phase 3 study, known as EMPOWER, that is designed to follow patients for 1 year to evaluate the efficacy and safety of dexpramipexole in patients with ALS. There are over 900 patients participating in the study worldwide. Dexpramipexole has been granted fast track status by the FDA and has received orphan drug designation for the treatment of ALS from both the FDA and EMA.

We have a license agreement with Knopp Neurosciences, Inc. (Knopp) for the development, manufacture and commercialization of dexpramipexole. For information about this relationship, please read Note 19, Investments in Variable Interest Entities to our consolidated financial statements included in this report.

PEGylated interferon beta-1a

PEGylated interferon beta-1a is designed to prolong the effects and reduce the dosing frequency of interferon beta-1a. In the fourth quarter of 2011 we completed patient enrollment in a Phase 3 trial of PEGylated interferon beta-1a in relapsing MS, known as ADVANCE, that is designed to have a one year primary endpoint and involve approximately 1,500 patients. The FDA has granted PEGylated interferon beta-1a fast track status.

TYSABRI (SPMS)

As part of our efforts with Elan to identify additional applications for TYSABRI, we began patient enrollment in a Phase 3b study of TYSABRI in secondary progressive MS, known as ASCEND. The study is designed to have an endpoint of approximately two years and involve approximately 850 patients.

Long-Lasting Recombinant Factors VIII and IX

Factor VIII is a proprietary fusion protein that is being tested in hemophilia A, a disorder in which blood clotting is impaired. In November 2010, we began patient enrollment in a registrational trial of Factor VIII in hemophilia A, known as A-LONG. This study will involve approximately 150 patients. Factor VIII has received orphan drug and fast track designation for the treatment of hemophilia A from both the FDA and EMA.

Factor IX is a proprietary fusion protein that is being tested in hemophilia B, a disorder in which blood clotting is impaired. In December 2009, we began patient enrollment in a registrational trial of Factor IX in hemophilia B, known as B-LONG. This study will involve approximately 100 patients. Factor IX has received orphan drug and fast track designation for the treatment of hemophilia B from both the FDA and EMA.

In 2011, we received opinions from the EMA’s Pediatric Committee (PDCO) agreeing to pediatric investigational plans for Factor VIII and Factor IX. In accordance with the PDCO’s opinion, we plan to initiate global pediatric trials in previously-treated patients less than 12 years of age as soon as sufficient data are available from studies of older patients. The PDCO opinions for Factor VIII and Factor IX are under guidelines published by the EMA for the development of Factor IX and Factor VIII products. Pediatric data from these trials will be required in the initial submission of Marketing Authorization Applications to the European regulatory agency.

We collaborate with Swedish Orphan Biovitrum AB on the commercialization of long-lasting recombinant Factors VIII and IX. For information about this collaboration, please read Note 20, Collaborations to our consolidated financial statements included in this report.

GA101

We collaborate with Genentech, Inc., a wholly-owned member of the Roche Group, on the development and commercialization of GA101, a monoclonal antibody. Genentech and Roche are managing the following Phase 3 trials of GA101:

• GOYA: investigating the efficacy and safety of GA101 in combination with CHOP chemotherapy compared to RITUXAN with CHOP chemotherapy in previously untreated patients with CD20-positive diffuse large B-cell lymphoma.

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• GALLIUM: investigating the efficacy and safety of GA101 in combination with chemotherapy followed by maintenance with GA101 compared to RITUXAN in combination with chemotherapy followed by maintenance with RITUXAN in previously untreated patients with indolent non-Hodgkin’s lymphoma.

• GADOLIN: investigating the efficacy and safety of GA101 plus bendamustine compared with bendamustine alone in patients with RITUXAN-refractory, indolent non-Hodgkin’s lymphoma.

• CLL11: investigating the safety and efficacy of GA101 plus chlorambucil compared to RITUXAN plus chlorambucil or chlorambucil alone in previously untreated chronic lymphocytic leukemia patients with co-morbidities.

For information about our collaboration with Genentech, please read Note 20, Collaborations to our consolidated financial statements included in this report.

Business Development

In January 2012, we entered into an exclusive, worldwide option and development agreement with Isis Pharmaceuticals, Inc. (Isis) under which both companies will develop and commercialize Isis’ antisense investigational drug, ISIS-SMN_Rx, for the treatment of spinal muscular atrophy. For additional information about this transaction, please read Note 27, Subsequent Events to our consolidated financial statements included in this report.

In December 2011, we entered into an agreement with Samsung BioLogics Co. Ltd. (Samsung) to establish an entity to develop, manufacture and market biosimilars. Completion of the transaction is subject to customary closing conditions. For additional information about this transaction, please read Note 19, Investments in Variable Interest Entities to our consolidated financial statements included in this report.

In October 2011, we entered into an exclusive, worldwide collaboration and license agreement with Portola Pharmaceuticals, Inc. under which both companies will develop and commercialize highly selective, novel oral Syk inhibitors for the treatment of various autoimmune and inflammatory diseases, including rheumatoid arthritis and systemic lupus erythematosus. For additional information about this transaction, please read Note 20, Collaborations to our consolidated financial statements included in this report.

In September 2011, we acquired from the Dompé Group the noncontrolling interests in our joint venture sales affiliates in Italy and Switzerland. For additional information about this transaction, please read Note 2, Acquisitions to our consolidated financial statements included in this report.

Patents and Other Proprietary Rights

Patents are important to developing and protecting our competitive position. We regularly seek patent protection in the U.S. and in selected countries outside the U.S. for inventions originating from our research and development efforts. In addition, we license rights to various patents and patent applications, generally, in return for the payment of royalties to the patent owner. U.S. patents, as well as most foreign patents, are generally effective for 20 years from the date the earliest (priority) application was filed; however, U.S. patents that issue on applications filed before June 8, 1995 may be effective until 17 years from the issue date, if that is later than the 20 year date. In some cases, the patent term may be extended to recapture a portion of the term lost during FDA regulatory review or because of U.S. Patent and Trademark Office (USPTO) delays in prosecuting the application. The duration of foreign patents varies similarly, in accordance with local law.

Regulatory data protection also can provide meaningful protection for our products. Regulatory data protection provides to the holder of a drug or biologic marketing authorization, for a set period of time, the exclusive use of the proprietary pre-clinical and clinical data that it compiled at significant cost and submitted to the applicable regulatory authority to obtain approval of its product. After the set period of time, third parties are then permitted to rely upon the data to obtain approval of their abbreviated applications to market generic drugs and biosimilars. Although the World Trade Organization’s agreement on trade-related aspects of intellectual property rights (TRIPS) requires signatory countries to provide regulatory data protection to innovative pharmaceutical products, implementation and enforcement varies widely from country to country.

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We also rely upon other forms of unpatented confidential information to remain competitive. We protect such information principally through confidentiality agreements with our employees, consultants, outside scientific collaborators, scientists whose research we sponsor and other advisers. In the case of our employees, these agreements also provide, in compliance with relevant law, that inventions and other intellectual property conceived by such employees during their employment shall be our exclusive property.

Our trademarks, including RITUXAN and AVONEX, are important to us and are generally covered by trademark applications or registrations in the USPTO and the patent or trademark offices of other countries. We also use trademarks licensed from third parties, such as the mark TYSABRI which we license from Elan. Trademark protection varies in accordance with local law, and continues in some countries as long as the mark is used and in other countries as long as the mark is registered. Trademark registrations generally are for fixed but renewable terms.

A discussion of certain risks and uncertainties that may affect our patent position and proprietary rights is set forth in the “Risk Factors” section of this report.

Additional information about the patents and other proprietary rights covering our marketed products and BG-12 is set forth below.

AVONEX and Beta Interferon

Our U.S. patent No. 7,588,755, granted in September 2009, claims the use of recombinant beta interferon for immunomodulation or treating a viral condition, viral disease, cancers or tumors. This patent, which expires in September 2026, covers, among other things, the treatment of MS with our product AVONEX. A discussion of certain legal proceedings related to this patent is set forth in Note 21, Litigation to our consolidated financial statements included in this report.

We have non-exclusive rights under certain third-party patents and patent applications to manufacture, use and sell AVONEX, including a patent owned by the Japanese Foundation for Cancer Research, which expires in 2013 in the U.S., and a European patent owned by Rentschler Biotechnologie GmbH, which expires in 2012. Additionally, we and third parties own pending U.S. patent applications related to recombinant interferon-beta protein and nucleic acid. These applications, which fall outside of the GATT amendments to the U.S. patent statute, are not published by the USPTO and, if they mature into granted patents, may be entitled to a term of seventeen years from the grant date. There are two pending interference proceedings in the USPTO involving such third party applications, and additional interferences could be declared in the future. We do not know which, if any, such applications will mature into patents with claims relevant to our AVONEX product.

TYSABRI

We and our collaborator, Elan, have patents and patent applications covering TYSABRI in the U.S. and other countries. These patents and patent applications cover TYSABRI and related manufacturing methods, as well as various methods of treatment using the product. In the U.S., the principal patents covering the product and use of the product to treat MS generally expire between 2015 and 2020. Additional U.S. patents and applications covering other indications, including treatment of inflammatory bowel disease, and methods of manufacturing, generally expire between 2012 and 2020. In the rest of world, patents on the product and methods of manufacturing the product generally expire between 2015 and 2020, subject to any supplemental protection (i.e., patent term extension) certificates that may be obtained. In the rest of world, patents and patent applications covering methods of treatment using TYSABRI generally expire between 2012 and 2020.

RITUXAN and Anti-CD20 Antibodies

We have several U.S. patents and patent applications, and numerous corresponding foreign counterparts, directed to anti-CD20 antibody technology, including RITUXAN. The principal patents with claims to RITUXAN or its uses expire in the U.S. between 2015 and 2018 and in the rest of the world in 2013, subject to any available patent term extensions. In addition, we and our collaborator, Genentech, have filed numerous

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patent applications directed to anti-CD20 antibodies and their uses to treat various diseases. These pending patent applications have the potential of issuing as patents in the U.S. and in the rest of world with claims to anti-CD20 antibody molecules for periods beyond those stated above for RITUXAN. In 2008, a European patent of ours claiming the treatment with anti-CD20 antibodies of certain auto-immune indications, including RA, was revoked by the European Patent Office. We are appealing that decision.

Genentech, our collaborator on RITUXAN, has secured an exclusive license to five U.S. patents and counterpart U.S. and foreign patent applications assigned to Xoma Corporation that relate to chimeric antibodies against the CD20 antigen. These patents expire between 2007 and 2014. Genentech has granted us a non-exclusive sublicense to make, have made, use and sell RITUXAN under these patents and patent applications. We, along with Genentech, share the cost of any royalties due to Xoma in our co-promotion territory on sales of RITUXAN.

FAMPYRA

We have an exclusive license under two European granted patents, several pending European patent applications and numerous corresponding non-U.S. counterpart applications related to FAMPYRA. One of the granted European patents claims pharmaceutical formulations containing aminopyridines such as fampridine. This patent expired in November 2011 but is subject to pending supplemental protection (i.e., patent term extension) certificates which, if granted, will extend to 2016. The other European patent, EP Patent 1732548B1, which claims sustained-release aminopyridine compositions for increasing walking speed in patients with MS, was granted in 2011. The patent expires in 2025 but is subject to pending supplemental protection certificates which, if granted, will extend to 2026. In addition we have a license under several pending applications directed to various uses of fampridine, some of which, if granted, would expire as late as 2030.

In addition to patent protection, FAMPYRA is protected by regulatory data protection in Europe until 2021.

BG-12

We have several U.S. patents and patent applications, and a number of corresponding foreign counterparts, related to BG-12. The principal U.S. patents are U.S. 6,509,376, having claims to formulations of dimethyl fumarate (the active ingredient of BG-12) for use in the therapy of autoimmune diseases including MS, and U.S. 7,320,999 having claims to a method of treating MS using dimethyl fumarate. U.S. 6,509,376 and U.S. 7,320,999, expire in 2019 and 2020, respectively, subject to any available patent term extension following product approval. The granted European patent, EP 1131065, is directed to formulations of dimethyl fumarate and to uses thereof for treating autoimmune diseases, including MS. EP 1131065 expires in 2019, subject to any potential supplemental patent certificates that may be available. The pending applications, if granted, would expire as late as 2032, subject to any potential patent term extensions that may be available following product approval.

In addition to patent protection, BG-12 is entitled to regulatory data protection. In the U.S., BG-12 is entitled to the 5 year data exclusivity given to new chemical entities. In the E.U. there are a number of ways to obtain data exclusivity and we have confirmation from the EMA that BG-12 would, in principle, be eligible for 8 years data exclusivity plus 2 years market exclusivity based on information planned to be submitted to the agency as part of the European centralized filing pathway.

Sales, Marketing and Distribution

We focus our sales and marketing efforts on specialist physicians in private practice or at major medical centers. We use customary pharmaceutical company practices to market our products and to educate physicians, such as sales representatives calling on individual physicians, advertisements, professional symposia, direct mail, public relations and other methods. We provide customer service and other related programs for our products, such as disease and product-specific websites, insurance research services and order, delivery and fulfillment services. We have also established programs in the U.S. which provide qualified uninsured or underinsured patients with marketed products at no or reduced charge, based on specific eligibility criteria. Additional information about our sales, marketing and distribution efforts for our marketed products is set forth below.

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AVONEX

We continue to focus our marketing and sales activities on maximizing the potential of AVONEX in the U.S. and the rest of world in the face of increased competition. The principal markets for AVONEX are the U.S., Germany, France and Italy. In the U.S., Canada, Brazil, Argentina, Australia, Japan and most of the major countries of the E.U., we market and sell AVONEX through our own sales forces and marketing groups and distribute AVONEX principally through wholesale distributors of pharmaceutical products, mail order specialty distributors or shipping service providers. In other countries, we sell AVONEX to distribution partners who are then responsible for most marketing and distribution activities.

TYSABRI

The principal markets for TYSABRI are the U.S., France, Germany, Italy, Spain and the United Kingdom.

In the U.S., we are principally responsible for marketing TYSABRI for MS and use our own sales force and marketing group for this. Elan is responsible for TYSABRI distribution in the U.S. and uses a third party distributor to ship TYSABRI directly to customers.

In the rest of world, we are responsible for TYSABRI marketing and distribution and we use a combination of our own sales force and marketing group and third party service providers.

RITUXAN

The Roche Group and its sub-licensees market and sell RITUXAN worldwide. We collaborate with Genentech on the development and commercialization of RITUXAN, but Genentech maintains sole responsibility for the U.S. sales and marketing efforts related to RITUXAN. RITUXAN is generally sold to wholesalers, specialty distributors and directly to hospital pharmacies.

FAMPYRA

We market and sell FAMPYRA outside the U.S. through our own sales forces and marketing groups. Our development and commercialization rights do not include the U.S. market.

FUMADERM

FUMADERM is marketed only in Germany, through our own sales force and marketing group.

Competition

Competition in the biotechnology and pharmaceutical industries is intense and comes from many and varied sources, including specialized biotechnology firms and large pharmaceutical companies. Many of our competitors are working to develop products similar to those we are developing or already market and have considerable experience in undertaking clinical trials and in obtaining regulatory approval to market pharmaceutical products. Certain of these companies have substantially greater financial, marketing and research and development resources than we do.

We believe that competition and leadership in the industry will be based on managerial and technological superiority and establishing patent and other proprietary positions through research and development. The achievement of a leadership position also depends largely upon our ability to identify and exploit commercially the products resulting from research and the availability of adequate financial resources to fund facilities, equipment, personnel, clinical testing, manufacturing and marketing. Another key aspect of remaining competitive within the industry is recruiting and retaining qualified scientists and technicians. We believe that we have been successful in attracting skilled and experienced scientific personnel.

Competition among products approved for sale may be based, among other things, on patent position, product efficacy, safety, convenience, reliability, availability and price. In addition, early entry of a new pharmaceutical product into the market may have important advantages in gaining product acceptance and

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market share. Accordingly, the relative speed with which we can develop products, complete the testing and approval process and supply commercial quantities of products will have an important impact on our competitive position.

We may face increased competitive pressures as a result of the emergence of biosimilars. In the U.S., most of our marketed products, including AVONEX, TYSABRI and RITUXAN, are licensed under the Public Health Service Act (PHSA) as biological products. In March 2010, U.S. healthcare reform legislation amended the PHSA to authorize the FDA to approve biological products, known as biosimilars or follow-on biologics, that are shown to be highly similar to previously approved biological products based upon potentially abbreviated data packages. The approval pathway for biosimilars does, however, grant a biologics manufacturer a 12 year period of exclusivity from the date of approval of its biological product before biosimilar competition can be introduced. Biosimilars legislation has also been in place in the E.U. since 2003. In November 2010, draft guidelines issued by the EMA for approving biosimilars of marketed monoclonal antibody products were adopted by the Committee for Medicinal Products for Human Use (CHMP). These guidelines are now out for public consultation. If a biosimilar version of one of our products were approved, it could reduce our sales of that product.

Additional information about the competition that our marketed products face is set forth below.

AVONEX AND TYSABRI

Each of AVONEX and TYSABRI competes with the following products:

• COPAXONE (glatiramer acetate), which is marketed by Teva Pharmaceutical Industries Ltd. in the U.S. and copromoted by Teva Pharmaceutical Industries and Sanofi-Aventis in Europe. COPAXONE generated worldwide revenues of approximately $3.3 billion in 2010.

• REBIF (interferon-beta-1a), which is co-promoted by EMD Serono, a subsidiary of Merck Serono, and Pfizer Inc. in the U.S. and is marketed by Merck Serono in the E.U. REBIF generated worldwide revenues of approximately $2.3 billion in 2010.

• BETASERON (interferon-beta-1b), which is marketed by Bayer HealthCare Pharmaceuticals, the U.S. pharmaceuticals affiliate of Bayer Schering Pharma AG, in the U.S. and is marketed under the name BETAFERON by Bayer Schering Pharma AG in the E.U. BETASERON and BETAFERON together generated worldwide revenues of approximately $1.7 billion in 2010.

• EXTAVIA (interferon-beta-1b), which is marketed by Novartis AG in the U.S., E.U. and other markets. EXTAVIA generated worldwide revenues of approximately $124.0 million in 2010.

• GILENYA (fingolimod), which is marketed by Novartis AG in the U.S., E.U. and other markets. GILENYA was launched in October 2010 as the first oral MS drug approved in the U.S. GILENYA generated revenue of approximately $15.0 million in 2010 and $494.0 million in 2011.

Along with us, a number of companies are working to develop additional treatments for MS that may in the future compete with AVONEX, TYSABRI or both. For example, teriflunomide (developed by Sanofi-Aventis) and LEMTRADA (alemtuzumab) (developed by Genzyme Corporation) have filed or are expected to file for marketing approval as treatments for MS. In addition, the commercialization of certain of our own pipeline product candidates, such as BG-12, may also negatively impact future sales of AVONEX, TYSABRI or both.

FAMPYRA

FAMPYRA is indicated as a treatment to improve walking in adult patients with MS who have walking disability and is the first treatment that addresses this unmet medical need with demonstrated efficacy in people with all types of MS. AMPYRA (dalfampridine) is protected by exclusivity rights that prohibit a generic version of the drug from being manufactured. However, the exclusivity rights are set to expire in 2017, which is the earliest predictable date that a generic version may be available. There are no commercially available generic versions of FAMPYRA.

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FUMADERM

FUMADERM competes with several different types of therapies in the psoriasis market within Germany, including oral systemics such as methotrexate and cyclosporine.

RITUXAN IN ONCOLOGY

RITUXAN competes with several different types of therapies in the oncology market, including:

• CAMPATH (alemtuzumab) (marketed by Bayer HealthCare Pharmaceuticals), which is indicated for B-cell CLL.

• TREANDA (bendamustine HCL) (marketed by Cephalon) and ARZERRA (ofatumumab) (marketed by GenMab in collaboration with GlaxoSmithKline), which is indicated for refractory CLL patients to both alemtuzumab and fludarabine.

We are also aware of other anti-CD20 molecules in development, including our own product candidate GA101, that, if successfully developed and registered, may compete with RITUXAN in the oncology market.

RITUXAN IN RA

RITUXAN competes with several different types of therapies in the RA market, including:

• traditional therapies for RA, including disease-modifying anti-rheumatic drugs such as steroids, methotrexate and cyclosporine, and pain relievers such as acetaminophen.

• TNF inhibitors, such as REMICADE (infliximab) and SIMPONI (golimumab) (marketed by Johnson & Johnson), HUMIRA (adalimumab) (marketed by Abbott Laboratories), ENBREL (etanercept) (marketed by Amgen, Inc. and Pfizer) and CIMZIA (certolizumab pegol) (marketed by UCB, S.A.).

• ORENCIA (abatacept) (marketed by Bristol-Myers Squibb Company).

• ACTEMRA (tocilizumab) (marketed by the Roche Group).

We are also aware of other products in development that, if successfully developed and registered, may compete with RITUXAN in the RA market.

Regulatory

Our current and contemplated activities and the products and processes that will result from such activities are subject to substantial government regulation.

Regulation of Pharmaceuticals

Product Approval and Post-Approval Regulation in the United States

Before new pharmaceutical products may be sold in the U.S., preclinical studies and clinical trials of the products must be conducted and the results submitted to the FDA for approval. With limited exceptions, the FDA requires companies to register both pre-approval and post-approval clinical trials and disclose clinical trial results in public databases. Failure to register a trial or disclose study results within the required time periods could result in penalties, including civil monetary penalties. Clinical trial programs must establish efficacy, determine an appropriate dose and dosing regimen, and define the conditions for safe use. This is a high-risk process that requires stepwise clinical studies in which the candidate product must successfully meet predetermined endpoints. The results of the preclinical and clinical testing of a product are then submitted to the FDA in the form of a Biologics License Application (BLA) or a New Drug Application (NDA). In response to a BLA or NDA, the FDA may grant marketing approval, request additional information or deny the application if it determines the application does not provide an adequate basis for approval.

The receipt of regulatory approval often takes a number of years, involves the expenditure of substantial resources and depends on a number of factors, including the severity of the disease in question, the availability of alternative treatments, potential safety signals observed in preclinical or clinical tests, and the risks and benefits

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of the product as demonstrated in clinical trials. The FDA has substantial discretion in the product approval process, and it is impossible to predict with any certainty whether and when the FDA will grant marketing approval. The agency may on occasion require the sponsor of a BLA or NDA to conduct additional clinical studies or to provide other scientific or technical information about the product, and these additional requirements may lead to unanticipated delay or expense.

The FDA has developed three distinct approaches intended to make therapeutically important drugs available as rapidly as possible, especially when the drugs are the first available treatment or have advantages over existing treatments: accelerated approval, fast track and priority review.

The FDA may grant “accelerated approval” status to products that treat serious or life-threatening illnesses and that provide meaningful therapeutic benefits to patients over existing treatments. Under this pathway, the FDA may approve a product based on surrogate endpoints, or clinical endpoints other than survival or irreversible morbidity. When approval is based on surrogate endpoints or clinical endpoints other than survival or morbidity, the sponsor will be required to conduct additional post-approval clinical studies to verify and describe clinical benefit. Under the Agency’s Accelerated Approval regulations, if the FDA concludes that a drug that has shown to be effective can be safely used only if distribution or use is restricted, it will require certain post-marketing restrictions as necessary to assure safe use. In addition, for products approved under accelerated approval, sponsors must submit all copies of their promotional materials, including advertisements, to the FDA at least thirty days prior to initial dissemination. The FDA may withdraw approval under accelerated approval after a hearing if, for instance, post-marketing studies fail to verify any clinical benefit, it becomes clear that restrictions on the distribution of the product are inadequate to ensure its safe use, or if a sponsor fails to comply with the conditions of the accelerated approval.

In addition, the FDA may grant “fast track” status to products that treat serious diseases and fill an unmet medical need. Fast track is a process designed to expedite the review of such products by providing, among other things, more frequent meetings with the FDA to discuss the product’s development plan, more frequent written correspondence from the FDA about trial design, eligibility for accelerated approval, and rolling review, which allows submission of individually completed sections of a NDA or BLA for FDA review before the entire filing is completed. Fast track status does not ensure that a product will be developed more quickly or receive FDA approval.

Finally, the FDA may grant “priority review” status to products that offer major advances in treatment or provide a treatment where no adequate therapy exists. Priority review is intended to reduce the time it takes for the FDA to review a NDA or BLA, with the goal for completing a priority review being six months (compared to ten months under standard review).

Regardless of the approval pathway employed, the FDA may require a sponsor to conduct additional post-marketing studies as a condition of approval to provide data on safety and effectiveness. If a sponsor fails to conduct the required studies, the agency may withdraw its approval. In addition, regardless of the approval pathway, if the FDA concludes that a drug that has shown to be effective can be safely used only if distribution or use is restricted, it can mandate post-marketing restrictions as necessary to assure safe use. In such a case, the sponsor may be required to establish rigorous systems to assure use of the product under safe conditions. These systems are usually referred to as Risk Evaluation and Mitigation Strategies (REMS). The FDA can impose financial penalties for failing to comply with certain post-marketing commitments, including REMS. In addition, any changes to an approved REMS must be reviewed and approved by the FDA prior to implementation.

The FDA tracks information on side effects and adverse events reported during clinical studies and after marketing approval. Non-compliance with the FDA’s safety reporting requirements may result in civil or criminal penalties. Side effects or adverse events that are reported during clinical trials can delay, impede, or prevent marketing approval. Based on new safety information that emerges after approval, the FDA can mandate product labeling changes, impose a new REMS or the addition of elements to an existing REMS, require new post-marketing studies (including additional clinical trials), or suspend or withdraw approval of the product. These requirements may affect our ability to maintain marketing approval of our products or require us to make significant expenditures to obtain or maintain such approvals.

If we seek to make certain types of changes to an approved product, such as adding a new indication, making certain manufacturing changes, or changing manufacturers or suppliers of certain ingredients or components, the FDA will need to review and approve such changes in advance. In the case of a new indication,

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we are required to demonstrate with additional clinical data that the product is safe and effective for a use other than that initially approved. FDA regulatory review may result in denial or modification of the planned changes, or requirements to conduct additional tests or evaluations that can substantially delay or increase the cost of the planned changes.

In addition, the FDA regulates all advertising and promotion activities for products under its jurisdiction both before and after approval. A company can make only those claims relating to safety and efficacy that are approved by the FDA. However, physicians may prescribe legally available drugs for uses that are not described in the drug’s labeling. Such off-label uses are common across medical specialties, and often reflect a physician’s belief that the off-label use is the best treatment for patients. The FDA does not regulate the behavior of physicians in their choice of treatments, but the FDA regulations do impose stringent restrictions on manufacturers’ communications regarding off-label uses. Failure to comply with applicable FDA requirements may subject a company to adverse publicity, enforcement action by the FDA, corrective advertising, and the full range of civil and criminal penalties available to the FDA.

Product Approval and Post-Approval Regulation Outside the United States

We market our products in numerous jurisdictions outside the U.S. Most of these jurisdictions have product approval and post-approval regulatory processes that are similar in principle to those in the U.S. In Europe, where most of our ex-U.S. efforts are focused, there are several tracks for marketing approval, depending on the type of product for which approval is sought. Under the centralized procedure, a company submits a single application to the EMA. The marketing application is similar to the NDA or BLA in the U.S. and is evaluated by the CHMP, the expert scientific committee of the EMA. If the CHMP determines that the marketing application fulfills the requirements for quality, safety, and efficacy, it will submit a favorable opinion to the European Commission (EC). The CHMP opinion is not binding, but is typically adopted by the EC. A marketing application approved by the EC is valid in all member states. The centralized procedure is required for all biological products, orphan medicinal products, and new treatments for neurodegenerative disorders, and it is available for certain other products, including those which constitute a significant therapeutic, scientific or technical innovation.

In addition to the centralized procedure, Europe also has: (1) a nationalized procedure, which requires a separate application to and approval determination by each country; (2) a decentralized procedure, whereby applicants submit identical applications to several countries and receive simultaneous approval; and (3) a mutual recognition procedure, where applicants submit an application to one country for review and other countries may accept or reject the initial decision. Regardless of the approval process employed, various parties share responsibilities for the monitoring, detection, and evaluation of adverse events post-approval, including national authorities, the EMA, the EC, and the marketing authorization holder. In some regions, it is possible to receive an “accelerated” review whereby the national regulatory authority will commit to truncated review timelines for products that meet specific medical needs.

Good Manufacturing Practices

Regulatory agencies regulate and inspect equipment, facilities, and processes used in the manufacturing and testing of pharmaceutical and biologic products prior to approving a product. If, after receiving clearance from regulatory agencies, a company makes a material change in manufacturing equipment, location, or process, additional regulatory review and approval may be required. We also must adhere to current Good Manufacturing Practices (cGMP) and product-specific regulations enforced by regulatory agencies following product approval. The FDA, the EMA and other regulatory agencies also conduct periodic visits to re-inspect equipment, facilities, and processes following the initial approval of a product. If, as a result of these inspections, it is determined that our equipment, facilities, or processes do not comply with applicable regulations and conditions of product approval, regulatory agencies may seek civil, criminal, or administrative sanctions or remedies against us, including significant financial penalties and the suspension of our manufacturing operations.

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Good Clinical Practices

The FDA, the EMA and other regulatory agencies promulgate regulations and standards for designing, conducting, monitoring, auditing and reporting the results of clinical trials to ensure that the data and results are accurate and that the rights and welfare of trial participants are adequately protected (commonly referred to as current Good Clinical Practices (cGCP)). Regulatory agencies enforce cGCP through periodic inspections of trial sponsors, principal investigators and trial sites, contract research organizations (CROs), and institutional review boards. If our studies fail to comply with applicable cGCP, the clinical data generated in our clinical trials may be deemed unreliable and relevant regulatory agencies may require us to perform additional clinical trials before approving our marketing applications. Noncompliance can also result in civil or criminal sanctions. We rely on third parties, including CROs, to carry out many of our clinical trial-related activities. Failure of such third parties to comply with cGCP can likewise result in rejection of our clinical trial data or other sanctions.

Orphan Drug Act

Under the U.S. Orphan Drug Act, the FDA may grant orphan drug designation to drugs intended to treat a “rare disease or condition,” which generally is a disease or condition that affects fewer than 200,000 individuals in the U.S. If a product which has an orphan drug designation subsequently receives the first FDA approval for the indication for which it has such designation, the product is entitled to orphan exclusivity, i.e., the FDA may not approve any other applications to market the same drug for the same indication for a period of seven years following marketing approval, except in certain very limited circumstances, such as if the later product is shown to be clinically superior to the orphan product. Legislation similar to the U.S. Orphan Drug Act has been enacted in other countries to encourage the research, development and marketing of medicines to treat, prevent or diagnose rare diseases. In the E.U., medicinal products intended for diagnosis, prevention or treatment of life-threatening or very serious diseases affecting less than five in 10,000 people receive 10-year market exclusivity, protocol assistance, and access to the centralized procedure for marketing authorization.

Regulation Pertaining to Pricing and Reimbursement

In both domestic and foreign markets, sales of our products depend, in part, on the availability and amount of reimbursement by third party payers, including governments and private health plans. Governments may regulate coverage, reimbursement and pricing of our products to control cost or affect utilization of our products. Private health plans may also seek to manage cost and utilization by implementing coverage and reimbursement limitations. Substantial uncertainty exists regarding the reimbursement by third party payors of newly approved health care products. The U.S. and foreign governments regularly consider reform measures that affect health care coverage and costs. Such reforms may include changes to the coverage and reimbursement of our products which may have a significant impact on our business.

Within the U.S.

Medicaid is a joint federal and state program that is administered by the states for low income and disabled beneficiaries. Under the Medicaid Drug Rebate Program, we are required to pay a rebate for each unit of product reimbursed by the state Medicaid programs. The amount of the rebate for each product is set by law as the greater of 23.1% of the average manufacturer price (AMP) or the difference between AMP and the best price available from us to any customer (with limited exceptions). The rebate amount must be adjusted upward if AMP increases more than inflation (measured by the Consumer Price Index — Urban). The adjustment can cause the rebate amount to exceed the minimum 23.1% rebate amount. The rebate amount is calculated each quarter based on our report of current AMP and best price for each of our products to the Centers for Medicare & Medicaid Services. The requirements for calculating AMP and best price are complex. We are required to report any revisions to AMP or best price previously reported within a certain period, which revisions could affect our rebate liability for prior quarters. In addition, if we fail to provide information timely or we are found to have knowingly submitted false information to the government, the statute provides for civil monetary penalties.

Medicare is a federal program that is administered by the federal government that covers individuals age 65 and over as well as those with certain disabilities. Medicare Part B generally covers drugs that must be administered by physicians or other health care practitioners; are provided in connection with certain durable

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medical equipment; or are certain oral anti-cancer drugs and certain oral immunosuppressive drugs. Medicare Part B pays for such drugs under a payment methodology based on the average sales price (ASP) of the drugs. Manufacturers, including us, are required to provide ASP information to the Centers for Medicare & Medicaid Services on a quarterly basis. The manufacturer-submitted information is used to calculate Medicare payment rates. The current payment rate for Medicare Part B drugs is ASP plus 6% outside the hospital outpatient setting and ASP plus 4% for most drugs in the hospital outpatient setting. The payment rates for drugs in the hospital outpatient setting are subject to periodic adjustment. The Centers for Medicare & Medicaid Services also has the statutory authority to adjust payment rates for specific drugs outside the hospital outpatient setting based on a comparison of ASP payment rates to widely available market prices or to AMP, which could decrease Medicare payment rates, but the authority has not yet been implemented. If a manufacturer is found to have made a misrepresentation in the reporting of ASP, the statute provides for civil monetary penalties.

Medicare Part D provides coverage to enrolled Medicare patients for self-administered drugs (i.e., drugs that do not need to be injected or otherwise administered by a physician). Medicare Part D is administered by private prescription drug plans approved by the U.S. government and each drug plan establishes its own Medicare Part D formulary for prescription drug coverage and pricing, which the drug plan may modify from time-to-time. The prescription drug plans negotiate pricing with manufacturers and may condition formulary placement on the availability of manufacturer discounts. Manufacturers, including us, are required to provide a 50% discount on brand name prescription drugs utilized by Medicare Part D beneficiaries when those beneficiaries reach the coverage gap in their drug benefits.

Our products are subject to discounted pricing when purchased by federal agencies via the Federal Supply Schedule (FSS). FFS participation is required for our products to be covered and reimbursed by the Veterans Administration, Department of Defense, Coast Guard, and Public Health Service (PHS). Coverage under Medicaid, the Medicare Part B program and the PHS pharmaceutical pricing program is also conditioned upon FSS participation. FSS pricing is negotiated periodically with the Department of Veterans Affairs. FSS pricing is intended not to exceed the price that we charge our most-favored non-federal customer for a product. In addition, prices for drugs purchased by the Veterans Administration, Department of Defense (including drugs purchased by military personnel and dependents through the TriCare retail pharmacy program), Coast Guard, and PHS are subject to a cap on pricing equal to 76% of the non-federal average manufacturer price (non-FAMP). An additional discount applies if non-FAMP increases more than inflation (measured by the Consumer Price Index — Urban). In addition, if we fail to provide information timely or we are found to have knowingly submitted false information to the government, the governing statute provides for civil monetary penalties in addition to other penalties available to the government.

To maintain coverage of our products under the Medicaid Drug Rebate Program and Medicare Part B, we are required to extend discounts to certain purchasers under the PHS pharmaceutical pricing program. Purchasers eligible for discounts include hospitals that serve a disproportionate share of financially needy patients, community health clinics and other entities that receive health services grants from the PHS.

Outside the U.S.

Outside the U.S., the E.U. represents our major market. Within the E.U., our products are paid for by a variety of payors, with governments being the primary source of payment. Governments may determine or influence coverage of products. Governments may also set prices or otherwise regulate pricing. Negotiating prices with governmental authorities can delay commercialization of our products. Governments may use a variety of cost-containment measures to products, including price cuts, mandatory rebates, value-based pricing, and reference pricing (i.e., referencing prices in other countries and using those reference prices to set a price). Recent budgetary pressures in many E.U. countries are causing governments to consider or implement various cost-containment measures, such as price freezes, increased price cuts and rebates. If budget pressures continue, governments may implement additional cost-containment measures. For additional information related to our concentration of credit risk associated with certain international accounts receivable balances, please read the subsection below entitled “Market Risk—Credit Risk” in the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” section of this report.

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Regulation Pertaining to Sales and Marketing

We are subject to various federal and state laws pertaining to health care “fraud and abuse,” including anti-kickback laws and false claims laws. Anti-kickback laws generally prohibit a prescription drug manufacturer from soliciting, offering, receiving, or paying any remuneration to generate business, including the purchase or prescription of a particular drug. Although the specific provisions of these laws vary, their scope is generally broad and there may be no regulations, guidance or court decisions that clarify how the laws apply to particular industry practices. There is therefore a possibility that our practices might be challenged under the anti-kickback or similar laws. False claims laws prohibit anyone from knowingly and willingly presenting, or causing to be presented for payment to third party payors (including Medicare and Medicaid) claims for reimbursed drugs or services that are false or fraudulent, claims for items or services not provided as claimed, or claims for medically unnecessary items or services. Our activities relating to the sale and marketing of our products may be subject to scrutiny under these laws. Violations of fraud and abuse laws may be punishable by criminal or civil sanctions, including fines and civil monetary penalties, and exclusion from federal health care programs (including Medicare and Medicaid). Federal and state authorities are paying increased attention to enforcement of these laws within the pharmaceutical industry and private individuals have been active in alleging violations of the laws and bringing suits on behalf of the government under the False Claims Act. If we were subject to allegations concerning, or were convicted of violating, these laws, our business could be harmed.

Laws and regulations have been enacted by the federal government and various states to regulate the sales and marketing practices of pharmaceutical manufacturers. The laws and regulations generally limit financial interactions between manufacturers and health care providers or require disclosure to the government and public of such interactions. The laws include federal “sunshine” provisions enacted in 2010 as part of the comprehensive federal health care reform legislation. The sunshine provisions apply to pharmaceutical manufacturers with products reimbursed under certain government programs and require those manufacturers to disclose annually to the federal government (for re-disclosure to the public) certain payments made to physicians and certain other healthcare practitioners or to teaching hospitals. State laws may also require disclosure of pharmaceutical pricing information and marketing expenditures. Many of these laws and regulations contain ambiguous requirements. Given the lack of clarity in laws and their implementation, our reporting actions could be subject to the penalty provisions of the pertinent federal and state laws and regulations.

Other Regulations

Foreign Anti-Corruption

We are subject to various federal and foreign laws that govern our international business practices with respect to payments to government officials. Those laws include the U.S. Foreign Corrupt Practices Act (FCPA), which prohibits U.S. companies and their representatives from paying, offering to pay, promising, or authorizing the payment of anything of value to any foreign government official, government staff member, political party, or political candidate for the purpose of obtaining or retaining business or to otherwise obtain favorable treatment or influence a person working in an official capacity. In many countries, the health care professionals we regularly interact with may meet the FCPA’s definition of a foreign government official. The FCPA also requires public companies to make and keep books and records that accurately and fairly reflect their transactions and to devise and maintain an adequate system of internal accounting controls.

In July 2011, the U.K. Bribery Act 2010 (Bribery Act) became effective. The Bribery Act proscribes giving and receiving bribes in the public and private sectors, bribing a foreign public official, and failing to have adequate procedures to prevent employees and other agents from giving bribes. U.S. companies that conduct business in the United Kingdom generally will be subject to the Bribery Act. Penalties under the Bribery Act include potentially unlimited fines for companies and criminal sanctions for corporate officers under certain circumstances.

NIH Guidelines

We conduct research at our U.S. facilities in compliance with the current U.S. National Institutes of Health Guidelines for Research Involving Recombinant DNA Molecules (NIH Guidelines). By local ordinance, we are required to, among other things, comply with the NIH Guidelines in relation to our facilities in Cambridge, Massachusetts and Research Triangle Park, North Carolina and are required to operate pursuant to certain permits.

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Other Laws

Our present and future business has been and will continue to be subject to various other laws and regulations. Various laws, regulations and recommendations relating to safe working conditions, laboratory practices, the experimental use of animals, and the purchase, storage, movement, import and export and use and disposal of hazardous or potentially hazardous substances, including radioactive compounds and infectious disease agents, used in connection with our research work are or may be applicable to our activities. Certain agreements entered into by us involving exclusive license rights may be subject to national or international antitrust regulatory control, the effect of which cannot be predicted. The extent of government regulation, which might result from future legislation or administrative action, cannot accurately be predicted.

Manufacturing and Raw Materials

We are focused on the manufacture of biologics at our facilities, but also market small molecule products that are manufactured using an outsourced network. We operate licensed biological bulk-manufacturing facilities in Research Triangle Park, North Carolina (RTP) and Cambridge, Massachusetts, including a 250,000 square foot large-scale manufacturing plant with 90,000 liters of bioreactor capacity in RTP. We also have a large-scale biologics manufacturing facility in Hillerød, Denmark that, based on our current global manufacturing strategy, is expected to begin commercial operations in the second half of 2012, upon completion of the facility’s validation activities.

We currently manufacture AVONEX drug substance at our RTP and Cambridge facilities. We currently manufacture TYSABRI drug substance at our RTP facility through a high-titer process and plan to also manufacture TYSABRI drug substance in our Hillerød facility in the second half of 2012. Genentech is responsible for all worldwide manufacturing activities for bulk RITUXAN and has sourced the manufacture of certain bulk RITUXAN requirements to a third party. Acorda Therapeutics supplies FAMPYRA to us pursuant to its supply agreement with Alkermes, Inc. We use third parties to manufacture the active pharmaceutical ingredient and the final product for FUMADERM.

We source all of our fill-finish and the majority of final product storage operations for our products, along with a substantial part of our packaging operations, to a concentrated group of third party contractors. We have internal label and pack capability for clinical and commercial products at our Cambridge and Hillerød facilities. Raw materials and supplies required for the production of AVONEX, TYSABRI, FAMPYRA and FUMADERM are procured from various suppliers in quantities adequate to meet our needs. Continuity of supply of raw materials is assured using a strategy of dual sourcing where possible or by a risk-based inventory strategy. Each of our third party service providers, suppliers and manufacturers is subject to routine cGMP inspections by the FDA or comparable agencies in other jurisdictions.

We believe that our manufacturing facilities represent sufficient capacity for our own growing pipeline of products, as well as the products of potential partners. In December 2011, we entered into an agreement with Samsung to establish an entity based in Korea to develop, manufacture and market biosimilars. Samsung will take a leading role in the entity, which will contract with Biogen Idec for technical development services and biologics manufacturing. Completion of the transaction is subject to customary closing conditions.

Important factors that could adversely affect our manufacturing operations are discussed in the “Risk Factors” section of this report.

Our Employees

As of December 31, 2011, we had approximately 5,000 employees worldwide.

Our Executive Officers (as of February 3, 2012)

George A. Scangos, Ph.D., 63, is our Chief Executive Officer and has served in this position since July 2010. From 1996 to July 2010, Dr. Scangos served as President and Chief Executive Officer of Exelixis, Inc., a drug discovery and development company, where he continues to serve on the board. From 1993 to 1996,

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Dr. Scangos served as President of Bayer Biotechnology, where he was responsible for research, business development, process development, manufacturing, engineering and quality assurance of Bayer’s biological products. Before joining Bayer in 1987, Dr. Scangos was a Professor of Biology at Johns Hopkins University for six years. Dr. Scangos served as non-executive Chairman of Anadys Pharmaceuticals, Inc., a biopharmaceutical company, from 2005 to July 2010 and was a director of the company from 2003 to July 2010. Dr. Scangos served as the Chair of the California Healthcare Institute in 2010 and was a member of the Board of the Global Alliance for TB Drug Developments until 2010. He is also a member of the Board of Visitors of the University of California, San Francisco School of Pharmacy, and the National Board of Visitors of the University of California, Davis School of Medicine. He is currently an Adjunct Professor of Biology at Johns Hopkins. Dr. Scangos was a Jane Coffin Childs Post-Doctoral Fellow at Yale University. Dr. Scangos holds a B.A. in Biology from Cornell University and a Ph.D. in Microbiology from the University of Massachusetts.

Susan H. Alexander, 55, is our Executive Vice President, General Counsel and Corporate Secretary and has served in these positions since January 2006. From 2003 to January 2006, Ms. Alexander served as the Senior Vice President, General Counsel and Corporate Secretary of PAREXEL International Corporation, a biopharmaceutical services company. From 2001 to 2003, Ms. Alexander served as General Counsel of IONA Technologies, a software company. From 1995 to 2001, Ms. Alexander served as Counsel at Cabot Corporation, a specialty chemicals and performance materials company. Prior to that, Ms. Alexander was a partner at the law firms of Hinckley, Allen & Snyder and Fine & Ambrogne.

Paul J. Clancy, 50, is our Executive Vice President, Finance and Chief Financial Officer and has served in these positions since August 2007. Mr. Clancy joined Biogen, Inc. in 2001 and has held several senior executive positions with us, including Vice President of Business Planning, Portfolio Management and U.S. Marketing, and Senior Vice President of Finance with responsibilities for leading the Treasury, Tax, Investor Relations and Business Planning groups. Prior to that, he spent 13 years at PepsiCo, a food and beverage company, serving in a range of financial and general management positions. He holds a B.S. in finance from Babson College and a M.B.A. from Columbia University.

John G. Cox, 49, is our Executive Vice President, Pharmaceutical Operations and Technology and has served in this position since June 2010. Mr. Cox joined Biogen, Inc. in 2003 and has held several senior executive positions with us, including Senior Vice President of Technical Operations, Senior Vice President of Global Manufacturing, and Vice President of Manufacturing and General Manager of Biogen Idec’s operations in RTP. Prior to that, Mr. Cox held a number of senior operational roles at Diosynth, a life sciences manufacturing and services company, where he worked in technology transfer, validation and purification. Prior to that, Mr. Cox focused on the same areas at Wyeth Corporation, a life sciences company, from 1993 to 2000.

Kenneth Di Pietro, 53, is our Executive Vice President, Human Resources and has served in this position since January 2012. Mr. Di Pietro joined Biogen Idec from Lenovo Group, a technology company, where he served as Senior Vice President, Human Resources from 2005 to June 2011. From 2003 to 2005, he served as Corporate Vice President, Human Resources at Microsoft Corporation, a technology company. From 1999 to 2002, Mr. Di Pietro worked as Vice President, Human Resources at Dell Inc., a technology company. Prior to that, he spent 17 years at PepsiCo, a food and beverage company, serving in a range of human resource and general management positions. Mr. Di Pietro received his B.S. in Labor Relations from Cornell University.

Robert E. Gagnon, 37, is our Vice President, Finance, Chief Accounting Officer and Controller and, since February 1, 2012, our Vice President, Business Planning. Mr. Gagnon will continue to serve as Vice President, Finance, Chief Accounting Officer and Controller, positions he has held since November 2010, until a successor is appointed. From July 2007 to November 2010, Mr. Gagnon served as our Vice President, Finance and Controller and from 2005 to July 2007 he served as our Director of Corporate Accounting. Prior to that, Mr. Gagnon worked in the business advisory and assurance practices of PricewaterhouseCoopers LLP and Deloitte & Touche LLP. Mr. Gagnon is a certified public accountant and holds an M.B.A. from the MIT Sloan School of Management.

Steven H. Holtzman, 57, is our Executive Vice President, Corporate Development and has served in this position since January 2011. Prior to that, Mr. Holtzman was a founder of Infinity Pharmaceuticals, Inc., a drug discovery and development company, where he has served as Chair of the Board of Directors since 2001, and served as Executive Chair of the Board of Directors in 2010 and as Chief Executive Officer from 2001 to December 2009. From 1994 to 2001, Mr. Holtzman was Chief Business Officer at Millennium Pharmaceuticals

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Inc., a biopharmaceutical company. From 1986 to 1994, he was the co-founder, member of the Board of Directors and Executive Vice President of DNX Corporation, a biotechnology company. From 1996 to 2001, Mr. Holtzman served as presidential appointee to the national Bioethics Advisory Commission.

Tony Kingsley, 48, is our Executive Vice President, Global Commercial Operations and has served in this position since November 2011. From January 2010 to November 2011, Mr. Kingsley served as our Senior Vice President, U.S. Commercial Operations. Prior to that, he served as Senior Vice President and General Manager of the Gynecological Surgical Products business at Hologic, Inc., a provider of diagnostic and surgical products, from October 2007 to November 2009, and as Division President, Diagnostic Products at Cytyc Corp., a provider of diagnostic and medical device products, from July 2006 to October 2007. In those roles, Mr. Kingsley ran commercial, manufacturing and research and development functions. From 1991 to 2006, he was a Partner at McKinsey & Company focusing on the biotechnology, pharmaceutical and medical device industries.

Douglas E. Williams, Ph.D., 53, is our Executive Vice President, Research and Development and has served in this position since January 2011. Prior to that, Dr. Williams held several senior executive positions at ZymoGenetics Inc., a biopharmaceutical company, including Chief Executive Officer and a director from January 2009 to October 2010, President and Chief Scientific Officer from July 2007 to January 2009, and Executive Vice President, Research and Development and Chief Scientific Officer from 2004 to July 2007. Prior to that, he held leadership positions within the biotechnology industry, including Chief Scientific Officer and Executive Vice President of Research and Development at Seattle Genetics Inc., a biotechnology company, from 2003 to 2004, and Senior Vice President and Washington Site Leader at Amgen Inc., a biotechnology company, in 2002. Dr. Williams also served in a series of scientific and senior leadership positions over a decade at Immunex Corp., a biopharmaceutical company, including Executive Vice President and Chief Technology Officer, Senior Vice President of Discovery Research, Vice President of Research and Development and as a director. Prior to that, Dr. Williams served on the faculty of the Indiana University School of Medicine and the Department of Laboratory Medicine at the Roswell Park Memorial Institute in Buffalo, New York.

Item  1A. Risk Factors

We are substantially dependent on revenues from our three principal products.

Our current and future revenues depend upon continued sales of our three principal products, AVONEX, TYSABRI and RITUXAN, which represented substantially all of our total revenues during 2011. Although we have developed and continue to develop additional products for commercial introduction, we may be substantially dependent on sales from these three products for many years. Any negative developments relating to any of these products, such as safety or efficacy issues, the introduction or greater acceptance of competing products, including biosimilars, or adverse regulatory or legislative developments, may reduce our revenues and adversely affect our results of operations. Our competitors are introducing additional multiple sclerosis products in an increasingly crowded market and if they have a similar or more attractive profile in terms of efficacy, convenience or safety, future sales of AVONEX, TYSABRI or both could be adversely affected.

TYSABRI’s sales growth is important to our success.

We expect that our revenue growth over the next several years will be dependent in part upon sales of TYSABRI. If we are not successful in growing sales of TYSABRI, our future business plans, revenue growth and results of operations may be adversely affected.

TYSABRI’s sales growth cannot be certain given the significant restrictions on use and the significant safety warnings in the label, including the risk of developing progressive multifocal leukoencephalopathy (PML), a serious brain infection. The risk of developing PML increases with prior immunosuppressant use, which may cause patients who have previously received immunosuppressants or their physicians to refrain from using or prescribing TYSABRI. The risk of developing PML also increases with longer treatment duration, which may cause prescribing physicians or patients to suspend treatment with TYSABRI. The risk of developing PML also increases with exposure to JC virus, which may be assessed through the presence of anti-JCV antibodies. Patients testing positive for anti-JCV antibodies or their physicians, may refrain from using or prescribing TYSABRI. Increased incidences of PML could limit sales growth, prompt regulatory review, require significant changes to

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the label or result in market withdrawal. Additional regulatory restrictions on the use of TYSABRI or safety-related label changes, including enhanced risk management programs, whether as a result of additional cases of PML, changes to the criteria for confirming PML diagnosis or otherwise, may significantly reduce expected revenues and require significant expense and management time to address the associated legal and regulatory issues.

As we continue to research and develop protocols and therapies intended to reduce risk and improve outcomes of PML in patients, regulatory authorities may not agree with our perspective on such protocols and therapies. Our efforts at stratifying patients into groups with lower or higher risk for developing PML may not result in corresponding changes to the TYSABRI label. Furthermore, our risk stratification efforts may have an adverse impact on prescribing behavior and reduce sales of TYSABRI. The potential utility of the JC virus antibody assay as a risk stratification tool may be diminished as a result of both the assay’s false negative rate as well as the possibility that a patient who initially tests negative for the JC virus antibody may acquire the JC virus after testing.

Our long-term success depends upon the successful development and commercialization of other product candidates.

Our long-term viability and growth will depend upon the successful development and commercialization of new products from our research and development activities, including products licensed from third parties. We have several late-stage clinical programs expected to have near-term data readouts or registration submissions that could impact our prospects for additional revenue growth and will require significant pre-launch investments that may not be recovered if the applicable product candidate does not receive marketing approval.

Product development and commercialization are very expensive and involve a high degree of risk. Only a small number of research and development programs result in the commercialization of a product. Success in preclinical work or early stage clinical trials does not ensure that later stage or larger scale clinical trials will be successful, and positive results in a registrational trial may not be replicated in any subsequent confirmatory trials. Clinical trials may indicate that our product candidates have harmful side effects or raise other safety concerns that may significantly reduce the likelihood of regulatory approval, result in significant restrictions on use and safety warnings in any approved label, adversely affect placement within the treatment paradigm, or otherwise significantly diminish the commercial potential of the product candidate. Even if later stage clinical trials are successful, product candidates may fail to receive marketing approval or may receive more restricted marketing approval than anticipated if regulatory authorities disagree with our view of the data or require additional studies.

Conducting clinical trials is a complex, time-consuming and expensive process. Our ability to complete our clinical trials in a timely fashion depends in large part on a number of key factors including protocol design, regulatory and institutional review board approval, the rate of patient enrollment in clinical trials, and compliance with extensive current Good Clinical Practices. We have opened clinical sites and are enrolling patients in a number of new countries where our experience is more limited, and we are in many cases using the services of third party clinical trial providers. If we fail to adequately manage the design, execution and regulatory aspects of our large, complex and diverse clinical trials, our studies and ultimately our regulatory approvals may be delayed or we may fail to gain approval for our product candidates altogether.

Our ability to successfully commercialize a product candidate that receives marketing approval depends on a number of factors, including the medical community’s acceptance of the product, the effectiveness of our sales force and marketing efforts, the size of the patient population and our ability to identify new patients, pricing and the extent of reimbursement from third party payors, the ability to obtain and maintain data or market exclusivity for our products in the relevant indication(s), the availability or introduction of competing treatments that are deemed more effective, safer, more convenient, or less expensive, manufacturing the product in a timely and cost-effective manner, and compliance with complex regulatory requirements.

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We are preparing regulatory submissions for BG-12, our investigational oral compound for the treatment of relapsing MS, based on positive results from two pivotal trials. Factors that may prevent us from successfully commercializing BG-12 include:

• regulatory authorities may not accept or approve our regulatory submissions for BG-12, or they may require additional information that delays approval, or they may grant more restricted approval than anticipated;

• unexpected safety risks or other concerns may arise from additional data or analysis;

• there is intense competition in the increasingly crowded MS market, including the possibility of future competition from generic versions of BG-12;

• we rely on third parties to manufacture BG-12 and these third parties may not supply BG-12 in a timely and cost-effective manner or in compliance with applicable regulations;

• our sales and marketing efforts may not result in product revenues that meet the investment community’s high expectations for BG-12; and

• the other risks and uncertainties described in these “Risk Factors.”

If we fail to compete effectively, our business and market position would suffer.

The biotechnology and pharmaceutical industry is intensely competitive. We compete in the marketing and sale of our products, the development of new products and processes, the acquisition of rights to new products with commercial potential and the hiring and retention of personnel. We compete with biotechnology and pharmaceutical companies that have a greater number of products on the market and in the product pipeline, greater financial and other resources and other technological or competitive advantages. One or more of our competitors may benefit from significantly greater sales and marketing capabilities, may develop products that are accepted more widely than ours and may receive patent protection that dominates, blocks or adversely affects our product development or business. In addition, healthcare reform legislation enacted in the U.S. in 2010 has created a pathway for the U.S. Food and Drug Administration (FDA) to approve biosimilars, which could compete on price and differentiation with products that we now or could in the future market. The introduction by our competitors of more efficacious, safer, cheaper, or more convenient alternatives to our products could reduce our revenues and the value of our product development efforts.

Adverse safety events can negatively affect our business and stock price.

Adverse safety events involving our marketed products may have a negative impact on our commercialization efforts. Later discovery of safety issues with our products that were not known at the time of their approval by the FDA or other regulatory agencies worldwide could cause product liability events, additional regulatory scrutiny and requirements for additional labeling, withdrawal of products from the market and the imposition of fines or criminal penalties. Any of these actions could result in material write-offs of inventory, material impairments of intangible assets, goodwill and fixed assets, material restructuring charges and other adverse impacts on our results of operations. In addition, the reporting of adverse safety events involving our products and public rumors about such events could cause our stock price to decline or experience periods of volatility.

We depend, to a significant extent, on reimbursement from third party payors and a reduction in the extent of reimbursement could reduce our product sales and revenue.

Sales of our products are dependent, in large part, on the availability and extent of reimbursement from government health administration authorities, private health insurers and other organizations. Changes in government regulations or private third-party payors’ reimbursement policies may reduce reimbursement for our products and adversely affect our future results. In addition, when a new medical product is approved, the availability of government and private reimbursement for that product is uncertain, as is the amount for which that product will be reimbursed. We cannot predict the availability or amount of reimbursement for our product candidates.

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In the U.S., federal and state legislatures, health agencies and third-party payors continue to focus on containing the cost of health care. The 2010 Patient Protection and Affordable Care Act, which has already imposed significant health care cost containment measures, also encourages the development of comparative effectiveness research and any adverse findings for our products from such research may reduce the extent of reimbursement for our products. In addition, the Budget Control Act of 2011 mandates, among other things, reductions in Medicare payment rates if a sufficient deficit reduction plan is not approved, and a reduction in funding for Medicare, Medicaid or similar government programs may adversely affect our future results. Economic pressure on state budgets may result in states increasingly seeking to achieve budget savings through mechanisms that limit coverage or payment for our drugs. In recent years, some states have considered legislation that would control the prices of drugs. State Medicaid programs are increasingly requesting manufacturers to pay supplemental rebates and requiring prior authorization by the state program for use of any drug for which supplemental rebates are not being paid. Managed care organizations continue to seek price discounts and, in some cases, to impose restrictions on the coverage of particular drugs. Government efforts to reduce Medicaid expenses may lead to increased use of managed care organizations by Medicaid programs. This may result in managed care organizations influencing prescription decisions for a larger segment of the population and a corresponding constraint on prices and reimbursement for our products.

In the European Union and some other international markets, the government provides health care at low cost to consumers and regulates pharmaceutical prices, patient eligibility or reimbursement levels to control costs for the government-sponsored health care system. Many countries are reducing their public expenditures and we expect to see strong efforts to reduce healthcare costs in our international markets, including patient access restrictions, suspensions on price increases, prospective and possibly retroactive price reductions and other recoupments and increased mandatory discounts or rebates, recoveries of past price increases, and greater importation of drugs from lower-cost countries to higher-cost countries. These cost control measures likely would reduce our revenues. In addition, certain countries set prices by reference to the prices in other countries where our products are marketed. Thus, our inability to secure adequate prices in a particular country may not only limit the marketing of our products within that country, but may also adversely affect our ability to obtain acceptable prices in other markets. This may create the opportunity for third party cross border trade or influence our decision to sell or not to sell a product, thus adversely affecting our geographic expansion plans and revenues.

Adverse market and economic conditions may exacerbate certain risks affecting our business.

Sales of our products are dependent on reimbursement from government health administration authorities, private health insurers, distribution partners and other organizations. These organizations may be unable to satisfy their reimbursement obligations or may delay payment due to deteriorating global economic conditions, uncertainty about the direction and relative strength of the U.S. economy and resolution of the U.S. budget deficit, the growing European financial crisis, volatility in the credit and financial markets, and other disruptions due to natural disasters, political instability or otherwise. These adverse market and economic conditions also may cause governmental health authorities to reduce the extent of reimbursements and private insurers to increase their scrutiny of claims. A reduction in the availability or extent of reimbursement could reduce our product sales and revenue, or result in additional allowances or significant bad debts, which may adversely affect our results of operations.

We depend on collaborators and other third-parties for both product and royalty revenue and the clinical development of future products, which are outside of our full control.

We have a number of collaborators and partners, and have both in-licensed and out-licensed several products and programs. These collaborations are subject to several risks:

• Our RITUXAN revenues are dependent on the efforts of Genentech and the Roche Group. Their interests may not always be aligned with our interests and they may not market RITUXAN in the same manner or to the same extent that we would, which could adversely affect our RITUXAN revenues.

• Under our collaboration agreement with Genentech, the successful development and commercialization of GA101 and certain other anti-CD20 products will decrease our percentage of the collaboration’s co-promotion profits.

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• We are not fully in control of the royalty or profit sharing revenues we receive from collaborators, which may be adversely affected by patent expirations, pricing or health care reforms, other legal and regulatory developments, new indication approvals, and the introduction of competitive products, which may affect the sales of collaboration products.

• Any failure on the part of our collaborators to comply with applicable laws and regulatory requirements in the sale and marketing of our products or to fulfill any responsibilities they may have to protect and enforce any intellectual property rights underlying our products could have an adverse effect on our revenues as well as involve us in possible legal proceedings.

• Collaborations often require the parties to cooperate, and failure to do so effectively could have an adverse impact on product sales by our collaborators, and could adversely affect the clinical development or regulatory approvals of products under joint control.

In addition, we rely on third parties for several other aspects of our business. As a sponsor of clinical trials of our products, we rely on third party contract research organizations to carry out many of our clinical trial related activities. These activities include initiating and monitoring the conduct of studies at clinical trial sites and identifying any noncompliance with the study protocol or current Good Clinical Practices. The failure of a contract research organization to conduct these activities with proper vigilance and competence and in accordance with current Good Clinical Practices can result in regulatory authorities rejecting our clinical trial data or, in some circumstances, the imposition of civil or criminal sanctions against us.

If we do not successfully execute our growth initiatives through the acquisition, partnering and in-licensing of products, technologies or companies, our future performance could be adversely affected.

We anticipate growing through both internal development projects as well as external opportunities, which include the acquisition, partnering and in-licensing of products, technologies and companies or the entry into strategic alliances and collaborations. The availability of high quality opportunities is limited and we are not certain that we will be able to identify candidates that we and our shareholders consider suitable or complete transactions on terms that are acceptable to us and our shareholders. In order to pursue such opportunities, we may require significant additional financing, which may not be available to us on favorable terms, if at all. Even if we are able to successfully identify and complete acquisitions, we may not be able to integrate them or take full advantage of them and therefore may not realize the benefits that we expect. If we are unsuccessful in our external growth program, we may not be able to grow our business significantly and we may incur asset impairment or restructuring charges as a result of unsuccessful transactions.

If we fail to comply with the extensive legal and regulatory requirements affecting the health care industry, we could face increased costs, penalties and a loss of business.

Our activities, and the activities of our collaborators and third party providers, are subject to extensive government regulation and oversight both in the U.S. and in foreign jurisdictions. The FDA and comparable agencies in other jurisdictions directly regulate many of our most critical business activities, including the conduct of preclinical and clinical studies, product manufacturing, advertising and promotion, product distribution, adverse event reporting and product risk management. Our interactions in the U.S. or abroad with physicians and other health care providers that prescribe or purchase our products are also subject to government regulation designed to prevent fraud and abuse in the sale and use of the products and place greater restrictions on the marketing practices of health care companies. Healthcare companies are facing heightened scrutiny of their relationships with healthcare providers from anti-corruption enforcement officials. In addition, pharmaceutical and biotechnology companies have been the target of lawsuits and investigations alleging violations of government regulation, including claims asserting submission of incorrect pricing information, impermissible off-label promotion of pharmaceutical products, payments intended to influence the referral of federal or state health care business, submission of false claims for government reimbursement, antitrust violations, or violations related to environmental matters. These risks may be heightened as we continue to expand our global operations and introduce additional products to the market.

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Regulations governing the health care industry are subject to change, including:

• new laws, regulations or judicial decisions, or new interpretations of existing laws, regulations or decisions, related to health care availability, pricing or marketing practices, compliance with wage and hour laws and other employment practices, method of delivery, payment for health care products and services, tracking payments and other transfers of value made to physicians and teaching hospitals, and extensive anti-bribery and anti-corruption prohibitions;

• changes in the FDA and foreign regulatory approval processes that may delay or prevent the approval of new products and result in lost market opportunity;

• changes in FDA and foreign regulations that may require additional safety monitoring, labeling changes, restrictions on product distribution or use, or other measures after the introduction of our products to market, which could increase our costs of doing business, adversely affect the future permitted uses of approved products, or otherwise adversely affect the market for our products; and

• changes in the tax laws relating to our operations.

Examples of previously enacted and possible future changes in laws that could adversely affect our business include the enactment in the U.S. of health care reform, potential regulations easing the entry of competing follow-on biologics in the marketplace, new legislation or implementation of existing statutory provisions on importation of lower-cost competing drugs from other jurisdictions, and enhanced penalties for and investigations into non-compliance with U.S. fraud and abuse laws.

Violations of governmental regulation may be punishable by criminal and civil sanctions against us, including fines and civil monetary penalties and exclusion from participation in government programs, including Medicare and Medicaid, as well as against executives overseeing our business. In addition to penalties for violation of laws and regulations, we could be required to repay amounts we received from government payors, or pay additional rebates and interest if we are found to have miscalculated the pricing information we have submitted to the government. Whether or not we have complied with the law, an investigation into alleged unlawful conduct could increase our expenses, damage our reputation, divert management time and attention and adversely affect our business.

Uncertainty over intellectual property in the biotechnology industry has been the source of litigation, which is inherently costly and unpredictable.

We are aware that others, including various universities and companies working in the biotechnology field, have filed patent applications and have been granted patents in the U.S. and in other countries claiming subject matter potentially useful to our business. Some of those patents and patent applications claim only specific products or methods of making such products, while others claim more general processes or techniques useful or now used in the biotechnology industry. There is considerable uncertainty within the biotechnology industry about the validity, scope and enforceability of many issued patents in the U.S. and elsewhere in the world, and, to date, there is no consistent policy regarding the breadth of claims allowed in biotechnology patents. We cannot currently determine the ultimate scope and validity of patents which may be granted to third parties in the future or which patents might be asserted to be infringed by the manufacture, use and sale of our products.

There has been, and we expect that there may continue to be, significant litigation in the industry regarding patents and other intellectual property rights. Litigation and administrative proceedings concerning patents and other intellectual property rights may be protracted, expensive and distracting to management. Competitors may sue us as a way of delaying the introduction of our products. Any litigation, including any interference proceedings to determine priority of inventions, oppositions to patents in foreign countries or litigation against our partners may be costly and time consuming and could harm our business. We expect that litigation may be necessary in some instances to determine the validity and scope of certain of our proprietary rights. Litigation may be necessary in other instances to determine the validity, scope or non-infringement of certain patent rights claimed by third parties to be pertinent to the manufacture, use or sale of our products. Ultimately, the outcome of such litigation could adversely affect the validity and scope of our patent or other proprietary rights or hinder our ability to manufacture and market our products.

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If we are unable to adequately protect and enforce our intellectual property rights, our competitors may take advantage of our development efforts or our acquired technology.

We have filed numerous patent applications in the U.S. and various other countries seeking protection of the processes, products and other inventions originating from our research and development. Patents have been issued on many of these applications. We have also obtained rights to various patents and patent applications under licenses with third parties, which provide for the payment of royalties by us. The ultimate degree of patent protection that will be afforded to biotechnology products and processes, including ours, in the U.S. and in other important markets remains uncertain and is dependent upon the scope of protection decided upon by the patent offices, courts and lawmakers in these countries. Our patents may not afford us substantial protection or commercial benefit. Similarly, our pending patent applications or patent applications licensed from third parties may not ultimately be granted as patents and we may not prevail if patents that have been issued to us are challenged in court. In addition, court decisions or patent office regulations that place additional restrictions on patent claims or that facilitate patent challenges could also reduce our ability to protect our intellectual property rights. If we cannot prevent others from exploiting our inventions, we will not derive the benefit from them that we currently expect.

We also rely upon other forms of unpatented confidential information, and we cannot ensure that others will not independently develop substantially equivalent proprietary information and techniques or otherwise gain access to our trade secrets or disclose such technology, or that we can meaningfully protect such rights. We protect such information principally through confidentiality agreements with our employees, consultants, outside scientific collaborators, scientists whose research we sponsor and other advisers. These agreements may not provide meaningful protection or adequate remedies for our unpatented confidential information in the event of use or disclosure of such information.

If our products infringe the intellectual property rights of others, we may incur damages and be required to incur the expense of obtaining a license.

A substantial number of patents have already been issued to other biotechnology and pharmaceutical companies. To the extent that valid third party patent rights cover our products or services, we or our strategic collaborators would be required to seek licenses from the holders of these patents in order to manufacture, use or sell these products and services, and payments under them would reduce our profits from these products and services. We are currently unable to predict the extent to which we may wish or be required to acquire rights under such patents and the availability and cost of acquiring such rights, or whether a license to such patents will be available on acceptable terms or at all. There may be patents in the U.S. or in foreign countries or patents issued in the future that are unavailable to license on acceptable terms. Our inability to obtain such licenses may hinder our ability to manufacture and market our products.

Our sales and operations are subject to the risks of doing business internationally.

We are increasing our presence in international markets, which subjects us to many risks, such as:

• the inability to obtain necessary foreign regulatory or pricing approvals of products in a timely manner;

• fluctuations in currency exchange rates;

• difficulties in staffing and managing international operations;

• the imposition of governmental controls;

• less favorable intellectual property or other applicable laws;

• increasingly complex standards for complying with foreign laws and regulations that may differ substantially from country to country and may conflict with corresponding U.S. laws and regulations;

• the emergence of far-reaching anti-bribery and anti-corruption legislation in the U.K. and elsewhere and escalation of investigations and prosecutions pursuant to such laws;

• restrictions on direct investments by foreign entities and trade restrictions;

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• greater political or economic instability; and

• changes in tax laws and tariffs.

In addition, our international operations are subject to regulation under U.S. law. For example, the Foreign Corrupt Practices Act prohibits U.S. companies and their representatives from offering, promising, authorizing or making payments to foreign officials for the purpose of obtaining or retaining business abroad. In many countries, the health care professionals we regularly interact with may meet the definition of a foreign government official for purposes of the Foreign Corrupt Practices Act. Failure to comply with domestic or foreign laws could result in various adverse consequences, including possible delay in approval or refusal to approve a product, recalls, seizures, withdrawal of an approved product from the market, the imposition of civil or criminal sanctions and the prosecution of executives overseeing our international operations.

Manufacturing issues could substantially increase our costs and limit supply of our products.

The process of manufacturing our products is complex, highly regulated and subject to several risks:

• Biologics manufacturing is extremely susceptible to product loss due to contamination, equipment failure, or vendor or operator error. We may need to close a manufacturing facility for an extended period of time due to microbial, viral or other contamination.

• We rely on third party suppliers and manufacturers for, among other things, RITUXAN manufacturing, clinical and commercial requirements for small molecule product candidates such as BG-12, our fill-finish operations, the majority of our final product storage, and a substantial portion of our packaging operations. In addition, due to the unique manner in which our products are manufactured, we rely on single source providers of several raw materials and manufacturing supplies. These third parties may not perform their obligations in a timely and cost-effective manner or in compliance with applicable regulations. Finding alternative providers could take a significant amount of time and involve significant expense due to the specialized nature of the services and the need to obtain regulatory approval of any significant changes to our suppliers or manufacturing methods. We cannot be certain that we could reach agreement with alternative providers or that the FDA or other regulatory authorities would approve our use of such alternatives.

• We rely solely on our manufacturing facility in Research Triangle Park, North Carolina for the production of TYSABRI. Our global bulk supply of TYSABRI depends on the uninterrupted and efficient operation of this facility, which could be adversely affected by equipment failures, labor shortages, natural disasters, power failures and numerous other factors. If we are unable to meet demand for TYSABRI for any reason, we would need to rely on a limited number of qualified third party contract manufacturers.

• We and our third party providers are generally required to maintain compliance with current Good Manufacturing Practice and other stringent requirements and are subject to inspections by the FDA and comparable agencies in other jurisdictions to confirm such compliance. Any delay, interruption or other issues that arise in the manufacture, fill-finish, packaging, or storage of our products as a result of a failure of our facilities or the facilities or operations of third parties to pass any regulatory agency inspection could significantly impair our ability to develop and commercialize our products. Significant noncompliance could also result in the imposition of monetary penalties or other civil or criminal sanctions and damage our reputation.

Any adverse developments affecting our manufacturing operations or the operations of our third-party suppliers and manufacturers may result in shipment delays, product recalls or other interruptions in the commercial supply of our products. We may also have to take inventory write-offs and incur other charges and expenses for products that fail to meet specifications, undertake costly remediation efforts or seek more costly manufacturing alternatives. Such developments could increase our manufacturing costs, cause us to lose revenue or market share, diminish our profitability or damage our reputation.

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Our investments in properties, including our manufacturing facilities, may not be fully realizable.

We own or lease real estate primarily consisting of buildings that contain research laboratories, office space, and biologic manufacturing operations. For strategic or other operational reasons, we may decide to further consolidate or co-locate certain aspects of our business operations or dispose of one or more of our properties, some of which may be located in markets that are experiencing high vacancy rates and decreasing property values. If we determine that the fair value of any of our owned properties, including any properties we may classify as held for sale, is lower than their book value we may not realize the full investment in these properties and incur significant impairment charges. If we decide to fully or partially vacate a leased property, we may incur significant cost, including lease termination fees, rent expense in excess of sublease income and impairment of leasehold improvements. In addition, we may not fully utilize our manufacturing facilities, resulting in idle time at facilities or substantial excess manufacturing capacity, due to reduced expectations of product demand, improved yields on production and other factors. Any of these events may have an adverse impact on our results of operations.

Our effective tax rate may fluctuate and we may incur obligations in tax jurisdictions in excess of accrued amounts.

As a global biotechnology company, we are subject to taxation in numerous countries, states and other jurisdictions. As a result, our effective tax rate is derived from a combination of applicable tax rates in the various places that we operate. In preparing our financial statements, we estimate the amount of tax that will become payable in each of such places. Our effective tax rate, however, may be different than experienced in the past due to numerous factors, including changes in the mix of our profitability from country to country, the results of audits of our tax filings, changes in accounting for income taxes and changes in tax laws. Any of these factors could cause us to experience an effective tax rate significantly different from previous periods or our current expectations.

In addition, our inability to secure or sustain acceptable arrangements with tax authorities and previously enacted or future changes in the tax laws, among other things, may result in tax obligations in excess of amounts accrued in our financial statements.

In the U.S., there are several proposals under consideration to reform tax law, including proposals that may reduce or eliminate the deferral of U.S. income tax on our unrepatriated earnings, scrutinize certain transfer pricing structures, and reduce or eliminate certain foreign tax credits. Our future reported financial results may be adversely affected by tax law changes which restrict or eliminate certain foreign tax credits or our ability to deduct expenses attributable to foreign earnings, or otherwise affect the treatment of our unrepatriated earnings.

The growth of our business depends on our ability to attract and retain qualified personnel and key relationships.

The achievement of our commercial, research and development and external growth objectives depends upon our ability to attract and retain qualified scientific, manufacturing, sales and marketing and executive personnel and to develop and maintain relationships with qualified clinical researchers and key distributors. Competition for these people and relationships is intense and comes from a variety of sources, including pharmaceutical and biotechnology companies, universities and non-profit research organizations.

Pending and future product liability claims may adversely affect our business and our reputation.

The administration of drugs in humans, whether in clinical studies or commercially, carries the inherent risk of product liability claims whether or not the drugs are actually the cause of an injury. Our products or product candidates may cause, or may appear to have caused, injury or dangerous drug interactions, and we may not learn about or understand those effects until the product or product candidate has been administered to patients for a prolonged period of time.

We are subject from time to time to lawsuits based on product liability and related claims. We cannot predict with certainty the eventual outcome of any pending or future litigation. We may not be successful in defending ourselves in the litigation and, as a result, our business could be materially harmed. These lawsuits

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may result in large judgments or settlements against us, any of which could have a negative effect on our financial condition and business if in excess of our insurance coverage. Additionally, lawsuits can be expensive to defend, whether or not they have merit, and the defense of these actions may divert the attention of our management and other resources that would otherwise be engaged in managing our business.

Our operating results are subject to significant fluctuations.

Our quarterly revenues, expenses and net income (loss) have fluctuated in the past and are likely to fluctuate significantly in the future due to the timing of charges and expenses that we may take. In recent periods, for instance, we have recorded charges that include:

• the cost of restructurings;

• impairments that we are required to take with respect to investments;

• impairments that we are required to take with respect to fixed assets, including those that are recorded in connection with the sale of fixed assets;

• inventory write-downs for failed quality specifications, charges for excess or obsolete inventory and charges for inventory write downs relating to product suspensions;

• milestone payments under license and collaboration agreements; and

• payments in connection with acquisitions and other business development activity.

Our revenues are also subject to foreign exchange rate fluctuations due to the global nature of our operations. We recognize foreign currency gains or losses arising from our operations in the period in which we incur those gains or losses. Although we have foreign currency forward contracts to hedge specific forecasted transactions denominated in foreign currencies, our efforts to reduce currency exchange losses may not be successful. As a result, currency fluctuations among our reporting currency, the U.S. dollar, and the currencies in which we do business will affect our operating results, often in unpredictable ways. Our net income may also fluctuate due to the impact of charges we may be required to take with respect to foreign currency hedge transactions. In particular, we may incur higher charges from hedge ineffectiveness than we expect or from the termination of a hedge relationship.

These examples are only illustrative and other risks, including those discussed in these “Risk Factors,” could also cause fluctuations in our reported earnings. In addition, our operating results during any one period do not necessarily suggest the anticipated results of future periods.

Our portfolio of marketable securities is significant and subject to market, interest and credit risk that may reduce its value.

We maintain a significant portfolio of marketable securities. Changes in the value of this portfolio could adversely affect our earnings. In particular, the value of our investments may decline due to increases in interest rates, downgrades of the bonds and other securities included in our portfolio, instability in the global financial markets that reduces the liquidity of securities included in our portfolio, declines in the value of collateral underlying the mortgage and asset-backed securities included in our portfolio, and other factors. Each of these events may cause us to record charges to reduce the carrying value of our investment portfolio or sell investments for less than our acquisition cost. Although we attempt to mitigate these risks by investing in high quality securities and continuously monitoring our portfolio’s overall risk profile, the value of our investments may nevertheless decline.

Our level of indebtedness could adversely affect our business and limit our ability to plan for or respond to changes in our business.

As of December 31, 2011, we had $1.1 billion of outstanding indebtedness, and we may incur additional debt in the future. Our level of indebtedness could adversely affect our business by, among other things:

• requiring us to dedicate a substantial portion of our cash flow from operations to payments on our indebtedness, thereby reducing the availability of our cash flow for other purposes, including business development efforts and research and development;

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• limiting our flexibility in planning for, or reacting to, changes in our business and the industry in which we operate, thereby placing us at a competitive disadvantage compared to our competitors that may have less debt; and

• increasing our vulnerability to adverse economic and industry conditions.

Our business involves environmental risks, which include the cost of compliance and the risk of contamination or injury.

Our business and the business of several of our strategic partners, including Genentech and Elan, involve the controlled use of hazardous materials, chemicals, biologics and radioactive compounds. Although we believe that our safety procedures for handling and disposing of such materials comply with state and federal standards, there will always be the risk of accidental contamination or injury. If we were to become liable for an accident, or if we were to suffer an extended facility shutdown, we could incur significant costs, damages and penalties that could harm our business. Biologics manufacturing also requires permits from government agencies for water supply and wastewater discharge. If we do not obtain appropriate permits, or permits for sufficient quantities of water and wastewater, we could incur significant costs and limits on our manufacturing volumes that could harm our business.

Provisions in our most significant collaboration agreements may discourage a third party from attempting to acquire us.

Provisions in our collaboration agreements with Elan and Genentech might discourage a takeover attempt that could be viewed as beneficial to shareholders who wish to receive a premium for their shares from a potential bidder. Our collaboration agreements with Elan and Genentech respectively allow Elan to purchase our rights to TYSABRI and Genentech to purchase our rights to RITUXAN and certain anti-CD20 products developed under the agreement if we undergo a change of control and certain other conditions are met, which may limit our attractiveness to potential acquirers.

The possibility that activist shareholders may seek representation on or control of our Board of Directors could result in costs and disruption to our operations and cause uncertainty about the direction of our business.

We faced proxy contests in 2008, 2009 and 2010 and future proxy contests could be costly and time-consuming, disrupt our operations and divert the attention of management and our employees from executing our strategic plan. Our directors are elected annually, which may increase our vulnerability to hostile and potentially abusive takeover tactics.

Item  1B. Unresolved Staff Comments

None.

Item  2. Properties

Below is a summary of our owned and leased properties as of December 31, 2011.

Massachusetts

In Cambridge, we own approximately 508,000 square feet of real estate space, consisting of a building that houses a research laboratory, office space and a cogeneration plant totaling approximately 263,000 square feet and a building that contains research, development and quality laboratories which total approximately 245,000 square feet.

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In July 2011, we executed leases for two office buildings to be built in Cambridge, Massachusetts, with a planned occupancy during the second half of 2013. Construction of these facilities began in late 2011. These buildings, totaling approximately 500,000 square feet, will serve as the future location of our corporate headquarters and commercial operations. The buildings will also provide additional general and administrative and research and development office space.

We currently lease a total of approximately 650,000 square feet in Massachusetts, which is summarized as follows:

• 353,000 square feet of office space housing our principal executive offices in Weston, which we expect to vacate upon completion of the two new buildings in Cambridge Massachusetts;

• 220,000 square feet in Cambridge, which is comprised of a 67,000 square foot biologics manufacturing facility and office space of 153,000 square feet;

• 41,000 square feet of office and laboratory space in Waltham, of which approximately 16,000 square feet will expire during the first half of 2012; and

• 36,000 square feet of warehouse space in Somerville.

Our Massachusetts lease agreements expire at various dates through the year 2028.

North Carolina

We manufacture bulk AVONEX, TYSABRI and other products in our pipeline at our facilities located in Research Triangle Park, North Carolina, where we own approximately 550,000 square feet of real estate space, which is summarized as follows:

• 175,000 square feet related to a large-scale biologics manufacturing facility;

• 167,000 square feet of laboratory and office space;

• 105,000 square feet related to a biologics manufacturing facility;

• 60,000 square feet of warehouse space; and

• 43,000 square feet related to a large-scale purification facility.

In addition, we lease approximately 50,000 square feet of office space in Durham, North Carolina.

We are planning to increase the laboratory space in our Research Triangle Park campus and consolidate all of our North Carolina activities by moving local general and administrative offices and patient services to an 180,000 square foot office building which is currently being built on the campus, with a planned occupancy during the second half of 2012.

Denmark

We own approximately 60 acres of land in Hillerød, Denmark, upon which we have been constructing a large-scale biologics manufacturing facility totaling approximately 225,000 square feet. Based on our current manufacturing strategy, we plan to begin commercial operations in the second half of 2012, upon completion of the facility’s validation activities.

We also own approximately 310,000 square feet of additional space, which is currently in use at this location and is summarized as follows:

• 140,000 square feet of warehouse, utilities and support space;

• 70,000 square feet related to a label and packaging facility;

• 50,000 square feet of administrative space; and

• 50,000 square feet related to a laboratory facility.

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Other International

We lease office and laboratory space in Zug, Switzerland, our international headquarters, the United Kingdom, Germany, France, Denmark, and numerous other countries. Our international lease agreements expire at various dates through the year 2023.

Item  3. Legal Proceedings

For a discussion of legal matters as of December 31, 2011, please read Note 21, Litigation to our consolidated financial statements included in this report, which is incorporated into this item by reference.

Item  4. Mine Safety Disclosures

Not applicable.

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PART II

Item 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities

Market and Stockholder Information

Our common stock trades on The NASDAQ Global Select Market under the symbol “BIIB.” The following table shows the high and low sales price for our common stock as reported by The NASDAQ Global Select Market for each quarter in the years ended December 31, 2011 and 2010:

	Common Stock Price
	2011				2010
	High		Low		High		Low
First Quarter	$	73.53	$	64.28	$	60.28	$	52.16
Second Quarter	$	109.63	$	72.70	$	57.99	$	45.96
Third Quarter	$	109.14	$	83.83	$	58.64	$	46.15
Fourth Quarter	$	120.66	$	87.72	$	68.60	$	55.63

As of January 31, 2012, there were approximately 972 stockholders of record of our common stock.

In addition, as of January 31, 2012, 104 stockholders of record of Biogen, Inc. common stock have yet to exchange their shares of Biogen, Inc. common stock for our common stock as contemplated by the merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation in November 2003.

Dividends

We have not paid cash dividends since our inception. We do not anticipate paying any cash dividends in the near term.

Issuer Purchases of Equity Securities

The following table summarizes our common stock repurchase activity during the fourth quarter of 2011:

Period	Total Number of Shares Purchased (#)		Average Price Paid per Share ($)		Total Number of Shares Purchased as Part of Publicly Announced  Programs (#)		Maximum Number of Shares That May Yet Be Purchased Under Our Programs ($ in millions)
2011 Repurchase Program
Oct-11		—		—		—		15,000,000
Nov-11		458,352		108.89		458,352		14,541,648
Dec-11		559,179		109.96		559,179		13,982,469
Total		1,017,531		109.48

On February 11, 2011, we announced that our Board of Directors authorized the repurchase of up to 20.0 million shares of our common stock. We expect to use this repurchase program principally to offset common stock issuance under our share-based compensation plans. This repurchase program does not have an expiration date.

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Stock Performance Graph

The graph below compares the five-year cumulative total stockholder return on our common stock, the S&P 500 Index and the Nasdaq Pharmaceutical Index, assuming the investment of $100.00 on December 31, 2006 with dividends being reinvested. The stock price performance in the graph below is not necessarily indicative of future price performance.

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Item 6. Selected Consolidated Financial Data

BIOGEN IDEC INC. AND SUBSIDIARIES

SELECTED FINANCIAL DATA

	For the Years Ended December 31,
	2011			2010			2009		2008			2007
(In millions, except per share amounts)	(11) (12) (13) (14)			(7) (8) (9) (10)			(4) (5) (6)		(3)			(1) (2)
Results of Operations
Product revenues	$	3,836.1		$	3,470.1		$	3,152.9	$	2,839.7		$	2,136.8
Revenues from unconsolidated joint business		996.6			1,077.2			1,094.9		1,128.2			926.1
Other revenues		215.9			169.1			129.5		129.6			108.7
Total revenues		5,048.6			4,716.4			4,377.3		4,097.5			3,171.6
Cost and expenses:
Cost of sales, excluding amortization of acquired intangible assets		466.8			400.3			382.1		402.0			335.2
Research and development		1,219.6			1,248.6			1,283.1		1,072.1			925.2
Selling, general and administrative		1,056.1			1,031.5			911.0		925.3			776.1
Collaboration profit sharing		317.8			258.1			215.9		136.0			14.1
Amortization of acquired intangible assets		208.6			208.9			289.8		332.7			257.5
Fair value adjustment of contingent consideration		36.1			—			—		—			—
Restructuring charge		19.0			75.2			—		—			—
Acquired in-process research and development		—			245.0			—		25.0			84.2
Facility impairments and gain on dispositions, net		—			—			—		(9.2	)		(0.4	)
Total cost and expenses		3,323.9			3,467.5			3,081.9		2,883.9			2,391.8
Income from operations		1,724.7			1,248.9			1,295.4		1,213.6			779.8
Other income (expense), net		(13.5	)		(19.0	)		37.3		(57.7	)		72.4
Income before income tax expense		1,711.2			1,229.9			1,332.7		1,155.9			852.2
Income tax expense		444.5			331.3			355.6		365.8			272.4
Net income		1,266.7			898.6			977.1		790.1			579.8
Net income (loss) attributable to noncontrolling interests, net of tax		32.3			(106.7	)		6.9		6.9			(58.4	)
Net income attributable to Biogen Idec Inc.	$	1,234.4		$	1,005.3		$	970.1	$	783.2		$	638.2
Diluted Earnings Per Share
Diluted earnings per share attributable to Biogen Idec Inc.	$	5.04		$	3.94		$	3.35	$	2.65		$	1.99
Weighted-average shares used in calculating diluted earnings per share attributable to Biogen Idec Inc.		245.0			254.9			289.5		295.0			320.2
Financial Condition
Cash, cash equivalents and marketable securities	$	3,107.4		$	1,950.8		$	2,457.8	$	2,262.8		$	2,115.8
Total assets	$	9,049.6		$	8,092.5		$	8,551.9	$	8,479.0		$	8,628.8
Notes payable, line of credit and other financing arrangements, less current portion	$	1,060.8		$	1,066.4		$	1,080.2	$	1,085.4		$	51.8
Total Biogen Idec Inc. shareholders’ equity	$	6,425.5		$	5,396.5		$	6,221.5	$	5,806.1		$	5,534.3

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In addition to the following notes, the financial data included within the tables above should be read in conjunction with our consolidated financial statements and related notes and the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections of this report and our previously filed Forms 10-K.

(1) Included in total cost and expenses in 2007 is a charge of $18.4 million for in-process research and development related to the acquisition of Biogen Idec Hemophilia, formerly Syntonix Pharmaceuticals Inc., and $64.3 million related to our collaboration with Neurimmune SubOne and our former collaboration with Cardiokine Biopharma LLC, which we consolidated as we determined that we were the primary beneficiary of these relationships. The $64.3 million was offset by an equal amount of noncontrolling interest, resulting in no net impact to the results of our operations.

(2) In July 2007, we purchased approximately 56.4 million shares of our common stock pursuant to a tender offer. We funded the transaction through existing cash and cash equivalents of $1,490.5 million and a short term loan of $1,500.0 million.

(3) Included in total cost and expenses in 2008 is $25.0 million for in-process research and development related to a milestone payment made to the former shareholders of Conforma Therapeutics pursuant to the terms of our acquisition of Conforma Therapeutics in 2006.

(4) Total cost and expenses in 2009 includes the $110.0 million upfront payment made to Acorda Therapeutics, Inc. pursuant to our June 30, 2009 collaboration and license agreement to develop and commercialize products containing fampridine in markets outside the U.S.

(5) Changes in tax law in certain state jurisdictions in which we operate and the resolution of multiple federal, state and foreign tax audits, including the effective settlement of several uncertain tax positions resulted in a $58.3 million reduction to our 2009 income tax expense.

(6) In 2009, we repurchased 16.0 million shares of our common stock at a cost of $751.2 million under our 2006 and 2009 share repurchase programs.

(7) Included in total cost and expenses in 2010 is a charge to acquired in-process research and development of $40.0 million related to the achievement of a milestone by Biogen Idec Hemophilia, Inc. (formerly Syntonix Pharmaceuticals, Inc.).

(8) Included in total cost and expenses in 2010 is a charge to acquired in-process research and development of $205.0 million incurred in connection with the license agreement entered into with Knopp Neurosciences Inc. (Knopp), which we consolidated as we determined that we are the primary beneficiary of the entity. The $205.0 million charge was partially offset by an attribution of $145.0 million to the noncontrolling interest.

(9) Net income attributable to noncontrolling interest also includes a charge of $25.0 million related to the payment made in 2010 to Cardiokine Biopharma LLC pursuant to the termination of our lixivaptan collaboration.

(10) During 2010, we repurchased approximately 40.3 million shares of our common stock at a cost of approximately $2.1 billion under our 2010 and 2009 share repurchase authorizations.

(11) In the second quarter of 2011 our share of RITUXAN revenues from unconsolidated joint business was reduced by approximately $50.0 million to reflect our share of the approximately $125.0 million compensatory damages and interest that Genentech estimated might be awarded to Hoechst GmbH (Hoechst), in relation to Genentech’s ongoing arbitration with Hoechst.

(12) During 2011, we repurchased approximately 6.0 million shares of our common stock at a cost of approximately $498.0 million under our 2011 share repurchase authorization.

(13) Biogen Idec Inc.’s shareholders’ equity in 2011 reflects a reduction in additional paid in capital and noncontrolling interests totaling $187.3 million resulting from our purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH.

(14) Included in total cost and expenses in 2011 is a charge to research and development expense of $36.8 million related to an upfront payment made in connection with our collaboration and license agreement entered into with Portola Pharmaceuticals, Inc.

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Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations

The following discussion should be read in conjunction with our consolidated financial statements and related notes beginning on page F-1 of this report. Certain totals may not sum due to rounding.

Executive Summary

Introduction

Biogen Idec is a global biotechnology company that discovers, develops, manufactures and markets therapies for the treatment of neurodegenerative diseases, hemophilia and autoimmune disorders. Patients worldwide benefit from our leading multiple sclerosis therapies, and the company generates $5 billion in annual revenues.

In the near term, our current and future revenues are dependent upon continued sales of our three principal products, AVONEX, TYSABRI, and RITUXAN. In the longer term, our revenue growth will be dependent upon the successful clinical development, regulatory approval and launch of new commercial products, our ability to obtain and maintain patents and other rights related to our marketed products and assets originating from our research and development efforts, and successful execution of external business development opportunities. As part of our ongoing research and development efforts, we have devoted significant resources to conducting clinical studies to advance the development of new pharmaceutical products and to explore the utility of our existing products in treating disorders beyond those currently approved in their labels.

Financial Highlights

The following table is a summary of financial results achieved:

	For the Years Ended December 31,				% Change
					2011 compared to 2010
(In millions, except per share amounts and percentages)	2011 (1) (2) (4)		2010 (3) (4)
Total revenues	$	5,048.6	$	4,716.4		7.0	%
Income from operations	$	1,724.7	$	1,248.9		38.1	%
Net income attributable to Biogen Idec Inc.	$	1,234.4	$	1,005.3		22.8	%
Diluted earnings per share attributable to Biogen Idec Inc.	$	5.04	$	3.94		27.9	%

(1) Income from operations, as well as net income attributable to Biogen Idec Inc. for 2011, was reduced by a charge of $36.8 million to research and development expense incurred in connection with the collaboration and license agreement entered into with Portola Pharmaceuticals, Inc. in October 2011.

(2) In the second quarter of 2011 our share of RITUXAN revenues from unconsolidated joint business was reduced by approximately $50.0 million to reflect our share of the approximately $125.0 million compensatory damages and interest that Genentech estimated might be awarded to Hoechst GmbH (Hoechst), in relation to Genentech’s ongoing arbitration with Hoechst.

(3) Income from operations for 2010 was reduced by approximately $40.0 million related to the achievement of a milestone by Biogen Idec Hemophilia, Inc. (formerly Syntonix Pharmaceuticals, Inc.) and a $205.0 million charge incurred in connection with the collaboration and license agreement entered into with Knopp Neurosciences Inc. (Knopp), which we consolidated as we determined that we were the primary beneficiary of this relationship. The $205.0 million was partially offset by an attribution of $145.0 million to the noncontrolling interest. Net income attributable to noncontrolling interest also includes a charge of $25.0 million related to the payment made in 2010 to Cardiokine Biopharma LLC (Cardiokine) pursuant to the termination of our lixivaptan collaboration.

(4) Income from operations, as well as net income attributable to Biogen Idec Inc., for 2011 and 2010, was reduced by $19.0 million and $75.2 million, respectively, resulting from charges associated with our restructuring initiative announced in November 2010.

As described below under “Results of Operations,” our operating results for the year ended December 31, 2011, reflect the following:

• Worldwide AVONEX revenues totaled $2,686.6 million for 2011, representing an increase of 6.7% over 2010.

• Our share of TYSABRI revenues totaled $1,079.5 million for 2011, representing an increase of 19.9% over 2010.

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• Our share of RITUXAN revenues totaled $996.6 million for 2011, representing a decrease of 7.5% from 2010. This decrease was primarily the result of royalty expirations in our rest of world markets, a decrease in selling and development expenses incurred by us and reimbursed by Genentech, which are also included within our total unconsolidated joint business revenues, and our share of a charge recorded by the collaboration in relation to Genentech’s ongoing arbitration with Hoechst GmbH. These decreases were offset in part by an increase in our share of U.S. RITUXAN net product revenues which increased 6.0% over 2010.

• Total cost and expenses decreased 4.1% for 2011 compared to 2010. This decrease was primarily the result of the $245.0 million of IPR&D charges recognized in 2010 as well as a 2.3% decrease in research and development expense and a 74.7% decrease in restructuring charges recognized over 2010. These decreases were offset by a 16.6% increase in cost of sales, a 23.1% increase in collaboration profit sharing expense due to TYSABRI revenue growth, as well as a 2.4% increase in selling, general and administrative costs over the same period in 2010.

We generated $1,727.7 million of net cash flows from operations for 2011, which were primarily driven by earnings. Cash, cash equivalents and marketable securities totaled approximately $3,107.4 million as of December 31, 2011.

In February 2011, our Board of Directors authorized the repurchase of up to 20.0 million shares of our common stock. Under this authorization, in 2011, we repurchased approximately 6.0 million shares of our common stock at a cost of approximately $498.0 million.

Business Environment

We conduct our business primarily within the biotechnology and pharmaceutical industries, which are highly competitive. Many of our competitors are working to develop or have already developed products similar to those we are developing or already market. For example, along with us, a number of companies are working to develop or have already developed additional treatments for MS, including oral and other alternative formulations that may compete with AVONEX, TYSABRI or both. In addition, the commercialization of certain of our own pipeline product candidates, such as BG-12, may negatively impact future sales of AVONEX, TYSABRI or both. We may also face increased competitive pressures as a result of the emergence of biosimilars. In the U.S., AVONEX, TYSABRI, and RITUXAN are licensed under the Public Health Service Act (PHSA) as biological products. In March 2010, U.S. healthcare reform legislation amended the PHSA to authorize the U.S. Food and Drug Administration (FDA) to approve biological products, known as biosimilars or follow-on biologics, that are shown to be highly similar to previously approved biological products based upon potentially abbreviated data packages.

Global economic conditions continue to present challenges for our industry. Governments in many international markets in which we operate have announced or have already implemented austerity measures to constrain the overall level of government expenditures. These measures, which include efforts aimed at reforming health care coverage and reducing health care costs, and the deterioration of credit and economic conditions, particularly in certain countries in Europe, continue to exert pressure on product pricing, have delayed reimbursement for our products, and have negatively impacted our revenues and results of operations. For additional information about certain risks that could negatively impact our financial position or future results of operations, please read the “Risk Factors” section of this report.

Key Pipeline Developments

BG-12

During 2011, we announced positive top-line results from our two pivotal Phase 3 clinical trials, DEFINE and CONFIRM, designed to evaluate the investigational oral compound BG-12 as a monotherapy in relapsing MS. We are preparing regulatory submissions for BG-12 based upon the positive results from these two trials.

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We acquired BG-12 and FUMADERM (together, Fumapharm Products) as part of our acquisition of Fumapharm AG in 2006. We paid $220.0 million upon closing of the transaction and will pay an additional $15.0 million if a Fumapharm Product is approved for MS in the U.S. or E.U. We may also make additional milestone payments to Fumapharm AG based on attainment of certain sales levels of Fumapharm Products, less certain costs as defined in the acquisition agreement. For additional information about these contingent milestone payments, please read the “Contractual Obligations and Off-Balance Sheet Arrangements – Contingent Consideration” subsection of this “Management’s Discussion and Analysis of Financial Condition and Results of Operations.”

FAMPYRA

In July 2011, the European Commission (EC) granted a conditional marketing authorization for FAMPYRA in the E.U., which triggered a $25.0 million milestone payment. This payment was made to Acorda Therapeutics, Inc. (Acorda) in the third quarter of 2011. FAMPYRA is an oral compound indicated as a treatment to improve walking ability in adult patients with MS who have walking disability. FAMPYRA was commercially launched in Australia, Denmark, Germany, Norway and the U.K. in 2011. In 2012, we plan to launch FAMPYRA in Austria, Canada, Finland, France, Greece, Italy, Ireland, the Netherlands, Sweden and other markets. The exact timing of these launches remains subject to our ability to obtain reimbursement approval within the respective markets.

We have a license from Acorda to develop and commercialize FAMPYRA in all markets outside the U.S. Under the terms of our collaboration and license agreement, we will pay Acorda tiered royalties based on ex-U.S. net sales, and milestones based on new indications and ex-U.S. net sales. These milestones, which may total up to $400.0 million, include the $25.0 million payment for successful license of the product in the E.U. The next expected milestone would be $15.0 million, due when ex-U.S. net sales reach $100.0 million over a period of four consecutive quarters. For additional information about our collaboration with Acorda, please read Note 20, Collaborations to our consolidated financial statements included in this report.

Long-Lasting Recombinant Factors VIII and IX

We collaborate with Swedish Orphan Biovitrum AB (Sobi) on the commercialization of long-lasting recombinant Factors VIII and IX. In 2011, we received opinions from the EMA’s Pediatric Committee (PDCO) agreeing to pediatric investigational plans for Factor VIII and Factor IX. In accordance with the PDCO’s opinion, we plan to initiate global pediatric trials in previously-treated patients less than 12 years of age as soon as sufficient data are available from studies of older patients. The PDCO opinions for Factor VIII and Factor IX are under guidelines published by the EMA for the development of Factor IX and Factor VIII products. Pediatric data from these trials will be required in the initial submission of Marketing Authorization Applications to the European regulatory agency.

The Factor IX and Factor VIII hemophilia programs continue to advance according to plan with recruitment of patients in both phase III studies (B-LONG and A-LONG, respectively). For additional information about our collaboration with Sobi, please read Note 20, Collaborations to our consolidated financial statements included in this report.

Isis Pharmaceuticals, Inc.

In January 2012, we entered into an exclusive, worldwide option and development agreement with Isis Pharmaceuticals, Inc. (Isis) under which both companies will develop and commercialize Isis’ antisense investigational drug, ISIS-SMN_Rx, for the treatment of spinal muscular atrophy (SMA).

Under the terms of the agreement, Isis received an upfront payment of $29.0 million and is eligible to receive up to $45.0 million in milestone payments associated with the clinical development of ISIS-SMN_Rx prior to licensing. For additional information about our agreement with Isis, please read Note 27, Subsequent Events to our consolidated financial statements included in this report.

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Samsung Biosimilar Agreement

In December 2011, we entered into an agreement with Samsung BioLogics Co. Ltd. (Samsung) to establish an entity to develop, manufacture and market biosimilar pharmaceuticals. Under the terms of the agreement, Samsung will contribute approximately $255.0 million for an 85 percent stake in the entity and Biogen Idec will contribute approximately $45.0 million for the remaining 15 percent ownership interest. Our investment will initially be limited to this initial contribution as we have no obligation to provide any additional funding; however, we maintain an option to purchase additional stock in the entity in order to increase our ownership percentage up to 49.9 percent. The exercise of this option is within our control. Completion of the transaction is subject to customary closing conditions. For additional information about our agreement with Samsung, please read Note 19, Investment in Variable Interest Entities to our consolidated financial statements included in this report.

Portola Pharmaceuticals, Inc.

In October 2011, we entered into an exclusive, worldwide collaboration and license agreement with Portola Pharmaceuticals, Inc. (Portola) under which both companies will develop and commercialize highly selective, novel oral Syk inhibitors for the treatment of various autoimmune and inflammatory diseases, including rheumatoid arthritis and systemic lupus erythematosus. For additional information about this transaction, please read Note 20, Collaborations to our consolidated financial statements included in this report.

Results of Operations

Revenues

Revenues are summarized as follows:

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Product Revenues:
United States	$	1,954.8	$	1,744.4	$	1,638.0		12.1	%		6.5	%
Rest of world		1,881.3		1,725.7		1,514.9		9.0	%		13.9	%
Total product revenues		3,836.1		3,470.1		3,152.9		10.5	%		10.1	%
Unconsolidated joint business revenues		996.6		1,077.2		1,094.9		(7.5	)%		(1.6	)%
Other revenues		215.9		169.1		129.5		27.7	%		30.6	%
Total revenues	$	5,048.6	$	4,716.4	$	4,377.3		7.0	%		7.7	%

Product Revenues

Product revenues are summarized as follows:

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
AVONEX	$	2,686.6	$	2,518.4	$	2,322.9		6.7	%		8.4	%
TYSABRI		1,079.5		900.2		776.0		19.9	%		16.0	%
Other product revenues		70.0		51.5		54.0		35.9	%		(4.6	)%
Total product revenues	$	3,836.1	$	3,470.1	$	3,152.9		10.5	%		10.1	%

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AVONEX

Revenues from AVONEX are summarized as follows:

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
United States	$	1,628.3	$	1,491.6	$	1,406.2		9.2	%		6.1	%
Rest of world		1,058.3		1,026.8		916.7		3.1	%		12.0	%
Total AVONEX revenues	$	2,686.6	$	2,518.4	$	2,322.9		6.7	%		8.4	%

For 2011 compared to 2010, as well as for 2010 compared to 2009, the increase in U.S. AVONEX revenues was due to price increases offset by decreased commercial demand. Decreased commercial demand resulted in declines of approximately 3% and 6% in U.S. AVONEX unit sales volume for 2011 and 2010, respectively, from the prior year comparative periods.

For 2011 compared to 2010, as well as for 2010 compared to 2009, the increase in rest of world AVONEX revenues reflects an increase in commercial demand offset by price decreases in some countries. Increased commercial demand resulted in increases of approximately 6% in rest of world AVONEX unit sales in both 2011 and 2010, respectively, over their prior year comparative periods. The increase in rest of world AVONEX revenues for 2011 compared to 2010 also reflects the favorable impact of foreign currency exchange rates offset by losses recognized in relation to the settlement of certain cash flow hedge instruments under our foreign currency hedging program. The increase in rest of world AVONEX revenues for 2010 compared to 2009 also reflects gains recognized in relation to the settlement of certain cash flow hedge instruments under our foreign currency hedging program offset by the negative impact of foreign currency exchange rates.

Losses recognized in relation to the settlement of certain cash flow hedge instruments under our foreign currency hedging program totaled $30.6 million in 2011, compared to gains recognized of $35.0 million for 2010 and losses recognized of $39.5 million in 2009.

We expect AVONEX to continue facing increased competition in the MS marketplace in both the U.S. and rest of world. We and a number of other companies are working to develop or have already commercialized products to treat MS, including oral and other alternative formulations that may compete with AVONEX now and in the future. In addition, the continued growth of TYSABRI and the commercialization of our other pipeline product candidates, such as BG-12, may negatively impact future sales of AVONEX. Increased competition may also lead to reduced unit sales of AVONEX, as well as increasing price pressure.

TYSABRI

We collaborate with Elan Pharma International, Ltd (Elan) an affiliate of Elan Corporation, plc, on the development and commercialization of TYSABRI. For additional information about this collaboration, please read Note 20, Collaborations to our consolidated financial statements included in this report.

Revenues from TYSABRI are summarized as follows:

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
United States	$	326.5	$	252.8	$	231.8		29.2	%		9.1	%
Rest of world		753.0		647.4		544.2		16.3	%		19.0	%
Total TYSABRI revenues	$	1,079.5	$	900.2	$	776.0		19.9	%		16.0	%

For 2011 compared to 2010, as well as for 2010 compared to 2009, the increase in U.S. TYSABRI revenues was due to increased commercial demand and price increases. Increased commercial demand resulted in increases of approximately 12% and 10% in U.S. TYSABRI unit sales volume for 2011 and, 2010, respectively,

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over the prior year comparative periods. The increase in U.S. TYSABRI revenues for 2010 compared to 2009, resulting from increased commercial demand and price increases, was offset by the sale to Elan of previously written-down TYSABRI inventory which became saleable following the approval of our higher-yielding manufacturing process. As our sales price to Elan in the U.S. is set to effect an approximate equal sharing of the gross margin with Elan plus reimbursement for our cost of goods sold, the distribution of this specific inventory reduced our cost of sales, which reduced the price per unit we charged to Elan and reduced our revenues by $7.5 million in 2010 compared to 2009. This inventory was fully utilized during 2010.

Net sales of TYSABRI from our collaboration partner, Elan, to third-party customers in the U.S. for 2011, 2010, and 2009 totaled $746.5 million, $593.1 million, and $508.5 million, respectively.

For 2011 compared to 2010, as well as for 2010 compared to 2009, the increase in rest of world TYSABRI revenues reflects an increase in commercial demand offset by price decreases in some countries. Increased commercial demand resulted in increases of approximately 19% and 23% in rest of world TYSABRI unit sales for 2011 and 2010, respectively, over their prior year comparative periods. The increase in rest of world TYSABRI revenues for 2011 compared to 2010 also reflects the favorable impact of foreign currency exchange rates offset by the deferral of a portion of our revenues recognized on sales of TYSABRI in Italy made during the fourth quarter of 2011 and losses recognized in relation to the settlement of certain cash flow hedge instruments under our foreign currency hedging program. The increase in rest of world TYSABRI revenues for 2010 compared to 2009 reflects gains recognized in relation to the settlement of certain cash flow hedge instruments under our foreign currency hedging program offset by the negative impact of foreign currency exchange rates.

In the fourth quarter of 2011, Biogen Idec SRL received a notice from the Italian National Medicines Agency (AIFA) stating that sales of TYSABRI for the period from February 2009 through February 2011 exceeded by EUR 30.7 million a reimbursement limit established pursuant to a Price Determination Resolution (Price Resolution) granted by AIFA in February 2007. In December 2011, we filed an appeal against AIFA seeking a ruling that our interpretation of the Price Resolution is valid and that the position of AIFA is unenforceable. While we believe that we have good and valid grounds for our appeal, an unfavorable decision could negatively impact our results of operations. As a result of this dispute, we deferred $13.8 million of revenue recognized on sales of TYSABRI made in Italy during the fourth quarter of 2011 and expect that we will continue to defer a portion of our revenues on future sales of TYSABRI in Italy until this matter is resolved. For additional information, please read Note 21, Litigation to our consolidated financial statements included within this report.

Losses recognized in relation to the settlement of certain cash flow hedge instruments under our foreign currency hedging program totaled $6.3 million in 2011, compared to gains recognized of $10.7 million for 2010 and losses recognized of $10.1 million 2009.

We expect TYSABRI to continue facing increased competition in the MS marketplace in both the U.S. and rest of world. We and a number of other companies are working to develop or have already commercialized products to treat MS, including oral and other alternative formulations that may compete with TYSABRI now and in the future. The commercialization of our other pipeline product candidates, such as BG-12, also may negatively impact future sales of TYSABRI. Increased competition may also lead to reduced unit sales of TYSABRI, as well as increasing price pressure. In addition, safety warnings included in the TYSABRI label, such as the risk of PML, and any future safety-related label changes, may limit the growth of TYSABRI unit sales. We continue to research and develop protocols and therapies that may reduce risk and improve outcomes of PML in patients. Our efforts to stratify patients into lower or higher risk for developing PML, including through the JCV assay, and other ongoing or future clinical trials involving TYSABRI may have a negative impact on prescribing behavior in at least the short term, which may result in decreased product revenues from sales of TYSABRI.

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Other Product Revenues

Other product revenues are summarized as follows:

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
FUMADERM	$	54.7	$	51.2		49.6		6.8	%		3.2	%
FAMPYRA		13.6		—		—		*	*		*	*
Other		1.7		0.3		4.4		466.7	%		(93.2	)%
Total other product revenues	$	70.0	$	51.5	$	54.0		35.9	%		(4.6	)%

Unconsolidated Joint Business Revenues

We collaborate with Genentech on the development and commercialization of RITUXAN. For additional information related to this collaboration including information regarding the pre-tax co-promotion profit sharing formula for RITUXAN and its impact on future unconsolidated joint business revenues, please read Note 20, Collaborations to our consolidated financial statements included in this report.

Revenues from unconsolidated joint business are summarized as follows:

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Biogen Idec's share of pre-tax co-promotion profits in the U.S.	$	872.7	$	848.0	$	773.6		2.9	%		9.6	%
Reimbursement of our selling and development expenses in the U.S.		6.1		58.3		65.6		(89.5	)%		(11.1	)%
Revenue on sales of RITUXAN in the rest of world		117.8		170.9		255.7		(31.1	)%		(33.2	)%
Total unconsolidated joint business revenues	$	996.6	$	1,077.2	$	1,094.9		(7.5	)%		(1.6	)%

Biogen Idec’s Share of Pre-tax Co-Promotion Profits in the U.S.

The following table provides a summary of amounts comprising our share of pre-tax co-promotion profits in the U.S.:

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Product revenues, net	$	2,924.5	$	2,759.2	$	2,665.5		6.0	%		3.5	%
Cost and expenses		730.8		626.8		724.1		16.6	%		(13.4	)%
Pre-tax co-promotion profits in the U.S.	$	2,193.7	$	2,132.4	$	1,941.4		2.9	%		9.8	%
Biogen Idec's share of pre-tax co-promotion profits in the U.S.	$	872.7	$	848.0	$	773.6		2.9	%		9.6	%

For 2011 compared to 2010, as well as for 2010 compared to 2009, the increase in U.S. RITUXAN product revenues was primarily due to price increases and an increase in commercial demand. Increased commercial demand resulted in increases of approximately 4% and 2% in U.S. RITUXAN unit sales volume for 2011 and

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2010, respectively, over their prior year comparative periods. The increases for both comparative periods were negatively impacted by increases in reserves established for rebates and allowances related to the U.S. healthcare reform legislation enacted in March 2010.

Collaboration cost and expenses for 2011 compared to 2010, as well as for 2010 compared to 2009, were favorably impacted by Genentech assuming responsibility for the U.S. sales and marketing efforts for RITUXAN in the fourth quarter of 2010. The savings realized from the consolidation of the sales force in 2011 were offset by a charge of approximately $125.0 million recorded to the collaboration, representing an estimate of compensatory damages and interest that might be awarded to Hoechst GmbH (Hoechst), in relation to an intermediate decision by the arbitrator in Genentech’s ongoing arbitration with Hoechst. As a result of this charge to the collaboration, our share of RITUXAN revenues from unconsolidated joint business was reduced by approximately $50.0 million in the second quarter of 2011. This $50.0 million amount reflects the estimate of the loss that we may incur in the event of a final arbitration award unfavorable to Genentech. The actual amount of our share of any damages may vary from this estimate depending on the nature or amount of any damages awarded to Hoechst, or if the arbitrator’s final decision is successfully challenged by Genentech. For additional information related to this matter, please read Note 21, Litigation to our consolidated financial statements included within this report.

In addition, total collaboration cost and expenses for 2011 was further negatively impacted by a new fee which became payable in 2011 by all branded prescription drug manufacturers and importers. This fee is calculated based upon each organization’s percentage share of total branded prescription drug sales to qualifying U.S. government programs (such as Medicare, Medicaid and VA and PHS discount programs). We have reduced our share of pre-tax co-promotion profits in the U.S. by approximately $15.0 million in 2011 based upon our estimate of the fee that will be assessed to Genentech on qualifying sales of RITUXAN in 2011.

Under our collaboration agreement, our current pre-tax co-promotion profit-sharing formula, which resets annually, provides for a 40% share of pre-tax co-promotion profits if co-promotion operating profits exceed $50.0 million. For 2011, 2010, and 2009, the 40% threshold was met during the first quarter.

Reimbursement of Selling and Development Expense in the U.S.

In the fourth quarter of 2010, we and Genentech made an operational decision under which we eliminated our RITUXAN oncology and rheumatology sales force, with Genentech assuming responsibility for the U.S. sales and marketing efforts related to RITUXAN. As a result of this change, selling and development expense incurred by us in the U.S. and reimbursed by Genentech decreased for 2011 in comparison to 2010, as well as for 2010 compared to 2009. As discussed in Note 20, Collaborations to our consolidated financial statements included in this report, Genentech incurs the majority of continuing development costs for RITUXAN. Expenses incurred by Genentech in the development of RITUXAN are not recorded as research and development expense, but rather reduce our share of pre-tax co-promotion profits recorded as a component of unconsolidated joint business revenues.

Revenue on Sales of RITUXAN in the Rest of World

Revenue on sales of RITUXAN in the rest of world consists of our share of pre-tax co-promotion profits in Canada and royalty revenue on sales of RITUXAN outside the U.S. and Canada. For 2011 compared to 2010, as well as for 2010 compared to 2009, the decline in revenue on sales of RITUXAN in the rest of world was due to the expirations of royalties on a country-by-country basis in certain of our rest of world markets. In addition, revenue on sales of RITUXAN in the rest of world for 2010 were favorably impacted by receipt of $21.3 million representing the cumulative underpayment of past royalties owed to us on sales of RITUXAN in the rest of world.

The royalty period for sales in the rest of world with respect to all products is 11 years from the first commercial sale of such product on a country-by-country basis. The royalty periods for substantially all of the remaining royalty-bearing sales of RITUXAN in the rest of world markets will expire in 2012. As a result of these expirations, we expect royalty revenues on sales of RITUXAN in the rest of world to continue to decline in 2012. After 2012, we expect revenue on sales of RITUXAN in the rest of world will primarily be limited to our share of pre-tax co-promotion profits in Canada.

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Other Revenues

Other revenues are summarized as follows:

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Royalty revenues	$	158.5	$	137.4	$	124.4		15.4	%		10.5	%
Corporate partner revenues		57.4		31.7		5.1		81.1	%		521.6	%
Total other revenues	$	215.9	$	169.1	$	129.5		27.7	%		30.6	%

Royalty Revenues

We receive royalties on sales by our licensees of products covered under patents that we own. Sales of licensed products could vary significantly due to competition, manufacturing difficulties and other factors that are not within our control. In addition, the expiration or invalidation of any underlying patents could reduce or eliminate the royalty revenues derived from such patents.

For 2011 compared to 2010, as well as for 2010 compared to 2009, the increase in royalty revenues was primarily the result of an increase in sales of ANGIOMAX, which was licensed to The Medicines Company (TMC). Royalty revenues from the net worldwide sales of ANGIOMAX are recognized in an amount equal to the level of net sales achieved during a calendar year multiplied by the royalty rate in effect for that tier under our agreement with TMC. The royalty rate increases based upon which tier of total net sales are earned in any calendar year. The increased royalty rate is applied retroactively to the first dollar of net sales achieved during the year. This formula has the effect of increasing the amount of royalty revenue to be recognized in later quarters and, as a result, an adjustment is recorded in the periods in which an increase in royalty rate has been achieved. The increase in royalty revenues related to the sale of ANGIOMAX for 2011 compared to 2010 reflects a $14.7 million adjustment recorded in the fourth quarter of 2011, as net sales levels for 2011 achieved a new royalty tier.

Under the terms of our agreement, TMC is obligated to pay us royalties earned, on a country-by-country basis, until the later of (1) twelve years from the date of the first commercial sale of ANGIOMAX in such country or (2) the date upon which the product is no longer covered by a licensed patent in such country. The annual royalty rate is reduced by a specified percentage in any country where the product is no longer covered by a licensed patent and where sales have been reduced to a certain volume-based market share. TMC began selling ANGIOMAX in the U.S. in January 2001. The principal U.S. patent that covers ANGIOMAX ( ’404 Patent) was due to expire in March 2010 and TMC applied for an extension of the term of this patent. Initially, the U.S. Patent and Trademark Office (PTO) rejected TMC’s application because in its view the application was not timely filed. TMC sued the PTO in federal district court seeking to extend the term of the ’404 patent to December 2014. On August 3, 2010, the federal district court ordered the PTO to deem the application as timely filed. A generic manufacturer challenged the federal district court’s order in an appellate proceeding, but on January 23, 2012 the manufacturer filed a motion to dismiss its appeal. The PTO has granted an interim extension of the patent term until August 23, 2012 pending completion of its review of TMC’s application for extension to December 2014. In the event that TMC is unsuccessful in obtaining a patent term extension to December 2014 and third parties sell products comparable to ANGIOMAX, we would expect a significant decrease in royalty revenues due to increased competition, which may impact sales and result in lower royalty tiered rates.

Corporate Partner Revenues

We have also sold or exclusively licensed to third parties rights to certain products previously included within our product line. Supply agreement revenues received based upon those products are recorded as corporate partner revenue. Amounts recorded as corporate partner revenue also include amounts earned upon delivery of product under contract manufacturing agreements.

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For 2011 compared to 2010, as well as for 2010 compared to 2009, the increase in corporate partner revenues was primarily due to increased contract manufacturing activity. Corporate partner revenues for 2011 also includes a one-time cash payment of approximately $11.0 million received in exchange for entering into an asset transfer agreement in March 2011 related to two research and development programs that were discontinued in connection with our November 2010 restructuring initiative.

Reserves for Discounts and Allowances

Revenues from product sales are recorded net of applicable allowances for trade term discounts, wholesaler incentives, Medicaid rebates, Veterans Administration (VA) and Public Health Service (PHS) discounts, managed care rebates, product returns, and other governmental rebates or applicable allowances including those associated with the implementation of pricing actions in certain of international markets in which we operate.

Reserves established for these discounts and allowances are classified as reductions of accounts receivable (if the amount is payable to our direct customer) or a liability (if the amount is payable to a party other than our customer). These reserves are based on estimates of the amounts earned or to be claimed on the related sales. Our estimates take into consideration our historical experience, current contractual and statutory requirements, specific known market events and trends, and forecasted customer buying patterns. Actual amounts may ultimately differ from our estimates. If actual results vary, we will need to adjust these estimates, which could have an effect on earnings in the period of adjustment. The estimates we make with respect to these allowances represent the most significant judgments with regard to revenue recognition.

Reserves for discounts, contractual adjustments and returns that reduced gross product revenues are summarized as follows:

	For the Years Ended December 31,									% Change
										2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011			2010			2009
Discounts	$	96.0		$	77.9		$	74.0			23.2	%		5.3	%
Contractual adjustments		346.4			282.6			192.5			22.6	%		46.8	%
Returns		14.8			14.3			16.6			3.5	%		(13.9	)%
Total allowances	$	457.2		$	374.8		$	283.1			22.0	%		32.4	%
Gross product revenues	$	4,293.3		$	3,844.9		$	3,436.0			11.7	%		11.9	%
Percent of gross product revenues		10.6	%		9.7	%		8.2	%

Discount reserves include trade term discounts and wholesaler incentives. For 2011 compared to 2010, as well as for 2010 compared to 2009, the increase in discounts was primarily driven by increases in trade term and volume discounts and wholesaler incentives as a result of price increases and increased sales.

Contractual adjustment reserves relate to Medicaid and managed care rebates, VA and PHS discounts and other government rebates or applicable allowances. For 2011 compared to 2010, as well as for 2010 compared to 2009, the increase in contractual adjustments was due to higher reserves for managed care and Medicaid and VA programs principally associated with price increases in the U.S. and an increase in contractual rates as well as an increase in governmental rebates and allowances associated with the implementation of pricing actions in certain of the international markets in which we operate.

Product return reserves are established for returns made by wholesalers. In accordance with contractual terms, wholesalers are permitted to return product for reasons such as damaged or expired product. The majority of wholesaler returns are due to product expiration. Reserves for product returns are recorded in the period the related revenue is recognized, resulting in a reduction to product sales. For 2011 compared to 2010, as well as for 2010 compared to 2009, return reserves remained relatively unchanged.

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Cost and Expenses

A summary of total cost and expenses is as follows:

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Cost of sales, excluding amortization of acquired intangible assets	$	466.8	$	400.3	$	382.1		16.6	%		4.8	%
Research and development		1,219.6		1,248.6		1,283.1		(2.3	)%		(2.7	)%
Selling, general and administrative		1,056.1		1,031.5		911.0		2.4	%		13.2	%
Collaboration profit sharing		317.8		258.1		215.9		23.1	%		19.5	%
Amortization of acquired intangible assets		208.6		208.9		289.8		(0.2	)%		(27.9	)%
Fair value adjustment of contingent consideration		36.1		—		—		**			**
Restructuring charge		19.0		75.2		—		(74.7	)%		**
Acquired in-process research and development		—		245.0		—		(100.0	)%		**
Total cost and expenses	$	3,323.9	$	3,467.5	$	3,081.9		(4.1	)%		12.5	%

Cost of Sales, Excluding Amortization of Acquired Intangible Assets (Cost of Sales)

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Cost of sales, excluding amortization of acquired intangible assets	$	466.8	$	400.3	$	382.1		16.6	%		4.8	%

For 2011 compared to 2010, the increase in cost of sales was driven by higher unit sales volumes, increased contract manufacturing and production costs, and an increase in amounts written down related to excess, obsolete or unmarketable inventory. These increases were partially offset by the sale of inventory produced under our high-titer production process. Cost of sales for 2011 also includes increased costs associated with AVONEX PEN, the JC virus antibody assay, and sales of FAMPYRA, while cost of sales for 2010 included $6.7 million of period expense related to the shutdown for capital upgrades of our manufacturing facility in Research Triangle Park, North Carolina (RTP).

For 2010 compared to 2009, the increase in cost of sales was primarily due to higher unit sales volumes, increased contract manufacturing activity as well as $6.7 million of period expense incurred related to the shutdown for capital upgrades of our manufacturing facility in RTP. This comparative increase was offset by the sale of previously written-down TYSABRI inventory, which became saleable following approval of our new higher-yielding manufacturing process. The distribution of this inventory, which was fully utilized during 2010, reduced our cost of sales by $11.4 million compared to 2009. In addition, the sale of inventory produced under our new high-titer production process reduced our cost of sales by $8.4 million compared to 2009.

We expect an increase in total cost of sales for 2012 compared to 2011, as a result of higher expected sales volumes and increased contract manufacturing activity.

Our products are subject to strict quality control and monitoring which we perform throughout the manufacturing process. Periodically, certain batches or units of product may no longer meet quality specifications or may expire. The expiry associated with our inventory is generally between 6 months and 5 years, depending on the product. Obsolescence due to expiration has historically been insignificant.

Amounts written down related to excess, obsolete or unmarketable inventory are charged to cost of sales, and totaled $25.4 million, $11.8 million, and $16.9 million for the years ended December 31, 2011, 2010, and 2009, respectively.

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Research and Development

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Research and development	$	1,219.6	$	1,248.6	$	1,283.1		(2.3	)%		(2.7	)%

Research and development expense for 2011 compared to 2010, reflects our efforts to allocate resources within our research and development organization consistent with our restructuring initiative, which is described below under the heading Restructuring Charge, and resulted in a reduction in spending related to certain programs which were terminated or are in the process of being discontinued. These decreases were offset by research and development costs associated with initiatives to grow our business, which include increased clinical trial activity for certain of our late stage product candidates, such as dexpramipexole, Factor VIII, Factor IX, and PEGylated interferon beta-1a. Research and development expense for 2011 compared to 2010, also reflects a reduction in milestone and upfront payments recognized within research and development expense.

For 2010 compared to 2009, research and development expense decreased by $34.5 million. This decrease reflects a reduction in milestone and upfront payments recognized within research and development expense and a reduction in spending in certain deprioritized programs offset by increased clinical activity for our daclizumab, PEGylated interferon beta-1a, neublastin, Factor VIII and Factor IX programs as well as efforts to research and develop protocols that may reduce risk and improve outcomes of PML in patients treated with TYSABRI. In addition, our costs for the Factor VIII and Factor IX programs increased in 2010 following the restructuring of our collaboration agreement with Swedish Orphan Biovitrum, whereby we assumed full development and manufacturing responsibilities for these programs.

We intend to continue committing significant resources to targeted research and development opportunities where there is a significant unmet need and where the drug candidate has the potential to be highly differentiated. Specifically, we intend to continue to make significant investments in the advancement of BG-12 and our Factor VIII and Factor IX hemophilia programs. We also intend to continue to invest in bringing forward our MS pipeline and in pursuing therapies for other neurodegenerative diseases.

We expect total research and development expense in 2012 to be between 24% and 25% of total revenue, and as a result, we expect a modest increase in total research and development expense for 2012 compared to 2011.

Milestone and Upfront Payments included in Research and Development Expense

Milestone and upfront payments to our collaboration partners, included within research and development expense, totaled $45.9 million, $68.9 million and $151.5 million for 2011, 2010 and 2009, respectively.

Included in total research and development expense in 2011 is a charge of $36.8 million related to an upfront payment made in connection with our collaboration and license agreement entered into with Portola Pharmaceuticals, Inc. Research and development expense for 2010 included the $26.4 million upfront payment made to Knopp Neurosciences, Inc. (Knopp), which became payable to Knopp upon our entering a license agreement for dexpramipexole in August 2010 as well as a $30.0 milestone paid to Abbott Biotherapeutics Corp, formerly Facet Biotech, in May 2010 upon initiation of patient enrollment in a Phase 3 trial of daclizumab in relapsing MS.

For 2010 compared to 2009, the decrease in milestone and upfront payments was primarily the result of the $110.0 million upfront payment made to Acorda in 2009. The timing of future upfront fees and milestone payments may cause variability in future research and development expense.

Selling, General and Administrative

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Selling, general and administrative	$	1,056.1	$	1,031.5	$	911.0		2.4	%		13.2	%

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For 2011 compared to 2010, the increase in selling, general and administrative expenses was primarily due to initiatives to grow our business, the negative impact of foreign currency exchange rates and increased sales and marketing activities in support of AVONEX and TYSABRI, as well as costs incurred in support of the potential launch of BG-12, offset by a decrease in grant and sponsorship activity and savings realized through our restructuring initiatives, which are described below under the heading Restructuring Charge. Selling, general and administrative expenses for 2010 also included incremental charges totaling $18.6 million, which were recognized in relation to the modification of equity based compensation in accordance with the transition agreement entered into with James C. Mullen, who retired as our President and Chief Executive Officer on June 8, 2010.

For 2010 compared to 2009, the increase in selling, general and administrative expenses was primarily due to increased sales and marketing activities in support of AVONEX and TYSABRI, the incremental charges related to the transition agreement with Mr. Mullen discussed above, and increased grant and sponsorship activity.

We expect total selling, general and administrative expense in 2012 to be between 22% and 23% of total revenue. The expected increase in selling, general and administrative expenses to be incurred in 2012 over 2011 is related to the development of sales force and promotional spending in support of FAMPYRA and the potential launches of BG-12 and our Factor VIII and Factor IX programs.

Collaboration Profit Sharing

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Collaboration profit sharing	$	317.8	$	258.1	$	215.9		23.1	%		19.5	%

For 2011 compared to 2010, as well as for 2010 compared to 2009, the increases in collaboration profit sharing expense were due to the continued increase in TYSABRI rest of world sales resulting in higher rest of world net operating profits to be shared with Elan and resulting in growth in the third-party royalties Elan paid on behalf of the collaboration. For 2011, 2010, and 2009, our collaboration profit sharing expense included $55.5 million, $45.5 million and $40.0 million related to the reimbursement of third-party royalty payments made by Elan. For additional information about this collaboration, please read Note 20, Collaborations to our consolidated financial statements included in this report.

Amortization of Acquired Intangible Assets

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Amortization of acquired intangible assets	$	208.6	$	208.9	$	289.8		(0.2	)%		(27.9	)%

For 2011 compared to 2010, as well as for 2010 compared to 2009, the change in amortization of acquired intangible assets is primarily driven by the amount of amortization recorded in relation to our AVONEX core technology asset. Amortization for acquired intangible assets is expected to be in the range of approximately $160.0 million to $200.0 million annually through 2016.

AVONEX Core Technology Asset

Our most significant intangible asset is the core technology related to our AVONEX product. Our amortization policy reflects our belief that the economic benefit of our core technology is consumed as revenue is generated from our AVONEX product. We refer to this amortization methodology as the economic consumption model, which involves calculating a ratio of actual current period sales to total anticipated sales for the life of the

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product and applying this ratio to the carrying amount of the intangible asset. An analysis of the anticipated lifetime revenues of AVONEX is performed at least annually during our long range planning cycle, and this analysis serves as the basis for the calculation of our economic consumption model. We believe this process has allowed us to reliably determine the best estimate of the pattern in which we will consume the economic benefits of our core technology intangible asset.

The results of our long range planning cycle completed in the third quarter of 2009, were most significantly impacted by the issuance in the U.S. of the AVONEX ’755 Patent in September 2009. As a result of the increase in the total expected lifetime revenue of AVONEX and the extension of the assumed remaining life of our core intangible asset, amortization recorded for the third and fourth quarters of 2009 decreased significantly from those amounts recorded during the first half of 2009.

Amortization recorded for the first and second quarters of 2010 was also recorded based upon the results of the 2009 analysis. The results of our analysis completed in the third quarter of 2010 did not result in a significant change in the expected lifetime revenues of AVONEX, and as a result, amortization recorded in the third and fourth quarters of 2010 and the first two quarters of 2011 were comparable to amounts recorded in the previous four quarters.

Our most recent long range planning cycle was completed in the third quarter of 2011, which reflected a further increase in the expected lifetime revenue of AVONEX. This most recent increase in the expected lifetime revenues of AVONEX was primarily attributable to changes in expected impact of competitor products. As a result, amortization recorded for the third and fourth quarters of 2011 decreased from those amounts recorded in the first half of 2011. Based upon this most recent analysis, amortization of our core intangible asset related to AVONEX is expected to be in the range of approximately $100.0 million to $150.0 million annually through 2016.

We monitor events and expectations regarding product performance. If there are any indications that the assumptions underlying our most recent analysis would be different than those utilized within our current estimates, our analysis would be updated and may result in a significant change in the anticipated lifetime revenue of AVONEX determined during our most recent annual review. For example, the occurrence of an adverse event, such as the invalidation of our AVONEX ’755 Patent, could substantially increase the amount of amortization expense associated with our acquired intangible assets as compared to previous periods or our current expectations, which may result in a significant negative impact on our future results of operations.

Fair Value Adjustment of Contingent Consideration

	For the Years Ended December 31,						% Change
							2011 compared to 2010	2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Fair value adjustment of contingent consideration	$	36.1	$	—	$	—	**	**

The consideration for certain of our acquisitions includes future payments that are contingent upon the occurrence of a particular factor or factors. For acquisitions completed after January 1, 2009, we record a contingent consideration obligation for such contingent consideration payments at its fair value on the acquisition date. We revalue the acquisition-related contingent consideration obligation on a recurring basis each reporting period. Changes in the fair value of our contingent consideration obligations are recognized as a fair value adjustment of contingent consideration within our consolidated statements of income.

In connection with our acquisition of Biogen Idec International Neuroscience GmbH (BIN), formerly Panima Pharmaceuticals AG (Panima), in 2010, we recorded a liability of $81.2 million representing the acquisition date fair value of the contingent consideration. There was no significant change in the valuation of this liability from the acquisition date through December 31, 2010. The fair value of this contingent consideration obligation as of December 31, 2011 was $119.1 million. The increase in the fair value of this obligation, of $37.9 million since December 31, 2010, was primarily due to changes in the discount rate and in the probability and expected timing related to the achievement of certain remaining developmental milestones, offset by the payment of a $5.0 million developmental milestone.

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In addition, we also recorded a contingent consideration obligation of $38.8 million in the third quarter of 2011 related to our purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH, our respective sales affiliates in Italy and Switzerland. The fair value of this contingent consideration obligation as of December 31, 2011 was $31.9 million. The decrease in the fair value of this obligation, of $6.9 million since the acquisition date, was primarily due to changes in the discount rate and in the probability and expected timing related to the achievement of certain cumulative sales-based and developmental milestones.

Restructuring Charge

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Restructuring charge	$	19.0	$	75.2	$	—		(74.7	)%	**

In November 2010, we announced a number of strategic, operational, and organizational initiatives designed to provide a framework for the future growth of our business and realign our overall structure to become a more efficient and cost effective organization. As part of this initiative:

• We out-licensed or terminated certain research and development programs, including those in oncology and cardiovascular medicine, that are no longer a strategic fit for us.

• We completed a 13% reduction in workforce spanning our sales, research and development, and administrative functions.

• We vacated and recognized the sale of the San Diego, California facility as well as consolidated certain of our Massachusetts facilities. For a more detailed description of transactions affecting our facilities, please read Note 11, Property, Plant and Equipment to our consolidated financial statements included within this report.

As a result of these initiatives, we have begun to realize annual operating expense savings of which the substantial majority will be realized within research and development and selling, general and administrative expense. These savings, which are expected to approximate $300.0 million annually, are offset by costs associated with initiatives to grow our business. We have also increased our workforce to support our growth initiatives, including efforts to bring forward our late stage pipeline.

Costs associated with our workforce reduction are primarily related to employee severance and benefits. Facility consolidation costs are primarily comprised of charges associated with closing these facilities, related lease obligations and additional depreciation recognized when the expected useful lives of certain assets have been shortened due to the consolidation and closing of related facilities and the discontinuation of certain research and development programs. As of December 31, 2011, substantially all restructuring charges have been incurred and paid. We incurred $19.0 million of these charges during 2011, of which $12.8 million were related to our workforce reduction and $6.2 million related to the consolidation of our facilities. During the fourth quarter of 2010, we incurred $75.2 million of these charges, of which $67.2 million were related to our workforce reduction and $8.0 million were related to the consolidation of our facilities.

The following table summarizes the activity of our restructuring liability:

(In millions)	Workforce Reduction			Facility Consolidation			Total
Restructuring reserve as of December 31, 2010	$	60.6		$	5.8		$	66.4
Expense		15.8			2.4			18.2
Payments		(81.8	)		(3.9	)		(85.7	)
Adjustments to previous estimates, net		(2.9	)		—			(2.9	)
Other adjustments		8.6			(3.2	)		5.4
Restructuring reserve as of December 31, 2011	$	0.3		$	1.1		$	1.4

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Acquired In-process Research and Development (IPR&D)

	For the Years Ended December 31,						% Change
							2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010		2009
Acquired in-process research and development	$	—	$	245.0	$	—		(100.0	)%	**

In August 2010, we entered into a license agreement with Knopp for the development, manufacture and commercialization of dexpramipexole, an orally administered small molecule in clinical development for the treatment of ALS. As we determined that we are the primary beneficiary of this relationship, we consolidate the results of Knopp and recorded an IPR&D charge of approximately $205.0 million upon initial consolidation within our consolidated statements of income for 2010. We attributed approximately $145.0 million of the total IPR&D charge to the noncontrolling interest, representing the noncontrolling interest’s ownership interest in the equity of Knopp. For additional information related to this transaction, please read Note 19, Investments in Variable Interest Entities to our consolidated financial statements included in this report.

In connection with our acquisition of Biogen Idec Hemophilia Inc., formerly Syntonix Pharmaceuticals, Inc. (Syntonix), in January 2007, we agreed to make additional payments based upon the achievement of certain milestone events. One of these milestones was achieved when, in January 2010, we initiated patient enrollment in a registrational trial of Factor IX in hemophilia B. As a result of the achievement of this milestone we paid approximately $40.0 million to the former shareholders of Syntonix, which was reflected as a charge to acquired IPR&D within our consolidated statement of income for 2010.

Other Income (Expense), Net

Components of other income (expense), net, are summarized as follows:

	For the Years Ended December 31,									% Change
										2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011			2010			2009
Interest income	$	19.2		$	22.3		$	48.5			(13.9	)%		(54.0	)%
Interest expense		(33.0	)		(36.1	)		(35.8	)		(8.6	)%		(0.8	)%
Impairments on investments		(11.5	)		(21.3	)		(10.6	)		(46.0	)%		(100.9	)%
Foreign exchange gains (losses), net		(6.3	)		(3.5	)		11.4			80.0	%		(130.7	)%
Gain (loss) on sales of investments, net		17.4			16.3			22.8			6.7	%		(28.5	)%
Other, net		0.7			3.3			1.0			(78.8	)%		230.0	%
Total other income (expense), net	$	(13.5	)	$	(19.0	)	$	37.3			(28.9	)%		(151.0	)%

Interest Income

For 2011 compared to 2010, as well as for 2010 compared to 2009, interest income decreased primarily due to lower interest yields on cash, cash equivalents, and marketable securities offset by an increase in average cash balances. The decrease for 2010 compared to 2009, was also due to lower average cash balances.

Interest Expense

For 2011 compared to 2010 the decrease in interest expense was primarily due to an increase in the amount of capitalized interest. For 2010 compared to 2009, interest expense remained relatively unchanged.

For 2011, 2010 and 2009, we capitalized interest costs related to construction in progress totaling approximately $32.6 million, $28.6 million and $28.5 million, respectively, which reduced our interest expense by the same amount. Capitalized interest costs are primarily related to the development of our large-scale biologic manufacturing facility in Hillerød, Denmark.

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Impairment on Investments

In 2011, we recognized $11.5 million in charges for the impairment of our publicly-held strategic investments, investments in venture capital funds and investments in privately-held companies.

In 2010, we recognized $21.3 million in charges for the other-than-temporary impairment of our publicly held strategic investments, investments in venture capital funds and investments in privately held companies. The increase over amounts recognized in 2009 was primarily the result of one of our strategic investments, executing an equity offering at a price below our cost basis during the first quarter of 2010.

In 2009, we recognized impairment losses of $7.0 million on our publicly-held strategic investments and non-marketable securities and an additional $3.6 million in charges for the other-than-temporary impairment on our marketable debt securities primarily related to mortgage and asset-backed securities.

We may incur additional impairment charges on these investments in the future.

Income Tax Provision

	For the Years Ended December 31,									% Change
										2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011			2010			2009
Effective tax rate on pre-tax income		26.0	%		26.9	%		26.7	%		(3.3	)%		0.7	%
Income tax expense	$	444.5		$	331.3		$	355.6			34.2	%		(6.8	)%

Our effective tax rate fluctuates from year to year due to the global nature of our operations. The factors that most significantly impact our effective tax rate include variability in the allocation of our taxable earnings between multiple jurisdictions, changes in tax laws, the amount and characterization of our research and development expenses, acquisitions and licensing transactions.

Our effective tax rate for 2011 compared to 2010 decreased primarily due to our 2010 license and collaboration agreement with Knopp, which negatively impacted our 2010 effective tax rate due to the attribution to noncontrolling interest of $145.0 million of the associated IPR&D charge. As such, the attributed amount did not generate a tax deduction, causing our tax rate to be unfavorably impacted by 2.8%. In addition, during 2011, we experienced an increase in research and development expenditures eligible for the orphan drug credit, a lower effective state tax rate resulting from a change in state law and the settlement of outstanding matters related to state and federal audits. These favorable items were offset by a higher percentage of our 2011 profits being earned in higher tax rate jurisdictions, principally the U.S., and a non-deductible charge for contingent consideration associated with the acquisition of Panima.

For 2010 compared to 2009, our effective tax rate was negatively impacted due to the attribution to noncontrolling interest of $145.0 million of the IPR&D charge related to our license agreement with Knopp. The impact of the Knopp transaction was partially offset by a higher percentage of our profits being earned in lower rate international jurisdictions in 2010. This change in the location of our relative profits was caused by the growth of our international operations and lower 2010 domestic earnings as a proportion of total consolidated earnings.

During 2010, we also experienced a favorable impact on our effective tax rates due to a statutory increase in the U.S. manufacturers’ tax deduction and an increase in expenditures eligible for our orphan drug credit. In addition, our 2009 effective tax rate was increased by 2.1% as a result of the $110.0 million upfront payment incurred in connection with the collaboration and license agreement entered into with Acorda in the second quarter of 2009. Our effective tax rate for 2009 was also favorably impacted by 2.3% for changes in tax law which became effective during the first quarter of 2009 in certain state jurisdictions in which we operate and the favorable resolution of certain federal, state and foreign tax audits. The resolution of these tax audits resulted in a reduction of our reserves for several uncertain tax positions, which had a favorable impact of 2.1% on our 2009 effective tax rate.

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Our effective tax rate will continue to be dependent upon the allocation of our profits amongst jurisdictions, the percentage of our earnings which are subject to taxation in the U.S. and our level of deductible research and development spending. During 2012 we expect our effective tax rate to be between 24% and 26%. We expect this decrease in rate due to higher clinical trial spending on orphan drug credit eligible programs, including the Phase III studies for Factor VIII, Factor IX and dexpramipexole, and the cessation of certain inter-company royalties owed by a foreign affiliate of ours to a U.S. affiliate, on the international sales of one of our products.

Noncontrolling Interest

	For the Years Ended December 31,							% Change
								2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011		2010			2009
Net income (loss) attributable to noncontrolling interests, net of tax	$	32.3	$	(106.7	)	$	6.9		(130.3	)%		(1,646.4	)%

On September 6, 2011, we completed the purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH, our respective sales affiliates in Italy and Switzerland. Prior to this transaction, our consolidated financial statements reflected 100% of the operations of these joint venture investments and we recorded net income (loss) attributable to noncontrolling interests in our consolidated statements of income based on the percentage of ownership interest retained by our joint venture partners. We have continued to consolidate the operations of these entities following our purchase of the noncontrolling interest; however, as of September 6, 2011, we no longer allocate 50% of the earnings of these ventures to net income (loss) attributable to noncontrolling interests as Biogen Dompé SRL and Biogen Dompé Switzerland GmbH became wholly-owned subsidiaries of the Company. For additional information related to this transaction, please read Note 2, Acquisitions to our consolidated financial statements included within this report.

For 2011 compared to 2010, the change in net income attributable to noncontrolling interests, net of tax, primarily resulted from the impact of our Knopp transaction recorded in 2010, offset by the $25.0 million termination payment made to Cardiokine. Net income attributable to noncontrolling interests, net of tax, for 2011 also reflects a reduction in earnings from our foreign joint ventures due to our purchase of the noncontrolling interest in our joint venture investments described above, as well as the attribution of a $15.0 million milestone payment to Neurimmune SubOne AG (Neurimmune) upon our submission an Investigational New Drug application for BIIB037 (human anti-Amyloid ß mAb) in April 2011, and the attribution of a $10.0 million milestone payment to Knopp upon dosing the first patient in a registrational study for dexpramipexole in March 2011.

For 2010 compared to 2009, the decrease in net income attributable to noncontrolling interests was primarily the result of the attribution of $145.0 million of the $205.0 million IPR&D charge recognized upon consolidation of the Knopp variable interest entity to the noncontrolling interest in the third quarter of 2010 offset by the $25.0 million payment made to Cardiokine upon the termination of our license agreement and an attribution of earnings from our foreign joint ventures.

New Cambridge Leases

In July 2011, we executed leases for two office buildings to be built in Cambridge, Massachusetts with a planned occupancy during the second half of 2013. Construction of these facilities began in late 2011. These buildings will serve as the future location of our corporate headquarters and commercial operations. These buildings will also provide additional general and administrative and research and development office space.

As a result of our decision to relocate our corporate headquarters and centralize our campus in Cambridge, Massachusetts, we expect to vacate our Weston, Massachusetts facility upon completion of the new buildings. Based upon our most recent estimates, we expect to incur a charge of approximately $35.0 million upon vacating this facility when the new Cambridge buildings have been completed. This amount represents our remaining Weston lease obligation, net of our estimate of sublease income expected to be recovered. In addition, this

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decision has also resulted in a change in the expected useful lives of certain leasehold improvements and other assets, which have been shortened due to our anticipated departure from this facility and will result in approximately $25.0 million of additional depreciation that will be realized ratably from the third quarter of 2011 through the date upon which we expect to vacate the Weston facility. Approximately $4.7 million of this additional depreciation was recognized in 2011.

Market Risk

We conduct business globally. As a result, our international operations are subject to certain opportunities and risks which may affect our results of operations, including volatility in foreign currency exchange rates or weak economic conditions in the foreign markets in which we operate.

Foreign Currency Exchange Risk

Our results of operations are subject to foreign currency exchange rate fluctuations due to the global nature of our operations. While the financial results of our global activities are reported in U.S. dollars, the functional currency for most of our foreign subsidiaries is their respective local currency. Fluctuations in the foreign currency exchange rates of the countries in which we do business will affect our operating results, often in ways that are difficult to predict. For example, when the U.S. dollar strengthens against foreign currencies, the relative value of sales made in the respective foreign currencies decreases, conversely, when the U.S. dollar weakens against foreign currencies, the relative amount of such sales in U.S. dollars increases.

Our net income may also fluctuate due to the impact of our foreign currency hedging program, which is designed to mitigate, over time, a portion of the impact resulting from volatility in exchange rate changes on net income and earnings per share. We use foreign currency forward contracts to manage foreign currency risk with the majority of our forward contracts used to hedge certain forecasted revenue transactions denominated in foreign currencies. Other foreign currency gains or losses arising from our operations are recognized in the period in which we incur those gains or losses.

In addition, there is speculation that due to the global economic downturn the future of the euro may be uncertain. A significant number of our foreign subsidiaries have the euro as their local currency. In the event that certain countries, such as Greece, abandon the euro the resultant macroeconomic impact remains unknown. An abandonment of the euro, in any or all of the countries in which we operate, could have a significant impact on our results of operations. Our balance sheet exposure to Greece is limited as our only receivables in this market are due from our distributor, which totaled approximately $4.0 million as of December 31, 2011. In addition, we maintain no investment holdings backed by the Greek government.

Pricing Pressure

Global economic conditions continue to present challenges for our industry. The global economic downturn and the deterioration of credit and economic conditions continue to impact our results of operations, particularly in countries where government-sponsored healthcare systems are the primary payers for healthcare. Global economic conditions may be further impacted by additional negative economic developments in countries such as France, Italy, Portugal and Spain, whose sovereign debt obligations were recently downgraded and Greece, which is facing possible default of its sovereign debt obligations. As a result, many countries worldwide, particularly those within the European Union, are reducing their public expenditures in an effort to achieve cost savings.

Governments in a number of international markets, in which we operate, including Germany, France, Italy, the United Kingdom and Spain have announced or implemented austerity measures aimed at reducing healthcare costs to constrain the overall level of government expenditures. The implementation of measures varies by country and include among other things, mandatory rebates and discounts, price reductions and suspensions on pricing increases on pharmaceuticals. Certain implemented measures have already negatively impacted our revenues throughout 2010 and 2011. We expect to see continued efforts to achieve additional reductions in public expenditures and consequently expect that our revenues and results of operations will be further negatively impacted if these, similar or more extensive measures are, or continue to be, implemented in these and other

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countries in which we operate. Based upon our most recent estimates, we expect such measures will reduce our revenues in 2012 by approximately $40.0 to $60.0 million.

In addition, certain countries set prices by reference to the prices in other countries where our products are marketed. Thus, our inability to secure adequate prices in a particular country may impair our ability to obtain acceptable prices in existing and potential new markets and limit market growth. The continued implementation of pricing actions throughout Europe may also lead to higher levels of parallel trade.

Recent austerity measures that have or are expected to impact our results of operations include, but are not limited to, the following:

France: AVONEX reimbursement rates are subject to periodic pricing review. Following a therapeutic class review, revised prices for interferons and glatiramer acetate have recently been published in France. As a result, the price of AVONEX and AVONEX PEN will be reduced by 10% effective April 1, 2012 and October 1, 2012, respectively. We do not expect a change in TYSABRI pricing during 2012.

In September 2011, the French government announced that the national target for expenditures in public healthcare has been significantly reduced in an effort to decrease the social security deficit. To achieve this goal, additional austerity measures are being implemented, including an increase in the local pharmaceutical tax from 1.0% to 1.6%. Additional measures to reduce pricing and reimbursement rates and eligibility are expected. Our negotiations to establish the price of FAMPYRA will be subject to such measures.

Germany: Effective August 2010, the German government enacted a three-year freeze on drug price increases lasting through the end of 2013 and increased the mandatory rebate on drugs not covered by the reference pricing system from 6% to 16%. As a result, sales of AVONEX, TYSABRI, FUMADERM and FAMPYRA have been, and will continue to be, negatively impacted. In addition, the German government further implemented additional legislation in 2011 to manage pricing associated with new drug products introduced to the German market. Under this most recent legislation, drug manufacturers will have one year from the introduction of a new drug to agree pricing with health insurers and requires manufacturers to prove that the new drug product provides some form of added clinical benefit compared to existing drugs or it will be included in a reference pricing scheme. These new drug product pricing regulations may negatively impact revenues on sales of FAMPYRA beginning in the second half of 2012.

Italy: In December 2011, the Italian government approved emergency austerity and growth measures aimed at stabilizing and growing the local economy as well as balancing the country’s budget by 2013. Included within these austerity measures are actions to reduce pharmaceutical and healthcare spending which include limiting the reimbursement of prescription drugs; however, most of the cost-cutting measures in the austerity package related to pharmaceutical spending are due to be introduced in 2013 and 2014. In addition to these actions, additional measures may be implemented in 2012 which may impact revenues on future sales. Accordingly, the impact on revenues on sales of AVONEX, TYSABRI and FAMPYRA resulting from these expected actions in future periods is uncertain.

Furthermore, in the fourth quarter of 2011, Biogen Idec Italia SRL received a notice from the Italian National Medicines Agency (AIFA) stating that sales of TYSABRI for the period from February 2009 through February 2011 exceeded by Euro 30.7 million a reimbursement limit established pursuant to a Price Determination Resolution (Price Resolution) granted by AIFA in February 2007. In December, we filed an appeal against AIFA seeking a ruling that our interpretation of the Price Resolution is valid and that the position of AIFA is unenforceable. While we believe that we have good and valid grounds for our appeal, an unfavorable decision could negatively impact our results of operations. As a result of this dispute, we deferred $13.8 million of revenue recognized on sales of TYSABRI in Italy in the fourth quarter of 2011 and expect that we will continue to defer a portion of our revenues on future sales of TYSABRI in Italy until this matter is resolved. For additional information, please read Note 21, Litigation to our consolidated financial statements included within this report.

Spain: Our operations in Spain have been negatively impacted by the implementation of an incremental 7.5% rebate, which became effective in June 2010, on all branded drugs reimbursed under the Spanish National Health System. As a result, sales of AVONEX and TYSABRI have been negatively impacted.

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Additional discounts could be implemented beginning in mid-year 2012, which may negatively affect revenues on sales of our products in Spain in future periods. A periodic pricing review of TYSABRI is also expected in 2012.

United Kingdom: AVONEX pricing is subject to the Multiple Sclerosis Risk Sharing Scheme, which aims to ensure that therapies can be purchased at a cost effective price as assessed by the National Institute of Health and Clinical Excellence (NICE). Clinical outcomes from treated patients are entered into a health economic model, which allows monitoring of the cost-effectiveness of each of the drugs in the scheme. Actual and expected benefits of the drugs are compared and if there is a significant shortfall in actual compared to expected benefit for a particular product, the price of the product may be reduced. The results of this most recent analysis are expected in the second half of 2012.

In addition, while no specific price cuts have been imposed to date in the United Kingdom, measures to contain and reduce healthcare expenditures are also being considered. The implementation of these measures may negatively affect our revenues and results of operations in future periods.

Credit Risk

We are subject to credit risk from our accounts receivable related to our product sales. The majority of our accounts receivable arise from product sales in the U.S. and Europe with concentrations of credit risk limited due to the wide variety of customers and markets using our products, as well as their dispersion across many different geographic areas. Our accounts receivable are primarily due from wholesale distributors, public hospitals and other government entities. We monitor the financial performance and credit worthiness of our large customers so that we can properly assess and respond to changes in their credit profile. We operate in certain countries where the economic conditions continue to present challenges. We continue to monitor these conditions, including the volatility associated with international economies and the relevant financial markets, and assess their possible impact on our business. Our historical write-offs of accounts receivable have not been significant.

Within the European Union, our accounts receivable in Italy, Spain, and Portugal continue to be subject to significant payment delays due to government funding and reimbursement practices. The credit and economic conditions within these countries have continued to deteriorate. These conditions have increased, and may continue to increase, the average length of time that it takes to collect on our accounts receivable outstanding in these countries. Our accounts receivable exposure to Greece is limited as our only receivables in this market are due from our distributor.

Although our contractual payment terms have not changed, over the past year we have noted a lengthening in the time period required to collect accounts receivable balance in certain countries. In countries where we expect to collect receivables greater than one year, at the time of sale, we have discounted our revenues over the period of time that we estimate those amounts will be paid using our estimate of the country’s borrowing rate. The related receivables are classified at the time of sale as long-term assets.

Our net accounts receivable balances from product sales in these countries are summarized as follows:

	As of December 31, 2011
(In millions)	Current Balance Included within Accounts Receivable, net		Non-Current Balance Included within Investments and Other Assets		Total
Spain	$	68.5	$	65.5	$	134.0
Italy	$	19.4	$	48.7	$	68.1
Portugal	$	20.6	$	12.3	$	32.9
Greece	$	4.0	$	—	$	4.0

	As of December 31, 2010
(In millions)	Current Balance Included within Accounts Receivable, net		Non-Current Balance Included within Investments and Other Assets		Total
Spain	$	70.8	$	29.8	$	100.6
Italy	$	103.2	$	14.8	$	118.0
Portugal	$	17.8	$	5.5	$	23.3
Greece	$	3.9	$	—	$	3.9

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Approximately $56.0 million and $45.0 million of the aggregate balances for these countries were overdue more than one year as of December 31, 2011 and December 31, 2010, respectively. Amounts included as a component of investments and other assets within our consolidated balance sheets represent amounts that are expected to be collected beyond one year.

In connection with our purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL, we entered into a credit assignment agreement with Dompé Farmaceutici SpA. Under the terms of this agreement, Dompé Farmaceutici SpA purchased all of Biogen Dompé SRL’s outstanding receivables as of June 30, 2011, adjusted for cash received through September 5, 2011, for $104.6 million. We have no retained interests in these receivables and have accounted for this transaction as a sale recognizing a loss of $1.8 million upon their disposition. For additional information related to these transactions, please read Note 2, Acquisitions to our consolidated financial statements included within this report. As of December 31, 2011, our accounts receivable balances in Italy totaled $68.1 million, all of which resulted from sales of product subsequent to June 30, 2011.

In May 2011, European Union finance ministers approved a three-year EUR78 billion rescue package for Portugal. Under the terms of the package, Portugal is required to correct its excessive deficit by 2013 and improve the efficiency and effectiveness of its health care system, including through austerity measures aimed at reducing healthcare costs. These measures include plans to standardize control procedures to reduce outstanding balances payable to drug suppliers. In December 2011, the International Monetary Fund (IMF) approved the second review of Portugal’s progress under the rescue program, noting both that Portugal’s program remained broadly on track but that a continued deterioration of the economic conditions in Europe remains a serious risk. We will continue to monitor Portugal’s progress against program targets and assess the collectability of our outstanding receivables within this market.

Our concentrations of credit risk related to our accounts receivable from product sales in Greece to date have been limited as our receivables within this market are due from our distributor. As of December 31, 2011 and December 31, 2010, our accounts receivable balances due from this distributor totaled $4.0 million and $3.9 million, respectively. These receivables remain current and substantially in compliance with their contractual due dates. However, the majority of the sales by our distributor are to government funded hospitals and as a result our distributor maintains significant outstanding receivables with the government of Greece, which remains in a deep recession. In the event that Greece defaults on its debt and is unable to pay our distributor, we may be unable to collect some or all of our remaining amounts due from the distributor. In addition, the government of Greece may also require pharmaceutical creditors to accept mandatory, retroactive, price deductions in settlement of outstanding receivables and in this event we could be required to repay our distributor a portion of the amounts they have previously remitted to us. To date, we have not been required to repay such amounts to our distributor or take a discount in settlement of any outstanding receivables.

We believe that our allowance for doubtful accounts was adequate as of December 31, 2011 and 2010, respectively; however, if significant changes occur in the availability of government funding or the reimbursement practices of these or other governments, we may not be able to collect on amounts due to us from customers in such countries and our results of operations could be adversely affected.

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Financial Condition and Liquidity

Our financial condition is summarized as follows:

	As of December 31,						% Change 2011 compared to 2010
(In millions, except percentages)	2011			2010
Financial assets:
Cash and cash equivalents	$	514.5		$	759.6			(32.3	)%
Marketable securities — current		1,176.1			448.1			162.5	%
Marketable securities — non-current		1,416.7			743.1			90.6	%
Total cash, cash equivalents and marketable securities	$	3,107.3		$	1,950.8			59.3	%
Borrowings:
Current portion of notes payable, line of credit, and other financing arrangements	$	3.3		$	137.2			(97.6	)%
Notes payable, line of credit, and other financing arrangements		1,060.8			1,066.4			(0.5	)%
Total borrowings	$	1,064.1		$	1,203.5			(11.6	)%
Working Capital:
Current assets	$	2,975.4		$	2,540.4			17.1	%
Current liabilities		(912.9	)		(1,050.1	)		(13.1	)%
Total working capital	$	2,062.5		$	1,490.3			38.4	%

For the year ended December 31, 2011, certain significant cash flows were as follows:

• $3,697.0 million used for net purchases of marketable securities;

• $498.0 million used for share repurchases;

• $314.7 million in proceeds from the issuance of stock for share-based compensation arrangements;

• $332.7 million in total payments for income taxes;

• $208.0 million used for purchases of property, plant and equipment;

• $148.3 million of payments made for the purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH;

• $104.6 million in proceeds received from Dompé Farmaceutici SpA for the purchase of Biogen Dompé SRL’s outstanding receivables;

• $41.3 million in proceeds received from the sale of strategic investments;

• $36.8 million in upfront payment to Portola under our license agreement dated October 26, 2011 and a $8.2 million investment in the equity of Portola;

• $25.0 million milestone payment made to Acorda capitalized as an intangible asset.

For the year ended December 31, 2010, certain significant cash flows were as follows:

• $2,077.6 million used for share repurchases;

• $680.3 million in net proceeds received on sales and maturities of marketable securities;

• $394.7 million in total payments for income taxes;

• $183.5 million in proceeds from the issuance of stock for share-based compensation arrangements;

• $173.1 million used for purchases of property, plant and equipment;

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• $127.0 million in proceeds, net of transaction costs, received from sale of the San Diego facility;

• $26.4 million in upfront payments to Knopp under our license agreement dated August 17, 2010 and a $60.0 million investment in the equity of Knopp;

• $40.0 million payment made to the former shareholders of Syntonix recognized as IPR&D expense;

• $32.5 million payment made for the acquisition of Panima;

• $30.0 million milestone payment made to Abbott Biotherapeutics Corp (formerly Facet Biotech Corporation) recognized as research and development expense; and

• $25.0 million termination payment made to Cardiokine recognized as a distribution to a noncontrolling interest.

We have historically financed our operating and capital expenditures primarily through positive cash flows earned through our operations. We expect to continue funding our current and planned operating requirements principally through our cash flows from operations, as well as our existing cash resources. We believe that existing funds, when combined with cash generated from operations and our access to additional financing resources, if needed, are sufficient to satisfy our operating, working capital, strategic alliance, milestone payment, capital expenditure and debt service requirements for the foreseeable future. In addition, we may choose to opportunistically return cash to shareholders and pursue other business initiatives, including acquisition and licensing activities. We may, from time to time, also seek additional funding through a combination of new collaborative agreements, strategic alliances and additional equity and debt financings or from other sources should we identify a significant new opportunity.

We consider the unrepatriated cumulative earnings of certain of our foreign subsidiaries to be invested indefinitely outside the U.S. Of the total cash, cash equivalents and marketable securities at December 31, 2011, approximately $1.0 billion was generated from operations in foreign jurisdictions and is intended for use in our foreign operations or in connection with business development transactions outside of the U.S. In managing our day-to-day liquidity in the U.S., we do not rely on the unrepatriated earnings as a source of funds and we have not provided for U.S. federal or state income taxes on these undistributed foreign earnings.

For additional information related to certain risks that could negatively impact our financial position or future results of operations, please read the “Risk Factors” and “Quantitative and Qualitative Disclosures About Market Risk” sections of this report.

Preferred Stock

In March 2011, the remaining 8,221 shares of our Series A Preferred Stock were converted into 493,260 shares of common stock by the holder pursuant to the conversion terms of the Series A Preferred Stock. As of December 31, 2011, there are no shares of preferred stock issued and outstanding.

Share Repurchase Programs

In February 2011, our Board of Directors authorized the repurchase of up to 20.0 million shares of our common stock. We expect to use this repurchase program principally to offset common stock issued under our share-based compensation plans. This repurchase program does not have an expiration date. Under this authorization, we repurchased 6.0 million shares of our common stock at a cost of $498.0 million during 2011.

From January 1, 2012 through January 31, 2012, we repurchased approximately 3.5 million shares of our common stock at a total cost of approximately $401.5 million under our 2011 stock repurchase authorization. As of January 31, 2012, approximately 10.5 million shares of our common stock remain available for repurchase under this program.

During 2010, we repurchased approximately 40.3 million shares of our common stock at a cost of approximately $2.1 billion under our 2010 and 2009 stock repurchase authorizations. We retired all of these shares as they were acquired.

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Cash, Cash Equivalents and Marketable Securities

Until required for another use in our business, we invest our cash reserves in bank deposits, certificates of deposit, commercial paper, corporate notes, U.S. and foreign government instruments and other interest bearing marketable debt instruments in accordance with our investment policy. We mitigate credit risk in our cash reserves and marketable securities by maintaining a well-diversified portfolio that limits the amount of exposure as to institution, maturity, and investment type. For example, we limit our exposure to European sovereign debt securities and maintain no holdings with respect to certain euro-zone states, such as Portugal, Italy, Greece, and Spain. The value of our investments, however, may be adversely affected by increases in interest rates, downgrades in the credit rating of the corporate bonds included in our portfolio, instability in the global financial markets that reduces the liquidity of securities included in our portfolio, and by other factors which may result in declines in the value of the investments. Each of these events may cause us to record charges to reduce the carrying value of our investment portfolio if the declines are other-than-temporary or sell investments for less than our acquisition cost which could adversely impact our financial position and our overall liquidity. For a summary of the fair value and valuation methods of our marketable securities please read Note 8, Fair Value Measurements to our consolidated financial statements included within this report.

The increase in cash, cash equivalents and marketable securities from December 31, 2010, is primarily due to cash flows provided by operating activities, proceeds from the issuance of stock for share-based compensation arrangements, and proceeds received from the sale of strategic investments offset by share repurchases, tax payments, purchases of property, plant and equipment, and payments made for the purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH.

Borrowings

We have a $360.0 million senior unsecured revolving credit facility, which may be used for future working capital and general corporate purposes. The facility terminates in June 2012. During 2011, 2010 and 2009, there were no borrowings under this credit facility and we were in compliance with all applicable covenants.

We have $450.0 million aggregate principal amount of 6.0% Senior Notes due March 1, 2013 and $550.0 million aggregate principal amount of 6.875% Senior Notes due March 1, 2018 that were originally priced at 99.886% and 99.184% of par, respectively. The discount is amortized as additional interest expense over the period from issuance through maturity. These notes are senior unsecured obligations.

In connection with our 2006 distribution agreement with Fumedica, we issued notes totaling 61.4 million Swiss Francs which were payable to Fumedica in varying amounts from June 2008 through June 2018. Our remaining note payable to Fumedica had a present value of 18.6 million Swiss Francs ($19.7 million) and 20.7 million Swiss Franc ($22.0 million) as of December 31, 2011 and 2010, respectively.

In addition, balances outstanding under Biogen Dompé SRL’s credit line from us and Dompé Farmaceutici SpA were repaid in connection with our recent purchase of the noncontrolling interest in our joint venture investment in Biogen Dompé SRL. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

There have been no other significant changes in our borrowings since December 31, 2010. For a summary of the fair and carrying values of our outstanding borrowings as of December 31, 2011 and 2010, please read Note 8, Fair Value Measurements to our consolidated financial statements included within this report.

Working Capital

We define working capital as current assets less current liabilities. The increase in working capital from December 31, 2010, reflects an overall net increase in total current assets of $435.0 million and overall net decrease in total current liabilities of $137.2 million.

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The increase in total current assets was primarily due to the increase in marketable securities. The reduction in total current liabilities primarily reflects the decrease in taxes payable and the derecognition of the financing arrangement liability upon our recognition of the sale of the San Diego facility on August 31, 2011. For additional information related to the financing arrangement associated with our October 2010 sale and subsequent leaseback of the San Diego facility, please read Note 11, Property, Plant and Equipment to our consolidated financial statements included within this report.

Cash Flows

Our net cash flows are summarized as follows:

	For the Years Ended December 31,									% Change
										2011 compared to 2010			2010 compared to 2009
(In millions, except percentages)	2011			2010			2009
Net cash flows provided by operating activities	$	1,727.7		$	1,624.7		$	1,074.9			6.3	%		51.1	%
Net cash flows (used in) provided by investing activities	$	(1,650.3	)	$	345.3		$	(395.0	)		(577.9	)%		187.4	%
Net cash flows used in financing activities	$	(319.9	)	$	(1,784.9	)	$	(724.2	)		(82.1	)%		146.5	%

Operating Activities

Cash flows from operating activities represent the cash receipts and disbursements related to all of our activities other than investing and financing activities. Cash provided by operating activities was primarily driven by our earnings and changes in working capital. We expect cash provided from operating activities will continue to be our primary source of funds to finance operating needs and capital expenditures for the foreseeable future.

Operating cash flow is derived by adjusting our net income for:

• Non-cash operating items such as depreciation and amortization, impairment charges and share-based compensation charges;

• Changes in operating assets and liabilities which reflect timing differences between the receipt and payment of cash associated with transactions and when they are recognized in results of operations; and

• Changes associated with the payment of contingent milestones associated with our prior acquisitions of businesses.

For 2011 compared to 2010, the increase in cash provided by operating activities was driven by an increase in net income primarily resulting from increased product revenues and $104.6 million in proceeds from Dompé Farmaceutici SpA for the purchase of Biogen Dompé SRL’s outstanding receivables, offset by increased inventory balances and lower liabilities.

In addition, during the third quarter of 2011, we reached agreement with the IRS on the timing of the recognition of certain income and expense items. The effect of this agreement is primarily limited to the timing of these items, resulting in lower actual tax payments for 2011 and higher expected payments in subsequent periods. This agreement will have an insignificant effect on our income tax expense for all periods and no effect on our contingencies for uncertain tax positions.

For 2010 compared to 2009, the increase in net cash provided by operating activities was primarily driven by increased revenues and lower payments for U.S. federal income taxes offset by an increase in accounts receivable and receivables due from unconsolidated joint business.

Investing Activities

For 2011 compared to 2010, the decrease in net cash flows provided by investing activities is primarily due to an increase in the net purchases of marketable securities. Net purchases of marketable securities totaled $1,420.3 million in 2011, compared to proceeds received from sales and maturities of marketable securities

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totaling $680.3 million in 2010. Net cash flows used in investing activities for 2010 also reflect $85.0 million in net payments made to Knopp under our 2010 license and stock purchase agreements.

For 2010 compared to 2009, the increase in net cash provided by investing activities was primarily due to net proceeds received from sales and maturities of marketable securities, offset by the payments made to Knopp under our license and stock purchase agreements, the $32.5 million payment made upon our acquisition of Panima, our purchases of property, plant and equipment and the milestone payment made to the former shareholders of Syntonix. Net proceeds received from sales and maturities of marketable securities in 2010 totaled $680.3 million compared to net purchases of $229.1 million made in 2009.

Financing Activities

For 2011 compared to 2010, the decrease in net cash flows used in financing activities is due primarily to a decrease in the amounts of our common stock we repurchased and higher proceeds from the issuance of stock for share-based compensation arrangements in 2011, offset by the $148.3 million of payments made in 2011 for the purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH. During 2011, we repurchased 6.0 million shares of our common stock for approximately $498.0 million compared to 40.3 million shares of our common stock at a cost of approximately $2.1 billion in 2010. In addition, we received $314.7 million in 2011 compared to $183.5 million in 2010, related to stock option exercises and stock issuances under our employee stock purchase plan. Cash used in financing activities during 2011, also includes the repayment of amounts outstanding under Biogen Dompé SRL’s line of credit in connection with our recent purchase of the noncontrolling interest in our joint venture investment in Biogen Dompé SRL.

For 2010 compared to 2009, the increase in net cash used in financing activities was primarily due to increases in the amounts of our common stock repurchased compared to the same period in 2009. In 2010, we repurchased 40.3 million shares of our common stock for approximately $2.1 billion compared to 16.0 million shares at a cost of approximately $751.2 million in 2009. Cash used in financing activities also includes the $127.0 in net proceeds from the sale of the San Diego facility, which was accounted for as a financing arrangement until August 2011; and activity under our employee stock plans. We received $183.5 million in 2010 compared to $47.8 million in 2009, related to stock option exercises and stock issuances under our employee stock purchase plan.

Contractual Obligations and Off-Balance Sheet Arrangements

Contractual Obligations

The following table summarizes our contractual obligations as of December 31, 2011, excluding amounts related to uncertain tax positions, amounts payable to tax authorities, funding commitments, contingent milestone payments, contingent consideration and our financing arrangements, as described below.

	Payments Due by Period
(In millions)	Total		Less than 1 Year		1 to 3 Years		3 to 5 Years		After 5 Years
Non-cancellable operating leases (1), (2)	$	675.1	$	33.9	$	96.9	$	93.9	$	450.4
Notes payable and line of credit (3)		1,284.6		68.1		536.3		81.0		599.2
Purchase and other obligations (4)		79.3		58.4		19.1		1.6		0.2
Defined benefit obligation .		18.6		—		—		—		18.6
Total contractual obligations	$	2,057.6	$	160.4	$	652.3	$	176.5	$	1,068.4

(1) We lease properties and equipment for use in our operations. In addition to rent, the leases may require us to pay additional amounts for taxes, insurance, maintenance and other operating expenses. Amounts reflected within the table, detail future minimum rental commitments under non-cancelable operating leases as of December 31 for each of the periods presented.

(2) Includes future minimum rental commitments related to leases executed for two buildings to be built in Cambridge, Massachusetts, with a planned occupancy during the second half of 2013. The leases both have

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15 year terms and we have options to extend the term of each lease for two additional five-year terms. Future minimum rental commitments under the leases will total approximately $340.0 million over the initial 15 year terms. We are considered the owner, for accounting purposes, of these properties during the construction period. Accordingly, we have recorded an asset and a corresponding obligation totaling $2.2 million, representing the amount of construction cost incurred through December 31, 2011.

(3) Notes payable and line of credit includes principal and interest payments.

(4) Purchase and other obligations include our obligations of approximately $0.5 million related to the fair value of net liabilities on derivative contracts due in less than one year, approximately $9.2 million related to fixed obligations for the purchase of natural gas and approximately $29.2 million related to obligations for communication services

Tax Related Obligations

We exclude liabilities pertaining to uncertain tax positions from our summary of contractual obligations as we cannot make a reliable estimate of the period of cash settlement with the respective taxing authorities. As of December 31, 2011, we have approximately $58.4 million of liabilities associated with uncertain tax positions.

Other Funding Commitments

As of December 31, 2011, we have funding commitments of up to approximately $14.5 million as part of our investment in biotechnology oriented venture capital funds.

As of December 31, 2011, we have several ongoing clinical studies in various clinical trial stages. Our most significant clinical trial expenditures are to clinical research organizations (CROs). The contracts with CROs are generally cancellable, with notice, at our option. We have recorded accrued expenses of approximately $25.0 million on our consolidated balance sheet for expenditures incurred by CROs as of December 31, 2011. We have approximately $475.0 million in cancellable future commitments based on existing CRO contracts as of December 31, 2011 which are not included in the contractual obligations table above because of our termination rights.

Contingent Milestone Payments

Based on our development plans as of December 31, 2011, we have committed to make potential future milestone payments to third parties of up to approximately $1.9 billion as part of our various collaborations, including licensing and development programs. Payments under these agreements generally become due and payable only upon achievement of certain development, regulatory or commercial milestones. Because the achievement of these milestones had not occurred as of December 31, 2011, such contingencies have not been recorded in our financial statements.

We anticipate that we may pay approximately $40.0 million of milestone payments in 2012, provided various development, regulatory or commercial milestones are achieved. Amounts related to contingent milestone payments are not included in the contractual obligations table above as they are contingent on the successful achievement of certain development, regulatory approval and commercial milestones. These milestones may not be achieved.

Contingent Consideration

In connection with our purchase of the noncontrolling interests in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH and our acquisitions of Biogen Idec International Neuroscience GmbH, Biogen Idec Hemophilia Inc., and Fumapharm AG, we agreed to make additional payments based upon the achievement of certain milestone events. Amounts related to contingent milestone payments are not considered contractual obligations as they are contingent on the successful achievement of certain development, regulatory approval and commercial milestones. These milestones may not be achieved.

We completed our purchase of the noncontrolling interests in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH in September 2011. The purchase price for the

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noncontrolling interest included contingent consideration in the form of commercial and regulatory milestones up to $42.5 million in cash. For additional information related to our acquisition of the noncontrolling interest in our joint venture investments, please read Note 2, Acquisitions to our consolidated financial statements included within this report

We completed our acquisition of Biogen Idec International Neuroscience, GmbH (BIN), formerly Panima Pharmaceuticals, AG, in December 2010. The purchase price for BIN included contingent consideration in the form of developmental milestones up to $395.0 million in cash. For additional information related to our acquisition of BIN, please read Note 2, Acquisitions to our consolidated financial statements included within this report.

In connection with our acquisition of Biogen Idec Hemophilia Inc. (BIH), formerly Syntonix Pharmaceuticals, Inc., in January 2007, we agreed to pay up to an additional $80.0 million if certain milestone events associated with the development of BIH’s lead product, long-lasting recombinant Factor IX are achieved. The first $40.0 million contingent payment was achieved in the first quarter of 2010. An additional $20.0 million contingent payment will occur if prior to the tenth anniversary of the closing date, the FDA grants approval of a Biologic License Application for Factor IX. A second $20.0 million contingent payment will occur if prior to the tenth anniversary of the closing date, a marketing authorization is granted by the EMA for Factor IX. For additional information related to our acquisition of BIH, please read Note 2, Acquisitions to our consolidated financial statements included within this report.

In 2006, we acquired Fumapharm AG. As part of this acquisition we acquired FUMADERM and BG-12 (together, Fumapharm Products). We paid $220.0 million upon closing of the transaction and will pay an additional $15.0 million if a Fumapharm Product is approved for MS in the U.S. or E.U. We may also make the following additional milestone payments to Fumapharm AG based on the attainment of certain sales levels of Fumapharm Products, less certain costs as defined in the acquisition agreement:

	Cumulative Sales Level
Prior 12 Month Sales	$500M		$1.0B		$2.0B		$3.0B		Each  additional $1.0B up to $20.0B
	Payment Amount (In millions)
< $500 million	$	—	$	—	$	—	$	—	$	—
$500 million — $1.0 billion		22.0		25.0		50.0		50.0		50.0
$1.0 billion — $1.5 billion		—		50.0		100.0		100.0		100.0
$1.5 billion — $2.0 billion		—		—		150.0		150.0		150.0
$2.0 billion — $2.5 billion		—		—		200.0		200.0		200.0
$2.5 billion — $3.0 billion		—		—		—		250.0		250.0
> $3.0 billion		—		—		—		—		300.0

These milestone payments are considered contingent consideration and will be accounted for as an increase to goodwill as incurred, in accordance with the accounting standard applicable to business combinations when we acquired Fumapharm. Milestone payments are due within 30 days following the end of the quarter in which the applicable sales level has been reached and are based upon the total sales of Fumapharm Products in the prior twelve month period.

Financing Arrangement

In July 2011, we executed leases for two office buildings to be built in Cambridge, Massachusetts with a planned occupancy during the second half of 2013. Construction of these facilities began in late 2011. In accordance with accounting guidance applicable to entities involved with the construction of an asset that will be leased when the construction is completed, we are considered the owner, for accounting purposes, of these properties during the construction period. Accordingly, we will record an asset along with a corresponding financing obligation on our consolidated balance sheet for the amount of total project costs incurred related to the construction in progress for these buildings through completion of the construction period. Upon completion of the buildings, we will assess and determine if the assets and corresponding liabilities should be derecognized. As

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of December 31, 2011, cost incurred in relation to the construction of these buildings totaled approximately $2.2 million. The future payments related to these leases have been included in the above chart of contractual obligations.

Other Off-Balance Sheet Arrangements

We do not have any relationships with entities often referred to as structured finance or special purpose entities which would have been established for the purpose of facilitating off-balance sheet arrangements. As such, we are not exposed to any financing, liquidity, market or credit risk that could arise if we had engaged in such relationships. We consolidate variable interest entities if we are the primary beneficiary.

Legal Matters

For a discussion of legal matters as of December 31, 2011, please read Note 21, Litigation to our consolidated financial statements included in this report.

Critical Accounting Estimates

The preparation of our consolidated financial statements, which have been prepared in accordance with accounting principles generally accepted in the U.S. (U.S. GAAP), requires us to make estimates, judgments and assumptions that may affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. We base our estimates on historical experience and on various other assumptions that we believe are reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. We evaluate our estimates, judgments and assumptions on an ongoing basis. Actual results may differ from these estimates under different assumptions or conditions.

The most significant areas involving estimates, judgments and assumptions used in the preparation of our consolidated financial statements are as follows:

• Revenue recognition and related allowances;

• Collaborative relationships;

• Clinical trial expenses;

• Consolidation of variable interest entities;

• Valuation of contingent consideration resulting from a business combination;

• Valuation of acquired intangible assets, including in-process research and development;

• Inventory;

• Impairment and amortization of long-lived assets and accounting for goodwill;

• Investments, including fair value measures and impairments;

• Share-based compensation;

• Income taxes; and

• Contingencies.

Revenue Recognition and Related Allowances

We recognize revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; our price to the customer is fixed or determinable; and collectability is reasonably assured.

Product Revenues

Revenues from product sales are recognized when title and risk of loss have passed to the customer, which is typically upon delivery. However, sales of TYSABRI in the U.S. are recognized on the “sell-through” model,

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that is, upon shipment of the product by Elan to its third party distributor rather than upon shipment to Elan. The timing of distributor orders and shipments can cause variability in earnings.

Reserves for Discounts and Allowances

We establish reserves for trade term discounts, wholesaler incentives, Medicaid and managed care rebates, Veterans Administration and PHS discounts, product returns and other governmental discounts or applicable allowances associated with the implementation of pricing actions in certain of international markets in which we operate. These reserves are based on estimates of the amounts earned or to be claimed on the related sales. Our estimates take into consideration our historical experience, current contractual and statutory requirements, specific known market events and trends and forecasted customer buying patterns. If actual results vary, we may need to adjust these estimates, which could have an effect on earnings in the period of the adjustment. The estimates we make with respect to these allowances represent the most significant judgments with regard to revenue recognition.

In addition to the discounts and rebates described above and classified as a reduction of revenue, we also maintain certain customer service contracts with distributors and other customers in the distribution channel that provide us with inventory management and distribution services. We have established the fair value of these services and classified these customer service contracts as sales and marketing expense. If we had concluded that we did not receive a separate identifiable benefit or have sufficient evidence that the fair value did not exist for these services, we would have been required to classify these costs as a reduction of revenue.

Revenues from Unconsolidated Joint Business

We collaborate with Genentech on the development and commercialization of RITUXAN. Revenues from unconsolidated joint business consist of (1) our share of pre-tax co-promotion profits in the U.S.; (2) reimbursement of our selling and development expense in the U.S.; and (3) revenue on sales of RITUXAN in the rest of world, which consists of our share of pre-tax co-promotion profits in Canada and royalty revenue on sales of RITUXAN outside the U.S. and Canada by F. Hoffmann-La Roche Ltd. (Roche) and its sublicensees. Pre-tax co-promotion profits are calculated and paid to us by Genentech in the U.S. and by Roche in Canada. Pre-tax co-promotion profits consist of U.S. and Canadian sales of RITUXAN to third-party customers net of discounts and allowances less the cost to manufacture RITUXAN, third-party royalty expenses, and distribution, selling and marketing, and joint development expenses incurred by Genentech, Roche and us. We record our share of the pre-tax co-promotion profits in Canada and royalty revenues on sales of RITUXAN outside the U.S. on a cash basis. Additionally, our share of the pre-tax co-promotion profits in the U.S. includes estimates made by Genentech and those estimates are subject to change. Actual results may ultimately differ from our estimates.

Bad Debt Reserves

Bad debt reserves are based on our estimated uncollectible accounts receivable. Given our historical experience with bad debts, combined with our credit management policies and practices, we do not presently maintain significant bad debt reserves. However certain of our customers are based in countries where the economic conditions continue to present challenges. We continue to monitor these conditions and associated impacts on the financial performance and credit worthiness of our large customers so that we can properly assess and respond to changes in their credit profile. Our historical write-offs of accounts receivable have not exceeded management’s estimates.

Concentrations of Credit Risk

The majority of our receivables arise from product sales in the United States and Europe and are primarily due from wholesale distributors, large pharmaceutical companies, public hospitals and other government entities. We monitor the financial performance and credit worthiness of our large customers so that we can properly assess and respond to changes in their credit profile. We continue to monitor economic conditions, including the volatility associated with international economies, and associated impacts on the relevant financial markets and our business, especially in light of the global economic downturn. The credit and economic conditions within many of the international markets in which we operate, particularly in certain countries throughout Europe, such

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as Italy, Spain and Portugal, have continued to deteriorate throughout 2011. These conditions have resulted in, and may continue to result in, an increase in the average length of time that it takes to collect on our accounts receivable outstanding in these countries. To date, we have not experienced any significant losses with respect to the collection of our accounts receivable. If economic conditions worsen and/or the financial condition of our customers were to further deteriorate, our risk of collectability may increase, which may result in additional allowances and/or significant bad debts.

For additional information about related to our concentration of credit risk associated with our accounts receivable balances, please read the subsection above entitled “Credit Risk” in the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” section of this report.

Royalty Revenues

We receive royalty revenues under license agreements with a number of third parties that sell products based on technology we have developed or to which we own rights. The license agreements provide for the payment of royalties to us based on sales of these licensed products. There are no future performance obligations on our part under these license agreements. We record these revenues based on estimates of the sales that occurred during the relevant period. The relevant period estimates of sales are based on interim data provided by licensees and analysis of historical royalties that have been paid to us, adjusted for any changes in facts and circumstances, as appropriate. We maintain regular communication with our licensees in order to assess the reasonableness of our estimates. Differences between actual royalty revenues and estimated royalty revenues are adjusted for in the period in which they become known, typically the following quarter. Historically, adjustments have not been material when compared to actual amounts paid by licensees. To the extent we do not have sufficient ability to accurately estimate revenues, we record such revenues on a cash basis.

Collaborative Relationships

We evaluate our collaborative agreements for proper income statement classification based on the nature of the underlying activity. Amounts due from our collaborative partners related to development activities are generally reflected as a reduction of research and development expense, except as discussed in Note 20, Collaborations to our consolidated financial statements. As discussed within Note 20, Genentech incurs the majority of continuing development cost for RITUXAN. Expenses incurred by Genentech in the development of RITUXAN are not recorded as research and development expense, but rather reduce our share of pre-tax co-promotion profits recorded as a component of unconsolidated joint business revenue.

For collaborations with commercialized products, if we are the principal, we record revenue and the corresponding operating costs in their respective line items within our consolidated statements of income. If we are not the principal, we record operating costs as a reduction of revenue.

Clinical Trial Expenses

Clinical trial expenses include expenses associated with CROs. The invoicing from CROs for services rendered can lag several months. We accrue the cost of services rendered in connection with CRO activities based on our estimate of site management, monitoring costs, and project management costs. We maintain regular communication with our CROs to gauge the reasonableness of our estimates. Differences between actual clinical trial expenses and estimated clinical trial expenses recorded have not been material and are adjusted for in the period in which they become known.

Consolidation of Variable Interest Entities

We consolidate variable interest entities in which we are the primary beneficiary. For such consolidated entities where we own or are exposed to less than 100% of the economics, we record noncontrolling interest in our statement of income for the current results allocated to the third party equity interests.

In determining whether we are the primary beneficiary of a variable interest entity, we consider a number of factors, including our ability to direct the activities that most significantly affect the entity’s economic success,

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our contractual rights and responsibilities under the arrangement and the significance of the arrangement to each party. These considerations impact the way we account for our existing collaborative and joint venture relationships and may result in the future consolidation of companies or entities with which we have collaborative or other arrangements.

Valuation of Contingent Consideration Resulting from a Business Combination

For acquisitions completed after January 1, 2009, we record contingent consideration resulting from a business combination at its fair value on the acquisition date. Each reporting period thereafter, we revalue these obligations and record increases or decreases in their fair value as an adjustment to contingent consideration expense within the consolidated statement of income. Changes in the fair value of the contingent consideration obligations can result from adjustments to the discount rates and periods, updates in the assumed achievement or timing of any development milestones, or changes in the probability of certain clinical events and changes in the assumed probability associated with regulatory approval. These fair value measurements represent Level 3 measurements as they are based on significant inputs not observable in the market.

Significant judgment is employed in determining the appropriateness of these assumptions as of the acquisition date and for each subsequent period. Accordingly, changes in assumptions described above, could have a material impact on the amount of contingent consideration expense we record in any given period.

Valuation of Acquired Intangible Assets, including In-process Research and Development

We have acquired, and expect to continue to acquire, intangible assets through the acquisition of biotechnology companies or through the consolidation of variable interest entities. These intangible assets primarily consist of technology associated with human therapeutic products and in-process research and development product candidates. When significant identifiable intangible assets are acquired, we generally engage an independent third-party valuation firm to assist in determining the fair values of these assets as of the acquisition date. Management will determine the fair value of less significant identifiable intangible assets acquired. Discounted cash flow models are typically used in these valuations, and these models require the use of significant estimates and assumptions including but not limited to:

• estimating the timing of and expected costs to complete the in-process projects;

• projecting regulatory approvals;

• estimating future cash flows from product sales resulting from completed products and in process projects; and

• developing appropriate discount rates and probability rates by project.

We believe the fair values assigned to the intangible assets acquired are based upon reasonable estimates and assumptions given available facts and circumstances as of the acquisition dates.

If these projects are not successfully developed, the sales and profitability of the company may be adversely affected in future periods. Additionally, the value of the acquired intangible assets may become impaired. We believe that the foregoing assumptions used in the IPR&D analysis were reasonable at the time of the respective acquisition. No assurance can be given, however, that the underlying assumptions used to estimate expected project sales, development costs or profitability, or the events associated with such projects, will transpire as estimated.

Prior to January 1, 2009, we measured acquired IPR&D in a business combination at fair value and expensed it on acquisition date if that technology lacked an alternative future use, or capitalized it as an intangible asset if certain criteria were met; however, effective January 1, 2009, if we are purchasing a business, the acquired IPR&D is measured at fair value, capitalized as an intangible asset and tested for impairment at least annually until commercialization, after which time the IPR&D is amortized over its estimated useful life. If we acquire an asset or group of assets, that do not meet the definition of a business under applicable accounting

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standards; then the acquired IPR&D is expensed on its acquisition date. Future costs to develop these assets are recorded to expense as they are incurred if the technology lacks alternative future uses.

Inventory

Inventories are stated at the lower of cost or market with cost determined in a manner that approximates the first-in, first-out (FIFO) method. Included in inventory are raw materials used in the production of pre-clinical and clinical products, which are expensed as research and development costs when consumed.

Capitalization of Inventory Costs

Our policy is to capitalize inventory costs associated with our products prior to regulatory approval, when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. We consider numerous attributes in evaluating whether the costs to manufacture a particular product should be capitalized as an asset. We assess the regulatory approval process and where the particular product stands in relation to that approval process, including any known safety or efficacy concerns, potential labeling restrictions and other impediments to approval. We evaluate our anticipated research and development initiatives and constraints relating to the product and the indication in which it will be used. We consider our manufacturing environment including our supply chain in determining logistical constraints that could hamper approval or commercialization. We consider the shelf life of the product in relation to the expected timeline for approval and we consider patent related or contract issues that may prevent or delay commercialization. We also base our judgment on the viability of commercialization, trends in the marketplace and market acceptance criteria. Finally, we consider the reimbursement strategies that may prevail with respect to the product and assess the economic benefit that we are likely to realize.

We expense previously capitalized costs related to pre-approval inventory upon a change in such judgment, due to, among other potential factors, a denial or delay of approval by necessary regulatory bodies. As of December 31, 2011 and 2010, the carrying value of our inventory did not include any costs associated with products that had not yet received regulatory approval.

There is a risk inherent in these judgments and any changes we make in these judgments may have a material impact on our results in future periods.

Obsolescence and Unmarketable Inventory

We periodically review our inventories for excess or obsolete inventory and write-down obsolete or otherwise unmarketable inventory to its estimated net realizable value. If the actual net realizable value is less than that estimated by us, or if it is determined that inventory utilization will further diminish based on estimates of demand, additional inventory write-downs may be required. Additionally, our products are subject to strict quality control and monitoring which we perform throughout the manufacturing process. In the event that certain batches or units of product no longer meet quality specifications or become obsolete due to expiration, we will record a charge to cost of sales to write-down any obsolete or otherwise unmarketable inventory to its estimated net realizable value. In all cases product inventory is carried at the lower of cost or its estimated net realizable value.

Impairment and Amortization of Long-lived Assets and Accounting for Goodwill

Long-lived Assets Other than Goodwill

Long-lived assets to be held and used, including property plant and equipment as well as intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable.

If such circumstances are determined to exist, an estimate of undiscounted future cash flows produced by the long-lived asset, including its eventual residual value, is compared to the carrying value to determine whether impairment exists. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their estimated fair values.

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Our most significant intangible asset is the core technology related to our AVONEX product. We believe the economic benefit of our core technology is consumed as revenue is generated from our AVONEX product, which we refer to as the economic consumption amortization model. This amortization methodology involves calculating a ratio of actual current period sales to total anticipated sales for the life of the product and applying this ratio to the carrying amount of the intangible asset. An analysis of the anticipated product sales of AVONEX is performed at least annually during our long range planning cycle, and this analysis serves as the basis for the calculation of our economic consumption amortization model. This analysis is based upon certain assumptions that we evaluate on a periodic basis, such as the anticipated product sales of AVONEX and expected impact of competitor products and our own pipeline product candidates, as well as the issuance of new patents or the extension of existing patents. Although we believe this process has allowed us to reliably determine the best estimate of the pattern in which we will consume the economic benefits of our core technology intangible asset, the model could result in deferring amortization charges to future periods in certain instances, due to continued sales of the product at a nominal level after patent expiration or otherwise. We completed our most recent long range planning cycle in the third quarter of 2011. Based upon this analysis, amortization of our core intangible asset related to AVONEX is expected to be in the range of $100.0 million to $150.0 million annually through 2016.

We monitor events and expectations regarding product performance. If there are any indications that the assumptions underlying our most recent analysis would be different than those utilized within our current estimates, our analysis would be updated and may result in a significant change in the anticipated lifetime revenue of AVONEX determined during our most recent annual review. For example, the occurrence of an adverse event, such as the invalidation of our AVONEX ’755 Patent, could substantially increase the amount of amortization expense associated with our acquired intangible assets as compared to previous periods or our current expectations, which may result in a significant negative impact on our future results of operations.

We did not recognize an impairment charge related to our long-lived assets during 2011, 2010 and 2009.

Goodwill

Goodwill totaled approximately $1,146.3 million as of December 31, 2011, and relates largely to amounts that arose in connection with the merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation. Our goodwill balances represent the difference between the purchase price and the fair value of the identifiable tangible and intangible net assets when accounted for using the purchase method of accounting.

We assess our goodwill balance within our single reporting unit annually, as of October 31, and whenever events or changes in circumstances indicate the carrying value of goodwill may not be recoverable to determine whether any impairment in this asset may exist and, if so, the extent of such impairment. The provisions of this guidance require that we perform a two-step impairment test. In the first step, we compare the fair value of our reporting unit to its carrying value. If the carrying value of the net assets assigned to our reporting unit exceeds the fair value of our reporting unit, then the second step of the impairment test is performed in order to determine the implied fair value of our reporting unit’s goodwill. If the carrying value of our reporting unit’s goodwill exceeds its implied fair value, then the company records an impairment loss equal to the difference.

In September 2011, the FASB issued Accounting Standards Update No. 2011-08, “Intangibles — Goodwill and Other (Topic 350): Testing Goodwill for Impairment”. This newly issued accounting standard allows an entity the option to first assess qualitative factors to determine whether it is necessary to perform the current two-step impairment test. This ASU is effective for annual and interim goodwill impairment tests performed for fiscal years beginning after December 15, 2011, which for Biogen Idec means January 1, 2012. Early adoption is permitted; however, we have not elected to do so. For additional information related to this new accounting standard, please read the section entitled “New Accounting Pronouncements” within Note 1, Summary of Significant Accounting Policies to our consolidated financial statements included within this report.

We completed our required annual impairment test in the fourth quarter of 2011, 2010 and 2009 and determined in each of those periods that the carrying value of goodwill was not impaired. In each year, the fair value of our reporting unit, which includes goodwill, was significantly in excess of the carry value of our reporting unit.

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Investments, including Fair Value Measures and Impairments

We invest in various types of securities, including short-term and long-term marketable securities, principally corporate notes, government securities including government sponsored enterprise mortgage-backed securities and credit card and auto loan asset-backed securities, in which our excess cash balances are invested.

In accordance with the accounting standard for fair value measurements we have classified our financial assets as Level 1, 2 or 3 within the fair value hierarchy. Fair values determined by Level 1 inputs utilize quoted prices (unadjusted) in active markets for identical assets that we have the ability to access. Fair values determined by Level 2 inputs utilize data points that are observable such as quoted prices, interest rates and yield curves. Fair values determined by Level 3 inputs utilize unobservable data points for the asset.

As noted in Note 8, Fair Value Measurements to our consolidated financial statements, a majority of our financial assets have been classified as Level 2. These assets have been initially valued at the transaction price and subsequently valued utilizing third party pricing services. The pricing services use many observable market inputs to determine value, including reportable trades, benchmark yields, credit spreads, broker/dealer quotes, bids, offers, current spot rates and other industry and economic events. We validate the prices provided by our third party pricing services by understanding the models used, obtaining market values from other pricing sources, analyzing pricing data in certain instances and confirming those securities trade in active markets.

We also have some investments classified as Level 3 whose fair value is initially measured at transaction prices and subsequently valued using the pricing of recent financing or by reviewing the underlying economic fundamentals and liquidation value of the companies. We apply judgments and estimates when we validate the prices provided by third parties. While we believe the valuation methodologies are appropriate, the use of valuation methodologies is highly judgmental and changes in methodologies can have a material impact on our results of operations.

Impairment

We conduct periodic reviews to identify and evaluate each investment that has an unrealized loss, in accordance with the meaning of other-than-temporary impairment and its application to certain investments. An unrealized loss exists when the current fair value of an individual security is less than its amortized cost basis. Unrealized losses on available-for-sale debt securities that are determined to be temporary, and not related to credit loss, are recorded, net of tax, in accumulated other comprehensive income.

For available-for-sale debt securities with unrealized losses, management performs an analysis to assess whether we intend to sell or whether we would more likely than not be required to sell the security before the expected recovery of the amortized cost basis. Where we intend to sell a security, or may be required to do so, the security’s decline in fair value is deemed to be other-than-temporary and the full amount of the unrealized loss is reflected within earnings as an impairment loss.

Regardless of our intent to sell a security, we perform additional analysis on all securities with unrealized losses to evaluate losses associated with the creditworthiness of the security. Credit losses are identified where we do not expect to receive cash flows sufficient to recover the amortized cost basis of a security and are reflected within earnings as an impairment loss.

Share-Based Compensation

We make certain assumptions in order to value and record expense associated with awards made under our share-based compensation arrangements. Changes in these assumptions may lead to variability with respect to the amount of expense we recognize in connection with share-based payments.

Determining the appropriate valuation model and related assumptions requires judgment, and includes estimating the expected market price of our stock on vesting date and stock price volatility as well as the term of the expected awards. Determining the appropriate amount to expense based on the anticipated achievement of performance targets requires judgment, including forecasting the achievement of future financial targets. The

73

estimate of expense is revised periodically based on the probability of achieving the required performance targets and adjustments are made throughout the performance as appropriate. The cumulative impact of any revision is reflected in the period of change.

We also estimate forfeitures over the requisite service period when recognizing share-based compensation expense based on historical rates and forward-looking factors; these estimates are adjusted to the extent that actual forfeitures differ, or are expected to materially differ, from our estimates.

Income Taxes

We prepare and file income tax returns based on our interpretation of each jurisdiction’s tax laws and regulations. In preparing our consolidated financial statements, we estimate our income tax liability in each of the jurisdictions in which we operate by estimating our actual current tax expense together with assessing temporary differences resulting from differing treatment of items for tax and financial reporting purposes. These differences result in deferred tax assets and liabilities, which are included in our consolidated balance sheets. Significant management judgment is required in assessing the realizability of our deferred tax assets. In performing this assessment, we consider whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. In making this determination, under the applicable financial accounting standards, we are allowed to consider the scheduled reversal of deferred tax liabilities, projected future taxable income, and the effects of tax planning strategies. Our estimates of future taxable income include, among other items, our estimates of future income tax deductions related to the exercise of stock options. In the event that actual results differ from our estimates, we adjust our estimates in future periods and we may need to establish a valuation allowance, which could materially impact our financial position and results of operations.

We account for uncertain tax positions using a “more-likely-than-not” threshold for recognizing and resolving uncertain tax positions. We evaluate uncertain tax positions on a quarterly basis and consider various factors, that include, but are not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity and changes in facts or circumstances related to a tax position. We adjust the level of the liability to reflect any subsequent changes in the relevant facts surrounding the uncertain positions. Our liabilities for uncertain tax positions can be relieved only if the contingency becomes legally extinguished through either payment to the taxing authority or the expiration of the statute of limitations, the recognition of the benefits associated with the position meet the “more-likely-than-not” threshold or the liability becomes effectively settled through the examination process. We consider matters to be effectively settled once the taxing authority has completed all of its required or expected examination procedures, including all appeals and administrative reviews; we have no plans to appeal or litigate any aspect of the tax position; and we believe that it is highly unlikely that the taxing authority would examine or re-examine the related tax position. We also accrue for potential interest and penalties, related to unrecognized tax benefits in income tax expense.

As of December 31, 2011, our non-U.S. subsidiaries’ undistributed foreign earnings included in consolidated retained earnings and other basis differences aggregated approximately $2.7 billion. We intend to reinvest these earnings indefinitely in operations outside the U.S.; however, if we decide to repatriate funds in the future to execute our growth initiatives or to fund any other liquidity needs, the resultant tax consequences would negatively impact our results of operations. The residual U.S. tax liability, if such amounts were remitted, would be approximately $600 million to $700 million as of December 31, 2011.

Contingencies

We are currently involved in various claims and legal proceedings. On a quarterly basis, we review the status of each significant matter and assess its potential financial exposure. If the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount can be reasonably estimated, we accrue a liability for the estimated loss. Significant judgment is required in both the determination of probability and the determination as to whether an exposure is reasonably estimable. Because of uncertainties related to these matters, accruals are based only on the best information available at the time. As additional

74

information becomes available, we reassess the potential liability related to pending claims and litigation and may revise our estimates. These revisions in the estimates of the potential liabilities could have a material impact on our consolidated results of operations and financial position.

New Accounting Standards

For a discussion of new accounting standards please read Note 1, Summary of Significant Accounting Principles to our consolidated financial statements included in this report.

Item 7A.    Quantitative and Qualitative Disclosures About Market Risk

We have operations or maintain distribution relationships in the U.S., Europe, Middle East, Canada, Central and South America, Australia, New Zealand, Japan, China, India and elsewhere in Asia in connection with the sale of AVONEX and TYSABRI and in Germany in connection with the sale of FUMADERM. We also launched FAMPYRA in Australia and certain European countries during the second half of 2011. In addition, we receive royalty revenues based on worldwide product sales by our licensees and through Genentech on sales of RITUXAN in the rest of world. As a result, our financial position, results of operations and cash flows can be affected by market fluctuations in foreign exchange rates, primarily with respect to the Euro, Canadian dollar, Swiss franc, Danish krone, Swedish krona, British pound, and Japanese yen.

We use foreign currency forward contracts to manage foreign currency risk but do not engage in currency speculation. The majority of our forward contracts are used to hedge certain forecasted revenue transactions denominated in foreign currencies. We also use forward contracts to mitigate the foreign currency exposure related to certain balance sheet items. We have not elected hedge accounting for the balance sheet related items.

The following quantitative information includes the impact of currency movements on forward contracts used in both programs. As of December 31, 2011 and 2010, a hypothetical adverse 10% movement in foreign exchange rates compared to the U.S. dollar across all maturities (for example, a strengthening of the Euro) would result in a hypothetical decrease in the fair value of forward contracts of approximately $79.6 million and $65.5 million, respectively. Our use of this methodology to quantify the market risk of such instruments should not be construed as an endorsement of its accuracy or the accuracy of the related assumptions. The quantitative information about market risk is limited because it does not take into account all foreign currency operating transactions.

In addition, the fair value of our marketable securities is subject to change as a result of potential changes in market interest rates. The potential change in fair value for interest rate sensitive instruments has been assessed on a hypothetical 100 basis point adverse movement across all maturities. As of December 31, 2011 and 2010, we estimate that such hypothetical adverse 100 basis point movement would result in a hypothetical loss in fair value of approximately $17.9 million and $10.5 million, respectively, to our interest rate sensitive instruments.

The returns from cash, cash equivalents and marketable securities will vary as short-term interest rates change. A 100 basis-point adverse movement (decrease) in short-term interest rates would decrease interest income by approximately $14.8 million and $11.4 million as of December 31, 2011 and 2010, respectively.

Item 8.    Consolidated Financial Statements and Supplementary Data

The information required by this Item 8 is contained on pages F-1 through F-77 of this report and is incorporated herein by reference.

Item 9.    Changes in and Disagreements with Accountants on Accounting and Financial Disclosure

None.

Item 9A.    Controls and Procedures

Disclosure Controls and Procedures and Internal Control over Financial Reporting

Controls and Procedures

We have carried out an evaluation, under the supervision and with the participation of our management, including our principal executive officer and principal financial officer, of the effectiveness of the design and

75

operation of our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended), as of December 31, 2011. Based upon that evaluation, our principal executive officer and principal financial officer concluded that, as of the end of the period covered by this report, our disclosure controls and procedures are effective in ensuring that (a) the information required to be disclosed by us in the reports that we file or submit under the Securities Exchange Act is recorded, processed, summarized and reported within the time periods specified in the SEC’s rules and forms, and (b) such information is accumulated and communicated to our management, including our principal executive officer and principal financial officer, as appropriate to allow timely decisions regarding required disclosure. In designing and evaluating our disclosure controls and procedures, our management recognized that any controls and procedures, no matter how well designed and operated, can provide only reasonable assurance of achieving the desired control objectives, and our management necessarily was required to apply its judgment in evaluating the cost-benefit relationship of possible controls and procedures.

Changes in Internal Control over Financial Reporting

There were no changes in our internal control over financial reporting during the quarter ended December 31, 2011 that have materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

Management’s Annual Report on Internal Control over Financial Reporting

Our management is responsible for establishing and maintaining adequate internal control over our financial reporting. Internal control over financial reporting is defined in Rules 13a-15(f) and 15d-15(f) under the Securities Exchange Act as a process designed by, or under the supervision of, a company’s principal executive and principal financial officers and effected by a company’s board of directors, management and other personnel to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles in the U.S. (U.S. GAAP). Our internal control over financial reporting includes those policies and procedures that:

• pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect our transactions and dispositions of our assets;

• provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with U.S. GAAP, and that our receipts and expenditures are being made only in accordance with authorizations of our management and directors; and

• provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of our assets that could have a material effect on our financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Our management assessed the effectiveness of our internal control over financial reporting as of December 31, 2011. In making this assessment, management used the criteria set forth by the Committee of Sponsoring Organizations of the Treadway Commission (COSO) in Internal Control — Integrated Framework.

Based on our assessment, our management has concluded that, as of December 31, 2011, our internal control over financial reporting is effective based on those criteria.

The effectiveness of our internal control over financial reporting as of December 31, 2011 has been audited by PricewaterhouseCoopers LLP, an independent registered public accounting firm, as stated in their report, which is included herein.

Item 9B.    Other Information

None.

76

PART III

Item 10.    Directors, Executive Officers and Corporate Governance

The information concerning our executive officers is set forth under the heading “Our Executive Officers” in Part I of this report. The text of our code of business conduct, which includes the code of ethics that applies to our principal executive officer, principal financial officer, principal accounting officer or controller, and persons performing similar functions, is posted on our website, www.biogenidec.com, under the “Corporate Governance” subsection of the “About Us” section of the site. We intend to make all required disclosures regarding any amendments to, or waivers from, provisions of our code of business conduct at the same location of our website. Our corporate governance principles (also posted on www.biogenidec.com) prohibit our Board of Directors from granting any waiver of the code of ethics for any of our directors or executive officers. We include our website address in this report only as an inactive textual reference and do not intend it to be an active link to our website.

The response to the remainder of this item is incorporated by reference from the discussion responsive thereto in the sections entitled “Proposal 1 — Election of Directors,” “Corporate Governance,” “Stock Ownership — Section 16(a) Beneficial Ownership Reporting Compliance” and “Miscellaneous — Stockholder Proposals” contained in the proxy statement for our 2012 annual meeting of stockholders.

Item 11.    Executive Compensation

The response to this item is incorporated by reference from the discussion responsive thereto in the sections entitled “Executive Compensation and Related Information” and “Corporate Governance” contained in the proxy statement for our 2012 annual meeting of stockholders.

Item 12.    Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters

The response to this item is incorporated by reference from the discussion responsive thereto in the sections entitled “Stock Ownership” and “Equity Compensation Plan Information” contained in the proxy statement for our 2012 annual meeting of stockholders.

Item 13.    Certain Relationships and Related Transactions, and Director Independence

The response to this item is incorporated by reference from the discussion responsive thereto in the sections entitled “Certain Relationships and Related Person Transactions” and “Corporate Governance” contained in the proxy statement for our 2012 annual meeting of stockholders.

Item 14.    Principal Accountant Fees and Services

The response to this item is incorporated by reference from the discussion responsive thereto in the section entitled “Proposal 2 — Ratification of the Selection of our Independent Registered Public Accounting Firm” contained in the proxy statement for our 2012 annual meeting of stockholders.

77

PART IV

Item 15. Exhibits, Financial Statement Schedules

a. (1) Consolidated Financial Statements:

The following financial statements are filed as part of this report:

Financial Statements	Page Number
Consolidated Statements of Income		F-2
Consolidated Balance Sheets		F-3
Consolidated Statements of Cash Flows		F-4
Consolidated Statements of Equity		F-5
Notes to Consolidated Financial Statements		F-8
Report of Independent Registered Public Accounting Firm		F-77

(2) Financial Statement Schedules

Schedules are omitted because they are not applicable, or are not required, or because the information is included in the consolidated financial statements and notes thereto.

(3) Exhibits

The exhibits listed on the Exhibit Index beginning on page A-1, which is incorporated herein by reference, are filed or furnished as part of this report or are incorporated into this report by reference.

78

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

BIOGEN IDEC INC.
By:	/S/    GEORGE A. SCANGOS
	George A. Scangos
	Chief Executive Officer

Date: February 3, 2012

Pursuant to the requirements the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

Name	Capacity	Date
/S/    GEORGE A. SCANGOS George A. Scangos	Director and Chief Executive Officer (principal executive officer)	February 3, 2012
/S/    PAUL J. CLANCY Paul J. Clancy	Executive Vice President, Finance and Chief Financial Officer (principal financial officer)	February 3, 2012
/S/    ROBERT E. GAGNON Robert E. Gagnon	Vice President, Finance, Chief Accounting Officer and Controller (principal accounting officer)	February 3, 2012
/S/    WILLIAM D. YOUNG William D. Young	Director and Chairman of the Board of Directors	February 3, 2012
Alexander J. Denner	Director
/S/    CAROLINE D. DORSA Caroline D. Dorsa	Director	February 3, 2012
/S/    NANCY L. LEAMING Nancy L. Leaming	Director	February 3, 2012
Richard C. Mulligan	Director
/S/    ROBERT W. PANGIA Robert W. Pangia	Director	February 3, 2012
/S/    STELIOS PAPADOPOULOS Stelios Papadopoulos	Director	February 3, 2012

79

Name	Capacity	Date
/S/    BRIAN S. POSNER Brian S. Posner	Director	February 3, 2012
/S/    ERIC K. ROWINSKY Eric K. Rowinsky	Director	February 1, 2012
/S/    LYNN SCHENK Lynn Schenk	Director	February 3, 2012
/S/    STEPHEN A. SHERWIN Stephen A. Sherwin	Director	February 3, 2012

80

BIOGEN IDEC INC. AND SUBSIDIARIES

CONSOLIDATED FINANCIAL STATEMENTS

	Page Number
Consolidated Statements of Income		F-2
Consolidated Balance Sheets		F-3
Consolidated Statements of Cash Flows		F-4
Consolidated Statements of Equity		F-5
Notes to Consolidated Financial Statements		F-8
Report of Independent Registered Public Accounting Firm		F-77

See accompanying notes to these consolidated financial statements.

F-1

BIOGEN IDEC INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF INCOME

(In thousands, except per share amounts)

	For the Years Ended December 31,
	2011			2010			2009
Revenues:
Product	$	3,836,117		$	3,470,056		$	3,152,941
Unconsolidated joint business		996,597			1,077,244			1,094,863
Other		215,920			169,123			129,544
Total revenues		5,048,634			4,716,423			4,377,348
Cost and expenses:
Cost of sales, excluding amortization of acquired intangible assets		466,780			400,262			382,104
Research and development		1,219,602			1,248,604			1,283,068
Selling, general and administrative		1,056,133			1,031,540			911,034
Collaboration profit sharing		317,771			258,071			215,904
Amortization of acquired intangible assets		208,566			208,928			289,811
Fair value adjustment of contingent consideration		36,065			—			—
Restructuring charge		19,026			75,153			—
Acquired in-process research and development		—			244,976			—
Total cost and expenses		3,323,943			3,467,534			3,081,921
Income from operations		1,724,691			1,248,889			1,295,427
Other income (expense), net		(13,477	)		(18,983	)		37,252
Income before income tax expense		1,711,214			1,229,906			1,332,679
Income tax expense		444,528			331,333			355,617
Net income		1,266,686			898,573			977,062
Net income (loss) attributable to noncontrolling interests, net of tax		32,258			(106,700	)		6,930
Net income attributable to Biogen Idec Inc.	$	1,234,428		$	1,005,273		$	970,132
Net income per share:
Basic earnings per share attributable to Biogen Idec Inc.	$	5.09		$	3.98		$	3.37
Diluted earnings per share attributable to Biogen Idec Inc.	$	5.04		$	3.94		$	3.35
Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Idec Inc.		242,395			252,307			287,356
Diluted earnings per share attributable to Biogen Idec Inc.		245,033			254,867			289,476

See accompanying notes to these consolidated financial statements.

F-2

BIOGEN IDEC INC. AND SUBSIDIARIES

CONSOLIDATED BALANCE SHEETS

(In thousands, except per share amounts)

	As of December 31,
	2011			2010
ASSETS
Current assets:
Cash and cash equivalents	$	514,542		$	759,598
Marketable securities		1,176,115			448,146
Accounts receivable, net of allowances of $57,524 and $54,922, respectively		584,603			605,329
Due from unconsolidated joint business		228,724			222,459
Inventory		326,843			289,066
Other current assets		144,600			215,822
Total current assets		2,975,427			2,540,420
Marketable securities		1,416,737			743,101
Property, plant and equipment, net		1,571,387			1,641,634
Intangible assets, net		1,608,191			1,772,826
Goodwill		1,146,314			1,146,314
Investments and other assets		331,548			248,198
Total assets	$	9,049,604		$	8,092,493
LIABILITIES AND EQUITY
Current liabilities:
Current portion of notes payable, line of credit and other financing arrangements	$	3,292		$	137,153
Taxes payable		45,939			84,517
Accounts payable		186,448			162,529
Accrued expenses and other		677,210			665,923
Total current liabilities		912,889			1,050,122
Notes payable, line of credit and other financing arrangements		1,060,808			1,066,379
Long-term deferred tax liability		248,644			200,950
Other long-term liabilities		400,276			325,599
Total liabilities		2,622,617			2,643,050
Commitments and contingencies
Equity:
Biogen Idec Inc. shareholders’ equity
Preferred stock, par value $0.001 per share		—			—
Common stock, par value $0.0005 per share		128			124
Additional paid-in capital		4,185,048			3,895,103
Accumulated other comprehensive income (loss)		(26,535	)		(21,610	)
Retained earnings		3,106,761			1,872,481
Treasury stock, at cost; 13,518 shares and 7,662 shares, respectively		(839,903	)		(349,592	)
Total Biogen Idec Inc. shareholders’ equity		6,425,499			5,396,506
Noncontrolling interests		1,488			52,937
Total equity		6,426,987			5,449,443
Total liabilities and equity	$	9,049,604		$	8,092,493

See accompanying notes to these consolidated financial statements.

F-3

BIOGEN IDEC INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF CASH FLOWS

(In thousands)

	For the Years Ended December 31,
	2011			2010			2009
Cash flows from operating activities:
Net income	$	1,266,686		$	898,573		$	977,062
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization of property, plant and equipment, and intangible assets		358,933			355,744			427,961
Acquired in-process research and development		—			271,376			—
Share-based compensation		113,005			167,826			160,902
Fair value adjustment of contingent consideration		36,065			—			—
Excess tax benefit from shared-based compensation		(50,586	)		(13,136	)		(3,436	)
Deferred income taxes		153,576			(81,410	)		(137,351	)
Write-down of inventory to net realizable value		25,446			11,808			16,924
Impairment of marketable securities, investments and other assets		8,619			20,846			16,184
Non-cash interest (income) expense, foreign exchange remeasurement loss (gain), net and other		15,671			5,808			(7,892	)
Realized (gain) loss on sale of marketable securities and strategic investments		(15,062	)		(16,321	)		(23,974	)
Changes in operating assets and liabilities, net:
Accounts receivable		(73,374	)		(99,227	)		(100,442	)
Due from unconsolidated joint business		(6,265	)		(28,670	)		13,136
Inventory		(59,219	)		(4,527	)		(42,772	)
Other assets		(43,241	)		(12,584	)		22,271
Accrued expenses and other current liabilities		33,722			130,875			(48,942	)
Other liabilities and taxes payable		(36,235	)		17,692			(194,733	)
Net cash flows provided by operating activities		1,727,741			1,624,673			1,074,898
Cash flows from investing activities:
Proceeds from sales and maturities of marketable securities		2,276,720			2,668,694			3,319,007
Purchases of marketable securities		(3,696,995	)		(1,988,394	)		(3,548,119	)
Acquisitions		(5,000	)		(72,476	)		—
Acquisition of a variable interest entity, net		—			(84,952	)		—
Purchases of property, plant and equipment		(208,020	)		(173,055	)		(165,646	)
Proceeds from the sale of property, plant and equipment		2,207			—			—
Purchases of intangible assets		(44,155	)		—			—
Purchases of other investments		(16,324	)		(4,492	)		(44,086	)
Proceeds from the sale of strategic investments		41,273			—			13,822
Collateral received under securities lending		—			—			29,991
Net cash flows (used in) provided by investing activities		(1,650,294	)		345,325			(395,031	)
Cash flows from financing activities:
Purchase of treasury stock		(497,975	)		(2,077,579	)		(751,170	)
Proceeds from issuance of stock for share-based compensation arrangements		314,650			183,486			47,810
Excess tax benefit from share-based compensation		50,586			13,136			3,436
Change in cash overdraft		2,823			11,781			12,275
Acquisition of noncontrolling interests		(148,264	)		—			—
Net distributions to noncontrolling interests		(27,062	)		(23,475	)		4,356
Repayments of borrowings		(11,459	)		(18,073	)		(10,867	)
Net proceeds from financing arrangement for the sale of the San Diego facility		—			126,980			—
Repayments on financing arrangement for the sale of the San Diego facility		(3,161	)		(1,175	)		—
Obligation under securities lending		—			—			(29,991	)
Net cash flows used in financing activities		(319,862	)		(1,784,919	)		(724,151	)
Net (decrease) increase in cash and cash equivalents		(242,415	)		185,079			(44,284	)
Effect of exchange rate changes on cash and cash equivalents		(2,641	)		(7,370	)		3,788
Cash and cash equivalents, beginning of the year		759,598			581,889			622,385
Cash and cash equivalents, end of the year	$	514,542		$	759,598		$	581,889

See accompanying notes to these consolidated financial statements.

F-4

BIOGEN IDEC INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF EQUITY

(In thousands)

										Additional paid-in capital			Accumulated other comprehensive income (loss)												Total Biogen Idec  Inc. shareholders’ equity
	Preferred stock					Common stock										Retained earnings			Treasury stock									Noncontrolling interests			Total equity
	Shares			Amount		Shares		Amount											Shares			Amount
Balance, December 31, 2010		8		$	—		248,200	$	124	$	3,895,103		$	(21,610	)	$	1,872,481			(7,662	)	$	(349,592	)	$	5,396,506		$	52,937		$	5,449,443
Comprehensive income:
Net income																	1,234,428									1,234,428			32,258			1,266,686
Unrealized losses recognized on securities available for sale:
Unrealized losses recognized during the period, net of tax of $133														(224	)											(224	)					(224	)
Less: reclassification adjustment for gains included in net income, net of tax of $7,155														(12,184	)											(12,184	)					(12,184	)
Unrealized losses on securities available for sale, net of tax of $7,288														(12,408	)											(12,408	)					(12,408	)
Unrealized gains on foreign currency forward contracts:
Unrealized gains recognized during the period, net of tax of $3,647														32,830												32,830						32,830
Less: reclassification adjustment for losses included in net income, net of tax of $1,268														9,767												9,767						9,767
Unrealized gains on foreign currency forward contracts, net of tax of $4,915														42,597												42,597						42,597
Unrealized losses on pension benefit obligation, net of tax of $0														(9,280	)											(9,280	)					(9,280	)
Translation adjustment														(25,834	)											(25,834	)		4,903			(20,931	)
Total comprehensive income																										1,229,503			37,161			1,266,664
Distributions to noncontrolling interests																	(148	)								(148	)		(26,914	)		(27,062	)
Acquisitions of noncontrolling interests											(125,641	)														(125,641	)		(61,696	)		(187,337	)
Repurchase of common stock for Treasury pursuant to the 2011 share repurchase plan, at cost																				(6,018	)		(497,975	)		(497,975	)					(497,975	)
Issuance of common and treasury stock under stock option and stock purchase plans							5,458		3		306,982									162			7,664			314,649						314,649
Issuance of common stock under stock award plan							1,482		1		(50,954	)														(50,953	)					(50,953	)
Conversion of preferred stock		(8	)				493		—		—															—						—
Compensation expense related to share-based payments											117,347															117,347						117,347
Recharacterization of share-based awards from equity to cash-settled due to restructuring											(8,172	)														(8,172	)					(8,172	)
Tax benefit from share-based payments											50,383															50,383						50,383
Balance, December 31, 2011		—		$	—		255,633	$	128	$	4,185,048		$	(26,535	)	$	3,106,761			(13,518	)	$	(839,903	)	$	6,425,499		$	1,488		$	6,426,987

F-5

BIOGEN IDEC INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF EQUITY — (Continued)

(In thousands)

											Additional paid-in capital			Accumulated other comprehensive income (loss)												Total Biogen Idec  Inc. shareholders’ equity
	Preferred stock				Common stock												Retained earnings			Treasury stock									Noncontrolling interests			Total equity
	Shares		Amount		Shares			Amount												Shares			Amount
Balance, December 31, 2009		8	$	—		288,494		$	144		$	5,781,920		$	50,496		$	1,068,890			(13,639	)	$	(679,920	)	$	6,221,530		$	40,352		$	6,261,882
Comprehensive income:
Net income																		1,005,273									1,005,273			(106,700	)		898,573
Unrealized gains (losses) recognized on securities available for sale:
Unrealized gains recognized during the period, net of tax of $6,345															10,775												10,775						10,775
Less: reclassification adjustment for gains included in net income, net of tax of $5,656															(9,631	)											(9,631	)					(9,631	)
Unrealized gains on securities available for sale, net of tax of $689															1,144												1,144						1,144
Unrealized gains (losses) on foreign currency forward contracts:
Unrealized losses recognized during the period, net of tax of $1,268															(9,767	)											(9,767	)					(9,767	)
Less: reclassification adjustment for gains included in net income, net of tax of $304															(1,502	)											(1,502	)					(1,502	)
Unrealized losses on foreign currency forward contracts, net of tax of $964															(11,269	)											(11,269	)					(11,269	)
Unrealized losses on pension benefit obligation, net of tax of $0															(1,942	)											(1,942	)					(1,942	)
Translation adjustment															(60,039	)											(60,039	)		(2,240	)		(62,279	)
Total comprehensive income																											933,167			(108,940	)		824,227
Fair value of assets and liabilities acquired and assigned to noncontrolling interests (Note 19)																											—			145,000			145,000
Distributions to noncontrolling interests																											—			(33,891	)		(33,891	)
Capital contributions from noncontrolling interests																											—			2,488			2,488
Termination of relationship with less than majority owned subsidiary																											—			7,928			7,928
Repurchase of common stock for Treasury pursuant to the 2009 and 2010 share repurchase plans, at cost																					(40,294	)		(2,077,579	)		(2,077,579	)					(2,077,579	)
Retirement of common stock pursuant to the 2009 and 2010 share repurchase plans						(40,294	)		(20	)		(2,077,559	)								40,294			2,077,579			—						—
Issuance of treasury stock under stock option and stock purchase plans																		(28,632	)		4,020			212,118			183,486						183,486
Issuance of treasury stock under stock award plans																		(173,050	)		1,957			118,210			(54,840	)					(54,840	)
Compensation expense related to share-based payments												171,435															171,435						171,435
Tax benefit from share-based payments												19,307															19,307						19,307
Balance, December 31, 2010		8	$	—		248,200		$	124		$	3,895,103		$	(21,610	)	$	1,872,481			(7,662	)	$	(349,592	)	$	5,396,506		$	52,937		$	5,449,443

F-6

BIOGEN IDEC INC. AND SUBSIDIARIES

CONSOLIDATED STATEMENTS OF EQUITY — (Continued)

(In thousands)

											Additional paid-in capital			Accumulated other comprehensive income (loss)												Total Biogen Idec  Inc. shareholders’ equity
	Preferred stock				Common stock												Retained earnings			Treasury stock									Noncontrolling interests			Total equity
	Shares		Amount		Shares			Amount												Shares			Amount
Balance, December 31, 2008		8	$	—		297,253		$	149		$	6,073,957		$	(11,106	)	$	270,180			(9,207	)	$	(527,097	)	$	5,806,083		$	27,869		$	5,833,952
Comprehensive income:
Net income																		970,132									970,132			6,930			977,062
Unrealized gains recognized on securities available for sale:
Unrealized gains recognized during the period, net of tax of $4,136															7,191												7,191						7,191
Less: reclassification adjustment for gains included in net income, net of tax of $3,756															(6,396	)											(6,396	)					(6,396	)
Unrealized gains (losses) on securities available for sale, net of tax of $380															795												795						795
Unrealized gains on foreign currency forward contracts:
Unrealized gains recognized during the period, net of tax of $254															1,452												1,452						1,452
Less: reclassification adjustment for losses included in net income, net of tax of $3,836															40,216												40,216						40,216
Unrealized gains on foreign currency forward contracts, net of tax of $3,582															41,668												41,668						41,668
Unrealized gains on pension benefit obligation, net of tax of $67															501												501						501
Translation adjustment															18,638												18,638			1,197			19,835
Total comprehensive income																											1,031,734			8,127			1,039,861
Distributions to noncontrolling interests																											—			(2,832	)		(2,832	)
Capital contributions from noncontrolling interests																											—			7,188			7,188
Repurchase of common stock for Treasury, at cost																					(15,982	)		(751,170	)		(751,170	)					(751,170	)
Retirement of common stock pursuant to the 2009 share repurchase plan						(8,759	)		(5	)		(422,415	)								8,759			422,420			—						—
Issuance of treasury stock under stock option and stock purchase plans																		(27,191	)		1,181			75,001			47,810						47,810
Issuance of treasury stock under stock award plans																		(144,231	)		1,610			100,926			(43,305	)					(43,305	)
Compensation expense related to share-based payments												167,207															167,207						167,207
Tax benefit from share-based payments												(36,829	)														(36,829	)					(36,829	)
Balance, December 31, 2009		8	$	—		288,494		$	144		$	5,781,920		$	50,496		$	1,068,890			(13,639	)	$	(679,920	)	$	6,221,530		$	40,352		$	6,261,882

See accompanying notes to these consolidated financial statements.

F-7

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

1. Summary of Significant Accounting Policies

Business Overview

Biogen Idec is a global biotechnology company that discovers, develops, manufactures and markets therapies for the treatment of neurodegenerative diseases, hemophilia and autoimmune disorders. Patients worldwide benefit from our leading multiple sclerosis therapies, and the company generates $5 billion in annual revenues.

Consolidation

Our consolidated financial statements reflect our financial statements, those of our wholly-owned subsidiaries and those of certain variable interest entities in which we are the primary beneficiary. For consolidated entities in which we own or are exposed to less than 100% of the economics, we record net income (loss) attributable to noncontrolling interests in our consolidated statements of income equal to the percentage of the economic or ownership interest retained in such entities by the respective noncontrolling parties. All material intercompany balances and transactions are eliminated in consolidation.

In determining whether we are the primary beneficiary of an entity, we apply a qualitative approach that determines whether we have both (1) the power to direct the economically significant activities of the entity and (2) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. These considerations impact the way we account for our existing collaborative relationships and determine whether we consolidate companies or entities with which we have collaborative or other arrangements. Determination about whether an enterprise should consolidate a variable interest entity is required to be made continuously as changes to existing relationships or future transactions may result in us consolidating or deconsolidating our partner(s) to collaborations and other arrangements.

Use of Estimates

The preparation of our consolidated financial statements in accordance with U.S. GAAP requires management to make estimates, judgments, and assumptions that may affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. On an on-going basis, we evaluate our estimates and judgments and methodologies, including those related to revenue recognition and related allowances, our collaborative relationships, clinical trial expenses, the consolidation of variable interest entities, the valuation of contingent consideration resulting from a business combination, the valuation of acquired intangible assets including in-process research and development, inventory, impairment and amortization of long-lived assets including intangible assets, impairments of goodwill, share-based compensation, income taxes including the valuation allowance for deferred tax assets, the valuation of investments, derivatives and hedging activities, contingencies, litigation, and restructuring charges. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results may differ from these estimates under different assumptions or conditions.

Revenue Recognition

We recognize revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; our price to the customer is fixed or determinable; and collectability is reasonably assured.

F-8

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Product Revenues

Revenues from product sales are recognized when title and risk of loss have passed to the customer, which is typically upon delivery. However, sales of TYSABRI in the U.S. are recognized on the “sell-through” model, that is, upon shipment of the product by Elan Pharma International, Ltd. (Elan), an affiliate of Elan Corporation, plc, to its third party distributor rather than upon shipment to Elan. Product revenues are recorded net of applicable reserves for discounts and allowances.

Reserves for Discounts and Allowances

We establish reserves for trade term discounts, wholesaler incentives, Medicaid rebates, Veterans Administration (VA) and Public Health Service (PHS) discounts, managed care rebates, product returns and other governmental rebates or applicable allowances, including those associated with the implementation of pricing actions in certain of the international markets in which we operate. Reserves established for these discounts and allowances are classified as reductions of accounts receivable (if the amount is payable to our direct customer) or a liability (if the amount is payable to a party other than our customer). These reserves are based on estimates of the amounts earned or to be claimed on the related sales. Our estimates take into consideration our historical experience, current contractual and statutory requirements, specific known market events and trends, and forecasted customer buying patterns. Actual amounts may ultimately differ from our estimates. If actual results vary, we will need to adjust these estimates, which could have an effect on earnings in the period of adjustment. The estimates we make with respect to these allowances represent the most significant judgments with regard to revenue recognition.

Product revenue reserves are categorized as follows: discounts, contractual adjustments and returns.

Discount reserves include trade term discounts and wholesaler incentives. Trade term discounts and wholesaler incentive reserves primarily relate to estimated obligations for credits to be granted to wholesalers for remitting payment on their purchases within established incentive periods and credits to be granted to wholesalers for compliance with various contractually-defined inventory management practices, respectively. We determine these reserves based on our experience, including the timing of customer payments.

Contractual adjustment reserves primarily relate to Medicaid and managed care rebates, VA and PHS discounts and other governmental rebates or applicable allowances.

• Medicaid rebate reserves relate to our estimated obligations to states under established reimbursement arrangements. Rebate accruals are recorded in the same period the related revenue is recognized resulting in a reduction of product revenue and the establishment of a liability which is included in other current liabilities. Our liability for Medicaid rebates consists of estimates for claims that a state will make for the current quarter, claims for prior quarters that have been estimated for which an invoice has not been received, invoices received for claims from the prior quarters that have not been paid, and an estimate of potential claims that will be made for inventory that exists in the distribution channel at period end.

• VA rebates or chargeback reserves represent our estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices we charge to wholesalers which provide those products. The wholesaler charges us for the difference between what the wholesaler pays for the products and the ultimate selling price to the qualified healthcare providers. Rebate and chargeback reserves are established in the same period as the related revenue is recognized resulting in a reduction in product revenue and accounts receivable. Chargeback amounts are generally determined at the time of resale to the qualified healthcare provider from the wholesaler, and we generally issue credits for such amounts within a few weeks of the wholesaler notifying us about the resale. Our reserves for VA and chargebacks consists of amounts that we expect to

F-9

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

issue for inventory that exists at the wholesalers that we expect will be sold to qualified healthcare providers and chargebacks that wholesalers have claimed for which we have not issued a credit.

• Managed care rebate reserves represent our estimated obligations to third parties, primarily pharmacy benefit managers. Rebate accruals are recorded in the same period the related revenue is recognized resulting in a reduction of product revenue and the establishment of a liability which is included in accrued expenses and other current liabilities. These rebates result from performance-based goals that are primarily based on attaining contractually specified sales volumes and growth. The calculation of the accrual for these rebates is based on an estimate of the customer’s buying patterns and the resulting applicable contractual rebate rate(s) to be earned over a contractual period.

• Other governmental rebates or applicable allowances primarily relate to mandatory rebates and discounts in markets where government-sponsored healthcare systems are the primary payers for healthcare.

Product return reserves are established for returns expected to be made by wholesalers and are recorded in the period the related revenue is recognized, resulting in a reduction to product sales. In accordance with contractual terms, wholesalers are permitted to return product for reasons such as damaged or expired product. The majority of wholesaler returns are due to product expiration. Expired product return reserves are estimated through a comparison of historical return data to their related sales on a production lot basis. Historical rates of return are determined for each product and are adjusted for known or expected changes in the marketplace specific to each product.

In addition to the discounts and rebates described above and classified as a reduction of revenue, we also maintain certain customer service contracts with distributors and other customers in the distribution channel that provide us with inventory management and distribution services. We have established the fair value of these services and classified these customer service contracts as sales and marketing expense. If we had concluded that we did not receive a separate identifiable benefit or have sufficient evidence that the fair value did not exist for these services, we would have been required to classify these costs as a reduction of revenue.

In countries where we expect to collect receivables greater than one year, at the time of sale, we have discounted our revenues over the period of time that we estimate those amounts will be paid using our estimate of the country’s borrowing rate. The related receivables are classified at the time of sale as long-term assets. We will accrete interest income on these receivables, which will be recognized as a component of other income (expense), net within our consolidated statement of income.

We also distribute no-charge product to qualifying patients under our patient assistance and patient replacement goods program. This program is administered through one of our distribution partners, which ships product for qualifying patients from its own inventory received from us. Gross revenue and the related reserves are not recorded on product shipped under this program and cost of sales is recorded when the product is shipped.

Revenues from Unconsolidated Joint Business

We collaborate with Genentech on the development and commercialization of RITUXAN. Revenues from unconsolidated joint business consist of (1) our share of pre-tax co-promotion profits in the U.S.; (2) reimbursement of our selling and development expense in the U.S.; and (3) revenue on sales of RITUXAN in the rest of world, which consists of our share of pre-tax co-promotion profits in Canada and royalty revenue on sales of RITUXAN outside the U.S. and Canada by F. Hoffmann-La Roche Ltd. (Roche) and its sublicensees. Pre-tax co-promotion profits are calculated and paid to us by Genentech in the U.S. and by Roche in Canada. Pre-tax co-promotion profits consist of U.S. and Canadian sales of RITUXAN to third-party customers net of discounts and allowances less the cost to manufacture RITUXAN, third-party royalty expenses, and distribution, selling and marketing, and joint development expenses incurred by Genentech, Roche and us. We record our share of the pretax co-promotion profits in Canada and royalty revenues on sales of RITUXAN outside the U.S. on a cash basis. Additionally, our share of the pretax co-promotion profits in the U.S. includes estimates made by Genentech and those estimates are subject to change. Actual results may ultimately differ from our estimates.

F-10

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Royalty Revenues

We receive royalty revenues on sales by our licensees of other products covered under patents that we own. We do not have future performance obligations under these license arrangements. We record these revenues based on estimates of the sales that occurred during the relevant period. The relevant period estimates of sales are based on interim data provided by licensees and analysis of historical royalties that have been paid to us, adjusted for any changes in facts and circumstances, as appropriate. We maintain regular communication with our licensees in order to assess the reasonableness of our estimates. Differences between actual royalty revenues and estimated royalty revenues are adjusted for in the period in which they become known, typically the following quarter. Historically, adjustments have not been material when compared to actual amounts paid by licensees. If we are unable to accurately estimate revenue, then we record revenues on a cash basis.

Milestone Revenues

We execute collaborative and other agreements which may contain milestone payments. Revenues from milestones, if they are considered substantive, are recognized upon successful accomplishment of the milestones. Determining whether a milestone is substantive involves judgment, including an assessment of our involvement in achieving the milestones and whether the amount of the payment is commensurate to our performance. If not considered substantive, milestones are initially deferred and recognized over the remaining performance obligation.

Multiple-Element Revenue Arrangements

We may, from time to time, enter into transactions that involve the sale of products and related services under multiple element arrangements. In accounting for these transactions, we allocate revenue to the various elements based on their fair value. The fair value of a revenue generating element can be based on current selling prices offered by us or another party for current products or management’s best estimate of a selling price for future products. Revenue allocated to an individual element is recognized when all other revenue recognition criteria are met for that element.

Fair Value Measurements

We have certain financial assets and liabilities recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements.

• Level 1 — Fair values are determined utilizing quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access;

• Level 2 — Fair values are determined by utilizing quoted prices for identical or similar assets and liabilities in active markets or other market observable inputs such as interest rates, yield curves and foreign currency spot rates; and

• Level 3 — Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

Valuation of Investments

We validate the prices provided by our third party pricing services by reviewing their pricing methods and matrices, obtaining market values from other pricing sources, analyzing pricing data in certain instances and confirming that the relevant markets are active. After completing our validation procedures, we did not adjust or override any fair value measurements provided by our pricing services as of December 31, 2011 and 2010, respectively.

F-11

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Our strategic investments in publicly traded equity securities are classified as Level 1 assets as their fair values are readily determinable and based on quoted market prices.

The majority of our financial assets and liabilities have been classified as Level 2. Our financial assets and liabilities (which include our cash equivalents, derivative contracts, marketable debt securities, and plan assets for deferred compensation) have been initially valued at the transaction price and subsequently valued, at the end of each reporting period, typically utilizing third party pricing services or other market observable data. The pricing services utilize industry standard valuation models, including both income and market based approaches and observable market inputs to determine value. These observable market inputs include reportable trades, benchmark yields, credit spreads, broker/dealer quotes, bids, offers, current spot rates and other industry and economic events.

We also maintain venture capital investments classified as Level 3 whose fair value is initially measured at transaction prices and subsequently valued using the pricing of recent financing or by reviewing the underlying economic fundamentals and liquidation value of the companies. These investments are the only investments for which we used Level 3 inputs to determine the fair value. These investments include investments in certain biotechnology oriented venture capital funds which primarily invest in small privately-owned, venture-backed biotechnology companies. The fair value of our investments in these venture capital funds has been estimated using the net asset value of the fund. The investments cannot be redeemed within the funds. Distributions from each fund will be received as the underlying investments of the fund are liquidated. The funds and therefore a majority of the underlying assets of the funds will not be liquidated in the near future. The underlying assets in these funds are initially measured at transaction prices and subsequently valued using the pricing of recent financings or by reviewing the underlying economic fundamentals and liquidation value of the companies that the funds invest in. We apply judgments and estimates when we validate the prices provided by third parties. While we believe the valuation methodologies are appropriate, the use of valuation methodologies is highly judgmental and changes in methodologies can have a material impact on our results of operations. Gains and losses (realized and unrealized) included in earnings for the period are reported in other income (expense), net.

Valuation of Contingent Consideration Resulting from a Business Combination

We record contingent consideration resulting from business combinations completed after January 1, 2009 at its fair value on the acquisition date. Each reporting period thereafter, we revalue these obligations and record increases or decreases in their fair value as an adjustment to contingent consideration expense within our consolidated statement of income. Changes in the fair value of the contingent consideration obligations can result from adjustments to the discount rates and periods, updates in the assumed achievement or timing of any development milestones or changes in the probability of certain clinical events and changes in the assumed probability associated with regulatory approval. These fair value measurements represent Level 3 measurements as they are based on significant inputs not observable in the market.

Significant judgment is employed in determining the appropriateness of these assumptions as of the acquisition date and for each subsequent period. Accordingly, changes in assumptions described above, could have a material impact on the amount of contingent consideration expense we record in any given period.

Other

The carrying amounts reflected in the consolidated balance sheets for cash equivalents, current accounts receivable, due from unconsolidated joint business, other current assets, accounts payable, and accrued expenses and other, approximate fair value due to their short-term maturities.

F-12

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Cash and Cash Equivalents

We consider only those investments which are highly liquid, readily convertible to cash and that mature within three months from date of purchase to be cash equivalents. As of December 31, 2011 and 2010, cash equivalents were comprised of money market funds and commercial paper, repurchase agreements, and other debt securities with maturities less than 90 days.

Accounts Receivable

The majority of our accounts receivable arise from product sales and primarily represent amounts due from our wholesale distributors, public hospitals and other government entities. We monitor the financial performance and credit worthiness of our large customers so that we can properly assess and respond to changes in their credit profile. We provide reserves against trade receivables for estimated losses that may result from a customer’s inability to pay. Amounts determined to be uncollectible are charged or written-off against the reserve. To date, such losses have not exceeded management’s estimates.

Concentration of Credit Risk

Financial instruments that potentially subject us to concentrations of credit risk include cash and cash equivalents, investments, derivatives, and accounts receivable. We attempt to minimize the risks related to cash and cash equivalents and investments by using highly-rated financial institutions that invest in a broad and diverse range of financial instruments as previously defined by us. We have established guidelines relative to credit ratings and maturities intended to safeguard principal balances and maintain liquidity. Our investment portfolio is maintained in accordance with our investment policy, which defines allowable investments, specifies credit quality standards and limits the credit exposure of any single issuer. We minimize credit risk resulting from derivatives instruments by choosing only highly rated financial institutions as counterparties.

Concentrations of credit risk with respect to receivables, which are typically unsecured, are limited due to the wide variety of customers and markets using our products, as well as their dispersion across many different geographic areas. The majority of our accounts receivable arise from product sales in the United States and Europe and have standard payment terms which are generally between 30 and 90 days. We continue to monitor economic conditions, including the volatility associated with international economies, and associated impacts on the relevant financial markets and our business, especially in light of the global economic downturn. For additional information related to this concentration of credit risk, please read Note 5, Accounts Receivable to these consolidated financial statements.

As of December 31, 2011 and 2010, one wholesale distributor accounted for approximately 14.1% and 11.5% of consolidated receivables, respectively.

Inventory

Inventories are stated at the lower of cost or market with cost determined in a manner that approximates the first-in, first-out (FIFO) method. Included in inventory are raw materials used in the production of pre-clinical and clinical products, which are expensed as research and development costs when consumed.

Capitalization of Inventory Costs

We capitalize inventory costs associated with our products prior to regulatory approval, when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. We consider numerous attributes in evaluating whether the costs to manufacture a particular product should be capitalized as an asset. We assess the regulatory approval process and where the

F-13

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

particular product stands in relation to that approval process, including any known safety or efficacy concerns, potential labeling restrictions and other impediments to approval. We evaluate our anticipated research and development initiatives and constraints relating to the product and the indication in which it will be used. We consider our manufacturing environment including our supply chain in determining logistical constraints that could hamper approval or commercialization. We consider the shelf life of the product in relation to the expected timeline for approval and we consider patent related or contract issues that may prevent or delay commercialization. We also base our judgment on the viability of commercialization, trends in the marketplace and market acceptance criteria. Finally, we consider the reimbursement strategies that may prevail with respect to the product and assess the economic benefit that we are likely to realize. We expense previously capitalized costs related to pre-approval inventory upon a change in such judgment, due to, among other potential factors, a denial or delay of approval by necessary regulatory bodies.

As of December 31, 2011 and 2010, the carrying value of our inventory did not include any significant costs associated with products that had not yet received regulatory approval.

Obsolescence and Unmarketable Inventory

We periodically review our inventories for excess or obsolete inventory and write-down obsolete or otherwise unmarketable inventory to its estimated net realizable value. If the actual net realizable value is less than that estimated by us, or if it is determined that inventory utilization will further diminish based on estimates of demand, additional inventory write-downs may be required. Additionally, our products are subject to strict quality control and monitoring which we perform throughout the manufacturing process. In the event that certain batches or units of product no longer meet quality specifications or become obsolete due to expiration, we will record a charge to cost of sales to write-down any obsolete or otherwise unmarketable inventory to its estimated net realizable value. In all cases product inventory is carried at the lower of cost or its estimated net realizable value. Amounts written-down to unmarketable inventory are charged to cost of sales, excluding amortization of acquired intangible assets.

Marketable Securities and Other Investments

Marketable Debt Securities

Available-for-sale debt securities are recorded at fair market value and unrealized gains and losses are included in accumulated other comprehensive income (loss) in equity, net of related tax effects, unless the security has experienced a credit loss, we have determined that we have the intent to sell the security or we have determined that it is more likely than not that we will have to sell the security before its expected recovery. Realized gains and losses are reported in other income (expense), net, on a specific identification basis.

Strategic Investments

As part of our business development efforts, we will, from time to time, invest in equity securities of certain biotechnology companies. These investments are known as strategic investments and are classified as available-for-sale and accounted for as marketable equity investments or as cost investments based upon our ownership percentage and other factors that suggest we have significant influence and are included in investments and other assets within our consolidated balance sheet. When assessing whether a decline in the fair value of a strategic investment below our cost basis is other-than-temporary, we consider the fair market value of the security, the duration of the security’s decline, and prospects for the underlying business, including favorable or adverse clinical trial results, new product initiatives and new collaborative agreements with the companies in which we have invested.

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Non-Marketable Equity Securities

We also invest in equity securities of companies whose securities are not publicly traded and where fair value is not readily available. These investments are recorded using either the cost method or the equity method of accounting, depending on our ownership percentage and other factors that suggest we have significant influence. We monitor these investments to evaluate whether any decline in their value has occurred that would be other-than-temporary, based on the implied value of recent company financings, public market prices of comparable companies, and general market conditions and are included in investments and other assets within our consolidated balance sheet.

Evaluating Investments for Other-than-Temporary Impairments

We conduct periodic reviews to identify and evaluate each investment that has an unrealized loss, in accordance with the meaning of other-than-temporary impairment and its application to certain investments. An unrealized loss exists when the current fair value of an individual security is less than its amortized cost basis. Unrealized losses on available-for-sale securities that are determined to be temporary, and not related to credit loss, are recorded, net of tax, in accumulated other comprehensive income.

For available-for-sale debt securities with unrealized losses, management performs an analysis to assess whether we intend to sell or whether we would more likely than not be required to sell the security before the expected recovery of the amortized cost basis. Where we intend to sell a security, or may be required to do so, the security’s decline in fair value is deemed to be other-than-temporary and the full amount of the unrealized loss is reflected within earnings as an impairment loss.

Regardless of our intent to sell a security, we perform additional analysis on all securities with unrealized losses to evaluate losses associated with the creditworthiness of the security. Credit losses are identified where we do not expect to receive cash flows sufficient to recover the amortized cost basis of a security.

For equity securities, when assessing whether a decline in fair value below our cost basis is other-than-temporary, we consider the fair market value of the security, the duration of the security’s decline, and the financial condition of the issuer. We then consider our intent and ability to hold the equity security for a period of time sufficient to recover our carrying value. Where we have determined that we lack the intent and ability to hold an equity security to its expected recovery, the security’s decline in fair value is deemed to be other-than-temporary and is reflected within earnings as an impairment loss.

Property, Plant and Equipment

Property, plant and equipment are carried at cost, subject to review for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. The cost of normal, recurring, or periodic repairs and maintenance activities related to property, plant and equipment are expensed as incurred. The cost for planned major maintenance activities, including the related acquisition or construction of assets, is capitalized if the repair will result in future economic benefits.

Interest costs incurred during the construction of major capital projects are capitalized until the underlying asset is ready for its intended use, at which point the interest costs are amortized as depreciation expense over the life of the underlying asset. We also capitalize certain direct and incremental costs associated with the validation effort required for licensing by regulatory agencies of manufacturing equipment for the production of a commercially approved drug. These costs include primarily direct labor and material and are incurred in preparing the equipment for its intended use. The validation costs are amortized over the life of the related equipment.

In addition, we capitalize certain internal use computer software development costs. If the software is an integral part of production assets, these costs are included in machinery and equipment and are amortized on a straight-line basis over the estimated useful lives of the related software, which generally range from three to five years.

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We generally depreciate or amortize the cost of our property, plant and equipment using the straight-line method over the estimated useful lives of the respective assets, which are summarized as follows:

Asset Category	Useful Lives
Land	Not depreciated
Buildings	15 to 40 years
Leasehold Improvements	Lesser of the useful life or the term of the respective lease
Furniture and Fixtures	5 to 7 years
Machinery and Equipment	5 to 20 years
Computer Software and Hardware	3 to 5 years

When we dispose of property, plant and equipment, we remove the associated cost and accumulated depreciation from the related accounts on our consolidated balance sheet and include any resulting gain or loss in our consolidated statement of income.

Intangible Assets

Our intangible assets consist of patents, licenses, core developed technology, in-process research and development acquired after January 1, 2009, trademarks, trade names, assembled workforce and other distribution rights. The majority of our intangible assets were recorded in connection with the merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation in 2003. Our intangible assets are recorded at fair value at the time of their acquisition and are stated within our consolidated balance sheets net of accumulated amortization and impairments.

We amortize intangible assets over their estimated useful lives using the economic use method if anticipated future cash flows can be reasonably estimated; the straight-line method is used when cash flows cannot be reasonably estimated. Our amortization policy reflects the pattern that the economic benefits of the intangible assets are consumed. The useful lives of our intangible assets are primarily based on the legal or contractual life of the underlying patent or contract, which does not include additional years for the potential extension or renewal of the contract or patent. Intangible assets related to patents, licenses, core developed technology, assembled workforce, and other distribution rights are amortized over their remaining estimated useful lives. Intangible assets related to trademarks, trade names and in-process research and development prior to commercialization are not amortized because they have indefinite lives, but they are subject to review for impairment. We review our intangible assets with indefinite lives for impairment annually, as of October 31, and whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable.

Our most significant intangible asset is the core technology related to our AVONEX product. Our amortization policy reflects our belief that the economic benefit of our core technology is consumed as revenue is generated from AVONEX. We refer to this amortization methodology as the economic consumption model, which involves calculating a ratio of actual current period sales to total anticipated sales for the life of the product and applying this ratio to the carrying amount of the intangible asset. An analysis of the anticipated lifetime revenue of AVONEX is performed at least annually during our long range planning cycle, and this analysis serves as the basis for the calculation of our economic consumption amortization model. We believe this process has allowed us to reliably determine the best estimate of the pattern in which we will consume the economic benefits of our core technology intangible asset.

Acquired In-process Research and Development (IPR&D)

Acquired IPR&D represents the fair value assigned to research and development assets that we acquire that have not been completed at the date of acquisition. The value assigned to acquired IPR&D is determined by estimating the costs to develop the acquired technology into commercially viable products, estimating the

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resulting revenue from the projects, and discounting the net cash flows to present value. The revenue and costs projections used to value acquired IPR&D were, as applicable, reduced based on the probability of developing a new drug. Additionally, the projections considered the relevant market sizes and growth factors, expected trends in technology, and the nature and expected timing of new product introductions by us and our competitors. The resulting net cash flows from such projects are based on management’s estimates of cost of sales, operating expenses, and income taxes from such projects. The rates utilized to discount the net cash flows to their present value were commensurate with the stage of development of the projects and uncertainties in the economic estimates used in the projections described above.

We measured acquired IPR&D in business combinations completed prior to January 1, 2009, at fair value and expensed it on acquisition date if that technology lacked an alternative future use, or capitalized it as an intangible asset if certain criteria were met; however, effective January 1, 2009, if we are purchasing a business, the acquired IPR&D is measured at fair value, capitalized as an intangible asset and tested for impairment at least annually until commercialization, after which time the IPR&D is amortized over its estimated useful life. If we acquire an asset or group of assets that do not meet the definition of a business under applicable accounting standards, then the acquired IPR&D is expensed on its acquisition date. Future costs to develop these assets are recorded to expense as they are incurred if the technology lacks alternative future uses.

We review amounts capitalized as in-process research and development for impairment at least annually, as of October 31, and whenever events or changes in circumstances indicate that the carrying value of the assets might not be recoverable. In the event the carrying value of the assets are not expected to be recovered, the assets are written down to their estimated fair values.

Impairment of Long-Lived Assets

Long-lived assets to be held and used, including property, plant and equipment are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets or asset group may not be recoverable.

Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their estimated fair values. Long-lived assets to be disposed of are carried at fair value less costs to sell.

Goodwill

Goodwill relates largely to amounts that arose in connection with the merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation and represents the difference between the purchase price and the fair value of the identifiable tangible and intangible net assets when accounted for using the purchase method of accounting. Goodwill is not amortized, but is subject to periodic review for impairment. Goodwill is reviewed annually, as of October 31, and whenever events or changes in circumstances indicate that the carrying value of the goodwill might not be recoverable.

We apply a two-step impairment test. In the first step, we compare the fair value of our reporting unit to its carrying value. If the carrying value of the net assets assigned to the reporting unit exceeds the fair value of our reporting unit, then the second step of the impairment test is performed in order to determine the implied fair value of our reporting unit’s goodwill. If the carrying value of our reporting unit’s goodwill exceeds its implied fair value, then the company records an impairment loss equal to the difference. As described in Note 25, Segment Information to these consolidated financial statements, we operate in one business segment which we consider our only reporting unit.

In September 2011, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2011-08, “Intangibles — Goodwill and Other (Topic 350): Testing Goodwill for Impairment” (ASU

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2011-08). This newly issued accounting standard allows an entity the option to first assess qualitative factors to determine whether it is necessary to perform the current two-step impairment test. If an entity believes, as a result of its qualitative assessment, that it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount, the quantitative two-step impairment test is required; otherwise, no further testing is required. These amendments do not change the current guidance for testing other indefinite-lived intangible assets for impairment. This ASU is effective for annual and interim goodwill impairment tests performed for fiscal years beginning after December 15, 2011, which for Biogen Idec means January 1, 2012. Early adoption is permitted; however, we have not elected to do so. The adoption of this statement will not impact our financial position or results of operations.

Derivative Instruments and Hedging Activities

We recognize all derivative instruments as either assets or liabilities at fair value in our consolidated balance sheets. Changes in the fair value of derivatives are recorded each period in current earnings or accumulated other comprehensive income (loss), depending on whether a derivative is designated as part of a hedge transaction and, if it is, the type of hedge transaction. We classify the cash flows from these instruments in the same category as the cash flows from the hedged items. We do not hold or issue derivative instruments for trading or speculative purposes.

We assess, both at inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting the changes in cash flows or fair values of the hedged items. We also assess hedge ineffectiveness on a quarterly basis and record the gain or loss related to the ineffective portion to current earnings to the extent significant. If we determine that a forecasted transaction is no longer probable of occurring, we discontinue hedge accounting for the affected portion of the hedge instrument, and any related unrealized gain or loss on the contract is recognized in current earnings.

Translation of Foreign Currencies

The functional currency for most of our foreign subsidiaries is their local currency. For the Company’s non-U.S. subsidiaries that transact in functional currency other than the U.S. dollar, assets and liabilities are translated at current rates of exchange at the balance sheet date. Income and expense items are translated at the average foreign exchange rates for the period. Adjustments resulting from the translation of the financial statements of our foreign operations into U.S. dollars are excluded from the determination of net income and are recorded in accumulated other comprehensive income, a separate component of equity. For subsidiaries where the functional currency differs from the local currency, non-monetary assets and liabilities are translated at the rate of exchange in effect on the date assets were acquired while monetary assets and liabilities are translated at current rates of exchange as of the balance sheet date. Income and expense items are translated at the average foreign currency rates for the period. Translation adjustments of these subsidiaries are included in net income.

Accounting for Share-Based Compensation

Our share-based compensation programs grant awards which have included stock options, restricted stock units which vest based on stock performance known as market stock units (MSUs), performance-vested restricted stock units which will be settled in cash (CSPSs), performance-vested restricted stock units which settle in shares (PVRSUs), time-vested restricted stock units (RSUs) and shares issued under our employee stock purchase plan (ESPP). We charge the estimated fair value of awards against income over the requisite service period, which is generally the vesting period. Where awards are made with non-substantive vesting periods (for instance, where a portion of the award vests upon retirement eligibility), we estimate and recognize expense based on the period from the grant date to the date on which the employee is retirement eligible.

The fair values of our stock option grants are estimated as of the date of grant using a Black-Scholes option valuation model and reflect estimated forfeitures. The estimated fair values of the stock options are then expensed over the options’ vesting periods.

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The fair values of our RSUs are based on the market value of our stock on the date of grant. Compensation expense for RSUs is recognized over the applicable service period, adjusted for the effect of estimated forfeitures.

We apply an accelerated attribution method to recognize stock based compensation expense, net of estimated forfeitures, when accounting for our MSUs. The probability of actual shares expected to be earned is considered in the grant date valuation, therefore the expense will not be adjusted to reflect the actual units earned.

We apply an accelerated attribution method to recognize stock based compensation expense when accounting for our CSPSs and the fair value of the liability is remeasured at the end of each reporting period through expected cash settlement. Compensation expense associated with CSPSs is based upon the stock price and the number of units expected to be earned after assessing the probability that certain performance criteria will be met and the associated targeted payout level that is forecasted will be achieved, net of estimated forfeitures. Cumulative adjustments are recorded each quarter to reflect changes in the stock price and estimated outcome of the performance-related conditions until the date results are determined and settled.

We apply an accelerated attribution method to recognize stock based compensation expense when accounting for our PVRSUs. The number of units reflected as granted represents the target number of shares that are eligible to vest in full or in part and are earned subject to the attainment of certain performance criteria established at the beginning of the performance period. Compensation expense associated with these units is initially based upon the number of shares expected to vest after assessing the probability that certain performance criteria will be met and the associated targeted payout level that is forecasted will be achieved, net of estimated forfeitures. Cumulative adjustments are recorded quarterly to reflect subsequent changes in the estimated outcome of performance-related conditions until the date results are determined.

The purchase price of common stock under our ESPP is equal to 85% of the lower of (i) the market value per share of the common stock on the participant’s entry date into an offering period or (ii) the market value per share of the common stock on the purchase date. However, for each participant whose entry date is other than the start date of the offering period, the amount shall in no event be less than the market value per share of the common stock as of the beginning of the related offering period. The fair value of the discounted purchases made under our ESPP is calculated using the Black-Scholes model. The fair value of the look-back provision plus the 15% discount is recognized as compensation expense over the purchase period. We apply a graded vesting approach since our ESPP provides for multiple purchase periods and is, in substance, a series of linked awards.

Research and Development Expenses

Research and development expenses consist of upfront fees and milestones paid to collaborators and expenses incurred in performing research and development activities, including compensation and benefits, facilities expenses, overhead expenses, clinical trial and related clinical manufacturing expenses, fees paid to clinical research organizations (CROs) and other outside expenses. Research and development expenses are expensed as incurred. Payments we make for research and development services prior to the services being rendered are recorded as prepaid assets on our consolidated balance sheets and are expensed as the services are provided.

From time to time, we enter into development agreements in which we share expenses with a collaborative partner. We record payments received from our collaborative partners for their share of the development costs as a reduction of research and development expense, except as discussed within Note 20, Collaborations to these consolidated financial statements. Expenses incurred by Genentech in the development of RITUXAN are not recorded as research and development expense, but rather reduce our share of co-promotion profits recorded as a component of unconsolidated joint business revenues.

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Selling, General and Administrative Expenses

Selling, general and administrative expenses are primarily comprised of compensation and benefits associated with sales and marketing, finance, human resources, legal and other administrative personnel, outside marketing, advertising and legal expenses and other general and administrative costs.

Advertising costs are expensed as incurred. For the years ended December 31, 2011, 2010 and 2009, advertising costs totaled $45.3 million, $35.3 million and $26.5 million, respectively.

Income Taxes

The provision for income taxes includes federal, state, local and foreign taxes. Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the estimated future tax consequences of temporary differences between the financial statement carrying amounts and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year in which the temporary differences are expected to be recovered or settled. We evaluate the realizability of our deferred tax assets and establish a valuation allowance when it is more likely than not that all or a portion of deferred tax assets will not be realized.

We account for uncertain tax positions using a “more-likely-than-not” threshold for recognizing and resolving uncertain tax positions. We evaluate uncertain tax positions on a quarterly basis and consider various factors, including, but not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity and changes in facts or circumstances related to a tax position. We also accrue for potential interest and penalties, related to unrecognized tax benefits in income tax expense.

Contingencies

We are currently involved in various claims and legal proceedings. We account for potential litigation losses in accordance with FASB Accounting Standards Codification (ASC) No. 450, Contingencies (ASC 450). Under ASC 450, loss contingency provisions are recorded if the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount can be reasonably estimated or a range of loss can be determined. These accruals represent management’s best estimate of probable loss, as defined by ASC 450. Disclosure also is provided when it is reasonably possible that a loss will be incurred or when it is reasonably possible that the amount of a loss will exceed the recorded provision. On a quarterly basis, we review the status of each significant matter and assess its potential financial exposure. Significant judgment is required in both the determination of probability and the determination as to whether an exposure is reasonably estimable. Because of uncertainties related to these matters, accruals are based only on the best information available at the time. As additional information becomes available, we reassess the potential liability related to pending claims and litigation and may revise our estimates. These revisions in the estimates of the potential liabilities could have a material impact on our consolidated results of operations and financial position.

Restructuring Charges

We have made estimates and judgments regarding the amount and timing of our restructuring expense and liability, including current and future period termination benefits and other exit costs to be incurred when related actions take place. We have also assessed the recoverability of certain long-lived assets employed in the business and, in certain instances shortened the expected useful life of the assets based on changes in their expected use. When we determine that the useful lives of assets are shorter than we had originally estimated, we record additional depreciation to reflect the assets’ new shorter useful lives. Severance and other related costs and asset-related charges are reflected within our consolidated statement of income as a component of total restructuring charges incurred. Actual results may differ from these estimates. For additional information related to our recent restructuring efforts, please read Note 3, Restructuring, to these consolidated financial statements.

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Earnings per Share

Basic earnings per share is computed using the two-class method. Under the two-class method, undistributed net income is allocated to common stock and participating securities based on their respective rights to share in dividends. We have determined that our preferred shares meet the definition of participating securities and, to the extent any are outstanding during a period, have allocated a portion of net income to our preferred shares on a pro rata basis. Net income allocated to preferred shares is excluded from the calculation of basic earnings per share. For basic earnings per share, net income available to holders of common stock is divided by the weighted average number of shares of common stock outstanding. For purposes of calculating diluted earnings per share, net income is adjusted for the after-tax amount of net income allocable to preferred shares, and the denominator includes both the weighted average number of shares of common stock outstanding and potential dilutive shares of common stock from stock options, unvested restricted stock awards, restricted stock units and other convertible securities, to the extent they are dilutive.

New Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that are adopted by the Company as of the specified effective date. Unless otherwise discussed, we believe that the impact of recently issued standards that are not yet effective will not have a material impact on our financial position or results of operations upon adoption.

In December 2011, the FASB issued ASU 2011-11, Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities (ASU 2011-11). This newly issued accounting standard requires an entity to disclose both gross and net information about instruments and transactions eligible for offset in the statement of financial position as well as instruments and transactions executed under a master netting or similar arrangement and was issued to enable users of financial statements to understand the effects or potential effects of those arrangements on its financial position. This ASU is required to be applied retrospectively and is effective for fiscal years, and interim periods within those years, beginning on or after January 1, 2013. As this accounting standard only requires enhanced disclosure, the adoption of this standard is not expected to have an impact our financial position or results of operations.

In June 2011, the FASB issued ASU No. 2011-05, “Comprehensive Income (Topic 220): Presentation of Comprehensive Income” (ASU 2011-05). This newly issued accounting standard (1) eliminates the option to present the components of other comprehensive income as part of the statement of changes in stockholders’ equity; (2) requires the consecutive presentation of the statement of net income and other comprehensive income; and (3) requires an entity to present reclassification adjustments on the face of the financial statements from other comprehensive income to net income. The amendments in this ASU do not change the items that must be reported in other comprehensive income or when an item of other comprehensive income must be reclassified to net income nor do the amendments affect how earnings per share is calculated or presented. In December 2011, the FASB issued ASU No. 2011-12, Deferral of the Effective Date for Amendments to the Presentation of Reclassifications of Items Out of Accumulated Other Comprehensive Income in Accounting Standards Update No. 2011-05, which defers the requirement within ASU 2011-05 to present on the face of the financial statements the effects of reclassifications out of accumulated other comprehensive income on the components of net income and other comprehensive income for all periods presented. During the deferral, entities should continue to report reclassifications out of accumulated other comprehensive income consistent with the presentation requirements in effect prior to the issuance of ASU 2011-05. These ASUs are required to be applied retrospectively and are effective for fiscal years, and interim periods within those years, beginning after December 15, 2011, which for Biogen Idec means January 1, 2012. As these accounting standards do not change the items that must be reported in other comprehensive income or when an item of other comprehensive income must be reclassified to net income, the adoption of these standards is not expected to have an impact on our financial position or results of operations.

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In May 2011, the FASB issued ASU No. 2011-04, “Fair Value Measurement (Topic 820): Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs” (ASU 2011-04). This newly issued accounting standard clarifies the application of certain existing fair value measurement guidance and expands the disclosures for fair value measurements that are estimated using significant unobservable (Level 3) inputs. This ASU is effective on a prospective basis for annual and interim reporting periods beginning on or after December 15, 2011, which for Biogen Idec means January 1, 2012. The adoption of this standard is not expected to have a material impact on our financial position or results of operations.

2.    Acquisitions

Noncontrolling Interest in Joint Ventures

On September 6, 2011, we completed the purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH, our respective sales affiliates in Italy and Switzerland, from our joint venture partners, Dompé Farmaceutici SpA and Dompé International SA, respectively. This transaction was funded from our existing cash on hand and has been accounted for as the acquisition of a noncontrolling interest. The purchase price of these shares was comprised of cash payments totaling $152.9 million plus up to $42.5 million in contingent consideration payable upon the achievement of commercial and regulatory milestones using exchange rates at the time of the transaction. As these amounts reflect payments to acquire a noncontrolling interest, these payments and the accrual of a liability related to the contingent consideration were recorded as a reduction in the noncontrolling interest for these entities with the remainder to additional paid in capital.

Upon acquisition, we recorded a liability of $38.8 million representing the acquisition date fair value of the contingent consideration. This amount was estimated through a valuation model that incorporates probability weighted assumptions relating to the achievement of these milestones and thus the likelihood of us making payments. Subsequent changes in the fair value of this obligation will be recognized as adjustments to contingent consideration within our consolidated statements of income. For additional information related to our valuation of this obligation, please read Note 8, Fair Value Measurements to these consolidated financial statements.

In connection with our purchase of the noncontrolling interest in our joint venture investment in Biogen Dompé SRL, we entered into a credit assignment agreement with Dompé Farmaceutici SpA. Under the terms of this agreement, Dompé Farmaceutici SpA purchased all of Biogen Dompé SRL’s outstanding receivables as of June 30, 2011, adjusted for cash received through September 5, 2011, for $104.6 million. We have no retained interests in the receivables and have accounted for this transaction as a sale. The carrying value of these receivables exceeded their fair value, which was determined by management using significant inputs not observable in the market and thus represents a Level 3 fair value measurement, and accordingly we recognized a loss of $1.8 million upon their disposition.

In addition, balances outstanding under Biogen Dompé SRL’s credit line from Dompé Farmaceutici SpA, as described in Note 12, Indebtedness to these consolidated financial statements, were repaid in September 2011.

Biogen Idec International Neuroscience GmbH

In December 2010, we acquired 100% of the stock of Biogen Idec International Neuroscience GmbH (BIN), formerly Panima Pharmaceuticals AG, an affiliate of Neurimmune AG. The purchase price was comprised of a $32.5 million cash payment plus up to $395.0 million in contingent consideration payable upon the achievement of development milestones. BIN is a business involved in the discovery of antibodies designed to treat neurological disorders. Upon acquisition, we recorded a liability of $81.2 million representing the acquisition date fair value of the contingent consideration. Subsequent changes in the fair value of this obligation are recognized as adjustments to contingent consideration within our consolidated statements of income. We allocated $110.9 million and $25.6 million of the total purchase price to acquired IPR&D and goodwill, respectively. The amount allocated to acquired IPR&D represented the fair value of the IPR&D programs

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acquired. The goodwill recognized is primarily attributable to establishing a deferred tax liability for the acquired IPR&D asset, which is not deductible for income tax purposes. For additional information related to our valuation of our contingent consideration obligation, please read Note 8, Fair Value Measurements to these consolidated financial statements.

Biogen Idec Hemophilia Inc.

In connection with our acquisition of Biogen Idec Hemophilia Inc. (BIH), formerly Syntonix Pharmaceuticals, Inc. (Syntonix), in January 2007, we agreed to pay up to an additional $80.0 million if certain milestone events associated with the development of BIH’s lead product, long-lasting recombinant Factor IX, a product for the treatment of hemophilia B, are achieved. The first $40.0 million contingent payment was achieved in the first quarter of 2010 upon initiation of patient enrollment in a registrational trial of Factor IX. We recorded this payment as a charge to acquired in-process research and development within our consolidated statement of income in 2010, in accordance with the accounting standards applicable to business combinations when we acquired BIH.

An additional $20.0 million contingent payment will occur if prior to the tenth anniversary of the closing date, the FDA grants approval of a Biologic License Application for Factor IX. A second $20.0 million contingent payment will occur if prior to the tenth anniversary of the closing date, a marketing authorization is granted by the EMA for Factor IX. These payments will be capitalized as an intangible asset when the related milestones are achieved.

3.    Restructuring

In November 2010, we announced a number of strategic, operational, and organizational initiatives designed to provide a framework for the future growth of our business and realign our overall structure to become a more efficient and cost effective organization. As part of this initiative:

• We out-licensed or terminated certain research and development programs, including those in oncology and cardiovascular medicine, that are no longer a strategic fit for us.

• We completed a 13% reduction in workforce spanning our sales, research and development, and administrative functions.

• We vacated and recognized the sale of the San Diego, California facility as well as consolidated certain of our Massachusetts facilities. For a more detailed description of transactions affecting our facilities, please read Note 11, Property, Plant and Equipment to these consolidated financial statements.

Costs associated with our workforce reduction primarily relate to employee severance and benefits. Facility consolidation costs are primarily comprised of charges associated with closing these facilities, related lease obligations and additional depreciation recognized when the expected useful lives of certain assets have been shortened due to the consolidation and closing of related facilities and the discontinuation of certain research and development programs. As of December 31, 2011, substantially all restructuring charges have been incurred and paid. We incurred $19.0 million of these charges in 2011, of which $12.8 million were related to our workforce reduction and $6.2 million related to the consolidation of our facilities. During the fourth quarter of 2010, we incurred $75.2 million of these charges, of which $67.2 million were related to our workforce reduction and $8.0 million were related to the consolidation of our facilities.

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The following table summarizes the activity of our restructuring liability:

(In millions)	Workforce Reduction			Facility Consolidation			Total
Restructuring reserve as of December 31, 2010	$	60.6		$	5.8		$	66.4
Expense		15.8			2.4			18.2
Payments		(81.8	)		(3.9	)		(85.7	)
Adjustments to previous estimates, net		(2.9	)		—			(2.9	)
Other adjustments		8.6			(3.2	)		5.4
Restructuring reserve as of December 31, 2011	$	0.3		$	1.1		$	1.4

4.    Revenue Reserves

Reserves for Discounts and Allowances

An analysis of the amount of, and change in, reserves is summarized as follows:

(In millions)	Discounts			Contractual Adjustments			Returns			Total
2011
Beginning balance	$	13.9		$	107.0		$	21.1		$	142.0
Current provisions relating to sales in current year		96.0			360.4			15.7			472.1
Adjustments relating to prior years		—			(14.0	)		(0.9	)		(14.9	)
Payments/returns relating to sales in current year		(84.3	)		(266.0	)		(0.4	)		(350.7	)
Payments/returns relating to sales in prior years		(13.0	)		(68.1	)		(11.8	)		(92.9	)
Ending balance	$	12.6		$	119.3		$	23.7		$	155.6
(In millions)	Discounts			Contractual Adjustments			Returns			Total
2010
Beginning balance	$	13.9		$	70.3		$	18.9		$	103.1
Current provisions relating to sales in current year		80.6			285.0			16.1			381.7
Adjustments relating to prior years		(2.7	)		(2.4	)		(1.8	)		(6.9	)
Payments/returns relating to sales in current year		(68.7	)		(184.3	)		(0.8	)		(253.8	)
Payments/returns relating to sales in prior years		(9.2	)		(61.6	)		(11.3	)		(82.1	)
Ending balance	$	13.9		$	107.0		$	21.1		$	142.0
(In millions)	Discounts			Contractual Adjustments			Returns			Total
2009
Beginning balance	$	9.2		$	48.1		$	18.1		$	75.4
Current provisions relating to sales in current year		74.0			192.5			15.8			282.3
Adjustments relating to prior years		—			—			0.8			0.8
Payments/returns relating to sales in current year		(60.8	)		(124.4	)		(0.6	)		(185.8	)
Payments/returns relating to sales in prior years		(8.5	)		(45.9	)		(15.2	)		(69.6	)
Ending balance	$	13.9		$	70.3		$	18.9		$	103.1

F-24

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

The total reserves above, included in our consolidated balance sheets, are summarized as follows:

	As of December 31,
(In millions)	2011		2010
Reduction of accounts receivable	$	40.6	$	36.7
Current liability		115.0		105.3
Total reserves	$	155.6	$	142.0

5.    Accounts Receivable

Our accounts receivable primarily arise from product sales in the U.S. and Europe and mainly represent amounts due from our wholesale distributors, public hospitals and other government entities. The majority of our accounts receivable have standard payment terms which are generally between 30 and 90 days. We monitor the financial performance and credit worthiness of our large customers so that we can properly assess and respond to changes in their credit profile. We provide reserves against trade receivables for estimated losses that may result from a customer’s inability to pay. Amounts determined to be uncollectible are charged or written-off against the reserve. To date, such losses have not exceeded management’s estimates.

Concentrations of credit risk with respect to receivables, which are typically unsecured, are limited due to the wide variety of customers and markets using our products, as well as their dispersion across many different geographic areas. We monitor economic conditions, including volatility associated with international economies, and related impacts on the relevant financial markets and our business, especially in light of sovereign credit issues. The credit and economic conditions within Italy, Spain, Portugal and Greece, among other members of the European Union, have continued to deteriorate. These conditions have increased, and may continue to increase, the average length of time that it takes to collect on our accounts receivable outstanding in these countries.

Our net accounts receivable balances from product sales in these countries are summarized as follows:

	As of December 31, 2011
(In millions)	Current Balance Included within Accounts Receivable, net		Non-Current Balance  Included within Investments and Other Assets		Total
Spain	$	68.5	$	65.5	$	134.0
Italy	$	19.4	$	48.7	$	68.1
Portugal	$	20.6	$	12.3	$	32.9
Greece	$	4.0	$	—	$	4.0

	As of December 31, 2010
(In millions)	Current Balance Included within Accounts Receivable, net		Non-Current Balance  Included within Investments and Other Assets		Total
Spain	$	70.8	$	29.8	$	100.6
Italy	$	103.2	$	14.8	$	118.0
Portugal	$	17.8	$	5.5	$	23.3
Greece	$	3.9	$	—	$	3.9

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Approximately $56.0 million and $45.0 million of the aggregated balances for these countries were overdue more than one year as of December 31, 2011 and December 31, 2010, respectively. Amounts included as a component of investments and other assets within our consolidated balance sheets represent amounts that are expected to be collected beyond one year.

In connection with our purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL, we entered into a credit assignment agreement with Dompé Farmaceutici SpA. Under the terms of this agreement, Dompé Farmaceutici SpA purchased all of Biogen Dompé SRL’s outstanding receivables as of June 30, 2011, adjusted for cash received through September 5, 2011, for $104.6 million. We retained no interests in these receivables and accounted for this transaction as a sale recognizing a loss of $1.8 million upon their disposition. For additional information related to these transactions, please read Note 2, Acquisitions to these consolidated financial statements. As of December 31, 2011, our accounts receivable balances in Italy totaled $68.1 million, all of which resulted from sales of product subsequent to June 30, 2011.

6.    Inventory

The components of inventory are summarized as follows:

	As of December 31,
(In millions)	2011		2010
Raw materials	$	83.8	$	59.0
Work in process		169.4		142.2
Finished goods		73.6		87.9
Total inventory	$	326.8	$	289.1

The components of inventory by product are summarized as follows:

	As of December 31,
(In millions)	2011		2010
AVONEX	$	113.3	$	87.0
TYSABRI		114.7		117.0
Other		15.0		26.1
Total finished goods and work in process		243.0		230.1
Raw materials		83.8		59.0
Total inventory	$	326.8	$	289.1

Amounts written down related to excess, obsolete or unmarketable inventory are charged to cost of sales, and totaled $25.4 million, $11.8 million, and $16.9 million for the years ended December 31, 2011, 2010, and 2009, respectively.

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

7.    Intangible Assets and Goodwill

Intangible Assets

Intangible assets, net of accumulated amortization, impairment charges and adjustments, are summarized as follows:

		As of December 31, 2011							As of December 31, 2010
(In millions)	Estimated Life	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Out-licensed patents	12-23 years	$	578.0	$	(391.3	)	$	186.7	$	578.0	$	(350.2	)	$	227.8
Core developed technology	15-23 years		3,005.3		(1,801.1	)		1,204.2		3,005.3		(1,636.9	)		1,368.4
In-process research and development	Up to 15 years upon commercialization		110.9		—			110.9		110.9		—			110.9
Trademarks and tradenames	Indefinite		64.0		—			64.0		64.0		—			64.0
In-licensed rights and patents	6-16 years		47.2		(4.8	)		42.4		3.0		(1.3	)		1.7
Assembled workforce	4 years		2.1		(2.1	)		—		2.1		(2.1	)		—
Distribution rights	2 years		12.7		(12.7	)		—		12.7		(12.7	)		—
Total intangible assets		$	3,820.2	$	(2,212.0	)	$	1,608.2	$	3,776.0	$	(2,003.2	)	$	1,772.8

Total intangible assets was unchanged as of December 31, 2011 compared to December 31, 2010, excluding the impact of amortization and amounts recorded in connection with the license agreements for FAMPYRA and the JC virus assay described below. In December 2010, we completed our acquisition of BIN and allocated a $110.9 million of the purchase price to acquired IPR&D. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

Amortization of acquired intangible assets totaled $208.6 million, $208.9 million, and $289.8 million for the years ended December 31, 2011, 2010 and 2009, respectively. Amortization for acquired intangible assets is expected to be in the range of approximately $160.0 million to $200.0 million annually through 2016.

AVONEX Core Technology Asset

Our most significant intangible asset is the core technology related to our AVONEX product. The net book value of this asset as of December 31, 2011 was $1,192.1 million. Amortization of our core acquired intangible asset related to AVONEX is expected to be in the range of approximately $100.0 million to $150.0 million annually through 2016.

FAMPYRA

In July 2011, the European Commission (EC) granted a conditional marketing authorization for FAMPYRA in the E.U., which triggered a $25.0 million milestone payment. This payment was made to Acorda Therapeutics, Inc. (Acorda) in the third quarter of 2011 and was capitalized as an intangible asset.

Under the terms of our 2009 collaboration and license agreement, we will pay Acorda additional milestones based on new indications and ex-U.S. net sales. The next expected milestone would be $15.0 million, due when ex-U.S. net sales reach $100.0 million over a period of four consecutive quarters. We will capitalize these milestones upon achievement as an intangible asset. Amortization will utilize an economic consumption

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

model that will be based on an estimate of all of the probable payments we expect to make as contingent consideration, such as sales-based milestones, for entering into the license agreement.

For additional information related to our collaboration with Acorda, please read Note 20, Collaborations to these consolidated financial statements.

JC Virus Assay

In the first quarter of 2011, we licensed rights for the diagnostic and therapeutic application of recombinant virus-like particles, known as VP1 proteins, to detect antibodies of the JC virus (JCV) in serum or blood. Under the terms of this license, we expect to make payments totaling approximately $58.9 million through 2016. These payments include upfront and milestone payments as well as the greater of an annual maintenance fee or usage-based royalty payment. As of December 31, 2011, we recognized an intangible asset in the amount of $19.2 million, reflecting the total of upfront payments made and other time-based milestone payments. We will further capitalize additional payments due under this arrangement as an intangible asset upon achievement. Amortization will utilize an economic consumption model that will be based on an estimate of all of the probable payments we expect to make in relation to the total number of JCV assay tests performed through 2016.

Goodwill

The following table provides a roll forward of the changes in goodwill:

	As of December 31,
(In millions)	2011		2010
Beginning balance	$	1,146.3	$	1,138.6
Goodwill acquired during the year		—		25.6
Other		—		(17.9	)
Ending balance	$	1,146.3	$	1,146.3

As of December 31, 2011, we had no accumulated impairment losses related to goodwill.

In December 2010, we completed our acquisition of BIN and allocated a $25.6 million of the purchase price to goodwill. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements. During 2010, we also recorded a decrease to goodwill of $17.9 million to establish a deferred tax asset that existed at the time of the merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation in 2003.

8.    Fair Value Measurements

The tables below present information about our assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2011 and December 31, 2010, and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value:

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

(In millions)	As of December 31, 2011		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	399.8	$	—	$	399.8	$	—
Marketable debt securities:
Corporate debt securities		602.6		—		602.6		—
Government securities		1,716.5		—		1,716.5		—
Mortgage and other asset backed securities		273.8		—		273.8		—
Strategic investments		0.1		0.1		—		—
Venture capital investments		23.5		—		—		23.5
Derivative contracts		39.5		—		39.5		—
Plan assets for deferred compensation		11.6		—		11.6		—
Total	$	3,067.4	$	0.1	$	3,043.8	$	23.5
Liabilities:
Derivative contracts	$	0.5	$	—	$	0.5	$	—
Contingent consideration		151.0		—		—		151.0
Total	$	151.5	$	—	$	0.5	$	151.0

(In millions)	As of December 31, 2010		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	651.8	$	—	$	651.8	$	—
Marketable debt securities:
Corporate debt securities		313.0		—		313.0		—
Government securities		785.3		—		785.3		—
Mortgage and other asset backed securities		92.9		—		92.9		—
Strategic investments		44.8		44.8		—		—
Venture capital investments		20.8		—		—		20.8
Derivative contracts		1.3		—		1.3		—
Plan assets for deferred compensation		13.0		—		13.0		—
Total	$	1,922.9	$	44.8	$	1,857.3	$	20.8
Liabilities:
Derivative contracts	$	12.2	$	—	$	12.2	$	—
Contingent consideration		81.2		—		—		81.2
Total	$	93.4	$	—	$	12.2	$	81.2

There were no transfers between fair value measurement levels during the years ended December 31, 2011 and 2010, respectively.

Our strategic investments represent investments in publicly traded equity securities and are the only investments for which we used Level 1 inputs to determine their fair value. Our venture capital investments are comprised of investments in certain biotechnology oriented venture capital funds which primarily invest in small privately-owned, venture-backed biotechnology companies. Our venture capital investments are the only investments for which we used Level 3 inputs to determine their fair value and represented approximately 0.3%

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

of total assets of December 31, 2011 and 2010, respectively. The following table provides a roll forward of the fair value of our venture capital investments, which are all Level 3 assets:

	As of December 31,
(In millions)	2011			2010
Beginning balance	$	20.8		$	21.9
Unrealized gains included in earnings		2.4			—
Unrealized losses included in earnings		(1.4	)		(2.1	)
Purchases		1.7			2.1
Settlements		—			(1.1	)
Ending balance	$	23.5		$	20.8

The fair values of our debt instruments, which are all Level 2 liabilities, are summarized as follows:

	As of December 31,
(In millions)	2011		2010
Credit line from Dompé	$	—	$	8.1
Notes payable to Fumedica		22.4		24.2
6.0% Senior Notes due 2013		474.1		485.5
6.875% Senior Notes due 2018		663.9		618.0
Total fair value	$	1,160.4	$	1,135.8

The fair values of Biogen Dompé SRL’s credit line from us and Dompé Farmaceutici SpA and our note payable to Fumedica were estimated using market observable inputs, including current interest and foreign currency exchange rates. The fair value of our Senior Notes was determined through market, observable, and corroborated sources.

Balances outstanding under Biogen Dompé SRL’s credit line were repaid in connection with our recent purchase of the noncontrolling interest in our joint venture investment in Biogen Dompé SRL. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

Contingent Consideration Resulting from a Business Combination

We revalue the contingent consideration obligation for acquisitions completed after January 1, 2009 on a recurring basis each reporting period. Changes in the fair value of our contingent consideration obligations are recognized as a fair value adjustment of contingent consideration within our consolidated statements of income. These fair value measurements are based on significant inputs not observable in the market and therefore represent Level 3 measurements. The following table provides a roll forward of the changes in fair value of our contingent consideration obligations:

	As of December 31,
(In millions)	2011			2010
Fair value as of beginning of period	$	81.2		$	—
Acquisition date fair value of contingent consideration obligations related to acquisitions		38.8			81.2
Changes in the fair value of contingent consideration obligations		36.0			—
Payments of contingent consideration obligations		(5.0	)		—
Fair value as of end of period	$	151.0		$	81.2

F-30

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Upon completion of our purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH in September 2011, we recorded a contingent consideration obligation of $38.8 million. As of December 31, 2011, the fair value of this contingent consideration obligation was $31.9 million, of which $3.9 million was reflected as a component of accrued expenses and other, and $28.0 million was reflected as a component of other long-term liabilities within our consolidated balance sheet. Our most recent valuation was determined based upon probability weighted net cash outflow projections of $42.5 million, discounted using a rate of 3.8%, which is the cost of debt financing for market participants. The decrease in the fair value of this obligation, of $6.9 million since the acquisition date, was primarily due to changes in the discount rate and in the probability and expected timing related to the achievement of certain cumulative sales-based and developmental milestones.

In connection with our acquisition of BIN in the fourth quarter of 2010, we recorded a liability of $81.2 million, representing the acquisition date fair value of the contingent consideration. There was no significant change in the valuation of this liability from the acquisition date through December 31, 2010. As of December 31, 2011, the fair value of this contingent consideration obligation was $119.1 million, of which $6.9 million was reflected as a component of accrued expenses and other, and $112.2 million was reflected as a component of other long-term liabilities within our consolidated balance sheet. Our most recent valuation was determined based upon probability weighted net cash outflow projections of $390.0 million, discounted using a rate of 5.2%, which is the cost of debt financing for market participants. The increase in the fair value of this obligation, of $37.9 million since December 31, 2010, was primarily due to changes in the discount rate and in the probability and expected timing related to the achievement of certain remaining developmental milestones, offset by the payment of a $5.0 million developmental milestone.

9.    Financial Instruments

Marketable Securities, including Strategic Investments

The following tables summarize our marketable securities and strategic investments:

As of December 31, 2011 (In millions):	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale
Corporate debt securities:
Current	$	155.0	$	0.2	$	(0.1	)	$	154.9
Non-current		447.6		1.2		(1.5	)		447.9
Government securities:
Current		1,021.0		0.4		—			1,020.6
Non-current		695.5		0.9		(0.2	)		694.8
Mortgage and other asset backed securities:
Current		0.1		—		—			0.1
Non-current		273.7		0.5		(1.3	)		274.5
Total available-for-sale securities	$	2,592.9	$	3.2	$	(3.1	)	$	2,592.8
Other Investments
Strategic investments, non-current	$	0.1	$	—	$	(0.1	)	$	0.2

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

As of December 31, 2010 (In millions):	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale
Corporate debt securities:
Current	$	93.2	$	0.1	$	—		$	93.1
Non-current		219.8		2.1		(0.5	)		218.2
Government securities:
Current		352.8		0.2		—			352.6
Non-current		432.5		0.6		(0.6	)		432.5
Mortgage and other asset backed securities:
Current		2.1		—		—			2.1
Non-current		90.8		0.5		(0.2	)		90.5
Total available-for-sale securities	$	1,191.2	$	3.5	$	(1.3	)	$	1,189.0
Other Investments
Strategic investments, non-current	$	44.8	$	17.5	$	—		$	27.3

In the tables above, as of December 31, 2011 and 2010, government securities included $214.0 million and $163.5 million, respectively, of Federal Deposit Insurance Corporation (FDIC) guaranteed senior notes issued by financial institutions under the Temporary Liquidity Guarantee Programs.

The following table summarizes our financial assets with original maturities of less than 90 days included within cash and cash equivalents on the accompanying consolidated balance sheet:

	As of December 31,
(In millions)	2011		2010
Commercial paper	$	—	$	4.0
Repurchase agreements		8.8		26.0
Short-term debt securities		391.0		621.8
Total	$	399.8	$	651.8

The carrying values of our commercial paper, including accrued interest, repurchase agreements, and our short-term debt securities approximate fair value.

Summary of Contractual Maturities: Available-for-Sale Securities

The estimated fair value and amortized cost of our marketable securities, excluding strategic investments, available-for-sale by contractual maturity are summarized as follows:

	As of December 31, 2011				As of December 31, 2010
(In millions)	Estimated Fair  Value		Amortized Cost		Estimated Fair  Value		Amortized Cost
Due in one year or less	$	1,176.1	$	1,175.6	$	448.1	$	447.8
Due after one year through five years		1,251.6		1,251.4		664.1		662.4
Due after five years		165.2		165.8		79.0		78.8
Total available-for-sale securities	$	2,592.9	$	2,592.8	$	1,191.2	$	1,189.0

The average maturity of our marketable securities as of December 31, 2011 and 2010 was 14 months and 11 months, respectively.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Proceeds from Maturities and Sales of Marketable Securities, excluding Strategic Investments

The proceeds from maturities and sales of marketable securities, excluding strategic investments and cash equivalents, and resulting realized gains and losses are summarized as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Proceeds from maturities and sales	$	2,276.7	$	2,668.7	$	3,319.0
Realized gains	$	3.9	$	18.8	$	19.8
Realized losses	$	2.3	$	2.5	$	4.0

Proceeds were generally reinvested. Realized losses for the year ended December 31, 2011, primarily relate to sales of government and corporate securities. Realized losses for the year ended December 31, 2010, primarily relate to the sale of agency mortgage-backed securities and corporate debt securities. Realized losses for the year ended December 31, 2009, primarily relate to losses on the sale of non-agency mortgage-backed securities and corporate debt securities.

Strategic Investments

Strategic investments are included in investments and other assets on the accompanying consolidated balance sheets. In 2011, we sold four strategic investments for $40.6 million, which resulted in a net gain of $13.5 million. In 2010, we sold one strategic investment for $1.8 million, which resulted in an insignificant loss. In 2009 we sold two strategic investments for $5.9 million, which resulted in a $3.0 million gain.

In addition to the strategic investments and venture capital investments noted in Note 8, Fair Value Measurements to these consolidated financial statements, we hold other investments in equity securities of certain privately-owned biotechnology companies and biotechnology oriented venture capital funds accounted for using the cost method. The carrying value of these securities as of December 31, 2011 and 2010 was $39.2 million and $35.0 million, respectively. These securities are also included in investments and other assets on the accompanying consolidated balance sheets.

Impairments

Prior to the adoption of new accounting standards for the recognition, measurement and presentation of other-than-temporary impairments in April 2009 for debt securities, we recognized all other-than-temporary impairment amounts related to our marketable debt securities in earnings as required under the previously effective guidance which required that management assert that it had the ability and intent to hold a debt security until maturity or until we recovered the cost of our investment.

In 2011, we recognized $11.5 million in charges for the impairment of our publicly-held strategic investments, investments in venture capital funds and investments in privately-held companies.

In 2010, we recognized $21.3 million in charges for the other-than-temporary impairment of our publicly held strategic investments, investments in venture capital funds and investments in privately held companies. The increase over amounts recognized in 2009 was primarily the result of one of our strategic investments, executing an equity offering at a price below our cost basis during the first quarter of 2010.

In 2009, we recognized impairment losses of $7.0 million on our publicly-held strategic investments and non-marketable securities and an additional $3.6 million in charges for the other-than-temporary impairment on our marketable debt securities.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

10.    Derivative Instruments

Foreign Currency Forward Contracts

Due to the global nature of our operations, portions of our revenues are earned in currencies other than the U.S. dollar. The value of revenues measured in U.S. dollars is therefore subject to changes in currency exchange rates. In order to mitigate these changes we use foreign currency forward contracts to lock in exchange rates associated with a portion of our forecasted international revenues.

Foreign currency forward contracts in effect as of December 31, 2011 and 2010 had durations of 1 to 12 months. These contracts have been designated as cash flow hedges and accordingly, to the extent effective, any unrealized gains or losses on these foreign currency forward contracts are reported in accumulated other comprehensive income (loss). Realized gains and losses for the effective portion of such contracts are recognized in revenue when the sale of product in the currency being hedged is recognized. To the extent ineffective, hedge transaction gains and losses are reported in other income (expense), net.

The notional value of foreign currency forward contracts that were entered into to hedge forecasted revenues is summarized as follows:

	Notional Amount As of December 31,
Foreign Currency: (In millions)	2011		2010
Euro	$	496.4	$	460.3
Canadian dollar		22.9		24.0
Swedish krona		13.0		9.9
Total foreign currency forward contracts	$	532.3	$	494.2

The portion of the fair value of these foreign currency forward contracts that was included in accumulated other comprehensive income (loss) within total equity reflected gains of $36.5 million and losses of $11.0 million as of December 31, 2011 and 2010, respectively. We expect all contracts to be settled over the next 12 months and any amounts in accumulated other comprehensive income (loss) to be reported as an adjustment to revenue. We consider the impact of our and our counterparties’ credit risk on the fair value of the contracts as well as the ability of each party to execute its obligations under the contract. As of December 31, 2011 and 2010, respectively, credit risk did not materially change the fair value of our foreign currency forward contracts.

In relation to our foreign currency forward contracts, we recognized in other income (expense) net losses of $3.9 million, net gains of $0.4 million, and net losses of $1.1 million for the years ended December 31, 2011, 2010 and 2009, respectively, due to hedge ineffectiveness.

In addition, we recognized in product revenue $36.9 million of net losses, $45.7 million of net gains, and net losses of $49.7 million, for the years ended December 31, 2011, 2010 and 2009, respectively, for the settlement of certain effective cash flow hedge instruments. These settlements were recorded in the same period as the related forecasted revenues.

Summary of Derivatives Designated as Hedging Instruments

The following table summarizes the fair value and presentation in the consolidated balance sheets for derivatives designated as hedging instruments:

(In millions)	Balance Sheet Location	Fair Value As of December 31, 2011
Foreign Currency Contracts
Asset derivatives	Other current assets	$	32.6
Liability derivatives	Accrued expenses and other	$	—

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

(In millions)	Balance Sheet Location	Fair Value As of December 31, 2010
Foreign Currency Contracts
Asset derivatives	Other current assets	$	—
Liability derivatives	Accrued expenses and other	$	11.0

The following table summarizes the effect of derivatives designated as hedging instruments on the consolidated statements of income:

For the Years Ended (In millions)	Amount Recognized in Accumulated Other Comprehensive Income (Loss) on Derivative Gain/(Loss) (Effective Portion)			Income Statement Location (Effective Portion)	Amount Reclassified  from Accumulated  Other Comprehensive Income (Loss) into Income Gain/(Loss) (Effective Portion)			Income Statement Location (Ineffective Portion)	Amount of Gain/(Loss) Recorded (Ineffective Portion)
December 31, 2011:
Foreign currency contracts	$	36.5		Revenue	$	(36.9	)	Other income (expense)	$	(3.9	)
December 31, 2010:
Foreign currency contracts	$	(11.0	)	Revenue	$	45.7		Other income (expense)	$	0.4
December 31, 2009:
Foreign currency contracts	$	1.2		Revenue	$	(49.7	)	Other income (expense)	$	(1.1	)

Other Derivatives

We also enter into other foreign currency forward contracts, usually with one month durations, to mitigate the foreign currency risk related to certain balance sheet positions. We have not elected hedge accounting for these transactions.

The aggregate notional amount of our outstanding foreign currency contracts was $263.7 million and $160.8 million as of December 31, 2011 and 2010, respectively. The fair value of these contracts was a net asset of $6.4 million as of December 31, 2011 compared to a net asset of $0.1 million as of December 31, 2010. Net gains of $12.1 million and $6.0 million related to these contracts were recognized as a component of other income (expense), net, for years ended December 31, 2011 and 2010, respectively.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

11.    Property, Plant and Equipment

Property, plant and equipment are recorded at historical cost, net of accumulated depreciation. Components of property, plant and equipment, net are summarized as follows:

	As of December 31,
(In millions)	2011			2010
Land	$	51.9		$	107.6
Buildings		597.9			670.2
Leasehold improvements		102.7			100.8
Machinery and equipment		570.1			576.0
Computer software and hardware		439.7			392.8
Furniture and fixtures		37.6			54.5
Construction in progress		553.6			506.9
Total cost		2,353.5			2,408.8
Less: accumulated depreciation		(782.1	)		(767.2	)
Total property, plant and equipment, net	$	1,571.4		$	1,641.6

Our construction in progress balances are primarily related to the construction of our large-scale biologics manufacturing facility in Hillerød, Denmark, where we plan to manufacture TYSABRI drug substance. As of December 31, 2011 and 2010, the construction in progress balance related to this facility totaled $474.0 million and $440.2 million, respectively.

For 2011, 2010 and 2009, we capitalized interest costs related to construction in progress totaling approximately $32.6 million, $28.6 million and $28.5 million, respectively. Capitalized interest costs are primarily related to the development of our large-scale biologics manufacturing facility in Hillerød, Denmark.

Depreciation expense totaled $143.9 million, $144.9 million and $137.9 million for 2011, 2010 and 2009, respectively.

New Cambridge Leases

In July 2011, we executed leases for two office buildings to be built in Cambridge, Massachusetts with a planned occupancy during the second half of 2013. Construction of these facilities began in late 2011. These buildings, totaling approximately 500,000 square feet, will serve as the future location of our corporate headquarters and commercial operations. These buildings will also provide additional general and administrative and research and development office space. The leases both have 15 year terms and we have options to extend the term of each lease for two additional five-year terms. Future minimum rental commitments under these leases will total approximately $340.0 million over the initial 15 year lease terms. In addition to rent, the leases require us to pay additional amounts for taxes, insurance, maintenance and other operating expenses

In accordance with accounting guidance applicable to entities involved with the construction of an asset that will be leased when the construction is completed, we are considered the owner, for accounting purposes, of these properties during the construction period. Accordingly, we will record an asset along with a corresponding financing obligation on our consolidated balance sheet for the amount of total project costs incurred related to the construction in progress for these buildings through completion of the construction period. Upon completion of the buildings, we will assess and determine if the assets and corresponding liabilities should be derecognized. As of December 31, 2011, cost incurred in relation to the construction of these buildings totaled approximately $2.2 million.

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As a result of our decision to relocate our corporate headquarters and centralize our campus in Cambridge, Massachusetts, we expect to vacate our Weston, Massachusetts facility upon completion of the new buildings. Based upon our most recent estimates, we expect to incur a charge of approximately $35.0 million upon vacating this facility when the new Cambridge buildings have been completed. This amount represents our remaining Weston lease obligation, net of our estimate of sublease income expected to be recovered.

San Diego Facility

On October 1, 2010, we sold the San Diego facility for cash proceeds, net of transaction costs, of approximately $127.0 million. As part of this transaction, we agreed to lease back the San Diego facility for a period of 15 months. We accounted for this transaction as a financing arrangement as we determined that the transaction did not qualify as a sale due to our continuing involvement under the leaseback terms. Accordingly, we recorded an obligation for the proceeds received in October 2010 and the facility assets remained classified as held for use with the carrying value of the facility continued to be reflected as a component of property, plant and equipment, net within our consolidated balance sheets.

In the first quarter of 2011, we entered into an agreement to terminate our 15 month lease of the San Diego facility effective August 31, 2011. We have had no continuing involvement or remaining obligation after August 31, 2011 and have accounted for this transaction as a sale of property as of that date. No significant gain on sale was recognized and we did not recognize any impairment charges related to the San Diego facility.

12.    Indebtedness

Our indebtedness is summarized as follows:

	As of December 31,
(In millions)	2011		2010
Current portion:
Note payable to Fumedica	$	3.3	$	3.3
Credit line from Dompé		—		8.0
Financing arrangement for the sale of the San Diego facility		—		125.9
Current portion of notes payable, line of credit and other financing arrangements	$	3.3	$	137.2
Non-current portion:
6.0% Senior notes due 2013	$	449.9	$	449.8
6.875% Senior notes due 2018		592.3		597.9
Note payable to Fumedica		16.4		18.7
Financing arrangement for the construction of the Cambridge facilities		2.2		—
Non-current portion of notes payable, line of credit and other financing arrangements	$	1,060.8	$	1,066.4

The following is a summary description of our principal indebtedness as of December 31, 2011:

Senior Notes

On March 4, 2008, we issued $450.0 million aggregate principal amount of 6.0% Senior Notes due March 1, 2013 and $550.0 million aggregate principal amount of 6.875% Senior Notes due March 1, 2018 that were originally priced at 99.886% and 99.184% of par, respectively. The discount is amortized as additional interest expense over the period from issuance through maturity. These notes are senior unsecured obligations. Interest on the notes is payable March 1 and September 1 of each year. The notes may be redeemed at our option at any

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

time at 100% of the principal amount plus accrued interest and a specified make-whole amount. The notes contain a change of control provision that may require us to purchase the notes under certain circumstances. There is also an interest rate adjustment feature that requires us to pay interest at an increased rate on the notes if the credit rating on the notes declines below investment grade.

Upon the issuance of the debt we entered into interest rate swap contracts where we received a fixed rate and paid a variable rate, as further described in Note 10, Derivative Instruments to these consolidated financial statements. These contracts were terminated in December 2008. Upon termination of these swaps, the carrying amount of the 6.875% Senior Notes due in 2018 was increased by $62.8 million and is being amortized using the effective interest rate method over the remaining life of the Senior Notes and is being recognized as a reduction of interest expense. As of December 31, 2011, $45.4 million remains to be amortized.

Revolving Credit Facility

We have a $360.0 million senior unsecured revolving credit facility, which we may choose to use for future working capital and general corporate purposes. The terms of this revolving credit facility include various covenants, including financial covenants that require us to not exceed a maximum leverage ratio and, under certain circumstances, an interest coverage ratio. This facility terminates in June 2012. No borrowings have been made under this credit facility and as of December 31, 2011 and 2010 we were in compliance with all applicable covenants.

Notes Payable to Fumedica

In connection with our 2006 distribution agreement with Fumedica, we issued notes totaling 61.4 million Swiss Francs which were payable to Fumedica in varying amounts from June 2008 through June 2018. Our remaining note payable to Fumedica had a present value of 18.6 million Swiss Francs ($19.7 million) and 20.7 million Swiss Franc ($22.0 million) as of December 31, 2011 and 2010, respectively.

Credit Line from Dompé

On September 6, 2011, we completed the purchase of all the remaining outstanding shares of our joint venture investment in Biogen Dompé SRL, our sales affiliate in Italy, from our joint venture partner, Dompé Farmaceutici SpA. Balances outstanding under Biogen Dompé SRL’s credit line from us and Dompé Farmaceutici SpA were repaid in connection with this transaction. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

Financing Arrangements

During 2011 we recorded a financing obligation in relation to the construction of the two office buildings in Cambridge, Massachusetts, which will serve as the future location of our corporate headquarters and provide office space for our commercial operations, research and development and general and administrative functions. As of December 31, 2011, the financing obligation related to cost incurred in construction of these buildings totaled approximately $2.2 million.

During 2010 we also recorded a financing obligation in connection with our sale and subsequent lease back of the San Diego facility. We have had no continuing involvement or remaining obligation related to the San Diego facility after August 31, 2011.

For additional information related to these transactions, please read Note 11, Property, Plant & Equipment to these consolidated financial statements.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Debt Maturity

Our total debt, excluding amounts related to our financing arrangements, mature as follows:

(In millions)	As of December 31, 2011
2012	$	3.4
2013		453.4
2014		3.4
2015		3.4
2016		3.4
2017 and thereafter		556.7
Total	$	1,023.7

The fair value of our debt is disclosed in Note 8, Fair Value Measurements to these consolidated financial statements.

13.    Equity

Preferred Stock

The following table describes the number of shares authorized, issued and outstanding of our preferred stock as of December 31, 2011 and 2010:

	As of December 31, 2011						As of December 31, 2010
(In thousands)	Authorized		Issued		Outstanding		Authorized		Issued		Outstanding
Series A		1,750		—		—		1,750		8		8
Series X junior participating		1,000		—		—		1,000		—		—
Undesignated		5,250		—		—		5,250		—		—
Total preferred stock		8,000		—		—		8,000		8		8

We have 8,000,000 shares of Preferred Stock authorized, of which 1,750,000 shares have been designated as Series A Preferred Stock and 1,000,000 shares have been designated as Series X Junior Participating Preferred Stock. The shares may be issued without a vote or action of stockholders from time to time in classes or series with the designations, powers, preferences, and the relative, participating, optional or other special rights of the shares of each such class or series and any qualifications, limitations or restrictions thereon as set forth in the instruments governing such shares. Any such Preferred Stock may rank prior to common stock as to dividend rights, liquidation preference or both, and may have full or limited voting rights and may be convertible into shares of common stock.

There were 8,221 shares of Series A Preferred Stock issued and outstanding as of December 31, 2010. In March 2011, the remaining 8,221 shares of our Series A Preferred Stock were converted into 493,260 shares of common stock by the holder pursuant to the conversion terms of the Series A Preferred Stock. As of December 31, 2011, there are no shares of preferred stock issued and outstanding.

Common Stock

The following table describes the number of shares authorized, issued and outstanding of our common stock as of December 31, 2011 and 2010:

As of December 31, 2011

As of December 31, 2010

(In thousands)

Authorized

Issued

Outstanding

Authorized

Issued

Outstanding

Common stock

1,000,000

255,633

242,115

1,000,000

248,200

240,538

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Share Repurchases

In February 2011, our Board of Directors authorized the repurchase of up to 20.0 million shares of our common stock. We expect to use this repurchase program principally to offset common stock issued under our share-based compensation plans. This repurchase program does not have an expiration date. Under this authorization, we repurchased approximately 6.0 million shares of our common stock at a cost of $498.0 million during 2011. These repurchases were recorded as repurchases of Treasury Stock.

From January 1, 2012 through January 31, 2012, we repurchased approximately 3.5 million shares of our common stock at a total cost of approximately $401.5 million under our 2011 stock repurchase authorization. As of January 31, 2012, approximately 10.5 million shares of our common stock remain available to repurchase under this program.

During 2010, we repurchased approximately 40.3 million shares of our common stock at a cost of approximately $2.1 billion under our 2010 and 2009 stock repurchase authorizations. We retired all of these shares as they were acquired. In connection with this retirement, we recorded a reduction in additional paid-in-capital of approximately $2.1 billion. The 2010 and 2009 share repurchase programs were completed during 2010.

14.    Accumulated Other Comprehensive Income (Loss)

Accumulated other comprehensive income (loss) consisted of the following:

	As of December 31,
(In millions)	2011			2010
Translation adjustments	$	(50.3	)	$	(24.4	)
Unrealized gains (losses) on securities available for sale		—			12.4
Unrealized gains (losses) on foreign currency forward contracts		32.8			(9.8	)
Unfunded status of pension and postretirement benefit plans		(9.0	)		0.2
Accumulated other comprehensive income (loss)	$	(26.5	)	$	(21.6	)

Unrealized holding gains on securities available for sale is shown net of tax of $0.1 million and $7.3 million as of December 31, 2011 and 2010, respectively. Unrealized gains (losses) on foreign currency forward contracts are shown net of tax of $3.6 million and $1.3 million as of December 31, 2011 and 2010, respectively. The unfunded status of pension and retirement benefit plans is shown net of tax as of December 31, 2011 and 2010. Tax amounts in both years were immaterial. For discussion of the unfunded status of pension and retirement benefit plans, please read Note 24, Employee Benefit Plans to these consolidated financial statements.

Amounts comprising noncontrolling interests, as reported in our consolidated statements of equity as of December 31, 2011 and 2010 included accumulated translation adjustments of $5.1 million and $0.2 million, respectively.

Comprehensive income (loss) and its components are presented in the consolidated statements of equity.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

15.    Earnings per Share

Basic and diluted earnings per share are calculated as follows:

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Numerator:
Net income attributable to Biogen Idec Inc.	$	1,234.4		$	1,005.3		$	970.1
Adjustment for net income allocable to preferred stock		(0.5	)		(2.0	)		(1.7	)
Net income used in calculating basic and diluted earnings per share	$	1,233.9		$	1,003.3		$	968.4
Denominator:
Weighted average number of common shares outstanding		242.4			252.3			287.4
Effect of dilutive securities:
Stock options and employee stock purchase plan		1.0			0.9			0.6
Time-vested restricted stock units		1.3			1.6			1.4
Market stock units		0.3			0.1			—
Performance-vested restricted stock units settled in shares		—			—			0.1
Dilutive potential common shares		2.6			2.6			2.1
Shares used in calculating diluted earnings per share		245.0			254.9			289.5

The following amounts were not included in the calculation of net income per diluted share because their effects were anti-dilutive:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Numerator:
Net income allocable to preferred stock	$	0.5	$	2.0	$	1.7
Denominator:
Stock options		—		4.6		8.5
Time-vested restricted stock units		—		0.1		2.1
Market stock units		—		—		—
Performance-vested restricted stock units settled in shares		—		—		0.2
Convertible preferred stock		0.1		0.5		0.5
Total		0.1		5.2		11.3

Earnings per share for the years ended December 31, 2011 and 2010 reflects, on a weighted average basis, the repurchase of 6.0 million shares and 40.3 million shares, respectively, of our common stock under our share repurchase authorizations.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

16.    Share-based Payments

Share-based Compensation Expense

The following table summarizes share-based compensation expense included within our consolidated statements of income:

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Research and development	$	62.0		$	62.7		$	60.8
Selling, general and administrative		88.7			123.6			106.4
Restructuring charges		(0.6	)		6.8			—
Subtotal		150.1			193.1			167.2
Capitalized share-based compensation costs		(4.5	)		(3.5	)		(6.3	)
Share-based compensation expense included in total cost and expenses		145.6			189.6			160.9
Income tax effect		(44.6	)		(60.3	)		(49.4	)
Share-based compensation expense included in net income attributable to Biogen Idec Inc.	$	101.0		$	129.3		$	111.5

The following table summarizes share-based compensation expense associated with each of our share-based compensation programs:

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Stock options	$	5.9		$	26.1		$	21.6
Market stock units		14.6			10.0			—
Time-vested restricted stock units		89.6			129.4			133.7
Performance-vested restricted stock units settled in shares		1.0			5.3			4.6
Cash settled performance shares		32.7			15.0			—
Employee stock purchase plan		6.3			7.3			7.3
Subtotal		150.1			193.1			167.2
Capitalized share-based compensation costs		(4.5	)		(3.5	)		(6.3	)
Share-based compensation expense included in total cost and expenses	$	145.6		$	189.6		$	160.9

Windfall tax benefits from vesting of stock awards, exercises of stock options and ESPP participation were $50.6 million, $13.1 million and $3.4 million in 2011, 2010 and 2009, respectively. These amounts have been calculated under the alternative transition method in accordance with U.S. GAAP.

As of December 31, 2011, unrecognized compensation cost related to unvested share-based compensation was approximately $124.3 million, net of estimated forfeitures. We expect to recognize the cost of these unvested awards over a weighted-average period of 1.3 years.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Share-Based Compensation Plans

We have three share-based compensation plans pursuant to which awards are currently being made: (1) the Biogen Idec Inc. 2006 Non-Employee Directors Equity Plan (2006 Directors Plan); (2) the Biogen Idec Inc. 2008 Omnibus Equity Plan (2008 Omnibus Plan); and (3) the Biogen Idec Inc. 1995 Employee Stock Purchase Plan (ESPP). We have six share-based compensation plans under which there are outstanding awards, but from which no further awards can or will be made: (i) the IDEC Pharmaceuticals Corporation 1993 Non-Employee Directors Stock Option Plan; (ii) the IDEC Pharmaceuticals Corporation 1988 Stock Option Plan; (iii) the Biogen, Inc. 1985 Non-Qualified Stock Option Plan; (iv) the Biogen, Inc. 1987 Scientific Board Stock Option Plan; (v) the Biogen Idec Inc. 2003 Omnibus Equity Plan (2003 Omnibus Plan); and (vi) the Biogen Idec Inc. 2005 Omnibus Equity Plan (2005 Omnibus Plan). We have not made any awards pursuant to the 2005 Omnibus Plan since our stockholders approved the 2008 Omnibus Plan and do not intend to make any awards pursuant to the 2005 Omnibus Plan in the future, except that unused shares under the 2005 Omnibus Plan have been carried over for use under the 2008 Omnibus Plan.

Directors Plan

In May 2006, our stockholders approved the 2006 Directors Plan for share-based awards to our directors. Awards granted from the 2006 Directors Plan may include stock options, shares of restricted stock, restricted stock units, stock appreciation rights and other awards in such amounts and with such terms and conditions as may be determined by a committee of our Board of Directors, subject to the provisions of the plan. We have reserved a total of 1.6 million shares of common stock for issuance under the 2006 Directors Plan. The 2006 Directors Plan provides that awards other than stock options and stock appreciation rights will be counted against the total number of shares reserved under the plan in a 1.5-to-1 ratio.

Omnibus Plans

In June 2008, our stockholders approved the 2008 Omnibus Plan for share-based awards to our employees. Awards granted from the 2008 Omnibus Plan may include stock options, shares of restricted stock, restricted stock units, performance shares, shares of phantom stock, stock appreciation rights and other awards in such amounts and with such terms and conditions as may be determined by a committee of our Board of Directors, subject to the provisions of the plan. Shares of common stock available for issuance under the 2008 Omnibus Plan consist of 15.0 million shares reserved for this purpose, plus shares of common stock that remained available for issuance under the 2005 Omnibus Plan on the date that our stockholders approved the 2008 Omnibus Plan, plus shares that are subject to awards under the 2005 Omnibus Plan which remain unissued upon the cancellation, surrender, exchange or termination of such awards. The 2008 Omnibus Equity Plan provides that awards other than stock options and stock appreciation rights will be counted against the total number of shares available under the plan in a 1.5-to-1 ratio.

Stock Options

All stock option grants to employees are for a ten-year term and generally vest one-fourth per year over four years on the anniversary of the date of grant, provided the employee remains continuously employed with us. Stock option grants to directors are for ten-year terms and generally vest as follows: (1) grants made on the date of a director’s initial election to our Board of Directors vest one-third per year over three years on the anniversary of the date of grant and (2) grants made for service on our Board of Directors vest on the first anniversary of the date of grant, provided in each case that the director continues to serve on our Board of Directors through the vesting date. Options granted under all plans are exercisable at a price per share not less than the fair market value of the underlying common stock on the date of grant. The estimated fair value of options, including the effect of estimated forfeitures, is recognized over the options’ vesting periods. The fair

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

value of the stock options granted in 2010 and 2009 was estimated as of the date of grant using a Black-Scholes option valuation model that uses the following weighted-average assumptions:

	For the Years Ended December 31,
	2011			2010			2009
Expected option life (in years)		*	*		4.5			4.7
Expected stock price volatility		*	*		30.8	%		39.3	%
Risk-free interest rate		*	*		2.0	%		1.9	%
Expected dividend yield		*	*		0.0	%		0.0	%
Per share grant-date fair value		*	*	$	16.52		$	18.00

** There were no grants of stock options made in 2011.

The expected life of options granted is derived using assumed exercise rates based on historical exercise patterns and represents the period of time that options granted are expected to be outstanding. Expected stock price volatility is based upon implied volatility for our exchange-traded options and other factors, including historical volatility. After assessing all available information on either historical volatility, implied volatility, or both, we have concluded that a combination of both historical and implied volatility provides the best estimate of expected volatility. The risk-free interest rate used is determined by the market yield curve based upon risk-free interest rates established by the Federal Reserve, or non-coupon bonds that have maturities equal to the expected term. The dividend yield of zero is based upon the fact that we have not historically granted cash dividends, and do not expect to issue dividends in the foreseeable future. Stock options granted prior to January 1, 2006 were valued based on the grant date fair value of those awards, using the Black-Scholes option pricing model, as previously calculated for pro-forma disclosures.

The following table summarizes our stock option activity:

	Shares			Weighted Average Exercise Price
Outstanding at December 31, 2010		7,167,000		$	55.43
Granted		—		$	—
Exercised		(5,235,000	)	$	56.40
Cancelled		(241,000	)	$	53.30
Outstanding at December 31, 2011		1,691,000		$	52.75

The total intrinsic values of options exercised in 2011, 2010 and 2009 totaled $149.0 million, $50.5 million, and $6.7 million, respectively. The aggregate intrinsic values of options outstanding as of December 31, 2011 totaled $96.8 million. The weighted average remaining contractual term for options outstanding as of December 31, 2011 was 4.9 years.

Of the options outstanding, 1.3 million were exercisable as of December 31, 2011. The exercisable options had a weighted-average exercise price of $52.35. The aggregate intrinsic value of options exercisable as of December 31, 2011 was $73.6 million. The weighted average remaining contractual term for options exercisable as of December 31, 2011 was 4.1 years.

A total of 1.6 million vested and expected to vest options were outstanding as of December 31, 2011. These vested and expected to vest options had a weighted average exercise price of $52.74 and an aggregated intrinsic value of $94.3 million. The weighted average remaining contractual term of vested and expected to vest options as of December 31, 2011 was 4.8 years.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

The following table summarizes the amount of tax benefit realized for stock options and cash received from the exercise of stock options:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Tax benefit realized for stock options	$	47.5	$	16.0	$	1.5
Cash received from the exercise of stock options	$	291.9	$	160.0	$	25.2

Market Stock Units (MSUs)

MSUs awarded to employees vest in four equal annual increments beginning on the anniversary of the grant date. The vesting of these awards is subject to the respective employee’s continued employment. The number of MSUs granted represents the target number of units that are eligible to be earned based on the attainment of certain market-based criteria involving our stock price. The number of MSUs earned is calculated at each annual anniversary from the date of grant over the respective vesting periods, resulting in multiple performance periods. Participants may ultimately earn between 0% and 150% of the target number of units granted based on actual stock performance. Accordingly, additional MSUs may be issued or currently outstanding MSUs may be cancelled upon final determination of the number of awards earned. Compensation expense, including the effect of forfeitures, is recognized over the applicable service period.

The following table summarizes our MSU activity:

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2010		398,000		$	61.87
Granted (a)		398,000		$	74.19
Vested		(119,000	)	$	59.89
Forfeited		(96,000	)	$	65.37
Unvested at December 31, 2011		581,000		$	69.49

(a) MSUs granted in 2011, includes approximately 26,000 additional MSUs issued in 2011 based upon the attainment of performance criteria set for 2010 in relation to shares granted in 2010. The remainder of the MSUs granted in 2011 represents the target number of shares eligible to be earned at the time of grant. These grants were made in conjunction with the hiring of employees and our annual awards made in February 2011.

We value grants of MSUs using a lattice model with a Monte Carlo simulation. This valuation methodology utilizes several key assumptions, including the 60 calendar day average closing stock price on grant date, expected volatility of our stock price, risk-free rates of return and expected dividend yield. The assumptions used in our valuation are summarized as follows:

	For the Years Ended December 31,
	2011	2010
Expected dividend yield	0%	0%
Range of expected stock price volatility	25.7% - 33.4%	28.3% - 38.8%
Range of risk-free interest rates	0.3% - 1.9%	0.3% - 2.0%
60 calendar day average stock price on grant date	$66.78 - $101.16	$49.08 - $54.12
Weighted-average per share grant date fair value	$ 74.19	$ 61.87

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Cash Settled Performance Shares (CSPSs)

CSPSs awarded to employees vest in three equal annual increments beginning on the anniversary of the grant date. The vesting of these awards is subject to the respective employee’s continued employment with such awards settled in cash. The number of CSPSs granted represents the target number of units that are eligible to be earned based on the attainment of certain performance measures established at the beginning of the performance period, which ends on December 31^st of each year. Participants may ultimately earn between 0% and 200% of the target number of units granted based on the degree of actual performance metric achievement. Accordingly, additional CSPSs may be issued or currently outstanding CSPSs may be cancelled upon final determination of the number of units earned. CSPSs are settled in cash based on the 60 calendar day average closing stock price through each vesting date once the actual vested and earned number of units is known. Since no shares are issued, these awards will not dilute equity. Compensation expense, including the effect of forfeitures, is recognized over the applicable service period.

The following table summarizes our CSPS activity:

(In thousands)	Shares
Unvested at December 31, 2010		370,000
Granted (a)		490,000
Vested		(187,000	)
Forfeited		(111,000	)
Unvested at December 31, 2011		562,000

(a) CSPSs granted in 2011 includes approximately 95,000 additional CSPSs issued in 2011 based upon the attainment of performance criteria set for 2010 in relation to shares granted in 2010. The remainder of the CSPSs granted in 2011 represents the target number of shares eligible to be earned at the time of grant. These grants were made in conjunction with the hiring of employees and our annual awards made in February 2011.

During 2011, we paid $13.4 million of cash in settlement of CSPS awards upon vesting.

Time-Vested Restricted Stock Units (RSUs)

RSUs awarded to employees generally vest no sooner than one-third per year over three years on the anniversary of the date of grant, or upon the third anniversary of the date of the grant, provided the employee remains continuously employed with us, except as otherwise provided in the plan. Shares of our common stock will be delivered to the employee upon vesting, subject to payment of applicable withholding taxes. RSUs awarded to directors for service on our Board of Directors vest on the first anniversary of the date of grant, provided in each case that the director continues to serve on our Board of Directors through the vesting date. Shares of our common stock will be delivered to the director upon vesting and are not subject to any withholding taxes. The fair value of all RSUs is based on the market value of our stock on the date of grant. Compensation expense, including the effect of forfeitures, is recognized over the applicable service period.

The following table summarizes our RSU activity:

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2010		4,223,000		$	53.26
Granted		1,398,000		$	70.01
Vested		(1,980,000	)	$	53.72
Forfeited		(717,000	)	$	54.20
Unvested at December 31, 2011		2,924,000		$	60.72

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

RSUs granted in 2010 and 2009 had weighted average grant date fair values of $54.79 and $48.93, respectively.

Performance-Vested Restricted Stock Units (PVRSUs)

The following table summarizes our PVRSU activity:

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2010		154,000		$	49.24
Granted (a)		1,000		$	53.64
Vested		(75,000	)	$	49.51
Forfeited		(33,000	)	$	48.61
Unvested at December 31, 2011		47,000		$	49.34

(a) PVRSUs granted in 2011 represents additional shares earned for performance criteria set for 2010 in relation to shares granted in 2010. No other grants of PVRSUs were made in 2011.

Grant Activity

In 2010 and 2009, approximately 4,000 and 325,000 PVRSUs were granted with weighted average grant date fair values of $53.64 and $49.42 per share, respectively. The number of PVRSUs reflected as granted represents the target number of shares that are eligible to vest in full or in part and are earned subject to the attainment of certain performance criteria established at the beginning of the performance period, which ended December 31, 2009. Participants may ultimately earn up to 200% of the target number of shares granted in the event that the maximum performance thresholds are attained. Accordingly, additional PVRSUs may be issued upon final determination of the number of awards earned.

Once the earned number of performance-vested awards has been determined, the earned PVRSUs will then vest in three equal increments on (1) the later of the first anniversary of the grant date or the date of results determination; (2) the second anniversary of the grant date; and (3) the third anniversary of the grant date. The vesting of these awards is also subject to the respective employees’ continued employment. Compensation expense associated with these PVRSUs is initially based upon the number of shares expected to vest after assessing the probability that certain performance criteria will be met and the associated targeted payout level that is forecasted will be achieved, net of estimated forfeitures. Cumulative adjustments are recorded quarterly to reflect subsequent changes in the estimated outcome of performance-related conditions until the date results are determined.

Employee Stock Purchase Plan (ESPP)

The following table summarizes our ESPP activity:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Shares issued under ESPP		0.4		0.6		0.6
Cash received under ESPP	$	22.8	$	23.5	$	22.6

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Other

As part of the employee severance and benefits packages offered to employees affected by our workforce reduction made in connection with our 2010 restructuring initiative, we agreed to settle certain existing equity awards in cash, which resulted in an incremental charge of approximately $6.8 million recognized in the fourth quarter of 2010. This charge is reflected within our consolidated statement of income as a component of our total restructuring charge incurred in 2010.

In accordance with the transition agreement entered into with James C. Mullen who retired as our President and Chief Executive Officer on June 8, 2010, we agreed with Mr. Mullen, amongst other provisions, to vest all of Mr. Mullen’s then-unvested equity awards on the date of his retirement and allow Mr. Mullen to exercise his vested stock options until June 8, 2013 or their expiration, whichever is earlier. The modifications to Mr. Mullen’s existing stock options, RSUs and PVRSUs resulted in an incremental charge of approximately $18.6 million, which was recognized evenly over the service period from January 4, 2010 to June 8, 2010 as per the terms of the transition agreement.

17.    Income Taxes

Income Tax Expense

Income before income tax provision and the income tax expense consist of the following:

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Income before income taxes (benefit):
Domestic	$	1,408.9		$	846.4		$	1,073.8
Foreign		302.3			383.5			258.9
Total	$	1,711.2		$	1,229.9		$	1,332.7
Income tax expense (benefit):
Current
Federal	$	231.7		$	357.7		$	439.9
State		15.1			19.6			3.1
Foreign		44.1			35.4			50.0
Total	$	290.9		$	412.7		$	493.0
Deferred
Federal	$	160.9		$	(70.6	)	$	(94.8	)
State		(8.1	)		(6.6	)		(39.0	)
Foreign		0.8			(4.2	)		(3.6	)
Total		153.6			(81.4	)		(137.4	)
Total income tax expense	$	444.5		$	331.3		$	355.6

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Deferred Tax Assets and Liabilities

Significant components of our deferred tax assets and liabilities are summarized as follows:

	As of December 31,
(In millions)	2011			2010
Deferred tax assets
Tax credits	$	60.0		$	47.6
Inventory, other reserves, and accruals		104.1			203.1
Capitalized costs		5.3			6.7
Intangibles, net		75.8			61.8
Net operating loss		22.9			35.3
Share-based compensation		54.7			64.4
Other		45.7			70.3
Valuation allowance		(10.8	)		(10.8	)
Total deferred tax assets	$	357.7		$	478.4
Deferred tax liabilities
Purchased intangible assets	$	(384.8	)	$	(446.1	)
Unrealized gain on investments and cumulative translation adjustment		(3.5	)		(6.6	)
Inventory		(76.8	)		—
Depreciation, amortization and other		(133.1	)		(114.4	)
Total deferred tax liabilities	$	(598.2	)	$	(567.1	)

Tax Rate

Reconciliation between the U.S. federal statutory tax rate and our effective tax rate is summarized as follows:

	For the Years Ended December 31,
	2011			2010			2009
Statutory rate		35.0	%		35.0	%		35.0	%
State taxes		1.7			1.7			(0.1	)
Taxes on foreign earnings		(5.9	)		(10.7	)		(5.0	)
Credits and net operating loss utilization		(4.4	)		(3.0	)		(3.8	)
Purchased intangible assets		1.3			1.9			2.0
IPR&D		—			5.0			—
Permanent items		(1.2	)		(2.0	)		(1.3	)
Contingent consideration		0.7			—			—
Other		(1.2	)		(1.0	)		(0.1	)
Effective tax rate		26.0	%		26.9	%		26.7	%

As of December 31, 2011, we had net operating losses and general business credit carry forwards for federal income tax purposes of approximately $27.2 million and $1.9 million, respectively, which begin to expire in 2022. Additionally, for state income tax purposes, we had net operating loss carry forwards of approximately $57.1 million, which begin to expire in 2012. For state income tax purposes, we also had research and investment credit carry forwards of approximately $101.6 million, of which approximately $0.9 million begin to expire in 2012.

In assessing the realizability of our deferred tax assets, we have considered whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. In making this determination, under the applicable financial reporting standards, we are allowed to consider the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax planning strategies. Our estimates of future taxable income take into consideration, among other items, our estimates of future income tax deductions related to the exercise of stock options. Based upon the level of historical taxable income and income tax liability and projections for future taxable income over the periods in which the deferred tax assets are utilizable, we believe it is more likely than not that we will realize the benefits of the deferred tax assets of our wholly owned subsidiaries. At December 31, 2011, we have a full valuation allowance on the deferred tax assets of a variable interest entity which we consolidate, based on uncertainties related to the realization of some of those assets. These assets totalling $10.8 million are excluded from our credit and loss carryforwards described above. In the event that actual results differ from our estimates or we adjust our estimates in future periods, we may need to establish a valuation allowance, which could materially impact our financial position and results of operations.

As of December 31, 2011, undistributed foreign earnings of non-U.S. subsidiaries included in consolidated retained earnings and other basis differences aggregated approximately $2.7 billion. We intend to reinvest these earnings indefinitely in operations outside the U.S. The residual U.S. tax liability, if such amounts were remitted, would be approximately $600 million to $700 million as of December 31, 2011.

Accounting for Uncertainty in Income Taxes

A reconciliation of the beginning and ending amount of our unrecognized tax benefits is summarized as follows:

(In millions)	2011			2010			2009
Balance at January 1,	$	121.5		$	147.1		$	249.6
Additions based on tax positions related to the current period		2.2			3.6			14.4
Additions for tax positions of prior periods		48.6			13.3			77.4
Reductions for tax positions of prior periods		(75.8	)		(18.5	)		(88.7	)
Statute expirations		(2.3	)		(3.7	)		—
Settlements		(29.8	)		(20.3	)		(105.6	)
Balance at December 31,	$	64.4		$	121.5		$	147.1

We and our subsidiaries are routinely examined by various taxing authorities. We file income tax returns in the U.S. federal jurisdiction, and various states and foreign jurisdictions. With few exceptions, we are no longer subject to U.S. federal tax examination for years before 2010 or state, local, or non-U.S. income tax examinations by tax authorities for years before 2004. During the year, we adjusted our unrecognized tax benefits to reflect new information arising during our ongoing audit examinations.

In October 2011, in conjunction with our examination, the IRS has proposed a disallowance of approximately $130 million in deductions for tax years 2007, 2008 and 2009 related to payments for services from our Danish contract manufacturing affiliate. We believe that these deductions represent valid deductible business expenses and will vigorously defend our position.

Included in the balance of unrecognized tax benefits as of December 31, 2011, 2010, and 2009 are $31.3 million, $26.2 million, and $42.8 million (net of the federal benefit on state issues), respectively, of unrecognized tax benefits that, if recognized, would affect the effective income tax rate in future periods. We recognize potential interest and penalties accrued related to unrecognized tax benefits in income tax expense.

We do not anticipate any significant changes in our positions in the next twelve months other than expected settlements which have been classified as current liabilities within the accompanying balance sheet.

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NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

We recognize potential interest and penalties accrued related to unrecognized tax benefits in income tax expense. In 2011, as we settled certain uncertain tax positions, we recognized a net interest benefit of $12.9 million. During 2010, we recognized net interest expense of $0.7 million. In 2009, we recognized a net interest benefit of approximately $3.1 million. We have accrued approximately $3.9 million and $29.4 million for the payment of interest as of December 31, 2011 and 2010, respectively.

Contingencies

In 2006, the Massachusetts Department of Revenue (DOR) issued a Notice of Assessment against Biogen Idec MA Inc. (BIMA), one of our wholly-owned subsidiaries, for $38.9 million of corporate excise tax for 2002, which includes associated interest and penalties. The assessment asserted that the portion of sales attributable to Massachusetts (sales factor), the computation of BIMA’s research and development credits and certain deductions claimed by BIMA were not appropriate, resulting in unpaid taxes for 2002. We filed an abatement application with the DOR seeking abatements for 2001, 2002 and 2003. Our abatement application was denied and on July 25, 2007, we filed a petition with the Massachusetts Appellate Tax Board (the Massachusetts ATB) seeking, among other items, abatements of corporate excise tax for 2001, 2002 and 2003 and adjustments in certain credits and credit carry forwards for 2001, 2002 and 2003. On August 18, 2011, we reached a settlement with the DOR under which we agreed to pay $7.0 million in taxes, plus $5.0 million of interest, and agreed on the nature and amount of tax credits carried forward into 2004. This resolution did not have a significant impact on our results of operations, is related only to the 2001, 2002 and 2003 tax years, and does not resolve matters in dispute for subsequent periods.

On June 8, 2010, we received Notices of Assessment from the DOR against BIMA for $103.5 million of corporate excise tax, including associated interest and penalties, related to our 2004, 2005 and 2006 tax filings.

We filed an abatement application with the DOR seeking abatement for 2004, 2005 and 2006. Our abatement application was denied in December 2010, and we filed a petition appealing the denial with the ATB on February 3, 2011. For all periods under dispute, we believe that positions taken in our tax filings are valid and believe that we have meritorious defenses in these disputes. We are contesting these matters vigorously.

The audits of our tax filings for 2007 and 2008 have not yet been completed but have been prepared in a manner consistent with prior filings which may result in an assessment for those years. Due to tax law changes effective January 1, 2009, the computation and deductions at issue in previous tax filings have not been part of our tax filings in Massachusetts starting in 2009.

We believe that these assessments do not impact the level of liabilities for income tax contingencies. However, there is a possibility that we may not prevail in defending all of our assertions with the DOR. If these matters are resolved unfavorably in the future, the resolution could have a material adverse impact on the effective tax rate and our results of operations.

18.    Other Consolidated Financial Statement Detail

Supplemental Cash Flow Information

Supplemental disclosure of cash flow information for the years ended December 31, 2011, 2010 and 2009 is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Cash paid during the year for:
Interest	$	66.7	$	68.1	$	68.1
Income taxes	$	332.7	$	394.7	$	745.4

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

In September 2011, upon completion of our acquisition of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH, we recorded a contingent consideration liability of $38.8 million.

In connection with the construction of the new Cambridge facilities that will be leased by us when the construction is completed, we have recorded an asset along with a corresponding financing obligation on our consolidated balance sheet as of December 31, 2011 totaling approximately $2.2 million. For additional information related to these transactions, please read Note 11, Property, Plant & Equipment to these consolidated financial statements.

In December 2010, upon completion of our acquisition of BIN, we recorded $110.9 million of in-process research and development and $25.6 million of goodwill. In addition, we also assumed a contingent consideration liability of $81.2 million and a deferred tax liability of $23.7 million.

Other Income (Expense), Net

Components of other income (expense), net, are summarized as follows:

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Interest income	$	19.2		$	22.3		$	48.5
Interest expense		(33.0	)		(36.1	)		(35.8	)
Impairments on investments		(11.5	)		(21.3	)		(10.6	)
Gain (loss) on sales of investments, net		17.4			16.3			22.8
Foreign exchange gains (losses), net		(6.3	)		(3.5	)		11.4
Other, net		0.7			3.3			1.0
Total other income (expense), net	$	(13.5	)	$	(19.0	)	$	37.3

Other Current Assets

Other current assets consist of the following:

	As of December 31,
(In millions)	2011		2010
Deferred tax assets	$	8.1	$	112.2
Derivative assets		39.5		1.3
Prepaid taxes		15.2		31.4
Receivable from collaborations		11.4		7.3
Interest receivable		6.5		4.9
Other prepaid expenses		45.5		47.9
Other		18.4		10.8
Total other current assets	$	144.6	$	215.8

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Accrued Expenses and Other

Accrued expenses and other consists of the following:

	As of December 31,
(In millions)	2011		2010
Employee compensation and benefits	$	176.3	$	159.7
Revenue-related rebates		115.0		105.3
Deferred revenue		69.6		41.3
Royalties and licensing fees		47.4		45.1
Collaboration expenses		44.2		31.6
Clinical development expenses		40.8		24.4
Construction in progress accrual		22.8		16.4
Interest payable		21.6		21.6
Current portion of contingent consideration		10.8		11.9
Restructuring charges		1.4		66.4
Derivative liabilities		0.5		12.2
Other		126.8		130.0
Total accrued expenses and other	$	677.2	$	665.9

For a discussion of restructuring charges accrued as of December 31, 2011 and 2010, please read Note 3, Restructuring to these consolidated financial statements.

19.    Investments in Variable Interest Entities

Consolidated Variable Interest Entities

Our consolidated financial statements include the financial results of variable interest entities in which we are the primary beneficiary.

Investments in Joint Ventures

On September 6, 2011, we completed the purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH, our respective sales affiliates in Italy and Switzerland, from our joint venture partners, Dompé Farmaceutici SpA and Dompé International SA, respectively. Prior to this transaction, our consolidated financial statements reflected 100% of the operations of these joint venture investments and we recorded net income (loss) attributable to noncontrolling interests in our consolidated statements of income based on the percentage of ownership interest retained by our joint venture partners as we retained the power to direct the activities which most significantly and directly impacted their economic performance. We have continued to consolidate the operations of these entities following our purchase of the noncontrolling interest; however, as of September 6, 2011, we no longer allocate 50% of the earnings of these affiliates to net income (loss) attributable to noncontrolling interests as Biogen Dompé SRL and Biogen Dompé Switzerland GmbH became wholly-owned subsidiaries of the Company.

Until we completed our purchase of the noncontrolling interests, the assets of these joint ventures were restricted, from the standpoint of Biogen Idec, in that they were not available for our general business use outside the context of each joint venture. The joint ventures’ most significant assets were accounts receivable from the ordinary course of business. The holders of the liabilities of each joint venture, including the credit line from Dompé Farmaceutici SpA to Biogen Dompé SRL, had no recourse to Biogen Idec. Balances outstanding under Biogen Dompé SRL’s credit line were repaid in connection with this transaction. In addition, Dompé

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

Farmaceutici SpA purchased all of Biogen Dompé SRL’s outstanding receivables as of June 30, 2011, adjusted for cash received through September 5, 2011. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

Knopp

In August 2010, we entered into a license agreement with Knopp Neurosciences, Inc. (Knopp), a subsidiary of Knopp Holdings, LLC, for the development, manufacture and commercialization of dexpramipexole, an orally administered small molecule in clinical development for the treatment of amyotrophic lateral sclerosis (ALS). We are responsible for all development activities and, if successful, we will also be responsible for the manufacture and global commercialization of dexpramipexole. Under the terms of the license agreement we made a $26.4 million upfront payment and agreed to pay Knopp up to an additional $265.0 million in development and sales-based milestone payments, as well as royalties on future commercial sales. In addition, we also purchased 30.0% of the Class B common shares of Knopp for $60.0 million.

Due to the terms of the license agreement and our investment in Knopp, we determined that we are the primary beneficiary of Knopp as we have the power to direct the activities that most significantly impact Knopp’s economic performance. As such, we consolidate the results of Knopp. As the license agreement with Knopp only gives us access to the underlying intellectual property of dexpramipexole and we did not acquire any employees or other processes, we determined that this transaction was an acquisition of an asset rather than a business. Therefore, we recorded an IPR&D charge of approximately $205.0 million upon the initial consolidation of Knopp, which is included within our consolidated statement of income for 2010. The amount allocated to IPR&D represents the fair value of the intellectual property of Knopp, which as of the effective date of the agreement, had not reached technological feasibility and had no alternative future use. This charge was determined using internal models based on projected revenues and development costs and adjusted for industry-specific probabilities of success. We attributed approximately $145.0 million of the IPR&D charge to the noncontrolling interest.

In March 2011, we dosed the first patient in a registrational study for dexpramipexole. The achievement of this milestone resulted in a $10.0 million payment due to Knopp. As we consolidate Knopp, we recognized this payment as a charge to noncontrolling interests in the first quarter of 2011.

Although we have assumed responsibility for the development of dexpramipexole, we may also be required to reimburse certain Knopp expenses directly attributable to the license agreement. Any additional amounts incurred by Knopp that we reimburse will be reflected within total cost and expenses in our consolidated statements of income. Future development and sales-based milestone payments will also be reflected within our consolidated statements of income as a charge to noncontrolling interests, when such milestones are achieved.

A summary of activity related to this collaboration, excluding the initial accounting for the consolidation of Knopp, is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010
Total upfront payments made to Knopp	$	—	$	26.4
Milestone payments made to Knopp	$	10.0	$	—
Total development expense incurred by the collaboration excluding upfront and milestone payments	$	44.8	$	5.0
Biogen Idec’s share of expense reflected within our consolidated statements of income	$	54.8	$	31.4
Collaboration expense attributed to noncontrolling interests, net of tax	$	8.6	$	—

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BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

A summary of activity related to this collaboration since inception, along with an estimate of additional future development expenses expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Knopp	$	36.4
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	$	49.8
Estimate of additional amounts to be incurred by us in development of dexpramipexole	$	260.0

The assets and liabilities of Knopp are not significant to our financial position or results of operations. We have provided no financing to Knopp other than previously contractually required amounts disclosed above.

Neurimmune SubOne AG

In 2007, we entered into a collaboration agreement with Neurimmune SubOne AG (Neurimmune), a subsidiary of Neurimmune AG, for the development and commercialization of antibodies for the treatment of Alzheimer’s disease. Neurimmune conducts research to identify potential therapeutic antibodies and we are responsible for the development, manufacturing and commercialization of all products. Based upon our current development plans, we may pay Neurimmune up to $345.0 million in remaining milestone payments, as well as royalties on sales of any resulting commercial products.

We determined that we are the primary beneficiary of Neurimmune because we have the power through the collaboration to direct the activities that most significantly impact the entity’s economic performance and are required to fund 100% of the research and development costs incurred in support of the collaboration agreement.

Amounts that are incurred by Neurimmune for research and development expenses incurred in support of the collaboration that we reimburse are reflected in research and development expense in our consolidated statements of income. In April 2011, we submitted an Investigational New Drug application for BIIB037 (human anti-Amyloid ß mAb) a beta-amyloid removal therapy, which triggered a $15.0 million milestone payment due to Neurimmune. BIIB037 is being developed for the treatment of Alzheimer’s disease. As we consolidate Neurimmune, we recognized this payment as a charge to noncontrolling interests in the second quarter of 2011. Future milestone payments will be reflected within our consolidated statements of income as a charge to the noncontrolling interest, net of tax, when such milestones are achieved.

A summary of activity related to this collaboration is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Milestone payments made to Neurimmune	$	15.0	$	—	$	7.5
Total development expense incurred by the collaboration, excluding upfront and milestone payments	$	9.0	$	15.5	$	9.0
Biogen Idec’s share of expense reflected within our consolidated statements of income	$	24.0	$	15.5	$	16.5
Collaboration expense attributed to noncontrolling interests, net of tax	$	14.7	$	1.0	$	—

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A summary of activity related to this collaboration since inception, along with an estimate of additional future development expenses expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Neurimmune	$	35.0
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	$	40.0
Estimate of additional amounts to be incurred by us in development of the lead compound	$	800.0

The assets and liabilities of Neurimmune are not significant to our financial position or results of operations as it is a research and development organization. We have provided no financing to Neurimmune other than previously contractually required amounts.

In December 2010, we completed our acquisition of BIN from Neurimmune AG, a related party to this collaboration. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

Unconsolidated Variable Interest Entities

We have relationships with other variable interest entities which we do not consolidate as we lack the power to direct the activities that significantly impact the economic success of these entities. These relationships include investments in certain biotechnology companies and research collaboration agreements. For additional information related to our significant collaboration arrangements with unconsolidated variable interest entities, please read Note 20, Collaborations to these consolidated financial statements.

As of December 31, 2011, the total carrying value of our investments in biotechnology companies that we have determined to be variable interest entities is $14.6 million. Our maximum exposure to loss related to these variable interest entities is limited to the carrying value of our investments.

We have entered into research collaborations with certain variable interest entities where we are required to share or fund certain development activities. These development activities are included in research and development expense within our consolidated statements of income, as they are incurred. Depending on the collaborative arrangement, we may record funding receivables or payable balances with our partners, based on the nature of the cost-sharing mechanism and activity within the collaboration. As of December 31, 2011, we had no significant receivables or payables related to cost sharing arrangements with unconsolidated variable interest entities at December 31, 2011 and 2010, respectively.

We have provided no financing to these variable interest entities other than previously contractually required amounts.

Samsung Biosimilar Agreement

On December 5, 2011, we entered into an agreement with Samsung BioLogics Co. Ltd. (Samsung) to establish an entity to develop, manufacture and market biosimilar pharmaceuticals. Under the terms of the agreement, Samsung will contribute approximately $255.0 million for an 85 percent stake in the entity and Biogen Idec will contribute approximately $45.0 million for the remaining 15 percent ownership interest. Our investment will initially be limited to this initial contribution as we have no obligation to provide any additional funding; however, we maintain an option to purchase additional stock in the entity in order to increase our ownership percentage up to 49.9 percent. The exercise of this option is within our control.

Samsung will retain the contractual power to direct the activities of the entity which will most significantly and directly impact its economic performance. We will account for this investment under the equity method of

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accounting as we maintain the ability to exercise significant influence over the entity through a presence on the entity’s Board of Directors and our contractual relationship. Therefore, we will reflect our percentage of the entity’s income or loss within our consolidated statements of income.

Completion of the transaction is subject to customary closing conditions.

20.    Collaborations

In connection with our business strategy, we have entered into various collaboration agreements which provide us with rights to develop, produce and market products using certain know-how, technology and patent rights maintained by our collaborative partners. Terms of the various collaboration agreements may require us to make milestone payments upon the achievement of certain product research and development objectives and pay royalties on future sales, if any, of commercial products resulting from the collaboration.

Genentech (Roche Group)

We collaborate with Genentech, Inc., a wholly-owned member of the Roche Group, on the development and commercialization of RITUXAN and other anti-CD20 products. Our collaboration rights are limited to the U.S. and our rights to products licensed by Genentech are dependent upon Genentech’s underlying license rights.

Our collaboration agreement does not have a fixed term and will continue in effect until we mutually agree to terminate the collaboration, except that if we undergo a change in control, as defined in the collaboration agreement, Genentech has the right to present an offer to buy the rights to RITUXAN and we must either accept Genentech’s offer or purchase Genentech’s rights on the same terms as its offer. Genentech will also be deemed concurrently to have purchased our rights to the other anti-CD20 products now in development in exchange for a royalty. Our collaboration with Genentech was created through a contractual arrangement and not through a joint venture or other legal entity.

In October 2010, we amended our collaboration agreement with Genentech with regard to the development of ocrelizumab and agreed to terms for the development of GA101, as summarized below. This amendment did not have an impact on our share of the co-promotion operating profits of RITUXAN in either 2011 or 2010.

Ocrelizumab

Genentech is now solely responsible for the further development and commercialization of ocrelizumab and funding future costs. Genentech cannot develop ocrelizumab in CLL, NHL or RA without our consent. We will receive tiered royalties between 13.5% and 24% on U.S. sales of ocrelizumab. Commercialization of ocrelizumab will not impact the percentage of the co-promotion profits we receive for RITUXAN.

GA101

We will pay 35% of the development and commercialization expenses of GA101 and will receive between 35% and 39% of the profits of GA101 based upon the achievement of certain sales milestones. Before the October 2010 amendment and restatement of our collaboration agreement, we had paid 30% of the GA101 development expenses. During the fourth quarter of 2010, we paid approximately $10.0 million to compensate Genentech for our increased share of such previously incurred expenses. Commercialization of GA101 will impact our percentage of the co-promotion profits for RITUXAN, as summarized in the table below.

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RITUXAN

While Genentech is responsible for the worldwide manufacturing of RITUXAN, development and commercialization rights and responsibilities under this collaboration are divided as follows:

U.S.

We share with Genentech co-exclusive rights to develop, commercialize and market RITUXAN in the U.S. For 2010 and 2009, we contributed to the marketing and continued development of RITUXAN by maintaining a limited sales force dedicated to RITUXAN and performing limited development activity. However, during the fourth quarter of 2010, we agreed with Genentech to eliminate our current RITUXAN oncology and rheumatology sales force, with Genentech assuming sole responsibility for the U.S. sales and marketing of RITUXAN.

Canada

We and Genentech have assigned our rights under our collaboration agreement with respect to Canada to Roche.

Outside the U.S. and Canada

We have granted Genentech exclusive rights to develop, commercialize and market RITUXAN outside the U.S. and Canada. Under the terms of separate sublicense agreements between Genentech and Roche, development and commercialization of RITUXAN outside the U.S. and Canada is the responsibility of Roche and its sublicensees. We do not have any direct contractual arrangements with Roche or it sublicensees.

Under the terms of the collaboration agreement, we will be paid royalties between 10% and 12% on sales of RITUXAN outside the U.S. and Canada, with the royalty period lasting 11 years from the first commercial sale of RITUXAN on a country-by-country basis. The royalty periods for substantially all of the remaining royalty-bearing sales of RITUXAN in the rest of world markets will expire in 2012. As a result of these expirations, we expect royalty revenues on sales of RITUXAN in the rest of world to continue to decline in 2012. After 2012, we expect revenue on sales of RITUXAN in the rest of world will primarily be limited to our share of pre-tax co-promotion profits in Canada.

Co-promotion Profit-sharing Formula

Our current pretax co-promotion profit-sharing formula for RITUXAN, which resets annually, provides for a 30% share of co-promotion profits on the first $50.0 million of co-promotion operating profit with our share increasing to 40% if co-promotion operating profits exceed $50.0 million. Under the amended agreement, our share of the co-promotion profits for RITUXAN will change, as summarized in the table below, upon the following events:

• First New Product FDA Approval: the FDA’s first approval of an anti-CD20 product other than ocrelizumab and GA101 that is acquired or developed by Genentech and is subject to the collaboration agreement (New Product).

• First Non-CLL GA101 FDA Approval: the FDA’s first approval of GA101 in an indication other than CLL.

• GA101 CLL Sales Trigger: the first day of the quarter after U.S. gross sales of GA101 in any consecutive 12 month period reach $500.0 million.

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Our share of the co-promotion operating profits for RITUXAN is calculated as follows:

				Before First New Product FDA Approval
Co-promotion Operating Profits†	After First New Product FDA Approval			First Non-CLL GA101 FDA Approval Occurs First			GA101 CLL Sales Trigger Occurs First
I. First $50.0 million		30	%		30	%		30	%
II. Above $50.0 million		—			—			35	%
A. Until First GA101 Threshold Date		38	%		39	%		—
B. After First GA101 Threshold Date
1(a). Until First Threshold Date		37.5	%		—			—
1(b). After First Threshold Date and  until Second Threshold Date		35	%		—			—
1(c). After Second Threshold Date		30	%		—			—
2. Until Second GA101 Threshold  Date		—			37.5	%		—
C. After Second GA101 Threshold Date		—			35	%		—

† First GA101 Threshold Date means the earlier of (1) the date of the First Non-CLL GA101 FDA Approval if U.S. gross sales of GA101 for the preceding consecutive 12 month period were at least $150.0 million or (2) the first day of the calendar quarter after the date of the First Non-CLL GA101 FDA Approval that U.S. gross sales of GA101 within any consecutive 12 month period have reached $150.0 million.

Second GA101 Threshold Date means the first day of the calendar quarter after U.S. gross sales of GA101 within any consecutive 12 month period have reached $500.0 million.

First Threshold Date means the earlier of (1) the GA101 CLL Sales Trigger, (2) the Second GA101 Threshold Date and (3) the later of (a) the first date that U.S. gross sales of New Products in any calendar year reach $150.0 million and (b) January 1 of the calendar year following the calendar year in which the First New Product FDA Approval occurs if gross sales of New Products reached $150.0 million within the same calendar year in which the First New Product FDA Approval occurred.

Second Threshold Date means the later of (1) the first date that U.S. gross sales of New Products in any calendar year reach $350.0 million and (2) January 1 of the calendar year following the calendar year in which the First Threshold Date occurs.

Our collaboration agreement also provides that we will be paid low single digit royalties on sales outside the U.S. and Canada of new anti-CD20 products developed or licensed by Genentech or controlled by us. These royalties will be payable for a period of 11 years from the first commercial sale of such products on a country-by-country basis.

Unconsolidated Joint Business Revenues

Revenues from unconsolidated joint business consists of (1) our share of pre-tax co-promotion profits in the U.S. (2) reimbursement of our selling and development expenses in the U.S.; and (3) revenue on sales of RITUXAN in the rest of world, which consist of our share of pre-tax co-promotion profits in Canada and royalty revenue on sales of RITUXAN outside the U.S. and Canada by Roche, and its sublicensees. Pre-tax co-promotion profits are calculated and paid to us by Genentech in the U.S. and by Roche in Canada. Pre-tax co-promotion profits consist of U.S. and Canadian sales of RITUXAN to third-party customers net of discounts and allowances less the cost to manufacture RITUXAN, third-party royalty expenses, distribution, selling, and marketing expenses, and joint development expenses incurred by Genentech, Roche and us. We record our share of the

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pretax co-promotion profits in Canada and royalty revenues on sales of RITUXAN outside the U.S. on a cash basis. Additionally, our share of the pre-tax co-promotion profits in the U.S. includes estimates made by Genentech and those estimates are subject to change. Actual results may ultimately differ from our estimates.

In June 2011, the collaboration recognized a charge of approximately $125.0 million, representing an estimate of compensatory damages and interest that might be awarded to Hoechst GmbH (Hoechst), in relation to an intermediate decision by the arbitrator in Genentech’s ongoing arbitration with Hoechst. As a result of this charge to the collaboration, our share of RITUXAN revenues from unconsolidated joint business was reduced by approximately $50.0 million in the second quarter of 2011. This $50.0 million amount reflects the estimate of the loss that we may incur in the event of a final arbitration award unfavorable to Genentech. The actual amount of our share of any damages may vary from this estimate depending on the nature or amount of any damages awarded to Hoechst, or if the arbitrator’s final decision is successfully challenged by Genentech. For additional information related to this matter, please read Note 21, Litigation to these consolidated financial statements.

Revenues from unconsolidated joint business are summarized as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Biogen Idec’s share of pre-tax co-promotion profits in the U.S.	$	872.7	$	848.0	$	773.6
Reimbursement of our selling and development expenses in the U.S.		6.1		58.3		65.6
Revenue on sales of RITUXAN in the rest of world		117.8		170.9		255.7
Total unconsolidated joint business revenues	$	996.6	$	1,077.2	$	1,094.9

In 2011, 2010, and 2009, the 40% co-promotion profit-sharing threshold was met during the first quarter.

Currently, we record our share of the expenses incurred by the collaboration for the development of anti-CD20 products in research and development expense in our consolidated statements of income. We incurred $26.9 million, $50.6 million, and $62.5 million in development expense for the years ended December 31, 2011, 2010, and 2009, respectively. After an anti-CD20 product is approved, we will record our share of the development expenses related to that product as a reduction of our share of pre-tax co-promotion profits in revenues from unconsolidated joint business. As a result of the October 2010 amendment of our collaboration agreement with Genentech, we are no longer responsible for any development costs for ocrelizumab.

Elan

We collaborate with Elan on the development, manufacture and commercialization of TYSABRI. Under the terms of our collaboration agreement, we manufacture TYSABRI and collaborate with Elan on the product’s marketing, commercial distribution and ongoing development activities. The agreement is designed to effect an equal sharing of profits and losses generated by the activities of our collaboration. Under the agreement, however, once sales of TYSABRI exceeded specific thresholds, Elan was required to make milestone payments to us in order to continue sharing equally in the collaboration’s results. As of December 31, 2010, Elan has made milestone payments to us of $75.0 million in the third quarter of 2008 and $50.0 million in the first quarter of 2009. These amounts were recorded as deferred revenue upon receipt and are recognized as revenue in our consolidated statements of income based on the ratio of units shipped in the current period over the total units expected to be shipped over the remaining term of the collaboration. No additional milestone payments are required under the agreement to maintain the current profit sharing split and as of December 31, 2011, $100.6 million remains to be amortized. The term of our collaboration agreement extends until November 2019. Each of Biogen Idec and Elan has the option to buy the other party’s rights to TYSABRI upon expiration of the term or if the other party undergoes a change of control (as defined in the collaboration agreement). In addition,

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each of Biogen Idec and Elan can terminate the agreement for convenience or material breach by the other party, in which case, among other things, certain licenses, regulatory approvals and other rights related to the manufacture, sale and development of TYSABRI are required to be transferred to the party that is not terminating for convenience or is not in material breach of the agreement.

In the U.S., we sell TYSABRI to Elan who sells the product to third party distributors. Our sales price to Elan in the U.S. is set prior to the beginning of each quarterly period to effect an approximate equal sharing of the gross margin between Elan and us. We recognize revenue for sales in the U.S. of TYSABRI upon Elan’s shipment of the product to the third party distributors, at which time all revenue recognition criteria have been met. As of December 31, 2011 and 2010, we had deferred revenue of $23.8 million and $20.8 million, respectively, for shipments to Elan that remained in Elan’s ending inventory pending shipment of the product to the third party distributors. We incur manufacturing and distribution costs, research and development expenses, commercial expenses, and general and administrative expenses related to TYSABRI. We record these expenses to their respective line items within our consolidated statements of income when they are incurred. Research and development and sales and marketing expenses are shared equally with Elan and the reimbursement of these expenses is recorded as reductions of the respective expense categories. During the years ended December 31, 2011, 2010, and 2009, we recorded $47.5 million, $49.8 million and $25.3 million, respectively, as reductions of research and development expense for reimbursements from Elan. In addition, for the years ended December 31, 2011, 2010, and 2009, we recorded $77.3 million, $68.5 million and $62.5 million, respectively, as reductions of selling, general and administrative expense for reimbursements from Elan.

In the rest of world, we are responsible for distributing TYSABRI to customers and are primarily responsible for all operating activities. Generally, we recognize revenue for sales of TYSABRI in the rest of world at the time of product delivery to our customers. Payments are made to Elan for their share of the rest of world net operating profits to effect an equal sharing of collaboration operating profit. These payments also include the reimbursement for our portion of third-party royalties that Elan pays on behalf of the collaboration relating to rest of world sales. As rest of world sales of TYSABRI increase, our collaboration profit sharing expense is expected to increase. These amounts are reflected in the collaboration profit sharing line in our consolidated statements of income. For the years ended December 31, 2011, 2010 and 2009, $317.8 million, $258.1 million and $215.9 million, respectively, was reflected in the collaboration profit sharing line for our collaboration with Elan.

Acorda

In 2009, we entered into a collaboration and license agreement with Acorda Therapeutics, Inc. (Acorda) to develop and commercialize products containing fampridine in markets outside the U.S. We also have responsibility for regulatory activities and the future clinical development of related products in those markets. The $110.0 million upfront payment made on July 1, 2009 to Acorda was recorded as research and development expense during the second quarter 2009 as the product candidate had not received regulatory approval.

In July 2011, the European Commission (EC) granted a conditional marketing authorization for fampridine in the E.U., under the trade name FAMPYRA, which triggered a $25.0 million milestone payment. This payment was made to Acorda Therapeutics, Inc. (Acorda) in the third quarter of 2011 and was capitalized as an intangible asset. FAMPYRA is an oral compound indicated as a treatment to improve walking ability in adult patients with MS who have walking disability. As part of the conditions of the conditional marketing authorization for FAMPYRA, we will provide additional data from on-going clinical studies regarding FAMPYRA’s benefits and safety in the long term. A conditional marketing authorization is renewable annually and is granted to a medicinal product with a positive benefit/risk assessment that fulfills an unmet medical need when the benefit to public health of immediate availability outweighs the risk inherent in the fact that additional data are still required.

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FAMPYRA was commercially launched in Australia, Denmark, Germany, Norway, and the UK in 2011. In 2012, we plan to launch FAMPYRA in Austria, Canada, Finland, France, Greece, Italy, Ireland, the Netherlands, Sweden and other markets. The exact timing of these launches remains subject to our ability to obtain reimbursement approval within the respective markets.

We have a license from Acorda to develop and commercialize FAMPYRA in all markets outside the U.S. Under the terms of the collaboration and license agreement, we will pay Acorda tiered royalties based on the level of ex-U.S. net sales. We may pay up to $375.0 million of additional milestone payments to Acorda, based on the successful achievement of certain regulatory and commercial milestones. The next expected milestone would be $15.0 million, due when ex-U.S. net sales reach $100.0 million over a period of four consecutive quarters. We will capitalize these additional milestones as intangible assets upon achievement of the milestone and will be amortized utilizing an economic consumption model. Royalty payments will be recognized as a cost of goods sold.

In connection with the collaboration and license agreement, we have also entered into a supply agreement with Acorda for the commercial supply of FAMPYRA. This agreement is a sublicense arrangement of an existing agreement between Acorda and Elan whereby Elan is responsible for the manufacture of the commercial supply of FAMPYRA. In 2011, Alkermes acquired Elan Drug Technologies, the manufacturing unit of Elan. Alkermes has assumed responsibility for the manufacture and commercial supply of FAMPYRA.

A summary of activity related to this collaboration is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Upfront and milestones payments made to Acorda	$	25.0	$	—	$	110.0
Total expense incurred by Biogen Idec excluding upfront and milestones payments	$	22.3	$	22.8	$	4.7
Total expense reflected within our statements of income	$	22.3	$	22.8	$	114.7
Total capitalized as an intangible asset	$	25.0	$	—	$	—

A summary of activity related to this collaboration since inception, along with an estimate of additional future development expense expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Acorda	$	135.0
Total expense incurred by Biogen Idec, excluding upfront and milestone payments	$	49.9

We expect that we may incur approximately $50.0 million of additional cost associated with meeting the requirements of the conditional marketing authorization.

Portola Pharmaceuticals, Inc.

On October 26, 2011, we entered into an exclusive, worldwide collaboration and license agreement with Portola Pharmaceuticals, Inc. (Portola) under which both companies will develop and commercialize highly selective, novel oral Syk inhibitors for the treatment of various autoimmune and inflammatory diseases, including rheumatoid arthritis and systemic lupus erythematosus. The collaboration’s lead molecule, PRT062607, is currently in Phase 1 studies.

Under the terms of the agreement, we provided Portola with an upfront payment of $36.8 million in cash and purchased $8.2 million in Portola equity, with potential additional payments of up to $508.5 million based on the achievement of certain development and regulatory milestones. We will lead the global development and

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commercialization efforts for the Syk inhibitor program in major indications such as rheumatoid arthritis and lupus, while Portola will lead U.S. development and commercialization efforts for select smaller indications as well as discovery efforts for follow-on Syk inhibitors. Portola retains an option to co-promote alongside us in the U.S. in major indications. Worldwide costs and profits will be split by us and Portola 75% and 25%, respectively.

A summary of collective activity related to these programs is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Total expense incurred by the collaboration	$	1.1	$	—	$	—
Total expense reflected within our consolidated statements of income, excluding upfront and milestone payments	$	0.9	$	—	$	—

A summary of activity related to this collaboration since inception, along with an estimate of additional future development expense expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront payments paid to Portola	$	36.8
Total development expense incurred by Biogen Idec Inc., excluding upfront and milestone payments	$	0.9
Estimate of additional amounts to be incurred by Biogen Idec in development of PRT062607	$	675.0

Swedish Orphan Biovitrum

In January 2007, we acquired 100% of the stock of Syntonix. Syntonix had previously entered into a collaboration agreement with Swedish Orphan Biovitrum (Sobi) to jointly develop and commercialize Factor VIII and Factor IX hemophilia products. In February 2010, we restructured the collaboration agreement and assumed full development responsibilities and costs, as well as manufacturing rights. In addition, the cross-royalty rates were reduced and commercial rights for certain territories were changed. As a result, we now have commercial rights for North America (the Biogen North America Territory) and for rest of the world markets outside of Europe, Russia, Turkey and certain countries in the Middle East (the Biogen Direct Territory). Subject to the exercise of an option right, Sobi will have commercial rights in Europe, Russia, Turkey and certain countries in the Middle East (the Sobi Territory).

Under the terms of the option right, Sobi may, following our submission of a marketing authorization application to the EMA for each product developed under the collaboration, opt to take over final regulatory approval, pre-launch and commercialization activities in the Sobi Territory by making a payment into escrow of $10.0 million per product. Upon EMA regulatory approval of each such product, Sobi will be liable to reimburse us 50% of the sum of all shared manufacturing and development expenses incurred by us from October 1, 2009 through the date on which Sobi is registered as the marketing authorization holder for the applicable product, as well as 100% of certain development expenses incurred exclusively for the benefit of the Sobi Territory (the Opt-In Consideration). To effect Sobi’s reimbursement to us for the Opt-In Consideration exceeding the escrow payment for each product, the cross-royalty structure for direct sales in each company’s respective territories will be adjusted until the Opt-In Consideration is paid in full (the Reimbursement Period). The mechanism for reimbursement is outlined in the table below.

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Under the amended agreement amounts are payable as follows:

			Rates should Sobi exercise its option right(3)
Royalty and Net Revenue Share Rates:	Method	Rate prior to 1st commercial sale in the Sobi Territory:	Base Rate following 1st commercial sale in the Sobi Territory:	Rate during the Reimbursement Period:
Sobi rate to Biogen on net sales in the Sobi Territory	Royalty	N/A	10 to 12%	Base Rate plus 5%
Biogen rate to Sobi on net sales in the Biogen North America Territory	Royalty	2%	10 to 12%	Base Rate less 5%
Biogen rate to Sobi on net sales in the Biogen Direct Territory	Royalty	2%	15 to 17%	Base Rate less 5%
Biogen rate to Sobi on net revenue(1) from the Biogen Distributor Territory(2)	Net Revenue Share	10%	50%	Base Rate less 15%

(1) Net revenue represents Biogen Idec’s pre-tax receipts from third-party distributors, less expenses incurred by Biogen Idec in the conduct of commercialization activities supporting the distributor activities.

(2) The Biogen Distributor Territory represents Biogen territories where sales are derived utilizing a third-party distributor.

(3) A credit will be issued to Sobi against its reimbursement of the Opt-in Consideration in an amount equal to the difference in the rate paid by Biogen Idec to Sobi on sales in the Biogen territories for certain periods prior to the first commercial sale in the Sobi Territory versus the rate that otherwise would have been payable on such sales.

If the reimbursement of the opt-in consideration has not been achieved within six years of the first commercial sale of such product, we maintain the right to require Sobi to pay any remaining balances due to us within 90 days of the six year anniversary date of the first commercial sale.

Should Sobi not exercise its option right with respect to one or both products or should Sobi terminate the agreement with respect to one or both products we will obtain full worldwide development and commercialization rights for such affected products and we will be obligated to pay royalties to Sobi subject to separate terms, as defined under the restructured collaboration agreement. In addition, if EMA approval for any product is not granted within 18 months of the applicable EMA filing date, Sobi shall have the right to require that the escrow payment be refunded and revoke its option right for such product.

Amounts incurred by us in the development of long-lasting recombinant Factor VIII and Factor IX are reflected as research and development expenses in our consolidated statements of income. Prior to the restructuring of our collaboration agreement, our research and development expenses reflected reimbursement from Sobi in accordance with a cost-sharing agreement then in effect. Following the restructuring of our collaboration agreement, amounts incurred by us in the development of long-lasting recombinant Factor VIII and Factor IX are reflected as research and development expenses in our consolidated statements of income which include reimbursement of certain ongoing Sobi development expenses. A summary of collective activity related to these programs is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Total expense incurred by collaboration	$	129.6	$	78.9	$	44.9
Total expense reflected within our consolidated statements of income	$	129.6	$	78.5	$	22.5

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A summary of activity related to this collaboration since inception, along with an estimate of additional future development expense expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront and milestone payments received from Sobi	$	5.0
Total development expense incurred by Biogen Idec Inc., excluding upfront and milestone payments	$	262.7
Estimate of additional amounts expected to be incurred by Biogen Idec in development of Factors VIII and IX	$	420.0

Abbott Biotherapeutics Corp. (formerly Facet Biotech)

We have a collaboration agreement with Abbott Biotherapeutics Corp. (Abbott) aimed at advancing the development and commercialization of daclizumab in MS. Under the agreement, development and commercialization costs and profits are shared equally. In January 2010, we agreed with our collaborator, Abbott, to assume the manufacture of daclizumab.

Based upon our current development plans, we may incur up to an additional $60.0 million of payments upon achievement of development and commercial milestones related to the development of daclizumab.

A summary of activity related to this collaboration is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Total expense incurred by the collaboration	$	104.4	$	74.8	$	40.8
Biogen Idec’s share of expense reflected within our consolidated statements of income	$	52.2	$	37.4	$	20.4

Total expense incurred by the collaboration in 2010, reflects the $30.0 milestone paid to Abbott in May 2010 upon initiation of patient enrollment in a Phase 3 trial of daclizumab in relapsing MS. A summary of activity related to this collaboration since inception, along with an estimate of additional future development expense expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Abbott	$	80.0
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	$	212.1
Estimate of additional amounts to be incurred by us in development of current indications of daclizumab	$	280.0

Vernalis

In April 2011, we agreed to terminate our collaboration with Vernalis plc (Vernalis) for the development and commercialization of an adenosine A2a receptor antagonist for treatment of Parkinson’s disease effective April 11, 2011. Under the terms of the agreement, we have returned the program to Vernalis and have no further license to or continuing involvement in the development of, this compound and its related intellectual property. In exchange, we will receive a royalty on future net sales if this compound is ultimately commercialized. We funded development costs through the termination date and have no other remaining development obligations after that date. Development expense incurred by this collaboration in 2011 was insignificant.

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21.    Litigation

Massachusetts Department of Revenue

On June 8, 2010, we received Notices of Assessment from the DOR against BIMA for $103.5 million of corporate excise tax, including associated interest and penalties, related to our 2004, 2005 and 2006 tax filings. We filed an abatement application with the DOR seeking abatements for 2004, 2005, and 2006. Our abatement application was denied on December 15, 2010 and we filed a petition appealing the denial with the Massachusetts ATB on February 3, 2011. For all periods under dispute, we believe that positions taken in our tax filings are valid and believe that we have meritorious defenses in these disputes. We are contesting these matters vigorously.

Hoechst— Genentech Arbitration

On October 24, 2008, Hoechst GmbH (Hoechst), predecessor to Sanofi-Aventis Deutschland GmbH (Sanofi), filed with the ICC International Court of Arbitration (Paris) a request for arbitration against Genentech, claiming a breach of a license agreement (the Hoechst License) between Hoechst’s predecessor and Genentech that was entered as of January 1, 1991 and terminated by Genentech effective October 27, 2008. The Hoechst License granted Genentech certain rights with respect to later-issued U.S. Patents 5,849,522 (’522 patent) and 6,218,140 (’140 patent) and related patents outside the U.S. The Hoechst License provided for potential royalty payments of 0.5% on net sales of certain products defined by the agreement. Although we are not a party to the arbitration, we expect that any damages that may be awarded to Hoechst may be a cost charged to our collaboration with Genentech.

In June 2011, the arbitrator issued an intermediate decision suggesting that RITUXAN is covered by the Hoechst License and ordering Genentech to provide certain RITUXAN sales information for the period from December 15, 1998 to October 27, 2008. Based on our understanding of the arbitrator’s intermediate decision, in the second quarter of 2011 our share of RITUXAN revenues from unconsolidated joint business was reduced by approximately $50.0 million to reflect our share of the approximately $125.0 million compensatory damages and interest that Genentech estimated might be awarded to Hoechst. Hoechst has since claimed it is due damages of approximately EUR153.0 million for the period from December 15, 1998 to September 30, 2008 as well as additional royalties for later periods in an amount to be determined at a future hearing.

In July 2011, Genentech filed a Declaration of Appeal with the Court of Appeal in Paris to vacate the arbitrator’s intermediate decision. The arbitrator declined to stay further proceedings until the Declaration of Appeal was decided and informed the parties that the underlying issue of liability with respect to RITUXAN under the Hoechst License has not yet been decided. In October 2011, the arbitrator scheduled a hearing on liability and damages for spring 2012, and a decision could follow in late summer 2012. In view of these developments, Genentech did not pursue the Declaration of Appeal.

In light of the arbitrator’s ruling scheduling a hearing on liability and damages, the $50.0 million reduction of our share of RITUXAN revenues from unconsolidated joint business made in the second quarter of 2011 reflects the estimate of the loss that we may incur as a result of a final arbitration award unfavorable to Genentech. The actual amount of our share of any damages may vary from this estimate depending on the nature or amount of any damages awarded to Hoechst, or if any final decision awarding damages is successfully challenged by Genentech.

Sanofi ’522 and ’140 Patent Litigation

On October 27, 2008, Sanofi, successor to Hoechst, filed suit against Genentech and Biogen Idec in federal court in Texas (E.D. Tex.) (Texas Action) claiming that RITUXAN and certain other Genentech products infringe the ’522 patent and the ’140 patent. The patents are due to expire in December 2015. Sanofi seeks

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preliminary and permanent injunctions, compensatory and exemplary damages, and other relief. The same day Genentech and Biogen Idec filed a complaint against Sanofi in federal court in California (N.D. Cal.) (California Action) seeking a declaratory judgment that RITUXAN and other Genentech products do not infringe the ’522 patent or the ’140 patent and a declaratory judgment that those patents are invalid. The Texas Action was ordered transferred to the federal court in the Northern District of California and consolidated with the California Action and we refer to the two actions together as the “Consolidated Sanofi Patent Actions”. Certain damages that may be awarded to Sanofi in the Consolidated Sanofi Patent Actions may be a cost charged to our collaboration with Genentech.

On April 21, 2011, the court entered a separate and final judgment that the manufacture and sale of RITUXAN do not infringe the ’522 patent or the ’140 patent and stayed the trial of the remaining claims, including Biogen Idec’s and Genentech’s invalidity claims. Sanofi has appealed from the court’s non-infringement ruling to the U.S. Court of Appeals for the Federal Circuit and the appeal is scheduled for oral argument in February, 2012. We have not formed an opinion that a decision in favor of Sanofi in its appeal of the non-infringement ruling, or an unfavorable outcome on the now stayed invalidity claims in the Consolidated Sanofi Patent Actions, is either “probable” or “remote.” We believe that we have good and valid defenses and are vigorously defending against Sanofi’s allegations.

In the event that we and Genentech are found liable we estimate that the range of any potential loss could extend to a royalty of up to 0.5% of net sales of RITUXAN, based on, among other things, the royalty rate set forth in the terminated Hoechst License and an analysis of royalty rates charged for comparable technologies. We believe that Sanofi would seek a substantially higher royalty rate, and we will continue to vigorously oppose its claims and position.

We expect any damage award in the Consolidated Sanofi Patent Actions for damages incurred prior to the filing of litigation to be limited to the period running from October 27, 2002 to October 27, 2008 (six years before Sanofi filed the Texas Action). In addition, in the event that Genentech is ordered to pay royalties on RITUXAN sales under the Hoechst License described above, we do not anticipate that we or Genentech would be subject to any damages award in the Consolidated Sanofi Patent Actions for any period as to which Genentech is ordered to pay royalties in the arbitration.

’755 Patent Litigation

On September 15, 2009, we were issued 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. This patent, which expires in September 2026, covers, among other things, the treatment of MS with our product AVONEX. 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 of patent invalidity and non-infringement and seeking monetary relief in the form of attorneys’ fees, costs and expenses. On May 28, 2010, 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 noninfringement, 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

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amended its complaint to seek such a declaration. No trial date has yet been ordered, but we expect that the trial of the Consolidated ’755 Patent Actions will take place in 2013.

On August 16, 2010, BIMA amended its complaint to add Ares Trading S.A. (Ares), an affiliate of EMD Serono, as a defendant, and to seek a declaratory judgment that a purported “nonsuit and option agreement” between Ares and BIMA dated October 12, 2000, that provides Ares an option to obtain a license to the ’755 Patent, is not valid and enforceable. Ares moved to compel arbitration of the claims against it and on February 2, 2012 an arbitration panel ruled that the nonsuit and option agreement and Ares’ option to license the ’755 patent remain in force.

GSK ’612 Patent Litigation

On March 23, 2010, we and Genentech were issued U.S. Patent No. 7,682,612 (’612 Patent) relating to a method of treating CLL using an anti-CD20 antibody. The patent which expires in November 2019 covers, among other things, the treatment of CLL with RITUXAN. On March 23, 2010, we and Genentech filed a lawsuit in federal court in the Southern District of California against Glaxo Group Limited and GlaxoSmithKline LLC (collectively, GSK) alleging infringement of that patent based upon GSK’s manufacture, marketing and sale, offer to sell, and importation of ARZERRA. We seek damages, including a royalty and lost profits, and injunctive relief. GSK has filed a counterclaim seeking a declaratory judgment of patent invalidity, noninfringement, unenforceability, and inequitable conduct, and seeking monetary relief in the form of costs and attorneys’ fees.

In October, 2011, the court entered a claim construction order adverse to certain of Biogen Idec’s and Genentech’s arguments. In order to conserve judicial and party resources, and to allow Biogen Idec and Genentech to file an appeal prior to the full disposition of the case, the parties jointly moved for the entry of separate and final judgment in favor of GSK on Biogen Idec’s and Genentech’s claims, and in favor of GSK on GSK’s counterclaim for non-infringement. The court entered separate and final judgment on November 15, 2011, and stayed all further proceedings pending the outcome on appeal. Biogen Idec and Genentech filed a notice of appeal in the United States Court of Appeals for the Federal Circuit on December 5, 2011, and the appeal is pending.

Novartis V&D ’688 Patent Litigation

On January 26, 2011, Novartis Vaccines and Diagnostics, Inc. (Novartis V&D) filed suit against us in federal district court in Delaware, alleging that TYSABRI infringes U.S. Patent No. 5,688,688 “Vector for Expression of a Polypeptide in a Mammalian Cell” (’688 Patent), which was granted in November 1997 and expires in November 2014. Novartis V&D seeks a declaration of infringement, a finding of willful infringement, compensatory damages, treble damages, interest, costs and attorneys’ fees. We have not formed an opinion that an unfavorable outcome is either “probable” or “remote”, and are unable to estimate the magnitude or range of any potential loss. We believe that we have good and valid defenses to the complaint and will vigorously defend against it. A trial has been set for January 2014.

Italian National Medicines Agency

In the fourth quarter of 2011, Biogen Idec SRL received a notice from the Italian National Medicines Agency (Agenzia Italiana del Farmaco or AIFA) stating that sales of TYSABRI for the period from February 2009 through February 2011 exceeded by Euro 30.7 million a reimbursement limit established pursuant to a Price Determination Resolution (Price Resolution) granted by AIFA in February 2007. The Price Resolution set the initial price for the sale of TYSABRI in Italy and limited the amount of government reimbursement “for the first

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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 such resolutions that are not renegotiated prior to the expiration of their term.

On November 17, 2011, Biogen Idec SRL responded to AIFA that the reimbursement limit in the Price Resolution by its terms relates only to the first 24 months of TYSABRI sales, which began in February 2007. On December 23, 2011, we filed an appeal in the Regional Administrative Tribunal of Lazio (Ecc.mo Tribunale Amministrativo Regionale per il Lazio) in Rome against AIFA, seeking a ruling that our interpretation of the Price Resolution is valid and that the position of the AIFA is unenforceable. We have not formed an opinion that an unfavorable outcome is either “probable” or “remote”. While we believe that we have good and valid grounds for our appeal, an unfavorable outcome could negatively impact our results of operations.

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. In May 2011, the United States notified the court that it was not intervening at that time as to one defendant, and was declining to intervene as to all other defendants, including Biogen Idec; the District of Columbia notified the court that it was not intervening at that time; and the states notified the court that they were declining to intervene as to all defendants. The complaint was subsequently unsealed and served, and then amended. The amended complaint alleges that Biogen Idec and other defendants underreport Average Manufacturer Price information to the Centers for Medicare and Medicaid Services, thereby causing Biogen Idec and 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 or price concessions that they made to drug wholesalers to be discounts under applicable federal law. We and the other defendants filed a motion to dismiss the complaint on December 9, 2011, and the motion is pending. We have not formed an opinion that an unfavorable outcome is either “probable” or “remote,” or as to the magnitude or range of any potential loss. We believe that we have good and valid defenses and intend vigorously to defend against the allegations.

Government Review of Sales and Promotional Practices

Biogen Idec has learned that state and federal governmental authorities are investigating its sales and promotional practices. Biogen Idec has not received any requests for information in connection with this inquiry. We expect to cooperate fully with the government.

Canada Lease Dispute

On April 18, 2008, First Real Properties Limited filed suit against Biogen Idec Canada Inc. (BI Canada) in the Superior Court of Justice in London, Ontario alleging breach of an offer for lease of property signed by BI Canada in 2007 and an unsigned proposed lease for the same property. The plaintiff’s complaint seeks $7.0 million in damages, but the plaintiff recently submitted an expert report estimating the plaintiff’s damages to be $2.5 million after mitigation. The plaintiff also seeks costs of approximately $0.4 million and interest. A trial has been scheduled for March 2012. We have not formed an opinion that an unfavorable outcome is either “probable” or “remote.”

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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.

22.    Commitments and Contingencies

Leases

We rent laboratory and office space and certain equipment under non-cancelable operating leases. These lease agreements contain various clauses for renewal at our option and, in certain cases, escalation clauses typically linked to rates of inflation. Rental expense under these leases, which terminate at various dates through 2028, amounted to $46.2 million in 2011, $44.8 million in 2010 and $36.4 million in 2009. In addition to rent, the leases may require us to pay additional amounts for taxes, insurance, maintenance and other operating expenses.

As of December 31, 2011, minimum rental commitments under non-cancelable leases, net of income from subleases, for each of the next five years and total thereafter were as follows:

(In millions)	2012			2013			2014			2015		2016		Thereafter		Total
Minimum lease payments (1)	$	33.9		$	42.5		$	54.3		$	49.3	$	44.6	$	450.5	$	675.1
Less: income from subleases		(0.5	)		(0.5	)		(0.4	)		—		—		—		(1.4	)
Net minimum lease payments	$	33.4		$	42.0		$	53.9		$	49.3	$	44.6	$	450.5	$	673.7

(1) Includes future minimum rental commitments related to leases executed for two office buildings to be built in Cambridge, Massachusetts with a planned occupancy during the second half of 2013. The leases both have 15 year terms and we have options to extend the term of each lease for two additional five-year terms. Future minimum rental commitments under these leases will total approximately $340.0 million over the initial 15 year lease terms.

Balances also include remaining total minimum lease payments through 2025, totaling approximately $240.0 million, related to our current principal executive offices in Weston, Massachusetts, which we expect to vacate upon completion of the two new buildings in Cambridge Massachusetts.

For additional information related to these transactions, please read Note 11, Property, Plant and Equipment to these consolidated financial statements.

Under certain of our lease agreements, we are contractually obligated to return leased space to its original condition upon termination of the lease agreement. At the inception of a lease with such conditions, we record an asset retirement obligation liability and a corresponding capital asset in an amount equal to the estimated fair value of the obligation. In subsequent periods, for each such lease, we record interest expense to accrete the asset retirement obligation liability to full value and depreciate each capitalized asset retirement obligation asset, both over the term of the associated lease agreement. Our asset retirement obligations were not significant as of December 31, 2011 or 2010.

Tax Related Obligations

We exclude liabilities pertaining to uncertain tax positions from our summary of contractual obligations as we cannot make a reliable estimate of the period of cash settlement with the respective taxing authorities. As of December 31, 2011, we have approximately $58.4 million of liabilities associated with uncertain tax positions.

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Other Funding Commitments

As of December 31, 2011, we have funding commitments of up to approximately $14.5 million as part of our investment in biotechnology oriented venture capital funds.

As of December 31, 2011, we have several ongoing clinical studies in various clinical trial stages. Our most significant clinical trial expenditures are to clinical research organizations (CROs). The contracts with CROs are generally cancellable, with notice, at our option. We have recorded accrued expenses of $25.0 million on our consolidated balance sheet for expenditures incurred by CROs as of December 31, 2011. We have approximately $475.0 million in cancellable future commitments based on existing CRO contracts as of December 31, 2011.

Contingent Milestone Payments

Based on our development plans as of December 31, 2011, we have committed to make potential future milestone payments to third parties of up to approximately $1.9 billion as part of our various collaborations, including licensing and development programs. Payments under these agreements generally become due and payable only upon achievement of certain development, regulatory or commercial milestones. Because the achievement of these milestones had not occurred as of December 31, 2011, such contingencies have not been recorded in our financial statements.

Contingent Consideration

In connection with our purchase of the noncontrolling interests in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH and our acquisitions of Biogen Idec International Neuroscience GmbH, Biogen Idec Hemophilia Inc., and Fumapharm AG, we agreed to make additional payments based upon the achievement of certain milestone events. Amounts related to contingent milestone payments are not considered contractual obligations as they are contingent on the successful achievement of certain development, regulatory approval and commercial milestones. These milestones may not be achieved.

As the acquisitions of the noncontrolling interests in our joint venture investments and our acquisition of Biogen Idec International Neuroscience GmbH occurred after January 1, 2009, we record contingent consideration liabilities at their fair value on the acquisition date and revalue these obligations each reporting period. For additional information related to these transactions please read Note 2, Acquisitions, to these consolidated financial statements.

In connection with our acquisition of Biogen Idec Hemophilia Inc. (BIH), formerly Syntonix Pharmaceuticals, Inc., in January 2007, we agreed to pay up to an additional $80.0 million if certain milestone events associated with the development of BIH’s lead product, long-lasting recombinant Factor IX are achieved. The first $40.0 million contingent payment was achieved in the first quarter of 2010. An additional $20.0 million contingent payment will occur if prior to the tenth anniversary of the closing date, the FDA grants approval of a Biologic License Application for Factor IX. A second $20.0 million contingent payment will occur if prior to the tenth anniversary of the closing date, a marketing authorization is granted by the EMA for Factor IX. For additional information related to these transactions please read Note 2, Acquisitions to these consolidated financial statements.

In 2006, we acquired Fumapharm AG. As part of this acquisition we acquired FUMADERM and BG-12 (together, Fumapharm Products). We paid $220.0 million upon closing of the transaction and will pay an additional $15.0 million if a Fumapharm Product is approved for MS in the U.S. or E.U. We may also make additional milestone payments to Fumapharm AG based on the attainment of certain sales levels of Fumapharm Products, less certain costs as defined in the acquisition agreement. These milestone payments are considered

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contingent consideration and will be accounted for as an increase to goodwill as incurred, in accordance with the accounting standard applicable to business combinations when we acquired Fumapharm.

23.    Guarantees

As of December 31, 2011 and 2010, we did not have significant liabilities recorded for guarantees.

We enter into indemnification provisions under our agreements with other companies in the ordinary course of business, typically with business partners, contractors, clinical sites and customers. Under these provisions, we generally indemnify and hold harmless the indemnified party for losses suffered or incurred by the indemnified party as a result of our activities. These indemnification provisions generally survive termination of the underlying agreement. The maximum potential amount of future payments we could be required to make under these indemnification provisions is unlimited. However, to date we have not incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. As a result, the estimated fair value of these agreements is minimal. Accordingly, we have no liabilities recorded for these agreements as of December 31, 2011 and 2010.

24.    Employee Benefit Plans

We sponsor various retirement and pension plans. Our estimates of liabilities and expenses for these plans incorporate a number of assumptions, including expected rates of return on plan assets and interest rates used to discount future benefits.

401(k) Savings Plan

We maintain a 401(k) Savings Plan which is available to substantially all regular employees in the U.S. over the age of 21. Participants may make voluntary contributions. We make matching contributions according to the 401(k) Savings Plan’s matching formula. Beginning in January 2008, all past and current matching contributions will vest immediately. Previously, the matching contributions vested over four years of service by the employee. Participant contributions vest immediately. The 401(k) Savings Plan also holds certain transition contributions on behalf of participants who previously participated in the Biogen, Inc. Retirement Plan. The expense related to our 401(k) Savings Plan primarily consists of our matching contributions.

Expense related to our 401(k) Savings Plan totaled $24.8 million, $26.3 million and $27.9 million for the years ended December 31, 2011, 2010 and 2009, respectively.

Deferred Compensation Plan

We maintain a non-qualified deferred compensation plan, known as the Supplemental Savings Plan (SSP), which allows a select group of management employees in the U.S. to defer a portion of their compensation. The SSP also provides certain credits to highly compensated U.S. employees, which are paid by the company. These credits are known as the Restoration Match. The deferred compensation amounts are accrued when earned. Such deferred compensation is distributable in cash in accordance with the rules of the SSP. Deferred compensation amounts under such plan as of December 31, 2011 and 2010 totaled approximately $60.1 million and $62.2 million, respectively, and are included in other long-term liabilities within the accompanying consolidated balance sheets. The SSP also holds certain transition contributions on behalf of participants who previously participated in the Biogen, Inc. Retirement Plan. Beginning in 2008, the Restoration Match vests immediately. Previously, the Restoration Match and transition contributions vested over four and seven years of service, respectively, by the employee. Participant contributions vest immediately. Distributions to participants can be either in one lump sum payment or annual installments as elected by the participants.

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Pension Plan

Our retiree benefit plans include defined benefit plans for employees in our affiliates in Switzerland and Germany as well as other insignificant defined benefit plans in certain other countries in which we maintain an operating presence.

Our Swiss plan is a government-mandated retirement fund that provides employees with a minimum investment return. The minimum investment return is determined annually by Swiss government and was 2.0% in 2011, 2010 and 2009, respectively. Under this plan, both we and certain of our employees with annual earnings in excess of government determined amounts are required to make contributions into a fund managed by an independent investment fiduciary. Employer contributions must be in an amount at least equal to the employee’s contribution. Minimum employee contributions are based on the respective employee’s age, salary, and gender. As of December 31, 2011, the Plan had an unfunded net pension obligation of approximately $10.0 million and plan assets which totaled approximately $20.1 million. In 2011, 2010 and 2009, we recognized expense totaling $3.6 million, $3.0 million and $2.4 million, respectively, related to our Swiss plan.

The obligations under the German plan are unfunded and totaled $8.6 million and $8.2 million as of December 31, 2011 and 2010, respectively. Net periodic pension cost related to the German plan totaled $1.8 million, $1.1 million and $1.1 million for the years ended December 31, 2011, 2010 and 2009, respectively.

25.    Segment Information

We operate as one business segment, which is the business of discovering, developing, manufacturing and marketing therapies for the treatment of neurodegenerative diseases, hemophilia and autoimmune disorders and therefore, our chief operating decision-maker manages the operations of our Company as a single operating segment. Enterprise-wide disclosures about product revenues, other revenues and long-lived assets by geographic area and information relating to major customers are presented below. Revenues are primarily attributed to individual countries based on location of the customer or licensee.

Revenue by product is summarized as follows:

	For the Years Ended December 31,
	2011						2010						2009
(In millions)	United States		Rest of World		Total		United States		Rest of World		Total		United States		Rest of World		Total
AVONEX	$	1,628.3	$	1,058.3	$	2,686.6	$	1,491.6	$	1,026.8	$	2,518.4	$	1,406.2	$	916.7	$	2,322.9
TYSABRI		326.5		753.0		1,079.5		252.8		647.4		900.2		231.8		544.2		776.0
Other		—		70.0		70.0		—		51.5		51.5		—		54.0		54.0
Total product revenues	$	1,954.8	$	1,881.3	$	3,836.1	$	1,744.4	$	1,725.7	$	3,470.1	$	1,638.0	$	1,514.9	$	3,152.9

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Geographic Information

The following tables contain certain financial information by geographic area:

December 31, 2011 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,954.8	$	1,163.3	$	377.5	$	88.7	$	251.8	$	3,836.1
Revenues from unconsolidated joint business	$	878.8	$	29.9	$	—	$	30.7	$	57.2	$	996.6
Other revenues from external customers	$	187.0	$	28.3	$	0.6	$	—	$	—	$	215.9
Long-lived assets	$	1,012.5	$	816.6	$	1.6	$	5.3	$	2.4	$	1,838.4
December 31, 2010 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,744.4	$	1,090.7	$	362.4	$	69.0	$	203.6	$	3,470.1
Revenues from unconsolidated joint business	$	906.3	$	95.3	$	—	$	26.0	$	49.6	$	1,077.2
Other revenues from external customers	$	136.0	$	32.6	$	0.5	$	—	$	—	$	169.1
Long-lived assets	$	1,100.3	$	717.4	$	1.5	$	5.4	$	1.6	$	1,826.2
December 31, 2009 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,638.0	$	913.7	$	374.8	$	47.9	$	178.5	$	3,152.9
Revenues from unconsolidated joint business	$	839.2	$	190.2	$	—	$	24.1	$	41.4	$	1,094.9
Other revenues from external customers	$	102.8	$	26.2	$	0.5	$	—	$	—	$	129.5
Long-lived assets	$	1,092.7	$	705.6	$	1.4	$	3.6	$	2.1	$	1,805.4

(1) Represents amounts related to Europe less those attributable to Germany.

Revenues from Unconsolidated Joint Business

Approximately 20%, 23% and 25% of our total revenues in 2011, 2010 and 2009, respectively, are derived from our joint business arrangement with Genentech. For additional information related to our collaboration with Genentech, please read Note 20, Collaborations to these consolidated financial statements.

Significant Customers

We recorded revenue from two wholesale distributors accounting for 18% and 10% of gross product revenues in 2011, 18% and 11% of gross product revenue in 2010, and 18% and 12% of gross product revenues in 2009.

Other

As of December 31, 2011, 2010 and 2009, approximately $668.5 million, $644.7 million and $665.8 million, respectively, of our long-lived assets were related to our manufacturing facilities in Denmark.

F-74

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

26.    Quarterly Financial Data (Unaudited)

(In millions, except per share amounts)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total Year
2011			(a)				(b)
Product revenues	$	907.1	$	956.7	$	975.8	$	996.6	$	3,836.1
Unconsolidated joint business revenues	$	256.1	$	216.5	$	266.5	$	257.5	$	996.6
Other revenues	$	40.1	$	35.5	$	67.7	$	72.6	$	215.9
Total revenues	$	1,203.3	$	1,208.6	$	1,309.9	$	1,326.7	$	5,048.6
Gross Profit	$	1,100.2	$	1,108.1	$	1,186.4	$	1,187.1	$	4,581.9
Net income	$	308.8	$	304.0	$	353.7	$	300.2	$	1,266.7
Net income attributable to Biogen Idec Inc.	$	294.3	$	288.0	$	351.8	$	300.2	$	1,234.4
Basic earnings per share attributable to Biogen Idec Inc.	$	1.22	$	1.19	$	1.45	$	1.24	$	5.09
Diluted earnings per share attributable to Biogen Idec Inc.	$	1.20	$	1.18	$	1.43	$	1.22	$	5.04

(In millions, except per share amounts)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total Year
2010	(c)				(d)		(e)
Product revenues	$	824.2	$	859.2	$	876.9	$	909.8	$	3,470.1
Unconsolidated joint business revenues	$	254.9	$	306.4	$	258.0	$	258.0	$	1,077.3
Other revenues	$	29.7	$	47.1	$	41.0	$	51.4	$	169.1
Total revenues	$	1,108.9	$	1,212.7	$	1,175.8	$	1,219.0	$	4,716.4
Gross Profit	$	1,011.8	$	1,105.7	$	1,079.9	$	1,118.8	$	4,316.2
Net income	$	220.0	$	294.6	$	112.2	$	271.8	$	898.6
Net income attributable to Biogen Idec Inc.	$	217.4	$	293.4	$	254.1	$	240.3	$	1,005.3
Basic earnings per share attributable to Biogen Idec Inc	$	0.80	$	1.13	$	1.06	$	1.00	$	3.98
Diluted earnings per share attributable to Biogen Idec Inc	$	0.80	$	1.12	$	1.05	$	0.99	$	3.94

Full year amounts may not sum due to rounding.

(a) Our share of RITUXAN revenues from unconsolidated joint business was reduced by approximately $50.0 million in the second quarter of 2011 as a result of an accrual for estimated compensatory damages (including interest) relating to Genentech’s ongoing arbitration with Hoechst GmbH. For additional information related to this matter, please read Note 21, Litigation to these consolidated financial statements.

(b) Net income and net income attributable to Biogen Idec Inc. for the fourth quarter of 2011 includes a charge to research and development expense of $36.8 million related to an upfront payment made in connection with our collaboration and license agreement entered into with Portola Pharmaceuticals, Inc.

(c) Net income and net income attributable to Biogen Idec Inc. for the first quarter of 2010 includes a charge to acquired IPR&D of $40.0 million related to the achievement of a milestone by Biogen Idec Hemophilia, Inc. (formerly Syntonix Pharmaceuticals, Inc.).

(d) Net income and net income attributable to Biogen Idec Inc. for the third quarter of 2010 includes a charge to acquired IPR&D of $205.0 million incurred in connection with the license agreement entered into with Knopp Neurosciences Inc. (Knopp), which we consolidated as we determined that we are the primary beneficiary of the entity. The $205.0 million charge was partially offset by an attribution of $145.0 million to the noncontrolling interest.

(e) Net income and net income attributable to Biogen Idec Inc. for the fourth quarter of 2010 includes charges totaling $75.2 million related to our restructuring plan announced November 3, 2010.

F-75

BIOGEN IDEC INC. AND SUBSIDIARIES

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS — (Continued)

27.    Subsequent Events

Isis Pharmaceuticals, Inc.

On January 4, 2012, we entered into an exclusive, worldwide option and development agreement with Isis Pharmaceuticals, Inc. (Isis) under which both companies will develop and commercialize Isis’ antisense investigational drug, ISIS-SMN_Rx, for the treatment of spinal muscular atrophy (SMA).

Under the terms of the agreement, Isis received an upfront payment of $29.0 million and is eligible to receive up to $45.0 million in milestone payments associated with the clinical development of ISIS-SMN_Rx prior to licensing. Biogen Idec has the option to license ISIS-SMN_Rx until completion of the first successful Phase 2/3 trial. Isis could receive up to another $225.0 million in a license fee and regulatory milestone payments. Isis will be responsible for global development of ISIS-SMN_Rx through the completion of Phase 2/3 trials and we will provide advice on the clinical trial design and regulatory strategy. If we exercise our option, we will assume global development, regulatory and commercialization responsibilities.

F-76

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Board of Directors and Shareholders of Biogen Idec Inc.

In our opinion, the accompanying consolidated balance sheets and the related consolidated statements of income, equity and cash flows present fairly, in all material respects, the financial position of Biogen Idec Inc. and its subsidiaries at December 31, 2011 and 2010, and the results of their operations and their cash flows for each of the three years in the period ended December 31, 2011 in conformity with accounting principles generally accepted in the United States of America. Also in our opinion, the Company maintained, in all material respects, effective internal control over financial reporting as of December 31, 2011, based on criteria established in Internal Control — Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (COSO). The Company’s management is responsible for these financial statements, for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting, included in Management’s Annual Report on Internal Control over Financial Reporting. Our responsibility is to express opinions on these financial statements and on the Company’s internal control over financial reporting based on our integrated audits. We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement and whether effective internal control over financial reporting was maintained in all material respects. Our audits of the financial statements included examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. Our audit of internal control over financial reporting included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, and testing and evaluating the design and operating effectiveness of internal control based on the assessed risk. Our audits also included performing such other procedures as we considered necessary in the circumstances. We believe that our audits provide a reasonable basis for our opinions.

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (i) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (ii) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (iii) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

February 3, 2012

F-77

EXHIBIT INDEX

Exhibit No.	Description
3.1	Amended and Restated Certificate of Incorporation, as amended. Filed as Exhibit 3.1 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2011.
3.2	Second Amended and Restated Bylaws, as amended. Filed as Exhibit 3.2 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2011.
4.1	Reference is made to Exhibit 3.1 for a description of the rights, preferences and privileges of our Series A Preferred Stock and Series X Junior Participating Preferred Stock.
4.2	Indenture between Biogen Idec and The Bank of New York Trust Company, N.A. dated as of February 26, 2008. Filed as Exhibit 4.1 to our Registration Statement on Form S-3 (File No. 333-149379).
4.3	First Supplemental Indenture between Biogen Idec and The Bank of New York Trust Company, N.A. dated as of March 4, 2008. Filed as Exhibit 4.1 to our Current Report on Form 8-K filed on March 4, 2008.
10.1	Credit Agreement among Biogen Idec, Bank of America, N.A. as administrative agent, Merrill Lynch, Pierce, Fenner & Smith Incorporated and Goldman Sachs Credit Partners L.P. as co-syndication agents, and the other lenders party thereto dated June 29, 2007. Filed as Exhibit 99.2 to our Current Report on Form 8-K filed on July 2, 2007.
10.2	Amendment No. 1 to Credit Agreement among Biogen Idec, Bank of America, N.A. as administrative agent, and the other lenders party thereto dated as of March 5, 2009. Filed as Exhibit 10.1 to our Quarterly Report on Form 10-Q for the quarter ended March 31, 2009.
10.3†	Expression Technology Agreement between Biogen Idec and Genentech. Inc. dated March 16, 1995. Filed as an exhibit to Biogen Idec’s Quarterly Report on Form 10-Q for the quarter ended March 31, 1995.
10.4	Letter Agreement between Biogen Idec and Genentech, Inc. dated May 21, 1996. Filed as Exhibit 10.1 to our Current Report on Form 8-K filed on June 6, 1996.
10.5†	Second Amended and Restated Collaboration Agreement between Biogen Idec and Genentech, Inc. dated as of October 18, 2010. Filed as Exhibit 10.5 to our Annual Report on Form 10-K for the year ended December 31, 2010.
10.6†	Letter agreement regarding GA101 financial terms between Biogen Idec and Genentech, Inc. dated October 18, 2010. Filed as Exhibit 10.6 to our Annual Report on Form 10-K for the year ended December 31, 2010.
10.7†	ANTEGREN (now TYSABRI) Development and Marketing Collaboration Agreement between Biogen Idec and Elan Pharma International Limited dated August 15, 2000. Filed as Exhibit 10.48 to Biogen, Inc.’s Annual Report on Form 10-K for the year ended December 31, 2002 (File No. 0-12042) and incorporated herein by reference.
10.8*	Biogen Idec Inc. 2008 Omnibus Equity Plan. Filed as Appendix A to our Definitive Proxy Statement on Schedule 14A filed on May 8, 2008.
10.9*	Amendment to Biogen Idec Inc. 2008 Omnibus Equity Plan dated October 13, 2008. Filed as Exhibit 10.19 to our Annual Report on Form 10-K for the year ended December 31, 2008.
10.10*	Form of restricted stock unit award agreement under the Biogen Idec Inc. 2008 Omnibus Equity Plan. Filed as Exhibit 10.1 to our Current Report on Form 8-K filed on August 1, 2008.
10.11*	Form of nonqualified stock option award agreement under the Biogen Idec Inc. 2008 Omnibus Equity Plan. Filed as Exhibit 10.2 to our Current Report on Form 8-K filed on August 1, 2008.
10.12*	Form of cash-settled performance shares award agreement under the Biogen Idec Inc. 2008 Omnibus Equity Plan. Filed as Exhibit 10.1 to our Quarterly Report on Form 10-Q for the quarter ended March 31, 2010.

A-1

Exhibit No.	Description
10.13*	Form of market stock unit award agreement under the Biogen Idec Inc. 2008 Omnibus Equity Plan. Filed as Exhibit 10.2 to our Quarterly Report on Form 10-Q for the quarter ended March 31, 2010.
10.14*	Biogen Idec Inc. 2006 Non-Employee Directors Equity Plan, as amended. Filed as Appendix A to our Definitive Proxy Statement on Schedule 14A filed on April 28, 2010.
10.15*	Amendment to Biogen Idec Inc. 2006 Non-Employee Directors Equity Plan dated June 1, 2011. Filed as Exhibit 10.4 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2011.
10.16*	Biogen Idec Inc. 2005 Omnibus Equity Plan. Filed as Appendix A to our Definitive Proxy Statement on Schedule 14A filed on April 15, 2005.
10.17*	Amendment No. 1 to the Biogen Idec Inc. 2005 Omnibus Equity Plan dated April 4, 2006. Filed as Exhibit 10.1 to our Quarterly Report on Form 10-Q for the quarter ended March 31, 2007.
10.18*	Amendment No. 2 to the Biogen Idec Inc. 2005 Omnibus Equity Plan dated February 12, 2007. Filed as Exhibit 10.2 to our Quarterly Report on Form 10-Q for the quarter ended March 31, 2007.
10.19*	Amendment to the Biogen Idec Inc. 2005 Omnibus Equity Plan dated April 18, 2008. Filed as Exhibit 10.7 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2008.
10.20*	Amendment to Biogen Idec Inc. 2005 Omnibus Equity Plan dated October 13, 2008. Filed as Exhibit 10.30 to our Annual Report on Form 10-K for the year ended December 31, 2008.
10.21*	Biogen Idec Inc. 2003 Omnibus Equity Plan. Filed as Exhibit 10.73 to our Current Report on Form 8-K filed on November 12, 2003.
10.22*	Amendment to Biogen Idec Inc. 2003 Omnibus Equity Plan. Filed as Exhibit 10.1 to our Quarterly Report on Form 10-Q for the quarter ended March 31, 2005.
10.23*	Amendment to Biogen Idec Inc. 2003 Omnibus Equity Plan dated April 18, 2008. Filed as Exhibit 10.6 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2008.
10.24*	Amendment to Biogen Idec Inc. 2003 Omnibus Equity Plan dated October 13, 2008. Filed as Exhibit 10.34 to our Annual Report on Form 10-K for the year ended December 31, 2008.
10.25*	Biogen Idec Inc. 1995 Employee Stock Purchase Plan as amended and restated effective April 6, 2005. Filed as Appendix B to our Definitive Proxy Statement on Schedule 14A filed on April 15, 2005.
10.26*	IDEC Pharmaceuticals Corporation 1993 Non-Employee Directors Stock Option Plan, as amended and restated through February 19, 2003. Filed as Appendix B to our Definitive Proxy Statement on Schedule 14A filed on April 11, 2003.
10.27*	Amendment to IDEC Pharmaceuticals Corporation 1993 Non-Employee Directors Stock Option Plan dated April 18, 2008. Filed as Exhibit 10.5 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2008.
10.28*	Amendment to IDEC Pharmaceuticals Corporation 1993 Non-Employee Directors Stock Option Plan dated June 1, 2011. Filed as Exhibit 10.3 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2011.
10.29*	IDEC Pharmaceuticals Corporation 1988 Stock Option Plan, as amended and restated through February 19, 2003. Filed as Appendix A to our Definitive Proxy Statement on Schedule 14A filed on April 11, 2003.
10.30*	Amendment to the IDEC Pharmaceuticals Corporation 1988 Stock Option Plan dated April 16, 2004. Filed as Exhibit 10.1 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2004.
10.31*	Amendment to IDEC Pharmaceuticals Corporation 1988 Stock Option Plan dated April 18, 2008. Filed as Exhibit 10.4 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2008.
10.32*	Biogen, Inc. 1987 Scientific Board Stock Option Plan (as amended and restated through February 7, 2003). Filed as Exhibit 10.22 to Biogen, Inc.’s Annual Report on Form 10-K for the year ended December 31, 2002 (File No. 0-12042) and incorporated herein by reference.

A-2

Exhibit No.	Description
10.33*	Amendment to Biogen, Inc. 1987 Scientific Board Stock Option Plan dated April 18, 2008. Filed as Exhibit 10.3 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2008.
10.34*	Biogen, Inc. 1985 Non-Qualified Stock Option Plan, as amended and restated through April 11, 2003. Filed as Exhibit 10.22 to our Annual Report on Form 10-K for the year ended December 31, 2007.
10.35*	Amendment to Biogen, Inc. 1985 Non-Qualified Stock Option Plan dated April 18, 2008. Filed as Exhibit 10.2 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2008.
10.36*	Amendment to Biogen, Inc. 1985 Non-Qualified Stock Option Plan dated October 13, 2008. Filed as Exhibit 10.45 to our Annual Report on Form 10-K for the year ended December 31, 2008.
10.37*	Biogen Idec Inc. 2008 Performance-Based Management Incentive Plan. Filed as Appendix B to Biogen Idec’s Definitive Proxy Statement on Schedule 14A filed on May 8, 2008.
10.38*	Voluntary Executive Supplemental Savings Plan, as amended and restated effective January 1, 2004. Filed as Exhibit 10.13 to our Annual Report on Form 10-K for the year ended December 31, 2003.
10.39*+	Supplemental Savings Plan, as amended and restated effective January 1, 2012.
10.40*+	Voluntary Board of Directors Savings Plan, as amended and restated effective January 1, 2012.
10.41*	Biogen Idec Inc. Executive Severance Policy — U.S. Executive Vice President, as amended effective October 13, 2008. Filed as Exhibit 10.51 to our Annual Report on Form 10-K for the year ended December 31, 2008.
10.42*	Biogen Idec Inc. Executive Severance Policy — International Executive Vice President, as amended effective October 13, 2008. Filed as Exhibit 10.52 to our Annual Report on Form 10-K for the year ended December 31, 2008.
10.43*	Biogen Idec Inc. Executive Severance Policy — U.S. Senior Vice President, as amended effective October 13, 2008. Filed as Exhibit 10.53 to our Annual Report on Form 10-K for the year ended December 31, 2008.
10.44*	Biogen Idec Inc. Executive Severance Policy — International Senior Vice President, as amended effective October 13, 2008. Filed as Exhibit 10.54 to our Annual Report on Form 10-K for the year ended December 31, 2008.
10.45*	Annual Retainer Summary for Board of Directors. Filed as Exhibit 10.2 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2011.
10.46*	Form of indemnification agreement for directors and executive officers. Filed as Exhibit 10.1 to our Current Report on Form 8-K filed on June 7, 2011.
10.47*	Employment Agreement between Biogen Idec and George A. Scangos dated as of June 28, 2010. Filed as Exhibit 10.1 to our Current Report on Form 8-K filed on July 1, 2010.
10.48*	Employment Agreement between Biogen Idec and James C Mullen dated as of June 20, 2003. Filed as Exhibit 10.2 to our Registration Statement on Form S-4 (File No. 333-107098).
10.49*	First Amendment to Employment Agreement between Biogen Idec and James C. Mullen dated February 7, 2006. Filed as Exhibit 10.1 to our Current Report on Form 8-K filed on February 10, 2006.
10.50*	Second Amendment to Employment Agreement between Biogen Idec and James C. Mullen dated as of December 4, 2008. Filed as Exhibit 10.59 to our Annual Report on Form 10-K for the year ended December 31, 2008.
10.51*	Transition Agreement between Biogen Idec and James C. Mullen dated as of January 4, 2010. Filed as Exhibit 10.50 to our Annual Report on Form 10-K for the year ended December 31, 2009.
10.52*	Letter regarding employment arrangement of Paul J. Clancy dated August 17, 2007. Filed as Exhibit 10.49 to our Annual Report on Form 10-K for the year ended December 31, 2007.

A-3

Exhibit No.	Description
10.53*	Letter regarding employment arrangement of Francesco Granata dated January 6, 2010. Filed as Exhibit 10.55 to our Annual Report on Form 10-K for the year ended December 31, 2010.
10.54*	Amendment to letter regarding employment arrangement of Francesco Granata. Filed as Exhibit 10.1 to our Quarterly Report on Form 10-Q for the quarter ended June 30, 2011.
10.55*	Severance Plan for EVP, Global Commercial Operations (Francesco Granata). Filed as Exhibit 10.1 to our Quarterly Report on Form 10-Q for the quarter ended March 31, 2011.
10.56*	Separation Agreement between Biogen Idec and Francesco Granata dated September 29, 2011. Filed as Exhibit 10.1 to our Quarterly Report on Form 10-Q for the quarter ended September 30, 2011.
10.57*+	Letter regarding employment arrangement of Douglas E. Williams dated December 7, 2010.
10.58*+	Letter regarding employment arrangement of Steven H. Holtzman dated November 19, 2010.
21+	Subsidiaries.
23+	Consent of PricewaterhouseCoopers LLP, an Independent Registered Public Accounting Firm.
31.1+	Certification of the Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.
31.2+	Certification of the Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.
32.1++	Certification of the Chief Executive Officer and the Chief Financial Officer pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.
101++	The following materials from Biogen Idec Inc.’s Annual Report on Form 10-K for the year ended December 31, 2011, formatted in XBRL (Extensible Business Reporting Language): (i) the Consolidated Statements of Income, (ii) the Consolidated Balance Sheets, (iii) the Consolidated Statements of Cash Flows, (iv) the Consolidated Statement of Equity and (v) Notes to Consolidated Financial Statements.

  ^ References to “our” filings mean filings made by Biogen Idec Inc. and filings made by IDEC Pharmaceuticals Corporation prior to the merger with Biogen, Inc. Unless otherwise indicated, exhibits were previously filed with the Securities and Exchange Commission under Commission File Number 0-19311 and are incorporated herein by reference.

  * Management contract or compensatory plan or arrangement.

  † Confidential treatment has been granted or requested with respect to portions of this exhibit.

  + Filed herewith.

  ++ Furnished herewith.

A-4

EX-10.39

Exhibit 10.39

BIOGEN IDEC INC.

SUPPLEMENTAL SAVINGS PLAN

(Plan Provisions as in Effect on January 1, 2012)

TABLE OF CONTENTS

		Page
ARTICLE 1	INTRODUCTION		1
1.1	Purpose and Effective Date		1
ARTICLE 2	DEFINITIONS		1
2.1	401(k) restoration		1
2.2	Applicable compensation		1
2.3	Base salary		1
2.4	Biogen Idec		1
2.5	Biogen SERP		1
2.6	Board		1
2.7	Change in Control		1
2.8	Code		2
2.9	Committee		2
2.10	Compensation Committee		2
2.11	Disability		2
2.12	Employee		2
2.13	Employer		2
2.14	ERISA		2
2.15	Excess applicable compensation		2
2.16	Non-recurring bonus amounts		2
2.17	Participant		3
2.18	Plan		3
2.19	Plan year		3
2.20	Prior plan		3
2.21	Recurring bonus amounts		3
2.22	Savings Plan		3
2.23	Service		3
2.24	Transition credit		3
2.25	Voluntary deferred compensation		3
2.26	Years of service		3
ARTICLE 3	PARTICIPATION		3
3.1	Eligibility and Participation		3
3.2	End of Participation		4
ARTICLE 4	VOLUNTARY DEFERRALS BY PARTICIPANTS; EMPLOYER CREDITS		5
4.1	401(k) Restoration		5
4.2	Voluntary Deferrals		5
4.3	Transition Credit		5
4.4	Election Procedures		5
ARTICLE 5	PARTICIPANT ACCOUNTS		8
5.1	Participant Accounts		8
5.2	Participant’s Account Value		9
5.3	Vesting		10
ARTICLE 6	DISTRIBUTIONS TO PARTICIPANT		11
6.1	Distributions for Unforeseeable Emergency		11
6.2	Distributions Upon Change in Control		12
6.3	In-Service Distribution(s) at a Time Specified by Participant		12
6.4	Distribution upon Death of a Participant		12
6.5	Distribution upon Participants Termination of Employment		13
6.6	Installment Distributions in Certain Cases		13

6.7	Certain Other Distributions	14
6.8	Delay in Distributions	14
6.9	Compliance with Code Section 409A	14
ARTICLE 7	MISCELLANEOUS	15
7.1	Amendment or Termination of Plan	15
7.2	Benefits Not Currently Funded	15
7.3	No Assignment	16
7.4	Effect of Change in Control	16
7.5	Responsibilities and Authority of Committee	16
7.6	Limitation on Rights Created by Plan	17
7.7	Tax Withholding	17
7.8	Text Controls	17
7.9	Applicable State Law	17
7.10	Paperless Administration	17
	APPENDIX A	A-1
	APPENDIX B	B-1

ARTICLE 1

INTRODUCTION

1.1 Purpose and Effective Date. The purpose of this plan is to provide certain key executives and managers of Biogen Idec (or its subsidiaries) with additional tax-deferred savings opportunities supplementing those available under the Savings Plan. This plan allows certain eligible participants to make voluntary deferrals from base salary or recurring and/or non-recurring bonus amounts, if elected by a participant in accordance with the terms of the plan. In addition, certain participants whose compensation exceeds the Code Section 401(a)(17) limit applicable to the Savings Plan will receive an employer 401(k) restoration credit in accordance with Section 4.1, and certain participants received transition credits in accordance with Section 4.3.

This plan also contains certain account balances or benefits previously maintained under the amended and restated IDEC Pharmaceuticals Corporation Deferred Compensation Plan, the Biogen, Inc. Voluntary Executive Supplemental Savings Plan, and the Biogen, Inc. Supplemental Executive Retirement Plan.

The plan was amended and restated effective January 1, 2005 to comply with Code Section 409A and restated again effective February 1, 2008, October 1, 2008 and January 1, 2010. This amended and restated plan document is effective as of January 1, 2012 to expand the tax-deferred savings opportunities by allowing eligible participants to defer certain equity based awards granted under the Biogen Idec Inc. 2008 Omnibus Equity Plan (or successor long term incentive plan) whereby such awards are considered non-recurring bonus amounts hereunder. Certain historical information about the plan and any amendments thereto is set forth in Appendix A.

ARTICLE 2

DEFINITIONS

This section contains definitions of certain terms used in the plan. Where the context so requires, the masculine includes the feminine, the singular includes the plural, and the plural includes the singular.

2.1 401(k) restoration means that component of the plan under which an eligible participant’s account will receive an employer 401(k) restoration credit under Section 4.1 with respect to applicable compensation in excess of the limit imposed by Section 401(a)(17) of the Code.

2.2 Applicable compensation shall have the same meaning as in the Savings Plan except that applicable compensation under this plan shall also include voluntary deferrals made under Section 4.2 in addition to other salary reductions included in applicable compensation under the Savings Plan.

2.3 Base salary means the base salary established for any participant by his employer as in effect from time to time; the entire amount of a participant's base salary will be taken into account in accordance with the terms of this plan without regard to any dollar limitation on applicable compensation that may be imposed under the Savings Plan; base salary includes all components of a participant’s applicable compensation other than recurring and non-recurring bonus amounts.

2.4 Biogen Idec means Biogen Idec Inc., a Delaware corporation, or any successor to it or to all or the major portion of its assets or business which assumes the obligations of Biogen Idec Inc. under this plan.

2.5 Biogen SERP means the Biogen, Inc. Supplemental Executive Retirement Plan, as in effect immediately prior to January 1, 2004 (or other date of transfer referred to in Section 3.1(c)).

2.6 Board means the Board of Directors of Biogen Idec.

2.7 Change in Control

(a) For purposes of Section 5.3(f) and Section 7.4, a change in control means a “Corporate Change in Control” or a “Corporate Transaction” as each is defined in the Biogen Idec Inc. 2008 Omnibus Equity Plan.

1

(b) For purposes of Section 4.4(b) and Section 6.2, a change in control means (i) the acquisition by a person or group of stock of Biogen Idec that, together with stock previously held by such person or group, constitutes more than 50 percent of the total fair market value or total voting power of the stock of Biogen Idec; (ii) a change in the effective control of Biogen Idec resulting from either the acquisition by any person or group during a 12-month period of stock of Biogen Idec possessing 30 percent or more of the total voting power of Biogen Idec stock; or the replacement of a majority of the members of the Board during any 12-month period by directors whose appointment or election was not endorsed by a majority of the members of the Board in office immediately before the start of such 12-month period; or (iii) the acquisition by any person or group (during any 12-month period) of assets having a gross fair market value equal to or greater than 40 percent of the total gross fair market value of all assets of Biogen Idec. This subsection (b) and terms used herein will be interpreted in accordance with the regulations under Code Section 409A relating to a change in the ownership or effective control of a corporation or a change in the ownership of a substantial portion of the assets of a corporation.

This subsection 2.8(b) is effective as of the date of execution of this amended and restated plan document.

2.8 Code means the Internal Revenue Code of 1986, as amended, or any successor statute enacted in its place. Reference to any provision of the Code includes reference to any successor provision thereto.

2.9 Committee means the Retirement Committee, or such other committee designated by the Board to administer this Plan.

2.10 Compensation Committee means the Compensation and Management Development Committee of the Board (or any successor committee, however named, carrying out its functions).

2.11 Disability means “disability” as defined under the long-term disability program of Biogen Idec or another employer covering a participant, or, if no such program is in effect with respect to such participant, then “disability” means “total and permanent disability” as defined in Code Section 22(e)(3).

2.12 Employee means a person who is classified as a regular, common law employee of Biogen Idec (or other employer) under the regular personnel classifications and practices of his employer. An individual will not be considered an employee for purposes of this plan if the individual is classified as a consultant or contractor under Biogen Idec’s (or other employer’s) regular personnel classifications and practices or he is a party to an agreement to provide services to Biogen Idec (or other employer) without participating in this plan, notwithstanding that such individual may be treated as a common law employee for payroll tax or other legal purposes.

2.13 Employer means Biogen Idec and each direct or indirect subsidiary or other affiliate of Biogen Idec that employs persons who are or may be eligible to participate in this plan.

2.14 ERISA means the Employee Retirement Income Security Act of 1974, as amended, or any successor statute enacted in its place. Reference to any provision of ERISA includes reference to any successor provision thereto.

2.15 Excess applicable compensation means, for any plan year, the amount of a participant's applicable compensation in excess of the limit under Section 401(a)(17) of the Code applicable to such year and which therefore could not be considered under the Savings Plan, plus, if applicable, the amount by which a participant’s applicable compensation is reduced below such Code Section 401(a)(17) limit by reason of an election to reduce base salary or recurring and/or non-recurring bonus amounts under Section 4.2.

2.16 Non-recurring bonus amounts means any portion(s) of a participant’s compensation which constitutes a bonus payable in cash (including any equity-based compensation awards that are settled in cash) other than a recurring bonus amount. Effective January 1, 2012, non-recurring bonus amounts shall also include any restricted stock units, market stock units, or other equity based awards that may be granted under the Biogen Idec Inc. 2008 Omnibus Equity Plan (or successor long term incentive plan) on and after such date. Any component of a participant’s compensation which is a non-recurring bonus amount will be designated as such by the committee. The entire amount of any such non-recurring bonus amount will be taken into account in accordance with the terms of this plan without regard to any dollar limitation on applicable compensation that may be imposed under the Savings Plan.

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2.17 Participant means an employee of Biogen Idec (or other employer) who is eligible to participate in this plan in accordance with Section 3.1 and who has an account described in Section 5.1 or for whom an amount has been transferred to this plan from a prior plan or from the Biogen SERP.

2.18 Plan means the Biogen Idec Inc. Supplemental Savings Plan, as set forth in this plan instrument, and as it may be amended from time to time.

2.19 Plan year means the 12-month periods commencing on January 1, 2005 and on each subsequent January 1 while the plan remains in effect.

2.20 Prior plan means the amended and restated IDEC Pharmaceuticals Corporation Deferred Compensation Plan and the Biogen, Inc. Voluntary Executive Supplemental Savings Plan, each as in effect immediately prior to January 1, 2004 (or other date of transfer referred to in Section 3.1(c)).

2.21 Recurring bonus amounts means any portion(s) of a participant’s compensation which is (i) not base salary, (ii) is payable in cash (excluding any equity-based compensation awards that are settled in cash), and (iii) is a recurring and/or predictable component of the participant’s compensation for a calendar year such that the participant will know before the start of such calendar year that he is or may be eligible to receive such bonus if the criteria applicable to such bonus are satisfied (in full or in part). Recurring bonus amounts include (but are not limited to) a participant’s annual bonus, sales incentive compensation plan bonuses (if applicable to a participant), and similar bonuses (if any) but does not include any long term incentive award payments. The entire amount of any such recurring bonus amount will be taken into account in accordance with the terms of this plan without regard to any dollar limitation on applicable compensation that may be imposed under the Savings Plan.

2.22 Savings Plan means the Biogen Idec 401(k) Savings Plan, as amended from time to time. Any term defined in the Savings Plan will have the same meaning when used in this plan unless otherwise defined herein.

2.23 Service means the sum of a participant’s employment (a) with Biogen Idec since November 12, 2003 and (b) with either Biogen, Inc. or IDEC Pharmaceuticals Corporation prior to November 12, 2003 (including in each case service with any subsidiary or other affiliate of such entity).

2.24 Transition credit means an amount credited by Biogen Idec to a participant’s account under this plan that is equal to (a) the additional amount that would be contributed on behalf of the participant under the Savings Plan, as determined under Appendix C of the Savings Plan but without regard to the nondiscrimination limits or the Code Section 401(a)(17) or Code Section 415 limits that restrict additions to the participant’s account(s) under the Savings Plan, reduced by (b) the amount of the actual additional contribution on the participant’s behalf to the Savings Plan in accordance with Appendix C thereof.

2.25 Voluntary deferred compensation means that component of the plan which permits an eligible participant to defer from 1% to 80% of his base salary and from 1% to 100% of his recurring bonus and/or non-recurring bonus amounts in accordance with Section 4.2.

2.26 Years of service means full years of completed continuous service as a regular employee, determined in accordance with the personnel policies and practices of a participant’s employer.

ARTICLE 3

PARTICIPATION

3.1 Eligibility and Participation.

(a) Voluntary Deferred Compensation. An employee (i) who has the job title of Senior Director or Vice President or more senior officer of Biogen Idec (or other employer which is participating hereunder) or (ii) who is designated as eligible by the Compensation Committee will be eligible to be a participant in the voluntary deferred compensation component of the plan. Participation in this component of the plan is voluntary and no eligible employee will be required to participate.

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(b) Transition Credit. An employee (i) whose “additional employer contribution” as determined under Appendix C of the Savings Plan was limited because of limits on compensation, limits on annual additions or nondiscrimination requirements applicable to qualified plans under the Code and (ii) who was designated by the committee (either individually or by class) is eligible to be a participant in the transition contribution component of this plan (see Section 4.3).

(c) Prior Plans and Biogen SERP. Each employee who is not eligible to be a participant under subsection (a) or (b) above or (d) below, or who is eligible but declines to participate under subsection (a) above, but who was a prior plan participant and/or Biogen SERP participant and whose prior plan and/or Biogen SERP account balance (or supplemental pension formula benefit under Section 4.1 of the Biogen SERP, if applicable) was transferred to this plan effective as of January 1, 2004 (or such later date as the committee specified) is a participant solely with respect to such transferred prior plan and/or Biogen SERP account balance (or supplemental pension formula benefit, if applicable). This will not include a person who is a vested participant under the Biogen SERP but not an employee (i.e., a person who terminated employment from Biogen, Inc. or from Biogen Idec on or before the date of transfer referred to in the preceding sentence); such a person’s benefits under the Biogen SERP are governed by the provisions of Section 5.1(f) and Appendix B.

(d) 401(k) Restoration. An employee who satisfies the requirements of Section 4.1(a) below will be eligible to be a participant with respect to the employer 401(k) restoration component of the plan.

(e) Time of Eligibility and Participation. An employee who is newly hired or promoted into a position described in subsection (a)(i) above, or who is newly designated as eligible under subsection (a)(ii) above, will be deemed to be eligible on the date the committee (or its delegatee) sends him an enrollment form (see Section 4.4).

An eligible employee under subsection (a) above will become a participant hereunder when he makes a voluntary deferral under this plan. An eligible employee under subsection (b), (c) or (d) above will become a participant hereunder when Biogen Idec (or other employer) credits an amount to his account(s) hereunder.

(f) Top Hat Plan. Notwithstanding the preceding subsections (or any other provisions of the plan), no employee will be eligible to participate in any component of this plan at any time when he or she is not a member of a select group of management or highly compensated employees (within the meaning of ERISA Sections 201(2), 301(a)(3) and 401(a)(1)), as determined by the committee.

3.2 End of Participation. A participant's participation in this plan (or a particular component of this plan) will end upon the termination of his service as an employee of Biogen Idec (or other employer) because of death or any other reason, or upon his transfer to or reclassification as an employee who is not eligible to participate in the plan (or in such component).

In addition, in the case of a participant who was designated as eligible for a component of the plan by the Compensation Committee, his participation in such component will end upon the Compensation Committee's specifying that he is no longer eligible to participate. In such event, his participation will end effective as of the later of the date of the Compensation Committee's action or the date specified by the Compensation Committee; provided that no such action will retroactively deprive a participant of any amount credited to his account or any amount he was entitled to under this plan determined as of the effective date of his termination of participation.

Upon the termination of a participant's participation in this plan (or in a particular component of this plan) in accordance with this section, there will be no additional voluntary deferrals or employer credits to such participant's account(s) (or the account(s) related to such component), except to the extent required by Code Section 409A or the regulations or any rulings thereunder with respect to the balance of the plan year in which such termination of participation occurred. However, the participant will be entitled to receive amounts credited to his account(s) in accordance with this plan.

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ARTICLE 4

VOLUNTARY DEFERRALS BY PARTICIPANTS; EMPLOYER CREDITS

4.1 401(k) Restoration.

(a) Eligibility. Each employee who has excess applicable compensation during a plan year will receive employer credits under this section, but only if the individual is still an employee as of the end of the plan year (or other period—for example, quarterly) for which an amount is to be credited under subsection (c) below.

(b) Amount of Employer 401(k) Restoration Credits. For each plan year (or a shorter period of time specified by the committee), each employer will credit a 401(k) restoration amount to the account of each eligible participant (under subsection (a) above) employed by such employer who has excess applicable compensation during such plan year (or such shorter period of time). The employer's credits on behalf of such a participant will be equal to six percent of his excess applicable compensation during the plan year (or such shorter period of time).

(c) Time for Making Employer 401(k) Restoration Credits. Employer credit amounts under subsection (b) will be credited to participants' accounts at such time(s) as the committee determines after the end of each plan year (or such shorter periods of time—for example, quarterly—specified by the committee).

4.2 Voluntary Deferrals. Each eligible employee (under Section 3.1(a)) may make voluntary deferrals under the plan from his base salary in any whole percentage of his base salary from a minimum of 1% to a maximum of 80% by electing to reduce his base salary by such amount. In addition, each such eligible employee may make voluntary deferrals under the plan from his recurring bonus amounts (as defined in Section 2.21) in any whole percentage of his recurring bonus amounts from a minimum of 1% to a maximum of 100% by electing to reduce his recurring bonus amounts by such amount. Elections to reduce base salary and/or recurring bonus amounts will be in accordance with the requirements of Section 4.4(a)(i). Finally, each such eligible employee may make voluntary deferrals under the plan from his non-recurring bonus amounts (as defined in Section 2.16), if any, in any whole percentage of his non-recurring bonus amounts from a minimum of 1% to a maximum of 100%, by electing to reduce his non-recurring bonus amounts by such amount. Deferrals of any equity based awards shall not include any partial shares of common stock of Biogen Idec. Elections to reduce non-recurring bonus amounts must be made in accordance with the requirements of Section 4.4(a)(ii).

Notwithstanding the first sentence of the preceding paragraph, the committee (or its designee) may reduce the maximum base salary deferral an eligible employee may elect from 80% to such smaller percentage as the committee (or its designee) deems advisable, in the case of any participant or group of participants, so that all employee contributions (by salary reduction or otherwise) for benefit plan coverages applicable to such participant(s), withholding tax obligations applicable to such participant(s), and any other elective or non-elective application of the base salary of such participant(s) (such as, by way of illustration and not by way of limitation, charitable deductions) will be accommodated. Any such reduction applicable to a participant for a plan year will be made before the start of such plan year.

4.3 Transition Credit. Each eligible employee (under Section 3.1(b)) will receive a transition credit hereunder. The amount of such credit will be the amount the participant would have received under the terms and conditions of Appendix C of the Savings Plan if Code Section 401(a) nondiscrimination requirements and/or Code Section 401(a)(17) or 415 limits did not apply, reduced by any amount actually contributed to the Savings Plan on his behalf under such Appendix C. Any such transition credit amount hereunder will be credited at a time determined by the committee.

4.4 Election Procedures.

(a) (i) Voluntary Deferrals from Base Salary or Recurring Bonus Amounts. An eligible employee under Section 3.1(a) who wishes to reduce his base salary and/or recurring bonus amounts to be earned during a particular plan year in order to make voluntary deferrals under Section 4.2 must complete an enrollment form specifying the amount of his voluntary deferrals (with separate percentages for his base salary and recurring bonus amounts, if desired), agreeing to reduce his base salary and/or recurring bonus amounts by the amount(s) he specifies, and providing such other information as the committee may require.

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A participant's enrollment form electing such voluntary deferrals for any plan year must be filed with the committee by such deadline as the committee specifies, but in any event before the start of such plan year. A participant may change the amount of his voluntary deferrals with respect to any subsequent plan year by filing a new enrollment form before the start of such subsequent plan year, and the change will become effective as of the first day of such subsequent plan year. Once a participant has elected to defer base salary and/or recurring bonus amounts, his enrollment form will remain in effect for future plan years unless the participant changes or terminates his prior elections by filing a new enrollment form in accordance with the preceding sentence.

An individual who first becomes eligible under Section 3.1(a) during a plan year may make an initial election by filing an enrollment form with the committee not later than 30 days after the committee (or its delegatee) sends him an enrollment form. However, such a newly eligible employee may elect to defer only base salary and/or that portion of any recurring bonus amounts to be earned after the date of filing his completed enrollment form. An individual is considered first eligible only if either: (i) he had not during the preceding 24-month period been eligible to make voluntary deferrals under this plan or under another non-qualified deferred compensation plan maintained by Biogen Idec (or another employer or other subsidiary or affiliate of Biogen Idec); or (ii) he had received a complete distribution of his entire interest under the plan and subsequently, through rehire, promotion, transfer or designation, again becomes eligible to participate in this plan under Section 3.1.

After a plan year has begun, a participant may not change the amount of voluntary deferrals of base salary and/or recurring bonus amounts (if any) he had elected for such plan year. However, if during a plan year a participant either (i) has an unforeseeable emergency (as defined in Section 6.1) and receives a distribution under Section 6.1 or (ii) has a financial hardship (as defined in the Savings Plan) and receives a financial hardship withdrawal from the Savings Plan, the participant's deferral election will automatically be cancelled. For distributions referred to in (i) above, deferrals shall be cancelled for the balance of the year in which any such distribution is made. For distributions referred to in (ii) above, deferrals shall be cancelled through the end of the year in which falls the six-month anniversary of the hardship withdrawal.

(ii) Voluntary Deferrals From Non-Recurring Bonus Amounts. If an eligible employee (under Section 3.1(a)) becomes eligible to receive a non-recurring bonus amount (as designated by the committee in accordance with Section 2.16), such eligible employee may elect to make voluntary deferrals under Section 4.2 equal to all or a specified portion of such non-recurring bonus amount in accordance with such procedures as established by the committee. Elections made with respect to equity based awards shall apply to all tranches of such awards regardless of the date such award becomes nonforfeitable and shall apply with respect to any and all dividends or dividend equivalents provided with respect to such awards . All deferral elections hereunder must be made on an enrollment form approved by the committee, specifying the amount he elects to defer, agreeing to reduce his non-recurring bonus amount(s) by such amount, and providing such other information as the committee may require. If an eligible employee elects to defer restricted stock or market stock unit awards, such employee shall not be permitted to diversify the investment of such awards other than in Biogen Idec stock or stock equivalent.

A participant’s enrollment form must be filed with the committee by such deadline as the committee specifies in written procedures approved by the committee (or its delegatee) governing deferral elections for non-recurring bonus amounts. Any filing deadline will comply with the timing of elections requirements of the regulations under Code Section 409A. Accordingly, if the committee determines that a particular non-recurring bonus amount constitutes “performance-based compensation,” the timing requirements for electing to defer performance-based compensation may be applied. Furthermore, with respect to the initial election to defer payment of any equity based awards such as restricted stock unit awards, market stock unit awards or any other forfeitable rights that requires the participant to provide services for at least 12 months from the date the award is granted, the election to defer such compensation may be made within 30 days after the date of grant or, if earlier, 12 months in advance of the date such award or right becomes nonforfeitable provided that if death, disability or a change in control occurs which accelerates the vesting before the end of such 12-month period, the deferral election will not be effective. The committee’s written procedures will be deemed to constitute part of this plan for purposes of the written plan document requirements of the regulations under Code Section 409A.

If an individual first becomes eligible under Section 3.1(a) during a plan year and after the deadline provided in the preceding paragraph, he may make an election to defer his non-recurring bonus amounts (if any) for such plan year in accordance with the rules specified in the third paragraph of subsection (i) above. In addition, the

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rules in the fourth paragraph of subsection (i) above will apply to any non-recurring bonus amounts deferral election the participant made for any plan year in which he receives a distribution under Section 6.1 or a financial hardship withdrawal from the Savings Plan.

(b) Form and Time of Payment.

(i) Initial Election. Each participant must specify the form of payment (lump sum or installments in accordance with Section 6.4(a), 6.5(a) and/or Section 6.6(a) below, as applicable) of his accounts hereunder in the event of the participant's death or other termination of employment (including as a result of disability). The time and form of payments under the plan are governed by the provisions of Article 6 and participant elections must conform to the requirements of such provisions. Any election as to medium of payment with respect to equity based awards (i.e. whether such award will be settled in stock or cash) shall be subject to the terms of the Biogen Idec Inc. 2008 Omnibus Equity Plan (or successor long term incentive plan) and/or award agreement thereunder. Any such election shall not be considered an election as to time or form of payment and shall not be subject to the restrictions under this Section.

In addition, a participant may elect payment of his accounts under Section 6.2 in the event of a change in control (as defined in Section 2.7(b)).

In addition, a participant who is an active Employee may (but is not required to) specify one or more in-service distributions to the participant in accordance with Section 6.3 if desired by the participant. A participant who declines to elect such an in-service distribution is deemed to have elected payment only after death (Section 6.4) or termination of employment (Section 6.5) or, if applicable, a change in control (Section 6.2); such a participant may not thereafter make a change of election under subsection (ii) with respect to an in-service distribution from the plan.

A participant’s initial election of a time and form of payment hereunder must be made by whichever of the following dates applies to the participant (or the earlier of such dates, if both apply to a particular participant): (A) the deadline for filing the participant’s initial enrollment form under subsection (a) above; or (B) January 30 of the year following the year for which an amount is first credited to the participant under Section 3.1(c), Section 4.1 or Section 4.3 (provided that this clause (B) will not apply to a participant if he was previously eligible for employer credits or contributions (as opposed to voluntary deferrals) under this plan or under any other account balance non-qualified deferred compensation plan maintained by Biogen Idec (or another employer or other subsidiary or affiliate of Biogen Idec).

(ii) Change of Election. Notwithstanding subsection (i) above, the following changes of election will be permitted. If such a subsequent election becomes effective as provided below, then the participant’s account(s) will be payable at the time and in the form specified in his subsequent election.

(A) In-Service Distributions. In the case of an eligible participant who elected an in-service distribution, at any time that is at least one year prior to the date for payment originally elected by the participant, if the participant is still an employee of Biogen Idec (or another employer or other subsidiary or affiliate) at such time, the participant may make one subsequent election to defer the time when any previously elected in-service distribution under Section 6.3 from his account(s) would otherwise be payable (or installment payments would otherwise begin) to a subsequent date specified by him, and/or may elect another form of payment or a different number of installments with respect to the in-service distribution of his account(s), subject in all cases to the requirements of this section and to the requirements of Section 6.3.

(B) Death or Termination of Employment. A participant who is still an employee of Biogen Idec (or another employer or other subsidiary or affiliate) may make one subsequent election to change the form of payment hereunder that will be used following his death or other termination of employment. Such an election must comply with the applicable requirements of Sections 6.4(a), 6.5(a) and 6.6(a) (as applicable).

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(C) Effectiveness of Subsequent Election. A participant’s subsequent election under this subsection (ii) will become effective only if the following requirements are satisfied: (1) the subsequent election does not take effect until one year after the date of the subsequent election and the participant remains an employee of Biogen Idec (or another employer or other subsidiary or affiliate) during such one year period, (2) the election extends the date for payment, or the start date for installment payments, by at least five years, and (3) in the case of a subsequent election to defer a previously elected in-service distribution (under subsection (A) above), the subsequent election is made at least 12 months before the date previously elected for such in-service distribution.

No election under this subsection (ii) may operate to accelerate any payment or distribution hereunder or violate any requirement of Code Section 409A or the regulations and rulings thereunder.

A participant may make only one subsequent election under subsection (ii) (A) and only one subsequent election under subsection (ii)(B). Such subsequent election(s) may be made at the same or at different times. Also, the committee may permit additional election opportunities (in accordance with the transition or other rules under the regulations or other Internal Revenue Service guidance under Code Section 409A or in such other circumstances as the committee deems appropriate). Any such additional subsequent elections under subsection (ii) must satisfy all the requirements of this section and any other applicable requirements under the plan or, alternatively, must satisfy such requirements as the committee may impose in connection with a new election under a Code Section 409A transition or other rule.

ARTICLE 5

PARTICIPANT ACCOUNTS

5.1 Participant Accounts.

(a) Employer 401(k) Restoration Accounts. Employer credits on a participant’s behalf under Section 4.1 will be credited to an account in the name of such participant. Such account will be called his employer 401(k) restoration account.

(b) Voluntary Deferred Compensation Accounts. Voluntary deferrals by a participant under Section 4.2 will be credited to an account in the name of such participant. Such account will be called his voluntary deferred compensation account.

(c) Transition Accounts. Transition credits on a participant’s behalf under Section 4.3 will be credited to an account in the name of such participant. Such account will be called his transition account.

(d) Prior Plan Account. Account balances as of December 31, 2003 (or such later date as the committee specified) for a participant in a prior plan were transferred to this plan from such prior plan and the transferred amount was credited to an account in the name of such participant. Such account is called his prior plan account.

(e) Biogen SERP Account. Amounts transferred to this plan from the Biogen SERP on behalf of a participant were credited to an account in the name of such participant. Such account is called his Biogen SERP account. The amount so transferred on behalf of a participant in the excess benefit formulas in Section 4.2 of the Biogen SERP was the amount credited to such participant’s Biogen SERP cash balance account as of December 31, 2003 (or such later date of transfer as the committee specified). The amount so transferred on behalf of a participant in the supplemental pension formula in Section 4.1 of the SERP was the present value as of December 31, 2003 (or such later date of transfer as the committee specified) of the participant’s SERP accrued supplemental pension as of such date (calculated in accordance with the terms of the SERP in effect on such date).

(f) Certain Special Provisions. Participants’ prior plan accounts and Biogen SERP accounts will be governed by the applicable provisions of this plan as in effect from time to time.

For persons who were participants in the Biogen SERP before the transfer date referred to in subsection (e) above and are entitled to a vested SERP benefit thereunder, but who are not active participants under this plan and therefore do not have an account hereunder, the amount transferred to this plan in respect of their Biogen SERP benefit will be governed by Appendix B hereto, as in effect from time to time.

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(g) 409A. For purposes of applying Code Section 409A, as provided in the regulations thereunder, a participant’s voluntary deferred compensation account is disaggregated from his or her other accounts hereunder.

5.2 Participant’s Account Value.

(a) Deemed Investment Results. Except as otherwise provided below, a participant’s accounts will be credited with deemed investment results as if the amounts credited to his accounts were invested in one or more designated investment funds (as described below) and all dividends and distributions on shares or other interests of a particular investment fund were reinvested in such fund. The investment funds available for this purpose will be those from time to time available as investment options for participants’ accounts under the Savings Plan, plus the investment funds specified in subsections (b) and (c) below (in the case of eligible participants). Notwithstanding the foregoing, with respect to the portion of a participant’s voluntary deferred compensation account attributable to restricted stock or market stock units or other equity based awards , such portion will be deemed to be invested in shares of common stock of Biogen Idec as described in the long term incentive plan sponsored by Biogen Idec. Investment funds hereunder are for the sole purpose of providing the basis for crediting deemed investment results to participants’ accounts, and do not represent any actual funds or assets held hereunder for the benefit of participants.

Each participant will indicate with his initial enrollment form (or another form specified by the committee) the investment fund or funds (and the proportion in each fund when the participant designates more than one) he wishes to designate for this purpose. Thereafter, a participant may change his designation with respect to either the deemed investment of future credits to his account(s) hereunder or the deemed transfer of amounts from a previously designated investment fund to another fund. The committee shall establish the frequency with which such a change may be made, the method of making such a change, and the effective date of such a change, and shall prescribe such other rules and procedures as it deems appropriate. Such designation will remain in effect until subsequently changed by the participant in accordance with this paragraph. Following a participant’s death and before the payment of any amount due to the participant’s beneficiary hereunder has been completed, the beneficiary will exercise the participant’s designation powers under this section.

Notwithstanding the preceding paragraph, the committee may establish one or more default investment funds that will be used to determine deemed investment results in the case of any participant or group of participants who have not made a designation under the preceding paragraph. Such default investment fund(s) will be used to determine deemed investment results applicable to the account of such participant or participants until any such participant makes a designation of investment fund(s) in accordance with the plan.

Deemed investment results under this subsection will be credited to a participant’s accounts effective as of the last day of each plan year (and as of such other valuation dates during a plan year as the committee may establish).

The value of a participant’s accounts at any point in time will be his voluntary deferrals, employer 401(k) restoration credits, transition credits on his behalf, and prior plan and/or Biogen SERP transfer amounts, increased or decreased by deemed investment results as provided in this section through the most recent valuation date, and reduced by any distributions from the participant’s accounts.

(b) Fixed Rate Option. In addition to the investment funds offered under the Savings Plan as described in (a) above, a participant who is an active Employee may elect to have his accounts credited with the deemed investment results as if they were invested in a fixed rate option earning a rate of return specified by the committee. The rate of return under the fixed rate option will be 8% for the 2008 plan year. The rate of return of future plan years will be determined each year by the committee.

(c) Exception for Certain Prior Plan Accounts. Former participants in the IDEC Pharmaceuticals Corporation Deferred Compensation Plan whose accounts were credited with interest under the fixed rate option available under that plan immediately prior to the date such account was transferred to this plan may continue to

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have such transferred amount credited with deemed investment results equal to the interest rate under that fixed rate option. Any additional contributions made under this plan will be credited with deemed investment results as described in subsection (a) or (b) above. Amounts being credited with interest under this subsection (c) may be transferred to an option described in subsection (a) or (b) above, but no amounts credited to a participant’s accounts may be transferred into the fixed rate option under this subsection (c) (even if such amounts had previously been invested in such investment fund and then transferred to another investment fund).

(d) Special Rule for Transferred Prior Plan Accounts and Transferred Biogen SERP Accounts. In connection with the transfer of participants’ prior plan account balances and Biogen SERP account balances to this plan, transferred account balances were initially credited with deemed investment results as if the participant had selected the money market fund investment option under the Savings Plan. Deemed investment results in accordance with the preceding sentence will apply to such transferred account balances until a participant changes such designation in accordance with subsection (a) above.

(e) Bookkeeping Accounts. Participants’ accounts and subaccounts will be maintained on the books of the participant’s employer for bookkeeping purposes only; such accounts will not represent any property or any secured or priority interest in any trust or in any segregated asset.

In order to facilitate the administration of the plan, the committee may arrange for a participant’s account to be divided for recordkeeping purposes into two or more subaccounts, in accordance with procedures established by the committee.

5.3 Vesting.

(a) Employer 401(k) Restoration Account.

(i) Before January 1, 2008. This subsection (i) will apply to participants who incur a termination of employment before January 1, 2008.

A participant who is an active employee will have a fully vested interest in his employer 401(k) restoration account at all times on and after his 55^th birthday. Before that date, such a participant will have a vested interest in that percentage of his employer 401(k) restoration account specified in the following table based upon his number of years of service under the plan:

Years of Service	Vested Percentage
Less than 1		0	%
1		25	%
2		50	%
3		75	%
4 or more		100	%

(ii) On or After January 1, 2008. This subsection (ii) will apply to participants who are active employees on or after January 1, 2008 (i.e., have not incurred a termination of employment with Biogen Idec, or another employer or other subsidiary or affiliate of Biogen Idec, before January 1, 2008). Each such participant will have a fully vested interest in his employer 401(k) restoration account at all times.

(b) Voluntary Deferred Compensation Account. A participant will have a fully vested interest in his voluntary deferred compensation account at all times except that any equity based awards deferred hereunder shall be subject to such vesting requirements as provided under the Biogen Idec Inc. 2008 Omnibus Equity Plan (or successor long term incentive plan) and/or any award agreement applicable to such award.

(c) Transition Account.

(i) Before January 1, 2008. This subsection (i) will apply to participants who incur a termination of employment before January 1, 2008.

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A participant who is an active employee will have a fully vested interest in his transition account at all times on and after his 65^th birthday. Before that date, such a participant will have a vested interest in that percentage of his transition contribution account specified in the following table based upon his number of years of service under the plan:

Years of Service	Vested Percentage
Less than 2		0	%
2		20	%
3		50	%
4		60	%
5		70	%
6		80	%
7 or more		100	%

(ii) On or After January 1, 2008. This subsection (ii) will apply to participants who are active employees on or after January 1, 2008 (i.e., have not incurred a termination of employment with Biogen Idec, or another employer or other subsidiary or affiliate of Biogen Idec, before January 1, 2008). Each such participant will have a fully vested interest in his transition account at all times.

(d) Prior Plan Account. A participant will have a fully vested interest in his prior plan account at all times.

(e) Biogen SERP Account. A participant who is an active employee will have a fully vested interest in his Biogen SERP account at all times effective January 1, 2004.

(f) Full Vesting upon Death, Disability or Change in Control. Notwithstanding subsections (a)(i) and (c)(i) above (for participants to whom such subsections apply):

(i) If a participant’s employment by his employer (or another Biogen Idec subsidiary or affiliate) is terminated because of the participant’s death or disability, all his accounts hereunder will be fully vested regardless of his number of years of service.

(ii) In the event of a change in control (as defined in Section 2.7(a)), all accounts of all participants still employed by Biogen Idec at such time will be fully vested regardless of a participant’s number of years of service.

(g) Forfeiture of Non-Vested Account Balances. If a participant terminates employment with his employer (and all other Biogen Idec subsidiaries or affiliates) under circumstances such that he is not fully vested in one or more accounts in accordance with the preceding subsections, the non-vested balance(s) as of the date of termination of employment will be forfeited and cancelled.

(h) Meaning of “Fully Vested.” Reference to any account of a participant as “fully vested” means that such account is not subject to forfeiture; however, all participant accounts, including fully vested accounts, are subject to (i) fluctuation as a result of the crediting of deemed investment results (including losses) to such accounts as provided in the plan and (ii) the possibility of the insolvency or bankruptcy of Biogen Idec (or other employer) (see Section 7.2(a)).

ARTICLE 6

DISTRIBUTIONS TO PARTICIPANT

6.1 Distributions for Unforeseeable Emergency. If a participant has an unforeseeable emergency prior to his termination of employment with his employer, he may apply to the committee for a distribution from the plan. If such application for an unforeseeable emergency distribution is approved by the committee, distribution of the approved amount will be made on the date of approval by the committee. The amount of the distribution will be the amount reasonably needed to alleviate the participant’s unforeseeable emergency (including the amount necessary to

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pay any federal, state or local income taxes and penalties reasonably anticipated to result from the distribution), as determined by the committee, up to a maximum of the participant’s vested account balances. Such a distribution will be made from the participant’s vested accounts in a single lump sum payment.

An unforeseeable emergency is a severe financial hardship affecting the participant resulting from illness or accident of the participant or the participant’s spouse, dependent or designated beneficiary, the need to rebuild the participant’s principal residence following damage not covered by insurance, or other similar extraordinary and unforeseeable circumstances arising as a result of events beyond the participant’s control. A circumstance or exigency of the participant does not constitute an unforeseeable emergency to the extent that the participant’s financial need is or may be relieved through reimbursement or compensation by insurance or otherwise, or by liquidation of assets (to the extent that such liquidation would not itself cause severe hardship).

The committee will determine whether a participant has incurred an unforeseeable emergency and the amount needed to alleviate the unforeseeable emergency. A participant is not entitled to a distribution under this section regardless of the participant’s circumstances or exigencies, and all such distributions and the amounts thereof are subject to the determination of the committee.

6.2 Distribution Upon a Change in Control. In the event of a change in control (as defined in Section 2.7(b)), a participant who elected payment of his accounts under the second paragraph of Section 4.4(b)(i) will receive a lump sum payment equal to the amount credited to his accounts hereunder. Such payment will be made 30 days after the occurrence of the change in control (but not before January 1, 2008 in the case of a change in control that occurs during 2007). This Section 6.2 is effective as of December 26, 2007.

6.3 In-Service Distribution(s) at a Time Specified by Participant. A participant who is an active Employee may, in accordance with this section and Section 4.4, elect an in-service distribution at a specified future date (but not earlier than five years after the time the participant is making such election) of all or any portion of his vested accounts. If, in his initial enrollment or subsequent change of election form, the participant designated payment of all or any portion of his vested account(s) at a specified time(s) and he is still an employee of Biogen Idec (or another employer or other subsidiary or affiliate) at such time(s), the participant will receive payment of the amount elected, payable on the designated date(s). A participant’s election for in-service distributions under this Section 6.3 may be for a single payment or up to five annual payments (with the first payment on the date specified by the participant and subsequent payments made in each subsequent calendar year until all such annual payments have been distributed), in each case in an amount or portion specified by the participant in his initial enrollment or other subsequent change of election form (whichever applies). Each payment will be the amount specified (or the entire vested balance remaining in the participant’s accounts, if less). Payments with respect to an in-service distribution election of a flat dollar amount (as opposed to a percentage of the participant’s vested account) by a participant who has deferred equity based awards shall be paid from the portion of the participant’s vested account that is not attributable to such equity based awards.

Any amount in a participant’s accounts hereunder not distributed to the participant under this Section 6.3 will be distributed under Section 6.2 or under Section 6.4 or 6.5, whichever may be applicable, and Section 6.6, if applicable. If a participant is receiving multiple payments under this Section 6.3 and dies or otherwise terminates employment, or (if applicable) there is a change in control, payments under this subsection will cease and subsequent payments will be governed by Section 6.4 or 6.5, or Section 6.2, as the case may be.

6.4 Distribution upon Death of a Participant.

(a) In general. If a participant dies while still an employee of Biogen Idec (or another employer or other subsidiary or affiliate) or after termination of such employment, but before the complete distribution of his vested accounts hereunder, his beneficiary will receive the total amount remaining in his vested accounts. Except as otherwise provided in Section 6.6, distribution will be made in a single sum payment within 90 days of the date of death.

(b) Beneficiary. Each participant may designate one or more beneficiaries to receive a distribution payable under subsection (a) above and may revoke or change such a designation at any time. If the participant names two or more beneficiaries, distribution to them will be in such proportions as the participant designates or, if the participant does not so designate, in equal shares. Any such designation of beneficiary will be made in accordance with such procedures or in such form as the committee may prescribe or deem acceptable.

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Any portion of a distribution payable upon the death of a participant that is not disposed of by a designation of beneficiary under the preceding paragraph, for any reason whatsoever, will be paid to the beneficiary determined under the following rules:

(i) If at the participant’s death the participant has an account under the Savings Plan and there is a valid designation of beneficiary under the Savings Plan, the beneficiary(ies) will be the same person(s) who is (are) the Savings Plan beneficiary(ies) (in the same proportions, if more than one).

(ii) If subsection (a) does not apply, the participant’s account(s) hereunder will be paid to the participant’s spouse if living at his death, otherwise equally to the participant’s natural and adopted children living at his death (and the issue of a deceased child by right of representation), otherwise to the participant’s estate. For purposes of the preceding sentence, a spouse includes a spouse of the same gender as the participant if the marriage occurred in a jurisdiction that recognizes as valid marriages between persons of the same gender.

The committee may direct payment in accordance with a prior designation of beneficiary (and will be fully protected in so doing) if such direction (i) is given before a later designation is received, or (ii) is due to the committee’s inability to verify the authenticity of a later designation. Such a distribution will discharge all liability therefor under the plan.

6.5 Distribution upon Participant’s Termination of Employment.

(a) Time and Form of Payment. Following a participant’s termination of employment (including as a result of disability) for any reason other than death, except as otherwise provided in Section 6.6, the participant will receive a single sum payment equal to his vested account balance, payable on the first business day following the six-month anniversary of the participant’s termination of employment.

(b) Termination of Employment. For purposes of this plan, a participant will have a termination of employment only if the provisions of the regulations under Code Section 409A defining “separation from service” are satisfied.

6.6 Installment Distributions in Certain Cases.

(a) Participant. Notwithstanding the provisions of Section 6.5, a participant may, at the time of filing his initial enrollment form under Section 4.4(b)(i) (or, if applicable, in a subsequent election under Section 4.4(b)(ii)), designate that the amount payable to him hereunder upon termination of employment will be paid in a number (minimum of two and maximum of fifteen) of annual installment payments, as specified by the participant. However, in the event the participant’s vested account balance as of the date that installment distributions would begin in accordance with Section 6.5 is equal to or less than the limit under Code Section 402(g)(1)(B) and (g)(4) (as in effect at such time—for example, $15,500 during 2008), such vested account balance will be automatically paid in the form of a lump sum payment to the extent not prohibited by the regulations under Code Section 409A.

(b) Beneficiary. Notwithstanding Section 6.4, a participant may at the time of filing his initial enrollment form under Section 4.4 (or, if applicable, in a subsequent election), designate that, if the participant dies before receiving the entire amount payable to him hereunder, the beneficiary will receive either:

(i) A number of annual installment payments equal to:

(A) the number the participant elected for himself under subsection (a) above (if the participant dies before receiving any installment payments), or

(B) the number of remaining installment payments due to the participant under subsection (a) above (if the participant dies after receiving one or more installment payments); or

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(ii) A single payment.

Payment to the beneficiary (or the first installment) will be made at the time provided in Section 6.4(a).

If the participant fails to designate the form of payment to the beneficiary, the default form of payment will be a single payment under (ii) above.

(c) Installment Payments. Where installment payments are due, the first annual installment payment will be made on the date specified in Section 6.4 or 6.5 (whichever is applicable) and subsequent annual installments will be made in each subsequent calendar year until all such annual payments have been distributed. The amount of each annual installment payment will be determined by multiplying the then amount of the participant’s vested account balances by a fraction whose numerator is one and whose denominator is the number of remaining annual installment payments. Installment payments with respect to equity based awards shall be made in shares and shall not include any fractional shares.

(d) Death of Beneficiary. If a participant’s designated beneficiary is receiving installment payments and dies before receiving payment of all the annual installments, the deceased beneficiary’s estate will receive a lump sum payment of the amount remaining to be distributed to such beneficiary. Such payment will be made within 90 days of the date of death.

(e) Deemed Single Payment. As provided in the regulations under Code Section 409A, installment payments to a participant will be deemed a single payment on the date of the first installment for purposes of the anti-acceleration rule (Section 4.4(b) and Section 6.9) and the rules governing the timing of changes in elections with respect to time and form of payment hereunder (Section 4.4(b)).

6.7 Certain Other Distributions. In addition to the distributions provided for in the preceding sections of this Article 6, the committee may provide for a distribution from a participant’s account(s) under the following circumstances:

(a) Domestic Relations Order. Distribution of the amount necessary to fulfill the requirements of a domestic relations order (as defined in Code Section 414(p)) requiring the payment of all or a portion of the participant’s vested account(s) to another individual (see Section 7.3(b)).

(b) Conflicts of Interest. Distribution to the extent reasonably necessary to comply with a federal government ethics agreement or a federal, state, local or foreign ethics or conflicts of interest law (as described in the regulations under Code Section 409A).

(c) Violation of Code Section 409A. In the event that, notwithstanding the intent that this plan satisfy in form and operation the requirements of Code Section 409A, it is determined that the requirements of Code Section 409A have been violated with respect to one or more accounts of any participant or group of participants, distribution of the amount determined to be includable in taxable income of such participant or participants as a result of such a violation of Code Section 409A shall be made to such participant(s).

(d) Other Circumstances. Distribution of any amount specifically permitted by Code Section 409A and the regulations thereunder.

6.8 Delay in Distributions. Notwithstanding the provisions of any of the foregoing sections in this Article 6, the committee may delay the making of any payment due to a subsequent date, provided that the delayed payment is made not later than the latest time permitted under Code Section 409A and the regulations and rulings thereunder (generally, the later of the end of the calendar year in which the specified payment date occurs or the 15^th day of the third month after the specified payment date).

6.9 Compliance with Code Section 409A. Notwithstanding any other provision of this plan (including, without limitation, Section 6.7(c)), distributions and elections respecting distributions are intended to be and will be administered in accordance with the provisions of Code Section 409A and the regulations and rulings thereunder (including the provisions prohibiting acceleration of payment unless specifically permitted by such regulations and rulings).

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ARTICLE 7

MISCELLANEOUS

7.1 Amendment or Termination of Plan. Biogen Idec, by action of the Board or of the Compensation Committee (or such other committee thereof or officer or officers of Biogen Idec to whom the Board or Compensation Committee has delegated this authority), at any time and from time to time, may amend or modify any or all of the provisions of this plan or may terminate this plan without the consent of any participant (or beneficiary or other person claiming through a participant). In addition, any amendment may be made by the committee, or by the Executive Vice President – Chief Financial Officer, or the Executive Vice President – Human Resources of Biogen Idec except for an amendment that would materially increase or reduce the benefits of the plan to participants or materially increase the cost of maintaining the plan to the employers; such committee or specified officer(s) may not terminate the plan.

Notwithstanding the preceding paragraph, no termination or amendment of the plan may reduce the amounts credited to the accounts of any participant under the plan (including a participant whose employment with the employer was terminated before such plan termination or amendment) or the vested percentages of such accounts. However, Biogen Idec may change the deemed investment options under Section 5.2, and Biogen Idec may upon termination of this plan pay participants’ account balances to the participants regardless of the times elected for payment (or the start of installment payments) elected by the participants and may pay such amounts in single sum payments regardless of whether installment distributions would otherwise be payable under Section 6.6; provided that any such distributions upon plan termination must be permitted by Code Section 409A and the regulations and rulings thereunder. In addition, Biogen Idec may, from time to time, make any amendment that it deems necessary or desirable to satisfy the applicable requirements of the tax laws and rulings and regulations thereunder in order to preserve, if possible, the tax deferral features of this plan for participants. No diminution or restriction on a participant’s opportunity to make elections or withdrawals, or exercise other privileges or rights hereunder, pursuant to the preceding sentence will be deemed to violate the rights of any participant or beneficiary hereunder so long as such change does not effect a forfeiture of any of a participant’s account balances hereunder or render an account balance (or portion thereof) which previously was nonforfeitable forfeitable. Any amendment that is required by Code Section 409A and the regulations and rulings thereunder to have a delayed effective date will be effective no earlier than such required date.

7.2 Benefits Not Currently Funded.

(a) Nothing in this plan will be construed to create a trust or to obligate Biogen Idec to segregate a fund, purchase an insurance contract or other investment, or in any other way currently to fund the future payment of any benefits hereunder, nor will anything herein be construed to give any participant or any other person rights to any specific assets of Biogen Idec or any other entity. However, in order to make provision for its obligations hereunder, Biogen Idec (or other employer) may in its discretion purchase an insurance contract or other investment; any such contract or investment will be a general asset belonging to Biogen Idec (or other employer), and no participant or beneficiary will have any rights to any such asset. The rights of a participant or beneficiary hereunder will be solely those of a general, unsecured creditor of his employer.

(b) Notwithstanding subsection (a) above, Biogen Idec (or other employer) in its sole discretion may establish a grantor trust of which it is treated as the owner under Code Section 671 to provide for the payment of benefits hereunder, subject to such terms and conditions as Biogen Idec (or other employer) may deem necessary or advisable to ensure that trust assets and benefit payments are not includable, by reason of the trust, in the taxable income of trust beneficiaries before actual distribution and that the existence of the trust does not cause the plan or any other arrangement to be considered funded for purposes of Title I of ERISA. Biogen Idec may terminate any such trust in accordance with its terms.

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7.3 No Assignment.

(a) No participant or beneficiary will have any power or right to transfer, assign, anticipate or otherwise encumber any benefit or amount payable under this plan, nor shall any such benefit or amount payable be subject to seizure or attachment by any creditor of a participant or a beneficiary, or to any other legal, equitable or other process, or be liable for, or subject to, the debts, liabilities or other obligations of a participant or beneficiary except as otherwise required by law.

(b) Notwithstanding subsection (a) above, all or a portion of a participant’s account balances may be assigned to the participant’s spouse, former spouse, or other dependent (for purposes of this section, an “alternate recipient”) in connection with a domestic relations order (as defined in Code Section 414(p)) awarding such portion(s) to the alternate recipient. However, no such order may award to an alternate recipient greater rights than the participant has with respect to his account. If any portion of an account so assigned is not fully vested at such time, such portion will vest only in accordance with the applicable provisions of this plan based upon the participant’s years of service. Upon receipt of a copy of the relevant provisions of any such order or property settlement agreement, certified or represented to the committee’s satisfaction to be accurate and in effect, and an acknowledgment by the alternate recipient that such alternate recipient will be responsible for income taxes on such amounts when distributed or made available to such alternate recipient and that such amounts are subject to income tax withholding as provided in this plan, and such other information (including the alternate recipient’s social security number) as the committee may reasonably request, the committee will assign such amount to a separate account hereunder and will distribute such account to the alternate recipient in the form of a single sum payment as soon as administratively possible, as permitted by Reg. 1.409A-3(j)(4)(ii) (except for any unvested amounts) as provided in Section 6.7(a).

7.4 Effect of Change in Control.

(a) Amendments. Notwithstanding Section 7.1, following the occurrence of a change in control (as defined in Section 2.7(a)): no amendment will be made following a change in control without the consent of the affected participant (or beneficiary or other person claiming through a participant) that adversely affects the rights of a participant (or beneficiary or other person claiming through a participant) under the plan as in effect immediately before such change in control, including (i) the right to make elections concerning the form and time of payment of distributions in accordance with Section 4.4(b) and the right to receive distributions in the form elected by the participant thereunder; and (ii) the right to the investment funds or options specified herein for the determination of deemed investment results applicable to participants’ accounts, as in effect immediately before such change in control. In particular, for purposes of clause (ii) of the preceding sentence: (i) the committee may not set the rate of return under Section 5.2(b) at a rate lower than that available under life insurance or annuity contracts obtained by a vendor or service provider (currently, The Newport Group) for purposes of the plan; and (ii) the committee will maintain a menu of investment funds under Section 5.2(a) that is substantially similar (in terms of investment styles and ability to position account(s) on a risk/reward spectrum) to the array of funds available immediately prior to the change in control.

(b) Termination. The plan will not be terminated before the payment of all benefits hereunder in accordance with the terms of the plan as in effect immediately before such change in control without the consent of a majority of the participants (including, in the case of the deceased participant, the beneficiary or other person claiming through such deceased participant). This subsection (b) will not preclude the merger of this plan into a nonqualified deferred compensation plan maintained by a successor to Biogen Idec provided that the benefits and rights of participants hereunder (including this Section 7.4) are preserved in such successor plan.

(c) Effective Date. This Section 7.4 is effective as of December 26, 2007.

7.5 Responsibilities and Authority of Committee. The committee will control and manage the operation and administration of the plan except to the extent that such responsibilities are specifically assigned hereunder to Biogen Idec, the Board or the Compensation Committee, or to a specified officer of Biogen Idec.

The committee will have all powers and authority necessary or appropriate to carry out its responsibilities for the operation and administration of the plan. It will have discretionary authority to interpret and apply all plan provisions and may correct any defect, supply any omission or reconcile any inconsistency or ambiguity in such manner as it deems advisable. It will make all final determinations concerning eligibility, benefits and rights

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hereunder, and all other matters concerning plan administration and interpretation. All determinations and actions of the committee will be conclusive and binding upon all persons, except as otherwise provided herein or by law, and except that the committee may revoke or modify a determination or action previously made in error. It is intended that any action or inaction by the committee will be given the maximum possible deference by any reviewing body (whether a court or other reviewing body), and will be reversed by such reviewing court or other body only if found to be arbitrary and capricious.

Biogen Idec will be the “plan administrator” and the “named fiduciary” for purposes of ERISA.

7.6 Limitation on Rights Created by Plan. Nothing appearing in the plan will be construed (a) to give any person any benefit, right or interest except as expressly provided herein, or (b) to create a contract of employment or to give any employee the right to continue as an employee or to affect or modify his terms of employment in any way.

7.7 Tax Withholding. Any payment hereunder to a participant, beneficiary or alternate recipient will be subject to withholding of income and other taxes to the extent required by law. In addition, amounts that were owed as FICA or other withholding on amounts previously credited to a participant’s account hereunder, but that were not correctly paid at the time owed, may in the discretion of the committee be deducted from the participant’s account.

7.8 Text Controls. Headings and titles are for convenience only, and the text will control in all matters.

7.9 Applicable State Law. To the extent that state law applies, the provisions of the plan will be construed, enforced and administered according to the laws of the Commonwealth of Massachusetts.

7.10 Paperless Administration. The committee may establish procedures whereby an electronic, internet or voice recognized authorization or election will or may be utilized under the plan in lieu a written form or document otherwise required by the terms of the plan. In such event, any reference herein to a written election, authorization or other form shall be deemed to include such other authorization or election.

BIOGEN IDEC INC.
By:	/s/ Paul J. Clancy
Dated: December 13, 2011

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APPENDIX A

Historical Information; Amendments

A.1 Adoption of Plan Document. This plan document, effective as of January 1, 2004, was approved by the Corporation (Biogen Idec Inc.) under the initial name of “Biogen Idec Inc. Voluntary Executive Supplemental Savings Plan.” Prior to execution of the plan document, the name of the plan was changed to “Biogen Idec Inc. Supplemental Savings Plan.”

By appropriate votes, (i) the IDEC Pharmaceuticals Corporation Deferred Compensation Plan maintained by IDEC Pharmaceuticals Corporation, (ii) the Biogen, Inc. Voluntary Executive Supplemental Savings Plan maintained by Biogen, Inc., and (iii) the Biogen, Inc. Supplemental Executive Retirement Plan maintained by Biogen, Inc. prior to the merger transaction, were merged into this plan.

A.2 2005 Amendment and Restatement. The plan was amended and restated in its entirety, effective as of January 1, 2005 (except as otherwise specified), primarily to comply with the requirements of Code Section 409A and regulations thereunder. During the period from January 1, 2005 until the date of execution of this amended and restated plan document, the plan was interpreted and administered in accordance with a good faith interpretation of the requirements of Code Section 409A and applicable guidance of the Internal Revenue Service thereunder.

The provisions herein relating to distributions and other changes upon the occurrence of a change in control (primarily Sections 2.7(b), 4.4(b), 6.2 and 7.4) are effective as of the date of execution of this amended and restated plan document. The provisions relating to full vesting of all accounts (subsections 5.3(a) and (c)) and the increase in the threshold for the payment of a lump sum in place of installments from $10,000 to the Code Section 402(g)(1)(B) and (g)(4) limit (the last sentence of subsection 6.6(a)) are effective as of January 1, 2008.

A.3 February 2008 Restatement. The plan was amended and restated in its entirety effective as of February 1, 2008, primarily to provide for the deferral of non-recurring bonus amounts.

A.4 October 2008 Restatement. The plan was amended and restated in its entirety effective October 1, 2008, to update the reference in the Change in Control definition to the 2008 Omnibus Equity Plan and to modify the distribution provisions applicable to inactive participants with Biogen SERP accounts whereby distributions shall be made as of July 1, 2009 in either a lump sum payment or in installments. For a participant who elects installments, the participant’s account shall no longer be credited with interest credits under Section B.3 but shall be invested in the same manner as other plan participants.

A.5 January 2010 Restatement. The plan was amended and restated in its entirety effective January 1, 2010, to allow an employee who is eligible under Section 3.1(a) to elect to defer payments made under Biogen Idec’s long term incentive award program which are settled in cash. Such amounts are considered non-recurring bonus amounts hereunder.

A.6 January 2012 Restatement. The plan was amended and restated in its entirety effective as of January 1, 2012 to expand the tax-deferred savings opportunities by allowing eligible participants to defer certain equity based awards granted under the Biogen Idec Inc. 2008 Omnibus Equity Plan (or successor long term incentive plan) whether or not settled in cash or shares. Such amounts are considered non-recurring bonus amounts hereunder.

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APPENDIX B

Biogen, Inc. Supplemental Executive Retirement Plan

B.1 Applicability.

(a) The provisions of this Appendix B will govern the treatment of transferred Biogen SERP account balances (or supplemental pension benefit formula benefit under Section 4.1(a) of the Biogen SERP, if applicable) of persons who were entitled to a benefit under the Biogen SERP but who were not active employees of Biogen Idec or any of its subsidiaries or other affiliates as of the date of transfer. To the extent that the provisions of this Appendix B are applicable, they will govern over any other provisions of this plan.

A participant whose Biogen SERP account (or supplemental pension formula benefit, if applicable) is governed by this Appendix will be referred to as an “Appendix B participant.”

(b) This Appendix B will not apply to any transferred Biogen SERP account balances of any person who was an active employee of Biogen Idec (or any of its subsidiaries or other affiliates) as of the date of transfer as described in Section 3.1(c) and 5.1(e). The other provisions of this plan (including, without limitation, the crediting of deemed investment experience and the distribution provisions) will govern such transferred SERP account balance.

(c) For purposes of Code Section 409A, prior to the changes made to this Appendix B effective October 1, 2008, this Appendix B will be treated as a separate grandfathered non-qualified deferred compensation plan not subject to the requirements of such section.

B.2 Amount Transferred.

For an Appendix B participant in the excess benefit formulas in Section 4.2 of the Biogen SERP, the amount transferred from the Biogen SERP to this plan on behalf of an Appendix B participant was the vested amount in the Appendix B participant’s Biogen SERP account as of his or her date of termination of employment, with subsequent interest credits on such amounts in accordance with the terms of the Biogen SERP. The full vesting provisions of Section 5.3(e) of this plan will not apply to an Appendix B participant.

B.3 Interest Credits.

For periods prior to July 1, 2009, interest credits shall continue to be added to each Appendix B participant’s Biogen SERP account as of the last day of the plan year based on the amount of the participant’s Biogen SERP account balance as of the first day of the plan year in the same manner as interest credits were added before such transfer.

The annual rate of interest used to determine the interest credit shall be the annual average of the yield on the one-year Treasury Bill constant maturity rate for the preceding plan year plus 100 basis points. However, in no event shall the annual interest rate be less than 5.25% or more than 10.0%.

Notwithstanding the foregoing, for any plan year in which a plan benefit commences, an interest credit shall be added on the amount of the participant’s Biogen SERP account balance as of the first day of the plan year for the period from the first day of such plan year until the participant’s expected date of distribution. The interest rate shall be the annual interest rate as described above multiplied by the number of complete months since the end of the prior plan year divided by 12. Interest credits shall continue to be made during any period in which payment of an Appendix B participant’s benefit is being deferred. In no event will interest credits be made after benefits have commenced.

Effective July 1, 2009, for any Appendix B participant who elects to receive his distribution in installments rather than a lump sum payment commencing as of such date in accordance with Section B.4, the participant’s Biogen SERP account balance shall no longer be credited with interest credits under this Section B.3 but shall be invested in accordance with Section 5.2.

B-1

B.4 Distributions.

(a) With respect to an Appendix B participant who has not commenced distribution of his Biogen SERP account by October 1, 2008, distribution of such participant’s Biogen SERP account shall be made, or commence, as of July 1, 2009. Such a participant shall be furnished a distribution election form whereby the participant may elect to receive his Biogen SERP account as of such date in either a single lump sum payment or in installments as prescribed in Section 6.6. If a participant fails to make an election, the default form of payment will be a single lump sum payment. The lump sum payment amount shall be the amount credited to the participant’s account as of such date of payment including interest credits, as described in Section B.3, to such date. If the participant elects payment of his Biogen SERP account in installments, Section 6.6 shall apply in determining the amount and timing of the annual installments and payment in the event of death.

(b) Prior to October 1, 2008, an Appendix B participant’s Biogen SERP account (or supplemental pension formula benefit, if applicable) will be paid in the same form and beginning at approximately the same time that his benefit under the Retirement Plan is payable, subject to the following rules. Notwithstanding the preceding sentence, if a participant elects a lump sum form of payment under the Retirement Plan, payment in such form under this plan will be subject to the approval of the committee.

(i) Annuity Options. If an Appendix B participant’s Biogen SERP account balance (or supplemental pension formula benefit, if applicable) is payable in any form other than a lump sum, the actuarial factors used to convert his Biogen SERP account balance to such other form of payment will be the same as the factors used for such purpose in the Retirement Plan.

(ii) Lump Sum. If an Appendix B participant’s Biogen SERP account is payable in a single sum, the payment amount is the amount credited to the participant’s account as of the date of payment, with interest credits hereunder to such date (or as close thereto as is practicable). For a participant with a supplemental pension benefit under Section 4.1(a) of the Biogen SERP, the amount of lump sum payment shall be the supplemental pension amount converted to a single lump sum using the assumptions set forth in the Biogen Retirement Plan for such purpose.

(iii) Lump Sum Override. Notwithstanding the preceding provisions of this section, if an Appendix B participant’s Biogen SERP account balance (or lump sum value of his supplemental pension benefit, if applicable) is $10,000 or less as of the date that distribution would be made, such amount will be paid in the form of a lump sum payment.

B.5 Death Benefits.

(a) Applicability of this Section. This section specifies the benefits payable upon the death of an Appendix B participant, either before or after the date his benefit payments hereunder begin. Except as specified in this section, no benefits are payable upon the death of an Appendix B participant.

(b) Preretirement Death Benefits. If an Appendix B participant dies before the date when his Biogen SERP account balance is converted to an annuity (or installments) or paid to such participant, his beneficiary will receive payment of the participant’s Biogen SERP account balance (or value of supplemental pension benefit, if applicable). Such amount will be paid in a single payment to the beneficiary.

(c) Death After Benefit Payments Begin. If a participant dies while receiving installment payments hereunder, his beneficiary will receive the death benefit as described in Section 6.6.

B-2

EX-10.40

Exhibit 10.40

BIOGEN IDEC INC.

VOLUNTARY BOARD OF DIRECTORS SAVINGS PLAN

(Plan Provisions as in Effect on January 1, 2012)

TABLE OF CONTENTS

		Page
ARTICLE 1	INTRODUCTION		1
1.1	Purpose and Effective Date		1
ARTICLE 2	DEFINITIONS		1
2.1	Biogen Idec		1
2.2	Board		1
2.3	Change in Control		1
2.4	Committee		1
2.5	Director		1
2.6	Equity Plan Award		1
2.7	Fees		1
2.8	Participant		2
2.9	Plan		2
2.10	Plan Year		2
2.11	Retainer		2
2.12	Savings Plan		2
ARTICLE 3	PARTICIPATION		2
3.1	Eligibility and Participation		2
3.2	End of Participation		2
ARTICLE 4	VOLUNTARY DEFERRALS BY PARTICIPANTS		2
4.1	Voluntary Deferrals		2
4.2	Election Procedures		2
ARTICLE 5	PARTICIPANT ACCOUNTS		4
5.1	Participant Accounts		4
5.2	Vesting		5
ARTICLE 6	DISTRIBUTIONS TO PARTICIPANT		6
6.1	Distributions for Unforeseeable Emergency		6
6.2	In-Service Distribution(s) at a Time Specified by Participant		6
6.3	Distribution Upon a Change in Control		6
6.4	Distribution Upon Death of a Participant		7
6.5	Other Distributions		7
6.6	Installment Distributions in Certain Cases		7
6.7	Certain Other Distributions		8
6.8	Delay in Distributions		8
6.9	Compliance with Code Section 409A		9
ARTICLE 7	MISCELLANEOUS		9
7.1	Amendment or Termination of Plan		9
7.2	Benefits Not Currently Funded		9
7.3	No Assignment		10
7.4	Effect of Change in Control		10
7.5	Responsibilities and Authority of Committee		10
7.6	Limitation on Rights Created by Plan		11
7.7	Tax Withholding		11
7.8	Text Controls		11
7.9	Applicable State Law		11
7.10	Paperless Administration		11
APPENDIX A			A-1

ARTICLE 1

INTRODUCTION

1.1 Purpose and Effective Date. The purpose of this plan is to provide members of the Board of Directors of Biogen Idec with a tax-deferred savings opportunity. This plan allows participants to defer all or a portion of their cash directors’ fees and retainer by so electing before such fees and retainer have been earned.

This amended and restated plan is effective as of January 1, 2012 to expand the tax-deferred savings opportunities by allowing members of the Board of Directors to defer certain equity based awards granted under the Biogen Idec Inc. 2006 Non-Employee Directors Equity Plan (or successor plan). Certain historical information about the plan and any amendments thereto is set forth in Appendix A.

ARTICLE 2

DEFINITIONS

This section contains definitions of terms used in the plan. Where the context so requires, the masculine includes the feminine, the singular includes the plural, and the plural includes the singular.

2.1 Biogen Idec means Biogen Idec Inc., a Delaware corporation, or any successor to all or the major portion of its assets or business which assumes the obligations of Biogen Idec Inc. under this plan.

2.2 Board means the Board of Directors of Biogen Idec.

2.3 Change in Control

(a) For purposes of Section 7.4: a change in control means a “Corporate Change in Control” or a “Corporate Transaction” as each is defined in the Biogen Idec Inc. 2008 Omnibus Equity Plan.

(b) For purposes of Section 4.2(b) and Section 6.3: a change in control means (i) the acquisition by a person or group of stock of Biogen Idec that, together with stock previously held by such person or group, constitutes more than 50 percent of the total fair market value or total voting power of the stock of Biogen Idec; (ii) a change in the effective control of Biogen Idec resulting from either the acquisition by any person or group during a 12-month period of stock of Biogen Idec possessing 30 percent or more of the total voting power of Biogen Idec stock; or the replacement of a majority of the members of the Board during any 12-month period by directors whose appointment or election was not endorsed by a majority of the members of the Board in office immediately before the start of such 12-month period; or (iii) the acquisition by any person or group (during any 12-month period) of assets having a gross fair market value equal to or greater than 40 percent of the total gross fair market value of all assets of Biogen Idec. This subsection (b) and terms used herein will be interpreted in accordance with the regulations under Code Section 409A relating to a change in the ownership or effective control of a corporation or a change in the ownership of a substantial portion of the assets of a corporation.

This subsection 2.3(b) is effective as of the date of execution of this amended and restated plan document.

2.4 Committee means the Retirement Committee, or such other committee designated by the Board to administer this Plan.

2.5 Director means an individual serving as a non-employee director of Biogen Idec in accordance with its articles and by-laws.

2.6 Equity Plan Award means an award granted pursuant to the Biogen Idec Inc.2006 Non-Employee Directors Equity Plan, or successor plan thereto.

2.7 Fees means the cash amounts payable to a director as compensation for his or her attendance at a meeting of the Board or a committee of the Board or for other special services.

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2.8 Participant means a director who has made a voluntary deferral hereunder or for whom an amount has been transferred to this plan.

2.9 Plan means the Biogen Idec Inc. Voluntary Board of Directors Savings Plan, as set forth in this plan instrument, and as it may be amended from time to time.

2.10 Plan Year means the 12-month periods commencing on January 1, 2005 and on each subsequent January 1 while this plan remains in effect.

2.11 Retainer means the cash amount payable to a director as an annual retainer for service in such capacity, as in effect from time to time.

2.12 Savings Plan means the Biogen Idec 401(k) Savings Plan, as amended from time to time. Any term defined in the Savings Plan will have the same meaning when used in this plan unless otherwise defined herein.

ARTICLE 3

PARTICIPATION

3.1 Eligibility and Participation. Each director will be eligible to be a participant in this plan as long as he is a director. A director will become a participant hereunder when he makes a voluntary deferral to this plan or when his account balance under the Biogen, Inc. Voluntary Board of Directors Savings Plan (the “Biogen Directors Plan”) is transferred to this plan. Voluntary deferrals under this plan are voluntary and no director will be required to make such deferrals.

3.2 End of Participation. A participant’s participation in this plan will end upon the termination of his service as a director of Biogen Idec because of death, retirement, resignation, failure of reelection, or any other reason. Upon the termination of a participant’s participation in this plan in accordance with this section, the participant may make no further voluntary deferrals hereunder. However, the participant will be entitled to receive any amounts in his account in accordance with this plan.

ARTICLE 4

VOLUNTARY DEFERRALS BY PARTICIPANTS

4.1 Voluntary Deferrals. Each director may make voluntary deferrals to the plan from his fees, retainer, or equity plan award in any whole percentage of such fees, retainer, and/or equity plan award from a minimum of 1% to a maximum of 100%, by electing to reduce his fees, retainer, and/or equity plan award by such amount in accordance with this plan. If a director’s fees include separately identified types of fees (for example, meeting fees or special service fees), the committee may permit separate elections to defer with respect to different categories of fees. Deferrals of any equity plan awards shall not include any partial shares of common stock of Biogen Idec.

All amounts by which a participant reduces his fees, retainer, and/or equity plan award hereunder are referred to herein as the participant’s voluntary deferrals.

4.2 Election Procedures

(a) Voluntary Deferrals. A director who wishes to reduce his fees, retainer, and or equity plan award to be earned during a particular plan year in order to make voluntary deferrals under Section 4.1 must complete an enrollment form specifying the amount of his voluntary deferrals (with separate percentages for his meeting fees, special service fees (if any) and/or retainer, if desired), agreeing to reduce such fees, retainer, and/or equity plan award by the amount(s) he specifies, and providing such other information as the committee may require. Elections made with respect to equity plan awards shall apply to all tranches of such awards regardless of the date such award becomes nonforfeitable and shall apply with respect to any and all dividends or dividend equivalents provided with respect to such awards. All deferral elections hereunder must be made on an enrollment form approved by the committee, specifying the amount he elects to defer, agreeing to reduce his fees, retainer, and/or equity plan award by such amount, and providing such other information as the committee may require. If a director elects to defer an equity plan award, he or she shall not be permitted to diversify the investment of such awards other than in Biogen Idec stock or stock equivalent.

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A director’s enrollment form electing voluntary deferrals for any plan year must be filed with the committee by such deadline as the committee specifies, but in any event before the start of such plan year. In addition, in the case of an individual who anticipates being elected as a director during a plan year, such person may make an election hereunder in anticipation of his or her election and such election will be effective with respect to fees, retainer, and/or equity plan award to be earned after the date of such election; such an election will be effective as of the date when it is made but will be subject to such individual’s actual election as a director. Further, in the case of a newly elected director, who did not make an election under the preceding sentence, such person may elect to defer his fees, retainer, and/or equity plan award for the plan year of his election to office, within 30 days after the committee sends him an enrollment form, provided that such election will relate only to fees, retainer, and equity plan award to be earned after the date of filing his completed enrollment form, and provided further that such person had not previously been eligible to make voluntary deferrals under this plan for a period of at least 24 months. Any filing deadline will comply with the timing of elections requirements of the regulations under Code Section 409A. Accordingly, with respect to the initial election to defer payment of any equity plan awards or any other forfeitable rights that requires the participant to provide services for at least 12 months from the date the award is granted, the election to defer such compensation may be made within 30 days after the date of grant or, if earlier, 12 months in advance of the date such award or right becomes nonforfeitable provided that if death, disability or a change in control occurs which accelerates the vesting before the end of such 12-month period, the deferral election will not be effective. The committee’s written procedures will be deemed to constitute part of this plan for purposes of the written plan document requirements of the regulations under Code Section 409A. A participant may change the amount of his voluntary deferrals with respect to any subsequent plan year by filing a new enrollment form before the start of such subsequent plan year, and the change will become effective as of the first day of such subsequent plan year. Once a participant has elected to defer fees, retainer, and/or equity plan awards his enrollment form will remain in effect for future plan years unless the participant changes or terminates his prior elections by filing a new enrollment form in accordance with the preceding sentence.

After a plan year has begun, a participant may not change the amount of voluntary deferrals (if any) he had elected for such plan year. However, if during a plan year a participant has an unforeseeable emergency (as defined in Section 6.1) and receives a distribution under Section 6.1, the participant’s voluntary deferral election for the balance of that year will automatically be cancelled.

(b) Form and Time of Payment.

(i) Initial Election. Each participant in the initial enrollment form filed hereunder or another form designated by the committee must specify the form of payment (lump sum or installments in accordance with Section 6.4(a), 6.5 and/or 6.6(a) below, as applicable) of his account hereunder in the event of the participant’s death or other termination of service as a director (including as a result of disability). In addition, effective as of the date of execution of this amended and restated plan document, a participant may elect payment of his account under Section 6.3 in the event of a change in control (as defined in Section 2.3(b)).

In addition, a participant may (but is not required to) specify one or more in-service distributions to the participant in accordance with Section 6.2 if desired by the participant.

The time and form payments under the plan are governed by the provisions of Article 6 and participant elections must conform to the requirements of such provisions. Any election as to medium of payment with respect to equity plan award (i.e. whether such award will be settled in stock or cash) shall be subject to the terms of the Biogen Idec Inc. 2006 Non-Employee Directors Equity Plan (or successor plan) and/or award agreement thereunder. Any such election shall not be considered an election as to time or form of payment and shall not be subject to the restrictions under this Section.

(ii) Change of Election. Notwithstanding subsection (i) above, the following changes of election will be permitted. If such a subsequent election becomes effective as provided below, then the participant’s account will be payable at the time and in the form specified in his subsequent election.

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(A) In-Service Distributions. In the case of a participant who elected an in-service distribution, at any time that is at least one year prior to the date for payment originally elected by the participant, if the participant is still a director of Biogen Idec at such time, the participant may make one subsequent election to defer the time when any previously elected in-service distribution under Section 6.2 from his account would otherwise be payable (or installment payments would otherwise begin) to a subsequent date specified by him, and/or may elect another form of payment or a different number of installments with respect to the in-service distribution of his account, subject in all cases to the requirements of this section and to the requirements of Section 6.2.

(B) Death or Termination of Employment. A participant who is still a director of Biogen Idec may make one subsequent election to change the form of payment hereunder that will be used following his death or other termination of employment. Such an election must comply with the applicable requirements of Sections 6.4, 6.5 and 6.6 (as applicable).

(C) Effectiveness of Subsequent Election. A participant’s subsequent election under this subsection (ii) will become effective only if the following requirements are satisfied: (1) the subsequent election does not take effect until one year after the date of the subsequent election and the participant remains a director of Biogen Idec during such one year period, (2) the election extends the date for payment, or the start date for installment payments, by at least five years, and (3) in the case of a subsequent election to defer a previously elected in-service distribution (under subsection (A) above), the subsequent election is made at least 12 months before the date previously elected for such in-service distribution.

No election under this subsection (ii) may operate to accelerate any payment or distribution hereunder or violate any requirement of Code Section 409A or the regulations and rulings thereunder.

A participant may make only one subsequent election under subsection (ii) (A) and only one subsequent election under subsection (ii)(B). Such subsequent election(s) may be made at the same or at different times. Also, the committee may permit additional election opportunities (in accordance with the transition or other rules under the regulations or other Internal Revenue Service guidance under Code Section 409A or in such other circumstances as the committee deems appropriate). Any such additional subsequent elections under subsection (ii) must satisfy all the requirements of this section and any other applicable requirements under the plan or, alternatively, must satisfy such requirements as the committee may impose in connection with a new election under a Code Section 409A transition or other rule.

ARTICLE 5

PARTICIPANT ACCOUNTS

5.1 Participant Accounts.

(a) Voluntary Deferrals Accounts. Voluntary deferrals by a participant from his fees and/or retainer hereunder will be credited to an account in the name of such participant. Such account will be called his voluntary deferrals account.

(b) Participant’s Account Value. Except as otherwise provided below, a participant’s account will be credited with deemed investment results as if his voluntary deferrals account were invested in one or more designated investment funds and all dividends and distributions on shares of a particular investment fund were reinvested in shares of such fund. The investment funds available for this purpose will be those from time to time available as investment options under the Savings Plan.

In addition to the investment funds offered under the Savings Plan as described in the preceding paragraph, a participant may elect to have his account credited with the deemed investment results as if such amounts were invested in a fixed income option earning a rate of return specified by the committee. The rate of return under the fixed income option will be 8% for the 2008 plan year. The rate of return of future plan years will be determined by the committee.

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Notwithstanding the foregoing, with respect to the portion of a participant’s voluntary deferred compensation account attributable to the equity plan awards , such portion will be deemed to be invested in shares of common stock of Biogen Idec, and the participant shall not be permitted to designate any other investment fund for this purpose.

Investment funds hereunder are for the sole purpose of providing a basis for crediting deemed investment results to participants’ accounts, and do not represent any actual funds or assets held hereunder for the benefit of participants.

Each participant will indicate with his initial enrollment form (or other form specified by the committee) the investment fund or funds (and the proportion in each fund when the participant designates more than one) he wishes to designate for this purpose. Thereafter, a participant may change his designation either with respect to the deemed investment of future voluntary deferrals or the deemed transfer of amounts from a previously designated investment fund to another fund. The committee shall establish the frequency by which such a change may be made, the method of making such a change, and the effective date of such a change and shall prescribe such other rules and procedures as it deems appropriate. Such designation will remain in effect until subsequently changed by the participant in accordance with this paragraph. Following a participant’s death and before the payment of any amount due to the participant’s beneficiary hereunder has been completed, the beneficiary will exercise the participant’s designation powers under this section.

Notwithstanding the preceding paragraph, the committee may establish one or more default investment funds that will be used to determine deemed investment results in the case of any participant or group of participants who have not made a designation under the preceding paragraph. Such default investment fund(s) will be used to determine deemed investment results applicable to the account of such participant or participants until any such participant makes a designation of investment fund(s) in accordance with the plan.

Deemed investment results under this subsection will be credited to a participant’s account effective as of the last day of each plan year (and as of such other valuation dates during a plan year as the committee may establish).

The value of a participant’s account at any point in time will be his voluntary deferrals (plus, if applicable, his transferred account balance from the Biogen Directors Plan), increased or decreased by deemed investment results as provided in this subsection (b) through the end of the most recent valuation date, and reduced by any distributions from the participant’s account.

Notwithstanding the foregoing, in connection with the transfer of participants’ Biogen Directors Plan account balances to this plan, transferred account balances will be initially credited with deemed investment results as if the participant had selected the money market fund investment option under the Savings Plan. Deemed investment results in accordance with the preceding sentence will apply to such transferred account balances until a participant changes such designation in accordance with this section.

(c) Bookkeeping Accounts. Participants’ accounts and subaccounts will be maintained on Biogen Idec’s books for bookkeeping purposes only; such accounts will not represent any property or any secured or priority interest in any trust or in any segregated asset.

In order to facilitate the administration of the plan, the committee may arrange for a participant’s voluntary deferrals account to be divided for recordkeeping purposes into two or more subaccounts, in accordance with procedures established by the committee.

5.2 Vesting. A participant will have a fully vested interest in his voluntary deferrals account at all times except that any equity plan awards deferred hereunder shall be subject to such vesting requirements as provided under the Biogen Idec Inc. 2006 Non-Employee Directors Equity Plan (or successor plan) and/or award agreement applicable to such award. For this purpose, “fully vested” means that such account is not subject to forfeiture; however, all participant accounts are subject to (i) fluctuation as a result of the crediting of deemed investment results (including losses) to such accounts as provided in the plan and (ii) the possibility of the insolvency or bankruptcy of Biogen Idec (see Section 7.2(a)).

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ARTICLE 6

DISTRIBUTIONS TO PARTICIPANT

6.1 Distributions for Unforeseeable Emergency. If a participant has an unforeseeable emergency prior to his termination of service as a director, he may apply to the committee for a distribution from his vested account. If such application for an unforeseeable emergency distribution is approved by the committee, distribution of the approved amount will be made on the date of approval by the committee. The amount of the distribution will be the amount reasonably needed to alleviate the participant’s unforeseeable emergency (including the amount necessary to pay any federal, state or local income taxes and penalties reasonably anticipated to result from the distribution), as determined by the committee, up to a maximum of the participant’s account balance. Such a distribution will be made from the participant’s account in a single lump sum payment. If such a participant’s account has two or more subaccounts, the committee will determine which subaccount(s) will be debited to reflect the unforeseeable emergency distribution.

An unforeseeable emergency is a severe financial hardship affecting the participant resulting from illness of the participant or spouse, dependent or designated beneficiary, need to rebuild the participant’s principal residence following damage not covered by insurance, or other similar extraordinary and unforeseeable circumstances arising as a result of events beyond the participant’s control. A circumstance or exigency of the participant does not constitute an unforeseeable emergency to the extent that the participant’s financial need is or may be relieved through reimbursement or compensation by insurance or otherwise, by liquidation of assets (to the extent that such liquidation would not itself cause severe hardship), or by cessation of voluntary deferrals in accordance with Section 4.1.

The committee will determine whether a participant has incurred an unforeseeable emergency and the amount needed to alleviate the unforeseeable emergency. A participant is not entitled to a distribution under this section regardless of the participant’s circumstances or exigencies, and all such distributions and the amounts thereof are subject to the determination of the committee.

6.2. In-Service Distribution(s) at a Time Specified by Participant. A participant shall be permitted, in accordance with this section, to elect an in-service distribution at a specified date (but not earlier than five years after the date he is making such election) of the portion of his vested account that is not invested in the fixed income option described in the second paragraph of Section 5.1(b). If, in his initial enrollment or other election form (or, if applicable, a subsequent election under Section 4.2(b)(ii)), the participant elected payment of such portion of his vested account (or a specified part of such portion) at a specified time(s) and he is still a director at such time(s), the participant will receive payment of the amount elected, payable on the designated date(s). A participant’s election for in-service distributions under this Section 6.2 may be for a single payment or up to five annual payments (with the first payment on the date specified by the participant and subsequent payments on anniversaries of such date), in each case in an amount or portion specified by the participant in his enrollment or other election form. Each payment will be the amount specified (or the entire balance remaining in the participant’s account, if less). Payments with respect to an in-service distribution election of a flat dollar amount (as opposed to a percentage of the participant’s vested account) by a participant who has deferred equity plan awards shall be paid from the portion of the participant’s vested account that is not attributable to such equity based awards.

Any amount in a participant’s vested account hereunder not distributed to the participant under this Section 6.2 will be distributed under Section 6.3, 6.4 or 6.5, whichever may be applicable, and Section 6.6 (if applicable). If a participant is receiving multiple payments under this Section 6.2 and dies or otherwise terminates service as a director, payments under this subsection will cease and subsequent payments will be governed by Section 6.4 or 6.5, as the case may be.

6.3 Distribution Upon a Change in Control. In the event of a change in control (as defined in Section 2.3(b), a participant who elected payment of his account under Section 4.2(b)(i) will receive a lump sum payment equal to the amount credited to his account hereunder. Such payment will be made 30 days after the occurrence of the change in control (but not before January 1, 2008 in the case of a change in control that occurs during 2007). This Section 6.2 is effective as of the date of execution of this amended and restated plan document.

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6.4 Distribution upon Death of a Participant.

(a) In general. If a participant dies before his entire vested account balance has been distributed, his beneficiary will receive the amount remaining in the participant’s vested account. Except as provided in Section 6.6, distribution will be made in a single sum payment on the first day of the month after the committee receives appropriate evidence of the participant’s death and of the right of any beneficiary to receive such payment (and in the case of payment to the participant’s estate, the appointment of a personal representative).

(b) Beneficiary. A participant may designate one or more beneficiaries to receive a distribution payable under subsection (a) above and may revoke or change such a designation at any time. If the participant names two or more beneficiaries, distribution to them will be in such proportions as the participant designates or, if the participant does not so designate, in equal shares. Any designation of beneficiary will be made in accordance with such procedures or in such form as the committee may prescribe or deem acceptable.

Any portion of a distribution payable upon the death of a participant that is not disposed of by a designation of beneficiary under the preceding paragraph, for any reason whatsoever, will be paid to the participant’s spouse if living at his death, otherwise equally to the participant’s natural and adopted children (and the issue of a deceased child by right of representation), otherwise to the participant’s estate.

The committee may direct payment in accordance with a prior designation of beneficiary (and will be fully protected in so doing) if such direction (i) is given before a later designation is received, or (ii) is due to the committee’s inability to verify the authenticity of a later designation. Such a distribution will discharge all liability therefor under the plan.

6.5 Other Distributions. Except in the case of the participant’s death (in which case distribution is made in accordance with Section 6.4), distribution of a participant’s account will be made at the time elected by the participant in accordance with Section 4.2. In the absence of such an election, distribution of the participant’s account will be made on the first day of the month after the participant’s termination of service as a director. Distribution will be made in a single lump sum payment.

In applying the distribution provisions of this Article 6, in the case of a participant who terminates service as a director but thereupon becomes an employee of Biogen Idec (or a subsidiary or other affiliate of Biogen Idec), such participant will be deemed not to have a termination of service as a director until he terminates employment with Biogen Idec (or subsidiary or other affiliate).

6.6 Installment Distributions in Certain Cases.

(a) Participant. Notwithstanding the provisions of Section 6.5, a participant may, at the time of filing his initial enrollment form under Section 4.2(b)(i) (or, if applicable, in a subsequent election under Section 4.2(b)(ii)), designate that the amount payable to him hereunder upon termination of service as a director will be paid in a number (minimum of two and maximum of fifteen) of annual installment payments, as specified by the participant. However, in the event the participant’s account balance as of the date that installment distribution would begin in accordance with Section 6.5 is equal to or less than the limit under Code Section 402(g)(1)(B) and (g)(4) as in effect when installments would begin (for example, $15,500 for 2008)), such account balance will automatically be paid in the form of a lump sum payment to the extent not prohibited by the regulations under Code Section 409A.

(b) Beneficiary. Notwithstanding Section 6.4, a participant may at the time of filing his initial enrollment form under Section 4.2 (or, if applicable, in a subsequent election) designate that, if the participant dies before receiving the entire amount payable to him hereunder, the beneficiary will receive either:

(i) A number of annual installment payments equal to:

(A) the number the participant elected for himself under subsection (a) above (if the participant dies before receiving any installment payments), or

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(B) the number of remaining installment payments due to the participant under subsection (a) above (if the participant dies after receiving one or more installment payments); or

(ii) a single payment.

Payment to the beneficiary (or the first installment) will be made or begin as provided in Section 6.4(a).

If the participant fails to designate the form of payment to the beneficiary, the default form of payment will be a single payment under (ii) above.

(c) Installment Payments. Where installment payments are due, the first annual installment payment will be made on the date specified in Section 6.4 or 6.5 (whichever is applicable) and subsequent annual installments will be paid on succeeding anniversaries of the first payment date. The amount of each annual installment payment will be determined by multiplying the amount then remaining to be paid by a fraction whose numerator is one and whose denominator is the number of remaining annual installment payments. Installment payments with respect to the portion of a participant’s vested account equity based awards shall be made in shares and shall not include any fractional shares

(d) Death of Beneficiary. If a participant’s designated beneficiary is receiving installment payments and dies before receiving payment of all the annual installments, the designated beneficiary’s estate will receive a lump sum payment of the amount remaining to the distributed to such deceased beneficiary. Such payment will be made on the first day of the month next following the committee’s receipt of satisfactory evidence of the death of the designated beneficiary and the appointment of a personal representative.

(e) Deemed Single Payment. As provided in the regulations under Code Section 409A, installment payments to a participant will be deemed a single payment on the date of the first installment for purposes of the anti-acceleration rule (Section 4.2(b) and Section 6.9) and the rules governing the timing of changes in elections with respect to time and form of payment hereunder (Section 4.2(b)).

6.7 Certain Other Distributions. In addition to the distributions provided for in the preceding sections of this Article 6, the committee may provide for a distribution from a participant’s account under the following circumstances:

(a) Domestic Relations Order. Distribution of the amount necessary to fulfill the requirements of a domestic relations order (as defined in Code Section 414(p)) requiring the payment of all or a portion of participant’s account to another individual (see Section 7.3(b)).

(b) Conflicts of Interest. Distribution to the extent reasonably necessary to comply with a federal government ethics agreement or a federal, state, local or foreign ethics or conflicts of interest law (as described in the regulations under Code Section 409A.

(c) Violation of Code Section 409A. In the event that, notwithstanding the intent that this plan satisfy in form and operation the requirements of Code Section 409A, it is determined that the requirements of Code Section 409A have been violated with respect to any participant or group of participants, distribution of the amount determined to be includable in taxable income of such participant or participants as a result of such violation of Code Section 409A.

(d) Other Circumstances. Distribution of any amount specifically permitted by Code Section 409A and the regulations thereunder.

6.8 Delay in Distributions. Notwithstanding the provisions of any of the foregoing sections in this Article 6, the committee may delay the making of any payment to a subsequent date, provided that the delayed payment is made not later than the latest time permitted under Code Section 409A and the regulations and rulings thereunder (generally, the later of the end of the calendar year in which the specified payment date occurs or the 15^th day of the third month after the specified payment date).

8

6.9 Compliance with Code Section 409A. Notwithstanding any other provision of this plan (including, without limitation, Section 6.7(c)), distributions and elections respecting distributions are intended to be and will be administered in accordance with the provisions of Code Section 409A and the regulations and rulings thereunder (including the provisions prohibiting acceleration of payment unless specifically permitted by such regulations and rulings).

ARTICLE 7

MISCELLANEOUS

7.1 Amendment or Termination of Plan. Biogen Idec, by action of the Board or of the Compensation Committee (or such committee thereof or officer or officers of Biogen Idec to whom the Board has delegated this authority), at any time and from time to time, may amend or modify any or all of the provisions of this plan or may terminate this plan without the consent of any participant (or beneficiary or other person claiming through a participant). In addition, any amendment may be made by the committee, or the Executive Vice President - Chief Financial Officer, or the Executive Vice President - Human Resources of Biogen Idec except for an amendment that would materially increase or reduce the benefits of the plan to participants or materially increase the cost of maintaining the plan to Biogen Idec; such committee or specified officers may not terminate the plan.

No termination or amendment of the plan may reduce the amount credited to the account of any participant under the plan (including a participant whose service as a director terminated before such plan termination or amendment). However, Biogen Idec may change the deemed investment options under Section 5.1(b), and Biogen Idec may upon termination of this plan pay participants’ account balances to the participants regardless of the times elected for payment (or the start of installment payments) elected by the participants and may pay such amounts in single sum payments regardless of whether installment distributions would otherwise be payable under Section 6.6; provided that any such distributions upon plan termination must be permitted by Code Section 409A and the regulations and rulings thereunder. In addition, Biogen Idec may, from time to time, make any amendment that it deems necessary or desirable to satisfy the applicable requirements of the tax laws and rulings and regulations thereunder in order to preserve, if possible, the tax deferral features of this plan for participants. No diminution or restriction on a participant’s opportunity to make elections or withdrawals, or exercise other privileges or rights hereunder pursuant to the preceding sentence will be deemed to violate the rights of any participant or beneficiary hereunder so long as such change does not render a participant’s account balance forfeitable. Any amendment that is required by Code Section 409A and the regulations and rulings thereunder to have a delayed effective date will be effective no earlier than such required date.

7.2 Benefits Not Currently Funded.

(a) Nothing in this plan will be construed to create a trust or to obligate Biogen Idec to segregate a fund, purchase an insurance contract or other investment, or in any other way currently to fund the future payment of any benefits hereunder, nor will anything herein be construed to give any participant or any other person rights to any specific assets of Biogen Idec or any other entity. However, in order to make provision for its obligations hereunder, Biogen Idec may in its discretion purchase an insurance contract or other investment; any such contract or investment will be a general asset belonging to Biogen Idec, and no participant or beneficiary will have any rights to any such asset. The rights of a participant or beneficiary hereunder will be solely those of a general, unsecured creditor of Biogen Idec.

(b) Notwithstanding subsection (a) above, Biogen Idec in its sole discretion may establish a grantor trust of which it is treated as the owner under Code Section 671 to provide for the payment of benefits hereunder, subject to such terms and conditions as Biogen Idec may deem necessary or advisable to ensure that trust assets and benefit payments hereunder are not includable, by reason of the trust, in the taxable income of trust beneficiaries before actual distribution and that the existence of the trust does not cause the plan or any other arrangement to be considered funded for purposes of Title I of the Employee Retirement Income Security Act of 1974, as amended (“ERISA”) or for purposes of the Internal Revenue Code of 1986, as amended. Biogen Idec may terminate any such trust in accordance with its terms.

9

7.3 No Assignment.

(a) No participant or beneficiary will have any power or right to transfer, assign, anticipate or otherwise encumber any benefit or amount payable under this plan, nor shall any such benefit or amount payable be subject to seizure or attachment by any creditor of a participant or a beneficiary, or to any other legal, equitable or other process, or be liable for, or subject to, the debts, liabilities or other obligations of a participant or beneficiary except as otherwise required by law.

(b) Notwithstanding subsection (a) above, all or a portion of a participant’s account balance may be assigned to the participant’s spouse, former spouse, or other dependent (for purposes of this section, an “alternate recipient”) in connection with a domestic relations order (as defined in Code Section 414(p)) awarding such portion to the alternate recipient. However, no such order may award an alternate recipient greater rights than the participant has with respect to his account. Upon receipt of a copy of the relevant provisions of any such order or property settlement agreement, certified to be accurate and in effect by the participant, and an acknowledgment by the alternate recipient that such alternate recipient will be responsible for income taxes on such amounts when distributed or made available to such alternate recipient and that such amounts are subject to income tax withholding as provided in this plan, and such other information (including the alternate recipient’s social security number) as the committee may reasonably request, the committee will assign such amount to a separate account hereunder and will distribute such account to the alternate recipient in the form of a single sum payment as soon as administratively possible, as permitted by Reg. 1.409A-3(j)(4)(ii) (except for any unvested amounts).

7.4 Effect of Change in Control.

(a) Amendments. Notwithstanding Section 7.1, following the occurrence of a change in control (as defined in Section 2.3(a)): No amendment will be made following a change in control without the consent of the affected participant (or beneficiary or other person claiming through a participant) that adversely affects the rights of a participant (or beneficiary or other person claiming through a participant) under the plan as in effect immediately before such change in control, including (i) the right to make elections concerning the form and time of payment of distributions in accordance with Section 4.2(b) and the right to receive distributions in the form elected by the participant thereunder; and (ii) the right to the investment funds or options specified herein for the determination of deemed investment results applicable to participants’ accounts, as in effect immediately before such change in control. In particular, for purposes of clause (ii) of the preceding sentence (i) the committee may not set the rate of return of the fixed income option under Section 5.1(b) at a rate lower than that available under life insurance or annuity contracts obtained by a vendor or service provider (currently, The Todd Organization) for purposes of the plan; and (ii) the committee will maintain a menu of investment funds under Section 5.1(b) that is substantially similar (in terms of investment styles and ability to position an account on a risk/reward spectrum) to the array of funds available immediately prior to the change in control.

(b) Termination. The plan will not be terminated before the payment of all benefits hereunder in accordance with the terms of the plan as in effect immediately before such change in control without the consent of a majority of the participants (including, in the case of the deceased participant, the beneficiary or other person claiming through such deceased participant). This subsection (b) will not preclude the merger of this plan into a nonqualified deferred compensation plan maintained by a successor to Biogen Idec provided that the benefits and rights of participants hereunder (including this Section 7.4) are preserved in such successor plan.

(c) Effective Date. This Section 7.4 is effective as of the date of execution of this amended and restated plan document.

7.5 Responsibilities and Authority of Committee. The committee will control and manage the operation and administration of the plan except to the extent that such responsibilities are specifically assigned hereunder to Biogen Idec, the Board, the Compensation Committee (or a delegatee of the Board or the Compensation Committee).

The committee will have all powers and authority necessary or appropriate to carry out its responsibilities for the operation and administration of the plan. It will have discretionary authority to interpret and apply all plan provisions and to correct any defect, supply any omission or reconcile any inconsistency or ambiguity in such manner as it deems advisable. It will make all final determinations concerning eligibility, benefits and rights hereunder, and all other matters concerning plan administration and interpretation. All determinations and actions of

10

the committee will be conclusive and binding upon all persons, except as otherwise provided herein or by law, and except that the committee may revoke or modify a determination or action previously made in error. It is intended that any action or inaction by the committee will be given the maximum possible deference by any reviewing body (whether a court or other reviewing body), and will be reversed by such reviewing court or other body only if found to be arbitrary and capricious.

Biogen Idec will be the “plan administrator” and the “named fiduciary” for purposes of ERISA.

7.6 Limitation on Rights Created by Plan. Nothing appearing in the plan will be construed (a) to give any person any benefit, right or interest except as expressly provided herein, or (b) to create a contract of employment or to give any director the right to continue in such capacity or to affect or modify the terms of his service as a director in any way.

7.7 Tax Withholding. Any payment hereunder to a participant, beneficiary or alternate recipient will be subject to withholding of income and other taxes to the extent required by law.

7.8 Text Controls. Headings and titles are for convenience only, and the text will control in all matters.

7.9 Applicable State Law. To the extent that state law applies, the provisions of the plan will be construed, enforced and administered according to the laws of the Commonwealth of Massachusetts.

7.10 Paperless Administration. The committee may establish procedures whereby an electronic, internet or voice recognized authorization or election will or may be utilized under the plan in lieu a written form or document otherwise required by the terms of the plan. In such event, any reference herein to a written election, authorization or other form shall be deemed to include such other authorization or election.

BIOGEN IDEC INC.
By:	/s/ Paul J. Clancy
Dated: December 13, 2011

11

APPENDIX A

Historical Information; Amendments

A.1 Adoption of Plan Document. This plan document was approved by the Board of Directors of the Corporation (Biogen Idec Inc.), effective as of January 1, 2004.

By appropriate votes, the account balances of certain directors who previously were participants under the Biogen, Inc. Voluntary Board of Directors Savings Plan, maintained by Biogen, Inc. prior to the merger transaction, were transferred to and merged into this plan.

A.2 2005 Amendment and Restatement. The plan was amended and restated in its entirety, effective as of January 1, 2005 (except as otherwise specified), primarily to comply with the requirements of Code Section 409A and regulations thereunder. During the period from January 1, 2005 until the date of execution of this amended and restated plan document, the plan was interpreted and administered in accordance with a good faith interpretation of the requirements of Code Section 409A and applicable guidance of the Internal Revenue Service thereunder.

The provisions herein relating to distributions and other changes upon the occurrence of a change in control (primarily Sections 2.3, 4.2(b), 6.3 and 7.4) are effective as of the date of execution of this amended and restated plan document. The provisions relating to the increase in the threshold for the payment of a lump sum in place of installments from $10,000 to the Code Section 402(g)(1)(B) and (g)(4) limit (the last sentence of Section 6.6(a)) are effective as of January 1, 2008.

A.3 2012 Amendment and Restatement. The plan was amended and restated in its entirety, effective as of January 1, 2012 to expand the tax-deferred savings opportunities by allowing members of the Board of Directors to defer certain equity based awards granted under the Biogen Idec Inc. 2006 Non-Employee Directors Equity Plan (or successor plan).

A-1

EX-10.57

Exhibit 10.57

[Biogen Idec Logo]

December 7, 2010

Dear Doug:

I am pleased to extend you this offer of employment to join Biogen Idec as Executive Vice President, Research and Development. This position will report to me, George Scangos, Chief Executive Officer. The position will be based at our Weston, Massachusetts facility.

Base Salary: Your starting bi-weekly salary will be $24,230.77, which is equivalent to an annual salary of $630,000.02, and which will be paid in accordance with our standard payroll policies.

One-Time Cash Sign-on Bonus: Upon employment, you will receive $250,000 as a one-time cash bonus. The bonus will be paid to you within two pay periods after your start date provided that you sign the enclosed Cash Sign-On Bonus Agreement, which describes the terms and conditions of the cash sign-on bonus.

Annual Bonus Plan: You will be eligible to participate in the Biogen Idec Annual Bonus Plan, with a target bonus opportunity of 55% of your annualized base salary. Based upon your start date, your target bonus amount may be pro-rated. Eligibility details and other terms of the Plan are included in the current year’s Plan document, which will be made available upon your employment with the Company.

Long-Term Incentive: You will be granted Cash-Settled Performance Shares (CSPS) in connection with the commencement of your employment. The approximate grant date value of your CSPS award will be $1,000,000. You will also be granted Market Stock Units (MSU) in connection with the commencement of your employment. The approximate grant date value of your MSU award will be $1,000,000. Your CSPS and MSU awards will be granted on the first trading day of the month following your start date.

The actual terms of your CSPS and MSU awards will be communicated to you following the grant date. Your grants will be awarded under the Biogen Idec Inc. 2008 Omnibus Equity Plan. You are considered a “designated employee,” as defined in the 2008 Omnibus Equity Plan. Our 2008 Omnibus Equity Plan and Prospectus are available to you on Biogen Idec’s benefits website at www.mybenergy.com. Please read these documents for information about your Long-term Incentive grants.

Stock Trading Plan: As an Executive Vice President of the Company, you are required to enter into a 10b5-1 stock trading plan for all open market trades in Biogen Idec stock. A 10b5-1 plan allows you to buy or sell Biogen Idec securities at pre-defined times and/or prices and provides an affirmative defense against insider trading liability. More information on 10b5-1 trading plans will be made available upon your employment with the Company.

Employee Benefits: Biogen Idec offers a robust and highly competitive employee benefits program. As an employee, you will be able to choose from a menu of options through our flexible benefits program. These benefits include a 401(k) savings plan; group health care, including medical, dental, prescription drug and vision coverage; life, dependent life and disability insurance; as well as flexible spending accounts for eligible medical and dependent care expenses. You are also entitled to 20 vacation days per year, accrued on a per pay period basis. Additional benefit offerings include an Employee Stock Purchase Plan (ESPP) and work/life benefits such as a concierge service and access to subsidized backup dependent care. Please visit Biogen Idec’s benefits website at www.mybenergy.com to familiarize yourself with Biogen Idec’s complete benefit plan offerings.

Additional Executive Benefits

Supplemental Savings Plan: You will be entitled to participate in Biogen Idec’s Supplemental Savings Plan (SSP). This plan allows you to make pre-tax deferrals of up to 80% of your base salary and up to 100% of your Annual Bonus payment and certain other eligible incentive payments. Your contributions to this plan may be limited by your contributions towards other plans (e.g., 401(k), ESPP, medical, etc.). You will be provided with SSP enrollment information upon your employment with the Company.

Life Insurance: You will be provided life insurance coverage equal to three times your annual base salary, subject to meeting the medical standards stated in the group term life insurance policy for U.S. employees. Biogen Idec pays the premium for this insurance. The IRS requires employers to impute the value of company-paid life insurance for coverage over $50,000. This imputed income will be displayed on your pay stub.

Severance: Under certain circumstances, you will be entitled to receive severance benefits. Your severance benefits are explained in detail in the attached executive severance document. If your total severance benefits will trigger 280G excise taxes, you may elect to have Biogen Idec reduce the amount of your total payment to reduce your total payments to an amount below the 280G trigger. To facilitate your decision, Biogen Idec will estimate whether any 280G excise tax will be owed on severance and the amount of that excise tax.

Tax Preparation, Financial and Estate Planning: You are entitled to reimbursement of up to $7,500 per calendar year (January 1—December 31) for expenses incurred due to tax preparation, financial and/or estate planning services, as well as the purchase of tax preparation and/or financial planning software. You will be provided with details of this benefit upon your employment with the Company. Reimbursement must be made no later than the end of the calendar year following the year in which the expense is incurred, and must be requested within the deadlines and processes established in the policy.

You are required to satisfy the following contingencies prior to employment at Biogen Idec.

• Drug Screen: A completed drug-screening test is required within 48 hours of accepting this offer of employment. Please see the enclosed information regarding Biogen Idec’s Pre-Employment Drug Testing program. Your employment is subject to Biogen Idec receiving negative results (i.e., no drugs found) from your drug test. If you have not received confirmation of your test results from Human Resources within a week prior to your start date, please contact me to confirm your test results prior to starting.

• Background Check: Your employment is subject to satisfactory completion of Biogen Idec’s background check, which includes verification of employment history, educational and professional licenses, degrees and/or credentials, a criminal records check, a Social Security Number search and verification of any other professional qualifications that your position responsibilities at Biogen Idec may warrant. Completion of your online Application for Employment authorizes Biogen Idec to conduct these background checks. If you have any questions about the background check, please contact me.

• New Employee Forms: Upon your acceptance of Biogen Idec’s offer of employment, please visit our Company website, www.biogenidec.com. Under·’Careers,’ click·’New Employees.’ This site contains the forms you must complete in order to add you to Biogen Idec’s Payroll and Human Resources systems. Completion of these forms is required within 48 hours of accepting this offer of employment at Biogen Idec. Your username is your Social Security Number (without dashes) and your password is L83348R.

• Authorization to Work in the United States: The Federal government requires you to provide proper identification verifying your eligibility to work in the United States. Please bring documents necessary to complete the Employment Eligibility Verification Form I-9 on your first day of employment.

• Signed Proprietary Agreement: In order to protect Biogen Idec’s substantial investment in creating and maintaining its confidential and proprietary information, and to maintain goodwill with our customers, vendors and other business partners, you will be required to sign our ‘Employee Proprietary Information and Inventions and Dispute Resolution Agreement’ as a condition of employment. A copy of the Agreement is enclosed with this letter for your reference. Please sign and return this Agreement with your signed acceptance of our offer.

Your employment at Biogen Idec is employment at-will. This means that just as you are free to leave your employment at any time, with or without cause or notice, Biogen Idec also has the same right to terminate your employment at any time, with or without cause or notice.

To confirm your acceptance of this offer of employment, please sign and return this letter and keep the other copy for your records. Review and complete the enclosed New Employee Checklist with actions required in order to begin your acceptance process. Your new employee paperwork and drug screen should be completed within 48 hours of accepting this offer of employment. The New Employee Checklist provides instructions for your first day of employment.

We are very excited about the prospect of you joining Biogen Idec. We encourage you to accept this offer of employment by December 15, 2010.

Best regards,

/s/ George Scangos

George Scangos, Ph.D.

Chief Executive Officer

I accept this offer of employment and acknowledge the contingencies of employment described above, including the at-will nature of my employment.

ACCEPTED:

/s/ Douglas Williams	December 11, 2010	January 10, 2011
Douglas Williams	Signature Date	Start Date

EX-10.58

Exhibit 10.58

[Biogen Idec Logo]

November 19, 2010 REVISED

Dear Steve:

I am pleased to extend you this offer of employment to join Biogen Idec as Executive Vice President, Corporate Development and Strategy. This position will report to me, George Scangos, Chief Executive Officer. The position will be based at our Weston, Massachusetts facility.

Base Salary: Your starting bi-weekly salary will be $23,076.93, which is equivalent to an annual salary of $600,000.18, and which will be paid in accordance with our standard payroll policies.

One-Time Cash Sign-on Bonus: Upon employment, you will receive $350,000 as a one-time cash bonus. The bonus will be paid to you within two pay periods after your start date provided that you sign the enclosed Cash Sign-On Bonus Agreement, which describes the terms and conditions of the cash sign-on bonus.

Annual Bonus Plan: You will be eligible to participate in the Biogen Idec Annual Bonus Plan, with a target bonus opportunity of 55% of your annualized base salary. Based upon your start date, your target bonus amount may be pro-rated. Eligibility details and other terms of the Plan are included in the current year’s Plan document, which will be made available upon your employment with the Company.

Long-Term Incentive: You will be granted Cash-Settled Performance Shares (CSPS) in connection with the commencement of your employment. The approximate grant date value of your CSPS award will be $1,000,000. You will also be granted Market Stock Units (MSU) in connection with the commencement of your employment. The approximate grant date value of your MSU award will be $1,000,000. Your CSPS and MSU awards will be granted on the first trading day of the month following your start date.

The actual terms of your CSPS and MSU awards will be communicated to you following the grant date. Your grants will be awarded under the Biogen Idec Inc. 2008 Omnibus Equity Plan. You are considered a “designated employee,” as defined in the 2008 Omnibus Equity Plan. Our 2008 Omnibus Equity Plan and Prospectus are available to you on Biogen Idec’s benefits website at www.mybenergy.com. Please read these documents for information about your Long-term Incentive grants.

Stock Trading Plan: As an Executive Vice President of the Company, you are required to enter into a 10b5-1 stock trading plan for all open market trades in Biogen Idec stock. A 10b5-1 plan allows you to buy or sell Biogen Idec securities at pre-defined times and/or prices and provides an affirmative defense against insider trading liability. More information on 10b5-1 trading plans will be made available upon your employment with the Company.

Employee Benefits: Biogen Idec offers a robust and highly competitive employee benefits program. As an employee, you will be able to choose from a menu of options through our flexible benefits program. These benefits include a 401(k) savings plan; group health care, including medical, dental, prescription drug and vision coverage; life, dependent life and disability insurance; as well as flexible spending accounts for eligible medical and dependent care expenses. You are also entitled to 20 vacation days per year, accrued on a per pay period basis. Additional benefit offerings include an Employee Stock Purchase Plan (ESPP) and work/life benefits such as a concierge service and access to subsidized backup dependent care. Please visit Biogen Idec’s benefits website at www.mybenergy.com to familiarize yourself with Biogen Idec’s complete benefit plan offerings.

Additional Executive Benefits

Supplemental Savings Plan: You will be entitled to participate in Biogen Idec’s Supplemental Savings Plan (SSP). This plan allows you to make pre-tax deferrals of up to 80% of your base salary and up to 100% of your Annual Bonus payment and certain other eligible incentive payments. Your contributions to this plan may be limited by your contributions towards other plans (e.g., 401(k), ESPP, medical, etc.). You will be provided with SSP enrollment information upon your employment with the Company.

Life Insurance: You will be provided life insurance coverage equal to three times your annual base salary, subject to meeting the medical standards stated in the group term life insurance policy for U.S. employees. Biogen Idec pays the premium for this insurance. The IRS requires employers to impute the value of company-paid life insurance for coverage over $50,000. This imputed income will be displayed on your pay stub.

Severance: Under certain circumstances, you will be entitled to receive severance benefits. Your severance benefits are explained in detail in the attached executive severance document. If your total severance benefits will trigger 280G excise taxes, you may elect to have Biogen Idec reduce the amount of your total payment to reduce your total payments to an amount below the 280G trigger. To facilitate your decision, Biogen Idec will estimate whether any 280G excise tax will be owed on severance and the amount of that excise tax.

Tax Preparation, Financial and Estate Planning: You are entitled to reimbursement of up to $7,500 per calendar year (January 1—December 31) for expenses incurred due to tax preparation, financial and/or estate planning services, as well as the purchase of tax preparation and/or financial planning software. You will be provided with details of this benefit upon your employment with the Company. Reimbursement must be made no later than the end of the calendar year following the year in which the expense is incurred, and must be requested within the deadlines and processes established in the policy.

You are required to satisfy the following contingencies prior to employment at Biogen Idec.

• Drug Screen: A completed drug-screening test is required within 48 hours of accepting this offer of employment. Please see the enclosed information regarding Biogen Idec’s Pre-Employment Drug Testing program. Your employment is subject to Biogen Idec receiving negative results (i.e., no drugs found) from your drug test. If you have not received confirmation of your test results from Human Resources within a week prior to your start date, please contact me to confirm your test results prior to starting.

• Background Check: Your employment is subject to satisfactory completion of Biogen Idec’s background check, which includes verification of employment history, educational and professional licenses, degrees and/or credentials, a criminal records check, a Social Security Number search and verification of any other professional qualifications that your position responsibilities at Biogen Idec may warrant. Completion of your online Application for Employment authorizes Biogen Idec to conduct these background checks. If you have any questions about the background check, please contact me.

• New Employee Forms: Upon your acceptance of Biogen Idec’s offer of employment, please visit our Company website, www.biogenidec.com. Under·’Careers,’ click·’New Employees.’ This site contains the forms you must complete in order to add you to Biogen Idec’s Payroll and Human Resources systems. Completion of these forms is required within 48 hours of accepting this offer of employment at Biogen Idec. Your username is your Social Security Number (without dashes) and your password will be provided upon your acceptance of this offer.

• Authorization to Work in the United States: The Federal government requires you to provide proper identification verifying your eligibility to work in the United States. Please bring documents necessary to complete the Employment Eligibility Verification Form I-9 on your first day of employment.

• Signed Proprietary Agreement: In order to protect Biogen Idec’s substantial investment in creating and maintaining its confidential and proprietary information, and to maintain goodwill with our customers, vendors and other business partners, you will be required to sign our ‘Employee Proprietary Information and Inventions and Dispute Resolution Agreement’ as a condition of employment. A copy of the Agreement is enclosed with this letter for your reference. Please sign and return this Agreement with your signed acceptance of our offer.

Your employment at Biogen Idec is employment at-will. This means that just as you are free to leave your employment at any time, with or without cause or notice, Biogen Idec also has the same right to terminate your employment at any time, with or without cause or notice.

To confirm your acceptance of this offer of employment, please sign and return this letter and keep the other copy for your records. Review and complete the enclosed New Employee Checklist with actions required in order to begin your acceptance process. Your new employee paperwork and drug screen should be completed within 48 hours of accepting this offer of employment. The New Employee Checklist provides instructions for your first day of employment.

We are very excited about the prospect of you joining Biogen Idec. We encourage you to accept this offer of employment by November 12, 2010.

Best regards,

/s/ George Scangos

George Scangos, Ph.D.

Chief Executive Officer

I accept this offer of employment and acknowledge the contingencies of employment described above, including the at-will nature of my employment.

ACCEPTED:

/s/ Steven Holtzman	December 4, 2010	January 3, 2011
Steven Holtzman	Signature Date	Start Date

EX-21

Exhibit 21

BIOGEN IDEC INC.

The following is a list of subsidiaries of Biogen Idec Inc. as of December 31, 2011, omitting some subsidiaries which, considered in the aggregate, would not constitute a significant subsidiary.

SUBSIDIARY	STATE OR OTHER JURISDICTION OF INCORPORATION OR ORGANIZATION
Biogen Idec MA Inc.	Massachusetts
Biogen Idec New Ventures, Inc.	Delaware
Biogen Idec Manufacturing Holding LLC	Delaware
Biogen Idec Holding I Inc.	Delaware
Biogen Idec Holding II Inc.	Delaware
Biogen Idec Realty Corporation	Massachusetts
Biogen Idec Realty Limited Partnership	Massachusetts
Biogen Idec U.S. Corporation	Massachusetts
Biogen Idec U.S. Limited Partnership	Massachusetts
Biogen Idec (RTP) Realty LLC	Delaware
The Biogen Idec Foundation Inc.	Massachusetts
Biogen Idec U.S. Pacific LLC	Delaware
Biogen Idec U.S. West Corporation	Delaware
Biogen Idec Therapeutics Inc.	Delaware
Biogen Idec Nobel Research Center, LLC	Delaware
Conforma Therapeutics Corporation	Delaware
Biogen Idec Hemophilia Inc.	Delaware
Biogen Idec Canada Inc.	Delaware
Biogen Idec SRO, Inc.	Delaware
Biogen Idec (Argentina) SRL	Argentina
Biogen Idec Australia PTY Ltd	Australia
Biogen Idec Austria GmbH	Austria
Biogen Idec Belgium N.V./S.A.	Belgium
Biogen Idec Brazil Produtos Farmaceuticos LTDA	Brazil
Biogen Idec (Czech Republic) s.r.o.	Czech Republic
Biogen Idec (Denmark) A/S	Denmark
Biogen Idec (Denmark) Manufacturing ApS	Denmark
Biogen Idec Holding APS	Denmark
Biogen Idec Finland OY	Finland
Biogen Idec France S.A.S.	France
Biogen Idec GmbH	Germany
Biogen Idec Biotech India Pvt. Ltd.	India
Biogen Idec (Ireland) Ltd.	Ireland
Biogen Idec Japan Ltd.	Japan
Biogen Idec Mexico S. DE R.L. DE C.V.	Mexico
Biogen Idec B.V.	The Netherlands
Biogen Idec International B.V.	The Netherlands
Biogen Idec Norway AS	Norway
Biogen Idec NZ Ltd.	New Zealand
Biogen Idec Portugal Sociedade Farmaceutica, Unipessoal, Lda.	Portugal
Biogen Idec Iberia, S.L.	Spain
Biogen Idec (Slovak Republic) s.r.o.	Slovak Republic
Biogen Idec promet s farmacevtskimi in biotehnoloskimi proizvodi d.o.o	Slovenia
Biogen Idec Sweden AB	Sweden
Biogen Idec International GmbH	Switzerland
Eidetica Biopharma GmbH	Switzerland
Biogen Idec Ltd.	UK
Biogen Idec Switzerland AG	Switzerland
Biogen Idec Italia SRL	Italy
Biogen Idec Luxembourg Holding SARL	Luxembourg
Biogen Idec International Holding Limited	Bermuda
Arrowpark Interseas Ltd	Isle of Man
Wolter Interseas Ltd	Isle of Man

Biogen Idec Management Services GmbH	Switzerland
Biogen Idec (Denmark) New Manufacturing ApS	Denmark
Fundacion Biogen Idec	Spain
Biogen Idec (Hong Kong) Limited	Hong Kong
Biogen Idec (Singapore) Pte Ltd	Singapore
Biogen Idec Hungary KFT	Hungary
Biogen Idec Uruguay SA	Uruguay
Biogen Idec Chile Spa	Chile
Biogen Idec International Neuroscience GmbH	Switzerland
Biogen Idec Poland	Poland
Biogen Idec Pharmaceutical Consultancy (Shanghai) Co., Ltd.	China
Biogen Idec Research Ltd.	UK

EX-23

Exhibit 23

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration Statement on Form S-4 (No. 333-107098) and registration statements on Form S-8 (Nos. 333-97211, 333-106794, 333-47904, 333-65494, 333-110432, 333-110433, 333-128339, 333-152456, 333-128339, 333-140817 and 333-170133) of Biogen Idec Inc. of our report dated February 3, 2012 relating to the financial statements and the effectiveness of internal control over financial reporting, which appears in this Form 10-K.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts

February 3, 2012

EX-31.1

Exhibit 31.1

CERTIFICATION OF CHIEF EXECUTIVE OFFICER PURSUANT TO

SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, George A. Scangos, certify that:

1. I have reviewed this annual report of Biogen Idec Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c) Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d) Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: February 3, 2012	/s/ George A. Scangos
	George A. Scangos Chief Executive Officer

EX-31.2

Exhibit 31.2

CERTIFICATION OF CHIEF FINANCIAL OFFICER PURSUANT TO

SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Paul J. Clancy, certify that:

1. I have reviewed this annual report of Biogen Idec Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d. Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: February 3, 2012	/s/ Paul J. Clancy
	Paul J. Clancy
	Executive Vice President and Chief Financial Officer

EX-32.1

Exhibit 32

CERTIFICATION

PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

Pursuant to section 906 of the Sarbanes-Oxley Act of 2002 (subsections (a) and (b) of section 1350, chapter 63 of title 18, United States Code), each of the undersigned officers of Biogen Idec Inc., a Delaware corporation (the “Company”), does hereby certify, to such officer’s knowledge, that:

The Annual Report on Form 10-K for the year ended December 31, 2011 (the “Form 10-K”) of the Company fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, and the information contained in the Form 10-K fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated: February 3, 2012	/s/ George A. Scangos
	George A. Scangos Chief Executive Officer [principal executive officer]

Dated: February 3, 2012	/s/ Paul J. Clancy
	Paul J. Clancy Executive Vice President and Chief Financial Officer [principal financial officer]

A signed original of this written statement required by Section 906 has been provided to the Company and will be retained by the Company and furnished to the Securities and Exchange Commission or its staff upon request.

XML

Accounts Receivable (Tables)

12 Months Ended

Dec. 31, 2011

Accounts Receivable [Abstract]

Net accounts receivable balances on product sales from different countries

	As of December 31, 2011
(In millions)	Current Balance Included within Accounts Receivable, net		Non-Current Balance  Included within Investments and Other Assets		Total
Spain	$	68.5	$	65.5	$	134.0
Italy	$	19.4	$	48.7	$	68.1
Portugal	$	20.6	$	12.3	$	32.9
Greece	$	4.0	$	—	$	4.0

	As of December 31, 2010
(In millions)	Current Balance Included within Accounts Receivable, net		Non-Current Balance  Included within Investments and Other Assets		Total
Spain	$	70.8	$	29.8	$	100.6
Italy	$	103.2	$	14.8	$	118.0
Portugal	$	17.8	$	5.5	$	23.3
Greece	$	3.9	$	—	$	3.9

XML

Collaborations (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Co-promotion profit sharing formula
Above $50.0 million	40.00%				40.00%				40.00%	40.00%	40.00%
Revenues from unconsolidated joint business
Revenue on sales of RITUXAN in the rest of world	$ 996,600,000	$ 975,800,000	$ 956,700,000	$ 907,100,000	$ 909,800,000	$ 876,900,000	$ 859,200,000	$ 824,200,000	$ 3,836,117,000	$ 3,470,056,000	$ 3,152,941,000
Total unconsolidated joint business revenues	257,500,000	266,500,000	216,500,000	256,100,000	258,000,000	258,000,000	306,400,000	254,900,000	996,597,000	1,077,244,000	1,094,863,000
U.S [Member]
Revenues from unconsolidated joint business
Revenue on sales of RITUXAN in the rest of world									1,954,800,000	1,744,400,000	1,638,000,000
Roche Group - Genentech [Member]
Revenues from unconsolidated joint business
Biogen Idec's share of pre-tax co-promotion profits in the U.S									872,700,000
Total unconsolidated joint business revenues									996,600,000	1,077,200,000	1,094,900,000
Roche Group - Genentech [Member] | U.S [Member]
Revenues from unconsolidated joint business
Biogen Idec's share of pre-tax co-promotion profits in the U.S										848,000,000	773,600,000
Reimbursement of our selling and development expenses in the U.S									6,100,000	58,300,000	65,600,000
RITUXAN [Member]
Co-promotion profit sharing formula
First $50.0 million	30.00%								30.00%
RITUXAN [Member] | Roche Group - Genentech [Member] | Outside the U.S [Member]
Revenues from unconsolidated joint business
Revenue on sales of RITUXAN in the rest of world									$ 117,800,000	$ 170,900,000	$ 255,700,000
RITUXAN [Member] | After First New Product FDA Approval [Member]
Co-promotion profit sharing formula
First $50.0 million	30.00%								30.00%
Until First GA101 Threshold Date	38.00%								38.00%
After First GA101 Threshold Date
Until First Threshold Date	37.50%								37.50%
After First Threshold Date and until Second Threshold Date	35.00%								35.00%
After Second Threshold Date	30.00%								30.00%
First Non CLL GA 101 FD Approval Occurs First | RITUXAN [Member] | Before First New Product FDA Approval [Member]
Co-promotion profit sharing formula
First $50.0 million	30.00%								30.00%
Until First GA101 Threshold Date	39.00%								39.00%
After First GA101 Threshold Date
Until Second GA101 Threshold Date	37.50%								37.50%
After Second GA101 Threshold Date	35.00%								35.00%
GA 101 CLL Sales Trigger Occurs First [Member] | RITUXAN [Member] | Before First New Product FDA Approval [Member]
Co-promotion profit sharing formula
First $50.0 million	30.00%								30.00%
Above $50.0 million	35.00%								35.00%

XML

Collaborations (Tables)

12 Months Ended

Dec. 31, 2011

Other Consolidated Financial Statement Detail / Collaborations [Abstract]

Co-promotion profit sharing formula

				Before First New Product FDA Approval
Co-promotion Operating Profits†	After First New Product FDA Approval			First Non-CLL GA101 FDA Approval Occurs First			GA101 CLL Sales Trigger Occurs First
I. First $50.0 million		30	%		30	%		30	%
II. Above $50.0 million		—			—			35	%
A. Until First GA101 Threshold Date		38	%		39	%		—
B. After First GA101 Threshold Date
1(a). Until First Threshold Date		37.5	%		—			—
1(b). After First Threshold Date and  until Second Threshold Date		35	%		—			—
1(c). After Second Threshold Date		30	%		—			—
2. Until Second GA101 Threshold  Date		—			37.5	%		—
C. After Second GA101 Threshold Date		—			35	%		—

† First GA101 Threshold Date means the earlier of (1) the date of the First Non-CLL GA101 FDA Approval if U.S. gross sales of GA101 for the preceding consecutive 12 month period were at least $150.0 million or (2) the first day of the calendar quarter after the date of the First Non-CLL GA101 FDA Approval that U.S. gross sales of GA101 within any consecutive 12 month period have reached $150.0 million.

Second GA101 Threshold Date means the first day of the calendar quarter after U.S. gross sales of GA101 within any consecutive 12 month period have reached $500.0 million.

First Threshold Date means the earlier of (1) the GA101 CLL Sales Trigger, (2) the Second GA101 Threshold Date and (3) the later of (a) the first date that U.S. gross sales of New Products in any calendar year reach $150.0 million and (b) January 1 of the calendar year following the calendar year in which the First New Product FDA Approval occurs if gross sales of New Products reached $150.0 million within the same calendar year in which the First New Product FDA Approval occurred.

Second Threshold Date means the later of (1) the first date that U.S. gross sales of New Products in any calendar year reach $350.0 million and (2) January 1 of the calendar year following the calendar year in which the First Threshold Date occurs.

Revenues from unconsolidated joint business

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Biogen Idec’s share of pre-tax co-promotion profits in the U.S.	$	872.7	$	848.0	$	773.6
Reimbursement of our selling and development expenses in the U.S.		6.1		58.3		65.6
Revenue on sales of RITUXAN in the rest of world		117.8		170.9		255.7
Total unconsolidated joint business revenues	$	996.6	$	1,077.2	$	1,094.9

Summary of activity related to collaboration with Acorda

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Upfront and milestones payments made to Acorda	$	25.0	$	—	$	110.0
Total expense incurred by Biogen Idec excluding upfront and milestones payments	$	22.3	$	22.8	$	4.7
Total expense reflected within our statements of income	$	22.3	$	22.8	$	114.7
Total capitalized as an intangible asset	$	25.0	$	—	$	—

Summary of activity related to collaboration, along with an estimate of additional future development expense

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Acorda	$	135.0
Total expense incurred by Biogen Idec, excluding upfront and milestone payments	$	49.9

Summary of activity related to collaboration with Portola Pharmaceuticals, Inc.

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Total expense incurred by the collaboration	$	1.1	$	—	$	—
Total expense reflected within our consolidated statements of income, excluding upfront and milestone payments	$	0.9	$	—	$	—

Summary of activity related to collaboration, along with an estimate of additional future development expense

(In millions)	As of December 31, 2011
Total upfront payments paid to Portola	$	36.8
Total development expense incurred by Biogen Idec Inc., excluding upfront and milestone payments	$	0.9
Estimate of additional amounts to be incurred by Biogen Idec in development of PRT062607	$	675.0

Mechanism for reimbursement, under the amended agreement amounts payable

			Rates should Sobi exercise its option right (3)
Royalty and Net Revenue Share Rates:	Method	Rate prior to 1st commercial sale in the Sobi Territory:	Base Rate following 1st commercial sale in the Sobi Territory:	Rate during the Reimbursement Period:
Sobi rate to Biogen on net sales in the Sobi Territory	Royalty	N/A	10 to 12%	Base Rate plus 5%
Biogen rate to Sobi on net sales in the Biogen North America Territory	Royalty	2%	10 to 12%	Base Rate less 5%
Biogen rate to Sobi on net sales in the Biogen Direct Territory	Royalty	2%	15 to 17%	Base Rate less 5%
Biogen rate to Sobi on net revenue (1) from the Biogen Distributor Territory (2)	Net Revenue Share	10%	50%	Base Rate less 15%

(1) Net revenue represents Biogen Idec’s pre-tax receipts from third-party distributors, less expenses incurred by Biogen Idec in the conduct of commercialization activities supporting the distributor activities.

(2) The Biogen Distributor Territory represents Biogen territories where sales are derived utilizing a third-party distributor.

(3) A credit will be issued to Sobi against its reimbursement of the Opt-in Consideration in an amount equal to the difference in the rate paid by Biogen Idec to Sobi on sales in the Biogen territories for certain periods prior to the first commercial sale in the Sobi Territory versus the rate that otherwise would have been payable on such sales.

Summary of activity related to collaboration with Swedish Orphan Biovitrum

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Total expense incurred by collaboration	$	129.6	$	78.9	$	44.9
Total expense reflected within our consolidated statements of income	$	129.6	$	78.5	$	22.5

Summary of activity related to collaboration, along with an estimate of additional future development expense

(In millions)	As of December 31, 2011
Total upfront and milestone payments received from Sobi	$	5.0
Total development expense incurred by Biogen Idec Inc., excluding upfront and milestone payments	$	262.7
Estimate of additional amounts expected to be incurred by Biogen Idec in development of Factors VIII and IX	$	420.0

Summary of activity related to collaboration with Facet Biotech

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Total expense incurred by the collaboration	$	104.4	$	74.8	$	40.8
Biogen Idec’s share of expense reflected within our consolidated statements of income	$	52.2	$	37.4	$	20.4

Summary of activity related to collaboration, along with an estimate of additional future development expense

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Abbott	$	80.0
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	$	212.1
Estimate of additional amounts to be incurred by us in development of current indications of daclizumab	$	280.0

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Accumulated Other Comprehensive Income (Loss) (Tables)

12 Months Ended

Dec. 31, 2011

Equity/Accumulated Other Comprehensive Income (Loss) [Abstract]

Summary of Accumulated Other Comprehensive Income (Loss)

	As of December 31,
(In millions)	2011			2010
Translation adjustments	$	(50.3	)	$	(24.4	)
Unrealized gains (losses) on securities available for sale		—			12.4
Unrealized gains (losses) on foreign currency forward contracts		32.8			(9.8	)
Unfunded status of pension and postretirement benefit plans		(9.0	)		0.2
Accumulated other comprehensive income (loss)	$	(26.5	)	$	(21.6	)

XML

Commitments and Contingencies (Details Textual) (USD $)	12 Months Ended				12 Months Ended				12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2006 FUMADERM and BG-12 [Member]	Dec. 31, 2010 Biogen Idec Hemophilia [Member]	Dec. 31, 2011 Biogen Idec Hemophilia [Member]	Dec. 31, 2007 Biogen Idec Hemophilia [Member]	Dec. 31, 2011 Weston Facility [Member]	Dec. 31, 2011 San Diego Facility [Member]	Dec. 31, 2011 New Cambridge Leases [Member]	Jul. 14, 2011 New Cambridge Leases [Member]
Business Acquisition [Line Items]
Sale Leaseback Transaction Period In Years									15 years
Total minimum lease payments								$ 240,000,000
Fair value of contingent consideration	151,000,000	81,200,000	0				80,000,000
Milestone payment payable to Acorda Therapeutics, Inc. (Acorda)					40,000,000
Additional contingent payment for Biologic License						20,000,000
Additional contingent payment for marketing authorization						20,000,000
Amount paid in cash				220,000,000
Contingent payment achieved in first quarter				15,000,000
Commitments And Contingencies (Textual) [Abstract]
Lease Rent Expense which terminates at various dates	46,200,000	44,800,000	36,400,000
Future minimum rental commitments	675,100,000									340,000,000	340,000,000
Liabilities associated with uncertain tax positions	58,400,000
Funding commitments, Approximately	14,500,000
Accrued expenses	25,000,000
Cancellable future commitments	475,000,000
Potential future milestone payments commitment, approximately	$ 1,900,000,000

XML

Fair Value Measurements (Details 1) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Fair value of venture capital investments
Beginning balance	$ 20.8	$ 21.9
Unrealized gains included in earnings	2.4
Unrealized losses included in earnings	(1.4)	(2.1)
Purchases	1.7	2.1
Settlements		(1.1)
Ending balance	$ 23.5	$ 20.8

XML

Segment Information (Details 1) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Geographic information
Product	$ 996,600,000	$ 975,800,000	$ 956,700,000	$ 907,100,000	$ 909,800,000	$ 876,900,000	$ 859,200,000	$ 824,200,000	$ 3,836,117,000	$ 3,470,056,000	$ 3,152,941,000
Revenues from unconsolidated joint business									996,600,000	1,077,200,000	1,094,900,000
Other revenues from external customers	72,600,000	67,700,000	35,500,000	40,100,000	51,400,000	41,000,000	47,100,000	29,700,000	215,920,000	169,123,000	129,544,000
Long-lived assets	1,838,400,000				1,826,200,000				1,838,400,000	1,826,200,000	1,805,400,000
Asia [Member]
Geographic information
Product									88,700,000	69,000,000	47,900,000
Revenues from unconsolidated joint business									30,700,000	26,000,000	24,100,000
Long-lived assets	5,300,000				5,400,000				5,300,000	5,400,000	3,600,000
Europe [Member]
Geographic information
Product									1,163,300,000	1,090,700,000	913,700,000
Revenues from unconsolidated joint business									29,900,000	95,300,000	190,200,000
Other revenues from external customers									28,300,000	32,600,000	26,200,000
Long-lived assets	816,600,000				717,400,000				816,600,000	717,400,000	705,600,000
Other [Member]
Geographic information
Product									251,800,000	203,600,000	178,500,000
Revenues from unconsolidated joint business									57,200,000	49,600,000	41,400,000
Long-lived assets	2,400,000				1,600,000				2,400,000	1,600,000	2,100,000
U.S [Member]
Geographic information
Product									1,954,800,000	1,744,400,000	1,638,000,000
Revenues from unconsolidated joint business									878,800,000	906,300,000	839,200,000
Other revenues from external customers									187,000,000	136,000,000	102,800,000
Long-lived assets	1,012,500,000				1,100,300,000				1,012,500,000	1,100,300,000	1,092,700,000
Germany [Member]
Geographic information
Product									377,500,000	362,400,000	374,800,000
Other revenues from external customers									600,000	500,000	500,000
Long-lived assets	$ 1,600,000				$ 1,500,000				$ 1,600,000	$ 1,500,000	$ 1,400,000

XML

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2011

Commitments and Contingencies [Abstract]

Minimum rental commitments under non-cancelable leases

(In millions)	2012			2013			2014			2015		2016		Thereafter		Total
Minimum lease payments (1)	$	33.9		$	42.5		$	54.3		$	49.3	$	44.6	$	450.5	$	675.1
Less: income from subleases		(0.5	)		(0.5	)		(0.4	)		—		—		—		(1.4	)
Net minimum lease payments	$	33.4		$	42.0		$	53.9		$	49.3	$	44.6	$	450.5	$	673.7

(1) Includes future minimum rental commitments related to leases executed for two office buildings to be built in Cambridge, Massachusetts with a planned occupancy during the second half of 2013. The leases both have 15 year terms and we have options to extend the term of each lease for two additional five-year terms. Future minimum rental commitments under these leases will total approximately $340.0 million over the initial 15 year lease terms.

Balances also include remaining total minimum lease payments through 2025, totaling approximately $240.0 million, related to our current principal executive offices in Weston, Massachusetts, which we expect to vacate upon completion of the two new buildings in Cambridge Massachusetts.

For additional information related to these transactions, please read Note 11, Property, Plant and Equipment to these consolidated financial statements.

XML

Financial Instruments (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Investment	Dec. 31, 2010 Investment	Dec. 31, 2009 Investment
Financial Instruments (Textual) [Abstract]
Federal Deposit Insurance Corporation guaranteed senior notes issued under the Temporary Liquidity Guarantee Program	$ 214.0	$ 163.5
Original maturities of commercial paper and short-term debt securities	less than 90 days
Average maturity of marketable securities, months	14 months	11 months
Sale of strategic investments	40.6	1.8	5.9
Number of strategic investments sold	4	1	2
Gain (loss) from sale of strategic equity investments	13.5		3.0
Impairment charges of our publicly-held strategic investments and for declines in value of funds that were determined to be other than temporary	11.5	21.3	10.6
Other- than-temporary impairment of publicly- held strategic investment		21.3	7.0
Impairment charges of our publicly-held strategic investments and for declines in value of funds recorded under cost method	11.5
Other-than-temporary impairment of available-for-sale securities primarily related to marketable debt securities			3.6
Strategic investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost basis of equity securities of certain privately-owned companies and venture capital funds	$ 39.2	$ 35.0

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Income Taxes (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Components of deferred tax assets and liabilities
Tax credits	$ 60.0	$ 47.6
Inventory, other reserves, and accruals	104.1	203.1
Capitalized costs	5.3	6.7
Intangibles, net	75.8	61.8
Net operating loss	22.9	35.3
Share-based compensation	54.7	64.4
Other	45.7	70.3
Valuation allowance	(10.8)	(10.8)
Total deferred tax assets	357.7	478.4
Purchased intangible assets	(384.8)	(446.1)
Unrealized gain on investments and cumulative translation adjustment	(3.5)	(6.6)
Inventory	(76.8)	0
Depreciation, amortization and other	(133.1)	(114.4)
Total deferred tax liabilities	$ (598.2)	$ (567.1)

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Indebtedness (Tables)

12 Months Ended

Dec. 31, 2011

Indebtedness [Abstract]

Summary of Indebtedness

	As of December 31,
(In millions)	2011		2010
Current portion:
Note payable to Fumedica	$	3.3	$	3.3
Credit line from Dompé		—		8.0
Financing arrangement for the sale of the San Diego facility		—		125.9
Current portion of notes payable, line of credit and other financing arrangements	$	3.3	$	137.2
Non-current portion:
6.0% Senior notes due 2013	$	449.9	$	449.8
6.875% Senior notes due 2018		592.3		597.9
Note payable to Fumedica		16.4		18.7
Financing arrangement for the construction of the Cambridge facilities		2.2		—
Non-current portion of notes payable, line of credit and other financing arrangements	$	1,060.8	$	1,066.4

Total debt maturities

(In millions)	As of December 31, 2011
2012	$	3.4
2013		453.4
2014		3.4
2015		3.4
2016		3.4
2017 and thereafter		556.7
Total	$	1,023.7

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Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2011

Quarterly Financial Data (Unaudited) [Abstract]

Quarterly Financial Data (Unaudited)

26.    Quarterly Financial Data (Unaudited)

(In millions, except per share amounts)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total Year
2011			(a)				(b)
Product revenues	$	907.1	$	956.7	$	975.8	$	996.6	$	3,836.1
Unconsolidated joint business revenues	$	256.1	$	216.5	$	266.5	$	257.5	$	996.6
Other revenues	$	40.1	$	35.5	$	67.7	$	72.6	$	215.9
Total revenues	$	1,203.3	$	1,208.6	$	1,309.9	$	1,326.7	$	5,048.6
Gross Profit	$	1,100.2	$	1,108.1	$	1,186.4	$	1,187.1	$	4,581.9
Net income	$	308.8	$	304.0	$	353.7	$	300.2	$	1,266.7
Net income attributable to Biogen Idec Inc.	$	294.3	$	288.0	$	351.8	$	300.2	$	1,234.4
Basic earnings per share attributable to Biogen Idec Inc.	$	1.22	$	1.19	$	1.45	$	1.24	$	5.09
Diluted earnings per share attributable to Biogen Idec Inc.	$	1.20	$	1.18	$	1.43	$	1.22	$	5.04

(In millions, except per share amounts)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total Year
2010	(c)				(d)		(e)
Product revenues	$	824.2	$	859.2	$	876.9	$	909.8	$	3,470.1
Unconsolidated joint business revenues	$	254.9	$	306.4	$	258.0	$	258.0	$	1,077.3
Other revenues	$	29.7	$	47.1	$	41.0	$	51.4	$	169.1
Total revenues	$	1,108.9	$	1,212.7	$	1,175.8	$	1,219.0	$	4,716.4
Gross Profit	$	1,011.8	$	1,105.7	$	1,079.9	$	1,118.8	$	4,316.2
Net income	$	220.0	$	294.6	$	112.2	$	271.8	$	898.6
Net income attributable to Biogen Idec Inc.	$	217.4	$	293.4	$	254.1	$	240.3	$	1,005.3
Basic earnings per share attributable to Biogen Idec Inc	$	0.80	$	1.13	$	1.06	$	1.00	$	3.98
Diluted earnings per share attributable to Biogen Idec Inc	$	0.80	$	1.12	$	1.05	$	0.99	$	3.94

Full year amounts may not sum due to rounding.

(a) Our share of RITUXAN revenues from unconsolidated joint business was reduced by approximately $50.0 million in the second quarter of 2011 as a result of an accrual for estimated compensatory damages (including interest) relating to Genentech’s ongoing arbitration with Hoechst GmbH. For additional information related to this matter, please read Note 21, Litigation to these consolidated financial statements.

(b) Net income and net income attributable to Biogen Idec Inc. for the fourth quarter of 2011 includes a charge to research and development expense of $36.8 million related to an upfront payment made in connection with our collaboration and license agreement entered into with Portola Pharmaceuticals, Inc.

(c) Net income and net income attributable to Biogen Idec Inc. for the first quarter of 2010 includes a charge to acquired IPR&D of $40.0 million related to the achievement of a milestone by Biogen Idec Hemophilia, Inc. (formerly Syntonix Pharmaceuticals, Inc.).

(d) Net income and net income attributable to Biogen Idec Inc. for the third quarter of 2010 includes a charge to acquired IPR&D of $205.0 million incurred in connection with the license agreement entered into with Knopp Neurosciences Inc. (Knopp), which we consolidated as we determined that we are the primary beneficiary of the entity. The $205.0 million charge was partially offset by an attribution of $145.0 million to the noncontrolling interest.

(e) Net income and net income attributable to Biogen Idec Inc. for the fourth quarter of 2010 includes charges totaling $75.2 million related to our restructuring plan announced November 3, 2010.

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Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Foreign currency forward contracts that were entered into to hedge forecasted revenue
Total foreign currency forward contracts	$ 532.3	$ 494.2
Derivative Instruments (Textual) [Abstract]
Lower Range of Durations of foreign currency forward contracts	1 month	1 month
Higher Range of Durations of foreign currency forward contracts	12 months	12 months
Gain/Loss on fair value of Foreign currency forward contracts	36.5	(11.0)
Expected Settlement time for contracts, in months	next 12 months
Gains and losses in earnings of Foreign currency forward contracts due to hedge ineffectiveness	(3.9)	0.4	(1.1)
Gains/(Losses) in product revenue for the settlement of certain effective cash flow hedge instruments	(36.9)	45.7	(49.7)
Aggregate notional amount of outstanding foreign currency contracts	263.7	160.8
Fair Value of outstanding foreign currency contracts	6.4	0.1
Net (gains) losses of other income (expense) related to foreign currency forward contracts	12.1	6.0
Foreign Exchange Contract [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member]
Summary of Derivatives designated as Hedging Instruments
Derivative Asset, Fair Value	32.6	0
Foreign Exchange Contract [Member] | Accrued Expenses and Other Liabilities [Member] | Designated as Hedging Instrument [Member]
Summary of Derivatives designated as Hedging Instruments
Derivative Liability, Fair Value	0	11.0
Euro [Member]
Foreign currency forward contracts that were entered into to hedge forecasted revenue
Total foreign currency forward contracts	496.4	460.3
Canadian Dollar [Member]
Foreign currency forward contracts that were entered into to hedge forecasted revenue
Total foreign currency forward contracts	22.9	24.0
Swedish krona [Member]
Foreign currency forward contracts that were entered into to hedge forecasted revenue
Total foreign currency forward contracts	$ 13.0	$ 9.9

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Collaborations (Details Textual)	1 Months Ended	3 Months Ended	12 Months Ended					12 Months Ended	3 Months Ended		12 Months Ended									12 Months Ended				3 Months Ended	12 Months Ended		3 Months Ended	12 Months Ended
	Jun. 30, 2011 USD ($)	Jun. 30, 2011 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2011 EUR (€)	Jan. 31, 2007 Biogen Idec Hemophilia [Member]	Dec. 31, 2011 Roche Group - Genentech [Member] Member	Mar. 31, 2009 Elan [Member] USD ($)	Sep. 30, 2008 Elan [Member] USD ($)	Dec. 31, 2011 Elan [Member] USD ($)	Dec. 31, 2010 Elan [Member] USD ($)	Dec. 31, 2009 Elan [Member] USD ($)	Dec. 31, 2011 Acorda [Member] USD ($)	Dec. 31, 2009 Acorda [Member] USD ($)	Dec. 31, 2011 Portola Pharmaceuticals [Member] USD ($)	Dec. 31, 2011 Abbott Biotherapeutics [Member] USD ($)	Dec. 31, 2010 Abbott Biotherapeutics [Member] USD ($)	Dec. 31, 2011 Genentech [Member] USD ($)	Dec. 31, 2011 Swedish Orphan Biovitrum [Member] USD ($)	Dec. 31, 2011 RITUXAN [Member] USD ($)	Dec. 31, 2011 RITUXAN [Member] Maximum [Member]	Dec. 31, 2011 RITUXAN [Member] Minimum [Member]	Jun. 30, 2011 RITUXAN [Member] Genentech [Member] USD ($)	Dec. 31, 2011 Ocrelizumab [Member] Maximum [Member]	Dec. 31, 2011 Ocrelizumab [Member] Minimum [Member]	Dec. 31, 2010 GA101 [Member] USD ($)	Dec. 31, 2011 GA101 [Member] USD ($)	Dec. 31, 2011 GA101 [Member] Maximum [Member]	Dec. 31, 2011 GA101 [Member] Minimum [Member]	Dec. 31, 2011 New Anti-CD20 [Member] Third Party Anti CD-20 [Member] Roche Group - Genentech [Member] USD ($)	Dec. 31, 2010 New Anti-CD20 [Member] Third Party Anti CD-20 [Member] Roche Group - Genentech [Member] USD ($)	Dec. 31, 2009 New Anti-CD20 [Member] Third Party Anti CD-20 [Member] Roche Group - Genentech [Member] USD ($)
Collaborations (Textual) [Abstract]
Future royalties percentage to be received on sale of ocrelizumab																									24.00%	13.50%
Percentage of future development and commercialization expenses payable related to GA101																												35.00%
Profit sharing on sale of GA 101, percentage																													39.00%	35.00%
Sharing percentage of development expenses of GA 101, Prior to Amendment																												30.00%
Compensation payment under terms of Amendment for reimbursement of increased share of previously incurred expenses																											$ 10,000,000
Royalties to be received under the collaboration agreement																					10% to 12% royalties will be paid on sales of RITUXAN outside the U.S. and Canada for a period lasting 11 years
Period of collaboration agreement																					11 years
Royalty period for substantially all of the remaining royalty-bearing sales of RITUXAN in the rest of world																					expire through 2012
Number of members in Joint Development Committee								3
Percentage of Co promotion Operating Profits first fifty million																					30.00%
Percentage of share of co-promotion profits exceeding $50 million, prior to October 2010 amendment.																					40.00%
GA101 CLL Sales Trigger - US GA101 gross sales threshold																												500,000,000
Threshold of gross sales of GA 101 to be achieved in any 12 consecutive months under option two																					150,000,000
Threshold of gross sales of new product to be achieved in any calendar year under sub option three of option two																					350,000,000
Limit of gross sale of GA 101 to be achieved in preceding 12 months under option one																												150,000,000
Limit of gross sale of GA 101 to be achieved in any 12 months under option one																												150,000,000
Limit of gross sale of new product to be achieved in any calendar year under sub option one and two of option two																												150,000,000
Decrease in share of co-promotion profits due to estimated compensation damages		50,000,000																						50,000,000
Estimated range of possible loss, related to reduction of share of revenues	50,000,000	50,000,000				30,700,000													50,000,000
Research and development			1,219,602,000	1,248,604,000	1,283,068,000																										26,900,000	50,600,000	62,500,000
Milestone payments received under collaboration agreement									50,000,000	75,000,000
Milestone payment to be amortized			100,600,000
Deferred revenue for the inventory pending shipment of TYSABRI											23,800,000	20,800,000
Reimbursements of research and developments expense from Elan											47,500,000	49,800,000	25,300,000
Reimbursements of selling general and administrative expenses from Elan											77,300,000	68,500,000	62,500,000
Amount reflected in collaboration profit sharing line for collaboration											317,800,000	258,100,000	215,900,000
Total upfront and milestone payments made to Collaborative Partner														135,000,000		36,800,000	80,000,000	30,000,000
Total milestones payments made to Acorda														25,000,000	110,000,000
Foreign sales required to trigger milestone														100,000,000
Expected additional milestone payments for successful achievement of regulatory and commercial sales milestones														375,000,000		508,500,000
Expected additional milestone payments when certain sales threshold is met														15,000,000
Additional cost associated with conditional marketing authorization			50,000,000
Amount paid to purchase Portola equity																8,200,000
Percentage of costs and profit split by Portola			25.00%
Estimated additional payments upon achievement of development and commercial milestones.																		60,000,000
Stock acquired in acquisition							100.00%
Consideration per product																				10,000,000
Percentage of reimbursement expenses																				50.00%
Percentage of development reimbursement expenses																				100.00%
Reimbursement cost achieving period																				6 years
Time period for paying remaining balance due																				90 days
Percentage of royalty on net sales of product			10.00%
Percentage of royalties as per collaboration																						12.00%	10.00%
Term for revocation option right																				18 months
Co-promotion operating profit threshold for Rituxan in U S and Canada to determine share of co promotion operating profit prior to amendment			50,000,000
Estimates of compensatory damages and interest	$ 125,000,000
Percentage of share of Co promotion profits exceeding $50 million			40.00%	40.00%	40.00%
Percentage of costs and profit split by Biogen Idec Inc			75.00%

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Quarterly Financial Data (Unaudited) (Details Textual) (USD $)	3 Months Ended		12 Months Ended			3 Months Ended	12 Months Ended	3 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Sep. 30, 2010 Knopp [Member]	Dec. 31, 2010 Knopp [Member]	Mar. 31, 2010 Biogen Idec Hemophilia [Member]	Dec. 31, 2011 Portola Pharmaceuticals Inc [Member]	Jun. 30, 2011 Genentech [Member] RITUXAN [Member]
Schedule Of Development Milestone And Collaboration [Line Items]
Decrease in share of co-promotion profits due to estimated compensation damages	$ 50,000,000									$ 50,000,000
Research and development			1,219,602,000	1,248,604,000	1,283,068,000		205,000,000		36,800,000
Development expense			0	271,376,000		205,000,000		40,000,000
Collaboration and license expense attribution to the noncontrolling interest						145,000,000
Quarterly Financial Data Unaudited (Textual) [Abstract]
Expenses related to restructuring plan included in total cost and expenses		$ 75,200,000	$ 19,026,000	$ 75,153,000

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Fair Value Measurements (Details Textual) (USD $)	12 Months Ended					12 Months Ended				12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 6.0% Senior Notes due 2013 [Member]	Dec. 31, 2011 6.875% Senior Notes due 2018 [Member]	Dec. 31, 2011 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH [Member]	Sep. 06, 2011 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH [Member]	Dec. 31, 2011 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH [Member] Other Liabilities Current [Member]	Dec. 31, 2011 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH [Member] Other Liabilities Non Current [Member]	Dec. 31, 2011 Biogen Idec International Neuroscience GmbH [Member]	Dec. 31, 2010 Biogen Idec International Neuroscience GmbH [Member]	Dec. 31, 2011 Biogen Idec International Neuroscience GmbH [Member] Other Liabilities Current [Member]	Dec. 31, 2011 Biogen Idec International Neuroscience GmbH [Member] Other Liabilities Non Current [Member]
Investments and Acquisitions at Fair Value
Net cash outflow to determine valuations						$ 42,500,000				$ 390,000,000
Discount rate used for net cash outflow projections for fair value measurement						3.80%				5.20%
Fair value adjustment of contingent consideration	36,000,000					(6,900,000)				37,900,000
Payment to former shareholders of Syntonix Pharmaceuticals										5,000,000
Fair Value Measurements (Additional Textual) [Abstract]
Contingent consideration	$ 151,000,000	$ 81,200,000	$ 0			$ 31,900,000	$ 38,800,000	$ 3,900,000	$ 28,000,000	$ 119,100,000	$ 81,200,000	$ 6,900,000	$ 112,200,000
Debt Instrument [Line Items]
Interest rate on Senior Notes				6.00%	6.875%
Fair Value Measurements (Textual) [Abstract]
Venture capital investments as a percentage of our total assets	approximately 0.3% of total assets	approximately 0.3% of total assets
Percentage of venture capital investments to assets	0.30%

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Accumulated Other Comprehensive Income (Loss) (Details) (Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Noncontrolling Interest [Line Items]
Accumulated translation adjustment included in noncontrolling interest	$ (50.3)	$ (24.4)
Accumulated Other Comprehensive Income Loss (Textual) [Abstract]
Tax on unrealized holding gains (losses) on investments	0.1	7.3
Tax on unrealized holding gains (losses) on foreign currency forward contracts	3.6	1.3
Noncontrolling Interest [Member]
Noncontrolling Interest [Line Items]
Accumulated translation adjustment included in noncontrolling interest	$ 5.1	$ 0.2

XML

Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2011

Quarterly Financial Data (Unaudited) [Abstract]

Quarterly Financial Data (Unaudited)

(In millions, except per share amounts)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total Year
2011			(a)				(b)
Product revenues	$	907.1	$	956.7	$	975.8	$	996.6	$	3,836.1
Unconsolidated joint business revenues	$	256.1	$	216.5	$	266.5	$	257.5	$	996.6
Other revenues	$	40.1	$	35.5	$	67.7	$	72.6	$	215.9
Total revenues	$	1,203.3	$	1,208.6	$	1,309.9	$	1,326.7	$	5,048.6
Gross Profit	$	1,100.2	$	1,108.1	$	1,186.4	$	1,187.1	$	4,581.9
Net income	$	308.8	$	304.0	$	353.7	$	300.2	$	1,266.7
Net income attributable to Biogen Idec Inc.	$	294.3	$	288.0	$	351.8	$	300.2	$	1,234.4
Basic earnings per share attributable to Biogen Idec Inc.	$	1.22	$	1.19	$	1.45	$	1.24	$	5.09
Diluted earnings per share attributable to Biogen Idec Inc.	$	1.20	$	1.18	$	1.43	$	1.22	$	5.04

(In millions, except per share amounts)	First Quarter		Second Quarter		Third Quarter		Fourth Quarter		Total Year
2010	(c)				(d)		(e)
Product revenues	$	824.2	$	859.2	$	876.9	$	909.8	$	3,470.1
Unconsolidated joint business revenues	$	254.9	$	306.4	$	258.0	$	258.0	$	1,077.3
Other revenues	$	29.7	$	47.1	$	41.0	$	51.4	$	169.1
Total revenues	$	1,108.9	$	1,212.7	$	1,175.8	$	1,219.0	$	4,716.4
Gross Profit	$	1,011.8	$	1,105.7	$	1,079.9	$	1,118.8	$	4,316.2
Net income	$	220.0	$	294.6	$	112.2	$	271.8	$	898.6
Net income attributable to Biogen Idec Inc.	$	217.4	$	293.4	$	254.1	$	240.3	$	1,005.3
Basic earnings per share attributable to Biogen Idec Inc	$	0.80	$	1.13	$	1.06	$	1.00	$	3.98
Diluted earnings per share attributable to Biogen Idec Inc	$	0.80	$	1.12	$	1.05	$	0.99	$	3.94

Full year amounts may not sum due to rounding.

(a) Our share of RITUXAN revenues from unconsolidated joint business was reduced by approximately $50.0 million in the second quarter of 2011 as a result of an accrual for estimated compensatory damages (including interest) relating to Genentech’s ongoing arbitration with Hoechst GmbH. For additional information related to this matter, please read Note 21, Litigation to these consolidated financial statements.

(b) Net income and net income attributable to Biogen Idec Inc. for the fourth quarter of 2011 includes a charge to research and development expense of $36.8 million related to an upfront payment made in connection with our collaboration and license agreement entered into with Portola Pharmaceuticals, Inc.

(c) Net income and net income attributable to Biogen Idec Inc. for the first quarter of 2010 includes a charge to acquired IPR&D of $40.0 million related to the achievement of a milestone by Biogen Idec Hemophilia, Inc. (formerly Syntonix Pharmaceuticals, Inc.).

(d) Net income and net income attributable to Biogen Idec Inc. for the third quarter of 2010 includes a charge to acquired IPR&D of $205.0 million incurred in connection with the license agreement entered into with Knopp Neurosciences Inc. (Knopp), which we consolidated as we determined that we are the primary beneficiary of the entity. The $205.0 million charge was partially offset by an attribution of $145.0 million to the noncontrolling interest.

(e) Net income and net income attributable to Biogen Idec Inc. for the fourth quarter of 2010 includes charges totaling $75.2 million related to our restructuring plan announced November 3, 2010.

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Other Consolidated Financial Statement Detail (Details Textual) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 New Cambridge Leases [Member]	Dec. 31, 2011 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH [Member]	Sep. 06, 2011 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH [Member]	Dec. 31, 2011 Biogen Idec International Neuroscience GmbH [Member]	Dec. 31, 2010 Biogen Idec International Neuroscience GmbH [Member]
Other Consolidated Financial Statement Detail (Textual) [Abstract]
In process research and development								$ 110.9
Goodwill								25.6
Fair value of contingent consideration	151.0	81.2	0		31.9	38.8	119.1	81.2
Deferred tax liability assumed								23.7
Remaining obligation of financing arrangements				$ 2.2

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Financial Instruments (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Summary of Contractual Maturities: Available-for-Sale Securities
Due in one year or less, Estimated Fair Value	$ 1,176.1	$ 448.1
Due in one year or less, Amortized Cost	1,175.6	447.8
Due after one year through five years, Estimated Fair Value	1,251.6	664.1
Due after one year through five years, Amortized Cost	1,251.4	662.4
Due after five years, Estimated Fair Value	165.2	79.0
Due after five years, Amortized Cost	165.8	78.8
Total available-for-sale securities, Fair Value	2,592.9	1,191.2
Total available-for-sale securities, Amortized Cost	$ 2,592.8	$ 1,189.0

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Equity (Details)	Dec. 31, 2011	Dec. 31, 2010
Summary of Preferred Stock
Preferred stock, shares authorized	8,000,000	8,000,000
Preferred stock, shares issued	0	8,000
Preferred stock, shares outstanding	0	8,000
Summary of Common Stock
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	255,633,000	248,200,000
Common stock, shares outstanding	242,115,000	240,538,000
Undesignated [Member]
Summary of Preferred Stock
Preferred stock, shares authorized	5,250,000	5,250,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Series A [Member]
Summary of Preferred Stock
Preferred stock, shares authorized	1,750,000	1,750,000
Preferred stock, shares issued	0	8,221
Preferred stock, shares outstanding	0	8,221
Series X Junior Participating [Member]
Summary of Preferred Stock
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

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Property, Plant and Equipment (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Components of property, plant and equipment, net
Land	$ 51,900,000	$ 107,600,000
Buildings	597,900,000	670,200,000
Leasehold improvements	102,700,000	100,800,000
Machinery and equipment	570,100,000	576,000,000
Computer software and hardware	439,700,000	392,800,000
Furniture and fixtures	37,600,000	54,500,000
Construction in progress	553,600,000	506,900,000
Total cost	2,353,500,000	2,408,800,000
Less: accumulated depreciation	(782,100,000)	(767,200,000)
Total property, plant and equipment, net	$ 1,571,387,000	$ 1,641,634,000

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Equity (Details Textual) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended				1 Months Ended	12 Months Ended		1 Months Ended
	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Feb. 28, 2011	Jan. 31, 2012 Common stock	Dec. 31, 2011 Common stock	Dec. 31, 2010 Common stock	Mar. 31, 2011 Series A [Member]	Dec. 31, 2011 Series A [Member]	Dec. 31, 2010 Series A [Member]	Dec. 31, 2011 Series X Junior Participating [Member]	Dec. 31, 2010 Series X Junior Participating [Member]
Class of Stock [Line Items]
Preferred stock, shares authorized		8,000,000	8,000,000							1,750,000	1,750,000	1,000,000	1,000,000
Preferred stock, shares issued		0	8,000							0	8,221	0	0
Preferred stock, shares outstanding		0	8,000							0	8,221	0	0
Series A Preferred Stock shares Redeemed									8,221
Repurchase of common stock, shares						3,500,000	6,000,000	40,300,000
Repurchase of common stock, value		$ 497,975	$ 2,077,579	$ 751,170		$ 401,500	$ 498,000	$ 2,100,000
Common stock available for repurchase						10,500,000
Equity (Textual) [Abstract]
Total number of common stock shares issued on conversion of Series A Preferred Stock	493,260
Common stock shares authorized for repurchase					20,000,000

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Financial Instruments (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Proceeds from Marketable Securities, excluding Strategic Investments
Proceeds from maturities and sales	$ 2,276,720,000	$ 2,668,694,000	$ 3,319,007,000
Realized gains	3,900,000	18,800,000	19,800,000
Realized losses	$ 2,300,000	$ 2,500,000	$ 4,000,000

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Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Summary of fair and carrying value of debt instruments
Total fair value	$ 1,160.4	$ 1,135.8
Dompe [Member]
Summary of fair and carrying value of debt instruments
Notes payable, Fair Value	0	8.1
Notes Payable to Fumedica [Member]
Summary of fair and carrying value of debt instruments
Notes payable, Fair Value	22.4	24.2
6.0% Senior Notes due 2013 [Member]
Summary of fair and carrying value of debt instruments
Notes payable, Fair Value	474.1	485.5
6.875% Senior Notes due 2018 [Member]
Summary of fair and carrying value of debt instruments
Notes payable, Fair Value	$ 663.9	$ 618.0

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Other Consolidated Financial Statement Detail

12 Months Ended

Dec. 31, 2011

Other Consolidated Financial Statement Detail / Collaborations [Abstract]

Other Consolidated Financial Statement Detail

18.    Other Consolidated Financial Statement Detail

Supplemental Cash Flow Information

Supplemental disclosure of cash flow information for the years ended December 31, 2011, 2010 and 2009 is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Cash paid during the year for:
Interest	$	66.7	$	68.1	$	68.1
Income taxes	$	332.7	$	394.7	$	745.4

In September 2011, upon completion of our acquisition of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH, we recorded a contingent consideration liability of $38.8 million.

In connection with the construction of the new Cambridge facilities that will be leased by us when the construction is completed, we have recorded an asset along with a corresponding financing obligation on our consolidated balance sheet as of December 31, 2011 totaling approximately $2.2 million. For additional information related to these transactions, please read Note 11, Property, Plant & Equipment to these consolidated financial statements.

In December 2010, upon completion of our acquisition of BIN, we recorded $110.9 million of in-process research and development and $25.6 million of goodwill. In addition, we also assumed a contingent consideration liability of $81.2 million and a deferred tax liability of $23.7 million.

Other Income (Expense), Net

Components of other income (expense), net, are summarized as follows:

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Interest income	$	19.2		$	22.3		$	48.5
Interest expense		(33.0	)		(36.1	)		(35.8	)
Impairments on investments		(11.5	)		(21.3	)		(10.6	)
Gain (loss) on sales of investments, net		17.4			16.3			22.8
Foreign exchange gains (losses), net		(6.3	)		(3.5	)		11.4
Other, net		0.7			3.3			1.0
Total other income (expense), net	$	(13.5	)	$	(19.0	)	$	37.3

Other Current Assets

Other current assets consist of the following:

	As of December 31,
(In millions)	2011		2010
Deferred tax assets	$	8.1	$	112.2
Derivative assets		39.5		1.3
Prepaid taxes		15.2		31.4
Receivable from collaborations		11.4		7.3
Interest receivable		6.5		4.9
Other prepaid expenses		45.5		47.9
Other		18.4		10.8
Total other current assets	$	144.6	$	215.8

Accrued Expenses and Other

Accrued expenses and other consists of the following:

	As of December 31,
(In millions)	2011		2010
Employee compensation and benefits	$	176.3	$	159.7
Revenue-related rebates		115.0		105.3
Deferred revenue		69.6		41.3
Royalties and licensing fees		47.4		45.1
Collaboration expenses		44.2		31.6
Clinical development expenses		40.8		24.4
Construction in progress accrual		22.8		16.4
Interest payable		21.6		21.6
Current portion of contingent consideration		10.8		11.9
Restructuring charges		1.4		66.4
Derivative liabilities		0.5		12.2
Other		126.8		130.0
Total accrued expenses and other	$	677.2	$	665.9

For a discussion of restructuring charges accrued as of December 31, 2011 and 2010, please read Note 3, Restructuring to these consolidated financial statements.

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Share-Based Payments (Tables)

12 Months Ended

Dec. 31, 2011

Share-based Payments [Abstract]

Share-based compensation expense included in consolidated statements of income

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Research and development	$	62.0		$	62.7		$	60.8
Selling, general and administrative		88.7			123.6			106.4
Restructuring charges		(0.6	)		6.8			—
Subtotal		150.1			193.1			167.2
Capitalized share-based compensation costs		(4.5	)		(3.5	)		(6.3	)
Share-based compensation expense included in total cost and expenses		145.6			189.6			160.9
Income tax effect		(44.6	)		(60.3	)		(49.4	)
Share-based compensation expense included in net income attributable to Biogen Idec Inc.	$	101.0		$	129.3		$	111.5

Summary of share-based compensation expense associated with different programs

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Stock options	$	5.9		$	26.1		$	21.6
Market stock units		14.6			10.0			—
Time-vested restricted stock units		89.6			129.4			133.7
Performance-vested restricted stock units settled in shares		1.0			5.3			4.6
Cash settled performance shares		32.7			15.0			—
Employee stock purchase plan		6.3			7.3			7.3
Subtotal		150.1			193.1			167.2
Capitalized share-based compensation costs		(4.5	)		(3.5	)		(6.3	)
Share-based compensation expense included in total cost and expenses	$	145.6		$	189.6		$	160.9

Weighted average assumptions to estimate fair value of stock option grants awarded

	For the Years Ended December 31,
	2011			2010			2009
Expected option life (in years)		*	*		4.5			4.7
Expected stock price volatility		*	*		30.8	%		39.3	%
Risk-free interest rate		*	*		2.0	%		1.9	%
Expected dividend yield		*	*		0.0	%		0.0	%
Per share grant-date fair value		*	*	$	16.52		$	18.00

Stock option activity

	Shares			Weighted Average Exercise Price
Outstanding at December 31, 2010		7,167,000		$	55.43
Granted		—		$	—
Exercised		(5,235,000	)	$	56.40
Cancelled		(241,000	)	$	53.30
Outstanding at December 31, 2011		1,691,000		$	52.75

Tax benefit and cash received from stock option

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Tax benefit realized for stock options	$	47.5	$	16.0	$	1.5
Cash received from the exercise of stock options	$	291.9	$	160.0	$	25.2

Market Stock Units Activity

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2010		398,000		$	61.87
Granted (a)		398,000		$	74.19
Vested		(119,000	)	$	59.89
Forfeited		(96,000	)	$	65.37
Unvested at December 31, 2011		581,000		$	69.49

Assumptions used in valuation of market based stock units

	For the Years Ended December 31,
	2011	2010
Expected dividend yield	0%	0%
Range of expected stock price volatility	25.7% - 33.4%	28.3% - 38.8%
Range of risk-free interest rates	0.3% - 1.9%	0.3% - 2.0%
60 calendar day average stock price on grant date	$66.78 - $101.16	$49.08 - $54.12
Weighted-average per share grant date fair value	$ 74.19	$ 61.87

Cash settled performance shares

(In thousands)	Shares
Unvested at December 31, 2010		370,000
Granted (a)		490,000
Vested		(187,000	)
Forfeited		(111,000	)
Unvested at December 31, 2011		562,000

Time-Vested Restricted Stock Units Activity

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2010		4,223,000		$	53.26
Granted		1,398,000		$	70.01
Vested		(1,980,000	)	$	53.72
Forfeited		(717,000	)	$	54.20
Unvested at December 31, 2011		2,924,000		$	60.72

Performance-Vested Restricted Stock Units (PVRSUs) Activity

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2010		154,000		$	49.24
Granted (a)		1,000		$	53.64
Vested		(75,000	)	$	49.51
Forfeited		(33,000	)	$	48.61
Unvested at December 31, 2011		47,000		$	49.34

Shares issued under employee stock purchase plan

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Shares issued under ESPP		0.4		0.6		0.6
Cash received under ESPP	$	22.8	$	23.5	$	22.6

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Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2011

Fair Value Measurements [Abstract]

Summary of Assets and Liabilities Recorded at Fair Value

(In millions)	As of December 31, 2011		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	399.8	$	—	$	399.8	$	—
Marketable debt securities:
Corporate debt securities		602.6		—		602.6		—
Government securities		1,716.5		—		1,716.5		—
Mortgage and other asset backed securities		273.8		—		273.8		—
Strategic investments		0.1		0.1		—		—
Venture capital investments		23.5		—		—		23.5
Derivative contracts		39.5		—		39.5		—
Plan assets for deferred compensation		11.6		—		11.6		—
Total	$	3,067.4	$	0.1	$	3,043.8	$	23.5
Liabilities:
Derivative contracts	$	0.5	$	—	$	0.5	$	—
Contingent consideration		151.0		—		—		151.0
Total	$	151.5	$	—	$	0.5	$	151.0

(In millions)	As of December 31, 2010		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	651.8	$	—	$	651.8	$	—
Marketable debt securities:
Corporate debt securities		313.0		—		313.0		—
Government securities		785.3		—		785.3		—
Mortgage and other asset backed securities		92.9		—		92.9		—
Strategic investments		44.8		44.8		—		—
Venture capital investments		20.8		—		—		20.8
Derivative contracts		1.3		—		1.3		—
Plan assets for deferred compensation		13.0		—		13.0		—
Total	$	1,922.9	$	44.8	$	1,857.3	$	20.8
Liabilities:
Derivative contracts	$	12.2	$	—	$	12.2	$	—
Contingent consideration		81.2		—		—		81.2
Total	$	93.4	$	—	$	12.2	$	81.2

Fair value of venture capital investments

	As of December 31,
(In millions)	2011			2010
Beginning balance	$	20.8		$	21.9
Unrealized gains included in earnings		2.4			—
Unrealized losses included in earnings		(1.4	)		(2.1	)
Purchases		1.7			2.1
Settlements		—			(1.1	)
Ending balance	$	23.5		$	20.8

Summary of fair and carrying value of debt instruments

	As of December 31,
(In millions)	2011		2010
Credit line from Dompé	$	—	$	8.1
Notes payable to Fumedica		22.4		24.2
6.0% Senior Notes due 2013		474.1		485.5
6.875% Senior Notes due 2018		663.9		618.0
Total fair value	$	1,160.4	$	1,135.8

Fair value of contingent consideration obligations

	As of December 31,
(In millions)	2011			2010
Fair value as of beginning of period	$	81.2		$	—
Acquisition date fair value of contingent consideration obligations related to acquisitions		38.8			81.2
Changes in the fair value of contingent consideration obligations		36.0			—
Payments of contingent consideration obligations		(5.0	)		—
Fair value as of end of period	$	151.0		$	81.2

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Financial Instruments (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	$ 399.8	$ 651.8
Commercial Paper [Member]
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	0	4.0
Repurchase Agreements [Member]
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	8.8	26.0
Debt Securities [Member]
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash equivalents	$ 391.0	$ 621.8

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Share-Based Payments (Details 6) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Assumptions used in valuation of market based stock units
Expected dividend yield	0.00%	0.00%	0.00%
Range of expected stock price volatility	0.00%	30.80%	39.30%
Market stock units [Member]
Assumptions used in valuation of market based stock units
Expected dividend yield	0.00%	0.00%
Minimum range of risk-free interest rates	0.30%	0.30%
Maximum range of risk-free interest rates	1.90%	2.00%
60 calendar day average stock price on grant date minimum	66.78	49.08
60 calendar day average stock price on grant date maximum	101.16	54.12
Weighted average grant date fair value	74.19	61.87
Market stock units [Member] | Maximum [Member]
Assumptions used in valuation of market based stock units
Range of expected stock price volatility	33.40%	38.80%
Market stock units [Member] | Minimum [Member]
Assumptions used in valuation of market based stock units
Range of expected stock price volatility	25.70%	28.30%

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Restructuring (Tables)

12 Months Ended

Dec. 31, 2011

Restructuring [Abstract]

Restructuring liability

(In millions)	Workforce Reduction			Facility Consolidation			Total
Restructuring reserve as of December 31, 2010	$	60.6		$	5.8		$	66.4
Expense		15.8			2.4			18.2
Payments		(81.8	)		(3.9	)		(85.7	)
Adjustments to previous estimates, net		(2.9	)		—			(2.9	)
Other adjustments		8.6			(3.2	)		5.4
Restructuring reserve as of December 31, 2011	$	0.3		$	1.1		$	1.4

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Other Consolidated Financial Statement Detail (Tables)

12 Months Ended

Dec. 31, 2011

Other Consolidated Financial Statement Detail / Collaborations [Abstract]

Supplementary Cash Flow Information

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Cash paid during the year for:
Interest	$	66.7	$	68.1	$	68.1
Income taxes	$	332.7	$	394.7	$	745.4

Other income (expense), net

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Interest income	$	19.2		$	22.3		$	48.5
Interest expense		(33.0	)		(36.1	)		(35.8	)
Impairments on investments		(11.5	)		(21.3	)		(10.6	)
Gain (loss) on sales of investments, net		17.4			16.3			22.8
Foreign exchange gains (losses), net		(6.3	)		(3.5	)		11.4
Other, net		0.7			3.3			1.0
Total other income (expense), net	$	(13.5	)	$	(19.0	)	$	37.3

Other current assets

	As of December 31,
(In millions)	2011		2010
Deferred tax assets	$	8.1	$	112.2
Derivative assets		39.5		1.3
Prepaid taxes		15.2		31.4
Receivable from collaborations		11.4		7.3
Interest receivable		6.5		4.9
Other prepaid expenses		45.5		47.9
Other		18.4		10.8
Total other current assets	$	144.6	$	215.8

Accrued Expenses and Other

	As of December 31,
(In millions)	2011		2010
Employee compensation and benefits	$	176.3	$	159.7
Revenue-related rebates		115.0		105.3
Deferred revenue		69.6		41.3
Royalties and licensing fees		47.4		45.1
Collaboration expenses		44.2		31.6
Clinical development expenses		40.8		24.4
Construction in progress accrual		22.8		16.4
Interest payable		21.6		21.6
Current portion of contingent consideration		10.8		11.9
Restructuring charges		1.4		66.4
Derivative liabilities		0.5		12.2
Other		126.8		130.0
Total accrued expenses and other	$	677.2	$	665.9

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Intangible Assets and Goodwill (Details) (USD $)	12 Months Ended					3 Months Ended	12 Months Ended					12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended				12 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Biogen Idec International Neuroscience GmbH [Member]	Dec. 31, 2010 Biogen Idec International Neuroscience GmbH [Member]	Sep. 30, 2011 Acorda [Member]	Dec. 31, 2011 Acorda [Member]	Dec. 31, 2011 VP1 Protein [Member]	Dec. 31, 2011 AVONEX [Member]	Dec. 31, 2011 Out-licensed patents [Member] Year	Dec. 31, 2010 Out-licensed patents [Member]	Dec. 31, 2011 Core developed technology [Member] Year	Dec. 31, 2010 Core developed technology [Member]	Dec. 31, 2011 In-Process Research and Development [Member]	Dec. 31, 2010 In-Process Research and Development [Member]	Dec. 31, 2011 In-licensed rights and patents [Member] Year	Dec. 31, 2010 In-licensed rights and patents [Member]	Dec. 31, 2011 Assembled workforce [Member] Year	Dec. 31, 2010 Assembled workforce [Member]	Dec. 31, 2011 Distribution rights [Member] Year	Dec. 31, 2010 Distribution rights [Member]	Dec. 31, 2011 Trademarks and trade names [Member]	Dec. 31, 2010 Trademarks and trade names [Member]	Dec. 31, 2011 In-Process Research and Development [Member]	Dec. 31, 2010 In-Process Research and Development [Member]	Dec. 31, 2011 Trademarks and trade names [Member]	Dec. 31, 2010 Trademarks and trade names [Member]
Indefinite-lived Intangible Assets by Major Class [Line Items]
Estimated Life																								Up to 15 years upon commercialization		Indefinite
Cost and Net																								$ 110,900,000	$ 110,900,000	$ 64,000,000	$ 64,000,000
Intangible assets
Estimated Life (In Years)																		4		2
Estimated Life, Minimum (In Years)										12		15				6
Estimated Life, Maximum (In Years)										23		23				16
Cost										578,000,000	578,000,000	3,005,300,000	3,005,300,000			47,200,000	3,000,000	2,100,000	2,100,000	12,700,000	12,700,000
Total intangible assets, gross	3,820,200,000	3,776,000,000						19,200,000
Accumulated Amortization	(2,212,000,000)	(2,003,200,000)								(391,300,000)	(350,200,000)	(1,801,100,000)	(1,636,900,000)	0	0	(4,800,000)	(1,300,000)	(2,100,000)	(2,100,000)	(12,700,000)	(12,700,000)	0	0
Net	0								1,192,100,000	186,700,000	227,800,000	1,204,200,000	1,368,400,000			42,400,000	1,700,000		0		0
Intangible assets, net	1,608,191,000	1,772,826,000
Intangible Assets and Goodwill Additional (Textual) [Abstract]
Net book value of the core technology intangible asset related to our AVONEX product	0								1,192,100,000	186,700,000	227,800,000	1,204,200,000	1,368,400,000			42,400,000	1,700,000		0		0
Amortization of intangible assets for each of next five years, Minimum	160,000,000								100,000,000
Amortization of intangible assets for each of next five years, Maximum	200,000,000								150,000,000
Expected usage-based royalties to be earned through 2016 from license agreement								58,900,000
Intangible asset recognized to reflect the total of upfront and other time-based milestone payments expected to be made	3,820,200,000	3,776,000,000						19,200,000
Collaborative arrangements and noncollaborative arrangement transactions milestone payment based on sales
Milestone payment payable to Acorda Therapeutics, Inc. (Acorda)				5,000,000		25,000,000
Amount due on next expected milestone payment							15,000,000
Net sales over four consecutive quarters							100,000,000
Business Acquisition [Line Items]
Business acquisition, purchase price allocation, in process research and development					110,900,000
Business acquisition purchase price allocation goodwill amount					25,600,000
Intangible Assets and Goodwill (Textual) [Abstract]
Amortization of acquired intangible assets	208,600,000	208,900,000	289,800,000
Increase (decrease) in goodwill		17,900,000
Business acquisition purchase price allocation goodwill amount					$ 25,600,000

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Investments in Variable Interest Entities (Details Textual) (USD $)	12 Months Ended			1 Months Ended	12 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Samsung Bio-similar Agreement [Member]	Dec. 31, 2011 Neurimmune [Member]	Dec. 31, 2009 Neurimmune [Member]	Mar. 31, 2011 Knopp [Member]	Dec. 31, 2011 Knopp [Member]	Dec. 31, 2010 Knopp [Member]	Dec. 31, 2010 Common Class B [Member] Knopp [Member]
Variable Interest Entity [Line Items]
Purchase of common shares in variable interest entities										30.00%
Investment in Variable Interest Entities (Textual) [Abstract]
Total upfront and reimbursement payment made to collaborative partner									$ 26,400,000
Remaining potential development milestone payments and royalties on commercial sales under the terms of collaboration agreement					345,000,000				265,000,000
Purchase Consideration for Variable Interest Entities									60,000,000
IPR&D charge recorded related to collaboration agreement	1,219,602,000	1,248,604,000	1,283,068,000						205,000,000
IPR&D charge allocated to noncontrolling interest									145,000,000
Payment recognized as a charge to noncontrolling interests, net of tax							10,000,000
Percentage of funding for R&D cost required in support of the collaboration agreement					100.00%
Milestone Payments Made During Period					15,000,000	7,500,000		10,000,000
Schedule of Equity Method Investments [Line Items]
Contribution from Samsung to develop, manufacture and market bio-similar pharmaceuticals				255,000,000
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage				85.00%
Proceeds from Contributions from Parent				45,000,000
Percentage of stake in entity minimum				15.00%
Percentage of stake in entity maximum				49.90%
Percentage of operations of joint venture investments on financial statements	100.00%
Percentage of net income (loss) attributable to noncontrolling interests	50.00%
Investment in biotechnology companies that are determined to be unconsolidated variable interest entities	14,600,000
Significant receivables or payables related to cost sharing arrangements with unconsolidated variable interest entities	$ 0	$ 0

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Revenue Reserves (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Analysis of the amount of, and change in, reserves
Beginning balance	$ 142.0	$ 103.1	$ 75.4
Current provisions relating to sales in current year	472.1	381.7	282.3
Adjustments relating to prior years	(14.9)	(6.9)	0.8
Payments/returns relating to sales in current year	(350.7)	(253.8)	(185.8)
Payments/returns relating to sales in prior years	(92.9)	(82.1)	(69.6)
Ending balance	155.6	142.0	103.1
Discounts [Member]
Analysis of the amount of, and change in, reserves
Beginning balance	13.9	13.9	9.2
Current provisions relating to sales in current year	96.0	80.6	74.0
Adjustments relating to prior years	0	(2.7)
Payments/returns relating to sales in current year	(84.3)	(68.7)	(60.8)
Payments/returns relating to sales in prior years	(13.0)	(9.2)	(8.5)
Ending balance	12.6	13.9	13.9
Contractual Adjustments [Member]
Analysis of the amount of, and change in, reserves
Beginning balance	107.0	70.3	48.1
Current provisions relating to sales in current year	360.4	285.0	192.5
Adjustments relating to prior years	(14.0)	(2.4)
Payments/returns relating to sales in current year	(266.0)	(184.3)	(124.4)
Payments/returns relating to sales in prior years	(68.1)	(61.6)	(45.9)
Ending balance	119.3	107.0	70.3
Returns [Member]
Analysis of the amount of, and change in, reserves
Beginning balance	21.1	18.9	18.1
Current provisions relating to sales in current year	15.7	16.1	15.8
Adjustments relating to prior years	(0.9)	(1.8)	0.8
Payments/returns relating to sales in current year	(0.4)	(0.8)	(0.6)
Payments/returns relating to sales in prior years	(11.8)	(11.3)	(15.2)
Ending balance	$ 23.7	$ 21.1	$ 18.9

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Equity (Tables)

12 Months Ended

Dec. 31, 2011

Equity/Accumulated Other Comprehensive Income (Loss) [Abstract]

Summary of Preferred Stock

	As of December 31, 2011						As of December 31, 2010
(In thousands)	Authorized		Issued		Outstanding		Authorized		Issued		Outstanding
Series A		1,750		—		—		1,750		8		8
Series X junior participating		1,000		—		—		1,000		—		—
Undesignated		5,250		—		—		5,250		—		—
Total preferred stock		8,000		—		—		8,000		8		8

Summary of Common Stock

As of December 31, 2011

As of December 31, 2010

(In thousands)

Authorized

Issued

Outstanding

Authorized

Issued

Outstanding

Common stock

1,000,000

255,633

242,115

1,000,000

248,200

240,538

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Acquisitions

12 Months Ended

Dec. 31, 2011

Acquisitions [Abstract]

Acquisitions

2.    Acquisitions

Noncontrolling Interest in Joint Ventures

On September 6, 2011, we completed the purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH, our respective sales affiliates in Italy and Switzerland, from our joint venture partners, Dompé Farmaceutici SpA and Dompé International SA, respectively. This transaction was funded from our existing cash on hand and has been accounted for as the acquisition of a noncontrolling interest. The purchase price of these shares was comprised of cash payments totaling $152.9 million plus up to $42.5 million in contingent consideration payable upon the achievement of commercial and regulatory milestones using exchange rates at the time of the transaction. As these amounts reflect payments to acquire a noncontrolling interest, these payments and the accrual of a liability related to the contingent consideration were recorded as a reduction in the noncontrolling interest for these entities with the remainder to additional paid in capital.

Upon acquisition, we recorded a liability of $38.8 million representing the acquisition date fair value of the contingent consideration. This amount was estimated through a valuation model that incorporates probability weighted assumptions relating to the achievement of these milestones and thus the likelihood of us making payments. Subsequent changes in the fair value of this obligation will be recognized as adjustments to contingent consideration within our consolidated statements of income. For additional information related to our valuation of this obligation, please read Note 8, Fair Value Measurements to these consolidated financial statements.

In connection with our purchase of the noncontrolling interest in our joint venture investment in Biogen Dompé SRL, we entered into a credit assignment agreement with Dompé Farmaceutici SpA. Under the terms of this agreement, Dompé Farmaceutici SpA purchased all of Biogen Dompé SRL’s outstanding receivables as of June 30, 2011, adjusted for cash received through September 5, 2011, for $104.6 million. We have no retained interests in the receivables and have accounted for this transaction as a sale. The carrying value of these receivables exceeded their fair value, which was determined by management using significant inputs not observable in the market and thus represents a Level 3 fair value measurement, and accordingly we recognized a loss of $1.8 million upon their disposition.

In addition, balances outstanding under Biogen Dompé SRL’s credit line from Dompé Farmaceutici SpA, as described in Note 12, Indebtedness to these consolidated financial statements, were repaid in September 2011.

Biogen Idec International Neuroscience GmbH

In December 2010, we acquired 100% of the stock of Biogen Idec International Neuroscience GmbH (BIN), formerly Panima Pharmaceuticals AG, an affiliate of Neurimmune AG. The purchase price was comprised of a $32.5 million cash payment plus up to $395.0 million in contingent consideration payable upon the achievement of development milestones. BIN is a business involved in the discovery of antibodies designed to treat neurological disorders. Upon acquisition, we recorded a liability of $81.2 million representing the acquisition date fair value of the contingent consideration. Subsequent changes in the fair value of this obligation are recognized as adjustments to contingent consideration within our consolidated statements of income. We allocated $110.9 million and $25.6 million of the total purchase price to acquired IPR&D and goodwill, respectively. The amount allocated to acquired IPR&D represented the fair value of the IPR&D programs acquired. The goodwill recognized is primarily attributable to establishing a deferred tax liability for the acquired IPR&D asset, which is not deductible for income tax purposes. For additional information related to our valuation of our contingent consideration obligation, please read Note 8, Fair Value Measurements to these consolidated financial statements.

Biogen Idec Hemophilia Inc.

In connection with our acquisition of Biogen Idec Hemophilia Inc. (BIH), formerly Syntonix Pharmaceuticals, Inc. (Syntonix), in January 2007, we agreed to pay up to an additional $80.0 million if certain milestone events associated with the development of BIH’s lead product, long-lasting recombinant Factor IX, a product for the treatment of hemophilia B, are achieved. The first $40.0 million contingent payment was achieved in the first quarter of 2010 upon initiation of patient enrollment in a registrational trial of Factor IX. We recorded this payment as a charge to acquired in-process research and development within our consolidated statement of income in 2010, in accordance with the accounting standards applicable to business combinations when we acquired BIH.

An additional $20.0 million contingent payment will occur if prior to the tenth anniversary of the closing date, the FDA grants approval of a Biologic License Application for Factor IX. A second $20.0 million contingent payment will occur if prior to the tenth anniversary of the closing date, a marketing authorization is granted by the EMA for Factor IX. These payments will be capitalized as an intangible asset when the related milestones are achieved.

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Collaborations (Details 4) (Swedish Orphan Biovitrum [Member], USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of activity related to collaboration with Swedish Orphan Biovitrum
Total expense incurred by collaboration	$ 129,600,000	$ 78,900,000	$ 44,900,000
Total expense reflected within our consolidated statements of income	129,600,000	78,500,000	22,500,000
Summary of activity related to collaboration, along with an estimate of additional future development expense
Total upfront and milestone payments received from Sobi	5,000,000
Total expense incurred by Biogen Idec, excluding upfront and milestone payments	262,700,000
Factors VIII And IX [Member]
Summary of activity related to collaboration, along with an estimate of additional future development expense
Estimate of additional amounts to be incurred by us in Product development	$ 420,000,000

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Revenue Reserves (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Summary of total product revenue reserves included in consolidated balance sheets
Reduction of accounts receivable	$ 40.6	$ 36.7
Current liability	115.0	105.3
Total reserves	$ 155.6	$ 142.0	$ 103.1	$ 75.4

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Subsequent Events (Details) (New Contract [Member], ISIS Pharmaceuticals [Member], USD $) In Millions, unless otherwise specified	1 Months Ended
	Jan. 31, 2012
New Contract [Member] | ISIS Pharmaceuticals [Member]
Subsequent Events (Textual) [Abstract]
Upfront payment	$ 29.0
Upfront milestone payments	45.0
License fee	$ 225.0

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Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2011

Financial Instruments [Abstract]

Marketable Securities including Strategic Investments

As of December 31, 2011 (In millions):	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale
Corporate debt securities:
Current	$	155.0	$	0.2	$	(0.1	)	$	154.9
Non-current		447.6		1.2		(1.5	)		447.9
Government securities:
Current		1,021.0		0.4		—			1,020.6
Non-current		695.5		0.9		(0.2	)		694.8
Mortgage and other asset backed securities:
Current		0.1		—		—			0.1
Non-current		273.7		0.5		(1.3	)		274.5
Total available-for-sale securities	$	2,592.9	$	3.2	$	(3.1	)	$	2,592.8
Other Investments
Strategic investments, non-current	$	0.1	$	—	$	(0.1	)	$	0.2

As of December 31, 2010 (In millions):	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale
Corporate debt securities:
Current	$	93.2	$	0.1	$	—		$	93.1
Non-current		219.8		2.1		(0.5	)		218.2
Government securities:
Current		352.8		0.2		—			352.6
Non-current		432.5		0.6		(0.6	)		432.5
Mortgage and other asset backed securities:
Current		2.1		—		—			2.1
Non-current		90.8		0.5		(0.2	)		90.5
Total available-for-sale securities	$	1,191.2	$	3.5	$	(1.3	)	$	1,189.0
Other Investments
Strategic investments, non-current	$	44.8	$	17.5	$	—		$	27.3

Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents

	As of December 31,
(In millions)	2011		2010
Commercial paper	$	—	$	4.0
Repurchase agreements		8.8		26.0
Short-term debt securities		391.0		621.8
Total	$	399.8	$	651.8

Summary of Contractual Maturities: Available-for-Sale Securities

	As of December 31, 2011				As of December 31, 2010
(In millions)	Estimated Fair  Value		Amortized Cost		Estimated Fair  Value		Amortized Cost
Due in one year or less	$	1,176.1	$	1,175.6	$	448.1	$	447.8
Due after one year through five years		1,251.6		1,251.4		664.1		662.4
Due after five years		165.2		165.8		79.0		78.8
Total available-for-sale securities	$	2,592.9	$	2,592.8	$	1,191.2	$	1,189.0

Proceeds from Marketable Securities, excluding Strategic Investments

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Proceeds from maturities and sales	$	2,276.7	$	2,668.7	$	3,319.0
Realized gains	$	3.9	$	18.8	$	19.8
Realized losses	$	2.3	$	2.5	$	4.0

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Commitments and Contingencies

12 Months Ended

Dec. 31, 2011

Commitments and Contingencies [Abstract]

Commitments and Contingencies

22.    Commitments and Contingencies

Leases

We rent laboratory and office space and certain equipment under non-cancelable operating leases. These lease agreements contain various clauses for renewal at our option and, in certain cases, escalation clauses typically linked to rates of inflation. Rental expense under these leases, which terminate at various dates through 2028, amounted to $46.2 million in 2011, $44.8 million in 2010 and $36.4 million in 2009. In addition to rent, the leases may require us to pay additional amounts for taxes, insurance, maintenance and other operating expenses.

As of December 31, 2011, minimum rental commitments under non-cancelable leases, net of income from subleases, for each of the next five years and total thereafter were as follows:

(In millions)	2012			2013			2014			2015		2016		Thereafter		Total
Minimum lease payments (1)	$	33.9		$	42.5		$	54.3		$	49.3	$	44.6	$	450.5	$	675.1
Less: income from subleases		(0.5	)		(0.5	)		(0.4	)		—		—		—		(1.4	)
Net minimum lease payments	$	33.4		$	42.0		$	53.9		$	49.3	$	44.6	$	450.5	$	673.7

(1) Includes future minimum rental commitments related to leases executed for two office buildings to be built in Cambridge, Massachusetts with a planned occupancy during the second half of 2013. The leases both have 15 year terms and we have options to extend the term of each lease for two additional five-year terms. Future minimum rental commitments under these leases will total approximately $340.0 million over the initial 15 year lease terms.

Balances also include remaining total minimum lease payments through 2025, totaling approximately $240.0 million, related to our current principal executive offices in Weston, Massachusetts, which we expect to vacate upon completion of the two new buildings in Cambridge Massachusetts.

For additional information related to these transactions, please read Note 11, Property, Plant and Equipment to these consolidated financial statements.

Under certain of our lease agreements, we are contractually obligated to return leased space to its original condition upon termination of the lease agreement. At the inception of a lease with such conditions, we record an asset retirement obligation liability and a corresponding capital asset in an amount equal to the estimated fair value of the obligation. In subsequent periods, for each such lease, we record interest expense to accrete the asset retirement obligation liability to full value and depreciate each capitalized asset retirement obligation asset, both over the term of the associated lease agreement. Our asset retirement obligations were not significant as of December 31, 2011 or 2010.

Tax Related Obligations

We exclude liabilities pertaining to uncertain tax positions from our summary of contractual obligations as we cannot make a reliable estimate of the period of cash settlement with the respective taxing authorities. As of December 31, 2011, we have approximately $58.4 million of liabilities associated with uncertain tax positions.

Other Funding Commitments

As of December 31, 2011, we have funding commitments of up to approximately $14.5 million as part of our investment in biotechnology oriented venture capital funds.

As of December 31, 2011, we have several ongoing clinical studies in various clinical trial stages. Our most significant clinical trial expenditures are to clinical research organizations (CROs). The contracts with CROs are generally cancellable, with notice, at our option. We have recorded accrued expenses of $25.0 million on our consolidated balance sheet for expenditures incurred by CROs as of December 31, 2011. We have approximately $475.0 million in cancellable future commitments based on existing CRO contracts as of December 31, 2011.

Contingent Milestone Payments

Based on our development plans as of December 31, 2011, we have committed to make potential future milestone payments to third parties of up to approximately $1.9 billion as part of our various collaborations, including licensing and development programs. Payments under these agreements generally become due and payable only upon achievement of certain development, regulatory or commercial milestones. Because the achievement of these milestones had not occurred as of December 31, 2011, such contingencies have not been recorded in our financial statements.

Contingent Consideration

In connection with our purchase of the noncontrolling interests in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH and our acquisitions of Biogen Idec International Neuroscience GmbH, Biogen Idec Hemophilia Inc., and Fumapharm AG, we agreed to make additional payments based upon the achievement of certain milestone events. Amounts related to contingent milestone payments are not considered contractual obligations as they are contingent on the successful achievement of certain development, regulatory approval and commercial milestones. These milestones may not be achieved.

As the acquisitions of the noncontrolling interests in our joint venture investments and our acquisition of Biogen Idec International Neuroscience GmbH occurred after January 1, 2009, we record contingent consideration liabilities at their fair value on the acquisition date and revalue these obligations each reporting period. For additional information related to these transactions please read Note 2, Acquisitions, to these consolidated financial statements.

In connection with our acquisition of Biogen Idec Hemophilia Inc. (BIH), formerly Syntonix Pharmaceuticals, Inc., in January 2007, we agreed to pay up to an additional $80.0 million if certain milestone events associated with the development of BIH’s lead product, long-lasting recombinant Factor IX are achieved. The first $40.0 million contingent payment was achieved in the first quarter of 2010. An additional $20.0 million contingent payment will occur if prior to the tenth anniversary of the closing date, the FDA grants approval of a Biologic License Application for Factor IX. A second $20.0 million contingent payment will occur if prior to the tenth anniversary of the closing date, a marketing authorization is granted by the EMA for Factor IX. For additional information related to these transactions please read Note 2, Acquisitions to these consolidated financial statements.

In 2006, we acquired Fumapharm AG. As part of this acquisition we acquired FUMADERM and BG-12 (together, Fumapharm Products). We paid $220.0 million upon closing of the transaction and will pay an additional $15.0 million if a Fumapharm Product is approved for MS in the U.S. or E.U. We may also make additional milestone payments to Fumapharm AG based on the attainment of certain sales levels of Fumapharm Products, less certain costs as defined in the acquisition agreement. These milestone payments are considered contingent consideration and will be accounted for as an increase to goodwill as incurred, in accordance with the accounting standard applicable to business combinations when we acquired Fumapharm.

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Litigation

12 Months Ended

Dec. 31, 2011

Litigation [Abstract]

Litigation

21.    Litigation

Massachusetts Department of Revenue

On June 8, 2010, we received Notices of Assessment from the DOR against BIMA for $103.5 million of corporate excise tax, including associated interest and penalties, related to our 2004, 2005 and 2006 tax filings. We filed an abatement application with the DOR seeking abatements for 2004, 2005, and 2006. Our abatement application was denied on December 15, 2010 and we filed a petition appealing the denial with the Massachusetts ATB on February 3, 2011. For all periods under dispute, we believe that positions taken in our tax filings are valid and believe that we have meritorious defenses in these disputes. We are contesting these matters vigorously.

Hoechst— Genentech Arbitration

On October 24, 2008, Hoechst GmbH (Hoechst), predecessor to Sanofi-Aventis Deutschland GmbH (Sanofi), filed with the ICC International Court of Arbitration (Paris) a request for arbitration against Genentech, claiming a breach of a license agreement (the Hoechst License) between Hoechst’s predecessor and Genentech that was entered as of January 1, 1991 and terminated by Genentech effective October 27, 2008. The Hoechst License granted Genentech certain rights with respect to later-issued U.S. Patents 5,849,522 (’522 patent) and 6,218,140 (’140 patent) and related patents outside the U.S. The Hoechst License provided for potential royalty payments of 0.5% on net sales of certain products defined by the agreement. Although we are not a party to the arbitration, we expect that any damages that may be awarded to Hoechst may be a cost charged to our collaboration with Genentech.

In June 2011, the arbitrator issued an intermediate decision suggesting that RITUXAN is covered by the Hoechst License and ordering Genentech to provide certain RITUXAN sales information for the period from December 15, 1998 to October 27, 2008. Based on our understanding of the arbitrator’s intermediate decision, in the second quarter of 2011 our share of RITUXAN revenues from unconsolidated joint business was reduced by approximately $50.0 million to reflect our share of the approximately $125.0 million compensatory damages and interest that Genentech estimated might be awarded to Hoechst. Hoechst has since claimed it is due damages of approximately EUR153.0 million for the period from December 15, 1998 to September 30, 2008 as well as additional royalties for later periods in an amount to be determined at a future hearing.

In July 2011, Genentech filed a Declaration of Appeal with the Court of Appeal in Paris to vacate the arbitrator’s intermediate decision. The arbitrator declined to stay further proceedings until the Declaration of Appeal was decided and informed the parties that the underlying issue of liability with respect to RITUXAN under the Hoechst License has not yet been decided. In October 2011, the arbitrator scheduled a hearing on liability and damages for spring 2012, and a decision could follow in late summer 2012. In view of these developments, Genentech did not pursue the Declaration of Appeal.

In light of the arbitrator’s ruling scheduling a hearing on liability and damages, the $50.0 million reduction of our share of RITUXAN revenues from unconsolidated joint business made in the second quarter of 2011 reflects the estimate of the loss that we may incur as a result of a final arbitration award unfavorable to Genentech. The actual amount of our share of any damages may vary from this estimate depending on the nature or amount of any damages awarded to Hoechst, or if any final decision awarding damages is successfully challenged by Genentech.

Sanofi ’522 and ’140 Patent Litigation

On October 27, 2008, Sanofi, successor to Hoechst, filed suit against Genentech and Biogen Idec in federal court in Texas (E.D. Tex.) (Texas Action) claiming that RITUXAN and certain other Genentech products infringe the ’522 patent and the ’140 patent. The patents are due to expire in December 2015. Sanofi seeks preliminary and permanent injunctions, compensatory and exemplary damages, and other relief. The same day Genentech and Biogen Idec filed a complaint against Sanofi in federal court in California (N.D. Cal.) (California Action) seeking a declaratory judgment that RITUXAN and other Genentech products do not infringe the ’522 patent or the ’140 patent and a declaratory judgment that those patents are invalid. The Texas Action was ordered transferred to the federal court in the Northern District of California and consolidated with the California Action and we refer to the two actions together as the “Consolidated Sanofi Patent Actions”. Certain damages that may be awarded to Sanofi in the Consolidated Sanofi Patent Actions may be a cost charged to our collaboration with Genentech.

On April 21, 2011, the court entered a separate and final judgment that the manufacture and sale of RITUXAN do not infringe the ’522 patent or the ’140 patent and stayed the trial of the remaining claims, including Biogen Idec’s and Genentech’s invalidity claims. Sanofi has appealed from the court’s non-infringement ruling to the U.S. Court of Appeals for the Federal Circuit and the appeal is scheduled for oral argument in February, 2012. We have not formed an opinion that a decision in favor of Sanofi in its appeal of the non-infringement ruling, or an unfavorable outcome on the now stayed invalidity claims in the Consolidated Sanofi Patent Actions, is either “probable” or “remote.” We believe that we have good and valid defenses and are vigorously defending against Sanofi’s allegations.

In the event that we and Genentech are found liable we estimate that the range of any potential loss could extend to a royalty of up to 0.5% of net sales of RITUXAN, based on, among other things, the royalty rate set forth in the terminated Hoechst License and an analysis of royalty rates charged for comparable technologies. We believe that Sanofi would seek a substantially higher royalty rate, and we will continue to vigorously oppose its claims and position.

We expect any damage award in the Consolidated Sanofi Patent Actions for damages incurred prior to the filing of litigation to be limited to the period running from October 27, 2002 to October 27, 2008 (six years before Sanofi filed the Texas Action). In addition, in the event that Genentech is ordered to pay royalties on RITUXAN sales under the Hoechst License described above, we do not anticipate that we or Genentech would be subject to any damages award in the Consolidated Sanofi Patent Actions for any period as to which Genentech is ordered to pay royalties in the arbitration.

’755 Patent Litigation

On September 15, 2009, we were issued 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. This patent, which expires in September 2026, covers, among other things, the treatment of MS with our product AVONEX. 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 of patent invalidity and non-infringement and seeking monetary relief in the form of attorneys’ fees, costs and expenses. On May 28, 2010, 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 noninfringement, 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 yet been ordered, but we expect that the trial of the Consolidated ’755 Patent Actions will take place in 2013.

On August 16, 2010, BIMA amended its complaint to add Ares Trading S.A. (Ares), an affiliate of EMD Serono, as a defendant, and to seek a declaratory judgment that a purported “nonsuit and option agreement” between Ares and BIMA dated October 12, 2000, that provides Ares an option to obtain a license to the ’755 Patent, is not valid and enforceable. Ares moved to compel arbitration of the claims against it and on February 2, 2012 an arbitration panel ruled that the nonsuit and option agreement and Ares’ option to license the ’755 patent remain in force.

GSK ’612 Patent Litigation

On March 23, 2010, we and Genentech were issued U.S. Patent No. 7,682,612 (’612 Patent) relating to a method of treating CLL using an anti-CD20 antibody. The patent which expires in November 2019 covers, among other things, the treatment of CLL with RITUXAN. On March 23, 2010, we and Genentech filed a lawsuit in federal court in the Southern District of California against Glaxo Group Limited and GlaxoSmithKline LLC (collectively, GSK) alleging infringement of that patent based upon GSK’s manufacture, marketing and sale, offer to sell, and importation of ARZERRA. We seek damages, including a royalty and lost profits, and injunctive relief. GSK has filed a counterclaim seeking a declaratory judgment of patent invalidity, noninfringement, unenforceability, and inequitable conduct, and seeking monetary relief in the form of costs and attorneys’ fees.

In October, 2011, the court entered a claim construction order adverse to certain of Biogen Idec’s and Genentech’s arguments. In order to conserve judicial and party resources, and to allow Biogen Idec and Genentech to file an appeal prior to the full disposition of the case, the parties jointly moved for the entry of separate and final judgment in favor of GSK on Biogen Idec’s and Genentech’s claims, and in favor of GSK on GSK’s counterclaim for non-infringement. The court entered separate and final judgment on November 15, 2011, and stayed all further proceedings pending the outcome on appeal. Biogen Idec and Genentech filed a notice of appeal in the United States Court of Appeals for the Federal Circuit on December 5, 2011, and the appeal is pending.

Novartis V&D ’688 Patent Litigation

On January 26, 2011, Novartis Vaccines and Diagnostics, Inc. (Novartis V&D) filed suit against us in federal district court in Delaware, alleging that TYSABRI infringes U.S. Patent No. 5,688,688 “Vector for Expression of a Polypeptide in a Mammalian Cell” (’688 Patent), which was granted in November 1997 and expires in November 2014. Novartis V&D seeks a declaration of infringement, a finding of willful infringement, compensatory damages, treble damages, interest, costs and attorneys’ fees. We have not formed an opinion that an unfavorable outcome is either “probable” or “remote”, and are unable to estimate the magnitude or range of any potential loss. We believe that we have good and valid defenses to the complaint and will vigorously defend against it. A trial has been set for January 2014.

Italian National Medicines Agency

In the fourth quarter of 2011, Biogen Idec SRL received a notice from the Italian National Medicines Agency (Agenzia Italiana del Farmaco or AIFA) stating that sales of TYSABRI for the period from February 2009 through February 2011 exceeded by Euro 30.7 million a reimbursement limit established pursuant to a Price Determination Resolution (Price Resolution) granted by AIFA in February 2007. 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 such resolutions that are not renegotiated prior to the expiration of their term.

On November 17, 2011, Biogen Idec SRL responded to AIFA that the reimbursement limit in the Price Resolution by its terms relates only to the first 24 months of TYSABRI sales, which began in February 2007. On December 23, 2011, we filed an appeal in the Regional Administrative Tribunal of Lazio (Ecc.mo Tribunale Amministrativo Regionale per il Lazio) in Rome against AIFA, seeking a ruling that our interpretation of the Price Resolution is valid and that the position of the AIFA is unenforceable. We have not formed an opinion that an unfavorable outcome is either “probable” or “remote”. While we believe that we have good and valid grounds for our appeal, an unfavorable outcome could negatively impact our results of operations.

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. In May 2011, the United States notified the court that it was not intervening at that time as to one defendant, and was declining to intervene as to all other defendants, including Biogen Idec; the District of Columbia notified the court that it was not intervening at that time; and the states notified the court that they were declining to intervene as to all defendants. The complaint was subsequently unsealed and served, and then amended. The amended complaint alleges that Biogen Idec and other defendants underreport Average Manufacturer Price information to the Centers for Medicare and Medicaid Services, thereby causing Biogen Idec and 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 or price concessions that they made to drug wholesalers to be discounts under applicable federal law. We and the other defendants filed a motion to dismiss the complaint on December 9, 2011, and the motion is pending. We have not formed an opinion that an unfavorable outcome is either “probable” or “remote,” or as to the magnitude or range of any potential loss. We believe that we have good and valid defenses and intend vigorously to defend against the allegations.

Government Review of Sales and Promotional Practices

Biogen Idec has learned that state and federal governmental authorities are investigating its sales and promotional practices. Biogen Idec has not received any requests for information in connection with this inquiry. We expect to cooperate fully with the government.

Canada Lease Dispute

On April 18, 2008, First Real Properties Limited filed suit against Biogen Idec Canada Inc. (BI Canada) in the Superior Court of Justice in London, Ontario alleging breach of an offer for lease of property signed by BI Canada in 2007 and an unsigned proposed lease for the same property. The plaintiff’s complaint seeks $7.0 million in damages, but the plaintiff recently submitted an expert report estimating the plaintiff’s damages to be $2.5 million after mitigation. The plaintiff also seeks costs of approximately $0.4 million and interest. A trial has been scheduled for March 2012. We have not formed an opinion that an unfavorable outcome is either “probable” or “remote.”

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.

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Share-Based Payments (Details 9) (Performance vested restricted stock units [Member], USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Performance vested restricted stock units [Member]
Performance-Vested Restricted Stock Units (PVRSUs)
Beginning Balance, Unvested, Shares	154,000
Beginning Balance, Weighted Average Grant Date Fair Value	$ 49.24
Shares, Granted	1,000	4,000	325,000
Weighted Average Grant Date Fair Value, Granted	$ 53.64	$ 53.64	$ 49.42
Shares, Vested	(75,000)
Weighted Average Grant Date Fair Value, Vested	$ 49.51
Shares, Forfeited	(33,000)
Weighted Average Grant Date Fair Value, Forfeited	$ 48.61
Ending Balance, Unvested, Shares	47,000	154,000
Ending Balance, Weighted Average Grant Date Fair Value	$ 49.34	$ 49.24

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Segment Information (Tables)

12 Months Ended

Dec. 31, 2011

Segment Information [Abstract]

Revenue by product

	For the Years Ended December 31,
	2011						2010						2009
(In millions)	United States		Rest of World		Total		United States		Rest of World		Total		United States		Rest of World		Total
AVONEX	$	1,628.3	$	1,058.3	$	2,686.6	$	1,491.6	$	1,026.8	$	2,518.4	$	1,406.2	$	916.7	$	2,322.9
TYSABRI		326.5		753.0		1,079.5		252.8		647.4		900.2		231.8		544.2		776.0
Other		—		70.0		70.0		—		51.5		51.5		—		54.0		54.0
Total product revenues	$	1,954.8	$	1,881.3	$	3,836.1	$	1,744.4	$	1,725.7	$	3,470.1	$	1,638.0	$	1,514.9	$	3,152.9

Geographic information

December 31, 2011 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,954.8	$	1,163.3	$	377.5	$	88.7	$	251.8	$	3,836.1
Revenues from unconsolidated joint business	$	878.8	$	29.9	$	—	$	30.7	$	57.2	$	996.6
Other revenues from external customers	$	187.0	$	28.3	$	0.6	$	—	$	—	$	215.9
Long-lived assets	$	1,012.5	$	816.6	$	1.6	$	5.3	$	2.4	$	1,838.4
December 31, 2010 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,744.4	$	1,090.7	$	362.4	$	69.0	$	203.6	$	3,470.1
Revenues from unconsolidated joint business	$	906.3	$	95.3	$	—	$	26.0	$	49.6	$	1,077.2
Other revenues from external customers	$	136.0	$	32.6	$	0.5	$	—	$	—	$	169.1
Long-lived assets	$	1,100.3	$	717.4	$	1.5	$	5.4	$	1.6	$	1,826.2
December 31, 2009 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,638.0	$	913.7	$	374.8	$	47.9	$	178.5	$	3,152.9
Revenues from unconsolidated joint business	$	839.2	$	190.2	$	—	$	24.1	$	41.4	$	1,094.9
Other revenues from external customers	$	102.8	$	26.2	$	0.5	$	—	$	—	$	129.5
Long-lived assets	$	1,092.7	$	705.6	$	1.4	$	3.6	$	2.1	$	1,805.4

(1) Represents amounts related to Europe less those attributable to Germany.

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Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2011

Derivative Instruments [Abstract]

Foreign currency forward contracts that were entered into to hedge forecasted revenue

	Notional Amount As of December 31,
Foreign Currency: (In millions)	2011		2010
Euro	$	496.4	$	460.3
Canadian dollar		22.9		24.0
Swedish krona		13.0		9.9
Total foreign currency forward contracts	$	532.3	$	494.2

Summary of Derivatives designated as Hedging Instruments

(In millions)	Balance Sheet Location	Fair Value As of December 31, 2011
Foreign Currency Contracts
Asset derivatives	Other current assets	$	32.6
Liability derivatives	Accrued expenses and other	$	—

(In millions)	Balance Sheet Location	Fair Value As of December 31, 2010
Foreign Currency Contracts
Asset derivatives	Other current assets	$	—
Liability derivatives	Accrued expenses and other	$	11.0

Summary of the effect of derivatives designated as hedging instruments on the consolidated statements of income

For the Years Ended (In millions)	Amount Recognized in Accumulated Other Comprehensive Income (Loss) on Derivative Gain/(Loss) (Effective Portion)			Income Statement Location (Effective Portion)	Amount Reclassified  from Accumulated  Other Comprehensive Income (Loss) into Income Gain/(Loss) (Effective Portion)			Income Statement Location (Ineffective Portion)	Amount of Gain/(Loss) Recorded (Ineffective Portion)
December 31, 2011:
Foreign currency contracts	$	36.5		Revenue	$	(36.9	)	Other income (expense)	$	(3.9	)
December 31, 2010:
Foreign currency contracts	$	(11.0	)	Revenue	$	45.7		Other income (expense)	$	0.4
December 31, 2009:
Foreign currency contracts	$	1.2		Revenue	$	(49.7	)	Other income (expense)	$	(1.1	)

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Guarantees

12 Months Ended

Dec. 31, 2011

Guarantees [Abstract]

Guarantees

23.    Guarantees

As of December 31, 2011 and 2010, we did not have significant liabilities recorded for guarantees.

We enter into indemnification provisions under our agreements with other companies in the ordinary course of business, typically with business partners, contractors, clinical sites and customers. Under these provisions, we generally indemnify and hold harmless the indemnified party for losses suffered or incurred by the indemnified party as a result of our activities. These indemnification provisions generally survive termination of the underlying agreement. The maximum potential amount of future payments we could be required to make under these indemnification provisions is unlimited. However, to date we have not incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. As a result, the estimated fair value of these agreements is minimal. Accordingly, we have no liabilities recorded for these agreements as of December 31, 2011 and 2010.

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Employee Benefit Plans

12 Months Ended

Dec. 31, 2011

Employee Benefit Plans [Abstract]

Employee Benefit Plans

24.    Employee Benefit Plans

We sponsor various retirement and pension plans. Our estimates of liabilities and expenses for these plans incorporate a number of assumptions, including expected rates of return on plan assets and interest rates used to discount future benefits.

401(k) Savings Plan

We maintain a 401(k) Savings Plan which is available to substantially all regular employees in the U.S. over the age of 21. Participants may make voluntary contributions. We make matching contributions according to the 401(k) Savings Plan’s matching formula. Beginning in January 2008, all past and current matching contributions will vest immediately. Previously, the matching contributions vested over four years of service by the employee. Participant contributions vest immediately. The 401(k) Savings Plan also holds certain transition contributions on behalf of participants who previously participated in the Biogen, Inc. Retirement Plan. The expense related to our 401(k) Savings Plan primarily consists of our matching contributions.

Expense related to our 401(k) Savings Plan totaled $24.8 million, $26.3 million and $27.9 million for the years ended December 31, 2011, 2010 and 2009, respectively.

Deferred Compensation Plan

We maintain a non-qualified deferred compensation plan, known as the Supplemental Savings Plan (SSP), which allows a select group of management employees in the U.S. to defer a portion of their compensation. The SSP also provides certain credits to highly compensated U.S. employees, which are paid by the company. These credits are known as the Restoration Match. The deferred compensation amounts are accrued when earned. Such deferred compensation is distributable in cash in accordance with the rules of the SSP. Deferred compensation amounts under such plan as of December 31, 2011 and 2010 totaled approximately $60.1 million and $62.2 million, respectively, and are included in other long-term liabilities within the accompanying consolidated balance sheets. The SSP also holds certain transition contributions on behalf of participants who previously participated in the Biogen, Inc. Retirement Plan. Beginning in 2008, the Restoration Match vests immediately. Previously, the Restoration Match and transition contributions vested over four and seven years of service, respectively, by the employee. Participant contributions vest immediately. Distributions to participants can be either in one lump sum payment or annual installments as elected by the participants.

Pension Plan

Our retiree benefit plans include defined benefit plans for employees in our affiliates in Switzerland and Germany as well as other insignificant defined benefit plans in certain other countries in which we maintain an operating presence.

Our Swiss plan is a government-mandated retirement fund that provides employees with a minimum investment return. The minimum investment return is determined annually by Swiss government and was 2.0% in 2011, 2010 and 2009, respectively. Under this plan, both we and certain of our employees with annual earnings in excess of government determined amounts are required to make contributions into a fund managed by an independent investment fiduciary. Employer contributions must be in an amount at least equal to the employee’s contribution. Minimum employee contributions are based on the respective employee’s age, salary, and gender. As of December 31, 2011, the Plan had an unfunded net pension obligation of approximately $10.0 million and plan assets which totaled approximately $20.1 million. In 2011, 2010 and 2009, we recognized expense totaling $3.6 million, $3.0 million and $2.4 million, respectively, related to our Swiss plan.

The obligations under the German plan are unfunded and totaled $8.6 million and $8.2 million as of December 31, 2011 and 2010, respectively. Net periodic pension cost related to the German plan totaled $1.8 million, $1.1 million and $1.1 million for the years ended December 31, 2011, 2010 and 2009, respectively.

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Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2011

Summary of Significant Accounting Policies [Abstract]

Summary of Significant Accounting Policies

1. Summary of Significant Accounting Policies

Business Overview

Biogen Idec is a global biotechnology company that discovers, develops, manufactures and markets therapies for the treatment of neurodegenerative diseases, hemophilia and autoimmune disorders. Patients worldwide benefit from our leading multiple sclerosis therapies, and the company generates $5 billion in annual revenues.

Consolidation

Our consolidated financial statements reflect our financial statements, those of our wholly-owned subsidiaries and those of certain variable interest entities in which we are the primary beneficiary. For consolidated entities in which we own or are exposed to less than 100% of the economics, we record net income (loss) attributable to noncontrolling interests in our consolidated statements of income equal to the percentage of the economic or ownership interest retained in such entities by the respective noncontrolling parties. All material intercompany balances and transactions are eliminated in consolidation.

In determining whether we are the primary beneficiary of an entity, we apply a qualitative approach that determines whether we have both (1) the power to direct the economically significant activities of the entity and (2) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. These considerations impact the way we account for our existing collaborative relationships and determine whether we consolidate companies or entities with which we have collaborative or other arrangements. Determination about whether an enterprise should consolidate a variable interest entity is required to be made continuously as changes to existing relationships or future transactions may result in us consolidating or deconsolidating our partner(s) to collaborations and other arrangements.

Use of Estimates

The preparation of our consolidated financial statements in accordance with U.S. GAAP requires management to make estimates, judgments, and assumptions that may affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. On an on-going basis, we evaluate our estimates and judgments and methodologies, including those related to revenue recognition and related allowances, our collaborative relationships, clinical trial expenses, the consolidation of variable interest entities, the valuation of contingent consideration resulting from a business combination, the valuation of acquired intangible assets including in-process research and development, inventory, impairment and amortization of long-lived assets including intangible assets, impairments of goodwill, share-based compensation, income taxes including the valuation allowance for deferred tax assets, the valuation of investments, derivatives and hedging activities, contingencies, litigation, and restructuring charges. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results may differ from these estimates under different assumptions or conditions.

Revenue Recognition

We recognize revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; our price to the customer is fixed or determinable; and collectability is reasonably assured.

Product Revenues

Revenues from product sales are recognized when title and risk of loss have passed to the customer, which is typically upon delivery. However, sales of TYSABRI in the U.S. are recognized on the “sell-through” model, that is, upon shipment of the product by Elan Pharma International, Ltd. (Elan), an affiliate of Elan Corporation, plc, to its third party distributor rather than upon shipment to Elan. Product revenues are recorded net of applicable reserves for discounts and allowances.

Reserves for Discounts and Allowances

We establish reserves for trade term discounts, wholesaler incentives, Medicaid rebates, Veterans Administration (VA) and Public Health Service (PHS) discounts, managed care rebates, product returns and other governmental rebates or applicable allowances, including those associated with the implementation of pricing actions in certain of the international markets in which we operate. Reserves established for these discounts and allowances are classified as reductions of accounts receivable (if the amount is payable to our direct customer) or a liability (if the amount is payable to a party other than our customer). These reserves are based on estimates of the amounts earned or to be claimed on the related sales. Our estimates take into consideration our historical experience, current contractual and statutory requirements, specific known market events and trends, and forecasted customer buying patterns. Actual amounts may ultimately differ from our estimates. If actual results vary, we will need to adjust these estimates, which could have an effect on earnings in the period of adjustment. The estimates we make with respect to these allowances represent the most significant judgments with regard to revenue recognition.

Product revenue reserves are categorized as follows: discounts, contractual adjustments and returns.

Discount reserves include trade term discounts and wholesaler incentives. Trade term discounts and wholesaler incentive reserves primarily relate to estimated obligations for credits to be granted to wholesalers for remitting payment on their purchases within established incentive periods and credits to be granted to wholesalers for compliance with various contractually-defined inventory management practices, respectively. We determine these reserves based on our experience, including the timing of customer payments.

Contractual adjustment reserves primarily relate to Medicaid and managed care rebates, VA and PHS discounts and other governmental rebates or applicable allowances.

• Medicaid rebate reserves relate to our estimated obligations to states under established reimbursement arrangements. Rebate accruals are recorded in the same period the related revenue is recognized resulting in a reduction of product revenue and the establishment of a liability which is included in other current liabilities. Our liability for Medicaid rebates consists of estimates for claims that a state will make for the current quarter, claims for prior quarters that have been estimated for which an invoice has not been received, invoices received for claims from the prior quarters that have not been paid, and an estimate of potential claims that will be made for inventory that exists in the distribution channel at period end.

• VA rebates or chargeback reserves represent our estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices we charge to wholesalers which provide those products. The wholesaler charges us for the difference between what the wholesaler pays for the products and the ultimate selling price to the qualified healthcare providers. Rebate and chargeback reserves are established in the same period as the related revenue is recognized resulting in a reduction in product revenue and accounts receivable. Chargeback amounts are generally determined at the time of resale to the qualified healthcare provider from the wholesaler, and we generally issue credits for such amounts within a few weeks of the wholesaler notifying us about the resale. Our reserves for VA and chargebacks consists of amounts that we expect to issue for inventory that exists at the wholesalers that we expect will be sold to qualified healthcare providers and chargebacks that wholesalers have claimed for which we have not issued a credit.

• Managed care rebate reserves represent our estimated obligations to third parties, primarily pharmacy benefit managers. Rebate accruals are recorded in the same period the related revenue is recognized resulting in a reduction of product revenue and the establishment of a liability which is included in accrued expenses and other current liabilities. These rebates result from performance-based goals that are primarily based on attaining contractually specified sales volumes and growth. The calculation of the accrual for these rebates is based on an estimate of the customer’s buying patterns and the resulting applicable contractual rebate rate(s) to be earned over a contractual period.

• Other governmental rebates or applicable allowances primarily relate to mandatory rebates and discounts in markets where government-sponsored healthcare systems are the primary payers for healthcare.

Product return reserves are established for returns expected to be made by wholesalers and are recorded in the period the related revenue is recognized, resulting in a reduction to product sales. In accordance with contractual terms, wholesalers are permitted to return product for reasons such as damaged or expired product. The majority of wholesaler returns are due to product expiration. Expired product return reserves are estimated through a comparison of historical return data to their related sales on a production lot basis. Historical rates of return are determined for each product and are adjusted for known or expected changes in the marketplace specific to each product.

In addition to the discounts and rebates described above and classified as a reduction of revenue, we also maintain certain customer service contracts with distributors and other customers in the distribution channel that provide us with inventory management and distribution services. We have established the fair value of these services and classified these customer service contracts as sales and marketing expense. If we had concluded that we did not receive a separate identifiable benefit or have sufficient evidence that the fair value did not exist for these services, we would have been required to classify these costs as a reduction of revenue.

In countries where we expect to collect receivables greater than one year, at the time of sale, we have discounted our revenues over the period of time that we estimate those amounts will be paid using our estimate of the country’s borrowing rate. The related receivables are classified at the time of sale as long-term assets. We will accrete interest income on these receivables, which will be recognized as a component of other income (expense), net within our consolidated statement of income.

We also distribute no-charge product to qualifying patients under our patient assistance and patient replacement goods program. This program is administered through one of our distribution partners, which ships product for qualifying patients from its own inventory received from us. Gross revenue and the related reserves are not recorded on product shipped under this program and cost of sales is recorded when the product is shipped.

Revenues from Unconsolidated Joint Business

We collaborate with Genentech on the development and commercialization of RITUXAN. Revenues from unconsolidated joint business consist of (1) our share of pre-tax co-promotion profits in the U.S.; (2) reimbursement of our selling and development expense in the U.S.; and (3) revenue on sales of RITUXAN in the rest of world, which consists of our share of pre-tax co-promotion profits in Canada and royalty revenue on sales of RITUXAN outside the U.S. and Canada by F. Hoffmann-La Roche Ltd. (Roche) and its sublicensees. Pre-tax co-promotion profits are calculated and paid to us by Genentech in the U.S. and by Roche in Canada. Pre-tax co-promotion profits consist of U.S. and Canadian sales of RITUXAN to third-party customers net of discounts and allowances less the cost to manufacture RITUXAN, third-party royalty expenses, and distribution, selling and marketing, and joint development expenses incurred by Genentech, Roche and us. We record our share of the pretax co-promotion profits in Canada and royalty revenues on sales of RITUXAN outside the U.S. on a cash basis. Additionally, our share of the pretax co-promotion profits in the U.S. includes estimates made by Genentech and those estimates are subject to change. Actual results may ultimately differ from our estimates.

Royalty Revenues

We receive royalty revenues on sales by our licensees of other products covered under patents that we own. We do not have future performance obligations under these license arrangements. We record these revenues based on estimates of the sales that occurred during the relevant period. The relevant period estimates of sales are based on interim data provided by licensees and analysis of historical royalties that have been paid to us, adjusted for any changes in facts and circumstances, as appropriate. We maintain regular communication with our licensees in order to assess the reasonableness of our estimates. Differences between actual royalty revenues and estimated royalty revenues are adjusted for in the period in which they become known, typically the following quarter. Historically, adjustments have not been material when compared to actual amounts paid by licensees. If we are unable to accurately estimate revenue, then we record revenues on a cash basis.

Milestone Revenues

We execute collaborative and other agreements which may contain milestone payments. Revenues from milestones, if they are considered substantive, are recognized upon successful accomplishment of the milestones. Determining whether a milestone is substantive involves judgment, including an assessment of our involvement in achieving the milestones and whether the amount of the payment is commensurate to our performance. If not considered substantive, milestones are initially deferred and recognized over the remaining performance obligation.

Multiple-Element Revenue Arrangements

We may, from time to time, enter into transactions that involve the sale of products and related services under multiple element arrangements. In accounting for these transactions, we allocate revenue to the various elements based on their fair value. The fair value of a revenue generating element can be based on current selling prices offered by us or another party for current products or management’s best estimate of a selling price for future products. Revenue allocated to an individual element is recognized when all other revenue recognition criteria are met for that element.

Fair Value Measurements

We have certain financial assets and liabilities recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements.

• Level 1 — Fair values are determined utilizing quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access;

• Level 2 — Fair values are determined by utilizing quoted prices for identical or similar assets and liabilities in active markets or other market observable inputs such as interest rates, yield curves and foreign currency spot rates; and

• Level 3 — Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

Valuation of Investments

We validate the prices provided by our third party pricing services by reviewing their pricing methods and matrices, obtaining market values from other pricing sources, analyzing pricing data in certain instances and confirming that the relevant markets are active. After completing our validation procedures, we did not adjust or override any fair value measurements provided by our pricing services as of December 31, 2011 and 2010, respectively.

Our strategic investments in publicly traded equity securities are classified as Level 1 assets as their fair values are readily determinable and based on quoted market prices.

The majority of our financial assets and liabilities have been classified as Level 2. Our financial assets and liabilities (which include our cash equivalents, derivative contracts, marketable debt securities, and plan assets for deferred compensation) have been initially valued at the transaction price and subsequently valued, at the end of each reporting period, typically utilizing third party pricing services or other market observable data. The pricing services utilize industry standard valuation models, including both income and market based approaches and observable market inputs to determine value. These observable market inputs include reportable trades, benchmark yields, credit spreads, broker/dealer quotes, bids, offers, current spot rates and other industry and economic events.

We also maintain venture capital investments classified as Level 3 whose fair value is initially measured at transaction prices and subsequently valued using the pricing of recent financing or by reviewing the underlying economic fundamentals and liquidation value of the companies. These investments are the only investments for which we used Level 3 inputs to determine the fair value. These investments include investments in certain biotechnology oriented venture capital funds which primarily invest in small privately-owned, venture-backed biotechnology companies. The fair value of our investments in these venture capital funds has been estimated using the net asset value of the fund. The investments cannot be redeemed within the funds. Distributions from each fund will be received as the underlying investments of the fund are liquidated. The funds and therefore a majority of the underlying assets of the funds will not be liquidated in the near future. The underlying assets in these funds are initially measured at transaction prices and subsequently valued using the pricing of recent financings or by reviewing the underlying economic fundamentals and liquidation value of the companies that the funds invest in. We apply judgments and estimates when we validate the prices provided by third parties. While we believe the valuation methodologies are appropriate, the use of valuation methodologies is highly judgmental and changes in methodologies can have a material impact on our results of operations. Gains and losses (realized and unrealized) included in earnings for the period are reported in other income (expense), net.

Valuation of Contingent Consideration Resulting from a Business Combination

We record contingent consideration resulting from business combinations completed after January 1, 2009 at its fair value on the acquisition date. Each reporting period thereafter, we revalue these obligations and record increases or decreases in their fair value as an adjustment to contingent consideration expense within our consolidated statement of income. Changes in the fair value of the contingent consideration obligations can result from adjustments to the discount rates and periods, updates in the assumed achievement or timing of any development milestones or changes in the probability of certain clinical events and changes in the assumed probability associated with regulatory approval. These fair value measurements represent Level 3 measurements as they are based on significant inputs not observable in the market.

Significant judgment is employed in determining the appropriateness of these assumptions as of the acquisition date and for each subsequent period. Accordingly, changes in assumptions described above, could have a material impact on the amount of contingent consideration expense we record in any given period.

Other

The carrying amounts reflected in the consolidated balance sheets for cash equivalents, current accounts receivable, due from unconsolidated joint business, other current assets, accounts payable, and accrued expenses and other, approximate fair value due to their short-term maturities.

Cash and Cash Equivalents

We consider only those investments which are highly liquid, readily convertible to cash and that mature within three months from date of purchase to be cash equivalents. As of December 31, 2011 and 2010, cash equivalents were comprised of money market funds and commercial paper, repurchase agreements, and other debt securities with maturities less than 90 days.

Accounts Receivable

The majority of our accounts receivable arise from product sales and primarily represent amounts due from our wholesale distributors, public hospitals and other government entities. We monitor the financial performance and credit worthiness of our large customers so that we can properly assess and respond to changes in their credit profile. We provide reserves against trade receivables for estimated losses that may result from a customer’s inability to pay. Amounts determined to be uncollectible are charged or written-off against the reserve. To date, such losses have not exceeded management’s estimates.

Concentration of Credit Risk

Financial instruments that potentially subject us to concentrations of credit risk include cash and cash equivalents, investments, derivatives, and accounts receivable. We attempt to minimize the risks related to cash and cash equivalents and investments by using highly-rated financial institutions that invest in a broad and diverse range of financial instruments as previously defined by us. We have established guidelines relative to credit ratings and maturities intended to safeguard principal balances and maintain liquidity. Our investment portfolio is maintained in accordance with our investment policy, which defines allowable investments, specifies credit quality standards and limits the credit exposure of any single issuer. We minimize credit risk resulting from derivatives instruments by choosing only highly rated financial institutions as counterparties.

Concentrations of credit risk with respect to receivables, which are typically unsecured, are limited due to the wide variety of customers and markets using our products, as well as their dispersion across many different geographic areas. The majority of our accounts receivable arise from product sales in the United States and Europe and have standard payment terms which are generally between 30 and 90 days. We continue to monitor economic conditions, including the volatility associated with international economies, and associated impacts on the relevant financial markets and our business, especially in light of the global economic downturn. For additional information related to this concentration of credit risk, please read Note 5, Accounts Receivable to these consolidated financial statements.

As of December 31, 2011 and 2010, one wholesale distributor accounted for approximately 14.1% and 11.5% of consolidated receivables, respectively.

Inventory

Inventories are stated at the lower of cost or market with cost determined in a manner that approximates the first-in, first-out (FIFO) method. Included in inventory are raw materials used in the production of pre-clinical and clinical products, which are expensed as research and development costs when consumed.

Capitalization of Inventory Costs

We capitalize inventory costs associated with our products prior to regulatory approval, when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. We consider numerous attributes in evaluating whether the costs to manufacture a particular product should be capitalized as an asset. We assess the regulatory approval process and where the particular product stands in relation to that approval process, including any known safety or efficacy concerns, potential labeling restrictions and other impediments to approval. We evaluate our anticipated research and development initiatives and constraints relating to the product and the indication in which it will be used. We consider our manufacturing environment including our supply chain in determining logistical constraints that could hamper approval or commercialization. We consider the shelf life of the product in relation to the expected timeline for approval and we consider patent related or contract issues that may prevent or delay commercialization. We also base our judgment on the viability of commercialization, trends in the marketplace and market acceptance criteria. Finally, we consider the reimbursement strategies that may prevail with respect to the product and assess the economic benefit that we are likely to realize. We expense previously capitalized costs related to pre-approval inventory upon a change in such judgment, due to, among other potential factors, a denial or delay of approval by necessary regulatory bodies.

As of December 31, 2011 and 2010, the carrying value of our inventory did not include any significant costs associated with products that had not yet received regulatory approval.

Obsolescence and Unmarketable Inventory

We periodically review our inventories for excess or obsolete inventory and write-down obsolete or otherwise unmarketable inventory to its estimated net realizable value. If the actual net realizable value is less than that estimated by us, or if it is determined that inventory utilization will further diminish based on estimates of demand, additional inventory write-downs may be required. Additionally, our products are subject to strict quality control and monitoring which we perform throughout the manufacturing process. In the event that certain batches or units of product no longer meet quality specifications or become obsolete due to expiration, we will record a charge to cost of sales to write-down any obsolete or otherwise unmarketable inventory to its estimated net realizable value. In all cases product inventory is carried at the lower of cost or its estimated net realizable value. Amounts written-down to unmarketable inventory are charged to cost of sales, excluding amortization of acquired intangible assets.

Marketable Securities and Other Investments

Marketable Debt Securities

Available-for-sale debt securities are recorded at fair market value and unrealized gains and losses are included in accumulated other comprehensive income (loss) in equity, net of related tax effects, unless the security has experienced a credit loss, we have determined that we have the intent to sell the security or we have determined that it is more likely than not that we will have to sell the security before its expected recovery. Realized gains and losses are reported in other income (expense), net, on a specific identification basis.

Strategic Investments

As part of our business development efforts, we will, from time to time, invest in equity securities of certain biotechnology companies. These investments are known as strategic investments and are classified as available-for-sale and accounted for as marketable equity investments or as cost investments based upon our ownership percentage and other factors that suggest we have significant influence and are included in investments and other assets within our consolidated balance sheet. When assessing whether a decline in the fair value of a strategic investment below our cost basis is other-than-temporary, we consider the fair market value of the security, the duration of the security’s decline, and prospects for the underlying business, including favorable or adverse clinical trial results, new product initiatives and new collaborative agreements with the companies in which we have invested.

Non-Marketable Equity Securities

We also invest in equity securities of companies whose securities are not publicly traded and where fair value is not readily available. These investments are recorded using either the cost method or the equity method of accounting, depending on our ownership percentage and other factors that suggest we have significant influence. We monitor these investments to evaluate whether any decline in their value has occurred that would be other-than-temporary, based on the implied value of recent company financings, public market prices of comparable companies, and general market conditions and are included in investments and other assets within our consolidated balance sheet.

Evaluating Investments for Other-than-Temporary Impairments

We conduct periodic reviews to identify and evaluate each investment that has an unrealized loss, in accordance with the meaning of other-than-temporary impairment and its application to certain investments. An unrealized loss exists when the current fair value of an individual security is less than its amortized cost basis. Unrealized losses on available-for-sale securities that are determined to be temporary, and not related to credit loss, are recorded, net of tax, in accumulated other comprehensive income.

For available-for-sale debt securities with unrealized losses, management performs an analysis to assess whether we intend to sell or whether we would more likely than not be required to sell the security before the expected recovery of the amortized cost basis. Where we intend to sell a security, or may be required to do so, the security’s decline in fair value is deemed to be other-than-temporary and the full amount of the unrealized loss is reflected within earnings as an impairment loss.

Regardless of our intent to sell a security, we perform additional analysis on all securities with unrealized losses to evaluate losses associated with the creditworthiness of the security. Credit losses are identified where we do not expect to receive cash flows sufficient to recover the amortized cost basis of a security.

For equity securities, when assessing whether a decline in fair value below our cost basis is other-than-temporary, we consider the fair market value of the security, the duration of the security’s decline, and the financial condition of the issuer. We then consider our intent and ability to hold the equity security for a period of time sufficient to recover our carrying value. Where we have determined that we lack the intent and ability to hold an equity security to its expected recovery, the security’s decline in fair value is deemed to be other-than-temporary and is reflected within earnings as an impairment loss.

Property, Plant and Equipment

Property, plant and equipment are carried at cost, subject to review for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. The cost of normal, recurring, or periodic repairs and maintenance activities related to property, plant and equipment are expensed as incurred. The cost for planned major maintenance activities, including the related acquisition or construction of assets, is capitalized if the repair will result in future economic benefits.

Interest costs incurred during the construction of major capital projects are capitalized until the underlying asset is ready for its intended use, at which point the interest costs are amortized as depreciation expense over the life of the underlying asset. We also capitalize certain direct and incremental costs associated with the validation effort required for licensing by regulatory agencies of manufacturing equipment for the production of a commercially approved drug. These costs include primarily direct labor and material and are incurred in preparing the equipment for its intended use. The validation costs are amortized over the life of the related equipment.

In addition, we capitalize certain internal use computer software development costs. If the software is an integral part of production assets, these costs are included in machinery and equipment and are amortized on a straight-line basis over the estimated useful lives of the related software, which generally range from three to five years.

We generally depreciate or amortize the cost of our property, plant and equipment using the straight-line method over the estimated useful lives of the respective assets, which are summarized as follows:

Asset Category	Useful Lives
Land	Not depreciated
Buildings	15 to 40 years
Leasehold Improvements	Lesser of the useful life or the term of the respective lease
Furniture and Fixtures	5 to 7 years
Machinery and Equipment	5 to 20 years
Computer Software and Hardware	3 to 5 years

When we dispose of property, plant and equipment, we remove the associated cost and accumulated depreciation from the related accounts on our consolidated balance sheet and include any resulting gain or loss in our consolidated statement of income.

Intangible Assets

Our intangible assets consist of patents, licenses, core developed technology, in-process research and development acquired after January 1, 2009, trademarks, trade names, assembled workforce and other distribution rights. The majority of our intangible assets were recorded in connection with the merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation in 2003. Our intangible assets are recorded at fair value at the time of their acquisition and are stated within our consolidated balance sheets net of accumulated amortization and impairments.

We amortize intangible assets over their estimated useful lives using the economic use method if anticipated future cash flows can be reasonably estimated; the straight-line method is used when cash flows cannot be reasonably estimated. Our amortization policy reflects the pattern that the economic benefits of the intangible assets are consumed. The useful lives of our intangible assets are primarily based on the legal or contractual life of the underlying patent or contract, which does not include additional years for the potential extension or renewal of the contract or patent. Intangible assets related to patents, licenses, core developed technology, assembled workforce, and other distribution rights are amortized over their remaining estimated useful lives. Intangible assets related to trademarks, trade names and in-process research and development prior to commercialization are not amortized because they have indefinite lives, but they are subject to review for impairment. We review our intangible assets with indefinite lives for impairment annually, as of October 31, and whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable.

Our most significant intangible asset is the core technology related to our AVONEX product. Our amortization policy reflects our belief that the economic benefit of our core technology is consumed as revenue is generated from AVONEX. We refer to this amortization methodology as the economic consumption model, which involves calculating a ratio of actual current period sales to total anticipated sales for the life of the product and applying this ratio to the carrying amount of the intangible asset. An analysis of the anticipated lifetime revenue of AVONEX is performed at least annually during our long range planning cycle, and this analysis serves as the basis for the calculation of our economic consumption amortization model. We believe this process has allowed us to reliably determine the best estimate of the pattern in which we will consume the economic benefits of our core technology intangible asset.

Acquired In-process Research and Development (IPR&D)

Acquired IPR&D represents the fair value assigned to research and development assets that we acquire that have not been completed at the date of acquisition. The value assigned to acquired IPR&D is determined by estimating the costs to develop the acquired technology into commercially viable products, estimating the resulting revenue from the projects, and discounting the net cash flows to present value. The revenue and costs projections used to value acquired IPR&D were, as applicable, reduced based on the probability of developing a new drug. Additionally, the projections considered the relevant market sizes and growth factors, expected trends in technology, and the nature and expected timing of new product introductions by us and our competitors. The resulting net cash flows from such projects are based on management’s estimates of cost of sales, operating expenses, and income taxes from such projects. The rates utilized to discount the net cash flows to their present value were commensurate with the stage of development of the projects and uncertainties in the economic estimates used in the projections described above.

We measured acquired IPR&D in business combinations completed prior to January 1, 2009, at fair value and expensed it on acquisition date if that technology lacked an alternative future use, or capitalized it as an intangible asset if certain criteria were met; however, effective January 1, 2009, if we are purchasing a business, the acquired IPR&D is measured at fair value, capitalized as an intangible asset and tested for impairment at least annually until commercialization, after which time the IPR&D is amortized over its estimated useful life. If we acquire an asset or group of assets that do not meet the definition of a business under applicable accounting standards, then the acquired IPR&D is expensed on its acquisition date. Future costs to develop these assets are recorded to expense as they are incurred if the technology lacks alternative future uses.

We review amounts capitalized as in-process research and development for impairment at least annually, as of October 31, and whenever events or changes in circumstances indicate that the carrying value of the assets might not be recoverable. In the event the carrying value of the assets are not expected to be recovered, the assets are written down to their estimated fair values.

Impairment of Long-Lived Assets

Long-lived assets to be held and used, including property, plant and equipment are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets or asset group may not be recoverable.

Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their estimated fair values. Long-lived assets to be disposed of are carried at fair value less costs to sell.

Goodwill

Goodwill relates largely to amounts that arose in connection with the merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation and represents the difference between the purchase price and the fair value of the identifiable tangible and intangible net assets when accounted for using the purchase method of accounting. Goodwill is not amortized, but is subject to periodic review for impairment. Goodwill is reviewed annually, as of October 31, and whenever events or changes in circumstances indicate that the carrying value of the goodwill might not be recoverable.

We apply a two-step impairment test. In the first step, we compare the fair value of our reporting unit to its carrying value. If the carrying value of the net assets assigned to the reporting unit exceeds the fair value of our reporting unit, then the second step of the impairment test is performed in order to determine the implied fair value of our reporting unit’s goodwill. If the carrying value of our reporting unit’s goodwill exceeds its implied fair value, then the company records an impairment loss equal to the difference. As described in Note 25, Segment Information to these consolidated financial statements, we operate in one business segment which we consider our only reporting unit.

In September 2011, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2011-08, “Intangibles — Goodwill and Other (Topic 350): Testing Goodwill for Impairment” (ASU 2011-08). This newly issued accounting standard allows an entity the option to first assess qualitative factors to determine whether it is necessary to perform the current two-step impairment test. If an entity believes, as a result of its qualitative assessment, that it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount, the quantitative two-step impairment test is required; otherwise, no further testing is required. These amendments do not change the current guidance for testing other indefinite-lived intangible assets for impairment. This ASU is effective for annual and interim goodwill impairment tests performed for fiscal years beginning after December 15, 2011, which for Biogen Idec means January 1, 2012. Early adoption is permitted; however, we have not elected to do so. The adoption of this statement will not impact our financial position or results of operations.

Derivative Instruments and Hedging Activities

We recognize all derivative instruments as either assets or liabilities at fair value in our consolidated balance sheets. Changes in the fair value of derivatives are recorded each period in current earnings or accumulated other comprehensive income (loss), depending on whether a derivative is designated as part of a hedge transaction and, if it is, the type of hedge transaction. We classify the cash flows from these instruments in the same category as the cash flows from the hedged items. We do not hold or issue derivative instruments for trading or speculative purposes.

We assess, both at inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting the changes in cash flows or fair values of the hedged items. We also assess hedge ineffectiveness on a quarterly basis and record the gain or loss related to the ineffective portion to current earnings to the extent significant. If we determine that a forecasted transaction is no longer probable of occurring, we discontinue hedge accounting for the affected portion of the hedge instrument, and any related unrealized gain or loss on the contract is recognized in current earnings.

Translation of Foreign Currencies

The functional currency for most of our foreign subsidiaries is their local currency. For the Company’s non-U.S. subsidiaries that transact in functional currency other than the U.S. dollar, assets and liabilities are translated at current rates of exchange at the balance sheet date. Income and expense items are translated at the average foreign exchange rates for the period. Adjustments resulting from the translation of the financial statements of our foreign operations into U.S. dollars are excluded from the determination of net income and are recorded in accumulated other comprehensive income, a separate component of equity. For subsidiaries where the functional currency differs from the local currency, non-monetary assets and liabilities are translated at the rate of exchange in effect on the date assets were acquired while monetary assets and liabilities are translated at current rates of exchange as of the balance sheet date. Income and expense items are translated at the average foreign currency rates for the period. Translation adjustments of these subsidiaries are included in net income.

Accounting for Share-Based Compensation

Our share-based compensation programs grant awards which have included stock options, restricted stock units which vest based on stock performance known as market stock units (MSUs), performance-vested restricted stock units which will be settled in cash (CSPSs), performance-vested restricted stock units which settle in shares (PVRSUs), time-vested restricted stock units (RSUs) and shares issued under our employee stock purchase plan (ESPP). We charge the estimated fair value of awards against income over the requisite service period, which is generally the vesting period. Where awards are made with non-substantive vesting periods (for instance, where a portion of the award vests upon retirement eligibility), we estimate and recognize expense based on the period from the grant date to the date on which the employee is retirement eligible.

The fair values of our stock option grants are estimated as of the date of grant using a Black-Scholes option valuation model and reflect estimated forfeitures. The estimated fair values of the stock options are then expensed over the options’ vesting periods.

The fair values of our RSUs are based on the market value of our stock on the date of grant. Compensation expense for RSUs is recognized over the applicable service period, adjusted for the effect of estimated forfeitures.

We apply an accelerated attribution method to recognize stock based compensation expense, net of estimated forfeitures, when accounting for our MSUs. The probability of actual shares expected to be earned is considered in the grant date valuation, therefore the expense will not be adjusted to reflect the actual units earned.

We apply an accelerated attribution method to recognize stock based compensation expense when accounting for our CSPSs and the fair value of the liability is remeasured at the end of each reporting period through expected cash settlement. Compensation expense associated with CSPSs is based upon the stock price and the number of units expected to be earned after assessing the probability that certain performance criteria will be met and the associated targeted payout level that is forecasted will be achieved, net of estimated forfeitures. Cumulative adjustments are recorded each quarter to reflect changes in the stock price and estimated outcome of the performance-related conditions until the date results are determined and settled.

We apply an accelerated attribution method to recognize stock based compensation expense when accounting for our PVRSUs. The number of units reflected as granted represents the target number of shares that are eligible to vest in full or in part and are earned subject to the attainment of certain performance criteria established at the beginning of the performance period. Compensation expense associated with these units is initially based upon the number of shares expected to vest after assessing the probability that certain performance criteria will be met and the associated targeted payout level that is forecasted will be achieved, net of estimated forfeitures. Cumulative adjustments are recorded quarterly to reflect subsequent changes in the estimated outcome of performance-related conditions until the date results are determined.

The purchase price of common stock under our ESPP is equal to 85% of the lower of (i) the market value per share of the common stock on the participant’s entry date into an offering period or (ii) the market value per share of the common stock on the purchase date. However, for each participant whose entry date is other than the start date of the offering period, the amount shall in no event be less than the market value per share of the common stock as of the beginning of the related offering period. The fair value of the discounted purchases made under our ESPP is calculated using the Black-Scholes model. The fair value of the look-back provision plus the 15% discount is recognized as compensation expense over the purchase period. We apply a graded vesting approach since our ESPP provides for multiple purchase periods and is, in substance, a series of linked awards.

Research and Development Expenses

Research and development expenses consist of upfront fees and milestones paid to collaborators and expenses incurred in performing research and development activities, including compensation and benefits, facilities expenses, overhead expenses, clinical trial and related clinical manufacturing expenses, fees paid to clinical research organizations (CROs) and other outside expenses. Research and development expenses are expensed as incurred. Payments we make for research and development services prior to the services being rendered are recorded as prepaid assets on our consolidated balance sheets and are expensed as the services are provided.

From time to time, we enter into development agreements in which we share expenses with a collaborative partner. We record payments received from our collaborative partners for their share of the development costs as a reduction of research and development expense, except as discussed within Note 20, Collaborations to these consolidated financial statements. Expenses incurred by Genentech in the development of RITUXAN are not recorded as research and development expense, but rather reduce our share of co-promotion profits recorded as a component of unconsolidated joint business revenues.

Selling, General and Administrative Expenses

Selling, general and administrative expenses are primarily comprised of compensation and benefits associated with sales and marketing, finance, human resources, legal and other administrative personnel, outside marketing, advertising and legal expenses and other general and administrative costs.

Advertising costs are expensed as incurred. For the years ended December 31, 2011, 2010 and 2009, advertising costs totaled $45.3 million, $35.3 million and $26.5 million, respectively.

Income Taxes

The provision for income taxes includes federal, state, local and foreign taxes. Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the estimated future tax consequences of temporary differences between the financial statement carrying amounts and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year in which the temporary differences are expected to be recovered or settled. We evaluate the realizability of our deferred tax assets and establish a valuation allowance when it is more likely than not that all or a portion of deferred tax assets will not be realized.

We account for uncertain tax positions using a “more-likely-than-not” threshold for recognizing and resolving uncertain tax positions. We evaluate uncertain tax positions on a quarterly basis and consider various factors, including, but not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity and changes in facts or circumstances related to a tax position. We also accrue for potential interest and penalties, related to unrecognized tax benefits in income tax expense.

Contingencies

We are currently involved in various claims and legal proceedings. We account for potential litigation losses in accordance with FASB Accounting Standards Codification (ASC) No. 450, Contingencies (ASC 450). Under ASC 450, loss contingency provisions are recorded if the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount can be reasonably estimated or a range of loss can be determined. These accruals represent management’s best estimate of probable loss, as defined by ASC 450. Disclosure also is provided when it is reasonably possible that a loss will be incurred or when it is reasonably possible that the amount of a loss will exceed the recorded provision. On a quarterly basis, we review the status of each significant matter and assess its potential financial exposure. Significant judgment is required in both the determination of probability and the determination as to whether an exposure is reasonably estimable. Because of uncertainties related to these matters, accruals are based only on the best information available at the time. As additional information becomes available, we reassess the potential liability related to pending claims and litigation and may revise our estimates. These revisions in the estimates of the potential liabilities could have a material impact on our consolidated results of operations and financial position.

Restructuring Charges

We have made estimates and judgments regarding the amount and timing of our restructuring expense and liability, including current and future period termination benefits and other exit costs to be incurred when related actions take place. We have also assessed the recoverability of certain long-lived assets employed in the business and, in certain instances shortened the expected useful life of the assets based on changes in their expected use. When we determine that the useful lives of assets are shorter than we had originally estimated, we record additional depreciation to reflect the assets’ new shorter useful lives. Severance and other related costs and asset-related charges are reflected within our consolidated statement of income as a component of total restructuring charges incurred. Actual results may differ from these estimates. For additional information related to our recent restructuring efforts, please read Note 3, Restructuring, to these consolidated financial statements.

Earnings per Share

Basic earnings per share is computed using the two-class method. Under the two-class method, undistributed net income is allocated to common stock and participating securities based on their respective rights to share in dividends. We have determined that our preferred shares meet the definition of participating securities and, to the extent any are outstanding during a period, have allocated a portion of net income to our preferred shares on a pro rata basis. Net income allocated to preferred shares is excluded from the calculation of basic earnings per share. For basic earnings per share, net income available to holders of common stock is divided by the weighted average number of shares of common stock outstanding. For purposes of calculating diluted earnings per share, net income is adjusted for the after-tax amount of net income allocable to preferred shares, and the denominator includes both the weighted average number of shares of common stock outstanding and potential dilutive shares of common stock from stock options, unvested restricted stock awards, restricted stock units and other convertible securities, to the extent they are dilutive.

New Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that are adopted by the Company as of the specified effective date. Unless otherwise discussed, we believe that the impact of recently issued standards that are not yet effective will not have a material impact on our financial position or results of operations upon adoption.

In December 2011, the FASB issued ASU 2011-11, Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities (ASU 2011-11). This newly issued accounting standard requires an entity to disclose both gross and net information about instruments and transactions eligible for offset in the statement of financial position as well as instruments and transactions executed under a master netting or similar arrangement and was issued to enable users of financial statements to understand the effects or potential effects of those arrangements on its financial position. This ASU is required to be applied retrospectively and is effective for fiscal years, and interim periods within those years, beginning on or after January 1, 2013. As this accounting standard only requires enhanced disclosure, the adoption of this standard is not expected to have an impact our financial position or results of operations.

In June 2011, the FASB issued ASU No. 2011-05, “Comprehensive Income (Topic 220): Presentation of Comprehensive Income” (ASU 2011-05). This newly issued accounting standard (1) eliminates the option to present the components of other comprehensive income as part of the statement of changes in stockholders’ equity; (2) requires the consecutive presentation of the statement of net income and other comprehensive income; and (3) requires an entity to present reclassification adjustments on the face of the financial statements from other comprehensive income to net income. The amendments in this ASU do not change the items that must be reported in other comprehensive income or when an item of other comprehensive income must be reclassified to net income nor do the amendments affect how earnings per share is calculated or presented. In December 2011, the FASB issued ASU No. 2011-12, Deferral of the Effective Date for Amendments to the Presentation of Reclassifications of Items Out of Accumulated Other Comprehensive Income in Accounting Standards Update No. 2011-05, which defers the requirement within ASU 2011-05 to present on the face of the financial statements the effects of reclassifications out of accumulated other comprehensive income on the components of net income and other comprehensive income for all periods presented. During the deferral, entities should continue to report reclassifications out of accumulated other comprehensive income consistent with the presentation requirements in effect prior to the issuance of ASU 2011-05. These ASUs are required to be applied retrospectively and are effective for fiscal years, and interim periods within those years, beginning after December 15, 2011, which for Biogen Idec means January 1, 2012. As these accounting standards do not change the items that must be reported in other comprehensive income or when an item of other comprehensive income must be reclassified to net income, the adoption of these standards is not expected to have an impact on our financial position or results of operations.

In May 2011, the FASB issued ASU No. 2011-04, “Fair Value Measurement (Topic 820): Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs” (ASU 2011-04). This newly issued accounting standard clarifies the application of certain existing fair value measurement guidance and expands the disclosures for fair value measurements that are estimated using significant unobservable (Level 3) inputs. This ASU is effective on a prospective basis for annual and interim reporting periods beginning on or after December 15, 2011, which for Biogen Idec means January 1, 2012. The adoption of this standard is not expected to have a material impact on our financial position or results of operations.

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Segment Information

12 Months Ended

Dec. 31, 2011

Segment Information [Abstract]

Segment Information

25.    Segment Information

We operate as one business segment, which is the business of discovering, developing, manufacturing and marketing therapies for the treatment of neurodegenerative diseases, hemophilia and autoimmune disorders and therefore, our chief operating decision-maker manages the operations of our Company as a single operating segment. Enterprise-wide disclosures about product revenues, other revenues and long-lived assets by geographic area and information relating to major customers are presented below. Revenues are primarily attributed to individual countries based on location of the customer or licensee.

Revenue by product is summarized as follows:

	For the Years Ended December 31,
	2011						2010						2009
(In millions)	United States		Rest of World		Total		United States		Rest of World		Total		United States		Rest of World		Total
AVONEX	$	1,628.3	$	1,058.3	$	2,686.6	$	1,491.6	$	1,026.8	$	2,518.4	$	1,406.2	$	916.7	$	2,322.9
TYSABRI		326.5		753.0		1,079.5		252.8		647.4		900.2		231.8		544.2		776.0
Other		—		70.0		70.0		—		51.5		51.5		—		54.0		54.0
Total product revenues	$	1,954.8	$	1,881.3	$	3,836.1	$	1,744.4	$	1,725.7	$	3,470.1	$	1,638.0	$	1,514.9	$	3,152.9

Geographic Information

The following tables contain certain financial information by geographic area:

December 31, 2011 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,954.8	$	1,163.3	$	377.5	$	88.7	$	251.8	$	3,836.1
Revenues from unconsolidated joint business	$	878.8	$	29.9	$	—	$	30.7	$	57.2	$	996.6
Other revenues from external customers	$	187.0	$	28.3	$	0.6	$	—	$	—	$	215.9
Long-lived assets	$	1,012.5	$	816.6	$	1.6	$	5.3	$	2.4	$	1,838.4
December 31, 2010 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,744.4	$	1,090.7	$	362.4	$	69.0	$	203.6	$	3,470.1
Revenues from unconsolidated joint business	$	906.3	$	95.3	$	—	$	26.0	$	49.6	$	1,077.2
Other revenues from external customers	$	136.0	$	32.6	$	0.5	$	—	$	—	$	169.1
Long-lived assets	$	1,100.3	$	717.4	$	1.5	$	5.4	$	1.6	$	1,826.2
December 31, 2009 (In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenues from external customers	$	1,638.0	$	913.7	$	374.8	$	47.9	$	178.5	$	3,152.9
Revenues from unconsolidated joint business	$	839.2	$	190.2	$	—	$	24.1	$	41.4	$	1,094.9
Other revenues from external customers	$	102.8	$	26.2	$	0.5	$	—	$	—	$	129.5
Long-lived assets	$	1,092.7	$	705.6	$	1.4	$	3.6	$	2.1	$	1,805.4

(1) Represents amounts related to Europe less those attributable to Germany.

Revenues from Unconsolidated Joint Business

Approximately 20%, 23% and 25% of our total revenues in 2011, 2010 and 2009, respectively, are derived from our joint business arrangement with Genentech. For additional information related to our collaboration with Genentech, please read Note 20, Collaborations to these consolidated financial statements.

Significant Customers

We recorded revenue from two wholesale distributors accounting for 18% and 10% of gross product revenues in 2011, 18% and 11% of gross product revenue in 2010, and 18% and 12% of gross product revenues in 2009.

Other

As of December 31, 2011, 2010 and 2009, approximately $668.5 million, $644.7 million and $665.8 million, respectively, of our long-lived assets were related to our manufacturing facilities in Denmark.

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Indebtedness (Details) In Thousands, unless otherwise specified	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2011 Note payable to Fumedica [Member] USD ($)	Dec. 31, 2010 Note payable to Fumedica [Member] USD ($)	Dec. 31, 2006 Note payable to Fumedica [Member] CHF	Dec. 31, 2011 Credit line from Dompe [Member] USD ($)	Dec. 31, 2010 Credit line from Dompe [Member] USD ($)	Dec. 31, 2011 6.0% Senior notes due 2013 [Member] USD ($)	Dec. 31, 2010 6.0% Senior notes due 2013 [Member] USD ($)	Dec. 31, 2011 6.875% Senior notes due 2018 [Member] USD ($)	Dec. 31, 2010 6.875% Senior notes due 2018 [Member] USD ($)	Dec. 31, 2011 Financing arrangements [Member] USD ($)	Dec. 31, 2010 Financing arrangements [Member] USD ($)
Current portion:
Current portion of notes payable, line of credit and other financing arrangements	$ 3,292	$ 137,153	$ 3,300	$ 3,300		$ 0	$ 8,000					$ 0	$ 125,900
Non-current portion:
Non-current portion of notes payable, line of credit and other financing arrangements	$ 1,060,808	$ 1,066,379	$ 16,400	$ 18,700	61,400			$ 449,900	$ 449,800	$ 592,300	$ 597,900	$ 2,200	$ 0

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Collaborations (Details 2) (Portola Pharmaceuticals [Member], USD $)	12 Months Ended
	Dec. 31, 2011
Summary of activity related to collaboration with Portola Pharmaceuticals, Inc.
Total expense incurred by collaboration	$ 1,100,000
Total expense reflected within our consolidated statements of income, excluding upfront and milestone payments	900,000
Summary of activity related to collaboration, along with an estimate of additional future development expense
Total upfront and milestone payments made to Collaborative Partner	36,800,000
PRT 062607 [Member]
Summary of activity related to collaboration, along with an estimate of additional future development expense
Estimate of additional amounts to be incurred by us in Product development	$ 675,000,000

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Inventory (Tables)

12 Months Ended

Dec. 31, 2011

Inventory [Abstract]

Components of inventories

	As of December 31,
(In millions)	2011		2010
Raw materials	$	83.8	$	59.0
Work in process		169.4		142.2
Finished goods		73.6		87.9
Total inventory	$	326.8	$	289.1

Components of inventory by product

	As of December 31,
(In millions)	2011		2010
AVONEX	$	113.3	$	87.0
TYSABRI		114.7		117.0
Other		15.0		26.1
Total finished goods and work in process		243.0		230.1
Raw materials		83.8		59.0
Total inventory	$	326.8	$	289.1

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Investments in Variable Interest Entities (Tables)

12 Months Ended

Dec. 31, 2011

Investments in Variable Interest Entities [Abstract]

Summary of activity related to collaboration with Knopp

	For the Years Ended December 31,
(In millions)	2011		2010
Total upfront payments made to Knopp	$	—	$	26.4
Milestone payments made to Knopp	$	10.0	$	—
Total development expense incurred by the collaboration excluding upfront and milestone payments	$	44.8	$	5.0
Biogen Idec’s share of expense reflected within our consolidated statements of income	$	54.8	$	31.4
Collaboration expense attributed to noncontrolling interests, net of tax	$	8.6	$	—

Summary of activity related to collaboration with Knopp along with an estimate of additional future development expense

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Knopp	$	36.4
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	$	49.8
Estimate of additional amounts to be incurred by us in development of dexpramipexole	$	260.0

Summary of activity related to collaboration with Neurimmune

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Milestone payments made to Neurimmune	$	15.0	$	—	$	7.5
Total development expense incurred by the collaboration, excluding upfront and milestone payments	$	9.0	$	15.5	$	9.0
Biogen Idec’s share of expense reflected within our consolidated statements of income	$	24.0	$	15.5	$	16.5
Collaboration expense attributed to noncontrolling interests, net of tax	$	14.7	$	1.0	$	—

Summary of activity related to collaboration with Neurimmune along with an estimate of additional future development expense

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Neurimmune	$	35.0
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	$	40.0
Estimate of additional amounts to be incurred by us in development of the lead compound	$	800.0

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Fair Value Measurements (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Fair value of contingent consideration obligations
Fair value as of beginning of period	$ 81.2	$ 0
Acquisition date fair value of contingent consideration obligations related to acquisitions	38.8	81.2
Changes in the fair value of contingent consideration obligations	36.0
Payments of contingent consideration obligations	(5.0)
Fair value as of end of period	$ 151.0	$ 81.2

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Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues:
Product	$ 3,836,117	$ 3,470,056	$ 3,152,941
Unconsolidated joint business	996,597	1,077,244	1,094,863
Other	215,920	169,123	129,544
Total revenues	5,048,634	4,716,423	4,377,348
Cost and expenses:
Cost of sales, excluding amortization of acquired intangible assets	466,780	400,262	382,104
Research and development	1,219,602	1,248,604	1,283,068
Selling, general and administrative	1,056,133	1,031,540	911,034
Collaboration profit sharing	317,771	258,071	215,904
Amortization of acquired intangible assets	208,566	208,928	289,811
Fair value adjustment of contingent consideration	36,065
Restructuring charge	19,026	75,153
Acquired in-process research and development		244,976
Total cost and expenses	3,323,943	3,467,534	3,081,921
Income from operations	1,724,691	1,248,889	1,295,427
Other income (expense), net	(13,477)	(18,983)	37,252
Income before income tax expense	1,711,214	1,229,906	1,332,679
Income tax expense	444,528	331,333	355,617
Net income	1,266,686	898,573	977,062
Net income (loss) attributable to noncontrolling interests, net of tax	32,258	(106,700)	6,930
Net income attributable to Biogen Idec Inc.	$ 1,234,428	$ 1,005,273	$ 970,132
Net income per share:
Basic earnings per share attributable to Biogen Idec Inc.	$ 5.09	$ 3.98	$ 3.37
Diluted earnings per share attributable to Biogen Idec Inc.	$ 5.04	$ 3.94	$ 3.35
Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Idec Inc.	242,395	252,307	287,356
Diluted earnings per share attributable to Biogen Idec Inc.	245,033	254,867	289,476

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Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2011

Property, Plant and Equipment [Abstract]

Components of property, plant and equipment, net

	As of December 31,
(In millions)	2011			2010
Land	$	51.9		$	107.6
Buildings		597.9			670.2
Leasehold improvements		102.7			100.8
Machinery and equipment		570.1			576.0
Computer software and hardware		439.7			392.8
Furniture and fixtures		37.6			54.5
Construction in progress		553.6			506.9
Total cost		2,353.5			2,408.8
Less: accumulated depreciation		(782.1	)		(767.2	)
Total property, plant and equipment, net	$	1,571.4		$	1,641.6

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Share-Based Payments (Details 5) (Market stock units [Member], USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Market stock units [Member]
Market stock units activity
Beginning Balance, Unvested, Shares	398,000
Beginning Balance, Weighted Average Grant Date Fair Value	$ 61.87
Shares, Granted	398,000
Weighted Average Grant Date Fair Value, Granted	$ 74.19	$ 61.87
Shares, Vested	(119,000)
Weighted Average Grant Date Fair Value, Vested	$ 59.89
Shares, Forfeited	(96,000)
Weighted Average Grant Date Fair Value, Forfeited	$ 65.37
Ending Balance, Unvested, Shares	581,000	398,000
Ending Balance, Weighted Average Grant Date Fair Value	$ 69.49	$ 61.87

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Collaborations (Details 1) (Acorda [Member], USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Acorda [Member]
Summary of activity related to collaboration with Acorda
Total upfront and milestone payments made to Acorda	$ 25,000,000		$ 110,000,000
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	22,300,000	22,800,000	4,700,000
Total expense reflected within our consolidated statements of income, excluding upfront and milestone payments	22,300,000	22,800,000	114,700,000
Total capitalized as an intangible asset	25,000,000
Summary of activity related to collaboration, along with an estimate of additional future development expense
Total upfront and milestone payments made to Collaborative Partner	135,000,000
Total expense incurred by Biogen Idec, excluding upfront and milestone payments	$ 49,900,000

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Consolidated Statements of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Total Biogen Idec Inc. shareholders' equity	Preferred stock	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Retained earnings	Treasury stock	Noncontrolling interests
Beginning Balance at Dec. 31, 2008	$ 5,833,952	$ 5,806,083	$ 0	$ 149	$ 6,073,957	$ (11,106)	$ 270,180	$ (527,097)	$ 27,869
Beginning Balance, shares at Dec. 31, 2008			8	297,253				(9,207)
Comprehensive income:
Net income	977,062	970,132					970,132		6,930
Unrealized gains (losses) recognized on securities available for sale
Unrealized gains (losses) recognized during the period, net of tax of $133, $6,345, $4,136 for 2011, 2010 and 2009, respectively	7,191	7,191				7,191
Less: reclassification adjustment for gains included in net income, net of tax of $7,155, $5,656, $3,756 for 2011, 2010 and 2009, respectively	(6,396)	(6,396)				(6,396)
Net unrealized gains (losses) on securities available for sale, net of tax of $7,288, $689, $380 for 2011, 2010 and 2009, respectively	795	795				795
Unrealized gains (losses) on foreign currency forward contracts
Unrealized gains (losses) recognized during the period, net of tax of $3,647, $1,268, $254 for 2011, 2010 and 2009, respectively	1,452	1,452				1,452
Less: reclassification adjustment for (gains) losses included in net income, net of tax of $1,268, $304, $3,836 for 2011, 2010 and 2009, respectively	40,216	40,216				40,216
Unrealized gains (losses) on foreign currency forward contracts , net of tax of $4,915, $964, $3,582 for 2011, 2010 and 2009, respectively	41,668	41,668				41,668
Unrealized gains (losses) on pension benefit obligation
Unrealized gains (losses) on pension benefit obligation, net of tax of $0, $0, $67 for 2011, 2010 and 2009, respectively	501	501				501
Translation adjustment	19,835	18,638				18,638			1,197
Total comprehensive income	1,039,861	1,031,734							8,127
Distributions to noncontrolling interests	(2,832)								(2,832)
Capital contributions from noncontrolling interests	7,188								7,188
Repurchase of common stock for Treasury pursuant to the 2011, 2010 and 2009 share repurchase plans, at cost	(751,170)	(751,170)						(751,170)
Repurchase of common stock for Treasury pursuant to the 2011, 2010 and 2009 stock repurchase plans, at cost, shares								(15,982)
Retirement of common stock pursuant to the 2009 and 2010 share repurchase plans				(5)	(422,415)			422,420
Retirement of common stock pursuant to the 2009 and 2010 share repurchase plans, shares				(8,759)				8,759
Issuance of common and treasury stock under stock option and stock purchase plans	47,810	47,810					(27,191)	75,001
Issuance of common and treasury stock under stock option and stock purchase plans, shares								1,181
Issuance of common stock under stock award plan	(43,305)	(43,305)					(144,231)	100,926
Issuance of common under stock award plan, shares								1,610
Compensation expense related to share-based payments	167,207	167,207			167,207
Tax benefit from share-based payments	(36,829)	(36,829)			(36,829)
Ending Balance at Dec. 31, 2009	6,261,882	6,221,530	0	144	5,781,920	50,496	1,068,890	(679,920)	40,352
Ending Balance, shares at Dec. 31, 2009			8	288,494				(13,639)
Comprehensive income:
Net income	898,573	1,005,273					1,005,273		(106,700)
Unrealized gains (losses) recognized on securities available for sale
Unrealized gains (losses) recognized during the period, net of tax of $133, $6,345, $4,136 for 2011, 2010 and 2009, respectively	10,775	10,775				10,775
Less: reclassification adjustment for gains included in net income, net of tax of $7,155, $5,656, $3,756 for 2011, 2010 and 2009, respectively	(9,631)	(9,631)				(9,631)
Net unrealized gains (losses) on securities available for sale, net of tax of $7,288, $689, $380 for 2011, 2010 and 2009, respectively	1,144	1,144				1,144
Unrealized gains (losses) on foreign currency forward contracts
Unrealized gains (losses) recognized during the period, net of tax of $3,647, $1,268, $254 for 2011, 2010 and 2009, respectively	(9,767)	(9,767)				(9,767)
Less: reclassification adjustment for (gains) losses included in net income, net of tax of $1,268, $304, $3,836 for 2011, 2010 and 2009, respectively	(1,502)	(1,502)				(1,502)
Unrealized gains (losses) on foreign currency forward contracts , net of tax of $4,915, $964, $3,582 for 2011, 2010 and 2009, respectively	(11,269)	(11,269)				(11,269)
Unrealized gains (losses) on pension benefit obligation
Unrealized gains (losses) on pension benefit obligation, net of tax of $0, $0, $67 for 2011, 2010 and 2009, respectively	(1,942)	(1,942)				(1,942)
Translation adjustment	(62,279)	(60,039)				(60,039)			(2,240)
Total comprehensive income	824,227	933,167							(108,940)
Fair value of assets and liabilities acquired and assigned to noncontrolling interests (Note19)	145,000								145,000
Distributions to noncontrolling interests	(33,891)								(33,891)
Capital contributions from noncontrolling interests	2,488								2,488
Termination of relationship with less than majority owned subsidiary	7,928								7,928
Repurchase of common stock for Treasury pursuant to the 2011, 2010 and 2009 share repurchase plans, at cost	(2,077,579)	(2,077,579)						(2,077,579)
Repurchase of common stock for Treasury pursuant to the 2011, 2010 and 2009 stock repurchase plans, at cost, shares								(40,294)
Retirement of common stock pursuant to the 2009 and 2010 share repurchase plans				(20)	(2,077,559)			2,077,579
Retirement of common stock pursuant to the 2009 and 2010 share repurchase plans, shares				(40,294)				40,294
Issuance of common and treasury stock under stock option and stock purchase plans	183,486	183,486					(28,632)	212,118
Issuance of common and treasury stock under stock option and stock purchase plans, shares								4,020
Issuance of common stock under stock award plan	(54,840)	(54,840)					(173,050)	118,210
Issuance of common under stock award plan, shares								1,957
Compensation expense related to share-based payments	171,435	171,435			171,435
Tax benefit from share-based payments	19,307	19,307			19,307
Ending Balance at Dec. 31, 2010	5,449,443	5,396,506	0	124	3,895,103	(21,610)	1,872,481	(349,592)	52,937
Ending Balance, shares at Dec. 31, 2010			8	248,200				(7,662)
Comprehensive income:
Net income	1,266,686	1,234,428					1,234,428		32,258
Unrealized gains (losses) recognized on securities available for sale
Unrealized gains (losses) recognized during the period, net of tax of $133, $6,345, $4,136 for 2011, 2010 and 2009, respectively	(224)	(224)				(224)
Less: reclassification adjustment for gains included in net income, net of tax of $7,155, $5,656, $3,756 for 2011, 2010 and 2009, respectively	(12,184)	(12,184)				(12,184)
Net unrealized gains (losses) on securities available for sale, net of tax of $7,288, $689, $380 for 2011, 2010 and 2009, respectively	(12,408)	(12,408)				(12,408)
Unrealized gains (losses) on foreign currency forward contracts
Unrealized gains (losses) recognized during the period, net of tax of $3,647, $1,268, $254 for 2011, 2010 and 2009, respectively	32,830	32,830				32,830
Less: reclassification adjustment for (gains) losses included in net income, net of tax of $1,268, $304, $3,836 for 2011, 2010 and 2009, respectively	9,767	9,767				9,767
Unrealized gains (losses) on foreign currency forward contracts , net of tax of $4,915, $964, $3,582 for 2011, 2010 and 2009, respectively	42,597	42,597				42,597
Unrealized gains (losses) on pension benefit obligation
Unrealized gains (losses) on pension benefit obligation, net of tax of $0, $0, $67 for 2011, 2010 and 2009, respectively	(9,280)	(9,280)				(9,280)
Translation adjustment	(20,931)	(25,884)				(25,834)			4,903
Total comprehensive income	1,266,664	1,229,503							37,161
Distributions to noncontrolling interests	(27,062)	(148)					(148)		(26,914)
Acquisitions of noncontrolling interests	(187,337)	(125,641)			(125,641)				(61,696)
Repurchase of common stock for Treasury pursuant to the 2011, 2010 and 2009 share repurchase plans, at cost	(497,975)	(497,975)						(497,975)
Repurchase of common stock for Treasury pursuant to the 2011, 2010 and 2009 stock repurchase plans, at cost, shares								(6,018)
Issuance of common and treasury stock under stock option and stock purchase plans	314,649	314,649		3	306,982			7,664
Issuance of common and treasury stock under stock option and stock purchase plans, shares				5,458				162
Issuance of common stock under stock award plan	(50,953)	(50,953)		1	(50,954)
Issuance of common under stock award plan, shares	5,235,000			1,482
Conversion of preferred stock	0
Conversion of preferred stock, shares			(8)	493
Compensation expense related to share-based payments	117,347	117,347			117,347
Recharacterization of share-based awards from equity to cash-settled due to restructuring	(8,172)	(8,172)			(8,172)
Tax benefit from share-based payments	50,383	50,383			50,383
Ending Balance at Dec. 31, 2011	$ 6,426,987	$ 6,425,499	$ 0	$ 128	$ 4,185,048	$ (26,535)	$ 3,106,761	$ (839,903)	$ 1,488
Ending Balance, shares at Dec. 31, 2011			0	255,633				(13,518)

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Share-Based Payments (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2011
Stock Option Activity [Abstract]
Beginning Balance, Outstanding shares	7,167,000
Beginning Balance, Weighted Average Exercise Price	$ 55.43
Shares, Granted	0
Weighted Average Exercise Price, Granted	$ 0.00
Shares, Exercised	(5,235,000)
Weighted Average Exercise Price, Exercised	$ 56.40
Shares, Cancelled	(241,000)
Weighted Average Exercise Price, Cancelled	$ 53.30
Ending Balance, Outstanding shares	1,691,000
Ending Balance, Weighted Average Exercise Price	$ 52.75

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Acquisitions (Details) (USD $)						12 Months Ended		12 Months Ended				12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH [Member]	Sep. 06, 2011 Biogen Dompe SRL and Biogen Dompe Switzerland GmbH [Member]	Dec. 31, 2011 Biogen Dompe SRL [Member]	Sep. 06, 2011 Biogen Dompe SRL [Member]	Dec. 31, 2010 Biogen Idec Hemophilia [Member]	Dec. 31, 2011 Biogen Idec Hemophilia [Member]	Dec. 31, 2007 Biogen Idec Hemophilia [Member]	Jan. 31, 2007 Biogen Idec Hemophilia [Member]	Dec. 31, 2011 Biogen Idec International Neuroscience GmbH [Member]	Dec. 31, 2010 Biogen Idec International Neuroscience GmbH [Member]
Acquisitions (Textual) [Abstract]
Cash portion of consideration					$ 152,900,000								$ 32,500,000
Value of contingent consideration					42,500,000								395,000,000
Stock acquired in acquisition											100.00%		100.00%
Receivables purchased as part of acquisition						104,600,000	104,600,000
Loss recognized upon disposition						1,800,000
Fair value of contingent consideration	151,000,000	81,200,000	0	31,900,000	38,800,000					80,000,000		119,100,000	81,200,000
Payment to former shareholders of Syntonix Pharmaceuticals								40,000,000				5,000,000
Additional contingent payment for Biologic License									20,000,000
Additional contingent payment for marketing authorization									20,000,000
In process research and development													110,900,000
Goodwill													$ 25,600,000

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Share-Based Payments (Details 8) (Time Vested Restricted Stock Units [Member], USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Time Vested Restricted Stock Units [Member]
Time-vested restricted stock units
Beginning Balance, Unvested, Shares	4,223,000
Beginning Balance, Weighted Average Grant Date Fair Value	$ 53.26
Shares, Granted	1,398,000
Weighted Average Grant Date Fair Value, Granted	$ 70.01	$ 54.79	$ 48.93
Shares, Vested	(1,980,000)
Weighted Average Grant Date Fair Value, Vested	$ 53.72
Shares, Forfeited	(717,000)
Weighted Average Grant Date Fair Value, Forfeited	$ 54.20
Ending Balance, Unvested, Shares	2,924,000	4,223,000
Ending Balance, Weighted Average Grant Date Fair Value	$ 60.72	$ 53.26

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Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2011

Summary of Significant Accounting Policies [Abstract]

Business Overview

Biogen Idec is a global biotechnology company that discovers, develops, manufactures and markets therapies for the treatment of neurodegenerative diseases, hemophilia and autoimmune disorders. Patients worldwide benefit from our leading multiple sclerosis therapies, and the company generates $5 billion in annual revenues.

Consolidation

Our consolidated financial statements reflect our financial statements, those of our wholly-owned subsidiaries and those of certain variable interest entities in which we are the primary beneficiary. For consolidated entities in which we own or are exposed to less than 100% of the economics, we record net income (loss) attributable to noncontrolling interests in our consolidated statements of income equal to the percentage of the economic or ownership interest retained in such entities by the respective noncontrolling parties. All material intercompany balances and transactions are eliminated in consolidation.

In determining whether we are the primary beneficiary of an entity, we apply a qualitative approach that determines whether we have both (1) the power to direct the economically significant activities of the entity and (2) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. These considerations impact the way we account for our existing collaborative relationships and determine whether we consolidate companies or entities with which we have collaborative or other arrangements. Determination about whether an enterprise should consolidate a variable interest entity is required to be made continuously as changes to existing relationships or future transactions may result in us consolidating or deconsolidating our partner(s) to collaborations and other arrangements.

Use of Estimates

The preparation of our consolidated financial statements in accordance with U.S. GAAP requires management to make estimates, judgments, and assumptions that may affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. On an on-going basis, we evaluate our estimates and judgments and methodologies, including those related to revenue recognition and related allowances, our collaborative relationships, clinical trial expenses, the consolidation of variable interest entities, the valuation of contingent consideration resulting from a business combination, the valuation of acquired intangible assets including in-process research and development, inventory, impairment and amortization of long-lived assets including intangible assets, impairments of goodwill, share-based compensation, income taxes including the valuation allowance for deferred tax assets, the valuation of investments, derivatives and hedging activities, contingencies, litigation, and restructuring charges. We base our estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results may differ from these estimates under different assumptions or conditions.

Revenue recognition

We recognize revenue when all of the following criteria are met: persuasive evidence of an arrangement exists; delivery has occurred or services have been rendered; our price to the customer is fixed or determinable; and collectability is reasonably assured.

Product Revenues

Revenues from product sales are recognized when title and risk of loss have passed to the customer, which is typically upon delivery. However, sales of TYSABRI in the U.S. are recognized on the “sell-through” model, that is, upon shipment of the product by Elan Pharma International, Ltd. (Elan), an affiliate of Elan Corporation, plc, to its third party distributor rather than upon shipment to Elan. Product revenues are recorded net of applicable reserves for discounts and allowances.

Reserves for Discounts and Allowances

We establish reserves for trade term discounts, wholesaler incentives, Medicaid rebates, Veterans Administration (VA) and Public Health Service (PHS) discounts, managed care rebates, product returns and other governmental rebates or applicable allowances, including those associated with the implementation of pricing actions in certain of the international markets in which we operate. Reserves established for these discounts and allowances are classified as reductions of accounts receivable (if the amount is payable to our direct customer) or a liability (if the amount is payable to a party other than our customer). These reserves are based on estimates of the amounts earned or to be claimed on the related sales. Our estimates take into consideration our historical experience, current contractual and statutory requirements, specific known market events and trends, and forecasted customer buying patterns. Actual amounts may ultimately differ from our estimates. If actual results vary, we will need to adjust these estimates, which could have an effect on earnings in the period of adjustment. The estimates we make with respect to these allowances represent the most significant judgments with regard to revenue recognition.

Product revenue reserves are categorized as follows: discounts, contractual adjustments and returns.

Discount reserves include trade term discounts and wholesaler incentives. Trade term discounts and wholesaler incentive reserves primarily relate to estimated obligations for credits to be granted to wholesalers for remitting payment on their purchases within established incentive periods and credits to be granted to wholesalers for compliance with various contractually-defined inventory management practices, respectively. We determine these reserves based on our experience, including the timing of customer payments.

Contractual adjustment reserves primarily relate to Medicaid and managed care rebates, VA and PHS discounts and other governmental rebates or applicable allowances.

• Medicaid rebate reserves relate to our estimated obligations to states under established reimbursement arrangements. Rebate accruals are recorded in the same period the related revenue is recognized resulting in a reduction of product revenue and the establishment of a liability which is included in other current liabilities. Our liability for Medicaid rebates consists of estimates for claims that a state will make for the current quarter, claims for prior quarters that have been estimated for which an invoice has not been received, invoices received for claims from the prior quarters that have not been paid, and an estimate of potential claims that will be made for inventory that exists in the distribution channel at period end.

• VA rebates or chargeback reserves represent our estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices we charge to wholesalers which provide those products. The wholesaler charges us for the difference between what the wholesaler pays for the products and the ultimate selling price to the qualified healthcare providers. Rebate and chargeback reserves are established in the same period as the related revenue is recognized resulting in a reduction in product revenue and accounts receivable. Chargeback amounts are generally determined at the time of resale to the qualified healthcare provider from the wholesaler, and we generally issue credits for such amounts within a few weeks of the wholesaler notifying us about the resale. Our reserves for VA and chargebacks consists of amounts that we expect to issue for inventory that exists at the wholesalers that we expect will be sold to qualified healthcare providers and chargebacks that wholesalers have claimed for which we have not issued a credit.

• Managed care rebate reserves represent our estimated obligations to third parties, primarily pharmacy benefit managers. Rebate accruals are recorded in the same period the related revenue is recognized resulting in a reduction of product revenue and the establishment of a liability which is included in accrued expenses and other current liabilities. These rebates result from performance-based goals that are primarily based on attaining contractually specified sales volumes and growth. The calculation of the accrual for these rebates is based on an estimate of the customer’s buying patterns and the resulting applicable contractual rebate rate(s) to be earned over a contractual period.

• Other governmental rebates or applicable allowances primarily relate to mandatory rebates and discounts in markets where government-sponsored healthcare systems are the primary payers for healthcare.

Product return reserves are established for returns expected to be made by wholesalers and are recorded in the period the related revenue is recognized, resulting in a reduction to product sales. In accordance with contractual terms, wholesalers are permitted to return product for reasons such as damaged or expired product. The majority of wholesaler returns are due to product expiration. Expired product return reserves are estimated through a comparison of historical return data to their related sales on a production lot basis. Historical rates of return are determined for each product and are adjusted for known or expected changes in the marketplace specific to each product.

In addition to the discounts and rebates described above and classified as a reduction of revenue, we also maintain certain customer service contracts with distributors and other customers in the distribution channel that provide us with inventory management and distribution services. We have established the fair value of these services and classified these customer service contracts as sales and marketing expense. If we had concluded that we did not receive a separate identifiable benefit or have sufficient evidence that the fair value did not exist for these services, we would have been required to classify these costs as a reduction of revenue.

In countries where we expect to collect receivables greater than one year, at the time of sale, we have discounted our revenues over the period of time that we estimate those amounts will be paid using our estimate of the country’s borrowing rate. The related receivables are classified at the time of sale as long-term assets. We will accrete interest income on these receivables, which will be recognized as a component of other income (expense), net within our consolidated statement of income.

We also distribute no-charge product to qualifying patients under our patient assistance and patient replacement goods program. This program is administered through one of our distribution partners, which ships product for qualifying patients from its own inventory received from us. Gross revenue and the related reserves are not recorded on product shipped under this program and cost of sales is recorded when the product is shipped.

Revenues from Unconsolidated Joint Business

We collaborate with Genentech on the development and commercialization of RITUXAN. Revenues from unconsolidated joint business consist of (1) our share of pre-tax co-promotion profits in the U.S.; (2) reimbursement of our selling and development expense in the U.S.; and (3) revenue on sales of RITUXAN in the rest of world, which consists of our share of pre-tax co-promotion profits in Canada and royalty revenue on sales of RITUXAN outside the U.S. and Canada by F. Hoffmann-La Roche Ltd. (Roche) and its sublicensees. Pre-tax co-promotion profits are calculated and paid to us by Genentech in the U.S. and by Roche in Canada. Pre-tax co-promotion profits consist of U.S. and Canadian sales of RITUXAN to third-party customers net of discounts and allowances less the cost to manufacture RITUXAN, third-party royalty expenses, and distribution, selling and marketing, and joint development expenses incurred by Genentech, Roche and us. We record our share of the pretax co-promotion profits in Canada and royalty revenues on sales of RITUXAN outside the U.S. on a cash basis. Additionally, our share of the pretax co-promotion profits in the U.S. includes estimates made by Genentech and those estimates are subject to change. Actual results may ultimately differ from our estimates.

Royalty Revenues

We receive royalty revenues on sales by our licensees of other products covered under patents that we own. We do not have future performance obligations under these license arrangements. We record these revenues based on estimates of the sales that occurred during the relevant period. The relevant period estimates of sales are based on interim data provided by licensees and analysis of historical royalties that have been paid to us, adjusted for any changes in facts and circumstances, as appropriate. We maintain regular communication with our licensees in order to assess the reasonableness of our estimates. Differences between actual royalty revenues and estimated royalty revenues are adjusted for in the period in which they become known, typically the following quarter. Historically, adjustments have not been material when compared to actual amounts paid by licensees. If we are unable to accurately estimate revenue, then we record revenues on a cash basis.

Milestone Revenues

We execute collaborative and other agreements which may contain milestone payments. Revenues from milestones, if they are considered substantive, are recognized upon successful accomplishment of the milestones. Determining whether a milestone is substantive involves judgment, including an assessment of our involvement in achieving the milestones and whether the amount of the payment is commensurate to our performance. If not considered substantive, milestones are initially deferred and recognized over the remaining performance obligation.

Multiple-Element Revenue Arrangements

We may, from time to time, enter into transactions that involve the sale of products and related services under multiple element arrangements. In accounting for these transactions, we allocate revenue to the various elements based on their fair value. The fair value of a revenue generating element can be based on current selling prices offered by us or another party for current products or management’s best estimate of a selling price for future products. Revenue allocated to an individual element is recognized when all other revenue recognition criteria are met for that element.

Fair Value Measurements

We have certain financial assets and liabilities recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements.

• Level 1 — Fair values are determined utilizing quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access;

• Level 2 — Fair values are determined by utilizing quoted prices for identical or similar assets and liabilities in active markets or other market observable inputs such as interest rates, yield curves and foreign currency spot rates; and

• Level 3 — Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

Valuation of Investments

We validate the prices provided by our third party pricing services by reviewing their pricing methods and matrices, obtaining market values from other pricing sources, analyzing pricing data in certain instances and confirming that the relevant markets are active. After completing our validation procedures, we did not adjust or override any fair value measurements provided by our pricing services as of December 31, 2011 and 2010, respectively.

Our strategic investments in publicly traded equity securities are classified as Level 1 assets as their fair values are readily determinable and based on quoted market prices.

The majority of our financial assets and liabilities have been classified as Level 2. Our financial assets and liabilities (which include our cash equivalents, derivative contracts, marketable debt securities, and plan assets for deferred compensation) have been initially valued at the transaction price and subsequently valued, at the end of each reporting period, typically utilizing third party pricing services or other market observable data. The pricing services utilize industry standard valuation models, including both income and market based approaches and observable market inputs to determine value. These observable market inputs include reportable trades, benchmark yields, credit spreads, broker/dealer quotes, bids, offers, current spot rates and other industry and economic events.

We also maintain venture capital investments classified as Level 3 whose fair value is initially measured at transaction prices and subsequently valued using the pricing of recent financing or by reviewing the underlying economic fundamentals and liquidation value of the companies. These investments are the only investments for which we used Level 3 inputs to determine the fair value. These investments include investments in certain biotechnology oriented venture capital funds which primarily invest in small privately-owned, venture-backed biotechnology companies. The fair value of our investments in these venture capital funds has been estimated using the net asset value of the fund. The investments cannot be redeemed within the funds. Distributions from each fund will be received as the underlying investments of the fund are liquidated. The funds and therefore a majority of the underlying assets of the funds will not be liquidated in the near future. The underlying assets in these funds are initially measured at transaction prices and subsequently valued using the pricing of recent financings or by reviewing the underlying economic fundamentals and liquidation value of the companies that the funds invest in. We apply judgments and estimates when we validate the prices provided by third parties. While we believe the valuation methodologies are appropriate, the use of valuation methodologies is highly judgmental and changes in methodologies can have a material impact on our results of operations. Gains and losses (realized and unrealized) included in earnings for the period are reported in other income (expense), net.

Other

The carrying amounts reflected in the consolidated balance sheets for cash equivalents, current accounts receivable, due from unconsolidated joint business, other current assets, accounts payable, and accrued expenses and other, approximate fair value due to their short-term maturities.

In May 2011, the FASB issued ASU No. 2011-04, “Fair Value Measurement (Topic 820): Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs” (ASU 2011-04). This newly issued accounting standard clarifies the application of certain existing fair value measurement guidance and expands the disclosures for fair value measurements that are estimated using significant unobservable (Level 3) inputs. This ASU is effective on a prospective basis for annual and interim reporting periods beginning on or after December 15, 2011, which for Biogen Idec means January 1, 2012. The adoption of this standard is not expected to have a material impact on our financial position or results of operations.

Cash and Cash Equivalents

We consider only those investments which are highly liquid, readily convertible to cash and that mature within three months from date of purchase to be cash equivalents. As of December 31, 2011 and 2010, cash equivalents were comprised of money market funds and commercial paper, repurchase agreements, and other debt securities with maturities less than 90 days.

Accounts Receivable

The majority of our accounts receivable arise from product sales and primarily represent amounts due from our wholesale distributors, public hospitals and other government entities. We monitor the financial performance and credit worthiness of our large customers so that we can properly assess and respond to changes in their credit profile. We provide reserves against trade receivables for estimated losses that may result from a customer’s inability to pay. Amounts determined to be uncollectible are charged or written-off against the reserve. To date, such losses have not exceeded management’s estimates.

Concentration of Credit Risk

Financial instruments that potentially subject us to concentrations of credit risk include cash and cash equivalents, investments, derivatives, and accounts receivable. We attempt to minimize the risks related to cash and cash equivalents and investments by using highly-rated financial institutions that invest in a broad and diverse range of financial instruments as previously defined by us. We have established guidelines relative to credit ratings and maturities intended to safeguard principal balances and maintain liquidity. Our investment portfolio is maintained in accordance with our investment policy, which defines allowable investments, specifies credit quality standards and limits the credit exposure of any single issuer. We minimize credit risk resulting from derivatives instruments by choosing only highly rated financial institutions as counterparties.

Concentrations of credit risk with respect to receivables, which are typically unsecured, are limited due to the wide variety of customers and markets using our products, as well as their dispersion across many different geographic areas. The majority of our accounts receivable arise from product sales in the United States and Europe and have standard payment terms which are generally between 30 and 90 days. We continue to monitor economic conditions, including the volatility associated with international economies, and associated impacts on the relevant financial markets and our business, especially in light of the global economic downturn. For additional information related to this concentration of credit risk, please read Note 5, Accounts Receivable to these consolidated financial statements.

Inventory

Inventories are stated at the lower of cost or market with cost determined in a manner that approximates the first-in, first-out (FIFO) method. Included in inventory are raw materials used in the production of pre-clinical and clinical products, which are expensed as research and development costs when consumed.

Capitalization of Inventory Costs

We capitalize inventory costs associated with our products prior to regulatory approval, when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. We consider numerous attributes in evaluating whether the costs to manufacture a particular product should be capitalized as an asset. We assess the regulatory approval process and where the particular product stands in relation to that approval process, including any known safety or efficacy concerns, potential labeling restrictions and other impediments to approval. We evaluate our anticipated research and development initiatives and constraints relating to the product and the indication in which it will be used. We consider our manufacturing environment including our supply chain in determining logistical constraints that could hamper approval or commercialization. We consider the shelf life of the product in relation to the expected timeline for approval and we consider patent related or contract issues that may prevent or delay commercialization. We also base our judgment on the viability of commercialization, trends in the marketplace and market acceptance criteria. Finally, we consider the reimbursement strategies that may prevail with respect to the product and assess the economic benefit that we are likely to realize. We expense previously capitalized costs related to pre-approval inventory upon a change in such judgment, due to, among other potential factors, a denial or delay of approval by necessary regulatory bodies.

As of December 31, 2011 and 2010, the carrying value of our inventory did not include any significant costs associated with products that had not yet received regulatory approval.

Obsolescence and Unmarketable Inventory

We periodically review our inventories for excess or obsolete inventory and write-down obsolete or otherwise unmarketable inventory to its estimated net realizable value. If the actual net realizable value is less than that estimated by us, or if it is determined that inventory utilization will further diminish based on estimates of demand, additional inventory write-downs may be required. Additionally, our products are subject to strict quality control and monitoring which we perform throughout the manufacturing process. In the event that certain batches or units of product no longer meet quality specifications or become obsolete due to expiration, we will record a charge to cost of sales to write-down any obsolete or otherwise unmarketable inventory to its estimated net realizable value. In all cases product inventory is carried at the lower of cost or its estimated net realizable value. Amounts written-down to unmarketable inventory are charged to cost of sales, excluding amortization of acquired intangible assets.

Marketable Securities and Other Investments

Marketable Debt Securities

Available-for-sale debt securities are recorded at fair market value and unrealized gains and losses are included in accumulated other comprehensive income (loss) in equity, net of related tax effects, unless the security has experienced a credit loss, we have determined that we have the intent to sell the security or we have determined that it is more likely than not that we will have to sell the security before its expected recovery. Realized gains and losses are reported in other income (expense), net, on a specific identification basis.

Strategic Investments

As part of our business development efforts, we will, from time to time, invest in equity securities of certain biotechnology companies. These investments are known as strategic investments and are classified as available-for-sale and accounted for as marketable equity investments or as cost investments based upon our ownership percentage and other factors that suggest we have significant influence and are included in investments and other assets within our consolidated balance sheet. When assessing whether a decline in the fair value of a strategic investment below our cost basis is other-than-temporary, we consider the fair market value of the security, the duration of the security’s decline, and prospects for the underlying business, including favorable or adverse clinical trial results, new product initiatives and new collaborative agreements with the companies in which we have invested.

Non-Marketable Equity Securities

We also invest in equity securities of companies whose securities are not publicly traded and where fair value is not readily available. These investments are recorded using either the cost method or the equity method of accounting, depending on our ownership percentage and other factors that suggest we have significant influence. We monitor these investments to evaluate whether any decline in their value has occurred that would be other-than-temporary, based on the implied value of recent company financings, public market prices of comparable companies, and general market conditions and are included in investments and other assets within our consolidated balance sheet.

Evaluating Investments for Other-than-Temporary Impairments

We conduct periodic reviews to identify and evaluate each investment that has an unrealized loss, in accordance with the meaning of other-than-temporary impairment and its application to certain investments. An unrealized loss exists when the current fair value of an individual security is less than its amortized cost basis. Unrealized losses on available-for-sale securities that are determined to be temporary, and not related to credit loss, are recorded, net of tax, in accumulated other comprehensive income.

For available-for-sale debt securities with unrealized losses, management performs an analysis to assess whether we intend to sell or whether we would more likely than not be required to sell the security before the expected recovery of the amortized cost basis. Where we intend to sell a security, or may be required to do so, the security’s decline in fair value is deemed to be other-than-temporary and the full amount of the unrealized loss is reflected within earnings as an impairment loss.

Regardless of our intent to sell a security, we perform additional analysis on all securities with unrealized losses to evaluate losses associated with the creditworthiness of the security. Credit losses are identified where we do not expect to receive cash flows sufficient to recover the amortized cost basis of a security.

For equity securities, when assessing whether a decline in fair value below our cost basis is other-than-temporary, we consider the fair market value of the security, the duration of the security’s decline, and the financial condition of the issuer. We then consider our intent and ability to hold the equity security for a period of time sufficient to recover our carrying value. Where we have determined that we lack the intent and ability to hold an equity security to its expected recovery, the security’s decline in fair value is deemed to be other-than-temporary and is reflected within earnings as an impairment loss.

Property, Plant and Equipment

Property, plant and equipment are carried at cost, subject to review for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. The cost of normal, recurring, or periodic repairs and maintenance activities related to property, plant and equipment are expensed as incurred. The cost for planned major maintenance activities, including the related acquisition or construction of assets, is capitalized if the repair will result in future economic benefits.

Interest costs incurred during the construction of major capital projects are capitalized until the underlying asset is ready for its intended use, at which point the interest costs are amortized as depreciation expense over the life of the underlying asset. We also capitalize certain direct and incremental costs associated with the validation effort required for licensing by regulatory agencies of manufacturing equipment for the production of a commercially approved drug. These costs include primarily direct labor and material and are incurred in preparing the equipment for its intended use. The validation costs are amortized over the life of the related equipment.

In addition, we capitalize certain internal use computer software development costs. If the software is an integral part of production assets, these costs are included in machinery and equipment and are amortized on a straight-line basis over the estimated useful lives of the related software, which generally range from three to five years.

We generally depreciate or amortize the cost of our property, plant and equipment using the straight-line method over the estimated useful lives of the respective assets, which are summarized as follows:

Asset Category	Useful Lives
Land	Not depreciated
Buildings	15 to 40 years
Leasehold Improvements	Lesser of the useful life or the term of the respective lease
Furniture and Fixtures	5 to 7 years
Machinery and Equipment	5 to 20 years
Computer Software and Hardware	3 to 5 years

When we dispose of property, plant and equipment, we remove the associated cost and accumulated depreciation from the related accounts on our consolidated balance sheet and include any resulting gain or loss in our consolidated statement of income.

Intangible Assets

Our intangible assets consist of patents, licenses, core developed technology, in-process research and development acquired after January 1, 2009, trademarks, trade names, assembled workforce and other distribution rights. The majority of our intangible assets were recorded in connection with the merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation in 2003. Our intangible assets are recorded at fair value at the time of their acquisition and are stated within our consolidated balance sheets net of accumulated amortization and impairments.

We amortize intangible assets over their estimated useful lives using the economic use method if anticipated future cash flows can be reasonably estimated; the straight-line method is used when cash flows cannot be reasonably estimated. Our amortization policy reflects the pattern that the economic benefits of the intangible assets are consumed. The useful lives of our intangible assets are primarily based on the legal or contractual life of the underlying patent or contract, which does not include additional years for the potential extension or renewal of the contract or patent. Intangible assets related to patents, licenses, core developed technology, assembled workforce, and other distribution rights are amortized over their remaining estimated useful lives. Intangible assets related to trademarks, trade names and in-process research and development prior to commercialization are not amortized because they have indefinite lives, but they are subject to review for impairment. We review our intangible assets with indefinite lives for impairment annually, as of October 31, and whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable.

Our most significant intangible asset is the core technology related to our AVONEX product. Our amortization policy reflects our belief that the economic benefit of our core technology is consumed as revenue is generated from AVONEX. We refer to this amortization methodology as the economic consumption model, which involves calculating a ratio of actual current period sales to total anticipated sales for the life of the product and applying this ratio to the carrying amount of the intangible asset. An analysis of the anticipated lifetime revenue of AVONEX is performed at least annually during our long range planning cycle, and this analysis serves as the basis for the calculation of our economic consumption amortization model. We believe this process has allowed us to reliably determine the best estimate of the pattern in which we will consume the economic benefits of our core technology intangible asset.

Impairment of Long-Lived Assets

Long-lived assets to be held and used, including property, plant and equipment are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets or asset group may not be recoverable.

Determination of recoverability is based on an estimate of undiscounted future cash flows resulting from the use of the asset and its eventual disposition. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their estimated fair values. Long-lived assets to be disposed of are carried at fair value less costs to sell.

Goodwill

Goodwill relates largely to amounts that arose in connection with the merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation and represents the difference between the purchase price and the fair value of the identifiable tangible and intangible net assets when accounted for using the purchase method of accounting. Goodwill is not amortized, but is subject to periodic review for impairment. Goodwill is reviewed annually, as of October 31, and whenever events or changes in circumstances indicate that the carrying value of the goodwill might not be recoverable.

We apply a two-step impairment test. In the first step, we compare the fair value of our reporting unit to its carrying value. If the carrying value of the net assets assigned to the reporting unit exceeds the fair value of our reporting unit, then the second step of the impairment test is performed in order to determine the implied fair value of our reporting unit’s goodwill. If the carrying value of our reporting unit’s goodwill exceeds its implied fair value, then the company records an impairment loss equal to the difference. As described in Note 25, Segment Information to these consolidated financial statements, we operate in one business segment which we consider our only reporting unit.

In September 2011, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2011-08, “Intangibles — Goodwill and Other (Topic 350): Testing Goodwill for Impairment” (ASU 2011-08). This newly issued accounting standard allows an entity the option to first assess qualitative factors to determine whether it is necessary to perform the current two-step impairment test. If an entity believes, as a result of its qualitative assessment, that it is more-likely-than-not that the fair value of a reporting unit is less than its carrying amount, the quantitative two-step impairment test is required; otherwise, no further testing is required. These amendments do not change the current guidance for testing other indefinite-lived intangible assets for impairment. This ASU is effective for annual and interim goodwill impairment tests performed for fiscal years beginning after December 15, 2011, which for Biogen Idec means January 1, 2012. Early adoption is permitted; however, we have not elected to do so. The adoption of this statement will not impact our financial position or results of operations.

Acquired In Process Research and Development (IPR&D)

Acquired IPR&D represents the fair value assigned to research and development assets that we acquire that have not been completed at the date of acquisition. The value assigned to acquired IPR&D is determined by estimating the costs to develop the acquired technology into commercially viable products, estimating the resulting revenue from the projects, and discounting the net cash flows to present value. The revenue and costs projections used to value acquired IPR&D were, as applicable, reduced based on the probability of developing a new drug. Additionally, the projections considered the relevant market sizes and growth factors, expected trends in technology, and the nature and expected timing of new product introductions by us and our competitors. The resulting net cash flows from such projects are based on management’s estimates of cost of sales, operating expenses, and income taxes from such projects. The rates utilized to discount the net cash flows to their present value were commensurate with the stage of development of the projects and uncertainties in the economic estimates used in the projections described above.

We measured acquired IPR&D in business combinations completed prior to January 1, 2009, at fair value and expensed it on acquisition date if that technology lacked an alternative future use, or capitalized it as an intangible asset if certain criteria were met; however, effective January 1, 2009, if we are purchasing a business, the acquired IPR&D is measured at fair value, capitalized as an intangible asset and tested for impairment at least annually until commercialization, after which time the IPR&D is amortized over its estimated useful life. If we acquire an asset or group of assets that do not meet the definition of a business under applicable accounting standards, then the acquired IPR&D is expensed on its acquisition date. Future costs to develop these assets are recorded to expense as they are incurred if the technology lacks alternative future uses.

Valuation of Contingent Consideration Resulting from a Business Combination

We record contingent consideration resulting from business combinations completed after January 1, 2009 at its fair value on the acquisition date. Each reporting period thereafter, we revalue these obligations and record increases or decreases in their fair value as an adjustment to contingent consideration expense within our consolidated statement of income. Changes in the fair value of the contingent consideration obligations can result from adjustments to the discount rates and periods, updates in the assumed achievement or timing of any development milestones or changes in the probability of certain clinical events and changes in the assumed probability associated with regulatory approval. These fair value measurements represent Level 3 measurements as they are based on significant inputs not observable in the market.

Significant judgment is employed in determining the appropriateness of these assumptions as of the acquisition date and for each subsequent period. Accordingly, changes in assumptions described above, could have a material impact on the amount of contingent consideration expense we record in any given period.

Derivative Instruments and Hedging Activities

We recognize all derivative instruments as either assets or liabilities at fair value in our consolidated balance sheets. Changes in the fair value of derivatives are recorded each period in current earnings or accumulated other comprehensive income (loss), depending on whether a derivative is designated as part of a hedge transaction and, if it is, the type of hedge transaction. We classify the cash flows from these instruments in the same category as the cash flows from the hedged items. We do not hold or issue derivative instruments for trading or speculative purposes.

We assess, both at inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting the changes in cash flows or fair values of the hedged items. We also assess hedge ineffectiveness on a quarterly basis and record the gain or loss related to the ineffective portion to current earnings to the extent significant. If we determine that a forecasted transaction is no longer probable of occurring, we discontinue hedge accounting for the affected portion of the hedge instrument, and any related unrealized gain or loss on the contract is recognized in current earnings.

Translation of Foreign Currencies

The functional currency for most of our foreign subsidiaries is their local currency. For the Company’s non-U.S. subsidiaries that transact in functional currency other than the U.S. dollar, assets and liabilities are translated at current rates of exchange at the balance sheet date. Income and expense items are translated at the average foreign exchange rates for the period. Adjustments resulting from the translation of the financial statements of our foreign operations into U.S. dollars are excluded from the determination of net income and are recorded in accumulated other comprehensive income, a separate component of equity. For subsidiaries where the functional currency differs from the local currency, non-monetary assets and liabilities are translated at the rate of exchange in effect on the date assets were acquired while monetary assets and liabilities are translated at current rates of exchange as of the balance sheet date. Income and expense items are translated at the average foreign currency rates for the period. Translation adjustments of these subsidiaries are included in net income.

Accounting for Share-Based Compensation

Our share-based compensation programs grant awards which have included stock options, restricted stock units which vest based on stock performance known as market stock units (MSUs), performance-vested restricted stock units which will be settled in cash (CSPSs), performance-vested restricted stock units which settle in shares (PVRSUs), time-vested restricted stock units (RSUs) and shares issued under our employee stock purchase plan (ESPP). We charge the estimated fair value of awards against income over the requisite service period, which is generally the vesting period. Where awards are made with non-substantive vesting periods (for instance, where a portion of the award vests upon retirement eligibility), we estimate and recognize expense based on the period from the grant date to the date on which the employee is retirement eligible.

The fair values of our stock option grants are estimated as of the date of grant using a Black-Scholes option valuation model and reflect estimated forfeitures. The estimated fair values of the stock options are then expensed over the options’ vesting periods.

The fair values of our RSUs are based on the market value of our stock on the date of grant. Compensation expense for RSUs is recognized over the applicable service period, adjusted for the effect of estimated forfeitures.

We apply an accelerated attribution method to recognize stock based compensation expense, net of estimated forfeitures, when accounting for our MSUs. The probability of actual shares expected to be earned is considered in the grant date valuation, therefore the expense will not be adjusted to reflect the actual units earned.

We apply an accelerated attribution method to recognize stock based compensation expense when accounting for our CSPSs and the fair value of the liability is remeasured at the end of each reporting period through expected cash settlement. Compensation expense associated with CSPSs is based upon the stock price and the number of units expected to be earned after assessing the probability that certain performance criteria will be met and the associated targeted payout level that is forecasted will be achieved, net of estimated forfeitures. Cumulative adjustments are recorded each quarter to reflect changes in the stock price and estimated outcome of the performance-related conditions until the date results are determined and settled.

We apply an accelerated attribution method to recognize stock based compensation expense when accounting for our PVRSUs. The number of units reflected as granted represents the target number of shares that are eligible to vest in full or in part and are earned subject to the attainment of certain performance criteria established at the beginning of the performance period. Compensation expense associated with these units is initially based upon the number of shares expected to vest after assessing the probability that certain performance criteria will be met and the associated targeted payout level that is forecasted will be achieved, net of estimated forfeitures. Cumulative adjustments are recorded quarterly to reflect subsequent changes in the estimated outcome of performance-related conditions until the date results are determined.

The purchase price of common stock under our ESPP is equal to 85% of the lower of (i) the market value per share of the common stock on the participant’s entry date into an offering period or (ii) the market value per share of the common stock on the purchase date. However, for each participant whose entry date is other than the start date of the offering period, the amount shall in no event be less than the market value per share of the common stock as of the beginning of the related offering period. The fair value of the discounted purchases made under our ESPP is calculated using the Black-Scholes model. The fair value of the look-back provision plus the 15% discount is recognized as compensation expense over the purchase period. We apply a graded vesting approach since our ESPP provides for multiple purchase periods and is, in substance, a series of linked awards.

Research and Development Expenses

Research and development expenses consist of upfront fees and milestones paid to collaborators and expenses incurred in performing research and development activities, including compensation and benefits, facilities expenses, overhead expenses, clinical trial and related clinical manufacturing expenses, fees paid to clinical research organizations (CROs) and other outside expenses. Research and development expenses are expensed as incurred. Payments we make for research and development services prior to the services being rendered are recorded as prepaid assets on our consolidated balance sheets and are expensed as the services are provided.

From time to time, we enter into development agreements in which we share expenses with a collaborative partner. We record payments received from our collaborative partners for their share of the development costs as a reduction of research and development expense, except as discussed within Note 20, Collaborations to these consolidated financial statements. Expenses incurred by Genentech in the development of RITUXAN are not recorded as research and development expense, but rather reduce our share of co-promotion profits recorded as a component of unconsolidated joint business revenues.

Selling, General and Administrative Expenses

Selling, general and administrative expenses are primarily comprised of compensation and benefits associated with sales and marketing, finance, human resources, legal and other administrative personnel, outside marketing, advertising and legal expenses and other general and administrative costs.

Advertising costs are expensed as incurred. For the years ended December 31, 2011, 2010 and 2009, advertising costs totaled $45.3 million, $35.3 million and $26.5 million, respectively.

Income Taxes

The provision for income taxes includes federal, state, local and foreign taxes. Income taxes are accounted for under the liability method. Deferred tax assets and liabilities are recognized for the estimated future tax consequences of temporary differences between the financial statement carrying amounts and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the year in which the temporary differences are expected to be recovered or settled. We evaluate the realizability of our deferred tax assets and establish a valuation allowance when it is more likely than not that all or a portion of deferred tax assets will not be realized.

We account for uncertain tax positions using a “more-likely-than-not” threshold for recognizing and resolving uncertain tax positions. We evaluate uncertain tax positions on a quarterly basis and consider various factors, including, but not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity and changes in facts or circumstances related to a tax position. We also accrue for potential interest and penalties, related to unrecognized tax benefits in income tax expense.

Contingencies

We are currently involved in various claims and legal proceedings. We account for potential litigation losses in accordance with FASB Accounting Standards Codification (ASC) No. 450, Contingencies (ASC 450). Under ASC 450, loss contingency provisions are recorded if the potential loss from any claim, asserted or unasserted, or legal proceeding is considered probable and the amount can be reasonably estimated or a range of loss can be determined. These accruals represent management’s best estimate of probable loss, as defined by ASC 450. Disclosure also is provided when it is reasonably possible that a loss will be incurred or when it is reasonably possible that the amount of a loss will exceed the recorded provision. On a quarterly basis, we review the status of each significant matter and assess its potential financial exposure. Significant judgment is required in both the determination of probability and the determination as to whether an exposure is reasonably estimable. Because of uncertainties related to these matters, accruals are based only on the best information available at the time. As additional information becomes available, we reassess the potential liability related to pending claims and litigation and may revise our estimates. These revisions in the estimates of the potential liabilities could have a material impact on our consolidated results of operations and financial position.

Restructuring Charges

We have made estimates and judgments regarding the amount and timing of our restructuring expense and liability, including current and future period termination benefits and other exit costs to be incurred when related actions take place. We have also assessed the recoverability of certain long-lived assets employed in the business and, in certain instances shortened the expected useful life of the assets based on changes in their expected use. When we determine that the useful lives of assets are shorter than we had originally estimated, we record additional depreciation to reflect the assets’ new shorter useful lives. Severance and other related costs and asset-related charges are reflected within our consolidated statement of income as a component of total restructuring charges incurred. Actual results may differ from these estimates. For additional information related to our recent restructuring efforts, please read Note 3, Restructuring, to these consolidated financial statements.

Earnings per Share

Basic earnings per share is computed using the two-class method. Under the two-class method, undistributed net income is allocated to common stock and participating securities based on their respective rights to share in dividends. We have determined that our preferred shares meet the definition of participating securities and, to the extent any are outstanding during a period, have allocated a portion of net income to our preferred shares on a pro rata basis. Net income allocated to preferred shares is excluded from the calculation of basic earnings per share. For basic earnings per share, net income available to holders of common stock is divided by the weighted average number of shares of common stock outstanding. For purposes of calculating diluted earnings per share, net income is adjusted for the after-tax amount of net income allocable to preferred shares, and the denominator includes both the weighted average number of shares of common stock outstanding and potential dilutive shares of common stock from stock options, unvested restricted stock awards, restricted stock units and other convertible securities, to the extent they are dilutive.

Disclosures about Offsetting Assets and Liabilities

In December 2011, the FASB issued ASU 2011-11, Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities (ASU 2011-11). This newly issued accounting standard requires an entity to disclose both gross and net information about instruments and transactions eligible for offset in the statement of financial position as well as instruments and transactions executed under a master netting or similar arrangement and was issued to enable users of financial statements to understand the effects or potential effects of those arrangements on its financial position. This ASU is required to be applied retrospectively and is effective for fiscal years, and interim periods within those years, beginning on or after January 1, 2013. As this accounting standard only requires enhanced disclosure, the adoption of this standard is not expected to have an impact our financial position or results of operations.

Comprehensive Income

In June 2011, the FASB issued ASU No. 2011-05, “Comprehensive Income (Topic 220): Presentation of Comprehensive Income” (ASU 2011-05). This newly issued accounting standard (1) eliminates the option to present the components of other comprehensive income as part of the statement of changes in stockholders’ equity; (2) requires the consecutive presentation of the statement of net income and other comprehensive income; and (3) requires an entity to present reclassification adjustments on the face of the financial statements from other comprehensive income to net income. The amendments in this ASU do not change the items that must be reported in other comprehensive income or when an item of other comprehensive income must be reclassified to net income nor do the amendments affect how earnings per share is calculated or presented. In December 2011, the FASB issued ASU No. 2011-12, Deferral of the Effective Date for Amendments to the Presentation of Reclassifications of Items Out of Accumulated Other Comprehensive Income in Accounting Standards Update No. 2011-05, which defers the requirement within ASU 2011-05 to present on the face of the financial statements the effects of reclassifications out of accumulated other comprehensive income on the components of net income and other comprehensive income for all periods presented. During the deferral, entities should continue to report reclassifications out of accumulated other comprehensive income consistent with the presentation requirements in effect prior to the issuance of ASU 2011-05. These ASUs are required to be applied retrospectively and are effective for fiscal years, and interim periods within those years, beginning after December 15, 2011, which for Biogen Idec means January 1, 2012. As these accounting standards do not change the items that must be reported in other comprehensive income or when an item of other comprehensive income must be reclassified to net income, the adoption of these standards is not expected to have an impact on our financial position or results of operations.

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Inventory (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Components of inventories
Raw materials	$ 83,800,000	$ 59,000,000
Work in process	169,400,000	142,200,000
Finished goods	73,600,000	87,900,000
Total inventory	$ 326,843,000	$ 289,066,000

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Earnings per Share

12 Months Ended

Dec. 31, 2011

Earnings per Share [Abstract]

Earnings per Share

15.    Earnings per Share

Basic and diluted earnings per share are calculated as follows:

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Numerator:
Net income attributable to Biogen Idec Inc.	$	1,234.4		$	1,005.3		$	970.1
Adjustment for net income allocable to preferred stock		(0.5	)		(2.0	)		(1.7	)
Net income used in calculating basic and diluted earnings per share	$	1,233.9		$	1,003.3		$	968.4
Denominator:
Weighted average number of common shares outstanding		242.4			252.3			287.4
Effect of dilutive securities:
Stock options and employee stock purchase plan		1.0			0.9			0.6
Time-vested restricted stock units		1.3			1.6			1.4
Market stock units		0.3			0.1			—
Performance-vested restricted stock units settled in shares		—			—			0.1
Dilutive potential common shares		2.6			2.6			2.1
Shares used in calculating diluted earnings per share		245.0			254.9			289.5

The following amounts were not included in the calculation of net income per diluted share because their effects were anti-dilutive:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Numerator:
Net income allocable to preferred stock	$	0.5	$	2.0	$	1.7
Denominator:
Stock options		—		4.6		8.5
Time-vested restricted stock units		—		0.1		2.1
Market stock units		—		—		—
Performance-vested restricted stock units settled in shares		—		—		0.2
Convertible preferred stock		0.1		0.5		0.5
Total		0.1		5.2		11.3

Earnings per share for the years ended December 31, 2011 and 2010 reflects, on a weighted average basis, the repurchase of 6.0 million shares and 40.3 million shares, respectively, of our common stock under our share repurchase authorizations.

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Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2011

Summary of Significant Accounting Policies [Abstract]

Property, plant and equipment estimated useful lives

Asset Category	Useful Lives
Land	Not depreciated
Buildings	15 to 40 years
Leasehold Improvements	Lesser of the useful life or the term of the respective lease
Furniture and Fixtures	5 to 7 years
Machinery and Equipment	5 to 20 years
Computer Software and Hardware	3 to 5 years

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Share-Based Payments (Details 7) (Cash settled performance shares [Member])	12 Months Ended
	Dec. 31, 2011
Cash settled performance shares [Member]
Cash settled performance shares
Beginning Balance, Unvested, Shares	370,000,000
Shares, Granted	490,000,000
Shares, Vested	(187,000,000)
Shares, Forfeited	(111,000,000)
Ending Balance, Unvested, Shares	562,000,000

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Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenue by product
Product	$ 996,600	$ 975,800	$ 956,700	$ 907,100	$ 909,800	$ 876,900	$ 859,200	$ 824,200	$ 3,836,117	$ 3,470,056	$ 3,152,941
U.S [Member]
Revenue by product
Product									1,954,800	1,744,400	1,638,000
Rest of world [Member]
Revenue by product
Product									1,881,300	1,725,700	1,514,900
AVONEX [Member]
Revenue by product
Product									2,686,600	2,518,400	2,322,900
AVONEX [Member] | U.S [Member]
Revenue by product
Product									1,628,300	1,491,600	1,406,200
AVONEX [Member] | Rest of world [Member]
Revenue by product
Product									1,058,300	1,026,800	916,700
TYSABRI [Member]
Revenue by product
Product									1,079,500	900,200	776,000
TYSABRI [Member] | U.S [Member]
Revenue by product
Product									326,500	252,800	231,800
TYSABRI [Member] | Rest of world [Member]
Revenue by product
Product									753,000	647,400	544,200
Other products [Member]
Revenue by product
Product									70,000	51,500	54,000
Other products [Member] | Rest of world [Member]
Revenue by product
Product									$ 70,000	$ 51,500	$ 54,000

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Income Taxes

12 Months Ended

Dec. 31, 2011

Income Taxes [Abstract]

Income Taxes

17.    Income Taxes

Income Tax Expense

Income before income tax provision and the income tax expense consist of the following:

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Income before income taxes (benefit):
Domestic	$	1,408.9		$	846.4		$	1,073.8
Foreign		302.3			383.5			258.9
Total	$	1,711.2		$	1,229.9		$	1,332.7
Income tax expense (benefit):
Current
Federal	$	231.7		$	357.7		$	439.9
State		15.1			19.6			3.1
Foreign		44.1			35.4			50.0
Total	$	290.9		$	412.7		$	493.0
Deferred
Federal	$	160.9		$	(70.6	)	$	(94.8	)
State		(8.1	)		(6.6	)		(39.0	)
Foreign		0.8			(4.2	)		(3.6	)
Total		153.6			(81.4	)		(137.4	)
Total income tax expense	$	444.5		$	331.3		$	355.6

Deferred Tax Assets and Liabilities

Significant components of our deferred tax assets and liabilities are summarized as follows:

	As of December 31,
(In millions)	2011			2010
Deferred tax assets
Tax credits	$	60.0		$	47.6
Inventory, other reserves, and accruals		104.1			203.1
Capitalized costs		5.3			6.7
Intangibles, net		75.8			61.8
Net operating loss		22.9			35.3
Share-based compensation		54.7			64.4
Other		45.7			70.3
Valuation allowance		(10.8	)		(10.8	)
Total deferred tax assets	$	357.7		$	478.4
Deferred tax liabilities
Purchased intangible assets	$	(384.8	)	$	(446.1	)
Unrealized gain on investments and cumulative translation adjustment		(3.5	)		(6.6	)
Inventory		(76.8	)		—
Depreciation, amortization and other		(133.1	)		(114.4	)
Total deferred tax liabilities	$	(598.2	)	$	(567.1	)

Tax Rate

Reconciliation between the U.S. federal statutory tax rate and our effective tax rate is summarized as follows:

	For the Years Ended December 31,
	2011			2010			2009
Statutory rate		35.0	%		35.0	%		35.0	%
State taxes		1.7			1.7			(0.1	)
Taxes on foreign earnings		(5.9	)		(10.7	)		(5.0	)
Credits and net operating loss utilization		(4.4	)		(3.0	)		(3.8	)
Purchased intangible assets		1.3			1.9			2.0
IPR&D		—			5.0			—
Permanent items		(1.2	)		(2.0	)		(1.3	)
Contingent consideration		0.7			—			—
Other		(1.2	)		(1.0	)		(0.1	)
Effective tax rate		26.0	%		26.9	%		26.7	%

As of December 31, 2011, we had net operating losses and general business credit carry forwards for federal income tax purposes of approximately $27.2 million and $1.9 million, respectively, which begin to expire in 2022. Additionally, for state income tax purposes, we had net operating loss carry forwards of approximately $57.1 million, which begin to expire in 2012. For state income tax purposes, we also had research and investment credit carry forwards of approximately $101.6 million, of which approximately $0.9 million begin to expire in 2012.

In assessing the realizability of our deferred tax assets, we have considered whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. In making this determination, under the applicable financial reporting standards, we are allowed to consider the scheduled reversal of deferred tax liabilities, projected future taxable income, and tax planning strategies. Our estimates of future taxable income take into consideration, among other items, our estimates of future income tax deductions related to the exercise of stock options. Based upon the level of historical taxable income and income tax liability and projections for future taxable income over the periods in which the deferred tax assets are utilizable, we believe it is more likely than not that we will realize the benefits of the deferred tax assets of our wholly owned subsidiaries. At December 31, 2011, we have a full valuation allowance on the deferred tax assets of a variable interest entity which we consolidate, based on uncertainties related to the realization of some of those assets. These assets totalling $10.8 million are excluded from our credit and loss carryforwards described above. In the event that actual results differ from our estimates or we adjust our estimates in future periods, we may need to establish a valuation allowance, which could materially impact our financial position and results of operations.

As of December 31, 2011, undistributed foreign earnings of non-U.S. subsidiaries included in consolidated retained earnings and other basis differences aggregated approximately $2.7 billion. We intend to reinvest these earnings indefinitely in operations outside the U.S. The residual U.S. tax liability, if such amounts were remitted, would be approximately $600 million to $700 million as of December 31, 2011.

Accounting for Uncertainty in Income Taxes

A reconciliation of the beginning and ending amount of our unrecognized tax benefits is summarized as follows:

(In millions)	2011			2010			2009
Balance at January 1,	$	121.5		$	147.1		$	249.6
Additions based on tax positions related to the current period		2.2			3.6			14.4
Additions for tax positions of prior periods		48.6			13.3			77.4
Reductions for tax positions of prior periods		(75.8	)		(18.5	)		(88.7	)
Statute expirations		(2.3	)		(3.7	)		—
Settlements		(29.8	)		(20.3	)		(105.6	)
Balance at December 31,	$	64.4		$	121.5		$	147.1

We and our subsidiaries are routinely examined by various taxing authorities. We file income tax returns in the U.S. federal jurisdiction, and various states and foreign jurisdictions. With few exceptions, we are no longer subject to U.S. federal tax examination for years before 2010 or state, local, or non-U.S. income tax examinations by tax authorities for years before 2004. During the year, we adjusted our unrecognized tax benefits to reflect new information arising during our ongoing audit examinations.

In October 2011, in conjunction with our examination, the IRS has proposed a disallowance of approximately $130 million in deductions for tax years 2007, 2008 and 2009 related to payments for services from our Danish contract manufacturing affiliate. We believe that these deductions represent valid deductible business expenses and will vigorously defend our position.

Included in the balance of unrecognized tax benefits as of December 31, 2011, 2010, and 2009 are $31.3 million, $26.2 million, and $42.8 million (net of the federal benefit on state issues), respectively, of unrecognized tax benefits that, if recognized, would affect the effective income tax rate in future periods. We recognize potential interest and penalties accrued related to unrecognized tax benefits in income tax expense.

We do not anticipate any significant changes in our positions in the next twelve months other than expected settlements which have been classified as current liabilities within the accompanying balance sheet.

We recognize potential interest and penalties accrued related to unrecognized tax benefits in income tax expense. In 2011, as we settled certain uncertain tax positions, we recognized a net interest benefit of $12.9 million. During 2010, we recognized net interest expense of $0.7 million. In 2009, we recognized a net interest benefit of approximately $3.1 million. We have accrued approximately $3.9 million and $29.4 million for the payment of interest as of December 31, 2011 and 2010, respectively.

Contingencies

In 2006, the Massachusetts Department of Revenue (DOR) issued a Notice of Assessment against Biogen Idec MA Inc. (BIMA), one of our wholly-owned subsidiaries, for $38.9 million of corporate excise tax for 2002, which includes associated interest and penalties. The assessment asserted that the portion of sales attributable to Massachusetts (sales factor), the computation of BIMA’s research and development credits and certain deductions claimed by BIMA were not appropriate, resulting in unpaid taxes for 2002. We filed an abatement application with the DOR seeking abatements for 2001, 2002 and 2003. Our abatement application was denied and on July 25, 2007, we filed a petition with the Massachusetts Appellate Tax Board (the Massachusetts ATB) seeking, among other items, abatements of corporate excise tax for 2001, 2002 and 2003 and adjustments in certain credits and credit carry forwards for 2001, 2002 and 2003. On August 18, 2011, we reached a settlement with the DOR under which we agreed to pay $7.0 million in taxes, plus $5.0 million of interest, and agreed on the nature and amount of tax credits carried forward into 2004. This resolution did not have a significant impact on our results of operations, is related only to the 2001, 2002 and 2003 tax years, and does not resolve matters in dispute for subsequent periods.

On June 8, 2010, we received Notices of Assessment from the DOR against BIMA for $103.5 million of corporate excise tax, including associated interest and penalties, related to our 2004, 2005 and 2006 tax filings.

We filed an abatement application with the DOR seeking abatement for 2004, 2005 and 2006. Our abatement application was denied in December 2010, and we filed a petition appealing the denial with the ATB on February 3, 2011. For all periods under dispute, we believe that positions taken in our tax filings are valid and believe that we have meritorious defenses in these disputes. We are contesting these matters vigorously.

The audits of our tax filings for 2007 and 2008 have not yet been completed but have been prepared in a manner consistent with prior filings which may result in an assessment for those years. Due to tax law changes effective January 1, 2009, the computation and deductions at issue in previous tax filings have not been part of our tax filings in Massachusetts starting in 2009.

We believe that these assessments do not impact the level of liabilities for income tax contingencies. However, there is a possibility that we may not prevail in defending all of our assertions with the DOR. If these matters are resolved unfavorably in the future, the resolution could have a material adverse impact on the effective tax rate and our results of operations.

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Intangible Assets and Goodwill (Details 1) (USD $)	12 Months Ended
	Dec. 31, 2010	Dec. 31, 2011
Summary of roll forward of the changes in goodwill
Goodwill, Beginning balance	$ 1,138,600,000	$ 1,146,314,000
Goodwill acquired during the year	25,600,000
Other	(17,900,000)
Goodwill, Ending balance	$ 1,146,314,000	$ 1,146,314,000

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Other Consolidated Financial Statement Detail (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash paid during the year for:
Interest	$ 66,700,000	$ 68,100,000	$ 68,100,000
Income taxes	332,700,000	394,700,000	745,400,000
Other income (expense), net
Interest income	19,200,000	22,300,000	48,500,000
Interest expense	(33,000,000)	(36,100,000)	(35,800,000)
Impairments of investments	(11,500,000)	(21,300,000)	(10,600,000)
Gain (loss) on sales of investments, net	17,400,000	16,300,000	22,800,000
Foreign exchange gains (losses), net	(6,300,000)	(3,500,000)	11,400,000
Other, net	700,000	3,300,000	1,000,000
Total other income (expense), net	(13,477,000)	(18,983,000)	37,252,000
Other current assets
Deferred tax assets	8,100,000	112,200,000
Derivative assets	39,500,000	1,300,000
Prepaid taxes	15,200,000	31,400,000
Receivable from collaborations	11,400,000	7,300,000
Interest receivable	6,500,000	4,900,000
Other prepaid expenses	45,500,000	47,900,000
Other	18,400,000	10,800,000
Total other current assets	144,600,000	215,822,000
Accrued Expenses and Other
Employee compensation and benefits	176,300,000	159,700,000
Revenue-related rebates	115,000,000	105,300,000
Deferred revenue	69,600,000	41,300,000
Royalties and licensing fees	47,400,000	45,100,000
Collaboration expenses	44,200,000	31,600,000
Clinical development expenses	40,800,000	24,400,000
Construction in progress accrual	22,800,000	16,400,000
Interest payable	21,600,000	21,600,000
Current portion of contingent consideration	(10,800,000)	(11,900,000)
Restructuring charges	1,400,000	66,400,000
Derivative liabilities	500,000	12,200,000
Other	126,800,000	130,000,000
Total accrued expenses and other	$ 677,210,000	$ 665,923,000

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Consolidated Statements of Equity (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Tax effect on unrealized gains (losses) recognized on securities available for sale	$ 133	$ 6,345	$ 4,136
Reclassification adjustment on securities available for sale	7,155	5,656	3,756
Tax effect on net unrealized gains (losses) recognized on securities available for sale	7,288	689	380
Tax effect of unrealized gains (losses) recognized on foreign currency forward contracts	3,647	1,268	254
Reclassification adjustment on foreign currency forward contracts	1,268	304	3,836
Tax effect of net unrealized gains (losses) recognized on foreign currency forward contracts	4,915	964	3,582
Tax effect of net unrealized gains (losses) recognized on pension benefit obligation	0	0	67
Accumulated other comprehensive income (loss)
Tax effect on unrealized gains (losses) recognized on securities available for sale	133	6,345	4,136
Reclassification adjustment on securities available for sale	7,155	5,656	3,756
Tax effect on net unrealized gains (losses) recognized on securities available for sale	7,288	689	380
Tax effect of unrealized gains (losses) recognized on foreign currency forward contracts	3,647	1,268	254
Reclassification adjustment on foreign currency forward contracts	1,268	304	3,836
Tax effect of net unrealized gains (losses) recognized on foreign currency forward contracts	4,915	964	3,582
Tax effect of net unrealized gains (losses) recognized on pension benefit obligation	0	0	67
Total Biogen Idec Inc. shareholders' equity
Tax effect on unrealized gains (losses) recognized on securities available for sale	133	6,345	4,136
Reclassification adjustment on securities available for sale	7,155	5,656	3,756
Tax effect on net unrealized gains (losses) recognized on securities available for sale	7,288	689	380
Tax effect of unrealized gains (losses) recognized on foreign currency forward contracts	3,647	1,268	254
Reclassification adjustment on foreign currency forward contracts	1,268	304	3,836
Tax effect of net unrealized gains (losses) recognized on foreign currency forward contracts	4,915	964	3,582
Tax effect of net unrealized gains (losses) recognized on pension benefit obligation	$ 0	$ 0	$ 67

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Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 514,542	$ 759,598
Marketable securities	1,176,115	448,146
Accounts receivable, net of allowances of $57,524 and $54,922, respectively	584,603	605,329
Due from unconsolidated joint business	228,724	222,459
Inventory	326,843	289,066
Other current assets	144,600	215,822
Total current assets	2,975,427	2,540,420
Marketable securities	1,416,737	743,101
Property, plant and equipment, net	1,571,387	1,641,634
Intangible assets, net	1,608,191	1,772,826
Goodwill	1,146,314	1,146,314
Investments and other assets	331,548	248,198
Total assets	9,049,604	8,092,493
Current liabilities:
Current portion of notes payable, line of credit and other financing arrangements	3,292	137,153
Taxes payable	45,939	84,517
Accounts payable	186,448	162,529
Accrued expenses and other	677,210	665,923
Total current liabilities	912,889	1,050,122
Notes payable, line of credit and other financing arrangements	1,060,808	1,066,379
Long-term deferred tax liability	248,644	200,950
Other long-term liabilities	400,276	325,599
Total liabilities	2,622,617	2,643,050
Commitments and contingencies
Biogen Idec Inc. shareholders' equity
Preferred stock, par value $0.001 per share
Common stock, par value $0.0005 per share	128	124
Additional paid-in capital	4,185,048	3,895,103
Accumulated other comprehensive income (loss)	(26,535)	(21,610)
Retained earnings	3,106,761	1,872,481
Treasury stock, at cost; 13,518 shares and 7,662 shares, respectively	(839,903)	(349,592)
Total Biogen Idec Inc. shareholders' equity	6,425,499	5,396,506
Noncontrolling interests	1,488	52,937
Total equity	6,426,987	5,449,443
Total liabilities and equity	$ 9,049,604	$ 8,092,493

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Derivative Instruments

12 Months Ended

Dec. 31, 2011

Derivative Instruments [Abstract]

Derivative Instruments

10.    Derivative Instruments

Foreign Currency Forward Contracts

Due to the global nature of our operations, portions of our revenues are earned in currencies other than the U.S. dollar. The value of revenues measured in U.S. dollars is therefore subject to changes in currency exchange rates. In order to mitigate these changes we use foreign currency forward contracts to lock in exchange rates associated with a portion of our forecasted international revenues.

Foreign currency forward contracts in effect as of December 31, 2011 and 2010 had durations of 1 to 12 months. These contracts have been designated as cash flow hedges and accordingly, to the extent effective, any unrealized gains or losses on these foreign currency forward contracts are reported in accumulated other comprehensive income (loss). Realized gains and losses for the effective portion of such contracts are recognized in revenue when the sale of product in the currency being hedged is recognized. To the extent ineffective, hedge transaction gains and losses are reported in other income (expense), net.

The notional value of foreign currency forward contracts that were entered into to hedge forecasted revenues is summarized as follows:

	Notional Amount As of December 31,
Foreign Currency: (In millions)	2011		2010
Euro	$	496.4	$	460.3
Canadian dollar		22.9		24.0
Swedish krona		13.0		9.9
Total foreign currency forward contracts	$	532.3	$	494.2

The portion of the fair value of these foreign currency forward contracts that was included in accumulated other comprehensive income (loss) within total equity reflected gains of $36.5 million and losses of $11.0 million as of December 31, 2011 and 2010, respectively. We expect all contracts to be settled over the next 12 months and any amounts in accumulated other comprehensive income (loss) to be reported as an adjustment to revenue. We consider the impact of our and our counterparties’ credit risk on the fair value of the contracts as well as the ability of each party to execute its obligations under the contract. As of December 31, 2011 and 2010, respectively, credit risk did not materially change the fair value of our foreign currency forward contracts.

In relation to our foreign currency forward contracts, we recognized in other income (expense) net losses of $3.9 million, net gains of $0.4 million, and net losses of $1.1 million for the years ended December 31, 2011, 2010 and 2009, respectively, due to hedge ineffectiveness.

In addition, we recognized in product revenue $36.9 million of net losses, $45.7 million of net gains, and net losses of $49.7 million, for the years ended December 31, 2011, 2010 and 2009, respectively, for the settlement of certain effective cash flow hedge instruments. These settlements were recorded in the same period as the related forecasted revenues.

Summary of Derivatives Designated as Hedging Instruments

The following table summarizes the fair value and presentation in the consolidated balance sheets for derivatives designated as hedging instruments:

(In millions)	Balance Sheet Location	Fair Value As of December 31, 2011
Foreign Currency Contracts
Asset derivatives	Other current assets	$	32.6
Liability derivatives	Accrued expenses and other	$	—

(In millions)	Balance Sheet Location	Fair Value As of December 31, 2010
Foreign Currency Contracts
Asset derivatives	Other current assets	$	—
Liability derivatives	Accrued expenses and other	$	11.0

The following table summarizes the effect of derivatives designated as hedging instruments on the consolidated statements of income:

For the Years Ended (In millions)	Amount Recognized in Accumulated Other Comprehensive Income (Loss) on Derivative Gain/(Loss) (Effective Portion)			Income Statement Location (Effective Portion)	Amount Reclassified  from Accumulated  Other Comprehensive Income (Loss) into Income Gain/(Loss) (Effective Portion)			Income Statement Location (Ineffective Portion)	Amount of Gain/(Loss) Recorded (Ineffective Portion)
December 31, 2011:
Foreign currency contracts	$	36.5		Revenue	$	(36.9	)	Other income (expense)	$	(3.9	)
December 31, 2010:
Foreign currency contracts	$	(11.0	)	Revenue	$	45.7		Other income (expense)	$	0.4
December 31, 2009:
Foreign currency contracts	$	1.2		Revenue	$	(49.7	)	Other income (expense)	$	(1.1	)

Other Derivatives

We also enter into other foreign currency forward contracts, usually with one month durations, to mitigate the foreign currency risk related to certain balance sheet positions. We have not elected hedge accounting for these transactions.

The aggregate notional amount of our outstanding foreign currency contracts was $263.7 million and $160.8 million as of December 31, 2011 and 2010, respectively. The fair value of these contracts was a net asset of $6.4 million as of December 31, 2011 compared to a net asset of $0.1 million as of December 31, 2010. Net gains of $12.1 million and $6.0 million related to these contracts were recognized as a component of other income (expense), net, for years ended December 31, 2011 and 2010, respectively.

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Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income before income taxes (benefit):
Domestic	$ 1,408,900,000	$ 846,400,000	$ 1,073,800,000
Foreign	302,300,000	383,500,000	258,900,000
Total	1,711,214,000	1,229,906,000	1,332,679,000
Current
Federal	231,700,000	357,700,000	439,900,000
State	15,100,000	19,600,000	3,100,000
Foreign	44,100,000	35,400,000	50,000,000
Total	290,900,000	412,700,000	493,000,000
Deferred
Federal	160,900,000	(70,600,000)	(94,800,000)
State	(8,100,000)	(6,600,000)	(39,000,000)
Foreign	800,000	(4,200,000)	(3,600,000)
Total	153,576,000	(81,410,000)	(137,351,000)
Total income tax expense	$ 444,528,000	$ 331,333,000	$ 355,617,000

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Share-Based Payments (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2011 Year	Dec. 31, 2010 Year	Dec. 31, 2009 Year
Weighted-average assumptions to estimate the fair value of the stock option grants awarded
Expected option life (in years)	0.0	4.5	4.7
Expected stock price volatility	0.00%	30.80%	39.30%
Risk-free interest rate	0.00%	2.00%	1.90%
Expected dividend yield	0.00%	0.00%	0.00%
Per share grant-date fair value	$ 0.00	$ 16.52	$ 18.00

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Share-Based Payments (Details) (USD $)	12 Months Ended												3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Total share-based compensation expense, net of tax [Member]	Dec. 31, 2010 Total share-based compensation expense, net of tax [Member]	Dec. 31, 2009 Total share-based compensation expense, net of tax [Member]	Dec. 31, 2011 Research and development [Member]	Dec. 31, 2010 Research and development [Member]	Dec. 31, 2009 Research and development [Member]	Dec. 31, 2011 Selling, general and administrative [Member]	Dec. 31, 2010 Selling, general and administrative [Member]	Dec. 31, 2009 Selling, general and administrative [Member]	Dec. 31, 2010 Restructuring Charges [Member]	Dec. 31, 2011 Restructuring Charges [Member]	Dec. 31, 2010 Restructuring Charges [Member]
Share-based Compensation Expense included in consolidated statements of income
Share-based compensation expense	$ 117,347,000	$ 171,435,000	$ 167,207,000	$ 101,000,000	$ 129,300,000	$ 111,500,000	$ 62,000,000	$ 62,700,000	$ 60,800,000	$ 88,700,000	$ 123,600,000	$ 106,400,000	$ 6,800,000	$ (600,000)	$ 6,800,000
Subtotal	150,100,000	193,100,000	167,200,000
Capitalized share-based payment costs	(4,500,000)	(3,500,000)	(6,300,000)
Share-based compensation expense included in total costs and expenses	145,600,000	189,600,000	160,900,000
Income tax effect	$ (44,600,000)	$ (60,300,000)	$ (49,400,000)

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Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Employee Benefit Plans (Textual) [Abstract]
Expenses related to savings plan	$ 24.8	$ 26.3	$ 27.9
Employee Benefit Plan obligations	20.1
Unfunded net pension	10.0
Percentage of minimum investment return	2.00%	2.00%	2.00%
Pension Expense	3.6	3.0	2.4
Savings plan [Member]
Employee Benefit Plans (Textual) [Abstract]
Minimum qualifying age for Employee Benefit Plan (in years)	21 years
Previous matching contributions vesting period (in years)	4 years
Supplemental savings plan [Member]
Employee Benefit Plans (Textual) [Abstract]
Deferred compensation related to Employee Benefit Plan	60.1	62.2
Deferred compensation plan [Member]
Employee Benefit Plans (Textual) [Abstract]
Previous Restoration Match vesting period (in years)	4 years
Previous transition contributions vesting period (in years)	7 years
German plan [Member]
Employee Benefit Plans (Textual) [Abstract]
Employee Benefit Plan obligations	8.6	8.2
Periodic pension cost	$ 1.8	$ 1.1	$ 1.1

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Litigation (Details) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended	12 Months Ended			12 Months Ended
	Jun. 30, 2011 USD ($)	Jun. 30, 2011 EUR (€)	Sep. 30, 2011	Dec. 31, 2011 EUR (€) LegalMatter	Jun. 08, 2010 USD ($)	Dec. 31, 2006 USD ($)	Dec. 31, 2011 Canada Lease Dispute [Member] USD ($)
Loss Contingencies [Line Items]
Compensatory damages	$ 125.0						$ 7.0
Plaintiffs estimated expert report of damages							2.5
Cost seeks for damages							0.4
Litigation Details (Textual) [Abstract]
Notice of Assessment under consideration for corporate excise tax					103.5	38.9
Stipulated royalty rate			0.50%
Decrease in share of co-promotion profits due to estimated compensation damages	50.0
Damages claimed		153.0
Maximum percentage estimation range of potential loss for royalty as percentage of net sales				0.50%
Number of consolidated lawsuits				2
Period of statutory limitations for damages in patent cases				6 years
Limited period for government reimbursement				24 months
Automatic renewal period for the resolution				24 months
Reimbursement limit stated in the resolution				24 months
Payment in case of any unfavorable determination received	$ 50.0			€ 30.7

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Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2011	Jan. 31, 2012	Jun. 30, 2011
Document And Entity Information [Abstract]
Entity Registrant Name	BIOGEN IDEC INC.
Entity Central Index Key	0000875045
Document Type	10-K
Document Period End Date	Dec. 31, 2011
Amendment Flag	false
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 25,908,506,479
Entity Common Stock, Shares Outstanding		238,725,065

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Segment Information (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Distributor Segment	Dec. 31, 2010	Dec. 31, 2009
Revenue from External Customer [Line Items]
Long-lived assets related to operations in Denmark	$ 1,838.4	$ 1,826.2	$ 1,805.4
Segment Information (Textual) [Abstract]
Number of reportable segment	1
Number of wholesale distributors	2
Revenues from unconsolidated joint business in percentage	20.00%	23.00%	25.00%
Distributor One [Member]
Revenue from External Customer [Line Items]
Entity wide percentage of revenue from major distributors	18.00%	18.00%	18.00%
Distributor Two [Member]
Revenue from External Customer [Line Items]
Entity wide percentage of revenue from major distributors	10.00%	11.00%	12.00%
DENMARK
Revenue from External Customer [Line Items]
Long-lived assets related to operations in Denmark	$ 668.5	$ 644.7	$ 665.8

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Property, Plant and Equipment

12 Months Ended

Dec. 31, 2011

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

11.    Property, Plant and Equipment

Property, plant and equipment are recorded at historical cost, net of accumulated depreciation. Components of property, plant and equipment, net are summarized as follows:

	As of December 31,
(In millions)	2011			2010
Land	$	51.9		$	107.6
Buildings		597.9			670.2
Leasehold improvements		102.7			100.8
Machinery and equipment		570.1			576.0
Computer software and hardware		439.7			392.8
Furniture and fixtures		37.6			54.5
Construction in progress		553.6			506.9
Total cost		2,353.5			2,408.8
Less: accumulated depreciation		(782.1	)		(767.2	)
Total property, plant and equipment, net	$	1,571.4		$	1,641.6

Our construction in progress balances are primarily related to the construction of our large-scale biologics manufacturing facility in Hillerød, Denmark, where we plan to manufacture TYSABRI drug substance. As of December 31, 2011 and 2010, the construction in progress balance related to this facility totaled $474.0 million and $440.2 million, respectively.

For 2011, 2010 and 2009, we capitalized interest costs related to construction in progress totaling approximately $32.6 million, $28.6 million and $28.5 million, respectively. Capitalized interest costs are primarily related to the development of our large-scale biologics manufacturing facility in Hillerød, Denmark.

Depreciation expense totaled $143.9 million, $144.9 million and $137.9 million for 2011, 2010 and 2009, respectively.

New Cambridge Leases

In July 2011, we executed leases for two office buildings to be built in Cambridge, Massachusetts with a planned occupancy during the second half of 2013. Construction of these facilities began in late 2011. These buildings, totaling approximately 500,000 square feet, will serve as the future location of our corporate headquarters and commercial operations. These buildings will also provide additional general and administrative and research and development office space. The leases both have 15 year terms and we have options to extend the term of each lease for two additional five-year terms. Future minimum rental commitments under these leases will total approximately $340.0 million over the initial 15 year lease terms. In addition to rent, the leases require us to pay additional amounts for taxes, insurance, maintenance and other operating expenses

In accordance with accounting guidance applicable to entities involved with the construction of an asset that will be leased when the construction is completed, we are considered the owner, for accounting purposes, of these properties during the construction period. Accordingly, we will record an asset along with a corresponding financing obligation on our consolidated balance sheet for the amount of total project costs incurred related to the construction in progress for these buildings through completion of the construction period. Upon completion of the buildings, we will assess and determine if the assets and corresponding liabilities should be derecognized. As of December 31, 2011, cost incurred in relation to the construction of these buildings totaled approximately $2.2 million.

As a result of our decision to relocate our corporate headquarters and centralize our campus in Cambridge, Massachusetts, we expect to vacate our Weston, Massachusetts facility upon completion of the new buildings. Based upon our most recent estimates, we expect to incur a charge of approximately $35.0 million upon vacating this facility when the new Cambridge buildings have been completed. This amount represents our remaining Weston lease obligation, net of our estimate of sublease income expected to be recovered.

San Diego Facility

On October 1, 2010, we sold the San Diego facility for cash proceeds, net of transaction costs, of approximately $127.0 million. As part of this transaction, we agreed to lease back the San Diego facility for a period of 15 months. We accounted for this transaction as a financing arrangement as we determined that the transaction did not qualify as a sale due to our continuing involvement under the leaseback terms. Accordingly, we recorded an obligation for the proceeds received in October 2010 and the facility assets remained classified as held for use with the carrying value of the facility continued to be reflected as a component of property, plant and equipment, net within our consolidated balance sheets.

In the first quarter of 2011, we entered into an agreement to terminate our 15 month lease of the San Diego facility effective August 31, 2011. We have had no continuing involvement or remaining obligation after August 31, 2011 and have accounted for this transaction as a sale of property as of that date. No significant gain on sale was recognized and we did not recognize any impairment charges related to the San Diego facility.

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Derivative Instruments (Details 1) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of the effect of derivatives designated as hedging instruments on the consolidated statements of income
Amount Reclassified from Accumulated Other Comprehensive Income into Income Gain/(Loss) (Effective Portion)	$ (36.9)	$ 45.7	$ (49.7)
Foreign Exchange Contract [Member] | Revenue [Member]
Summary of the effect of derivatives designated as hedging instruments on the consolidated statements of income
Amount Recognized in Accumulated Other Comprehensive Income on Derivative Gain/(Loss) (Effective Portion)	36.5	(11.0)	1.2
Amount Reclassified from Accumulated Other Comprehensive Income into Income Gain/(Loss) (Effective Portion)	(36.9)	45.7	(49.7)
Foreign Exchange Contract [Member] | Other income (expense) [Member]
Summary of the effect of derivatives designated as hedging instruments on the consolidated statements of income
Amount of Gain/(Loss) Recorded (Ineffective Portion)	$ (3.9)	$ 0.4	$ (1.1)

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Earnings per Share (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Numerator:
Net income attributable to Biogen Idec Inc	$ 300,200,000	$ 351,800,000	$ 288,000,000	$ 294,300,000	$ 240,300,000	$ 254,100,000	$ 293,400,000	$ 217,400,000	$ 1,234,428,000	$ 1,005,273,000	$ 970,132,000
Adjustment for net income allocable to preferred stock									(500,000)	(2,000,000)	(1,700,000)
Net income used in calculating basic and diluted earnings per share									1,233,900,000	1,003,300,000	968,400,000
Denominator:
Weighted average number of common shares outstanding									242,395,000	252,307,000	287,356,000
Effect of dilutive securities:
Dilutive potential common shares									2,600,000	2,600,000	2,100,000
Shares used in calculating diluted earnings per share									245,033,000	254,867,000	289,476,000
Numerator:
Net income allocable to preferred stock									$ 500,000	$ 2,000,000	$ 1,700,000
Denominator:
Total									100,000	5,200,000	11,300,000
Earnings Per Share (Textual) [Abstract]
Repurchase of common stock									6,000,000	40,300,000
Stock options and employee stock purchase plan [Member]
Effect of dilutive securities:
Stock options and employee stock purchase plan									1,000,000	900,000	600,000
Denominator:
Total									0	4,600,000	8,500,000
Market stock units [Member]
Effect of dilutive securities:
Stock options and employee stock purchase plan									300,000	100,000
Denominator:
Total									0
Time Vested Restricted Stock Units [Member]
Effect of dilutive securities:
Stock options and employee stock purchase plan									1,300,000	1,600,000	1,400,000
Denominator:
Total									0	100,000	2,100,000
Performance vested restricted stock units settled in shares [Member]
Effect of dilutive securities:
Stock options and employee stock purchase plan											100,000
Denominator:
Total											200,000
Convertible preferred stock [Member]
Denominator:
Total									100,000	500,000	500,000

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Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts receivable	$ 57,524	$ 54,922
Preferred stock, par value	$ 0.001	$ 0.001
Common stock, par value	$ 0.0005	$ 0.0005
Treasury stock at cost, shares	13,518	7,662

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Accounts Receivable

12 Months Ended

Dec. 31, 2011

Accounts Receivable [Abstract]

Accounts Receivable

5.    Accounts Receivable

Our accounts receivable primarily arise from product sales in the U.S. and Europe and mainly represent amounts due from our wholesale distributors, public hospitals and other government entities. The majority of our accounts receivable have standard payment terms which are generally between 30 and 90 days. We monitor the financial performance and credit worthiness of our large customers so that we can properly assess and respond to changes in their credit profile. We provide reserves against trade receivables for estimated losses that may result from a customer’s inability to pay. Amounts determined to be uncollectible are charged or written-off against the reserve. To date, such losses have not exceeded management’s estimates.

Concentrations of credit risk with respect to receivables, which are typically unsecured, are limited due to the wide variety of customers and markets using our products, as well as their dispersion across many different geographic areas. We monitor economic conditions, including volatility associated with international economies, and related impacts on the relevant financial markets and our business, especially in light of sovereign credit issues. The credit and economic conditions within Italy, Spain, Portugal and Greece, among other members of the European Union, have continued to deteriorate. These conditions have increased, and may continue to increase, the average length of time that it takes to collect on our accounts receivable outstanding in these countries.

Our net accounts receivable balances from product sales in these countries are summarized as follows:

	As of December 31, 2011
(In millions)	Current Balance Included within Accounts Receivable, net		Non-Current Balance  Included within Investments and Other Assets		Total
Spain	$	68.5	$	65.5	$	134.0
Italy	$	19.4	$	48.7	$	68.1
Portugal	$	20.6	$	12.3	$	32.9
Greece	$	4.0	$	—	$	4.0

	As of December 31, 2010
(In millions)	Current Balance Included within Accounts Receivable, net		Non-Current Balance  Included within Investments and Other Assets		Total
Spain	$	70.8	$	29.8	$	100.6
Italy	$	103.2	$	14.8	$	118.0
Portugal	$	17.8	$	5.5	$	23.3
Greece	$	3.9	$	—	$	3.9

Approximately $56.0 million and $45.0 million of the aggregated balances for these countries were overdue more than one year as of December 31, 2011 and December 31, 2010, respectively. Amounts included as a component of investments and other assets within our consolidated balance sheets represent amounts that are expected to be collected beyond one year.

In connection with our purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL, we entered into a credit assignment agreement with Dompé Farmaceutici SpA. Under the terms of this agreement, Dompé Farmaceutici SpA purchased all of Biogen Dompé SRL’s outstanding receivables as of June 30, 2011, adjusted for cash received through September 5, 2011, for $104.6 million. We retained no interests in these receivables and accounted for this transaction as a sale recognizing a loss of $1.8 million upon their disposition. For additional information related to these transactions, please read Note 2, Acquisitions to these consolidated financial statements. As of December 31, 2011, our accounts receivable balances in Italy totaled $68.1 million, all of which resulted from sales of product subsequent to June 30, 2011.

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Revenue Reserves

12 Months Ended

Dec. 31, 2011

Revenue Reserves [Abstract]

Revenue Reserves

4.    Revenue Reserves

Reserves for Discounts and Allowances

An analysis of the amount of, and change in, reserves is summarized as follows:

(In millions)	Discounts			Contractual Adjustments			Returns			Total
2011
Beginning balance	$	13.9		$	107.0		$	21.1		$	142.0
Current provisions relating to sales in current year		96.0			360.4			15.7			472.1
Adjustments relating to prior years		—			(14.0	)		(0.9	)		(14.9	)
Payments/returns relating to sales in current year		(84.3	)		(266.0	)		(0.4	)		(350.7	)
Payments/returns relating to sales in prior years		(13.0	)		(68.1	)		(11.8	)		(92.9	)
Ending balance	$	12.6		$	119.3		$	23.7		$	155.6
(In millions)	Discounts			Contractual Adjustments			Returns			Total
2010
Beginning balance	$	13.9		$	70.3		$	18.9		$	103.1
Current provisions relating to sales in current year		80.6			285.0			16.1			381.7
Adjustments relating to prior years		(2.7	)		(2.4	)		(1.8	)		(6.9	)
Payments/returns relating to sales in current year		(68.7	)		(184.3	)		(0.8	)		(253.8	)
Payments/returns relating to sales in prior years		(9.2	)		(61.6	)		(11.3	)		(82.1	)
Ending balance	$	13.9		$	107.0		$	21.1		$	142.0
(In millions)	Discounts			Contractual Adjustments			Returns			Total
2009
Beginning balance	$	9.2		$	48.1		$	18.1		$	75.4
Current provisions relating to sales in current year		74.0			192.5			15.8			282.3
Adjustments relating to prior years		—			—			0.8			0.8
Payments/returns relating to sales in current year		(60.8	)		(124.4	)		(0.6	)		(185.8	)
Payments/returns relating to sales in prior years		(8.5	)		(45.9	)		(15.2	)		(69.6	)
Ending balance	$	13.9		$	70.3		$	18.9		$	103.1

The total reserves above, included in our consolidated balance sheets, are summarized as follows:

	As of December 31,
(In millions)	2011		2010
Reduction of accounts receivable	$	40.6	$	36.7
Current liability		115.0		105.3
Total reserves	$	155.6	$	142.0

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Share-based Payments

12 Months Ended

Dec. 31, 2011

Share-based Payments [Abstract]

Share-based Payments

16.    Share-based Payments

Share-based Compensation Expense

The following table summarizes share-based compensation expense included within our consolidated statements of income:

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Research and development	$	62.0		$	62.7		$	60.8
Selling, general and administrative		88.7			123.6			106.4
Restructuring charges		(0.6	)		6.8			—
Subtotal		150.1			193.1			167.2
Capitalized share-based compensation costs		(4.5	)		(3.5	)		(6.3	)
Share-based compensation expense included in total cost and expenses		145.6			189.6			160.9
Income tax effect		(44.6	)		(60.3	)		(49.4	)
Share-based compensation expense included in net income attributable to Biogen Idec Inc.	$	101.0		$	129.3		$	111.5

The following table summarizes share-based compensation expense associated with each of our share-based compensation programs:

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Stock options	$	5.9		$	26.1		$	21.6
Market stock units		14.6			10.0			—
Time-vested restricted stock units		89.6			129.4			133.7
Performance-vested restricted stock units settled in shares		1.0			5.3			4.6
Cash settled performance shares		32.7			15.0			—
Employee stock purchase plan		6.3			7.3			7.3
Subtotal		150.1			193.1			167.2
Capitalized share-based compensation costs		(4.5	)		(3.5	)		(6.3	)
Share-based compensation expense included in total cost and expenses	$	145.6		$	189.6		$	160.9

Windfall tax benefits from vesting of stock awards, exercises of stock options and ESPP participation were $50.6 million, $13.1 million and $3.4 million in 2011, 2010 and 2009, respectively. These amounts have been calculated under the alternative transition method in accordance with U.S. GAAP.

As of December 31, 2011, unrecognized compensation cost related to unvested share-based compensation was approximately $124.3 million, net of estimated forfeitures. We expect to recognize the cost of these unvested awards over a weighted-average period of 1.3 years.

Share-Based Compensation Plans

We have three share-based compensation plans pursuant to which awards are currently being made: (1) the Biogen Idec Inc. 2006 Non-Employee Directors Equity Plan (2006 Directors Plan); (2) the Biogen Idec Inc. 2008 Omnibus Equity Plan (2008 Omnibus Plan); and (3) the Biogen Idec Inc. 1995 Employee Stock Purchase Plan (ESPP). We have six share-based compensation plans under which there are outstanding awards, but from which no further awards can or will be made: (i) the IDEC Pharmaceuticals Corporation 1993 Non-Employee Directors Stock Option Plan; (ii) the IDEC Pharmaceuticals Corporation 1988 Stock Option Plan; (iii) the Biogen, Inc. 1985 Non-Qualified Stock Option Plan; (iv) the Biogen, Inc. 1987 Scientific Board Stock Option Plan; (v) the Biogen Idec Inc. 2003 Omnibus Equity Plan (2003 Omnibus Plan); and (vi) the Biogen Idec Inc. 2005 Omnibus Equity Plan (2005 Omnibus Plan). We have not made any awards pursuant to the 2005 Omnibus Plan since our stockholders approved the 2008 Omnibus Plan and do not intend to make any awards pursuant to the 2005 Omnibus Plan in the future, except that unused shares under the 2005 Omnibus Plan have been carried over for use under the 2008 Omnibus Plan.

Directors Plan

In May 2006, our stockholders approved the 2006 Directors Plan for share-based awards to our directors. Awards granted from the 2006 Directors Plan may include stock options, shares of restricted stock, restricted stock units, stock appreciation rights and other awards in such amounts and with such terms and conditions as may be determined by a committee of our Board of Directors, subject to the provisions of the plan. We have reserved a total of 1.6 million shares of common stock for issuance under the 2006 Directors Plan. The 2006 Directors Plan provides that awards other than stock options and stock appreciation rights will be counted against the total number of shares reserved under the plan in a 1.5-to-1 ratio.

Omnibus Plans

In June 2008, our stockholders approved the 2008 Omnibus Plan for share-based awards to our employees. Awards granted from the 2008 Omnibus Plan may include stock options, shares of restricted stock, restricted stock units, performance shares, shares of phantom stock, stock appreciation rights and other awards in such amounts and with such terms and conditions as may be determined by a committee of our Board of Directors, subject to the provisions of the plan. Shares of common stock available for issuance under the 2008 Omnibus Plan consist of 15.0 million shares reserved for this purpose, plus shares of common stock that remained available for issuance under the 2005 Omnibus Plan on the date that our stockholders approved the 2008 Omnibus Plan, plus shares that are subject to awards under the 2005 Omnibus Plan which remain unissued upon the cancellation, surrender, exchange or termination of such awards. The 2008 Omnibus Equity Plan provides that awards other than stock options and stock appreciation rights will be counted against the total number of shares available under the plan in a 1.5-to-1 ratio.

Stock Options

All stock option grants to employees are for a ten-year term and generally vest one-fourth per year over four years on the anniversary of the date of grant, provided the employee remains continuously employed with us. Stock option grants to directors are for ten-year terms and generally vest as follows: (1) grants made on the date of a director’s initial election to our Board of Directors vest one-third per year over three years on the anniversary of the date of grant and (2) grants made for service on our Board of Directors vest on the first anniversary of the date of grant, provided in each case that the director continues to serve on our Board of Directors through the vesting date. Options granted under all plans are exercisable at a price per share not less than the fair market value of the underlying common stock on the date of grant. The estimated fair value of options, including the effect of estimated forfeitures, is recognized over the options’ vesting periods. The fair value of the stock options granted in 2010 and 2009 was estimated as of the date of grant using a Black-Scholes option valuation model that uses the following weighted-average assumptions:

	For the Years Ended December 31,
	2011			2010			2009
Expected option life (in years)		*	*		4.5			4.7
Expected stock price volatility		*	*		30.8	%		39.3	%
Risk-free interest rate		*	*		2.0	%		1.9	%
Expected dividend yield		*	*		0.0	%		0.0	%
Per share grant-date fair value		*	*	$	16.52		$	18.00

** There were no grants of stock options made in 2011.

The expected life of options granted is derived using assumed exercise rates based on historical exercise patterns and represents the period of time that options granted are expected to be outstanding. Expected stock price volatility is based upon implied volatility for our exchange-traded options and other factors, including historical volatility. After assessing all available information on either historical volatility, implied volatility, or both, we have concluded that a combination of both historical and implied volatility provides the best estimate of expected volatility. The risk-free interest rate used is determined by the market yield curve based upon risk-free interest rates established by the Federal Reserve, or non-coupon bonds that have maturities equal to the expected term. The dividend yield of zero is based upon the fact that we have not historically granted cash dividends, and do not expect to issue dividends in the foreseeable future. Stock options granted prior to January 1, 2006 were valued based on the grant date fair value of those awards, using the Black-Scholes option pricing model, as previously calculated for pro-forma disclosures.

The following table summarizes our stock option activity:

	Shares			Weighted Average Exercise Price
Outstanding at December 31, 2010		7,167,000		$	55.43
Granted		—		$	—
Exercised		(5,235,000	)	$	56.40
Cancelled		(241,000	)	$	53.30
Outstanding at December 31, 2011		1,691,000		$	52.75

The total intrinsic values of options exercised in 2011, 2010 and 2009 totaled $149.0 million, $50.5 million, and $6.7 million, respectively. The aggregate intrinsic values of options outstanding as of December 31, 2011 totaled $96.8 million. The weighted average remaining contractual term for options outstanding as of December 31, 2011 was 4.9 years.

Of the options outstanding, 1.3 million were exercisable as of December 31, 2011. The exercisable options had a weighted-average exercise price of $52.35. The aggregate intrinsic value of options exercisable as of December 31, 2011 was $73.6 million. The weighted average remaining contractual term for options exercisable as of December 31, 2011 was 4.1 years.

A total of 1.6 million vested and expected to vest options were outstanding as of December 31, 2011. These vested and expected to vest options had a weighted average exercise price of $52.74 and an aggregated intrinsic value of $94.3 million. The weighted average remaining contractual term of vested and expected to vest options as of December 31, 2011 was 4.8 years.

The following table summarizes the amount of tax benefit realized for stock options and cash received from the exercise of stock options:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Tax benefit realized for stock options	$	47.5	$	16.0	$	1.5
Cash received from the exercise of stock options	$	291.9	$	160.0	$	25.2

Market Stock Units (MSUs)

MSUs awarded to employees vest in four equal annual increments beginning on the anniversary of the grant date. The vesting of these awards is subject to the respective employee’s continued employment. The number of MSUs granted represents the target number of units that are eligible to be earned based on the attainment of certain market-based criteria involving our stock price. The number of MSUs earned is calculated at each annual anniversary from the date of grant over the respective vesting periods, resulting in multiple performance periods. Participants may ultimately earn between 0% and 150% of the target number of units granted based on actual stock performance. Accordingly, additional MSUs may be issued or currently outstanding MSUs may be cancelled upon final determination of the number of awards earned. Compensation expense, including the effect of forfeitures, is recognized over the applicable service period.

The following table summarizes our MSU activity:

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2010		398,000		$	61.87
Granted (a)		398,000		$	74.19
Vested		(119,000	)	$	59.89
Forfeited		(96,000	)	$	65.37
Unvested at December 31, 2011		581,000		$	69.49

(a) MSUs granted in 2011, includes approximately 26,000 additional MSUs issued in 2011 based upon the attainment of performance criteria set for 2010 in relation to shares granted in 2010. The remainder of the MSUs granted in 2011 represents the target number of shares eligible to be earned at the time of grant. These grants were made in conjunction with the hiring of employees and our annual awards made in February 2011.

We value grants of MSUs using a lattice model with a Monte Carlo simulation. This valuation methodology utilizes several key assumptions, including the 60 calendar day average closing stock price on grant date, expected volatility of our stock price, risk-free rates of return and expected dividend yield. The assumptions used in our valuation are summarized as follows:

	For the Years Ended December 31,
	2011	2010
Expected dividend yield	0%	0%
Range of expected stock price volatility	25.7% - 33.4%	28.3% - 38.8%
Range of risk-free interest rates	0.3% - 1.9%	0.3% - 2.0%
60 calendar day average stock price on grant date	$66.78 - $101.16	$49.08 - $54.12
Weighted-average per share grant date fair value	$ 74.19	$ 61.87

Cash Settled Performance Shares (CSPSs)

CSPSs awarded to employees vest in three equal annual increments beginning on the anniversary of the grant date. The vesting of these awards is subject to the respective employee’s continued employment with such awards settled in cash. The number of CSPSs granted represents the target number of units that are eligible to be earned based on the attainment of certain performance measures established at the beginning of the performance period, which ends on December 31 ^st of each year. Participants may ultimately earn between 0% and 200% of the target number of units granted based on the degree of actual performance metric achievement. Accordingly, additional CSPSs may be issued or currently outstanding CSPSs may be cancelled upon final determination of the number of units earned. CSPSs are settled in cash based on the 60 calendar day average closing stock price through each vesting date once the actual vested and earned number of units is known. Since no shares are issued, these awards will not dilute equity. Compensation expense, including the effect of forfeitures, is recognized over the applicable service period.

The following table summarizes our CSPS activity:

(In thousands)	Shares
Unvested at December 31, 2010		370,000
Granted (a)		490,000
Vested		(187,000	)
Forfeited		(111,000	)
Unvested at December 31, 2011		562,000

(a) CSPSs granted in 2011 includes approximately 95,000 additional CSPSs issued in 2011 based upon the attainment of performance criteria set for 2010 in relation to shares granted in 2010. The remainder of the CSPSs granted in 2011 represents the target number of shares eligible to be earned at the time of grant. These grants were made in conjunction with the hiring of employees and our annual awards made in February 2011.

During 2011, we paid $13.4 million of cash in settlement of CSPS awards upon vesting.

Time-Vested Restricted Stock Units (RSUs)

RSUs awarded to employees generally vest no sooner than one-third per year over three years on the anniversary of the date of grant, or upon the third anniversary of the date of the grant, provided the employee remains continuously employed with us, except as otherwise provided in the plan. Shares of our common stock will be delivered to the employee upon vesting, subject to payment of applicable withholding taxes. RSUs awarded to directors for service on our Board of Directors vest on the first anniversary of the date of grant, provided in each case that the director continues to serve on our Board of Directors through the vesting date. Shares of our common stock will be delivered to the director upon vesting and are not subject to any withholding taxes. The fair value of all RSUs is based on the market value of our stock on the date of grant. Compensation expense, including the effect of forfeitures, is recognized over the applicable service period.

The following table summarizes our RSU activity:

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2010		4,223,000		$	53.26
Granted		1,398,000		$	70.01
Vested		(1,980,000	)	$	53.72
Forfeited		(717,000	)	$	54.20
Unvested at December 31, 2011		2,924,000		$	60.72

RSUs granted in 2010 and 2009 had weighted average grant date fair values of $54.79 and $48.93, respectively.

Performance-Vested Restricted Stock Units (PVRSUs)

The following table summarizes our PVRSU activity:

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2010		154,000		$	49.24
Granted (a)		1,000		$	53.64
Vested		(75,000	)	$	49.51
Forfeited		(33,000	)	$	48.61
Unvested at December 31, 2011		47,000		$	49.34

(a) PVRSUs granted in 2011 represents additional shares earned for performance criteria set for 2010 in relation to shares granted in 2010. No other grants of PVRSUs were made in 2011.

Grant Activity

In 2010 and 2009, approximately 4,000 and 325,000 PVRSUs were granted with weighted average grant date fair values of $53.64 and $49.42 per share, respectively. The number of PVRSUs reflected as granted represents the target number of shares that are eligible to vest in full or in part and are earned subject to the attainment of certain performance criteria established at the beginning of the performance period, which ended December 31, 2009. Participants may ultimately earn up to 200% of the target number of shares granted in the event that the maximum performance thresholds are attained. Accordingly, additional PVRSUs may be issued upon final determination of the number of awards earned.

Once the earned number of performance-vested awards has been determined, the earned PVRSUs will then vest in three equal increments on (1) the later of the first anniversary of the grant date or the date of results determination; (2) the second anniversary of the grant date; and (3) the third anniversary of the grant date. The vesting of these awards is also subject to the respective employees’ continued employment. Compensation expense associated with these PVRSUs is initially based upon the number of shares expected to vest after assessing the probability that certain performance criteria will be met and the associated targeted payout level that is forecasted will be achieved, net of estimated forfeitures. Cumulative adjustments are recorded quarterly to reflect subsequent changes in the estimated outcome of performance-related conditions until the date results are determined.

Employee Stock Purchase Plan (ESPP)

The following table summarizes our ESPP activity:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Shares issued under ESPP		0.4		0.6		0.6
Cash received under ESPP	$	22.8	$	23.5	$	22.6

Other

As part of the employee severance and benefits packages offered to employees affected by our workforce reduction made in connection with our 2010 restructuring initiative, we agreed to settle certain existing equity awards in cash, which resulted in an incremental charge of approximately $6.8 million recognized in the fourth quarter of 2010. This charge is reflected within our consolidated statement of income as a component of our total restructuring charge incurred in 2010.

In accordance with the transition agreement entered into with James C. Mullen who retired as our President and Chief Executive Officer on June 8, 2010, we agreed with Mr. Mullen, amongst other provisions, to vest all of Mr. Mullen’s then-unvested equity awards on the date of his retirement and allow Mr. Mullen to exercise his vested stock options until June 8, 2013 or their expiration, whichever is earlier. The modifications to Mr. Mullen’s existing stock options, RSUs and PVRSUs resulted in an incremental charge of approximately $18.6 million, which was recognized evenly over the service period from January 4, 2010 to June 8, 2010 as per the terms of the transition agreement.

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Indebtedness

12 Months Ended

Dec. 31, 2011

Indebtedness [Abstract]

Indebtedness

12.    Indebtedness

Our indebtedness is summarized as follows:

	As of December 31,
(In millions)	2011		2010
Current portion:
Note payable to Fumedica	$	3.3	$	3.3
Credit line from Dompé		—		8.0
Financing arrangement for the sale of the San Diego facility		—		125.9
Current portion of notes payable, line of credit and other financing arrangements	$	3.3	$	137.2
Non-current portion:
6.0% Senior notes due 2013	$	449.9	$	449.8
6.875% Senior notes due 2018		592.3		597.9
Note payable to Fumedica		16.4		18.7
Financing arrangement for the construction of the Cambridge facilities		2.2		—
Non-current portion of notes payable, line of credit and other financing arrangements	$	1,060.8	$	1,066.4

The following is a summary description of our principal indebtedness as of December 31, 2011:

Senior Notes

On March 4, 2008, we issued $450.0 million aggregate principal amount of 6.0% Senior Notes due March 1, 2013 and $550.0 million aggregate principal amount of 6.875% Senior Notes due March 1, 2018 that were originally priced at 99.886% and 99.184% of par, respectively. The discount is amortized as additional interest expense over the period from issuance through maturity. These notes are senior unsecured obligations. Interest on the notes is payable March 1 and September 1 of each year. The notes may be redeemed at our option at any time at 100% of the principal amount plus accrued interest and a specified make-whole amount. The notes contain a change of control provision that may require us to purchase the notes under certain circumstances. There is also an interest rate adjustment feature that requires us to pay interest at an increased rate on the notes if the credit rating on the notes declines below investment grade.

Upon the issuance of the debt we entered into interest rate swap contracts where we received a fixed rate and paid a variable rate, as further described in Note 10, Derivative Instruments to these consolidated financial statements. These contracts were terminated in December 2008. Upon termination of these swaps, the carrying amount of the 6.875% Senior Notes due in 2018 was increased by $62.8 million and is being amortized using the effective interest rate method over the remaining life of the Senior Notes and is being recognized as a reduction of interest expense. As of December 31, 2011, $45.4 million remains to be amortized.

Revolving Credit Facility

We have a $360.0 million senior unsecured revolving credit facility, which we may choose to use for future working capital and general corporate purposes. The terms of this revolving credit facility include various covenants, including financial covenants that require us to not exceed a maximum leverage ratio and, under certain circumstances, an interest coverage ratio. This facility terminates in June 2012. No borrowings have been made under this credit facility and as of December 31, 2011 and 2010 we were in compliance with all applicable covenants.

Notes Payable to Fumedica

In connection with our 2006 distribution agreement with Fumedica, we issued notes totaling 61.4 million Swiss Francs which were payable to Fumedica in varying amounts from June 2008 through June 2018. Our remaining note payable to Fumedica had a present value of 18.6 million Swiss Francs ($19.7 million) and 20.7 million Swiss Franc ($22.0 million) as of December 31, 2011 and 2010, respectively.

Credit Line from Dompé

On September 6, 2011, we completed the purchase of all the remaining outstanding shares of our joint venture investment in Biogen Dompé SRL, our sales affiliate in Italy, from our joint venture partner, Dompé Farmaceutici SpA. Balances outstanding under Biogen Dompé SRL’s credit line from us and Dompé Farmaceutici SpA were repaid in connection with this transaction. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

Financing Arrangements

During 2011 we recorded a financing obligation in relation to the construction of the two office buildings in Cambridge, Massachusetts, which will serve as the future location of our corporate headquarters and provide office space for our commercial operations, research and development and general and administrative functions. As of December 31, 2011, the financing obligation related to cost incurred in construction of these buildings totaled approximately $2.2 million.

During 2010 we also recorded a financing obligation in connection with our sale and subsequent lease back of the San Diego facility. We have had no continuing involvement or remaining obligation related to the San Diego facility after August 31, 2011.

For additional information related to these transactions, please read Note 11, Property, Plant & Equipment to these consolidated financial statements.

Debt Maturity

Our total debt, excluding amounts related to our financing arrangements, mature as follows:

(In millions)	As of December 31, 2011
2012	$	3.4
2013		453.4
2014		3.4
2015		3.4
2016		3.4
2017 and thereafter		556.7
Total	$	1,023.7

The fair value of our debt is disclosed in Note 8, Fair Value Measurements to these consolidated financial statements.

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Indebtedness (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Total debt maturities
2012	$ 3.4
2013	453.4
2014	3.4
2015	3.4
2016	3.4
2017 and thereafter	556.7
Total	$ 1,023.7

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Fair Value Measurements

12 Months Ended

Dec. 31, 2011

Fair Value Measurements [Abstract]

Fair Value Measurements

8.    Fair Value Measurements

The tables below present information about our assets and liabilities that are measured at fair value on a recurring basis as of December 31, 2011 and December 31, 2010, and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value:

(In millions)	As of December 31, 2011		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	399.8	$	—	$	399.8	$	—
Marketable debt securities:
Corporate debt securities		602.6		—		602.6		—
Government securities		1,716.5		—		1,716.5		—
Mortgage and other asset backed securities		273.8		—		273.8		—
Strategic investments		0.1		0.1		—		—
Venture capital investments		23.5		—		—		23.5
Derivative contracts		39.5		—		39.5		—
Plan assets for deferred compensation		11.6		—		11.6		—
Total	$	3,067.4	$	0.1	$	3,043.8	$	23.5
Liabilities:
Derivative contracts	$	0.5	$	—	$	0.5	$	—
Contingent consideration		151.0		—		—		151.0
Total	$	151.5	$	—	$	0.5	$	151.0

(In millions)	As of December 31, 2010		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	651.8	$	—	$	651.8	$	—
Marketable debt securities:
Corporate debt securities		313.0		—		313.0		—
Government securities		785.3		—		785.3		—
Mortgage and other asset backed securities		92.9		—		92.9		—
Strategic investments		44.8		44.8		—		—
Venture capital investments		20.8		—		—		20.8
Derivative contracts		1.3		—		1.3		—
Plan assets for deferred compensation		13.0		—		13.0		—
Total	$	1,922.9	$	44.8	$	1,857.3	$	20.8
Liabilities:
Derivative contracts	$	12.2	$	—	$	12.2	$	—
Contingent consideration		81.2		—		—		81.2
Total	$	93.4	$	—	$	12.2	$	81.2

There were no transfers between fair value measurement levels during the years ended December 31, 2011 and 2010, respectively.

Our strategic investments represent investments in publicly traded equity securities and are the only investments for which we used Level 1 inputs to determine their fair value. Our venture capital investments are comprised of investments in certain biotechnology oriented venture capital funds which primarily invest in small privately-owned, venture-backed biotechnology companies. Our venture capital investments are the only investments for which we used Level 3 inputs to determine their fair value and represented approximately 0.3% of total assets of December 31, 2011 and 2010, respectively. The following table provides a roll forward of the fair value of our venture capital investments, which are all Level 3 assets:

	As of December 31,
(In millions)	2011			2010
Beginning balance	$	20.8		$	21.9
Unrealized gains included in earnings		2.4			—
Unrealized losses included in earnings		(1.4	)		(2.1	)
Purchases		1.7			2.1
Settlements		—			(1.1	)
Ending balance	$	23.5		$	20.8

The fair values of our debt instruments, which are all Level 2 liabilities, are summarized as follows:

	As of December 31,
(In millions)	2011		2010
Credit line from Dompé	$	—	$	8.1
Notes payable to Fumedica		22.4		24.2
6.0% Senior Notes due 2013		474.1		485.5
6.875% Senior Notes due 2018		663.9		618.0
Total fair value	$	1,160.4	$	1,135.8

The fair values of Biogen Dompé SRL’s credit line from us and Dompé Farmaceutici SpA and our note payable to Fumedica were estimated using market observable inputs, including current interest and foreign currency exchange rates. The fair value of our Senior Notes was determined through market, observable, and corroborated sources.

Balances outstanding under Biogen Dompé SRL’s credit line were repaid in connection with our recent purchase of the noncontrolling interest in our joint venture investment in Biogen Dompé SRL. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

Contingent Consideration Resulting from a Business Combination

We revalue the contingent consideration obligation for acquisitions completed after January 1, 2009 on a recurring basis each reporting period. Changes in the fair value of our contingent consideration obligations are recognized as a fair value adjustment of contingent consideration within our consolidated statements of income. These fair value measurements are based on significant inputs not observable in the market and therefore represent Level 3 measurements. The following table provides a roll forward of the changes in fair value of our contingent consideration obligations:

	As of December 31,
(In millions)	2011			2010
Fair value as of beginning of period	$	81.2		$	—
Acquisition date fair value of contingent consideration obligations related to acquisitions		38.8			81.2
Changes in the fair value of contingent consideration obligations		36.0			—
Payments of contingent consideration obligations		(5.0	)		—
Fair value as of end of period	$	151.0		$	81.2

Upon completion of our purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH in September 2011, we recorded a contingent consideration obligation of $38.8 million. As of December 31, 2011, the fair value of this contingent consideration obligation was $31.9 million, of which $3.9 million was reflected as a component of accrued expenses and other, and $28.0 million was reflected as a component of other long-term liabilities within our consolidated balance sheet. Our most recent valuation was determined based upon probability weighted net cash outflow projections of $42.5 million, discounted using a rate of 3.8%, which is the cost of debt financing for market participants. The decrease in the fair value of this obligation, of $6.9 million since the acquisition date, was primarily due to changes in the discount rate and in the probability and expected timing related to the achievement of certain cumulative sales-based and developmental milestones.

In connection with our acquisition of BIN in the fourth quarter of 2010, we recorded a liability of $81.2 million, representing the acquisition date fair value of the contingent consideration. There was no significant change in the valuation of this liability from the acquisition date through December 31, 2010. As of December 31, 2011, the fair value of this contingent consideration obligation was $119.1 million, of which $6.9 million was reflected as a component of accrued expenses and other, and $112.2 million was reflected as a component of other long-term liabilities within our consolidated balance sheet. Our most recent valuation was determined based upon probability weighted net cash outflow projections of $390.0 million, discounted using a rate of 5.2%, which is the cost of debt financing for market participants. The increase in the fair value of this obligation, of $37.9 million since December 31, 2010, was primarily due to changes in the discount rate and in the probability and expected timing related to the achievement of certain remaining developmental milestones, offset by the payment of a $5.0 million developmental milestone.

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Restructuring (Details) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2010
Restructuring liability
Restructuring reserves as of December 31, 2010		$ 66,400,000
Expense		18,200,000
Payments		(85,700,000)
Adjustments to previous estimates, net		(2,900,000)
Other adjustments		5,400,000
Restructuring reserves as of Dec 31, 2011	66,400,000	1,400,000	66,400,000
Restructuring (Textual) [Abstract]
Restructuring charge	75,200,000	19,026,000	75,153,000
Restructuring (Textual) [Abstract]
Headcount reduction percentage due to consolidation of sites		13.00%
Workforce reduction [Member]
Restructuring liability
Restructuring reserves as of December 31, 2010		60,600,000
Expense		15,800,000
Payments		(81,800,000)
Adjustments to previous estimates, net		(2,900,000)
Other adjustments		8,600,000
Restructuring reserves as of Dec 31, 2011	60,600,000	300,000	60,600,000
Restructuring (Textual) [Abstract]
Restructuring charge		12,800,000	67,200,000
Facility consolidation [Member]
Restructuring liability
Restructuring reserves as of December 31, 2010		5,800,000
Expense		2,400,000
Payments		(3,900,000)
Other adjustments		(3,200,000)
Restructuring reserves as of Dec 31, 2011	5,800,000	1,100,000	5,800,000
Restructuring (Textual) [Abstract]
Restructuring charge		$ 6,200,000	$ 8,000,000

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Investments in Variable Interest Entities (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Knopp [Member]
Summary of activity related to collaboration
Total upfront and reimbursement payment made to collaborative partner		$ 26,400,000
Milestone payment payable to Acorda Therapeutics, Inc. (Acorda)	10,000,000
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	44,800,000	5,000,000
Biogen Idec's share of expense reflected within our consolidated statements of income	54,800,000	31,400,000
Collaboration expense attributed to noncontrolling interests, net of tax	8,600,000
Total upfront and milestone payments made to Collaborative Partner	36,400,000
Total expense incurred by Biogen Idec, excluding upfront and milestone payments	49,800,000
Estimate of additional amounts to be incurred by us in development of the lead compound	260,000,000
Neurimmune [Member]
Summary of activity related to collaboration
Milestone payment payable to Acorda Therapeutics, Inc. (Acorda)	15,000,000		7,500,000
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	9,000,000	15,500,000	9,000,000
Biogen Idec's share of expense reflected within our consolidated statements of income	24,000,000	15,500,000	16,500,000
Collaboration expense attributed to noncontrolling interests, net of tax	14,700,000	1,000,000
Total upfront and milestone payments made to Collaborative Partner	35,000,000
Total expense incurred by Biogen Idec, excluding upfront and milestone payments	40,000,000
Estimate of additional amounts to be incurred by us in development of the lead compound	$ 800,000,000

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Inventory

12 Months Ended

Dec. 31, 2011

Inventory [Abstract]

Inventory

6.    Inventory

The components of inventory are summarized as follows:

	As of December 31,
(In millions)	2011		2010
Raw materials	$	83.8	$	59.0
Work in process		169.4		142.2
Finished goods		73.6		87.9
Total inventory	$	326.8	$	289.1

The components of inventory by product are summarized as follows:

	As of December 31,
(In millions)	2011		2010
AVONEX	$	113.3	$	87.0
TYSABRI		114.7		117.0
Other		15.0		26.1
Total finished goods and work in process		243.0		230.1
Raw materials		83.8		59.0
Total inventory	$	326.8	$	289.1

Amounts written down related to excess, obsolete or unmarketable inventory are charged to cost of sales, and totaled $25.4 million, $11.8 million, and $16.9 million for the years ended December 31, 2011, 2010, and 2009, respectively.

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Intangible Assets and Goodwill

12 Months Ended

Dec. 31, 2011

Intangible Assets and Goodwill [Abstract]

Intangible Assets and Goodwill

7.    Intangible Assets and Goodwill

Intangible Assets

Intangible assets, net of accumulated amortization, impairment charges and adjustments, are summarized as follows:

		As of December 31, 2011							As of December 31, 2010
(In millions)	Estimated Life	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Out-licensed patents	12-23 years	$	578.0	$	(391.3	)	$	186.7	$	578.0	$	(350.2	)	$	227.8
Core developed technology	15-23 years		3,005.3		(1,801.1	)		1,204.2		3,005.3		(1,636.9	)		1,368.4
In-process research and development	Up to 15 years upon commercialization		110.9		—			110.9		110.9		—			110.9
Trademarks and tradenames	Indefinite		64.0		—			64.0		64.0		—			64.0
In-licensed rights and patents	6-16 years		47.2		(4.8	)		42.4		3.0		(1.3	)		1.7
Assembled workforce	4 years		2.1		(2.1	)		—		2.1		(2.1	)		—
Distribution rights	2 years		12.7		(12.7	)		—		12.7		(12.7	)		—
Total intangible assets		$	3,820.2	$	(2,212.0	)	$	1,608.2	$	3,776.0	$	(2,003.2	)	$	1,772.8

Total intangible assets was unchanged as of December 31, 2011 compared to December 31, 2010, excluding the impact of amortization and amounts recorded in connection with the license agreements for FAMPYRA and the JC virus assay described below. In December 2010, we completed our acquisition of BIN and allocated a $110.9 million of the purchase price to acquired IPR&D. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

Amortization of acquired intangible assets totaled $208.6 million, $208.9 million, and $289.8 million for the years ended December 31, 2011, 2010 and 2009, respectively. Amortization for acquired intangible assets is expected to be in the range of approximately $160.0 million to $200.0 million annually through 2016.

AVONEX Core Technology Asset

Our most significant intangible asset is the core technology related to our AVONEX product. The net book value of this asset as of December 31, 2011 was $1,192.1 million. Amortization of our core acquired intangible asset related to AVONEX is expected to be in the range of approximately $100.0 million to $150.0 million annually through 2016.

FAMPYRA

In July 2011, the European Commission (EC) granted a conditional marketing authorization for FAMPYRA in the E.U., which triggered a $25.0 million milestone payment. This payment was made to Acorda Therapeutics, Inc. (Acorda) in the third quarter of 2011 and was capitalized as an intangible asset.

Under the terms of our 2009 collaboration and license agreement, we will pay Acorda additional milestones based on new indications and ex-U.S. net sales. The next expected milestone would be $15.0 million, due when ex-U.S. net sales reach $100.0 million over a period of four consecutive quarters. We will capitalize these milestones upon achievement as an intangible asset. Amortization will utilize an economic consumption model that will be based on an estimate of all of the probable payments we expect to make as contingent consideration, such as sales-based milestones, for entering into the license agreement.

For additional information related to our collaboration with Acorda, please read Note 20, Collaborations to these consolidated financial statements.

JC Virus Assay

In the first quarter of 2011, we licensed rights for the diagnostic and therapeutic application of recombinant virus-like particles, known as VP1 proteins, to detect antibodies of the JC virus (JCV) in serum or blood. Under the terms of this license, we expect to make payments totaling approximately $58.9 million through 2016. These payments include upfront and milestone payments as well as the greater of an annual maintenance fee or usage-based royalty payment. As of December 31, 2011, we recognized an intangible asset in the amount of $19.2 million, reflecting the total of upfront payments made and other time-based milestone payments. We will further capitalize additional payments due under this arrangement as an intangible asset upon achievement. Amortization will utilize an economic consumption model that will be based on an estimate of all of the probable payments we expect to make in relation to the total number of JCV assay tests performed through 2016.

Goodwill

The following table provides a roll forward of the changes in goodwill:

	As of December 31,
(In millions)	2011		2010
Beginning balance	$	1,146.3	$	1,138.6
Goodwill acquired during the year		—		25.6
Other		—		(17.9	)
Ending balance	$	1,146.3	$	1,146.3

As of December 31, 2011, we had no accumulated impairment losses related to goodwill.

In December 2010, we completed our acquisition of BIN and allocated a $25.6 million of the purchase price to goodwill. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements. During 2010, we also recorded a decrease to goodwill of $17.9 million to establish a deferred tax asset that existed at the time of the merger of Biogen, Inc. and IDEC Pharmaceuticals Corporation in 2003.

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Financial Instruments

12 Months Ended

Dec. 31, 2011

Financial Instruments [Abstract]

Financial Instruments

9.    Financial Instruments

Marketable Securities, including Strategic Investments

The following tables summarize our marketable securities and strategic investments:

As of December 31, 2011 (In millions):	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale
Corporate debt securities:
Current	$	155.0	$	0.2	$	(0.1	)	$	154.9
Non-current		447.6		1.2		(1.5	)		447.9
Government securities:
Current		1,021.0		0.4		—			1,020.6
Non-current		695.5		0.9		(0.2	)		694.8
Mortgage and other asset backed securities:
Current		0.1		—		—			0.1
Non-current		273.7		0.5		(1.3	)		274.5
Total available-for-sale securities	$	2,592.9	$	3.2	$	(3.1	)	$	2,592.8
Other Investments
Strategic investments, non-current	$	0.1	$	—	$	(0.1	)	$	0.2

As of December 31, 2010 (In millions):	Fair Value		Gross Unrealized Gains		Gross Unrealized Losses			Amortized Cost
Available-for-sale
Corporate debt securities:
Current	$	93.2	$	0.1	$	—		$	93.1
Non-current		219.8		2.1		(0.5	)		218.2
Government securities:
Current		352.8		0.2		—			352.6
Non-current		432.5		0.6		(0.6	)		432.5
Mortgage and other asset backed securities:
Current		2.1		—		—			2.1
Non-current		90.8		0.5		(0.2	)		90.5
Total available-for-sale securities	$	1,191.2	$	3.5	$	(1.3	)	$	1,189.0
Other Investments
Strategic investments, non-current	$	44.8	$	17.5	$	—		$	27.3

In the tables above, as of December 31, 2011 and 2010, government securities included $214.0 million and $163.5 million, respectively, of Federal Deposit Insurance Corporation (FDIC) guaranteed senior notes issued by financial institutions under the Temporary Liquidity Guarantee Programs.

The following table summarizes our financial assets with original maturities of less than 90 days included within cash and cash equivalents on the accompanying consolidated balance sheet:

	As of December 31,
(In millions)	2011		2010
Commercial paper	$	—	$	4.0
Repurchase agreements		8.8		26.0
Short-term debt securities		391.0		621.8
Total	$	399.8	$	651.8

The carrying values of our commercial paper, including accrued interest, repurchase agreements, and our short-term debt securities approximate fair value.

Summary of Contractual Maturities: Available-for-Sale Securities

The estimated fair value and amortized cost of our marketable securities, excluding strategic investments, available-for-sale by contractual maturity are summarized as follows:

	As of December 31, 2011				As of December 31, 2010
(In millions)	Estimated Fair  Value		Amortized Cost		Estimated Fair  Value		Amortized Cost
Due in one year or less	$	1,176.1	$	1,175.6	$	448.1	$	447.8
Due after one year through five years		1,251.6		1,251.4		664.1		662.4
Due after five years		165.2		165.8		79.0		78.8
Total available-for-sale securities	$	2,592.9	$	2,592.8	$	1,191.2	$	1,189.0

The average maturity of our marketable securities as of December 31, 2011 and 2010 was 14 months and 11 months, respectively.

Proceeds from Maturities and Sales of Marketable Securities, excluding Strategic Investments

The proceeds from maturities and sales of marketable securities, excluding strategic investments and cash equivalents, and resulting realized gains and losses are summarized as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Proceeds from maturities and sales	$	2,276.7	$	2,668.7	$	3,319.0
Realized gains	$	3.9	$	18.8	$	19.8
Realized losses	$	2.3	$	2.5	$	4.0

Proceeds were generally reinvested. Realized losses for the year ended December 31, 2011, primarily relate to sales of government and corporate securities. Realized losses for the year ended December 31, 2010, primarily relate to the sale of agency mortgage-backed securities and corporate debt securities. Realized losses for the year ended December 31, 2009, primarily relate to losses on the sale of non-agency mortgage-backed securities and corporate debt securities.

Strategic Investments

Strategic investments are included in investments and other assets on the accompanying consolidated balance sheets. In 2011, we sold four strategic investments for $40.6 million, which resulted in a net gain of $13.5 million. In 2010, we sold one strategic investment for $1.8 million, which resulted in an insignificant loss. In 2009 we sold two strategic investments for $5.9 million, which resulted in a $3.0 million gain.

In addition to the strategic investments and venture capital investments noted in Note 8, Fair Value Measurements to these consolidated financial statements, we hold other investments in equity securities of certain privately-owned biotechnology companies and biotechnology oriented venture capital funds accounted for using the cost method. The carrying value of these securities as of December 31, 2011 and 2010 was $39.2 million and $35.0 million, respectively. These securities are also included in investments and other assets on the accompanying consolidated balance sheets.

Impairments

Prior to the adoption of new accounting standards for the recognition, measurement and presentation of other-than-temporary impairments in April 2009 for debt securities, we recognized all other-than-temporary impairment amounts related to our marketable debt securities in earnings as required under the previously effective guidance which required that management assert that it had the ability and intent to hold a debt security until maturity or until we recovered the cost of our investment.

In 2011, we recognized $11.5 million in charges for the impairment of our publicly-held strategic investments, investments in venture capital funds and investments in privately-held companies.

In 2010, we recognized $21.3 million in charges for the other-than-temporary impairment of our publicly held strategic investments, investments in venture capital funds and investments in privately held companies. The increase over amounts recognized in 2009 was primarily the result of one of our strategic investments, executing an equity offering at a price below our cost basis during the first quarter of 2010.

In 2009, we recognized impairment losses of $7.0 million on our publicly-held strategic investments and non-marketable securities and an additional $3.6 million in charges for the other-than-temporary impairment on our marketable debt securities.

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Accounts Receivable (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Biogen Dompe SRL [Member]	Sep. 06, 2011 Biogen Dompe SRL [Member]	Dec. 31, 2011 Italy [Member]	Dec. 31, 2010 Italy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable In Countries With Deteriorated Credit And Economic Conditions					$ 68.1	$ 118.0
Receivables purchased as part of acquisition			104.6	104.6
Loss recognized upon disposition			1.8
Accounts Receivable (Textual) [Abstract]
Payment terms of accounts receivable arising from product sales	Between 30 and 90 days
Minimum term for accounts receivable	30 days
Maximum term for accounts receivable	90 days
Accounts receivable outstanding for greater than one year	$ 56.0	$ 45.0

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Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Minimum rental commitments under non-cancelable leases
Minimum lease payments, 2011	$ 33.9
Minimum lease payments, 2012	42.5
Minimum lease payments, 2013	54.3
Minimum lease payments, 2014	49.3
Minimum lease payments, 2015	44.6
Minimum lease payments, Thereafter	450.5
Minimum lease payments, Total	675.1
Less: income from subleases, 2011	(0.5)
Less: income from subleases, 2012	(0.5)
Less: income from subleases, 2013	(0.4)
Less: income from subleases, 2014	0
Less: income from subleases, 2015	0
Less: income from subleases, Thereafter	0
Less: income from subleases, Total	(1.4)
Net minimum lease payments, 2011	33.4
Net minimum lease payments, 2012	42.0
Net minimum lease payments, 2013	53.9
Net minimum lease payments, 2014	49.3
Net minimum lease payments, 2015	44.6
Net minimum lease payments, Thereafter	450.5
Net minimum lease payments, Total	$ 673.7

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Indebtedness (Details Textual)	12 Months Ended										12 Months Ended
	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2011 Note payable to Fumedica [Member] USD ($)	Dec. 31, 2011 Note payable to Fumedica [Member] CHF	Dec. 31, 2010 Note payable to Fumedica [Member] USD ($)	Dec. 31, 2010 Note payable to Fumedica [Member] CHF	Dec. 31, 2006 Note payable to Fumedica [Member] CHF	Dec. 31, 2011 6.0% Senior notes due 2013 [Member] USD ($)	Dec. 31, 2010 6.0% Senior notes due 2013 [Member] USD ($)	Mar. 04, 2008 6.0% Senior notes due 2013 [Member] USD ($)	Dec. 31, 2011 6.875% Senior notes due 2018 [Member] USD ($)	Dec. 31, 2010 6.875% Senior notes due 2018 [Member] USD ($)	Mar. 04, 2008 6.875% Senior notes due 2018 [Member] USD ($)	Dec. 31, 2011 New Cambridge Leases [Member] USD ($)
Debt Instrument [Line Items]
Principal amount senior notes										$ 450,000,000			$ 550,000,000
Redemption percentage par value of senior notes										99.886%			99.184%
Interest rate on Senior Notes										6.00%			6.875%
Increased carrying amount of interest rate swap											62,800,000
Notes payable, line of credit and other financing arrangements	1,060,808,000	1,066,379,000	16,400,000		18,700,000		61,400,000	449,900,000	449,800,000		592,300,000	597,900,000
Present value of notes payable			19,700,000	18,600,000	22,000,000	20,700,000
Remaining obligation of financing arrangements														2,200,000
Indebtedness (Textual) [Abstract]
Notes redemption condition	100% of the principal amount plus accrued interest and a specified make-whole amount
Percentage of redemption of notes	100.00%
Debt issuance costs	8,000,000
Interest to be amortized on debt	45,400,000
Senior unsecured revolving credit facility	360,000,000
Borrowings under revolving credit facility	$ 0	$ 0

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Inventory (Details 1) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Components of inventory [Line Items]
Total finished goods and work in process	$ 243,000,000	$ 230,100,000
Raw materials	83,800,000	59,000,000
Total inventory	326,843,000	289,066,000
Inventory (Textual) [Abstract]
Write-downs on excess, obsolete or unmarketable inventory	25,446,000	11,808,000	16,924,000
AVONEX [Member]
Components of inventory [Line Items]
Total finished goods and work in process	113,300,000	87,000,000
TYSABRI [Member]
Components of inventory [Line Items]
Total finished goods and work in process	114,700,000	117,000,000
Other products [Member]
Components of inventory [Line Items]
Total finished goods and work in process	$ 15,000,000	$ 26,100,000

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Share-Based Payments (Details Textual) (USD $)	5 Months Ended	12 Months Ended			3 Months Ended	12 Months Ended
	Jun. 08, 2010	Dec. 31, 2011 Plan Year	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2010 Restructuring Charges [Member]	Dec. 31, 2011 Restructuring Charges [Member]	Dec. 31, 2010 Restructuring Charges [Member]	Dec. 31, 2011 Time Vested Restricted Stock Units [Member]	Dec. 31, 2010 Time Vested Restricted Stock Units [Member]	Dec. 31, 2009 Time Vested Restricted Stock Units [Member]	Dec. 31, 2011 Performance vested restricted stock units [Member] Increment	Dec. 31, 2010 Performance vested restricted stock units [Member]	Dec. 31, 2009 Performance vested restricted stock units [Member]	Dec. 31, 2011 Employee Stock Option [Member]	Dec. 31, 2011 Market stock units [Member] Increment	Dec. 31, 2010 Market stock units [Member]	Dec. 31, 2011 Cash settled performance shares [Member] Increment	Dec. 31, 2010 Cash settled performance shares [Member]	Dec. 31, 2011 Directors Plan [Member]	Dec. 31, 2011 Omnibus Plans [Member]	Dec. 31, 2011 Attainment Of Performance Criteria [Member] Market stock units [Member]	Dec. 31, 2011 Attainment Of Performance Criteria [Member] Cash settled performance shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares of common stock for issuance																			1,600,000	15,000,000
Ratio of total number of shares reserved under the plan																			1.5-to-1	1.5-to-1
Grant vested to employees		one-third per year over three years						one-third per year over three years						one-fourth per year over four years
Percentage of earnings of the target number of units granted based on actual stock performance (Minimum)															0.00%		0.00%
Percentage of earnings of the target number of units granted based on actual stock performance (Maximum)															150.00%		200.00%
Number of days for calculation of average closing stock price																	60 days
Number of shares granted								1,398,000			1,000	4,000	325,000		398,000						26,000	95,000
Weighted average grant date fair value								$ 70.01	$ 54.79	$ 48.93	$ 53.64	$ 53.64	$ 49.42		$ 74.19	$ 61.87
Maximum percentage of earnings of target number of shares granted if maximum threshold limit is attained													200.00%
Number of annual increments for MSU award															4
Number of equal annual increments											3						3
Share-based compensation expense		$ 117,347,000	$ 171,435,000	$ 167,207,000	$ 6,800,000	$ (600,000)	$ 6,800,000	$ 89,600,000	$ 129,400,000	$ 133,700,000					$ 14,600,000	$ 10,000,000	$ 32,700,000	$ 15,000,000
Cash in settlement of CSPS awards upon vesting		13,400,000
Share-Based Payments (Textual) [Abstract]
Windfall tax benefits from vesting of stock awards, exercises of stock options and ESPP participation		50,600,000	13,100,000	3,400,000
Unrecognized compensation cost related to unvested share-based compensation		124,300,000
Weighted-average period to recognize the cost of unvested awards		1.3
Number of share-based compensation plans pursuant to which awards are currently being made		3
Number of share-based compensation plans pursuant to which no further awards will be made		6
Term of stock option grants to employees		10 years
Term of stock option vest to employees (in years)		4 years
Term of stock option grants to directors		10 years
Term of grant vested to board of director		3 years
Number of shares granted under stock options		0
Outstanding stock options exercisable		1,300,000
Weighted-average exercise price		$ 52.35
Aggregate intrinsic value of options exercisable		73,600,000
Weighted average remaining contractual term for options exercisable		4.1
Total of vested and expected to vest options outstanding		1,600,000
Weighted average exercise price for vested and expected to vest options		$ 52.74
Aggregate intrinsic value of vested and expected to vest options		94,300,000
Weighted average remaining contractual term of vested and expected to vest options		4.8
Stock options		0
Total intrinsic value of options exercised		149,000,000	50,500,000	6,700,000
Aggregate intrinsic values of options outstanding		96,800,000
Weighted average remaining contractual term for options outstanding		4.9
Incremental charge related to stock options Rsus and Pvrsus	$ 18,600,000

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Accounts Receivable (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Accounts receivable balances on product sales from different countries
Accounts receivable, net current	$ 584,603,000	$ 605,329,000
Italy [Member]
Accounts receivable balances on product sales from different countries
Accounts receivable, net current	19,400,000	103,200,000
Accounts receivable, net non-current	48,700,000	14,800,000
Accounts Receivable, Total	68,100,000	118,000,000
Spain [Member]
Accounts receivable balances on product sales from different countries
Accounts receivable, net current	68,500,000	70,800,000
Accounts receivable, net non-current	65,500,000	29,800,000
Accounts Receivable, Total	134,000,000	100,600,000
Portugal [Member]
Accounts receivable balances on product sales from different countries
Accounts receivable, net current	20,600,000	17,800,000
Accounts receivable, net non-current	12,300,000	5,500,000
Accounts Receivable, Total	32,900,000	23,300,000
Greece [Member]
Accounts receivable balances on product sales from different countries
Accounts receivable, net current	4,000,000	3,900,000
Accounts receivable, net non-current	0	0
Accounts Receivable, Total	$ 4,000,000	$ 3,900,000

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Share-Based Payments (Details 1) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of share based compensation expense associated with different programs
Share-based compensation expense	$ 117,347,000	$ 171,435,000	$ 167,207,000
Subtotal	150,100,000	193,100,000	167,200,000
Capitalized share-based payment costs	(4,500,000)	(3,500,000)	(6,300,000)
Share-based compensation expense included in total costs and expenses	145,600,000	189,600,000	160,900,000
Stock Options [Member]
Summary of share based compensation expense associated with different programs
Share-based compensation expense	5,900,000	26,100,000	21,600,000
Market stock units [Member]
Summary of share based compensation expense associated with different programs
Share-based compensation expense	14,600,000	10,000,000
Time Vested Restricted Stock Units [Member]
Summary of share based compensation expense associated with different programs
Share-based compensation expense	89,600,000	129,400,000	133,700,000
Performance vested restricted stock units settled in shares [Member]
Summary of share based compensation expense associated with different programs
Share-based compensation expense	1,000,000	5,300,000	4,600,000
Cash settled performance shares [Member]
Summary of share based compensation expense associated with different programs
Share-based compensation expense	32,700,000	15,000,000
Employee Stock Purchase Plan [Member]
Summary of share based compensation expense associated with different programs
Share-based compensation expense	$ 6,300,000	$ 7,300,000	$ 7,300,000

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Subsequent Events

12 Months Ended

Dec. 31, 2011

Subsequent Events [Abstract]

Subsequent Events

27.    Subsequent Events

Isis Pharmaceuticals, Inc.

On January 4, 2012, we entered into an exclusive, worldwide option and development agreement with Isis Pharmaceuticals, Inc. (Isis) under which both companies will develop and commercialize Isis’ antisense investigational drug, ISIS-SMN _Rx, for the treatment of spinal muscular atrophy (SMA).

Under the terms of the agreement, Isis received an upfront payment of $29.0 million and is eligible to receive up to $45.0 million in milestone payments associated with the clinical development of ISIS-SMN_Rx prior to licensing. Biogen Idec has the option to license ISIS-SMN_Rx until completion of the first successful Phase 2/3 trial. Isis could receive up to another $225.0 million in a license fee and regulatory milestone payments. Isis will be responsible for global development of ISIS-SMN _Rx through the completion of Phase 2/3 trials and we will provide advice on the clinical trial design and regulatory strategy. If we exercise our option, we will assume global development, regulatory and commercialization responsibilities.

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Income Taxes (Tables)

12 Months Ended

Dec. 31, 2011

Income Taxes [Abstract]

Income before income tax provision and the income tax expense

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Income before income taxes (benefit):
Domestic	$	1,408.9		$	846.4		$	1,073.8
Foreign		302.3			383.5			258.9
Total	$	1,711.2		$	1,229.9		$	1,332.7
Income tax expense (benefit):
Current
Federal	$	231.7		$	357.7		$	439.9
State		15.1			19.6			3.1
Foreign		44.1			35.4			50.0
Total	$	290.9		$	412.7		$	493.0
Deferred
Federal	$	160.9		$	(70.6	)	$	(94.8	)
State		(8.1	)		(6.6	)		(39.0	)
Foreign		0.8			(4.2	)		(3.6	)
Total		153.6			(81.4	)		(137.4	)
Total income tax expense	$	444.5		$	331.3		$	355.6

Components of deferred tax assets and liabilities

	As of December 31,
(In millions)	2011			2010
Deferred tax assets
Tax credits	$	60.0		$	47.6
Inventory, other reserves, and accruals		104.1			203.1
Capitalized costs		5.3			6.7
Intangibles, net		75.8			61.8
Net operating loss		22.9			35.3
Share-based compensation		54.7			64.4
Other		45.7			70.3
Valuation allowance		(10.8	)		(10.8	)
Total deferred tax assets	$	357.7		$	478.4
Deferred tax liabilities
Purchased intangible assets	$	(384.8	)	$	(446.1	)
Unrealized gain on investments and cumulative translation adjustment		(3.5	)		(6.6	)
Inventory		(76.8	)		—
Depreciation, amortization and other		(133.1	)		(114.4	)
Total deferred tax liabilities	$	(598.2	)	$	(567.1	)

Reconciliation between the U.S. federal statutory tax rate and effective tax rate

	For the Years Ended December 31,
	2011			2010			2009
Statutory rate		35.0	%		35.0	%		35.0	%
State taxes		1.7			1.7			(0.1	)
Taxes on foreign earnings		(5.9	)		(10.7	)		(5.0	)
Credits and net operating loss utilization		(4.4	)		(3.0	)		(3.8	)
Purchased intangible assets		1.3			1.9			2.0
IPR&D		—			5.0			—
Permanent items		(1.2	)		(2.0	)		(1.3	)
Contingent consideration		0.7			—			—
Other		(1.2	)		(1.0	)		(0.1	)
Effective tax rate		26.0	%		26.9	%		26.7	%

Reconciliation of beginning and ending amount of unrecognized tax benefits

(In millions)	2011			2010			2009
Balance at January 1,	$	121.5		$	147.1		$	249.6
Additions based on tax positions related to the current period		2.2			3.6			14.4
Additions for tax positions of prior periods		48.6			13.3			77.4
Reductions for tax positions of prior periods		(75.8	)		(18.5	)		(88.7	)
Statute expirations		(2.3	)		(3.7	)		—
Settlements		(29.8	)		(20.3	)		(105.6	)
Balance at December 31,	$	64.4		$	121.5		$	147.1

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Accumulated Other Comprehensive Income (Loss)

12 Months Ended

Dec. 31, 2011

Equity/Accumulated Other Comprehensive Income (Loss) [Abstract]

Accumulated Other Comprehensive Income (Loss)

14.    Accumulated Other Comprehensive Income (Loss)

Accumulated other comprehensive income (loss) consisted of the following:

	As of December 31,
(In millions)	2011			2010
Translation adjustments	$	(50.3	)	$	(24.4	)
Unrealized gains (losses) on securities available for sale		—			12.4
Unrealized gains (losses) on foreign currency forward contracts		32.8			(9.8	)
Unfunded status of pension and postretirement benefit plans		(9.0	)		0.2
Accumulated other comprehensive income (loss)	$	(26.5	)	$	(21.6	)

Unrealized holding gains on securities available for sale is shown net of tax of $0.1 million and $7.3 million as of December 31, 2011 and 2010, respectively. Unrealized gains (losses) on foreign currency forward contracts are shown net of tax of $3.6 million and $1.3 million as of December 31, 2011 and 2010, respectively. The unfunded status of pension and retirement benefit plans is shown net of tax as of December 31, 2011 and 2010. Tax amounts in both years were immaterial. For discussion of the unfunded status of pension and retirement benefit plans, please read Note 24, Employee Benefit Plans to these consolidated financial statements.

Amounts comprising noncontrolling interests, as reported in our consolidated statements of equity as of December 31, 2011 and 2010 included accumulated translation adjustments of $5.1 million and $0.2 million, respectively.

Comprehensive income (loss) and its components are presented in the consolidated statements of equity.

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Collaborations (Details 3)	12 Months Ended
	Dec. 31, 2011
Sobi rate to Biogen on net sales in the Sobi Territory [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Reimbursement, under the amended agreement, Method	Royalty
Rate during the reimbursement period	Base Rate plus 5%
Sobi rate to Biogen on net sales in the Sobi Territory [Member] | Sobi Territory [Member] | Maximum [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Base rate following first commercial sale in the territory	12.00%
Sobi rate to Biogen on net sales in the Sobi Territory [Member] | Sobi Territory [Member] | Minimum [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Base rate following first commercial sale in the territory	10.00%
Biogen rate to sobi on net sales in the Biogen North America Territory [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Reimbursement, under the amended agreement, Method	Royalty
Rate during the reimbursement period	Base Rate less 5%
Biogen rate to sobi on net sales in the Biogen North America Territory [Member] | Sobi Territory [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Rate prior to first commercial sale in the territory	2.00%
Biogen rate to sobi on net sales in the Biogen North America Territory [Member] | Sobi Territory [Member] | Maximum [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Base rate following first commercial sale in the territory	12.00%
Biogen rate to sobi on net sales in the Biogen North America Territory [Member] | Sobi Territory [Member] | Minimum [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Base rate following first commercial sale in the territory	10.00%
Biogen rate to sobi on net sales in the Biogen direct Territory [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Reimbursement, under the amended agreement, Method	Royalty
Rate during the reimbursement period	Base Rate less 5%
Biogen rate to sobi on net sales in the Biogen direct Territory [Member] | Sobi Territory [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Rate prior to first commercial sale in the territory	2.00%
Biogen rate to sobi on net sales in the Biogen direct Territory [Member] | Sobi Territory [Member] | Maximum [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Base rate following first commercial sale in the territory	17.00%
Biogen rate to sobi on net sales in the Biogen direct Territory [Member] | Sobi Territory [Member] | Minimum [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Base rate following first commercial sale in the territory	15.00%
Biogen rate to Sobi on net revenue from the Biogen distributor Territory [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Reimbursement, under the amended agreement, Method	Net Revenue Share
Rate during the reimbursement period	Base Rate less 15%
Biogen rate to Sobi on net revenue from the Biogen distributor Territory [Member] | Sobi Territory [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Rate prior to first commercial sale in the territory	10.00%
Biogen rate to Sobi on net revenue from the Biogen distributor Territory [Member] | Sobi Territory [Member] | Maximum [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Base rate following first commercial sale in the territory	50.00%
Biogen rate to Sobi on net revenue from the Biogen distributor Territory [Member] | Sobi Territory [Member] | Minimum [Member]
Mechanism for reimbursement, under the amended agreement amounts payable
Base rate following first commercial sale in the territory	0.00%

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Investments in Variable Interest Entities

12 Months Ended

Dec. 31, 2011

Investments in Variable Interest Entities [Abstract]

Investments in Variable Interest Entities

19.    Investments in Variable Interest Entities

Consolidated Variable Interest Entities

Our consolidated financial statements include the financial results of variable interest entities in which we are the primary beneficiary.

Investments in Joint Ventures

On September 6, 2011, we completed the purchase of the noncontrolling interest in our joint venture investments in Biogen Dompé SRL and Biogen Dompé Switzerland GmbH, our respective sales affiliates in Italy and Switzerland, from our joint venture partners, Dompé Farmaceutici SpA and Dompé International SA, respectively. Prior to this transaction, our consolidated financial statements reflected 100% of the operations of these joint venture investments and we recorded net income (loss) attributable to noncontrolling interests in our consolidated statements of income based on the percentage of ownership interest retained by our joint venture partners as we retained the power to direct the activities which most significantly and directly impacted their economic performance. We have continued to consolidate the operations of these entities following our purchase of the noncontrolling interest; however, as of September 6, 2011, we no longer allocate 50% of the earnings of these affiliates to net income (loss) attributable to noncontrolling interests as Biogen Dompé SRL and Biogen Dompé Switzerland GmbH became wholly-owned subsidiaries of the Company.

Until we completed our purchase of the noncontrolling interests, the assets of these joint ventures were restricted, from the standpoint of Biogen Idec, in that they were not available for our general business use outside the context of each joint venture. The joint ventures’ most significant assets were accounts receivable from the ordinary course of business. The holders of the liabilities of each joint venture, including the credit line from Dompé Farmaceutici SpA to Biogen Dompé SRL, had no recourse to Biogen Idec. Balances outstanding under Biogen Dompé SRL’s credit line were repaid in connection with this transaction. In addition, Dompé Farmaceutici SpA purchased all of Biogen Dompé SRL’s outstanding receivables as of June 30, 2011, adjusted for cash received through September 5, 2011. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

Knopp

In August 2010, we entered into a license agreement with Knopp Neurosciences, Inc. (Knopp), a subsidiary of Knopp Holdings, LLC, for the development, manufacture and commercialization of dexpramipexole, an orally administered small molecule in clinical development for the treatment of amyotrophic lateral sclerosis (ALS). We are responsible for all development activities and, if successful, we will also be responsible for the manufacture and global commercialization of dexpramipexole. Under the terms of the license agreement we made a $26.4 million upfront payment and agreed to pay Knopp up to an additional $265.0 million in development and sales-based milestone payments, as well as royalties on future commercial sales. In addition, we also purchased 30.0% of the Class B common shares of Knopp for $60.0 million.

Due to the terms of the license agreement and our investment in Knopp, we determined that we are the primary beneficiary of Knopp as we have the power to direct the activities that most significantly impact Knopp’s economic performance. As such, we consolidate the results of Knopp. As the license agreement with Knopp only gives us access to the underlying intellectual property of dexpramipexole and we did not acquire any employees or other processes, we determined that this transaction was an acquisition of an asset rather than a business. Therefore, we recorded an IPR&D charge of approximately $205.0 million upon the initial consolidation of Knopp, which is included within our consolidated statement of income for 2010. The amount allocated to IPR&D represents the fair value of the intellectual property of Knopp, which as of the effective date of the agreement, had not reached technological feasibility and had no alternative future use. This charge was determined using internal models based on projected revenues and development costs and adjusted for industry-specific probabilities of success. We attributed approximately $145.0 million of the IPR&D charge to the noncontrolling interest.

In March 2011, we dosed the first patient in a registrational study for dexpramipexole. The achievement of this milestone resulted in a $10.0 million payment due to Knopp. As we consolidate Knopp, we recognized this payment as a charge to noncontrolling interests in the first quarter of 2011.

Although we have assumed responsibility for the development of dexpramipexole, we may also be required to reimburse certain Knopp expenses directly attributable to the license agreement. Any additional amounts incurred by Knopp that we reimburse will be reflected within total cost and expenses in our consolidated statements of income. Future development and sales-based milestone payments will also be reflected within our consolidated statements of income as a charge to noncontrolling interests, when such milestones are achieved.

A summary of activity related to this collaboration, excluding the initial accounting for the consolidation of Knopp, is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010
Total upfront payments made to Knopp	$	—	$	26.4
Milestone payments made to Knopp	$	10.0	$	—
Total development expense incurred by the collaboration excluding upfront and milestone payments	$	44.8	$	5.0
Biogen Idec’s share of expense reflected within our consolidated statements of income	$	54.8	$	31.4
Collaboration expense attributed to noncontrolling interests, net of tax	$	8.6	$	—

A summary of activity related to this collaboration since inception, along with an estimate of additional future development expenses expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Knopp	$	36.4
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	$	49.8
Estimate of additional amounts to be incurred by us in development of dexpramipexole	$	260.0

The assets and liabilities of Knopp are not significant to our financial position or results of operations. We have provided no financing to Knopp other than previously contractually required amounts disclosed above.

Neurimmune SubOne AG

In 2007, we entered into a collaboration agreement with Neurimmune SubOne AG (Neurimmune), a subsidiary of Neurimmune AG, for the development and commercialization of antibodies for the treatment of Alzheimer’s disease. Neurimmune conducts research to identify potential therapeutic antibodies and we are responsible for the development, manufacturing and commercialization of all products. Based upon our current development plans, we may pay Neurimmune up to $345.0 million in remaining milestone payments, as well as royalties on sales of any resulting commercial products.

We determined that we are the primary beneficiary of Neurimmune because we have the power through the collaboration to direct the activities that most significantly impact the entity’s economic performance and are required to fund 100% of the research and development costs incurred in support of the collaboration agreement.

Amounts that are incurred by Neurimmune for research and development expenses incurred in support of the collaboration that we reimburse are reflected in research and development expense in our consolidated statements of income. In April 2011, we submitted an Investigational New Drug application for BIIB037 (human anti-Amyloid ß mAb) a beta-amyloid removal therapy, which triggered a $15.0 million milestone payment due to Neurimmune. BIIB037 is being developed for the treatment of Alzheimer’s disease. As we consolidate Neurimmune, we recognized this payment as a charge to noncontrolling interests in the second quarter of 2011. Future milestone payments will be reflected within our consolidated statements of income as a charge to the noncontrolling interest, net of tax, when such milestones are achieved.

A summary of activity related to this collaboration is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Milestone payments made to Neurimmune	$	15.0	$	—	$	7.5
Total development expense incurred by the collaboration, excluding upfront and milestone payments	$	9.0	$	15.5	$	9.0
Biogen Idec’s share of expense reflected within our consolidated statements of income	$	24.0	$	15.5	$	16.5
Collaboration expense attributed to noncontrolling interests, net of tax	$	14.7	$	1.0	$	—

A summary of activity related to this collaboration since inception, along with an estimate of additional future development expenses expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Neurimmune	$	35.0
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	$	40.0
Estimate of additional amounts to be incurred by us in development of the lead compound	$	800.0

The assets and liabilities of Neurimmune are not significant to our financial position or results of operations as it is a research and development organization. We have provided no financing to Neurimmune other than previously contractually required amounts.

In December 2010, we completed our acquisition of BIN from Neurimmune AG, a related party to this collaboration. For additional information related to this transaction, please read Note 2, Acquisitions to these consolidated financial statements.

Unconsolidated Variable Interest Entities

We have relationships with other variable interest entities which we do not consolidate as we lack the power to direct the activities that significantly impact the economic success of these entities. These relationships include investments in certain biotechnology companies and research collaboration agreements. For additional information related to our significant collaboration arrangements with unconsolidated variable interest entities, please read Note 20, Collaborations to these consolidated financial statements.

As of December 31, 2011, the total carrying value of our investments in biotechnology companies that we have determined to be variable interest entities is $14.6 million. Our maximum exposure to loss related to these variable interest entities is limited to the carrying value of our investments.

We have entered into research collaborations with certain variable interest entities where we are required to share or fund certain development activities. These development activities are included in research and development expense within our consolidated statements of income, as they are incurred. Depending on the collaborative arrangement, we may record funding receivables or payable balances with our partners, based on the nature of the cost-sharing mechanism and activity within the collaboration. As of December 31, 2011, we had no significant receivables or payables related to cost sharing arrangements with unconsolidated variable interest entities at December 31, 2011 and 2010, respectively.

We have provided no financing to these variable interest entities other than previously contractually required amounts.

Samsung Biosimilar Agreement

On December 5, 2011, we entered into an agreement with Samsung BioLogics Co. Ltd. (Samsung) to establish an entity to develop, manufacture and market biosimilar pharmaceuticals. Under the terms of the agreement, Samsung will contribute approximately $255.0 million for an 85 percent stake in the entity and Biogen Idec will contribute approximately $45.0 million for the remaining 15 percent ownership interest. Our investment will initially be limited to this initial contribution as we have no obligation to provide any additional funding; however, we maintain an option to purchase additional stock in the entity in order to increase our ownership percentage up to 49.9 percent. The exercise of this option is within our control.

Samsung will retain the contractual power to direct the activities of the entity which will most significantly and directly impact its economic performance. We will account for this investment under the equity method of accounting as we maintain the ability to exercise significant influence over the entity through a presence on the entity’s Board of Directors and our contractual relationship. Therefore, we will reflect our percentage of the entity’s income or loss within our consolidated statements of income.

Completion of the transaction is subject to customary closing conditions.

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Share-Based Payments (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Tax benefit and cash received from stock option
Tax benefit realized for stock options	$ 47.5	$ 16.0	$ 1.5
Cash received from the exercise of stock options	$ 291.9	$ 160.0	$ 25.2

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Earnings per Share (Tables)

12 Months Ended

Dec. 31, 2011

Earnings per Share [Abstract]

Basic and diluted earnings per share

	For the Years Ended December 31,
(In millions)	2011			2010			2009
Numerator:
Net income attributable to Biogen Idec Inc.	$	1,234.4		$	1,005.3		$	970.1
Adjustment for net income allocable to preferred stock		(0.5	)		(2.0	)		(1.7	)
Net income used in calculating basic and diluted earnings per share	$	1,233.9		$	1,003.3		$	968.4
Denominator:
Weighted average number of common shares outstanding		242.4			252.3			287.4
Effect of dilutive securities:
Stock options and employee stock purchase plan		1.0			0.9			0.6
Time-vested restricted stock units		1.3			1.6			1.4
Market stock units		0.3			0.1			—
Performance-vested restricted stock units settled in shares		—			—			0.1
Dilutive potential common shares		2.6			2.6			2.1
Shares used in calculating diluted earnings per share		245.0			254.9			289.5

Anti dilutive securities excluded from computation of dilutive earnings per share

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Numerator:
Net income allocable to preferred stock	$	0.5	$	2.0	$	1.7
Denominator:
Stock options		—		4.6		8.5
Time-vested restricted stock units		—		0.1		2.1
Market stock units		—		—		—
Performance-vested restricted stock units settled in shares		—		—		0.2
Convertible preferred stock		0.1		0.5		0.5
Total		0.1		5.2		11.3

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Income Taxes (Details 2)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation between the U.S. federal statutory tax rate and effective tax rate
Statutory rate	35.00%	35.00%	35.00%
State taxes	1.70%	1.70%	(0.10%)
Taxes on foreign earnings	(5.90%)	(10.70%)	(5.00%)
Credits and net operating loss utilization	(4.40%)	(3.00%)	(3.80%)
Purchased intangible assets	1.30%	1.90%	2.00%
IPR&D		5.00%
Permanent items	(1.20%)	(2.00%)	(1.30%)
Contingent consideration	0.70%
Other	(1.20%)	(1.00%)	(0.10%)
Effective tax rate	26.00%	26.90%	26.70%

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Intangible Assets and Goodwill (Tables)

12 Months Ended

Dec. 31, 2011

Intangible Assets and Goodwill [Abstract]

Intangible assets

		As of December 31, 2011							As of December 31, 2010
(In millions)	Estimated Life	Cost		Accumulated Amortization			Net		Cost		Accumulated Amortization			Net
Out-licensed patents	12-23 years	$	578.0	$	(391.3	)	$	186.7	$	578.0	$	(350.2	)	$	227.8
Core developed technology	15-23 years		3,005.3		(1,801.1	)		1,204.2		3,005.3		(1,636.9	)		1,368.4
In-process research and development	Up to 15 years upon commercialization		110.9		—			110.9		110.9		—			110.9
Trademarks and tradenames	Indefinite		64.0		—			64.0		64.0		—			64.0
In-licensed rights and patents	6-16 years		47.2		(4.8	)		42.4		3.0		(1.3	)		1.7
Assembled workforce	4 years		2.1		(2.1	)		—		2.1		(2.1	)		—
Distribution rights	2 years		12.7		(12.7	)		—		12.7		(12.7	)		—
Total intangible assets		$	3,820.2	$	(2,212.0	)	$	1,608.2	$	3,776.0	$	(2,003.2	)	$	1,772.8

Summary of roll forward of the changes in goodwill

	As of December 31,
(In millions)	2011		2010
Beginning balance	$	1,146.3	$	1,138.6
Goodwill acquired during the year		—		25.6
Other		—		(17.9	)
Ending balance	$	1,146.3	$	1,146.3

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Income Taxes (Details Textual) (USD $)	1 Months Ended	12 Months Ended
	Aug. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007	Aug. 18, 2011	Jun. 08, 2010	Dec. 31, 2006
Income Taxes (Textual) [Abstract]
Full valuation allowance on deferred tax assets		$ 10,800,000
Undistributed foreign earnings of non U.S. subsidiaries		2,700,000,000
Unrecognized tax benefits		31,300,000	26,200,000	42,800,000
Proposed disallowance by tax authorities for payment for services				130,000,000	130,000,000	130,000,000
Notice of Assessment of corporate excise tax including penalties and interest								103,500,000	38,900,000
Amount for settlement of exchange for payment of tax	7,000,000
Tax adjustments and settlement interest							5,000,000
Net interest expense (benefit)		12,900,000	700,000	3,100,000
Accrued payment of interest		3,900,000	29,400,000
Maximum [Member]
Tax Credit Carryforward [Line Items]
Residual U.S. tax liability		700,000,000
Minimum [Member]
Tax Credit Carryforward [Line Items]
Residual U.S. tax liability		600,000,000
General Business [Member] | Domestic country [Member]
Tax Credit Carryforward [Line Items]
Net operating losses credit carry forwards		27,200,000
Credit carry forwards		1,900,000
Tax credit carryforward, expiration dates		2022
General Business [Member] | State and local jurisdiction [Member]
Tax Credit Carryforward [Line Items]
Net Operating losses credit carry forwards, State		57,100,000
Tax credit carryforward, expiration dates		2012
Research [Member]
Tax Credit Carryforward [Line Items]
Credit carry forwards		101,600,000
Research [Member] | State and local jurisdiction [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforward, expiration dates		2012
Carrying balance of research and investment credit expire in 2012		$ 900,000

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Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net income	$ 1,266,686	$ 898,573	$ 977,062
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization of property, plant and equipment, and intangible assets	358,933	355,744	427,961
Acquired in-process research and development	0	271,376
Share-based compensation	113,005	167,826	160,902
Fair value adjustment of contingent consideration	36,065
Excess tax benefit from share-based compensation	(50,586)	(13,136)	(3,436)
Deferred income taxes	153,576	(81,410)	(137,351)
Write-down of inventory to net realizable value	25,446	11,808	16,924
Impairment of marketable securities, investments and other assets	8,619	20,846	16,184
Non-cash interest (income) expense, foreign exchange remeasurement loss (gain), net and other	15,671	5,808	(7,892)
Realized (gain) loss on sale of marketable securities and strategic investments	(15,062)	(16,321)	(23,974)
Changes in operating assets and liabilities, net:
Accounts receivable	(73,374)	(99,227)	(100,442)
Due from unconsolidated joint business	(6,265)	(28,670)	13,136
Inventory	(59,219)	(4,527)	(42,772)
Other assets	(43,241)	(12,584)	22,271
Accrued expenses and other current liabilities	33,722	130,875	(48,942)
Other liabilities and taxes payable	(36,235)	17,692	(194,733)
Net cash flows provided by operating activities	1,727,741	1,624,673	1,074,898
Cash flows from investing activities:
Proceeds from sales and maturities of marketable securities	2,276,720	2,668,694	3,319,007
Purchases of marketable securities	(3,696,995)	(1,988,394)	(3,548,119)
Acquisitions	(5,000)	(72,476)
Acquisition of a variable interest entity, net		(84,952)
Purchases of property, plant and equipment	(208,020)	(173,055)	(165,646)
Proceeds from the sale of property, plant and equipment	2,207
Purchases of intangible assets	(44,155)
Purchases of other investments	(16,324)	(4,492)	(44,086)
Proceeds from the sale of strategic investments	41,273		13,822
Collateral received under securities lending			29,991
Net cash flows (used in) provided by investing activities	(1,650,294)	345,325	(395,031)
Cash flows from financing activities:
Purchase of treasury stock	(497,975)	(2,077,579)	(751,170)
Proceeds from issuance of stock for share-based compensation arrangements	314,650	183,486	47,810
Excess tax benefit from share-based compensation	50,586	13,136	3,436
Change in cash overdraft	2,823	11,781	12,275
Acquisition of noncontrolling interests	(148,264)
Net distributions to noncontrolling interests	(27,062)	(23,475)	4,356
Repayments of borrowings	(11,459)	(18,073)	(10,867)
Net proceeds from financing arrangement for the sale of the San Diego facility	0	126,980
Repayments on financing arrangement for the sale of the San Diego facility	(3,161)	(1,175)
Obligation under securities lending			(29,991)
Net cash flows used in financing activities	(319,862)	(1,784,919)	(724,151)
Net (decrease) increase in cash and cash equivalents	(242,415)	185,079	(44,284)
Effect of exchange rate changes on cash and cash equivalents	(2,641)	(7,370)	3,788
Cash and cash equivalents, beginning of the year	759,598	581,889	622,385
Cash and cash equivalents, end of the year	$ 514,542	$ 759,598	$ 581,889

XML

Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Income (Loss)
Translation adjustments	$ (50,300,000)	$ (24,400,000)
Unrealized gains (losses) on securities available for sale	0	12,400,000
Unrealized gains (losses) on foreign currency forward contracts	32,800,000	(9,800,000)
Unfunded status of pension and postretirement benefit plans	(9,000,000)	200,000
Accumulated other comprehensive income (loss)	$ (26,535,000)	$ (21,610,000)

XML

Restructuring

12 Months Ended

Dec. 31, 2011

Restructuring [Abstract]

Restructuring

3.    Restructuring

In November 2010, we announced a number of strategic, operational, and organizational initiatives designed to provide a framework for the future growth of our business and realign our overall structure to become a more efficient and cost effective organization. As part of this initiative:

• We out-licensed or terminated certain research and development programs, including those in oncology and cardiovascular medicine, that are no longer a strategic fit for us.

• We completed a 13% reduction in workforce spanning our sales, research and development, and administrative functions.

• We vacated and recognized the sale of the San Diego, California facility as well as consolidated certain of our Massachusetts facilities. For a more detailed description of transactions affecting our facilities, please read Note 11, Property, Plant and Equipment to these consolidated financial statements.

Costs associated with our workforce reduction primarily relate to employee severance and benefits. Facility consolidation costs are primarily comprised of charges associated with closing these facilities, related lease obligations and additional depreciation recognized when the expected useful lives of certain assets have been shortened due to the consolidation and closing of related facilities and the discontinuation of certain research and development programs. As of December 31, 2011, substantially all restructuring charges have been incurred and paid. We incurred $19.0 million of these charges in 2011, of which $12.8 million were related to our workforce reduction and $6.2 million related to the consolidation of our facilities. During the fourth quarter of 2010, we incurred $75.2 million of these charges, of which $67.2 million were related to our workforce reduction and $8.0 million were related to the consolidation of our facilities.

The following table summarizes the activity of our restructuring liability:

(In millions)	Workforce Reduction			Facility Consolidation			Total
Restructuring reserve as of December 31, 2010	$	60.6		$	5.8		$	66.4
Expense		15.8			2.4			18.2
Payments		(81.8	)		(3.9	)		(85.7	)
Adjustments to previous estimates, net		(2.9	)		—			(2.9	)
Other adjustments		8.6			(3.2	)		5.4
Restructuring reserve as of December 31, 2011	$	0.3		$	1.1		$	1.4

XML

Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Business (Textual) [Abstract]
Total revenues	$ 1,326,700,000	$ 1,309,900,000	$ 1,208,600,000	$ 1,203,300,000	$ 1,219,000,000	$ 1,175,800,000	$ 1,212,700,000	$ 1,108,900,000	$ 5,048,634,000	$ 4,716,423,000	$ 4,377,348,000
Interest in subsidiary (less than given percentage)									100.00%
Percentage of operations of joint venture investments on financial statements									100.00%
Percentage of net income (loss) attributable to noncontrolling interests									50.00%
Payment terms of accounts receivable arising from product sales									Between 30 and 90 days
Percentage of receivables of wholesale distributor accounted in consolidated receivables	14.10%				11.50%				14.10%	11.50%
Estimated useful lives of leasehold improvements									Lesser of the useful life or the term of the respective lease
Purchase price of common stock under the ESPP									85% of the lower of (i) the market value per share of the common stock on the participant’s entry date into an offering period or (ii) the market value per share of the common stock on the purchase date
Percentage of market value per share of common stock									85.00%
Compensation expense recognized over the purchase period									fair value of the look-back provision plus the 15% discount
Discount rate recognized in compensation expense									15.00%
Advertising costs									$ 45,300,000	$ 35,300,000	$ 26,500,000
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipments Useful Life, Minimum									15
Property, Plant and Equipments Useful Life, Maximum									40
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipments Useful Life, Minimum									5
Property, Plant and Equipments Useful Life, Maximum									7
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipments Useful Life, Minimum									5
Property, Plant and Equipments Useful Life, Maximum									20
Computer Software and Hardware [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipments Useful Life, Minimum									3
Property, Plant and Equipments Useful Life, Maximum									5

XML

Property, Plant and Equipment (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended			1 Months Ended	12 Months Ended				1 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Oct. 31, 2010 San Diego Facility [Member]	Dec. 31, 2011 San Diego Facility [Member]	Dec. 31, 2011 Hillerod, Denmark Facility [Member]	Dec. 31, 2010 Hillerod, Denmark Facility [Member]	Dec. 31, 2009 Hillerod, Denmark Facility [Member]	Jul. 31, 2011 New Cambridge Leases [Member] sqft	Dec. 31, 2011 New Cambridge Leases [Member]	Jul. 14, 2011 New Cambridge Leases [Member]
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 143.9	$ 144.9	$ 137.9
Property, Plant and Equipment (Textual) [Abstract]
Net proceeds from sale of San Diego facility				127.0
Lease transaction period in months					15 months
Construction in progress balance related to biologic manufacturing facility	553.6	506.9				474.0	440.2
Interest cost capitalization related to large-scale biologic manufacturing facility						32.6	28.6	28.5
Area of office building under lease									500,000
Future minimum rental commitments	675.1									340.0	340.0
Operating leases term									15 years
Construction cost incurred not yet paid										2.2
Expected charges to vacate building										$ 35.0

XML

Income Taxes (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation of the beginning and ending of unrecognized tax benefits
Balance at January 1	$ 121.5	$ 147.1	$ 249.6
Additions based on tax positions related to the current period	2.2	3.6	14.4
Additions for tax positions of prior periods	48.6	13.3	77.4
Reductions for tax positions of prior periods	(75.8)	(18.5)	(88.7)
Statute expirations	(2.3)	(3.7)
Settlements	(29.8)	(20.3)	(105.6)
Balance at December 31	$ 64.4	$ 121.5	$ 147.1

XML

Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Liabilities:
Contingent consideration	$ 151.0	$ 81.2	$ 0
Fair Value, Measurements, Recurring [Member]
Assets:
Cash Equivalents, Fair Value Disclosure	399.8	651.8
Derivative contracts	39.5	1.3
Plan assets for deferred compensation	11.6	13.0
Total	3,067.4	1,922.9
Liabilities:
Derivative contracts	0.5	12.2
Contingent consideration	151.0	81.2
Total	151.5	93.4
Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	602.6	313.0
Fair Value, Measurements, Recurring [Member] | Government securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	1,716.5	785.3
Fair Value, Measurements, Recurring [Member] | Mortgage and other asset backed securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	273.8	92.9
Fair Value, Measurements, Recurring [Member] | Strategic investments [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0.1	44.8
Fair Value, Measurements, Recurring [Member] | Venture capital investments [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	23.5	20.8
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash Equivalents, Fair Value Disclosure	0	0
Derivative contracts	0	0
Plan assets for deferred compensation	0	0
Total	0.1	44.8
Liabilities:
Derivative contracts	0	0
Contingent consideration	0	0
Total	0	0
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0	0
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Government securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0	0
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mortgage and other asset backed securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0	0
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Strategic investments [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0.1	44.8
Quoted Prices in Active Markets, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Venture capital investments [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0	0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring [Member]
Assets:
Cash Equivalents, Fair Value Disclosure	399.8	651.8
Derivative contracts	39.5	1.3
Plan assets for deferred compensation	11.6	13.0
Total	3,043.8	1,857.3
Liabilities:
Derivative contracts	0.5	12.2
Contingent consideration	0	0
Total	0.5	12.2
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	602.6	313.0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring [Member] | Government securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	1,716.5	785.3
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring [Member] | Mortgage and other asset backed securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	273.8	92.9
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring [Member] | Strategic investments [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0	0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring [Member] | Venture capital investments [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring [Member]
Assets:
Cash Equivalents, Fair Value Disclosure	0	0
Derivative contracts	0	0
Plan assets for deferred compensation	0	0
Total	23.5	20.8
Liabilities:
Derivative contracts	0	0
Contingent consideration	151.0	81.2
Total	151.0	81.2
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring [Member] | Corporate debt securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring [Member] | Government securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring [Member] | Mortgage and other asset backed securities [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring [Member] | Strategic investments [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring [Member] | Venture capital investments [Member]
Assets:
Fair Value, Measured on Recurring Basis, Investments	$ 23.5	$ 20.8

XML

Collaborations

12 Months Ended

Dec. 31, 2011

Other Consolidated Financial Statement Detail / Collaborations [Abstract]

Collaborations

20.    Collaborations

In connection with our business strategy, we have entered into various collaboration agreements which provide us with rights to develop, produce and market products using certain know-how, technology and patent rights maintained by our collaborative partners. Terms of the various collaboration agreements may require us to make milestone payments upon the achievement of certain product research and development objectives and pay royalties on future sales, if any, of commercial products resulting from the collaboration.

Genentech (Roche Group)

We collaborate with Genentech, Inc., a wholly-owned member of the Roche Group, on the development and commercialization of RITUXAN and other anti-CD20 products. Our collaboration rights are limited to the U.S. and our rights to products licensed by Genentech are dependent upon Genentech’s underlying license rights.

Our collaboration agreement does not have a fixed term and will continue in effect until we mutually agree to terminate the collaboration, except that if we undergo a change in control, as defined in the collaboration agreement, Genentech has the right to present an offer to buy the rights to RITUXAN and we must either accept Genentech’s offer or purchase Genentech’s rights on the same terms as its offer. Genentech will also be deemed concurrently to have purchased our rights to the other anti-CD20 products now in development in exchange for a royalty. Our collaboration with Genentech was created through a contractual arrangement and not through a joint venture or other legal entity.

In October 2010, we amended our collaboration agreement with Genentech with regard to the development of ocrelizumab and agreed to terms for the development of GA101, as summarized below. This amendment did not have an impact on our share of the co-promotion operating profits of RITUXAN in either 2011 or 2010.

Ocrelizumab

Genentech is now solely responsible for the further development and commercialization of ocrelizumab and funding future costs. Genentech cannot develop ocrelizumab in CLL, NHL or RA without our consent. We will receive tiered royalties between 13.5% and 24% on U.S. sales of ocrelizumab. Commercialization of ocrelizumab will not impact the percentage of the co-promotion profits we receive for RITUXAN.

GA101

We will pay 35% of the development and commercialization expenses of GA101 and will receive between 35% and 39% of the profits of GA101 based upon the achievement of certain sales milestones. Before the October 2010 amendment and restatement of our collaboration agreement, we had paid 30% of the GA101 development expenses. During the fourth quarter of 2010, we paid approximately $10.0 million to compensate Genentech for our increased share of such previously incurred expenses. Commercialization of GA101 will impact our percentage of the co-promotion profits for RITUXAN, as summarized in the table below.

RITUXAN

While Genentech is responsible for the worldwide manufacturing of RITUXAN, development and commercialization rights and responsibilities under this collaboration are divided as follows:

U.S.

We share with Genentech co-exclusive rights to develop, commercialize and market RITUXAN in the U.S. For 2010 and 2009, we contributed to the marketing and continued development of RITUXAN by maintaining a limited sales force dedicated to RITUXAN and performing limited development activity. However, during the fourth quarter of 2010, we agreed with Genentech to eliminate our current RITUXAN oncology and rheumatology sales force, with Genentech assuming sole responsibility for the U.S. sales and marketing of RITUXAN.

Canada

We and Genentech have assigned our rights under our collaboration agreement with respect to Canada to Roche.

Outside the U.S. and Canada

We have granted Genentech exclusive rights to develop, commercialize and market RITUXAN outside the U.S. and Canada. Under the terms of separate sublicense agreements between Genentech and Roche, development and commercialization of RITUXAN outside the U.S. and Canada is the responsibility of Roche and its sublicensees. We do not have any direct contractual arrangements with Roche or it sublicensees.

Under the terms of the collaboration agreement, we will be paid royalties between 10% and 12% on sales of RITUXAN outside the U.S. and Canada, with the royalty period lasting 11 years from the first commercial sale of RITUXAN on a country-by-country basis. The royalty periods for substantially all of the remaining royalty-bearing sales of RITUXAN in the rest of world markets will expire in 2012. As a result of these expirations, we expect royalty revenues on sales of RITUXAN in the rest of world to continue to decline in 2012. After 2012, we expect revenue on sales of RITUXAN in the rest of world will primarily be limited to our share of pre-tax co-promotion profits in Canada.

Co-promotion Profit-sharing Formula

Our current pretax co-promotion profit-sharing formula for RITUXAN, which resets annually, provides for a 30% share of co-promotion profits on the first $50.0 million of co-promotion operating profit with our share increasing to 40% if co-promotion operating profits exceed $50.0 million. Under the amended agreement, our share of the co-promotion profits for RITUXAN will change, as summarized in the table below, upon the following events:

• First New Product FDA Approval: the FDA’s first approval of an anti-CD20 product other than ocrelizumab and GA101 that is acquired or developed by Genentech and is subject to the collaboration agreement (New Product).

• First Non-CLL GA101 FDA Approval: the FDA’s first approval of GA101 in an indication other than CLL.

• GA101 CLL Sales Trigger: the first day of the quarter after U.S. gross sales of GA101 in any consecutive 12 month period reach $500.0 million.

Our share of the co-promotion operating profits for RITUXAN is calculated as follows:

				Before First New Product FDA Approval
Co-promotion Operating Profits†	After First New Product FDA Approval			First Non-CLL GA101 FDA Approval Occurs First			GA101 CLL Sales Trigger Occurs First
I. First $50.0 million		30	%		30	%		30	%
II. Above $50.0 million		—			—			35	%
A. Until First GA101 Threshold Date		38	%		39	%		—
B. After First GA101 Threshold Date
1(a). Until First Threshold Date		37.5	%		—			—
1(b). After First Threshold Date and  until Second Threshold Date		35	%		—			—
1(c). After Second Threshold Date		30	%		—			—
2. Until Second GA101 Threshold  Date		—			37.5	%		—
C. After Second GA101 Threshold Date		—			35	%		—

† First GA101 Threshold Date means the earlier of (1) the date of the First Non-CLL GA101 FDA Approval if U.S. gross sales of GA101 for the preceding consecutive 12 month period were at least $150.0 million or (2) the first day of the calendar quarter after the date of the First Non-CLL GA101 FDA Approval that U.S. gross sales of GA101 within any consecutive 12 month period have reached $150.0 million.

Second GA101 Threshold Date means the first day of the calendar quarter after U.S. gross sales of GA101 within any consecutive 12 month period have reached $500.0 million.

First Threshold Date means the earlier of (1) the GA101 CLL Sales Trigger, (2) the Second GA101 Threshold Date and (3) the later of (a) the first date that U.S. gross sales of New Products in any calendar year reach $150.0 million and (b) January 1 of the calendar year following the calendar year in which the First New Product FDA Approval occurs if gross sales of New Products reached $150.0 million within the same calendar year in which the First New Product FDA Approval occurred.

Second Threshold Date means the later of (1) the first date that U.S. gross sales of New Products in any calendar year reach $350.0 million and (2) January 1 of the calendar year following the calendar year in which the First Threshold Date occurs.

Our collaboration agreement also provides that we will be paid low single digit royalties on sales outside the U.S. and Canada of new anti-CD20 products developed or licensed by Genentech or controlled by us. These royalties will be payable for a period of 11 years from the first commercial sale of such products on a country-by-country basis.

Unconsolidated Joint Business Revenues

Revenues from unconsolidated joint business consists of (1) our share of pre-tax co-promotion profits in the U.S. (2) reimbursement of our selling and development expenses in the U.S.; and (3) revenue on sales of RITUXAN in the rest of world, which consist of our share of pre-tax co-promotion profits in Canada and royalty revenue on sales of RITUXAN outside the U.S. and Canada by Roche, and its sublicensees. Pre-tax co-promotion profits are calculated and paid to us by Genentech in the U.S. and by Roche in Canada. Pre-tax co-promotion profits consist of U.S. and Canadian sales of RITUXAN to third-party customers net of discounts and allowances less the cost to manufacture RITUXAN, third-party royalty expenses, distribution, selling, and marketing expenses, and joint development expenses incurred by Genentech, Roche and us. We record our share of the pretax co-promotion profits in Canada and royalty revenues on sales of RITUXAN outside the U.S. on a cash basis. Additionally, our share of the pre-tax co-promotion profits in the U.S. includes estimates made by Genentech and those estimates are subject to change. Actual results may ultimately differ from our estimates.

In June 2011, the collaboration recognized a charge of approximately $125.0 million, representing an estimate of compensatory damages and interest that might be awarded to Hoechst GmbH (Hoechst), in relation to an intermediate decision by the arbitrator in Genentech’s ongoing arbitration with Hoechst. As a result of this charge to the collaboration, our share of RITUXAN revenues from unconsolidated joint business was reduced by approximately $50.0 million in the second quarter of 2011. This $50.0 million amount reflects the estimate of the loss that we may incur in the event of a final arbitration award unfavorable to Genentech. The actual amount of our share of any damages may vary from this estimate depending on the nature or amount of any damages awarded to Hoechst, or if the arbitrator’s final decision is successfully challenged by Genentech. For additional information related to this matter, please read Note 21, Litigation to these consolidated financial statements.

Revenues from unconsolidated joint business are summarized as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Biogen Idec’s share of pre-tax co-promotion profits in the U.S.	$	872.7	$	848.0	$	773.6
Reimbursement of our selling and development expenses in the U.S.		6.1		58.3		65.6
Revenue on sales of RITUXAN in the rest of world		117.8		170.9		255.7
Total unconsolidated joint business revenues	$	996.6	$	1,077.2	$	1,094.9

In 2011, 2010, and 2009, the 40% co-promotion profit-sharing threshold was met during the first quarter.

Currently, we record our share of the expenses incurred by the collaboration for the development of anti-CD20 products in research and development expense in our consolidated statements of income. We incurred $26.9 million, $50.6 million, and $62.5 million in development expense for the years ended December 31, 2011, 2010, and 2009, respectively. After an anti-CD20 product is approved, we will record our share of the development expenses related to that product as a reduction of our share of pre-tax co-promotion profits in revenues from unconsolidated joint business. As a result of the October 2010 amendment of our collaboration agreement with Genentech, we are no longer responsible for any development costs for ocrelizumab.

Elan

We collaborate with Elan on the development, manufacture and commercialization of TYSABRI. Under the terms of our collaboration agreement, we manufacture TYSABRI and collaborate with Elan on the product’s marketing, commercial distribution and ongoing development activities. The agreement is designed to effect an equal sharing of profits and losses generated by the activities of our collaboration. Under the agreement, however, once sales of TYSABRI exceeded specific thresholds, Elan was required to make milestone payments to us in order to continue sharing equally in the collaboration’s results. As of December 31, 2010, Elan has made milestone payments to us of $75.0 million in the third quarter of 2008 and $50.0 million in the first quarter of 2009. These amounts were recorded as deferred revenue upon receipt and are recognized as revenue in our consolidated statements of income based on the ratio of units shipped in the current period over the total units expected to be shipped over the remaining term of the collaboration. No additional milestone payments are required under the agreement to maintain the current profit sharing split and as of December 31, 2011, $100.6 million remains to be amortized. The term of our collaboration agreement extends until November 2019. Each of Biogen Idec and Elan has the option to buy the other party’s rights to TYSABRI upon expiration of the term or if the other party undergoes a change of control (as defined in the collaboration agreement). In addition, each of Biogen Idec and Elan can terminate the agreement for convenience or material breach by the other party, in which case, among other things, certain licenses, regulatory approvals and other rights related to the manufacture, sale and development of TYSABRI are required to be transferred to the party that is not terminating for convenience or is not in material breach of the agreement.

In the U.S., we sell TYSABRI to Elan who sells the product to third party distributors. Our sales price to Elan in the U.S. is set prior to the beginning of each quarterly period to effect an approximate equal sharing of the gross margin between Elan and us. We recognize revenue for sales in the U.S. of TYSABRI upon Elan’s shipment of the product to the third party distributors, at which time all revenue recognition criteria have been met. As of December 31, 2011 and 2010, we had deferred revenue of $23.8 million and $20.8 million, respectively, for shipments to Elan that remained in Elan’s ending inventory pending shipment of the product to the third party distributors. We incur manufacturing and distribution costs, research and development expenses, commercial expenses, and general and administrative expenses related to TYSABRI. We record these expenses to their respective line items within our consolidated statements of income when they are incurred. Research and development and sales and marketing expenses are shared equally with Elan and the reimbursement of these expenses is recorded as reductions of the respective expense categories. During the years ended December 31, 2011, 2010, and 2009, we recorded $47.5 million, $49.8 million and $25.3 million, respectively, as reductions of research and development expense for reimbursements from Elan. In addition, for the years ended December 31, 2011, 2010, and 2009, we recorded $77.3 million, $68.5 million and $62.5 million, respectively, as reductions of selling, general and administrative expense for reimbursements from Elan.

In the rest of world, we are responsible for distributing TYSABRI to customers and are primarily responsible for all operating activities. Generally, we recognize revenue for sales of TYSABRI in the rest of world at the time of product delivery to our customers. Payments are made to Elan for their share of the rest of world net operating profits to effect an equal sharing of collaboration operating profit. These payments also include the reimbursement for our portion of third-party royalties that Elan pays on behalf of the collaboration relating to rest of world sales. As rest of world sales of TYSABRI increase, our collaboration profit sharing expense is expected to increase. These amounts are reflected in the collaboration profit sharing line in our consolidated statements of income. For the years ended December 31, 2011, 2010 and 2009, $317.8 million, $258.1 million and $215.9 million, respectively, was reflected in the collaboration profit sharing line for our collaboration with Elan.

Acorda

In 2009, we entered into a collaboration and license agreement with Acorda Therapeutics, Inc. (Acorda) to develop and commercialize products containing fampridine in markets outside the U.S. We also have responsibility for regulatory activities and the future clinical development of related products in those markets. The $110.0 million upfront payment made on July 1, 2009 to Acorda was recorded as research and development expense during the second quarter 2009 as the product candidate had not received regulatory approval.

In July 2011, the European Commission (EC) granted a conditional marketing authorization for fampridine in the E.U., under the trade name FAMPYRA, which triggered a $25.0 million milestone payment. This payment was made to Acorda Therapeutics, Inc. (Acorda) in the third quarter of 2011 and was capitalized as an intangible asset. FAMPYRA is an oral compound indicated as a treatment to improve walking ability in adult patients with MS who have walking disability. As part of the conditions of the conditional marketing authorization for FAMPYRA, we will provide additional data from on-going clinical studies regarding FAMPYRA’s benefits and safety in the long term. A conditional marketing authorization is renewable annually and is granted to a medicinal product with a positive benefit/risk assessment that fulfills an unmet medical need when the benefit to public health of immediate availability outweighs the risk inherent in the fact that additional data are still required.

FAMPYRA was commercially launched in Australia, Denmark, Germany, Norway, and the UK in 2011. In 2012, we plan to launch FAMPYRA in Austria, Canada, Finland, France, Greece, Italy, Ireland, the Netherlands, Sweden and other markets. The exact timing of these launches remains subject to our ability to obtain reimbursement approval within the respective markets.

We have a license from Acorda to develop and commercialize FAMPYRA in all markets outside the U.S. Under the terms of the collaboration and license agreement, we will pay Acorda tiered royalties based on the level of ex-U.S. net sales. We may pay up to $375.0 million of additional milestone payments to Acorda, based on the successful achievement of certain regulatory and commercial milestones. The next expected milestone would be $15.0 million, due when ex-U.S. net sales reach $100.0 million over a period of four consecutive quarters. We will capitalize these additional milestones as intangible assets upon achievement of the milestone and will be amortized utilizing an economic consumption model. Royalty payments will be recognized as a cost of goods sold.

In connection with the collaboration and license agreement, we have also entered into a supply agreement with Acorda for the commercial supply of FAMPYRA. This agreement is a sublicense arrangement of an existing agreement between Acorda and Elan whereby Elan is responsible for the manufacture of the commercial supply of FAMPYRA. In 2011, Alkermes acquired Elan Drug Technologies, the manufacturing unit of Elan. Alkermes has assumed responsibility for the manufacture and commercial supply of FAMPYRA.

A summary of activity related to this collaboration is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Upfront and milestones payments made to Acorda	$	25.0	$	—	$	110.0
Total expense incurred by Biogen Idec excluding upfront and milestones payments	$	22.3	$	22.8	$	4.7
Total expense reflected within our statements of income	$	22.3	$	22.8	$	114.7
Total capitalized as an intangible asset	$	25.0	$	—	$	—

A summary of activity related to this collaboration since inception, along with an estimate of additional future development expense expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Acorda	$	135.0
Total expense incurred by Biogen Idec, excluding upfront and milestone payments	$	49.9

We expect that we may incur approximately $50.0 million of additional cost associated with meeting the requirements of the conditional marketing authorization.

Portola Pharmaceuticals, Inc.

On October 26, 2011, we entered into an exclusive, worldwide collaboration and license agreement with Portola Pharmaceuticals, Inc. (Portola) under which both companies will develop and commercialize highly selective, novel oral Syk inhibitors for the treatment of various autoimmune and inflammatory diseases, including rheumatoid arthritis and systemic lupus erythematosus. The collaboration’s lead molecule, PRT062607, is currently in Phase 1 studies.

Under the terms of the agreement, we provided Portola with an upfront payment of $36.8 million in cash and purchased $8.2 million in Portola equity, with potential additional payments of up to $508.5 million based on the achievement of certain development and regulatory milestones. We will lead the global development and commercialization efforts for the Syk inhibitor program in major indications such as rheumatoid arthritis and lupus, while Portola will lead U.S. development and commercialization efforts for select smaller indications as well as discovery efforts for follow-on Syk inhibitors. Portola retains an option to co-promote alongside us in the U.S. in major indications. Worldwide costs and profits will be split by us and Portola 75% and 25%, respectively.

A summary of collective activity related to these programs is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Total expense incurred by the collaboration	$	1.1	$	—	$	—
Total expense reflected within our consolidated statements of income, excluding upfront and milestone payments	$	0.9	$	—	$	—

A summary of activity related to this collaboration since inception, along with an estimate of additional future development expense expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront payments paid to Portola	$	36.8
Total development expense incurred by Biogen Idec Inc., excluding upfront and milestone payments	$	0.9
Estimate of additional amounts to be incurred by Biogen Idec in development of PRT062607	$	675.0

Swedish Orphan Biovitrum

In January 2007, we acquired 100% of the stock of Syntonix. Syntonix had previously entered into a collaboration agreement with Swedish Orphan Biovitrum (Sobi) to jointly develop and commercialize Factor VIII and Factor IX hemophilia products. In February 2010, we restructured the collaboration agreement and assumed full development responsibilities and costs, as well as manufacturing rights. In addition, the cross-royalty rates were reduced and commercial rights for certain territories were changed. As a result, we now have commercial rights for North America (the Biogen North America Territory) and for rest of the world markets outside of Europe, Russia, Turkey and certain countries in the Middle East (the Biogen Direct Territory). Subject to the exercise of an option right, Sobi will have commercial rights in Europe, Russia, Turkey and certain countries in the Middle East (the Sobi Territory).

Under the terms of the option right, Sobi may, following our submission of a marketing authorization application to the EMA for each product developed under the collaboration, opt to take over final regulatory approval, pre-launch and commercialization activities in the Sobi Territory by making a payment into escrow of $10.0 million per product. Upon EMA regulatory approval of each such product, Sobi will be liable to reimburse us 50% of the sum of all shared manufacturing and development expenses incurred by us from October 1, 2009 through the date on which Sobi is registered as the marketing authorization holder for the applicable product, as well as 100% of certain development expenses incurred exclusively for the benefit of the Sobi Territory (the Opt-In Consideration). To effect Sobi’s reimbursement to us for the Opt-In Consideration exceeding the escrow payment for each product, the cross-royalty structure for direct sales in each company’s respective territories will be adjusted until the Opt-In Consideration is paid in full (the Reimbursement Period). The mechanism for reimbursement is outlined in the table below.

Under the amended agreement amounts are payable as follows:

			Rates should Sobi exercise its option right (3)
Royalty and Net Revenue Share Rates:	Method	Rate prior to 1st commercial sale in the Sobi Territory:	Base Rate following 1st commercial sale in the Sobi Territory:	Rate during the Reimbursement Period:
Sobi rate to Biogen on net sales in the Sobi Territory	Royalty	N/A	10 to 12%	Base Rate plus 5%
Biogen rate to Sobi on net sales in the Biogen North America Territory	Royalty	2%	10 to 12%	Base Rate less 5%
Biogen rate to Sobi on net sales in the Biogen Direct Territory	Royalty	2%	15 to 17%	Base Rate less 5%
Biogen rate to Sobi on net revenue (1) from the Biogen Distributor Territory (2)	Net Revenue Share	10%	50%	Base Rate less 15%

(1) Net revenue represents Biogen Idec’s pre-tax receipts from third-party distributors, less expenses incurred by Biogen Idec in the conduct of commercialization activities supporting the distributor activities.

(2) The Biogen Distributor Territory represents Biogen territories where sales are derived utilizing a third-party distributor.

(3) A credit will be issued to Sobi against its reimbursement of the Opt-in Consideration in an amount equal to the difference in the rate paid by Biogen Idec to Sobi on sales in the Biogen territories for certain periods prior to the first commercial sale in the Sobi Territory versus the rate that otherwise would have been payable on such sales.

If the reimbursement of the opt-in consideration has not been achieved within six years of the first commercial sale of such product, we maintain the right to require Sobi to pay any remaining balances due to us within 90 days of the six year anniversary date of the first commercial sale.

Should Sobi not exercise its option right with respect to one or both products or should Sobi terminate the agreement with respect to one or both products we will obtain full worldwide development and commercialization rights for such affected products and we will be obligated to pay royalties to Sobi subject to separate terms, as defined under the restructured collaboration agreement. In addition, if EMA approval for any product is not granted within 18 months of the applicable EMA filing date, Sobi shall have the right to require that the escrow payment be refunded and revoke its option right for such product.

Amounts incurred by us in the development of long-lasting recombinant Factor VIII and Factor IX are reflected as research and development expenses in our consolidated statements of income. Prior to the restructuring of our collaboration agreement, our research and development expenses reflected reimbursement from Sobi in accordance with a cost-sharing agreement then in effect. Following the restructuring of our collaboration agreement, amounts incurred by us in the development of long-lasting recombinant Factor VIII and Factor IX are reflected as research and development expenses in our consolidated statements of income which include reimbursement of certain ongoing Sobi development expenses. A summary of collective activity related to these programs is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Total expense incurred by collaboration	$	129.6	$	78.9	$	44.9
Total expense reflected within our consolidated statements of income	$	129.6	$	78.5	$	22.5

A summary of activity related to this collaboration since inception, along with an estimate of additional future development expense expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront and milestone payments received from Sobi	$	5.0
Total development expense incurred by Biogen Idec Inc., excluding upfront and milestone payments	$	262.7
Estimate of additional amounts expected to be incurred by Biogen Idec in development of Factors VIII and IX	$	420.0

Abbott Biotherapeutics Corp. (formerly Facet Biotech)

We have a collaboration agreement with Abbott Biotherapeutics Corp. (Abbott) aimed at advancing the development and commercialization of daclizumab in MS. Under the agreement, development and commercialization costs and profits are shared equally. In January 2010, we agreed with our collaborator, Abbott, to assume the manufacture of daclizumab.

Based upon our current development plans, we may incur up to an additional $60.0 million of payments upon achievement of development and commercial milestones related to the development of daclizumab.

A summary of activity related to this collaboration is as follows:

	For the Years Ended December 31,
(In millions)	2011		2010		2009
Total expense incurred by the collaboration	$	104.4	$	74.8	$	40.8
Biogen Idec’s share of expense reflected within our consolidated statements of income	$	52.2	$	37.4	$	20.4

Total expense incurred by the collaboration in 2010, reflects the $30.0 milestone paid to Abbott in May 2010 upon initiation of patient enrollment in a Phase 3 trial of daclizumab in relapsing MS. A summary of activity related to this collaboration since inception, along with an estimate of additional future development expense expected to be incurred by us, is as follows:

(In millions)	As of December 31, 2011
Total upfront and milestone payments made to Abbott	$	80.0
Total development expense incurred by Biogen Idec, excluding upfront and milestone payments	$	212.1
Estimate of additional amounts to be incurred by us in development of current indications of daclizumab	$	280.0

Vernalis

In April 2011, we agreed to terminate our collaboration with Vernalis plc (Vernalis) for the development and commercialization of an adenosine A2a receptor antagonist for treatment of Parkinson’s disease effective April 11, 2011. Under the terms of the agreement, we have returned the program to Vernalis and have no further license to or continuing involvement in the development of, this compound and its related intellectual property. In exchange, we will receive a royalty on future net sales if this compound is ultimately commercialized. We funded development costs through the termination date and have no other remaining development obligations after that date. Development expense incurred by this collaboration in 2011 was insignificant.

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Collaborations (Details 5) (Abbott Biotherapeutics [Member], USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of activity related to collaboration with Facet Biotech
Total expense incurred by collaboration	$ 104,400,000	$ 74,800,000	$ 40,800,000
Total expense reflected within our consolidated statements of income	52,200,000	37,400,000	20,400,000
Summary of activity related to collaboration, along with an estimate of additional future development expense
Total upfront and milestone payments made to Collaborative Partner	80,000,000	30,000,000
Total expense incurred by Biogen Idec, excluding upfront and milestone payments	212,100,000
Daclizumab And Volociximab [Member]
Summary of activity related to collaboration, along with an estimate of additional future development expense
Estimate of additional amounts to be incurred by us in Product development	$ 280,000,000

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Quarterly Financial Data (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Selected Quarterly Financial Information [Abstract]
Revenue on sales of RITUXAN in the rest of world	$ 996,600,000	$ 975,800,000	$ 956,700,000	$ 907,100,000	$ 909,800,000	$ 876,900,000	$ 859,200,000	$ 824,200,000	$ 3,836,117,000	$ 3,470,056,000	$ 3,152,941,000
Unconsolidated joint business revenues	257,500,000	266,500,000	216,500,000	256,100,000	258,000,000	258,000,000	306,400,000	254,900,000	996,597,000	1,077,244,000	1,094,863,000
Other	72,600,000	67,700,000	35,500,000	40,100,000	51,400,000	41,000,000	47,100,000	29,700,000	215,920,000	169,123,000	129,544,000
Total revenues	1,326,700,000	1,309,900,000	1,208,600,000	1,203,300,000	1,219,000,000	1,175,800,000	1,212,700,000	1,108,900,000	5,048,634,000	4,716,423,000	4,377,348,000
Gross Profit	1,187,100,000	1,186,400,000	1,108,100,000	1,100,200,000	1,118,800,000	1,079,900,000	1,105,700,000	1,011,800,000	4,581,900,000	4,316,200,000
Net income	300,200,000	353,700,000	304,000,000	308,800,000	271,800,000	112,200,000	294,600,000	220,000,000	1,266,686,000	898,573,000	977,062,000
Net income attributable to Biogen Idec Inc	$ 300,200,000	$ 351,800,000	$ 288,000,000	$ 294,300,000	$ 240,300,000	$ 254,100,000	$ 293,400,000	$ 217,400,000	$ 1,234,428,000	$ 1,005,273,000	$ 970,132,000
Basic earnings per share attributable to Biogen Idec Inc.	$ 1.24	$ 1.45	$ 1.19	$ 1.22	$ 1.00	$ 1.06	$ 1.13	$ 0.80	$ 5.09	$ 3.98	$ 3.37
Diluted earnings per share attributable to Biogen Idec Inc.	$ 1.22	$ 1.43	$ 1.18	$ 1.20	$ 0.99	$ 1.05	$ 1.12	$ 0.80	$ 5.04	$ 3.94	$ 3.35

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Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Marketable Securities including Strategic Investments
Fair Value	$ 2,592.9	$ 1,191.2
Gross Unrealized Gains	3.2	3.5
Gross Unrealized Losses	(3.1)	(1.3)
Amortized Cost	2,592.8	1,189.0
Corporate debt securities Current [Member]
Marketable Securities including Strategic Investments
Fair Value	155.0	93.2
Gross Unrealized Gains	0.2	0.1
Gross Unrealized Losses	(0.1)	0
Amortized Cost	154.9	93.1
Corporate debt securities Non-current [Member]
Marketable Securities including Strategic Investments
Fair Value	447.6	219.8
Gross Unrealized Gains	1.2	2.1
Gross Unrealized Losses	(1.5)	(0.5)
Amortized Cost	447.9	218.2
Government securities Current [Member]
Marketable Securities including Strategic Investments
Fair Value	1,021.0	352.8
Gross Unrealized Gains	0.4	0.2
Gross Unrealized Losses	0	0
Amortized Cost	1,020.6	352.6
Government securities Non-current [Member]
Marketable Securities including Strategic Investments
Fair Value	695.5	432.5
Gross Unrealized Gains	0.9	0.6
Gross Unrealized Losses	(0.2)	(0.6)
Amortized Cost	694.8	432.5
Mortgage and other asset backed securities Current [Member]
Marketable Securities including Strategic Investments
Fair Value	0.1	2.1
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Amortized Cost	0.1	2.1
Mortgage and other asset backed securities Non-current [Member]
Marketable Securities including Strategic Investments
Fair Value	273.7	90.8
Gross Unrealized Gains	0.5	0.5
Gross Unrealized Losses	(1.3)	(0.2)
Amortized Cost	274.5	90.5
Other strategic investments Non-current [Member]
Marketable Securities including Strategic Investments
Gross Unrealized Gains	0	17.5
Gross Unrealized Losses	(0.1)	0
Amortized Cost	0.2	27.3
Strategic investments, non-current Fair Value	$ 0.1	$ 44.8

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Revenue Reserves (Tables)

12 Months Ended

Dec. 31, 2011

Revenue Reserves [Abstract]

Analysis of the amount of, and change in, reserves

(In millions)	Discounts			Contractual Adjustments			Returns			Total
2011
Beginning balance	$	13.9		$	107.0		$	21.1		$	142.0
Current provisions relating to sales in current year		96.0			360.4			15.7			472.1
Adjustments relating to prior years		—			(14.0	)		(0.9	)		(14.9	)
Payments/returns relating to sales in current year		(84.3	)		(266.0	)		(0.4	)		(350.7	)
Payments/returns relating to sales in prior years		(13.0	)		(68.1	)		(11.8	)		(92.9	)
Ending balance	$	12.6		$	119.3		$	23.7		$	155.6
(In millions)	Discounts			Contractual Adjustments			Returns			Total
2010
Beginning balance	$	13.9		$	70.3		$	18.9		$	103.1
Current provisions relating to sales in current year		80.6			285.0			16.1			381.7
Adjustments relating to prior years		(2.7	)		(2.4	)		(1.8	)		(6.9	)
Payments/returns relating to sales in current year		(68.7	)		(184.3	)		(0.8	)		(253.8	)
Payments/returns relating to sales in prior years		(9.2	)		(61.6	)		(11.3	)		(82.1	)
Ending balance	$	13.9		$	107.0		$	21.1		$	142.0
(In millions)	Discounts			Contractual Adjustments			Returns			Total
2009
Beginning balance	$	9.2		$	48.1		$	18.1		$	75.4
Current provisions relating to sales in current year		74.0			192.5			15.8			282.3
Adjustments relating to prior years		—			—			0.8			0.8
Payments/returns relating to sales in current year		(60.8	)		(124.4	)		(0.6	)		(185.8	)
Payments/returns relating to sales in prior years		(8.5	)		(45.9	)		(15.2	)		(69.6	)
Ending balance	$	13.9		$	70.3		$	18.9		$	103.1

Total reserves, included in consolidated balance sheets

	As of December 31,
(In millions)	2011		2010
Reduction of accounts receivable	$	40.6	$	36.7
Current liability		115.0		105.3
Total reserves	$	155.6	$	142.0

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Equity

12 Months Ended

Dec. 31, 2011

Equity/Accumulated Other Comprehensive Income (Loss) [Abstract]

Equity

13.    Equity

Preferred Stock

The following table describes the number of shares authorized, issued and outstanding of our preferred stock as of December 31, 2011 and 2010:

	As of December 31, 2011						As of December 31, 2010
(In thousands)	Authorized		Issued		Outstanding		Authorized		Issued		Outstanding
Series A		1,750		—		—		1,750		8		8
Series X junior participating		1,000		—		—		1,000		—		—
Undesignated		5,250		—		—		5,250		—		—
Total preferred stock		8,000		—		—		8,000		8		8

We have 8,000,000 shares of Preferred Stock authorized, of which 1,750,000 shares have been designated as Series A Preferred Stock and 1,000,000 shares have been designated as Series X Junior Participating Preferred Stock. The shares may be issued without a vote or action of stockholders from time to time in classes or series with the designations, powers, preferences, and the relative, participating, optional or other special rights of the shares of each such class or series and any qualifications, limitations or restrictions thereon as set forth in the instruments governing such shares. Any such Preferred Stock may rank prior to common stock as to dividend rights, liquidation preference or both, and may have full or limited voting rights and may be convertible into shares of common stock.

There were 8,221 shares of Series A Preferred Stock issued and outstanding as of December 31, 2010. In March 2011, the remaining 8,221 shares of our Series A Preferred Stock were converted into 493,260 shares of common stock by the holder pursuant to the conversion terms of the Series A Preferred Stock. As of December 31, 2011, there are no shares of preferred stock issued and outstanding.

Common Stock

The following table describes the number of shares authorized, issued and outstanding of our common stock as of December 31, 2011 and 2010:

As of December 31, 2011

As of December 31, 2010

(In thousands)

Authorized

Issued

Outstanding

Authorized

Issued

Outstanding

Common stock

1,000,000

255,633

242,115

1,000,000

248,200

240,538

Share Repurchases

In February 2011, our Board of Directors authorized the repurchase of up to 20.0 million shares of our common stock. We expect to use this repurchase program principally to offset common stock issued under our share-based compensation plans. This repurchase program does not have an expiration date. Under this authorization, we repurchased approximately 6.0 million shares of our common stock at a cost of $498.0 million during 2011. These repurchases were recorded as repurchases of Treasury Stock.

From January 1, 2012 through January 31, 2012, we repurchased approximately 3.5 million shares of our common stock at a total cost of approximately $401.5 million under our 2011 stock repurchase authorization. As of January 31, 2012, approximately 10.5 million shares of our common stock remain available to repurchase under this program.

During 2010, we repurchased approximately 40.3 million shares of our common stock at a cost of approximately $2.1 billion under our 2010 and 2009 stock repurchase authorizations. We retired all of these shares as they were acquired. In connection with this retirement, we recorded a reduction in additional paid-in-capital of approximately $2.1 billion. The 2010 and 2009 share repurchase programs were completed during 2010.

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Share-Based Payments (Details 10) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Shares issued under employee stock purchase plan
Shares issued under ESPP	0.4	0.6	0.6
Cash received under ESPP	$ 22.8	$ 23.5	$ 22.6