Business (Policies)	9 Months Ended
Sep. 30, 2011
Business and Collaborations [Abstract]
Overview	Biogen Idec is a global biotechnology company focused on discovering, developing, manufacturing and marketing therapies for serious diseases with a focus on neurology, immunology and hemophilia. We currently have five marketed products: AVONEX, TYSABRI, RITUXAN, FAMPYRA, and FUMADERM. Our marketed products are used for the treatment of multiple sclerosis (MS), non-Hodgkin’s lymphoma (NHL), rheumatoid arthritis (RA), Crohn’s disease, chronic lymphocytic leukemia (CLL), and psoriasis.
Basis of Presentation	In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of our financial statements for interim periods in accordance with accounting principles generally accepted in the United States (U.S. GAAP). The information included in this quarterly report on Form 10-Q should be read in conjunction with our consolidated financial statements and the accompanying notes included in our Annual Report on Form 10-K for the year ended December 31, 2010 (2010 Form 10-K). Our accounting policies are described in the “Notes to Consolidated Financial Statements” in our 2010 Form 10-K and updated, as necessary, in this Form 10-Q. The year-end condensed consolidated balance sheet data presented for comparative purposes was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. The results of operations for the three and nine months ended September 30, 2011 are not necessarily indicative of the operating results for the full year or for any other subsequent interim period.
Consolidation	Our condensed 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 less than a 100% interest, 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 have been 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 evaluated 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 condensed 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, 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.
Subsequent Events	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 RA and systemic lupus erythematosus. The collaboration’s lead molecule, PRT062607, is currently in Phase 1 studies. Under the terms of the agreement, we will provide Portola with an upfront payment of $36.0 million in cash and purchase $9.0 million in Portola equity, with 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 RA 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. Completion of the transaction is subject to customary closing conditions, including antitrust clearance by the U.S. government under the Hart-Scott-Rodino Act.
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* 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. 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). In addition, we 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 to 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. *Unconsolidated Joint Business Revenues* 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, distribution, selling and marketing, and 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 supplied by Genentech. *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 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 ever unable to accurately estimate revenue, then we record revenues on a cash basis.
Intangibles - Goodwill and Other	In September 2011, the 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. We are currently evaluating the potential impact the early adoption of this statement may have on our financial position and 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. This ASU is required to be applied retrospectively and is effective for fiscal years and interim periods within those years beginning after December 15, 2011, which for Biogen Idec means January 1, 2012. As this accounting standard only requires enhanced disclosure, the adoption of this standard will not impact our financial position or results of operations.
Fair Value Measurement	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. We do not expect that adoption of this standard will have a material impact on our financial position or results of operations. In January 2010, we adopted a newly issued accounting standard which requires additional disclosure about the amounts of and reasons for significant transfers in and out of Level 1 and Level 2 fair value measurements. This standard also clarified existing disclosure requirements related to the level of disaggregation of fair value measurements for each class of assets and liabilities and requires disclosures about inputs and valuation techniques used to measure fair value for both recurring and nonrecurring Level 2 and Level 3 measurements. In addition, effective for interim and annual periods beginning after December 15, 2010, which for Biogen Idec was January 1, 2011; this standard further requires an entity to present disaggregated information about activity in Level 3 fair value measurements on a gross basis, rather than as one net amount. As this newly issued accounting standard only requires enhanced disclosure, the adoption of this standard did not impact our financial position or results of operations.

Business (Policies)

9 Months Ended

Sep. 30, 2011

Business and Collaborations [Abstract]

Biogen Idec is a global biotechnology company focused on discovering, developing, manufacturing and marketing therapies for serious diseases with a focus on neurology, immunology and hemophilia. We currently have five marketed products: AVONEX, TYSABRI, RITUXAN, FAMPYRA, and FUMADERM. Our marketed products are used for the treatment of multiple sclerosis (MS), non-Hodgkin’s lymphoma (NHL), rheumatoid arthritis (RA), Crohn’s disease, chronic lymphocytic leukemia (CLL), and psoriasis.

Basis of Presentation

In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of our financial statements for interim periods in accordance with accounting principles generally accepted in the United States (U.S. GAAP). The information included in this quarterly report on Form 10-Q should be read in conjunction with our consolidated financial statements and the accompanying notes included in our Annual Report on Form 10-K for the year ended December 31, 2010 (2010 Form 10-K). Our accounting policies are described in the “Notes to Consolidated Financial Statements” in our 2010 Form 10-K and updated, as necessary, in this Form 10-Q. The year-end condensed consolidated balance sheet data presented for comparative purposes was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. The results of operations for the three and nine months ended September 30, 2011 are not necessarily indicative of the operating results for the full year or for any other subsequent interim period.

Consolidation

Our condensed 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 less than a 100% interest, 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 have been 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 evaluated 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 condensed 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, 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.

Subsequent Events

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 RA and systemic lupus erythematosus. The collaboration’s lead molecule, PRT062607, is currently in Phase 1 studies.

Under the terms of the agreement, we will provide Portola with an upfront payment of $36.0 million in cash and purchase $9.0 million in Portola equity, with 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 RA 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.

Completion of the transaction is subject to customary closing conditions, including antitrust clearance by the U.S. government under the Hart-Scott-Rodino Act.

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

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. 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). In addition, we 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 to 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.

Unconsolidated Joint Business Revenues

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, distribution, selling and marketing, and 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 supplied by Genentech.

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 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 ever unable to accurately estimate revenue, then we record revenues on a cash basis.

Intangibles - Goodwill and Other

In September 2011, the 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. We are currently evaluating the potential impact the early adoption of this statement may have on our financial position and 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. This ASU is required to be applied retrospectively and is effective for fiscal years and interim periods within those years beginning after December 15, 2011, which for Biogen Idec means January 1, 2012. As this accounting standard only requires enhanced disclosure, the adoption of this standard will not impact our financial position or results of operations.

Fair Value Measurement

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. We do not expect that adoption of this standard will have a material impact on our financial position or results of operations.

In January 2010, we adopted a newly issued accounting standard which requires additional disclosure about the amounts of and reasons for significant transfers in and out of Level 1 and Level 2 fair value measurements. This standard also clarified existing disclosure requirements related to the level of disaggregation of fair value measurements for each class of assets and liabilities and requires disclosures about inputs and valuation techniques used to measure fair value for both recurring and nonrecurring Level 2 and Level 3 measurements. In addition, effective for interim and annual periods beginning after December 15, 2010, which for Biogen Idec was January 1, 2011; this standard further requires an entity to present disaggregated information about activity in Level 3 fair value measurements on a gross basis, rather than as one net amount. As this newly issued accounting standard only requires enhanced disclosure, the adoption of this standard did not impact our financial position or results of operations.