Granted (in shares) Number of shares granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Purchased intangible assets Deferred Tax Liabilities, Intangible Assets Issuance of common stock under stock option and stock purchase plans (in shares) Stock Issued During Period, Shares, Treasury Stock Reissued Total payment to enter collaboration agreement Total payment to enter collaboration agreement Total payment to enter collaboration agreement Intangible assets Intangible Assets Excluding Goodwill [Table Text Block] Intangible assets excluding goodwill. Payments and other Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Denali and Sangamo Denali and Sangamo [Member] Denali and Sangamo Technological and regulatory success, probability Technological and Regulatory Success, Probability Technological and Regulatory Success, Probability Series A Series A Preferred Stock [Member] GERMANY GERMANY Liabilities associated with uncertain tax positions Liability for Uncertainty in Income Taxes, Current ZINBRYTA ZINBRYTA [Member] ZINBRYTA [Member] Gains (losses) on net investment hedges, net of tax Other Comprehensive Income (Loss), Derivative, Excluded Component, Increase (Decrease), after Adjustments and Tax Number of equal annual increments Number Of Equal Annual Increments Number of equal annual increments. Series X junior participating Series X Preferred Stock [Member] Series X preferred stock. Pre-tax charge Pre-tax Charge, Payment of Early Call Premium and Write off of Remaining Unamortized Debt Issuance Costs, Net of Derivative Gain Pre-tax Charge, Payment of Early Call Premium and Write off of Remaining Unamortized Debt Issuance Costs, Net of Derivative Gain Research and Development Expenses Research, Development, and Computer Software, Policy [Policy Text Block] Other Foreign Earnings Other Foreign Earnings [Member] Other Foreign Earnings [Member] Statistical Measurement [Domain] Statistical Measurement [Domain] LIABILITIES AND EQUITY Liabilities and Equity [Abstract] Upfront payment for collaboration agreement Upfront payment for collaboration agreement Upfront payment for collaboration agreement Share-based Compensation Arrangement by Share-based Payment Award Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Distribution to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Purchase of subsidiaries and affiliates Payments to Acquire Interest in Subsidiaries and Affiliates Ionis Pharmaceuticals Ionis Pharmaceuticals [Member] Ionis Pharmaceuticals [Member] Preferred stock Preferred Stock [Member] Denali Therapeutics Denali Therapeutics Inc. [Member] Denali Therapeutics Inc. Security Exchange Name Security Exchange Name Royalty percentage to be received Future Royalties Percentage To Be Received On Sale Of Product Future royalties percentage to be received on sale of product. Foreign earnings type [Domain] Foreign earnings type [Domain] [Domain] for Foreign earnings type [Axis] Operating lease supplemental cash flow disclosure Operating lease supplemental cash flow disclosure [Table Text Block] Operating lease supplemental cash flow disclosure [Table Text Block] Performance stock units settled in cash activity Performance Stock Units Settled in Cash [Table Text Block] Performance Stock Units Settled in Cash [Table Text Block] Total deferred charges and prepaid taxes Total deferred charges and prepaid taxes Total deferred charges and prepaid taxes DENMARK DENMARK Amortized Cost Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract] Cash settled performance shares activity Schedule Of Cash Settled Performance Shares Activity [Table Text Block] Schedule Of Cash Settled Performance Shares Activity. SPINRAZA SPINRAZA [Member] SPINRAZA [Member] Proceeds from borrowings Proceeds from Issuance of Long-term Debt Retirement of common stock pursuant to the share repurchase program, at cost Treasury Stock, Retired, Cost Method, Amount Total current liabilities Liabilities, Current Reclassification out of Accumulated Other Comprehensive Income Reclassification out of Accumulated Other Comprehensive Income [Member] Performance units Performance Shares [Member] Beginning balance, weighted average grant date fair value (in dollars per share) Ending balance, weighted average grant date fair value (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Realized losses Debt Securities, Available-for-sale, Realized Loss Capitalized inventory Other Inventory, Capitalized Costs, Gross ASSETS Assets [Abstract] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Investment, Name [Axis] Equity Method Investee, Name [Axis] Investment, Name [Axis] Accounting Policies [Abstract] Accounting Policies [Abstract] Revenue, Major Customer [Line Items] Revenue, Major Customer [Line Items] Acquisition of Nightstar Therapeutics plc, net of cash acquired Payments to Acquire Business Two, Net of Cash Acquired Research and development asset [Domain] Research and development asset [Domain] [Domain] for Research and development asset [Axis] Cash paid for amounts included in the measurement of lease liabilities Operating Lease, Payments 2023 Long-Term Debt, Maturity, Year Three Future percentage of co-promotion operating profits Future percentage of co-promotion operating profits Future percentage of co-promotion operating profits UCB Pharma S.A. UCB Pharma S.A. [Member] UCB Pharma S.A. 3.150% Senior Notes due May 1, 2050 3.15% Senior Notes due May 1, 2050 [Member] 3.15% Senior Notes due May 1, 2050 Major Distributor [Axis] Major Distributor [Axis] Major Distributor. Future contingent payment for annual worldwide net sales up to $2.0 billion Future contingent payment for annual worldwide net sales up to $2.0 billion Future contingent payment for annual worldwide net sales up to $2.0 billion 2021 Lessee, Operating Lease, Liability, to be Paid, Year One Repurchase of common stock pursuant to the share repurchase program, at cost (in shares) Repurchase of common stock, at cost (in shares) Treasury Stock, Shares, Acquired Proceeds from marketable securities, excluding strategic investments Realized Gain (Loss) on Investments [Table Text Block] Beginning balance, outstanding shares (in shares) Ending balance, outstanding shares (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number 2024 Lessee, Operating Lease, Liability, to be Paid, Year Four Summary of assets and liabilities recorded at fair value Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Unrecognized compensation cost related to unvested share-based compensation Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Litigation Legal Matters and Contingencies [Text Block] Total number of shares of common stock for issuance (in shares) Number Of Shares Of Common Stock For Issuance Total number of shares of common stock for issuance. AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] State Current State and Local Tax Expense (Benefit) Tax credit carryforward, amount Tax Credit Carryforward, Amount Preferred stock, par value $0.001 per share Preferred Stock, Value, Issued Distributor Two Distributor Two [Member] Distributor two. SWITZERLAND SWITZERLAND Adjustments relating to prior years Adjustments To Product Revenue Reserves Relating To Sales In Prior Years Adjustments to product revenue reserves relating to sales in prior years. Operating expenses Operating Expenses Buildings Building [Member] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Other long-term liabilities Other Liabilities, Noncurrent Deferred tax asset Deferred Income Tax Assets, Net Other comprehensive income: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Royalties payable period, post FDA approval Royalties Payable Period, Post FDA Approval Royalties Payable Period, Post FDA Approval Market stock units Market Stock Units [Member] Market stock units. 3.625% Senior Notes due September 15, 2022 Senior Notes Three Point Six Two Five Percent Due Twenty Twenty Two [Member] Senior Notes Three Point Six Two Five Percent Due Twenty Twenty Two [Member] Work in process Inventory, Work in Process, Net of Reserves Net gains (losses) of other income (expense) related to foreign currency forward contracts Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments Effect of exchange rate changes on cash and cash equivalents Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Inventory Inventory, Net Measurement Frequency [Domain] Measurement Frequency [Domain] Share-based Payment Arrangement, Tranche Three Share-based Payment Arrangement, Tranche Three [Member] Loss Contingency, Information about Litigation Matters [Abstract] Loss Contingency, Information about Litigation Matters [Abstract] Share based payment arrangement, term Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items] Inventory [Axis] Inventory [Axis] Statement [Line Items] Statement [Line Items] Divestiture of Denmark manufacturing operations Effective Income Tax Rate Reconciliation, Disposition of Asset, Percent IMRALDI IMRALDI [Member] IMRALDI [Member] Class of Stock [Domain] Class of Stock [Domain] Debt instrument, term Debt Instrument, Term Collaborative Arrangement and Arrangement Other than Collaborative [Table] Collaborative Arrangement and Arrangement Other than Collaborative [Table] Percentage of revenue from major distributors Entity Wide Percentage Of Revenue From Major Distributors Entity wide percentage of revenue from major distributors. Measurement Input Type [Domain] Measurement Input Type [Domain] Statement [Table] Statement [Table] Statistical Measurement [Axis] Statistical Measurement [Axis] Investments in Variable Interest Entities [Abstract] Investments in Variable Interest Entities [Abstract] Investments In Variable Interest Entities. U.S. tax reform Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Transition toll tax liabilities Deferred Tax Liabilities, Undistributed Foreign Earnings Expected additional milestone payments when certain sales threshold is met Expected Additional Milestone Payments When Meeting Certain Sales Threshold Expected additional milestone payments when meeting certain sales threshold. Fair Value, Nonrecurring Fair Value, Nonrecurring [Member] Weighted Average Weighted Average [Member] Other research and discovery Other research and discovery [Member] Other research and discovery [Member] Net Gains/(Losses) Reclassified from AOCI into Operating Income (in millions) Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax Entity Small Business Entity Small Business Consolidation Consolidation, Policy [Policy Text Block] Foreign sales required to trigger milestone Foreign Sales Required To Trigger Milestone Foreign sales required to trigger milestone. Indebtedness Debt Disclosure [Text Block] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Collaborative Arrangement Collaborative Arrangement [Member] Fumarate Fumarate [Member] Fumarate [Member] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Amendment Flag Amendment Flag Weighted-average shares used in calculating: Weighted-average shares used in calculating: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Business Acquisition, Contingent Consideration [Line Items] Business Acquisition, Contingent Consideration [Line Items] Omnibus Plan number of shares authorized (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Other Accrued Liabilities, Current Other Accrued Liabilities, Current Future minimum batch production for Denmark manufacturing operations Purchase Commitment, Remaining Minimum Amount Committed 4.050% Senior Notes due September 15, 2025 Senior Notes Four Point Zero Five Percent Due Twenty Twenty Five [Member] Senior Notes Four Point Zero Five Percent Due Twenty Twenty Five [Member] Measurement Frequency [Axis] Measurement Frequency [Axis] March 2019 Share Repurchase Program Share Repurchase Program 3 [Member] Share Repurchase Program 3 Accounting for Share-Based Compensation Compensation Related Costs, Policy [Policy Text Block] Financial Instruments [Domain] Financial Instruments [Domain] Summary of fair and carrying value of debt instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Equity Method of Accounting Equity Method Investments [Policy Text Block] Upfront and milestone payments made to collaborative partner Upfront And Milestone Payments Made To Collaborative Partner Total upfront and milestone payments made to collaborative partner. Deferred Tax Asset/Liability Type [Domain] Deferred Tax Asset/Liability Type [Domain] [Domain] for Deferred Tax Asset/Liability Type [Axis] Cash equivalents Cash Equivalents, at Carrying Value Due from related parties Due from Related Parties Fumapharm AG Fumapharm AG [Member] Fumapharm AG [Member] Derivative Instruments and Hedging Activities Derivatives, Policy [Policy Text Block] Acquired In-process Research and Development (IPR&D) In Process Research and Development, Policy [Policy Text Block] Minimum qualifying age for employee benefit plan Minimum Qualifying Age For Employee Benefit Plan Minimum qualifying age for employee benefit plan. Operating lease, renewal term Lessee, Operating Lease, Renewal Term Accrued income taxes Accrued Income Taxes, Noncurrent Contingencies Commitments and Contingencies, Policy [Policy Text Block] Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items] Dilutive potential common shares (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Property, Plant and Equipment, Type [Axis] Long-Lived Tangible Asset [Axis] Beginning balance Ending balance Revenue-related reserves for discounts and allowances SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount Net Gains/(Losses) Recognized in Other Comprehensive Income (Effective Portion) (in millions) Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease) Income Statement Location [Domain] Income Statement Location [Domain] Income Statement Location [Domain] 2022 Lessee, Operating Lease, Liability, to be Paid, Year Two Summary of the effect of derivatives designated as net investment hedging instruments on our consolidated statement of income Schedule of Net Investment Hedges in Accumulated Other Comprehensive Income (Loss) [Table Text Block] State and Local Jurisdiction State and Local Jurisdiction [Member] Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities [Abstract] Selling, general and administrative Selling, General and Administrative Expense FUMADERM FUMADERM [Member] FUMADERM [Member] Furniture and fixtures Furniture and Fixtures, Gross Foreign exchange contract Foreign Exchange Contract [Member] Operating lease costs Lease, Cost [Table Text Block] Facility Location [Domain] Facility Location [Domain] -- None. No documentation exists for this element. -- 2023 Lessee, Operating Lease, Liability, to be Paid, Year Three Investments and other assets Other Assets, Noncurrent Plan Name [Axis] Plan Name [Axis] Cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Gain (loss) on investments, net Gain (Loss) on Sale of Investments Ratio of total number of shares reserved under the plan Ratio Of Number Of Shares Reserved Under Plan Ratio of total number of shares reserved under the plan. SOD1 SOD1 [Member] SOD1 [Member] Total assets Assets Impairment Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill) Performance units Performance Units [Member] Performance Units [Member] Beginning balance, unvested shares (in shares) Ending balance, unvested shares (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Intangible assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets Retirement Plan Sponsor Location [Axis] Retirement Plan Sponsor Location [Axis] iPerian iPerian [Member] iPerian [Member] Redemption percentage par value of senior notes Percentage Par Value Of Senior Notes Percentage Par Value Of Senior Notes Antidilutive Securities [Axis] Antidilutive Securities [Axis] Marketable equity securities, amortized cost Equity Securities, FV-NI, Cost Number of share-based compensation plans pursuant to which awards are currently being made Number Of Share Based Compensation Plans Pursuant To Which Awards Are Currently Being Made Number of share-based compensation plans pursuant to which awards are currently being made. Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Axis] Concentration of Credit Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Facility Type [Domain] Facility Type [Domain] Facility Type BENEPALI BENEPALI [Member] BENEPALI [Member] Unrealized gains (losses) recognized during the period on equity securities Equity Securities, FV-NI, Unrealized Gain (Loss) Total liabilities Liabilities Revenues Sales [Member] Retirement Plan Type [Axis] Retirement Plan Type [Axis] Claims asserted Loss Contingency, Damages Sought, Value Range of expected stock price volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Less: interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Percentage of minimum investment return Percentage Of Minimum Investment Return Percentage of minimum investment return. Marketable equity securities, gross unrealized gains Equity Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Equity Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Post-acquisition equity compensation Post-acquisition equity compensation [Member] Post-acquisition equity compensation [Member] Total reserves included in consolidated balance sheet Summary Of Product Revenue Reserves Included In Consolidated Balance Sheets [Table Text Block] Summary of total product revenue reserves included in consolidated balance sheets. Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Net interest expense Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense Quoted Prices in Active Markets (Level 1) Fair Value, Inputs, Level 1 [Member] Reduction in contingent consideration Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Asset Inventory Increase (Decrease) in Inventories Due from anti-CD20 therapeutic programs Due from unconsolidated joint business Receivable from unconsolidated joint business for our share of the pre-tax co-promotion profits generated from our co-promotion arrangement for sales of RITUXAN. Option exercise fee Contract Option Exercise Fee Contract Option Exercise Fee Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Due from anti-CD20 therapeutic programs Increase (Decrease) in Other Operating Assets and Liabilities, Net Limit of gross sale of GAZYVA to be achieved in any 12 months under option one Threshold Of Gross Sales To Be Achieved In Any Twelve Consecutive Months Under Option One Threshold of gross sales to be achieved in any twelve consecutive months under option one. Depreciation, amortization and other Deferred Tax Liabilities Depreciation Amortization Other Deferred tax liabilities depreciation amortization other. Additional paid-in capital Additional Paid-in Capital [Member] Other income (expense), net Schedule of Other Nonoperating Income (Expense) [Table Text Block] Intangibles, net Deferred Tax Assets, Goodwill and Intangible Assets JAPAN JAPAN Fair Value by Asset Class [Axis] Asset Class [Axis] Beginning balance (in shares) Ending balance (in shares) Shares, Issued Stromedix, Inc. Stromedix [Member] Stromedix. Derivative contracts Foreign Currency Contract, Asset, Fair Value Disclosure Cash and Cash Equivalents [Line Items] Cash and Cash Equivalents [Line Items] Machinery and Equipment Machinery and Equipment [Member] Fair Value Measurements Fair Value of Financial Instruments, Policy [Policy Text Block] Other Segment Geographical Groups Of Countries Group Other [Member] Segment geographical groups of countries group other. Common stock outstanding (in shares) Common Stock, Shares, Outstanding Investment in Samsung Bioepis Equity Method Investments Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Revolving Credit Facility Revolving Credit Facility [Member] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Investments in Variable Interest Entities Variable Interest Entity Disclosure [Text Block] Administrative Space Administrative Space [Member] Administrative Space Forward contracts duration Derivative, Term of Contract Other Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Beginning balance, weighted average exercise price (in dollars per share) Ending balance, weighted average exercise price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Summary of activity related to the UCB collaboration Summary of Activity Related to the UCB Collaboration [Table Text Block] Summary of Activity Related to the UCB Collaboration Common stock authorized (in shares) Common Stock, Shares Authorized Cash received from the exercise of stock options Proceeds from Stock Options Exercised Stock options and employee stock purchase plan (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Total cost Property, plant and equipment, gross Property, Plant and Equipment, Gross Federal Deferred Federal Income Tax Expense (Benefit) Operating expenses Operating Expense [Member] Unfunded net pension Defined Benefit Plan, Funded (Unfunded) Status of Plan Purchase of common stock Purchase of common stock Purchase of common stock SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Interferon Interferon [Member] Interferon Collaborative arrangements and non-collaborative arrangement transactions Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] Income Statement [Abstract] Income Statement [Abstract] Accumulated other comprehensive loss AOCI Attributable to Parent [Member] Summary of contractual maturities: available-for-sale securities Investments Classified by Contractual Maturity Date [Table Text Block] Accrued Royalties, Current Accrued Royalties, Current Research and development costs, percentage Research and Development Costs, Percentage Research and Development Costs, Percentage Short-term derivative Short-term derivative [Member] Short-term derivative [Member] Shares issued under employee stock purchase plan Shares Issued Under Employee Stock Purchase Plan [Table Text Block] Shares issued under employee stock purchase plan. Additions Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] Use of Estimates Use of Estimates, Policy [Policy Text Block] Income Tax Authority [Domain] Income Tax Authority [Domain] Net change in acquired and in-licensed rights and patents Finite-Lived Intangible Assets, Period Increase (Decrease) Computer Software and Hardware Software and Software Development Costs [Member] Consolidated Entities [Axis] Consolidated Entities [Axis] Twelve months Twelve months [Member] Twelve months [Member] Performance stock units settled in stock activity Performance Stock Units Settled in Stock [Table Text Block] Performance Stock Units Settled in Stock [Table Text Block] Realized investment gains (losses) Realized Investment Gains (Losses) Scenario [Domain] Scenario [Domain] Purchases of property, plant and equipment Payments to Acquire Property, Plant, and Equipment Contingent consideration obligations Fair Value Fair value, beginning of year Fair value, end of year Business Combination, Contingent Consideration, Liability Intangible Assets and Goodwill Goodwill and Intangible Assets Disclosure [Text Block] Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Abstract] Interest in subsidiary (less than given percentage) Interest In Subsidiary Interest in subsidiary. Summary of activity related to BAN2401 and Elenbecestat collaboration Summary Of Activity Related To Collaboration With Company Eight [Table Text Block] [Table Text Block] Summary Of Activity Related To Collaboration With Company Eight [Table Text Block] [Table Text Block] Neurimmune Neurimmune Neurimmune [Member] Neurimmune. Director Director [Member] Loss on equity method investment Eisai's share of aducanumab milestone expense reflected in collaboration profit sharing in our consolidated statements of income Income (Loss) from Equity Method Investments Expected Payment Timeline of Milestone [Axis] Expected Payment Timeline of Milestone [Axis] Expected Payment Timeline of Milestone [Axis] E2609 and BAN2401 E2609 and BAN2401 [Member] E2609 and BAN2401 [Member] Income before income tax expense and equity in loss of investee, net of tax Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Computer software and hardware Computer software and hardware Computer software and hardware Hedging Designation [Axis] Hedging Designation [Axis] Reclassification out of Accumulated Other Comprehensive Income [Domain] Reclassification out of Accumulated Other Comprehensive Income [Domain] Accumulated impairment losses related to goodwill Goodwill, Impaired, Accumulated Impairment Loss Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Net increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect Components of inventory Schedule of Inventory, Current [Table Text Block] Tax benefit and cash received from stock option exercises Cash Proceeds Received and Tax Benefit from Share-based Payment Awards [Table Text Block] Marketable equity securities, fair value Equity Securities, FV-NI Entity [Domain] Entity [Domain] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Percentage of development costs incurred Percentage of Development Costs Incurred Percentage of Development Costs Incurred Increase to goodwill Increase to goodwill Goodwill, Acquired During Period Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block] Collaboration expenses Collaboration expenses accrual Collaboration expenses accrual Other revenues Other revenues [Table Text Block] Other revenues [Table Text Block] Property, plant and equipment, useful life Property, Plant and Equipment, Useful Life Inventories Inventories [Member] Employee stock purchase plan Employee Stock Purchase Plan [Member] Employee stock purchase plan. Goodwill [Line Items] Goodwill [Line Items] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Twenty billion Twenty billion [Member] Twenty billion [Member] Analysis of change in reserves Analysis Of Amount Of And Change In Product Revenue Reserves [Table Text Block] Analysis of amount of and change in product revenue reserves. Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Fair Value Total marketable debt securities Debt Securities, Available-for-sale Royalty operating profit threshold for highest royalty rate percentage Royalty operating profit threshold for highest royalty rate percentage Royalty operating profit threshold for highest royalty rate percentage Finished goods Inventory, Finished Goods, Net of Reserves Equity in (income) loss of investee, net of tax Income (Loss) from Equity Method Investments, Net of Tax Income (Loss) from Equity Method Investments, Net of Tax Share-based Payment Arrangement [Abstract] Share-based Payment Arrangement [Abstract] Net Gains/(Losses) Recognized in Net Income (Amounts Excluded from Effectiveness Testing) (in millions) Other Comprehensive Income (Loss), Derivative, Excluded Component, Increase (Decrease), before Adjustments and Tax Net contribution (distribution) to noncontrolling interest Payments of Capital Distribution Consolidated Entities [Domain] Consolidated Entities [Domain] Revenue from External Customer [Line Items] Revenue from External Customer [Line Items] Operating lease liability, current Operating Lease, Liability, Current Summary of the effect of derivatives designated as cash flow hedging instruments on our consolidated statements of income Derivative Instruments, Gain (Loss) [Table Text Block] Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Derivative Instruments, Gain (Loss) [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Summary of the fair value for our outstanding derivatives Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Fair Value Measurements Fair Value Disclosures [Text Block] Reduction of accounts receivable Accounts Receivable [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Interest rate swap Interest Rate Swap [Member] Customer [Domain] Customer [Domain] Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] British pound United Kingdom, Pounds Internal reorganization of certain intellectual property rights Effective Income Tax Rate Reconciliation, Intellectual Property Rights Reorganization Effective Income Tax Rate Reconciliation, Intellectual Property Rights Reorganization Cumulative Effect, Period of Adoption, Adjustment Cumulative Effect, Period of Adoption, Adjustment [Member] Cumulative sales level [Axis] Cumulative sales level [Axis] Cumulative sales level [Axis] Intangible Assets Goodwill and Intangible Assets, Intangible Assets, Policy [Policy Text Block] 2.250% Senior Notes due May 1, 2030 2.25% Senior Notes due May 1, 2030 [Member] 2.25% Senior Notes due May 1, 2030 Entity Registrant Name Entity Registrant Name Business Acquisition [Line Items] Business Acquisition [Line Items] Weighted average discount rate Operating Lease, Weighted Average Discount Rate, Percent Assets: Assets, Fair Value Disclosure [Abstract] Other changes in operating assets and liabilities, net Increase (Decrease) in Other Operating Liabilities Number of days for calculation of average closing stock price Number Of Days For Calculation Of Average Closing Stock Price Number of days for calculation of average closing stock price. Sangamo Therapeutics, Inc. Agreement Sangamo Therapeutics, Inc. Agreement [Member] Sangamo Therapeutics, Inc. Agreement Denmark Manufacturing Operations Denmark Manufacturing Operations [Member] Denmark Manufacturing Operations [Member] Issuance of common stock under stock option and stock purchase plans Stock Issued During Period, Value, Treasury Stock Reissued Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Payment terms of accounts receivable arising from product sales Payment Terms Of Accounts Receivable Payment terms of accounts receivable. Due in one year or less Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Global licensing collaboration, payment, selection of targets Global Licensing Collaboration Agreement, Payment, Selection of Targets Global Licensing Collaboration Agreement, Payment, Selection of Targets After Second GAZYVA Threshold Date After Second GAZYVA Threshold Date Percentage Of Co Promotion Operating Profits Greater Than First Fifty Million Option Two Sub Option Three Percentage of co promotion operating profits greater than first fifty million option two sub option three. Sublease Sublease [Member] Sublease [Member] Summary of financial assets with maturities of less than 90 days included within cash and cash equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Schedule of Employee Stock Ownership Plan (ESOP) Disclosures [Table] Schedule of Employee Stock Ownership Plan (ESOP) Disclosures [Table] Gross Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Tax Credit Carryforward [Table] Tax Credit Carryforward [Table] Summary of activity related to Aducanumab collaboration Summary of Activity Related to Aducanumab Collaboration [Table Text Block] [Table Text Block] for Summary of Activity Related to Aducanumab Collaboration [Table] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Total deferred tax assets Deferred Tax Assets, Net of Valuation Allowance Other tax expense (benefit) Other Tax Expense (Benefit) Gains (Losses) on Net Investment Hedge, Net of Tax Gains (losses) on net investment hedge Accumulated Other Comprehensive Income (Loss), Derivative Qualifying as Hedge, Excluded Component, Including Portion Attributable to Noncontrolling Interest [Member] Goodwill Goodwill, beginning of year Goodwill, end of year Goodwill Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Summary of significant unobservable inputs Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Total other comprehensive income (loss), net of tax Net current period other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Cumulative sales level Cumulative sales level Cumulative sales level Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Settlement refund (payment) Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Net operating loss Deferred Tax Assets, Operating Loss Carryforwards Facility Type [Axis] Facility Type [Axis] Facility Type Income tax assets and liabilities Increase (Decrease) in Income Taxes Payable Less: Net gains (losses) recognized on equity securities sold during the period and on capital distributions Equity Securities, FV-NI, Realized Gain (Loss) Aggregate principal amount Senior notes aggregate principal amount Debt Instrument, Face Amount Income tax expense, reduction in deferred tax assets and liabilities, net Income Tax Expense, Reduction in Deferred Tax Assets and Liabilities, Net Income Tax Expense, Reduction in Deferred Tax Assets and Liabilities, Net Other current assets Other Assets, Current Government securities Non-current Government Securities Non-current [Member] Government Securities Non Current. Unobservable Input Business Combination, Contingent Consideration, Liability, Measurement Input Summary of roll forward of the changes in goodwill Schedule of Goodwill [Table Text Block] Cancelled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, by Asset Class Asset Class [Domain] Number of ophthalmolgy biosimilar products Number of Ophthalmolgy Biosimilar Products, Exclusive Rights Number of Ophthalmolgy Biosimilar Products, Exclusive Rights Equity [Abstract] Equity [Abstract] Total Assets, Fair Value Disclosure Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Divestitures Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Gain (loss) on investments Gain (Loss) on Securities [Table Text Block] Numerator: Numerator [Abstract] Numerator. 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Warehouse, Utilities and Support Space Warehouse, Utilities and Support Space [Member] Warehouse, Utilities and Support Space Entity Address, City or Town Entity Address, City or Town Employee-related Liabilities, Current Employee-related Liabilities, Current Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Acquisitions of intangible assets Payments to Acquire Intangible Assets Total Biogen Inc. shareholders’ equity Share-based compensation expense included in net income attributable to Biogen Inc. Parent [Member] 2025 Lessee, Operating Lease, Liability, to be Paid, Year Five Financial Instrument [Axis] Financial Instrument [Axis] Intellectual Property Intellectual Property [Member] Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table] Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table] Co-promotion profit sharing formula Co Promotion Profit Sharing Formula [Abstract] Co-promotion profit sharing formula. Product, net Total product revenues Product [Member] Indefinite-lived Intangible Assets by Major Class [Axis] Indefinite-lived Intangible Assets [Axis] Due after five years Available For Sale Securities Debt Maturities After Five Years Fair Value This item represents the fair value of debt securities, which are expected to mature after five years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities. 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Foreign currency forward contracts that were entered into to hedge forecasted revenue Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Corporate debt securities Current Corporate Debt Securities Current [Member] Corporate debt securities Current. Accrued expenses and other Total accrued expenses and other Other Liabilities, Current After First GAZYVA Threshold Date until Second GAZYVA Threshold Date After First GAZYVA Threshold Date until Second GAZYVA Threshold Date Percentage Of Co Promotion Operating Profits Greater Than First Fifty Million Option Two Sub Option Two Percentage of co promotion operating profits greater than first fifty million option two sub option two. Business Overview Business Overview [Policy Text Block] Describes an overview of the company and its operations. 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Total development expense incurred by the collaboration related to the advancement of BAN2401 and elenbecestat Expense Incurred By Collaboration Total expense incurred by collaboration. Unfunded Status of Postretirement Benefit Plans, net of tax Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Disposal Group Name [Domain] Disposal Group Name [Domain] Range of durations of foreign currency forward contracts Derivative, Remaining Maturity Biogen Inc. shareholders’ equity Stockholders' Equity Attributable to Parent [Abstract] Pension cost (reversal) Pension Cost (Reversal of Cost) Acorda Acorda [Member] Acorda. 2025 Finite-Lived Intangible Asset, Expected Amortization, Year Five Document Fiscal Period Focus Document Fiscal Period Focus Average stock price on grant date maximum Average Stock Price On Grant Date In Dollars Maximum Average stock price on grant date in dollars maximum. 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Total Financial and Nonfinancial Liabilities, Fair Value Disclosure Diluted earnings per share attributable to Biogen Inc. 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Maximum Maximum Maximum [Member] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Noncontrolling interests Noncontrolling Interest [Member] Share-based compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Distributor One Distributor One [Member] Distributor one. 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Marketable equity securities, non-current Equity Securities, Non-Current [Member] Equity Securities, Non-Current Biogen Idec International Neuroscience GmbH Biogen Idec International Neuroscience Member Biogen idec international neuroscience. Notes payable, fair value Notes Payable, Fair Value Disclosure Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Additional reduction in royalty rate payable on commercial sales Additional reduction in royalty rate payable on commercial sales Additional reduction in royalty rate payable on commercial sales Foreign Income (Loss) from Continuing Operations before Income Taxes, Foreign Entity Shell Company Entity Shell Company Fair value, measurements, recurring Fair Value, Recurring Fair Value, Recurring [Member] Net Gains/(Losses) Recognized in Other Comprehensive Income (Amounts Excluded from Effectiveness Testing) (in millions) Derivatives used in net investment hedge, net of tax, excluded component increase (decrease) Derivatives used in net investment hedge, net of tax, excluded component increase (decrease) Entity Public Float Entity Public Float Total sales and marketing expense incurred by the collaboration Total UCB development expense Expense incurred by the collaboration Expense incurred by the collaboration Contingent Consideration Business Combinations Policy [Policy Text Block] Document Type Document Type Earnings in the form of cash and cash equivalents Foreign earnings in the form of cash and cash equivalents [Member] Foreign earnings in the form of cash and cash equivalents [Member] ICFR Auditor Attestation Flag ICFR Auditor Attestation Flag Other, net Other Nonoperating Income (Expense) Expected costs to sell disposal group Disposal Group, Including Discontinued Operation, Other Expense License fee License Fee License Fee Treasury stock Treasury Stock [Member] Employee Benefit Plans Retirement Benefits [Text Block] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain] Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Schedule of Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] In-process research and development In Process Research and Development [Member] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Write-downs on excess, obsolete, unmarketable or other inventory Inventory Write-down Deferred tax liabilities, goodwill Deferred Tax Liabilities, Goodwill Leases Lessee, Leases [Policy Text Block] Contractual obligation Contractual Obligation Other current assets Other Current Assets [Member] Payments/returns relating to sales in prior years Payments Returns Applied Against Product Revenue Reserves Relating To Prior Year Payments/ returns applied against product revenue reserves relating to prior year. Due after one year through five years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Line of Credit Line of Credit [Member] Deferred tax liability Deferred Income Tax Liabilities, Net Derivative Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Intangible assets, net Total intangible assets Intangible Assets, Net (Excluding Goodwill) Ending Book Value Intangible Assets, Net (Excluding Goodwill) 2020 Share Repurchase Program Share Repurchase Program 5 [Member] Share Repurchase Program 5 Trademarks and trade names Trademarks and Trade Names [Member] Income from operations Operating Income (Loss) TYSABRI TYSABRI product [Member] TYSABRI product [Member] Expected license fee and regulatory milestone payments Expected License Fee And Regulatory Milestone Payments Expected license fee and regulatory milestone payments. Deferred tax assets, value, reduction in value Deferred Tax Assets, Value, Reduction in Value Deferred Tax Assets, Value, Reduction in Value Defined Contribution Plan Disclosure [Line Items] Defined Contribution Plan Disclosure [Line Items] Biogen's share of pre-tax profits in the U.S. for RITUXAN and GAZYVA Biogen's share of pre-tax profits in the U.S. for RITUXAN and GAZYVA, including the reimbursement of selling and development expenses Share Of Co Promotion Profits Share of co promotion profits. Investment in common stock, value Investment in common stock, value Investment in common stock, value Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Commitments, contingencies and guarantees (Notes 21 and 22) Commitments and Contingencies Marketable securities Debt Securities, Available-for-sale, Noncurrent Share-based Payment Arrangement, Tranche Two Share-based Payment Arrangement, Tranche Two [Member] Purchase of treasury stock Payments for repurchase of common stock Payments for Repurchase of Common Stock Vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Thereafter Lessee, Operating Lease, Liability, to be Paid, after Year Five Furniture and Fixtures Furniture and Fixtures [Member] Taxes payable Taxes Payable, Current Entity Address, State or Province Entity Address, State or Province Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Accounts payable Accounts Payable, Current Sublease income Sublease Income Schedule of Cash and Cash Equivalents [Table] Schedule of Cash and Cash Equivalents [Table] Retained earnings Retained Earnings (Accumulated Deficit) Operating lease assets Operating Lease, Right-of-Use Asset Reduction in deferred tax liability, undistributed foreign earnings Reduction in deferred tax liability, undistributed foreign earnings Reduction in deferred tax liability, undistributed foreign earnings Income taxes paid Income Taxes Paid Equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Contractual Adjustments Contractual Adjustments [Member] Contractual adjustments. Customer [Axis] Customer [Axis] Income Taxes Income Tax, Policy [Policy Text Block] Hedging Designation [Domain] Hedging Designation [Domain] Samsung Bioepis, ownership percentage before additional purchase transaction Equity Method Investment, Ownership Percentage Before Additional Purchase Transaction Equity Method Investment, Ownership Percentage Before Additional Purchase Transaction Net lease cost Lease, Cost Government securities US Treasury and Government [Member] Investment in Samsung Bioepis Payments to increase investment in Samsung Bioepis Payments to Acquire Equity Method Investments Market stock units activity Schedule Of Market Stock Units Activity [Table Text Block] Schedule Of Market Stock Units Activity. Costs associated with the senior Nnotes offerings Payments of Financing Costs 2015 ESPP 2015 ESPP [Member] 2015 ESPP [Member] Machinery and equipment Machinery and Equipment, Gross Other Payments for (Proceeds from) Other Investing Activities Domestic Plan Domestic Plan [Member] Mortgage and other asset backed securities Current Mortgage And Other Asset Backed Securities Current [Member] Mortgage and other asset backed securities Current. Cumulative Effect, Period of Adoption, Adjusted Balance Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Construction in progress Construction in Progress, Gross 2026 and thereafter Long-Term Debt, Maturity, after Year Five Advertising costs Advertising Expense Inventory [Line Items] Inventory [Line Items] Marketable Securities and Other Investments Investment, Policy [Policy Text Block] Reduction in royalty rate Reduction in royalty rate Reduction in royalty rate Business Acquisition [Axis] Business Acquisition [Axis] Share-based compensation expense included in total cost and expenses Share Based Compensation Expense Included In Costs And Expenses Share based compensation expense included in costs and expenses. 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GILTI Effective Tax Rate Reconciliation, GILTI tax Effective Tax Rate Reconciliation, GILTI tax Current provisions relating to sales in current year Current Provisions To Product Revenue Reserves Relating To Sales In Current Year Current provisions to product revenue reserves relating to sales in current year. 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Amortized Cost Debt Securities, Available-for-sale, Amortized Cost Divestitures [Abstract] Divestitures [Abstract] Divestitures [Abstract] Gross Unrealized Gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] 2024 Long-Term Debt, Maturity, Year Four Interest costs capitalized Interest Costs Capitalized Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Axis] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Weighted-average period to recognize the cost of unvested awards Weighted Average Period To Recognize Cost Of Nonvested Awards Weighted-average period to recognize the cost of nonvested awards. Percentage of co promotion operating profits first fifty million Percentage Of Co Promotion Operating Profits First Fifty Million Percentage of co promotion operating profits first fifty million. 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Asset derivative instruments Derivative Asset, Fair Value, Gross Asset Joint venture ownership percentage Joint Venture OwnerShip Percentage By Third Party. Joint venture owner ship percentage by third party. 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Plan Name [Domain] Plan Name [Domain] Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Samsung Bioepis, ownership percentage Equity Method Investment, Ownership Percentage Revenues Revenue from Contract with Customer [Text Block] Non-current notes payable Total Notes Payable, Noncurrent Operating lease assets obtained in exchange for lease obligations Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Foreign exchange gains (losses), net Foreign Currency Transaction Gain (Loss), before Tax Limit of gross sale of GAZYVA to be achieved in preceding 12 months under option one Threshold Of Gross Sales Of To Be Achieved In Preceding Twelve Consecutive Months Under Option One Threshold of gross sales of to be achieved in preceding twelve consecutive months under option one. Inventory Inventory, Policy [Policy Text Block] Income tax expense Income tax benefit (expense) Total income tax expense Income Tax Expense (Benefit) Cash and cash equivalents Cash and cash equivalents, beginning of the year Cash and cash equivalents, end of the year Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Property, Plant and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Total debt maturities Schedule of Maturities of Long-term Debt [Table Text Block] Research and development asset [Axis] Research and development asset [Axis] Research and development asset [Axis] Title of Individual [Domain] Title of Individual [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Indefinite-lived Intangible Assets, Major Class Name [Domain] Local Phone Number Local Phone Number Total transaction value Payments to Acquire Businesses, Gross Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Share-based Payment Arrangement, Tranche One Share-based Payment Arrangement, Tranche One [Member] Total intrinsic value of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Time-vested restricted stock units activity Time Vested Restricted Stock Units Activity [Table Text Block] Time Vested Restricted Stock Units Activity. Tax expense on disposal group Discontinued Operation, Tax Effect of Discontinued Operation Fair value of contingent consideration obligations Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Contract Manufacturing Customer Contract Manufacturing Customer [Member] Contract Manufacturing Customer Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Pfizer Pfizer [Member] Pfizer [Member] Reductions for tax positions of prior periods Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions FAMPYRA FAMPYRA [Member] FAMPYRA [Member] Issuance of common stock under stock award plan Stock Issued During Period, Value, Stock Options Exercised Payments for pre-combination equity compensation Other Payments to Acquire Businesses Subtotal Share-based Payment Arrangement, Expense, after Tax Maximum contingent consideration in the form of development and approval milestones Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Selling, General and Administrative Expenses Selling, General and Administrative Expenses, Policy [Policy Text Block] Senior unsecured revolving credit facility maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Percentage receivables of wholesale distributor accounted in consolidated receivables Percentage Receivables Of Wholesale Distributor Accounted In Consolidated Receivables Percentage receivables of wholesale distributor accounted in consolidated receivables. Award Type [Axis] Award Type [Axis] Global licensing collaboration, shares purchased (in shares) Global Licensing Collaboration Agreement, Shares, Purchased Global Licensing Collaboration Agreement, Shares, Purchased Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Prepaid research and discovery services Prepaid Expense and Other Assets Lease Arrangement, Type [Domain] Lease Contractual Term [Domain] Total fair value of vested awards Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Aducanumab Aducanumab [Member] Aducanumab [Member] Retained earnings Retained Earnings Retained Earnings [Member] Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Elimination of goodwill allocated to Hillerød, Denmark manufacturing operations Goodwill, Written off Related to Sale of Business Unit Contingent consideration payments Contingent payment Payment for Contingent Consideration Liability, Financing Activities Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Net cash flows provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities (Gain)/loss on divestiture of Hillerod, Denmark manufactuing operations Income (Loss) from Individually Significant Component Disposed of or Held-for-sale, Excluding Discontinued Operations, Attributable to Parent, before Income Tax Award Type [Domain] Award Type [Domain] Other Relationships Other Relationships [Member] Other Relationships Corporate debt securities Corporate Debt Securities [Member] 2.900% Senior Notes due September 15, 2020 Notes Payable, Current Cancellable future commitments Other Commitment Property, Plant and Equipment Property, Plant and Equipment Disclosure [Text Block] Treasury stock, at cost; 23.8 million and 23.8 million shares, respectively Treasury Stock, Value Earnings per Share Earnings Per Share [Text Block] Current liabilities: Liabilities, Current [Abstract] Statutory rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Research and development Research and Development Expense (Excluding Acquired in Process Cost) Research and Development Expense (Excluding Acquired in Process Cost) New Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Discount rate Measurement Input, Discount Rate [Member] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Revenues from anti-CD20 therapeutic programs Revenues from anti-cd20 therapeutic programs [Member] Revenues from anti-cd20 therapeutic programs