Expense incurred by the collaboration
Expense incurred by the collaboration
Expense incurred by the collaboration
Expense incurred by the collaboration
Business Acquisition [Axis]
Business Acquisition [Axis]
Due in one year or less, estimated fair value
Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One
Amounts reclassified from accumulated other comprehensive income, net of tax
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax
Intangible assets
Intangible Assets Excluding Goodwill [Table Text Block]
Intangible assets excluding goodwill.
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]
Net income
Net income
Net income
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest
Deferred tax asset
Deferred Income Tax Assets, Net
Entity Address, Postal Zip Code
Entity Address, Postal Zip Code
Foreign currency and other adjustments
Restructuring Reserve, Accrual Adjustment
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment [Abstract]
Marketable equity securities
Investments, Fair Value Disclosure
Debt Instrument [Axis]
Debt Instrument [Axis]
Payments/Returns Relating To Sales in Prior Year
Payments Returns Applied Against Product Revenue Reserves Relating To Prior Year
Payments/ returns applied against product revenue reserves relating to prior year.
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income Tax Disclosure [Abstract]
Income Tax Disclosure [Abstract]
Debt Instrument, Fair Value Disclosure
Debt Instrument, Fair Value Disclosure
Restructuring reserve, beginning
Restructuring reserve, ending
Restructuring Reserve
Foreign exchange contract
Foreign Exchange Contract [Member]
Denali Therapeutics
Denali Therapeutics Inc [Member]
Denali Therapeutics Inc
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.
Additional paid-in capital
Additional Paid in Capital
Other income (expense), net
Schedule of Other Nonoperating Income (Expense) [Table Text Block]
Financial Instruments [Domain]
Financial Instruments [Domain]
SPINRAZA
SPINRAZA [Member]
SPINRAZA [Member]
Other
Payments for (Proceeds from) Other Investing Activities
TYSABRI
TYSABRI product [Member]
TYSABRI product [Member]
Statistical Measurement [Domain]
Statistical Measurement [Domain]
Depreciation
Depreciation
Indefinite-lived Intangible Assets, Major Class Name [Domain]
Indefinite-Lived Intangible Assets, Major Class Name [Domain]
Issuance of common stock under award plan, shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period
Centers for Medicare and Medicaid Service
Centers for Medicare and Medicaid Service [Member]
Centers for Medicare and Medicaid Service
Biogen's share of pre-tax profits in the U.S. for RITUXAN and GAZYVA
Share Of Co Promotion Profits
Share of co promotion profits.
Proceeds from sales and maturities of marketable securities
Proceeds from Sale and Maturity of Marketable Securities
Summary of the effect of cash flow derivatives designated as hedging instruments on the condensed consolidated statements of income
Derivative Instruments, Gain (Loss) [Table Text Block]
Share-based Payment Arrangement [Abstract]
Share-Based Payment Arrangement [Abstract]
Litigation
Legal Matters and Contingencies [Text Block]
Net (distribution) contribution to noncontrolling interest
Proceeds from (Payments to) Noncontrolling Interests
Other current assets
Other Current Assets [Member]
Reclassification out of Accumulated Other Comprehensive Income [Axis]
Reclassification out of Accumulated Other Comprehensive Income [Axis]
Other
Other Noncash Income (Expense)
Derivative contracts
Foreign Currency Contracts, Liability, Fair Value Disclosure
Net income attributable to Biogen Inc.
Net income attributable to Biogen Inc.
Net Income (Loss) Attributable to Parent
Measurement Input Type [Domain]
Measurement Input Type [Domain]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Due after one year through five years, estimated fair value
Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five
Short-term debt securities
Debt Securities [Member]
Share Repurchase Program [Domain]
Share Repurchase Program [Domain]
Other
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent
Equity Component [Domain]
Equity Component [Domain]
Scenario [Axis]
Scenario [Axis]
Discount rates
Measurement Input, Discount Rate [Member]
Total
Assets, Fair Value Disclosure
Investment, Name [Domain]
Investment, Name [Domain]
Loss Contingency, Estimate of Possible Loss
Loss Contingency, Estimate of Possible Loss
Contractual adjustments
Contractual Adjustments [Member]
Contractual adjustments.
Reconciliation between the U.S. federal statutory tax rate and effective tax rate
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Subtotal
Subtotal
Share-Based Payment Arrangement, Expense, after Tax
Effect of dilutive securities:
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Completed technology
Out Licensed Patents [Member]
Out-licensed patents.
Marketable debt securities
Fair value
Debt Securities, Available-for-Sale
Distributor Two
Distributor Two [Member]
Distributor two.
Hedging Designation [Domain]
Hedging Designation [Domain]
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.
Percentage of stake in entity
Equity Method Investment, Ownership Percentage Before Additional Purchase Transaction
Equity Method Investment, Ownership Percentage Before Additional Purchase Transaction
Derivative Instrument [Axis]
Derivative Instrument [Axis]
Loss Contingency, Information about Litigation Matters [Abstract]
Loss Contingency, Information about Litigation Matters [Abstract]
Market stock units
Market Stock Units [Member]
Market stock units.
Statement of Cash Flows [Abstract]
Statement of Cash Flows [Abstract]
Entity Address, State or Province
Entity Address, State or Province
Quoted Prices in Active Markets (Level 1)
Fair Value, Inputs, Level 1 [Member]
Foreign currency forward contracts that were entered into to hedge forecasted revenue
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]
Fair value of post-combination equity compensation
Business Combination, Separately Recognized Transactions, Expenses and Losses Recognized
Mortgage and other asset backed securities Current
Mortgage And Other Asset Backed Securities Current [Member]
Mortgage and other asset backed securities Current.
Award Type [Axis]
Award Type [Axis]
Reduction in royalty rate
Reduction in royalty rate
Reduction in royalty rate
Neurimmune tax impacts
Effective Tax Rate Reconciliation, NuerImmune Tax Impacts
Effective Tax Rate Reconciliation, NuerImmune Tax Impacts
Net cash flow provided by (used in) operating activities
Net Cash Provided by (Used in) Operating Activities
Contingent Commercialized Rights, Number Of Products
Contingent Commercialized Rights, Number Of Products
Contingent Commercialized Rights, Number Of Products
Share-based compensation expense included in total costs and expenses
Share Based Compensation Expense Included In Costs And Expenses
Share based compensation expense included in costs and expenses.
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table]
Marketable debt and equity securities
Debt Securities, Available-for-Sale [Table Text Block]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Line Items]
All Currencies [Domain]
All Currencies [Domain]
IMRALDI
IMRALDI [Member]
IMRALDI [Member]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table]
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table]
Cost and expenses:
Costs and Expenses [Abstract]
Percentage of revenues from major distributors
Entity Wide Percentage Of Revenue From Major Distributors
Entity wide percentage of revenue from major distributors.
Legal Entity [Axis]
Legal Entity [Axis]
Schedule of Cash and Cash Equivalents [Table]
Schedule of Cash and Cash Equivalents [Table]
Total liabilities
Liabilities
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax
Geographical [Axis]
Geographical [Axis]
Investments in Variable Interest Entities [Abstract]
Investments in Variable Interest Entities [Abstract]
Investments In Variable Interest Entities.
Cash flows from investing activities:
Net Cash Provided by (Used in) Investing Activities [Abstract]
Reclassification out of Accumulated Other Comprehensive Income
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]
Entity Common Stock, Shares Outstanding
Entity Common Stock, Shares Outstanding
Other research and discovery
Other research and discovery [Member]
Other research and discovery [Member]
Fair Value Hierarchy and NAV [Domain]
Fair Value Hierarchy and NAV [Domain]
Marketable securities
Debt Securities, Available-for-Sale, Current
Unrealized gains (losses) on securities available for sale
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member]
Document Type
Document Type
Range of durations of foreign currency forward contracts
Derivative, Remaining Maturity
Plan assets for deferred compensation
Plan Assets For Deferred Compensation Fair Value Disclosure
Fair values as of the balance sheet date of all assets of deferred compensation plans.
GILTI
Effective Tax Rate Reconciliation, GILTI tax
Effective Tax Rate Reconciliation, GILTI tax
Assets:
Assets, Fair Value Disclosure [Abstract]
Finite-Lived Intangible Assets, Major Class Name [Domain]
Finite-Lived Intangible Assets, Major Class Name [Domain]
Restructuring Type [Axis]
Restructuring Type [Axis]
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.
Employee related costs
Severance Costs
Fumarate
Fumarate [Member]
Fumarate [Member]
Product and Service [Domain]
Product and Service [Domain]
Entity Shell Company
Entity Shell Company
Deferred income taxes
Deferred Income Tax Expense (Benefit)
Summary of Activity Related to Sangamo Therapeutics
Summary of Activity Related to Sangamo Therapeutics [Table Text Block]
Summary of Activity Related to Sangamo Therapeutics
Accrued expense and other current liabilities
Increase (Decrease) in Accrued Liabilities
Other restructuring costs
Other Restructuring Costs
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 [Member]
BYOOVIZ
BYOOVIZ [Member]
BYOOVIZ
Financial Instrument [Axis]
Financial Instrument [Axis]
Collaborative Arrangement, Profit (Loss) Sharing Components [Domain]
Collaborative Arrangement, Profit (Loss) Sharing Components [Domain]
Collaborative Arrangement, Profit (Loss) Sharing Components
Discounts
Reserve for Cash Discounts [Member]
Reserve for Cash Discounts [Member]
SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain]
SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain]
Proceeds from divestiture of interest in joint venture
Proceeds from Divestiture of Interest in Joint Venture
Number of wholesalers
Number of Wholesalers
Number of Wholesalers
Document Period End Date
Document Period End Date
4.050% Senior Notes due 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]
Gain on sale of equity interest in Samsung Bioepis
Gain (Loss) on Sale of Investments
Expected profit share percentage
Equity Method Investments, Expected Profit Share
Equity Method Investments, Expected Profit Share
Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table]
Schedule of Business Acquisitions by Acquisition, Contingent Consideration [Table]
Payable Due To Termination Agreement
Accrued Payment To Termination Agreement
Accrued Payment To Termination Agreement
Schedule of Accumulated Other Comprehensive Income (Loss)
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
Total assets
Assets
Business Acquisition, Contingent Consideration [Line Items]
Business Acquisition, Contingent Consideration [Line Items]
Net income per share:
Earnings Per Share [Abstract]
Earnings Per Share [Abstract]
Income Statement Location [Axis]
Income Statement Location [Axis]
Gains (losses) on net investment hedge
Accumulated Other Comprehensive Income (Loss), Derivative Qualifying as Hedge, Excluded Component, Including Portion Attributable to Noncontrolling Interest [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, by Antidilutive Securities [Axis]
Antidilutive Securities [Axis]
Fair Value
Equity Securities, FV-NI, Current
Investment in biotechnology companies that are determined to be unconsolidated variable interest entities
Investment in biotechnology companies that are determined to be unconsolidated variable interest entities
Investment in biotechnology companies that are determined to be unconsolidated variable interest entities.
Schedule of Restructuring and Related Costs [Table]
Schedule of Restructuring and Related Costs [Table]
Ionis, Sangamo, Denali and Sage
Ionis, Sangamo, Denali and Sage [Member]
Ionis, Sangamo, Denali and Sage
Divestitures [Abstract]
Divestitures [Abstract]
Divestitures [Abstract]
Net cash flow provided by (used in) financing activities
Net Cash Provided by (Used in) Financing Activities
Gain (loss) recognized in net income, excluded component
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net
Accounting Policies [Abstract]
Accounting Policies [Abstract]
Stock Repurchase Program, Authorized Amount
Stock Repurchase Program, Authorized Amount
Collaboration expense
Employee-related Liabilities, Current
Mortgage and other asset backed securities
Asset-Backed Securities [Member]
Biogen Idec Inc. shareholders' equity
Stockholders' Equity Attributable to Parent [Abstract]
Taxes on foreign earnings
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent
Gain (loss) on foreign currency derivative instruments not designated as hedging instruments
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments
Research and development asset [Domain]
Research and development asset [Domain]
Research and development asset [Domain]
Earnings per Share
Earnings Per Share [Text Block]
Customer [Axis]
Customer [Axis]
Japan, Yen
Japan, Yen
Other long-term liabilities
Other Noncurrent Liabilities [Member]
Due after one year through five years, amortized cost
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five
Summary of financial assets with original maturities of less than 90 days included within cash and cash equivalents
Cash Equivalents, at Carrying Value [Abstract]
Collaborative Arrangement, Profit (Loss) Sharing Components [Axis]
Collaborative Arrangement, Profit (Loss) Sharing Components [Axis]
Collaborative Arrangement, Profit (Loss) Sharing Components
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.
Comprehensive income (loss) attributable to noncontrolling interests, net of tax
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest
Summary of fair value and presentation of derivatives
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]
Award Type [Domain]
Award Type [Domain]
Income Tax Contingency [Table]
Income Tax Contingency [Table]
Facility Location [Domain]
Facility Location [Domain]
-- None. No documentation exists for this element. --
Other comprehensive income (loss), before reclassifications, net of tax
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax
Biologics Manufacturing
Biologics Manufacturing [Member]
Biologics Manufacturing
Derivative Contract [Domain]
Derivative Contract [Domain]
Net Investment Hedging
Net Investment Hedging [Member]
Entity Registrant Name
Entity Registrant Name
Gain due to lease termination
Gain (Loss) On Restructuring Charges
Gain (Loss) On Restructuring Charges
Co-promotion profit sharing formula
Co Promotion Profit Sharing Formula [Table Text Block]
Co-promotion profit sharing formula.
Currency translation adjustments
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Entity Address, City or Town
Entity Address, City or Town
Unrealized gains (losses) on cash flow hedges
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Total equity
Beginning balance
Ending balance
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest
Other revenues from anti-CD20 therapeutic programs
Other revenues from anti-CD20 therapeutic programs
Other revenues from anti-CD20 therapeutic programs consists of revenue on sales of RITUXAN outside the U.S., which consist of our share of pre-tax co-promotion profits in Canada and royalty revenue on sales of Ocrevus.
Consolidation
Consolidation, Policy [Policy Text Block]
Fair Value by Asset Class
Asset Class [Domain]
Facility Type [Domain]
Facility Type [Domain]
Facility Type
Minimum
Minimum [Member]
Noncontrolling interests
Stockholders' Equity Attributable to Noncontrolling Interest
Due in one year or less, amortized cost
Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One
Statement of Financial Position [Abstract]
Statement of Financial Position [Abstract]
Entity Emerging Growth Company
Entity Emerging Growth Company
BENEPALI
BENEPALI [Member]
BENEPALI [Member]
Royalty
Royalty [Member]
Raw materials
Inventory, Raw Materials, Net of Reserves
Excess and obsolescence charges related to inventory
Inventory Write-down
Unrealized Gain (Loss) on Derivatives
Unrealized Gain (Loss) on Derivatives
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table]
SEC Schedule, 12-09, Valuation and Qualifying Accounts Disclosure [Table]
Investment, Name [Axis]
Investment, Name [Axis]
Fair Value Measurements
Fair Value Disclosures [Text Block]
Trading Symbol
Trading Symbol
Entity File Number
Entity File Number
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss) [Line Items]
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
Expected future amortization expense, 2027
Finite-Lived Intangible Asset, Expected Amortization, Year Four
Research and development expense asset acquired
Research and Development Expense
Strategic Investments
Strategic Investments [Member]
Strategic investments.
Total reserves included in consolidated balance sheets
Summary Of Product Revenue Reserves Included In Consolidated Balance Sheets [Table Text Block]
Summary of total product revenue reserves included in consolidated balance sheets.
Comprehensive income (loss) attributable to noncontrolling interests, net of tax
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest
Accelerated depreciation expense
Restructuring and Related Cost, Accelerated Depreciation
Inventory
Inventory
Inventory, Net Current and Noncurrent
Inventory, Net Current and Noncurrent
Investments in Variable Interest Entities
Variable Interest Entity Disclosure [Text Block]
Effective tax rate
Effective Income Tax Rate Reconciliation, Percent
Future Contingent Milestone Types [Domain]
Future Contingent Milestone Types [Domain]
[Domain] for Future Contingent Milestone Types [Axis]
Option exercise fee
Contract Option Exercise Fee
Contract Option Exercise Fee
Use of estimates
Use of Estimates, Policy [Policy Text Block]
Cash equivalents
Cash and Cash Equivalents, Fair Value Disclosure
Other comprehensive income:
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Payables to divestiture of interest in joint venture
Payables To Divestiture Of Interest In Joint Venture
Payables To Divestiture Of Interest In Joint Venture
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.
Schedule of Variable Interest Entities [Table]
Schedule of Variable Interest Entities [Table]
Total revenue
Product revenues
Total revenues from anti-CD20 therapeutic programs
Revenues
TECFIDERA
TECFIDERA [Member]
TECFIDERA [Member]
Derivative Instruments, Unrealized Gain (Loss)
Derivative Instruments, Unrealized Gain (Loss) [Table Text Block]
Derivative Instruments, Unrealized Gain (Loss)
Unrealized gains (losses) on cash flow hedges, net of tax
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax
Proceeds from marketable debt securities
Realized Gain (Loss) on Investments [Table Text Block]
Income Taxes
Income Tax Disclosure [Text Block]
Reduction in contingent consideration
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Asset
Due to Related Parties
Due to Related Parties
Finished goods
Inventory, Finished Goods, Net of Reserves
Sangamo Therapeutics, Inc. Agreement
Sangamo Therapeutics, Inc. aaAgreement [Member]
Sangamo Therapeutics, Inc. Agreement [Member]
Total intangible assets, gross
Intangible Assets, Gross (Excluding Goodwill)
Summary of roll forward of the changes in goodwill
Schedule of Goodwill [Table Text Block]
Basic earnings per share attributable to Biogen Inc.
Earnings Per Share, Basic
Percentage of future development costs
Percentage Of Future Development Costs
Percentage Of Future Development Costs
OCREVUS
OCREVUS [Member]
OCREVUS
Construction in progress
Construction in Progress, Gross
Payment Due At First Anniversary
Payment Due At First Anniversary [Member]
Payment Due At First Anniversary
Unfunded status of postretirement benefit plans
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Administrative Space
Administrative Space [Member]
Administrative Space
Counterparty Name [Domain]
Counterparty Name [Domain]
Treasury stock
Treasury Stock [Member]
Indefinite-lived Intangible Assets [Axis]
Indefinite-Lived Intangible Assets [Axis]
Total Biogen Inc. shareholders’ equity
Stockholders' Equity Attributable to Parent
Derivative Maturity [Axis]
Derivative Maturity [Axis]
Derivative Maturity [Axis]
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
Derivative Instruments
Derivative Instruments and Hedging Activities Disclosure [Text Block]
Overnight reverse repurchase agreements
Repurchase Agreements [Member]
Gross Unrealized Losses
Equity Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, Before Tax
Equity Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, Before Tax
Entity Interactive Data Current
Entity Interactive Data Current
Accumulated Amortization
Finite-Lived Intangible Assets, Accumulated Amortization
Number of square feet
Number of Square Feet
Number of Square Feet
Property, Plant and Equipment [Table]
Property, Plant and Equipment [Table]
Performance stock units settled in stock
Performance Stock Units Settled in Stock [Member]
Performance Stock Units Settled in Stock [Member]
Changes in operating assets and liabilities, net:
Increase (Decrease) in Operating Capital [Abstract]
Numerator:
Net Income (Loss) Attributable to Parent [Abstract]
Expected future amortization expense, 2026
Finite-Lived Intangible Asset, Expected Amortization, Year Three
Interferon
Interferon [Member]
Interferon
Fair value of contingent consideration obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]
Money market funds
Money Market Funds [Member]
FUMADERM And ADUHELM
FUMADERM And ADUHELM [Member]
FUMADERM And ADUHELM
Corporate debt securities Non-current
Corporate Debt Securities Non Current [Member]
Corporate Debt Securities Non Current.
Retained earnings
Retained Earnings [Member]
Other income (expense)
Other Nonoperating Income (Expense) [Member]
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents [Line Items]
Samsung Bioepis
Samsung Biosimilar Agreement [Member]
Samsung bio-similar agreement.
Net increase (decrease) in cash and cash equivalents
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect
Common stock
Common Stock [Member]
Share-based compensation expense included in condensed consolidated statements of income
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]
Total other comprehensive income (loss), net of tax
Other comprehensive income (loss), net of tax
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent
Gains (losses) on net investment hedges, net of tax
Derivatives used in Net Investment Hedge, Net of Tax, Period Increase (Decrease)
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]
Number of reportable segments
Number of Reportable Segments
Contingent consideration obligations
Fair value, beginning of period
Fair value, end of period
Business Combination, Contingent Consideration, Liability
Statement [Table]
Statement [Table]
Risk-adjusted discount rates
Other Assets, Measurement Input
Other Assets, Measurement Input
Document Quarterly Report
Document Quarterly Report
Gain on interest rate swap
Gain (Loss) on Derivative Instruments, Net, Pretax
Current assets:
Assets, Current [Abstract]
Unrealized Gain on Derivatives
Unrealized Gain on Derivatives
Unrealized Gain on Derivatives
Long-term operating lease liabilities
Operating Lease, Liability, Noncurrent
Statistical Measurement [Axis]
Statistical Measurement [Axis]
Less: Net (gains) losses realized on equity securities
Net gains (losses) realized during the period on equity securities
Equity Securities, FV-NI, Realized Gain (Loss)
Other Consolidated Financial Statement Detail
Additional Financial Information Disclosure [Text Block]
Reclassification out of Accumulated Other Comprehensive Income [Domain]
Reclassification out of Accumulated Other Comprehensive Income [Domain]
Cost and Net
Indefinite-lived Intangible Assets (Excluding Goodwill)
Indefinite-Lived Intangible Assets (Excluding Goodwill)
Retained earnings
Retained Earnings (Accumulated Deficit)
Returns
Sales Returns and Allowances [Member]
Cash equivalents
Cash Equivalents, at Carrying Value
Accounts receivable, net
Accounts Receivable, after Allowance for Credit Loss, Current
Other Income (Expense), Net
Interest Income (Expense), Net [Abstract]
Schedule of Finite-Lived Intangible Assets [Table]
Schedule of Finite-Lived Intangible Assets [Table]
Government securities
US Treasury and Government [Member]
Equity Components [Axis]
Equity Components [Axis]
Scenario [Domain]
Scenario [Domain]
Fair Value, Recurring
Fair Value, Measurements Recurring
Fair Value, Recurring [Member]
Document Fiscal Year Focus
Document Fiscal Year Focus
Interest in subsidiary (less than given percentage)
Interest In Subsidiary
Interest in subsidiary.
Cash flow from operating activities:
Net Cash Provided by (Used in) Operating Activities [Abstract]
Statement [Line Items]
Statement [Line Items]
Neurimmune
Neurimmune [Member]
Neurimmune.
E2609 and BAN2401
E2609 and BAN2401 [Member]
E2609 and BAN2401 [Member]
Fair Value Hierarchy and NAV [Axis]
Fair Value Hierarchy and NAV [Axis]
Cost
Finite-Lived Intangible Assets, Gross
Selling, general and administrative
Selling, General and Administrative Expense
Canadian dollar
Canada, Dollars
Royalties and licensing fees
Accrued Royalties, Current
Summary of share based compensation expense associated with different programs [Abstract]
Summary of share based compensation expense associated with different programs [Abstract]
Summary of share-based compensation expense associated with different programs.
Gross unrealized losses
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax
Operating lease assets
Operating Lease, Right-of-Use Asset
Product, net
Product [Member]
Accumulated Other Comprehensive Income
AOCI Attributable to Parent [Member]
Type of Restructuring [Domain]
Type of Restructuring [Domain]
Document Transition Report
Document Transition Report
Foreign Tax Authority
Foreign Tax Authority [Member]
Local Phone Number
Local Phone Number
Collaboration profit sharing
Collaboration Profit Sharing [Member]
Collaboration Profit Sharing
Inventory
Increase (Decrease) in Inventories
New accounting pronouncements
New Accounting Pronouncements, Policy [Policy Text Block]
Collaboration expense
Collaboration expenses accrual
Collaboration expenses accrual
Beginning balance, shares
Ending balance, shares
Common Stock, Shares, Outstanding
Other revenues
Other revenues [Table Text Block]
Other revenues [Table Text Block]
Derivative Maturity [Domain]
Derivative Maturity [Domain]
[Domain] for Derivative Maturity [Axis]
Capital contribution from noncontrolling interest
Noncontrolling Interest, Capital Contribution
Noncontrolling Interest, Capital Contribution
Goodwill
Goodwill, beginning of period
Goodwill, end of period
Goodwill
Component of accrued expenses and other
Other Current Liabilities [Member]
Future Contingent Milestone Types [Axis]
Future Contingent Milestone Types [Axis]
Future Contingent Milestone Types [Axis]
Employee stock purchase plan
Employee Stock Purchase Plan [Member]
Employee stock purchase plan.
Total
Liabilities, Fair Value Disclosure
Notes Payable
Notes Payable
Adjustments to reconcile net income to net cash flow from operating activities:
Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]
Intangible Assets and Goodwill
Goodwill and Intangible Assets Disclosure [Text Block]
Income tax (benefit) expense
Income Tax Expense (Benefit)
Income Tax Expense (Benefit)
Geographical [Domain]
Geographical [Domain]
Collaborative Arrangement and Arrangement Other than Collaborative [Table]
Collaborative Arrangement and Arrangement Other than Collaborative [Table]
Deferred tax assets, unrecognized tax benefit
Deferred Tax Assets, Valuation Allowance
Deferred tax liability
Deferred Income Tax Liabilities, Net
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.
Income Statement [Abstract]
Income Statement [Abstract]
Hedging Relationship [Axis]
Hedging Relationship [Axis]
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
Additional paid-in capital
Additional Paid-in Capital [Member]
Balance Sheet Location [Domain]
Balance Sheet Location [Domain]
Document Fiscal Period Focus
Document Fiscal Period Focus
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
Cost of sales, excluding amortization and impairment of acquired intangible assets
Cost of Goods and Services Sold
Amounts payable
Accounts Payable, To Collaborator
Accounts Payable, To Collaborator
Diluted earnings per share attributable to Biogen Inc.
Shares used in calculating diluted earnings per share
Weighted Average Number of Shares Outstanding, Diluted
Accumulated depreciation
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment
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 [Member]
Components of inventory
Schedule of Inventory, Current [Table Text Block]
Derivative liability, fair value
Derivative Liability, Subject to Master Netting Arrangement, before Offset
Term of collaboration agreement
Term of collaboration agreement
Term of collaboration agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Domain]
Collaborative Arrangement and Arrangement Other than Collaborative [Domain]
UCB Pharma S.A.
UCB Pharma S.A. [Member]
UCB Pharma S.A. [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale [Line Items]
Reduction of accounts receivable
Accounts Receivable [Member]
Other current assets, receivable
Other Assets, Current, Fair Value Disclosure,
Other Assets, Current, Fair Value Disclosure,
Common stock, par value $0.0005 per share
Common Stock, Value, Issued
Debt Instrument, Name [Domain]
Debt Instrument, Name [Domain]
Business Acquisition, Acquiree [Domain]
Business Acquisition, Acquiree [Domain]
Preferred stock
Preferred Stock [Member]
Royalty Attributed To OCREVUS
Royalty Attributed To OCREVUS [Member]
Royalty Attributed To OCREVUS
Biosimilars
Biosimilars [Member]
Biosimilars
Other (income) expense, net
Other (income) expense
Other (income) expense
Other Operating Income (Expense), Net
(Gains) losses on investments, net
Realized Investment Gains (Losses)
Summary of assets and liabilities recorded at fair value
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]
(Gain) loss on strategic investments
Increase (Decrease) in Equity Securities, FV-NI
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]
Decrease in unrecognized tax benefits is reasonably possible
Decrease in Unrecognized Tax Benefits is Reasonably Possible
Share-based Compensation Expense included in consolidated statements of income
Share-Based Payment Arrangement, Recognized Amount [Abstract]
Variable Interest Entity [Line Items]
Variable Interest Entity [Line Items]
Cash and cash equivalents
Cash and cash equivalents, beginning of the period
Cash and cash equivalents, end of the period
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents
Currency translation adjustment
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax
Unrealized Loss on Derivatives
Unrealized Loss on Derivatives
Unrealized Loss on Derivatives
Net income (loss) attributable to noncontrolling interests, net of tax
Net Income (Loss) Attributable to Noncontrolling Interest
Accumulated impairment losses related to goodwill
Goodwill, Impaired, Accumulated Impairment Loss
Current liabilities:
Liabilities, Current [Abstract]
Foreign Exchange Forward
Foreign Exchange Forward [Member]
Investment in Samsung Bioepis
Equity Method Investments
Nightstar
Nightstar [Member]
Nightstar [Member]
Foreign exchange (gains) losses, net
Foreign Currency Transaction Gain (Loss), before Tax
Parent
Total share-based compensation expense, net of tax
Parent [Member]
Percentage Of Co Promotion Operating Profits Greater Than First Fifty Million Option Two Sub Option Four
Percentage Of Co Promotion Operating Profits Greater Than First Fifty Million Option Two Sub Option Four
Percentage Of Co Promotion Operating Profits Greater Than First Fifty Million Option Two Sub Option Four
Reclassification out of Accumulated Other Comprehensive Income
Reclassification out of Accumulated Other Comprehensive Income [Member]
Income Statement Location [Domain]
Income Statement Location [Domain]
Cash Flow Hedging [Member]
Cash Flow Hedging [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amendment Flag
Amendment Flag
Useful life
Finite-Lived Intangible Asset, Useful Life
Net cash flow provided by (used in) investing activities
Net Cash Provided by (Used in) Investing Activities
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.
Government securities Current
Government Securities Current [Member]
Government securities Current.
Investment Type [Axis]
Investment Type [Axis]
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]
Revenues from anti-CD20 therapeutic programs
Revenues from anti-CD20 therapeutic programs
Revenues from anti-CD20 therapeutic programs [Table Text Block]
Revenues from anti-CD20 therapeutic programs
Other comprehensive income (loss), net of tax
Other Comprehensive Income (Loss), Net of Tax
Comprehensive income (loss) attributable to Biogen Inc.
Comprehensive Income (Loss), Net of Tax, Attributable to Parent
Collaboration agreement term
Collaboration Agreement Term
Collaboration Agreement Term
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]
Genentech
Roche Group Genentech Member
Roche group Genentech.
Gross unrealized gains
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax
5.200% Senior Notes due 2045
Senior Notes Five Point Two Percent Due Twenty Forty Five [Member]
Senior Notes Five Point Two Percent Due Twenty Forty Five [Member]
Entity Current Reporting Status
Entity Current Reporting Status
Potential future milestone payments commitment to third party
Potential Future Milestone Payments Commitment To Third Party Approximately
Potential future milestone payments commitment to third party approximately.
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets Disclosure [Abstract]
Accrued expense and other
Total accrued expense and other
Other Liabilities, Current
Investments and other assets
Other Assets, Noncurrent
Payment
Payments for Restructuring
Depreciation and amortization
Depreciation, Depletion and Amortization
Disaggregation of Revenue [Table]
Disaggregation of Revenue [Table]
Solothurn, Switzerland
Solothurn, Switzerland [Member]
Solothurn, Switzerland [Member]
Statutory rate
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent
Summary of Contractual Maturities: Available-for-Sale Securities
Available-for-Sale Securities, Debt Maturities [Abstract]
Facility Type [Axis]
Facility Type [Axis]
Facility Type
Issuance of common stock under stock option and stock purchase plans
Stock Issued During Period, Value, Treasury Stock Reissued
Counterparty Name [Axis]
Counterparty Name [Axis]
Workforce Reduction
Workforce Reduction [Member]
Workforce Reduction
Due from anti-CD20 therapeutic programs
Increase (Decrease) in Due from Related Parties
Accumulated Other Comprehensive Income (Loss) [Table]
Accumulated Other Comprehensive Income (Loss) [Table]
Government securities Non-current
Government Securities Non-current [Member]
Government Securities Non Current.
Other revenues [Abstract]
Other revenues [Abstract]
Other revenues [Abstract]
Reclassification out of Accumulated Other Comprehensive Income [Table]
Reclassification out of Accumulated Other Comprehensive Income [Table]
Schedule of Stock by Class [Table]
Schedule of Stock by Class [Table]
Entity Incorporation, State or Country Code
Entity Incorporation, State or Country Code
State taxes
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent
Other
Stockholders' Equity, Other
Collaborative arrangements and non-collaborative arrangement transactions
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Basis of presentation
Basis of Accounting, Policy [Policy Text Block]
Effect of exchange rate changes on cash and cash equivalents
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Continuing Operations
Property, plant and equipment, net
Property, Plant and Equipment, Net
Currency [Axis]
Currency [Axis]
Collaboration profit sharing/(loss reimbursement)
Collaboration profit (loss) sharing
Collaboration profit (loss) sharing
GAZYVA
GAZYVA [Member]
GAZYVA [Member]
Estimated future amortization for acquired intangible assets
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]
(Gain) loss on fair value remeasurement of contingent consideration
Contingent consideration
Contingent consideration impairment
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings
Options
Share-Based Payment Arrangement, Option [Member]
Treasury stock, at cost
Treasury Stock, Value
Unrealized gains (losses) on pension benefit obligation, net of tax
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax
AVONEX
AVONEX [Member]
AVONEX
LEQEMBI Collaboration
LEQEMBI Collaboration [Member]
LEQEMBI Collaboration
VUMERITY
VUMERITY [Member]
VUMERITY
Recognized net reductions to operating expense
Collaborative Arrangement, Profit (Loss) Sharing
Collaborative Arrangement, Profit (Loss) Sharing
Issuance of common stock under stock award plan
Stock Issued During Period, Value, Stock Options Exercised
Other, net
Other Nonoperating Income (Expense)
Notes payable
Long-Term Debt
Balance Sheet Location [Axis]
Balance Sheet Location [Axis]
Unrealized gains (losses) on securities available for sale, net of tax
OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax
Restructuring, Business Transformation and Other Cost Saving Initiatives
Restructuring and Related Activities Disclosure [Text Block]
Performance stock units settled in cash
Performance Stock Units Settled in Cash [Member]
Performance Stock Units Settled in Cash [Member]
Swiss franc
Switzerland, Francs
Payment Due At Second Anniversary
Payment Due At Second Anniversary [Member]
Payment Due At Second Anniversary
Statement of Comprehensive Income [Abstract]
Statement of Comprehensive Income [Abstract]
Operating Expenses
Operating Expenses
Maximum
Maximum [Member]
Accumulated other comprehensive income (loss)
Accumulated other comprehensive income (loss), net of tax beginning balance
Balance, January 1, 2018
Accumulated other comprehensive income (loss), net of tax ending balance
Accumulated Other Comprehensive Income (Loss), Net of Tax
PLEGRIDY
PLEGRIDY [Member]
PLEGRIDY
Schedule of Business Acquisitions, by Acquisition [Table]
Schedule of Business Acquisitions, by Acquisition [Table]
Net (gains) losses recognized on equity securities
Equity Securities, FV-NI, Gain (Loss)
Total current assets
Assets, Current
Designated as hedging instrument
Designated as Hedging Instrument [Member]
Taxes payable
Taxes Payable, Current
Time-vested restricted stock units
Time Vested Restricted Stock Units [Member]
Time vested restricted stock units.
Intangible assets
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Cash flows, revenue
Cash flows, revenue [Member]
Cash flows, revenue [Member]
Business Acquisition [Line Items]
Business Acquisition [Line Items]
Other
Goodwill, Other Increase (Decrease)
Entity Small Business
Entity Small Business
Expense reflected within statements of income
Expense reflected within statements of income
Expense reflected within statements of income
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Abstract]
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Abstract]
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Abstract]
Measurement Frequency [Domain]
Measurement Frequency [Domain]
Equity
Stockholders' Equity Note Disclosure [Text Block]
Net
Finite-Lived Intangible Assets, Net
Purchases of marketable securities
Payments to Acquire Debt Securities, Available-for-Sale
Summary of significant accounting policies
Significant Accounting Policies [Text Block]
Disaggregation of Revenue [Abstract]
Disaggregation of Revenue [Abstract]
Summary of fair and carrying value of debt instruments
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]
Property, Plant and Equipment
Property, Plant and Equipment Disclosure [Text Block]
Amounts receivable
Accounts Receivable, From Collaborator
Accounts Receivable, From Collaborator
2020 Share Repurchase Program
2020 Share Repurchase Program [Member]
2020 Share Repurchase Program [Member]
Income tax effect
Share-Based Payment Arrangement, Expense, Tax Benefit
Mortgage and other asset backed securities Non-current
Mortgage And Other Asset Backed Securities Non Current [Member]
Mortgage And Other Asset Backed Securities Non Current.
Accounts receivable
Increase (Decrease) in Accounts Receivable
Title of 12(b) Security
Title of 12(b) Security
Other assets, receivable
Other Assets, Fair Value Disclosure
Payments/Returns Relating To Sales in Current Year
Payments Returns Applied Against Product Revenue Reserves Relating To Current Year
Payments/ returns applied against product revenue reserves relating to current year.
Pretax profit sharing formula
Pretax Profit Sharing Formula [Table Text Block]
Pretax Profit Sharing Formula [Table Text Block]
Consolidated Entities [Axis]
Consolidated Entities [Axis]
Notes payable, fair value
Notes Payable, Fair Value Disclosure
Gain/Loss on fair value of foreign currency forward contracts
Unrealized Gain (Losses) on Foreign Currency Derivatives, Net, before Tax
Amount of net unrealized gain (loss) related to the change in fair value of foreign currency exchange rate derivatives designated as cash flow hedging instruments. Recorded in accumulated other comprehensive income to the extent that the cash flow hedge is determined to be effective.
Percentage of future development costs related to Eisai
Percentage of future development costs related to Eisai
Percentage of future development costs related to Eisai
Total cost and expense
Costs and Expenses
Contract manufacturing, royalty and other revenue
Product and Service, Other [Member]
Debt Instrument [Line Items]
Debt Instrument [Line Items]
RITUXAN
RITUXAN [Member]
RITUXAN.
Warehouse, Utilities and Support Space
Warehouse, Utilities and Support Space [Member]
Warehouse, Utilities and Support Space
Income Tax Contingency [Line Items]
Income Tax Contingency [Line Items]
Class of Stock [Line Items]
Class of Stock [Line Items]
3.250% Senior Notes, Due February 15, 2051
3.250% Senior Notes, Due February 15, 2051 [Member]
3.250% Senior Notes, Due February 15, 2051
Beginning Balance
Ending Balance
Total Reserves
Revenue-related reserves for discounts and allowances
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount
Selling, general and administrative
Selling, general and administrative
Selling, General and Administrative Expenses [Member]
Investments, Debt and Equity Securities [Abstract]
Investments, Debt and Equity Securities [Abstract]
Expected future amortization expense, 2025
Finite-Lived Intangible Asset, Expected Amortization, Year Two
Cash flows, operating expenses
Cash flows, operating expenses [Member]
Cash flows, operating expenses [Member]
LIABILITIES AND EQUITY
Liabilities and Equity [Abstract]
Amortized Cost
Amortized Cost
Debt Securities, Available-for-Sale, Amortized Cost
Fair Value, Recurring and Nonrecurring [Table]
Fair Value, Recurring and Nonrecurring [Table]
Acquisitions of intangible assets
Payments to Acquire Intangible Assets
Financial Instruments
Cash, Cash Equivalents, and Marketable Securities [Text Block]
Weighted-average shares used in calculating:
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Inventory
Inventory, current
Inventory, Net
Accounts payable
Accounts Payable, Current
Restructuring charges
Expense
Restructuring Charges
Due after five years, estimated fair value
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.
Amortized Cost
Equity Securities, FV-NI, Cost
Hedging Relationship [Domain]
Hedging Relationship [Domain]
Summary of contractual maturities: available-for-sale securities
Investments Classified by Contractual Maturity Date [Table Text Block]
Hedging Designation [Axis]
Hedging Designation [Axis]
Average maturity of marketable securities, months
Average Maturity Of Marketable Securities
Average remaining time to maturity of marketable debt securities, available-for-sale securities.
Entity Filer Category
Entity Filer Category
Equity:
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Basic earnings per share attributable to Biogen Inc.
Weighted average number of common shares outstanding
Weighted Average Number of Shares Outstanding, Basic
Corporate debt securities Current
Corporate Debt Securities Current [Member]
Corporate debt securities Current.
U.S.
UNITED STATES
Disposal Groups, Including Discontinued Operations [Table]
Disposal Groups, Including Discontinued Operations [Table]
Equity Securities, Current
Equity Securities, Current [Member]
Equity Securities, Current
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.
Accrued Expenses and Other
Accrued Liabilities, Current [Abstract]
Liabilities:
Liabilities, Fair Value Disclosure [Abstract]
Equity, ownership interest
Equity Method Investment, Ownership Percentage
Summary of assets and liabilities recorded at fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Overview
Business Overview [Policy Text Block]
Describes an overview of the company and its operations.
Compensation related to share-based payments
Share-based compensation expense
Share-Based Payment Arrangement, Expense
Commitments, contingencies and guarantees
Commitments and Contingencies
Summary of Activity Related to BAN2401 and Elenbecestat Collaboration
Summary of Activity Related to E2609 and BAN2401 Collaboration [Table Text Block]
[Table Text Block] for Summary of Activity Related to E2609 and BAN2401 Collaboration [Table]
Security Exchange Name
Security Exchange Name
Gain (loss) on sale
Gain (Loss) on Disposition of Assets
Derivative, Notional Amount
Derivative, Notional Amount
Preferred stock, par value $0.001 per share
Preferred Stock, Value, Issued
Additional milestone payment
Additional Milestone Payment
Additional milestone payment.
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment [Line Items]
ADUHELM
ADUHELM [Member]
ADUHELM
Income tax assets and liabilities
Increase (Decrease) in Income Taxes Payable
Due after five years, amortized cost
Available For Sale Securities Debt Maturities After Five Years Amortized Cost
This item represents debt securities, at cost, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any, 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.
Total development expense incurred by the collaboration related to the advancement of LEQEMBI
Expense Incurred By Collaboration
Total expense incurred by collaboration.
Cover [Abstract]
Cover [Abstract]
Schedule of Long-term Debt Instruments [Table]
Schedule of Long-Term Debt Instruments [Table]
Significant Unobservable Inputs (Level 3)
Fair Value, Inputs, Level 3 [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
Marketable equity securities
Debt Securities, Trading, and Equity Securities, FV-NI, Cost [Abstract]
Marketable securities
Debt Securities, Available-for-Sale, Noncurrent
Credits and net operating loss utilization
Effective Income Tax Rate Reconciliation, Tax Credit, Percent
Share-based Payments
Share-Based Payment Arrangement [Text Block]
Restructuring and Related Activities [Abstract]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Summary of share-based compensation expense associated with each of our share-based compensating programs
Share-Based Payment Arrangement, Cost by Plan [Table Text Block]
Work in process
Inventory, Work in Process, Net of Reserves
Revenues
Revenue from Contract with Customer [Text Block]
Investment Type Categorization [Domain]
Investments [Domain]
Noncontrolling interest
Noncontrolling Interest [Member]
Forecast
Forecast [Member]
Payments related to issuance of stock for share-based compensation arrangements, net
Payment, Tax Withholding, Share-Based Payment Arrangement
Total liabilities and equity
Liabilities and Equity
Operating expense
Operating Expense [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Axis]
Collaborative Arrangement and Arrangement Other than Collaborative [Axis]
Summary of roll forward of the changes in goodwill
Goodwill [Roll Forward]
Amount remaining under 2019 Share Repurchase Program
Stock Repurchase Program, Remaining Authorized Repurchase Amount
Investments, All Other Investments [Abstract]
Investments, All Other Investments [Abstract]
Stock units
Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements
Revenue
Sales [Member]
Rest of World
Non-US [Member]
Collaboration agreement term
Period Of Collaboration Agreement
Period Of Collaboration Agreement
SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis]
SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis]
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Not designated as hedging instrument
Not Designated as Hedging Instrument [Member]
Issuance of common stock under stock option and stock purchase plans, shares
Stock Issued During Period, Shares, Treasury Stock Reissued
Sales trigger gross sales threshold
Sales Trigger Gross Sales Threshold
Sales trigger gross sales threshold.
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Significant Other Observable Inputs (Level 2)
Fair Value, Inputs, Level 2 [Member]
Current Fiscal Year End Date
Current Fiscal Year End Date
Strategic investment portfolio
Strategic Investment Portfolio
Strategic investment portfolio.
Realized gains
Debt Securities, Available-for-Sale, Realized Gain
FLIXABI
FLIXABI [Member]
FLIXABI [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net
Intangible assets, net
Intangible Assets, Net (Excluding Goodwill)
Diluted earnings per share attributable to Biogen Inc.
Earnings Per Share, Diluted
Inventory [Line Items]
Inventory [Line Items]
Due from anti-CD20 therapeutic programs
Due from anti-CD20 therapeutic programs
Receivable from anti-CD20 therapeutic programs for our share of the pre-tax co-promotion profits generated from our co-promotion arrangement for sales of RITUXAN.
Trademarks and Trade Names
Trademarks and Trade Names [Member]
Purchased intangible assets
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Depreciation and Amortization, Percent
Inventory, Idle Capacity Charges And Contractual Commitments
Inventory, Idle Capacity Charges And Contractual Commitments [Member]
Inventory, Idle Capacity Charges And Contractual Commitments
Proceeds from sales of strategic investments
Proceeds from Sale of Other Investments
Total current liabilities
Liabilities, Current
Other current assets
Other Assets, Current
Inventory, Current [Table]
Inventory, Current [Table]
Accrued income taxes
Accrued Income Taxes, Noncurrent
Schedule of Available-for-sale Securities [Table]
Schedule of Available-for-Sale Securities [Table]
Facility Location [Axis]
Facility Location [Axis]
-- None. No documentation exists for this element. --
BIIB054
BIIB054 [Member]
BIIB054
Restructuring Cost and Reserve [Line Items]
Restructuring Cost and Reserve [Line Items]
Dispositions
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]
Share Repurchase Program [Axis]
Share Repurchase Program [Axis]
Due from Related Parties
Due from Related Parties
Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table]
Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table]
Corporate debt securities
Corporate Debt Securities [Member]
Net unrealized (gains) losses recognized on equity securities
Net gains recognized on the increase in fair value of equity securities
Equity Securities, FV-NI, Unrealized Gain (Loss)
Derivative asset, fair value
Derivative Asset, Subject to Master Netting Arrangement, before Offset
Entity Address, Address Line One
Entity Address, Address Line One
Other
Proceeds from (Payments for) Other Financing Activities
Capitalized share-based compensation costs
Share-Based Payment Arrangement, Amount Capitalized
Estimated additional payments upon achievement of development and commercial milestones
Estimated Additional Payments Upon Achievement Of Development And Commercial Milestones
Estimated additional payments upon achievement of development and commercial milestones.
Product and Service [Axis]
Product and Service [Axis]
Sage Therapeutics
Sage Therapeutics Inc. [Member]
Sage Therapeutics Inc.
Gain on derivative used in net investment hedge
Other Comprehensive Income (Loss), Net Investment Hedge, Gain (Loss), Reclassification, before Tax
Fair Value Disclosures [Abstract]
Fair Value Disclosures [Abstract]
Interest expense
Interest Expense
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Marketable debt securities
Debt Securities, Available-for-Sale [Abstract]
Amortization and impairment of acquired intangible assets
Amortization and Impairment of Acquired Intangible Assets
Amortization and Impairment of Acquired Intangible Assets
Proceeds from maturities and sales
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale
Inventory, noncurrent
Inventory, Noncurrent
MS Product Revenues
MS Product Revenues [Member]
MS Product Revenues [Member]
Accrued expenses and other
Schedule of Accrued Liabilities [Table Text Block]
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 Disclosure [Text Block]
Equity [Abstract]
Equity [Abstract]
Research and development asset [Axis]
Research and development asset [Axis]
Research and development asset [Axis]
Inventory Disclosure [Abstract]
Inventory Disclosure [Abstract]
Entity Tax Identification Number
Entity Tax Identification Number
Derivatives [Line Items]
Derivatives, Fair Value [Line Items]
Derivative contracts
Foreign Currency Contract, Asset, Fair Value Disclosure
Contract manufacturing and other revenue
Contract manufacturing and other revenue [Member]
Other corporate revenues [Member]
Other noncurrent assets
Other Noncurrent Assets [Member]
Revenues by product
Disaggregation of Revenue [Table Text Block]
Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract]
Equity Securities, FV-NI, Gain (Loss), Alternative [Abstract]
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer [Abstract]
Expected future amortization expense, 2023 (remaining three months)
Finite-Lived Intangible Asset, Expected Amortization, Remainder of Fiscal Year
Consolidated Entities [Domain]
Consolidated Entities [Domain]
FAMPYRA
FAMPYRA [Member]
FAMPYRA [Member]
Research and development
Research and Development Expense (Excluding Acquired in Process Cost)
Reconciliation between the U.S. federal statutory tax rate and effective tax rate
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]
Accrued expenses and other
Accrued Liabilities [Member]
Schedule of Restructuring Reserve by Type of Cost
Schedule of Restructuring Reserve by Type of Cost [Table Text Block]
Dilutive potential common shares
Weighted Average Number of Shares Outstanding, Diluted, Adjustment
Commercial paper
Commercial Paper [Member]
Expected future amortization expense, 2028
Finite-Lived Intangible Asset, Expected Amortization, Year Five
Eisai
Eisai [Member]
Eisai [Member]
Entity Central Index Key
Entity Central Index Key
Antidilutive Securities, Name [Domain]
Antidilutive Securities, Name [Domain]
Interest income
Investment Income, Interest
Measurement Frequency [Axis]
Measurement Frequency [Axis]
Finite-Lived Intangible Assets by Major Class [Axis]
Finite-Lived Intangible Assets by Major Class [Axis]
Co-promotion operating profit threshold for Rituxan in US and Canada to determine share of co promotion operating profit prior to amendment
Co Promotion Operating Profit Threshold To Determine Share Of Co Promotion Operating Profit Prior To Amendment
Co promotion operating profit threshold to determine share of co promotion operating profit prior to amendment.
Collaborative and Other Relationships
Collaborative Arrangement Disclosure [Text Block]
Distributor One
Distributor One [Member]
Distributor one.
Other
Other Accrued Liabilities, Current
Measurement Input Type [Axis]
Measurement Input Type [Axis]
Mosunetuzumab
Mosunetuzumab [Member]
Mosunetuzumab
Entity [Domain]
Entity [Domain]
City Area Code
City Area Code
ASSETS
Assets [Abstract]
Other changes in operating assets and liabilities, net
Increase (Decrease) in Other Operating Assets and Liabilities, Net
Euro
Euro Member Countries, Euro
Statement of Stockholders' Equity [Abstract]
Statement of Stockholders' Equity [Abstract]
Basic and diluted earnings per share
Basic And Diluted Earnings Per Share [Abstract]
Basic and diluted earnings per share.
Summary of Activity Related to Denali Therapeutics Collaboration
Summary of Activity Related to Denali Therapeutics Collaboration [Table Text Block]
Summary of Activity Related to Denali Therapeutics Collaboration
Cash flows from financing activities:
Net Cash Provided by (Used in) Financing Activities [Abstract]
Gain (loss) on investments in equity securities
Gain (Loss) on Securities [Table Text Block]
Cumulative translation loss
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax
Asset Class [Axis]
Asset Class [Axis]
Share-based compensation
Share-Based Payment Arrangement, Noncash Expense
Summary of Activity Related to Sage Therapeutics
Summary of Activity Related to Sage Therapeutics [Table Text Block]
Summary of Activity Related to Sage Therapeutics
Other long-term liabilities
Other Liabilities, Noncurrent
(Gain) loss on equity method investments
(Gain) loss on equity method investments
Income (Loss) from Equity Method Investments
Equity Securities, Non-Current
Equity Securities, Non-Current [Member]
Equity Securities, Non-Current
Asset impairment charges
Asset Impairment Charges
Purchases of property, plant and equipment
Payments to Acquire Property, Plant, and Equipment
Research and development
Research and development
Research and Development Expense [Member]
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue [Line Items]
Expected future amortization expense, 2024
Finite-Lived Intangible Asset, Expected Amortization, Year One
Basic and diluted earnings per share
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Realized losses
Debt Securities, Available-for-Sale, Realized Loss
Cost of Sales
Cost of Sales [Member]
Gains (losses) on net investment hedge, excluded component
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)
Customer [Domain]
Customer [Domain]
Revenue from anti-CD20 therapeutic programs
Revenues from anti-cd20 therapeutic programs [Member]
Revenues from anti-cd20 therapeutic programs