XML 189 R107.htm IDEA: XBRL DOCUMENT
v3.22.4

Share-Based Payments - Narrative (Details) $ / shares in Units, $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2017 shares | Jun. 30, 2015 shares | May 31, 2006 shares | Mar. 31, 2018 | Dec. 31, 2022 USD ($) Increment plan $ / shares shares | Dec. 31, 2021 USD ($) $ / shares | Dec. 31, 2020 USD ($) $ / shares | Dec. 31, 2013 Increment
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Unrecognized compensation cost related to unvested share-based compensation |  |  |  |  | $ 290.5 |  |  |
Weighted-average period to recognize the cost of unvested awards |  |  |  |  | 2 years |  |  |
Number of share-based compensation plans pursuant to which awards are currently being made | plan |  |  |  |  | 3 |  |  |
Total intrinsic value of options exercised |  |  |  |  |  |  | $ 2.9 |
Shares issued under ESPP (in shares) | shares |  | 6,200,000 |  |  |  |  |  |
Stock Options |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Share based payment arrangement, term |  |  |  |  | 10 years |  |  |
Market Stock Units (MSUs) |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Number of equal annual increments | Increment |  |  |  |  | 3 |  |  | 4
Percentage of earnings of the target number of units granted based on actual stock performance |  |  |  |  | 0.00% |  |  | 0.00%
Percentage of earnings of the target number of units granted based on actual stock performance |  |  |  |  | 200.00% |  |  | 150.00%
Total fair value of vested awards |  |  |  |  | $ 18.8 | $ 22.5 | $ 26.9 |
Granted (in dollars per share) | $ / shares |  |  |  |  | $ 0 | $ 358.77 | $ 398.61 |
Cash Settled Performance Units (CSPUs) |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Number of equal annual increments | Increment |  |  |  |  | 3 |  |  |
Percentage of earnings of the target number of units granted based on actual stock performance |  |  |  |  | 0.00% |  |  |
Percentage of earnings of the target number of units granted based on actual stock performance |  |  |  |  | 200.00% |  |  |
Number of days for calculation of average closing stock price |  |  |  |  | 30 days |  |  |
Cash settlement of awards upon vesting |  |  |  |  |  |  | $ 3.8 |
Performance Units (PUs) |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Number of equal annual increments | Increment |  |  |  |  | 3 |  |  |
Percentage of earnings of the target number of units granted based on actual stock performance |  |  |  |  | 0.00% |  |  |
Percentage of earnings of the target number of units granted based on actual stock performance |  |  |  |  | 200.00% |  |  |
Number of days for calculation of average closing stock price |  |  |  |  | 30 days |  |  |
Total fair value of vested awards |  |  |  |  | $ 9.5 | $ 15.5 |  |
Cash settlement of awards upon vesting |  |  |  |  |  |  | 3.4 |
Granted (in dollars per share) | $ / shares |  |  |  |  | $ 294.43 |  |  |
PSUs Settled in Stock |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Vesting period |  |  |  | 3 years |  |  |  |
Percentage of earnings of the target number of units granted based on actual stock performance |  |  |  |  | 0.00% |  |  |
Percentage of earnings of the target number of units granted based on actual stock performance |  |  |  |  | 200.00% |  |  |
Granted (in dollars per share) | $ / shares |  |  |  |  | $ 294.43 |  |  |
PSUs Settled in Cash |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Vesting period |  |  |  | 3 years |  |  |  |
Percentage of earnings of the target number of units granted based on actual stock performance |  |  |  |  | 0.00% |  |  |
Percentage of earnings of the target number of units granted based on actual stock performance |  |  |  |  | 200.00% |  |  |
Number of days for calculation of average closing stock price |  |  |  |  | 30 days |  |  |
Total fair value of vested awards |  |  |  |  | $ 11.0 | 9.9 |  |
Time-Vested Restricted Stock Units (RSUs) |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Vesting period |  |  |  |  | 3 years |  |  |
Total fair value of vested awards |  |  |  |  | $ 116.3 | $ 132.2 | $ 140.5 |
Granted (in dollars per share) | $ / shares |  |  |  |  | $ 221.28 | $ 276.90 | $ 318.87 |
Directors Plan |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Total number of shares of common stock for issuance (in shares) | shares |  |  | 1,600,000 |  |  |  |  |
Ratio of total number of shares reserved under the plan |  |  | 1.5 |  |  |  |  |
2017 Omnibus Equity Plan |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Ratio of total number of shares reserved under the plan | 1.5 |  |  |  |  |  |  |
Omnibus Plan number of shares authorized (in shares) | shares | 8,000,000 |  |  |  |  |  |  |
2017 Omnibus Equity Plan | Chief Executive Officer |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award |  |  |  |  |  |  |  |
Stock options granted (in shares) | shares |  |  |  |  | 81,000 |  |  |
Stock options granted, weighted average price (in dollars per share) | $ / shares |  |  |  |  | $ 139.10 |  |  |
Stock options granted, grant date fair value |  |  |  |  | $ 11.2 |  |  |
Vesting period |  |  |  |  | 3 years |  |  |

X
- Definition Maximum target number of market stock units granted based on stock performance in percent. + References No definition available. + Details
Name: | biib_MaximumTargetNumberOfMarketStockUnitsGrantedBasedOnStockPerformanceInPercent
Namespace Prefix: | biib_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Minimum target number of market stock units granted based on stock performance in percent. + References No definition available. + Details
Name: | biib_MinimumTargetNumberOfMarketStockUnitsGrantedBasedOnStockPerformanceInPercent
Namespace Prefix: | biib_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of days for calculation of average closing stock price. + References No definition available. + Details
Name: | biib_NumberOfDaysForCalculationOfAverageClosingStockPrice
Namespace Prefix: | biib_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of equal annual increments. + References No definition available. + Details
Name: | biib_NumberOfEqualAnnualIncrements
Namespace Prefix: | biib_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of share-based compensation plans pursuant to which awards are currently being made. + References No definition available. + Details
Name: | biib_NumberOfShareBasedCompensationPlansPursuantToWhichAwardsAreCurrentlyBeingMade
Namespace Prefix: | biib_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Total number of shares of common stock for issuance. + References No definition available. + Details
Name: | biib_NumberOfSharesOfCommonStockForIssuance
Namespace Prefix: | biib_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Ratio of total number of shares reserved under the plan. + References No definition available. + Details
Name: | biib_RatioOfNumberOfSharesReservedUnderPlan
Namespace Prefix: | biib_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted-average period to recognize the cost of nonvested awards. + References No definition available. + Details
Name: | biib_WeightedAveragePeriodToRecognizeCostOfNonvestedAwards
Namespace Prefix: | biib_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate cash paid by the entity during the period to settle equity instruments granted under equity-based payment arrangements. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (k) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of cost not yet recognized for nonvested award under share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(01) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares authorized for issuance under share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Gross number of share options (or share units) granted during the period. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(01) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(1) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of shares issued during the period as a result of an employee stock purchase plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI https://asc.fasb.org/extlink&oid=126973232&loc=d3e21463-112644 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI https://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=biib_MarketStockUnitsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=biib_CashSettledPerformanceSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=biib_PerformanceStockUnitsSettledinStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=biib_PerformanceStockUnitsSettledinCashMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AwardTypeAxis=biib_TimeVestedRestrictedStockUnitsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PlanNameAxis=biib_DirectorsPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PlanNameAxis=biib_A2017OmnibusEquityPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_TitleOfIndividualAxis=srt_ChiefExecutiveOfficerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |