XML 53 R2.htm IDEA: XBRL DOCUMENT
v3.25.1

Pay vs Performance Disclosure - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Pay vs Performance Disclosure |  |  |  |  |
Pay vs Performance Disclosure, Table | Pay Versus Performance As discussed in our CD&A above, our CMDC has implem en ted executive compensation programs designed to link a substantial part of our NEOs compensation to financial, strategic, and market-based measures and align realizable compensation with stockholder returns. The following table sets forth additional compensation information for our NEOs, calculated in accordance with SEC regulations, for fiscal years 2024, 2023, 2022, 2021 and 2020. Pay versus Performance (PVP) Tabular Disclosure: The table below contains information about the relationship between compensation actually paid, as computed in accordance with SEC rules, to our CEO and non-CEO NEOs as a group, and our financial performance for the five years 2020 – 2024. The cumulative Total Stockholder Return depicts a hypothetical $100 investment in our common stock on December 31, 2019, and shows the value of that investment over time for each calendar year. A hypothetical $100 investment in the NBI using the same methodology is shown for comparison. The CMDC did not consider the PVP disclosure below in making its pay decisions for any of the fiscal years shown. In addition, the average non-CEO NEO incumbents differ year to year and may comprise different roles with different individual and market-based considerations impacting compensation decisions. Comparing the summary compensation table total average and compensation actually paid average for the non-CEO NEOs year-over-year does not accurately depict changes in these values for the same individuals. Narrative to Pay versus Performance Table For the fiscal year ending December 31, 2024, the most important financial measures we identified for the purposes of the PVP disclosure requirement linking compensation actually paid (CAP) to our NEOs to company performance are total stockholder return, revenue, Non-GAAP EPS, and performance against our pipeline metrics. CAP reflects, among other items, adjustments to the fair value of equity awards during the years presented. Factors impacting the fair value of equity awards include the price of our common stock at year end, as well as the projected and actual achievement of performance goals under our equity awards. These adjustments contributed significantly to the CAP value reported for each year. LTIs represent a large percentage of our NEOs’ target compensation. Because the value of our LTI awards is tied to the value of our common stock, TSR will have a significant influence on the value of such awards and thereafter aligns the value of realizable pay to long-term stockholder value creation. Revenue and EPS were significant components in the annual bonus plan scorecard for each of the presented years and are important measures of our company’s financial performance. Net income is included for disclosure requirements, but there is no relationship between net income and CAP in our incentive plans except where it applies to EPS. Successfully advancing therapies through our pipeline and performing against our pipeline milestone metrics are key value drivers for our company’s long-term growth. Pipeline performance has also driven significant changes in the price of our common stock, and therefore impacts the CAP calculation. We recognize our pipeline as a critical area of focus for our strategy and the long-term success of our company.
Fiscal Year |  | SCT Total for CEO: C. Viehbacher (1) |  | SCT Total for Former CEO: M. Vounatsos (1) |  | Compensation Actually Paid to CEO (2) |  | Compensation Actually Paid to Former CEO (2) |  | Average SCT Total for Other NEOs (3) |  | Average Compensation Actually Paid for Other NEOs (3) |  | Value of $100 Initial Fixed Investment Based on TSR (4) |  | Value of $100 Initial Fixed Investment Based on Nasdaq Biotech Index TSR (4) |  | Net Income ($M) |  | Company Selected Measure: Revenue (5)
2024 |  | $24,166,665 |  | — |  | $1,250,864 |  | — |  | $6,365,146 |  | ($228,942) |  | $51.54 |  | $113.84 |  | $1,632 |  | $9,032M
2023 |  | $4,069,913 |  | — |  | ($4,498,193) |  | — |  | $6,258,401 |  | $4,222,331 |  | $87.21 |  | $115.42 |  | $1,161 |  | $9,675M
2022 |  | $30,488,593 |  | $26,625,221 |  | $27,551,849 |  | $5,898,711 |  | $5,878,461 |  | $4,969,529 |  | $93.32 |  | $111.27 |  | $3,047 |  | $10,326M
2021 |  | — |  | $17,689,665 |  | — |  | $15,211,025 |  | $5,761,560 |  | $5,081,944 |  | $80.85 |  | $124.89 |  | $1,556 |  | $11,054M
2020 |  | — |  | $18,659,829 |  | — |  | $8,578,367 |  | $6,525,375 |  | $4,363,668 |  | $82.52 |  | $125.69 |  | $4,001 |  | $13,952M
Notes to Pay Vs. Performance Table
(1) | The dollar amounts reported are the amounts of total compensation reported for our CEO, Mr. Viehbacher, and our former CEO, Mr. Vounatsos in the Summary Compensation Table for fiscal years 2024, 2023, 2022, 2021 and 2020. Mr. Vounatsos served as CEO for each of the full fiscal years 2021 and 2020, while Mr. Viehbacher and Mr. Vounatsos both served as CEO in fiscal year 2022.
(2) | The dollar amounts reported represent the amount of “compensation actually paid”, as computed in accordance with SEC rules. The dollar amounts do not reflect the actual amounts of compensation paid to our CEO and other NEOs during the applicable year, but also include (i) the year-end fair value of equity awards granted during the reported year and (ii) the change in fair value of equity awards that were unvested at the end of the prior year, measured through the date the awards vested or were forfeited, or through the end of the reported fiscal year.
(3) | For 2024, reflects compensation information for our NEOs, other than our CEO and former CEO, as described in the CD&A of this Proxy Statement. For 2023, reflects compensation information for Mr. McDonnell, Ms. Alexander, Ms. Murphy and Mr. Izzar, for 2022, reflects compensation information for Mr. McDonnell, Ms. Alexander, Dr. Gregory, Ms. Murphy and Mr. Guindo, our former EVP of Global Product Strategy and Commercialization. For 2021, reflects compensation information for Mr. McDonnell, Ms. Alexander, Mr. Guindo and Dr. Sandrock, our former EVP of R&D. For 2020, reflects compensation information for Mr. McDonnell, Ms. Alexander, Mr. Guindo, Dr. Sandrock and Mr. Capello, our former CFO.
(4) | Reflects cumulative total stockholder return of the NBI as of December 31, 2024. The NBI is the peer group used by Biogen for the purposes of Item 201(e) of Regulation S-K under the Exchange Act in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024.
(5) | Revenue was adjusted to neutralize the effects of foreign exchange rate fluctuations.
The following tables set forth the adjustments made during each year in the PVP table to arrive at “compensation actually paid ” to our Principal Executive Officer during each year.
Fiscal Year |  | Summary Compensation Table Total for CEO |  | Summary Compensation Table Total for former CEO |  | Reported Value of Equity Awards for CEO (1) |  | Reported Value of Equity Awards for former CEO (1) |  | Equity Award Adjustments for CEO (2) |  | Equity Award Adjustments for former CEO (2) |  | Compensation Actually Paid to CEO |  | Compensation Actually Paid to former CEO
2024 |  | $24,166,665 |  | — |  | $18,010,911 |  | — |  | ($4,904,890) |  | — |  | $1,250,864 |  | —
2023 |  | $4,069,913 |  | — |  | — |  | — |  | ($8,568,106) |  | — |  | ($4,498,193) |  | —
2022 |  | $30,488,593 |  | $26,625,221 |  | $30,000,655 |  | $15,389,732 |  | $27,063,911 |  | ($5,336,778) |  | $27,551,849 |  | $5,898,711
2021 |  | — |  | $17,689,665 |  | — |  | $14,084,314 |  | — |  | $11,605,674 |  | — |  | $15,211,025
2020 |  | — |  | $18,659,829 |  | — |  | $13,887,064 |  | — |  | $3,805,602 |  | — |  | $8,578,367
(1) | Represents the grant date fair value of equity awards to our CEO and former CEO, as reported in the “Stock Awards” and “Option Awards” columns in the Summary Compensation Table for each applicable year.
(2) | Represents the year-over-year change in the fair value of equity awards to our CEO and former CEO, as itemized in the table below. No awards vested in the year they were granted.
Fair Value of Equity Awards for CEO and former CEO |  | 2024 |  | 2023 |  | 2022 |  |  | 2021 |  | 2020
|  | Mr. Viehbacher |  |  |  | Mr. Vounatsos |
As of year-end for awards granted during the year |  | $8,702,498 |  | — |  |  | $27,063,911 |  |  |  | $1,996,870 |  |  | $10,985,776 |  | $8,893,002
Year-over-year increase or decrease of unvested awards granted in prior years |  | ($12,329,483) |  | ($7,204,687) |  |  | — |  |  |  | ($6,247,880) |  |  | ($687,744) |  | ($3,618,885)
Increase or decrease from prior fiscal year-end for awards that vested during the year |  | ($1,277,904) |  | ($1,363,419) |  |  | — |  |  |  | ($1,085,768) |  |  | $1,307,643 |  | ($1,468,515)
Total Equity Award Adjustments |  | ($4,904,890) |  | ($8,568,106) |  |  | $27,063,911 |  |  |  | ($5,336,778) |  |  | $11,605,674 |  | $3,805,602
The following tables set forth the adjustments made during each year in the PVP table to arrive at “compensation actually paid” to our non-CEO NEOs during each year.
Fiscal Year |  | Average Summary Compensation Table Total for Non-CEO NEOs |  | Average Reported Value of Equity Awards for Non-CEO NEOs (1) |  | Average Equity Award Adjustments for Non-CEO NEOs (2) |  | Average Compensation Actually Paid to Non-CEO NEOs
2024 |  | $6,365,146 |  | $4,156,541 |  | ($2,437,548) |  | ($228,942)
2023 |  | $6,258,401 |  | $4,503,143 |  | $2,467,073 |  | $4,222,331
2022 |  | $5,878,461 |  | $4,223,226 |  | $3,314,294 |  | $4,969,529
2021 |  | $5,761,560 |  | $4,105,942 |  | $3,426,326 |  | $5,081,944
2020 |  | $6,525,375 |  | $4,158,006 |  | $1,996,299 |  | $4,363,668
(1) | Represents the average of the grant date fair value of the equity awards to our NEOs (other than our CEO and former CEO), as reported in the “Stock Awards” column in the Summary Compensation Tables for each applicable year.
(2) | Represents the average of the year-over-year change in fair value of equity awards to our NEOs (other than our CEO and former CEO), as itemized in the table below. No awards vested in the year they were granted.
Average Fair Value of Equity Awards for non-CEO NEOs |  | 2024 |  | 2023 |  | 2022 |  | 2021 |  | 2020
As of year-end for awards granted during the year |  | $2,008,250 |  | $3,523,016 |  | $3,809,706 |  | $3,295,987 |  | $2,904,846
Year-over-year increase or decrease of unvested awards granted in prior years |  | ($4,156,500) |  | ($1,027,351) |  | ($241,427) |  | ($150,316) |  | ($741,028)
Increase or decrease from prior fiscal year-end for awards that vested during the year |  | ($289,298) |  | ($28,591) |  | ($253,985) |  | $280,656 |  | ($167,520)
Total Equity Award Adjustments |  | ($2,437,548) |  | $2,467,073 |  | $3,314,294 |  | $3,426,326 |  | $1,996,299
Company Selected Measure Name | Revenue |  |  |  |
Named Executive Officers, Footnote | For 2024, reflects compensation information for our NEOs, other than our CEO and former CEO, as described in the CD&A of this Proxy Statement. For 2023, reflects compensation information for Mr. McDonnell, Ms. Alexander, Ms. Murphy and Mr. Izzar, for 2022, reflects compensation information for Mr. McDonnell, Ms. Alexander, Dr. Gregory, Ms. Murphy and Mr. Guindo, our former EVP of Global Product Strategy and Commercialization. For 2021, reflects compensation information for Mr. McDonnell, Ms. Alexander, Mr. Guindo and Dr. Sandrock, our former EVP of R&D. For 2020, reflects compensation information for Mr. McDonnell, Ms. Alexander, Mr. Guindo, Dr. Sandrock and Mr. Capello, our former CFO. |  |  |  |
Peer Group Issuers, Footnote | Reflects cumulative total stockholder return of the NBI as of December 31, 2024. The NBI is the peer group used by Biogen for the purposes of Item 201(e) of Regulation S-K under the Exchange Act in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024. |  |  |  |
Adjustment To PEO Compensation, Footnote | The following tables set forth the adjustments made during each year in the PVP table to arrive at “compensation actually paid ” to our Principal Executive Officer during each year.
Fiscal Year |  | Summary Compensation Table Total for CEO |  | Summary Compensation Table Total for former CEO |  | Reported Value of Equity Awards for CEO (1) |  | Reported Value of Equity Awards for former CEO (1) |  | Equity Award Adjustments for CEO (2) |  | Equity Award Adjustments for former CEO (2) |  | Compensation Actually Paid to CEO |  | Compensation Actually Paid to former CEO
2024 |  | $24,166,665 |  | — |  | $18,010,911 |  | — |  | ($4,904,890) |  | — |  | $1,250,864 |  | —
2023 |  | $4,069,913 |  | — |  | — |  | — |  | ($8,568,106) |  | — |  | ($4,498,193) |  | —
2022 |  | $30,488,593 |  | $26,625,221 |  | $30,000,655 |  | $15,389,732 |  | $27,063,911 |  | ($5,336,778) |  | $27,551,849 |  | $5,898,711
2021 |  | — |  | $17,689,665 |  | — |  | $14,084,314 |  | — |  | $11,605,674 |  | — |  | $15,211,025
2020 |  | — |  | $18,659,829 |  | — |  | $13,887,064 |  | — |  | $3,805,602 |  | — |  | $8,578,367
(1) | Represents the grant date fair value of equity awards to our CEO and former CEO, as reported in the “Stock Awards” and “Option Awards” columns in the Summary Compensation Table for each applicable year.
(2) | Represents the year-over-year change in the fair value of equity awards to our CEO and former CEO, as itemized in the table below. No awards vested in the year they were granted.
Fair Value of Equity Awards for CEO and former CEO |  | 2024 |  | 2023 |  | 2022 |  |  | 2021 |  | 2020
|  | Mr. Viehbacher |  |  |  | Mr. Vounatsos |
As of year-end for awards granted during the year |  | $8,702,498 |  | — |  |  | $27,063,911 |  |  |  | $1,996,870 |  |  | $10,985,776 |  | $8,893,002
Year-over-year increase or decrease of unvested awards granted in prior years |  | ($12,329,483) |  | ($7,204,687) |  |  | — |  |  |  | ($6,247,880) |  |  | ($687,744) |  | ($3,618,885)
Increase or decrease from prior fiscal year-end for awards that vested during the year |  | ($1,277,904) |  | ($1,363,419) |  |  | — |  |  |  | ($1,085,768) |  |  | $1,307,643 |  | ($1,468,515)
Total Equity Award Adjustments |  | ($4,904,890) |  | ($8,568,106) |  |  | $27,063,911 |  |  |  | ($5,336,778) |  |  | $11,605,674 |  | $3,805,602
Non-PEO NEO Average Total Compensation Amount | $ 6,365,146 | $ 6,258,401 | $ 5,878,461 | $ 5,761,560 | $ 6,525,375
Non-PEO NEO Average Compensation Actually Paid Amount | $ (228,942) | 4,222,331 | 4,969,529 | 5,081,944 | 4,363,668
Adjustment to Non-PEO NEO Compensation Footnote | The following tables set forth the adjustments made during each year in the PVP table to arrive at “compensation actually paid” to our non-CEO NEOs during each year.
Fiscal Year |  | Average Summary Compensation Table Total for Non-CEO NEOs |  | Average Reported Value of Equity Awards for Non-CEO NEOs (1) |  | Average Equity Award Adjustments for Non-CEO NEOs (2) |  | Average Compensation Actually Paid to Non-CEO NEOs
2024 |  | $6,365,146 |  | $4,156,541 |  | ($2,437,548) |  | ($228,942)
2023 |  | $6,258,401 |  | $4,503,143 |  | $2,467,073 |  | $4,222,331
2022 |  | $5,878,461 |  | $4,223,226 |  | $3,314,294 |  | $4,969,529
2021 |  | $5,761,560 |  | $4,105,942 |  | $3,426,326 |  | $5,081,944
2020 |  | $6,525,375 |  | $4,158,006 |  | $1,996,299 |  | $4,363,668
(1) | Represents the average of the grant date fair value of the equity awards to our NEOs (other than our CEO and former CEO), as reported in the “Stock Awards” column in the Summary Compensation Tables for each applicable year.
(2) | Represents the average of the year-over-year change in fair value of equity awards to our NEOs (other than our CEO and former CEO), as itemized in the table below. No awards vested in the year they were granted.
Average Fair Value of Equity Awards for non-CEO NEOs |  | 2024 |  | 2023 |  | 2022 |  | 2021 |  | 2020
As of year-end for awards granted during the year |  | $2,008,250 |  | $3,523,016 |  | $3,809,706 |  | $3,295,987 |  | $2,904,846
Year-over-year increase or decrease of unvested awards granted in prior years |  | ($4,156,500) |  | ($1,027,351) |  | ($241,427) |  | ($150,316) |  | ($741,028)
Increase or decrease from prior fiscal year-end for awards that vested during the year |  | ($289,298) |  | ($28,591) |  | ($253,985) |  | $280,656 |  | ($167,520)
Total Equity Award Adjustments |  | ($2,437,548) |  | $2,467,073 |  | $3,314,294 |  | $3,426,326 |  | $1,996,299
Tabular List, Table |
Most Important Performance Measures
Revenue
Total Shareholder Return
Non-GAAP Earnings Per Share
Achievement of Pipeline Milestones
Total Shareholder Return Amount | $ 51.54 | 87.21 | 93.32 | 80.85 | 82.52
Peer Group Total Shareholder Return Amount | 113.84 | 115.42 | 111.27 | 124.89 | 125.69
Net Income (Loss) | $ 1,632,000,000 | $ 1,161,000,000 | $ 3,047,000,000 | $ 1,556,000,000 | $ 4,001,000,000
Company Selected Measure Amount | 9,032,000,000 | 9,675,000,000 | 10,326,000,000 | 11,054,000,000 | 13,952,000,000
Measure:: 1 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name | Revenue |  |  |  |
Measure:: 2 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name | Total Shareholder Return |  |  |  |
Measure:: 3 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name | Non-GAAP Earnings Per Share |  |  |  |
Measure:: 4 |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Name | Achievement of Pipeline Milestones |  |  |  |
Mr.Viehbacher [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
PEO Total Compensation Amount | $ 24,166,665 | $ 4,069,913 | $ 30,488,593 |  |
PEO Actually Paid Compensation Amount | $ 1,250,864 | (4,498,193) | 27,551,849 |  |
PEO Name | Mr. Viehbacher |  |  |  |
Mr.Vounatsos [Member] |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
PEO Total Compensation Amount |  |  | 26,625,221 | $ 17,689,665 | $ 18,659,829
PEO Actually Paid Compensation Amount |  |  | 5,898,711 | 15,211,025 | 8,578,367
PEO Name | Mr. Vounatsos |  |  |  |
PEO | Mr.Viehbacher [Member] | Equity Awards Adjustments |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | $ (4,904,890) | (8,568,106) | 27,063,911 |  |
PEO | Mr.Viehbacher [Member] | Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 18,010,911 |  | 30,000,655 |  |
PEO | Mr.Viehbacher [Member] | Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 8,702,498 |  | 27,063,911 |  |
PEO | Mr.Viehbacher [Member] | Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (12,329,483) | (7,204,687) |  |  |
PEO | Mr.Viehbacher [Member] | Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (1,277,904) | (1,363,419) |  |  |
PEO | Mr.Vounatsos [Member] | Equity Awards Adjustments |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  | (5,336,778) | 11,605,674 | 3,805,602
PEO | Mr.Vounatsos [Member] | Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  | 15,389,732 | 14,084,314 | 13,887,064
PEO | Mr.Vounatsos [Member] | Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  | 1,996,870 | 10,985,776 | 8,893,002
PEO | Mr.Vounatsos [Member] | Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  | (6,247,880) | (687,744) | (3,618,885)
PEO | Mr.Vounatsos [Member] | Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount |  |  | (1,085,768) | 1,307,643 | (1,468,515)
Non-PEO NEO | Equity Awards Adjustments |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (2,437,548) | 2,467,073 | 3,314,294 | 3,426,326 | 1,996,299
Non-PEO NEO | Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 4,156,541 | 4,503,143 | 4,223,226 | 4,105,942 | 4,158,006
Non-PEO NEO | Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | 2,008,250 | 3,523,016 | 3,809,706 | 3,295,987 | 2,904,846
Non-PEO NEO | Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | (4,156,500) | (1,027,351) | (241,427) | (150,316) | (741,028)
Non-PEO NEO | Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year |  |  |  |  |
Pay vs Performance Disclosure |  |  |  |  |
Adjustment to Compensation, Amount | $ (289,298) | $ (28,591) | $ (253,985) | $ 280,656 | $ (167,520)

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 3 + Details
Name: | ecd_AdjToCompAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 3 + Details
Name: | ecd_AdjToNonPeoNeoCompFnTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 3 + Details
Name: | ecd_AdjToPeoCompFnTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph vi + Details
Name: | ecd_CoSelectedMeasureAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph vi + Details
Name: | ecd_CoSelectedMeasureName
Namespace Prefix: | ecd_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph vi + Details
Name: | ecd_MeasureName
Namespace Prefix: | ecd_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 3 + Details
Name: | ecd_NamedExecutiveOfficersFnTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph iii + Details
Name: | ecd_NonPeoNeoAvgCompActuallyPaidAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph ii + Details
Name: | ecd_NonPeoNeoAvgTotalCompAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph iv + Details
Name: | ecd_PeerGroupIssuersFnTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph iv + Details
Name: | ecd_PeerGroupTotalShareholderRtnAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph iii + Details
Name: | ecd_PeoActuallyPaidCompAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 3 + Details
Name: | ecd_PeoName
Namespace Prefix: | ecd_
Data Type: | xbrli:normalizedStringItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph ii + Details
Name: | ecd_PeoTotalCompAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 1 + Details
Name: | ecd_PvpTable
Namespace Prefix: | ecd_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 1 + Details
Name: | ecd_PvpTableTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 6 + Details
Name: | ecd_TabularListTableTextBlock
Namespace Prefix: | ecd_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-K -Number 229 -Section 402 -Subsection v -Paragraph 2 -Subparagraph iv + Details
Name: | ecd_TotalShareholderRtnAmt
Namespace Prefix: | ecd_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-6 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-9 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 805 -SubTopic 60 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org/1943274/2147476176/805-60-65-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 323 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478666/740-323-65-2 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(20)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(g)(1)(ii)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 323 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481687/323-10-50-3 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 28 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-28 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482765/220-10-50-6 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-3 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-1 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 1 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480175/815-40-65-1 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-8 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-11 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-11 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 250 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483443/250-10-50-4 Reference 17: http://www.xbrl.org/2003/role/exampleRef -Topic 946 -SubTopic 830 -Name Accounting Standards Codification -Section 55 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479168/946-830-55-10 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section 45 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479105/946-220-45-7 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(18)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1 Reference 20: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-07(9)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1 Reference 21: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-09(1)(d)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3 Reference 22: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(4)(i)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 23: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(4)(ii)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 24: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(4)(iii)(A)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 25: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(4)(iv)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 26: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1A -Subparagraph (SX 210.13-01(a)(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A Reference 27: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(4)(i)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 28: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(4)(iii)(A)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 29: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(4)(iii)(B)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 30: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(4)(iv)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 31: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1B -Subparagraph (SX 210.13-02(a)(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B Reference 32: http://www.xbrl.org/2003/role/disclosureRef -Topic 260 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 60B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B Reference 33: http://www.xbrl.org/2003/role/disclosureRef -Topic 205 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 7 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483499/205-20-50-7 Reference 34: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482740/230-10-45-28 Reference 35: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1A -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-1A Reference 36: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1B -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-1B Reference 37: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(22)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1 + Details
Name: | us-gaap_NetIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | ecd_MeasureAxis=1
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_MeasureAxis=2
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_MeasureAxis=3
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_MeasureAxis=4
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_IndividualAxis=biib_Mr.viehbacherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_IndividualAxis=biib_Mr.vounatsosMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_ExecutiveCategoryAxis=ecd_PeoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_EqtyAwrdsAdjsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_EqtyAwrdsInSummryCompstnTblForAplblYrMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_YrEndFrValOfEqtyAwrdsGrntdInCvrdYrOutsdngAndUnvstdMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_ChngInFrValOfOutsdngAndUnvstdEqtyAwrdsGrntdInPrrYrsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_AdjToCompAxis=ecd_ChngInFrValAsOfVstngDtOfPrrYrEqtyAwrdsVstdInCvrdYrMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ecd_ExecutiveCategoryAxis=ecd_NonPeoNeoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |