XML 128 R46.htm IDEA: XBRL DOCUMENT
v3.22.4

Equity (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2022
Equity [Abstract] |
Summary of common stock | The following table describes the number of shares authorized, issued and outstanding of our common stock as of December 31, 2022, 2021 and 2020:
| As of December 31, 2022 |  | As of December 31, 2021 |  | As of December 31, 2020
(In millions) | Authorized |  | Issued |  | Outstanding |  | Authorized |  | Issued |  | Outstanding |  | Authorized |  | Issued |  | Outstanding
Common stock | 1,000.0 |  |  | 167.9 |  |  | 144.0 |  |  | 1,000.0 |  |  | 170.8 |  |  | 147.0 |  |  | 1,000.0 |  |  | 176.2 |  |  | 152.4 |
Schedule of Accumulated Other Comprehensive Income (Loss) | The following tables summarize the changes in accumulated other comprehensive income (loss), net of tax by component:
|  | December 31, 2022
(In millions) |  | Unrealized Gains (Losses) on Securities Available for Sale, Net of Tax |  | Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax |  | Gains (Losses) on Net Investment Hedges, Net of Tax(1) |  | Unrealized Gains (Losses) on Pension Benefit Obligation, Net of Tax |  | Currency Translation Adjustments |  | Total
Balance, December 31, 2021 |  | $ | (2.2) |  |  | $ | 53.8 |  |  | $ | 25.5 |  |  | $ | (44.8) |  |  | $ | (139.0) |  |  | $ | (106.7) |
Other comprehensive income (loss) before reclassifications |  | (23.5) |  |  | 137.3 |  |  | 12.6 |  |  | 43.7 |  |  | (83.1) |  |  | 87.0 |
Amounts reclassified from accumulated other comprehensive income (loss) |  | 10.0 |  |  | (176.0) |  |  | (38.1) |  |  | — |  |  | 58.9 |  |  | (145.2) |
Net current period other comprehensive income (loss) |  | (13.5) |  |  | (38.7) |  |  | (25.5) |  |  | 43.7 |  |  | (24.2) |  |  | (58.2) |
Balance, December 31, 2022 |  | $ | (15.7) |  |  | $ | 15.1 |  |  | $ | — |  |  | $ | (1.1) |  |  | $ | (163.2) |  |  | $ | (164.9) |
(1) Beginning in the second quarter of 2022 we no longer held net investment hedges as they were closed with the sale of our 49.9% equity interest in Samsung Bioepis in April 2022. For additional information on the sale of our equity interest in Samsung Bioepis, please read Note 3, Dispositions, to these consolidated financial statements.
|  | December 31, 2021
(In millions) |  | Unrealized Gains (Losses) on Securities Available for Sale, Net of Tax |  | Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax |  | Gains (Losses) on Net Investment Hedges, Net of Tax |  | Unrealized Gains (Losses) on Pension Benefit Obligation, Net of Tax |  | Currency Translation Adjustments |  | Total
Balance, December 31, 2020 |  | $ | 1.4 |  |  | $ | (179.0) |  |  | $ | (8.5) |  |  | $ | (66.3) |  |  | $ | (46.6) |  |  | $ | (299.0) |
Other comprehensive income (loss) before reclassifications |  | (6.6) |  |  | 178.2 |  |  | 33.4 |  |  | 21.5 |  |  | (92.4) |  |  | 134.1 |
Amounts reclassified from accumulated other comprehensive income (loss) |  | 3.0 |  |  | 54.6 |  |  | 0.6 |  |  | — |  |  | — |  |  | 58.2 |
Net current period other comprehensive income (loss) |  | (3.6) |  |  | 232.8 |  |  | 34.0 |  |  | 21.5 |  |  | (92.4) |  |  | 192.3 |
Balance, December 31, 2021 |  | $ | (2.2) |  |  | $ | 53.8 |  |  | $ | 25.5 |  |  | $ | (44.8) |  |  | $ | (139.0) |  |  | $ | (106.7) |
|  | December 31, 2020
(In millions) |  | Unrealized Gains (Losses) on Securities Available for Sale, Net of Tax |  | Unrealized Gains (Losses) on Cash Flow Hedges, Net of Tax |  | Gains (Losses) on Net Investment Hedges, Net of Tax |  | Unrealized Gains (Losses) on Pension Benefit Obligation, Net of Tax |  | Currency Translation Adjustments |  | Total
Balance, December 31, 2019 |  | $ | 4.2 |  |  | $ | 7.8 |  |  | $ | 25.1 |  |  | $ | (32.8) |  |  | $ | (139.5) |  |  | $ | (135.2) |
Other comprehensive income (loss) before reclassifications |  | (9.3) |  |  | (165.0) |  |  | (30.7) |  |  | (33.5) |  |  | 92.9 |  |  | (145.6) |
Amounts reclassified from accumulated other comprehensive income (loss) |  | 6.5 |  |  | (21.8) |  |  | (2.9) |  |  | — |  |  | — |  |  | (18.2) |
Net current period other comprehensive income (loss) |  | (2.8) |  |  | (186.8) |  |  | (33.6) |  |  | (33.5) |  |  | 92.9 |  |  | (163.8) |
Balance, December 31, 2020 |  | $ | 1.4 |  |  | $ | (179.0) |  |  | $ | (8.5) |  |  | $ | (66.3) |  |  | $ | (46.6) |  |  | $ | (299.0) |
Reclassification out of Accumulated Other Comprehensive Income | The following table summarizes the amounts reclassified from accumulated other comprehensive income (loss):
(In millions) |  | Amounts Reclassified from Accumulated Other Comprehensive Income (Loss) |  | Income Statement Location
| For the Years Ended December 31, |
| 2022 |  | 2021 |  | 2020 |
Gains (losses) on securities available for sale |  | $ | (12.6) |  |  | $ | (3.8) |  |  | $ | (8.2) |  |  | Other (income) expense
|  | 2.6 |  |  | 0.8 |  |  | 1.7 |  |  | Income tax (benefit) expense
Gains (losses) on cash flow hedges |  | 201.6 |  |  | (60.0) |  |  | 18.3 |  |  | Revenue
|  | (5.5) |  |  | (0.8) |  |  | 3.3 |  |  | Operating expense
|  | (0.3) |  |  | 0.2 |  |  | 0.3 |  |  | Other (income) expense
|  | (19.8) |  |  | 6.0 |  |  | (0.1) |  |  | Income tax (benefit) expense
Gains (losses) on net investment hedges(1) |  | 38.1 |  |  | (0.6) |  |  | 2.9 |  |  | Other (income) expense
Currency Translation Adjustments |  | (58.9) |  |  | — |  |  | — |  |  | Other (income) expense
Total reclassifications, net of tax |  | $ | 145.2 |  |  | $ | (58.2) |  |  | $ | 18.2 |  |  |
(1)

X
- Definition Summary of common stock. + References No definition available. + Details
Name: | biib_SummaryOfCommonStockTableTextBlock
Namespace Prefix: | biib_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_EquityAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of information about items reclassified out of accumulated other comprehensive income (loss). + References No definition available. + Details
Name: | us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of accumulated other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669686-108580 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 20 -URI https://asc.fasb.org/extlink&oid=118261656&loc=d3e32211-110900 + Details
Name: | us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration