Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Statement of Comprehensive Income [Abstract] | ||||
| Net (loss) income attributable to Biogen Inc. | $ (20.6) | $ 466.5 | $ 396.4 | $ 1,341.8 |
| Other comprehensive income (loss): | ||||
| Unrealized gains (losses) on securities available for sale, net of tax | 0.0 | 0.0 | (0.2) | 0.0 |
| Unrealized gains (losses) on cash flow hedges, net of tax | 12.2 | 26.5 | 79.6 | (137.1) |
| Unrealized gains (losses) on pension benefit obligation, net of tax | (0.2) | 0.0 | (1.0) | 1.0 |
| Currency translation adjustments, net of tax | (4.6) | (3.2) | (16.7) | 57.5 |
| Total other comprehensive income (loss), net of tax | 7.4 | 23.3 | 61.7 | (78.6) |
| Comprehensive income (loss) attributable to Biogen Inc. | $ (13.2) | $ 489.8 | $ 458.1 | $ 1,263.2 |
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- Definition Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount, after tax and adjustment, of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount, after tax and reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount after tax of other comprehensive income (loss) attributable to parent entity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- References No definition available.
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- Definition Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- References No definition available.
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