Pay vs Performance Disclosure - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pay vs Performance Disclosure
Net income attributable to Biogen Inc.	$ 1,632.2	$ 1,161.1	$ 3,046.9

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details