Segment Information (Tables)

12 Months Ended

Dec. 31, 2025

Segment Reporting [Abstract]

Geographic information

The following tables contain certain financial information by geographic area:

	December 31, 2025
(In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenue from external customers	$	3,547.9	$	1,871.6	$	853.0	$	419.1	$	427.8	$	7,119.4
Revenue from anti-CD20 therapeutic programs	1,775.4		1.8		—		—		83.4		1,860.6
Contract manufacturing, royalty and other revenue	414.7		10.8		—		307.4		—		732.9
Long-lived assets	1,236.7		2,053.8		12.2		5.9		12.2		3,320.8
	December 31, 2024
(In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenue from external customers	$	3,237.3	$	2,171.5	$	955.6	$	366.9	$	482.2	$	7,213.5
Revenue from anti-CD20 therapeutic programs	1,673.6		0.6		—		—		75.7		1,749.9
Contract manufacturing, royalty and other revenue	395.0		0.4		—		257.2		—		652.6
Long-lived assets	1,366.1		2,139.2		13.3		8.5		10.6		3,537.7
	December 31, 2023
(In millions)	U.S.		Europe(1)		Germany		Asia		Other		Total
Product revenue from external customers	$	3,141.4	$	2,127.4	$	868.0	$	649.4	$	460.5	$	7,246.7
Revenue from anti-CD20 therapeutic programs	1,618.5		0.4		—		—		70.7		1,689.6
Contract manufacturing, royalty and other revenue	673.6		11.7		—		214.0		—		899.3
Long-lived assets	1,443.0		2,248.0		17.5		8.3		12.9		3,729.7

(1) Represents amounts related to Europe less those attributable to Germany.

Reconciliation of revenue from segments to consolidated

The following table includes additional information about reported segment revenue, significant segment expense and segment measure of profitability:

	For the Years Ended December 31,
(In millions)	2025		2024		2023
Total revenue	$	9,890.6	$	9,675.9	$	9,835.6
Less cost and expense:
Cost of sales, excluding amortization and impairment of acquired intangible assets:
Product cost of sales	1,587.2		1,604.2		1,787.2
Royalty cost of sales	817.0		706.2		746.2
Research and development:
Research and discovery	183.2		201.5		212.5
Early stage programs	257.7		286.6		361.0
Late stage programs	232.0		209.7		250.5
Marketed products	412.8		534.7		766.1
Other research and development costs(1)	692.9		747.8		855.3
Acquired in-process research and development, upfront and milestone expense	471.8		61.5		16.6
Selling, general and administrative	2,433.6		2,403.7		2,549.7
Other segment expense(2)	1,509.5		1,287.8		1,129.4
Net Income attributable to Biogen Inc.	$	1,292.9	$	1,632.2	$	1,161.1

(1) Other research and development costs primarily consist of indirect costs incurred in support of overall research and development activities and non-specific programs, including activities that benefit multiple programs, such as management costs, as well as depreciation, information technology and facility-based expenses and are not allocated to a specific program or stage.

(2) Other segment expense includes: amortization and impairment of acquired intangible assets; collaboration profit sharing/(loss reimbursement); (gain) loss on fair value remeasurement of contingent consideration; impairment of ROU asset; restructuring charges; gain on sale of priority review voucher, net; other (income) expense, net; income tax (benefit) expense; and net income attributable to noncontrolling interests, net of tax.