Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Total revenue	$ 2,463.0	$ 2,531.8
Cost and expenses:
Cost of sales, excluding amortization and impairment of acquired intangible assets	662.8	753.9
Research and development	570.6	551.7
Selling, general and administrative	605.0	634.9
Amortization and impairment of acquired intangible assets	50.2	66.9
Collaboration profit sharing/(loss reimbursement)	57.1	(117.3)
(Gain) loss on fair value remeasurement of contingent consideration	0.0	(7.1)
Restructuring charges	9.6	38.1
Other (income) expense, net	69.4	263.3
Total cost and expense	2,024.7	2,184.4
Income before income tax expense and equity in loss of investee, net of tax	438.3	347.4
Income tax (benefit) expense	50.7	125.6
Equity in (income) loss of investee, net of tax	0.0	3.3
Net income	387.6	218.5
Net income (loss) attributable to noncontrolling interests, net of tax	(0.3)	(85.3)
Net income attributable to Biogen Inc.	$ 387.9	$ 303.8
Net income per share:
Basic earnings per share attributable to Biogen Inc.	$ 2.69	$ 2.06
Diluted earnings per share attributable to Biogen Inc.	$ 2.67	$ 2.06
Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Inc.	144,400	147,100
Diluted earnings per share attributable to Biogen Inc.	145,200	147,600
Product, net
Total revenue	$ 1,763.3	$ 2,066.3
LEQEMBI Collaboration
Total revenue	(18.9)	0.0
Revenue from anti-CD20 therapeutic programs
Total revenue	399.5	399.4
Contract manufacturing, royalty and other revenue
Total revenue	$ 319.1	$ 66.1