Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Total revenue	$ 2,531.8	$ 2,694.0
Cost and expenses:
Cost of sales, excluding amortization and impairment of acquired intangible assets	753.9	478.1
Research and development	551.7	514.2
Selling, general and administrative	634.9	595.0
Amortization and impairment of acquired intangible assets	66.9	98.1
Collaboration profit (loss) sharing	(117.3)	68.5
(Gain) loss on fair value remeasurement of contingent consideration	(7.1)	(33.8)
Restructuring charges	38.1	0.0
Total cost and expense	1,921.1	1,720.1
Income from operations	610.7	973.9
Other income (expense), net	(263.3)	(506.9)
Income before income tax expense and equity in loss of investee, net of tax	347.4	467.0
Income tax (benefit) expense	125.6	44.2
Equity in (income) loss of investee, net of tax	3.3	18.2
Net income	218.5	404.6
Net income (loss) attributable to noncontrolling interests, net of tax	(85.3)	(5.6)
Net income attributable to Biogen Inc.	$ 303.8	$ 410.2
Net income per share:
Basic earnings per share attributable to Biogen Inc.	$ 2.06	$ 2.70
Diluted earnings per share attributable to Biogen Inc.	$ 2.06	$ 2.69
Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Inc.	147,100	151,900
Diluted earnings per share attributable to Biogen Inc.	147,600	152,300
Product, net
Total revenue	$ 2,066.3	$ 2,211.7
Revenue from anti-CD20 therapeutic programs
Total revenue	399.4	389.0
Other
Total revenue	$ 66.1	$ 93.3