Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenues:
Product, net	$ 2,309.4	$ 2,172.3
Revenues from anti-CD20 therapeutic programs	329.5	330.6
Other	87.9	52.0
Total revenues	2,726.8	2,555.0
Cost and expenses:
Cost of sales, excluding amortization of acquired intangible assets	313.0	312.4
Research and development	437.3	460.5
Selling, general and administrative	497.3	560.4
Amortization of acquired intangible assets	88.8	95.9
Restructuring charges	9.7	0.0
(Gain) loss on fair value remeasurement of contingent consideration	2.3	7.8
Total cost and expenses	1,348.4	1,437.1
Income from operations	1,378.4	1,117.9
Other income (expense), net	(52.8)	(15.0)
Income before income tax expense and equity in loss of investee, net of tax	1,325.6	1,102.9
Income tax expense	356.4	281.9
Equity in loss of investee, net of tax	0.0	0.8
Net income	969.2	820.2
Net income (loss) attributable to noncontrolling interests, net of tax	(1.7)	(2.4)
Net income attributable to Biogen Inc.	$ 970.9	$ 822.5
Net income per share:
Basic earnings per share attributable to Biogen Inc.	$ 4.44	$ 3.50
Diluted earnings per share attributable to Biogen Inc.	$ 4.43	$ 3.49
Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Inc.	218.9	235.0
Diluted earnings per share attributable to Biogen Inc.	219.3	235.6