Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues:
Product, net	$ 2,380.1	$ 2,309.4
Revenues from anti-CD20 therapeutic programs	340.6	329.5
Other	90.0	87.9
Total revenues	2,810.7	2,726.8
Cost and expenses:
Cost of sales, excluding amortization of acquired intangible assets	384.6	313.0
Research and development	423.4	437.3
Selling, general and administrative	499.1	497.3
Amortization of acquired intangible assets	448.5	88.8
Collaboration profit (loss) sharing	20.8	0.0
(Gain) loss on fair value remeasurement of contingent consideration	10.0	2.3
Restructuring charges	0.0	9.7
Total cost and expenses	1,786.4	1,348.4
Income from operations	1,024.3	1,378.4
Other income (expense), net	(37.6)	(52.8)
Income before income tax expense and equity in loss of investee, net of tax	986.7	1,325.6
Income tax expense	239.2	356.4
Equity in loss of investee, net of tax	0.0	0.0
Net income	747.5	969.2
Net income (loss) attributable to noncontrolling interests, net of tax	(0.1)	(1.7)
Net income attributable to Biogen Inc.	$ 747.6	$ 970.9
Net income per share:
Basic earnings per share attributable to Biogen Inc.	$ 3.47	$ 4.44
Diluted earnings per share attributable to Biogen Inc.	$ 3.46	$ 4.43
Weighted-average shares used in calculating:
Basic earnings per share attributable to Biogen Inc.	215.6	218.9
Diluted earnings per share attributable to Biogen Inc.	215.9	219.3