Segment Reporting (Segment Revenue and Contribution) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 3,765.7	$ 3,572.3
Contribution margin	2,136.5	2,132.3
Unallocated corporate and shared functional costs, including G&A expenses	529.5	555.9
Expense related to the unwind of inventory fair value adjustments	33.5	480.4
One-time employee related costs	0.0	(4.0)
Costs relating to license arrangements	10.0	0.0
Amortization of acquired intangible assets	484.0	364.0
Integration and acquisition costs	239.7	116.0
Reorganization costs	5.3	5.5
Gain on sale of product rights	0.0	(5.5)
Depreciation	140.2	122.9
Operating income from continuing operations	$ 694.3	$ 497.1
Operating margin percentage	18.40%	13.90%
Other expense, net	$ (101.2)	$ (134.7)
Income from continuing operations before income taxes and equity in earnings/(losses) of equity method investees	593.1	362.4
Rare Disease
Segment Reporting Information [Line Items]
Revenues	2,828.3	2,603.3
Contribution margin	1,366.6	1,339.7
Neuroscience
Segment Reporting Information [Line Items]
Revenues	937.4	969.0
Contribution margin	$ 769.9	$ 792.6