Fair Value (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Assets:
Cash and cash equivalents	$ 1,843.0		$ 3,002.2
Short-term investments	8.0		20.6
Available-for-sale securities	3.7		4.3
Foreign currency derivative instruments	0.4		0.2
Cost method investments	15.8		14.2
Liabilities:
Short-term debt	38.7		28.7
Interest rate and foreign currency derivative instruments	29.7		48.9
Contingent purchase price obligations	261.0		386.1
Long-term debt, including current portion	5,080.6		5,035.1
Carrying Amount
Assets:
Cash and cash equivalents	1,843.0		3,002.2
Short-term investments	8.0		20.6
Available-for-sale securities	3.7		4.3
Foreign currency derivative instruments	0.4		0.2
Cost method investments	15.8		14.2
Liabilities:
Short-term debt	38.7		28.7
Interest rate and foreign currency derivative instruments	29.7		48.9
Contingent purchase price obligations	261.0		386.1
Long-term debt, including current portion	4,927.4		4,920.6
Contingent purchase price obligations
Changes in Contingent Purchase Price Obligations [Roll Forward]
January 1	386.1	$ 322.0
Acquisitions	41.7	156.0
Revaluation and interest	0.2	16.7
Payments	(182.9)	(86.8)
Foreign currency translation	15.9	(3.4)
September 30	261.0	$ 404.5
Fair Value, Measurements, Recurring [Member]
Assets:
Cash and cash equivalents	1,843.0		3,002.2
Short-term investments	8.0		20.6
Available-for-sale securities	3.7		4.3
Foreign currency derivative instruments	0.4		0.2
Liabilities:
Interest rate and foreign currency derivative instruments	29.7		48.9
Contingent purchase price obligations	261.0		386.1
Fair Value, Measurements, Recurring [Member] | Level 1
Assets:
Cash and cash equivalents	1,843.0		3,002.2
Short-term investments	8.0		20.6
Available-for-sale securities	3.7		4.3
Fair Value, Measurements, Recurring [Member] | Level 2
Assets:
Foreign currency derivative instruments	0.4		0.2
Liabilities:
Interest rate and foreign currency derivative instruments	29.7		48.9
Fair Value, Measurements, Recurring [Member] | Level 3
Liabilities:
Contingent purchase price obligations	$ 261.0		$ 386.1