Fair Value (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Assets:
Cash and cash equivalents	$ 1,913.3		$ 3,796.0
Short-term investments	5.4		0.4
Investment in equity securities	1.6		1.4
Foreign currency derivative instruments	0.2		1.0
Investment in equity securities without readily determinable fair value	11.9		14.4
Liabilities:
Short-term debt	20.8		11.8
Interest rate and foreign currency derivative instruments	79.3		39.5
Contingent purchase price obligations	235.3		215.6
Long-term debt, including current portion	4,865.1		5,056.9
Carrying Amount
Assets:
Cash and cash equivalents	1,913.3		3,796.0
Short-term investments	5.4		0.4
Investment in equity securities	1.6		1.4
Foreign currency derivative instruments	0.2		1.0
Investment in equity securities without readily determinable fair value	11.9		14.4
Liabilities:
Short-term debt	20.8		11.8
Interest rate and foreign currency derivative instruments	79.3		39.5
Contingent purchase price obligations	235.3		215.6
Long-term debt, including current portion	4,866.8		4,912.9
Contingent purchase price obligations
Changes in Contingent Purchase Price Obligations [Roll Forward]
January 1	215.6	$ 386.1
Acquisitions	79.7	22.2
Revaluation and interest	4.9	(0.4)
Payments	(51.3)	(146.4)
Foreign currency translation	(13.6)	6.7
June 30	235.3	$ 268.2
Fair Value, Measurements, Recurring [Member]
Assets:
Cash and cash equivalents	1,913.3		3,796.0
Short-term investments	5.4		0.4
Investment in equity securities	1.6		1.4
Foreign currency derivative instruments	0.2		1.0
Liabilities:
Interest rate and foreign currency derivative instruments	79.3		39.5
Contingent purchase price obligations	235.3		215.6
Fair Value, Measurements, Recurring [Member] | Level 1
Assets:
Cash and cash equivalents	1,913.3		3,796.0
Short-term investments	5.4		0.4
Investment in equity securities	1.6		1.4
Fair Value, Measurements, Recurring [Member] | Level 2
Assets:
Foreign currency derivative instruments	0.2		1.0
Liabilities:
Interest rate and foreign currency derivative instruments	79.3		39.5
Fair Value, Measurements, Recurring [Member] | Level 3
Liabilities:
Contingent purchase price obligations	$ 235.3		$ 215.6