Fair Value (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Assets:
Cash and cash equivalents	$ 3,449.7		$ 3,652.4
Short-term investments	5.4		5.5
Marketable equity investments	1.6		1.5
Foreign currency derivative instruments	0.4		0.0
Non-marketable equity securities	11.8		11.8
Liabilities:
Short-term debt	595.4		8.1
Interest rate and foreign currency derivative instruments	31.1		52.9
Contingent purchase price obligations	146.7		146.5
Long-term debt, including current portion	4,948.6		4,821.3
Carrying Amount
Assets:
Cash and cash equivalents	3,449.7		3,652.4
Short-term investments	5.4		5.5
Marketable equity investments	1.6		1.5
Foreign currency derivative instruments	0.4		0.0
Non-marketable equity securities	11.8		11.8
Liabilities:
Short-term debt	595.4		8.1
Interest rate and foreign currency derivative instruments	31.1		52.9
Contingent purchase price obligations	146.7		146.5
Long-term debt, including current portion	4,901.8		4,883.7
Contingent purchase price obligations
Changes in Contingent Purchase Price Obligations [Roll Forward]
January 1	146.5	$ 215.6
Acquisitions	1.8	68.1
Revaluation and interest	1.2	1.1
Payments	(2.5)	(5.2)
Foreign currency translation	(0.3)	2.1
March 31	146.7	$ 281.7
Fair Value, Measurements, Recurring [Member]
Assets:
Cash and cash equivalents	3,449.7		3,652.4
Short-term investments	5.4		5.5
Marketable equity investments	1.6		1.5
Foreign currency derivative instruments	0.4
Liabilities:
Interest rate and foreign currency derivative instruments	31.1		52.9
Contingent purchase price obligations	146.7		146.5
Fair Value, Measurements, Recurring [Member] | Level 1
Assets:
Cash and cash equivalents	3,449.7		3,652.4
Short-term investments	5.4		5.5
Marketable equity investments	1.6		1.5
Fair Value, Measurements, Recurring [Member] | Level 2
Assets:
Foreign currency derivative instruments	0.4
Liabilities:
Interest rate and foreign currency derivative instruments	31.1		52.9
Fair Value, Measurements, Recurring [Member] | Level 3
Liabilities:
Contingent purchase price obligations	$ 146.7		$ 146.5