Fair Value (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Assets:
Cash and cash equivalents	$ 2,440.4		$ 3,652.4
Short-term investments	5.2		5.5
Marketable equity investments	1.5		1.5
Foreign currency derivative instruments	0.2		0.0
Non-marketable equity securities	10.3		11.8
Liabilities:
Short-term debt	7.9		8.1
Interest rate and foreign currency derivative instruments	0.5		52.9
Contingent purchase price obligations	144.9		146.5
Long-term debt, including current portion	5,294.6		4,821.3
Carrying Amount
Assets:
Cash and cash equivalents	2,440.4		3,652.4
Short-term investments	5.2		5.5
Marketable equity investments	1.5		1.5
Foreign currency derivative instruments	0.2		0.0
Non-marketable equity securities	10.3		11.8
Liabilities:
Short-term debt	7.9		8.1
Interest rate and foreign currency derivative instruments	0.5		52.9
Contingent purchase price obligations	144.9		146.5
Long-term debt, including current portion	5,110.4		4,883.7
Contingent purchase price obligations
Changes in Contingent Purchase Price Obligations [Roll Forward]
January 1	146.5	$ 215.6
Acquisitions	42.9	84.1
Revaluation and interest	2.2	8.7
Payments	(43.7)	(66.4)
Foreign currency translation	(3.0)	(17.0)
September 30	144.9	$ 225.0
Fair Value, Recurring [Member]
Assets:
Cash and cash equivalents	2,440.4		3,652.4
Short-term investments	5.2		5.5
Marketable equity investments	1.5		1.5
Foreign currency derivative instruments	0.2
Liabilities:
Interest rate and foreign currency derivative instruments	0.5		52.9
Contingent purchase price obligations	144.9		146.5
Fair Value, Recurring [Member] | Level 1
Assets:
Cash and cash equivalents	2,440.4		3,652.4
Short-term investments	5.2		5.5
Marketable equity investments	1.5		1.5
Fair Value, Recurring [Member] | Level 2
Assets:
Foreign currency derivative instruments	0.2
Liabilities:
Interest rate and foreign currency derivative instruments	0.5		52.9
Fair Value, Recurring [Member] | Level 3
Liabilities:
Contingent purchase price obligations	$ 144.9		$ 146.5