Fair Value on a Recurring and Nonrecurring Basis (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2020	Dec. 31, 2019
Fair value assets and liabilities measured on recurring and nonrecurring basis
Contingent acquisition liability, total change		$ (19.4)
Long-term Debt, Fair Value		$ 4,381.3	$ 3,565.5
Discount rate floor contingent acquisition obligations		1.00%
Discount rate ceiling contingent acquisition obligations		4.00%
Discount rate floor long-term debt		0.50%
Discount rate ceiling long-term debt		3.50%
Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents		$ 103.1	786.0
Contingent acquisition obligations	[1]	0.0	0.0
Long-term Debt, Fair Value		0.0	0.0
Level 2
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents		0.0	0.0
Contingent acquisition obligations	[1]	0.0	0.0
Long-term Debt, Fair Value		4,335.9	3,520.0
Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents		0.0	0.0
Contingent acquisition obligations	[1]	94.7	114.1
Long-term Debt, Fair Value		45.4	45.5
Fair Value, Total [Member]
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents		103.1	786.0
Contingent acquisition obligations	[1]	94.7	114.1
Long-term Debt, Fair Value		$ 4,381.3	$ 3,565.5

[1] Contingent acquisition obligations includes deferred acquisition payments and unconditional obligations to purchase additional noncontrolling equity shares of consolidated subsidiaries. Fair value measurement of the obligations is based upon actual and projected operating performance targets as specified in the related agreements. The decrease in this balance of $19.4 from December 31, 2019 to September 30, 2020 is primarily due to acquisition payments, partially offset by valuation adjustments, an increase in deferred acquisition payments and exercises of put options. The amounts payable within the next twelve months are classified in accrued liabilities; any amounts payable thereafter are classified in other non-current liabilities.