Fair Value on a Recurring and Nonrecurring Basis (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2019	Dec. 31, 2018
Fair value assets and liabilities measured on recurring and nonrecurring basis
Contingent acquisition liability, total change		$ (42.2)
Level 1
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents		132.4	$ 132.1
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		3,595.2	3,605.6
Level 3
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents		0.0	0.0
Contingent acquisition obligations	[1]	106.2	148.4
Long-term Debt, Fair Value		44.3	38.0
Fair Value, Total [Member]
Fair value assets and liabilities measured on recurring and nonrecurring basis
Cash equivalents		132.4	132.1
Contingent acquisition obligations	[1]	106.2	148.4
Long-term Debt, Fair Value		$ 3,639.5	$ 3,643.6

[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 $42.2 from December 31, 2018 to September 30, 2019 is primarily due to payments and a reclassification from an arrangement during the second quarter of 2019. The amounts payable within the next twelve months are classified in accrued liabilities; any amounts payable thereafter are classified in other non-current liabilities.