Goodwill and Other Intangible Assets, Net (Finite-lived Intangible Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-lived Intangible Assets
Gross Intangible Assets, Beginning Balance	$ 749.9	$ 748.0
Acquisitions	25.5	6.9
Divestitures	0.0	(5.0)
Gross Intangible Assets, Ending Balance	775.4	749.9
Accumulated Amortization, Beginning Balance	(567.6)	(501.6)
Additions Charged to Expense	(66.7)	(66.9)
Divestitures	0.0	0.9
Accumulated Amortization, Ending Balance	(634.3)	(567.6)
Net Intangibles	141.1	182.3
Customer relationships, franchise and other municipal agreements
Finite-lived Intangible Assets
Gross Intangible Assets, Beginning Balance	650.8	651.6
Acquisitions	15.2	4.2
Divestitures	0.0	(5.0)
Gross Intangible Assets, Ending Balance	666.0	650.8
Accumulated Amortization, Beginning Balance	(492.5)	(431.0)
Additions Charged to Expense	(62.2)	(62.4)
Divestitures	0.0	0.9
Accumulated Amortization, Ending Balance	(554.7)	(492.5)
Net Intangibles	111.3	158.3
Non-compete agreements
Finite-lived Intangible Assets
Gross Intangible Assets, Beginning Balance	32.1	30.8
Acquisitions	3.5	1.3
Divestitures	0.0	0.0
Gross Intangible Assets, Ending Balance	35.6	32.1
Accumulated Amortization, Beginning Balance	(25.3)	(22.1)
Additions Charged to Expense	(3.2)	(3.2)
Divestitures	0.0	0.0
Accumulated Amortization, Ending Balance	(28.5)	(25.3)
Net Intangibles	7.1	6.8
Other intangibles assets
Finite-lived Intangible Assets
Gross Intangible Assets, Beginning Balance	67.0	65.6
Acquisitions	6.8	1.4
Divestitures	0.0	0.0
Gross Intangible Assets, Ending Balance	73.8	67.0
Accumulated Amortization, Beginning Balance	(49.8)	(48.5)
Additions Charged to Expense	(1.3)	(1.3)
Divestitures	0.0	0.0
Accumulated Amortization, Ending Balance	(51.1)	(49.8)
Net Intangibles	$ 22.7	$ 17.2