Accumulated Other Comprehensive (Loss) Income, Reclassifications out of Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Interest expense		$ 30.1	$ 43.0	$ 115.4	$ 128.7
Total before tax		32.4	(22.1)	(166.3)	(60.3)
Provision (benefit) for income taxes		(4.4)	9.1	41.2	33.3
Net of tax		$ 28.0	$ (13.0)	(125.1)	(27.0)
Reclassification out of Accumulated Other Comprehensive (Loss) Income [Member]
Income Statement [Abstract]
Net of tax				10.9	6.5
Loss on Cash Flow Hedges - Interest Rate Swaps [Member] | Reclassification out of Accumulated Other Comprehensive (Loss) Income [Member]
Income Statement [Abstract]
Interest expense				13.9	8.1
Total before tax				13.9	8.1
Provision (benefit) for income taxes				(5.3)	(3.1)
Net of tax				8.6	5.0
Amortization of Defined Benefit Pension and Other Postretirement Benefit Items [Member] | Reclassification out of Accumulated Other Comprehensive (Loss) Income [Member]
Income Statement [Abstract]
Net periodic benefit cost	[1]			3.7	2.4
Total before tax				3.7	2.4
Provision (benefit) for income taxes				(1.4)	(0.9)
Net of tax				$ 2.3	$ 1.5

[1] These components are included in the computation of net periodic benefit cost. See Note 7 "Pension and Other Postretirement Benefits" for additional details.