Accumulated Other Comprehensive (Loss) Income, Reclassifications out of Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Interest expense		$ 99.6	$ 140.7	$ 170.3
Total before tax		349.5	(112.7)	(63.2)
Income tax benefit		(80.1)	131.2	31.9
Net of tax		269.4	18.5	(31.3)
Reclassification out of Accumulated Other Comprehensive (Loss) Income [Member]
Income Statement [Abstract]
Net of tax		12.9	14.6	9.1
Loss on Cash Flow Hedges - Interest Rate Swaps [Member] | Reclassification out of Accumulated Other Comprehensive (Loss) Income [Member]
Income Statement [Abstract]
Interest expense		15.1	18.5	11.6
Total before tax		15.1	18.5	11.6
Income tax benefit		(3.6)	(7.0)	(4.4)
Net of tax		11.5	11.5	7.2
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]	1.8	5.0	3.0
Total before tax		1.8	5.0	3.0
Income tax benefit		(0.4)	(1.9)	(1.1)
Net of tax		$ 1.4	$ 3.1	$ 1.9

[1] These components are included in the computation of net periodic benefit cost (see Note 11 "Benefit Plans" for additional details).