Changes in Equity and Comprehensive Income Changes in Equity and Comprehensive Income (Details of Accumulated Other Comprehensive Income Components) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Deferred Tax Assets, Other Comprehensive Loss	$ 117.0		$ 117.0		$ 119.8
Income Tax Expense (Benefit)	(28.5)	$ (31.3)	(83.6)	$ (77.9)
Amounts reclassified from accumulated other comprehensive income			6.8
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	3.3	(2.5)	9.8	(7.5)
Income Tax Expense (Benefit)	1.0	(0.9)	3.0	(2.3)
Amounts reclassified from accumulated other comprehensive income	2.3	1.6	6.8	5.2
Reclassification out of Accumulated Other Comprehensive Income [Member] | Prior-Service Costs, Pension [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
PriorServiceCostsCOS	(0.1)	(0.3)	(0.4)	(0.8)
PriorServiceCostSG&A	0.0	0.1	0.1	0.2
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(0.1)	(0.2)	(0.3)	(0.6)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net Loss (Gain), Pension [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Defined Benefit Plan, Amortization of Gains (Losses)	3.5	(2.9)	10.5	(8.7)
NetlossgainCOS	4.7	3.9	14.2	11.8
NetlossgainSG&A	(1.2)	(1.0)	(3.7)	(3.1)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Prior-Service Costs, Postretirement [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	0.0	(0.1)	(0.1)	(0.3)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net Loss(Gain), Postretirement [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Defined Benefit Plan, Amortization of Gains (Losses)	$ (0.1)	$ 0.1	$ (0.3)	$ 0.3