Changes in Equity and Accumulated Other Comprehensive Loss (Details of Accumulated Other Comprehensive Income Components) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Tax impact	$ 19.6	$ 17.1	$ 71.9	$ 36.6
Amounts reclassified from accumulated other comprehensive income			15.3
Deferred tax assets, other comprehensive loss	151.5		151.5		$ 148.2
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	6.1	4.4	18.6	13.5
Tax impact	0.9	1.1	3.3	3.1
Amounts reclassified from accumulated other comprehensive income	5.2	3.3	15.3	10.4
Pension Plan
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Amortization of prior service cost	(0.1)	(0.1)	(0.2)	(0.2)
Defined Benefit Plan, Amortization of Gain (Loss)	6.5	4.8	19.6	14.5
Other Postretirement Benefits Plan
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Amortization of prior service cost	(0.3)	(0.3)	(0.8)	(0.8)
Defined Benefit Plan, Amortization of Gain (Loss)	$ 0.0	$ 0.0	$ 0.0	$ 0.0