Pension And Other Postretirement Benefits (Components Of The Plans' Net Periodic Benefits Cost) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	[1]	$ 8.1	$ 7.3	$ 24.1	$ 21.9
Interest cost	[1]	13.1	18.1	40.1	54.5
Expected return on assets	[1]	(28.3)	(27.2)	(85.1)	(81.6)
Amortization of prior service credit	[1]	0.2	0.0	0.6	0.0
Recognized actuarial loss	[1]	8.6	11.3	26.0	34.1
Settlement loss	[1]	(8.0)	(1.9)	(8.0)	(1.9)
Total Net Periodic Benefits Cost		9.7	11.4	13.7	30.8
Other Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Service Cost	[1]	1.7	1.3	4.9	3.9
Interest cost	[1]	3.8	4.8	11.6	14.4
Expected return on assets	[1]	(3.6)	(3.3)	(10.8)	(9.9)
Amortization of prior service credit	[1]	(0.4)	(0.8)	(1.4)	(2.4)
Recognized actuarial loss	[1]	1.2	0.5	3.8	1.5
Settlement loss	[1]	0.0	0.0	0.0	0.0
Total Net Periodic Benefits Cost		$ 2.7	$ 2.5	$ 8.1	$ 7.5

[1] (1)The service cost component and all non-service cost components of net periodic benefit cost are presented in "Operation and maintenance" and "Other, net", respectively, on the Condensed Statements of Consolidated Income (Loss) (unaudited).