Pension And Other Postretirement Benefits (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 0.7
Defined Benefit Plan, Pension Asset, (Increase)Decrease For Remeasurement Due To Settlement	(5.8)
Change in Regulatory Assets Due to Interim Measurement	2.1
Change in Accumulated Other Comprehensive Income Due to Interim Measurement	0.4
Change to Defined Benefit Plan Net Periodic Costs Due to Interim Measurement	4.0
Other Postretirement Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 5.1