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Pension And Other Postretirement Benefits (Narrative) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2021
Jun. 30, 2021
Mar. 31, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Pension Plan            
Defined Benefit Plan Disclosure [Line Items]            
Employer contributions         $ 3.3  
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      
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment $ 2.9 $ 3.3 $ 3.3 $ 8.0 9.5 $ 8.0
Other Postretirement Benefit Plan            
Defined Benefit Plan Disclosure [Line Items]            
Employer contributions         15.0  
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment $ 0.0     $ 0.0 $ 0.0 $ 0.0