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Pension and Other Postretirement Benefits (Schedule Of Reconciliation Of The Plans Funded Status And Amounts Reflected) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]      
Noncurrent liabilities $ (192.1) $ (231.3)  
COVID-19 related regulatory asset 2,477.3 2,460.2  
Regulatory Liabilities 1,581.7 1,789.3  
Unrecognized Pension Benefit And Other Postretirement Benefit Costs      
Defined Benefit Plan Disclosure [Line Items]      
Regulatory Liabilities 0.0 0.0  
Unrecognized Pension Benefit And Other Postretirement Benefit Costs      
Defined Benefit Plan Disclosure [Line Items]      
COVID-19 related regulatory asset 485.3 561.6  
Fair Value, Inputs, Level 1, 2 and 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets at beginning of year 1,663.6    
Fair value of plan assets at end of year 1,579.9 1,663.6  
Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year 1,401.8 1,427.4  
Service cost 21.9 20.5 $ 27.8
Interest cost 64.9 68.4 40.5
Plan participants' contributions 0.0 0.0  
Plan amendments 0.0 0.0  
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (64.8) 27.4  
Defined Benefit Plan, Benefit Obligation, Benefits Paid 136.4 141.9  
Estimated benefits paid by incurred subsidy 0.0 0.0  
Projected benefit obligation at end of year 1,287.4 1,401.8 1,427.4
Actual return on plan assets 43.7 142.8  
Employer contributions 2.4 3.1  
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant 0.0 0.0  
Benefits paid (136.4) (141.9)  
Defined Benefit Plan, Funded (Unfunded) Status of Plan 49.1 25.0  
Noncurrent assets 66.5 44.1  
Current liabilities (2.3) (2.2)  
Noncurrent liabilities (15.1) (16.9)  
Net amount recognized at end of year 49.1 25.0  
Unrecognized prior service cost 0.3 0.3  
Unrecognized actuarial loss 451.4 500.4  
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability 451.7 500.7  
Pension Plan | Underfunded Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year 1,382.7    
Projected benefit obligation at end of year 1,269.9 1,382.7  
Fair value of plan assets at beginning of year 1,426.8    
Fair value of plan assets at end of year 1,336.4 1,426.8  
Defined Benefit Plan, Funded (Unfunded) Status of Plan 66.5 44.1  
Pension Plan | Underfunded Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year 19.1    
Projected benefit obligation at end of year 17.4 19.1  
Defined Benefit Plan, Funded (Unfunded) Status of Plan (17.4) (19.1)  
Pension Plan | Fair Value, Inputs, Level 1, 2 and 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets at beginning of year 1,426.8 1,422.8  
Fair value of plan assets at end of year 1,336.5 1,426.8 1,422.8
Noncurrent assets 1,336.4    
Other Postretirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year 468.8 449.0  
Service cost 5.0 5.1 6.5
Interest cost 22.0 21.8 12.0
Plan participants' contributions 3.6 4.2  
Plan amendments 0.0 3.4  
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (22.5) 29.1  
Defined Benefit Plan, Benefit Obligation, Benefits Paid 40.7 44.3  
Estimated benefits paid by incurred subsidy 0.1 0.5  
Projected benefit obligation at end of year 436.3 468.8 449.0
Actual return on plan assets 20.0 28.2  
Employer contributions 23.6 23.4  
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant 3.8 4.3  
Benefits paid (40.7) (44.3)  
Defined Benefit Plan, Funded (Unfunded) Status of Plan (193.1) (232.3)  
Noncurrent assets 0.0 0.0  
Current liabilities (1.0) (1.0)  
Net amount recognized at end of year (193.1) (232.3)  
Unrecognized prior service cost 3.8 2.1  
Unrecognized actuarial loss 47.0 76.6  
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability 50.8 78.7  
Other Postretirement Benefits | Fair Value, Inputs, Level 1, 2 and 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets at beginning of year 236.5 224.9  
Fair value of plan assets at end of year 243.2 $ 236.5 $ 224.9
Noncurrent assets $ 243.5