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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, 2022
Dec. 31, 2021
Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]      
Noncurrent liabilities $ (223.1) $ (261.5)  
COVID-19 related regulatory asset 2,580.8 2,492.2  
Regulatory Liabilities 2,012.6 1,980.0  
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 607.5 512.1  
Fair Value, Inputs, Level 1, 2 and 3      
Defined Benefit Plan Disclosure [Line Items]      
Fair value of plan assets at beginning of year 2,275.4    
Fair value of plan assets at end of year 1,647.7 2,275.4  
Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year 1,852.4 2,058.4  
Service cost 27.8 30.2 $ 32.0
Interest cost 40.5 31.4 51.6
Plan participants' contributions 0.0 0.0  
Plan amendments 0.2 0.0  
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (318.7) (68.7)  
Defined Benefit Plan, Benefit Obligation, Benefits Paid 174.8 198.9  
Estimated benefits paid by incurred subsidy 0.0 0.0  
Projected benefit obligation at end of year 1,427.4 1,852.4 2,058.4
Actual return on plan assets (386.8) 58.9  
Employer contributions 2.7 4.0  
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant 0.0 0.0  
Benefits paid (174.8) (198.9)  
Defined Benefit Plan, Funded (Unfunded) Status of Plan (4.6) 129.3  
Noncurrent assets 18.3 159.3  
Current liabilities (2.6) (2.8)  
Noncurrent liabilities (20.3) (27.2)  
Net amount recognized at end of year (4.6) 129.3  
Unrecognized prior service cost 0.4 0.3  
Unrecognized actuarial loss 564.2 438.0  
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability 564.6 438.3  
Pension Plan | Underfunded Plan [Member]      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year 1,822.4    
Projected benefit obligation at end of year 1,404.5 1,822.4  
Fair value of plan assets at beginning of year 1,981.7    
Fair value of plan assets at end of year 1,422.8 1,981.7  
Defined Benefit Plan, Funded (Unfunded) Status of Plan 18.3 159.3  
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 1,981.7 2,117.7  
Fair value of plan assets at end of year 1,422.8 1,981.7 2,117.7
Other Postretirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Benefit obligation at beginning of year 556.2 590.8  
Service cost 6.5 6.2 6.6
Interest cost 12.0 9.9 15.4
Plan participants' contributions 4.1 4.2  
Plan amendments 2.1 0.1  
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (89.9) (14.8)  
Defined Benefit Plan, Benefit Obligation, Benefits Paid 42.3 40.6  
Estimated benefits paid by incurred subsidy 0.3 0.4  
Projected benefit obligation at end of year 449.0 556.2 590.8
Actual return on plan assets (51.9) 23.9  
Employer contributions 21.3 19.8  
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant 4.1 4.2  
Benefits paid (42.3) (40.6)  
Defined Benefit Plan, Funded (Unfunded) Status of Plan (224.1) (262.5)  
Noncurrent assets 0.0 0.0  
Current liabilities (1.0) (1.0)  
Net amount recognized at end of year (224.1) (262.5)  
Unrecognized prior service cost (3.4) (7.8)  
Unrecognized actuarial loss 64.0 88.5  
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability 60.6 80.7  
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 293.7 286.4  
Fair value of plan assets at end of year $ 224.9 $ 293.7 $ 286.4