v3.25.4
Pension and Other Postretirement Benefits (Schedule Of Reconciliation Of The Plans Funded Status And Amounts Reflected) (Details) - USD ($)
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Sep. 30, 2025
Defined Benefit Plan Disclosure [Line Items]        
Noncurrent liabilities $ (136,800,000) $ (192,100,000)    
COVID-19 related regulatory asset 2,499,400,000 2,477,300,000   $ 5.7
Regulatory Liabilities 1,773,400,000 1,581,700,000   $ 23.3
Unrecognized Pension Benefit And Other Postretirement Benefit Costs        
Defined Benefit Plan Disclosure [Line Items]        
Regulatory Liabilities 0 0    
Unrecognized Pension Benefit And Other Postretirement Benefit Costs        
Defined Benefit Plan Disclosure [Line Items]        
COVID-19 related regulatory asset 433,100,000 485,300,000    
Fair Value, Inputs, Level 1, 2 and 3        
Defined Benefit Plan Disclosure [Line Items]        
Fair value of plan assets at beginning of year 1,579,900,000      
Fair value of plan assets at end of year 1,596,400,000 1,579,900,000    
Pension Plan        
Defined Benefit Plan Disclosure [Line Items]        
Benefit obligation at beginning of year 1,287,400,000 1,401,800,000    
Service cost 19,700,000 21,900,000 $ 20,500,000  
Interest cost 64,100,000 64,900,000 68,400,000  
Plan participants' contributions 0 0    
Plan amendments 0 0    
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) 34,800,000 (64,800,000)    
Defined Benefit Plan, Benefit Obligation, Benefits Paid 135,200,000 136,400,000    
Estimated benefits paid by incurred subsidy 0 0    
Projected benefit obligation at end of year 1,270,800,000 1,287,400,000 1,401,800,000  
Actual return on plan assets 132,800,000 43,700,000    
Employer contributions 2,000,000.0 2,400,000    
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant 0 0    
Benefits paid (135,200,000) (136,400,000)    
Defined Benefit Plan, Funded (Unfunded) Status of Plan 65,300,000 49,100,000    
Noncurrent assets 82,800,000 66,500,000    
Current liabilities (2,600,000) (2,300,000)    
Noncurrent liabilities (14,900,000) (15,100,000)    
Net amount recognized at end of year 65,300,000 49,100,000    
Unrecognized prior service cost 200,000 300,000    
Unrecognized actuarial loss 413,800,000 451,400,000    
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability 414,000,000.0 451,700,000    
Pension Plan | Underfunded Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Benefit obligation at beginning of year 1,269,900,000      
Projected benefit obligation at end of year 1,253,300,000 1,269,900,000    
Fair value of plan assets at beginning of year 1,336,400,000      
Fair value of plan assets at end of year 1,336,100,000 1,336,400,000    
Defined Benefit Plan, Funded (Unfunded) Status of Plan 82,800,000 66,500,000    
Pension Plan | Underfunded Plan [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Benefit obligation at beginning of year 17,400,000      
Projected benefit obligation at end of year 17,500,000 17,400,000    
Defined Benefit Plan, Funded (Unfunded) Status of Plan (17,500,000) (17,400,000)    
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 1,336,500,000 1,426,800,000    
Fair value of plan assets at end of year 1,336,100,000 1,336,500,000 1,426,800,000  
Noncurrent assets 1,338,400,000 1,336,400,000    
Other Postretirement Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Benefit obligation at beginning of year 436,300,000 468,800,000    
Service cost 4,000,000.0 5,000,000.0 5,100,000  
Interest cost 21,600,000 22,000,000.0 21,800,000  
Plan participants' contributions 4,000,000.0 3,600,000    
Plan amendments (30,300,000) 0    
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) (1,800,000) (22,500,000)    
Defined Benefit Plan, Benefit Obligation, Benefits Paid 39,000,000.0 40,700,000    
Estimated benefits paid by incurred subsidy 100,000 100,000    
Projected benefit obligation at end of year 394,900,000 436,300,000 468,800,000  
Actual return on plan assets 28,700,000 20,000,000.0    
Employer contributions 20,700,000 23,600,000    
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant 4,000,000.0 3,800,000    
Benefits paid (39,000,000.0) (40,700,000)    
Defined Benefit Plan, Funded (Unfunded) Status of Plan (137,300,000) (193,100,000)    
Noncurrent assets 500,000 0    
Current liabilities (1,000,000.0) (1,000,000.0)    
Net amount recognized at end of year (137,300,000) (193,100,000)    
Unrecognized prior service cost (23,800,000) 3,800,000    
Unrecognized actuarial loss 28,100,000 47,000,000.0    
Defined Benefit Plan Amounts Recognized In Other Comprehensive Income Or Regulatory Asset Or Liability 4,300,000 50,800,000    
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 243,200,000 236,500,000    
Fair value of plan assets at end of year 257,600,000 243,200,000 $ 236,500,000  
Noncurrent assets $ 258,000,000.0 $ 243,500,000