v3.25.4
Pension and Other Postretirement Benefits (Narrative) (Details) - USD ($)
 9 Months Ended 12 Months Ended
Sep. 30, 2025
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]        
Settlement loss   $ (1.7)    
COVID-19 related regulatory asset $ 5.7 2,499,400,000 $ 2,477,300,000  
Regulatory Liabilities 23.3 $ 1,773,400,000 1,581,700,000  
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax $ 17.6      
Discount Rate   553.00%    
Defined Benefit Plan, Assumed Health Care Cost Trend Rate, Description   9.97%    
Ultimate Trend   475.00%    
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Change Due to Subsequent Interim Measurement, Weighted-Average Expected Long-Term Rate of Return on Plan Assets   688.00%    
Pension Plan        
Defined Benefit Plan Disclosure [Line Items]        
Defined Benefit Plan, Accumulated Benefit Obligation   $ 1,263,000,000 1,278,400,000  
Funded status of plan   (65,300,000) (49,100,000)  
Employer contributions   2,000,000.0 2,400,000  
Settlement loss   6,500,000 $ 7,200,000 $ 9,200,000
Expected contribution   $ 2,700,000    
Expected return on plan assets   7.30% 7.02% 7.00%
Discount Rate   5.28% 5.58%  
Net prior service cost/(credit)   $ 0 $ 0  
Other Postretirement Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Funded status of plan   137,300,000 193,100,000  
Employer contributions   20,700,000 23,600,000  
Settlement loss   3,500,000 $ 0 $ 0
Expected contribution   $ 18,300,000    
Expected return on plan assets   7.09% 7.06% 6.96%
Discount Rate   5.45% 5.66%  
Ultimate Trend   4.75% 4.75%  
Net prior service cost/(credit)   $ (30,300,000) $ 0  
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