XML 117 R99.htm IDEA: XBRL DOCUMENT v3.25.0.1
Pension and Other Postretirement Benefits (Narrative) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]      
COVID-19 related regulatory asset $ 2,477.3 $ 2,460.2  
Pension Plan      
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Accumulated Benefit Obligation 1,278.4 1,390.9  
Funded status of plan (49.1) (25.0)  
Employer contributions 2.4 3.1  
Settlement loss 7.2 $ 9.2 $ 12.4
Expected contribution $ 2.3    
Expected return on plan assets 7.02% 7.00% 4.80%
Other Postretirement Benefits      
Defined Benefit Plan Disclosure [Line Items]      
Funded status of plan $ 193.1 $ 232.3  
Employer contributions 23.6 23.4  
Settlement loss 0.0 $ 0.0 $ 0.0
Expected contribution $ 21.3    
Expected return on plan assets 7.06% 6.96% 5.72%
Unrecognized Pension Benefit And Other Postretirement Benefit Costs      
Defined Benefit Plan Disclosure [Line Items]      
COVID-19 related regulatory asset $ 485.3 $ 561.6