v3.26.3
Accumulated Other Comprehensive Loss (Components Of Accumulated Other Comprehensive Loss) (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance $ 11,894.4 $ 10,996.9 $ 11,659.9 $ 10,668.3
Other Comprehensive Income (Loss) before reclassifications (4.4) 15.1 (7.9) 17.0
Amounts reclassified from accumulated other comprehensive income (loss) 0.3 0.1 0.5 0.4
Net current-period other comprehensive income (loss) (4.1) 15.2 (7.4) 17.4
Ending balance 11,954.4 11,241.8 11,954.4 11,241.8
Interest Rate Risk        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Net current-period other comprehensive income (loss)     (0.3)  
Accumulated Other Comprehensive Income (Loss)        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (9.5) (28.2) (6.2) (30.4)
Net current-period other comprehensive income (loss) (4.1)   (7.4)  
Ending balance (13.6) (13.0) (13.6) (13.0)
Gains and Losses on Securities        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (0.4) (2.2) 0.1 (4.0)
Other Comprehensive Income (Loss) before reclassifications (4.4) 1.3 (5.1) 3.1
Amounts reclassified from accumulated other comprehensive income (loss) 0.1 0.0 0.3 0.0
Net current-period other comprehensive income (loss) (4.3) 1.3 (4.8) 3.1
Ending balance (4.7) (0.9) (4.7) (0.9)
Gains and Losses on Cash Flow Hedges        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance (13.8) (13.4) (13.6) (13.2)
Other Comprehensive Income (Loss) before reclassifications (0.1) 0.0 0.0 0.0
Amounts reclassified from accumulated other comprehensive income (loss) 0.0 (0.1) (0.3) (0.3)
Net current-period other comprehensive income (loss) (0.1) (0.1)   (0.3)
Ending balance (13.9) (13.5) (13.9) (13.5)
Pension and OPEB Items        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Beginning balance 4.7 (12.6) 7.3 (13.2)
Other Comprehensive Income (Loss) before reclassifications 0.1 13.8 (2.8) 13.9
Amounts reclassified from accumulated other comprehensive income (loss) 0.2 0.2 0.5 0.7
Net current-period other comprehensive income (loss) 0.3 14.0 (2.3) 14.6
Ending balance $ 5.0 $ 1.4 $ 5.0 $ 1.4