v3.25.4
Income Taxes: Effective Tax Rate Differences From Statutory Tax Rates (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Income Tax Disclosure [Abstract]      
Income before income taxes $ 343.5 $ 320.0 $ 301.6
U.S. Federal statutory rate 72.1 67.2 63.3
State and local income taxes, net of federal income tax effect 2.8 4.7 (3.4)
Tax credits      
Energy-related tax credits, net of transferability discount (15.3) (15.0) (16.9)
Other (2.2) (2.8) (2.7)
Nontaxable or Nondeductible Items      
Nontaxable or Nondeductible Items 3.2 1.9 1.9
Changes in Unrecognized Tax Benefits 1.6 0.9 0.9
Regulatory      
Amortization of excess deferred income taxes (5.3) (7.7) (8.8)
Flow-through adjustments (5.0) (7.0) (5.3)
Other (2.0) (0.6) 0.2
Other (6.2) (5.3) (3.6)
Effective Tax Rate $ 43.7 $ 36.3 $ 25.6
U.S. Federal statutory rate, percent 21.00% 21.00% 21.00%
State and local income taxes, net of federal income tax effect, percent 0.80% 1.50% (1.10%)
Tax credits      
Energy-related tax credits, net of transferability discount, percent (4.50%) (4.70%) (5.60%)
Other, percent (0.70%) (0.90%) (0.90%)
Nontaxable or Nondeductible Items      
Nontaxable or Nondeductible Items, percent 0.90% 0.60% 0.60%
Changes in Unrecognized Tax Benefits, percent 0.50% 0.30% 0.30%
Regulatory      
Amortization of excess deferred income taxes, percent (1.50%) (2.40%) (2.90%)
Flow-through adjustments, percent (1.50%) (2.20%) (1.80%)
Other, percent (0.60%) (0.20%) 0.10%
Other, percent (1.70%) (1.70%) (1.20%)
Effective Tax Rate, percent 12.70% 11.30% 8.50%