Property, Plant and Equipment with Corresponding Depreciation Rates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant and equipment in service	$ 3,328.1	$ 2,977.6
Total property, plant and equipment in service, Composite Rate	3.10%	2.90%	3.20%
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 647.3	$ 571.7
Property Plant And Equipment, Net of Depreciation	2,680.8	2,405.9
Construction in Progress, Gross	205.0	165.5
Carrying Value	2,885.8	2,571.4
Property, Plant and Equipment [Line Items]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	647.3	571.7
Construction in Progress, Gross	205.0	165.5
Regulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Transmission	871.7	759.9
Distribution	2,277.2	2,044.7
General	20.7	20.0
Non-depreciable	115.8	112.0
Total property, plant and equipment in service	$ 3,285.4	$ 2,936.6
Transmission, Composite Rate	2.40%	2.00%
Distribution, Composite Rate	3.50%	3.30%
General, Composite Rate	5.80%	5.60%
Unregulated Operation [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Non-depreciable	$ 5.4	$ 5.4
Other	37.3	35.6
Total property, plant and equipment in service	$ 42.7	$ 41.0
Other, Composite Rate	3.50%	3.50%