Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 719.7	$ 644.1	$ 1,460.8	$ 1,226.7
Provision for Rate Refund
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	0.0	0.0	3.0	0.0
Integrated Market
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	26.3	17.1	47.6	32.1
Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	42.1	42.5	81.9	78.1
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	8.4	7.4	13.7	15.5
Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	251.3	239.0	534.9	460.4
Commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	218.5	177.6	425.1	326.4
Industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	58.4	55.2	120.0	108.2
Oilfield
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	52.5	47.6	111.9	97.3
Public Authority and Street Light
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	62.2	57.7	122.7	108.7
System Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 642.9	$ 577.1	$ 1,314.6	$ 1,101.0