Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 544.6	$ 578.1
Provision for Rate Refund
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1.4	(0.6)
Integrated market
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	12.7	22.8
Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	35.2	35.8
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	11.0	6.6
Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	205.5	226.8
Commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	134.4	128.1
Industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	51.9	57.4
Oilfield
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	47.4	53.2
Public Authority and Street Light
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	45.1	48.0
System Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 484.3	$ 513.5