Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 2,607.3	$ 3,304.2	$ 3,588.7
Provision for Rate Refund
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2.0	(1.2)	0.0
Integrated Market
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	71.6	163.8	468.9
Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	143.0	131.7	140.2
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	41.6	20.8	1.1
Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,008.6	1,272.6	1,309.1
Commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	674.6	803.3	749.1
Industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	229.6	317.3	323.1
Oilfield
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	207.8	304.3	312.8
Public Authority and Street Light
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	228.5	291.6	284.4
System Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 2,349.1	$ 2,989.1	$ 2,978.5