Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,304.2	$ 3,588.7	$ 2,069.8
Provision for Rate Refund
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	(1.2)	0.0	3.8
Integrated Market
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	163.8	468.9	49.6
Transmission
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	131.7	140.2	143.3
Other
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	20.8	1.1	30.7
Residential
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,272.6	1,309.1	842.7
Commercial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	803.5	749.2	465.6
Industrial
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	317.2	323.0	192.6
Oilfield
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	304.2	312.8	169.2
Public Authority and Street Light
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	291.6	284.4	172.3
System Sales Revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 2,989.1	$ 2,978.5	$ 1,842.4