Selected Balance Sheet Data - Property, Plant and Equipment (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 4,556	$ 4,478
Less accumulated depreciation	(1,585)	(1,564)
Property, plant and equipment, net	2,971	2,914
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,649	3,579
Natural gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	471	465
Common and other property
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	264	260
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 172	$ 174