Selected Balance Sheet Data - Property, Plant and Equipment (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 4,364	$ 4,138
Less accumulated depreciation	(1,544)	(1,478)
Property, plant and equipment, net	2,820	2,660
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,507	3,348
Natural gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	445	423
Common and other property
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	255	233
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 157	$ 134