Selected Balance Sheet Data - Property, Plant and Equipment (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 4,790	$ 4,478
Less accumulated depreciation	(1,635)	(1,564)
Property, plant and equipment, net	3,155	2,914
Electric plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,767	3,579
Natural gas plant
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	496	465
Common and other property
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	290	260
Construction work in progress
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 237	$ 174