Utility Plant and Nonutility Property - Property, Plant and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Gross nonutility property	$ 44	$ 45
Generation
Property Plant And Equipment [Line Items]
Utility plant in service	6,053	5,921
Transmission
Property Plant And Equipment [Line Items]
Utility plant in service	2,037	1,963
Distribution
Property Plant And Equipment [Line Items]
Utility plant in service	5,191	4,909
Storage
Property Plant And Equipment [Line Items]
Utility plant in service	76	74
General and other
Property Plant And Equipment [Line Items]
Utility plant in service	601	563
Intangible
Property Plant And Equipment [Line Items]
Utility plant in service	242	250
Construction Work In Progress
Property Plant And Equipment [Line Items]
Utility plant in service	481	460
Nuclear Fuel
Property Plant And Equipment [Line Items]
Utility plant in service	603	575
Total Gross Utility Plant
Property Plant And Equipment [Line Items]
Utility plant in service	$ 15,284	$ 14,715