Revenue from Contracts with Customers - NPC (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Operating revenue	$ 6,346	$ 6,030
Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	2,688	2,256
NPC
Disaggregation of Revenue [Line Items]
Other revenue	5	5
Operating revenue	599	415
NPC | Regulated
Disaggregation of Revenue [Line Items]
Total Customer Revenue	594	410
NPC | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	576	394
NPC | Regulated | Wholesale, transmission and other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	18	16
NPC | Customer Revenue | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	573	389
NPC | Customer Revenue | Regulated | Retail electric | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	293	214
NPC | Customer Revenue | Regulated | Retail electric | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	136	96
NPC | Customer Revenue | Regulated | Retail electric | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	138	78
NPC | Customer Revenue | Regulated | Retail electric | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	6	1
NPC | Distribution only service | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	$ 3	$ 5