Revenue from Contracts with Customers - NPC (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Operating revenue	$ 6,111	$ 6,346
Regulated | Regulated retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	2,714	2,688
NPC
Disaggregation of Revenue [Line Items]
Other revenue	1	5
Operating revenue	561	599
NPC | Regulated
Disaggregation of Revenue [Line Items]
Total Customer Revenue	560	594
NPC | Regulated | Regulated retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	543	576
NPC | Regulated | Wholesale, transmission and other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	17	18
NPC | Customer Revenue | Regulated | Regulated retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	539	573
NPC | Customer Revenue | Regulated | Regulated retail electric | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	271	293
NPC | Customer Revenue | Regulated | Regulated retail electric | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	133	136
NPC | Customer Revenue | Regulated | Regulated retail electric | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	134	138
NPC | Customer Revenue | Regulated | Regulated retail electric | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1	6
NPC | Distribution only service | Regulated | Regulated retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	$ 4	$ 3