Revenue from Contracts with Customers - NPC (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Operating revenue	$ 6,229	$ 6,612	$ 12,575	$ 12,642
Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	2,844	2,591	5,532	4,847
NPC
Disaggregation of Revenue [Line Items]
Other revenue	4	5	9	11
Operating revenue	781	639	1,380	1,054
NPC | Regulated
Disaggregation of Revenue [Line Items]
Total Customer Revenue	777	634	1,371	1,043
NPC | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	762	616	1,338	1,009
NPC | Regulated | Wholesale, transmission and other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	15	18	33	34
NPC | Customer Revenue | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	758	611	1,331	999
NPC | Customer Revenue | Regulated | Retail electric | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	404	353	697	566
NPC | Customer Revenue | Regulated | Retail electric | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	177	131	313	226
NPC | Customer Revenue | Regulated | Retail electric | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	173	124	311	203
NPC | Customer Revenue | Regulated | Retail electric | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	4	3	10	4
NPC | Distribution only service | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	$ 4	$ 5	$ 7	$ 10