Revenue from Contracts with Customers - NPC (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Total Customer Revenue	$ 4,745	$ 4,199	$ 9,464	$ 8,911
Operating revenue	6,612	6,064	12,642	12,145
Other revenue
Disaggregation of Revenue [Line Items]
Operating revenue	195	102	299	239
Regulated
Disaggregation of Revenue [Line Items]
Total Customer Revenue	3,989	3,587	8,104	7,681
Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	2,591	2,411	4,847	4,519
NPC
Disaggregation of Revenue [Line Items]
Operating revenue	639	559	1,054	929
NPC | Other revenue
Disaggregation of Revenue [Line Items]
Operating revenue	5	5	11	11
NPC | Regulated
Disaggregation of Revenue [Line Items]
Total Customer Revenue	634	554	1,043	918
NPC | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	616	539	1,009	889
NPC | Regulated | Wholesale, transmission and other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	18	15	34	29
NPC | Customer Revenue | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	611	534	999	879
NPC | Customer Revenue | Regulated | Retail electric | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	353	326	566	521
NPC | Customer Revenue | Regulated | Retail electric | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	131	110	226	194
NPC | Customer Revenue | Regulated | Retail electric | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	124	95	203	158
NPC | Customer Revenue | Regulated | Retail electric | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	3	3	4	6
NPC | Distribution only service | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	$ 5	$ 5	$ 10	$ 10