Revenue from Contracts with Customers - NPC (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Operating revenue	$ 7,500	$ 6,968	$ 20,142	$ 19,113
Regulated
Disaggregation of Revenue [Line Items]
Total Customer Revenue	5,055	4,430	13,159	12,111
Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	3,513	3,096	8,360	7,615
NPC
Disaggregation of Revenue [Line Items]
Other revenue	6	6	16	16
Operating revenue	1,003	802	2,057	1,731
NPC | Regulated
Disaggregation of Revenue [Line Items]
Total Customer Revenue	997	796	2,041	1,715
NPC | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	966	768	1,975	1,658
NPC | Regulated | Wholesale, transmission and other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	31	28	66	57
NPC | Customer Revenue | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	961	762	1,960	1,641
NPC | Customer Revenue | Regulated | Retail electric | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	582	477	1,149	998
NPC | Customer Revenue | Regulated | Retail electric | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	172	129	398	323
NPC | Customer Revenue | Regulated | Retail electric | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	202	152	404	310
NPC | Customer Revenue | Regulated | Retail electric | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	5	4	9	10
NPC | Distribution only service | Regulated | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	$ 5	$ 6	$ 15	$ 17