Revenue from Contracts with Customers - SPPC (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
Regulated | Retail gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	164	109	552	607
SPPC
Disaggregation of Revenue [Line Items]
Operating revenue	258	209	537	429
SPPC | Other revenue
Disaggregation of Revenue [Line Items]
Operating revenue	0	1	2	2
SPPC | Regulated electric
Disaggregation of Revenue [Line Items]
Operating revenue	230	189	457	370
SPPC | Regulated electric | Other revenue
Disaggregation of Revenue [Line Items]
Operating revenue	0	1	1	1
SPPC | Regulated natural gas
Disaggregation of Revenue [Line Items]
Operating revenue	28	20	80	59
SPPC | Regulated natural gas | Other revenue
Disaggregation of Revenue [Line Items]
Operating revenue	0	0	1	1
SPPC | Regulated
Disaggregation of Revenue [Line Items]
Total Customer Revenue	258	208	535	427
SPPC | Regulated | Wholesale, transmission and other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	14	12	35	28
SPPC | Regulated | Regulated electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	230	188	456	369
SPPC | Regulated | Regulated electric | Wholesale, transmission and other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	14	12	35	28
SPPC | Regulated | Regulated natural gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	28	20	79	58
SPPC | Regulated | Regulated natural gas | Wholesale, transmission and other
Disaggregation of Revenue [Line Items]
Total Customer Revenue	0	0	0	0
SPPC | Regulated | Total retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	244	196	500	399
SPPC | Regulated | Total retail | Regulated electric | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	216	176	421	341
SPPC | Regulated | Total retail | Regulated natural gas | Retail gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	28	20	79	58
SPPC | Regulated | Customer Revenue
Disaggregation of Revenue [Line Items]
Total Customer Revenue	243	195	497	397
SPPC | Regulated | Customer Revenue | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	98	81	213	176
SPPC | Regulated | Customer Revenue | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	88	69	172	132
SPPC | Regulated | Customer Revenue | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	56	44	109	86
SPPC | Regulated | Customer Revenue | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1	1	3	3
SPPC | Regulated | Customer Revenue | Regulated electric | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	215	175	418	339
SPPC | Regulated | Customer Revenue | Regulated electric | Retail electric | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	79	68	162	138
SPPC | Regulated | Customer Revenue | Regulated electric | Retail electric | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	82	64	151	117
SPPC | Regulated | Customer Revenue | Regulated electric | Retail electric | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	53	42	102	81
SPPC | Regulated | Customer Revenue | Regulated electric | Retail electric | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1	1	3	3
SPPC | Regulated | Customer Revenue | Regulated natural gas | Retail gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	28	20	79	58
SPPC | Regulated | Customer Revenue | Regulated natural gas | Retail gas | Residential
Disaggregation of Revenue [Line Items]
Total Customer Revenue	19	13	51	38
SPPC | Regulated | Customer Revenue | Regulated natural gas | Retail gas | Commercial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	6	5	21	15
SPPC | Regulated | Customer Revenue | Regulated natural gas | Retail gas | Industrial
Disaggregation of Revenue [Line Items]
Total Customer Revenue	3	2	7	5
SPPC | Regulated | Customer Revenue | Regulated natural gas | Retail gas | Other retail
Disaggregation of Revenue [Line Items]
Total Customer Revenue	0	0	0	0
SPPC | Regulated | Distribution only service
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1	1	3	2
SPPC | Regulated | Distribution only service | Regulated electric | Retail electric
Disaggregation of Revenue [Line Items]
Total Customer Revenue	1	1	3	2
SPPC | Regulated | Distribution only service | Regulated natural gas | Retail gas
Disaggregation of Revenue [Line Items]
Total Customer Revenue	$ 0	$ 0	$ 0	$ 0