Segment Information - SPPC (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) operatingSegment reportableSegment	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | operatingSegment			8
Operating revenue	$ 7,500	$ 6,968	$ 20,142	$ 19,113
Operating income	1,823	1,834	4,266	4,375
Interest expense	(555)	(531)	(1,637)	(1,593)
Allowance for equity funds	43	34	123	90
Interest and dividend income	40	18	93	65
Other, net	5	8	(16)	64
(Loss) income before income tax benefit and equity loss	(1,895)	1,675	884	4,189
Assets	132,004		$ 132,004		$ 132,065
SPPC
Segment Reporting Information [Line Items]
Number of reportable segments | reportableSegment			2
Operating revenue	330	282	$ 867	711
Operating income	74	75	135	139
Interest expense	(15)	(14)	(42)	(41)
Capitalized interest	1	1	2	2
Allowance for equity funds	1	2	5	5
Interest and dividend income	5	3	12	6
Other, net	1	3	3	9
(Loss) income before income tax benefit and equity loss	67	70	115	120
Assets	4,627		4,627		4,223
SPPC | Regulated electric
Segment Reporting Information [Line Items]
Regulated electric	310	266	767	636
Operating revenue	310	266	767	636
Operating income	74	74	123	126
Assets	4,136		4,136		3,829
SPPC | Regulated natural gas
Segment Reporting Information [Line Items]
Regulated natural gas	20	16	100	75
Operating revenue	20	16	100	75
Operating income	0	$ 1	12	$ 13
Assets	428		428		365
SPPC | Other
Segment Reporting Information [Line Items]
Assets	$ 63		$ 63		$ 29