Segment Information - SPPC (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) operatingSegment reportableSegment	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | operatingSegment	8
Operating revenue	$ 6,346	$ 6,030
Operating income (loss)	667	1,236
Interest expense	(586)	(532)
Allowance for equity funds	49	38
Interest and dividend income	86	23
Other, net	40	5
Income (loss) before income tax expense (benefit) and equity income (loss)	979	(470)
Assets	$ 134,454		$ 133,840
SPPC
Segment Reporting Information [Line Items]
Number of reportable segments | reportableSegment	2
Operating revenue	$ 400	279
Operating income (loss)	35	38
Interest expense	(16)	(13)
Capitalized interest	2	1
Allowance for equity funds	2	2
Interest and dividend income	7	3
Other, net	1	2
Income (loss) before income tax expense (benefit) and equity income (loss)	31	33
Assets	4,683		4,732
SPPC | Regulated electric
Segment Reporting Information [Line Items]
Regulated electric	304	227
Operating revenue	304	227
Operating income (loss)	25	30
Assets	4,193		4,224
SPPC | Regulated natural gas
Segment Reporting Information [Line Items]
Regulated natural gas	96	52
Operating revenue	96	52
Operating income (loss)	10	$ 8
Assets	460		441
SPPC | Other
Segment Reporting Information [Line Items]
Assets	$ 30		$ 67