Segment Information - SPPC (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) reportableSegment operatingSegment	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | operatingSegment			8
Operating revenue	$ 6,229	$ 6,612	$ 12,575	$ 12,642
Operating income (loss)	1,046	1,207	1,713	2,443
Interest expense	(599)	(550)	(1,185)	(1,082)
Allowance for equity funds	61	42	110	80
Interest and dividend income	127	30	213	53
Other, net	78	(26)	118	(21)
Income (loss) before income tax expense (benefit) and equity income (loss)	1,049	3,249	2,028	2,779
Assets	137,751		$ 137,751		$ 133,840
SPPC
Segment Reporting Information [Line Items]
Number of reportable segments | reportableSegment			2
Operating revenue	337	258	$ 737	537
Operating income (loss)	26	23	61	61
Interest expense	(15)	(14)	(31)	(27)
Capitalized interest	3	0	5	1
Allowance for equity funds	3	2	5	4
Interest and dividend income	5	4	12	7
Other, net	1	0	2	2
Income (loss) before income tax expense (benefit) and equity income (loss)	23	15	54	48
Assets	4,684		4,684		4,732
SPPC | Regulated electric
Segment Reporting Information [Line Items]
Regulated electric	293	230	597	457
Operating revenue	293	230	597	457
Operating income (loss)	23	19	48	49
Assets	4,182		4,182		4,224
SPPC | Regulated natural gas
Segment Reporting Information [Line Items]
Regulated natural gas	44	28	140	80
Operating revenue	44	28	140	80
Operating income (loss)	3	$ 4	13	$ 12
Assets	444		444		441
SPPC | Other
Segment Reporting Information [Line Items]
Assets	$ 58		$ 58		$ 67