Segment Information - SPPC (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) reportableSegment operatingSegment	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | operatingSegment	8
Revenues	$ 25,920	$ 25,602	$ 26,337
Cost of sales	6,616	7,057	6,757
Interest and dividend income	443	412	154
Income tax expense (benefit)	(1,582)	(1,699)	(1,916)
Other segment items	(114)	33	3,019
Net income attributable to parent	4,300	3,020	2,721
Capital expenditures	9,013	9,148	7,505
Total assets	$ 140,140	137,840	133,840
SPPC
Segment Reporting Information [Line Items]
Number of reportable segments | reportableSegment	2
Revenues	$ 1,262	1,431	1,193
Cost of sales	682	865	666
Operations and maintenance	245	204	189
Depreciation and amortization	181	185	149
Interest expense	86	66	58
Interest and dividend income	12	22	18
Income tax expense (benefit)	10	16	19
Other segment items	15	0	(12)
Net income attributable to parent	85	117	118
Capital expenditures	674	388	351
Total assets	5,327	4,772	4,732
SPPC | Other
Segment Reporting Information [Line Items]
Total assets	42	67	67
SPPC | Electric
Segment Reporting Information [Line Items]
Revenues	1,080	1,194	1,025
SPPC | Electric | Operating segments
Segment Reporting Information [Line Items]
Revenues	1,080	1,194	1,025
Cost of sales	561	689	555
Operations and maintenance	213	182	170
Depreciation and amortization	162	168	132
Interest expense	79	62	55
Interest and dividend income	12	20	16
Income tax expense (benefit)	12	14	15
Other segment items	17	(1)	(12)
Net income attributable to parent	82	98	102
Capital expenditures	643	350	304
Total assets	4,767	4,251	4,224
SPPC | Natural Gas
Segment Reporting Information [Line Items]
Revenues	182	237	168
SPPC | Natural Gas | Operating segments
Segment Reporting Information [Line Items]
Revenues	182	237	168
Cost of sales	121	176	111
Operations and maintenance	32	22	19
Depreciation and amortization	19	17	17
Interest expense	7	4	3
Interest and dividend income	0	2	2
Income tax expense (benefit)	(2)	2	4
Other segment items	(2)	1	0
Net income attributable to parent	3	19	16
Capital expenditures	31	38	47
Total assets	$ 518	$ 454	$ 441