Income Taxes - SPPC - Reconciliation of Effective Income Tax Rate (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Amount
U.S. federal statutory income tax rate	$ 184	$ 200
Effects of ratemaking	(19)	(25)
Total	$ (430)	$ (399)
Percent
U.S. federal statutory income tax rate	21.00%	21.00%
Effects of ratemaking	(2.30%)	(2.60%)
Effective income tax rate	(49.00%)	(41.80%)
SPPC
Amount
U.S. federal statutory income tax rate	$ 6	$ 6
Effects of ratemaking	(5)	(3)
Total	$ 1	$ 3
Percent
U.S. federal statutory income tax rate	21.00%	21.00%
Effects of ratemaking	(17.40%)	(11.00%)
Effective income tax rate	3.60%	10.00%

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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+ Details