Fair Value Measurements - SPPC - Level 3 (Details) - Commodity derivatives - SPPC - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (16)	$ (13)	$ (33)
Changes in fair value recognized in net regulatory assets	(27)	(50)	(21)
Settlements	30	47	41
Ending balance	$ (13)	$ (16)	$ (13)