Fair Value Measurements - SPPC - Level 3 (Details) - Commodity - SPPC - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (36)	$ (54)	$ (13)	$ (33)
Changes in fair value recognized in regulatory assets	(8)	1	(45)	(25)
Settlements	32	36	46	41
Ending balance	$ (12)	$ (17)	$ (12)	$ (17)