Fair Value Measurements - SPPC - Level 3 (Details) - Commodity Derivatives - SPPC - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 7	$ (1)	$ 2
Changes in fair value recognized in net regulatory assets	(25)	(2)	(5)
Settlements	(15)	10	2
Ending balance	$ (33)	$ 7	$ (1)