Fair Value Measurements - NPC - Level 3 (Details) - NPC - Commodity - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (175)	$ 25	$ (113)	$ 15
Changes in fair value recognized in regulatory assets	(4)	6	(81)	11
Settlements	113	(45)	128	(40)
Ending balance	$ (66)	$ (14)	$ (66)	$ (14)