Fair Value Measurements - NPC - Level 3 (Details) - NPC - Commodity - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (116)	$ (168)	$ (52)	$ (113)
Changes in fair value recognized in regulatory assets	(54)	(21)	(119)	(77)
Settlements	44	14	45	15
Ending balance	$ (126)	$ (175)	$ (126)	$ (175)