Fair Value Measurements - NPC - Level 3 (Details) - NPC - Commodity - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (168)	$ 27	$ (113)	$ 15
Changes in fair value recognized in regulatory assets	(21)	(6)	(77)	5
Settlements	14	4	15	5
Ending balance	$ (175)	$ 25	$ (175)	$ 25