Fair Value Measurements - MEC - Level 3 (Details) - MEC - 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	$ (5)	$ 4	$ 5	$ (5)
Changes in fair value recognized in regulatory assets	(14)	31	(27)	44
Settlements	5	(9)	8	(13)
Ending balance	$ (14)	$ 26	$ (14)	$ 26