Fair Value Measurements - MEC - Level 3 (Details) - MEC - Commodity Derivatives - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ (5)	$ 2	$ 1
Changes in fair value recognized in net regulatory assets	37	(2)	2
Settlements	(27)	(5)	(1)
Ending balance	$ 5	$ (5)	$ 2