Fair Value Measurements - MEC - Level 3 (Details) - MEC - 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	$ 4	$ 1	$ (5)	$ 2
Changes in fair value recognized in regulatory assets	31	0	44	0
Settlements	(9)	(2)	(13)	(3)
Ending balance	$ 26	$ (1)	$ 26	$ (1)