Income Taxes - MEC - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Deferred income tax assets:
Regulatory liabilities	$ 1,323	$ 1,349
AROs	283	304
Other	741	686
Total deferred income tax assets	3,159	3,159
Valuation allowances	(187)	(164)
Total deferred income tax assets, net	2,972	2,995
Deferred income tax liabilities:
Property-related items	(12,244)	(11,814)
Regulatory assets	(898)	(764)
Other	(510)	(478)
Total deferred income tax liabilities	(15,650)	(15,933)
Net deferred income tax liability	(12,678)	(12,938)
Operating loss carryforwards	10,570
State
Deferred income tax liabilities:
Operating loss carryforwards	9,653
MEC
Deferred income tax assets:
Regulatory liabilities	194	240
AROs	191	220
Revenue sharing	87	33
State carryforwards	61	55
Employee benefits	37	26
Other	24	(3)
Total deferred income tax assets	594	571
Valuation allowances	(2)	(1)
Total deferred income tax assets, net	592	570
Deferred income tax liabilities:
Property-related items	(3,895)	(3,843)
Regulatory assets	(128)	(112)
Other	(2)	(4)
Total deferred income tax liabilities	(4,025)	(3,959)
Net deferred income tax liability	(3,433)	$ (3,389)
MEC | State
Deferred income tax liabilities:
Operating loss carryforwards	$ 921