Income Taxes - MEC - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current:
Federal	$ (1,463)	$ (1,701)	$ (1,537)
State	(65)	(177)	(121)
Total current	(1,449)	(1,778)	(1,572)
Deferred:
Federal	(408)	1,037	1,438
State	(49)	(476)	424
Total deferred	(462)	650	1,883
Investment tax credits	(5)	(4)	(3)
Total	(1,916)	(1,132)	308
MEC
Current:
Federal	(769)	(736)	(684)
State	(34)	(92)	(94)
Total current	(803)	(828)	(778)
Deferred:
Federal	77	189	201
State	(43)	(35)	8
Total deferred	34	154	209
Investment tax credits	(1)	(1)	(1)
Total	$ (770)	$ (675)	$ (570)