Income Taxes - MEC - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Current:
Federal	$ (1,333)	$ (1,650)	$ (1,463)
State	(16)	118	(65)
Total current	(1,315)	(1,442)	(1,449)
Deferred:
Federal	(371)	(114)	(408)
State	(29)	(275)	(49)
Total deferred	(306)	(356)	(462)
Investment tax credits	39	99	(5)
Total	(1,582)	(1,699)	(1,916)
MEC
Current:
Federal	(885)	(755)	(769)
State	(35)	(28)	(34)
Total current	(920)	(783)	(803)
Deferred:
Federal	80	109	77
State	2	(18)	(43)
Total deferred	82	91	34
Investment tax credits	(1)	(1)	(1)
Total	$ (839)	$ (693)	$ (770)