Statements of Changes in Shareholder's Equity - MEC - USD ($) $ in Millions	Total	Additional Paid-in Capital	Retained Earnings	MEC	MEC Common Stock	MEC Additional Paid-in Capital	MEC Retained Earnings
Balance at Dec. 31, 2020				$ 8,065	$ 0	$ 561	$ 7,504
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 5,790			894			894
Other equity transactions	(8)	$ (3)		1			1
Balance at Dec. 31, 2021				8,960	0	561	8,399
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,721			961			961
Common stock dividends				(275)			(275)
Other equity transactions	(6)	$ 1	$ (12)	(1)			(1)
Balance at Dec. 31, 2022	46,832			9,645	0	561	9,084
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	3,020			982			982
Common stock dividends				(1,025)			(1,025)
Other equity transactions	(9)			1			1
Balance at Dec. 31, 2023	$ 48,434			$ 9,603	$ 0	$ 561	$ 9,042