Statements of Changes in Shareholder's Equity (Unaudited) - 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)	$ 4,207			737			737
Other equity transactions	(3)
Balance at Sep. 30, 2021				8,802	0	561	8,241
Balance at Jun. 30, 2021				8,426	0	561	7,865
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,922			377			377
Other equity transactions	(2)			(1)			(1)
Balance at Sep. 30, 2021				8,802	0	561	8,241
Balance at Dec. 31, 2021	46,694			8,960	0	561	8,399
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	1,926			756			756
Common stock dividend				(50)			(50)
Other equity transactions	(6)	$ 1	$ (13)	(1)			(1)
Balance at Sep. 30, 2022	45,858			9,665	0	561	9,104
Balance at Jun. 30, 2022				9,411	0	561	8,850
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(842)			305			305
Common stock dividend				(50)			(50)
Other equity transactions	(1)		$ (1)	(1)			(1)
Balance at Sep. 30, 2022	$ 45,858			$ 9,665	$ 0	$ 561	$ 9,104