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)	$ 2,285			360			360
Other equity transactions	(1)			1			1
Balance at Jun. 30, 2021				8,426	0	561	7,865
Balance at Mar. 31, 2021				8,212	0	561	7,651
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,281			213			213
Other equity transactions	(4)		$ (1)	1			1
Balance at Jun. 30, 2021				8,426	0	561	7,865
Balance at Dec. 31, 2021	46,694			8,960	0	561	8,399
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,768			451			451
Other equity transactions	(5)	$ 1	(12)
Balance at Jun. 30, 2022	47,304			9,411	0	561	8,850
Balance at Mar. 31, 2022				9,204	0	561	8,643
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	2,897			207			207
Other equity transactions	(10)	$ 1	$ (11)
Balance at Jun. 30, 2022	$ 47,304			$ 9,411	$ 0	$ 561	$ 8,850