Statements of Changes in Shareholder's Equity - MEC - USD ($) $ in Millions	Total	Additional Paid-in Capital	MEC	MEC Common Stock	MEC Additional Paid-in Capital	MEC Retained Earnings
Balance at Dec. 31, 2018			$ 6,446	$ 0	$ 561	$ 5,885
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to parent	$ 2,950		793			793
Other equity transactions	3		1			1
Balance at Dec. 31, 2019			7,240	0	561	6,679
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to parent	6,943		826			826
Other equity transactions	0	$ (1)	(1)			(1)
Balance at Dec. 31, 2020	43,010		8,065	0	561	7,504
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to parent	5,790		894			894
Other equity transactions	(1)		1			1
Balance at Dec. 31, 2021	$ 46,694		$ 8,960	$ 0	$ 561	$ 8,399