Statements of Changes in Shareholder's Equity (Unaudited) - MEC - USD ($) $ in Millions	Total	Retained Earnings	MEC	MEC Common Stock	MEC Additional Paid-in Capital	MEC Retained Earnings
Balance at Dec. 31, 2021			$ 8,960	$ 0	$ 561	$ 8,399
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ (129)		244			244
Other equity transactions	5	$ (1)
Balance at Mar. 31, 2022			9,204	0	561	8,643
Balance at Dec. 31, 2022	46,832		9,645	0	561	9,084
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	989		242			242
Dividends declared			(100)			(100)
Other equity transactions			1			1
Balance at Mar. 31, 2023	$ 47,853		$ 9,788	$ 0	$ 561	$ 9,227