Statements of Common Stockholders' Equity - MPC - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Mississippi Power	Mississippi Power Common Stock	Mississippi Power Paid-In Capital	Mississippi Power Retained Earnings	Mississippi Power Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Dec. 31, 2018		1,035					1
Beginning balance at Dec. 31, 2018	$ 29,039	$ 5,164	$ 11,094	$ 8,706	$ (203)	$ 1,609	$ 38	$ 4,546	$ (2,971)	$ (4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated Net Income	4,739					139			139
Return of capital to parent company						(150)		(150)
Capital contributions from parent company						53		53
Other comprehensive income (loss)	(118)				(118)	1				1
Cash dividends on common stock	(2,570)			(2,570)
Other	18		21	2
Ending balance (in shares) at Dec. 31, 2019		1,054					1
Ending balance at Dec. 31, 2019	31,759	$ 5,257	11,734	10,877	(321)	1,652	$ 38	4,449	(2,832)	(3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated Net Income	3,119					152			152
Return of capital to parent company						(74)		(74)
Capital contributions from parent company						86		86
Other comprehensive income (loss)	(75)				(75)	1				1
Cash dividends on common stock	(2,685)			(2,685)		(74)			(74)
Other	(12)		(10)		1	(1)		(1)
Ending balance (in shares) at Dec. 31, 2020		1,058					1
Ending balance at Dec. 31, 2020	32,234	$ 5,268	11,834	11,311	(395)	1,742	$ 38	4,460	(2,754)	(2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Consolidated Net Income	2,393					159			159
Capital contributions from parent company						122		122
Other comprehensive income (loss)	158				158	1				1
Cash dividends on common stock	(2,777)			(2,777)		(157)			(157)
Other	(7)		(8)	2					(1)	1
Ending balance (in shares) at Dec. 31, 2021		1,061					1
Ending balance at Dec. 31, 2021	$ 32,276	$ 5,279	$ 11,950	$ 10,929	$ (237)	$ 1,867	$ 38	$ 4,582	$ (2,753)	$ 0