ASSET RETIREMENT OBLIGATIONS - Details of AROs Included in the Balance Sheets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	$ 10,840	$ 11,687
Liabilities incurred	90	36
Liabilities settled	(617)	(455)
Accretion expense	403	406
Cash flow revisions	(399)	(834)
Balance at end of year	10,317	10,840
Alabama Power
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	4,287	4,334
Liabilities incurred	0	0
Liabilities settled	(270)	(205)
Accretion expense	156	158
Cash flow revisions	(15)	0
Balance at end of year	4,158	4,287
Georgia Power
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	6,034	6,824
Liabilities incurred	90	35
Liabilities settled	(304)	(212)
Accretion expense	230	231
Cash flow revisions	(385)	(844)
Balance at end of year	5,665	6,034
Mississippi Power
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	179	190
Liabilities incurred	0	0
Liabilities settled	(18)	(20)
Accretion expense	5	6
Cash flow revisions	2	3
Balance at end of year	168	179
Southern Power
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	144	131
Liabilities incurred	0	0
Liabilities settled	0	0
Accretion expense	6	6
Cash flow revisions	0	7
Balance at end of year	$ 150	$ 144