ASSET RETIREMENT OBLIGATIONS - Details of AROs Included in the Balance Sheets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	$ 11,687	$ 10,684
Liabilities incurred	36	26
Liabilities settled	(455)	(456)
Accretion	406	407
Cash flow revisions	(834)	1,026
Balance at end of year	10,840	11,687
Alabama Power
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	4,334	3,974
Liabilities incurred	0	0
Liabilities settled	(205)	(202)
Accretion	158	156
Cash flow revisions	0	406
Balance at end of year	4,287	4,334
Georgia Power
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	6,824	6,265
Liabilities incurred	35	3
Liabilities settled	(212)	(210)
Accretion	231	236
Cash flow revisions	(844)	530
Balance at end of year	6,034	6,824
Mississippi Power
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	190	176
Liabilities incurred	0	0
Liabilities settled	(20)	(24)
Accretion	6	7
Cash flow revisions	3	31
Balance at end of year	179	190
Southern Power
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	131	95
Liabilities incurred	0	23
Liabilities settled	0	0
Accretion	6	5
Cash flow revisions	7	8
Balance at end of year	$ 144	$ 131