FINANCING - Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Finance lease obligations	$ 298	$ 314
Unamortized fair value adjustment	302	330
Unamortized debt premium (discount), net	(198)	(193)
Unamortized debt issuance expense	(290)	(273)
Total long-term debt	59,686	54,941
Less: Amount due within one year	2,476	4,285
Long-Term Debt	$ 57,210	50,656
Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.16%
Long-term debt, gross	$ 40,235	35,683
Junior subordinated notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.33%
Long-term debt, gross	$ 8,333	8,836
FFB loans
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.88%
Long-term debt, gross	$ 4,788	4,874
Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.77%
Long-term debt, gross	$ 3,400	2,844
First mortgage bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.64%
Long-term debt, gross	$ 2,500	2,275
Medium-term notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	7.03%
Long-term debt, gross	$ 84	84
Other long-term debt
Debt Instrument [Line Items]
Weighted Average Interest Rate	5.44%
Long-term debt, gross	$ 234	167
Alabama Power
Debt Instrument [Line Items]
Finance lease obligations	5	5
Unamortized debt premium (discount), net	(20)	(18)
Unamortized debt issuance expense	(73)	(72)
Total long-term debt	11,183	10,630
Less: Amount due within one year	223	301
Long-Term Debt	$ 10,960	10,329
Alabama Power | Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.95%
Long-term debt, gross	$ 9,875	9,675
Alabama Power | Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.94%
Long-term debt, gross	$ 1,321	995
Alabama Power | Other long-term debt
Debt Instrument [Line Items]
Weighted Average Interest Rate	7.04%
Long-term debt, gross	$ 75	45
Georgia Power
Debt Instrument [Line Items]
Finance lease obligations	240	238
Unamortized debt premium (discount), net	(19)	(18)
Unamortized debt issuance expense	(122)	(117)
Total long-term debt	16,700	14,910
Less: Amount due within one year	502	901
Long-Term Debt	$ 16,198	14,009
Georgia Power | Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.34%
Long-term debt, gross	$ 9,575	7,925
Georgia Power | Junior subordinated notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	5.00%
Long-term debt, gross	$ 270	270
Georgia Power | FFB loans
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.88%
Long-term debt, gross	$ 4,788	4,874
Georgia Power | Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.64%
Long-term debt, gross	$ 1,968	1,738
Mississippi Power
Debt Instrument [Line Items]
Finance lease obligations	16	17
Unamortized debt premium (discount), net	1	2
Unamortized debt issuance expense	(9)	(10)
Total long-term debt	1,644	1,545
Less: Amount due within one year	201	1
Long-Term Debt	$ 1,443	1,544
Mississippi Power | Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.27%
Long-term debt, gross	$ 1,525	1,425
Mississippi Power | Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.08%
Long-term debt, gross	$ 111	111
Southern Power
Debt Instrument [Line Items]
Finance lease obligations	0	0
Unamortized debt premium (discount), net	(4)	(5)
Unamortized debt issuance expense	(13)	(14)
Total long-term debt	2,711	2,979
Less: Amount due within one year	0	290
Long-Term Debt	2,711	2,689
Fair value gain (loss)	$ (12)	(31)
Southern Power | Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.05%
Long-term debt, gross	$ 2,728	2,998
Southern Company Gas
Debt Instrument [Line Items]
Finance lease obligations	0	0
Unamortized fair value adjustment	302	330
Unamortized debt premium (discount), net	(8)	(8)
Unamortized debt issuance expense	(34)	(30)
Total long-term debt	7,833	7,442
Less: Amount due within one year	0	400
Long-Term Debt	$ 7,833	7,042
Southern Company Gas | Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.36%
Long-term debt, gross	$ 4,930	4,769
Southern Company Gas | First mortgage bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.64%
Long-term debt, gross	$ 2,500	2,275
Southern Company Gas | Medium-term notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	7.03%
Long-term debt, gross	$ 84	84
Southern Company Gas | Other long-term debt
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.81%
Long-term debt, gross	$ 59	$ 22