FINANCING - Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Long-term debt, gross	$ 54,600	$ 52,100
Finance lease obligations	314	215
Unamortized fair value adjustment	330	359
Unamortized debt premium (discount), net	(193)	(216)
Debt Issuance Costs, Net	(273)	(243)
Unamortized debt issuance expense	(273)	(243)
Total long-term debt	54,941	52,277
Less: Amount due within one year	4,285	2,157
Long-Term Debt	$ 50,656	50,120
Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.87%
Long-term debt, gross	$ 35,683	33,120
Junior subordinated notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.58%
Long-term debt, gross	$ 8,836	8,918
FFB loans
Debt Instrument [Line Items]
Weighted Average Interest Rate	2.88%
Long-term debt, gross	$ 4,874	4,962
Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.25%
Long-term debt, gross	$ 2,844	2,662
First mortgage bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.46%
Long-term debt, gross	$ 2,275	2,100
Medium-term notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	7.03%
Long-term debt, gross	$ 84	130
Other long-term debt
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.96%
Long-term debt, gross	$ 167	270
Alabama Power
Debt Instrument [Line Items]
Long-term debt, gross	10,600	9,700
Finance lease obligations	5	4
Unamortized debt premium (discount), net	(18)	(18)
Debt Issuance Costs, Net	(72)	(64)
Unamortized debt issuance expense	(72)	(64)
Total long-term debt	10,630	9,687
Less: Amount due within one year	301	751
Long-Term Debt	$ 10,329	8,936
Alabama Power \| Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.86%
Long-term debt, gross	$ 9,675	8,725
Alabama Power \| Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.44%
Long-term debt, gross	$ 995	995
Alabama Power \| Other long-term debt
Debt Instrument [Line Items]
Weighted Average Interest Rate	5.62%
Long-term debt, gross	$ 45	45
Georgia Power
Debt Instrument [Line Items]
Long-term debt, gross	14,700	13,600
Finance lease obligations	238	136
Unamortized debt premium (discount), net	(18)	(11)
Debt Issuance Costs, Net	(117)	(114)
Unamortized debt issuance expense	(117)	(114)
Total long-term debt	14,910	13,784
Less: Amount due within one year	901	675
Long-Term Debt	$ 14,009	13,109
Georgia Power \| Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.90%
Long-term debt, gross	$ 7,925	6,825
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	$ 4,874	4,962
Georgia Power \| Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.13%
Long-term debt, gross	$ 1,738	1,591
Georgia Power \| Other long-term debt
Debt Instrument [Line Items]
Long-term debt, gross	0	125
Mississippi Power
Debt Instrument [Line Items]
Long-term debt, gross	1,500	1,500
Finance lease obligations	17	18
Unamortized debt premium (discount), net	2	2
Debt Issuance Costs, Net	(10)	(10)
Unamortized debt issuance expense	(10)	(10)
Total long-term debt	1,545	1,511
Less: Amount due within one year	1	1
Long-Term Debt	$ 1,544	1,510
Mississippi Power \| Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.93%
Long-term debt, gross	$ 1,425	1,425
Mississippi Power \| Pollution control revenue bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.55%
Long-term debt, gross	$ 111	76
Southern Power
Debt Instrument [Line Items]
Long-term debt, gross	3,000	3,700
Finance lease obligations	0	0
Unamortized debt premium (discount), net	(5)	(6)
Debt Issuance Costs, Net	(14)	(17)
Unamortized debt issuance expense	(14)	(17)
Total long-term debt	2,979	3,688
Less: Amount due within one year	290	679
Long-Term Debt	2,689	3,009
Fair value gain (loss)	$ (31)	5
Southern Power \| Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.92%
Long-term debt, gross	$ 2,998	3,711
Southern Company Gas
Debt Instrument [Line Items]
Long-term debt, gross	7,400	6,900
Finance lease obligations	0	0
Unamortized fair value adjustment	330	359
Unamortized debt premium (discount), net	(8)	(35)
Debt Issuance Costs, Net	(30)	0
Unamortized debt issuance expense	(30)	0
Total long-term debt	7,442	6,902
Less: Amount due within one year	400	47
Long-Term Debt	$ 7,042	6,855
Southern Company Gas \| Senior notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	4.08%
Long-term debt, gross	$ 4,769	4,348
Southern Company Gas \| First mortgage bonds
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.46%
Long-term debt, gross	$ 2,275	2,100
Southern Company Gas \| Medium-term notes
Debt Instrument [Line Items]
Weighted Average Interest Rate	7.03%
Long-term debt, gross	$ 84	130
Southern Company Gas \| Other long-term debt
Debt Instrument [Line Items]
Weighted Average Interest Rate	3.81%
Long-term debt, gross	$ 22	$ 0

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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