FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Assets:
Derivative asset	$ 141	$ 213
Liabilities:
Derivative liability	617	125
Collateral already posted, aggregate fair value	41
Recurring
Assets:
Cash equivalents	1,447	1,174
Other investments	35	44
Total	3,856	4,023
Liabilities:
Contingent consideration	12	14
Other	13
Total	753	181
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	1,427	1,160
Other investments	9	9
Total	2,271	2,174
Liabilities:
Contingent consideration	0	0
Other	0
Total	32	10
Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	20	14
Other investments	26	35
Total	1,424	1,699
Liabilities:
Contingent consideration	0	0
Other	13
Total	709	157
Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0	0
Other investments	0	0
Total	0	0
Liabilities:
Contingent consideration	12	14
Other	0
Total	12	14
Recurring \| Fair Value Measured at Net Asset Value Per Share (NAV)
Assets:
Total	161	150
Alabama Power
Assets:
Derivative asset	38	50
Liabilities:
Derivative liability	15	6
Collateral already posted, aggregate fair value	0
Alabama Power \| Recurring
Assets:
Cash equivalents	458	853
Other investments	26	35
Total	1,671	2,267
Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	438	839
Other investments	0	0
Total	966	1,482
Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	20	14
Other investments	26	35
Total	544	635
Alabama Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0	0
Other investments	0	0
Total	0	0
Alabama Power \| Recurring \| Fair Value Measured at Net Asset Value Per Share (NAV)
Assets:
Total	161	150
Georgia Power
Assets:
Derivative asset	21	67
Liabilities:
Derivative liability	41	0
Georgia Power \| Recurring
Assets:
Cash equivalents	355
Total	1,415	1,292
Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	355
Total	640	336
Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0
Total	775	956
Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0
Total	0	0
Mississippi Power
Assets:
Derivative asset	42	52
Liabilities:
Derivative liability	15	1
Mississippi Power \| Recurring
Assets:
Cash equivalents	47	40
Total	106	96
Mississippi Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	47	40
Total	47	40
Mississippi Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0	0
Total	59	56
Mississippi Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0	0
Total	0	0
Southern Power
Assets:
Derivative asset	8	4
Liabilities:
Derivative liability	59	16
Other		13
Collateral already posted, aggregate fair value	15
Southern Power \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Other		0
Southern Power \| Significant Other Observable Inputs (Level 2)
Liabilities:
Other		13
Southern Power \| Significant Unobservable Inputs (Level 3)
Liabilities:
Other		0
Southern Power \| Recurring
Liabilities:
Contingent consideration	12
Other	13
Total	84	43
Southern Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Contingent consideration	0
Other	0
Total	0	0
Southern Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Liabilities:
Contingent consideration	0
Other	13
Total	72	29
Southern Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Contingent consideration	12
Other	0
Total	12	14
Southern Company Gas
Assets:
Derivative asset	28	27
Liabilities:
Derivative liability	110	16
Collateral already posted, aggregate fair value	41	3
Southern Company Gas \| Recurring
Assets:
Cash equivalents	50	2
Total	98	61
Liabilities:
Total	151	27
Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	50	2
Total	72	26
Liabilities:
Total	32	10
Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0	0
Total	26	35
Liabilities:
Total	119	17
Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0	0
Total	0	0
Liabilities:
Total	0	0
Energy-related derivatives \| Recurring
Assets:
Derivative asset	199	219
Liabilities:
Derivative liability	210	46
Energy-related derivatives \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	18	24
Liabilities:
Derivative liability	32	10
Energy-related derivatives \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	181	195
Liabilities:
Derivative liability	178	36
Energy-related derivatives \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Alabama Power \| Recurring
Assets:
Derivative asset	62	55
Liabilities:
Derivative liability	39	11
Energy-related derivatives \| Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	62	55
Liabilities:
Derivative liability	39	11
Energy-related derivatives \| Alabama Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Georgia Power \| Recurring
Assets:
Derivative asset	42	75
Liabilities:
Derivative liability	62	8
Energy-related derivatives \| Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	42	75
Liabilities:
Derivative liability	62	8
Energy-related derivatives \| Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Mississippi Power \| Recurring
Assets:
Derivative asset	59	56
Liabilities:
Derivative liability	32	5
Energy-related derivatives \| Mississippi Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Mississippi Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	59	56
Liabilities:
Derivative liability	32	5
Energy-related derivatives \| Mississippi Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Southern Power \| Recurring
Assets:
Derivative asset	8	4
Liabilities:
Derivative liability	12
Energy-related derivatives \| Southern Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0
Energy-related derivatives \| Southern Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	8	4
Liabilities:
Derivative liability	12
Energy-related derivatives \| Southern Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0
Energy-related derivatives \| Southern Company Gas \| Recurring
Assets:
Derivative asset	28	29
Liabilities:
Derivative liability	65	22
Energy-related derivatives \| Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	18	24
Liabilities:
Derivative liability	32	10
Energy-related derivatives \| Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	10	5
Liabilities:
Derivative liability	33	12
Energy-related derivatives \| Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Recurring
Assets:
Derivative asset	12	19
Liabilities:
Derivative liability	302	29
Interest rate derivatives \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	12	19
Liabilities:
Derivative liability	302	29
Interest rate derivatives \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Southern Company Gas \| Recurring
Assets:
Derivative asset		6
Liabilities:
Derivative liability	86	5
Interest rate derivatives \| Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset		0
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset		6
Liabilities:
Derivative liability	86	5
Interest rate derivatives \| Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset		0
Liabilities:
Derivative liability	0	0
Foreign currency derivatives \| Recurring
Liabilities:
Derivative liability	216	79
Foreign currency derivatives \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivative liability	0	0
Foreign currency derivatives \| Recurring \| Significant Other Observable Inputs (Level 2)
Liabilities:
Derivative liability	216	79
Foreign currency derivatives \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability	0	0
Foreign currency derivatives \| Southern Power \| Recurring
Liabilities:
Derivative liability	47	16
Contingent consideration		14
Foreign currency derivatives \| Southern Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivative liability	0	0
Contingent consideration		0
Foreign currency derivatives \| Southern Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Liabilities:
Derivative liability	47	16
Contingent consideration		0
Foreign currency derivatives \| Southern Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability	0	0
Contingent consideration		14
Domestic equity \| Recurring
Assets:
Nuclear decommissioning trusts	829	1,016
Domestic equity \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	651	791
Domestic equity \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	178	225
Domestic equity \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Domestic equity \| Alabama Power \| Recurring
Assets:
Nuclear decommissioning trusts	565	684
Domestic equity \| Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	396	468
Domestic equity \| Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	169	216
Domestic equity \| Alabama Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Domestic equity \| Georgia Power \| Recurring
Assets:
Nuclear decommissioning trusts	256	324
Domestic equity \| Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	255	323
Domestic equity \| Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	1	1
Domestic equity \| Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Domestic equity \| Southern Company Gas \| Recurring
Assets:
Non-qualified deferred compensation trusts	8	8
Domestic equity \| Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Non-qualified deferred compensation trusts	0	0
Domestic equity \| Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Non-qualified deferred compensation trusts	8	8
Domestic equity \| Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Non-qualified deferred compensation trusts	0	0
Foreign equity \| Recurring
Assets:
Nuclear decommissioning trusts	275	353
Foreign equity \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	125	165
Foreign equity \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	150	188
Foreign equity \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Alabama Power \| Recurring
Assets:
Nuclear decommissioning trusts	125	165
Foreign equity \| Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	125	165
Foreign equity \| Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Alabama Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Georgia Power \| Recurring
Assets:
Nuclear decommissioning trusts	149	185
Foreign equity \| Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	149	185
Foreign equity \| Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Southern Company Gas \| Recurring
Assets:
Non-qualified deferred compensation trusts	1	3
Foreign equity \| Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Non-qualified deferred compensation trusts	0	0
Foreign equity \| Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Non-qualified deferred compensation trusts	1	3
Foreign equity \| Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Non-qualified deferred compensation trusts	0	0
U.S. Treasury and government agency securities \| Recurring
Assets:
Nuclear decommissioning trusts	285	314
U.S. Treasury and government agency securities \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	0	0
U.S. Treasury and government agency securities \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	285	314
U.S. Treasury and government agency securities \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
U.S. Treasury and government agency securities \| Alabama Power \| Recurring
Assets:
Nuclear decommissioning trusts	19	21
U.S. Treasury and government agency securities \| Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	0	0
U.S. Treasury and government agency securities \| Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	19	21
U.S. Treasury and government agency securities \| Alabama Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
U.S. Treasury and government agency securities \| Georgia Power \| Recurring
Assets:
Nuclear decommissioning trusts	266	293
U.S. Treasury and government agency securities \| Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	0	0
U.S. Treasury and government agency securities \| Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	266	293
U.S. Treasury and government agency securities \| Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:

FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)
$ in Millions

Dec. 31, 2022

Dec. 31, 2021

Assets:

Derivative asset

$ 141

$ 213

Liabilities:

Derivative liability

617

125

Collateral already posted, aggregate fair value