FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets:
Derivative asset	$ 32	$ 141
Liabilities:
Derivative liability	659	617
Collateral already posted, aggregate fair value	62
Recurring
Assets:
Cash equivalents	268	1,447
Other investments	44	35
Total	2,806	3,856
Liabilities:
Contingent consideration	19	12
Other	13
Total	776	753
Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	253	1,427
Other investments	9	9
Total	1,238	2,271
Liabilities:
Contingent consideration	3	0
Other	0
Total	49	32
Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	15	20
Other investments	27	26
Total	1,382	1,424
Liabilities:
Contingent consideration	0	0
Other	13
Total	711	709
Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0	0
Other investments	8	0
Total	8	0
Liabilities:
Contingent consideration	16	12
Other	0
Total	16	12
Recurring \| Fair Value Measured at Net Asset Value Per Share (NAV)
Assets:
Total	178	161
Alabama Power
Assets:
Derivative asset	5	38
Liabilities:
Derivative liability	100	15
Collateral already posted, aggregate fair value	0
Alabama Power \| Recurring
Assets:
Cash equivalents	134	458
Other investments	27	26
Total	1,435	1,671
Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	119	438
Other investments	0	0
Total	715	966
Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	15	20
Other investments	27	26
Total	542	544
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	178	161
Georgia Power
Assets:
Derivative asset	2	21
Liabilities:
Derivative liability	113	41
Georgia Power \| Recurring
Assets:
Cash equivalents		355
Total	1,176	1,415
Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents		355
Total	371	640
Georgia Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents		0
Total	805	775
Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents		0
Total	0	0
Mississippi Power
Assets:
Derivative asset	1	42
Liabilities:
Derivative liability	47	15
Mississippi Power \| Recurring
Assets:
Cash equivalents	17	47
Total	32	106
Mississippi Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	17	47
Total	17	47
Mississippi Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0	0
Total	15	59
Mississippi Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0	0
Total	0	0
Southern Power
Assets:
Derivative asset	3	8
Liabilities:
Derivative liability	27	59
Other		13
Collateral already posted, aggregate fair value	0
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	19
Other	13
Total	59	84
Southern Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Contingent consideration	3
Other	0
Total	3	0
Southern Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Liabilities:
Contingent consideration	0
Other	13
Total	40	72
Southern Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Contingent consideration	16
Other	0
Total	16	12
Southern Company Gas
Assets:
Derivative asset	21	28
Liabilities:
Derivative liability	87	110
Collateral already posted, aggregate fair value	62	41
Southern Company Gas \| Recurring
Assets:
Cash equivalents		50
Total	26	98
Liabilities:
Total	137	151
Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents		50
Total	9	72
Liabilities:
Total	46	32
Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents		0
Total	17	26
Liabilities:
Total	91	119
Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents		0
Total	0	0
Liabilities:
Total	0	0
Energy-related derivatives \| Recurring
Assets:
Derivative asset	55	199
Liabilities:
Derivative liability	358	210
Energy-related derivatives \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	6	18
Liabilities:
Derivative liability	46	32
Energy-related derivatives \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	49	181
Liabilities:
Derivative liability	312	178
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	15	62
Liabilities:
Derivative liability	110	39
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	15	62
Liabilities:
Derivative liability	110	39
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	13	42
Liabilities:
Derivative liability	124	62
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	13	42
Liabilities:
Derivative liability	124	62
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	15	59
Liabilities:
Derivative liability	61	32
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	15	59
Liabilities:
Derivative liability	61	32
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	3	8
Liabilities:
Derivative liability	5	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	0
Energy-related derivatives \| Southern Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	3	8
Liabilities:
Derivative liability	5	12
Energy-related derivatives \| Southern Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset	0	0
Liabilities:
Derivative liability	0	0
Energy-related derivatives \| Southern Company Gas \| Recurring
Assets:
Derivative asset	9	28
Liabilities:
Derivative liability	58	65
Energy-related derivatives \| Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset	6	18
Liabilities:
Derivative liability	46	32
Energy-related derivatives \| Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset	3	10
Liabilities:
Derivative liability	12	33
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
Liabilities:
Derivative liability	264	302
Interest rate derivatives \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Derivative asset		0
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Derivative asset		12
Liabilities:
Derivative liability	264	302
Interest rate derivatives \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Derivative asset		0
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Southern Company Gas \| Recurring
Liabilities:
Derivative liability	79	86
Interest rate derivatives \| Southern Company Gas \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Liabilities:
Derivative liability	0	0
Interest rate derivatives \| Southern Company Gas \| Recurring \| Significant Other Observable Inputs (Level 2)
Liabilities:
Derivative liability	79	86
Interest rate derivatives \| Southern Company Gas \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability	0	0
Foreign currency derivatives \| Recurring
Liabilities:
Derivative liability	122	216
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	122	216
Foreign currency derivatives \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability	0	0
Foreign currency derivatives \| Southern Power \| Recurring
Liabilities:
Derivative liability	22	47
Contingent consideration		12
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	22	47
Contingent consideration		0
Foreign currency derivatives \| Southern Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liability	0	0
Contingent consideration		12
Domestic equity \| Recurring
Assets:
Nuclear decommissioning trusts	980	829
Domestic equity \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	764	651
Domestic equity \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	216	178
Domestic equity \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Domestic equity \| Alabama Power \| Recurring
Assets:
Nuclear decommissioning trusts	651	565
Domestic equity \| Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	443	396
Domestic equity \| Alabama Power \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	208	169
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	322	256
Domestic equity \| Georgia Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	321	255
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	7	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	7	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	316	275
Foreign equity \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	145	125
Foreign equity \| Recurring \| Significant Other Observable Inputs (Level 2)
Assets:
Nuclear decommissioning trusts	171	150
Foreign equity \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Foreign equity \| Alabama Power \| Recurring
Assets:
Nuclear decommissioning trusts	145	125
Foreign equity \| Alabama Power \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	145	125
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	170	149
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	170	149
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	1
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	1
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	369	285
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	369	285
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	20	19
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	20	19
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	349	266
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	349	266
U.S. Treasury and government agency securities \| Georgia Power \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Nuclear decommissioning trusts	0	0
Municipal bonds \| Recurring
Assets:
Nuclear decommissioning trusts	48	51
Municipal bonds \| Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Nuclear decommissioning trusts	0	0
Municipal bonds \| Recurring \| Significant Other Observable Inputs (Level 2)

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

Dec. 31, 2023

Dec. 31, 2022

Assets:

Derivative asset

$ 32

$ 141

Liabilities:

Derivative liability

659

617

Collateral already posted, aggregate fair value