INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Deferred tax liabilities —
Deferred income tax liabilities	$ 18,066	$ 17,451
Deferred tax assets —
Deferred income tax assets	8,398	8,914
Valuation allowance	(257)	(207)
Net deferred income tax assets	8,141	8,707
Net deferred income taxes liabilities	9,925	8,744
Accumulated deferred income taxes – assets	(111)	(118)
Accumulated deferred income taxes – liabilities	10,036	8,862
Net deferred income taxes liabilities	9,925	8,744
Accelerated depreciation
Deferred tax liabilities —
Deferred income tax liabilities	9,443	9,300
Property basis differences
Deferred tax liabilities —
Deferred income tax liabilities	2,350	2,301
Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	888	820
Deferred tax assets —
Deferred income tax assets	890	1,035
AROs
Deferred tax liabilities —
Deferred income tax liabilities	876	868
Under recovered fuel and natural gas costs
Deferred tax liabilities —
Deferred income tax liabilities	805	315
AROs
Deferred tax liabilities —
Deferred income tax liabilities	2,006	2,232
Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	677	825
Remaining book value of retired assets
Deferred tax liabilities —
Deferred income tax liabilities	400	271
Premium on reacquired debt
Deferred tax liabilities —
Deferred income tax liabilities	66	72
Other
Deferred tax liabilities —
Deferred income tax liabilities	555	368
ITC and PTC carryforwards
Deferred tax assets —
Deferred income tax assets	1,685	1,750
Estimated loss on plants under construction
Deferred tax assets —
Deferred income tax assets	888	825
Other state deferred tax attributes
Deferred tax assets —
Deferred income tax assets	388	361
Federal effect of net state deferred tax assets/liabilities
Deferred tax liabilities —
Deferred income tax liabilities		0
Deferred tax assets —
Deferred income tax assets	365	305
Other property basis differences
Deferred tax assets —
Deferred income tax assets	207	231
State effect of federal deferred taxes
Deferred tax assets —
Deferred income tax assets	136	135
Other partnership basis differences
Deferred tax assets —
Deferred income tax assets	111	160
Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)
Deferred tax assets —
Deferred income tax assets	137	268
Long-term debt fair value adjustment
Deferred tax assets —
Deferred income tax assets	85	91
Other comprehensive losses
Deferred tax assets —
Deferred income tax assets	72	92
Other
Deferred tax assets —
Deferred income tax assets	552	561
Leveraged lease basis differences
Deferred tax liabilities —
Deferred income tax liabilities		61
Storm damage reserves
Deferred tax liabilities —
Deferred income tax liabilities		18
AROs
Deferred tax assets —
Deferred income tax assets	2,882	3,100
Alabama Power
Deferred tax liabilities —
Deferred income tax liabilities	6,024	5,737
Deferred tax assets —
Deferred income tax assets	2,043	2,164
Valuation allowance	0	0
Net deferred income tax assets	2,043	2,164
Net deferred income taxes liabilities	3,981	3,573
Accumulated deferred income taxes – assets	0	0
Accumulated deferred income taxes – liabilities	3,981	3,573
Net deferred income taxes liabilities	3,981	3,573
Alabama Power | Accelerated depreciation
Deferred tax liabilities —
Deferred income tax liabilities	2,564	2,541
Alabama Power | Property basis differences
Deferred tax liabilities —
Deferred income tax liabilities	1,303	1,182
Alabama Power | Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	284	268
Deferred tax assets —
Deferred income tax assets	198	225
Alabama Power | AROs
Deferred tax liabilities —
Deferred income tax liabilities	499	329
Alabama Power | Under recovered fuel and natural gas costs
Deferred tax liabilities —
Deferred income tax liabilities	185	47
Alabama Power | AROs
Deferred tax liabilities —
Deferred income tax liabilities	679	863
Alabama Power | Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	180	205
Alabama Power | Remaining book value of retired assets
Deferred tax liabilities —
Deferred income tax liabilities	142	145
Alabama Power | Premium on reacquired debt
Deferred tax liabilities —
Deferred income tax liabilities	9	10
Alabama Power | Other
Deferred tax liabilities —
Deferred income tax liabilities	179	147
Alabama Power | ITC and PTC carryforwards
Deferred tax assets —
Deferred income tax assets	12	12
Alabama Power | Estimated loss on plants under construction
Deferred tax assets —
Deferred income tax assets	0	0
Alabama Power | Other state deferred tax attributes
Deferred tax assets —
Deferred income tax assets	0	0
Alabama Power | Federal effect of net state deferred tax assets/liabilities
Deferred tax liabilities —
Deferred income tax liabilities		0
Deferred tax assets —
Deferred income tax assets	175	165
Alabama Power | Other property basis differences
Deferred tax assets —
Deferred income tax assets	0	0
Alabama Power | State effect of federal deferred taxes
Deferred tax assets —
Deferred income tax assets	136	135
Alabama Power | Other partnership basis differences
Deferred tax assets —
Deferred income tax assets	0	0
Alabama Power | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)
Deferred tax assets —
Deferred income tax assets	127	237
Alabama Power | Long-term debt fair value adjustment
Deferred tax assets —
Deferred income tax assets	0	0
Alabama Power | Other comprehensive losses
Deferred tax assets —
Deferred income tax assets	4	5
Alabama Power | Other
Deferred tax assets —
Deferred income tax assets	213	193
Alabama Power | Leveraged lease basis differences
Deferred tax liabilities —
Deferred income tax liabilities		0
Alabama Power | Storm damage reserves
Deferred tax liabilities —
Deferred income tax liabilities		0
Alabama Power | AROs
Deferred tax assets —
Deferred income tax assets	1,178	1,192
Georgia Power
Deferred tax liabilities —
Deferred income tax liabilities	7,426	6,965
Deferred tax assets —
Deferred income tax assets	3,844	4,019
Valuation allowance	(125)	(73)
Net deferred income tax assets	3,719	3,946
Net deferred income taxes liabilities	3,707	3,019
Accumulated deferred income taxes – assets	0	0
Accumulated deferred income taxes – liabilities	3,707	3,019
Net deferred income taxes liabilities	3,707	3,019
Georgia Power | Accelerated depreciation
Deferred tax liabilities —
Deferred income tax liabilities	3,447	3,340
Georgia Power | Property basis differences
Deferred tax liabilities —
Deferred income tax liabilities	693	781
Georgia Power | Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	412	382
Deferred tax assets —
Deferred income tax assets	304	342
Georgia Power | AROs
Deferred tax liabilities —
Deferred income tax liabilities	324	494
Georgia Power | Under recovered fuel and natural gas costs
Deferred tax liabilities —
Deferred income tax liabilities	548	109
Georgia Power | AROs
Deferred tax liabilities —
Deferred income tax liabilities	1,285	1,325
Georgia Power | Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	226	256
Georgia Power | Remaining book value of retired assets
Deferred tax liabilities —
Deferred income tax liabilities	253	121
Georgia Power | Premium on reacquired debt
Deferred tax liabilities —
Deferred income tax liabilities	57	62
Georgia Power | Other
Deferred tax liabilities —
Deferred income tax liabilities	181	77
Georgia Power | ITC and PTC carryforwards
Deferred tax assets —
Deferred income tax assets	673	704
Georgia Power | Estimated loss on plants under construction
Deferred tax assets —
Deferred income tax assets	888	825
Georgia Power | Other state deferred tax attributes
Deferred tax assets —
Deferred income tax assets	12	11
Georgia Power | Federal effect of net state deferred tax assets/liabilities
Deferred tax liabilities —
Deferred income tax liabilities		0
Deferred tax assets —
Deferred income tax assets	88	41
Georgia Power | Other property basis differences
Deferred tax assets —
Deferred income tax assets	79	90
Georgia Power | State effect of federal deferred taxes
Deferred tax assets —
Deferred income tax assets	0	0
Georgia Power | Other partnership basis differences
Deferred tax assets —
Deferred income tax assets	0	0
Georgia Power | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)
Deferred tax assets —
Deferred income tax assets	0	19
Georgia Power | Long-term debt fair value adjustment
Deferred tax assets —
Deferred income tax assets	0	0
Georgia Power | Other comprehensive losses
Deferred tax assets —
Deferred income tax assets	5	15
Georgia Power | Other
Deferred tax assets —
Deferred income tax assets	186	153
Georgia Power | Leveraged lease basis differences
Deferred tax liabilities —
Deferred income tax liabilities		0
Georgia Power | Storm damage reserves
Deferred tax liabilities —
Deferred income tax liabilities		18
Georgia Power | AROs
Deferred tax assets —
Deferred income tax assets	1,609	1,819
Mississippi Power
Deferred tax liabilities —
Deferred income tax liabilities	717	698
Deferred tax assets —
Deferred income tax assets	399	393
Valuation allowance	(41)	(41)
Net deferred income tax assets	358	352
Net deferred income taxes liabilities	359	346
Accumulated deferred income taxes – assets	(107)	(118)
Accumulated deferred income taxes – liabilities	466	464
Net deferred income taxes liabilities	359	346
Mississippi Power | Accelerated depreciation
Deferred tax liabilities —
Deferred income tax liabilities	338	330
Mississippi Power | Property basis differences
Deferred tax liabilities —
Deferred income tax liabilities	179	169
Mississippi Power | Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	43	41
Deferred tax assets —
Deferred income tax assets	47	57
Mississippi Power | AROs
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Mississippi Power | Under recovered fuel and natural gas costs
Deferred tax liabilities —
Deferred income tax liabilities	40	15
Mississippi Power | AROs
Deferred tax liabilities —
Deferred income tax liabilities	42	44
Mississippi Power | Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	30	38
Mississippi Power | Remaining book value of retired assets
Deferred tax liabilities —
Deferred income tax liabilities	5	5
Mississippi Power | Premium on reacquired debt
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Mississippi Power | Other
Deferred tax liabilities —
Deferred income tax liabilities	40	34
Mississippi Power | ITC and PTC carryforwards
Deferred tax assets —
Deferred income tax assets	0	0
Mississippi Power | Estimated loss on plants under construction
Deferred tax assets —
Deferred income tax assets	0	0
Mississippi Power | Other state deferred tax attributes
Deferred tax assets —
Deferred income tax assets	239	246
Mississippi Power | Federal effect of net state deferred tax assets/liabilities
Deferred tax liabilities —
Deferred income tax liabilities		22
Deferred tax assets —
Deferred income tax assets	0	0
Mississippi Power | Other property basis differences
Deferred tax assets —
Deferred income tax assets	0	0
Mississippi Power | State effect of federal deferred taxes
Deferred tax assets —
Deferred income tax assets	0	0
Mississippi Power | Other partnership basis differences
Deferred tax assets —
Deferred income tax assets	0	0
Mississippi Power | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)
Deferred tax assets —
Deferred income tax assets	9	12
Mississippi Power | Long-term debt fair value adjustment
Deferred tax assets —
Deferred income tax assets	0	0
Mississippi Power | Other comprehensive losses
Deferred tax assets —
Deferred income tax assets	0	0
Mississippi Power | Other
Deferred tax assets —
Deferred income tax assets	62	34
Mississippi Power | Leveraged lease basis differences
Deferred tax liabilities —
Deferred income tax liabilities		0
Mississippi Power | Storm damage reserves
Deferred tax liabilities —
Deferred income tax liabilities		0
Mississippi Power | AROs
Deferred tax assets —
Deferred income tax assets	42	44
Southern Power
Deferred tax liabilities —
Deferred income tax liabilities	1,376	1,446
Deferred tax assets —
Deferred income tax assets	1,124	1,258
Valuation allowance	(27)	(27)
Net deferred income tax assets	1,097	1,231
Net deferred income taxes liabilities	279	215
Accumulated deferred income taxes – assets	0	0
Accumulated deferred income taxes – liabilities	279	215
Net deferred income taxes liabilities	279	215
Southern Power | Accelerated depreciation
Deferred tax liabilities —
Deferred income tax liabilities	1,351	1,421
Southern Power | Property basis differences
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Power | Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	11	11
Deferred tax assets —
Deferred income tax assets	9	7
Southern Power | AROs
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Power | Under recovered fuel and natural gas costs
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Power | AROs
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Power | Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Power | Remaining book value of retired assets
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Power | Premium on reacquired debt
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Power | Other
Deferred tax liabilities —
Deferred income tax liabilities	14	14
Southern Power | ITC and PTC carryforwards
Deferred tax assets —
Deferred income tax assets	794	827
Southern Power | Estimated loss on plants under construction
Deferred tax assets —
Deferred income tax assets	0	0
Southern Power | Other state deferred tax attributes
Deferred tax assets —
Deferred income tax assets	51	52
Southern Power | Federal effect of net state deferred tax assets/liabilities
Deferred tax liabilities —
Deferred income tax liabilities		0
Deferred tax assets —
Deferred income tax assets	28	27
Southern Power | Other property basis differences
Deferred tax assets —
Deferred income tax assets	109	121
Southern Power | State effect of federal deferred taxes
Deferred tax assets —
Deferred income tax assets	0	0
Southern Power | Other partnership basis differences
Deferred tax assets —
Deferred income tax assets	111	160
Southern Power | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)
Deferred tax assets —
Deferred income tax assets	0	0
Southern Power | Long-term debt fair value adjustment
Deferred tax assets —
Deferred income tax assets	0	0
Southern Power | Other comprehensive losses
Deferred tax assets —
Deferred income tax assets	5	11
Southern Power | Other
Deferred tax assets —
Deferred income tax assets	17	53
Southern Power | Leveraged lease basis differences
Deferred tax liabilities —
Deferred income tax liabilities		0
Southern Power | Storm damage reserves
Deferred tax liabilities —
Deferred income tax liabilities		0
Southern Power | AROs
Deferred tax assets —
Deferred income tax assets	0	0
Southern Company Gas
Deferred tax liabilities —
Deferred income tax liabilities	1,852	1,874
Deferred tax assets —
Deferred income tax assets	301	328
Valuation allowance	(9)	(9)
Net deferred income tax assets	292	319
Net deferred income taxes liabilities	1,560	1,555
Accumulated deferred income taxes – assets	0	0
Accumulated deferred income taxes – liabilities	1,560	1,555
Net deferred income taxes liabilities	1,560	1,555
Southern Company Gas | Accelerated depreciation
Deferred tax liabilities —
Deferred income tax liabilities	1,505	1,428
Southern Company Gas | Property basis differences
Deferred tax liabilities —
Deferred income tax liabilities	150	148
Southern Company Gas | Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	68	57
Deferred tax assets —
Deferred income tax assets	89	77
Southern Company Gas | AROs
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Company Gas | Under recovered fuel and natural gas costs
Deferred tax liabilities —
Deferred income tax liabilities	32	144
Southern Company Gas | AROs
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Company Gas | Employee benefit obligations
Deferred tax liabilities —
Deferred income tax liabilities	15	15
Southern Company Gas | Remaining book value of retired assets
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Company Gas | Premium on reacquired debt
Deferred tax liabilities —
Deferred income tax liabilities	0	0
Southern Company Gas | Other
Deferred tax liabilities —
Deferred income tax liabilities	82	82
Southern Company Gas | ITC and PTC carryforwards
Deferred tax assets —
Deferred income tax assets	0	0
Southern Company Gas | Estimated loss on plants under construction
Deferred tax assets —
Deferred income tax assets	0	0
Southern Company Gas | Other state deferred tax attributes
Deferred tax assets —
Deferred income tax assets	7	5
Southern Company Gas | Federal effect of net state deferred tax assets/liabilities
Deferred tax liabilities —
Deferred income tax liabilities		0
Deferred tax assets —
Deferred income tax assets	92	93
Southern Company Gas | Other property basis differences
Deferred tax assets —
Deferred income tax assets	0	0
Southern Company Gas | State effect of federal deferred taxes
Deferred tax assets —
Deferred income tax assets	0	0
Southern Company Gas | Other partnership basis differences
Deferred tax assets —
Deferred income tax assets	0	0
Southern Company Gas | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)
Deferred tax assets —
Deferred income tax assets	0	0
Southern Company Gas | Long-term debt fair value adjustment
Deferred tax assets —
Deferred income tax assets	85	91
Southern Company Gas | Other comprehensive losses
Deferred tax assets —
Deferred income tax assets	0	0
Southern Company Gas | Other
Deferred tax assets —
Deferred income tax assets	28	62
Southern Company Gas | Leveraged lease basis differences
Deferred tax liabilities —
Deferred income tax liabilities		0
Southern Company Gas | Storm damage reserves
Deferred tax liabilities —
Deferred income tax liabilities		0
Southern Company Gas | AROs
Deferred tax assets —
Deferred income tax assets	$ 0	$ 0