SEGMENT AND RELATED INFORMATION - Financial Data for Business Segments (Details) $ in Millions	1 Months Ended		3 Months Ended					12 Months Ended
	Dec. 31, 2021 USD ($) project	Jul. 31, 2021 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2023 USD ($) project	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Total operating revenues								$ 25,253	$ 29,279	$ 23,113
Depreciation and amortization								4,525	3,663	3,565
Interest income								85	59	22
Earnings from equity method investments								144	151	76
Interest expense								2,446	2,022	1,837
Income taxes (benefit)								496	795	267
Segment net income (loss)								3,976	3,524	2,393
Goodwill	$ 5,280		$ 5,161		$ 5,161			5,161	5,161	5,280
Total assets	127,534		139,331		134,891			139,331	134,891	127,534
Segment and Related Information (Textual) [Abstract]
Estimated loss on Plant Vogtle Units 3 and 4								(68)	183	1,692
Impairment charges								$ 0	251	2
Gain (loss) on termination of leveraged leases	93
Gain (loss) on termination of leveraged leases, after tax	$ 99
Number of international projects subject to leveraged lease terminated | project	2							2
Southern Company Gas
Segment Reporting Information [Line Items]
Total operating revenues								$ 4,702	5,962	4,380
Operating Segments | Electric Utilities
Segment Reporting Information [Line Items]
Total operating revenues								19,998	22,873	18,300
Depreciation and amortization								3,865	3,029	2,953
Interest income								76	47	21
Earnings from equity method investments								(1)	0	1
Interest expense								1,274	1,067	968
Income taxes (benefit)								583	848	219
Segment net income (loss)								3,994	3,672	2,247
Goodwill	$ 2		2		2			2	2	2
Total assets	101,774		112,645		108,283			112,645	108,283	101,774
Operating Segments | Traditional Electric Operating Companies
Segment Reporting Information [Line Items]
Total operating revenues								18,358	20,408	16,614
Depreciation and amortization								3,361	2,513	2,436
Interest income								69	44	20
Earnings from equity method investments								(1)	0	1
Interest expense								1,145	929	821
Income taxes (benefit)								571	828	232
Segment net income (loss)								3,637	3,318	1,981
Goodwill	0		0		0			0	0	0
Total assets	89,051		100,429		95,861			100,429	95,861	89,051
Operating Segments | Southern Power
Segment Reporting Information [Line Items]
Total operating revenues								2,189	3,369	2,216
Depreciation and amortization								504	516	517
Interest income								7	3	1
Earnings from equity method investments								0	0	0
Interest expense								129	138	147
Income taxes (benefit)								12	20	(13)
Segment net income (loss)								357	354	266
Goodwill	2		2		2			2	2	2
Total assets	13,390		12,761		13,081			12,761	13,081	13,390
Operating Segments | Southern Company Gas
Segment Reporting Information [Line Items]
Total operating revenues								4,702	5,962	4,380
Depreciation and amortization								582	559	536
Interest income								9	3	0
Earnings from equity method investments								140	148	50
Interest expense								310	263	238
Income taxes (benefit)								211	180	275
Segment net income (loss)								615	572	539
Goodwill	5,015		5,015		5,015			5,015	5,015	5,015
Total assets	23,560		25,083		24,621			25,083	24,621	23,560
Operating Segments | All Other
Segment Reporting Information [Line Items]
Total operating revenues								718	593	582
Depreciation and amortization								78	75	76
Interest income								26	16	4
Earnings from equity method investments								5	3	24
Interest expense								879	694	631
Income taxes (benefit)								(298)	(233)	(227)
Segment net income (loss)								(635)	(711)	(384)
Goodwill	263		144		144			144	144	263
Total assets	2,975		2,446		2,665			2,446	2,665	2,975
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total operating revenues								(165)	(149)	(149)
Depreciation and amortization								0	0	0
Interest income								(26)	(7)	(3)
Earnings from equity method investments								0	0	1
Interest expense								(17)	(2)	0
Income taxes (benefit)								0	0	0
Segment net income (loss)								2	(9)	(9)
Goodwill	0		0		0			0	0	0
Total assets	(775)		(843)		(678)			(843)	(678)	(775)
Intersegment Eliminations | Electric Utilities
Segment Reporting Information [Line Items]
Total operating revenues								(549)	(904)	(530)
Depreciation and amortization								0	0	0
Interest income								0	0	0
Earnings from equity method investments								0	0	0
Interest expense								0	0	0
Income taxes (benefit)								0	0	0
Segment net income (loss)								0	0	0
Goodwill	0		0		0			0	0	0
Total assets	(667)		(545)		(659)			(545)	(659)	(667)
Georgia Power
Segment Reporting Information [Line Items]
Total operating revenues								10,118	11,584	9,260
Depreciation and amortization								1,681	1,430	1,371
Interest expense								626	485	421
Income taxes (benefit)								448	370	(168)
Total assets			56,817		53,163			56,817	53,163
Segment and Related Information (Textual) [Abstract]
Estimated loss on Plant Vogtle Units 3 and 4								(68)	183	1,692
Georgia Power | Traditional Electric Operating Companies | Plant Vogtle Units 3 and 4
Segment and Related Information (Textual) [Abstract]
Estimated loss on Plant Vogtle Units 3 and 4								(68)	183	1,700
Estimated loss on Plant Vogtle Units 3 and 4, net of tax								(50)	137	1,300
Southern Power
Segment Reporting Information [Line Items]
Total operating revenues								2,189	3,369	2,216
Depreciation and amortization								504	516	517
Interest expense								129	138	147
Income taxes (benefit)								12	20	(13)
Segment net income (loss)								357	354	266
Total assets			12,761		13,081			12,761	13,081
Segment and Related Information (Textual) [Abstract]
Amount awarded from other party								9
Gain (loss) on dispositions								20	2	41
Southern Power | Southern Power vs First Solar | Settled Litigation
Segment and Related Information (Textual) [Abstract]
Litigation settlement								18
Southern Power | Wind Generating Facility
Segment and Related Information (Textual) [Abstract]
Gain (loss) on dispositions								37		37
Gain (loss) on dispositions, after tax								28
Southern Company Gas
Segment Reporting Information [Line Items]
Total operating revenues								4,702	5,962	4,380
Depreciation and amortization								582	559	536
Earnings from equity method investments								140	148	50
Interest expense								310	263	238
Income taxes (benefit)								211	180	275
Segment net income (loss)								615	572	539
Goodwill			5,015		5,015			5,015	5,015
Total assets	23,560		25,083		24,621			25,083	24,621	23,560
Segment and Related Information (Textual) [Abstract]
Estimated loss on regulatory disallowance								(96)	0	0
Gain (loss) on dispositions								7	4	127
Impairment charges								0	131	0
Southern Company Gas | PennEast Pipeline
Segment Reporting Information [Line Items]
Earnings from equity method investments								0	0	(81)
Income taxes (benefit)										7
Segment and Related Information (Textual) [Abstract]
Impairment charges						$ 2	$ 82	84		84
Impairment charges, after tax						$ 2	$ 58	67		67
Southern Company Gas | Operating Segments
Segment Reporting Information [Line Items]
Total operating revenues								4,685	5,937	4,374
Depreciation and amortization								581	537	505
Earnings from equity method investments								140	148	50
Interest expense								310	259	237
Income taxes (benefit)								195	217	213
Segment net income (loss)								630	671	626
Total assets	23,971		26,055		25,233			26,055	25,233	23,971
Southern Company Gas | Operating Segments | All Other
Segment Reporting Information [Line Items]
Total operating revenues								36	55	38
Depreciation and amortization								1	22	31
Earnings from equity method investments								0	0	0
Interest expense								0	4	1
Income taxes (benefit)								16	(37)	62
Segment net income (loss)								(15)	(99)	(87)
Total assets	12,114		9,675		8,943			9,675	8,943	12,114
Southern Company Gas | Intersegment Eliminations
Segment Reporting Information [Line Items]
Total operating revenues								(19)	(30)	(32)
Depreciation and amortization								0	0	0
Earnings from equity method investments								0	0	0
Interest expense								0	0	0
Income taxes (benefit)								0	0	0
Segment net income (loss)								0	0	0
Total assets	$ (12,525)		(10,647)		(9,555)			(10,647)	$ (9,555)	(12,525)
Nicor Gas
Segment and Related Information (Textual) [Abstract]
Estimated loss on regulatory disallowance			(58)	$ (38)				96
Estimated loss on regulatory disallowance, after tax			$ (44)	$ (28)				72
Spare Parts | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Power
Segment and Related Information (Textual) [Abstract]
Gain on sale								16
Gain on sale, after tax								12
Natural Gas Storage Facilities | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Company Gas
Segment and Related Information (Textual) [Abstract]
Gain (loss) on dispositions					(131)
Gain (loss) on dispositions, after tax					$ (99)
Sequent | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Company Gas
Segment and Related Information (Textual) [Abstract]
Gain (loss) on dispositions		$ 121						121		121
Gain (loss) on dispositions, after tax		92						92		92
Deferred tax expense, increase from change in appointment rate		$ 85						$ 85		$ 85