Segment and Related Information - Schedule of Financial Data for Business Segments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Operating revenues	$ 6,980	$ 8,378	$ 19,208	$ 22,232
Net income	1,422	1,472	3,121	3,611
Goodwill	5,161		5,161		$ 5,161
Total assets	138,321		138,321		134,891
Amount awarded			18
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	653	1,180	1,686	2,618
Net income	100	95	288	265
Total assets	13,090		13,090		13,081
Amount awarded	18
After tax amount awarded	9		9
SOUTHERN POWER CO | Disposal Group, Disposed of by Sale | Spare Parts
Segment Reporting Information [Line Items]
Gain (loss) on sale			16
Gain (loss) on sale, after tax			12
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	689	857	3,417	3,998
Net income	82	83	475	516
Goodwill	5,015		5,015		5,015
Total assets	24,823		24,823		24,621
GEORGIA POWER CO
Segment Reporting Information [Line Items]
Operating revenues	3,237	3,889	7,805	9,218
Total assets	56,149		56,149		53,163
GEORGIA POWER CO | Disposal Group, Disposed of by Sale | Spare Parts
Segment Reporting Information [Line Items]
Gain (loss) on sale		(70)		(18)
Gain (loss) on sale, after tax		(52)		(13)
Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	6,167	7,427	15,414	17,943
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	689	857	3,417	3,998
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	683	844	3,402	3,977
Net income	96	81	484	506
Total assets	25,686		25,686		25,233
Operating Segments | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	6,167	7,427	15,414	17,943
Net income	1,519	1,540	3,140	3,521
Goodwill	2		2		2
Total assets	111,986		111,986		108,283
Operating Segments | Traditional Electric Operating Companies
Segment Reporting Information [Line Items]
Operating revenues	5,674	6,938	14,145	16,716
Net income	1,419	1,445	2,852	3,256
Goodwill	0		0		0
Total assets	99,464		99,464		95,861
Operating Segments | SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	653	1,180	1,686	2,618
Net income	100	95	288	265
Goodwill	2		2		2
Total assets	13,090		13,090		13,081
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	689	857	3,417	3,998
Net income	82	83	475	516
Goodwill	5,015		5,015		5,015
Total assets	24,823		24,823		24,621
Operating Segments | All Other
Segment Reporting Information [Line Items]
Operating revenues	154	135	499	418
Net income	(179)	(152)	(490)	(415)
Goodwill	144		144		144
Total assets	2,370		2,370		2,665
Operating Segments | All Other | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	8	16	30	43
Net income	(14)	2	(9)	10
Total assets	9,795		9,795		8,943
Eliminations
Segment Reporting Information [Line Items]
Operating revenues	(30)	(41)	(122)	(127)
Net income	0	1	(4)	(11)
Goodwill	0		0		0
Total assets	(858)		(858)		(678)
Eliminations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	(2)	(3)	(15)	(22)
Net income	0	0	0	0
Total assets	(10,658)		(10,658)		(9,555)
Eliminations | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	(160)	(691)	(417)	(1,391)
Net income	0	$ 0	0	$ 0
Goodwill	0		0		0
Total assets	$ (568)		$ (568)		$ (659)