Segment and Related Information - Schedule of Financial Data for Business Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Segment Reporting Information [Line Items]
Operating revenues	$ 6,648	$ 5,910
Net income	1,032	1,135
Goodwill	5,280		$ 5,280
Total assets	128,639		127,534
Estimated loss on Plant Vogtle Units 3 and 4	0	48
Gain on sale	20	41
GEORGIA POWER CO
Segment Reporting Information [Line Items]
Operating revenues	2,208	1,970
Total assets	49,206		48,461
Estimated loss on Plant Vogtle Units 3 and 4	0	48
Estimated loss on Plant Vogtle Units 3 and 4, net of tax		36
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	539	440
Segment net income (loss)	72	97
Total assets	13,766		13,390
Gain on sale	2	39
SOUTHERN POWER CO | Wind Generating Facility
Segment Reporting Information [Line Items]
Gain on sale		37
Gain on sale, net of tax		28
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	2,058	1,694
Segment net income (loss)	319	398
Goodwill	5,015		5,015
Total assets	23,377		23,560
Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	4,509	4,117
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	2,058	1,694
Gas distribution operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Goodwill	4,034		4,034
Wholesale Gas Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues		298
Gas marketing services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Goodwill	981		981
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	2,054	1,701
Segment net income (loss)	309	394
Total assets	24,147		23,971
Operating Segments | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	4,509	4,117
Net income	846	853
Goodwill	2		2
Total assets	103,599		101,774
Operating Segments | Traditional Electric Operating Companies
Segment Reporting Information [Line Items]
Operating revenues	4,191	3,764
Net income	774	756
Goodwill	0		0
Total assets	90,460		89,051
Operating Segments | SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	539	440
Net income	72	97
Goodwill	2		2
Total assets	13,766		13,390
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	2,058	1,694
Net income	319	398
Goodwill	5,015		5,015
Total assets	23,377		23,560
Operating Segments | Gas distribution operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	1,803	1,200
Segment net income (loss)	214	183
Total assets	21,034		20,917
Operating Segments | Gas Pipeline Investments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	8	8
Segment net income (loss)	29	29
Total assets	1,473		1,467
Operating Segments | Wholesale Gas Services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	0	298
Segment net income (loss)	0	126
Total assets	0		31
Operating Segments | Gas marketing services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	243	195
Segment net income (loss)	66	56
Total assets	1,640		1,556
Operating Segments | All Other
Segment Reporting Information [Line Items]
Operating revenues	123	134
Net income	(125)	(108)
Goodwill	263		263
Total assets	4,236		2,975
Operating Segments | All Other | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	16	7
Segment net income (loss)	10	4
Total assets	12,017		12,114
Eliminations
Segment Reporting Information [Line Items]
Operating revenues	(42)	(35)
Net income	(8)	(8)
Goodwill	0		0
Total assets	(2,573)		(775)
Eliminations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	(12)	(14)
Segment net income (loss)	0	0
Total assets	(12,787)		(12,525)
Eliminations | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	(221)	(87)
Net income	0	$ 0
Goodwill	0		0
Total assets	$ (627)		$ (667)