Segment and Related Information - Schedule of Financial Data for Business Segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2022
Segment Reporting Information [Line Items]
Operating revenues	$ 6,480	$ 6,648
Net income	862	1,032
Goodwill	5,161			$ 5,161
Total assets	134,756			134,891
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	508	539
Total assets	13,134			13,081
SOUTHERN POWER CO | Disposal Group, Disposed of by Sale | Spare Parts
Segment Reporting Information [Line Items]
Gain on sale	16
Gain on sale, after tax			$ 12
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	1,875	2,058
Net income	309	319
Goodwill	5,015			5,015
Total assets	24,222			24,621
Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	4,483	4,509
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	1,875	2,058
Gas distribution operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Goodwill	4,034			4,034
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	1,872	2,054
Net income	302	309
Total assets	25,402			25,233
Operating Segments | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	4,483	4,509
Net income	712	846
Goodwill	2			2
Total assets	108,782			108,283
Operating Segments | Traditional Electric Operating Companies
Segment Reporting Information [Line Items]
Operating revenues	4,113	4,191
Net income	610	774
Goodwill	0			0
Total assets	96,223			95,861
Operating Segments | SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Operating revenues	508	539
Net income	102	72
Goodwill	2			2
Total assets	13,134			13,081
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	1,875	2,058
Net income	309	319
Goodwill	5,015			5,015
Total assets	24,222			24,621
Operating Segments | Gas distribution operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	1,618	1,803
Net income	221	214
Total assets	22,223			22,040
Operating Segments | Gas Pipeline Investments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	8	8
Net income	31	29
Total assets	1,583			1,577
Operating Segments | Gas marketing services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	246	243
Net income	50	66
Total assets	1,596			1,616
Operating Segments | All Other
Segment Reporting Information [Line Items]
Operating revenues	166	123
Net income	(154)	(125)
Goodwill	144			144
Total assets	2,606			2,665
Operating Segments | All Other | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	12	16
Net income	7	10
Total assets	9,598			8,943
Eliminations
Segment Reporting Information [Line Items]
Operating revenues	(44)	(42)
Net income	(5)	(8)
Goodwill	0			0
Total assets	(854)			(678)
Eliminations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Operating revenues	(9)	(12)
Net income	0	0
Total assets	(10,778)			(9,555)
Eliminations | Electric Utilities
Segment Reporting Information [Line Items]
Operating revenues	(138)	(221)
Net income	0	$ 0
Goodwill	0			0
Total assets	$ (575)			$ (659)