Segment and Related Information - Schedule of Business Segment Financial Data (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Total operating revenues	$ 7,274	$ 6,980	$ 20,383	$ 19,208
Net income	1,535	1,422	3,867	3,121
Total assets	143,956		143,956		$ 139,331
SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Total operating revenues	682	689	3,220	3,417
Net income	38	82	555	475
Total assets	25,545		25,545		25,083
GEORGIA POWER CO
Segment Reporting Information [Line Items]
Total operating revenues	3,472	3,237	8,745	7,805
Total assets	60,498		60,498		56,817
SOUTHERN POWER CO
Segment Reporting Information [Line Items]
Total operating revenues	600	653	1,597	1,686
Net income	82	100	264	288
Total assets	12,646		12,646		12,761
Nicor Gas
Segment Reporting Information [Line Items]
Pre-tax charge to income			38
After-tax charge to income			28
Operating Segments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Total operating revenues	677	683	3,210	3,402
Net income	43	96	552	484
Total assets	26,735		26,735		26,055
Operating Segments | Gas distribution operations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Total operating revenues	616	619	2,828	3,002
Net income	21	70	403	352
Total assets	23,543		23,543		22,906
Operating Segments | Gas Pipeline Investments | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Total operating revenues	8	8	24	24
Net income	24	24	77	73
Total assets	1,573		1,573		1,534
Operating Segments | Gas marketing services | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Total operating revenues	53	56	358	376
Net income	(2)	2	72	59
Total assets	1,619		1,619		1,615
Operating Segments | All Other
Segment Reporting Information [Line Items]
Total operating revenues	215	154	598	499
Net income	(201)	(179)	(569)	(490)
Total assets	2,347		2,347		2,446
Operating Segments | All Other | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Total operating revenues	6	8	19	30
Net income	(5)	(14)	3	(9)
Total assets	9,910		9,910		9,675
Eliminations
Segment Reporting Information [Line Items]
Total operating revenues	(45)	(30)	(128)	(122)
Net income	(2)	0	(13)	(4)
Total assets	(600)		(600)		(843)
Eliminations | SOUTHERN Co GAS
Segment Reporting Information [Line Items]
Total operating revenues	(1)	(2)	(9)	(15)
Net income	0	$ 0	0	$ 0
Total assets	$ (11,100)		$ (11,100)		$ (10,647)