SEGMENT AND RELATED INFORMATION - Financial Data for Business Segments (Details) $ in Millions			1 Months Ended		3 Months Ended							6 Months Ended		12 Months Ended
	Dec. 13, 2021 project	Jul. 01, 2021 USD ($)	Jan. 31, 2020 USD ($)	Jan. 31, 2019 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) project	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Total operating revenues														$ 23,113	$ 20,375	$ 21,419
Depreciation and amortization														3,565	3,518	3,038
Interest income														22	37	60
Operating income (loss)														3,698	4,885	7,736
Earnings from equity method investments														76	153	162
Interest expense														1,837	1,821	1,736
Income taxes (benefit)														267	393	1,798
Segment net income (loss)														2,393	3,119	4,739
Goodwill					$ 5,280				$ 5,280		$ 5,280	$ 5,280	$ 5,280	5,280	5,280	5,280
Assets held for sale					42				60		789	42	42	42	60	789
Total assets					127,534				122,935		118,700	127,534	127,534	127,534	122,935	118,700
Segment and Related Information (Textual) [Abstract]
Estimated loss on Plant Vogtle Units 3 and 4														1,692		0
Gain (loss) on dispositions														176	66	2,588
Impairment charges														2	0	168
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
Lease, impairment loss										$ 154	17			$ 7	206	0
Lease, impairment loss, after tax										$ 74	13
Electric Utilities
Segment Reporting Information [Line Items]
Total operating revenues														18,300	16,497	17,095
Depreciation and amortization														2,953	2,941	2,472
Interest income														21	30	47
Earnings from equity method investments														1	0	5
Interest expense														968	976	987
Income taxes (benefit)														219	517	708
Segment net income (loss)														2,247	3,115	3,268
Goodwill					2				2		2	2	2	2	2	2
Assets held for sale					39				5		618	39	39	39	5	618
Total assets					101,774				98,041		94,650	101,774	101,774	101,774	98,041	94,650
Southern Company Gas
Segment Reporting Information [Line Items]
Total operating revenues														4,380	3,434	3,792
All Other
Segment and Related Information (Textual) [Abstract]
Lease, impairment loss							$ 7		18						206
Lease, impairment loss, after tax							6		14						105
Operating Segments | Traditional Electric Operating Companies | Electric Utilities
Segment Reporting Information [Line Items]
Total operating revenues														16,614	15,135	15,569
Depreciation and amortization														2,436	2,447	1,993
Interest income														20	26	38
Earnings from equity method investments														1	0	2
Interest expense														821	825	818
Income taxes (benefit)														232	514	764
Segment net income (loss)														1,981	2,877	2,929
Goodwill					0				0		0	0	0	0	0	0
Assets held for sale					39				5		0	39	39	39	5	0
Total assets					89,051				85,486		81,063	89,051	89,051	89,051	85,486	81,063
Operating Segments | Southern Power | Electric Utilities
Segment Reporting Information [Line Items]
Total operating revenues														2,216	1,733	1,938
Depreciation and amortization														517	494	479
Interest income														1	4	9
Earnings from equity method investments														0	0	3
Interest expense														147	151	169
Income taxes (benefit)														(13)	3	(56)
Segment net income (loss)														266	238	339
Goodwill					2				2		2	2	2	2	2	2
Assets held for sale					0				0		618	0	0	0	0	618
Total assets					13,390				13,235		14,300	13,390	13,390	13,390	13,235	14,300
Operating Segments | Southern Company Gas
Segment Reporting Information [Line Items]
Total operating revenues														4,380	3,434	3,792
Depreciation and amortization														536	500	487
Interest income														0	5	3
Earnings from equity method investments														50	141	157
Interest expense														238	231	232
Income taxes (benefit)														275	173	130
Segment net income (loss)														539	590	585
Goodwill					5,015				5,015		5,015	5,015	5,015	5,015	5,015	5,015
Assets held for sale					0				0		171	0	0	0	0	171
Total assets					23,560				22,630		21,687	23,560	23,560	23,560	22,630	21,687
Operating Segments | All Other
Segment Reporting Information [Line Items]
Total operating revenues														582	596	690
Depreciation and amortization														76	77	79
Interest income														4	6	16
Earnings from equity method investments														24	12	0
Interest expense														631	614	517
Income taxes (benefit)														(227)	(297)	960
Segment net income (loss)														(384)	(592)	908
Goodwill					263				263		263	263	263	263	263	263
Assets held for sale					3				55		0	3	3	3	55	0
Total assets					2,975				3,168		3,511	2,975	2,975	2,975	3,168	3,511
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total operating revenues														(149)	(152)	(158)
Depreciation and amortization														0	0	0
Interest income														(3)	(4)	(6)
Earnings from equity method investments														1	0	0
Interest expense														0	0	0
Income taxes (benefit)														0	0	0
Segment net income (loss)														(9)	6	(22)
Goodwill					0				0		0	0	0	0	0	0
Assets held for sale					0				0		0	0	0	0	0	0
Total assets					(775)				(904)		(1,148)	(775)	(775)	(775)	(904)	(1,148)
Intersegment Eliminations | Electric Utilities
Segment Reporting Information [Line Items]
Total operating revenues														(530)	(371)	(412)
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	0	0
Assets held for sale					0				0		0	0	0	0	0	0
Total assets					(667)				(680)		(713)	(667)	(667)	(667)	(680)	(713)
Georgia Power
Segment Reporting Information [Line Items]
Total operating revenues														9,260	8,309	8,408
Depreciation and amortization														1,371	1,425	981
Operating income (loss)														568	1,972	2,461
Interest expense														421	425	409
Income taxes (benefit)														(168)	152	472
Total assets					48,461				47,080			48,461	48,461	48,461	47,080
Segment and Related Information (Textual) [Abstract]
Estimated loss on Plant Vogtle Units 3 and 4					480	$ 264	460	$ 48						1,692	325	0
Estimated loss on Plant Vogtle Units 3 and 4, net of tax					358	197	343	$ 36
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														1,700	325
Estimated loss on Plant Vogtle Units 3 and 4, net of tax														1,300	242
Southern Power
Segment Reporting Information [Line Items]
Total operating revenues														2,216	1,733	1,938
Depreciation and amortization														517	494	479
Operating income (loss)														291	342	395
Interest expense														147	151	169
Income taxes (benefit)														(13)	3	(56)
Segment net income (loss)														266	238	339
Total assets					13,390				13,235			13,390	13,390	13,390	13,235
Segment and Related Information (Textual) [Abstract]
Gain (loss) on dispositions														41	39	24
Southern Power | Wind Generating Facility
Segment and Related Information (Textual) [Abstract]
Gain (loss) on dispositions														37		17
Gain (loss) on dispositions, after tax														28
Southern Company Gas
Segment Reporting Information [Line Items]
Total operating revenues														4,380	3,434	3,792
Depreciation and amortization														536	500	487
Operating income (loss)														1,055	812	770
Earnings from equity method investments														50	141	157
Interest expense														238	231	232
Income taxes (benefit)														275	173	130
Segment net income (loss)														539	590	585
Goodwill					5,015				5,015			5,015	5,015	5,015	5,015
Total assets					23,560				22,630		21,687	23,560	23,560	23,560	22,630	21,687
Segment and Related Information (Textual) [Abstract]
Gain (loss) on dispositions														127	22	0
Impairment charges														0	0	115
Southern Company Gas | PennEast Pipeline
Segment Reporting Information [Line Items]
Earnings from equity method investments														(81)	7	6
Income taxes (benefit)														7
Segment and Related Information (Textual) [Abstract]
Impairment charges						2	82							84
Impairment charges, after tax						$ 2	$ 58							67
Southern Company Gas | Gas distribution operations
Segment Reporting Information [Line Items]
Goodwill					4,034				4,034			4,034	4,034	4,034	4,034
Southern Company Gas | Gas marketing services
Segment Reporting Information [Line Items]
Goodwill					981				981			981	981	981	981
Southern Company Gas | Operating Segments
Segment Reporting Information [Line Items]
Total operating revenues														4,374	3,466	3,810
Depreciation and amortization														505	470	454
Operating income (loss)														1,095	814	924
Earnings from equity method investments														50	141	162
Interest expense														237	228	225
Income taxes (benefit)														213	178	200
Segment net income (loss)														626	592	677
Total assets					23,971				23,040		22,228	23,971	23,971	23,971	23,040	22,228
Southern Company Gas | Operating Segments | All Other
Segment Reporting Information [Line Items]
Total operating revenues														38	36	44
Depreciation and amortization														31	30	33
Operating income (loss)														(40)	(7)	(154)
Earnings from equity method investments														0	0	(5)
Interest expense														1	3	7
Income taxes (benefit)														62	(5)	(70)
Segment net income (loss)														(87)	(2)	(92)
Total assets					12,114				11,336		10,759	12,114	12,114	12,114	11,336	10,759
Southern Company Gas | Operating Segments | Gas distribution operations
Segment Reporting Information [Line Items]
Total operating revenues														3,679	2,952	3,028
Depreciation and amortization														482	442	422
Operating income (loss)														708	655	573
Earnings from equity method investments														0	0	0
Interest expense														207	192	187
Income taxes (benefit)														120	114	63
Segment net income (loss)														412	390	337
Total assets					20,917				19,090		18,204	20,917	20,917	20,917	19,090	18,204
Southern Company Gas | Operating Segments | Gas Pipeline Investments
Segment Reporting Information [Line Items]
Total operating revenues														32	32	32
Depreciation and amortization														5	5	5
Operating income (loss)														21	20	20
Earnings from equity method investments														50	141	162
Interest expense														25	29	30
Income taxes (benefit)														27	33	58
Segment net income (loss)														19	99	94
Total assets					1,467				1,597		1,678	1,467	1,467	1,467	1,597	1,678
Southern Company Gas | Operating Segments | Wholesale gas services
Segment Reporting Information [Line Items]
Total operating revenues														188	74	294
Depreciation and amortization														0	1	1
Operating income (loss)														241	20	219
Earnings from equity method investments														0	0	0
Interest expense														2	4	5
Income taxes (benefit)														32	3	52
Segment net income (loss)														107	14	163
Total assets					31				850		850	31	31	31	850	850
Southern Company Gas | Operating Segments | Gas marketing services
Segment Reporting Information [Line Items]
Total operating revenues														475	408	456
Depreciation and amortization														18	22	26
Operating income (loss)														125	119	112
Earnings from equity method investments														0	0	0
Interest expense														3	3	3
Income taxes (benefit)														34	28	27
Segment net income (loss)														88	89	83
Total assets					1,556				1,503		1,496	1,556	1,556	1,556	1,503	1,496
Southern Company Gas | Intersegment Eliminations
Segment Reporting Information [Line Items]
Total operating revenues														(32)	(68)	(62)
Depreciation and amortization														0	0	0
Operating income (loss)														0	5	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)				$ (11,746)		$ (11,300)	(12,525)	(12,525)	(12,525)	(11,746)	(11,300)
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
Gain (loss) on dispositions, after tax		$ 92												92
Deferred tax expense, increase from change in appointment rate												$ 85	$ 85	$ 85
Mankato | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Power
Segment and Related Information (Textual) [Abstract]
Gain (loss) on dispositions			$ 39
Gain (loss) on dispositions, after tax			$ 23
Gain on sale															39
Gain on sale, after tax															$ 23
Plant Nacogdoches | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Southern Power
Segment and Related Information (Textual) [Abstract]
Gain (loss) on dispositions																23
Gain (loss) on dispositions, after tax																88
Gulf Power | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Segment and Related Information (Textual) [Abstract]
Gain (loss) on dispositions				$ 2,600												2,600
Gain (loss) on dispositions, after tax				$ 1,400												1,400
PowerSecure International, Inc. Lighting Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Segment and Related Information (Textual) [Abstract]
Gain (loss) on dispositions																(58)
Gain (loss) on dispositions, after tax																(52)
Natural Gas Storage Facility | Southern Company Gas
Segment and Related Information (Textual) [Abstract]
Impairment charges																115
Impairment charges, after tax																$ 86