Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating Revenues:
Operating revenues	$ 5,620	$ 5,995	$ 15,258	$ 16,505
Operating Expenses:
Total cost of sales	71	79	654	956
Other operations and maintenance	1,286	1,296	3,785	3,898
Depreciation and amortization	889	760	2,619	2,267
Taxes other than income taxes	304	303	932	931
Estimated loss on Plant Vogtle Units 3 and 4	0	0	149	0
Impairment charges	0	110	0	142
(Gain) loss on dispositions, net	0	(6)	(39)	(2,512)
Total operating expenses	3,785	3,982	11,102	9,459
Operating Income (Loss)	1,835	2,013	4,156	7,046
Other Income and (Expense):
Allowance for equity funds used during construction	38	33	106	96
Earnings from equity method investments	33	39	105	120
Interest expense, net of amounts capitalized	(443)	(434)	(1,343)	(1,294)
Impairment of leveraged lease	0	0	(154)	0
Other income (expense), net	113	61	319	239
Total other income and (expense)	(259)	(301)	(967)	(839)
Earnings (Loss) Before Income Taxes	1,576	1,712	3,189	6,207
Income taxes (benefit)	293	367	443	1,872
Consolidated Net Income	1,283	1,345	2,746	4,335
Dividends on preferred stock of subsidiaries	4	4	11	11
Net income attributable to noncontrolling interests	28	25	3	26
Net Income	$ 1,251	$ 1,316	$ 2,732	$ 4,298
Earnings per share -
Basic (in dollars per share)	$ 1.18	$ 1.26	$ 2.58	$ 4.12
Diluted (in dollars per share)	$ 1.18	$ 1.25	$ 2.57	$ 4.09
Average number of shares of common stock outstanding (in millions)
Basic (in shares)	1,058	1,048	1,058	1,043
Diluted (in shares)	1,064	1,057	1,064	1,051
Cost, Product and Service [Extensible List]			us-gaap:NaturalGasUsRegulatedMember
Retail electric revenues
Operating Revenues:
Operating revenues	$ 4,243	$ 4,512	$ 10,503	$ 11,136
Wholesale electric revenues
Operating Revenues:
Operating revenues	584	625	1,473	1,667
Other electric revenues
Operating Revenues:
Operating revenues	164	163	484	492
Natural gas
Operating Revenues:
Operating revenues	477	498	2,362	2,661
Operating Expenses:
Total cost of sales	71	79	654	956
Other
Operating Revenues:
Operating revenues	152	197	436	549
Operating Expenses:
Total cost of sales	72	114	201	316
Fuel
Operating Expenses:
Total cost of sales	933	1,072	2,190	2,836
Purchased power
Operating Expenses:
Total cost of sales	230	254	611	625
Alternative revenue programs
Operating Revenues:
Operating revenues	(1)	0	6	0
ALABAMA POWER CO
Operating Revenues:
Operating revenues	1,729	1,841	4,445	4,762
Operating Expenses:
Other operations and maintenance	387	409	1,078	1,221
Depreciation and amortization	205	195	606	593
Taxes other than income taxes	103	101	311	301
Total operating expenses	1,109	1,165	2,962	3,303
Operating Income (Loss)	620	676	1,483	1,459
Other Income and (Expense):
Allowance for equity funds used during construction	12	13	34	41
Interest expense, net of amounts capitalized	(84)	(83)	(255)	(248)
Other income (expense), net	30	11	78	36
Total other income and (expense)	(42)	(59)	(143)	(171)
Earnings (Loss) Before Income Taxes	578	617	1,340	1,288
Income taxes (benefit)	130	144	307	295
Consolidated Net Income	448	473	1,033	993
Dividends on preferred stock of subsidiaries	4	4	11	11
Net Income	444	469	1,022	982
ALABAMA POWER CO | Retail electric revenues
Operating Revenues:
Operating revenues	1,575	1,694	4,003	4,286
ALABAMA POWER CO | Wholesale electric revenues
Operating Revenues:
Operating revenues	73	71	184	194
ALABAMA POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Operating revenues	11	2	36	66
ALABAMA POWER CO | Other
Operating Revenues:
Operating revenues	70	74	222	216
ALABAMA POWER CO | Fuel
Operating Expenses:
Total cost of sales	306	310	721	864
ALABAMA POWER CO | Purchased power
Operating Expenses:
Total cost of sales	64	77	153	160
ALABAMA POWER CO | Purchased power, affiliates
Operating Expenses:
Total cost of sales	44	73	93	164
GEORGIA POWER CO
Operating Revenues:
Operating revenues	2,617	2,755	6,371	6,706
Operating Expenses:
Other operations and maintenance	483	473	1,411	1,385
Depreciation and amortization	358	250	1,064	733
Taxes other than income taxes	123	127	344	348
Estimated loss on Plant Vogtle Units 3 and 4	0	0	149	0
Total operating expenses	1,620	1,594	4,596	4,451
Operating Income (Loss)	997	1,161	1,775	2,255
Other Income and (Expense):
Allowance for equity funds used during construction			63	49
Interest expense, net of amounts capitalized	(106)	(103)	(322)	(304)
Other income (expense), net	54	36	156	113
Total other income and (expense)	(52)	(67)	(166)	(191)
Earnings (Loss) Before Income Taxes	945	1,094	1,609	2,064
Income taxes (benefit)	172	255	198	466
Consolidated Net Income	773	839	1,411	1,598
GEORGIA POWER CO | Retail electric revenues
Operating Revenues:
Operating revenues	2,435	2,567	5,870	6,181
GEORGIA POWER CO | Wholesale electric revenues
Operating Revenues:
Operating revenues	34	39	85	107
GEORGIA POWER CO | Other
Operating Revenues:
Operating revenues	148	149	416	418
GEORGIA POWER CO | Fuel
Operating Expenses:
Total cost of sales	368	443	826	1,132
GEORGIA POWER CO | Purchased power
Operating Expenses:
Total cost of sales	146	151	409	393
GEORGIA POWER CO | Purchased power, affiliates
Operating Expenses:
Total cost of sales	142	150	393	460
MISSISSIPPI POWER CO
Operating Revenues:
Operating revenues	336	370	895	970
Operating Expenses:
Other operations and maintenance	62	72	202	204
Depreciation and amortization	47	48	135	144
Taxes other than income taxes	31	30	90	85
Total operating expenses	249	277	711	767
Operating Income (Loss)	87	93	184	203
Other Income and (Expense):
Interest expense, net of amounts capitalized	(14)	(17)	(45)	(52)
Other income (expense), net	6	4	19	15
Total other income and (expense)	(8)	(13)	(26)	(37)
Earnings (Loss) Before Income Taxes	79	80	158	166
Income taxes (benefit)	12	15	20	27
Consolidated Net Income	67	65	138	139
MISSISSIPPI POWER CO | Retail electric revenues
Operating Revenues:
Operating revenues	232	251	630	669
MISSISSIPPI POWER CO | Wholesale electric revenues
Operating Revenues:
Operating revenues	61	64	164	178
MISSISSIPPI POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Operating revenues	36	51	82	109
MISSISSIPPI POWER CO | Other
Operating Revenues:
Operating revenues	7	4	19	14
MISSISSIPPI POWER CO | Fuel
Operating Expenses:
Total cost of sales	103	121	266	319
MISSISSIPPI POWER CO | Purchased power
Operating Expenses:
Total cost of sales	6	6	18	15
SOUTHERN POWER CO
Operating Revenues:
Operating revenues	523	574	1,337	1,527
Operating Expenses:
Other operations and maintenance	89	85	245	250
Depreciation and amortization	129	120	367	357
Taxes other than income taxes	10	10	29	32
(Gain) loss on dispositions, net	0	0	(39)	(23)
Total operating expenses	384	407	1,000	1,147
Operating Income (Loss)	139	167	337	380
Other Income and (Expense):
Interest expense, net of amounts capitalized	(36)	(43)	(114)	(127)
Other income (expense), net	13	6	19	48
Total other income and (expense)	(23)	(37)	(95)	(79)
Earnings (Loss) Before Income Taxes	116	130	242	301
Income taxes (benefit)	14	19	27	(41)
Consolidated Net Income	102	111	215	342
Net income attributable to noncontrolling interests	28	25	3	26
Net Income	74	86	212	316
SOUTHERN POWER CO | Wholesale electric revenues
Operating Revenues:
Operating revenues	418	455	1,047	1,197
SOUTHERN POWER CO | Wholesale revenues, affiliates
Operating Revenues:
Operating revenues	101	116	279	320
SOUTHERN POWER CO | Other
Operating Revenues:
Operating revenues	4	3	11	10
SOUTHERN POWER CO | Fuel
Operating Expenses:
Total cost of sales	137	166	346	449
SOUTHERN POWER CO | Purchased power
Operating Expenses:
Total cost of sales	19	26	52	82
SOUTHERN Co GAS
Operating Revenues:
Operating revenues	477	498	2,362	2,661
Operating Expenses:
Other operations and maintenance	217	208	696	642
Depreciation and amortization	125	121	368	359
Taxes other than income taxes	35	33	154	161
Impairment charges	0	92	0	92
Total operating expenses	448	533	1,872	2,210
Operating Income (Loss)	29	(35)	490	451
Other Income and (Expense):
Earnings from equity method investments	33	35	106	115
Interest expense, net of amounts capitalized	(57)	(56)	(171)	(174)
Other income (expense), net	12	5	33	16
Total other income and (expense)	(12)	(16)	(32)	(43)
Earnings (Loss) Before Income Taxes	17	(51)	458	408
Income taxes (benefit)	3	(22)	98	61
Consolidated Net Income	14	(29)	360	347
Net Income	14	(29)	360	347
SOUTHERN Co GAS | Natural gas
Operating Revenues:
Operating revenues	478	498	2,356	2,661
Operating Expenses:
Total cost of sales	71	79	654	956
SOUTHERN Co GAS | Alternative revenue programs
Operating Revenues:
Operating revenues	$ (1)	$ 0	$ 6	$ 0