Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								6 Months Ended		12 Months Ended			60 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Summarized quarterly financial information
Operating revenues	$ 5,181	$ 6,264	$ 4,459	$ 3,992	$ 3,568	$ 5,401	$ 4,337	$ 4,183			$ 19,896	$ 17,489	$ 18,467
Operating Income (Loss)	587	1,917	1,185	940	578	1,649	1,098	957			4,629	4,282	3,642
Net Income (Loss) After Dividends on Preferred and Preference Stock	$ 197	$ 1,139	$ 623	$ 489	$ 271	$ 959	$ 629	$ 508			$ 2,448	$ 2,367	$ 1,963
Basic EPS (in dollars per share)	$ 0.20	$ 1.18	$ 0.67	$ 0.53	$ 0.30	$ 1.05	$ 0.69	$ 0.56			$ 2.57	$ 2.60	$ 2.19
Diluted EPS (in dollars per share)	0.20	1.17	0.66	0.53	0.30	1.05	0.69	0.56			2.55	2.59	2.18
Cash dividends (in dollars per share)	0.5600	0.5600	0.5600	0.5425	0.5425	0.5425	0.5425	0.525			$ 2.2225	$ 2.1525	$ 2.0825
Trading Price Range, High, Per Common Share (in dollars per share)	52.23	54.64	53.64	51.73	47.5	46.84	45.44	53.16
Trading Price Range, Low, Per Common Share (in dollars per share)	$ 46.20	$ 50	$ 47.62	$ 46	$ 43.38	$ 41.81	$ 41.4	$ 43.55
Income tax expense (benefit)											$ 951	$ 1,194	$ 977
Georgia Power [Member]
Summarized quarterly financial information
Operating revenues	$ 1,762	$ 2,698	$ 2,051	$ 1,872	$ 1,641	$ 2,691	$ 2,016	$ 1,978			8,383	8,326	8,988
Operating Income (Loss)	258	1,054	656	509	376	964	554	454			2,477	2,348	2,296
Net Income (Loss) After Dividends on Preferred and Preference Stock	113	599	349	269	196	551	277	236			1,330	1,260	1,225
Income tax expense (benefit)											780	769	729
Alabama Power [Member]
Summarized quarterly financial information
Operating revenues	1,329	1,785	1,444	1,331	1,217	1,695	1,455	1,401			5,889	5,768	5,942
Operating Income (Loss)	252	650	430	333	264	555	398	346			1,665	1,563	1,525
Net Income (Loss) After Dividends on Preferred and Preference Stock	102	351	213	156	121	295	200	169			822	785	761
Income tax expense (benefit)											531	506	512
Gulf Power [Member]
Summarized quarterly financial information
Operating revenues	349	436	365	335	313	429	384	357			1,485	1,483	1,590
Operating Income (Loss)	54	90	74	65	58	91	69	72			283	290	281
Net Income (Loss) After Dividends on Preferred and Preference Stock	23	45	34	29	28	48	35	37			131	148	140
Income tax expense (benefit)											91	92	88
Mississippi Power [Member]
Summarized quarterly financial information
Operating revenues	277	352	277	257	246	341	275	276			1,163	1,138	1,243
Operating Income (Loss)	(166)	9	(28)	(10)	(143)	(66)	12	24			(195)	(173)	(689)
Net Income (Loss) After Dividends on Preferred and Preference Stock	(89)	26	2	11	(71)	(21)	49	35			(50)	(8)	(329)
Income tax expense (benefit)											(104)	(72)	(285)
Southern Power [Member]
Summarized quarterly financial information
Operating revenues	389	500	373	315	304	401	337	348			1,577	1,390	1,501
Operating Income (Loss)	28	134	81	47	55	129	75	67			290	326	255
Net Income (Loss) After Dividends on Preferred and Preference Stock	23	176	89	50	34	102	46	33
Income tax expense (benefit)											(195)	21	(3)
Kemper IGCC [Member]
Summarized quarterly financial information
Pre-Tax Charge To Income	206	88	81	53	183	150	23	9
After Tax Charge To Income	127	54	50	33	113	93	14	6			264	226	536
Kemper IGCC [Member] | Mississippi Power [Member]
Summarized quarterly financial information
Pre-Tax Charge To Income	206	88	81	53	183	150	23	9			348	365	868	$ 2,760
After Tax Charge To Income	127	54	50	33	113	93	14	6			215	226	536	$ 1,710
Restatement Adjustment
Summarized quarterly financial information
Income tax expense (benefit)		(9)	(11)	(5)
Restatement Adjustment | Georgia Power [Member]
Summarized quarterly financial information
Net Income (Loss) After Dividends on Preferred and Preference Stock							(47)
Predecessor [Member] | Southern Company Gas [Member]
Summarized quarterly financial information
Operating revenues			571	1,334	962	584	674	1,721		$ 1,905		3,941	5,385
Operating Income (Loss)			(27)	348	216	59	107	364		321		746	1,095
EBIT			(23)	351	221	62	111	367		328		761	1,112
Net Income (Loss) After Dividends on Preferred and Preference Stock			$ (51)	$ 182	$ 107	$ 11	$ 42	$ 193		131		353	482
Income tax expense (benefit)										$ 87		$ 213	$ 350
Successor [Member] | Southern Company Gas [Member]
Summarized quarterly financial information
Operating revenues	1,109	543							$ 1,652
Operating Income (Loss)	185	12							197
EBIT	221	50
Net Income (Loss) After Dividends on Preferred and Preference Stock	$ 110	$ 4							114
Income tax expense (benefit)									$ 76
Scenario, Previously Reported [Member]
Summarized quarterly financial information
Basic EPS (in dollars per share)		$ 1.17	$ 0.65	$ 0.53
Diluted EPS (in dollars per share)		$ 1.16	$ 0.65	$ 0.53
Accounting Standards Update 2016-09 | Georgia Power [Member]
Summarized quarterly financial information
Prior period reclassification adjustment		$ 1	$ 2	$ 1							$ 1
Accounting Standards Update 2016-09 | Alabama Power [Member]
Summarized quarterly financial information
Prior period reclassification adjustment		$ 2	$ 2	$ 1