Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Summarized quarterly financial information
Operating revenues	$ 3,568	$ 5,401	$ 4,337	$ 4,183	$ 4,017	$ 5,339	$ 4,467	$ 4,644	$ 17,489	$ 18,467	$ 17,087
Operating Income (Loss)	578	1,649	1,098	957	561	1,278	1,103	700	4,282	3,642	3,255
Net Income (Loss) After Dividends on Preferred and Preference Stock	$ 271	$ 959	$ 629	$ 508	$ 283	$ 718	$ 611	$ 351	$ 2,367	$ 1,963	$ 1,644
Basic Earnings, Per Common Share (in dollars per share)	$ 0.30	$ 1.05	$ 0.69	$ 0.56	$ 0.31	$ 0.80	$ 0.68	$ 0.39	$ 2.60	$ 2.19	$ 1.88
Diluted Earnings, Per Common Share (in dollars per share)	0.30	1.05	0.69	0.56	0.31	0.80	0.68	0.39	2.59	2.18	1.87
Cash dividends (in dollars per share)	0.5425	0.5425	0.5425	0.525	0.525	0.525	0.525	0.5075	$ 2.1525	$ 2.0825	$ 2.0125
Trading Price Range, High, Per Common Share (in dollars per share)	47.5	46.84	45.44	53.16	51.28	45.47	46.81	44
Trading Price Range, Low, Per Common Share (in dollars per share)	$ 43.38	$ 41.81	$ 41.4	$ 43.55	$ 43.55	$ 41.87	$ 42.55	$ 40.27
Alabama Power [Member]
Summarized quarterly financial information
Operating revenues	$ 1,217	$ 1,695	$ 1,455	$ 1,401	$ 1,328	$ 1,669	$ 1,437	$ 1,508	$ 5,768	$ 5,942	$ 5,618
Operating Income (Loss)	264	555	398	346	267	520	357	381	1,563	1,525	1,476
Net Income (Loss) After Dividends on Preferred and Preference Stock	121	295	200	169	119	282	173	187	785	761	712
Georgia Power [Member]
Summarized quarterly financial information
Operating revenues	1,641	2,691	2,016	1,978	1,902	2,631	2,186	2,269	8,326	8,988	8,274
Operating Income (Loss)	376	964	554	454	288	920	572	516	2,348	2,296	2,240
Net Income (Loss) After Dividends on Preferred and Preference Stock	196	551	277	236	123	525	311	266	1,260	1,225	1,174
Gulf Power [Member]
Summarized quarterly financial information
Operating revenues	313	429	384	357	361	438	384	407	1,483	1,590	1,440
Operating Income (Loss)	58	91	69	72	50	88	69	74	290	281	265
Net Income (Loss) After Dividends on Preferred and Preference Stock	28	48	35	37	23	46	34	37	148	140	124
Mississippi Power [Member]
Summarized quarterly financial information
Operating revenues	246	341	275	276	246	355	311	331	1,138	1,243	1,145
Operating Income (Loss)	(143)	(66)	12	24	(71)	(349)	56	(325)	(173)	(689)	(922)
Net Income (Loss) After Dividends on Preferred and Preference Stock	(71)	(21)	49	35	(24)	(195)	62	(172)	(8)	(329)	(477)
Southern Power [Member]
Summarized quarterly financial information
Operating revenues	304	401	337	348	386	435	329	351	1,390	1,501	1,275
Operating Income (Loss)	55	129	75	67	40	105	51	59	326	255	290
Net Income (Loss) After Dividends on Preferred and Preference Stock	34	102	46	33	44	64	$ 31	33
Kemper IGCC [Member]
Summarized quarterly financial information
Pre-Tax Charge To Income	183	150	23	9	70	418		380	365	868	1,200
After Tax Charge To Income	113	93	14	6	43	258		235	226	536	729
Kemper IGCC [Member] | Mississippi Power [Member]
Summarized quarterly financial information
Pre-Tax Charge To Income	183	150	23	9	70	418		380	365	868	1,100
After Tax Charge To Income	$ 113	$ 93	$ 14	$ 6	$ 43	$ 258		$ 235	$ 226	$ 536	$ 681