Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	$ 18,678	$ 16,256
Deferred tax assets -
Total - deferred tax assets	6,358	5,241
Valuation allowance	(2)	(49)
Total deferred tax liabilities, net	6,356	5,192
Accumulated deferred income taxes	12,322	11,082
Accelerated depreciation [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	12,767	11,125
Property basis differences [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	1,543	1,332
Leveraged lease basis differences [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	308	299
Employee benefit obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	579	613
Deferred tax assets -
Total - deferred tax assets	1,720	1,675
Premium on reacquired debt [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	95	103
Regulatory assets associated with employee benefit obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	1,378	1,390
Regulatory assets associated with asset retirement obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	1,422	871
Other deferred tax liabilities [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	586	523
Federal effect of state deferred taxes [Member]
Deferred tax assets -
Total - deferred tax assets	479	430
Over recovered fuel clause [Member]
Deferred tax assets -
Total - deferred tax assets	104	0
Other property basis differences [Member]
Deferred tax assets -
Total - deferred tax assets	695	453
Deferred costs [Member]
Deferred tax assets -
Total - deferred tax assets	83	86
Investment Tax Credit Carryforward [Member]
Deferred tax assets -
Total - deferred tax assets	742	480
Unbilled revenues [Member]
Deferred tax assets -
Total - deferred tax assets	111	67
Other Comprehensive Income Losses [Member]
Deferred tax assets -
Total - deferred tax assets	85	89
Asset retirement obligations-asset [Member]
Deferred tax assets -
Total - deferred tax assets	1,422	871
Kemper IGCC Loss [Member]
Deferred tax assets -
Total - deferred tax assets	451	631
Deferred State Tax Assets [Member]
Deferred tax assets -
Total - deferred tax assets	220	117
Other deferred tax assets [Member]
Deferred tax assets -
Total - deferred tax assets	246	342
Alabama Power [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	5,752	4,998
Deferred tax assets -
Total - deferred tax assets	1,511	1,141
Accumulated deferred income taxes	4,241	3,857
Accumulated deferred income taxes	4,241	3,857
Alabama Power [Member] | Accelerated depreciation [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	3,917	3,429
Alabama Power [Member] | Property basis differences [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	456	457
Alabama Power [Member] | Leveraged lease basis differences [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	28	30
Alabama Power [Member] | Employee benefit obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	200	215
Deferred tax assets -
Total - deferred tax assets	407	400
Alabama Power [Member] | Regulatory assets associated with employee benefit obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	375	366
Alabama Power [Member] | Regulatory assets associated with asset retirement obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	312	285
Alabama Power [Member] | Other deferred tax liabilities [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	175	157
Alabama Power [Member] | Federal effect of state deferred taxes [Member]
Deferred tax assets -
Total - deferred tax assets	242	219
Alabama Power [Member] | Unbilled revenues [Member]
Deferred tax assets -
Total - deferred tax assets	39	42
Alabama Power [Member] | Other Comprehensive Income Losses [Member]
Deferred tax assets -
Total - deferred tax assets	20	19
Alabama Power [Member] | Other deferred tax assets [Member]
Deferred tax assets -
Total - deferred tax assets	180	90
Alabama Power [Member] | Asset retirement obligation [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	289	59
Deferred tax assets -
Total - deferred tax assets	600	344
Alabama Power [Member] | Storm Reserve [Member]
Deferred tax assets -
Total - deferred tax assets	23	27
Georgia Power [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	7,644	7,210
Deferred tax assets -
Total - deferred tax assets	2,017	1,736
Accumulated deferred income taxes	5,627	5,474
Accumulated deferred income taxes	5,627	5,474
Georgia Power [Member] | Accelerated depreciation [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	4,909	4,732
Georgia Power [Member] | Property basis differences [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	943	811
Georgia Power [Member] | Employee benefit obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	310	329
Deferred tax assets -
Total - deferred tax assets	642	642
Georgia Power [Member] | Premium on reacquired debt [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	61	66
Georgia Power [Member] | Regulatory assets associated with employee benefit obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	528	534
Georgia Power [Member] | Regulatory assets associated with asset retirement obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	706	497
Deferred tax assets -
Total - deferred tax assets	706	497
Georgia Power [Member] | Other deferred tax liabilities [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	187	160
Georgia Power [Member] | Federal effect of state deferred taxes [Member]
Deferred tax assets -
Total - deferred tax assets	150	148
Georgia Power [Member] | Over recovered fuel clause [Member]
Deferred tax assets -
Total - deferred tax assets	45	0
Georgia Power [Member] | Other property basis differences [Member]
Deferred tax assets -
Total - deferred tax assets	88	86
Georgia Power [Member] | Deferred costs [Member]
Deferred tax assets -
Total - deferred tax assets	83	86
Georgia Power [Member] | Unbilled revenues [Member]
Deferred tax assets -
Total - deferred tax assets	47	46
Georgia Power [Member] | Other deferred tax assets [Member]
Deferred tax assets -
Total - deferred tax assets	59	63
Georgia Power [Member] | Under recovered fuel clause [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	0	81
Georgia Power [Member] | Cost of removal [Member]
Deferred tax assets -
Total - deferred tax assets	6	11
Georgia Power [Member] | Tax credit carryforward [Member]
Deferred tax assets -
Total - deferred tax assets	188	152
Georgia Power [Member] | Federal Tax Credit Carryforward [Member]
Deferred tax assets -
Total - deferred tax assets	3	5
Gulf Power [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	1,109	968
Deferred tax assets -
Total - deferred tax assets	216	171
Accumulated deferred income taxes	893	797
Accumulated deferred income taxes	893	797
Gulf Power [Member] | Accelerated depreciation [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	812	777
Gulf Power [Member] | Property basis differences [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	133	52
Gulf Power [Member] | Employee benefit obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	39	34
Gulf Power [Member] | Regulatory assets associated with employee benefit obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	59	60
Gulf Power [Member] | Regulatory assets associated with asset retirement obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	40	7
Gulf Power [Member] | Other deferred tax liabilities [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	26	22
Gulf Power [Member] | Federal effect of state deferred taxes [Member]
Deferred tax assets -
Total - deferred tax assets	33	31
Gulf Power [Member] | Other deferred tax assets [Member]
Deferred tax assets -
Total - deferred tax assets	19	18
Gulf Power [Member] | Pension and other employee benefits [Member]
Deferred tax assets -
Total - deferred tax assets	65	66
Gulf Power [Member] | Fuel Recovery Clause [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	0	16
Gulf Power [Member] | Asset retirement obligation [Member]
Deferred tax assets -
Total - deferred tax assets	40	7
Gulf Power [Member] | Other Postretirement Benefits [Member]
Deferred tax assets -
Total - deferred tax assets	26	18
Gulf Power [Member] | Tax credit carryforward [Member]
Deferred tax assets -
Total - deferred tax assets	18	18
Gulf Power [Member] | Property damage reserves-liability [Member]
Deferred tax assets -
Total - deferred tax assets	15	13
Mississippi Power [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	2,162	1,397
Deferred tax assets -
Total - deferred tax assets	1,400	1,251
Accumulated deferred income taxes	762	146
Deferred state tax asset	0	34
Accumulated deferred income taxes	762	180
Mississippi Power [Member] | Accelerated depreciation [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	1,618	1,068
Mississippi Power [Member] | Property basis differences [Member]
Deferred tax assets -
Total - deferred tax assets	451	263
Mississippi Power [Member] | Regulatory assets associated with employee benefit obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	66	68
Mississippi Power [Member] | Regulatory assets associated with asset retirement obligations [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	71	19
Mississippi Power [Member] | Other deferred tax liabilities [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	163	52
Mississippi Power [Member] | Federal effect of state deferred taxes [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	0	1
Deferred tax assets -
Total - deferred tax assets	8	0
Mississippi Power [Member] | Over recovered fuel clause [Member]
Deferred tax assets -
Total - deferred tax assets	51	0
Mississippi Power [Member] | Unbilled revenues [Member]
Deferred tax assets -
Total - deferred tax assets	16	15
Mississippi Power [Member] | Kemper IGCC Loss [Member]
Deferred tax assets -
Total - deferred tax assets	451	631
Mississippi Power [Member] | Other deferred tax assets [Member]
Deferred tax assets -
Total - deferred tax assets	13	15
Mississippi Power [Member] | Energy Cost Management Clause Over Recovered [Member]
Deferred tax assets -
Total - deferred tax assets	0	1
Mississippi Power [Member] | NOL State Carryforward [Member]
Deferred tax assets -
Total - deferred tax assets	152	57
Mississippi Power [Member] | Deferred Federal Tax Assets [Member]
Deferred tax assets -
Total - deferred tax assets	48	0
Mississippi Power [Member] | Energy Cost Management Clause Under Recovered [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	13	0
Mississippi Power [Member] | Pension and other employee benefits [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	30	35
Deferred tax assets -
Total - deferred tax assets	92	92
Mississippi Power [Member] | Kemper IGCC regulatory assets [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	86	62
Mississippi Power [Member] | Under recovered fuel clause [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	0	3
Mississippi Power [Member] | Asset retirement obligation [Member]
Deferred tax assets -
Total - deferred tax assets	71	19
Mississippi Power [Member] | Rate Differential [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	115	89
Mississippi Power [Member] | Property insurance [Member]
Deferred tax assets -
Total - deferred tax assets	25	24
Mississippi Power [Member] | Premium on long-term debt [Member]
Deferred tax assets -
Total - deferred tax assets	18	21
Mississippi Power [Member] | Interest rate hedges [Member]
Deferred tax assets -
Total - deferred tax assets	4	5
Mississippi Power [Member] | Kemper Rate Factor - Regulatory Liability Retail [Member]
Deferred tax assets -
Total - deferred tax assets	0	108
Southern Power [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	1,393	1,032
Deferred tax assets -
Total - deferred tax assets	794	481
Valuation allowance	(2)	(8)
Total deferred tax liabilities, net	792	473
Accumulated deferred income taxes	601	559
Accumulated deferred income taxes	601	559
Southern Power [Member] | Other deferred tax liabilities [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	4	6
Southern Power [Member] | Federal effect of state deferred taxes [Member]
Deferred tax assets -
Total - deferred tax assets	40	29
Southern Power [Member] | Other property basis differences [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	3	3
Southern Power [Member] | Investment Tax Credit Carryforward [Member]
Deferred tax assets -
Total - deferred tax assets	149	102
Southern Power [Member] | Other deferred tax assets [Member]
Deferred tax assets -
Total - deferred tax assets	18	4
Southern Power [Member] | Accelerated depreciation and other property basis differences [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	1,364	1,006
Southern Power [Member] | Levelized capacity revenues [Member]
Deferred tax liabilities -
Deferred Tax Liabilities, Gross	22	17
Deferred tax assets -
Total - deferred tax assets	4	5
Southern Power [Member] | State Net Operating Loss [Member]
Deferred tax assets -
Total - deferred tax assets	13	15
Southern Power [Member] | Tax credit carryforward [Member]
Deferred tax assets -
Total - deferred tax assets	15	15
Southern Power [Member] | Unrealized Tax Credits [Member]
Deferred tax assets -
Total - deferred tax assets	551	305
Southern Power [Member] | Unrealized Loss [Member]
Deferred tax assets -
Total - deferred tax assets	$ 4	6
Scenario, Previously Reported [Member]
Deferred tax assets -
Accumulated deferred income taxes		$ 11,064