Contingencies and Regulatory Matters (Details) (USD $)	9 Months Ended		9 Months Ended						0 Months Ended		1 Months Ended	6 Months Ended	9 Months Ended							1 Months Ended									1 Months Ended		9 Months Ended	12 Months Ended								1 Months Ended		9 Months Ended						1 Months Ended														9 Months Ended		3 Months Ended		9 Months Ended	3 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Kivalina Case [Member]	Sep. 30, 2013 Alabama Power [Member] Coal_Fired_Generating_Facilities claim	Aug. 13, 2013 Alabama Power [Member] Provisions	Dec. 31, 2012 Alabama Power [Member]	Aug. 13, 2013 Alabama Power [Member] Minimum [Member]	Aug. 13, 2013 Alabama Power [Member] Maximum [Member]	May 14, 2013 Georgia Power [Member] Purchased_Power_Agreement	Apr. 22, 2013 Georgia Power [Member] Purchased_Power_Agreement MW	May 31, 2013 Georgia Power [Member] Property	Jun. 30, 2013 Georgia Power [Member]	Sep. 30, 2013 Georgia Power [Member] Property Coal_Fired_Generating_Facilities MW	Jun. 28, 2013 Georgia Power [Member]	May 21, 2013 Georgia Power [Member]	Jan. 02, 2013 Georgia Power [Member]	Dec. 31, 2012 Georgia Power [Member]	Jan. 02, 2012 Georgia Power [Member]	Jan. 02, 2011 Georgia Power [Member]	Oct. 31, 2013 Georgia Power [Member] Subsequent Event [Member]	Nov. 01, 2013 Georgia Power [Member] Subsequent Event [Member]	Oct. 15, 2013 Georgia Power [Member] Subsequent Event [Member]	Sep. 30, 2013 Georgia Power [Member] Minimum [Member]	Sep. 30, 2013 Georgia Power [Member] Maximum [Member]	Sep. 30, 2013 Gulf Power [Member]	Dec. 31, 2012 Gulf Power [Member]	Nov. 04, 2013 Gulf Power [Member] Subsequent Event [Member]	Jul. 12, 2013 Gulf Power [Member] Subsequent Event [Member]	Mar. 31, 2012 Mississippi Power [Member]	May 31, 2010 Mississippi Power [Member] MW	Sep. 30, 2013 Mississippi Power [Member] mi	Dec. 31, 2012 Mississippi Power [Member]	Sep. 19, 2013 Mississippi Power [Member]	Jun. 04, 2013 Mississippi Power [Member]	Mar. 15, 2013 Mississippi Power [Member]	Mar. 05, 2013 Mississippi Power [Member]	Feb. 01, 2013 Mississippi Power [Member]	Jan. 18, 2013 Mississippi Power [Member]	Dec. 31, 2010 Mississippi Power [Member]	Oct. 31, 2013 Mississippi Power [Member] Subsequent Event [Member]	Jul. 11, 2013 Mississippi Power [Member] Subsequent Event [Member] Customer	Sep. 30, 2013 Mississippi Power [Member] Minimum [Member]	Sep. 30, 2013 Mississippi Power [Member] Maximum [Member]	Sep. 30, 2013 Mississippi Power [Member] MRA Revenue [Member]	Dec. 31, 2012 Mississippi Power [Member] MRA Revenue [Member]	Sep. 30, 2013 Mississippi Power [Member] MB Revenue [Member]	Dec. 31, 2012 Mississippi Power [Member] MB Revenue [Member]	Oct. 31, 2013 Mississippi Power [Member] Cost Cap Exceptions [Member]	Oct. 28, 2013 Mississippi Power [Member] Cost Cap Exceptions [Member]	Oct. 28, 2013 Mississippi Power [Member] Non Capital Kemper IGCC Related Costs [Member] Subsequent Event [Member]	Sep. 30, 2013 Gulf Power and Mississippi Power [Member]	Apr. 17, 2013 Plant Bowen [Member] Georgia Power [Member] MW	Apr. 17, 2013 Plant Branch Unit Two [Member] Georgia Power [Member] MW	Jul. 11, 2013 Plant Boulevard [Member] Georgia Power [Member] Subsequent Event [Member] MW	Jul. 11, 2013 Plant Branch Units Three And Four [Member] Georgia Power [Member] Subsequent Event [Member] MW	Jul. 11, 2013 Plant Yates [Member] Georgia Power [Member] Subsequent Event [Member] MW	Jul. 11, 2013 Plant McManus [Member] Georgia Power [Member] Subsequent Event [Member] MW	Jul. 11, 2013 Plant Kraft [Member] Georgia Power [Member] Subsequent Event [Member] MW	Sep. 30, 2013 Utility Scale Projects [Member] Georgia Power [Member] MW	Sep. 30, 2013 Electric Distribution [Member] Georgia Power [Member] MW	Jul. 12, 2013 Electric Transmission [Member] Gulf Power [Member] Subsequent Event [Member]	Sep. 30, 2013 Electricity Generation Plant, Non-Nuclear [Member] Mississippi Power [Member]	Apr. 04, 2013 Plant Bowen Unit One [Member] Georgia Power [Member] MW	Sep. 30, 2013 Kemper IGCC [Member]	Mar. 31, 2013 Kemper IGCC [Member]	Sep. 30, 2013 Kemper IGCC [Member]	Sep. 30, 2013 Kemper IGCC [Member] Mississippi Power [Member]	Jun. 30, 2013 Kemper IGCC [Member] Mississippi Power [Member]	Mar. 31, 2013 Kemper IGCC [Member] Mississippi Power [Member]	Sep. 30, 2013 Kemper IGCC [Member] Mississippi Power [Member]	Dec. 31, 2012 Kemper IGCC [Member] Mississippi Power [Member]	Apr. 04, 2013 Plant Bowen Unit Two [Member] Georgia Power [Member] MW	Sep. 30, 2013 Regulatory Clause Revenues, under-recovered [Member] Alabama Power [Member]	Sep. 30, 2013 Deferred Under Recovered Regulatory Clause Revenue [Member] Alabama Power [Member]	Sep. 30, 2013 Current Liabilities [Member]	Sep. 30, 2013 Current Liabilities [Member] Georgia Power [Member]	Dec. 31, 2012 Current Liabilities And Other Deferred Credits And Liabilities [Member]	Dec. 31, 2012 Current Liabilities And Other Deferred Credits And Liabilities [Member] Georgia Power [Member]	Sep. 19, 2013 Capital Lease Obligations [Member] Mississippi Power [Member]	Aug. 13, 2013 Current Rate Stabilization And Equalization [Member] Alabama Power [Member] Minimum [Member]	Aug. 13, 2013 Current Rate Stabilization And Equalization [Member] Alabama Power [Member] Maximum [Member]	Aug. 13, 2013 Current Rate Stabilization And Equalization [Member] Alabama Power [Member] Maximum [Member]
Loss Contingencies [Line Items]
Estimated Loss On Plant																																																																						$ 1,140,000,000
Significant Assumption Of Inflation Rate Used To Determine Costs For Rate Making				4.50%
Environmental Matters
Number of coal fired generating facilities at which new source review violations occurred				5									3
Number of dismissed claims against Subsidiary				5
Total number of claims				8
Claims left for summary disposition or trial against Alabama Power				3
Civil penalties under Clean Air Act, per day, per violation, minimum	25,000
Civil penalties under Clean Air Act, per day, per violation, maximum	37,500
Damages from lost property values and relocating village cost, lower range			95,000,000
Damages from lost property values and relocating village cost, upper range			400,000,000
Environmental remediation liability													18,000,000												52,000,000
Civil penalties per day violation rate													37,500
Number of times of punitive damages in comparison to cost incurred by Environmental Protection Agency													3
Damages awarded				17,000,000									27,000,000
Amount have been recognized in the financial statements for the second claim													0
Increase in annual base wholesale revenues																															22,600,000
Increase in base rate under cost based electric tariff due to settlement																															24,200,000
Revenue to be received from increase in base rate													334,000,000																		18,000,000
Estimated Increase In ECCR Tariff													132,000,000
Estimated Increase In Demand Side Management Tariffs													5,000,000
Estimated Increase In Municipal Franchise Fee Tariff													11,000,000
Period For Levelized Revenue Requirements													3 years
Test Period For PSC																				1 year
Excess Revenues																				165,000,000
Retail Regulatory Matters
Under recovered rate CNP balance				22,000,000	50,000,000	9,000,000
Under recovered rate CNP environmental balance				12,000,000		21,000,000
Under recovered certified power purchase agreements																																																																									4,000,000	8,000,000
Over recovered fuel costs				43,000,000																						17,100,000
Under recovered regulatory clause revenues						4,000,000																			10,000,000
Fuel Vendor Payment																									26,600,000
Accumulated reserve balance for future storms				95,000,000		103,000,000
Period To Amortize Expense				3 years
Outage Expenditures				70,000,000
Over recovered fuel cost balance																																																																											108,000,000	114,000,000	230,000,000	230,000,000
PSC Retail Rate Increase														482,000,000														74,400,000						7,100,000																											16,400,000
Proposed Change in Annual Revenues																											65,200,000
Percentage Of PSC Retail Rate Increase														6.10%																				0.90%
Retail Rate Of Return On Common Equity							13.00%	14.50%					10.00%	11.50%									10.25%	12.25%	11.50%
Adjusting Point Of Rate Of Return On Common Equity					13.75%
Allowed Equity Ratio					45.00%
Number Of Provisions					2
Weighted Cost Of Equity							5.75%	6.21%																																																																								5.85%	6.53%
Adjusting Point Of Weighted Cost Of Equity					5.98%																																																																													6.19%
Number Of Basis Points					7								50
Percent Of Basis Points					0.07%
Capacity Of Units Approved For Decertification Of Units																																																				32	319	28	1,016	579	122	316
Period Extension Of The MATS Rule													1 year
Energy From Solar Generation													525																																														425	100
Number of wind PPAs										2
Energy from wind-powered generating facilities										250
Number Of Biomass PPAs									2
Capacity of small power production facility													169
Number Of Biomass Facilities											2		4
Additional contractual obligations in 2015													1,000,000		13,000,000
Additional contractual obligations in 2016													11,000,000		47,000,000
Additional contractual obligations in 2017													12,000,000		49,000,000
Additional contractual obligations thereafter													249,000,000		1,290,000,000
Proportionate share owed in consortium agreement													45.70%
Increase In NCCR Tariff																50,000,000		35,000,000	223,000,000		65,000,000
Amortization to earnings of financing costs capitalized over the five year period													91,000,000
Amortization to earnings of financing costs capitalized, amortization term													5 years
Costs included in CWIP													41,000,000																		2,410,000,000
Construction and capital costs included in semi-annual construction monitoring report																						2,200,000,000
Increase (decrease) in projected certified construction capital costs													5.00%
Estimated In-service Capital Cost													4,800,000,000
Cost incurred by Mississippi Power associated with plant including regulatory filing costs													2,000,000,000
Construction Capital Costs												2,400,000,000
Reduction in projected in-service cost due to recovered cost													425,000,000
Under recovered purchased power capacity costs																									6,400,000	800,000
Under recovered environmental cost																									7,900,000	1,900,000
Under recovered energy conservation costs																									5,700,000	800,000
Required Customers For Energy Efficiency Programs																																									25,000
Required Period For Filing Quick Start Plans																															6 months
Period For Quick Start Plans To Be In Effect																																										2 years	3 years
Annual PEP Filing Rate Increase																																				1.925%		1.99%
Annual PEP Filing Rate Increase Amount																																				15,300,000		15,800,000
Potential additional revenues in 2013 as a result of late implementation of the 2013 PEP rate increase																															3,300,000
Annual PEP lookback refund to customers																																			4,700,000
Psc Approved Annual Property Damage Reserve Accrual																																					3,200,000
Ownership percentage in scrubber project																									50.00%						50.00%
Estimated cost of scrubber project																															330,000,000																				660,000,000
Scrubber project expenditures amount																															139,200,000																				278,300,000
Allowance For Funds Used During Construction Cost																															6,600,000
Annual adjustment in retail fuel cost recovery factor, percentage decrease																																				4.70%
Annual adjustment in retail fuel cost recovery factor, amount																																				35,500,000
Amount of over recovered retail fuel costs included in balance sheets																															21,800,000	56,600,000
Amount of over recovered fuel costs																																												9,100,000	19,000,000	600,000	2,100,000
Amount of under recovered emissions allowance costs																															3,400,000	400,000
Storm reserve balance																															59,200,000
Integrated Coal Gasification Combined Cycle [Abstract]
Plant Capacity Under Coal Gasification Combined Cycle Technology																														582
Co Two Pipeline Infrastructure																															61
Estimated Cost																																																														2,400,000,000								2,880,000,000
Alternate Financing																																																														1,000,000,000
Cost Of Plant																																																																						3,610,000,000
Costs associated with CCP12 grant funds																															245,000,000
Maximum Cap Construction Cost																																								4,020,000,000																														2,940,000,000
Estimated Cost of Pipeline Infrastructure																															91,900,000																		115,000,000
Cost Of Lignite Mine																															223,900,000																		245,000,000
AFUDC Cost																															232,200,000																	426,000,000
General Exceptions																															67,600,000																	101,000,000
Regulatory Assets																																																		91,000,000
Pre-tax charge to income																																																																150,000,000	540,000,000	1,100,000,000	150,000,000	450,000,000	462,000,000		78,000,000
After tax charge to income	16,000,000																																																															93,000,000	333,500,000	704,000,000	92,600,000	277,900,000	285,300,000		48,200,000
Costs included in CWIP													41,000,000																		2,410,000,000
Cost deferred in other regulatory assets																															59,100,000
Other deferred charges and assets	3,800,000																														3,900,000
Previously expensed																															1,000,000
Settlement Agreement To Increase Rates																																											172,000,000
Collaboration Period To File Settlement Agreement																															3 months
Beginning Period Of Operation Of Plant																															7 years
Period Of Time For Decision On Rate Recovery Plan Within Filing																															4 months
Prudence Review Of Plant Cost Within Settlement Agreement																															6 months
Increase Retail Rates In Year One																															15.00%
Increase Retail Rates In Year Two																															3.00%
Settlement Agreement Collection Amount To Mitigate Rate Impact Year Two																																				156,000,000
Regulatory Liabilities	27,000,000																														62,000,000
Other Regulatory Liabilities, Current	89,000,000	107,000,000		45,000,000		3,000,000							18,000,000				73,000,000								14,316,000	25,887,000					11,846,000	5,376,000																																3,000,000		3,000,000
Other regulatory liabilities, deferred	375,000,000	289,000,000		211,000,000		183,000,000																			47,090,000	47,863,000					117,804,000	56,984,000																																24,000,000		24,000,000
Reduced percentage interest transferred under asset purchase agreement																																15.00%
Purchase of Interest																																17.50%							17.50%
Deposit received																													150,000,000
Maximum period to refund deposit upon termination of asset purchase agreement																													60 days
Maximum period of discretion in the event senior unsecured credit rating falls																													15 days
Agreement To Sell Air Separation Unit																																	79,000,000
Period Of Nitrogen Supply Agreement																																	20 years
Capital Lease Obligations																																	82,900,000
Debt Instrument, Interest Rate, Stated Percentage																																																																															4.90%
Internal Revenue Code Section Forty Eight Tax Credits Phase I																															133,000,000
Internal Revenue Code Section Forty Eight Tax Credits Phase I I																															279,000,000
Minimum percentage of carbon dioxide that must be capture and sequester to remain eligible for the phase II tax credits																															65.00%
Tax Credit Carryforward, Amount																															276,400,000
Additional Bonus Depreciation For Property Acquired Future Periods																															50.00%
Percent Of Designated Customer Value Benchmark Survey				33.30%
Electric Generating Units, Capacity																																																															700									700
Earnings Above ROE Range To Share With Customers													66.70%
Earnings Above ROE Range To Retain													33.30%
Required Period For Filing Comprehensive Portfolio Plans																															1 year
SignificantAssumption Of Trust Earnings Rate Used To Determine Costs For Rate Making				7.00%
Asset retirement obligation, current				102,000,000
Certain Regulatory Assets																															$ 55,200,000