Contingencies and Regulatory Matters (Details) (USD $)	3 Months Ended		1 Months Ended	3 Months Ended			0 Months Ended	3 Months Ended							1 Months Ended		3 Months Ended	12 Months Ended												3 Months Ended			12 Months Ended			0 Months Ended				0 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Kivalina Case [Member]	Jul. 31, 2007 Alabama Power [Member]	Mar. 31, 2013 Alabama Power [Member] Coal_Fired_Generating_Facilities claim	Dec. 31, 2012 Alabama Power [Member]	Dec. 31, 2011 Alabama Power [Member]	Apr. 05, 2012 Georgia Power [Member]	Mar. 31, 2013 Georgia Power [Member] Coal_Fired_Generating_Facilities	Jan. 02, 2013 Georgia Power [Member]	Dec. 31, 2012 Georgia Power [Member]	Jan. 02, 2012 Georgia Power [Member]	Jan. 02, 2011 Georgia Power [Member]	Mar. 31, 2013 Gulf Power [Member]	Dec. 31, 2012 Gulf Power [Member]	Mar. 31, 2012 Mississippi Power [Member]	May 31, 2010 Mississippi Power [Member] MW	Mar. 31, 2013 Mississippi Power [Member] mi	Dec. 31, 2012 Mississippi Power [Member]	Mar. 15, 2013 Mississippi Power [Member]	Mar. 05, 2013 Mississippi Power [Member]	Jan. 18, 2013 Mississippi Power [Member]	Jul. 27, 2010 Mississippi Power [Member]	Mar. 31, 2013 Mississippi Power [Member] Maximum [Member]	Mar. 31, 2013 Mississippi Power [Member] MRA Revenue [Member]	Dec. 31, 2012 Mississippi Power [Member] MRA Revenue [Member]	Mar. 31, 2013 Mississippi Power [Member] MB Revenue [Member]	Dec. 31, 2012 Mississippi Power [Member] MB Revenue [Member]	Mar. 31, 2013 Gulf Power and Mississippi Power [Member]	Apr. 04, 2013 Plant Bowen [Member] Georgia Power [Member] MW	Mar. 31, 2013 Electricity Generation Plant, Non-Nuclear [Member] Mississippi Power [Member]	Mar. 31, 2013 Kemper IGCC [Member]	Mar. 31, 2013 Kemper IGCC [Member] Mississippi Power [Member]	Dec. 31, 2012 Kemper IGCC [Member] Mississippi Power [Member]	Mar. 31, 2013 Deferred Under Recovered Regulatory Clause Revenue [Member] Alabama Power [Member]	Mar. 31, 2013 Regulatory Clause Revenues, under-recovered [Member] Alabama Power [Member]	Apr. 17, 2013 Subsequent Event [Member] Georgia Power [Member] Purchased_Power_Agreement Property MW	May 09, 2013 Subsequent Event [Member] Gulf Power [Member]	May 09, 2013 Subsequent Event [Member] Gulf Power [Member] Minimum [Member]	May 09, 2013 Subsequent Event [Member] Gulf Power [Member] Maximum [Member]	Apr. 23, 2013 Subsequent Event [Member] Mississippi Power [Member]	Apr. 23, 2013 Subsequent Event [Member] Mississippi Power [Member] Cost Cap Exceptions [Member]	Apr. 17, 2013 Subsequent Event [Member] Plant Bowen [Member] Georgia Power [Member] MW
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					57,000,000
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							27,000,000
Claims awarded to companies related to nuclear fuel disposal litigation			17,000,000
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
Revised rate period																	12 months
Revenue to be received from increase in base rate																	18,000,000
Retail Regulatory Matters
Under recovered rate CNP balance				7,000,000		9,000,000
Under recovered rate CNP environmental balance				19,000,000	21,000,000
Under recovered certified power purchase agreements																																		11,000,000	8,000,000
Over recovered fuel costs				21,000,000									5,100,000	17,100,000
Under recovered regulatory clause revenues					4,000,000
Accumulated reserve balance for future storms				93,000,000	103,000,000
Over recovered fuel cost balance								182,000,000		230,000,000
Capacity Of Units Approved For Decertification Of Units																																										32
Number of wind PPAs																																				2
Number of wind farms																																				2
Energy from wind-powered generating facilities																																				250
Capacity of small power production facility																																				50
Additional contractual obligations in 2015																																				13,000,000
Additional contractual obligations in 2016																																				47,000,000
Additional contractual obligations in 2017																																				48,000,000
Additional contractual obligations thereafter																																				1,300,000,000
Proportionate share owed in consortium agreement								45.70%
Increase In NCCR Tariff									50,000,000		35,000,000	223,000,000
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								50,000,000									2,290,000,000
Construction and capital costs included in semi-annual construction monitoring report								2,000,000,000		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
Reduction in projected in-service cost due to recovered cost								425,000,000
Number Of Days Until Request Base Rate Change																																					60 days
Proposed Change in Annual Revenues																																						75,000,000	80,000,000
Over recovered purhcased power capacity costs													1,800,000
Over recovered purchased power capacity costs														800,000
Under recovered environmental cost													8,900,000	1,900,000
Under recovered energy conservation costs													3,000,000	800,000
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
Ownership percentage in scrubber project													50.00%				50.00%
Estimated cost of scrubber project																	330,000,000											660,000,000
Scrubber project expenditures amount																	91,600,000											183,200,000
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																	60,900,000	56,600,000
Amount of over recovered fuel costs																								18,100,000	19,000,000	1,700,000	2,100,000
Amount of under recovered emissions allowance costs																	400,000	400,000
Storm reserve balance																	57,200,000
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
Costs associated with CCP12 grant funds																	245,000,000
Maximum Cap Construction Cost																																2,410,000,000								3,420,000,000
Estimated Cost of Pipeline Infrastructure																	84,400,000																								132,000,000
Cost Of Lignite Mine																	188,900,000																								245,000,000
AFUDC Cost																	156,400,000																								324,000,000
General Exceptions																	43,100,000																								102,000,000
Pre-Tax Charge Of Income																															540,000,000	462,000,000	78,000,000
After Tax Charge To Income	16,000,000																														333,500,000	285,300,000	48,200,000
Costs included in CWIP								50,000,000									2,290,000,000
Cost deferred in other regulatory assets																	43,400,000
Other deferred charges and assets	3,800,000																3,800,000
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
Settlement Agreement Collection Amount To Mitigate Rate Impact Year One																				126,000,000
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
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																	412,000,000
Unusable Tax Credits Until Future Period																	$ 178,800,000
Carry Forward For Unused Tax Credits																	20 years
Additional Bonus Depreciation For Property Acquired Future Periods																	50.00%
Electric Generating Units, Capacity																													1,400