Contingencies and Regulatory Matters (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended		9 Months Ended	1 Months Ended	9 Months Ended		0 Months Ended		1 Months Ended	9 Months Ended					0 Months Ended							9 Months Ended	12 Months Ended	13 Months Ended														9 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 entities	Sep. 30, 2011	Dec. 31, 2009	Jun. 14, 2012	Sep. 30, 2012 Kivalina Case [Member]	Jul. 31, 2007 Alabama Power [Member]	Sep. 30, 2012 Alabama Power [Member] Coal_Fired_Generating_Facilities claim	Dec. 31, 2011 Alabama Power [Member]	Sep. 26, 2012 Georgia Power [Member]	Apr. 05, 2012 Georgia Power [Member]	Jul. 31, 2007 Georgia Power [Member]	Sep. 30, 2012 Georgia Power [Member] MW Coal_Fired_Generating_Facilities	Aug. 21, 2012 Georgia Power [Member]	Jun. 01, 2012 Georgia Power [Member]	Dec. 31, 2011 Georgia Power [Member]	Sep. 26, 2012 Georgia Power [Member] Maximum [Member] MW	Nov. 05, 2012 Gulf Power [Member] kWh	Mar. 12, 2012 Gulf Power [Member]	Sep. 30, 2012 Gulf Power [Member]	Jun. 19, 2012 Gulf Power [Member]	Dec. 31, 2011 Gulf Power [Member]	Mar. 12, 2012 Gulf Power [Member] Minimum [Member]	Mar. 12, 2012 Gulf Power [Member] Maximum [Member]	Sep. 30, 2012 Mississippi Power [Member]	Dec. 31, 2009 Mississippi Power [Member]	Apr. 30, 2012 Mississippi Power [Member]	Jul. 09, 2012 Mississippi Power [Member]	Feb. 14, 2012 Mississippi Power [Member]	Feb. 02, 2012 Mississippi Power [Member]	Dec. 31, 2011 Mississippi Power [Member]	May 26, 2010 Mississippi Power [Member]	Sep. 30, 2012 Mississippi Power [Member] Hurricane Isaac [Member]	Jun. 14, 2012 Mississippi Power [Member] Minimum [Member]	Jun. 14, 2012 Mississippi Power [Member] Maximum [Member]	Sep. 30, 2012 Mississippi Power [Member] MRA Revenue [Member]	Dec. 31, 2011 Mississippi Power [Member] MRA Revenue [Member]	Sep. 30, 2012 Mississippi Power [Member] MB Revenue [Member]	Dec. 31, 2011 Mississippi Power [Member] MB Revenue [Member]	Sep. 30, 2012 Gulf Power and Mississippi Power [Member]	Sep. 30, 2012 Electricity Generation Plant, Non-Nuclear [Member] Mississippi Power [Member]	Sep. 30, 2012 Mine [Member] Gulf Power [Member]	Sep. 30, 2012 Mine [Member] Mississippi Power [Member]	Sep. 30, 2012 Kemper IGCC [Member] Mississippi Power [Member]	Sep. 30, 2012 Kemper IGCC [Member] Mississippi Power [Member] Minimum [Member]	Sep. 30, 2012 Kemper IGCC [Member] Mississippi Power [Member] Maximum [Member]	Nov. 01, 2012 Subsequent Event [Member] Georgia Power [Member]
Insurance Recovery
MC Asset Recovery insurance settlement	$ 0	$ 0	$ 19,000,000	$ 0	$ 202,000,000
Amount of insurance claim received in respect of litigation settlement						25,000,000
Legal fee related to insurance recoveries						6,000,000
Net amount received of insurance claim in respect of litigation settlement						19,000,000
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
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														20,000,000							61,000,000
Civil penalties per violation rate														37,500
Number of times of punitive damages in comparison to cost incurred by Environmental Protection Agency														3
Claims awarded to companies related to nuclear fuel disposal litigation								17,000,000					30,000,000
Damages awarded												27,000,000
Amount have been recognized in the financial statements for the second claim														0
Increase in base rate under cost based electric tariff due to settlement																										22,600,000
Revised rate period																										12 months
Revenue to be received from increase in base rate																										17,000,000
Number of entities received notice from TCEQ requesting their participation in anticipated site redemption			100
Retail Regulatory Matters
Under recovered rate CNP balance									14,000,000	6,000,000
Under Recovered Rate Cnp Environmental Balance									12,000,000	11,000,000
Over recovered fuel cost balance														199,000,000
Under recovered regulatory clause revenues										31,000,000							137,000,000
Accumulated reserve balance for future storms									102,000,000
Increase In DSM Tariffs														16,000,000
Increase trraditional base tariffs														58,000,000
Percentage of decrease in fuel rates																19.00%						7.80%
Decrease in annual billings for fuel costs														122,000,000		567,000,000						58,800,000
Over recovered fuel cost threshold														200,000,000
Capacity of units include application request by Georgia Power that country PSC certify purchase from four PPAs selected through 2015 request for proposal process														998
Additional capacity of units included in application request by subsidiaries for future period requests														50
Contractual obligations due 2015														13,000,000
Contractual obligations due 2016														16,000,000
Contractual obligations due thereafter														376,000,000
Additional solar capacity which may be acquired by subsidiary																		210
Additional Solar Capacity Related Long Term Contracts Period											3 years
Cost incurred by Mississippi Power associated with plant including regulatory filing costs														1,700,000,000												2,100,000,000
Reduction in projected in-service cost due to recovered cost														4,400,000,000
Certified cost														6,100,000,000
Construction and capital costs included in semi-annual construction monitoring report															2,000,000,000
Increase In NCCR Tariff																																																50,000,000
Amortization to earnings of financing costs capitalized over the five year period														91,000,000
Costs included in CWIP														59,000,000												2,000,000,000
Contractor's estimated adjustment to contract price														425,000,000
Increase in retail rates and charges																				64,000,000
Previously approved interim retail rate increase																				38,500,000
Retail rate of return on common equity																								9.25%	11.25%
Average retail rate of return on common equity																				10.25%
Increase in retail rates and charges in next fiscal year																				4,000,000
Net effect in rate of approved changes																			1.90%
Units using by residential customer																			1,000
Over recovered fuel costs									1,000,000												28,500,000		9,900,000
Over recovered purchased power capacity costs																					3,300,000		8,000,000
Estimated cost of scrubber project																										330,000,000															660,000,000
Over recovered environmental cost																					6,900,000		10,000,000
Under recovered energy conservation costs																							3,100,000																				200,000
Amount approved for property damage reserve																															3,700,000
Percentage of increase in annual revenue																														0.30%
Percentage of decrease in annual revenue after revised notice																														0.16%
Ownership percentage in Scrubber project																					50.00%					50.00%
Scrubber project expenditures amount																										59,200,000															118,400,000
Revenue request to recover financing costs for stipulated rate increase																																			55,300,000	58,600,000
Interim rates under bond subject to refund																													55,300,000
Amount of over recovered retail fuel costs included in the balance sheets																										52,800,000						42,400,000
Amount of over recovered fuel costs																																					16,800,000	14,300,000	2,100,000	2,200,000
Amount of over recovered MRA emissions allowance cost included in the balance sheets																										200,000						1,700,000
Strom Restoration Cost																																		9,700,000
Storm Reserve Balance																										58,700,000
Integrated Coal Gasification Combined Cycle [Abstract]
Estimated cost																																										2,400,000,000			2,880,000,000
Grant funds receivable during construction																										245,300,000
Maximum cap construction cost																										2,880,000,000
Percentage of financing costs of construction work in progress																																	100.00%
Amount of government construction cost incentive received																																	296,000,000
Estimated cost less cost cap																																														40,000,000	50,000,000
Estimated capital cost of mine																										245,000,000
Cost incurred for use of mine																										127,000,000
Term of management fee contract with liberty fuels company																																												40 years
Tax credits (Phase I)																											133,000,000
Tax credit (Phase II)																												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%
Received or accrued tax benefits related to Tax credit																										276,800,000
Percentage interest acquired under asset purchase agreement																										17.50%
Percentage interest transferred under asset purchase agreement																										17.50%
Reduced percentage interest transferred under asset purchase agreement																										15.00%
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
Costs included in CWIP														59,000,000												2,000,000,000
Costs associated with CCP12 grant funds																										245,300,000
Cost deferred in other regulatory assets																										30,200,000
Other deferred charges and assets																										3,000,000
Previously expensed																										1,000,000
Deferred construction cost under review																										51,000,000
Portion of deferred construction cost under review																										46,000,000
Deferred cost related to construction																										5,000,000
Civil Penalties under Clean Air Act Per Day Lower Range Limit			25,000
Civil Penalties under Clean Air Act Per Day Upper Range Limit			$ 37,500