Contingencies and Regulatory Matters - Narrative (Details) (USD $)	9 Months Ended	3 Months Ended		9 Months Ended		0 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended					9 Months Ended		3 Months Ended		9 Months Ended			0 Months Ended		1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended							9 Months Ended							1 Months Ended	12 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended	0 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended		19 Months Ended			9 Months Ended		12 Months Ended												0 Months Ended			1 Months Ended	0 Months Ended				9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014 Alabama Power [Member]	Sep. 30, 2013 Alabama Power [Member]	Sep. 30, 2014 Alabama Power [Member]	Sep. 30, 2013 Alabama Power [Member]	Aug. 28, 2014 Georgia Power [Member]	May 20, 2014 Georgia Power [Member] WindFarms Purchased_Power_Agreement	Sep. 30, 2014 Georgia Power [Member]	Sep. 30, 2013 Georgia Power [Member]	Sep. 30, 2014 Georgia Power [Member]	Sep. 30, 2013 Georgia Power [Member]	Dec. 31, 2013 Georgia Power [Member]	Jan. 01, 2014 Georgia Power [Member]	Jan. 01, 2013 Georgia Power [Member]	Jan. 01, 2012 Georgia Power [Member]	Jan. 01, 2011 Georgia Power [Member]	Sep. 30, 2014 Georgia Power [Member] Minimum [Member]	Sep. 30, 2014 Georgia Power [Member] Maximum [Member]	Sep. 30, 2014 Gulf Power [Member]	Sep. 30, 2013 Gulf Power [Member]	Sep. 30, 2014 Gulf Power [Member] clause	Sep. 30, 2013 Gulf Power [Member]	Dec. 31, 2012 Gulf Power [Member]	Aug. 01, 2014 Mississippi Power [Member]	May 20, 2014 Mississippi Power [Member]	Jan. 31, 2014 Mississippi Power [Member]	Mar. 31, 2013 Mississippi Power [Member]	Sep. 30, 2014 Mississippi Power [Member]	Sep. 30, 2013 Mississippi Power [Member]	Sep. 30, 2014 Mississippi Power [Member]	Sep. 30, 2013 Mississippi Power [Member]	Dec. 31, 2013 Mississippi Power [Member]	Dec. 31, 2012 Mississippi Power [Member]	Aug. 01, 2014 Mississippi Power [Member]	May 06, 2014 Mississippi Power [Member]	Apr. 01, 2014 Mississippi Power [Member]	Jan. 02, 2014 Mississippi Power [Member]	Dec. 31, 2010 Mississippi Power [Member]	Sep. 30, 2014 Mississippi Power [Member] Minimum [Member]	Sep. 30, 2014 Mississippi Power [Member] Maximum [Member]	Jan. 31, 2013 Mississippi Power [Member] Maximum [Member]	Sep. 30, 2014 Gulf Power and Mississippi Power [Member]	Dec. 31, 2012 Gulf Power and Mississippi Power [Member]	May 20, 2014 Wind Farm [Member] Georgia Power [Member] MW	Jan. 10, 2014 Plant Mitchell Unit 3 [Member] Georgia Power [Member] MW	Feb. 28, 2013 Electricity Generation Plant, Non-Nuclear [Member] Mississippi Power [Member]	Dec. 31, 2012 Electricity Generation Plant, Non-Nuclear [Member] Mississippi Power [Member]	Sep. 30, 2014 Kemper IGCC [Member]	Mar. 31, 2014 Kemper IGCC [Member]	Sep. 30, 2013 Kemper IGCC [Member]	Sep. 30, 2014 Kemper IGCC [Member]	Sep. 30, 2013 Kemper IGCC [Member]	Dec. 31, 2013 Kemper IGCC [Member]	Aug. 01, 2014 Kemper IGCC [Member] Mississippi Power [Member]	Sep. 30, 2014 Kemper IGCC [Member] Mississippi Power [Member]	Mar. 31, 2014 Kemper IGCC [Member] Mississippi Power [Member]	Sep. 30, 2014 Kemper IGCC [Member] Mississippi Power [Member]		Dec. 31, 2013 Kemper IGCC [Member] Mississippi Power [Member]	Dec. 31, 2012 Kemper IGCC [Member] Mississippi Power [Member]	Sep. 30, 2014 Kemper IGCC [Member] Mississippi Power [Member]	Aug. 09, 2014 Kemper IGCC [Member] Mississippi Power [Member]	Sep. 30, 2013 Kemper IGCC [Member] Mississippi Power [Member] MW	Sep. 30, 2014 Kemper IGCC [Member] Mississippi Power [Member] Minimum [Member]	Sep. 30, 2014 Kemper IGCC [Member] Mississippi Power [Member] Maximum [Member]	Dec. 31, 2010 Mine [Member] Mississippi Power [Member]	Aug. 01, 2014 Plant Watson Units 4 And 5 [Member] Mississippi Power [Member] MW	Sep. 30, 2014 Plant Greene County Units 1 And 2 [Member] Mississippi Power [Member]	Aug. 01, 2014 Plant Greene County Units 1 And 2 [Member] Mississippi Power [Member] MW	Aug. 01, 2014 Plant Sweatt Units 1 And 2 [Member] Mississippi Power [Member] MW	Sep. 30, 2014 Other deferred charges and assets [Member] Georgia Power [Member]	Dec. 31, 2013 Current Liabilities And Other Deferred Credits And Liabilities [Member] Georgia Power [Member]	Sep. 30, 2014 Construction in Progress [Member] Mississippi Power [Member]	Sep. 30, 2014 Storm Reserve [Member] Georgia Power [Member]	Dec. 31, 2013 Storm Reserve [Member] Georgia Power [Member]	Oct. 31, 2014 Subsequent Event [Member] Georgia Power [Member]	Oct. 03, 2014 Subsequent Event [Member] Georgia Power [Member]	Oct. 22, 2014 Subsequent Event [Member] Gulf Power [Member]	Oct. 17, 2014 Subsequent Event [Member] Mississippi Power [Member]	Oct. 09, 2014 Subsequent Event [Member] Mississippi Power [Member]	Nov. 06, 2014 Subsequent Event [Member] Mississippi Power [Member]	Oct. 06, 2014 Subsequent Event [Member] Kemper IGCC [Member] Mississippi Power [Member]	Oct. 06, 2014 Subsequent Event [Member] Kemper IGCC [Member] Mississippi Power [Member]	Dec. 31, 2013 Non-Affiliate Capital Lease PPA [Member] Georgia Power [Member]	Sep. 30, 2014 Non-Affiliate Operating Lease PPA [Member] Georgia Power [Member]	Sep. 30, 2014 Current Estimate [Member] Kemper IGCC [Member] Mississippi Power [Member]
Contingencies and Regulatory Matters (Textual) [Abstract]
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
Environmental remediation liability								19,000,000		19,000,000									49,500,000		49,500,000							600,000		600,000
Civil penalties per day violation rate								37,500		37,500
Number of times of punitive damages in comparison to cost incurred by Environmental Protection Agency								3		3
Damages awarded				17,000,000						27,000,000
Increase in base rate under cost based electric tariff due to settlement																									10,100,000
Traditional Base Tariffs																																																																													107,000,000
Environmental Compliance Cost Recovery Tariff																																																																													32,000,000
Demand-Side Management Tariffs																																																																													3,000,000
Municipal Franchise Fee Tariff																																																																													3,000,000
Number Of Wind PPAs							2
Number Of Wind Farms							2
Electric Generating Units, Capacity (in MW's)																																												250	155																		75				750		200	80
Capital Leases, Future Minimum Payments Due																																																																																				641,000,000
Increase In Operating Leases Future Minimum Payments Due								103,000,000		103,000,000
Operating Leases, Future Minimum Payments, Due in 2015																																																																																					113,000,000
Operating Leases, Future Minimum Payments, Due in 2016																																																																																					117,000,000
Operating Leases, Future Minimum Payments, Due in 2017																																																																																					145,000,000
Operating Leases, Future Minimum Payments, Due in 2018																																																																																					150,000,000
Operating Leases, Future Minimum Payments, Due in 2019 and Thereafter																																																																																					1,700,000,000
Over recovered fuel cost balance																																																																							175,000,000	58,000,000
Regulatory Assets																																																							104,300,000		104,300,000				104,300,000							5,500,000						105,000,000	37,000,000
Projected Balance Of Regulatory Assets																																																							180,000,000		180,000,000				180,000,000
Proportionate share owed in consortium agreement										45.70%
Increase In NCCR Tariff													60,000,000	50,000,000	35,000,000	223,000,000																																																												27,000,000
Amortization to earnings of financing costs capitalized over the five year period								91,000,000		91,000,000
Amortization to earnings of financing costs capitalized, amortization term										5 years
Costs included in CWIP								23,000,000		23,000,000
Increase (decrease) in projected certified construction capital costs										5.00%
Estimated In-service Capital Cost																	4,400,000,000	4,800,000,000
Cost incurred on plant including regulatory filing costs								2,000,000,000		2,000,000,000
Construction Capital Costs												2,600,000,000
Approval Of All Costs By The PSC						200,000,000
Reduction in projected in-service cost due to recovered cost										425,000,000
Reduction In Depreciation Expense																					62,500,000
Reduction In Depreciation Expense Year One																					5,400,000
Number Of Regulatory Clauses																					4
Annual Retail Revenues																																																																														41,200,000	6,700,000
Projected Fuel Cost Over Or Under Recovery Threshold As Percentage Of Projected Fuel Revenue																					10.00%
Under recovered regulatory clause revenues																			41,300,000		41,300,000							13,100,000		13,100,000
Psc Approved Annual Property Damage Reserve Accrual																																				3,300,000
Ownership percentage in scrubber project																							50.00%										50.00%
Estimated cost of scrubber project																																	330,000,000										660,000,000
Scrubber project expenditures amount																												236,300,000		236,300,000												464,100,000
Allowance For Funds Used During Construction Cost																														16,100,000
Over Recovered Fuel Cost																																14,500,000
Percentage Of PSC Retail Rate Increase																																			0.38%
PSC Retail Rate Increase																																			3,600,000
Estimated Cost																																															2,400,000,000										4,060,000,000	[1]		2,880,000,000																										4,860,000,000	[1]
Costs associated with CCP12 grant funds																																	245,300,000
Costs included in CWIP								23,000,000		23,000,000
Loss Contingency, Estimate of Possible Loss																																																																									1,980,000,000
Cost deferred in other regulatory assets																												104,300,000		104,300,000
Other deferred charges and assets																												3,900,000		3,900,000
Previously expensed																												1,100,000		1,100,000
Pre-tax charge to income																																																418,000,000	380,000,000	150,000,000	798,000,000	1,140,000,000	1,180,000,000		418,000,000	380,000,000			1,180,000,000
After tax charge to income																																																258,100,000	234,700,000	92,600,000	492,800,000	704,000,000	728,700,000		258,100,000	234,700,000			728,700,000
Costs Due To Extension Of In-service Date																																							20,000,000	30,000,000
Period Rate Plan For Cost Accrued Through Additional Prudence Review																																	7 years
Maximum Cap Construction Cost																																																									4,970,000,000	[1],[2]																												6,100,000,000	[1],[2]
Alternate Financing																																														1,000,000,000
Settlement Agreement To Increase Rates																																									172,000,000
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 For Plant Construction																																																									121,900,000				220,000,000
Retail Revenues		1,512,000,000	1,438,000,000	4,058,000,000	3,800,000,000			2,452,000,000	2,314,000,000	6,502,000,000	5,922,000,000								365,971,000	335,916,000	979,435,000	901,343,000						228,331,000	230,710,000	646,695,000	613,274,000																										16,800,000				27,100,000
Reduced percentage interest transferred under asset purchase agreement																																	15.00%
Revenue Requirement Obligations																																																																130,000,000	160,000,000
Revisions To Revenue Requirement																																							60,000,000	70,000,000
Amortization Period For Construction Project																														40 years
Term of Management Fee Contract																																																																		40 years
Percentage of Carbon Dioxide Captured from Project																												70.00%		70.00%
Percentage of Contract to Purchase Carbon Dioxide from Project																												30.00%		30.00%
Purchase of Interest																																	17.50%					17.50%																																													15.00%
Capacity Revenues Under Power Supply Agreement																																17,500,000
Deposit received																																	150,000,000				75,000,000
Maximum period of discretion in the event senior unsecured credit rating falls																														15 days
Acquisition Period For SMEPA																																																																																		180 days
Interest Bearing Refundable Deposit Related to Asset Sale																										75,000,000				75,000,000	0																																																	50,000,000	50,000,000
Internal Revenue Code Section Forty Eight Tax Credits Phase I I																														279,000,000
Tax Credit Carryforward, Amount																												276,400,000		276,400,000
Tax Credit Carryforward, Utilized																												140,000,000		140,000,000
Minimum percentage of carbon dioxide that must be capture and sequester to remain eligible for the phase II tax credits																														65.00%
Additional Bonus Depreciation For Property Acquired Future Periods																																50.00%
Positive Impact From Bonus Depreciation																																																														100,000,000
Period Of Refraining From Intervening In Regulatory Proceedings																																																						3 years
Grant For Energy Efficiency And Renewable Program																																		15,000,000
Period Of Grant For Energy Efficiency and Renewable Program																								15 years
Conservation Fund																																		2,000,000
Funds Paid Towards Energy Efficiency And Renewable Program																												$ 7,000,000

[1] The 2012 MPSC CPCN Order approved a construction cost cap of up to $2.88 billion, net of the DOE Grants and excluding the Cost Cap Exceptions. The Current Estimate and Actual Costs include non-incremental operating and maintenance costs related to the combined cycle and associated common facilities placed in service in August 2014 that are subject to the $2.88 billion cost cap.

[2] Amounts in the Current Estimate reflect costs through March 31, 2016.