Contingencies and Regulatory Matters - Narrative (Details) (USD $)	3 Months Ended			12 Months Ended		0 Months Ended			1 Months Ended	6 Months Ended	12 Months Ended	18 Months Ended	1 Months Ended	0 Months Ended	1 Months Ended	0 Months Ended	1 Months Ended		12 Months Ended	25 Months Ended	0 Months Ended	1 Months Ended		12 Months Ended
	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	May 07, 2015	Feb. 27, 2015	Jan. 29, 2015	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2008	Jun. 30, 2014	May 31, 2014	Apr. 16, 2015 MW	Dec. 31, 2013	Feb. 25, 2015	Oct. 31, 2014	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2015 mi	Oct. 06, 2014	Feb. 28, 2013	Jan. 31, 2013	Dec. 31, 2010	Feb. 02, 2015	Jan. 31, 2014	Apr. 23, 2015
Loss Contingencies [Line Items]
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
Revenues	4,183,000,000		4,644,000,000
Minimum [Member]
Loss Contingencies [Line Items]
Asset Retirement Obligation	525,000,000																			525,000,000
Maximum [Member]
Loss Contingencies [Line Items]
Asset Retirement Obligation	575,000,000																			575,000,000
Kemper IGCC [Member]
Loss Contingencies [Line Items]
Pre-tax charge to income	9,000,000		380,000,000	868,000,000	1,200,000,000
After tax charge to income	6,000,000		235,000,000	536,000,000	729,000,000
Unrecognized Tax Benefits	211,000,000																			211,000,000
Subsequent Event [Member]
Loss Contingencies [Line Items]
Period To Meet Market-based Rate Standards						60 days
Georgia Power [Member]
Loss Contingencies [Line Items]
Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation	27,000,000																			27,000,000
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
Claims Awarded to Companies Related to Nuclear Fuel Disposal Litigation									18,000,000
Additional Construction Capital Costs										200,000,000		2,800,000,000
Percentage of Proportionate Share Owed in Consortium Agreement	45.70%
Reduction in projected in-service cost due to recovered cost											425,000,000
Increase (Decrease) In Projected Certified Construction Capital Costs	5.00%
Delay Of Estimated In-service Date							18 months	18 months
Revenues	1,978,000,000		2,269,000,000
Georgia Power [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Damages In Connection With Counterclaim													113,000,000
Estimated In-service Capital Cost	4,400,000,000				4,400,000,000
Asset Retirement Obligation	10,000,000																			10,000,000
Georgia Power [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Additional Construction Capital Costs											114,000,000
Estimated In-service Capital Cost					4,800,000,000
Asset Retirement Obligation	20,000,000																			20,000,000
Georgia Power [Member] | Other deferred charges and assets [Member]
Loss Contingencies [Line Items]
Fuel cost recovery balance	151,000,000			199,000,000					199,000,000	199,000,000										151,000,000
Georgia Power [Member] | Plant Vogtle Units 3 And 4 [Member]
Loss Contingencies [Line Items]
Estimated In-service Capital Cost							5,000,000,000
Monthly Operational Readiness Costs							10,000,000
Monthly Financing Costs	30,000,000
Construction Financing Costs	2,500,000,000
Georgia Power [Member] | Subsequent Event [Member] | Plant Branch Units 1 and 3 and 4 [Member]
Loss Contingencies [Line Items]
Capacity Of Units Included In Request For Decertification Of Units (in MWs)														1,266
Georgia Power [Member] | Subsequent Event [Member] | Plant Yates Units 1 through 5 [Member]
Loss Contingencies [Line Items]
Capacity Of Units Included In Request For Decertification Of Units (in MWs)														579
Georgia Power [Member] | Subsequent Event [Member] | Plant McManus Units 1 and 2 [Member]
Loss Contingencies [Line Items]
Capacity Of Units Included In Request For Decertification Of Units (in MWs)														122
Georgia Power [Member] | Subsequent Event [Member] | Plant Mitchell Unit 3 [Member]
Loss Contingencies [Line Items]
Electric Generating Units, Capacity (in MW's)														155
Gulf Power [Member]
Loss Contingencies [Line Items]
Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation	47,000,000																			47,000,000
Reduction In Depreciation Expense															62,500,000
Reduction In Depreciation Expense Year One	19,600,000
Number Of Regulatory Clauses	4
Ownership percentage in scrubber project																			50.00%
Revenues	357,000,000		407,000,000
Gulf Power [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Asset Retirement Obligation	70,000,000																			70,000,000
Gulf Power [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Asset Retirement Obligation	80,000,000																			80,000,000
Mississippi Power [Member]
Loss Contingencies [Line Items]
Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation	500,000																			500,000
Psc Approved Annual Property Damage Reserve Accrual																									3,000,000
Ownership percentage in scrubber project																			50.00%
Estimated cost of scrubber project																			330,000,000
Scrubber project expenditures amount	290,000,000																			290,000,000
Allowance For Funds Used During Construction Cost	22,000,000
Revenues	276,000,000		331,000,000													8,000,000
Over Recovered Fuel Cost	15,000,000																			15,000,000
Under recovered regulatory clause revenues				2,000,000					2,000,000	2,000,000
Plant Capacity Under Coal Gasification Combined Cycle Technology (in MWs)	582
Co Two Pipeline Infrastructure (in miles)	61																			61
Costs associated with CCP12 grant funds																			245,000,000
Other Property And Investments	2,000,000																			2,000,000
Lignite Mining Costs	52,000,000																			52,000,000
Materials, Supplies, and Other	35,000,000																			35,000,000
Cost deferred in other regulatory assets	174,000,000																			174,000,000
Other deferred charges and assets	12,000,000																			12,000,000
Previously expensed	1,000,000																			1,000,000
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
Retail Rate Recovery																				294,000,000
Reduced percentage interest transferred under asset purchase agreement																		15.00%	15.00%
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%
Capacity Revenues Under Power Supply Agreement	4,000,000			17,000,000
Deposit received																			150,000,000							75,000,000
Interest Bearing Refundable Deposit Related to Asset Sale	0		75,000,000														50,000,000
Maximum period of discretion in the event senior unsecured credit rating falls	15 days
Internal Revenue Code Section Forty Eight Tax Credits Phase I I	279,000,000
Tax Credit Carryforward, Amount	276,000,000																			276,000,000
Tax Credit Carryforward Utilized	207,000,000																			207,000,000
Minimum percentage of carbon dioxide that must be capture and sequester to remain eligible for the phase II tax credits	65.00%
Mississippi Power [Member] | Mirror Construction Work In Progress [Member]
Loss Contingencies [Line Items]
Net Regulatory Assets	(311,000,000)																			(311,000,000)
Mississippi Power [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Asset Retirement Obligation	75,000,000																			75,000,000
Costs Due To Extension Of In-service Date	25,000,000
Mississippi Power [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Asset Retirement Obligation	85,000,000																			85,000,000
Costs Due To Extension Of In-service Date	30,000,000
Mississippi Power [Member] | Construction in Progress [Member]
Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss	2,060,000,000																			2,060,000,000
Mississippi Power [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Electric Generating Units, Capacity (in MW's)																		75
Estimated Cost	4,370,000,000	[1]																	2,880,000,000
Asset Retirement Obligation	24,000,000																			24,000,000
Pre-tax charge to income	9,000,000			868,000,000	1,100,000,000														78,000,000
After tax charge to income	6,000,000			536,000,000	681,000,000														48,000,000
Monthly Charge Of Allowance For Equity Funds Used During Construction	13,000,000
Monthly Cost Regulatory Assets Deferred	6,000,000
Regulatory Liabilities For Plant Construction																				294,000,000
Maximum Cap Construction Cost	5,400,000,000	[1],[2]
Regulatory Assets	174,000,000																			174,000,000
Projected Balance Of Regulatory Assets	266,000,000																			266,000,000
Purchase of Interest																					15.00%
Acquisition Period For SMEPA																					180 days
Unrecognized Tax Benefits	211,000,000																			211,000,000
Mississippi Power [Member] | Kemper IGCC [Member] | Current Estimate [Member]
Loss Contingencies [Line Items]
Estimated Cost	4,940,000,000	[1]
Maximum Cap Construction Cost	6,220,000,000	[1],[2]
Mississippi Power [Member] | Kemper IGCC [Member] | Property, Plant and Equipment [Member]
Loss Contingencies [Line Items]
Estimated Cost	3,270,000,000
Mississippi Power [Member] | Electricity Generation Plant, Non-Nuclear [Member]
Loss Contingencies [Line Items]
Estimated Cost																							2,400,000,000
Alternate Financing																						1,000,000,000
Mississippi Power [Member] | Mine [Member]
Loss Contingencies [Line Items]
Term of Management Fee Contract																								40 years
Mississippi Power [Member] | Subsequent Event [Member]
Loss Contingencies [Line Items]
AFUDC Cost						12,000,000
Percentage Of PSC Retail Rate Increase (Decrease)																											(0.35%)
PSC Retail Rate Increase (Decrease)																											(2,000,000)
Mississippi Power [Member] | Subsequent Event [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
AFUDC Cost						9,000,000
Alabama Power [Member]
Loss Contingencies [Line Items]
Claims Awarded to Companies Related to Nuclear Fuel Disposal Litigation									26,000,000
Non-environmental Costs	14,000,000
Recovery Of Non-environmental Costs	50,000,000
Revenues	1,401,000,000		1,508,000,000
Alabama Power [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Asset Retirement Obligation	330,000,000																			330,000,000
Alabama Power [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Asset Retirement Obligation	350,000,000																			350,000,000
Gulf Power and Mississippi Power [Member]
Loss Contingencies [Line Items]
Estimated cost of scrubber project																			660,000,000
Scrubber project expenditures amount	$ 570,000,000																			$ 570,000,000

[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 and exclude post-in-service costs for the lignite mine. See "Rate Recovery of Kemper IGCC Costs – 2013 MPSC Rate Order" for additional information.

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