Contingencies and Regulatory Matters - Narrative (Details)																1 Months Ended							3 Months Ended			6 Months Ended				12 Months Ended					18 Months Ended	28 Months Ended
		Aug. 05, 2015 MW	Jul. 10, 2015 USD ($)	Jun. 30, 2015 USD ($) mi	Jun. 25, 2015 USD ($)	Jun. 03, 2015 USD ($)	May. 15, 2015 USD ($)	Apr. 16, 2015 USD ($) MW	Apr. 01, 2015 USD ($)	Mar. 10, 2015 USD ($)	Feb. 27, 2015 USD ($)	Feb. 25, 2015 USD ($)	Jan. 29, 2015	Jan. 01, 2014 USD ($)	Mar. 19, 2013	Jun. 30, 2015 USD ($) mi	May. 31, 2015 USD ($)	Apr. 30, 2015 MW	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Feb. 28, 2013 USD ($)	Jan. 31, 2013 USD ($)	Jun. 30, 2015 USD ($) mi	Mar. 31, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) clause mi MW		Dec. 31, 2014 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2010	Dec. 31, 2008 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($) mi	May. 20, 2015 USD ($)	Apr. 23, 2015 USD ($)	Feb. 02, 2015 USD ($)	Oct. 06, 2014
Loss Contingencies [Line Items]
Revenues																							$ 4,337,000,000		$ 4,467,000,000	$ 8,520,000,000			$ 9,111,000,000
Asset Retirement Obligation				$ 2,914,000,000												$ 2,914,000,000			$ 2,201,000,000				2,914,000,000			2,914,000,000		$ 2,201,000,000		$ 2,201,000,000						$ 2,914,000,000
Return Of Interest Bearing Refundable Deposits Related to Assets Sale Plus Accrued Interest						$ 301,000,000
Unrecognized Tax Benefits				398,000,000												398,000,000			170,000,000				398,000,000			398,000,000		170,000,000		170,000,000						398,000,000
Kemper IGCC [Member]
Loss Contingencies [Line Items]
Pre-tax charge to income																							23,000,000			32,000,000			380,000,000	868,000,000	$ 1,200,000,000
After tax charge to income																							14,000,000			20,000,000			235,000,000	536,000,000	729,000,000
Unrecognized Tax Benefits				390,000,000												390,000,000							390,000,000			390,000,000										390,000,000
Alabama Power [Member]
Loss Contingencies [Line Items]
Civil Penalties Payment Related to NSR					$ 100,000
Civil Penalties Required Investment In Electric Transportation Infrastructure Projects					$ 1,500,000
Period to Invest in Electric Transportation Infrastructure Projects					3 years
Claims Awarded to Companies Related to Nuclear Fuel Disposal Litigation																			26,000,000
Non-environmental Costs																										30,000,000
Recovery Of Non-environmental Costs																										50,000,000
Electric Generating Units, Capacity (in MW's) | MW																		12,200
Revenues																							1,455,000,000		1,437,000,000	2,856,000,000			2,945,000,000
Asset Retirement Obligation				1,252,000,000												1,252,000,000			829,000,000				1,252,000,000			1,252,000,000		829,000,000		829,000,000						1,252,000,000
Alabama Power [Member] | Plant Gorgas Units 6 and 7 [Member]
Loss Contingencies [Line Items]
Capacity Of Units Included In Request For Decertification Of Units (in MWs) | MW																		200
Alabama Power [Member] | Plant Barry Units 1 And 2 [Member]
Loss Contingencies [Line Items]
Capacity Of Units Included In Request For Decertification Of Units (in MWs) | MW																		250
Georgia Power [Member]
Loss Contingencies [Line Items]
Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation				40,000,000												40,000,000							40,000,000			40,000,000										40,000,000
Civil penalties per day violation rate				$ 37,500												$ 37,500							$ 37,500			$ 37,500										$ 37,500
Number of times of punitive damages in comparison to cost incurred by Environmental Protection Agency				3												3							3			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%
Increase (Decrease) In Projected Certified Construction Capital Costs																										5.00%
Delay Of Estimated In-service Date											18 months		18 months
Revenues																							$ 2,016,000,000		2,186,000,000	$ 3,994,000,000			4,455,000,000
Asset Retirement Obligation				$ 1,356,000,000												$ 1,356,000,000			1,255,000,000				1,356,000,000			1,356,000,000		1,255,000,000		1,255,000,000						$ 1,356,000,000
Georgia Power [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Estimated In-service Capital Cost																										4,400,000,000					4,400,000,000
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
Georgia Power [Member] | Other deferred charges and assets [Member]
Loss Contingencies [Line Items]
Fuel cost recovery balance				106,000,000												106,000,000			199,000,000				106,000,000			106,000,000		199,000,000		199,000,000						106,000,000
Georgia Power [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) | MW								1,266
Georgia Power [Member] | Plant Yates Units 1 through 5 [Member]
Loss Contingencies [Line Items]
Capacity Of Units Included In Request For Decertification Of Units (in MWs) | MW								579
Georgia Power [Member] | Plant McManus Units 1 and 2 [Member]
Loss Contingencies [Line Items]
Capacity Of Units Included In Request For Decertification Of Units (in MWs) | MW								122
Georgia Power [Member] | Plant Mitchell Unit 3 [Member]
Loss Contingencies [Line Items]
Electric Generating Units, Capacity (in MW's) | MW								155
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
Gulf Power [Member]
Loss Contingencies [Line Items]
Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation				47,000,000												47,000,000							47,000,000			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 | clause																										4
Ownership percentage in scrubber project																																50.00%
Revenues																							384,000,000		384,000,000	$ 741,000,000			791,000,000
Asset Retirement Obligation				92,000,000												92,000,000			17,000,000				92,000,000			92,000,000		17,000,000		17,000,000						92,000,000
Mississippi Power [Member]
Loss Contingencies [Line Items]
Environmental Exit Costs, Assets Previously Disposed, Liability for Remediation				300,000												300,000							300,000			300,000										300,000
AFUDC Cost									$ 11,000,000
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				308,000,000												308,000,000							308,000,000			308,000,000										308,000,000
Allowance For Funds Used During Construction Cost																										27,000,000
Revenues												$ 8,000,000											275,000,000		$ 311,000,000	552,000,000			642,000,000
Over Recovered Fuel Cost				$ 24,000,000												$ 24,000,000							$ 24,000,000			$ 24,000,000										$ 24,000,000
Under recovered regulatory clause revenues																			2,000,000									2,000,000		2,000,000
Percentage Of PSC Retail Rate Increase (Decrease)																																						(0.35%)
PSC Retail Rate Increase (Decrease)																																						$ (2,000,000)
Plant Capacity Under Coal Gasification Combined Cycle Technology (in MWs) | MW																										582
Co Two Pipeline Infrastructure (in miles) | mi				61												61							61			61										61
Costs associated with CCP12 grant funds																																$ 245,000,000
Other Property And Investments				$ 2,000,000												$ 2,000,000							$ 2,000,000			$ 2,000,000										$ 2,000,000
Lignite Mining Costs				58,000,000												58,000,000							58,000,000			58,000,000										58,000,000
Materials, Supplies, and Other				41,000,000												41,000,000							41,000,000			41,000,000										41,000,000
Cost deferred in other regulatory assets				198,000,000												198,000,000							198,000,000			198,000,000										198,000,000
Other deferred charges and assets				16,000,000												16,000,000							16,000,000			16,000,000										16,000,000
Asset Retirement Obligation				148,000,000												148,000,000			48,000,000				148,000,000			148,000,000		48,000,000		48,000,000						148,000,000
Previously expensed				$ 1,000,000												$ 1,000,000							$ 1,000,000			$ 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																																				331,000,000
Carrying Costs Associated With Retail Rate Recovery																																				$ 22,000,000
Percentage of Carbon Dioxide Captured from Project				70.00%												70.00%							70.00%			70.00%										70.00%
Percentage of Contract to Purchase Carbon Dioxide from Project				30.00%												30.00%							30.00%			30.00%										30.00%
Reduced percentage interest transferred under asset purchase agreement																																15.00%
Interest Bearing Refundable Deposit Related to Assets Sale				$ 0												$ 0			275,000,000				$ 0			$ 0		275,000,000		275,000,000						$ 0	$ 275,000,000
Issuance Of Promissory Note From Parent In Exchange For Repayment Of Interest-bearing Refundable Deposit And Accrued Interest						$ 301,000,000										$ 301,000,000										301,000,000			$ 0
Bank Loans Period Of Extension						18 months										18 months
Internal Revenue Code Section Forty Eight Tax Credits Phase I I																										279,000,000
Tax Credit Carryforward, Amount				276,000,000												$ 276,000,000							276,000,000			276,000,000										276,000,000
Tax Credit Carryforward Utilized				242,000,000												242,000,000							242,000,000			$ 242,000,000										242,000,000
Minimum percentage of carbon dioxide that must be capture and sequester to remain eligible for the phase II tax credits																										65.00%
Unrecognized Tax Benefits				390,000,000												390,000,000			$ 165,000,000				390,000,000			$ 390,000,000		$ 165,000,000		165,000,000						390,000,000
Mississippi Power [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Costs Due To Extension Of In-service Date																										25,000,000
Mississippi Power [Member] | Maximum [Member]
Loss Contingencies [Line Items]
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				2,080,000,000												2,080,000,000							2,080,000,000			2,080,000,000										2,080,000,000
Mississippi Power [Member] | Plant Watson Units 4 And 5 [Member]
Loss Contingencies [Line Items]
Net Book Value Of Units Included In Request For Decertification Of Units								$ 32,000,000
Mississippi Power [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
AFUDC Cost				(11,000,000)					$ 8,000,000
Estimated Cost																										4,510,000,000	[1]					$ 2,880,000,000
Asset Retirement Obligation				24,000,000												24,000,000							24,000,000			24,000,000										24,000,000
Pre-tax charge to income																							23,000,000	$ 9,000,000						868,000,000	1,100,000,000	78,000,000
After tax charge to income																							14,000,000	$ 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																										7,000,000
Purchase of Interest																																								15.00%
Maximum Cap Construction Cost	[1],[2]																									5,600,000,000
Regulatory Assets				198,000,000												198,000,000							198,000,000			198,000,000										198,000,000
Projected Balance Of Regulatory Assets				276,000,000												276,000,000							276,000,000			276,000,000										276,000,000
Unrecognized Tax Benefits				390,000,000												390,000,000							390,000,000			390,000,000										390,000,000
Mississippi Power [Member] | Kemper IGCC [Member] | Current Estimate [Member]
Loss Contingencies [Line Items]
Estimated Cost	[1]																									4,960,000,000
Maximum Cap Construction Cost	[1],[2]																									6,230,000,000
Mississippi Power [Member] | Kemper IGCC [Member] | Traditional Rate Case [Member]
Loss Contingencies [Line Items]
Increase Retail Rates In Year One							11.80%
Increase Retail Rates In Year Two							12.00%
PSC Retail Rate Increase (Decrease) in Year One							$ 114,000,000
PSC Retail Rate Increase (Decrease) in Year Two							$ 120,000,000
Mississippi Power [Member] | Kemper IGCC [Member] | Rate Mitigation Plan 2017 [Member]
Loss Contingencies [Line Items]
Increase Retail Rates In Year One							2.60%
Increase Retail Rates In Year Two							19.00%
PSC Retail Rate Increase (Decrease) in Year One							$ 25,000,000
PSC Retail Rate Increase (Decrease) in Year Two							$ 197,000,000
Mississippi Power [Member] | Kemper IGCC [Member] | Property, Plant and Equipment [Member]
Loss Contingencies [Line Items]
Estimated Cost																										3,420,000,000
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
Gulf Power and Mississippi Power [Member]
Loss Contingencies [Line Items]
Estimated cost of scrubber project																																$ 660,000,000
Scrubber project expenditures amount				$ 604,000,000												604,000,000							$ 604,000,000			$ 604,000,000										$ 604,000,000
Subsequent Event [Member] | Alabama Power [Member] | Plant Greene County Units 1 And 2 [Member]
Loss Contingencies [Line Items]
Capacity Of Units Included In Request For Decertification Of Units (in MWs) | MW		300
Subsequent Event [Member] | Alabama Power [Member] | Plant Barry Unit 3 [Member]
Loss Contingencies [Line Items]
Capacity Of Units Included In Request For Decertification Of Units (in MWs) | MW		225
Subsequent Event [Member] | Mississippi Power [Member] | Kemper IGCC [Member]
Loss Contingencies [Line Items]
Period Of Inaction By The Public Service Commission For Rate Case Review			120 days
Subsequent Event [Member] | Mississippi Power [Member] | Kemper IGCC [Member] | In-Service Asset Proposal [Member]
Loss Contingencies [Line Items]
PSC Retail Rate Increase (Decrease)			$ 159,000,000
Pending Litigation [Member] | Plant Vogtle Units 3 And 4 [Member] | Georgia Power [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Reduction in Projected in Service Cost due to Recovered Cost										$ 591,000,000																								$ 425,000,000
Damages In Connection With Counterclaim																$ 714,000,000	$ 118,000,000													$ 113,000,000

[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. The Current Estimate and Actual Costs include the 15% undivided interest in the Kemper IGCC that was previously projected to be purchased by SMEPA. On May 20, 2015, SMEPA notified Mississippi Power of its termination of the asset purchase agreement (APA) and requested the return of a total of $275 million of deposits, which was returned with accrued interest on June 3, 2015.

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