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Financing - Narrative (Details) $ / shares in Units, shares in Thousands			1 Months Ended			3 Months Ended	6 Months Ended
	Jul. 15, 2015 USD ($)	Jun. 03, 2015 USD ($)	Jun. 30, 2015 USD ($)	May. 31, 2015 USD ($) $ / shares shares	Apr. 30, 2015 USD ($) loan	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2015 USD ($)
Debt Instrument [Line Items]
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support			$ 1,900,000,000			$ 1,900,000,000	$ 1,900,000,000
Derivative, Notional Amount			2,000,000,000			2,000,000,000	2,000,000,000
Alabama Power [Member]
Debt Instrument [Line Items]
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support			810,000,000			810,000,000	810,000,000
Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support			200,000,000			200,000,000	200,000,000
Remarketing Revenue Bond						80,000,000
Repayments of Senior Debt							250,000,000	$ 0
Alabama Power [Member] \| Five Point Two Zero Percent Class A Preferred Stock [Member]
Debt Instrument [Line Items]
Temporary Equity, Shares Outstanding \| shares				6,480
Temporary Equity, Dividend Rate Percentage				0.052
Redemption price (in dollars per share) \| $ / shares				$ 25
Alabama Power [Member] \| Five Point Three Zero Percent Class A Preferred Stock [Member]
Debt Instrument [Line Items]
Temporary Equity, Shares Outstanding \| shares				4,000
Temporary Equity, Dividend Rate Percentage				0.053
Redemption price (in dollars per share) \| $ / shares				$ 25
Alabama Power [Member] \| Five Point Six Two Five Percent Preference Stock [Member]
Debt Instrument [Line Items]
Temporary Equity, Shares Outstanding \| shares				6,000
Temporary Equity, Dividend Rate Percentage				0.05625
Redemption price (in dollars per share) \| $ / shares				$ 25
Alabama Power [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Redemption Amount Of Principal Notes									$ 250,000,000
Alabama Power [Member] \| Series DD [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage									5.65%
Alabama Power [Member] \| Series 2015A [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 175,000,000				$ 550,000,000
Debt Instrument, Interest Rate, Stated Percentage					3.75%				3.75%
Alabama Power [Member] \| Series 2007B [Member]
Debt Instrument [Line Items]
Remarketing Revenue Bond					$ 80,000,000
Alabama Power [Member] \| Series 2015B [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 250,000,000
Debt Instrument, Interest Rate, Stated Percentage					2.80%
Alabama Power [Member] \| Aggregate Stated Capital [Member] \| Five Point Two Zero Percent Class A Preferred Stock [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 162,000,000
Alabama Power [Member] \| Aggregate Stated Capital [Member] \| Five Point Three Zero Percent Class A Preferred Stock [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				100,000,000
Alabama Power [Member] \| Aggregate Stated Capital [Member] \| Five Point Six Two Five Percent Preference Stock [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				150,000,000
Georgia Power [Member]
Debt Instrument [Line Items]
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support			970,000,000			970,000,000	970,000,000
Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support			122,000,000			122,000,000	122,000,000
Line of Credit Facility, Current Borrowing Capacity			600,000,000			600,000,000	$ 600,000,000
Period Of Amortization Of Gain (Loss) On Settlement Of Derivatives							10 years
Repayments of Senior Debt							$ 125,000,000	0
Georgia Power [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Gain (Loss) on Settlement Of Derivatives			(6,000,000)			(6,000,000)	(6,000,000)
Georgia Power [Member] \| Maturity Date May 2025 [Member] \| Cash Flow Hedges Of Forecasted Debt [Member] \| Interest Rate Swap [Member]
Debt Instrument [Line Items]
Derivative, Notional Amount			$ 350,000,000			$ 350,000,000	350,000,000
Georgia Power [Member] \| Second Series 2008 [Member]
Debt Instrument [Line Items]
Long-term Pollution Control Bond					$ 65,000,000
Georgia Power [Member] \| Debt Held Since 2013 [Member]
Debt Instrument [Line Items]
Remarketing Revenue Bond				104,600,000			$ 104,600,000
Georgia Power [Member] \| Debt Due Two Thousand Forty Four [Member] \| Line of Credit [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			3.283%			3.283%	3.283%
Gulf Power [Member]
Debt Instrument [Line Items]
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support			$ 69,000,000			$ 69,000,000	$ 69,000,000
Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support			46,000,000			46,000,000	46,000,000
Mississippi Power [Member]
Debt Instrument [Line Items]
Amount of Variable Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support			$ 40,000,000			40,000,000	40,000,000
Number Of Floating Rate Bank Loans \| loan					3
Aggregate Principal Amount Of Floating Rate Bank Loan					$ 475,000,000
Debt Instrument, Description of Variable Rate Basis			one-month LIBOR		one-month LIBOR
Repayment Aggregate Principal Amount Of Floating Rate Bank Loan					$ 275,000,000
Bank Loans Period Of Extension		18 months	18 months
Promissory Note		$ 301,000,000	$ 301,000,000				301,000,000	$ 0
Mississippi Power [Member] \| Maturity April First Two Thousand Sixteen [Member]
Debt Instrument [Line Items]
Number Of Floating Rate Bank Loans \| loan					2
Aggregate Principal Amount Of Floating Rate Bank Loan					$ 425,000,000
Traditional Operating Companies [Member]
Debt Instrument [Line Items]
Amount of Fixed Rate Pollution Control Revenue Bonds Outstanding Requiring Liquidity Support			368,000,000			368,000,000	368,000,000
Southern Company [Member] \| Series 2015A [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 600,000,000			$ 600,000,000	$ 600,000,000
Debt Instrument, Interest Rate, Stated Percentage			2.75%			2.75%	2.75%
Southern Power [Member] \| Series 2015A [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 350,000,000
Debt Instrument, Interest Rate, Stated Percentage				1.50%
Southern Power [Member] \| Series 2015B [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 300,000,000
Debt Instrument, Interest Rate, Stated Percentage				2.375%
Subsequent Event [Member] \| Southern Power [Member] \| Series Two Thousand Three [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.875%
Repayments of Senior Debt	$ 525,000,000