Derivatives (Details 3) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 143
Fair value of derivative liabilities with contingent features
Derivative liabilities	10
Alabama Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	51
Fair value of derivative liabilities with contingent features
Derivative liabilities	2
Georgia Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	46
Fair value of derivative liabilities with contingent features
Derivative liabilities	4
Gulf Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	24
Fair value of derivative liabilities with contingent features
Derivative liabilities	2
Mississippi Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	20
Fair value of derivative liabilities with contingent features
Derivative liabilities	2
Southern Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	2
Fair value of derivative liabilities with contingent features
Derivative liabilities	0
Hedging Instruments for Regulatory Purposes [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	109
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	19
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	46
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	24
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	20
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	71
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	14
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	31
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	13
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	13
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Other deferred credits and liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	38
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Other deferred credits and liabilities [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	5
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Other deferred credits and liabilities [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	15
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Other deferred credits and liabilities [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	11
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Other deferred credits and liabilities [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	7
Cash Flow and Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	33
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	32
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	1
Cash Flow and Fair Value Hedging [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	1
Cash Flow and Fair Value Hedging [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Cash Flow and Fair Value Hedging [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Cash Flow and Fair Value Hedging [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Cash Flow and Fair Value Hedging [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Cash Flow and Fair Value Hedging [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	1
Cash Flow and Fair Value Hedging [Member] | Interest Rate Contract [Member] | Liabilities from risk management activities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	32
Cash Flow and Fair Value Hedging [Member] | Interest Rate Contract [Member] | Liabilities from risk management activities [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	32
Cash Flow and Fair Value Hedging [Member] | Interest Rate Contract [Member] | Liabilities from risk management activities [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Cash Flow and Fair Value Hedging [Member] | Interest Rate Contract [Member] | Liabilities from risk management activities [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Cash Flow and Fair Value Hedging [Member] | Interest Rate Contract [Member] | Liabilities from risk management activities [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Cash Flow and Fair Value Hedging [Member] | Interest Rate Contract [Member] | Liabilities from risk management activities [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Not Designated as Hedging Instrument [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	1
Not Designated as Hedging Instrument [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Not Designated as Hedging Instrument [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Not Designated as Hedging Instrument [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Not Designated as Hedging Instrument [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	0
Not Designated as Hedging Instrument [Member] | Energy-related derivatives [Member] | Liabilities from risk management activities [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 1