Derivatives (Details 1) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	$ 61
Energy-related derivatives [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(63)
Energy-related derivatives [Member] | Other deferred credits and liabilities [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	0	[1]
Energy-related derivatives [Member] | Other regulatory assets, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(71)
Energy-related derivatives [Member] | Other regulatory assets, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(38)
Energy-related derivatives [Member] | Other regulatory liabilities, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	17
Energy-related derivatives [Member] | Other regulatory liabilities, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	29
Alabama Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	11
Alabama Power [Member] | Energy-related derivatives [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(8)
Alabama Power [Member] | Energy-related derivatives [Member] | Other deferred credits and liabilities [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	0	[1]
Alabama Power [Member] | Energy-related derivatives [Member] | Other regulatory assets, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(14)
Alabama Power [Member] | Energy-related derivatives [Member] | Other regulatory assets, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(5)
Alabama Power [Member] | Energy-related derivatives [Member] | Other regulatory liabilities, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	3
Alabama Power [Member] | Energy-related derivatives [Member] | Other regulatory liabilities, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	8
Georgia Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	19
Georgia Power [Member] | Energy-related derivatives [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(27)
Georgia Power [Member] | Energy-related derivatives [Member] | Other deferred credits and liabilities [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	10	[1]
Georgia Power [Member] | Energy-related derivatives [Member] | Other regulatory assets, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(31)
Georgia Power [Member] | Energy-related derivatives [Member] | Other regulatory assets, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(15)
Georgia Power [Member] | Energy-related derivatives [Member] | Other regulatory liabilities, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	9
Georgia Power [Member] | Energy-related derivatives [Member] | Other regulatory liabilities, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	0
Gulf Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	11
Gulf Power [Member] | Energy-related derivatives [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(13)
Gulf Power [Member] | Energy-related derivatives [Member] | Other deferred credits and liabilities [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	0	[1]
Gulf Power [Member] | Energy-related derivatives [Member] | Other regulatory assets, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(13)
Gulf Power [Member] | Energy-related derivatives [Member] | Other regulatory assets, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(11)
Gulf Power [Member] | Energy-related derivatives [Member] | Other regulatory liabilities, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	4
Gulf Power [Member] | Energy-related derivatives [Member] | Other regulatory liabilities, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	7
Mississippi Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	5
Mississippi Power [Member] | Energy-related derivatives [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(15)
Mississippi Power [Member] | Energy-related derivatives [Member] | Other deferred credits and liabilities [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	0	[1]
Mississippi Power [Member] | Energy-related derivatives [Member] | Other regulatory assets, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(13)
Mississippi Power [Member] | Energy-related derivatives [Member] | Other regulatory assets, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	(7)
Mississippi Power [Member] | Energy-related derivatives [Member] | Other regulatory liabilities, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	1
Mississippi Power [Member] | Energy-related derivatives [Member] | Other regulatory liabilities, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory hedge unrealized gain (loss) recognized on balance sheet	4
Southern Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	2
Cash Flow and Fair Value Hedging [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	13
Cash Flow and Fair Value Hedging [Member] | Interest rate derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	6
Cash Flow and Fair Value Hedging [Member] | Interest rate derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	7
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member] | Interest rate derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member] | Interest rate derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member] | Interest rate derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member] | Interest rate derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member] | Interest rate derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member] | Interest rate derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member] | Interest rate derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member] | Interest rate derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member] | Interest rate derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member] | Interest rate derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Hedging Instruments for Regulatory Purposes [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	46
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	17
Hedging Instruments for Regulatory Purposes [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	29
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	11
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member] | Energy-related derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	3
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	8
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	19
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member] | Energy-related derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	9
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	10
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	11
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member] | Energy-related derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	4
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	7
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	5
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member] | Energy-related derivatives [Member] | Other Current Assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	1
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	4
Not Designated as Hedging Instrument [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	2
Not Designated as Hedging Instrument [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	1
Not Designated as Hedging Instrument [Member] | Energy-related derivatives [Member] | Assets From Risk Management Activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	1
Not Designated as Hedging Instrument [Member] | Alabama Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Alabama Power [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Alabama Power [Member] | Energy-related derivatives [Member] | Assets From Risk Management Activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Georgia Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Georgia Power [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Georgia Power [Member] | Energy-related derivatives [Member] | Assets From Risk Management Activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Gulf Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Gulf Power [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Gulf Power [Member] | Energy-related derivatives [Member] | Assets From Risk Management Activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Mississippi Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Mississippi Power [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Mississippi Power [Member] | Energy-related derivatives [Member] | Assets From Risk Management Activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0
Not Designated as Hedging Instrument [Member] | Southern Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	2
Not Designated as Hedging Instrument [Member] | Southern Power [Member] | Energy-related derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	1
Not Designated as Hedging Instrument [Member] | Southern Power [Member] | Energy-related derivatives [Member] | Assets From Risk Management Activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	$ 1

[1] Georgia Power includes Other regulatory liabilities, deferred in Other deferred credits and liabilities.