Derivatives - Financial Statement Presentation (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	$ 36,000	$ 29,000
Liability Derivatives	111,000	281,000
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(109,000)	(235,000)
Regulatory Hedge Unrealized Gain	23,000	14,000
Energy Related Derivative [Member] | Other regulatory assets, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(74,000)	(163,000)
Energy Related Derivative [Member] | Other regulatory assets, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(35,000)	(72,000)
Energy Related Derivative [Member] | Other regulatory liabilities, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	10,000	9,000
Energy Related Derivative [Member] | Other regulatory liabilities, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	13,000	5,000
Designated as hedging instruments in cash flow and fair value hedges [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	10,000	13,000
Liability Derivatives	0	35,000
Designated as hedging instruments in cash flow and fair value hedges [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Designated as hedging instruments in cash flow and fair value hedges [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	1,000
Designated as hedging instruments in cash flow and fair value hedges [Member] | Interest rate derivatives [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	7,000	6,000
Designated as hedging instruments in cash flow and fair value hedges [Member] | Interest rate derivatives [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	33,000
Designated as hedging instruments in cash flow and fair value hedges [Member] | Interest rate derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	3,000	7,000
Designated as hedging instruments in cash flow and fair value hedges [Member] | Interest rate derivatives [Member] | Other deferred credits and liabilities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	0
Designated as hedging instruments in cash flow and fair value hedges [Member] | Foreign currency derivatives [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Designated as hedging instruments in cash flow and fair value hedges [Member] | Foreign currency derivatives [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	1,000
Hedging Instruments for Regulatory Purposes [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	23,000	14,000
Liability Derivatives	109,000	235,000
Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	10,000	9,000
Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	74,000	163,000
Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	13,000	5,000
Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	35,000	72,000
Not designated as hedging instruments [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	3,000	2,000
Liability Derivatives	2,000	11,000
Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	1,000	0
Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	1,000	9,000
Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	2,000	0
Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	1,000	0
Not designated as hedging instruments [Member] | Foreign currency derivatives [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	2,000
Not designated as hedging instruments [Member] | Foreign currency derivatives [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	2,000
Southern Power [Member] | Energy Related Derivative [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	2,100	600
Liability Derivatives	1,300	9,800
Southern Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Energy Related Derivative [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Liability Derivatives	0	800
Southern Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Energy Related Derivative [Member] | Assets from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Southern Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	800
Southern Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Southern Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	0
Southern Power [Member] | Not designated as hedging instruments [Member] | Energy Related Derivative [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	2,100	600
Liability Derivatives	1,300	9,000
Southern Power [Member] | Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Assets from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	400	200
Southern Power [Member] | Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	700	8,800
Southern Power [Member] | Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	1,700	400
Southern Power [Member] | Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	600	200
Mississippi Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	2,519	1,688
Liability Derivatives	19,483	68,870
Mississippi Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	19
Liability Derivatives	37	15,879
Mississippi Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Mississippi Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	0
Mississippi Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Interest rate derivatives [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Mississippi Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Interest rate derivatives [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	15,208
Mississippi Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Foreign currency derivatives [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	19
Mississippi Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Foreign currency derivatives [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	625
Mississippi Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Foreign currency derivatives [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Mississippi Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Foreign currency derivatives [Member] | Other deferred credits and liabilities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	37	46
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	2,519	162
Liability Derivatives	19,446	51,152
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(19,446)	(51,152)
Regulatory Hedge Unrealized Gain	2,519	162
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	638	125
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	13,116	36,455
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	1,881	37
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	6,330	14,697
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory assets, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(13,116)	(36,455)
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory assets, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(6,330)	(14,697)
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory liabilities, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	638	125
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory liabilities, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	1,881	37
Mississippi Power [Member] | Not designated as hedging instruments [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	1,507
Liability Derivatives	0	1,839
Mississippi Power [Member] | Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Mississippi Power [Member] | Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	0
Mississippi Power [Member] | Not designated as hedging instruments [Member] | Foreign currency derivatives [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	1,507
Mississippi Power [Member] | Not designated as hedging instruments [Member] | Foreign currency derivatives [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	1,839
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	4,358	198
Liability Derivatives	27,112	40,983
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(27,112)	(40,983)
Regulatory Hedge Unrealized Gain	4,358	198
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	1,293	154
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	16,529	22,786
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	3,065	44
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	10,583	18,197
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory assets, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(16,529)	(22,786)
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory assets, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(10,583)	(18,197)
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory liabilities, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	1,293	154
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory liabilities, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	3,065	44
Gulf Power [Member] | Not designated as hedging instruments [Member] | Energy Related Derivative [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	4,358	198
Liability Derivatives	27,112	40,983
Gulf Power [Member] | Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Gulf Power [Member] | Not designated as hedging instruments [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	0
Alabama Power [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	5,000	0
Liability Derivatives	18,000	66,000
Alabama Power [Member] | Other regulatory assets [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(18,000)	(48,000)
Alabama Power [Member] | Other regulatory liabilities [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	5,000	0
Alabama Power [Member] | Energy Related Derivative [Member] | Other current Liabilities [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	2,000	0
Alabama Power [Member] | Energy Related Derivative [Member] | Other regulatory assets, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(14,000)	(36,000)
Alabama Power [Member] | Energy Related Derivative [Member] | Other regulatory assets, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(4,000)	(12,000)
Alabama Power [Member] | Energy Related Derivative [Member] | Other regulatory liabilities, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	3,000	0
Alabama Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Interest rate derivatives [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	0	0
Alabama Power [Member] | Designated as hedging instruments in cash flow and fair value hedges [Member] | Interest rate derivatives [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	0	18,000
Alabama Power [Member] | Hedging Instruments for Regulatory Purposes [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	5,000	0
Liability Derivatives	18,000	48,000
Alabama Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	2,000	0
Alabama Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	14,000	36,000
Alabama Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	3,000	0
Alabama Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	4,000	12,000
Georgia Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	11,000	13,000
Liability Derivatives	45,000	95,000
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	11,000	13,000
Georgia Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	6,000	8,000
Georgia Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Liabilities from risk management activities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	30,000	68,000
Georgia Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Fair value of energy-related derivatives and interest rate derivatives
Asset Derivatives	5,000	5,000
Georgia Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Fair value of energy-related derivatives and interest rate derivatives
Liability Derivatives	15,000	27,000
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	5,000	5,000
Georgia Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory assets, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(30,000)	(68,000)
Georgia Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory assets, deferred [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	(15,000)	(27,000)
Georgia Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory liabilities, current [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Gain	6,000	8,000
Georgia Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member] | Other regulatory assets [Member]
Pre-tax effect of unrealized derivative gains (losses)
Regulatory Hedge Unrealized Loss	$ (45,000)	$ (95,000)