Derivatives - Pre-tax Effect of Derivatives on Statements of Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	$ (109,000)	$ (235,000)
Regulatory Hedge Unrealized Gain	23,000	14,000
Derivative Asset, Fair Value, Gross Asset	36,000	29,000
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(19,000)	(28,000)	(1,000)
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(18,000)	(15,000)	(24,000)
Fuel [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0	0	0
Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(18,000)	(14,000)	(25,000)
Other operations and maintenance [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0	0	1,000
Other income (expense), net [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0	(1,000)	0
Energy Related Derivative [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0	0	1,000
Interest rate derivatives [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(19,000)	(28,000)	(3,000)
Foreign currency derivatives [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0	0	1,000
Southern Power [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(200)	100	1,500
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(10,100)	(12,000)	(10,400)
Southern Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,100	600
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(200)	100	1,500
Southern Power [Member] | Energy Related Derivative [Member] | Depreciation and amortization [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	400	400	400
Southern Power [Member] | Interest rate derivatives [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0	0	0
Southern Power [Member] | Interest rate derivatives [Member] | Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(10,500)	(11,400)	(10,800)
Southern Power [Member] | Interest rate derivatives [Member] | Other income (expense), net [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0	(1,000)	0
Mississippi Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,519	1,688
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	16,000
Alabama Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	5,000	0
Alabama Power [Member] | Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(3,000)	3,000	3,000
Alabama Power [Member] | Interest rate derivatives [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(18,000)	(14,000)	0
Gulf Power [Member] | Interest rate derivatives [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0	0	(1,405)
Gulf Power [Member] | Interest rate derivatives [Member] | Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(933)	(933)	(974)
Other regulatory assets deferred [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(35,000)	(72,000)
Other regulatory assets deferred [Member] | Alabama Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(4,000)	(12,000)
Other regulatory assets current [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(74,000)	(163,000)
Other regulatory assets current [Member] | Alabama Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(14,000)	(36,000)
Other regulatory liabilities current [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	10,000	9,000
Other regulatory liabilities deferred [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	13,000	5,000
Other regulatory liabilities deferred [Member] | Alabama Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	3,000	0
Hedging Instruments for Regulatory Purposes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	23,000	14,000
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(19,446)	(51,152)
Regulatory Hedge Unrealized Gain	2,519	162
Derivative Asset, Fair Value, Gross Asset	2,519	162
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	5,000	0
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	11,000	13,000
Derivative Asset, Fair Value, Gross Asset	11,000	13,000
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(27,112)	(40,983)
Regulatory Hedge Unrealized Gain	4,358	198
Derivative Asset, Fair Value, Gross Asset	4,358	198
Hedging Instruments for Regulatory Purposes [Member] | Other deferred charges and assets [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	13,000	5,000
Hedging Instruments for Regulatory Purposes [Member] | Other deferred charges and assets [Member] | Mississippi Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,881	37
Hedging Instruments for Regulatory Purposes [Member] | Other deferred charges and assets [Member] | Alabama Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	3,000	0
Hedging Instruments for Regulatory Purposes [Member] | Other deferred charges and assets [Member] | Georgia Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	5,000	5,000
Hedging Instruments for Regulatory Purposes [Member] | Other deferred charges and assets [Member] | Gulf Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	3,065	44
Hedging Instruments for Regulatory Purposes [Member] | Other Current Assets [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	10,000	9,000
Hedging Instruments for Regulatory Purposes [Member] | Other Current Assets [Member] | Mississippi Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	638	125
Hedging Instruments for Regulatory Purposes [Member] | Other Current Assets [Member] | Alabama Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,000	0
Hedging Instruments for Regulatory Purposes [Member] | Other Current Assets [Member] | Georgia Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	6,000	8,000
Hedging Instruments for Regulatory Purposes [Member] | Other Current Assets [Member] | Gulf Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,293	154
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory assets deferred [Member] | Mississippi Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(6,330)	(14,697)
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory assets deferred [Member] | Georgia Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(15,000)	(27,000)
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory assets deferred [Member] | Gulf Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(10,583)	(18,197)
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory assets current [Member] | Mississippi Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(13,116)	(36,455)
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory assets current [Member] | Georgia Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(30,000)	(68,000)
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory assets current [Member] | Gulf Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(16,529)	(22,786)
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory liabilities current [Member] | Mississippi Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	638	125
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory liabilities current [Member] | Georgia Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	6,000	8,000
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory liabilities current [Member] | Gulf Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	1,293	154
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory liabilities deferred [Member] | Mississippi Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	1,881	37
Hedging Instruments for Regulatory Purposes [Member] | Other regulatory liabilities deferred [Member] | Gulf Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	3,065	44
Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	(2,000)	(1,000)	13,000
Fair Value Hedging [Member] | Interest rate derivatives [Member] | Interest expense, net of amounts capitalized [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	(3,000)	3,000	10,000
Fair Value Hedging [Member] | Interest rate derivatives [Member] | Other operations and maintenance [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,000	(4,000)	3,000
Designated as Hedging Instrument [Member] | Mississippi Power [Member] | Cash Flow Hedging [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(774)	(14,364)	3
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1,073)	48	0
Designated as Hedging Instrument [Member] | Mississippi Power [Member] | Cash Flow Hedging [Member] | Energy Related Derivative [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0	(3)	3
Designated as Hedging Instrument [Member] | Mississippi Power [Member] | Cash Flow Hedging [Member] | Energy Related Derivative [Member] | Fuel [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	0	0	0
Designated as Hedging Instrument [Member] | Mississippi Power [Member] | Cash Flow Hedging [Member] | Interest rate derivatives [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(774)	(14,361)	0
Designated as Hedging Instrument [Member] | Mississippi Power [Member] | Cash Flow Hedging [Member] | Interest rate derivatives [Member] | Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1,073)	48	0
Designated as Hedging Instrument [Member] | Georgia Power [Member] | Interest rate derivatives [Member] | Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	$ (3,000)	$ (4,000)	$ (16,000)