Retirement Benefits - Change in APBO and Fair Value of Plan Assets, and Amounts Recognized in Balance Sheets (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	$ 4,032,000,000	$ 3,579,000,000
Current liabilities, other	(483,000,000)	(426,000,000)
Employee benefit obligations	(2,540,000,000)	(2,442,000,000)
Accumulated other comprehensive loss	(123,000,000)	(111,000,000)
Other Postretirement Benefits [Member]
Change in benefit obligation
Benefit obligation at beginning of year	1,787,000,000	1,752,000,000
Service cost	21,000,000	21,000,000	25,000,000
Interest cost	85,000,000	92,000,000	100,000,000
Benefits paid	(99,000,000)	(103,000,000)
Actuarial loss (gain)	71,000,000	29,000,000
Plan amendments	0	(12,000,000)
Retiree drug subsidy	7,000,000	8,000,000
Balance at end of year	1,872,000,000	1,787,000,000	1,752,000,000
Change in plan assets
Fair value of plan assets at beginning of year	765,000,000	802,000,000
Actual return (loss) on plan assets	93,000,000	4,000,000
Employer contributions	55,000,000	54,000,000
Benefits paid	(92,000,000)	(95,000,000)
Fair value of plan assets at end of year	821,000,000	765,000,000	802,000,000
Accrued liability	1,051,000,000	1,022,000,000
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	360,000,000	345,000,000
Current liabilities, other	(3,000,000)	(4,000,000)
Employee benefit obligations	(1,048,000,000)	(1,018,000,000)
Accumulated other comprehensive loss	7,000,000	6,000,000
Gulf Power [Member]
Change in benefit obligation
Service cost	9,101,000	8,431,000	7,853,000
Interest cost	17,199,000	17,074,000	17,305,000
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	372,294,000	323,116,000
Current liabilities, other	(19,930,000)	(22,916,000)
Employee benefit obligations	(126,871,000)	(109,740,000)
Accumulated other comprehensive loss	(1,581,000)	(2,154,000)
Gulf Power [Member] | Other Postretirement Benefits [Member]
Change in benefit obligation
Benefit obligation at beginning of year	70,923,000	69,617,000
Service cost	1,167,000	1,132,000	1,304,000
Interest cost	3,367,000	3,658,000	4,121,000
Benefits paid	(3,854,000)	(4,189,000)
Actuarial loss (gain)	3,468,000	292,000
Plan amendments	0	0
Retiree drug subsidy	324,000	413,000
Balance at end of year	75,395,000	70,923,000	69,617,000
Change in plan assets
Fair value of plan assets at beginning of year	14,978,000	15,697,000
Actual return (loss) on plan assets	2,131,000	514,000
Employer contributions	2,648,000	2,543,000
Benefits paid	(3,530,000)	(3,776,000)
Fair value of plan assets at end of year	16,227,000	14,978,000	15,697,000
Accrued liability	59,168,000	55,945,000
Amounts recognized in the consolidated balance sheets related to company's pension plans
Regulatory assets	2,169,000	239,000
Current liabilities, other	(661,000)	(624,000)
Employee benefit obligations	(58,507,000)	(55,321,000)
Mississippi Power [Member]
Change in benefit obligation
Service cost	9,416,000	8,838,000	8,300,000
Interest cost	18,019,000	17,827,000	17,916,000
Change in plan assets
Employer contributions	3,900,000	3,800,000	3,800,000
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	236,225,000	185,694,000
Current liabilities, other	(18,766,000)	(17,533,000)
Employee benefit obligations	(157,421,000)	(161,065,000)
Accumulated other comprehensive loss	(8,713,000)	(8,897,000)
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Change in benefit obligation
Benefit obligation at beginning of year	87,447,000	81,688,000
Service cost	1,038,000	1,012,000	1,305,000
Interest cost	4,155,000	4,292,000	4,763,000
Benefits paid	(4,432,000)	(4,094,000)
Actuarial loss (gain)	3,166,000	4,073,000
Plan amendments	0	0
Retiree drug subsidy	409,000	476,000
Balance at end of year	91,783,000	87,447,000	81,688,000
Change in plan assets
Fair value of plan assets at beginning of year	20,534,000	20,955,000
Actual return (loss) on plan assets	2,427,000	720,000
Employer contributions	3,052,000	2,477,000
Benefits paid	(4,023,000)	(3,618,000)
Fair value of plan assets at end of year	21,990,000	20,534,000	20,955,000
Accrued liability	69,793,000	66,913,000
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	15,454,000	13,324,000
Employee benefit obligations	(69,793,000)	(66,913,000)
Georgia Power [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	1,798,000,000	1,604,000,000
Current liabilities, other	(137,000,000)	(139,000,000)
Regulatory liabilities		(62,000,000)
Employee benefit obligations	(950,000,000)	(905,000,000)
Accumulated other comprehensive loss	(7,000,000)	(9,000,000)
Georgia Power [Member] | Other Postretirement Benefits [Member]
Change in benefit obligation
Benefit obligation at beginning of year	774,000,000	786,000,000
Service cost	7,000,000	7,000,000	9,000,000
Interest cost	37,000,000	41,000,000	44,000,000
Benefits paid	(46,000,000)	(48,000,000)
Actuarial loss (gain)	25,000,000	(4,000,000)
Plan amendments	0	(12,000,000)
Retiree drug subsidy	3,000,000	4,000,000
Balance at end of year	800,000,000	774,000,000	786,000,000
Change in plan assets
Fair value of plan assets at beginning of year	365,000,000	393,000,000
Actual return (loss) on plan assets	43,000,000	(4,000,000)
Employer contributions	17,000,000	20,000,000
Benefits paid	(43,000,000)	(44,000,000)
Fair value of plan assets at end of year	382,000,000	365,000,000	393,000,000
Accrued liability	418,000,000	409,000,000
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	187,000,000	186,000,000
Employee benefit obligations	(418,000,000)	(409,000,000)
Alabama Power [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	1,083,000,000	994,000,000
Current liabilities, other	(38,000,000)	(38,000,000)
Employee benefit obligations	(321,000,000)	(343,000,000)
Accumulated other comprehensive loss	(27,000,000)	(18,000,000)
Alabama Power [Member] | Other Postretirement Benefits [Member]
Change in benefit obligation
Benefit obligation at beginning of year	470,000,000	454,000,000
Service cost	5,000,000	5,000,000	6,000,000
Interest cost	22,000,000	24,000,000	26,000,000
Benefits paid	(24,000,000)	(27,000,000)
Actuarial loss (gain)	15,000,000	11,000,000
Plan amendments	0	0
Retiree drug subsidy	2,000,000	3,000,000
Balance at end of year	490,000,000	470,000,000	454,000,000
Change in plan assets
Fair value of plan assets at beginning of year	315,000,000	323,000,000
Actual return (loss) on plan assets	39,000,000	5,000,000
Employer contributions	11,000,000	11,000,000
Benefits paid	(22,000,000)	(24,000,000)
Fair value of plan assets at end of year	343,000,000	315,000,000	323,000,000
Accrued liability	147,000,000	155,000,000
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	89,000,000	96,000,000
Employee benefit obligations	$ (147,000,000)	$ (155,000,000)