Retirement Benefits - Changes in Projected Benefit Obligations and Fair Value of Plan Assets (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans [Member]
Change in benefit obligation
Benefit obligation at beginning of year	$ 9,302,000	$ 8,079,000
Service cost	232,000	198,000	184,000
Interest cost	389,000	393,000	389,000
Benefits paid	(357,000)	(336,000)
Actuarial loss (gain)	(703,000)	968,000
Balance at end of year	8,863,000	9,302,000	8,079,000
Change in plan assets
Fair value of plan assets at beginning of year	7,953,000	6,800,000
Actual return (loss) on plan assets	1,098,000	1,010,000
Employer contributions	39,000	479,000
Fair value of plan assets at end of year	8,733,000	7,953,000	6,800,000
Accrued liability	(130,000)	(1,349,000)
Other Postretirement Benefits [Member]
Change in benefit obligation
Benefit obligation at beginning of year	1,872,000	1,787,000
Service cost	24,000	21,000	21,000
Interest cost	74,000	85,000	92,000
Benefits paid	(94,000)	(99,000)
Actuarial loss (gain)	200,000	(71,000)
Retiree drug subsidy	6,000	7,000
Balance at end of year	1,682,000	1,872,000	1,787,000
Change in plan assets
Fair value of plan assets at beginning of year	821,000	765,000
Actual return (loss) on plan assets	129,000	93,000
Employer contributions	39,000	55,000
Benefits paid, net of drug subsidy	(88,000)	(92,000)
Fair value of plan assets at end of year	901,000	821,000	765,000
Accrued liability	(781,000)	(1,051,000)
Alabama Power [Member] | Pension Plans [Member]
Change in benefit obligation
Benefit obligation at beginning of year	2,218,000	1,932,000
Service cost	52,000	44,000	43,000
Interest cost	93,000	94,000	96,000
Benefits paid	(93,000)	(90,000)
Actuarial loss (gain)	(158,000)	238,000
Balance at end of year	2,112,000	2,218,000	1,932,000
Change in plan assets
Fair value of plan assets at beginning of year	2,077,000	1,885,000
Actual return (loss) on plan assets	285,000	274,000
Employer contributions	9,000	8,000
Fair value of plan assets at end of year	2,278,000	2,077,000	1,885,000
Accrued liability	166,000	(141,000)
Alabama Power [Member] | Other Postretirement Benefits [Member]
Change in benefit obligation
Benefit obligation at beginning of year	490,000	470,000
Service cost	6,000	5,000	5,000
Interest cost	19,000	22,000	24,000
Benefits paid	(24,000)	(24,000)
Actuarial loss (gain)	(62,000)	15,000
Retiree drug subsidy	2,000	2,000
Balance at end of year	431,000	490,000	470,000
Change in plan assets
Fair value of plan assets at beginning of year	343,000	315,000
Actual return (loss) on plan assets	61,000	39,000
Employer contributions	7,000	11,000
Benefits paid, net of drug subsidy	(22,000)	(22,000)
Fair value of plan assets at end of year	389,000	343,000	315,000
Accrued liability	(42,000)	(147,000)
Georgia Power [Member] | Pension Plans [Member]
Change in benefit obligation
Benefit obligation at beginning of year	3,312,000	2,909,000
Service cost	69,000	60,000	57,000
Interest cost	138,000	141,000	144,000
Benefits paid	(141,000)	(136,000)
Actuarial loss (gain)	(262,000)	338,000
Balance at end of year	3,116,000	3,312,000	2,909,000
Change in plan assets
Fair value of plan assets at beginning of year	2,827,000	2,575,000
Actual return (loss) on plan assets	387,000	377,000
Employer contributions	12,000	11,000
Fair value of plan assets at end of year	3,085,000	2,827,000	2,575,000
Accrued liability	(31,000)	(485,000)
Georgia Power [Member] | Other Postretirement Benefits [Member]
Change in benefit obligation
Benefit obligation at beginning of year	800,000	774,000
Service cost	7,000	7,000	7,000
Interest cost	31,000	37,000	41,000
Benefits paid	(45,000)	(46,000)
Actuarial loss (gain)	73,000	(25,000)
Retiree drug subsidy	3,000	3,000
Balance at end of year	723,000	800,000	774,000
Change in plan assets
Fair value of plan assets at beginning of year	382,000	365,000
Actual return (loss) on plan assets	56,000	43,000
Employer contributions	11,000	17,000
Benefits paid, net of drug subsidy	(42,000)	(43,000)
Fair value of plan assets at end of year	407,000	382,000	365,000
Accrued liability	(316,000)	(418,000)
Gulf Power [Member]
Change in benefit obligation
Service cost	11,128	9,101	8,431
Interest cost	17,321	17,199	17,074
Gulf Power [Member] | Pension Plans [Member]
Change in benefit obligation
Benefit obligation at beginning of year	413,501	352,834
Service cost	11,128	9,101
Interest cost	17,321	17,199
Benefits paid	(14,831)	(14,046)
Plan amendments	0	426
Actuarial loss (gain)	(31,791)	47,987
Balance at end of year	395,328	413,501
Change in plan assets
Fair value of plan assets at beginning of year	350,260	304,324
Actual return (loss) on plan assets	49,076	45,762
Employer contributions	1,134	14,220
Fair value of plan assets at end of year	385,639	350,260
Accrued liability	(9,689)	(63,241)
Gulf Power [Member] | Other Postretirement Benefits [Member]
Change in benefit obligation
Benefit obligation at beginning of year	75,395	70,923
Service cost	1,355	1,167	1,132
Interest cost	2,982	3,367	3,658
Benefits paid	(3,583)	(3,854)
Actuarial loss (gain)	7,900	(3,468)
Retiree drug subsidy	330	324
Balance at end of year	68,579	75,395	70,923
Change in plan assets
Fair value of plan assets at beginning of year	16,227	14,978
Actual return (loss) on plan assets	2,119	2,131
Employer contributions	2,381	2,648
Benefits paid, net of drug subsidy	(3,253)	(3,530)
Fair value of plan assets at end of year	17,474	16,227	14,978
Accrued liability	(51,105)	(59,168)
Mississippi Power [Member]
Change in benefit obligation
Service cost	11,067	9,416	8,838
Interest cost	18,062	18,019	17,827
Change in plan assets
Employer contributions	4,100	3,900	3,800
Mississippi Power [Member] | Pension Plans [Member]
Change in benefit obligation
Benefit obligation at beginning of year	432,553	369,680
Service cost	11,067	9,416
Interest cost	18,062	18,019
Benefits paid	(16,207)	(14,949)
Actuarial loss (gain)	(36,080)	50,387
Balance at end of year	409,395	432,553
Change in plan assets
Fair value of plan assets at beginning of year	351,749	282,100
Actual return (loss) on plan assets	49,431	39,668
Employer contributions	2,430	44,930
Fair value of plan assets at end of year	387,403	351,749
Accrued liability	(21,992)	(80,804)
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Change in benefit obligation
Benefit obligation at beginning of year	91,783	87,447
Service cost	1,151	1,038	1,012
Interest cost	3,619	4,155	4,292
Benefits paid	(4,080)	(4,432)
Actuarial loss (gain)	11,959	(3,166)
Retiree drug subsidy	426	409
Balance at end of year	80,940	91,783	87,447
Change in plan assets
Fair value of plan assets at beginning of year	21,990	20,534
Actual return (loss) on plan assets	2,379	2,427
Employer contributions	2,562	3,052
Benefits paid, net of drug subsidy	(3,654)	(4,023)
Fair value of plan assets at end of year	23,277	21,990	20,534
Accrued liability	$ (57,663)	$ (69,793)