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, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans [Member]
Change in benefit obligation
Benefit obligation at beginning of year	$ 8,079,000	$ 7,223,000
Service cost	198,000	184,000	172,000
Interest cost	393,000	389,000	391,000
Benefits paid	(336,000)	(324,000)
Actuarial loss (gain)	968,000	607,000
Balance at end of year	9,302,000	8,079,000	7,223,000
Fair value of plan assets at beginning of year	6,800,000	6,834,000
Actual return (loss) on plan assets	1,010,000	256,000
Employer contributions	479,000	34,000
Fair value of plan assets at end of year	7,953,000	6,800,000	6,834,000
Accrued liability	(1,349,000)	(1,279,000)
Gulf Power [Member]
Change in benefit obligation
Service cost	9,101	8,431	7,853
Interest cost	17,199	17,074	17,305
Gulf Power [Member] | Pension Plans [Member]
Change in benefit obligation
Benefit obligation at beginning of year	352,834	316,286
Service cost	9,101	8,431
Interest cost	17,199	17,074
Benefits paid	(14,046)	(13,807)
Plan amendments	426	0
Actuarial loss (gain)	47,987	24,850
Balance at end of year	413,501	352,834
Fair value of plan assets at beginning of year	304,324	307,828
Actual return (loss) on plan assets	45,762	9,552
Employer contributions	14,220	751
Fair value of plan assets at end of year	350,260	304,324
Accrued liability	(63,241)	(48,510)
Mississippi Power [Member]
Change in benefit obligation
Service cost	9,416	8,838	8,300
Interest cost	18,019	17,827	17,916
Employer contributions	3,900	3,800	3,800
Mississippi Power [Member] | Pension Plans [Member]
Change in benefit obligation
Benefit obligation at beginning of year	369,680	330,315
Service cost	9,416	8,838
Interest cost	18,019	17,827
Benefits paid	(14,949)	(14,587)
Plan amendments	0	0
Actuarial loss (gain)	50,387	27,287
Balance at end of year	432,553	369,680
Fair value of plan assets at beginning of year	282,100	283,698
Actual return (loss) on plan assets	39,668	10,805
Employer contributions	44,930	2,184
Fair value of plan assets at end of year	351,749	282,100
Accrued liability	(80,804)	(87,580)
Georgia Power [Member] | Pension Plans [Member]
Change in benefit obligation
Benefit obligation at beginning of year	2,909,000	2,674,000
Service cost	60,000	57,000	54,000
Interest cost	141,000	144,000	145,000
Benefits paid	(136,000)	(132,000)
Actuarial loss (gain)	338,000	166,000
Balance at end of year	3,312,000	2,909,000	2,674,000
Fair value of plan assets at beginning of year	2,575,000	2,621,000
Actual return (loss) on plan assets	377,000	76,000
Employer contributions	11,000	10,000
Fair value of plan assets at end of year	2,827,000	2,575,000	2,621,000
Accrued liability	(485,000)	(334,000)
Alabama Power [Member] | Pension Plans [Member]
Change in benefit obligation
Benefit obligation at beginning of year	1,932,000	1,779,000
Service cost	44,000	43,000	41,000
Interest cost	94,000	96,000	97,000
Benefits paid	(90,000)	(88,000)
Actuarial loss (gain)	238,000	102,000
Balance at end of year	2,218,000	1,932,000	1,779,000
Fair value of plan assets at beginning of year	1,885,000	1,933,000
Actual return (loss) on plan assets	274,000	32,000
Employer contributions	8,000	8,000
Fair value of plan assets at end of year	2,077,000	1,885,000	1,933,000
Accrued liability	$ (141,000)	$ (47,000)