Retirement Benefits - Pension Plan and Other Postretirement Benefit Plan Assets (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Pension Plans [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	100.00%
Total	100.00%	100.00%
Pension Plans [Member] | Domestic equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	26.00%
Total	28.00%	29.00%
Pension Plans [Member] | International equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	25.00%
Total	24.00%	25.00%
Pension Plans [Member] | Fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	23.00%
Total	27.00%	23.00%
Pension Plans [Member] | Special situations [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	3.00%
Total	1.00%	0.00%
Pension Plans [Member] | Real estate investments [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	14.00%
Total	13.00%	14.00%
Pension Plans [Member] | Private equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	9.00%
Total	7.00%	9.00%
Other Postretirement Benefits [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	100.00%
Total	100.00%	100.00%
Other Postretirement Benefits [Member] | Domestic equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	40.00%
Total	38.00%	39.00%
Other Postretirement Benefits [Member] | International equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	21.00%
Total	24.00%	18.00%
Other Postretirement Benefits [Member] | Domestic fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	25.00%
Total	28.00%	31.00%
Other Postretirement Benefits [Member] | Global fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	4.00%
Total	3.00%	4.00%
Other Postretirement Benefits [Member] | Special situations [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	1.00%
Total	0.00%	0.00%
Other Postretirement Benefits [Member] | Real estate investments [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	6.00%
Total	5.00%	5.00%
Other Postretirement Benefits [Member] | Private equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	3.00%
Total	2.00%	3.00%
Georgia Power [Member] | Pension Plans [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	100.00%
Total	100.00%	100.00%
Georgia Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	26.00%
Total	28.00%	29.00%
Georgia Power [Member] | Pension Plans [Member] | International equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	25.00%
Total	24.00%	25.00%
Georgia Power [Member] | Pension Plans [Member] | Fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	23.00%
Total	27.00%	23.00%
Georgia Power [Member] | Pension Plans [Member] | Special situations [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	3.00%
Total	1.00%	0.00%
Georgia Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	14.00%
Total	13.00%	14.00%
Georgia Power [Member] | Pension Plans [Member] | Private equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	9.00%
Total	7.00%	9.00%
Georgia Power [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	100.00%
Total	100.00%	100.00%
Georgia Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	41.00%
Total	34.00%	39.00%
Georgia Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	21.00%
Total	27.00%	22.00%
Georgia Power [Member] | Other Postretirement Benefits [Member] | Domestic fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	24.00%
Total	27.00%	26.00%
Georgia Power [Member] | Other Postretirement Benefits [Member] | Global fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	8.00%
Total	7.00%	8.00%
Georgia Power [Member] | Other Postretirement Benefits [Member] | Special situations [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	1.00%
Total	0.00%	0.00%
Georgia Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	3.00%
Total	3.00%	3.00%
Georgia Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	2.00%
Total	2.00%	2.00%
Gulf Power [Member] | Pension Plans [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	100.00%
Total	100.00%	100.00%
Gulf Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	26.00%
Total	28.00%	29.00%
Gulf Power [Member] | Pension Plans [Member] | International equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	25.00%
Total	24.00%	25.00%
Gulf Power [Member] | Pension Plans [Member] | Fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	23.00%
Total	27.00%	23.00%
Gulf Power [Member] | Pension Plans [Member] | Special situations [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	3.00%
Total	1.00%	0.00%
Gulf Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	14.00%
Total	13.00%	14.00%
Gulf Power [Member] | Pension Plans [Member] | Private equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	9.00%
Total	7.00%	9.00%
Gulf Power [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	100.00%
Total	100.00%	100.00%
Gulf Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	25.00%
Total	27.00%	28.00%
Gulf Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	24.00%
Total	23.00%	24.00%
Gulf Power [Member] | Other Postretirement Benefits [Member] | Domestic fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	25.00%
Total	29.00%	26.00%
Gulf Power [Member] | Other Postretirement Benefits [Member] | Special situations [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	3.00%
Total	1.00%	0.00%
Gulf Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	14.00%
Total	13.00%	13.00%
Gulf Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	9.00%
Total	7.00%	9.00%
Mississippi Power [Member] | Pension Plans [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	100.00%
Total	100.00%	100.00%
Mississippi Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	26.00%
Total	28.00%	29.00%
Mississippi Power [Member] | Pension Plans [Member] | International equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	25.00%
Total	24.00%	25.00%
Mississippi Power [Member] | Pension Plans [Member] | Fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	23.00%
Total	27.00%	23.00%
Mississippi Power [Member] | Pension Plans [Member] | Special situations [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	3.00%
Total	1.00%	0.00%
Mississippi Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	14.00%
Total	13.00%	14.00%
Mississippi Power [Member] | Pension Plans [Member] | Private equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	9.00%
Total	7.00%	9.00%
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	100.00%
Total	100.00%	100.00%
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	21.00%
Total	22.00%	22.00%
Mississippi Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	20.00%
Total	19.00%	20.00%
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	39.00%
Total	42.00%	40.00%
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Special situations [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	2.00%
Total	1.00%	0.00%
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	11.00%
Total	10.00%	11.00%
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	7.00%
Total	6.00%	7.00%
Alabama Power [Member] | Pension Plans [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	100.00%
Total	100.00%	100.00%
Alabama Power [Member] | Pension Plans [Member] | Domestic equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	26.00%
Total	28.00%	29.00%
Alabama Power [Member] | Pension Plans [Member] | International equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	25.00%
Total	24.00%	25.00%
Alabama Power [Member] | Pension Plans [Member] | Fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	23.00%
Total	27.00%	23.00%
Alabama Power [Member] | Pension Plans [Member] | Special situations [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	3.00%
Total	1.00%	0.00%
Alabama Power [Member] | Pension Plans [Member] | Real estate investments [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	14.00%
Total	13.00%	14.00%
Alabama Power [Member] | Pension Plans [Member] | Private equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	9.00%
Total	7.00%	9.00%
Alabama Power [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	100.00%
Total	100.00%	100.00%
Alabama Power [Member] | Other Postretirement Benefits [Member] | Domestic equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	44.00%
Total	46.00%	41.00%
Alabama Power [Member] | Other Postretirement Benefits [Member] | International equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	20.00%
Total	20.00%	14.00%
Alabama Power [Member] | Other Postretirement Benefits [Member] | Domestic fixed income [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	24.00%
Total	28.00%	38.00%
Alabama Power [Member] | Other Postretirement Benefits [Member] | Special situations [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	1.00%
Total	0.00%	0.00%
Alabama Power [Member] | Other Postretirement Benefits [Member] | Real estate investments [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	8.00%
Total	4.00%	4.00%
Alabama Power [Member] | Other Postretirement Benefits [Member] | Private equity [Member]
Defined Benefit Plan, Assets, Target Allocations [Abstract]
Defined Benefit Plan, Equity Securities, Target	3.00%
Total	2.00%	3.00%