Retirement Benefits - Textual (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to pension plan	$ 445,000,000
Annual salary increase on net periodic benefit costs	3.59%	3.84%	3.84%	4.18%
Annual increase or decrease in assumed medical care cost trend rate	1.00%
Total accumulated benefit obligation for the pension plans	8,500,000,000	7,400,000,000
Period over which company has elected to amortize changes in the market value of all plan assets	5 years
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected postretirement trust contributions	0
Discount rate on net periodic benefit costs	4.26%	4.98%	5.52%	5.93%
Projected benefit obligations	9,302,000,000	8,079,000,000	7,223,000,000
Total matching contributions	479,000,000	34,000,000
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected postretirement trust contributions	28,000,000
Discount rate on net periodic benefit costs	4.05%	4.88%	5.40%	5.83%
Projected benefit obligations	1,872,000,000	1,787,000,000	1,752,000,000
Total matching contributions	55,000,000	54,000,000
Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	8,700,000,000
Non Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	582,000,000
Employee Saving Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Matching limit of contribution by employer	85.00%
Maximum limit of contribution of employees base salary	6.00%
Total matching contributions	82,000,000	78,000,000	76,000,000
Alabama Power [Member]
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to pension plan	0
Annual salary increase on net periodic benefit costs	3.59%	3.84%	3.84%	4.18%
Annual increase or decrease in assumed medical care cost trend rate	1.00%
Total accumulated benefit obligation for the pension plans	2,000,000,000	1,800,000,000
Period over which company has elected to amortize changes in the market value of all plan assets	5 years
Alabama Power [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected postretirement trust contributions	0
Discount rate on net periodic benefit costs	4.27%	4.98%	5.52%	5.93%
Projected benefit obligations	2,218,000,000	1,932,000,000	1,779,000,000
Total matching contributions	8,000,000	8,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected postretirement trust contributions	4,000,000
Discount rate on net periodic benefit costs	4.06%	4.88%	5.41%	5.84%
Projected benefit obligations	490,000,000	470,000,000	454,000,000
Total matching contributions	11,000,000	11,000,000
Alabama Power [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	2,100,000,000
Alabama Power [Member] | Non Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations		121,000,000
Alabama Power [Member] | Employee Saving Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Matching limit of contribution by employer	85.00%
Maximum limit of contribution of employees base salary	6.00%
Total matching contributions	19,000,000	18,000,000	18,000,000
Gulf Power [Member]
Defined Benefit Plan Disclosure [Line Items]
Annual salary increase on net periodic benefit costs	3.59%	3.84%	3.84%	4.18%
Annual increase or decrease in assumed medical care cost trend rate	1.00%
Period over which company has elected to amortize changes in the market value of all plan assets	5 years
Gulf Power [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate on net periodic benefit costs	4.27%	4.98%	5.53%	5.93%
Total accumulated benefit obligation for the pension plans	371,000,000	321,000,000
Projected benefit obligations	413,501,000	352,834,000	316,286,000
Total matching contributions	14,220,000	751,000
Gulf Power [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected postretirement trust contributions	0
Discount rate on net periodic benefit costs	4.06%	4.88%	5.41%	5.84%
Projected benefit obligations	75,395,000	70,923,000	69,617,000
Total matching contributions	2,648,000	2,543,000
Gulf Power [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to pension plan	13,400,000
Expected postretirement trust contributions	0
Projected benefit obligations	393,000,000
Gulf Power [Member] | Non Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	20,000,000
Gulf Power [Member] | Employee Saving Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Matching limit of contribution by employer	85.00%
Maximum limit of contribution of employees base salary	6.00%
Total matching contributions	4,000,000	3,700,000	3,600,000
Georgia Power [Member]
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to pension plan	0
Expected postretirement trust contributions	24,000,000
Annual salary increase on net periodic benefit costs	3.59%	3.84%	3.84%	4.18%
Estimated investment management expenses	0.0030
Annual increase or decrease in assumed medical care cost trend rate	1.00%
Period over which company has elected to amortize changes in the market value of all plan assets	5 years
Georgia Power [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected postretirement trust contributions	0
Discount rate on net periodic benefit costs	4.27%	4.98%	5.52%	5.93%
Total accumulated benefit obligation for the pension plans	3,100,000,000	2,700,000,000
Projected benefit obligations	3,312,000,000	2,909,000,000	2,674,000,000
Total matching contributions	11,000,000	10,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate on net periodic benefit costs	4.04%	4.87%	5.40%	5.83%
Projected benefit obligations	800,000,000	774,000,000	786,000,000
Total matching contributions	17,000,000	20,000,000
Georgia Power [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	3,100,000,000
Georgia Power [Member] | Non Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	165,000,000
Georgia Power [Member] | Employee Saving Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Matching limit of contribution by employer	85.00%
Maximum limit of contribution of employees base salary	6.00%
Total matching contributions	24,000,000	24,000,000	23,000,000
Mississippi Power [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected postretirement trust contributions	1,000,000
Annual salary increase on net periodic benefit costs	3.59%	3.84%	3.84%	4.18%
Estimated investment management expenses	0.0030
Annual increase or decrease in assumed medical care cost trend rate	1.00%
Total accumulated benefit obligation for the pension plans	392,000,000	339,000,000
Total matching contributions	3,900,000	3,800,000	3,800,000
Mississippi Power [Member] | Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate on net periodic benefit costs	4.26%	4.98%	5.51%	5.92%
Projected benefit obligations	432,553,000	369,680,000	330,315,000
Total matching contributions	44,930,000	2,184,000
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate on net periodic benefit costs	4.04%	4.87%	5.39%	5.83%
Projected benefit obligations	91,783,000	87,447,000	81,688,000
Total matching contributions	3,052,000	2,477,000
Mississippi Power [Member] | Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Voluntary contribution to pension plan	43,000,000
Expected postretirement trust contributions	0
Projected benefit obligations	400,000,000
Mississippi Power [Member] | Non Qualified Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligations	$ 32,000,000
Mississippi Power [Member] | Employee Saving Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Matching limit of contribution by employer	85.00%
Maximum limit of contribution of employees base salary	6.00%