Income Taxes - Reconciliation of Federal Statutory Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	35.00%	35.00%	35.00%
State income tax, net of federal deduction	2.50%	2.40%	1.80%
Employee stock plans dividend deduction	(1.00%)	(1.10%)	(1.20%)
Non-deductible book depreciation	0.90%	0.70%	0.80%
Difference in prior years' deferred and current tax rate	(0.10%)	(0.10%)	(0.10%)
AFUDC-Equity	(1.30%)	(1.50%)	(2.20%)
ITC basis difference	(0.30%)	(0.20%)	(0.40%)
Other	(0.10%)	(0.20%)	(0.20%)
Effective income tax rate	35.60%	35.00%	33.50%
Southern Power [Member]
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	35.00%	35.00%	35.00%
State income tax, net of federal deduction	3.70%	0.60%	7.70%
Effective Income Tax Rate Reconciliation Amortization Tax Credits Investment	(1.00%)	(0.40%)	0.00%
ITC basis difference	(2.60%)	(3.10%)	(5.60%)
Other	(0.60%)	(0.30%)	(0.70%)
Effective income tax rate	34.50%	31.80%	36.40%
Gulf Power [Member]
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	35.00%	35.00%	35.00%
State income tax, net of federal deduction	3.30%	2.50%	2.70%
Non-deductible book depreciation	0.50%	0.50%	0.30%
Difference in prior years' deferred and current tax rate	(0.20%)	(0.30%)	(0.30%)
AFUDC-Equity	(0.90%)	(2.00%)	(1.30%)
Other	(0.20%)	(0.20%)	(0.50%)
Effective income tax rate	37.50%	35.50%	35.90%
Mississippi Power [Member]
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	35.00%	35.00%	35.00%
State income tax, net of federal deduction	2.00%	1.90%	2.80%
Employee stock plans dividend deduction	0.20%	0.30%	0.30%
Non-deductible book depreciation	(0.10%)	(0.10%)	(0.20%)
AFUDC-Equity	(11.30%)	(6.30%)	(1.00%)
Other	(0.70%)	(0.20%)	(0.80%)
Effective income tax rate	25.10%	30.60%	36.10%
Alabama Power [Member]
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	35.00%	35.00%	35.00%
State income tax, net of federal deduction	4.10%	4.30%	4.20%
Non-deductible book depreciation	0.90%	0.80%	0.80%
Difference in prior years' deferred and current tax rate	(0.10%)	(0.10%)	(0.10%)
AFUDC-Equity	(0.50%)	(0.60%)	(1.00%)
Other	(0.30%)	(0.40%)	(0.60%)
Effective income tax rate	39.10%	39.00%	38.30%
Georgia Power [Member]
Reconciliation of federal statutory income tax rate to effective income tax rate
Federal statutory rate	35.00%	35.00%	35.00%
State income tax, net of federal deduction	1.60%	1.50%	(0.30%)
Non-deductible book depreciation	1.20%	0.80%	1.00%
AFUDC-Equity	(1.00%)	(1.90%)	(3.60%)
Other	(0.10%)	(0.50%)	(0.20%)
Effective income tax rate	36.70%	34.90%	31.90%