Income Taxes - Impact of Unrecognized Tax Benefits on Effective Tax Rate, If Recognized (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Impact on effective tax rate
Tax positions impacting the effective tax rate	$ 5,000	$ 69,000	$ 217,000
Tax positions not impacting the effective tax rate	65,000	51,000	79,000
Balance of unrecognized tax benefits	70,000	120,000	296,000	199,000
Southern Power [Member]
Impact on effective tax rate
Tax positions impacting the effective tax rate	300	500	600
Tax positions not impacting the effective tax rate	2,600	2,100	1,700
Balance of unrecognized tax benefits	2,900	2,600	2,300	100
Gulf Power [Member]
Impact on effective tax rate
Tax positions impacting the effective tax rate	45	1,804	1,826
Tax positions not impacting the effective tax rate	4,962	1,088	2,044
Balance of unrecognized tax benefits	5,007	2,892	3,870	1,639
Mississippi Power [Member]
Impact on effective tax rate
Tax positions impacting the effective tax rate	3,656	4,144	3,058
Tax positions not impacting the effective tax rate	2,099	820	1,230
Balance of unrecognized tax benefits	5,755	4,964	4,288	3,026
Alabama Power [Member]
Impact on effective tax rate
Tax positions impacting the effective tax rate	0	5,000	6,000
Tax positions not impacting the effective tax rate	31,000	27,000	37,000
Balance of unrecognized tax benefits	31,000	32,000	43,000	6,000
Georgia Power [Member]
Impact on effective tax rate
Tax positions impacting the effective tax rate	0	28,000	202,000
Tax positions not impacting the effective tax rate	23,000	19,000	35,000
Balance of unrecognized tax benefits	$ 23,000	$ 47,000	$ 237,000	$ 181,000