Income Taxes - Accrued Interest for Unrecognized Tax Benefits (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Accrued Interest For Unrecognized Tax Benefits [Roll Forward]
Interest accrued at beginning of year	$ 10,000	$ 29,000	$ 21,000
Interest reclassified due to settlements	(9,000)	(24,000)	0
Interest accrued during the period	0	5,000	8,000
Balance at end of year	1,000	10,000	29,000
Southern Power [Member]
Reconciliation of Accrued Interest For Unrecognized Tax Benefits [Roll Forward]
Interest accrued at beginning of year	100	0	0
Interest accrued during the period	(100)	100	0
Balance at end of year	0	100	0
Gulf Power [Member]
Reconciliation of Accrued Interest For Unrecognized Tax Benefits [Roll Forward]
Interest accrued at beginning of year	283	210	90
Interest reclassified due to settlements	(283)	0	0
Interest accrued during the period	0	73	120
Balance at end of year	0	283	210
Mississippi Power [Member]
Reconciliation of Accrued Interest For Unrecognized Tax Benefits [Roll Forward]
Interest accrued at beginning of year	680	413	230
Interest accrued during the period	92	267	183
Balance at end of year	772	680	413
Alabama Power [Member]
Reconciliation of Accrued Interest For Unrecognized Tax Benefits [Roll Forward]
Interest accrued at beginning of year	1,900	1,500	300
Interest reclassified due to settlements	(1,900)	0	0
Interest accrued during the period	0	400	1,200
Balance at end of year	0	1,900	1,500
Georgia Power [Member]
Reconciliation of Accrued Interest For Unrecognized Tax Benefits [Roll Forward]
Interest accrued at beginning of year	6,000	27,000	20,000
Interest reclassified due to settlements	(6,000)	(24,000)	0
Interest accrued during the period	0	3,000	7,000
Balance at end of year	$ 0	$ 6,000	$ 27,000