Fair Value Measurements - Financial Instruments, Carrying Amount Not Equal to Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Long-term debt:
Long-term debt, Carrying Amount	$ 21,650,000	$ 21,530,000
Long-term debt, Fair Value	22,197,000	23,480,000
Alabama Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	6,228,000	6,179,000
Long-term debt, Fair Value	6,534,000	6,899,000
Georgia Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	8,593,000	9,624,000
Long-term debt, Fair Value	8,782,000	10,427,000
Gulf Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	1,233,163	1,245,870
Long-term debt, Fair Value	1,261,889	1,367,404
Mississippi Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	2,098,639	1,840,933
Long-term debt, Fair Value	2,045,519	1,956,799
Southern Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	1,620,000	1,306,000
Long-term debt, Fair Value	$ 1,660,000	$ 1,444,000