Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Long-term debt:
Long-term debt, Carrying Amount	$ 21,310
Long-term debt, Fair Value	23,517
Alabama Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	6,130
Long-term debt, Fair Value	6,955
Georgia Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	9,524
Long-term debt, Fair Value	10,408
Gulf Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	1,246
Long-term debt, Fair Value	1,382
Mississippi Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	1,767
Long-term debt, Fair Value	1,890
Southern Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	1,307
Long-term debt, Fair Value	$ 1,485