Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Long-term debt:
Long-term debt, Carrying Amount	$ 20,843
Long-term debt, Fair Value	25,499
Alabama Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	6,380
Long-term debt, Fair Value	7,789
Georgia Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	8,918
Long-term debt, Fair Value	11,837
Gulf Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	1,236
Long-term debt, Fair Value	1,349
Mississippi Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	1,668
Long-term debt, Fair Value	1,740
Southern Power [Member]
Long-term debt:
Long-term debt, Carrying Amount	1,303
Long-term debt, Fair Value	$ 1,393