Fair Value Measurements - Financial Instruments for which Carrying Amount did not Equal Fair Value (Details) $ in Millions	Jun. 30, 2016 USD ($)
Southern Company [Member]
Long-term debt:
Long-term debt, including securities due within one year, Carrying Amount	$ 37,953
Long-term debt, including securities due within one year, Fair Value	40,992
Alabama Power [Member]
Long-term debt:
Long-term debt, including securities due within one year, Carrying Amount	7,090
Long-term debt, including securities due within one year, Fair Value	7,940
Georgia Power [Member]
Long-term debt:
Long-term debt, including securities due within one year, Carrying Amount	10,603
Long-term debt, including securities due within one year, Fair Value	11,881
Gulf Power [Member]
Long-term debt:
Long-term debt, including securities due within one year, Carrying Amount	1,182
Long-term debt, including securities due within one year, Fair Value	1,275
Mississippi Power [Member]
Long-term debt:
Long-term debt, including securities due within one year, Carrying Amount	2,983
Long-term debt, including securities due within one year, Fair Value	2,967
Southern Power [Member]
Long-term debt:
Long-term debt, including securities due within one year, Carrying Amount	4,332
Long-term debt, including securities due within one year, Fair Value	$ 4,523