Derivatives - Schedule of Derivatives and Gains (Losses) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Notional amount of interest rate derivatives
Notional Amount	$ 350
Interest Rate Paid, basis spread on LIBOR	1.96%	[1]
Fair Value Hedging [Member]
Notional amount of interest rate derivatives
Interest Rate Received	4.15%
Interest Rate Paid	3-month LIBOR  + 1.96%	[1]
Hedge Maturity Date	May 01, 2014
Fair Value Gain (Loss) September 30, 2013	$ 7
Gas [Member]
Energy-related derivative contracts
Net Purchased mmBtu	267,000,000
Longest Hedge Date	2018
Longest Non-Hedge Date	2017
Gas [Member] | Alabama Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	68,000,000
Longest Hedge Date	2017
Gas [Member] | Georgia Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	67,000,000
Longest Hedge Date	2017
Gas [Member] | Gulf Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	85,000,000
Longest Hedge Date	2018
Gas [Member] | Mississippi Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	46,000,000
Longest Hedge Date	2017
Gas [Member] | Southern Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	1,000,000
Longest Non-Hedge Date	2017

[1] (a)Weighted average