Derivatives - Schedule of Derivatives and Gains (Losses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Notional amount of interest rate derivatives
Notional Amount	$ 350
Interest Rate Paid, basis spread on LIBOR	1.96%
Fair Value Hedging [Member]
Notional amount of interest rate derivatives
Interest Rate Received	4.15%
Weighted Average Interest Rate Paid	3-month LIBOR  + 1.96%
Hedge Maturity Date	May 31, 2014
Fair Value Gain (Loss) March 31, 2014	$ 3
Gas [Member]
Energy-related derivative contracts
Net Purchased mmBtu	256,000,000
Longest Hedge Date1	2018
Longest Non-hedge Date1	2017
Gas [Member] | Alabama Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	65,000,000
Longest Hedge Date1	2017
Gas [Member] | Georgia Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	53,000,000
Longest Hedge Date1	2017
Gas [Member] | Gulf Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	83,000,000
Longest Hedge Date1	2018
Gas [Member] | Mississippi Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	54,000,000
Longest Hedge Date1	2017
Gas [Member] | Southern Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	1,000,000
Longest Non-hedge Date1	2017