Derivatives - Energy-Related, Interest Rate, and Foreign Currency Derivatives Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Fair Value Hedging [Member]
Interest rate derivative contracts
Notional Amount	$ 350
Derivative, Maturity Date	May 01, 2014
Fair Value Gain (Loss)	$ 3
Interest Rate Received [Member] | Fair Value Hedging [Member]
Interest rate derivative contracts
Interest Rate Received	4.15%
Interest Rate Paid [Member] | Fair Value Hedging [Member]
Interest rate derivative contracts
Interest Rate Paid	3-month LIBOR + 1.96%
Interest Rate Paid, Description of Variable Rate Basis	3-month LIBOR
Interest Rate Paid, Spread on Variable Rate	1.96%
Alabama Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	69,000,000	[1]
Longest Hedge Date	2017
Mississippi Power [Member]
Energy-related derivative contracts
Net Purchased mmBtu	56,000,000	[2]
Longest Hedge Date	2017

[1] *million British thermal units (mmBtu)

[2] *mmBtu — million British thermal units