Derivatives - Schedule of Derivatives and Gains (Losses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Notional amount of interest rate derivatives
Notional Amount	$ 2,050
Fair Value Gain (Loss) at March 31, 2015	(37)
Alabama Power [Member] | Maturity Date October 2025 [Member] | Cash Flow Hedges Of Forecasted Debt [Member]
Notional amount of interest rate derivatives
Notional Amount	200
Interest Rate Received, Description	3-month LIBOR
Weighted Average Interest Rate Paid	2.93%
Hedge Maturity Date	Oct. 01, 2025
Fair Value Gain (Loss) at March 31, 2015	(14)
Alabama Power [Member] | Gas [Member]
Energy-related derivative contracts
Net Purchased mmBtu	54,000,000
Longest Hedge Date	2018
Georgia Power [Member] | Maturity Date May 2025 [Member] | Cash Flow Hedges Of Forecasted Debt [Member]
Notional amount of interest rate derivatives
Notional Amount	350
Interest Rate Received, Description	3-month LIBOR
Weighted Average Interest Rate Paid	2.57%
Hedge Maturity Date	May 01, 2025
Fair Value Gain (Loss) at March 31, 2015	(17)
Georgia Power [Member] | Maturity Date November 2025 [Member] | Cash Flow Hedges Of Forecasted Debt [Member]
Notional amount of interest rate derivatives
Notional Amount	350
Interest Rate Received, Description	3-month LIBOR
Weighted Average Interest Rate Paid	2.57%
Hedge Maturity Date	Nov. 01, 2025
Fair Value Gain (Loss) at March 31, 2015	(13)
Georgia Power [Member] | Maturity Date March 2016 [Member] | Cash Flow Hedges Of Existing Debt [Member]
Notional amount of interest rate derivatives
Notional Amount	250
Interest Rate Received, Description	3-month LIBOR + 0.32%
Interest Rate Received	0.32%
Weighted Average Interest Rate Paid	0.75%
Hedge Maturity Date	Mar. 01, 2016
Fair Value Gain (Loss) at March 31, 2015	0
Georgia Power [Member] | Maturity Date August 2016 [Member] | Cash Flow Hedges Of Existing Debt [Member]
Notional amount of interest rate derivatives
Notional Amount	200
Interest Rate Received, Description	3-month LIBOR + 0.40%
Interest Rate Received	0.40%
Weighted Average Interest Rate Paid	1.01%
Hedge Maturity Date	Aug. 01, 2016
Fair Value Gain (Loss) at March 31, 2015	0
Georgia Power [Member] | Maturity Date June 2018 [Member] | Fair Value Hedges Of Existing Debt [Member]
Notional amount of interest rate derivatives
Notional Amount	250
Interest Rate Received	5.40%
Weighted Average Interest Rate Paid	4.02%
Weighted Average Interest Rate Paid, Description	3-month LIBOR + 4.02%
Hedge Maturity Date	Jun. 01, 2018
Fair Value Gain (Loss) at March 31, 2015	2
Georgia Power [Member] | Maturity Date December 2019 [Member] | Fair Value Hedges Of Existing Debt [Member]
Notional amount of interest rate derivatives
Notional Amount	200
Interest Rate Received	4.25%
Weighted Average Interest Rate Paid	2.46%
Weighted Average Interest Rate Paid, Description	3-month LIBOR + 2.46%
Hedge Maturity Date	Dec. 01, 2019
Fair Value Gain (Loss) at March 31, 2015	4
Georgia Power [Member] | Gas [Member]
Energy-related derivative contracts
Net Purchased mmBtu	44,000,000
Longest Hedge Date	2017
Southern Company [Member] | Maturity Date August 2017 [Member] | Fair Value Hedges Of Existing Debt [Member]
Notional amount of interest rate derivatives
Notional Amount	250
Interest Rate Received	1.30%
Weighted Average Interest Rate Paid	0.17%
Weighted Average Interest Rate Paid, Description	3-month LIBOR + 0.17%
Hedge Maturity Date	Aug. 01, 2017
Fair Value Gain (Loss) at March 31, 2015	$ 1
Southern Company [Member] | Gas [Member]
Energy-related derivative contracts
Net Purchased mmBtu	241,000,000
Longest Hedge Date	2020
Longest Non-Hedge Date	2017
Gulf Power [Member] | Gas [Member]
Energy-related derivative contracts
Net Purchased mmBtu	92,000,000
Longest Hedge Date	2020
Mississippi Power [Member] | Gas [Member]
Energy-related derivative contracts
Net Purchased mmBtu	49,000,000
Longest Hedge Date	2018
Southern Power [Member] | Gas [Member]
Energy-related derivative contracts
Net Purchased mmBtu	2,000,000
Longest Non-Hedge Date	2017