Fair Value Measurements - Narrative (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Fair Value Measurements (Textual) [Abstract]
Increase (decrease) in fair value of funds including reinvested interest and dividends	$ 60	$ 112
Alabama Power [Member]
Fair Value Measurements (Textual) [Abstract]
Increase (decrease) in fair value of funds including reinvested interest and dividends	33	76
Georgia Power [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Notices Of Withdrawal Foreign Equity Funds	20.00%	20.00%
Maximum Number of Months Related to Maturities in Portfolio Not to Exceeded from Date of Purchase		13 months
Maximum Number of Days Related to Dollar Weighted Average Portfolio Maturities Regarding Commingled Funds		90 days
Fair Value Measurements (Textual) [Abstract]
Increase (decrease) in fair value of funds including reinvested interest and dividends	27	36
Minimum [Member] | Georgia Power [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Withdrawal Of Foreign Equity Fund Investment	1	1
Foreign Equity Fund Investment	$ 10	$ 10