Fair Value Measurements - Narrative (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Fair Value Measurements (Textual) [Abstract]
Increase in fair value of funds including reinvested interest and dividends	$ 59
Alabama Power [Member]
Fair Value Measurements (Textual) [Abstract]
Increase in fair value of funds including reinvested interest and dividends	38
Georgia Power [Member]
Fair Value Measurements (Textual) [Abstract]
Increase in fair value of funds including reinvested interest and dividends	21
Notices Of Withdrawal Foreign Equity Funds	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
Minimum [Member] | Georgia Power [Member]
Fair Value, Option, Quantitative Disclosures [Line Items]
Withdrawal Of Foreign Equity Fund Investment	1
Fair Value Measurements (Textual) [Abstract]
Foreign Equity Fund Investment	$ 10