Derivatives - Narrative (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 MMBTU
Derivatives (Textual) [Abstract]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints	11,000,000
Maximum potential collateral requirements arising the from credit-risk-related contingent features	$ 1,000,000
Alabama Power [Member]
Derivatives (Textual) [Abstract]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints	1,000,000
Maximum potential collateral requirements arising the from credit-risk-related contingent features	1,000,000
Georgia Power [Member]
Derivatives (Textual) [Abstract]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints	5,000,000
Maximum potential collateral requirements arising the from credit-risk-related contingent features	1,000,000
Gulf Power [Member]
Derivatives (Textual) [Abstract]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints	1,000,000
Maximum potential collateral requirements arising the from credit-risk-related contingent features	1,000,000
Mississippi Power [Member]
Derivatives (Textual) [Abstract]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints	1,000,000
Maximum potential collateral requirements arising the from credit-risk-related contingent features	1,000,000
Southern Power [Member]
Derivatives (Textual) [Abstract]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints	3,000,000
Maximum potential collateral requirements arising the from credit-risk-related contingent features	$ 1,000,000