Derivatives - Narrative (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 Btu
Derivatives (Textual) [Abstract]
Maximum Potential Collateral Requirements Arising from Credit Risk Related Contingent Features	59
Southern Company [Member]
Derivatives (Textual) [Abstract]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints	4,000,000
Georgia Power [Member]
Derivatives (Textual) [Abstract]
Expected volume of natural gas subject to option to sell back excess gas due to operational constraints	3,000,000
Maximum Potential Collateral Requirements Arising from Credit Risk Related Contingent Features	59
Southern 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 from Credit Risk Related Contingent Features	59
Alabama Power [Member]
Derivatives (Textual) [Abstract]
Maximum Potential Collateral Requirements Arising from Credit Risk Related Contingent Features	59
Gulf Power [Member]
Derivatives (Textual) [Abstract]
Maximum Potential Collateral Requirements Arising from Credit Risk Related Contingent Features	59
Mississippi Power [Member]
Derivatives (Textual) [Abstract]
Maximum Potential Collateral Requirements Arising from Credit Risk Related Contingent Features	59