Summary of Significant Accounting Policies - Property, Plant, and Equipment (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Public Utilities, Property, Plant and Equipment, Plant in Service [Abstract]
Generation	$ 37,892,000,000	$ 35,360,000,000
Transmission	9,884,000,000	9,289,000,000
Distribution	17,123,000,000	16,499,000,000
General	4,198,000,000	3,958,000,000
Plant acquisition adjustment	123,000,000	123,000,000
Utility plant in service	69,220,000,000	65,229,000,000
Information technology equipment and software	244,000,000	242,000,000
Communications equipment	439,000,000	437,000,000
Other	110,000,000	113,000,000
Other plant in service	793,000,000	792,000,000
Total plant in service	70,013,000,000	66,021,000,000
Alabama Power [Member]
Public Utilities, Property, Plant and Equipment, Plant in Service [Abstract]
Generation	11,670,000,000	11,314,000,000
Transmission	3,579,000,000	3,287,000,000
Distribution	6,196,000,000	5,934,000,000
General	1,623,000,000	1,545,000,000
Plant acquisition adjustment	12,000,000	12,000,000
Total plant in service	23,080,000,000	22,092,000,000
Georgia Power [Member]
Public Utilities, Property, Plant and Equipment, Plant in Service [Abstract]
Generation	15,201,000,000	14,872,000,000
Transmission	5,086,000,000	4,859,000,000
Distribution	8,913,000,000	8,620,000,000
General	1,855,000,000	1,753,000,000
Plant acquisition adjustment	28,000,000	28,000,000
Total plant in service	31,083,000,000	30,132,000,000
Gulf Power [Member]
Public Utilities, Property, Plant and Equipment, Plant in Service [Abstract]
Generation	2,637,817,000	2,607,166,000
Transmission	515,754,000	473,378,000
Distribution	1,156,872,000	1,117,024,000
General	182,734,000	164,065,000
Plant acquisition adjustment	1,776,000	2,031,000
Total plant in service	4,494,953,000	4,363,664,000
Mississippi Power [Member]
Public Utilities, Property, Plant and Equipment, Plant in Service [Abstract]
Generation	2,293,511,000	1,475,264,000
Transmission	664,618,000	633,903,000
Distribution	853,835,000	828,470,000
General	484,711,000	439,721,000
Plant acquisition adjustment	81,412,000	81,412,000
Total plant in service	$ 4,378,087,000	$ 3,458,770,000