Financing - Schedule of Credit Arrangements (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015
Line of Credit Facility [Line Items]
Expires, 2015	$ 478
Expires, 2016	565
Expires, 2017	30
Expires, 2018	4,130
Total	5,203
Unused	5,147
Executable Term Loans, One Year	153
Executable Term Loans, Two Years	40
Due Within One Year, Term Out	193
Due Within One Year, No Term Out	800
Southern Company [Member]
Line of Credit Facility [Line Items]
Expires, 2015	0
Expires, 2016	0
Expires, 2017	0
Expires, 2018	1,000
Total	1,000
Unused	1,000
Executable Term Loans, One Year	0
Executable Term Loans, Two Years	0
Due Within One Year, Term Out	0
Due Within One Year, No Term Out	0
Alabama Power [Member]
Line of Credit Facility [Line Items]
Expires, 2015	228
Expires, 2016	50
Expires, 2017	0
Expires, 2018	1,030
Total	1,308
Unused	1,308
Executable Term Loans, One Year	58
Executable Term Loans, Two Years	0
Due Within One Year, Term Out	58
Due Within One Year, No Term Out	170
Georgia Power [Member]
Line of Credit Facility [Line Items]
Expires, 2015	0
Expires, 2016	150
Expires, 2017	0
Expires, 2018	1,600
Total	1,750
Unused	1,736
Executable Term Loans, One Year	0
Executable Term Loans, Two Years	0
Due Within One Year, Term Out	0
Due Within One Year, No Term Out	150
Gulf Power [Member]
Line of Credit Facility [Line Items]
Expires, 2015	45
Expires, 2016	200
Expires, 2017	30
Expires, 2018	0
Total	275
Unused	275
Executable Term Loans, One Year	50
Executable Term Loans, Two Years	0
Due Within One Year, Term Out	50
Due Within One Year, No Term Out	195
Mississippi Power [Member]
Line of Credit Facility [Line Items]
Expires, 2015	135
Expires, 2016	165
Expires, 2017	0
Expires, 2018	0
Total	300
Unused	270
Executable Term Loans, One Year	25
Executable Term Loans, Two Years	40
Due Within One Year, Term Out	65
Due Within One Year, No Term Out	235
Southern Power [Member]
Line of Credit Facility [Line Items]
Expires, 2015	0
Expires, 2016	0
Expires, 2017	0
Expires, 2018	500
Total	500
Unused	488
Executable Term Loans, One Year	0
Executable Term Loans, Two Years	0
Due Within One Year, Term Out	0
Due Within One Year, No Term Out	0
Other Subsidiaries [Member]
Line of Credit Facility [Line Items]
Expires, 2015	70
Expires, 2016	0
Expires, 2017	0
Expires, 2018	0
Total	70
Unused	70
Executable Term Loans, One Year	20
Executable Term Loans, Two Years	0
Due Within One Year, Term Out	20
Due Within One Year, No Term Out	$ 50