Derivatives - Pre-tax Effects of Derivatives Designated as Cash Flow Hedging Instruments (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2015		Jun. 30, 2014	Dec. 31, 2014
Southern Company [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	$ (175)			$ (190)
Southern Company [Member] | Energy Related Derivative [Member] | Other regulatory assets current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(99)			(118)
Southern Company [Member] | Energy Related Derivative [Member] | Other regulatory assets deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(81)			(79)
Southern Company [Member] | Energy Related Derivative [Member] | Other regulatory liabilities current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	5	[1]		7	[2]
Southern Company [Member] | Energy Related Derivative [Member] | Other regulatory liabilities deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	0	[3]		0	[4]
Southern Company [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	31		$ 0
Southern Company [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(2)		(2)
Alabama Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(46)			(52)
Alabama Power [Member] | Energy Related Derivative [Member] | Other regulatory assets current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(31)			(32)
Alabama Power [Member] | Energy Related Derivative [Member] | Other regulatory assets deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(17)			(21)
Alabama Power [Member] | Energy Related Derivative [Member] | Other regulatory liabilities current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	2	[1]		1	[2]
Alabama Power [Member] | Energy Related Derivative [Member] | Other regulatory liabilities deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	0	[3]		0	[4]
Alabama Power [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	7		0
Alabama Power [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1)		0
Georgia Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(14)			(20)
Georgia Power [Member] | Energy Related Derivative [Member] | Other regulatory assets current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(15)			(23)
Georgia Power [Member] | Energy Related Derivative [Member] | Other regulatory assets deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(2)			(4)
Georgia Power [Member] | Energy Related Derivative [Member] | Other regulatory liabilities current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	3	[1]		6	[2]
Georgia Power [Member] | Energy Related Derivative [Member] | Other regulatory liabilities deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	0	[3]		1	[4]
Georgia Power [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	24		0
Georgia Power [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1)		0
Gulf Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(74)			(72)
Gulf Power [Member] | Energy Related Derivative [Member] | Other regulatory assets current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(32)			(37)
Gulf Power [Member] | Energy Related Derivative [Member] | Other regulatory assets deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(42)			(35)
Gulf Power [Member] | Energy Related Derivative [Member] | Other regulatory liabilities current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	0	[1]		0	[2]
Gulf Power [Member] | Energy Related Derivative [Member] | Other regulatory liabilities deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	0	[3]		0	[4]
Mississippi Power [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(41)			(45)
Mississippi Power [Member] | Energy Related Derivative [Member] | Other regulatory assets current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(21)			(26)
Mississippi Power [Member] | Energy Related Derivative [Member] | Other regulatory assets deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	(20)			(19)
Mississippi Power [Member] | Energy Related Derivative [Member] | Other regulatory liabilities current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	0	[1]		0	[2]
Mississippi Power [Member] | Energy Related Derivative [Member] | Other regulatory liabilities deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet	0	[3]		$ 0	[4]
Mississippi Power [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0		0
Mississippi Power [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)			(1)
Southern Power [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	0		0
Southern Power [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	$ 0		$ (1)

[1] Southern Company, Alabama Power, and Georgia Power include other regulatory liabilities, current in other current liabilities.

[2] Southern Company, Alabama Power, and Georgia Power include other regulatory liabilities, current in other current liabilities.

[3] Georgia Power includes other regulatory liabilities, deferred in other deferred credits and liabilities.Regulatory Hedge Unrealized Gain (Loss) Recognized on the Balance Sheet at December 31, 2014Derivative Category and Balance SheetLocation SouthernCompany AlabamaPower GeorgiaPower GulfPower MississippiPower (in millions)Energy-related derivatives: Other regulatory assets, current $(118) $(32) $(23) $(37) $(26)Other regulatory assets, deferred (79) (21) (4) (35) (19)Other regulatory liabilities, current (a) 7 1 6 — —Other regulatory liabilities, deferred (b) — — 1 — —Total energy-related derivative gains (losses) $(190) $(52) $(20) $(72) $(45)

[4] Georgia Power includes other regulatory liabilities, deferred in other deferred credits and liabilities.