Derivatives - Pre-tax Effects of Derivatives Designated as Cash Flow Hedging Instruments (Details) (Energy Related Derivative [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	$ (3)	$ (32)
Alabama Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	6	(1)
Georgia Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(8)	(16)
Gulf Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(1)	(10)
Mississippi Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0	(5)
Other regulatory assets current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(17)	(26)
Other regulatory assets current [Member] | Alabama Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(1)	(3)
Other regulatory assets current [Member] | Georgia Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(10)	(13)
Other regulatory assets current [Member] | Gulf Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(4)	(6)
Other regulatory assets current [Member] | Mississippi Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(2)	(4)
Other regulatory assets deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(26)	(29)
Other regulatory assets deferred [Member] | Alabama Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(5)	(5)
Other regulatory assets deferred [Member] | Georgia Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(6)	(8)
Other regulatory assets deferred [Member] | Gulf Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(9)	(11)
Other regulatory assets deferred [Member] | Mississippi Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	(6)	(6)
Other regulatory liabilities current [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	36	16
Other regulatory liabilities current [Member] | Alabama Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	11	5
Other regulatory liabilities current [Member] | Georgia Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	8	3
Other regulatory liabilities current [Member] | Gulf Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	10	5
Other regulatory liabilities current [Member] | Mississippi Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	7	3
Other regulatory liabilities deferred [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	4	7
Other regulatory liabilities deferred [Member] | Alabama Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	1	2
Other regulatory liabilities deferred [Member] | Georgia Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	0	2
Other regulatory liabilities deferred [Member] | Gulf Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	2	2
Other regulatory liabilities deferred [Member] | Mississippi Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total energy-related derivative gains (losses)	$ 1	$ 2