Derivatives - Pre-tax Effect of Derivatives on Balance Sheets and Statements of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	$ (217)	$ (197)
Regulatory Hedge Unrealized Gain	3	7
Interest rate derivatives [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(22)	(16)	$ 0
Interest rate derivatives [Member] | Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(9)	(8)	(14)
Other regulatory assets current [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(130)	(118)
Other regulatory assets deferred [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(87)	(79)
Other regulatory liabilities current [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	3	7
Other regulatory liabilities deferred [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	0	0
Alabama Power [Member] | Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(3)	(3)	(3)
Alabama Power [Member] | Interest rate derivatives [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(7)	(8)	0
Alabama Power [Member] | Other regulatory assets current [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(40)	(32)
Alabama Power [Member] | Other regulatory assets deferred [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(15)	(21)
Alabama Power [Member] | Other regulatory assets [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(55)	(53)
Alabama Power [Member] | Other Current Liabilities [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	1	1
Alabama Power [Member] | Other regulatory liabilities deferred [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	0	0
Alabama Power [Member] | Other regulatory liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	1	1
Gulf Power [Member] | Interest rate derivatives [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	1	0	0
Gulf Power [Member] | Interest rate derivatives [Member] | Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1)	(1)	(1)
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(100)	(72)
Regulatory Hedge Unrealized Gain	0	0
Gulf Power [Member] | Other regulatory assets current [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(49)	(37)
Gulf Power [Member] | Other regulatory assets deferred [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(51)	(35)
Gulf Power [Member] | Other regulatory liabilities current [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	0	0
Gulf Power [Member] | Other regulatory liabilities deferred [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	0	0
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(47)	(45)
Regulatory Hedge Unrealized Gain	0	0
Mississippi Power [Member] | Other regulatory assets current [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(29)	(26)
Mississippi Power [Member] | Other regulatory assets deferred [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(18)	(19)
Mississippi Power [Member] | Other regulatory liabilities current [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	0	0
Mississippi Power [Member] | Other regulatory liabilities deferred [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	0	0
Southern Power [Member] | Interest rate derivatives [Member] | Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(1)	(1)	(6)
Georgia Power [Member] | Interest rate derivatives [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(15)	(8)	0
Georgia Power [Member] | Interest rate derivatives [Member] | Interest expense, net of amounts capitalized [Member]
Pre-tax effect of derivatives designated as cash flow hedging instruments
Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(3)	(3)	$ (3)
Georgia Power [Member] | Other regulatory assets current [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(12)	(23)
Georgia Power [Member] | Other regulatory assets deferred [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(3)	(4)
Georgia Power [Member] | Other regulatory assets [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Loss	(15)	(27)
Georgia Power [Member] | Other regulatory liabilities current [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	2	6
Georgia Power [Member] | Other deferred credits and liabilities [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	0	1
Georgia Power [Member] | Other regulatory liabilities [Member] | Hedging Instruments for Regulatory Purposes [Member] | Energy Related Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Regulatory Hedge Unrealized Gain	$ 2	$ 7