Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2017	Jan. 31, 2018	Jun. 30, 2017
Document Information [Line Items]
Entity Registrant Name	SOUTHERN CO
Entity Central Index Key	0000092122
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 47.9
Entity Common Stock, Shares Outstanding (in shares)		1,008,159,482
ALABAMA POWER CO
Document Information [Line Items]
Entity Registrant Name	ALABAMA POWER CO
Entity Central Index Key	0000003153
Entity Well-known Seasoned Issuer	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		30,537,500
GEORGIA POWER CO
Document Information [Line Items]
Entity Registrant Name	GEORGIA POWER CO
Entity Central Index Key	0000041091
Entity Well-known Seasoned Issuer	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		9,261,500
GULF POWER CO
Document Information [Line Items]
Entity Registrant Name	GULF POWER CO
Entity Central Index Key	0000044545
Entity Well-known Seasoned Issuer	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		7,392,717
MISSISSIPPI POWER CO
Document Information [Line Items]
Entity Registrant Name	MISSISSIPPI POWER CO
Entity Central Index Key	0000066904
Entity Well-known Seasoned Issuer	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		1,121,000
SOUTHERN POWER CO
Document Information [Line Items]
Entity Registrant Name	SOUTHERN POWER CO
Entity Central Index Key	0001160661
Entity Well-known Seasoned Issuer	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		1,000
SOUTHERN Co GAS
Document Information [Line Items]
Entity Registrant Name	SOUTHERN Co GAS
Entity Central Index Key	0001004155
Entity Well-known Seasoned Issuer	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		100