Financing - Secured Debt (Details)	Dec. 31, 2018 USD ($) series	Dec. 31, 2017 USD ($)	Dec. 31, 2014
Debt Disclosure [Line Items]
Total	$ 7,863,000,000
Capitalized lease obligations	197,000,000	$ 204,000,000
Georgia Power
Debt Disclosure [Line Items]
Total	1,750,000,000
Capitalized lease obligations	142,000,000	154,000,000
Georgia Power | FFB Loan
Debt Disclosure [Line Items]
Total	2,625,000,000.000	2,600,000,000.0
Georgia Power | Plant Vogtle Units 3 And 4
Debt Disclosure [Line Items]
Percent ownership			45.70%
Georgia Power | Secured Debt
Debt Disclosure [Line Items]
Long-term debt	2,767,000,000	2,779,000,000
Mississippi Power
Debt Disclosure [Line Items]
Total	100,000,000
Mississippi Power | Secured Debt
Debt Disclosure [Line Items]
Long-term debt	270,000,000	270,000,000
Southern Company Gas
Debt Disclosure [Line Items]
Total	1,900,000,000
Southern Company Gas | Secured Debt
Debt Disclosure [Line Items]
Long-term debt	1,325,000,000	1,025,000,000
Gulf Power
Debt Disclosure [Line Items]
Total	280,000,000
Secured debt	$ 41,000,000	$ 41,000,000
Number of series of pollution controls revenue bonds | series	2