v3.10.0.1
Financing - Securities Due Within One Year (Details) - USD ($)
$ in Millions
Dec. 31, 2018
Dec. 31, 2017
Debt Disclosure [Line Items]    
Senior notes $ 2,950 $ 2,354
Long-term bank term loans   1,420
Revenue bonds 173 90
First mortgage bonds 50  
Capitalized leases 24 31
Other 1 (3)
Total 3,198 3,892
Alabama Power    
Debt Disclosure [Line Items]    
Senior notes 200  
Revenue bonds 0  
First mortgage bonds 0  
Capitalized leases 1  
Other 0  
Total 201  
Georgia Power    
Debt Disclosure [Line Items]    
Senior notes 500 750
Long-term bank term loans   100
Revenue bonds 108 0
First mortgage bonds 0  
Capitalized leases 13 11
Other (4) (4)
Total 617 857
Mississippi Power    
Debt Disclosure [Line Items]    
Senior notes 0 0
Long-term bank term loans   900
Revenue bonds 40 90
First mortgage bonds 0  
Capitalized leases 0 0
Other 0 (1)
Total 40 989
Long-term pollution control bond, current 40 40
Revenue bonds, current 50 50
Southern Power    
Debt Disclosure [Line Items]    
Senior notes 600 350
Long-term bank term loans   420
Revenue bonds 0 0
First mortgage bonds 0  
Capitalized leases 0 0
Other (1) 0
Total 599 770
Southern Company Gas    
Debt Disclosure [Line Items]    
Senior notes 300 155
Long-term bank term loans   0
Revenue bonds 0 0
First mortgage bonds 50  
Capitalized leases 0 0
Other 7 2
Total $ 357 $ 157