v3.26.1
Segment and Related Information - Narrative (Details)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2026
USD ($)
state
Jun. 30, 2025
USD ($)
Jun. 30, 2026
USD ($)
segment
state
Jun. 30, 2025
USD ($)
Segment Reporting [Line Items]        
Number of states in which entity operates | state 3   3  
Operating revenues $ 6,722 $ 6,734 $ 14,765 $ 14,328
Earnings from equity method investments 86 10 136 43
Other segment items 3,472 3,617 $ 8,138 7,812
Traditional Electric Operating Companies        
Segment Reporting [Line Items]        
Number of operating segments | segment     3  
Number of reportable segments | segment     1  
SOUTHERN POWER CO        
Segment Reporting [Line Items]        
Number of reportable segments | segment     1  
Operating revenues 354 362 $ 878 795
Earnings from equity method investments     0 0
SOUTHERN POWER CO | Kay Wind Facility        
Segment Reporting [Line Items]        
Depreciation before tax 140 42 293 69
Depreciation after tax 109 31 228 51
SOUTHERN POWER CO | Reportable Segment        
Segment Reporting [Line Items]        
Other segment items $ 329 296 $ 772 599
SOUTHERN Co GAS        
Segment Reporting [Line Items]        
Number of states in which entity operates | state 4   4  
Number of reportable segments | segment     3  
Operating revenues $ 948 972 $ 3,122 2,811
Earnings from equity method investments 32 23 78 62
Other segment items $ 554 599 $ 1,911 1,670
SOUTHERN Co GAS | Southern Natural Gas Company, LLC        
Segment Reporting [Line Items]        
Ownership percentage, equity method investment 50.00%   50.00%  
SOUTHERN Co GAS | Dalton Pipeline        
Segment Reporting [Line Items]        
Ownership percentage, equity method investment 50.00%   50.00%  
MISSISSIPPI POWER CO        
Segment Reporting [Line Items]        
Operating revenues $ 404 381 $ 867 788
MISSISSIPPI POWER CO | Reportable Segment        
Segment Reporting [Line Items]        
Other segment items 173 183 424 400
Traditional Electric Operating Companies | Wholesale revenues, affiliates | SOUTHERN POWER CO        
Segment Reporting [Line Items]        
Operating revenues $ 92 $ 114 $ 192 $ 229