v3.25.0.1
SEGMENT AND RELATED INFORMATION - Gas Revenues (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2023
Jun. 30, 2023
Dec. 31, 2022
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Segment Reporting Information [Line Items]            
Operating revenues       $ 26,724 $ 25,253 $ 29,279
Other segment items       13,995 13,954 19,426
Depreciation and amortization       4,755 4,525 3,663
Earnings from equity method investments       139 144 151
Interest expense       2,743 2,446 2,022
Income taxes (benefit)       969 496 795
Segment net income (loss)       4,401 3,976 3,524
Total assets $ 139,331   $ 134,891 145,180 139,331 134,891
Southern Company Gas            
Segment Reporting Information [Line Items]            
Operating revenues       4,456 4,702 5,962
Other segment items       2,613 3,124 4,536
Depreciation and amortization       650 582 559
Earnings from equity method investments       146 140 148
Interest expense       341 310 263
Income taxes (benefit)       258 211 180
Segment net income (loss)       740 615 572
Total assets 25,083   24,621 26,177 25,083 24,621
Estimated loss on regulatory disallowance       0 (96) 0
Southern Company Gas | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Natural Gas Storage Facilities            
Segment Reporting Information [Line Items]            
Gain on dispositions, net     (131)      
Gain (loss) on dispositions, after tax     (99)      
Nicor Gas            
Segment Reporting Information [Line Items]            
Estimated loss on regulatory disallowance (58) $ (38)   96    
Estimated loss on regulatory disallowance, after tax (44) $ (28)   72    
Operating Segments            
Segment Reporting Information [Line Items]            
Operating revenues       26,059 24,700 28,835
Other segment items       13,342 13,405 18,793
Depreciation and amortization       4,684 4,447 3,588
Earnings from equity method investments       154 139 148
Interest expense       1,713 1,584 1,330
Income taxes (benefit)       1,261 794 1,028
Segment net income (loss)       5,213 4,609 4,244
Total assets 137,728   132,904 143,382 137,728 132,904
Operating Segments | Southern Company Gas            
Segment Reporting Information [Line Items]            
Operating revenues       4,447 4,685 5,937
Other segment items       2,598 3,109 4,401
Depreciation and amortization       649 581 537
Earnings from equity method investments       146 140 148
Interest expense       349 310 259
Income taxes (benefit)       244 195 217
Segment net income (loss)       753 630 671
Total assets 26,055   25,233 27,336 26,055 25,233
All Other            
Segment Reporting Information [Line Items]            
Operating revenues       843 718 593
Other segment items       802 699 771
Depreciation and amortization       71 78 75
Earnings from equity method investments       (17) 5 3
Interest expense       1,030 879 694
Income taxes (benefit)       (292) (298) (233)
Segment net income (loss)       (785) (635) (711)
Total assets 2,446   2,665 2,371 2,446 2,665
All Other | Southern Company Gas            
Segment Reporting Information [Line Items]            
Operating revenues       23 36 55
Other segment items       29 34 165
Depreciation and amortization       1 1 22
Earnings from equity method investments       0 0 0
Interest expense       (8) 0 4
Income taxes (benefit)       14 16 (37)
Segment net income (loss)       (13) (15) (99)
Total assets 9,675   8,943 10,047 9,675 8,943
Eliminations            
Segment Reporting Information [Line Items]            
Operating revenues       (178) (165) (149)
Other segment items       (149) (150) (138)
Depreciation and amortization       0 0 0
Earnings from equity method investments       2 0 0
Interest expense       0 (17) (2)
Income taxes (benefit)       0 0 0
Segment net income (loss)       (27) 2 (9)
Total assets (843)   (678) (573) (843) (678)
Eliminations | Southern Company Gas            
Segment Reporting Information [Line Items]            
Operating revenues       (14) (19) (30)
Other segment items       (14) (19) (30)
Depreciation and amortization       0 0 0
Earnings from equity method investments       0 0 0
Interest expense       0 0 0
Income taxes (benefit)       0 0 0
Segment net income (loss)       0 0 0
Total assets (10,647)   (9,555) (11,206) (10,647) (9,555)
Gas distribution operations | Operating Segments | Southern Company Gas            
Segment Reporting Information [Line Items]            
Operating revenues       3,899 4,105 5,267
Other segment items       2,236 2,702 3,907
Depreciation and amortization       630 561 516
Earnings from equity method investments       0 0 0
Interest expense       311 275 229
Income taxes (benefit)       172 126 145
Segment net income (loss)       550 441 470
Total assets 22,906   22,040 24,067 22,906 22,040
Gas Pipeline Investments | Operating Segments | Southern Company Gas            
Segment Reporting Information [Line Items]            
Operating revenues       32 32 32
Other segment items       6 5 6
Depreciation and amortization       5 5 5
Earnings from equity method investments       146 140 148
Interest expense       35 32 27
Income taxes (benefit)       31 32 35
Segment net income (loss)       101 98 107
Total assets 1,534   1,577 1,573 1,534 1,577
Gas marketing services | Operating Segments | Southern Company Gas            
Segment Reporting Information [Line Items]            
Operating revenues       516 548 638
Other segment items       356 402 488
Depreciation and amortization       14 15 16
Earnings from equity method investments       0 0 0
Interest expense       3 3 3
Income taxes (benefit)       41 37 37
Segment net income (loss)       102 91 94
Total assets 1,615   1,616 1,696 1,615 1,616
Southern Company Gas            
Segment Reporting Information [Line Items]            
Operating revenues       4,456 4,702 5,962
Southern Company Gas | Gas distribution operations            
Segment Reporting Information [Line Items]            
Operating revenues       3,899 4,090 5,240
Southern Company Gas | Gas marketing services            
Segment Reporting Information [Line Items]            
Operating revenues       516 548 638
Southern Company Gas | Other Gas Revenue            
Segment Reporting Information [Line Items]            
Operating revenues       41 64 84
Southern Company Gas | Operating Segments            
Segment Reporting Information [Line Items]            
Operating revenues       4,456 4,702 5,962
Other segment items       2,613 3,124 4,536
Depreciation and amortization       650 582 559
Earnings from equity method investments       146 140 148
Interest expense       341 310 263
Income taxes (benefit)       258 211 180
Segment net income (loss)       740 615 572
Total assets $ 25,083   $ 24,621 $ 26,177 $ 25,083 $ 24,621