v3.25.0.1
RETIREMENT BENEFITS - Changes in Regulatory Assets (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance $ 6,523      
Total Stockholders' Equity (See accompanying statements) 36,674 $ 35,225 $ 34,532 $ 32,276
Total other comprehensive income (loss) 99 (10) 71  
Ending balance 7,041 6,523    
Regulatory asset   66 216  
Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Total Stockholders' Equity (See accompanying statements) (32) (56) (18) (76)
Total other comprehensive income (loss) 24 (38) 58  
Pension plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 2,913      
Ending balance 2,658 2,913    
Pension plans | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 2,913 2,371    
Total Stockholders' Equity (See accompanying statements) 52 79 24  
Reclassification adjustments 2 (7)    
Total other comprehensive income (loss) (27) 55    
Ending balance 2,658 2,913 2,371  
Pension plans | Pension and Other Postretirement Benefit Plans | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (56) (34)    
Total other comprehensive income (loss) (255) 542    
Pension plans | Net loss        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (29) 62    
Reclassification adjustments 1 (8)    
Pension plans | Net loss | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (199) 576    
Reclassification adjustments (55) (33)    
Pension plans | Change in prior service costs        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 1 1    
Pension plans | Change in prior service costs | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (1) (1)    
Pension plans | Amortization of regulatory assets | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Other Postretirement Benefits Plan        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 203      
Reclassification adjustments 3 7    
Ending balance 189 203    
Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance (208) (136)    
Total Stockholders' Equity (See accompanying statements) (14) (9) (4)  
Total other comprehensive income (loss) (5) (5)    
Ending balance (189) (208) (136)  
Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 11 5    
Total other comprehensive income (loss) 19 (72)    
Other Postretirement Benefits Plan | Net loss        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (8) (12)    
Other Postretirement Benefits Plan | Net loss | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (8) 77    
Reclassification adjustments 13 6    
Other Postretirement Benefits Plan | Change in prior service costs | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (2) (1)    
Other Postretirement Benefits Plan | Amortization of regulatory assets | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Alabama Power        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 2,720      
Total other comprehensive income (loss) 2 2 4  
Ending balance 2,356 2,720    
Regulatory asset 70 76 97  
Alabama Power | Pension plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 821      
Ending balance 741 821    
Alabama Power | Pension plans | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 821 679    
Ending balance 741 821 679  
Alabama Power | Pension plans | Pension and Other Postretirement Benefit Plans | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (17) (11)    
Total other comprehensive income (loss) (80) 142    
Alabama Power | Pension plans | Net loss | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (63) 153    
Reclassification adjustments (16) (10)    
Alabama Power | Pension plans | Change in prior service costs | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (1) (1)    
Alabama Power | Pension plans | Amortization of regulatory assets | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Alabama Power | Other Postretirement Benefits Plan        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 48      
Ending balance 45 48    
Alabama Power | Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance (48) (21)    
Ending balance (45) (48) (21)  
Alabama Power | Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 2 3    
Total other comprehensive income (loss) 3 (27)    
Alabama Power | Other Postretirement Benefits Plan | Net loss | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (1) 30    
Reclassification adjustments 3 3    
Alabama Power | Other Postretirement Benefits Plan | Change in prior service costs | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (1) 0    
Alabama Power | Other Postretirement Benefits Plan | Amortization of regulatory assets | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Georgia Power        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 5,090      
Total other comprehensive income (loss) 22 3 28  
Ending balance 6,139 5,090    
Regulatory asset     83  
Georgia Power | Pension plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 1,051      
Ending balance 973 1,051    
Georgia Power | Pension plans | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 1,051 887    
Ending balance 973 1,051 887  
Georgia Power | Pension plans | Pension and Other Postretirement Benefit Plans | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (20) (14)    
Total other comprehensive income (loss) (78) 164    
Georgia Power | Pension plans | Net loss | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (58) 178    
Reclassification adjustments (19) (13)    
Georgia Power | Pension plans | Change in prior service costs | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (1) (1)    
Georgia Power | Pension plans | Amortization of regulatory assets | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Georgia Power | Other Postretirement Benefits Plan        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 74      
Ending balance 64 74    
Georgia Power | Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance (74) (39)    
Ending balance (64) (74) (39)  
Georgia Power | Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 4 3    
Total other comprehensive income (loss) 10 (35)    
Georgia Power | Other Postretirement Benefits Plan | Net loss | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (6) 38    
Reclassification adjustments 5 4    
Georgia Power | Other Postretirement Benefits Plan | Change in prior service costs | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (1) (1)    
Georgia Power | Other Postretirement Benefits Plan | Amortization of regulatory assets | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Mississippi Power        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 90      
Total other comprehensive income (loss) 5 0 0  
Ending balance 59 90    
Regulatory asset 52 44 36  
Mississippi Power | Pension plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 152      
Ending balance 144 152    
Mississippi Power | Pension plans | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 152 123    
Ending balance 144 152 123  
Mississippi Power | Pension plans | Pension and Other Postretirement Benefit Plans | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (3) (2)    
Total other comprehensive income (loss) (8) 29    
Mississippi Power | Pension plans | Net loss | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (5) 31    
Reclassification adjustments (3) (2)    
Mississippi Power | Pension plans | Change in prior service costs | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Mississippi Power | Pension plans | Amortization of regulatory assets | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Mississippi Power | Other Postretirement Benefits Plan        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance (10)      
Ending balance 9 (10)    
Mississippi Power | Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance (10) (9)    
Ending balance (9) (10) (9)  
Mississippi Power | Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Total other comprehensive income (loss) 1 (1)    
Mississippi Power | Other Postretirement Benefits Plan | Net loss | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (1) 1    
Reclassification adjustments 0 0    
Mississippi Power | Other Postretirement Benefits Plan | Change in prior service costs | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Mississippi Power | Other Postretirement Benefits Plan | Amortization of regulatory assets | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Southern Company Gas        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance (2,225)      
Total other comprehensive income (loss) 32 (15) 7  
Ending balance (2,252) (2,225)    
Southern Company Gas | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Total Stockholders' Equity (See accompanying statements) 51 40 56 38
Total other comprehensive income (loss) 11 (16) 18  
Southern Company Gas | Pension plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 143      
Ending balance 126 143    
Regulatory asset 155 173    
Southern Company Gas | Pension plans | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 143 111    
Total Stockholders' Equity (See accompanying statements) (54) (45) (75)  
Reclassification adjustments 2 1    
Total other comprehensive income (loss) (9) 30    
Ending balance 126 143 111  
Southern Company Gas | Pension plans | Pension and Other Postretirement Benefit Plans | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (10) (2)    
Total other comprehensive income (loss) (17) 32    
Southern Company Gas | Pension plans | Net loss        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (11) 29    
Reclassification adjustments 0 0    
Southern Company Gas | Pension plans | Net loss | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (7) 34    
Reclassification adjustments (1) 0    
Southern Company Gas | Pension plans | Change in prior service costs        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 2 1    
Southern Company Gas | Pension plans | Change in prior service costs | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 2 2    
Southern Company Gas | Pension plans | Amortization of regulatory assets | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (11) (4)    
Southern Company Gas | Other Postretirement Benefits Plan        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance 68      
Reclassification adjustments 0 (8)    
Ending balance 84 68    
Regulatory asset 16 24    
Southern Company Gas | Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Beginning balance (68) (58)    
Total Stockholders' Equity (See accompanying statements) (15) (10) (2)  
Total other comprehensive income (loss) (5) (8)    
Ending balance (84) (68) (58)  
Southern Company Gas | Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (4) (10)    
Total other comprehensive income (loss) (16) (10)    
Southern Company Gas | Other Postretirement Benefits Plan | Net loss        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (5) 0    
Southern Company Gas | Other Postretirement Benefits Plan | Net loss | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) 12 0    
Reclassification adjustments 5 0    
Southern Company Gas | Other Postretirement Benefits Plan | Change in prior service costs | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
Southern Company Gas | Other Postretirement Benefits Plan | Amortization of regulatory assets | Regulatory Assets        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments (9) (10)    
SOUTHERN POWER CO        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Total Stockholders' Equity (See accompanying statements) 6,682 6,698 6,916 6,598
Total other comprehensive income (loss) 15 1 10  
SOUTHERN POWER CO | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Total Stockholders' Equity (See accompanying statements) (9) (16) (9) $ (29)
Total other comprehensive income (loss) 7 (7) 20  
SOUTHERN POWER CO | Pension plans | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Total Stockholders' Equity (See accompanying statements) 11 20 11  
Reclassification adjustments 0 0    
Total other comprehensive income (loss) (9) 9    
SOUTHERN POWER CO | Pension plans | Net loss        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) (9) 9    
Reclassification adjustments 0 0    
SOUTHERN POWER CO | Pension plans | Change in prior service costs        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
SOUTHERN POWER CO | Other Postretirement Benefits Plan        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Reclassification adjustments 0 0    
SOUTHERN POWER CO | Other Postretirement Benefits Plan | Pension and Other Postretirement Benefit Plans        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Total Stockholders' Equity (See accompanying statements) 0 1 $ 0  
Total other comprehensive income (loss) (1) 1    
SOUTHERN POWER CO | Other Postretirement Benefits Plan | Net loss        
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]        
Net gain (loss) $ (1) $ 1