XML 218 R159.htm IDEA: XBRL DOCUMENT v3.10.0.1
Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($)
$ in Millions
 6 Months Ended 12 Months Ended
Dec. 31, 2016
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Deferred tax liabilities —        
Deferred income tax liabilities   $ 15,207 $ 14,757  
Deferred tax assets —        
Deferred income tax assets   9,048 8,205  
Valuation allowance   (123) (184)  
Net deferred income tax assets   8,925 8,021  
Net deferred income taxes liabilities   6,282 6,736  
Accumulated deferred income taxes – assets   (276) (106)  
Accumulated deferred income taxes – liabilities   6,558 6,842  
Federal tax benefit   (167) 62 $ (1,184)
Accelerated depreciation        
Deferred tax liabilities —        
Deferred income tax liabilities   8,461 9,059  
Property basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   1,807 1,853  
Leveraged lease basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   253 251  
Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   477 527  
Deferred tax assets —        
Deferred income tax assets   1,273 1,339  
Premium on reacquired debt        
Deferred tax liabilities —        
Deferred income tax liabilities   88 54  
Storm damage reserves        
Deferred tax liabilities —        
Deferred income tax liabilities   111 89  
Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   975 1,044  
AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   1,232 821  
AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   1,210 370  
Other        
Deferred tax liabilities —        
Deferred income tax liabilities   593 689  
Federal effect of net state deferred tax liabilities        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Deferred tax assets —        
Deferred income tax assets   260 330  
Other property basis differences        
Deferred tax assets —        
Deferred income tax assets   251 343  
ITC and PTC carryforward        
Deferred tax assets —        
Deferred income tax assets   2,730 2,414  
Federal NOL carryforward        
Deferred tax assets —        
Deferred income tax assets     518  
Alternative minimum tax carryforward        
Deferred tax assets —        
Deferred income tax assets   62 69  
Other partnership basis difference        
Deferred tax assets —        
Deferred income tax assets   162 23  
Other comprehensive losses        
Deferred tax assets —        
Deferred income tax assets   82 84  
AROs        
Deferred tax assets —        
Deferred income tax assets   2,442 1,191  
Estimated loss on plants under construction        
Deferred tax assets —        
Deferred income tax assets   346 722  
Other deferred state tax attributes        
Deferred tax assets —        
Deferred income tax assets   415 330  
Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)        
Deferred tax assets —        
Deferred income tax assets   294 304  
Other        
Deferred tax assets —        
Deferred income tax assets   731 538  
Alabama Power        
Deferred tax liabilities —        
Deferred income tax liabilities   4,584 3,914  
Deferred tax assets —        
Deferred income tax assets   1,622 1,154  
Valuation allowance   0 0  
Net deferred income tax assets   1,622 1,154  
Net deferred income taxes liabilities   2,962 2,760  
Accumulated deferred income taxes – assets   0 0  
Accumulated deferred income taxes – liabilities   2,962 2,760  
Federal tax benefit   (91) (136) (103)
Alabama Power | Accelerated depreciation        
Deferred tax liabilities —        
Deferred income tax liabilities   2,236 2,135  
Alabama Power | Property basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   865 725  
Alabama Power | Leveraged lease basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Alabama Power | Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   149 162  
Deferred tax assets —        
Deferred income tax assets   286 286  
Alabama Power | Premium on reacquired debt        
Deferred tax liabilities —        
Deferred income tax liabilities   14 16  
Alabama Power | Storm damage reserves        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Alabama Power | Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   260 260  
Alabama Power | AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   276 249  
Alabama Power | AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   607 220  
Alabama Power | Other        
Deferred tax liabilities —        
Deferred income tax liabilities   177 147  
Alabama Power | Federal effect of net state deferred tax liabilities        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Deferred tax assets —        
Deferred income tax assets   155 143  
Alabama Power | Other property basis differences        
Deferred tax assets —        
Deferred income tax assets   0 0  
Alabama Power | ITC and PTC carryforward        
Deferred tax assets —        
Deferred income tax assets   11 9  
Alabama Power | Federal NOL carryforward        
Deferred tax assets —        
Deferred income tax assets     0  
Alabama Power | Alternative minimum tax carryforward        
Deferred tax assets —        
Deferred income tax assets   0 0  
Alabama Power | Other partnership basis difference        
Deferred tax assets —        
Deferred income tax assets   0 0  
Alabama Power | Other comprehensive losses        
Deferred tax assets —        
Deferred income tax assets   10 10  
Alabama Power | AROs        
Deferred tax assets —        
Deferred income tax assets   883 469  
Alabama Power | Estimated loss on plants under construction        
Deferred tax assets —        
Deferred income tax assets   0 0  
Alabama Power | Other deferred state tax attributes        
Deferred tax assets —        
Deferred income tax assets   0 0  
Alabama Power | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)        
Deferred tax assets —        
Deferred income tax assets   130 126  
Alabama Power | Other        
Deferred tax assets —        
Deferred income tax assets   147 111  
Georgia Power        
Deferred tax liabilities —        
Deferred income tax liabilities   6,098 5,025  
Deferred tax assets —        
Deferred income tax assets   3,078 1,850  
Valuation allowance   (42) 0  
Net deferred income tax assets   3,036 1,850  
Net deferred income taxes liabilities   3,062 3,175  
Accumulated deferred income taxes – assets   0 0  
Accumulated deferred income taxes – liabilities   3,062 3,175  
Federal tax benefit   (393) (256) (391)
Georgia Power | Accelerated depreciation        
Deferred tax liabilities —        
Deferred income tax liabilities   3,005 2,889  
Georgia Power | Property basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   633 606  
Georgia Power | Leveraged lease basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Georgia Power | Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   290 287  
Deferred tax assets —        
Deferred income tax assets   444 448  
Georgia Power | Premium on reacquired debt        
Deferred tax liabilities —        
Deferred income tax liabilities   74 34  
Georgia Power | Storm damage reserves        
Deferred tax liabilities —        
Deferred income tax liabilities   111 89  
Georgia Power | Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   344 349  
Georgia Power | AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   925 501  
Georgia Power | AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   575 130  
Georgia Power | Other        
Deferred tax liabilities —        
Deferred income tax liabilities   141 140  
Georgia Power | Federal effect of net state deferred tax liabilities        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Deferred tax assets —        
Deferred income tax assets   71 85  
Georgia Power | Other property basis differences        
Deferred tax assets —        
Deferred income tax assets   61 59  
Georgia Power | ITC and PTC carryforward        
Deferred tax assets —        
Deferred income tax assets   430 403  
Georgia Power | Federal NOL carryforward        
Deferred tax assets —        
Deferred income tax assets     0  
Georgia Power | Alternative minimum tax carryforward        
Deferred tax assets —        
Deferred income tax assets   0 0  
Georgia Power | Other partnership basis difference        
Deferred tax assets —        
Deferred income tax assets   0 0  
Georgia Power | Other comprehensive losses        
Deferred tax assets —        
Deferred income tax assets   3 4  
Georgia Power | AROs        
Deferred tax assets —        
Deferred income tax assets   1,500 631  
Georgia Power | Estimated loss on plants under construction        
Deferred tax assets —        
Deferred income tax assets   283 0  
Georgia Power | Other deferred state tax attributes        
Deferred tax assets —        
Deferred income tax assets   19 6  
Georgia Power | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)        
Deferred tax assets —        
Deferred income tax assets   127 123  
Georgia Power | Other        
Deferred tax assets —        
Deferred income tax assets   140 91  
Mississippi Power        
Deferred tax liabilities —        
Deferred income tax liabilities   702 699  
Deferred tax assets —        
Deferred income tax assets   515 1,103  
Valuation allowance   (41) (157)  
Net deferred income tax assets   474 946  
Net deferred income taxes liabilities   228    
Net deferred income taxes assets     (247)  
Accumulated deferred income taxes – assets   (150) (247)  
Accumulated deferred income taxes – liabilities   378 0  
Federal tax benefit   567 (194) 31
Mississippi Power | Accelerated depreciation        
Deferred tax liabilities —        
Deferred income tax liabilities   335 303  
Mississippi Power | Property basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   162 207  
Mississippi Power | Leveraged lease basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Mississippi Power | Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   25 28  
Deferred tax assets —        
Deferred income tax assets   62 62  
Mississippi Power | Premium on reacquired debt        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Mississippi Power | Storm damage reserves        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Mississippi Power | Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   45 46  
Mississippi Power | AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   31 33  
Mississippi Power | AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Mississippi Power | Other        
Deferred tax liabilities —        
Deferred income tax liabilities   68 73  
Mississippi Power | Federal effect of net state deferred tax liabilities        
Deferred tax liabilities —        
Deferred income tax liabilities   36 9  
Deferred tax assets —        
Deferred income tax assets   0 0  
Mississippi Power | Other property basis differences        
Deferred tax assets —        
Deferred income tax assets   0 0  
Mississippi Power | ITC and PTC carryforward        
Deferred tax assets —        
Deferred income tax assets   0 0  
Mississippi Power | Federal NOL carryforward        
Deferred tax assets —        
Deferred income tax assets     40  
Mississippi Power | Alternative minimum tax carryforward        
Deferred tax assets —        
Deferred income tax assets   32 32  
Mississippi Power | Other partnership basis difference        
Deferred tax assets —        
Deferred income tax assets   0 0  
Mississippi Power | Other comprehensive losses        
Deferred tax assets —        
Deferred income tax assets   0 0  
Mississippi Power | AROs        
Deferred tax assets —        
Deferred income tax assets   31 33  
Mississippi Power | Estimated loss on plants under construction        
Deferred tax assets —        
Deferred income tax assets   63 722  
Mississippi Power | Other deferred state tax attributes        
Deferred tax assets —        
Deferred income tax assets   251 133  
Mississippi Power | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)        
Deferred tax assets —        
Deferred income tax assets   29 27  
Mississippi Power | Other        
Deferred tax assets —        
Deferred income tax assets   47 54  
Southern Power        
Deferred tax liabilities —        
Deferred income tax liabilities   1,523 1,961  
Deferred tax assets —        
Deferred income tax assets   2,631 2,700  
Valuation allowance   (27) (13)  
Net deferred income tax assets   2,604 2,687  
Net deferred income taxes assets   (1,081) (726)  
Accumulated deferred income taxes – assets   (1,186) (925)  
Accumulated deferred income taxes – liabilities   105 199  
Federal tax benefit   (85) 566 $ (928)
Southern Power | Accelerated depreciation        
Deferred tax liabilities —        
Deferred income tax liabilities   1,483 1,922  
Southern Power | Property basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   0 2  
Southern Power | Leveraged lease basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Power | Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   6 7  
Deferred tax assets —        
Deferred income tax assets   7 8  
Southern Power | Premium on reacquired debt        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Power | Storm damage reserves        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Power | Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Power | AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Power | AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Power | Other        
Deferred tax liabilities —        
Deferred income tax liabilities   34 30  
Southern Power | Federal effect of net state deferred tax liabilities        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Deferred tax assets —        
Deferred income tax assets   22 42  
Southern Power | Other property basis differences        
Deferred tax assets —        
Deferred income tax assets   172 184  
Southern Power | ITC and PTC carryforward        
Deferred tax assets —        
Deferred income tax assets   2,128 2,002  
Southern Power | Federal NOL carryforward        
Deferred tax assets —        
Deferred income tax assets     333  
Southern Power | Alternative minimum tax carryforward        
Deferred tax assets —        
Deferred income tax assets   21 21  
Southern Power | Other partnership basis difference        
Deferred tax assets —        
Deferred income tax assets   162 23  
Southern Power | Other comprehensive losses        
Deferred tax assets —        
Deferred income tax assets     1  
Southern Power | AROs        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Power | Estimated loss on plants under construction        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Power | Other deferred state tax attributes        
Deferred tax assets —        
Deferred income tax assets   72 77  
Southern Power | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Power | Other        
Deferred tax assets —        
Deferred income tax assets   47 9  
Southern Company Gas        
Deferred tax liabilities —        
Deferred income tax liabilities   1,493 1,641  
Deferred tax assets —        
Deferred income tax assets   489 563  
Valuation allowance   (12) (11)  
Net deferred income tax assets   477 552  
Net deferred income taxes liabilities   1,016 1,089  
Accumulated deferred income taxes – assets   0 0  
Accumulated deferred income taxes – liabilities   1,016 1,089  
Federal tax benefit $ 0 (334) (103)  
Southern Company Gas | Accelerated depreciation        
Deferred tax liabilities —        
Deferred income tax liabilities   1,176 1,150  
Southern Company Gas | Property basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   134 204  
Southern Company Gas | Leveraged lease basis differences        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Company Gas | Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   6 4  
Deferred tax assets —        
Deferred income tax assets   150 185  
Southern Company Gas | Premium on reacquired debt        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Company Gas | Storm damage reserves        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Company Gas | Employee benefit obligations        
Deferred tax liabilities —        
Deferred income tax liabilities   45 75  
Southern Company Gas | AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Company Gas | AROs        
Deferred tax liabilities —        
Deferred income tax liabilities   0 0  
Southern Company Gas | Other        
Deferred tax liabilities —        
Deferred income tax liabilities   132 208  
Southern Company Gas | Federal effect of net state deferred tax liabilities        
Deferred tax liabilities —        
Deferred income tax liabilities     0  
Deferred tax assets —        
Deferred income tax assets   46 54  
Southern Company Gas | Other property basis differences        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Company Gas | ITC and PTC carryforward        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Company Gas | Federal NOL carryforward        
Deferred tax assets —        
Deferred income tax assets     92  
Southern Company Gas | Alternative minimum tax carryforward        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Company Gas | Other partnership basis difference        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Company Gas | Other comprehensive losses        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Company Gas | AROs        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Company Gas | Estimated loss on plants under construction        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Company Gas | Other deferred state tax attributes        
Deferred tax assets —        
Deferred income tax assets   0 0  
Southern Company Gas | Regulatory liability associated with the Tax Reform Legislation (not subject to normalization)        
Deferred tax assets —        
Deferred income tax assets   8 9  
Southern Company Gas | Other        
Deferred tax assets —        
Deferred income tax assets   $ 285 $ 223