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INCOME TAXES - Narrative (Details) - USD ($) $ in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jul. 31, 2021 | Dec. 31, 2023 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | $ 7,886 | $ 7,886 | $ 8,398 |
Income taxes (benefit) |  |  | 496 | 795 | $ 267
ITC and PTC carryforwards |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | 1,387 | 1,387 | 1,685 |
Southern Power |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | 773 | $ 773 | 1,124 |
Percentage reduction in tax basis of assets |  |  | 50.00% |  |
Income taxes (benefit) |  |  | $ 12 | 20 | (13)
Southern Power | ITCs and other credits carryforward |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Reduction in income tax expense, investment tax credits |  |  | 332 | 49 | 289
Southern Power | ITC and PTC carryforwards |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | 481 | 481 | 794 |
Southern Power | Production Tax Credit Carryforward |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Effective income tax rate reconciliation, tax credit, production, amount |  |  | 26 | 27 | 16
Proceeds from transferred tax credit |  | 12 |  |  |
Georgia Power |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | 3,718 | 3,718 | 3,844 |
Income taxes (benefit) |  |  | 448 | 370 | (168)
State investment tax credit carryforward |  |  | 452 |  |
Georgia Power | ITC and PTC carryforwards |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | 691 | 691 | 673 |
Georgia Power | Production Tax Credit Carryforward |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Payments for transferred tax credit |  |  | 39 |  |
Mississippi Power |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | 382 | 382 | 399 |
Income taxes (benefit) |  |  | 36 | 37 | 21
Mississippi Power | ITC and PTC carryforwards |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | 0 | 0 | 0 |
Southern Company Gas |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | 377 | 377 | 301 |
Income taxes (benefit) |  |  | 211 | 180 | 275
Southern Company Gas | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Sequent |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred tax expense, increase from change in appointment rate | $ 85 |  | 85 |  | 85
Southern Company Gas | ITC and PTC carryforwards |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | 0 | 0 | 0 |
State and Local Jurisdiction | Georgia Power |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Valuation allowance |  | 60 | 60 |  |
State and Local Jurisdiction | Georgia Power | ITCs and other credits carryforward |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Reduction in income tax expense, investment tax credits |  |  | 49 | 53 | 66
Deferred Charges Related To Income Taxes, Current | Other Noncurrent Assets | Southern Power | Unrealized Tax Credits |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Deferred income tax assets |  | 5 | 5 | $ 17 | $ 6
Mississippi | State and Local Jurisdiction | Mississippi Power |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Operating loss carryforwards, valuation allowance |  | 32 | 32 |  |
New York | State and Local Jurisdiction | Southern Power |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Operating loss carryforwards, valuation allowance |  | 25 | 25 |  |
Oklahoma | State and Local Jurisdiction | Southern Power |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Operating loss carryforwards, valuation allowance |  | 11 | 11 |  |
Florida | State and Local Jurisdiction | Southern Power |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Operating loss carryforwards, valuation allowance |  | $ 10 | $ 10 |  |

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