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Consolidated Entities and Equity Method Investments - Narrative (Details) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2025 USD ($) | Sep. 30, 2024 USD ($) | Sep. 30, 2025 USD ($) investor | Sep. 30, 2024 USD ($) | Dec. 31, 2024 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Equity investments in unconsolidated subsidiaries | $ 1,303 |  | $ 1,303 |  | $ 1,416
Assets | 153,248 |  | 153,248 |  | 145,180
Liabilities | 114,974 |  | 114,974 |  | 108,506
Earnings from equity method investments | 33 | $ 31 | 76 | $ 107 |
Southern Holdings Company |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Equity investments in unconsolidated subsidiaries | 116 |  | 116 |  | 128
Earnings from equity method investments | 0 | $ 0 | (20) | $ 0 |
SOUTHERN POWER CO |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Assets | 13,595 |  | 13,595 |  | 12,653
Liabilities | 7,018 |  | $ 7,018 |  | 5,971
SP Solar Holdings I, LP | SOUTHERN POWER CO |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Distribution made to limited partner, cash distributions paid, percentage |  |  | 67.00% |  |
SP Solar Holdings I, LP | Financial Investors |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Distribution made to limited partner, cash distributions paid, percentage |  |  | 33.00% |  |
SP Wind | SOUTHERN POWER CO |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Distribution made to limited partner, cash distributions paid, percentage |  |  | 60.00% |  |
Number of financial investors | investor |  |  | 3 |  |
SP Wind | Financial Investors |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Distribution made to limited partner, cash distributions paid, percentage |  |  | 40.00% |  |
Variable Interest Entity, Primary Beneficiary | SP Solar Holdings I, LP | SOUTHERN POWER CO |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Assets | 5,300 |  | $ 5,300 |  | 5,400
Liabilities | 365 |  | 365 |  | 372
Noncontrolling interests related to other partners' interests | 1,000 |  | 1,000 |  | 1,000
Variable Interest Entity, Primary Beneficiary | SP Wind | SOUTHERN POWER CO |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Assets | 1,800 |  | 1,800 |  | 2,000
Liabilities | 190 |  | 190 |  | 177
Noncontrolling interests related to other partners' interests | 30 |  | 30 |  | 35
Variable Interest Entity, Primary Beneficiary | Other Variable Interest Entities | SOUTHERN POWER CO |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Assets | 1,600 |  | 1,600 |  | 1,600
Liabilities | 241 |  | 241 |  | 224
Noncontrolling interests related to other partners' interests | $ 642 |  | $ 642 |  | $ 691

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