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FINANCING - Outstanding Classes of Capital Stock Narrative (Details) shares in Millions, $ in Millions | 12 Months Ended
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Dec. 31, 2023 USD ($) shares
Debt Instrument [Line Items] |
Stock issued employee and director stock plans (in shares) | 2.1
Proceeds from issuance of shares under share-based compensation plans | $ | $ 36
Number of shares reserved for issuance to stock-based compensation plan (in shares) | 131.0
Southern Company Common Stock |
Debt Instrument [Line Items] |
Remaining shares available for awards (in shares) | 26.9

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