CONTINGENCIES, COMMITMENTS, AND GUARANTEES - Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023
Recorded Unconditional Purchase Obligation [Line Items]
Notes payable	$ 1,338	$ 2,314
Alabama Power
Recorded Unconditional Purchase Obligation [Line Items]
Jointly owned affiliate equity	56
Jointly owned affiliate long term debt	80
Notes payable	0	$ 40
SEGCO \| Alabama Power
Recorded Unconditional Purchase Obligation [Line Items]
Guarantee of unsecured senior notes	100
Notes payable	$ 0

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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