Consolidated Entities and Equity Method Investments - Schedule of Equity Method Investments (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 1,365	$ 1,318
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,224	1,182
SOUTHERN Co GAS \| SNG
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,190	1,148
SOUTHERN Co GAS \| Other
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 34	$ 34

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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