Consolidated Entities and Equity Method Investments - Schedule of Earnings (Loss) from Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments	$ 10	$ 31	$ 43	$ 77
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments	23	32	62	76
SOUTHERN Co GAS | SNG
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments	23	32	62	76
Southern Holdings Company
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments	$ (14)	$ 0	$ (20)	$ 0