FINANCING - Outstanding Classes of Capital Stock Narrative (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Stock issued employee and director stock plans (in shares)	22,500
Number of shares reserved for issuance to stock-based compensation plan (in shares)	203,000
Effect of convertible senior notes (in shares)	0	0
Southern Company Common Stock
Debt Instrument [Line Items]
Remaining shares available for awards (in shares)	23,000