CONTINGENCIES, COMMITMENTS, AND GUARANTEES - Environmental Remediation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Georgia Power
Environmental Exit Cost [Line Items]
Costs recovered annually	$ 5,000,000	$ 5,000,000	$ 12,000,000
Environmental remediation liability, current	13,000,000	14,000,000
Accrued environmental remediation	0	0
Under recovered environmental remediation costs, other regulatory assets, current	5,000,000	5,000,000
Under recovered environmental remediation costs, other regulatory assets, deferred	11,000,000	15,000,000
Southern Company Gas
Environmental Exit Cost [Line Items]
Environmental remediation liability, current	24,000,000	30,000,000
Accrued environmental remediation	198,000,000	192,000,000
Under recovered environmental remediation costs, other regulatory assets, current	32,000,000	40,000,000
Under recovered environmental remediation costs, other regulatory assets, deferred	201,000,000	195,000,000
Alabama Power
Environmental Exit Cost [Line Items]
Environmental remediation liability, current	0	0
Southern Company
Environmental Exit Cost [Line Items]
Environmental remediation liability, current	37,000,000	44,000,000
Accrued environmental remediation	198,000,000	192,000,000
Under recovered environmental remediation costs, other regulatory assets, current	37,000,000	45,000,000
Under recovered environmental remediation costs, other regulatory assets, deferred	$ 212,000,000	$ 210,000,000
Environmental Loss Contingency, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current