CONTINGENCIES, COMMITMENTS, AND GUARANTEES - Environmental Remediation (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) site state	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Georgia Power
Environmental Exit Cost [Line Items]
Costs recovered annually	$ 5,000,000	$ 12,000,000	$ 12,000,000
Environmental remediation liability, current	14,000,000	15,000,000
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	15,000,000	20,000,000
Southern Company Gas
Environmental Exit Cost [Line Items]
Environmental remediation liability, current	30,000,000	49,000,000
Accrued environmental remediation	192,000,000	207,000,000
Under recovered environmental remediation costs, other regulatory assets, current	40,000,000	54,000,000
Under recovered environmental remediation costs, other regulatory assets, deferred	$ 195,000,000	215,000,000
Southern Company Gas | Manufactured Gas Plants
Environmental Exit Cost [Line Items]
Number of sites | site	40
Number of states in which subject to environmental remediation liabilities | state	4
Alabama Power
Environmental Exit Cost [Line Items]
Environmental remediation liability, current	$ 0	0
Southern Company
Environmental Exit Cost [Line Items]
Environmental remediation liability, current	44,000,000	65,000,000
Accrued environmental remediation	192,000,000	207,000,000
Under recovered environmental remediation costs, other regulatory assets, current	45,000,000	59,000,000
Under recovered environmental remediation costs, other regulatory assets, deferred	$ 210,000,000	$ 235,000,000
Environmental Loss Contingency, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current