CONTINGENCIES, COMMITMENTS, AND GUARANTEES - Environmental Remediation (Details)	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) state site	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Georgia Power
Environmental Exit Cost [Line Items]
Costs recovered annually		$ 12,000,000	$ 12,000,000	$ 12,000,000
Environmental remediation liability, current		15,000,000	17,000,000
Accrued environmental remediation		0	0
Under recovered environmental remediation costs, other regulatory assets, current		5,000,000	12,000,000
Under recovered environmental remediation costs, other regulatory assets, deferred		20,000,000	23,000,000
Georgia Power | Scenario, Forecast
Environmental Exit Cost [Line Items]
Costs recovered annually	$ 5,000,000
Southern Company Gas
Environmental Exit Cost [Line Items]
Environmental remediation liability, current		49,000,000	52,000,000
Accrued environmental remediation		207,000,000	197,000,000
Under recovered environmental remediation costs, other regulatory assets, current		54,000,000	59,000,000
Under recovered environmental remediation costs, other regulatory assets, deferred		$ 215,000,000	208,000,000
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		65,000,000	69,000,000
Accrued environmental remediation		207,000,000	197,000,000
Under recovered environmental remediation costs, other regulatory assets, current		59,000,000	71,000,000
Under recovered environmental remediation costs, other regulatory assets, deferred		$ 235,000,000	231,000,000
Environmental Loss Contingency, Current, Statement of Financial Position [Extensible Enumeration]		Other Liabilities, Current
Mississippi Power [Member]
Environmental Exit Cost [Line Items]
Environmental remediation liability, current		$ 0	$ 0