INCOME TAXES - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 31, 2021	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Line Items]
Deferred income tax assets		$ 7,886	$ 7,886	$ 8,398
Income taxes (benefit)			496	795	$ 267
ITC and PTC carryforwards
Income Tax Disclosure [Line Items]
Deferred income tax assets		1,387	1,387	1,685
Southern Power
Income Tax Disclosure [Line Items]
Deferred income tax assets		773	$ 773	1,124
Percentage reduction in tax basis of assets			50.00%
Income taxes (benefit)			$ 12	20	(13)
Southern Power | ITCs and other credits carryforward
Income Tax Disclosure [Line Items]
Reduction in income tax expense, investment tax credits			332	49	289
Southern Power | ITC and PTC carryforwards
Income Tax Disclosure [Line Items]
Deferred income tax assets		481	481	794
Southern Power | Production Tax Credit Carryforward
Income Tax Disclosure [Line Items]
Effective income tax rate reconciliation, tax credit, production, amount			26	27	16
Proceeds from transferred tax credit		12
Georgia Power
Income Tax Disclosure [Line Items]
Deferred income tax assets		3,718	3,718	3,844
Income taxes (benefit)			448	370	(168)
State investment tax credit carryforward			452
Georgia Power | ITC and PTC carryforwards
Income Tax Disclosure [Line Items]
Deferred income tax assets		691	691	673
Georgia Power | Production Tax Credit Carryforward
Income Tax Disclosure [Line Items]
Payments for transferred tax credit			39
Mississippi Power
Income Tax Disclosure [Line Items]
Deferred income tax assets		382	382	399
Income taxes (benefit)			36	37	21
Mississippi Power | ITC and PTC carryforwards
Income Tax Disclosure [Line Items]
Deferred income tax assets		0	0	0
Southern Company Gas
Income Tax Disclosure [Line Items]
Deferred income tax assets		377	377	301
Income taxes (benefit)			211	180	275
Southern Company Gas | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Sequent
Income Tax Disclosure [Line Items]
Deferred tax expense, increase from change in appointment rate	$ 85		85		85
Southern Company Gas | ITC and PTC carryforwards
Income Tax Disclosure [Line Items]
Deferred income tax assets		0	0	0
State and Local Jurisdiction | Georgia Power
Income Tax Disclosure [Line Items]
Valuation allowance		60	60
State and Local Jurisdiction | Georgia Power | ITCs and other credits carryforward
Income Tax Disclosure [Line Items]
Reduction in income tax expense, investment tax credits			49	53	66
Deferred Charges Related To Income Taxes, Current | Other Noncurrent Assets | Southern Power | Unrealized Tax Credits
Income Tax Disclosure [Line Items]
Deferred income tax assets		5	5	$ 17	$ 6
Mississippi | State and Local Jurisdiction | Mississippi Power
Income Tax Disclosure [Line Items]
Operating loss carryforwards, valuation allowance		32	32
New York | State and Local Jurisdiction | Southern Power
Income Tax Disclosure [Line Items]
Operating loss carryforwards, valuation allowance		25	25
Oklahoma | State and Local Jurisdiction | Southern Power
Income Tax Disclosure [Line Items]
Operating loss carryforwards, valuation allowance		11	11
Florida | State and Local Jurisdiction | Southern Power
Income Tax Disclosure [Line Items]
Operating loss carryforwards, valuation allowance		$ 10	$ 10