INCOME TAXES - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended		12 Months Ended
	Jul. 31, 2021	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Line Items]
Deferred income tax assets		$ 8,914	$ 8,914	$ 8,398	$ 8,914
ITC and PTC carryforwards
Income Tax Disclosure [Line Items]
Deferred income tax assets		1,750	1,750	1,685	1,750
Southern Power
Income Tax Disclosure [Line Items]
Deferred income tax assets		1,258	1,258	$ 1,124	1,258
Percentage reduction in tax basis of assets				50.00%
Southern Power | ITCs and other credits carryforward
Income Tax Disclosure [Line Items]
Reduction in income tax expense, investment tax credits				$ 49	289	$ 340
Southern Power | ITC and PTC carryforwards
Income Tax Disclosure [Line Items]
Deferred income tax assets		827	827	794	827
Southern Power | Production Tax Credit Carryforward
Income Tax Disclosure [Line Items]
Effective income tax rate reconciliation, tax credit, production, amount				27	16	15
Georgia Power
Income Tax Disclosure [Line Items]
Deferred income tax assets		4,019	4,019	3,844	4,019
State investment tax credit carryforward				434
Georgia Power | ITC and PTC carryforwards
Income Tax Disclosure [Line Items]
Deferred income tax assets		704	704	673	704
Mississippi Power
Income Tax Disclosure [Line Items]
Deferred income tax assets		393	393	399	393
Mississippi Power | ITC and PTC carryforwards
Income Tax Disclosure [Line Items]
Deferred income tax assets		0	0	0	0
Southern Company Gas
Income Tax Disclosure [Line Items]
Deferred income tax assets		328	328	301	328
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	85
Southern Company Gas | ITC and PTC carryforwards
Income Tax Disclosure [Line Items]
Deferred income tax assets		0	0	0	0
State and Local Jurisdiction | Georgia Power
Income Tax Disclosure [Line Items]
Valuation allowance				98
State and Local Jurisdiction | Georgia Power | ITCs and other credits carryforward
Income Tax Disclosure [Line Items]
Reduction in income tax expense, investment tax credits				53	66	67
Deferred Charges Related To Income Taxes, Current | Other Noncurrent Assets | Southern Power | Unrealized Tax Credits
Income Tax Disclosure [Line Items]
Deferred income tax assets		$ 6	$ 6	17	$ 6	$ 5
Mississippi | State and Local Jurisdiction | Mississippi Power
Income Tax Disclosure [Line Items]
Operating loss carryforwards, valuation allowance				32
New York | State and Local Jurisdiction | Southern Power
Income Tax Disclosure [Line Items]
Operating loss carryforwards, valuation allowance				25
Oklahoma | State and Local Jurisdiction | Southern Power
Income Tax Disclosure [Line Items]
Operating loss carryforwards, valuation allowance				11
Florida | State and Local Jurisdiction | Southern Power
Income Tax Disclosure [Line Items]
Operating loss carryforwards, valuation allowance				$ 10