REGULATORY MATTERS - APC Rate NDR and Reliability Reserve Accounting Order (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 05, 2022	Sep. 30, 2022	Jul. 12, 2022
Public Utilities, General Disclosures [Line Items]
Plant in service, net of depreciation	$ 82,232,000,000	$ 81,513,000,000
Other utility plant, net	599,000,000	0
Other regulatory assets	860,000,000	653,000,000
Revision of Prior Period, Reclassification, Adjustment
Public Utilities, General Disclosures [Line Items]
Plant in service, net of depreciation				$ (42,000,000)	$ (600,000,000)
Other utility plant, net					$ 600,000,000
Other regulatory assets				$ 42,000,000
Alabama Power
Public Utilities, General Disclosures [Line Items]
Minimum natural disaster reserve balance, triggering establishment charge	50,000,000
Natural disaster reserve authorized limit	75,000,000					$ 35,000,000
Maximum rate NDR charge per month, monthly nonresidential customer account	5					10.00
Maximum rate NDR charge per month, monthly residential customer account	2.50					$ 5.00
Additional accruals authorized by state PSCs		65,000,000	$ 100,000,000
Annual recovery amount	14,000,000	6,000,000	$ 5,000,000
Regulatory asset, amortization period	97,000,000	103,000,000
NDR, expected recovery amount	12,000,000
Plant in service, net of depreciation	23,002,000,000	22,822,000,000
Other utility plant, net	599,000,000	0
Other regulatory assets	$ 474,000,000	$ 208,000,000
Alabama Power | Minimum
Public Utilities, General Disclosures [Line Items]
Maximum period for recovery deferred stock related operations and maintenance costs and any future reserve deficits	24 months
Alabama Power | Maximum
Public Utilities, General Disclosures [Line Items]
Maximum period for recovery deferred stock related operations and maintenance costs and any future reserve deficits	48 months