SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 1,917	$ 1,798
Restricted cash:
Total cash, cash equivalents, and restricted cash	2,037	1,829	$ 1,068	$ 1,978
Other current assets
Restricted cash:
Restricted cash	62	2
Other Noncurrent Assets
Restricted cash:
Restricted cash	58	29
Southern Power
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	131	107
Restricted cash:
Total cash, cash equivalents, and restricted cash	133	135	182	279
Southern Power | Other current assets
Restricted cash:
Restricted cash	0	0
Southern Power | Other Noncurrent Assets
Restricted cash:
Restricted cash	3	29
Southern Power | Estimated Construction Completion Costs | Deuel Harvest
Restricted cash:
Restricted cash	3	10
Southern Power | Tax Equity Contributions | Garland
Restricted cash:
Restricted cash		19
Southern Company Gas
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	81	45
Restricted cash:
Total cash, cash equivalents, and restricted cash	83	48	19	49
Southern Company Gas | Other current assets
Restricted cash:
Restricted cash	2	2
Southern Company Gas | Other Noncurrent Assets
Restricted cash:
Restricted cash	0	0
Georgia Power
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	364	33
Restricted cash:
Total cash, cash equivalents, and restricted cash	480	$ 33	$ 9	$ 52
Georgia Power | Other current assets
Restricted cash:
Restricted cash	60
Georgia Power | Other Noncurrent Assets
Restricted cash:
Restricted cash	$ 56