LEASES - Balance Sheet Amounts Recorded for Operating and Financing Leases (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Operating Leases
Operating lease ROU assets, net	$ 1,531	$ 1,701
Operating lease obligations - current	197	250
Operating lease obligations - non-current	1,388	1,503
Total operating lease obligations	$ 1,585	$ 1,754
Finance Leases
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Plant in service, net of depreciation	Plant in service, net of depreciation
Finance lease ROU assets, net	$ 292	$ 197
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Finance lease obligations - current	$ 18	$ 16
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-Term Debt	Long-Term Debt
Finance lease obligations - non-current	$ 296	$ 199
Total finance lease obligations	314	215
Assets Subject to Power Purchase Agreement
Operating Leases
Total operating lease obligations	652	802
Alabama Power
Operating Leases
Operating lease ROU assets, net	$ 71	$ 108
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Operating lease obligations - current	$ 9	$ 54
Operating lease obligations - non-current	67	66
Total operating lease obligations	$ 76	$ 121
Finance Leases
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Plant in service, net of depreciation	Plant in service, net of depreciation
Finance lease ROU assets, net	$ 5	$ 4
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Finance lease obligations - current	$ 2	$ 1
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-Term Debt	Long-Term Debt
Finance lease obligations - non-current	$ 3	$ 3
Total finance lease obligations	5	4
Alabama Power | Assets Subject to Power Purchase Agreement
Operating Leases
Total operating lease obligations	59	104
Georgia Power
Operating Leases
Operating lease ROU assets, net	1,007	1,157
Operating lease obligations - current	151	156
Operating lease obligations - non-current	851	999
Total operating lease obligations	$ 1,002	$ 1,155
Finance Leases
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Plant in service, net of depreciation	Plant in service, net of depreciation
Finance lease ROU assets, net	$ 205	$ 104
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Finance lease obligations - current	$ 16	$ 10
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-Term Debt	Long-Term Debt
Finance lease obligations - non-current	$ 222	$ 126
Total finance lease obligations	238	136
Georgia Power | Assets Subject to Power Purchase Agreement
Operating Leases
Total operating lease obligations	$ 952	$ 1,110
Mississippi Power
Operating Leases
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other Assets, Noncurrent	Other Assets, Noncurrent
Operating lease ROU assets, net	$ 9	$ 10
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Operating lease obligations - current	$ 4	$ 4
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Intangible liabilities included in other deferred credits and liabilities	Intangible liabilities included in other deferred credits and liabilities
Operating lease obligations - non-current	$ 5	$ 6
Total operating lease obligations	$ 9	$ 10
Finance Leases
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Plant in service, net of depreciation	Plant in service, net of depreciation
Finance lease ROU assets, net	$ 16	$ 17
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Finance lease obligations - current	$ 1	$ 1
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-Term Debt	Long-Term Debt
Finance lease obligations - non-current	$ 16	$ 17
Total finance lease obligations	17	18
Southern Power
Operating Leases
Operating lease ROU assets, net	$ 489	$ 479
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Operating lease obligations - current	$ 28	$ 28
Operating lease obligations - non-current	514	497
Total operating lease obligations	542	525
Finance Leases
Finance lease ROU assets, net	0	0
Finance lease obligations - current	0	0
Finance lease obligations - non-current	0	0
Total finance lease obligations	0	0
Southern Company Gas
Operating Leases
Operating lease ROU assets, net	$ 57	$ 70
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Operating lease obligations - current	$ 9	$ 11
Operating lease obligations - non-current	51	59
Total operating lease obligations	60	70
Finance Leases
Finance lease ROU assets, net	0	0
Finance lease obligations - current	0	0
Finance lease obligations - non-current	0	0
Total finance lease obligations	$ 0	$ 0