LEASES - Balance Sheet Amounts Recorded for Operating and Financing Leases (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Operating Leases
Operating lease ROU assets, net	$ 1,432	$ 1,531
Operating lease obligations - current	183	197
Operating lease obligations - non-current	1,307	1,388
Total operating lease obligations	$ 1,490	$ 1,585
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	$ 272	$ 292
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Finance lease obligations - current	$ 11	$ 18
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-Term Debt	Long-Term Debt
Finance lease obligations - non-current	$ 287	$ 296
Total finance lease obligations	298	314
Assets Subject to Power Purchase Agreement
Operating Leases
Total operating lease obligations	566	652
Alabama Power
Operating Leases
Operating lease ROU assets, net	$ 87	$ 71
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Operating lease obligations - current	$ 12	$ 9
Operating lease obligations - non-current	81	67
Total operating lease obligations	$ 93	$ 76
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	$ 5
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Finance lease obligations - current	$ 2	$ 2
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	5
Alabama Power | Assets Subject to Power Purchase Agreement
Operating Leases
Total operating lease obligations	58	59
Georgia Power
Operating Leases
Operating lease ROU assets, net	884	1,007
Operating lease obligations - current	135	151
Operating lease obligations - non-current	740	851
Total operating lease obligations	$ 875	$ 1,002
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	$ 203	$ 205
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	$ 222	$ 222
Total finance lease obligations	240	238
Georgia Power | Assets Subject to Power Purchase Agreement
Operating Leases
Total operating lease obligations	$ 813	$ 952
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	$ 9
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Operating lease obligations - current	$ 3	$ 4
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Noncurrent	Other Liabilities, Noncurrent
Operating lease obligations - non-current	$ 6	$ 5
Total operating lease obligations	$ 9	$ 9
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	$ 15	$ 16
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	$ 15	$ 16
Total finance lease obligations	16	17
Southern Power
Operating Leases
Operating lease ROU assets, net	$ 488	$ 489
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Operating lease obligations - current	$ 29	$ 28
Operating lease obligations - non-current	517	514
Total operating lease obligations	546	542
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	$ 47	$ 57
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Current	Other Liabilities, Current
Operating lease obligations - current	$ 11	$ 9
Operating lease obligations - non-current	40	51
Total operating lease obligations	51	60
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