Regulatory Matters - APC Certificate of Convenience and Necessity (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2020
Public Utilities, General Disclosures [Line Items]
Construction work in progress	$ 8,496	$ 10,896
Plant in service, net of depreciation	88,374	82,232
ALABAMA POWER CO
Public Utilities, General Disclosures [Line Items]
Construction work in progress	1,759	1,526
Plant in service, net of depreciation	23,271	$ 23,002
ALABAMA POWER CO | Plant Barry Unit 8
Public Utilities, General Disclosures [Line Items]
Estimated in-service cost			$ 652
Construction work in progress	583
Construction in progress, work in progress amount	578
Plant in service, net of depreciation	$ 5