Introduction - Decommissioning Expenses (Details) $ in Millions	1 Months Ended	9 Months Ended
	Jun. 30, 2023	Sep. 30, 2023 USD ($)
Estimated Inflation Rate
Liability for Claims and Claims Adjustment Expense [Line Items]
ARO measurement input	0.045
Estimated Trust Earnings
Liability for Claims and Claims Adjustment Expense [Line Items]
ARO measurement input	0.070
ALABAMA POWER CO
Liability for Claims and Claims Adjustment Expense [Line Items]
Total site study costs		$ 2,048
ALABAMA POWER CO | Plant Farley
Liability for Claims and Claims Adjustment Expense [Line Items]
Decommissioning costs (term)		5 years
Radiated structures | ALABAMA POWER CO
Liability for Claims and Claims Adjustment Expense [Line Items]
Total site study costs		$ 1,402
Spent fuel management | ALABAMA POWER CO
Liability for Claims and Claims Adjustment Expense [Line Items]
Total site study costs		513
Non-radiated structures | ALABAMA POWER CO
Liability for Claims and Claims Adjustment Expense [Line Items]
Total site study costs		$ 133