REGULATORY MATTERS - APC Rate RSE (Details) - Alabama Power - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2019	Dec. 31, 2025	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2021
Public Utilities, General Disclosures [Line Items]
Rate adjustment period			2 years
Maximum percentage of rate RSE			4.00%
Maximum annual percentage of ratio rate			5.00%
Adjusting point of weighted cost of equity			5.98%
Percent of basis points			0.07%
Percent of designated customer value benchmark survey			33.33%
Authorized ROE			51.60%	51.60%
Weighted common equity return	6.15%			6.21%
Customer refundable fees, refund payments, tranche one, percentage			25.00%
Customer refundable fees, refund payments, tranche two, percentage			40.00%
Customer refundable fees, refund payments, tranche two, percentage			75.00%
Customer refundable fees, refund payments, tranche one, review year with rate RSE upward adjustment, percentage			50.00%
Contract with customer, liability, bill credits				$ 55	$ 50
Rate RSE increase						4.09%
Rate RSE increase amount						$ 228
Rate RSE refund liability			$ 181	$ 50	$ 53
Rate RSE refund liability, portion attributable to reduce under recovered balance			$ 126
Minimum
Public Utilities, General Disclosures [Line Items]
Public utilities, actual weighted common equity return, threshold, percentage			6.15%
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche one			6.15%	6.15%	6.15%
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche two			6.65%
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche three			7.15%
Public utilities, actual weighted common equity return, threshold, review year with rate RSE upward adjustment, percentage			6.15%
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, review year with rate RSE upward adjustment, percentage, tranche one			6.15%
Maximum
Public Utilities, General Disclosures [Line Items]
Public utilities, actual weighted common equity return, threshold, percentage			7.65%
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche one			6.65%
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche two			7.15%
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche three			7.65%
Customer refundable fees, refund payments, percentage			7.65%
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, review year with rate RSE upward adjustment, percentage, tranche one			6.90%
Customer refundable fees, refund payments, review year with rate RSE upward adjustment, percentage			6.90%
Scenario, Forecast
Public Utilities, General Disclosures [Line Items]
Authorized ROE		55.00%