REGULATORY MATTERS - APC Rate RSE (Details) - Alabama Power - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2024	Oct. 03, 2023	Feb. 28, 2022
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%
Authorized ROE		52.30%	52.20%
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
Rate RSE refund liability		$ 15	$ 62	$ 181
Rate RSE refund liability, portion attributable to reduce under recovered balance							$ 126
Customer refund		304
Deferred income taxes		$ 81				$ 24
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%
Deferred income taxes	$ 14				$ 67