INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	$ 2,651.9	$ 3,216.1
Deferred Tax Liabilities	(12,624.3)	(12,631.8)
Net Deferred Tax Liabilities	(9,972.4)	(9,415.7)
Property Related Temporary Differences	(8,939.7)	(8,809.0)
Amounts Due to Customers for Future Income Taxes	779.6	898.1
Securitized Assets	(133.4)	(81.8)
Regulatory Assets	(966.2)	(825.9)
Accrued Nuclear Decommissioning	(1,052.2)	(923.5)
Net Operating Loss Carryforward	110.3	155.6
Valuation Allowance	(35.0)	(37.4)
Tax Credit Carryforward	197.5	321.4
Operating Lease Liability	145.3	154.7
Investment in Partnership	(302.1)	(296.3)
Net Deferred Tax Liabilities	223.5	28.4
AEP TEXAS INC.
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	139.1	173.6
Deferred Tax Liabilities	(1,461.8)	(1,401.4)
Net Deferred Tax Liabilities	(1,322.7)	(1,227.8)
Property Related Temporary Differences	(1,364.0)	(1,274.0)
Amounts Due to Customers for Future Income Taxes	109.3	109.3
Securitized Assets	(26.5)	(46.7)
Regulatory Assets	(63.2)	(56.2)
Accrued Nuclear Decommissioning	0.0	0.0
Net Operating Loss Carryforward	0.0	0.0
Valuation Allowance	0.0	0.0
Tax Credit Carryforward	4.3	13.7
Operating Lease Liability	12.3	17.3
Investment in Partnership	0.0	0.0
Net Deferred Tax Liabilities	5.1	8.8
AEP TRANSMISSION COMPANY, LLC
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	172.6	188.0
Deferred Tax Liabilities	(1,451.2)	(1,335.7)
Net Deferred Tax Liabilities	(1,278.6)	(1,147.7)
Property Related Temporary Differences	(1,416.6)	(1,304.2)
Amounts Due to Customers for Future Income Taxes	121.4	120.8
Securitized Assets	0.0	0.0
Regulatory Assets	(0.2)	(0.7)
Accrued Nuclear Decommissioning	0.0	0.0
Net Operating Loss Carryforward	2.5	3.9
Valuation Allowance	(0.1)	(0.1)
Tax Credit Carryforward	0.0	0.0
Operating Lease Liability	0.3	0.4
Investment in Partnership	0.0	0.0
Net Deferred Tax Liabilities	14.1	32.2
APPALACHIAN POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	379.1	472.9
Deferred Tax Liabilities	(2,412.6)	(2,484.8)
Net Deferred Tax Liabilities	(2,033.5)	(2,011.9)
Property Related Temporary Differences	(1,784.8)	(1,805.9)
Amounts Due to Customers for Future Income Taxes	119.0	128.0
Securitized Assets	(25.7)	(32.6)
Regulatory Assets	(302.4)	(284.3)
Accrued Nuclear Decommissioning	0.0	0.0
Net Operating Loss Carryforward	0.4	0.2
Valuation Allowance	0.0	0.0
Tax Credit Carryforward	0.1	0.1
Operating Lease Liability	16.2	18.0
Investment in Partnership	(0.1)	(0.1)
Net Deferred Tax Liabilities	(56.2)	(35.3)
INDIANA MICHIGAN POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	1,072.2	1,014.0
Deferred Tax Liabilities	(2,248.0)	(2,183.9)
Net Deferred Tax Liabilities	(1,175.8)	(1,169.9)
Property Related Temporary Differences	(189.9)	(315.6)
Amounts Due to Customers for Future Income Taxes	73.1	103.2
Securitized Assets	0.0	0.0
Regulatory Assets	(49.2)	(27.7)
Accrued Nuclear Decommissioning	(1,052.2)	(923.5)
Net Operating Loss Carryforward	0.0	0.0
Valuation Allowance	0.0	0.0
Tax Credit Carryforward	39.6	7.2
Operating Lease Liability	13.5	14.1
Investment in Partnership	0.0	0.0
Net Deferred Tax Liabilities	(10.7)	(27.6)
OHIO POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	186.5	271.5
Deferred Tax Liabilities	(1,387.6)	(1,424.2)
Net Deferred Tax Liabilities	(1,201.1)	(1,152.7)
Property Related Temporary Differences	(1,290.9)	(1,243.2)
Amounts Due to Customers for Future Income Taxes	95.6	104.6
Securitized Assets	0.0	(5.3)
Regulatory Assets	(45.3)	(50.1)
Accrued Nuclear Decommissioning	0.0	0.0
Net Operating Loss Carryforward	2.9	2.6
Valuation Allowance	0.0	0.0
Tax Credit Carryforward	38.5	41.0
Operating Lease Liability	13.3	15.4
Investment in Partnership	(0.8)	(0.7)
Net Deferred Tax Liabilities	(14.4)	(17.0)
PUBLIC SERVICE COMPANY OF OKLAHOMA
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	266.9	282.4
Deferred Tax Liabilities	(1,197.5)	(1,113.6)
Net Deferred Tax Liabilities	(930.6)	(831.2)
Property Related Temporary Differences	(1,009.8)	(941.9)
Amounts Due to Customers for Future Income Taxes	80.7	99.0
Securitized Assets	0.0	0.0
Regulatory Assets	(53.1)	(67.2)
Accrued Nuclear Decommissioning	0.0	0.0
Net Operating Loss Carryforward	27.8	25.3
Valuation Allowance	0.0	0.0
Tax Credit Carryforward	26.5	53.8
Operating Lease Liability	27.1	28.2
Investment in Partnership	0.0	0.0
Net Deferred Tax Liabilities	(29.8)	(28.4)
SOUTHWESTERN ELECTRIC POWER COMPANY
Effective Income Tax Rate Reconciliation [Line Items]
Deferred Tax Assets	292.8	441.5
Deferred Tax Liabilities	(1,564.1)	(1,620.8)
Net Deferred Tax Liabilities	(1,271.3)	(1,179.3)
Property Related Temporary Differences	(1,353.1)	(1,306.0)
Amounts Due to Customers for Future Income Taxes	90.2	142.5
Securitized Assets	(81.1)	2.8
Regulatory Assets	(87.0)	(146.9)
Accrued Nuclear Decommissioning	0.0	0.0
Net Operating Loss Carryforward	36.5	47.5
Valuation Allowance	0.0	(1.8)
Tax Credit Carryforward	31.7	68.6
Operating Lease Liability	35.7	33.3
Investment in Partnership	(1.5)	(1.5)
Net Deferred Tax Liabilities	$ 57.3	$ (17.8)