EFFECTS OF REGULATION - Regulatory Liabilities - OPCo (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	$ 8,344.0	$ 8,182.4
Pending final regulatory determination
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	322.0	207.9
Approved for payment
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	$ 8,022.0	7,974.5
Does not pay/paying a return | Over-recovered Fuel Costs
Regulatory Liability [Line Items]
Remaining Refund Period	1 year
Does not pay/paying a return | Pending final regulatory determination
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	$ 146.0	104.8
Does not pay/paying a return | Pending final regulatory determination | FERC 2021 Transmission Formula Rate Challenge Refunds
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	131.3	103.1
Does not pay/paying a return | Pending final regulatory determination | Other Regulatory Liabilities Pending Final Regulatory Determination
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	14.7	1.7
Does not pay/paying a return | Approved for payment
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	2,495.6	2,151.4
Does not pay/paying a return | Approved for payment | Other Regulatory Liabilities Approved for Payment
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	90.1	106.5
Does not pay/paying a return | Approved for payment | Over-recovered Fuel Costs
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	$ 32.1	26.1
Remaining Refund Period	8 years
Pays/paying a return | Over-recovered Fuel Costs
Regulatory Liability [Line Items]
Remaining Refund Period	1 year
Pays/paying a return | Pending final regulatory determination
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	$ 176.0	103.1
Pays/paying a return | Pending final regulatory determination | Income Taxes, Net
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	176.0	103.1
Pays/paying a return | Approved for payment
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	5,526.4	5,823.1
Pays/paying a return | Approved for payment | Asset Removal Costs
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	3,828.0	3,563.5
Pays/paying a return | Approved for payment | Income Taxes, Net
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	1,622.1	2,179.7
Regulatory liabilities, not subject to rate normalization requirements, amount	$ 192.0	228.0
Regulatory liabilities, not subject to rate normalization requirements, refund period	10 years
Pays/paying a return | Approved for payment | Other Regulatory Liabilities Approved for Payment
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	$ 40.4	35.0
OHIO POWER COMPANY
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	987.7	1,003.6
OHIO POWER COMPANY | Approved for payment
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	914.8	946.4
OHIO POWER COMPANY | Does not pay/paying a return | Pending final regulatory determination
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	72.9	57.2
OHIO POWER COMPANY | Does not pay/paying a return | Pending final regulatory determination | FERC 2021 Transmission Formula Rate Challenge Refunds
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	72.7	57.0
OHIO POWER COMPANY | Does not pay/paying a return | Pending final regulatory determination | Other Regulatory Liabilities Pending Final Regulatory Determination
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	0.2	0.2
OHIO POWER COMPANY | Does not pay/paying a return | Approved for payment
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	63.2	62.7
OHIO POWER COMPANY | Does not pay/paying a return | Approved for payment | Other Regulatory Liabilities Approved for Payment
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	8.3	13.4
OHIO POWER COMPANY | Does not pay/paying a return | Approved for payment | Over-recovered Fuel Costs
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	$ 32.1	26.1
Remaining Refund Period	8 years
OHIO POWER COMPANY | Does not pay/paying a return | Approved for payment | Peak Demand Reduction/Energy Efficiency
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	$ 22.8	23.2
Remaining Refund Period	2 years
OHIO POWER COMPANY | Pays/paying a return | Approved for payment
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	$ 851.6	883.7
OHIO POWER COMPANY | Pays/paying a return | Approved for payment | Asset Removal Costs
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	480.0	475.5
OHIO POWER COMPANY | Pays/paying a return | Approved for payment | Income Taxes, Net
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	367.6	408.2
Regulatory liabilities, not subject to rate normalization requirements, amount	$ 100.0	132.0
Regulatory liabilities, not subject to rate normalization requirements, refund period	4 years
OHIO POWER COMPANY | Pays/paying a return | Approved for payment | Other Regulatory Liabilities Approved for Payment
Regulatory Liability [Line Items]
Total Noncurrent Regulatory Liabilities and Deferred Investment Tax Credits	$ 4.0	$ 0.0