Commitments, Guarantees and Contingencies (Details) - USD ($) $ in Millions		3 Months Ended
		Jun. 30, 2020	Sep. 30, 2020
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements			$ 49.8
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Asset Retirement Obligation, Period Increase (Decrease)		$ 199.0
AEP Texas Inc. [Member]
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements			11.4
Appalachian Power Co [Member]
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements			6.8
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Asset Retirement Obligation, Period Increase (Decrease)		$ 199.0
Indiana Michigan Power Co [Member]
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements			4.5
Ohio Power Co [Member]
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements			7.9
Public Service Co Of Oklahoma [Member]
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements			4.6
Southwestern Electric Power Co [Member]
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements			5.2
Rockport Lease [Member]
Present Value of Future Minimum Lease Payments, Sale Leaseback Transactions, Fiscal Year Maturity [Abstract]
Minimum Lease Payments, Sale Leaseback Transactions, Next Twelve Months	[1]		73.9
Minimum Lease Payments, Sale Leaseback Transactions, within Two Years	[1]		147.8
Minimum Lease Payments, Sale Leaseback Transactions, within Three Years	[1]		147.5
Minimum Lease Payments, Sale Leaseback Transactions	[1]		369.2
Rockport Lease [Member] | Indiana Michigan Power Co [Member]
Present Value of Future Minimum Lease Payments, Sale Leaseback Transactions, Fiscal Year Maturity [Abstract]
Minimum Lease Payments, Sale Leaseback Transactions, Next Twelve Months			37.0
Minimum Lease Payments, Sale Leaseback Transactions, within Two Years			73.9
Minimum Lease Payments, Sale Leaseback Transactions, within Three Years			73.7
Minimum Lease Payments, Sale Leaseback Transactions			184.6
Boat and Barge Leases [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Maximum Potential Lease Payments, AEPRO Barge and Boat Leases			50.0
Guarantor Obligations, Current Carrying Value			3.0
Guarantee Obligations Current Carrying Value Other Liabilities Current			1.0
Guarantee Obligations Current Carrying Value Other Liabilities Noncurrent			2.0
Letters of Credit [Member]
Maximum Future Payments for Letters of Credit [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility			197.3
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Letters of Credit Limit			1,200.0
Uncommitted Facility			405.0
Letters of Credit [Member] | AEP Texas Inc. [Member]
Maximum Future Payments for Letters of Credit [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility			2.2
June 2022 [Member] | Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Revolving Credit Facilities			$ 4,000.0

[1] AEP’s future minimum lease payments include equal shares from AEGCo and I&M.