Commitments, Guarantees and Contingencies (Details) $ in Millions	3 Months Ended
	Jun. 30, 2020 USD ($)
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements	$ 50.2
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	11.9
Appalachian Power Co [Member]
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements	7.2
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	4.2
Ohio Power Co [Member]
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements	7.5
Public Service Co Of Oklahoma [Member]
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements	4.7
Southwestern Electric Power Co [Member]
Maximum Potential Loss [Abstract]
Max Potential Loss on Master Lease Agreements	5.3
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	73.9	[1]
Minimum Lease Payments, Sale Leaseback Transactions, within Two Years	147.8	[1]
Minimum Lease Payments, Sale Leaseback Transactions, within Three Years	147.5	[1]
Minimum Lease Payments, Sale Leaseback Transactions	369.2	[1]
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	52.0
Guarantor Obligations, Current Carrying Value	4.0
Guarantee Obligations Current Carrying Value Other Liabilities Current	1.0
Guarantee Obligations Current Carrying Value Other Liabilities Noncurrent	3.0
Letters of Credit [Member]
Maximum Future Payments for Letters of Credit [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility	191.6
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	[2]
Letters of Credit [Member] | Ohio Power Co [Member]
Maximum Future Payments for Letters of Credit [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility	1.0
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.

[2] In July 2020, the maturity date was extended from July 2020 to July 2021.