Commitments, Guarantees and Contingencies (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Letters of Credit [Member]
Maximum Future Payments for Letters of Credit Under Uncommitted Facilities [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility	$ 190.2
Pollution Control Bonds Supported by Bilateral Letters of Credit [Abstract]
Variable Rate PCBs Supported	351.4
Bilateral Letters of Credit	355.4
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Revolving Credit Facilities	3,500.0
Letters of Credit Limit	1,200.0
Maximum Future Payments for Letters of Credit	2.0
Uncommitted Facility	225.0
Guarantees of Third Party Obligations [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Guarantees of Mine Reclamation, Amount	115.0
Estimated Final Cost Mine Reclamation	58.0
Total Amount Collected through a Rider for Final Mine Closure and Reclamation Costs	67.0
Amount Collected through a Rider for Final Mine Closure - Other Liabilities Noncurrent	15.0
Amount Collected through a Rider for Final Mine Closure - ARO Noncurrent	52.0
Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements	33.6
Appalachian Power Co [Member] | Letters of Credit [Member]
Pollution Control Bonds Supported by Bilateral Letters of Credit [Abstract]
Variable Rate PCBs Supported	104.4
Bilateral Letters of Credit	105.6
Appalachian Power Co [Member] | Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements	4.9
Indiana Michigan Power Co [Member] | Letters of Credit [Member]
Pollution Control Bonds Supported by Bilateral Letters of Credit [Abstract]
Variable Rate PCBs Supported	77.0
Bilateral Letters of Credit	77.9
Indiana Michigan Power Co [Member] | Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements	3.0
Ohio Power Co [Member] | Letters of Credit [Member]
Maximum Future Payments for Letters of Credit Under Uncommitted Facilities [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility	4.2
Ohio Power Co [Member] | Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements	5.3
Public Service Co Of Oklahoma [Member] | Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements	2.8
Southwestern Electric Power Co [Member] | Guarantees of Third Party Obligations [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Guarantees of Mine Reclamation, Amount	115.0
Estimated Final Cost Mine Reclamation	58.0
Total Amount Collected through a Rider for Final Mine Closure and Reclamation Costs	67.0
Amount Collected through a Rider for Final Mine Closure - Other Liabilities Noncurrent	15.0
Amount Collected through a Rider for Final Mine Closure - ARO Noncurrent	52.0
Southwestern Electric Power Co [Member] | Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements	3.1
Superfund and State Remediation [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Expense Recorded Due to Remediation Work Remaining Provision	8.0
Superfund and State Remediation [Member] | Indiana Michigan Power Co [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Expense Recorded Due to Remediation Work Remaining Provision	8.0
Railcar Lease [Member] | Indiana Michigan Power Co [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Future Minimum Lease Obligation for Remaining Railcars	$ 9.0
Guaranteed Sales Proceeds Percentage of Fair Value to Lessor Current Term	83.00%
Guaranteed Sales Proceeds Percentage of Fair Value to Lessor End of Max Lease Term	77.00%
Maximum Potential Loss on Guarantee of Return-and-Sale Option	$ 9.0
Railcar Lease [Member] | Southwestern Electric Power Co [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Future Minimum Lease Obligation for Remaining Railcars	$ 11.0
Guaranteed Sales Proceeds Percentage of Fair Value to Lessor Current Term	83.00%
Guaranteed Sales Proceeds Percentage of Fair Value to Lessor End of Max Lease Term	77.00%
Maximum Potential Loss on Guarantee of Return-and-Sale Option	$ 10.0
Boat and Barge Leases [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Maximum Potential Loss on Guarantee of Return-and-Sale Option	15.0
Maximum Potential Lease Payments, AEPRO Barge and Boat Leases	93.0
Maximum [Member] | Wage and Hours Lawsuit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Range of Possible Loss	30.0
Maximum [Member] | Wage and Hours Lawsuit [Member] | Public Service Co Of Oklahoma [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Range of Possible Loss	$ 30.0