Commitments, Guarantees and Contingencies (Details) $ in Millions	9 Months Ended
Sep. 30, 2016 USD ($)
Letters of Credit [Member]
Maximum Future Payments for Letters of Credit [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility	$ 147.2
Pollution Control Bonds Supported by Bilateral Letters of Credit [Abstract]
Variable Rate PCBs Supported	291.4
Bilateral Letters of Credit	294.7
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Revolving Credit Facilities	3,500.0
Letters of Credit Limit	1,200.0
Uncommitted Facility	300.0
Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements	36.8
Boat and Barge Leases [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Guarantee Liability related to AEPRO Boat and Barge Leases	14.0
Guarantee Liability related to AEPRO Boat and Barge Leases - Other Current Liabilities	3.0
Guarantee Liability related to AEPRO Boat and Barge Leases - Other Noncurrent Liabilities	11.0
Maximum Potential Lease Payments, AEPRO Barge and Boat Leases	87.0
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	5.5
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	3.4
Indiana Michigan Power Co [Member] \| Railcar Lease [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Future Minimum Lease Obligations 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	$ 9.0
Ohio Power Co [Member] \| Letters of Credit [Member]
Maximum Future Payments for Letters of Credit [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	5.8
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	3.0
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	68.0
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	53.0
Southwestern Electric Power Co [Member] \| Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements	3.5
Southwestern Electric Power Co [Member] \| Railcar Lease [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Future Minimum Lease Obligations 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	$ 10.0
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
June 2017 [Member] \| Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Revolving Credit Facilities	1,750.0
June 2021 [Member] \| Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Revolving Credit Facilities	3,000.0
July 2018 [Member] \| Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Revolving Credit Facilities	1,750.0
June 2018 [Member] \| Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Revolving Credit Facilities	$ 500.0

Amount collected through a rider for final mine closure and reclamation costs recorded in asset retirement obligations

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Amount collected through a rider for final mine closure and reclamation costs recorded in deferred credits and other noncurrent liabilities

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No definition available.

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Total amount collected through a rider for final mine closure and reclamation costs.

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Commitments, Guarantees and Contingencies.

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Amount of revolving credit facilities.

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Estimated final cost mine reclamation.

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The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees recorded under Other Current Liabilities.

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No definition available.

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The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees under Other Noncurrent Liabilities.

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Guarantees of mine reclamation, amount.

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- Definition

Maximum potential loss on master lease agreements.

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Maximum future payments for Letters of Credit issued under the uncommitted facility.

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- Definition

Future potential lease obligations under guaranteed AEPRO boat and barge leases.

+ References

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- Definition

Maximum potential loss related to the guarantee.

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- Definition

Sale proceeds guaranteed by lessor at the end of 20-year term.

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No definition available.

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- Definition

Sale proceeds guaranteed by lessor under current five year lease term.

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- Definition

Amount of letters of credit drawn on an uncommitted credit facility.

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- Definition

Amount of Pollution Control Bonds supported by bilateral letters of credit.

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No definition available.

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- Definition

The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 12
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- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
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-Section 50
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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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No definition available.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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- Definition

Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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