Commitments, Guarantees and Contingencies (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
Oct. 26, 2017	Sep. 30, 2017
Letters of Credit [Member]
Maximum Future Payments for Letters of Credit [Abstract]
Maximum Future Payments for Letters of Credit Issued Under the Uncommitted Facility		$ 123.2
Pollution Control Bonds Supported by Bilateral Letters of Credit [Abstract]
Variable Rate PCBs Supported		45.0
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Letters of Credit Limit		1,200.0
Uncommitted Facility		445.0
Guarantees of Third Party Obligations [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Guarantees of Mine Reclamation, Amount		115.0
Estimated Final Cost Mine Reclamation		76.0
Total Amount Collected through a Rider for Final Mine Closure and Reclamation Costs		71.0
Amount Collected, Rider Mine Close Other Assets Noncurrent		5.0
Amount Collected through a Rider for Final Mine Closure - ARO Noncurrent		76.0
Guarantees of Equity Method Investees [Member]
Maximum Potential Amount of Future Payments Associated with Guarantee		75.0
Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements		42.1
Boat and Barge Leases [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Maximum Potential Lease Payments, AEPRO Barge and Boat Leases		52.0
Guarantee Liability related to AEPRO Boat and Barge Leases		7.0
Guarantee Liability related to AEPRO Boat and Barge Leases - Other Current Liabilities		1.0
Guarantee Liability related to AEPRO Boat and Barge Leases - Other Noncurrent Liabilities		6.0
Appalachian Power Co [Member] \| Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements		8.8
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		$ 8.0
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		$ 8.0
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		0.6
Ohio Power Co [Member] \| Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements		6.0
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		3.3
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		76.0
Total Amount Collected through a Rider for Final Mine Closure and Reclamation Costs		71.0
Amount Collected, Rider Mine Close Other Assets Noncurrent		5.0
Amount Collected through a Rider for Final Mine Closure - ARO Noncurrent		76.0
Southwestern Electric Power Co [Member] \| Master Lease Agreements [Member]
Maximum Potential Loss on Master Lease Agreements [Abstract]
Max Potential Loss on Master Lease Agreements		3.7
Southwestern Electric 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		$ 10.0
Superfund and State Remediation [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Expense Recorded Due to Remediation Work Remaining Provision		3.0
Superfund and State Remediation [Member] \| Indiana Michigan Power Co [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Expense Recorded Due to Remediation Work Remaining Provision		3.0
June 2021 [Member] \| Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Revolving Credit Facilities		3,000.0
June 2018 [Member] \| Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Revolving Credit Facilities		500.0
August 2018 [Member] \| Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Uncommitted Facility		75.0
July 2019 [Member] \| Letters of Credit [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Bilateral Letters of Credit, Matured		$ 46.0
Subsequent Event [Member] \| Guarantees of Third Party Obligations [Member]
Commitments, Guarantees and Contingencies (Textuals) [Abstract]
Guarantees of Mine Reclamation, Amount	$ 140.0

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

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- Definition

Amount collected through a rider for final mine closure and reclamation costs recorded in deferred charges and other noncurrent assets.

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

The amount of bilateral letters of credit matured as of reporting date.

+ References

No definition available.

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- Definition

Commitments, Guarantees and Contingencies.

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Amount of revolving credit facilities.

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No definition available.

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- Definition

Estimated final cost mine reclamation.

+ References

No definition available.

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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 recorded under Other Current Liabilities.

+ References

No definition available.

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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 under Other Noncurrent Liabilities.

+ References

No definition available.

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- Definition

Guarantees of mine reclamation, amount.

+ References

No definition available.

+ Details

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- Definition

Maximum potential loss on master lease agreements.

+ References

No definition available.

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- References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

Maximum Potential Amount of Future Payments Associated with Guarantee

+ References

No definition available.

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- Definition

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

+ References

No definition available.

+ Details

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- References

No definition available.

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- Definition

Maximum potential loss related to the guarantee.

+ References

No definition available.

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- References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

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

+ References

No definition available.

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- Definition

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

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- 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
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13296-110859

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82913245&loc=d3e12069-110248

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Amount of a reclamation and mine closing liability that is associated with a legal obligation for the closure and reclamation of a mine including the removal of buildings, equipment, machinery and other physical remnants of mining, closure of tailings impoundments, leach pads and other mine features, and contouring, covering and revegetation of waste rock piles and other disturbed areas.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 5.Y.Q2)
-URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
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-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717

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