The period effect on effective tax rate ETR due to increase/decrease in income tax expense.

No definition available.

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- Definition

Illinois Corporate Income Tax Rate effective July 1, 2017, after legislation passed.

+ References

No definition available.

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- Definition

Increased Illinois Corporate Income Tax Rate including the Illinois Replacement Tax effective July 1, 2017.

+ References

No definition available.

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- Definition

Illinois Replacement Tax.

+ References

No definition available.

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- Definition

Income Taxes.

+ References

No definition available.

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- Definition

llinois Corporate Income Tax Rate prior to July 1, 2017.

+ References

No definition available.

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- Definition

Inital Illinois Corporate Income Tax Rate including the Illinois Replacement Tax.

+ References

No definition available.

+ Details

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- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

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- Definition

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

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-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e32123-109318

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Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
Income Taxes (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Federal Statutory Tax Rate			35.00%
Effective Income Tax Rate	33.00%	40.40%	35.30%	(195.60%)
Income Taxes (Textuals) [Abstract]
Pre July 1 2017 Illinois Corporate Income Tax Rate			5.25%
Effective July 1 2017 Illinois Corporate Income Tax Rate			7.00%
Illinois Replacement Tax			2.50%
Pre July 1, 2017 Total Illinois Corporate Income Tax Rate			7.75%
Effective July 1, 2017 Total Illinois Corporate Income Tax Rate			9.50%
2011 Audit Issue Settlement [Member]
Valuation Allowance			$ 56
Certain Assets Held for Sale and 2015 Federal Income Tax Return [Member]
Valuation Allowance	$ 66		$ 66
AEP Transmission Co [Member]
Federal Statutory Tax Rate			35.00%
Effective Income Tax Rate	33.50%	33.50%	33.80%	32.60%
Appalachian Power Co [Member]
Federal Statutory Tax Rate			35.00%
Effective Income Tax Rate	33.40%	36.10%	35.50%	36.20%
Income Taxes (Textuals) [Abstract]
Pre July 1 2017 Illinois Corporate Income Tax Rate			5.25%
Effective July 1 2017 Illinois Corporate Income Tax Rate			7.00%
Illinois Replacement Tax			2.50%
Pre July 1, 2017 Total Illinois Corporate Income Tax Rate			7.75%
Effective July 1, 2017 Total Illinois Corporate Income Tax Rate			9.50%
Indiana Michigan Power Co [Member]
Federal Statutory Tax Rate			35.00%
Effective Income Tax Rate	30.60%	31.80%	30.10%	29.50%
Income Taxes (Textuals) [Abstract]
Pre July 1 2017 Illinois Corporate Income Tax Rate			5.25%
Effective July 1 2017 Illinois Corporate Income Tax Rate			7.00%
Illinois Replacement Tax			2.50%
Pre July 1, 2017 Total Illinois Corporate Income Tax Rate			7.75%
Effective July 1, 2017 Total Illinois Corporate Income Tax Rate			9.50%
Ohio Power Co [Member]
Federal Statutory Tax Rate			35.00%
Effective Income Tax Rate	36.90%	31.70%	35.60%	33.40%
Income Taxes (Textuals) [Abstract]
Pre July 1 2017 Illinois Corporate Income Tax Rate			5.25%
Effective July 1 2017 Illinois Corporate Income Tax Rate			7.00%
Illinois Replacement Tax			2.50%
Pre July 1, 2017 Total Illinois Corporate Income Tax Rate			7.75%
Effective July 1, 2017 Total Illinois Corporate Income Tax Rate			9.50%
Public Service Co Of Oklahoma [Member]
Federal Statutory Tax Rate			35.00%
Effective Income Tax Rate	37.20%	37.70%	37.40%	36.80%
Southwestern Electric Power Co [Member]
Federal Statutory Tax Rate			35.00%
Effective Income Tax Rate	21.20%	28.90%	25.70%	26.70%
Income Taxes (Textuals) [Abstract]
Effect On Effective Tax Rate Due To Increase/Decrease In Income Tax Expense	$ 10