Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flow Hedges, Tax	$ (8.8)	$ (2.6)	$ 2.9
Securities Available for Sale, Tax	0.7	(0.3)	0.4
Amortization of Pension and OPEB Deferred Costs, Tax	0.3	0.6	2.6
Pension and OPEB Funded Status, Tax	(7.9)	(13.9)	0.6
Appalachian Power Co [Member]
Cash Flow Hedges, Tax	(0.4)	(0.1)	0.4
Amortization of Pension and OPEB Deferred Costs, Tax	(0.8)	(1.0)	(0.7)
Pension and OPEB Funded Status, Tax	(1.9)	(3.1)	1.5
Indiana Michigan Power Co [Member]
Cash Flow Hedges, Tax	0.7	0.6	0.8
Amortization of Pension and OPEB Deferred Costs, Tax	0.0	0.0	0.1
Pension and OPEB Funded Status, Tax	(0.4)	(1.9)	(0.3)
Ohio Power Co [Member]
Cash Flow Hedges, Tax	(0.7)	(0.7)	(0.8)
Public Service Co Of Oklahoma [Member]
Cash Flow Hedges, Tax	(0.4)	(0.4)	(0.4)
Southwestern Electric Power Co [Member]
Cash Flow Hedges, Tax	0.9	1.1	1.2
Amortization of Pension and OPEB Deferred Costs, Tax	(0.4)	(0.5)	(0.5)
Pension and OPEB Funded Status, Tax	$ (0.5)	$ (1.6)	$ (0.2)

Amount of tax expense (benefit) related to (increase) decrease in the value of the projected benefit obligation related to a change in an actuarial assumption and increase (decrease) in the value of the plan assets resulting from experience different from that assumed, that has not been recognized in net periodic benefit (cost) credit.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e640-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (i-k)
-URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669646-108580

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- Definition

Amount of tax expense (benefit), after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e640-108580

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e640-108580

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Amount of tax (expense) benefit, after reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans.

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