Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Cash Flow Hedges, Tax	$ 2.7	$ (8.1)	$ 3.9	$ (12.2)
Securities Available for Sale, Tax	0.0	0.5	0.0	1.5
Amortization of Pension and OPEB Deferred Costs, Tax	(0.4)	0.1	(11.1)	0.4
AEP Texas Inc. [Member]
Cash Flow Hedges, Tax	0.1	0.2	0.2	0.4
Amortization of Pension and OPEB Deferred Costs, Tax	0.0	0.0	0.0	0.1
Appalachian Power Co [Member]
Cash Flow Hedges, Tax	(0.1)	(0.1)	(0.2)	(0.3)
Amortization of Pension and OPEB Deferred Costs, Tax	(0.2)	(0.1)	(0.6)	(0.4)
Indiana Michigan Power Co [Member]
Cash Flow Hedges, Tax	0.1	0.1	0.3	0.5
Ohio Power Co [Member]
Cash Flow Hedges, Tax	(0.1)	(0.1)	(0.3)	(0.4)
Public Service Co Of Oklahoma [Member]
Cash Flow Hedges, Tax	0.0	(0.1)	(0.2)	(0.3)
Southwestern Electric Power Co [Member]
Cash Flow Hedges, Tax	0.8	0.2	1.0	0.6
Amortization of Pension and OPEB Deferred Costs, Tax	$ (0.1)	$ (0.1)	$ (0.3)	$ (0.3)

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.

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