Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flow Hedges, Tax	$ (21.1)	$ 3.9	$ (1.4)
Securities Available for Sale, Tax	0.0	0.0	1.9
Amortization of Pension and OPEB Deferred Costs, Tax	(1.5)	(1.4)	0.6
Pension and OPEB Funded Status, Tax	15.3	(8.8)	46.7
AEP Texas Inc. [Member]
Cash Flow Hedges, Tax	0.3	0.3	0.5
Amortization of Pension and OPEB Deferred Costs, Tax	0.0	0.1	0.1
Pension and OPEB Funded Status, Tax	0.3	(0.3)	0.6
Appalachian Power Co [Member]
Cash Flow Hedges, Tax	(0.2)	(0.2)	(0.4)
Amortization of Pension and OPEB Deferred Costs, Tax	(0.7)	(0.8)	(0.6)
Pension and OPEB Funded Status, Tax	3.6	(0.7)	6.3
Indiana Michigan Power Co [Member]
Cash Flow Hedges, Tax	0.4	0.4	0.7
Amortization of Pension and OPEB Deferred Costs, Tax	0.0	0.0	0.0
Pension and OPEB Funded Status, Tax	0.2	(0.2)	1.5
Ohio Power Co [Member]
Cash Flow Hedges, Tax	(0.3)	(0.4)	(0.6)
Public Service Co Of Oklahoma [Member]
Cash Flow Hedges, Tax	(0.3)	(0.3)	(0.4)
Southwestern Electric Power Co [Member]
Cash Flow Hedges, Tax	0.4	1.1	0.8
Amortization of Pension and OPEB Deferred Costs, Tax	(0.3)	(0.4)	(0.4)
Pension and OPEB Funded Status, Tax	$ 1.0	$ (0.8)	$ 2.5

Amount of tax expense (benefit) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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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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Amount, after reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income of defined benefit plan.

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