Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flow Hedges, Tax	$ 0.7	$ (8.7)
Securities Available for Sale, Tax	0.0	0.6
Amortization of Pension and OPEB Deferred Costs, Tax	(0.4)	0.1
AEP Texas Inc. [Member]
Cash Flow Hedges, Tax	0.1	0.1
Amortization of Pension and OPEB Deferred Costs, Tax	0.0	0.0
Appalachian Power Co [Member]
Cash Flow Hedges, Tax	(0.1)	(0.1)
Amortization of Pension and OPEB Deferred Costs, Tax	(0.2)	(0.2)
Indiana Michigan Power Co [Member]
Cash Flow Hedges, Tax	0.1	0.2
Ohio Power Co [Member]
Cash Flow Hedges, Tax	(0.1)	(0.1)
Public Service Co Of Oklahoma [Member]
Cash Flow Hedges, Tax	(0.1)	(0.1)
Southwestern Electric Power Co [Member]
Cash Flow Hedges, Tax	0.1	0.2
Amortization of Pension and OPEB Deferred Costs, Tax	$ (0.1)	$ (0.1)