Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		$ (95.4)	$ (171.0)	$ (67.8)	$ (156.3)
Change in Fair Value Recognized in AOCI		5.4	3.5	18.2	(17.1)
Commodity
Generation & Marketing Revenues		435.3	386.5	912.8	945.3
Purchased Electricity for Resale		776.7	669.2	1,767.0	1,438.8
Interest Rate
Interest Expense		242.3	222.9	476.3	444.7
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		(6.0)	9.0	(20.6)	18.0
Income Tax (Expense) Credit		(72.2)	(190.6)	(174.2)	(533.8)
Reclassification from AOCI, Net of Income Tax (Expense) Credit		(4.8)	5.9	(16.3)	11.8
Net Current Period Other Comprehensive Income (Loss)		0.6	9.4	1.9	(5.3)
ASU 2018-02 Adoption				(3.0)
ASU 2016-01 Adoption				0.0
Ending Balance in AOCI		(94.8)	(161.6)	(94.8)	(161.6)
Securities Available for Sale [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI			9.6	11.9	8.4
Change in Fair Value Recognized in AOCI			0.6	0.0	1.8
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit			0.0	0.0	0.0
Reclassification from AOCI, Net of Income Tax (Expense) Credit			0.0	0.0	0.0
Net Current Period Other Comprehensive Income (Loss)			0.6	0.0	1.8
ASU 2018-02 Adoption	[1]			0.0
ASU 2016-01 Adoption	[1]			(11.9)
Ending Balance in AOCI		0.0	10.2	0.0	10.2
Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(47.9)	(125.7)	(38.3)	(125.9)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		(1.5)	0.4	(3.3)	0.8
Reclassification from AOCI, Net of Income Tax (Expense) Credit		(1.2)	0.3	(2.6)	0.5
Net Current Period Other Comprehensive Income (Loss)		(1.2)	0.3	(2.6)	0.5
ASU 2018-02 Adoption	[1]			(8.2)
ASU 2016-01 Adoption	[1]			0.0
Ending Balance in AOCI		(49.1)	(125.4)	(49.1)	(125.4)
Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)				1.9	(5.3)
ASU 2018-02 Adoption	[1]			(17.0)
ASU 2016-01 Adoption	[1]			(11.9)
Commodity [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(32.0)	(39.6)	(28.4)	(23.1)
Change in Fair Value Recognized in AOCI		5.4	(1.8)	18.2	(23.6)
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		(4.7)	8.3	(17.8)	16.4
Reclassification from AOCI, Net of Income Tax (Expense) Credit		(3.8)	5.4	(14.1)	10.7
Net Current Period Other Comprehensive Income (Loss)		1.6	3.6	4.1	(12.9)
ASU 2018-02 Adoption	[1]			(6.1)
ASU 2016-01 Adoption	[1]			0.0
Ending Balance in AOCI		(30.4)	(36.0)	(30.4)	(36.0)
Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(15.5)	(15.3)	(13.0)	(15.7)
Change in Fair Value Recognized in AOCI		0.0	4.7	0.0	4.7
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		0.2	0.3	0.5	0.8
Reclassification from AOCI, Net of Income Tax (Expense) Credit		0.2	0.2	0.4	0.6
Net Current Period Other Comprehensive Income (Loss)		0.2	4.9	0.4	5.3
ASU 2018-02 Adoption	[1]			(2.7)
ASU 2016-01 Adoption	[1]			0.0
Ending Balance in AOCI		(15.3)	(10.4)	(15.3)	(10.4)
Reclassifications from Accumulated Other Comprehensive Income [Member]
Commodity
Generation & Marketing Revenues	[2]				(4.7)
Purchased Electricity for Resale	[2]	(4.7)	8.3	(17.8)	21.1
Interest Rate
Interest Expense	[2]	0.2	0.3	0.5	0.8
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(4.7)	(4.9)	(9.7)	(9.8)
Amortization of Actuarial (Gains)/Losses		3.2	5.3	6.4	10.6
Income Tax (Expense) Credit		(1.2)	3.1	(4.3)	6.2
Reclassifications from Accumulated Other Comprehensive Income [Member] | Securities Available for Sale [Member]
Commodity
Generation & Marketing Revenues	[2]				0.0
Purchased Electricity for Resale	[2]		0.0	0.0	0.0
Interest Rate
Interest Expense	[2]		0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)			0.0	0.0	0.0
Amortization of Actuarial (Gains)/Losses			0.0	0.0	0.0
Income Tax (Expense) Credit			0.0	0.0	0.0
Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Commodity
Generation & Marketing Revenues	[2]				0.0
Purchased Electricity for Resale	[2]	0.0	0.0	0.0	0.0
Interest Rate
Interest Expense	[2]	0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(4.7)	(4.9)	(9.7)	(9.8)
Amortization of Actuarial (Gains)/Losses		3.2	5.3	6.4	10.6
Income Tax (Expense) Credit		(0.3)	0.1	(0.7)	0.3
Reclassifications from Accumulated Other Comprehensive Income [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Commodity
Generation & Marketing Revenues	[2]				(4.7)
Purchased Electricity for Resale	[2]	(4.7)	8.3	(17.8)	21.1
Interest Rate
Interest Expense	[2]	0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0	0.0	0.0	0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0	0.0	0.0
Income Tax (Expense) Credit		(0.9)	2.9	(3.7)	5.7
Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Commodity
Generation & Marketing Revenues	[2]				0.0
Purchased Electricity for Resale	[2]	0.0	0.0	0.0	0.0
Interest Rate
Interest Expense	[2]	0.2	0.3	0.5	0.8
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0	0.0	0.0	0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0	0.0	0.0
Income Tax (Expense) Credit		0.0	0.1	0.1	0.2
AEP Texas Inc. [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(15.0)	(14.6)	(12.6)	(14.9)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Interest Rate
Interest Expense		36.6	35.3	71.6	70.3
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		0.3	0.5	0.7	0.9
Income Tax (Expense) Credit		(9.0)	(25.9)	(18.1)	(43.6)
Reclassification from AOCI, Net of Income Tax (Expense) Credit		0.3	0.3	0.6	0.6
Net Current Period Other Comprehensive Income (Loss)		0.3	0.3	0.6	0.6
ASU 2018-02 Adoption				(0.9)
Ending Balance in AOCI		(14.7)	(14.3)	(14.7)	(14.3)
AEP Texas Inc. [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(9.8)	(9.4)	(8.1)	(9.5)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		0.0	0.1	0.1	0.2
Reclassification from AOCI, Net of Income Tax (Expense) Credit		0.0	0.0	0.1	0.1
Net Current Period Other Comprehensive Income (Loss)		0.0	0.0	0.1	0.1
ASU 2018-02 Adoption	[1]			(1.8)
Ending Balance in AOCI		(9.8)	(9.4)	(9.8)	(9.4)
AEP Texas Inc. [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)				0.6	0.6
ASU 2018-02 Adoption	[1]			(2.7)
AEP Texas Inc. [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(5.2)	(5.2)	(4.5)	(5.4)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		0.3	0.4	0.6	0.7
Reclassification from AOCI, Net of Income Tax (Expense) Credit		0.3	0.3	0.5	0.5
Net Current Period Other Comprehensive Income (Loss)		0.3	0.3	0.5	0.5
ASU 2018-02 Adoption	[1]			(0.9)
Ending Balance in AOCI		(4.9)	(4.9)	(4.9)	(4.9)
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]	0.3	0.4	0.6	0.7
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.1)		(0.1)
Amortization of Actuarial (Gains)/Losses		0.1	0.1	0.2	0.2
Income Tax (Expense) Credit		0.0	0.2	0.1	0.3
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense	[2]	0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.1)		(0.1)
Amortization of Actuarial (Gains)/Losses		0.1	0.1	0.2	0.2
Income Tax (Expense) Credit		0.0	0.1	0.0	0.1
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[2]	0.3	0.4	0.6	0.7
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0		0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0	0.0	0.0
Income Tax (Expense) Credit		0.0	0.1	0.1	0.2
Appalachian Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		0.6	(8.9)	1.3	(8.4)
Change in Fair Value Recognized in AOCI		0.0	0.0	(0.7)	0.0
Commodity
Purchased Electricity for Resale		64.5	65.2	270.4	156.0
Interest Rate
Interest Expense		47.8	48.2	95.2	96.3
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		(1.2)	(0.7)	(1.6)	(1.5)
Income Tax (Expense) Credit		(15.8)	(29.9)	(43.8)	(93.5)
Reclassification from AOCI, Net of Income Tax (Expense) Credit		(1.0)	(0.5)	(1.3)	(1.0)
Net Current Period Other Comprehensive Income (Loss)		(1.0)	(0.5)	(2.0)	(1.0)
ASU 2018-02 Adoption				0.4
Ending Balance in AOCI		(0.4)	(9.4)	(0.4)	(9.4)
Appalachian Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(1.9)	(11.6)	(0.9)	(11.3)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		(1.0)	(0.4)	(2.0)	(0.9)
Reclassification from AOCI, Net of Income Tax (Expense) Credit		(0.8)	(0.3)	(1.6)	(0.6)
Net Current Period Other Comprehensive Income (Loss)		(0.8)	(0.3)	(1.6)	(0.6)
ASU 2018-02 Adoption	[1]			(0.2)
Ending Balance in AOCI		(2.7)	(11.9)	(2.7)	(11.9)
Appalachian Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)				(2.0)	(1.0)
ASU 2018-02 Adoption	[1]			0.3
Appalachian Power Co [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI				0.0
Change in Fair Value Recognized in AOCI				(0.7)
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit				0.9
Reclassification from AOCI, Net of Income Tax (Expense) Credit				0.7
Net Current Period Other Comprehensive Income (Loss)				0.0
ASU 2018-02 Adoption	[1]			0.0
Ending Balance in AOCI		0.0		0.0
Appalachian Power Co [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		2.5	2.7	2.2	2.9
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		(0.2)	(0.3)	(0.5)	(0.6)
Reclassification from AOCI, Net of Income Tax (Expense) Credit		(0.2)	(0.2)	(0.4)	(0.4)
Net Current Period Other Comprehensive Income (Loss)		(0.2)	(0.2)	(0.4)	(0.4)
ASU 2018-02 Adoption	[1]			0.5
Ending Balance in AOCI		2.3	2.5	2.3	2.5
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Commodity
Purchased Electricity for Resale	[2]			0.9
Interest Rate
Interest Expense	[2]	(0.2)	(0.3)	(0.5)	(0.6)
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(1.3)	(1.3)	(2.6)	(2.6)
Amortization of Actuarial (Gains)/Losses		0.3	0.9	0.6	1.7
Income Tax (Expense) Credit		(0.2)	(0.2)	(0.3)	(0.5)
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Commodity
Purchased Electricity for Resale	[2]			0.0
Interest Rate
Interest Expense	[2]	0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(1.3)	(1.3)	(2.6)	(2.6)
Amortization of Actuarial (Gains)/Losses		0.3	0.9	0.6	1.7
Income Tax (Expense) Credit		(0.2)	(0.1)	(0.4)	(0.3)
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Commodity
Purchased Electricity for Resale	[2]			0.9
Interest Rate
Interest Expense	[2]			0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)				0.0
Amortization of Actuarial (Gains)/Losses				0.0
Income Tax (Expense) Credit				0.2
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Commodity
Purchased Electricity for Resale	[2]			0.0
Interest Rate
Interest Expense	[2]	(0.2)	(0.3)	(0.5)	(0.6)
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0	0.0	0.0	0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0	0.0	0.0
Income Tax (Expense) Credit		0.0	(0.1)	(0.1)	(0.2)
Indiana Michigan Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(14.4)	(15.9)	(12.1)	(16.2)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Commodity
Purchased Electricity for Resale		63.2	31.0	118.8	68.3
Interest Rate
Interest Expense		31.4	27.8	61.1	55.5
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		0.6	0.5	1.1	1.0
Income Tax (Expense) Credit		(0.7)	(4.0)	(13.1)	(33.2)
Reclassification from AOCI, Net of Income Tax (Expense) Credit		0.5	0.4	0.9	0.7
Net Current Period Other Comprehensive Income (Loss)		0.5	0.4	0.9	0.7
ASU 2018-02 Adoption				(2.4)
Ending Balance in AOCI		(13.9)	(15.5)	(13.9)	(15.5)
Indiana Michigan Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(1.7)	(4.2)	(1.4)	(4.2)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		0.0	0.0	0.0	0.0
Reclassification from AOCI, Net of Income Tax (Expense) Credit		0.0	0.0	0.0	0.0
Net Current Period Other Comprehensive Income (Loss)		0.0	0.0	0.0	0.0
ASU 2018-02 Adoption	[1]			(0.3)
Ending Balance in AOCI		(1.7)	(4.2)	(1.7)	(4.2)
Indiana Michigan Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)				0.9	0.7
ASU 2018-02 Adoption	[1]			(2.7)
Indiana Michigan Power Co [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(12.7)	(11.7)	(10.7)	(12.0)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		0.6	0.5	1.1	1.0
Reclassification from AOCI, Net of Income Tax (Expense) Credit		0.5	0.4	0.9	0.7
Net Current Period Other Comprehensive Income (Loss)		0.5	0.4	0.9	0.7
ASU 2018-02 Adoption	[1]			(2.4)
Ending Balance in AOCI		(12.2)	(11.3)	(12.2)	(11.3)
Indiana Michigan Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]	0.6	0.5	1.1	1.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.2)	(0.2)	(0.4)	(0.4)
Amortization of Actuarial (Gains)/Losses		0.2	0.2	0.4	0.4
Income Tax (Expense) Credit		0.1	0.1	0.2	0.3
Indiana Michigan Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense	[2]	0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.2)	(0.2)	(0.4)	(0.4)
Amortization of Actuarial (Gains)/Losses		0.2	0.2	0.4	0.4
Income Tax (Expense) Credit		0.0	0.0	0.0	0.0
Indiana Michigan Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[2]	0.6	0.5	1.1	1.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0	0.0	0.0	0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0	0.0	0.0
Income Tax (Expense) Credit		0.1	0.1	0.2	0.3
Ohio Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI				1.9
Commodity
Purchased Electricity for Resale		162.9	156.4	368.4	344.7
Interest Rate
Interest Expense		25.3	26.1	50.5	51.1
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Credit		(19.0)	(33.4)	(39.5)	(79.7)
Net Current Period Other Comprehensive Income (Loss)				(0.6)	(0.5)
ASU 2018-02 Adoption				0.4
Ending Balance in AOCI		1.7		1.7
Ohio Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)				(0.6)	(0.5)
ASU 2018-02 Adoption				0.4
Ohio Power Co [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		2.0	2.8	1.9	3.0
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		(0.4)	(0.4)	(0.8)	(0.8)
Reclassification from AOCI, Net of Income Tax (Expense) Credit		(0.3)	(0.3)	(0.6)	(0.5)
Net Current Period Other Comprehensive Income (Loss)		(0.3)	(0.3)	(0.6)	(0.5)
ASU 2018-02 Adoption	[1]			0.4
Ending Balance in AOCI		1.7	2.5	1.7	2.5
Ohio Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[2]	(0.4)	(0.4)	(0.8)	(0.8)
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Credit		(0.1)	(0.1)	(0.2)	(0.3)
Public Service Co Of Oklahoma [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI				2.6
Commodity
Purchased Electricity for Resale		113.1	126.7	235.5	252.0
Interest Rate
Interest Expense		16.3	13.4	31.0	27.0
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Credit		(6.4)	(12.3)	(5.0)	(15.2)
Net Current Period Other Comprehensive Income (Loss)				(0.5)	(0.4)
ASU 2018-02 Adoption				0.5
Ending Balance in AOCI		2.6		2.6
Public Service Co Of Oklahoma [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)				(0.5)	(0.4)
ASU 2018-02 Adoption				0.5
Public Service Co Of Oklahoma [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		2.9	3.2	2.6	3.4
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		(0.4)	(0.3)	(0.7)	(0.6)
Reclassification from AOCI, Net of Income Tax (Expense) Credit		(0.3)	(0.2)	(0.5)	(0.4)
Net Current Period Other Comprehensive Income (Loss)		(0.3)	(0.2)	(0.5)	(0.4)
ASU 2018-02 Adoption	[1]			0.5
Ending Balance in AOCI		2.6	3.0	2.6	3.0
Public Service Co Of Oklahoma [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[2]	(0.4)	(0.3)	(0.7)	(0.6)
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Credit		(0.1)	(0.1)	(0.2)	(0.2)
Southwestern Electric Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(4.8)	(9.1)	(4.0)	(9.4)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Commodity
Purchased Electricity for Resale		53.4	46.3	96.1	78.7
Interest Rate
Interest Expense		30.9	30.9	63.1	60.8
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		0.1	0.2	0.2	0.6
Income Tax (Expense) Credit		(5.4)	(13.2)	(8.3)	(22.7)
Reclassification from AOCI, Net of Income Tax (Expense) Credit		0.1	0.1	0.2	0.4
Net Current Period Other Comprehensive Income (Loss)		0.1	0.1	0.2	0.4
ASU 2018-02 Adoption				(1.3)
Ending Balance in AOCI		(4.7)	(9.0)	(4.7)	(9.0)
Southwestern Electric Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		2.1	(2.2)	2.0	(2.0)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		(0.5)	(0.2)	(0.9)	(0.5)
Reclassification from AOCI, Net of Income Tax (Expense) Credit		(0.4)	(0.1)	(0.7)	(0.3)
Net Current Period Other Comprehensive Income (Loss)		(0.4)	(0.1)	(0.7)	(0.3)
ASU 2018-02 Adoption	[1]			0.4
Ending Balance in AOCI		1.7	(2.3)	1.7	(2.3)
Southwestern Electric Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)				0.2	0.4
ASU 2018-02 Adoption	[1]			(0.9)
Southwestern Electric Power Co [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(6.9)	(6.9)	(6.0)	(7.4)
Change in Fair Value Recognized in AOCI		0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Credit		0.6	0.4	1.1	1.1
Reclassification from AOCI, Net of Income Tax (Expense) Credit		0.5	0.2	0.9	0.7
Net Current Period Other Comprehensive Income (Loss)		0.5	0.2	0.9	0.7
ASU 2018-02 Adoption	[1]			(1.3)
Ending Balance in AOCI		(6.4)	(6.7)	(6.4)	(6.7)
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]	0.6	0.4	1.1	1.1
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.5)	(0.5)	(1.0)	(1.0)
Amortization of Actuarial (Gains)/Losses			0.3	0.1	0.5
Income Tax (Expense) Credit		0.0	0.1	0.0	0.2
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense	[2]	0.0	0.0	0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.5)	(0.5)	(1.0)	(1.0)
Amortization of Actuarial (Gains)/Losses			0.3	0.1	0.5
Income Tax (Expense) Credit		(0.1)	(0.1)	(0.2)	(0.2)
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[2]	0.6	0.4	1.1	1.1
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		0.0	0.0	0.0	0.0
Amortization of Actuarial (Gains)/Losses			0.0	0.0	0.0
Income Tax (Expense) Credit		$ 0.1	$ 0.2	$ 0.2	$ 0.4

[1] See Note 2 - New Accounting Pronouncements for additional information.

[2] Amounts reclassified to the referenced line item in the statements of income.