Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		$ (67.8)	$ (156.3)
Change in Fair Value Recognized in AOCI		12.8	(20.6)
Commodity
Generation & Marketing Revenues		477.5	558.8
Purchased Electricity for Resale		990.3	769.6
Interest Rate
Interest Expense		234.0	221.8
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		(14.6)	9.0
Income Tax (Expense) Credit		(102.0)	(343.2)
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		(11.5)	5.9
Net Current Period Other Comprehensive Income (Loss)		1.3	(14.7)
ASU 2018-02 Adoption		(3.0)
ASU 2016-01 Adoption		0.0
Ending Balance in AOCI		(95.4)	(171.0)
Securities Available for Sale [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		11.9	8.4
Change in Fair Value Recognized in AOCI		0.0	1.2
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.0	0.0
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		0.0	0.0
Net Current Period Other Comprehensive Income (Loss)		0.0	1.2
ASU 2018-02 Adoption	[1]	0.0
ASU 2016-01 Adoption	[1]	(11.9)
Ending Balance in AOCI		0.0	9.6
Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(38.3)	(125.9)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		(1.8)	0.4
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		(1.4)	0.2
Net Current Period Other Comprehensive Income (Loss)		(1.4)	0.2
ASU 2018-02 Adoption	[1]	(8.2)
ASU 2016-01 Adoption	[1]	0.0
Ending Balance in AOCI		(47.9)	(125.7)
Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Net Current Period Other Comprehensive Income (Loss)		1.3	(14.7)
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		(28.4)	(23.1)
Change in Fair Value Recognized in AOCI		12.8	(21.8)
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		(13.1)	8.1
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		(10.3)	5.3
Net Current Period Other Comprehensive Income (Loss)		2.5	(16.5)
ASU 2018-02 Adoption	[1]	(6.1)
ASU 2016-01 Adoption	[1]	0.0
Ending Balance in AOCI		(32.0)	(39.6)
Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(13.0)	(15.7)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.3	0.5
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		0.2	0.4
Net Current Period Other Comprehensive Income (Loss)		0.2	0.4
ASU 2018-02 Adoption	[1]	(2.7)
ASU 2016-01 Adoption	[1]	0.0
Ending Balance in AOCI		(15.5)	(15.3)
Reclassifications from Accumulated Other Comprehensive Income [Member]
Commodity
Generation & Marketing Revenues			(4.7)
Purchased Electricity for Resale		(13.1)	12.8
Interest Rate
Interest Expense		0.3	0.5
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		(5.0)	(4.9)
Amortization of Actuarial (Gains)/Losses		3.2	5.3
Income Tax (Expense) Credit		(3.1)	3.1
Reclassifications from Accumulated Other Comprehensive Income [Member] | Securities Available for Sale [Member]
Commodity
Generation & Marketing Revenues			0.0
Purchased Electricity for Resale		0.0	0.0
Interest Rate
Interest Expense		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0
Income Tax (Expense) Credit		0.0	0.0
Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Commodity
Generation & Marketing Revenues			0.0
Purchased Electricity for Resale		0.0	0.0
Interest Rate
Interest Expense		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		(5.0)	(4.9)
Amortization of Actuarial (Gains)/Losses		3.2	5.3
Income Tax (Expense) Credit		(0.4)	0.2
Reclassifications from Accumulated Other Comprehensive Income [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Commodity
Generation & Marketing Revenues			(4.7)
Purchased Electricity for Resale		(13.1)	12.8
Interest Rate
Interest Expense		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0
Income Tax (Expense) Credit		(2.8)	2.8
Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Commodity
Generation & Marketing Revenues			0.0
Purchased Electricity for Resale		0.0	0.0
Interest Rate
Interest Expense		0.3	0.5
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0
Income Tax (Expense) Credit		0.1	0.1
AEP Texas Inc. [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(12.6)	(14.9)
Change in Fair Value Recognized in AOCI		0.0	0.0
Interest Rate
Interest Expense		35.0	35.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.4	0.4
Income Tax (Expense) Credit		(9.1)	(17.7)
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		0.3	0.3
Net Current Period Other Comprehensive Income (Loss)		0.3	0.3
ASU 2018-02 Adoption		(0.9)
Ending Balance in AOCI		(15.0)	(14.6)
AEP Texas Inc. [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(8.1)	(9.5)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.1	0.1
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		0.1	0.1
Net Current Period Other Comprehensive Income (Loss)		0.1	0.1
ASU 2018-02 Adoption	[1]	(1.8)
Ending Balance in AOCI		(9.8)	(9.4)
AEP Texas Inc. [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Net Current Period Other Comprehensive Income (Loss)		0.3	0.3
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		(4.5)	(5.4)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.3	0.3
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		0.2	0.2
Net Current Period Other Comprehensive Income (Loss)		0.2	0.2
ASU 2018-02 Adoption	[1]	(0.9)
Ending Balance in AOCI		(5.2)	(5.2)
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense		0.3	0.3
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		0.0
Amortization of Actuarial (Gains)/Losses		0.1	0.1
Income Tax (Expense) Credit		0.1	0.1
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		0.0
Amortization of Actuarial (Gains)/Losses		0.1	0.1
Income Tax (Expense) Credit		0.0	0.0
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense		0.3	0.3
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0
Income Tax (Expense) Credit		0.1	0.1
AEP Transmission Co [Member]
Interest Rate
Interest Expense		19.9	16.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Income Tax (Expense) Credit		(22.5)	(28.5)
Appalachian Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		1.3	(8.4)
Change in Fair Value Recognized in AOCI		(0.7)	0.0
Commodity
Purchased Electricity for Resale		205.9	90.8
Interest Rate
Interest Expense		47.4	48.1
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		(0.4)	(0.8)
Income Tax (Expense) Credit		(28.0)	(63.6)
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		(0.3)	(0.5)
Net Current Period Other Comprehensive Income (Loss)		(1.0)	(0.5)
ASU 2018-02 Adoption		0.4
Ending Balance in AOCI		0.6	(8.9)
Appalachian Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(0.9)	(11.3)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		(1.0)	(0.5)
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		(0.8)	(0.3)
Net Current Period Other Comprehensive Income (Loss)		(0.8)	(0.3)
ASU 2018-02 Adoption	[1]	(0.2)
Ending Balance in AOCI		(1.9)	(11.6)
Appalachian Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Net Current Period Other Comprehensive Income (Loss)		(1.0)	(0.5)
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 [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.9
Reclassifications 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
Appalachian Power Co [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		2.2	2.9
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		(0.3)	(0.3)
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		(0.2)	(0.2)
Net Current Period Other Comprehensive Income (Loss)		(0.2)	(0.2)
ASU 2018-02 Adoption	[1]	0.5
Ending Balance in AOCI		2.5	2.7
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Commodity
Purchased Electricity for Resale		0.9
Interest Rate
Interest Expense		(0.3)	(0.3)
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		(1.3)	(1.3)
Amortization of Actuarial (Gains)/Losses		0.3	0.8
Income Tax (Expense) Credit		(0.1)	(0.3)
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Commodity
Purchased Electricity for Resale		0.0
Interest Rate
Interest Expense		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		(1.3)	(1.3)
Amortization of Actuarial (Gains)/Losses		0.3	0.8
Income Tax (Expense) Credit		(0.2)	(0.2)
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Commodity
Purchased Electricity for Resale		0.9
Interest Rate
Interest Expense		0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
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		0.0
Interest Rate
Interest Expense		(0.3)	(0.3)
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0
Income Tax (Expense) Credit		(0.1)	(0.1)
Indiana Michigan Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(12.1)	(16.2)
Change in Fair Value Recognized in AOCI		0.0	0.0
Commodity
Purchased Electricity for Resale		55.6	37.3
Interest Rate
Interest Expense		29.7	27.7
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.5	0.5
Income Tax (Expense) Credit		(12.4)	(29.2)
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		0.4	0.3
Net Current Period Other Comprehensive Income (Loss)		0.4	0.3
ASU 2018-02 Adoption		2.4
Ending Balance in AOCI		(14.4)	(15.9)
Indiana Michigan Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(1.4)	(4.2)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.0	0.0
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		0.0	0.0
Net Current Period Other Comprehensive Income (Loss)		0.0	0.0
ASU 2018-02 Adoption	[1]	(0.3)
Ending Balance in AOCI		(1.7)	(4.2)
Indiana Michigan Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Net Current Period Other Comprehensive Income (Loss)		0.4	0.3
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		(10.7)	(12.0)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.5	0.5
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		0.4	0.3
Net Current Period Other Comprehensive Income (Loss)		0.4	0.3
ASU 2018-02 Adoption	[1]	(2.4)
Ending Balance in AOCI		(12.7)	(11.7)
Indiana Michigan Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense		0.5	0.5
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		(0.2)	(0.2)
Amortization of Actuarial (Gains)/Losses		0.2	0.2
Income Tax (Expense) Credit		0.1	0.2
Indiana Michigan Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		(0.2)	(0.2)
Amortization of Actuarial (Gains)/Losses		0.2	0.2
Income Tax (Expense) Credit		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		0.5	0.5
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0
Income Tax (Expense) Credit		0.1	0.2
Ohio Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		1.9
Commodity
Purchased Electricity for Resale		205.5	188.3
Interest Rate
Interest Expense		25.2	25.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Income Tax (Expense) Credit		(20.5)	(46.3)
Net Current Period Other Comprehensive Income (Loss)		(0.3)	(0.2)
ASU 2018-02 Adoption		0.4
Ending Balance in AOCI		2.0
Ohio Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Net Current Period Other Comprehensive Income (Loss)		(0.3)	(0.2)
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		1.9	3.0
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		(0.4)	(0.4)
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		(0.3)	(0.2)
Net Current Period Other Comprehensive Income (Loss)		(0.3)	(0.2)
ASU 2018-02 Adoption	[1]	0.4
Ending Balance in AOCI		2.0	2.8
Ohio Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense		(0.4)	(0.4)
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Income Tax (Expense) Credit		(0.1)	(0.2)
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		122.4	125.3
Interest Rate
Interest Expense		14.7	13.6
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Income Tax (Expense) Credit		1.4	(2.9)
Net Current Period Other Comprehensive Income (Loss)		(0.2)	(0.2)
ASU 2018-02 Adoption		0.5
Ending Balance in AOCI		2.9
Public Service Co Of Oklahoma [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Net Current Period Other Comprehensive Income (Loss)		(0.2)	(0.2)
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		2.6	3.4
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		(0.3)	(0.3)
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		(0.2)	(0.2)
Net Current Period Other Comprehensive Income (Loss)		(0.2)	(0.2)
ASU 2018-02 Adoption	[1]	0.5
Ending Balance in AOCI		2.9	3.2
Public Service Co Of Oklahoma [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense		(0.3)	(0.3)
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Income Tax (Expense) Credit		(0.1)	(0.1)
Southwestern Electric Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(4.0)	(9.4)
Change in Fair Value Recognized in AOCI		0.0	0.0
Commodity
Purchased Electricity for Resale		42.7	32.4
Interest Rate
Interest Expense		32.2	29.9
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.1	0.4
Income Tax (Expense) Credit		(2.9)	(9.5)
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		0.1	0.3
Net Current Period Other Comprehensive Income (Loss)		0.1	0.3
ASU 2018-02 Adoption		(1.3)
Ending Balance in AOCI		(4.8)	(9.1)
Southwestern Electric Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		2.0	(2.0)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		(0.4)	(0.3)
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		(0.3)	(0.2)
Net Current Period Other Comprehensive Income (Loss)		(0.3)	(0.2)
ASU 2018-02 Adoption	[1]	0.4
Ending Balance in AOCI		2.1	(2.2)
Southwestern Electric Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Net Current Period Other Comprehensive Income (Loss)		0.1	0.3
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		(6.0)	(7.4)
Change in Fair Value Recognized in AOCI		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Reclassifications from AOCI, before Income Tax (Expense) Credit		0.5	0.7
Reclassifications from AOCI, Net of Income Tax (Expense) Credit		0.4	0.5
Net Current Period Other Comprehensive Income (Loss)		0.4	0.5
ASU 2018-02 Adoption	[1]	(1.3)
Ending Balance in AOCI		(6.9)	(6.9)
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense		0.5	0.7
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		(0.5)	(0.5)
Amortization of Actuarial (Gains)/Losses		0.1	0.2
Income Tax (Expense) Credit		0.0	0.1
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
Interest Rate
Interest Expense		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		(0.5)	(0.5)
Amortization of Actuarial (Gains)/Losses		0.1	0.2
Income Tax (Expense) Credit		(0.1)	(0.1)
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense		0.5	0.7
Amortization Of Pension And Other Postretirement Benefit Plans [Abstract]
Amortization of Prior Service Cost (Credit)		0.0	0.0
Amortization of Actuarial (Gains)/Losses		0.0	0.0
Income Tax (Expense) Credit		$ 0.1	$ 0.2

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