Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		$ (30.8)	$ (85.1)	$ (216.5)	$ (147.7)	$ (85.1)	$ (147.7)
Change in Fair Value Recognized in AOCI		136.0		3.7		326.4	(104.3)
Commodity
Generation & Marketing Revenues		3,826.5		3,494.0		8,107.6	7,241.5
Interest Rate
Interest Expense		301.6		294.0		591.8	586.1
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		(10.5)		50.5		(182.7)	100.1
Income Tax (Expense) Benefit		61.2		12.6		115.7	59.1
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(8.2)		39.9		(144.3)	79.1
Net Current Period Other Comprehensive Income (Loss)		127.8	54.3	43.6	(68.8)	182.1	(25.2)
Ending Balance in AOCI		97.0	(30.8)	(172.9)	(216.5)	97.0	(172.9)
Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		21.0	23.0	(34.5)	(32.7)	23.0	(32.7)
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) Benefit		(2.7)		(2.1)		(5.2)	(4.4)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(2.1)		(1.7)		(4.1)	(3.5)
Net Current Period Other Comprehensive Income (Loss)		(2.1)		(1.7)		(4.1)	(3.5)
Ending Balance in AOCI		18.9	21.0	(36.2)	(34.5)	18.9	(36.2)
Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		127.8	54.3	43.6	(68.8)
Commodity [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(18.5)	(60.6)	(128.5)	(103.5)	(60.6)	(103.5)
Change in Fair Value Recognized in AOCI		136.4		6.5		313.7	(58.8)
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		(9.6)		51.2		(180.8)	102.2
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(7.6)		40.6		(142.8)	80.9
Net Current Period Other Comprehensive Income (Loss)		128.8		47.1		170.9	22.1
Ending Balance in AOCI		110.3	(18.5)	(81.4)	(128.5)	110.3	(81.4)
Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(33.3)	(47.5)	(53.5)	(11.5)	(47.5)	(11.5)
Change in Fair Value Recognized in AOCI	[1]	(0.4)		(2.8)		12.7	(45.5)
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		1.8		1.4		3.3	2.3
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		1.5		1.0		2.6	1.7
Net Current Period Other Comprehensive Income (Loss)		1.1		(1.8)		15.3	(43.8)
Ending Balance in AOCI		(32.2)	(33.3)	(55.3)	(53.5)	(32.2)	(55.3)
Generation and Marketing [Member]
Commodity
Generation & Marketing Revenues		422.5		350.2		1,024.2	758.6
Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]	1.8		1.4		3.3	2.3
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(4.9)		(4.6)		(9.7)	(9.5)
Amortization of Actuarial (Gains) Losses		2.2		2.5		4.5	5.1
Income Tax (Expense) Benefit		(2.3)		10.6		(38.4)	21.0
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)		(4.9)		(4.6)		(9.7)	(9.5)
Amortization of Actuarial (Gains) Losses		2.2		2.5		4.5	5.1
Income Tax (Expense) Benefit		(0.6)		(0.4)		(1.1)	(0.9)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Commodity [Member] | Cash Flow Hedges [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)		0.0		0.0		0.0	0.0
Amortization of Actuarial (Gains) Losses		0.0		0.0		0.0	0.0
Income Tax (Expense) Benefit		(2.0)		10.6		(38.0)	21.3
Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[2]	1.8		1.4		3.3	2.3
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) Benefit		0.3		0.4		0.7	0.6
Reclassifications from Accumulated Other Comprehensive Income [Member] | Generation and Marketing [Member]
Commodity
Generation & Marketing Revenues	[2]	(0.1)		(0.1)		0.7	(0.2)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Generation and Marketing [Member] | Pension and OPEB [Member]
Commodity
Generation & Marketing Revenues	[2]	0.0		0.0		0.0	0.0
Reclassifications from Accumulated Other Comprehensive Income [Member] | Generation and Marketing [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Commodity
Generation & Marketing Revenues	[2]	(0.1)		(0.1)		0.7	(0.2)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Generation and Marketing [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Commodity
Generation & Marketing Revenues	[2]	0.0		0.0		0.0	0.0
Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale	[2]	(9.5)		51.3		(181.5)	102.4
Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Pension and OPEB [Member]
Commodity
Purchased Electricity for Resale	[2]	0.0		0.0		0.0	0.0
Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Commodity
Purchased Electricity for Resale	[2]	(9.5)		51.3		(181.5)	102.4
Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Commodity
Purchased Electricity for Resale	[2]	0.0		0.0		0.0	0.0
Apple Blossom and Black Oak [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Change in Fair Value Recognized in AOCI		4.0		2.0		0.0	7.0
AEP Texas Inc. [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(8.6)	(8.9)	(12.5)	(12.8)	(8.9)	(12.8)
Change in Fair Value Recognized in AOCI		(0.1)		0.0		0.0	0.0
Interest Rate
Interest Expense		45.3		42.2		88.3	84.7
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.4		0.3		0.7	0.7
Income Tax (Expense) Benefit		9.9		(18.6)		17.0	(11.2)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.4		0.3		0.6	0.6
Net Current Period Other Comprehensive Income (Loss)		0.3	0.3	0.3	0.3	0.6	0.6
Ending Balance in AOCI		(8.3)	(8.6)	(12.2)	(12.5)	(8.3)	(12.2)
AEP Texas Inc. [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(6.6)	(6.6)	(9.4)	(9.4)	(6.6)	(9.4)
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) Benefit		0.1		0.1		0.1	0.1
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.1		0.1		0.1	0.1
Net Current Period Other Comprehensive Income (Loss)		0.1		0.1		0.1	0.1
Ending Balance in AOCI		(6.5)	(6.6)	(9.3)	(9.4)	(6.5)	(9.3)
AEP Texas Inc. [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		0.3	0.3	0.3	0.3
AEP Texas Inc. [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(2.0)	(2.3)	(3.1)	(3.4)	(2.3)	(3.4)
Change in Fair Value Recognized in AOCI		(0.1)		0.0		0.0	0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.3		0.2		0.6	0.6
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.3		0.2		0.5	0.5
Net Current Period Other Comprehensive Income (Loss)		0.2		0.2		0.5	0.5
Ending Balance in AOCI		(1.8)	(2.0)	(2.9)	(3.1)	(1.8)	(2.9)
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]	0.3		0.2		0.6	0.6
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Actuarial (Gains) Losses		0.1		0.1		0.1	0.1
Income Tax (Expense) Benefit		0.0		0.0		0.1	0.1
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 Actuarial (Gains) Losses		0.1		0.1		0.1	0.1
Income Tax (Expense) Benefit		0.0		0.0		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	[2]	0.3		0.2		0.6	0.6
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Actuarial (Gains) Losses		0.0		0.0		0.0	0.0
Income Tax (Expense) Benefit		0.0		0.0		0.1	0.1
Appalachian Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		15.1	7.2	(0.1)	5.0	7.2	5.0
Change in Fair Value Recognized in AOCI		(0.2)		(0.6)		9.1	(4.5)
Interest Rate
Interest Expense		52.9		54.1		107.8	107.2
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		(1.3)		(1.4)		(3.1)	(3.0)
Income Tax (Expense) Benefit		10.7		(7.9)		15.7	2.5
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(1.0)		(1.2)		(2.4)	(2.4)
Net Current Period Other Comprehensive Income (Loss)		(1.2)	7.9	(1.8)	(5.1)	6.7	(6.9)
Ending Balance in AOCI		13.9	15.1	(1.9)	(0.1)	13.9	(1.9)
Appalachian Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		6.9	8.0	3.2	4.1	8.0	4.1
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) Benefit		(1.3)		(1.2)		(2.7)	(2.4)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(1.0)		(1.0)		(2.1)	(1.9)
Net Current Period Other Comprehensive Income (Loss)		(1.0)		(1.0)		(2.1)	(1.9)
Ending Balance in AOCI		5.9	6.9	2.2	3.2	5.9	2.2
Appalachian Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		(1.2)	7.9	(1.8)	(5.1)
Appalachian Power Co [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		8.2	(0.8)	(3.3)	0.9	(0.8)	0.9
Change in Fair Value Recognized in AOCI		(0.2)		(0.6)		9.1	(4.5)
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.0		(0.2)		(0.4)	(0.6)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0		(0.2)		(0.3)	(0.5)
Net Current Period Other Comprehensive Income (Loss)		(0.2)		(0.8)		8.8	(5.0)
Ending Balance in AOCI		8.0	8.2	(4.1)	(3.3)	8.0	(4.1)
Appalachian Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		75.9		50.4		166.0	173.0
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]	0.0		(0.2)		(0.4)	(0.6)
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(1.3)		(1.4)		(2.7)	(2.7)
Amortization of Actuarial (Gains) Losses				0.2			0.3
Income Tax (Expense) Benefit		(0.3)		(0.2)		(0.7)	(0.6)
Appalachian 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)		(1.3)		(1.4)		(2.7)	(2.7)
Amortization of Actuarial (Gains) Losses				0.2			0.3
Income Tax (Expense) Benefit		(0.3)		(0.2)		(0.6)	(0.5)
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[2]	0.0		(0.2)		(0.4)	(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
Income Tax (Expense) Benefit		0.0		0.0		(0.1)	(0.1)
Indiana Michigan Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(6.5)	(7.0)	(11.2)	(11.6)	(7.0)	(11.6)
Change in Fair Value Recognized in AOCI		0.0		0.0		0.0	0.0
Interest Rate
Interest Expense		29.1		28.1		56.4	58.8
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.4		0.5		1.0	1.0
Income Tax (Expense) Benefit		(5.8)		4.7		(6.5)	5.1
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.3		0.4		0.8	0.8
Net Current Period Other Comprehensive Income (Loss)		0.3	0.5	0.4	0.4	0.8	0.8
Ending Balance in AOCI		(6.2)	(6.5)	(10.8)	(11.2)	(6.2)	(10.8)
Indiana Michigan Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		1.3	1.3	(1.7)	(1.7)	1.3	(1.7)
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) Benefit		(0.1)		0.0		(0.1)	0.0
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(0.1)		0.0		(0.1)	0.0
Net Current Period Other Comprehensive Income (Loss)		(0.1)		0.0		(0.1)	0.0
Ending Balance in AOCI		1.2	1.3	(1.7)	(1.7)	1.2	(1.7)
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)		0.3	0.5	0.4	0.4
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		(7.8)	(8.3)	(9.5)	(9.9)	(8.3)	(9.9)
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) Benefit		0.5		0.5		1.1	1.0
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.4		0.4		0.9	0.8
Net Current Period Other Comprehensive Income (Loss)		0.4		0.4		0.9	0.8
Ending Balance in AOCI		(7.4)	(7.8)	(9.1)	(9.5)	(7.4)	(9.1)
Indiana Michigan Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		39.7		40.5		87.0	90.6
Indiana Michigan Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]	0.5		0.5		1.1	1.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.2)		(0.1)		(0.4)	(0.3)
Amortization of Actuarial (Gains) Losses		0.1		0.1		0.3	0.3
Income Tax (Expense) Benefit		0.1		0.1		0.2	0.2
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)		(0.1)		(0.4)	(0.3)
Amortization of Actuarial (Gains) Losses		0.1		0.1		0.3	0.3
Income Tax (Expense) Benefit		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]	0.5		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) Benefit		0.1		0.1		0.2	0.2
Ohio Power Co [Member]
Interest Rate
Interest Expense		31.7		30.1		63.3	59.0
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		11.2		11.2		17.3	20.9
Ohio Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		153.6		113.9		328.9	263.0
Public Service Co Of Oklahoma [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI			0.1			0.1
Interest Rate
Interest Expense		14.1		15.5		28.5	31.3
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		(1.8)		0.7		(1.6)	0.8
Net Current Period Other Comprehensive Income (Loss)			(0.1)	(0.3)	(0.2)
Ending Balance in AOCI		0.0				0.0
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)			(0.1)	(0.3)	(0.2)
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		0.0	0.1	0.9	1.1	0.1	1.1
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) Benefit		0.0		(0.4)		(0.1)	(0.7)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0		(0.3)		(0.1)	(0.5)
Net Current Period Other Comprehensive Income (Loss)		0.0		(0.3)		(0.1)	(0.5)
Ending Balance in AOCI		0.0	0.0	0.6	0.9	0.0	0.6
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]	0.0		(0.4)		(0.1)	(0.7)
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		0.0		(0.1)		0.0	(0.2)
Southwestern Electric Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		1.9	1.9	(1.3)	(1.3)	1.9	(1.3)
Change in Fair Value Recognized in AOCI		0.0		0.0		0.0	0.0
Interest Rate
Interest Expense		31.4		29.7		60.7	59.8
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.0		0.0		0.0	0.0
Income Tax (Expense) Benefit		7.1		7.9		12.7	1.7
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0		0.0		0.0	0.0
Net Current Period Other Comprehensive Income (Loss)		0.0		0.0		0.0	0.0
Ending Balance in AOCI		1.9	1.9	(1.3)	(1.3)	1.9	(1.3)
Southwestern Electric Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		1.8	2.2	0.1	0.5	2.2	0.5
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) Benefit		(0.5)		(0.4)		(1.0)	(0.9)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(0.4)		(0.3)		(0.8)	(0.7)
Net Current Period Other Comprehensive Income (Loss)		(0.4)		(0.3)		(0.8)	(0.7)
Ending Balance in AOCI		1.4	1.8	(0.2)	0.1	1.4	(0.2)
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		0.1	(0.3)	(1.4)	(1.8)	(0.3)	(1.8)
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) Benefit		0.5		0.4		1.0	0.9
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.4		0.3		0.8	0.7
Net Current Period Other Comprehensive Income (Loss)		0.4		0.3		0.8	0.7
Ending Balance in AOCI		0.5	$ 0.1	(1.1)	$ (1.4)	0.5	(1.1)
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]	0.5		0.4		1.0	0.9
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				0.1			0.1
Income Tax (Expense) Benefit		0.0		0.0		0.0	0.0
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				0.1			0.1
Income Tax (Expense) Benefit		(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]	0.5		0.4		1.0	0.9
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
Income Tax (Expense) Benefit		$ 0.1		$ 0.1		$ 0.2	$ 0.2

[1] The change in fair value includes $4 million and $2 million, respectively, for the three months ended June 30, 2021 and 2020 and $0 million and $7 million, respectively, for the six months ended June 30, 2021 and 2020 related to AEP's investment in joint venture wind farms acquired as part of the purchase of Sempra Renewables LLC.

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