Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended							9 Months Ended
		Sep. 30, 2019		Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019		Sep. 30, 2018
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		$ (230.7)			$ (120.4)	$ (94.8)		$ (67.8)	$ (120.4)		$ (67.8)
Change in Fair Value Recognized in AOCI		37.6				14.5			(96.8)		32.7
Commodity
Generation & Marketing Revenues		4,315.0				4,333.1			11,945.4		12,394.6
Interest Rate
Interest Expense		275.1				256.8			781.6		733.1
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		6.6				(7.3)			37.1		(27.9)
Income Tax (Expense) Benefit		40.6				(80.7)			30.7		93.5
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		5.2				(5.7)			29.3		(22.0)
Net Current Period Other Comprehensive Income (Loss)		42.8		$ (80.0)	(30.3)	8.8	$ 0.6	1.3	(67.5)		10.7
ASU 2018-02 Adoption								(3.0)
ASU 2016-01 Adoption								0.0
Ending Balance in AOCI		(187.9)		(230.7)		(86.0)	(94.8)		(187.9)		(86.0)
Securities Available for Sale [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI								11.9			11.9
Change in Fair Value Recognized in AOCI											0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit											0.0
Reclassification from AOCI, Net of Income Tax (Expense) Benefit											0.0
Net Current Period Other Comprehensive Income (Loss)											0.0
ASU 2018-02 Adoption											0.0
ASU 2016-01 Adoption											(11.9)
Ending Balance in AOCI						0.0					0.0
Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(87.6)			(84.8)	(49.1)		(38.3)	(84.8)		(38.3)
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) Benefit		(1.8)				(1.8)			(5.3)		(5.1)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(1.4)				(1.4)			(4.2)		(4.0)
Net Current Period Other Comprehensive Income (Loss)		(1.4)				(1.4)			(4.2)		(4.0)
ASU 2018-02 Adoption											(8.2)
ASU 2016-01 Adoption											0.0
Ending Balance in AOCI		(89.0)		(87.6)		(50.5)	(49.1)		(89.0)		(50.5)
Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		42.8		(80.0)	(30.3)	8.8	0.6	1.3
ASU 2018-02 Adoption								(17.0)			(17.0)
ASU 2016-01 Adoption								(11.9)			(11.9)
Commodity [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(127.2)			(23.0)	(30.4)		(28.4)	(23.0)		(28.4)
Change in Fair Value Recognized in AOCI		38.4				12.2			(92.3)		30.4
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		8.4				(5.9)			41.9		(23.7)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		6.6				(4.6)			33.1		(18.7)
Net Current Period Other Comprehensive Income (Loss)		45.0				7.6			(59.2)		11.7
ASU 2018-02 Adoption											(6.1)
ASU 2016-01 Adoption											0.0
Ending Balance in AOCI		(82.2)		(127.2)		(22.8)	(30.4)		(82.2)		(22.8)
Interest Rate [Member] | Cash Flow Hedges [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(15.9)			(12.6)	(15.3)		(13.0)	(12.6)		(13.0)
Change in Fair Value Recognized in AOCI		(0.8)	[1]			2.3			(4.5)	[1]	2.3
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.0				0.4			0.5		0.9
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0				0.3			0.4		0.7
Net Current Period Other Comprehensive Income (Loss)		(0.8)				2.6			(4.1)		3.0
ASU 2018-02 Adoption											(2.7)
ASU 2016-01 Adoption											0.0
Ending Balance in AOCI		(16.7)		(15.9)		(12.7)	(15.3)		(16.7)		(12.7)
Generation and Marketing Revenues [Member]
Commodity
Generation & Marketing Revenues		501.2				486.5			1,323.8		1,399.3
Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		783.9				784.7			2,306.4		2,551.7
Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]					0.4			0.5		0.9
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(4.8)				(5.0)			(14.3)		(14.7)
Amortization of Actuarial (Gains) Losses		3.0				3.2			9.0		9.6
Income Tax (Expense) Benefit		1.4				(1.6)			7.8		(5.9)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Securities Available for Sale [Member]
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) Benefit											0.0
Reclassifications from Accumulated Other Comprehensive Income [Member] | Pension and OPEB [Member]
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)		(4.8)				(5.0)			(14.3)		(14.7)
Amortization of Actuarial (Gains) Losses		3.0				3.2			9.0		9.6
Income Tax (Expense) Benefit		(0.4)				(0.4)			(1.1)		(1.1)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Commodity [Member] | Cash Flow Hedges [Member]
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		0.0
Amortization of Actuarial (Gains) Losses		0.0				0.0			0.0		0.0
Income Tax (Expense) Benefit		1.8				(1.3)			8.8		(5.0)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[2]					0.4			0.5		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			0.0		0.0
Income Tax (Expense) Benefit		0.0				0.1			0.1		0.2
Reclassifications from Accumulated Other Comprehensive Income [Member] | Generation and Marketing Revenues [Member]
Commodity
Generation & Marketing Revenues	[2]	(0.1)				(0.1)			(0.1)		(0.1)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Generation and Marketing Revenues [Member] | Securities Available for Sale [Member]
Commodity
Generation & Marketing Revenues	[2]										0.0
Reclassifications from Accumulated Other Comprehensive Income [Member] | Generation and Marketing Revenues [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 Revenues [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Commodity
Generation & Marketing Revenues	[2]	(0.1)				(0.1)			(0.1)		(0.1)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Generation and Marketing Revenues [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]	8.5				(5.8)			42.0		(23.6)
Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Securities Available for Sale [Member]
Commodity
Purchased Electricity for Resale	[2]										0.0
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]	8.5				(5.8)			42.0		(23.6)
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] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense		2.0							6.0
AEP Texas Inc. [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(14.5)			(15.1)	(14.7)		(12.6)	(15.1)		(12.6)
Change in Fair Value Recognized in AOCI		0.3				0.0			0.3		0.0
Interest Rate
Interest Expense		35.8				37.3			92.7		108.9
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.0				0.4			0.7		1.1
Income Tax (Expense) Benefit		13.7				8.3			(38.8)		26.4
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0				0.3			0.6		0.9
Net Current Period Other Comprehensive Income (Loss)		0.3		0.3	0.3	0.3	0.3	0.3	0.9		0.9
ASU 2018-02 Adoption								(0.9)
Ending Balance in AOCI		(14.2)		(14.5)		(14.4)	(14.7)		(14.2)		(14.4)
AEP Texas Inc. [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(10.6)			(10.7)	(9.8)		(8.1)	(10.7)		(8.1)
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				0.0			0.1		0.1
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		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											(1.8)
Ending Balance in AOCI		(10.6)		(10.6)		(9.8)	(9.8)		(10.6)		(9.8)
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	0.3	0.3
ASU 2018-02 Adoption								(2.7)			(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		(3.9)			(4.4)	(4.9)		(4.5)	(4.4)		(4.5)
Change in Fair Value Recognized in AOCI		0.3				0.0			0.3		0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.0				0.4			0.6		1.0
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0				0.3			0.5		0.8
Net Current Period Other Comprehensive Income (Loss)		0.3				0.3			0.8		0.8
ASU 2018-02 Adoption											(0.9)
Ending Balance in AOCI		(3.6)		(3.9)		(4.6)	(4.9)		(3.6)		(4.6)
AEP Texas Inc. [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]					0.4			0.6		1.0
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.1)							(0.1)		(0.1)
Amortization of Actuarial (Gains) Losses		0.1							0.2		0.2
Income Tax (Expense) Benefit		0.0				0.1			0.1		0.2
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
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.1)							(0.1)		(0.1)
Amortization of Actuarial (Gains) Losses		0.1							0.2		0.2
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]					0.4			0.6		1.0
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) Benefit		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		(6.7)			(5.0)	(0.4)		1.3	(5.0)		1.3
Change in Fair Value Recognized in AOCI		(0.3)				0.0			(0.3)		(0.7)
Interest Rate
Interest Expense		51.6				50.8			152.5		146.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		(0.8)				(1.3)			(2.9)		(2.9)
Income Tax (Expense) Benefit		(3.9)				(78.9)			(47.0)		(35.1)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(0.6)				(1.0)			(2.3)		(2.3)
Net Current Period Other Comprehensive Income (Loss)		(0.9)		(0.9)	(0.8)	(1.0)	(1.0)	(1.0)	(2.6)		(3.0)
ASU 2018-02 Adoption								0.4
Ending Balance in AOCI		(7.6)		(6.7)		(1.4)	(0.4)		(7.6)		(1.4)
Appalachian Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(8.1)			(6.8)	(2.7)		(0.9)	(6.8)		(0.9)
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		(0.8)				(0.9)			(2.4)		(2.9)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(0.6)				(0.7)			(1.9)		(2.3)
Net Current Period Other Comprehensive Income (Loss)		(0.6)				(0.7)			(1.9)		(2.3)
ASU 2018-02 Adoption											(0.2)
Ending Balance in AOCI		(8.7)		(8.1)		(3.4)	(2.7)		(8.7)		(3.4)
Appalachian 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)		(0.9)	(0.8)	(1.0)	(1.0)	(1.0)
ASU 2018-02 Adoption								0.3			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			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) Benefit											0.9
Reclassification from AOCI, Net of Income Tax (Expense) Benefit											0.7
Net Current Period Other Comprehensive Income (Loss)											0.0
ASU 2018-02 Adoption											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		1.4			1.8	2.3		2.2	1.8		2.2
Change in Fair Value Recognized in AOCI		(0.3)				0.0			(0.3)		0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.0				(0.4)			(0.5)		(0.9)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0				(0.3)			(0.4)		(0.7)
Net Current Period Other Comprehensive Income (Loss)		(0.3)				(0.3)			(0.7)		(0.7)
ASU 2018-02 Adoption											0.5
Ending Balance in AOCI		1.1		1.4		2.0	2.3		1.1		2.0
Appalachian Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		78.3				80.4			253.4		350.8
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]					(0.4)			(0.5)		(0.9)
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(1.4)				(1.3)			(4.0)		(3.9)
Amortization of Actuarial (Gains) Losses		0.6				0.4			1.6		1.0
Income Tax (Expense) Benefit		(0.2)				(0.3)			(0.6)		(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
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(1.4)				(1.3)			(4.0)		(3.9)
Amortization of Actuarial (Gains) Losses		0.6				0.4			1.6		1.0
Income Tax (Expense) Benefit		(0.2)				(0.2)			(0.5)		(0.6)
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Commodity [Member] | Cash Flow Hedges [Member]
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) Benefit											0.2
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[2]					(0.4)			(0.5)		(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			0.0		0.0
Income Tax (Expense) Benefit		0.0				(0.1)			(0.1)		(0.2)
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale	[2]										0.9
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Pension and OPEB [Member]
Commodity
Purchased Electricity for Resale	[2]										0.0
Appalachian Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Purchased Electricity for Resale [Member] | Commodity [Member] | Cash Flow Hedges [Member]
Commodity
Purchased Electricity for Resale	[2]										0.9
Appalachian Power Co [Member] | 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
Indiana Michigan Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(13.1)			(13.8)	(13.9)		(12.1)	(13.8)		(12.1)
Change in Fair Value Recognized in AOCI		0.4				0.0			0.4		0.0
Interest Rate
Interest Expense		28.8				34.5			85.9		95.6
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.0				0.4			0.9		1.5
Income Tax (Expense) Benefit		(2.3)				13.7			(5.1)		26.8
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0				0.3			0.7		1.2
Net Current Period Other Comprehensive Income (Loss)		0.4		0.3	0.4	0.3	0.5	0.4	1.1		1.2
ASU 2018-02 Adoption								(2.4)
Ending Balance in AOCI		(12.7)		(13.1)		(13.6)	(13.9)		(12.7)		(13.6)
Indiana Michigan Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(2.4)			(2.3)	(1.7)		(1.4)	(2.3)		(1.4)
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		0.0				0.0			(0.1)		0.0
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0				0.0			(0.1)		0.0
Net Current Period Other Comprehensive Income (Loss)		0.0				0.0			(0.1)		0.0
ASU 2018-02 Adoption											(0.3)
Ending Balance in AOCI		(2.4)		(2.4)		(1.7)	(1.7)		(2.4)		(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)		0.4		0.3	0.4	0.3	0.5	0.4
ASU 2018-02 Adoption								(2.7)			(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)			(11.5)	(12.2)		(10.7)	(11.5)		(10.7)
Change in Fair Value Recognized in AOCI		0.4				0.0			0.4		0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.0				0.4			1.0		1.5
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0				0.3			0.8		1.2
Net Current Period Other Comprehensive Income (Loss)		0.4				0.3			1.2		1.2
ASU 2018-02 Adoption											(2.4)
Ending Balance in AOCI		(10.3)		(10.7)		(11.9)	(12.2)		(10.3)		(11.9)
Indiana Michigan Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		44.8				48.9			163.3		167.7
Indiana Michigan Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]					0.4			1.0		1.5
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.2)				(0.2)			(0.6)		(0.6)
Amortization of Actuarial (Gains) Losses		0.2				0.2			0.5		0.6
Income Tax (Expense) Benefit		0.0				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
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.2)				(0.2)			(0.6)		(0.6)
Amortization of Actuarial (Gains) Losses		0.2				0.2			0.5		0.6
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]					0.4			1.0		1.5
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		0.0				0.1			0.2		0.3
Ohio Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI					1.0				1.0
Interest Rate
Interest Expense		27.9				26.1			78.1		76.6
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		11.2				(28.1)			40.9		11.4
Net Current Period Other Comprehensive Income (Loss)		(0.3)		(0.4)	(0.3)	(0.4)	(0.3)	(0.3)
ASU 2018-02 Adoption								0.4
Ending Balance in AOCI		0.0							0.0
Ohio Power Co [Member] | Accumulated Other Comprehensive Income [Member]
Amortization Of Pension And Other Postretirement Benefit Plans
Net Current Period Other Comprehensive Income (Loss)		(0.3)		(0.4)	(0.3)	(0.4)	(0.3)	(0.3)
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		0.3			1.0	1.7		1.9	1.0		1.9
Change in Fair Value Recognized in AOCI		(0.2)				0.0			(0.2)		0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		(0.1)				(0.5)			(1.0)		(1.3)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(0.1)				(0.4)			(0.8)		(1.0)
Net Current Period Other Comprehensive Income (Loss)		(0.3)				(0.4)			(1.0)		(1.0)
ASU 2018-02 Adoption											0.4
Ending Balance in AOCI		0.0		0.3		1.3	1.7		0.0		1.3
Ohio Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		158.3				166.3			454.0		534.7
Ohio Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member] | Interest Rate [Member] | Cash Flow Hedges [Member]
Interest Rate
Interest Expense	[2]	(0.1)				(0.5)			(1.0)		(1.3)
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		0.0				(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					2.1				2.1
Interest Rate
Interest Expense		16.1				16.4			50.3		47.4
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		6.9				3.6			7.2		8.6
Net Current Period Other Comprehensive Income (Loss)		(0.2)		(0.3)	(0.2)	(0.2)	(0.3)	(0.2)
ASU 2018-02 Adoption								0.5
Ending Balance in AOCI		1.4							1.4
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)		(0.2)		(0.3)	(0.2)	(0.2)	(0.3)	(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		1.6			2.1	2.6		2.6	2.1		2.6
Change in Fair Value Recognized in AOCI		(0.3)				0.0			(0.3)		0.0
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.2				(0.2)			(0.5)		(0.9)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.1				(0.2)			(0.4)		(0.7)
Net Current Period Other Comprehensive Income (Loss)		(0.2)				(0.2)			(0.7)		(0.7)
ASU 2018-02 Adoption											0.5
Ending Balance in AOCI		1.4		1.6		2.4	2.6		1.4		2.4
Public Service Co Of Oklahoma [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		115.3				116.8			340.7		352.3
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]	0.2				(0.2)			(0.5)		(0.9)
Amortization Of Pension And Other Postretirement Benefit Plans
Income Tax (Expense) Benefit		0.1				0.0			(0.1)		(0.2)
Southwestern Electric Power Co [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(5.2)			(5.4)	(4.7)		(4.0)	(5.4)		(4.0)
Change in Fair Value Recognized in AOCI		0.3				2.3			0.3		2.3
Interest Rate
Interest Expense		29.2				32.7			89.4		95.8
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		(0.3)				0.1			(0.1)		0.3
Income Tax (Expense) Benefit		(0.7)				9.6			0.0		17.9
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(0.3)				0.1			(0.1)		0.3
Net Current Period Other Comprehensive Income (Loss)		0.0		0.1	0.1	2.4	0.1	0.1	0.2		2.6
ASU 2018-02 Adoption								(1.3)
Ending Balance in AOCI		(5.2)		(5.2)		(2.3)	(4.7)		(5.2)		(2.3)
Southwestern Electric Power Co [Member] | Pension and OPEB [Member]
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance in AOCI		(2.7)			(2.1)	1.7		2.0	(2.1)		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) Benefit		(0.3)				(0.4)			(1.1)		(1.3)
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		(0.3)				(0.3)			(0.9)		(1.0)
Net Current Period Other Comprehensive Income (Loss)		(0.3)				(0.3)			(0.9)		(1.0)
ASU 2018-02 Adoption											0.4
Ending Balance in AOCI		(3.0)		(2.7)		1.4	1.7		(3.0)		1.4
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)				0.1	0.1	2.4	0.1	0.1
ASU 2018-02 Adoption								(0.9)			(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		(2.5)			$ (3.3)	(6.4)		$ (6.0)	(3.3)		(6.0)
Change in Fair Value Recognized in AOCI		0.3				2.3			0.3		2.3
Amortization Of Pension And Other Postretirement Benefit Plans
Reclassification from AOCI, before Income Tax (Expense) Benefit		0.0				0.5			1.0		1.6
Reclassification from AOCI, Net of Income Tax (Expense) Benefit		0.0				0.4			0.8		1.3
Net Current Period Other Comprehensive Income (Loss)		0.3				2.7			1.1		3.6
ASU 2018-02 Adoption											(1.3)
Ending Balance in AOCI		(2.2)		$ (2.5)		(3.7)	$ (6.4)		(2.2)		(3.7)
Southwestern Electric Power Co [Member] | Purchased Electricity for Resale [Member]
Commodity
Purchased Electricity for Resale		44.8				36.6			110.5		132.7
Southwestern Electric Power Co [Member] | Reclassifications from Accumulated Other Comprehensive Income [Member]
Interest Rate
Interest Expense	[2]					0.5			1.0		1.6
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.5)				(0.5)			(1.5)		(1.5)
Amortization of Actuarial (Gains) Losses		0.2				0.1			0.4		0.2
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
Amortization Of Pension And Other Postretirement Benefit Plans
Amortization of Prior Service Cost (Credit)		(0.5)				(0.5)			(1.5)		(1.5)
Amortization of Actuarial (Gains) Losses		0.2				0.1			0.4		0.2
Income Tax (Expense) Benefit		0.0				(0.1)			(0.2)		(0.3)
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			1.0		1.6
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) Benefit		$ 0.0				$ 0.1			$ 0.2		$ 0.3

[1] The change in fair value includes $2 million and $6 million related to AEP's investment in joint venture wind farms acquired as part of the purchase of Sempra Renewables LLC for the three and nine months ended September 30, 2019, respectively. See “Sempra Renewables LLC” section of Note 14 for additional information.

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