Revenue from Contracts with Customers (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2018		Sep. 30, 2017		Sep. 30, 2018		Sep. 30, 2017		Dec. 31, 2017
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		$ 4,333.1		$ 4,104.7		$ 12,394.6		$ 11,614.5
Total Revenues		4,333.1		4,104.7		12,394.6		11,614.5
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		1,018.6				1,018.6
Revenue Textuals [Abstract]
Revenue from Related Parties		0.0		0.0		0.0		0.0
2018 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		246.1				246.1
2019-2020 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		258.7				258.7
2021-2022 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		164.8				164.8
2022 and Forward [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		349.0				349.0
Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		3,372.0				9,464.7
Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		1,660.9				4,617.9
Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		955.2				2,656.5
Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		697.1				2,022.0
Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		58.8				168.3
Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		760.5				2,579.1
Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		240.8	[1]			944.7	[2]
Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		120.6	[3]			594.2	[4]
Marketing, Competitive Retail and Renewable [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		399.1				1,040.2
Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		194.6	[5]			379.6	[6]
Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		4,327.1				12,423.4
Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		6.0				(28.8)
Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		55.5		59.7		212.9		165.7
Total Revenues		58.6	[5]			78.5	[6]
Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(52.6)	[7]			(107.3)	[8]
AEP Texas Inc. [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		407.3
Total Revenues		433.4		431.2		1,193.3		1,164.3
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		74.2				74.2
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		14.3				14.3				$ 12.3
Revenue Textuals [Abstract]
Revenue from Related Parties		27.5		18.9		63.3		50.8
AEP Texas Inc. [Member] | 2018 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		74.2				74.2
AEP Texas Inc. [Member] | 2019-2020 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
AEP Texas Inc. [Member] | 2021-2022 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
AEP Texas Inc. [Member] | 2022 and Forward [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
AEP Texas Inc. [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		326.2				880.9
AEP Texas Inc. [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		178.8				453.6
AEP Texas Inc. [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		113.7				328.5
AEP Texas Inc. [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		27.2				79.7
AEP Texas Inc. [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		6.5				19.1
AEP Texas Inc. [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		73.6				229.6
AEP Texas Inc. [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0	[9]			0.0	[10]
AEP Texas Inc. [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		73.6	[11]			229.6	[12]
AEP Texas Inc. [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		7.5	[13]			21.8	[14]
AEP Texas Inc. [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers						1,132.3
AEP Texas Inc. [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		26.1				61.0
AEP Texas Inc. [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		1.4		0.8		3.0		2.1
Total Revenues		27.1	[15]			62.1	[16]
AEP Texas Inc. [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(1.0)	[17]			(1.1)	[18]
AEP Transmission Co [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]	206.8
Total Revenues		194.4	[19]	165.6	[20]	586.2	[19],[20]	534.8	[20]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		166.8				166.8
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		73.0				73.0				93.2
Revenue Textuals [Abstract]
Revenue from Related Parties		148.4		130.1	[20]	453.8	[20]	439.1	[20]
AEP Transmission Co [Member] | Short-term Contract with Customer [Member]
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		71.9				71.9				47.1
AEP Transmission Co [Member] | 2018 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		166.8				166.8
AEP Transmission Co [Member] | 2019-2020 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
AEP Transmission Co [Member] | 2021-2022 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
AEP Transmission Co [Member] | 2022 and Forward [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
AEP Transmission Co [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]	0.0				0.0
AEP Transmission Co [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]	0.0				0.0
AEP Transmission Co [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]	0.0				0.0
AEP Transmission Co [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]	0.0				0.0
AEP Transmission Co [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]	0.0				0.0
AEP Transmission Co [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]	206.6				612.9
AEP Transmission Co [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]	0.0	[9]			0.0	[10]
AEP Transmission Co [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]	206.6	[11]			612.9	[12]
Revenue Textuals [Abstract]
Revenue from Related Parties		146.0				448.0
AEP Transmission Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]	0.2	[13]			8.7	[14]
AEP Transmission Co [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[19]					621.6
AEP Transmission Co [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues	[19]	(12.4)				(35.4)
AEP Transmission Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0		(0.1)	[20]	0.1	[20]	0.0	[20]
Total Revenues	[19]	0.0	[15]			0.0	[16]
AEP Transmission Co [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues	[19]	(12.4)	[17]			(35.4)	[18]
Revenue Textuals [Abstract]
Revenue from Related Parties		48.0				48.0
Appalachian Power Co [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		764.1
Total Revenues		762.0		719.3		2,249.4		2,187.4
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		100.7				100.7
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		70.6				70.6				69.3
Revenue Textuals [Abstract]
Revenue from Related Parties		42.9		41.9		138.7		130.6
Appalachian Power Co [Member] | Short-term Contract with Customer [Member]
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		54.1				54.1				35.6
Appalachian Power Co [Member] | 2018 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		30.7				30.7
Appalachian Power Co [Member] | 2019-2020 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		32.9				32.9
Appalachian Power Co [Member] | 2021-2022 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		25.5				25.5
Appalachian Power Co [Member] | 2022 and Forward [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		11.6				11.6
Appalachian Power Co [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		652.8				1,974.5
Appalachian Power Co [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		320.9				1,017.2
Appalachian Power Co [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		155.6				443.8
Appalachian Power Co [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		157.1				455.9
Appalachian Power Co [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		19.2				57.6
Appalachian Power Co [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		95.4				254.3
Appalachian Power Co [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		74.5	[9]			194.1	[10]
Revenue Textuals [Abstract]
Revenue from Related Parties		30.0				100.0
Appalachian Power Co [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		20.9	[11]			60.2	[12]
Appalachian Power Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		15.9	[13]			42.2	[14]
Appalachian Power Co [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers						2,271.0
Appalachian Power Co [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(2.1)				(21.6)
Appalachian Power Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		2.3		3.0		7.6		11.8
Total Revenues		(0.9)	[15]			(0.9)	[16]
Appalachian Power Co [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(1.2)	[17]			(20.7)	[18]
Indiana Michigan Power Co [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		619.5
Total Revenues		629.7		557.7		1,796.2		1,585.5
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		13.6				13.6
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		51.7				51.7				50.0
Indiana Michigan Power Co [Member] | Short-term Contract with Customer [Member]
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		24.7				24.7				15.1
Indiana Michigan Power Co [Member] | 2018 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		6.3				6.3
Indiana Michigan Power Co [Member] | 2019-2020 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		3.0				3.0
Indiana Michigan Power Co [Member] | 2021-2022 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		2.9				2.9
Indiana Michigan Power Co [Member] | 2022 and Forward [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		1.4				1.4
Indiana Michigan Power Co [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		497.3				1,362.6
Indiana Michigan Power Co [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		207.4				559.4
Indiana Michigan Power Co [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		139.5				373.7
Indiana Michigan Power Co [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		148.7				424.1
Indiana Michigan Power Co [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		1.7				5.4
Indiana Michigan Power Co [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		99.8				366.6
Indiana Michigan Power Co [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		93.6	[9]			349.7	[10]
Indiana Michigan Power Co [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		6.2	[11]			16.9	[12]
Indiana Michigan Power Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		22.4	[13]			71.0	[14]
Indiana Michigan Power Co [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers						1,800.2
Indiana Michigan Power Co [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		10.2				(4.0)
Indiana Michigan Power Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		2.7		3.6		10.1		9.9
Total Revenues		8.7	[15]			0.0	[16]
Revenue Textuals [Abstract]
Revenue from Related Parties		17.0				57.0
Indiana Michigan Power Co [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		1.5	[17]			(4.0)	[18]
Ohio Power Co [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		740.9
Total Revenues		778.3		742.0		2,318.0		2,152.0
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		33.9				33.9
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		72.4				72.4				70.2
Revenue Textuals [Abstract]
Revenue from Related Parties		3.3		4.6		17.9		19.4
Ohio Power Co [Member] | Short-term Contract with Customer [Member]
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		42.5				42.5				26.1
Ohio Power Co [Member] | 2018 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		21.5				21.5
Ohio Power Co [Member] | 2019-2020 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		12.4				12.4
Ohio Power Co [Member] | 2021-2022 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
Ohio Power Co [Member] | 2022 and Forward [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
Ohio Power Co [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		756.0				2,188.8
Ohio Power Co [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		433.5				1,258.4
Ohio Power Co [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		222.9				632.8
Ohio Power Co [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		96.3				287.8
Ohio Power Co [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		3.3				9.8
Ohio Power Co [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		14.8				42.8
Ohio Power Co [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0	[9]			0.0	[10]
Ohio Power Co [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		14.8	[11]			42.8	[12]
Ohio Power Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		(29.9)	[13]			51.3	[14]
Ohio Power Co [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers						2,282.9
Ohio Power Co [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		37.4				35.1
Ohio Power Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		2.4		1.4		5.3		4.8
Total Revenues		74.3	[15]			82.3	[16]
Ohio Power Co [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(36.9)	[17]			(47.2)	[18]
Revenue Textuals [Abstract]
Revenue from Related Parties		48.0				48.0
Public Service Co Of Oklahoma [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		479.1
Total Revenues		481.4		442.8		1,216.5		1,091.6
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		4.5				4.5
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		39.8				39.8				32.9
Revenue Textuals [Abstract]
Revenue from Related Parties		1.1		1.1		3.7		3.2
Public Service Co Of Oklahoma [Member] | Short-term Contract with Customer [Member]
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		17.1				17.1				6.1
Public Service Co Of Oklahoma [Member] | 2018 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		4.5				4.5
Public Service Co Of Oklahoma [Member] | 2019-2020 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
Public Service Co Of Oklahoma [Member] | 2021-2022 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
Public Service Co Of Oklahoma [Member] | 2022 and Forward [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
Public Service Co Of Oklahoma [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		447.6				1,134.6
Public Service Co Of Oklahoma [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		220.8				531.4
Public Service Co Of Oklahoma [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		122.2				317.9
Public Service Co Of Oklahoma [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		80.2				220.4
Public Service Co Of Oklahoma [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		24.4				64.9
Public Service Co Of Oklahoma [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		26.0				56.1
Public Service Co Of Oklahoma [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		12.5	[9]			26.7	[10]
Public Service Co Of Oklahoma [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		13.5	[11]			29.4	[12]
Public Service Co Of Oklahoma [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		5.5	[13]			14.6	[14]
Public Service Co Of Oklahoma [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers						1,205.3
Public Service Co Of Oklahoma [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		2.3				11.2
Public Service Co Of Oklahoma [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		1.2		1.1		3.3		3.3
Total Revenues		0.0	[15]			0.0	[16]
Public Service Co Of Oklahoma [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		2.3	[17]			11.2	[18]
Southwestern Electric Power Co [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		535.6
Total Revenues		535.3		517.6		1,411.8		1,343.6
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		9.1				9.1
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		32.8				32.8				30.2
Revenue Textuals [Abstract]
Revenue from Related Parties		8.7		7.7		20.2		20.4
Southwestern Electric Power Co [Member] | Short-term Contract with Customer [Member]
Assets, Current [Abstract]
Affiliated Companies - Contracts with Customers		20.3				20.3				$ 11.0
Southwestern Electric Power Co [Member] | 2018 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		9.1				9.1
Southwestern Electric Power Co [Member] | 2019-2020 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
Southwestern Electric Power Co [Member] | 2021-2022 [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
Southwestern Electric Power Co [Member] | 2022 and Forward [Member]
Revenue, Performance Obligation [Abstract]
Fixed Performance Obligations		0.0				0.0
Southwestern Electric Power Co [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		446.3				1,145.4
Southwestern Electric Power Co [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		214.0				512.3
Southwestern Electric Power Co [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		142.6				378.6
Southwestern Electric Power Co [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		87.5				248.1
Southwestern Electric Power Co [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		2.2				6.4
Southwestern Electric Power Co [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		82.7				246.1
Southwestern Electric Power Co [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		53.2	[9]			168.8	[10]
Southwestern Electric Power Co [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		29.5	[11]			77.3	[12]
Southwestern Electric Power Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		6.6	[13]			18.0	[14]
Southwestern Electric Power Co [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers						1,409.5
Southwestern Electric Power Co [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(0.3)				2.3
Southwestern Electric Power Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.6		0.4		1.2		1.4
Total Revenues		0.0	[15]			0.0	[16]
Southwestern Electric Power Co [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(0.3)	[17]			2.3	[18]
Consolidation Eliminations [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0		0.0		0.0		0.0
Total Revenues		(247.6)		(226.1)		(674.1)		(727.9)
Revenue Textuals [Abstract]
Revenue from Related Parties		(247.6)		(226.1)		(674.1)		(727.9)
Consolidation Eliminations [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Consolidation Eliminations [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Consolidation Eliminations [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Consolidation Eliminations [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Consolidation Eliminations [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Consolidation Eliminations [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		(340.1)				(675.9)
Consolidation Eliminations [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		(98.5)	[1]			(155.2)	[2]
Consolidation Eliminations [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		(241.6)	[3]			(520.7)	[4]
Consolidation Eliminations [Member] | Marketing, Competitive Retail and Renewable [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Consolidation Eliminations [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		49.5	[5]			1.8	[6]
Consolidation Eliminations [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		(290.6)				(674.1)
Consolidation Eliminations [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		43.0				0.0
Consolidation Eliminations [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		43.0	[5]			0.0	[6]
Consolidation Eliminations [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		0.0	[7]			0.0	[8]
Consolidation Eliminations [Member] | AEP Transmission Co [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0		0.0		0.0		0.0
Total Revenues		0.0		0.0		0.0		0.0
Revenue Textuals [Abstract]
Revenue from Related Parties		0.0		0.0		0.0		0.0
Consolidation Eliminations [Member] | AEP Transmission Co [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0		0.0		0.0		0.0
Vertically Integrated Utilities [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		2,636.7		2,482.2		7,393.7		6,893.1
Revenue Textuals [Abstract]
Revenue from Related Parties		26.5		28.4		61.3		73.8
Vertically Integrated Utilities [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		2,289.4				6,395.1
Vertically Integrated Utilities [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		1,048.7				2,906.9
Vertically Integrated Utilities [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		618.5				1,693.9
Vertically Integrated Utilities [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		573.2				1,655.2
Vertically Integrated Utilities [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		49.0				139.1
Vertically Integrated Utilities [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		297.0				894.9
Vertically Integrated Utilities [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		224.2	[1]			686.5	[2]
Vertically Integrated Utilities [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		72.8	[3]			208.4	[4]
Vertically Integrated Utilities [Member] | Marketing, Competitive Retail and Renewable [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Vertically Integrated Utilities [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		40.3	[5]			121.8	[6]
Vertically Integrated Utilities [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		2,626.7				7,411.8
Vertically Integrated Utilities [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		10.0				(18.1)
Vertically Integrated Utilities [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		9.8	[5]			1.1	[6]
Vertically Integrated Utilities [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		0.2	[7]			(19.2)	[8]
Transmission And Distribution Utilities [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		1,211.5		1,173.3		3,510.9		3,313.2
Revenue Textuals [Abstract]
Revenue from Related Parties		30.6		23.6		60.9		70.5
Transmission And Distribution Utilities [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		1,082.6				3,069.6
Transmission And Distribution Utilities [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		612.2				1,711.0
Transmission And Distribution Utilities [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		336.7				962.6
Transmission And Distribution Utilities [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		123.9				366.8
Transmission And Distribution Utilities [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		9.8				29.2
Transmission And Distribution Utilities [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		88.0				272.6
Transmission And Distribution Utilities [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0	[1]			0.0	[2]
Transmission And Distribution Utilities [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		88.0	[3]			272.6	[4]
Transmission And Distribution Utilities [Member] | Marketing, Competitive Retail and Renewable [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Transmission And Distribution Utilities [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		69.9	[5]			165.1	[6]
Transmission And Distribution Utilities [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		1,240.5				3,507.3
Transmission And Distribution Utilities [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(29.0)				3.6
Transmission And Distribution Utilities [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		8.9	[5]			51.9	[6]
Transmission And Distribution Utilities [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(37.9)	[7]			(48.3)	[8]
AEP Transmission Holdco [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		187.2				605.2
AEP Transmission Holdco [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
AEP Transmission Holdco [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
AEP Transmission Holdco [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
AEP Transmission Holdco [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
AEP Transmission Holdco [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
AEP Transmission Holdco [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		201.4				633.9
AEP Transmission Holdco [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0	[1]			0.0	[2]
AEP Transmission Holdco [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		201.4	[3]			633.9	[4]
Revenue Textuals [Abstract]
Revenue from Related Parties		147.0				444.0
AEP Transmission Holdco [Member] | Marketing, Competitive Retail and Renewable [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
AEP Transmission Holdco [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.7	[5]			11.1	[6]
AEP Transmission Holdco [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		202.1				645.0
AEP Transmission Holdco [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(14.9)				(39.8)
AEP Transmission Holdco [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		0.0	[5]			0.0	[6]
AEP Transmission Holdco [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(14.9)	[7]			(39.8)	[8]
Generation And Marketing [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		521.6		465.5		1,487.4		1,467.5
Revenue Textuals [Abstract]
Revenue from Related Parties		35.1		24.0		88.1		80.7
Generation And Marketing [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Generation And Marketing [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Generation And Marketing [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Generation And Marketing [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Generation And Marketing [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Generation And Marketing [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		514.2				1,453.6
Generation And Marketing [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		115.1	[1]			413.4	[2]
Revenue Textuals [Abstract]
Revenue from Related Parties		35.0				87.0
Generation And Marketing [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0	[3]			0.0	[4]
Generation And Marketing [Member] | Marketing, Competitive Retail and Renewable [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		399.1				1,040.2
Generation And Marketing [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		12.7	[5]			15.0	[6]
Generation And Marketing [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		526.9				1,468.6
Generation And Marketing [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(5.3)				18.8
Generation And Marketing [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		(5.3)	[5]			18.8	[6]
Generation And Marketing [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		0.0	[7]			0.0	[8]
Other Segments [Member]
Disaggregation of Revenue [Abstract]
Total Revenues	[21]	23.7		31.3		71.5		86.7
Revenue Textuals [Abstract]
Revenue from Related Parties	[21]	20.1		16.7		55.1		46.8
Other Segments [Member] | Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Other Segments [Member] | Residential [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Other Segments [Member] | Commercial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Other Segments [Member] | Industrial [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Other Segments [Member] | Other Retail [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Other Segments [Member] | Wholesale and Competitive [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Other Segments [Member] | Generation [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0	[1]			0.0	[2]
Other Segments [Member] | Transmission [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0	[3]			0.0	[4]
Other Segments [Member] | Marketing, Competitive Retail and Renewable [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		0.0				0.0
Other Segments [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		21.5	[5]			64.8	[6]
Other Segments [Member] | Affiliated and Nonaffiliated [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers		21.5				64.8
Other Segments [Member] | Alternative and Other [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		2.2				6.7
Other Segments [Member] | Other Revenues [Member]
Disaggregation of Revenue [Abstract]
Revenue from Contracts with Customers	[21]	3.6		$ 14.6		16.4		$ 39.9
Total Revenues		2.2	[5]			6.7	[6]
Other Segments [Member] | Alternative [Member]
Disaggregation of Revenue [Abstract]
Total Revenues		$ 0.0	[7]			$ 0.0	[8]

[1] Amounts include affiliated and nonaffiliated revenues. The affiliated revenue for Generation & Marketing is $35 million. The remaining affiliated amounts are immaterial.

[2] Amounts include affiliated and nonaffiliated revenues. The affiliated revenue for Generation & Marketing is $87 million. The remaining affiliated amounts are immaterial.

[3] Amounts include affiliated and nonaffiliated revenues. The affiliated revenue for AEP Transmission Holdco is $147 million. The remaining affiliated amounts are immaterial.

[4] Amounts include affiliated and nonaffiliated revenues. The affiliated revenue for AEP Transmission Holdco is $444 million. The remaining affiliated amounts are immaterial.

[5] Amounts include affiliated and nonaffiliated revenues.

[6] Amounts include affiliated and nonaffiliated revenues.

[7] The alternative revenue for Transmission and Distribution Utilities is primarily the $48 million reduction in revenue relating to the Ohio tax settlement. See the “Ohio Tax Reform” section of Note 4 for additional information.

[8] The alternative revenue for Transmission and Distribution Utilities is primarily the $48 million reduction in revenue relating to the Ohio tax settlement. See the “Ohio Tax Reform” section of Note 4 for additional information.

[9] Amounts include affiliated and nonaffiliated revenues. The affiliated revenue for APCo is $30 million primarily relating to the PPA with Kingsport. The remaining affiliated amounts are immaterial.

[10] Amounts include affiliated and nonaffiliated revenues. The affiliated revenue for APCo is $100 million primarily relating to the PPA with Kingsport. The remaining affiliated amounts are immaterial.

[11] Amounts include affiliated and nonaffiliated revenues. The affiliated revenue for AEPTCo is $146 million. The remaining affiliated amounts are immaterial.

[12] Amounts include affiliated and nonaffiliated revenues. The affiliated revenue for AEPTCo is $448 million. The remaining affiliated amounts are immaterial.

[13] Amounts include affiliated and nonaffiliated revenues. The affiliated revenue for I&M is $17 million primarily relating to the barging, urea transloading and other transportation services. The remaining affiliated amounts are immaterial

[14] Amounts include affiliated and nonaffiliated revenues. The affiliated revenue for I&M is $57 million primarily relating to barging, urea transloading and other transportation services. The remaining affiliated amounts are immaterial

[15] Amounts include affiliated and nonaffiliated revenues.

[16] Amounts include affiliated and nonaffiliated revenues.

[17] The alternative revenue for OPCo is primarily the $48 million reduction in revenue relating to the Ohio tax settlement. See the “Ohio Tax Reform” section of Note 4 for additional information.

[18] The alternative revenue for OPCo is primarily the $48 million reduction in revenue relating to the Ohio tax settlement. See the “Ohio Tax Reform” section of Note

[19] The amounts presented reflect the revisions made to AEPTCo’s previously issued financial statements. For additional details on revisions made to AEPTCo’s financial statements, see Note 1- Significant Accounting Matters.

[20] The amounts presented reflect the revisions made to AEPTCo’s previously issued financial statements. For additional details on revisions made to AEPTCo’s financial statements, see Note 1- Significant Accounting Matters.

[21] Corporate and Other primarily includes the purchasing of receivables from certain AEP utility subsidiaries. This segment also includes Parent’s guarantee revenue received from affiliates, investment income, interest income and interest expense and other nonallocated costs.