Business Segments (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2022		Mar. 31, 2021		Dec. 31, 2021
Reportable Segment Information
Revenue from Contracts with Customers		$ 4,592.6		$ 4,281.1
Revenue from Related Parties		0.0		0.0
Revenues		4,592.6		4,281.1
Net Income (Loss)		718.1		578.8
Balance Sheet Information
Total Property, Plant and Equipment		89,175.0				$ 86,806.4
Accumulated Depreciation and Amortization		21,297.0				20,805.1
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		67,878.0				66,001.3
Total Assets	[1]	89,831.4				87,668.7
Long-term Debt Due Within One Year	[2]	3,008.4				2,153.8
Long-term Debt	[3]	30,855.7				31,300.7
Total Long-term Debt Outstanding	[4]	33,864.1				33,454.5
Interest Expense		313.4		290.2
Income Tax (Expense) Benefit		52.8		54.5
Reclassification out of Accumulated Other Comprehensive Income [Member]
Balance Sheet Information
Interest Expense	[5]	1.1		1.5
Income Tax (Expense) Benefit		(10.5)		(36.1)
Interest Rate [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Balance Sheet Information
Interest Expense	[5]	1.1		1.5
Income Tax (Expense) Benefit		0.2		0.4
Vertically Integrated Utilities [Member]
Reportable Segment Information
Revenue from Contracts with Customers		2,646.8		2,504.5
Transmission and Distribution Utilities Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		1,242.2		1,082.3
Generation and Marketing Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		609.5		601.7
Generation and Marketing Revenues [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reportable Segment Information
Revenue from Contracts with Customers	[5]	(0.1)		0.8
Generation and Marketing Revenues [Member] | Interest Rate [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Reportable Segment Information
Revenue from Contracts with Customers	[5]	0.0		0.0
Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		94.1		92.6
Revenues		165.4	[6]	4.8	[7]
AEP Transmission Co [Member]
Reportable Segment Information
Revenue from Related Parties		324.7		285.6
Revenues		400.4		361.7
Net Income (Loss)		155.4		151.7
Balance Sheet Information
Total Property, Plant and Equipment		12,994.3				12,708.5
Accumulated Depreciation and Amortization		830.5				772.8
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		12,163.8				11,935.7
Total Assets	[8]	12,714.4				12,524.4
Long-term Debt Due Within One Year		104.0				104.0
Long-term Debt		4,240.5				4,239.9
Total Long-term Debt Outstanding		4,344.5				4,343.9
Interest Income		0.1		0.1
Interest Expense		37.7		34.1
Income Tax (Expense) Benefit		45.5		39.6
AEP Transmission Co [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		0.0		0.1
Revenues		0.0	[9]	0.0	[10]
AEP Transmission Co [Member] | Transmission [Member]
Reportable Segment Information
Revenue from Contracts with Customers		75.7		76.0
Reconciling Adjustments [Member]
Reportable Segment Information
Revenue from Contracts with Customers		0.0		0.0
Revenue from Related Parties		(392.2)		(368.4)
Revenues		(392.2)		(368.4)
Net Income (Loss)		0.0		0.0
Balance Sheet Information
Total Assets	[11]	(5,274.1)				(4,409.1)
Reconciling Adjustments [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		(2.9)	[6]	(3.6)	[7]
Reconciling Adjustments [Member] | AEP Transmission Co [Member]
Reportable Segment Information
Revenue from Contracts with Customers		0.0		0.0
Revenue from Related Parties		0.0		0.0
Revenues		0.0		0.0
Net Income (Loss)		0.0		0.0
Balance Sheet Information
Total Assets	[12]	(4,450.5)				(4,429.4)
Reconciling Adjustments [Member] | AEP Transmission Co [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers				0.0
Vertically Integrated Utilities [Member]
Reportable Segment Information
Revenue from Related Parties		40.6		32.8
Revenues		2,687.4		2,537.3
Net Income (Loss)		299.2		271.4
Balance Sheet Information
Total Assets	[1]	48,073.4				46,974.2
Vertically Integrated Utilities [Member] | Vertically Integrated Utilities [Member]
Reportable Segment Information
Revenue from Contracts with Customers		2,646.8		2,504.5
Vertically Integrated Utilities [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		0.0	[6]	0.0	[7]
Transmission And Distribution Utilities [Member]
Reportable Segment Information
Revenue from Related Parties		4.6		5.8
Revenues		1,246.8		1,088.1
Net Income (Loss)		152.8		114.4
Balance Sheet Information
Total Assets		21,413.9				21,120.2
Transmission And Distribution Utilities [Member] | Transmission and Distribution Utilities Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		1,242.2		1,082.3
Transmission And Distribution Utilities [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		6.3	[6]	5.3	[7]
AEP Transmission Holdco [Member]
Reportable Segment Information
Revenue from Related Parties		328.0		289.1
Revenues		411.4		377.0
Net Income (Loss)		173.7		173.2
Balance Sheet Information
Total Assets	[1]	14,083.9				13,873.3
AEP Transmission Holdco [Member] | Transmission [Member]
Reportable Segment Information
Revenue from Contracts with Customers		83.4		87.9
Generation And Marketing [Member]
Reportable Segment Information
Revenue from Related Parties		9.8		32.5
Revenues		619.3		634.2
Net Income (Loss)		116.0		38.2
Balance Sheet Information
Total Assets		4,790.7				4,263.6
Generation And Marketing [Member] | Generation and Marketing Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		609.5		601.7
Generation And Marketing [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		159.2	[6],[13]	0.0	[7]
All Other [Member]
Reportable Segment Information
Revenue from Related Parties	[14]	9.2		8.2
Revenues	[14]	19.9		12.9
Net Income (Loss)	[14]	(23.6)		(18.4)
Balance Sheet Information
Total Assets	[14],[15]	6,743.6				5,846.5
All Other [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers	[14]	10.7		4.7
Revenues		2.8	[6]	3.1	[7]
State Transcos [Member] | AEP Transmission Co [Member]
Reportable Segment Information
Revenue from Related Parties		324.7		285.6
Revenues		400.4		361.7
Net Income (Loss)		155.4		151.7
Balance Sheet Information
Total Assets	[8]	12,768.6				12,564.3
State Transcos [Member] | AEP Transmission Co [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers				0.1
State Transcos [Member] | AEP Transmission Co [Member] | Transmission [Member]
Reportable Segment Information
Revenue from Contracts with Customers		75.7		76.0
AEPTCo Parent [Member] | AEP Transmission Co [Member]
Reportable Segment Information
Revenue from Contracts with Customers		0.0		0.0
Revenue from Related Parties		0.0		0.0
Revenues		0.0		0.0
Net Income (Loss)	[16]	0.0		0.0
Balance Sheet Information
Total Assets	[17]	$ 4,396.3				$ 4,389.5
AEPTCo Parent [Member] | AEP Transmission Co [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers				$ 0.0

[1] Amount includes Assets Held for Sale on the balance sheet. See “Disposition of KPCo and KTCo” section of Note 6 for additional information.

[2] Amount excludes $200 million and $200 million as of March 31, 2022 and December 31, 2021, respectively, of Long-term Debt Due Within One Year classified as Liabilities Held for Sale on the balance sheet. See “Disposition of KPCo and KTCo” section of Note 6 for additional information.

[3] Amount excludes $903 million and $903 million as of March 31, 2022 and December 31, 2021, respectively, of Long-term Debt classified as Liabilities Held for Sale on the balance sheet. See “Disposition of KPCo and KTCo” section of Note 6 for additional information.

[4] The book value amounts exclude Long-term Debt of $1.1 billion and $1.1 billion as of March 31, 2022 and December 31, 2021, respectively, classified as Liabilities Held for Sale on the balance sheets. See “Disposition of KPCo and KTCo” section of Note 6 for additional information.

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

[6] Amounts include affiliated and nonaffiliated revenues.

[7] Amounts include affiliated and nonaffiliated revenues

[8] Amount includes Assets Held for Sale on the balance sheet. See “Disposition of KPCo and KTCo” section of Note 6 for additional information.

[9] Amounts include affiliated and nonaffiliated revenues.

[10] Amounts include affiliated and nonaffiliated revenues.

[11] Reconciling Adjustments for Total Assets primarily include elimination of intercompany advances to affiliates and intercompany accounts receivable.

[12] Primarily relates to the elimination of Notes Receivable from the State Transcos.

[13] Generation & Marketing includes economic hedge activity.

[14] 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, interest expense and other nonallocated costs.

[15] Includes elimination of AEP Parent’s investments in wholly-owned subsidiary companies.

[16] Includes the elimination of AEPTCo Parent’s equity earnings in the State Transcos.

[17] Includes the elimination of AEPTCo Parent’s investments in State Transcos.