Business Segments (Details) - USD ($) $ in Millions		3 Months Ended								9 Months Ended
		Sep. 30, 2024		Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023		Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024		Sep. 30, 2023		Dec. 31, 2023
Reportable Segment Information
Interest Expense, Operating and Nonoperating		$ 498.8				$ 470.3				$ 1,400.0		$ 1,346.0
Revenue from Contracts with Customers		5,420.1				5,341.7				15,025.0		14,405.1
Revenues		5,420.1				5,341.7				15,025.0		14,405.1
Net Income (Loss)		961.7		$ 342.5	$ 1,005.7	958.3		$ 516.1	$ 400.4	2,309.9		1,874.8
Income Tax (Expense) Benefit		37.5				64.2				(97.7)		103.2
Balance Sheet Information
Total Property, Plant and Equipment		105,926.6								105,926.6				$ 101,246.4
Accumulated Depreciation and Amortization		25,852.8								25,852.8				24,553.0
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		80,073.8								80,073.8				76,693.4
Total Assets		100,119.1								100,119.1				96,684.0
Long-term Debt Due Within One Year		2,826.7								2,826.7				2,490.5
Long-term Debt		39,147.7								39,147.7				37,652.7
Total Long-term Debt Outstanding		41,974.4								41,974.4				40,143.2
Related Party
Reportable Segment Information
Revenue from Contracts with Customers		0.0				0.0				0.0		0.0
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reportable Segment Information
Interest Expense, Operating and Nonoperating	[1]	8.8				(1.3)				6.5		(1.1)
Income Tax (Expense) Benefit		1.8				(4.4)				(2.6)		9.8
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
Interest Expense, Operating and Nonoperating	[1]	8.8				(1.3)				6.5		(1.1)
Income Tax (Expense) Benefit		1.8				(0.2)				1.4		(0.2)
Vertically Integrated Utilities [Member]
Reportable Segment Information
Revenue from Contracts with Customers		3,248.8				3,158.1				8,722.0		8,603.4
Transmission and Distribution Utilities Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		1,568.5				1,535.2				4,480.5		4,321.3
Generation and Marketing Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		483.7				527.5				1,442.1		1,172.6
Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		119.1				120.9				380.4		307.8
Revenues		(62.8)	[2],[3]			8.5	[4],[5]			(166.4)	[6],[7]	(250.2)	[8],[9]
AEP Transmission Co [Member]
Reportable Segment Information
Interest Expense, Operating and Nonoperating		54.3				51.6				160.5		147.5
Interest Income		3.1				1.6				9.3		5.7
Revenues from Related Parties, Net of Provisions for Refund		395.9				369.9				1,157.1		1,080.0
Revenues		497.2				462.7				1,455.2		1,349.2
Net Income (Loss)		191.3		$ 175.7	$ 181.2	179.2		$ 175.7	$ 162.7	548.2		517.6
Income Tax (Expense) Benefit		53.7				46.1				153.5		142.9
Balance Sheet Information
Total Property, Plant and Equipment		16,909.0								16,909.0				15,789.0
Accumulated Depreciation and Amortization		1,509.4								1,509.4				1,291.3
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		15,399.6								15,399.6				14,497.7
Total Assets		15,894.3								15,894.3				15,072.5
Long-term Debt Due Within One Year		185.0								185.0				95.0
Long-term Debt		5,677.3								5,677.3				5,319.4
Total Long-term Debt Outstanding		5,862.3								5,862.3				5,414.4
AEP Transmission Co [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		404.4				374.7				1,188.2		1,097.9
AEP Transmission Co [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contract with Customers, Net of Provisions for Refund, Including Assessed Tax		0.2								3.0
Revenue from Contracts with Customers		0.2				0.0				3.0		0.0
Revenues		0.0	[10]			0.0	[11]			0.0	[12]	0.0	[13]
AEP Transmission Co [Member] | Transmission [Member]
Reportable Segment Information
Revenue from Contract with Customers, Net of Provisions for Refund, Including Assessed Tax		101.1				92.8				295.1		269.2
Revenue from Contracts with Customers		103.3				93.8				299.0		274.0
Reconciling Adjustments [Member]
Reportable Segment Information
Revenue from Contracts with Customers		0.0				0.0				0.0		0.0
Revenues		(508.0)				(508.4)				(1,524.8)		(1,416.3)
Net Income (Loss)		0.0				0.0				0.0		0.0
Balance Sheet Information
Total Assets	[14]	(3,315.5)								(3,315.5)				(4,324.6)
Reconciling Adjustments [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers	[15]	(508.0)				(508.4)				(1,524.8)		(1,416.3)
Reconciling Adjustments [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		(0.7)	[2],[3]			(0.7)	[4],[5]			4.9	[6],[7]	(3.6)	[8],[9]
Reconciling Adjustments [Member] | AEP Transmission Co [Member]
Reportable Segment Information
Revenue from Contracts with Customers		0.0				0.0				0.0		0.0
Revenues		0.0				0.0				0.0		0.0
Net Income (Loss)		0.0				0.0				0.0		0.0
Balance Sheet Information
Total Assets	[16]	(6,017.5)								(6,017.5)				(5,534.7)
Reconciling Adjustments [Member] | AEP Transmission Co [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		0.0				0.0				0.0		0.0
Reconciling Adjustments [Member] | AEP Transmission Co [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		0.0								0.0
Vertically Integrated Utilities [Member]
Reportable Segment Information
Revenues		3,303.0				3,205.4				8,869.9		8,737.7
Net Income (Loss)		572.5				514.0				1,201.5		1,054.6
Balance Sheet Information
Total Assets		53,723.0								53,723.0				51,802.1
Vertically Integrated Utilities [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		54.2				47.3				147.9		134.3
Vertically Integrated Utilities [Member] | Vertically Integrated Utilities [Member]
Reportable Segment Information
Revenue from Contracts with Customers		3,248.8				3,158.1				8,722.0		8,603.4
Vertically Integrated Utilities [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		(1.0)	[2],[3]			2.2	[4],[5]			(22.4)	[6],[7]	2.2	[8],[9]
Transmission And Distribution Utilities [Member]
Reportable Segment Information
Revenues		1,575.4				1,544.1				4,501.5		4,348.5
Net Income (Loss)		245.2				206.0				542.3		508.4
Balance Sheet Information
Total Assets		26,102.6								26,102.6				24,838.4
Transmission And Distribution Utilities [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		6.9				8.9				21.0		27.2
Transmission And Distribution Utilities [Member] | Transmission and Distribution Utilities Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		1,568.5				1,535.2				4,480.5		4,321.3
Transmission And Distribution Utilities [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		3.3	[2],[3]			2.8	[4],[5]			15.2	[6],[7]	20.0	[8],[9]
AEP Transmission Holdco [Member]
Reportable Segment Information
Revenues		512.5				476.7				1,499.7		1,390.8
Net Income (Loss)		215.8				203.9				627.5		583.6
Balance Sheet Information
Total Assets		17,490.1								17,490.1				16,575.6
AEP Transmission Holdco [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		399.4				382.7				1,167.4		1,118.4
AEP Transmission Holdco [Member] | Transmission [Member]
Reportable Segment Information
Revenue from Contracts with Customers		113.1				94.0				332.3		272.4
Generation And Marketing [Member]
Reportable Segment Information
Revenues		499.1				566.7				1,530.1		1,225.1
Net Income (Loss)		93.3				132.8				226.1		(62.2)
Balance Sheet Information
Total Assets		1,725.2								1,725.2				2,598.5
Generation And Marketing [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		15.4				39.2				88.0		52.5
Generation And Marketing [Member] | Generation and Marketing Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		483.7				527.5				1,442.1		1,172.6
Generation And Marketing [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		(65.1)	[2],[3]			3.4	[4],[5]			(158.9)	[6],[7]	(272.8)	[8],[9]
All Other [Member]
Reportable Segment Information
Revenues	[17]	38.1				57.2				148.6		119.3
Net Income (Loss)	[17]	(165.1)				(98.4)				(287.5)		(209.6)
Balance Sheet Information
Total Assets	[17],[18]	4,393.7								4,393.7				5,194.0
All Other [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers	[17]	32.1				30.3				100.5		83.9
All Other [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers	[17]	6.0				26.9				48.1		35.4
Revenues		0.7	[2],[3]			0.8	[4],[5]			(5.2)	[6],[7]	4.0	[8],[9]
State Transcos [Member] | AEP Transmission Co [Member]
Reportable Segment Information
Revenues		497.2				462.7				1,455.2		1,349.2
Net Income (Loss)		190.8				178.2				547.7		514.0
Balance Sheet Information
Total Assets		15,972.9								15,972.9				15,120.6
State Transcos [Member] | AEP Transmission Co [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		395.9				369.9				1,157.1		1,080.0
State Transcos [Member] | AEP Transmission Co [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		0.2								3.0
State Transcos [Member] | AEP Transmission Co [Member] | Transmission [Member]
Reportable Segment Information
Revenue from Contracts with Customers		101.1				92.8				295.1		269.2
AEPTCo Parent [Member] | AEP Transmission Co [Member]
Reportable Segment Information
Revenue from Contracts with Customers		0.0				0.0				0.0		0.0
Revenues		0.0				0.0				0.0		0.0
Net Income (Loss)	[19]	0.5				1.0				0.5		3.6
Balance Sheet Information
Total Assets	[20]	5,938.9								5,938.9				$ 5,486.6
AEPTCo Parent [Member] | AEP Transmission Co [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		0.0				$ 0.0				0.0		$ 0.0
AEPTCo Parent [Member] | AEP Transmission Co [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		$ 0.0								$ 0.0

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

[2] Amounts include affiliated and nonaffiliated revenues.

[3] Generation & Marketing includes economic hedge activity.

[4] Generation & Marketing includes economic hedge activity.

[5] Amounts include affiliated and nonaffiliated revenues

[6] Amounts include affiliated and nonaffiliated revenues.

[7] Generation & Marketing includes economic hedge activity.

[8] Generation & Marketing includes economic hedge activity.

[9] Amounts include affiliated and nonaffiliated revenues

[10] Amounts include affiliated and nonaffiliated revenues.

[11] Amounts include affiliated and nonaffiliated revenues.

[12] Amounts include affiliated and nonaffiliated revenues.

[13] Amounts include affiliated and nonaffiliated revenues.

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

[15] Represents inter-segment revenues.

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

[17] 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, income tax expense and other nonallocated costs.

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

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

[20] Primarily relates to Notes Receivable from the State Transcos.