Business Segments (Details) - USD ($) $ in Millions		3 Months Ended								9 Months Ended
		Sep. 30, 2023		Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022		Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023		Sep. 30, 2022		Dec. 31, 2022
Reportable Segment Information
Interest Expense		$ 470.3				$ 360.7				$ 1,346.0		$ 1,001.7
Revenue from Contracts with Customers		5,341.7				5,526.1				14,405.1		14,758.4
Revenues		5,341.7				5,526.1				14,405.1		14,758.4
Net Income (Loss)		958.3		$ 516.1	$ 400.4	683.3		$ 520.8	$ 718.1	1,874.8		1,922.2
Income Tax (Expense) Benefit		64.2				(16.1)				103.2		90.7
Balance Sheet Information
Total Property, Plant and Equipment		99,998.5								99,998.5				$ 97,021.4
Accumulated Depreciation and Amortization		24,177.4								24,177.4				23,682.3
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		75,821.1								75,821.1				73,339.1
Total Assets		95,125.6								95,125.6				93,403.3
Long-term Debt Due Within One Year		2,773.6								2,773.6				2,486.4
Long-term Debt		36,715.5								36,715.5				34,314.6
Total Long-term Debt Outstanding		39,489.1								39,489.1				36,801.0
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	[1]	(1.3)				0.9				(1.1)		3.1
Income Tax (Expense) Benefit		(4.4)				(47.3)				9.8		(92.2)
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	[1]	(1.3)				0.9				(1.1)		3.1
Income Tax (Expense) Benefit		(0.2)				0.1				(0.2)		0.6
Vertically Integrated Utilities [Member]
Reportable Segment Information
Revenue from Contracts with Customers		3,158.1				3,174.6				8,603.4		8,416.4
Transmission and Distribution Utilities Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		1,535.2				1,525.5				4,321.3		4,064.5
Generation and Marketing Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		527.5				733.1				1,172.6		1,997.0
Generation and Marketing Revenues [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reportable Segment Information
Revenue from Contracts with Customers	[1]					0.2						0.2
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	[1]					0.0						0.0
Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		120.9				92.9				307.8		280.5
Revenues		8.5	[2]			128.3	[3],[4]			(250.2)	[5],[6]	429.4	[7],[8]
AEP Transmission Co [Member]
Reportable Segment Information
Interest Expense		51.6				42.7				147.5		119.7
Interest Income		1.6				0.7				5.7		1.0
Revenues from Related Parties, Net of Provisions for Refund		369.9				331.3				1,080.0		933.8
Revenues		462.7				418.5				1,349.2		1,183.3
Net Income (Loss)		179.2		$ 175.7	$ 162.7	152.7		$ 118.5	$ 155.4	517.6		426.6
Income Tax (Expense) Benefit		46.1				44.3				142.9		124.1
Balance Sheet Information
Total Property, Plant and Equipment		15,540.1								15,540.1				14,366.9
Accumulated Depreciation and Amortization		1,221.2								1,221.2				1,027.0
TOTAL PROPERTY, PLANT AND EQUIPMENT - NET		14,318.9								14,318.9				13,339.9
Total Assets		14,712.0								14,712.0				13,814.2
Long-term Debt Due Within One Year		60.0								60.0				60.0
Long-term Debt		5,413.7								5,413.7				4,722.8
Total Long-term Debt Outstanding		5,473.7								5,473.7				4,782.8
AEP Transmission Co [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		374.7				340.6				1,097.9		999.5
AEP Transmission Co [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		0.0	[9]			0.0	[10]			0.0	[11]	0.0	[12]
AEP Transmission Co [Member] | Transmission [Member]
Reportable Segment Information
Revenue from Contract with Customers, Net of Provisions for Refund, Including Assessed Tax		92.8				87.2				269.2		249.5
Revenue from Contracts with Customers		93.8				89.1				274.0		261.7
Reconciling Adjustments [Member]
Reportable Segment Information
Revenue from Contracts with Customers		0.0				0.0				0.0		0.0
Revenues		(508.4)				(425.0)				(1,416.3)		(1,190.5)
Net Income (Loss)		0.0				0.0				0.0		0.0
Balance Sheet Information
Total Assets	[13]	(3,381.8)								(3,381.8)				(5,783.0)
Reconciling Adjustments [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		(508.4)				(425.0)				(1,416.3)		(1,190.5)
Reconciling Adjustments [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		(0.7)	[2]			(2.0)	[3],[4]			(3.6)	[5],[6]	(6.9)	[7],[8]
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	[14]	(5,610.0)								(5,610.0)				(4,878.8)
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
Vertically Integrated Utilities [Member]
Reportable Segment Information
Revenues		3,205.4				3,226.3				8,737.7		8,562.2
Net Income (Loss)		514.0				476.9				1,054.6		1,079.4
Balance Sheet Information
Total Assets		50,940.3								50,940.3				49,761.8
Vertically Integrated Utilities [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		47.3				51.7				134.3		145.8
Vertically Integrated Utilities [Member] | Vertically Integrated Utilities [Member]
Reportable Segment Information
Revenue from Contracts with Customers		3,158.1				3,174.6				8,603.4		8,416.4
Vertically Integrated Utilities [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		2.2	[2]			0.2	[3],[4]			2.2	[5],[6]	0.3	[7],[8]
Transmission And Distribution Utilities [Member]
Reportable Segment Information
Revenues		1,544.1				1,530.2				4,348.5		4,078.6
Net Income (Loss)		206.0				165.5				508.4		483.1
Balance Sheet Information
Total Assets		24,327.9								24,327.9				22,920.2
Transmission And Distribution Utilities [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		8.9				4.7				27.2		14.1
Transmission And Distribution Utilities [Member] | Transmission and Distribution Utilities Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		1,535.2				1,525.5				4,321.3		4,064.5
Transmission And Distribution Utilities [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		2.8	[2]			5.5	[3],[4]			20.0	[5],[6]	18.6	[7],[8]
AEP Transmission Holdco [Member]
Reportable Segment Information
Revenues		476.7				430.9				1,390.8		1,221.1
Net Income (Loss)		203.9				171.4				583.6		487.8
Balance Sheet Information
Total Assets		16,155.0								16,155.0				15,215.8
AEP Transmission Holdco [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		382.7				349.0				1,118.4		976.7
AEP Transmission Holdco [Member] | Transmission [Member]
Reportable Segment Information
Revenue from Contracts with Customers		94.0				81.9				272.4		244.4
Generation And Marketing [Member]
Reportable Segment Information
Revenues		566.7				735.4				1,225.1		2,014.3
Net Income (Loss)		132.8				96.2				(62.2)		278.1
Balance Sheet Information
Total Assets		2,517.0								2,517.0				4,520.1
Generation And Marketing [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		39.2				2.3				52.5		17.3
Generation And Marketing [Member] | Generation and Marketing Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers		527.5				733.1				1,172.6		1,997.0
Generation And Marketing [Member] | Other Revenues [Member]
Reportable Segment Information
Revenues		3.4	[2],[15]			122.8	[3],[4]			(272.8)	[5],[6]	410.5	[7],[8]
All Other [Member]
Reportable Segment Information
Revenues	[16]	57.2				28.3				119.3		72.7
Net Income (Loss)	[16]	(98.4)				(226.7)				(209.6)		(406.2)
Balance Sheet Information
Total Assets	[16],[17]	4,567.2								4,567.2				6,768.4
All Other [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers	[16]	30.3				17.3				83.9		36.6
All Other [Member] | Other Revenues [Member]
Reportable Segment Information
Revenue from Contracts with Customers	[16]	26.9				11.0				35.4		36.1
Revenues		0.8	[2]			1.8	[3],[4]			4.0	[5],[6]	6.9	[7],[8]
State Transcos [Member] | AEP Transmission Co [Member]
Reportable Segment Information
Revenues		462.7				418.5				1,349.2		1,183.3
Net Income (Loss)		178.2				152.6				514.0		426.4
Balance Sheet Information
Total Assets		14,760.8								14,760.8				13,875.6
State Transcos [Member] | AEP Transmission Co [Member] | Related Party
Reportable Segment Information
Revenue from Contracts with Customers		369.9				331.3				1,080.0		933.8
State Transcos [Member] | AEP Transmission Co [Member] | Transmission [Member]
Reportable Segment Information
Revenue from Contracts with Customers		92.8				87.2				269.2		249.5
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)	[18]	1.0				0.1				3.6		0.2
Balance Sheet Information
Total Assets	[19]	5,561.2								5,561.2				$ 4,817.4
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

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

[2] Amounts include affiliated and nonaffiliated revenues.

[3] Amounts include affiliated and nonaffiliated revenues

[4] Generation & Marketing includes economic hedge activity.

[5] Amounts include affiliated and nonaffiliated revenues.

[6] Generation & Marketing includes economic hedge activity.

[7] Amounts include affiliated and nonaffiliated revenues

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

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

[15] Generation & Marketing includes economic hedge activity.

[16] 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.

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

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

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