VARIABLE INTEREST ENTITIES - Schedule of Consolidated Assets And Liabilities Of Variable Interest Entities (Details) - USD ($) $ in Millions	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
ASSETS
Current Assets	$ 6,860.0			$ 5,788.8
Net Property, Plant and Equipment	88,017.7			82,415.6
Other Noncurrent Assets	15,375.8			14,873.6
TOTAL ASSETS	110,253.5			103,078.0
LIABILITIES AND EQUITY
Current Liabilities	9,997.6			13,009.3
Noncurrent Liabilities	68,715.9			63,044.8
Equity	31,479.3	$ 30,968.4	$ 27,364.0	26,986.1	$ 26,658.8	$ 26,175.7	$ 25,843.7	$ 25,285.9
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	110,253.5			103,078.0
SWEPCo
ASSETS
Current Assets	774.2			438.0
Net Property, Plant and Equipment	9,791.6			9,446.1
Other Noncurrent Assets	1,616.3			1,610.9
TOTAL ASSETS	12,182.1			11,495.0
LIABILITIES AND EQUITY
Current Liabilities	1,439.0			1,031.6
Noncurrent Liabilities	6,034.8			6,558.4
Equity	4,708.3	$ 4,519.4	$ 3,953.4	3,905.0	$ 3,796.1	$ 3,758.3	$ 3,928.4	$ 3,770.4
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	12,182.1			11,495.0
I&M
ASSETS
Current Assets	646.5			543.6
Net Property, Plant and Equipment	7,843.1			7,679.3
Other Noncurrent Assets	5,822.3			5,312.6
TOTAL ASSETS	14,311.9			13,535.5
LIABILITIES AND EQUITY
Current Liabilities	855.6			1,071.2
Noncurrent Liabilities	9,769.3			9,067.8
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	14,311.9			13,535.5
AEP Texas
ASSETS
Current Assets	965.7			500.4
Net Property, Plant and Equipment	15,117.6			14,043.5
Other Noncurrent Assets	729.2			655.7
TOTAL ASSETS	16,812.5			15,199.6
LIABILITIES AND EQUITY
Current Liabilities	1,258.8			1,407.1
Noncurrent Liabilities	9,829.3			8,907.9
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	16,812.5			15,199.6
APCo
ASSETS
Current Assets	1,035.0			1,094.9
Net Property, Plant and Equipment	13,939.2			13,612.5
Other Noncurrent Assets	2,018.9			1,958.5
TOTAL ASSETS	16,993.1			16,665.9
LIABILITIES AND EQUITY
Current Liabilities	1,278.3			2,025.5
Noncurrent Liabilities	9,656.6			8,892.4
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	16,993.1			16,665.9
Variable Interest Entity, Primary Beneficiary | Sabine | SWEPCo
ASSETS
Current Assets	2.0			6.0
Net Property, Plant and Equipment	0.0			0.0
Other Noncurrent Assets	92.9			110.8
TOTAL ASSETS	94.9			116.8
LIABILITIES AND EQUITY
Current Liabilities	18.1			20.1
Noncurrent Liabilities	76.8			96.3
Equity	0.0			0.4
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	94.9			116.8
Variable Interest Entity, Primary Beneficiary | DCC Fuel | I&M
ASSETS
Current Assets	86.7			79.3
Net Property, Plant and Equipment	152.2			132.3
Other Noncurrent Assets	76.4			63.6
TOTAL ASSETS	315.3			275.2
LIABILITIES AND EQUITY
Current Liabilities	86.5			79.2
Noncurrent Liabilities	228.8			196.0
Equity	0.0			0.0
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	315.3			275.2
Variable Interest Entity, Primary Beneficiary | AEP Texas Restoration Funding | AEP Texas
ASSETS
Current Assets	12.5			21.3
Net Property, Plant and Equipment	0.0			0.0
Other Noncurrent Assets	104.6			121.9
TOTAL ASSETS	117.1			143.2
LIABILITIES AND EQUITY
Current Liabilities	30.3			30.7
Noncurrent Liabilities	85.4			111.2
Equity	1.4			1.3
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	117.1			143.2
Variable Interest Entity, Primary Beneficiary | AEP Texas Restoration Funding | AEP Texas | Intersegment Eliminations
ASSETS
Other Noncurrent Assets	(1.0)			(1.0)
Variable Interest Entity, Primary Beneficiary | APCo Appalachian Consumer Rate Relief Funding | AEP Texas
ASSETS
Current Assets				14.2
Net Property, Plant and Equipment				0.0
Other Noncurrent Assets				109.6
TOTAL ASSETS				123.8
LIABILITIES AND EQUITY
Current Liabilities				30.5
Noncurrent Liabilities				91.4
Equity				1.9
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY				123.8
Variable Interest Entity, Primary Beneficiary | APCo Appalachian Consumer Rate Relief Funding | APCo
ASSETS
Current Assets	9.7
Net Property, Plant and Equipment	0.0
Other Noncurrent Assets	86.2
TOTAL ASSETS	95.9
LIABILITIES AND EQUITY
Current Liabilities	30.2
Noncurrent Liabilities	63.8
Equity	1.9
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	95.9
Variable Interest Entity, Primary Beneficiary | Recovery Funding | SWEPCo
ASSETS
Current Assets	9.1
Net Property, Plant and Equipment	0.0
Other Noncurrent Assets	315.3
TOTAL ASSETS	324.4
LIABILITIES AND EQUITY
Current Liabilities	18.4
Noncurrent Liabilities	304.3
Equity	1.7
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	324.4
Variable Interest Entity, Primary Beneficiary | Recovery Funding | APCo
ASSETS
Current Assets				3.4
Net Property, Plant and Equipment				0.0
Other Noncurrent Assets				331.4
TOTAL ASSETS				334.8
LIABILITIES AND EQUITY
Current Liabilities				24.4
Noncurrent Liabilities				308.7
Equity				1.7
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY				334.8
Variable Interest Entity, Primary Beneficiary | Recovery Funding | KPCo
ASSETS
Current Assets	14.2
Net Property, Plant and Equipment	0.0
Other Noncurrent Assets	465.0
TOTAL ASSETS	479.2
LIABILITIES AND EQUITY
Current Liabilities	24.1
Noncurrent Liabilities	452.7
Equity	2.4
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	479.2
Variable Interest Entity, Primary Beneficiary | Recovery Funding | KPCo | Intersegment Eliminations
ASSETS
Other Noncurrent Assets	(16.0)
Variable Interest Entity, Primary Beneficiary | AEP Credit
ASSETS
Current Assets	1,640.7			1,118.3
Net Property, Plant and Equipment	0.0			0.0
Other Noncurrent Assets	10.9			10.5
TOTAL ASSETS	1,651.6			1,128.8
LIABILITIES AND EQUITY
Current Liabilities	1,529.6			1,068.8
Noncurrent Liabilities	1.0			1.0
Equity	121.0			59.0
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	1,651.6			1,128.8
Variable Interest Entity, Primary Beneficiary | Protected Cell of EIS
ASSETS
Current Assets	227.2			218.5
Net Property, Plant and Equipment	0.0			0.0
Other Noncurrent Assets	0.5			0.0
TOTAL ASSETS	227.7			218.5
LIABILITIES AND EQUITY
Current Liabilities	64.7			54.7
Noncurrent Liabilities	94.2			96.0
Equity	68.8			67.8
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	227.7			218.5
Variable Interest Entity, Primary Beneficiary | Transource Energy
ASSETS
Current Assets	63.7			40.2
Net Property, Plant and Equipment	633.0			598.3
Other Noncurrent Assets	6.6			3.5
TOTAL ASSETS	703.3			642.0
LIABILITIES AND EQUITY
Current Liabilities	31.2			57.2
Noncurrent Liabilities	339.8			274.3
Equity	332.3			310.5
TOTAL LIABILITIES, MEZZANINE EQUITY AND TOTAL EQUITY	703.3			642.0
Variable Interest Entity, Primary Beneficiary | AEP Texas Restoration Funding | AEP Texas | Intersegment Eliminations
ASSETS
Other Noncurrent Assets	$ (4.0)			$ (5.0)