Rate Matters Regulated Operations (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
		Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP		$ 23,036.9	$ 23,036.9	$ 22,762.4
Accumulated Depreciation		20,116.6	20,116.6	19,007.6
Net Investment		62,786.4	62,786.4	60,138.1
Materials and Supplies		681.2	681.2	640.7
Asset Retirement Obligation, Revision of Estimate	[1],[2],[3],[4]		170.5
Regulatory Assets, Noncurrent		3,518.8	3,518.8	3,158.8
AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP		0.0	0.0	351.7
Accumulated Depreciation		1,541.5	1,541.5	1,758.1
Net Investment		9,545.0	9,545.0	8,845.1
Materials and Supplies		72.0	72.0	56.7
Asset Retirement Obligation, Revision of Estimate	[2],[3]		(16.8)
Regulatory Assets, Noncurrent		275.4	275.4	280.6
AEP Texas Inc. [Member] | Oklaunion Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Asset Retirement Obligation, Revision of Estimate			(17.0)
AEP Transmission Co [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation		531.8	531.8	402.3
Net Investment		10,389.5	10,389.5	9,490.9
Materials and Supplies		13.6	13.6	13.8
Regulatory Assets, Noncurrent		6.8	6.8	4.2
Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP		6,615.9	6,615.9	6,563.7
Accumulated Depreciation		4,652.7	4,652.7	4,432.3
Net Investment		11,285.8	11,285.8	11,081.9
Materials and Supplies		98.2	98.2	105.2
Asset Retirement Obligation, Revision of Estimate	[2],[3]		195.4
Regulatory Assets, Noncurrent		659.1	659.1	457.2
Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP		5,239.8	5,239.8	5,099.7
Accumulated Depreciation		3,502.4	3,502.4	3,294.3
Net Investment		7,001.8	7,001.8	6,899.7
Materials and Supplies		171.4	171.4	171.3
Regulatory Assets, Noncurrent		450.2	450.2	482.1
Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation		2,350.1	2,350.1	2,263.0
Net Investment		7,302.1	7,302.1	6,907.0
Materials and Supplies		67.0	67.0	52.3
Regulatory Assets, Noncurrent		401.7	401.7	351.8
Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP		1,474.1	1,474.1	1,574.6
Accumulated Depreciation		1,578.3	1,578.3	1,580.1
Net Investment		4,205.5	4,205.5	4,103.3
Materials and Supplies		53.4	53.4	46.8
Asset Retirement Obligation, Revision of Estimate	[2],[3]		(4.8)
Regulatory Assets, Noncurrent		388.9	388.9	375.2
Public Service Co Of Oklahoma [Member] | Oklaunion Generating Station [Member]
Public Utilities, General Disclosures [Line Items]
Asset Retirement Obligation, Revision of Estimate			(5.0)
Public Service Co Of Oklahoma [Member] | Oklaunion Generating Station [Member] | Generating Units Probable of Abandonment [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP		0.0	0.0
Accumulated Depreciation		0.0	0.0
Net Investment		0.0	0.0
Accelerated Depreciation Regulatory Asset	[5]	38.0	38.0
Materials and Supplies		3.4	3.4
Cost of Removal Regulatory Liability		5.2	$ 5.2
Expected Retirement Date			2020
Remaining Recovery Period			27 years
Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP		4,674.7	$ 4,674.7	4,691.4
Accumulated Depreciation		3,092.6	3,092.6	2,873.7
Net Investment		7,113.1	7,113.1	7,095.2
Materials and Supplies		99.2	99.2	94.0
Asset Retirement Obligation, Revision of Estimate	[1],[2],[3]		6.2
Regulatory Assets, Noncurrent		334.8	334.8	222.4
Southwestern Electric Power Co [Member] | Dolet Hills Power Station [Member]
Public Utilities, General Disclosures [Line Items]
Asset Retirement Obligation, Revision of Estimate			21.0
Southwestern Electric Power Co [Member] | Dolet Hills Power Station [Member] | Generating Units Probable of Abandonment [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP		346.7	346.7
Accumulated Depreciation		250.0	250.0
Net Investment		96.7	96.7
Accelerated Depreciation Regulatory Asset	[6]	50.4	50.4
Materials and Supplies		5.8	5.8
Cost of Removal Regulatory Liability		24.0	$ 24.0
Expected Retirement Date			2021
Remaining Recovery Period			27 years
Percent of Fuel Supply Provided by DHLC			100.00%
Asset Retirement Obligation, Revision of Estimate			$ 21.0
Share of Net Investment in Dolet Hills Power Station		153.0	153.0
Dolet Hills Lignite Company Unbilled Fixed Costs		36.0	36.0
Oxbow Unbilled Fixed Costs		10.0	10.0
Dolet Hills Lignite Company and Oxbow Lignite Billings		111.0
Requested Fuel Cost Deferral			36.0
Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[7]	316.6	316.6	181.7
Regulatory Assets Pending Final Regulatory Approval [Member] | Virginia Jurisdictional AMR Meters [Member]
Public Utilities, General Disclosures [Line Items]
Net Investment		52.0	52.0	51.0
Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		16.1	16.1	30.8
Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[7]	28.7	28.7	30.6
Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member] | Virginia Jurisdictional AMR Meters [Member]
Public Utilities, General Disclosures [Line Items]
Net Investment		52.0	52.0	51.0
Regulatory Assets Pending Final Regulatory Approval [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		3.1	3.1	7.7
Regulatory Assets Pending Final Regulatory Approval [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		6.6	6.6	0.1
Regulatory Assets Pending Final Regulatory Approval [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		47.7	47.7	34.6
Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		167.3	167.3	46.3
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Oklaunion Power Station Accelerated Depreciation [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		38.0	38.0	27.4
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Kentucky Deferred Purchase Power Expenses [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		38.5	38.5	30.2
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Plant Retirement Costs - Unrecovered Plant [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		35.2	35.2	35.2
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Dolet Hills Power Station Accelerated Depreciation [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		50.4	50.4	0.0
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | COVID-19
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		2.0	2.0	0.0
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Other Regulatory Assets Not Yet Being Recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		2.2	2.2	0.7
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member] | COVID-19 - Virginia
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		2.0	2.0	0.0
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member] | Plant Retirement Costs - Materials and Supplies [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.0	0.0	0.5
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Public Service Co Of Oklahoma [Member] | Oklaunion Power Station Accelerated Depreciation [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		38.0	38.0	27.4
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | Dolet Hills Power Station Accelerated Depreciation [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		50.4	50.4	0.0
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | Plant Retirement Costs - Unrecovered Plant, Louisiana [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		35.2	35.2	35.2
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | Other Regulatory Assets Not Yet Being Recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		2.2	2.2	0.2
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | COVID-19
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		20.3	20.3	0.0
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Plant Retirement Costs - Asset Retirement Obligation Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		25.9	25.9	30.1
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Storm Related Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		86.3	86.3	7.2
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Asset Retirement Obligation [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		8.7	8.7	7.2
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Vegetation Management Program [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[8]	3.8	3.8	29.4
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Vegetation Management Program [Member] | 2019 Texas Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		26.0	26.0
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Cook Plant Study Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[9]	0.0	0.0	7.6
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Other Regulatory Assets Not Yet Being Recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		5.3	5.3	6.7
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member] | COVID-19
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		10.9	10.9	0.0
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member] | Vegetation Management Program [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[8]	3.8	3.8	29.4
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member] | Vegetation Management Program [Member] | 2019 Texas Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		26.0	26.0
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member] | Other Regulatory Assets Not Yet Being Recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		1.4	1.4	1.4
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member] | Plant Retirement Costs - Asset Retirement Obligation Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		25.9	25.9	30.1
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member] | COVID-19 - West Virginia
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.8	0.8	0.0
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Indiana Michigan Power Co [Member] | COVID-19
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		3.1	3.1	0.0
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Indiana Michigan Power Co [Member] | Cook Plant Study Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[9]	0.0	0.0	7.6
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Indiana Michigan Power Co [Member] | Other Regulatory Assets Not Yet Being Recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.0	0.0	0.1
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Ohio Power Co [Member] | COVID-19
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		2.9	2.9	0.0
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Ohio Power Co [Member] | Storm Related Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		3.6	3.6	0.0
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Ohio Power Co [Member] | Other Regulatory Assets Not Yet Being Recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.1	0.1	0.1
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Public Service Co Of Oklahoma [Member] | COVID-19
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		0.3	0.3	0.0
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Public Service Co Of Oklahoma [Member] | Storm Related Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		9.4	9.4	7.2
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | COVID-19
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		1.7	1.7	0.0
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | Asset Retirement Obligation - Louisiana [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		8.5	8.5	7.2
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | Other Regulatory Assets Not Yet Being Recovered [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		2.0	2.0	3.7
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | Storm Related Costs - Louisiana
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent		$ 67.3	$ 67.3	$ 0.0

[1] Includes ARO related to Sabine and DHLC.

[2] Includes ARO related to asbestos removal.

[3] Includes ARO related to ash disposal facilities.

[4] Includes ARO related to nuclear decommissioning costs for the Cook Plant of $1.78 billion and $1.73 billion as of September 30, 2020 and December 31, 2019, respectively.

[5] In October 2018, PSO changed depreciation rates to utilize the 2020 end-of-life and defer depreciation expense to a regulatory asset for the amount in excess of the previously OCC-approved depreciation rates for Oklaunion Power Station.

[6] In January 2020, SWEPCo changed depreciation rates to utilize the 2026 end-of-life and defer depreciation expense to a regulatory asset for the amount in excess of the previously APSC-approved depreciation rates for Dolet Hills Power Station. In March 2020, SWEPCo changed depreciation rates again to utilize the accelerated 2021 end-of-life.

[7] APCo is currently in the process of retiring and replacing its Virginia jurisdictional Automated Meter Reading (AMR) meters with AMI meters. As of September 30, 2020 and December 31, 2019, APCo has approximately $52 million and $51 million, respectively, of Virginia jurisdictional AMR meters recorded in Total Property, Plant and Equipment - Net on its balance sheets. APCo is pursuing full recovery of these assets through its Virginia depreciation rates. See “2017-2019 Virginia Triennial Review” section below for additional information.

[8] In April 2020, $26 million of deferred expenses were approved for recovery. See “2019 Texas Base Rate Case” section below for additional information.

[9] Approved for recovery in the first quarter of 2020 in the Indiana Base Rate Case.