Rate Matters Regulated Operations (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended
		Apr. 22, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP			$ 23,186.5		$ 23,133.9
Accumulated Depreciation			20,916.8		20,411.4
Net Investment			64,696.1		63,901.6
Materials and Supplies			683.3		680.6
Regulatory Assets, Noncurrent			4,885.6		3,527.0
Customers			763.0		613.6
Proceeds from Issuance of Debt	[1]		1,964.6
February 2021 Storm Event
Public Utilities, General Disclosures [Line Items]
Capitalized Storm Costs			56.6
Incremental Other Operation and Maintenance Expenses			6.0
Deferred Storm Costs as a Regulated Asset			130.9
Total Estimated February 2021 Storm Restoration Expenditures			193.5
February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Customers			88.4
Total Estimated 2021 February Winter Storm Fuel Costs			1,273.4
February 2021 Severe Storm Fuel Costs | 364 Day Term Loan
Public Utilities, General Disclosures [Line Items]
Proceeds from Issuance of Debt			500.0
AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation			1,565.9		1,529.3
Net Investment			9,975.8		9,813.6
Materials and Supplies			69.8		70.0
Regulatory Assets, Noncurrent			274.5		266.8
Customers			129.3		112.8
AEP Transmission Co [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation			623.6		572.8
Net Investment			11,070.4		10,772.8
Materials and Supplies			8.8		8.5
Regulatory Assets, Noncurrent			14.0		15.1
Customers			25.6		22.9
Capital Contribution from Member			124.0	$ 185.0
AEP Transmission Co [Member] | Additional Paid-in Capital [Member]
Public Utilities, General Disclosures [Line Items]
Capital Contribution from Member			124.0	$ 185.0
Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP			6,643.9		6,633.7
Accumulated Depreciation			4,802.0		4,716.2
Net Investment			11,455.2		11,394.1
Materials and Supplies			101.2		99.6
Regulatory Assets, Noncurrent			727.1		686.3
Customers			146.4		142.8
Appalachian Power Co [Member] | Senior Unsecured Notes [Member]
Public Utilities, General Disclosures [Line Items]
Proceeds from Issuance of Debt	[1]		500.0
Appalachian Power Co [Member] | February 2021 Storm Event | Virginia
Public Utilities, General Disclosures [Line Items]
Capitalized Storm Costs			5.4
Incremental Other Operation and Maintenance Expenses			2.2
Deferred Storm Costs as a Regulated Asset			5.6
Total Estimated February 2021 Storm Restoration Expenditures			13.2
Appalachian Power Co [Member] | February 2021 Storm Event | West Virginia
Public Utilities, General Disclosures [Line Items]
Capitalized Storm Costs			19.6
Incremental Other Operation and Maintenance Expenses			0.0
Deferred Storm Costs as a Regulated Asset			39.1
Total Estimated February 2021 Storm Restoration Expenditures			58.7
Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP			5,302.4		5,264.7
Accumulated Depreciation			3,647.3		3,552.5
Net Investment			7,063.2		7,052.3
Materials and Supplies			172.8		175.8
Regulatory Assets, Noncurrent			403.4		404.8
Customers			32.7		44.0
Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Accumulated Depreciation			2,385.4		2,350.0
Net Investment			7,565.7		7,452.1
Materials and Supplies			67.3		66.9
Regulatory Assets, Noncurrent			392.3		385.8
Customers			66.1		50.0
Ohio Power Co [Member] | Senior Unsecured Notes [Member]
Public Utilities, General Disclosures [Line Items]
Proceeds from Issuance of Debt	[1]		450.0
Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP			1,481.7		1,480.7
Accumulated Depreciation			1,626.0		1,605.6
Net Investment			4,343.3		4,320.0
Materials and Supplies			53.3		54.0
Regulatory Assets, Noncurrent			1,067.6		375.0
Customers			37.7		30.8
Capital Contribution from Member			425.0
Public Service Co Of Oklahoma [Member] | Additional Paid-in Capital [Member]
Public Utilities, General Disclosures [Line Items]
Capital Contribution from Member			425.0
Public Service Co Of Oklahoma [Member] | Other Long Term Debt [Member]
Public Utilities, General Disclosures [Line Items]
Proceeds from Issuance of Debt	[1]		500.0
Public Service Co Of Oklahoma [Member] | February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Customers			0.0
Total Estimated 2021 February Winter Storm Fuel Costs			688.7
Public Service Co Of Oklahoma [Member] | Northeastern Plant, Unit 3 | Generating Units Probable of Abandonment [Member]
Public Utilities, General Disclosures [Line Items]
Net Investment			190.5
Accelerated Depreciation Regulatory Asset			114.8
Cost of Removal Regulatory Liability	[2]		$ 19.8
Expected Retirement Date	[3]		2026
Depreciation	[4]		$ 14.9
Public Service Co Of Oklahoma [Member] | February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Capital Contribution from Member			425.0
Public Service Co Of Oklahoma [Member] | February 2021 Severe Storm Fuel Costs | Subsequent Event [Member]
Public Utilities, General Disclosures [Line Items]
Capital Contribution from Member		$ 125.0
Public Service Co Of Oklahoma [Member] | February 2021 Severe Storm Fuel Costs | Other Long Term Debt [Member]
Public Utilities, General Disclosures [Line Items]
Proceeds from Issuance of Debt			100.0
Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Gross Investment Including CWIP			4,679.8		4,681.4
Accumulated Depreciation			3,275.2		3,158.5
Net Investment			7,047.3		7,088.2
Materials and Supplies			93.0		95.8
Regulatory Assets, Noncurrent			988.2		403.1
Net Over-Recovered Fuel Costs			20.0
Customers			119.4		27.1
Capital Contribution from Member			100.0
Southwestern Electric Power Co [Member] | Additional Paid-in Capital [Member]
Public Utilities, General Disclosures [Line Items]
Capital Contribution from Member			100.0
Southwestern Electric Power Co [Member] | Senior Unsecured Notes [Member]
Public Utilities, General Disclosures [Line Items]
Proceeds from Issuance of Debt	[1]		500.0
Southwestern Electric Power Co [Member] | 2020 Texas Fuel Reconciliation
Public Utilities, General Disclosures [Line Items]
Amount of Fuel Costs Under Review			1,700.0
Southwestern Electric Power Co [Member] | 2020 Texas Fuel Reconciliation | TEXAS
Public Utilities, General Disclosures [Line Items]
Amount of Fuel Costs Under Review			616.0
Recommended Disallowance from Staff or Intervenors			125.0
Southwestern Electric Power Co [Member] | February 2021 Storm Event
Public Utilities, General Disclosures [Line Items]
Capitalized Storm Costs			4.9
Incremental Other Operation and Maintenance Expenses			0.0
Deferred Storm Costs as a Regulated Asset			42.1
Total Estimated February 2021 Storm Restoration Expenditures			47.0
Southwestern Electric Power Co [Member] | February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Customers			88.4
Total Estimated 2021 February Winter Storm Fuel Costs			$ 584.7
Southwestern Electric Power Co [Member] | February 2021 Severe Storm Fuel Costs | Arkansas
Public Utilities, General Disclosures [Line Items]
Requested Weighted Average Cost of Capital			6.05%
Southwestern Electric Power Co [Member] | Dolet Hills Power Station [Member] | Generating Units Probable of Abandonment [Member]
Public Utilities, General Disclosures [Line Items]
Net Investment			$ 51.3
Accelerated Depreciation Regulatory Asset			92.6
Cost of Removal Regulatory Liability			$ 1.1
Expected Retirement Date	[5]		2021
Depreciation	[4]		$ 7.7
Southwestern Electric Power Co [Member] | Dolet Hills Power Station and Related Fuel Operations
Public Utilities, General Disclosures [Line Items]
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			150.0
Dolet Hills Lignite Company Unbilled Fixed Costs			126.0
Recovery of 2021 Dolet Hills Fuel Costs			20.0
Approved Deferral of Dolet Hills Fuel Costs			30.0
Southwestern Electric Power Co [Member] | Pirkey Power Plant and Related Fuel Operations
Public Utilities, General Disclosures [Line Items]
Share of Net Investment in Pirkey Power Plant			209.0
Pirkey Power Plant and Sabine Unbilled Fixed Costs			163.0
Southwestern Electric Power Co [Member] | Pirkey Generating Station (Unit No. 1) | Generating Units Probable of Abandonment [Member]
Public Utilities, General Disclosures [Line Items]
Net Investment			178.3
Accelerated Depreciation Regulatory Asset			30.8
Cost of Removal Regulatory Liability			$ 18.4
Expected Retirement Date	[6]		2023
Depreciation	[4]		$ 13.7
Southwestern Electric Power Co [Member] | Welsh Plant Unit 1 and 3 | Generating Units Probable of Abandonment [Member]
Public Utilities, General Disclosures [Line Items]
Net Investment			528.8
Accelerated Depreciation Regulatory Asset			14.2
Cost of Removal Regulatory Liability	[7]		$ 11.4
Expected Retirement Date	[8]		2028
Depreciation	[4]		$ 33.3
Southwestern Electric Power Co [Member] | February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Capital Contribution from Member			100.0
Southwestern Electric Power Co [Member] | February 2021 Severe Storm Fuel Costs | Senior Unsecured Notes [Member]
Public Utilities, General Disclosures [Line Items]
Proceeds from Issuance of Debt			500.0
Kentucky Power Co [Member] | February 2021 Storm Event
Public Utilities, General Disclosures [Line Items]
Capitalized Storm Costs			26.7
Incremental Other Operation and Maintenance Expenses			3.8
Deferred Storm Costs as a Regulated Asset			44.1
Total Estimated February 2021 Storm Restoration Expenditures			74.6
Regulatory Assets Pending Final Regulatory Approval [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			1,833.6		442.2
Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			46.0		32.9
Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			92.9		43.8
Regulatory Assets Pending Final Regulatory Approval [Member] | Indiana Michigan Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			3.4		4.3
Regulatory Assets Pending Final Regulatory Approval [Member] | Ohio Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			8.4		8.4
Regulatory Assets Pending Final Regulatory Approval [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			748.3		50.5
Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			835.8		247.3
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[9]		1,185.0
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			34.0		34.4
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			42.8		41.3
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
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			92.6		71.2
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			37.5		26.4
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[10]		1,185.0		0.0
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Pirkey Power Plant Accelerated Depreciation
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			30.8		12.2
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member] | Adavanced Metering System
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			16.4		16.3
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			4.0		3.7
Regulatory Assets Currently 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		0.5
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Public Service Co Of Oklahoma [Member] | February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[9]		688.7
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			34.0		34.4
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Public Service Co Of Oklahoma [Member] | February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[11]		688.7		0.0
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[9]		496.3
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			92.6		71.2
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
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			2.8		2.2
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | February 2021 Severe Storm Fuel Costs
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent	[12]		496.3		0.0
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | Pirkey Power Plant Accelerated Depreciation
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			30.8		12.2
Regulatory Assets Currently Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Southwestern Electric Power Co [Member] | Welsh Unit 1 and 3 Accelerated Depreciation
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			14.2		3.6
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			19.5		24.9
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
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			285.0		134.2
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			33.0		27.2
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Environmental Expense Deferral - Virginia
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			12.3		9.3
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			8.6		10.5
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member] | Storm Related Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			10.5		0.8
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			3.8		3.8
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			2.6		1.5
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | AEP Texas Inc. [Member] | Texas Retail Electric Provider Bad Debt Expense
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			4.1		0.0
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
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member] | Storm Related Costs [Member]
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			49.1		3.4
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			1.6		1.5
Regulatory Assets Currently Not Earning Return [Member] | Regulatory Assets Pending Final Regulatory Approval [Member] | Appalachian Power Co [Member] | Environmental Expense Deferral - Virginia
Public Utilities, General Disclosures [Line Items]
Regulatory Assets, Noncurrent			12.3		9.3
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			2.8		3.8
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			0.6		0.0
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			1.5		4.4
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			6.8		4.0
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		0.0
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			0.8		0.3
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			24.8		15.8
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			9.4		9.1
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			15.4		14.5
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			$ 139.1		$ 99.3

[1] Amounts indicated on the statements of cash flows are net of issuance costs and premium or discount and will not tie to the issuance amounts.

[2] Includes Northeastern Plant, Unit 4, which was retired in 2016. Removal of Northeastern Plant, Unit 4, will be performed with Northeastern Plant, Unit 3, after retirement.

[3] Northeastern Plant, Unit 3 is currently being recovered through 2040.

[4] Represents the amount of annual depreciation that has been collected from customers over the prior 12-month period

[5] Dolet Hills Power Station is currently being recovered through 2026 in the Louisiana jurisdiction and through 2046 in the Arkansas and Texas jurisdictions.

[6] Pirkey Power Plant is currently being recovered through 2025 in the Louisiana jurisdiction and through 2045 in the Arkansas and Texas jurisdictions.

[7] Includes Welsh Plant, Unit 2, which was retired in 2016. Removal of Welsh Plant, Unit 2, will be performed with Welsh Plant, Units 1 and 3, after retirement.

[8] Unit 1 is being recovered through 2027 in the Louisiana jurisdiction and through 2037 in the Arkansas and Texas jurisdictions. Unit 3 is being recovered through 2032 in the Louisiana jurisdiction and through 2042 in the Arkansas and Texas jurisdictions.

[9] (a) These costs were deferred as regulatory assets as of March 31, 2021.

[10] PSO and SWEPCo have active fuel clauses that allow for the recovery of prudently incurred fuel and purchased power expenses. However, the recovery of these costs from customers may be extended over longer than usual time periods to mitigate the impact on customer bills. See “Impacts of Severe Winter Weather” section below for additional information.

[11] PSO has an active fuel clause that allows for the recovery of prudently incurred fuel and purchased power expenses. However, the recovery of these costs from customers may be extended over longer than usual time periods to mitigate the impact on customer bills. See “Impacts of Severe Winter Weather” section below for additional information.

[12] SWEPCo has an active fuel clause that allows for the recovery of prudently incurred fuel and purchased power expenses. However, the recovery of these costs from customers may be extended over longer than usual time periods to mitigate the impact on customer bills. See “Impacts of Severe Winter Weather” section below for additional information