Rate Matters West Companies (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	May 06, 2020	Mar. 31, 2020	Dec. 31, 2019
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		$ 4,511.5	$ 4,319.8
AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		747.0	763.9
Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		144.9	133.4
Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		232.7	$ 216.9
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 56.0
Requested Return on Equity		10.50%
Refund for Excess ADIT		$ 21.0
Other Asset Impairment Charges		33.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Rate Case Expense [Member]
Public Utilities, General Disclosures [Line Items]
Write-off of Regulatory Expense		4.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Amount of 2019 Investments [Member]
Public Utilities, General Disclosures [Line Items]
Other Asset Impairment Charges		$ 10.0
ETT Interim Transmission Rates [Member]
Public Utilities, General Disclosures [Line Items]
Parent Ownership Interest In ETT		50.00%
AEP Share Of ETT Cumulative Revenues Subject To Review		$ 1,100.0
2012 Texas Base Rate Case [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
2013 Reversal Of Previously Recorded Regulatory Disallowances		114.0
Resulting Approved Base Rate Increase		52.0
2012 Texas Base Rate Case [Member] | Turk Generating Plant [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Property, Plant and Equipment, Net		$ 1,500.0
Texas Jurisdictional Share of Turk Plant		33.00%
2016 Texas Base Rate Case [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Return on Equity		10.00%
Requested Net Increase in Texas Annual Revenues		$ 69.0
Approved Net Increase in Texas Annual Revenues		$ 50.0
Approved Return on Common Equity		9.60%
Approved Additional Vegetation Management Expenses		$ 2.0
Impairment Charge Total		19.0
Impairment Charge Welsh Plant, Unit 2		7.0
Impairment Charge Disallowed Plant Investments		12.0
Additional Revenues Recognized to be Surcharged to Customers		32.0
Additional Recognized Expenses Consisting Primarily of Depreciation and Vegetation Management		7.0
Louisiana 2018 Formula Rate Filing [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		28.0
Adjusted Requested Annual Increase		18.0
Refund for Current Year Tax Reform Rate Change		11.0
Additional Refund for Current Year Tax Reform Rate Change		4.0
Staff Recommended Annual Rate Increase		14.0
Subsequent Event [Member] | 2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Approved Annual Revenue Decrease	$ 40.0
Refund for Excess ADIT Associated with Certain Depreciable Property	$ 275.0
Approved Return on Common Equity	9.40%
Public Utilities, Approved Debt Capital Structure, Percentage	57.50%
Public Utilities, Approved Equity Capital Structure, Percentage	42.50%
Subsequent Event [Member] | 2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Capital Investments [Member]
Public Utilities, General Disclosures [Line Items]
Disallowed Item in Commission Order	$ 23.0
Subsequent Event [Member] | 2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Rate Case Expense [Member]
Public Utilities, General Disclosures [Line Items]
Disallowed Item in Commission Order	4.0
Capitalized Vegetation Management Expenses [Member] | Subsequent Event [Member] | 2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Approved Item in Commission Order	26.0
Excess ADIT and Excess Federal Income Taxes to Distribution Customers [Member] | Subsequent Event [Member] | 2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Item to be Refunded in Commission Order	77.0
Excess ADIT and Excess Federal Income Taxes to Transmission Customers [Member] | Subsequent Event [Member] | 2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Item to be Refunded in Commission Order	31.0
Previously Collected Rates Subject to Reconciliation [Member] | 2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Provision for Refund		$ 30.0
Previously Collected Rates Subject to Reconciliation [Member] | Subsequent Event [Member] | 2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Item to be Refunded in Commission Order	$ 30.0