Rate Matters West Companies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) customer	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Public Utilities, General Disclosures [Line Items]
Other Asset Impairment Charges	$ 0.0	$ 156.4	$ 70.6
Total Property, Plant and Equipment, Net	63,901.6	60,138.1
AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Other Asset Impairment Charges	0.0	32.5	0.0
Total Property, Plant and Equipment, Net	9,813.6	8,845.1
Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Total Property, Plant and Equipment, Net	4,320.0	4,103.3
Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Provision for Refund	(2.0)	(32.0)	$ (6.7)
Total Property, Plant and Equipment, Net	7,088.2	$ 7,095.2
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
Approved Annual Revenue Decrease	$ 40.0
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%
Refund for Excess ADIT Associated with Certain Depreciable Property	$ 275.0
Other Asset Impairment Charges	33.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Excess ADIT and Excess Federal Income Taxes to Distribution Customers [Member]
Public Utilities, General Disclosures [Line Items]
Item to be Refunded in Commission Order	77.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Excess ADIT and Excess Federal Income Taxes to Transmission Customers [Member]
Public Utilities, General Disclosures [Line Items]
Item to be Refunded in Commission Order	31.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Previously Collected Rates Subject to Reconciliation [Member]
Public Utilities, General Disclosures [Line Items]
Item to be Refunded in Commission Order	30.0
Provision for Refund	30.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Vegetation Management
Public Utilities, General Disclosures [Line Items]
Approved Item in Commission Order	26.0
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
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
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
AEP Texas Interim Transmission and Distribution Rates [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
AEP Texas Cumulative Revenues Subject to Review	79.0
ETT Interim Transmission Rates [Member]
Public Utilities, General Disclosures [Line Items]
Approved Annual Revenue Decrease	$ 8.0
Parent Ownership Interest In ETT	50.00%
AEP Share Of ETT Cumulative Revenues Subject To Review	$ 1,200.0
Approved interim transmission cost of service line item decrease	2.0
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	$ 1,400.0
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%
Approved Return on Common Equity	9.60%
Requested Net Increase in Texas Annual Revenues	$ 69.0
Approved Net Increase in Texas Annual Revenues	50.0
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
Refund for Over Collections	$ 6.0
Hurricane Laura [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Customers without Power | customer	130,000
Incremental Other Operation and Maintenance Expenses	$ 84.0
Capitalized Storm Costs	23.0
Hurricane Laura [Member] | Southwestern Electric Power Co [Member] | Louisiana Jurisdiction [Member]
Public Utilities, General Disclosures [Line Items]
Incremental Other Operation and Maintenance Expenses	$ 82.0
Hurricane Delta [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Customers without Power | customer	23,000
Incremental Other Operation and Maintenance Expenses	$ 17.0
Capitalized Storm Costs	2.0
2020 Texas Base Rate Case [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase	$ 105.0
Requested Return on Equity	10.35%
Requested Net Annual Increase	$ 90.0
Amount of Increase Related to Vegetation Management	5.0
Amount of Increase Related to Annual Depreciation Expense	10.0
Amount of Increase Related to Storm Catastrophe Reserve	2.0
Requested Recovery of Dolet Hills Power Station	45.0
2020 Louisiana Base Rate Case [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase	$ 134.0
Requested Return on Equity	10.35%
Amount of Increase Related to Annual Depreciation Expense	$ 32.0
Amount of Increase Related to Recovering Deferred Hurricane Costs	10.0
OKTCo Radial Asset Transfer [Member] | Public Service Co Of Oklahoma [Member] | Net Book Value of Radial Assets [Member]
Public Utilities, General Disclosures [Line Items]
Total Property, Plant and Equipment, Net	$ 60.0