Rate Matters West Companies (Details) $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($) customer	Dec. 31, 2020 USD ($)
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	$ 4,151.0	$ 4,025.7
AEP Share of Independence Energy Connection Capital Costs	79.0
AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	539.4	614.1
Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	127.7	128.7
Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	195.5	$ 228.3
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	$ 229.0
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	$ 1,300.0
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
Estimated Reduced Annual Revenues	15.0
2012 Texas Base Rate Case [Member] | Southwestern Electric Power Co [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Turk AFUDC Disallowance	80.0
Estimated Turk AFUDC Refunds	0.0
2012 Texas Base Rate Case [Member] | Southwestern Electric Power Co [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Estimated Turk AFUDC Disallowance	100.0
Estimated Turk AFUDC Refunds	$ 160.0
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
Hurricane Laura [Member] | Southwestern Electric Power Co [Member] | Louisiana Jurisdiction [Member]
Public Utilities, General Disclosures [Line Items]
Incremental Other Operation and Maintenance Expenses	89.0
Capitalized Storm Costs	$ 18.0
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	$ 92.0
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	$ 18.0
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
Revised Requested Annual Increase	100.0
Revised Requested Net Annual Increase	85.0
Proposal for Decision Rate Increase	$ 41.0
Proposal for Decision Return on Equity	9.45%
2020 Texas Base Rate Case [Member] | Southwestern Electric Power Co [Member] | Capitalized Vegetation Management Expenses [Member]
Public Utilities, General Disclosures [Line Items]
Proposal for Decision Disallowance	$ 5.0
2020 Texas Base Rate Case [Member] | Southwestern Electric Power Co [Member] | Catastrophe Storm Reserve
Public Utilities, General Disclosures [Line Items]
Proposal for Decision Disallowance	2.0
2020 Louisiana Base Rate Case | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase	134.0
Staff Recommended Annual Rate Increase	$ 6.0
Requested Return on Equity	10.35%
Amount of Increase Related to Annual Depreciation Expense	$ 32.0
Staff Recommended Return on Common Equity	9.10%
Storm Expenses to be Requested in Separate Filing	$ 152.0
Revised Requested Annual Increase	114.0
Requested Annual Increase in Rebuttal	$ 95.0
2020 Louisiana Base Rate Case | Southwestern Electric Power Co [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity	9.35%
2020 Louisiana Base Rate Case | Southwestern Electric Power Co [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity	9.80%
2021 Oklahoma Base Rate Case | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase	$ 172.0
Requested Return on Equity	10.00%
Amount of Increase Related to Annual Depreciation Expense	$ 57.0
Amount of Increase Related to SPP Expenses	31.0
Proposed Grid Transformation Plan	100.0
Revised Requested Annual Increase	128.0
Proposed Settlement Annual Rate Increase	$ 51.0
Proposed Settlement Agreement ROE	9.40%
Recommended Disallowance from Staff or Intervenors	$ 41.0
2021 Oklahoma Base Rate Case | Public Service Co Of Oklahoma [Member] | Minimum [Member]
Public Utilities, General Disclosures [Line Items]
Staff and Intervenor Recommended Base Rate Increase/Decrease	$ 44.0
Staff and Intervenor Recommended Return on Equity	9.00%
2021 Oklahoma Base Rate Case | Public Service Co Of Oklahoma [Member] | Maximum [Member]
Public Utilities, General Disclosures [Line Items]
Staff and Intervenor Recommended Base Rate Increase/Decrease	$ 74.0
Staff and Intervenor Recommended Return on Equity	9.40%
2021 Oklahoma Base Rate Case | Oklaunion Power Station Accelerated Depreciation [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Amount of Increase Related to Annual Depreciation Expense	$ 45.0
2021 Arkansas Rate Case | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase	$ 85.0
Requested Return on Equity	10.35%
Amount of Increase Related to Annual Depreciation Expense	$ 14.0
Amount of Increase Related to SPP Expenses	6.0
Amount of Increase Related to North Central Wind Facilities	$ 41.0