Rate Matters West Companies (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Oct. 24, 2019	Sep. 30, 2019	Dec. 31, 2018
Public Utilities, General Disclosures [Line Items]
Secured Debt		$ 1,059.4	$ 1,111.4
Construction Work in Progress		5,244.5	4,393.9
AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		978.4	836.2
Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		128.8	94.0
Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		235.0	$ 199.3
AEP Texas Interim Transmission and Distribution Rates [Member]
Public Utilities, General Disclosures [Line Items]
AEP Texas Cumulative Revenues Subject to Review		1,300.0
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		1,300.0
2019 Texas Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 56.0
Requested Return on Equity		10.50%
Refund for Excess ADIT		$ 21.0
Staff Recommended Annual Decrease		$ 63.0
Staff Recommended Return on Common Equity		9.35%
Intervenor Recommended Refund for Excess ADIT Not Subject to Rate Normalization Requirements		$ 115.0
2019 Texas Base Rate Case [Member] | Deregulated Generation Assets and Deferred Fuel [Member]
Public Utilities, General Disclosures [Line Items]
Increase (Decrease) in Income Tax Expense (Benefit) from Tax Reform		$ 113.0
2019 Texas Base Rate Case [Member] | Debt [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Capital Structure		60.00%
Requested Capital Structure		55.00%
2019 Texas Base Rate Case [Member] | Equity [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Capital Structure		40.00%
Requested Capital Structure		45.00%
2019 Texas Base Rate Case [Member] | Interest [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Refund for Excess ADIT Not Subject to Rate Normalization Requirements		$ 2.0
2019 Texas Base Rate Case [Member] | Newly Constructed Transmission Operations Center and Other Service Centers [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		173.0
2019 Texas Base Rate Case [Member] | Storm Costs Hurricane Harvey [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		94.0
2019 Texas Base Rate Case [Member] | Capital Incentives [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		85.0
2019 Texas Base Rate Case [Member] | Capitalized Cross Arms [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		36.0
2019 Texas Base Rate Case [Member] | Capitalized Vegetation Management Expenses[Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		26.0
2019 Texas Base Rate Case [Member] | Capitalized Plant Costs for Third Party Damage [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		21.0
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
Staff Recommended Annual Decrease		$ 63.0
Staff Recommended Return on Common Equity		9.35%
Intervenor Recommended Refund for Excess ADIT Not Subject to Rate Normalization Requirements		$ 115.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Deregulated Generation Assets and Deferred Fuel [Member]
Public Utilities, General Disclosures [Line Items]
Increase (Decrease) in Income Tax Expense (Benefit) from Tax Reform		$ 113.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Debt [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Capital Structure		60.00%
Requested Capital Structure		55.00%
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Equity [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Capital Structure		40.00%
Requested Capital Structure		45.00%
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Interest [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Refund for Excess ADIT Not Subject to Rate Normalization Requirements		$ 2.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Newly Constructed Transmission Operations Center and Other Service Centers [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		173.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Storm Costs Hurricane Harvey [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		94.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Capital Incentives [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		85.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Capitalized Cross Arms [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		36.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Capitalized Vegetation Management Expenses[Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		26.0
2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member] | Capitalized Plant Costs for Third Party Damage [Member]
Public Utilities, General Disclosures [Line Items]
Recommended Disallowance		21.0
Texas Storm Cost Securitization [Member]
Public Utilities, General Disclosures [Line Items]
Excess ADIT		64.0
Secured Debt		235.0
Texas Restoration Carrying Costs		33.0
Debt Carrying Costs Recorded as Reduction to Interest Expense		21.0
Transmission Related Assets to be Recovered at a Later Time		95.0
Texas Storm Cost Securitization [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Excess ADIT		64.0
Secured Debt		235.0
Texas Restoration Carrying Costs		33.0
Debt Carrying Costs Recorded as Reduction to Interest Expense		21.0
Transmission Related Assets to be Recovered at a Later Time		$ 95.0
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		$ 987.0
2018 Oklahoma Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 88.0
Requested Return on Equity		10.30%
Amount Of Increased Depreciation Expense Requested		$ 13.0
Amount of Increase Related to Increased Storm Expense Amortization		7.0
Approved Annual Revenue Increase		$ 46.0
Approved Return on Common Equity		9.40%
Revenue Cap on New Distribution Reliability and Safety Rider		$ 5.0
2018 Oklahoma Base Rate Case [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 88.0
Requested Return on Equity		10.30%
Amount Of Increased Depreciation Expense Requested		$ 13.0
Amount of Increase Related to Increased Storm Expense Amortization		7.0
Approved Annual Revenue Increase		$ 46.0
Approved Return on Common Equity		9.40%
Revenue Cap on New Distribution Reliability and Safety Rider		$ 5.0
2012 Texas Base Rate Case [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] | 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]
Public Utilities, General Disclosures [Line Items]
Property, Plant and Equipment, Net		$ 1,500.0
Texas Jurisdictional Share of Turk Plant		33.00%
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]
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
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]
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
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
Welsh Plant, Units 1 And 3 - Environmental Projects [Member] | Welsh Plant, Units 1 and 3 [Member]
Public Utilities, General Disclosures [Line Items]
Property, Plant and Equipment, Net		612.0
Projected Capital Costs		550.0
Construction Work in Progress		399.0
Total Amount of Recovery Requested Related to Arkansas Retail Jurisdictional Share of Environmental Costs		79.0
Total Amount Of Recovery Requested Related To Louisiana Retail Jurisdictional Share Of Environmental Costs		131.0
Amount of LPSC Approved Eligible Welsh Plant Environmental Control Deferrals		10.0
Amount of LPSC Approved Eligible Welsh Plant Environmental Control Deferred Unrecognized Equity		5.0
Welsh Plant, Units 1 And 3 - Environmental Projects [Member] | Welsh Plant, Units 1 and 3 [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Property, Plant and Equipment, Net		612.0
Projected Capital Costs		550.0
Construction Work in Progress		399.0
Total Amount of Recovery Requested Related to Arkansas Retail Jurisdictional Share of Environmental Costs		79.0
Total Amount Of Recovery Requested Related To Louisiana Retail Jurisdictional Share Of Environmental Costs		131.0
Amount of LPSC Approved Eligible Welsh Plant Environmental Control Deferrals		10.0
Amount of LPSC Approved Eligible Welsh Plant Environmental Control Deferred Unrecognized Equity		5.0
2019 Arkansas Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 75.0
Requested Return on Equity		10.50%
Requested Annual Net Increase		$ 58.0
Requested Additional Vegetation Management Expenses		12.0
2019 Arkansas Base Rate Case [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		$ 75.0
Requested Return on Equity		10.50%
Requested Annual Net Increase		$ 58.0
Requested Additional Vegetation Management Expenses		$ 12.0
FERC Transmission Complaint - AEP SPP Participants [Member]
Public Utilities, General Disclosures [Line Items]
Approved Return on Common Equity		10.70%
Intervenor Recommended Return On Common Equity Range		8.36%
Second Intervenor Recommended Return on Common Equity		8.71%
Return On Common Equity Per Settlement Agreement		10.00%
Return on Common Equity Inclusive of RTO Per Settlement Agreement		10.50%
RTO Incentive Adder Per Settlement Agreement		0.50%
Minimum [Member] | 2019 Texas Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity		9.00%
Minimum [Member] | 2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Return on Common Equity		9.00%
Maximum [Member] | 2019 Texas Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Annual Decrease Maximum		$ 159.0
Intervenor Recommended Return on Common Equity		9.20%
Recommended Disallowance		$ 450.0
Maximum [Member] | 2019 Texas Base Rate Case [Member] | AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Annual Decrease Maximum		$ 159.0
Intervenor Recommended Return on Common Equity		9.20%
Recommended Disallowance		$ 450.0
Subsequent Event [Member] | 2019 Arkansas Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Adjusted Requested Annual Increase	$ 67.0
Settlement Agreement Annual Increase	$ 53.0
Settlement Agreement Return on Common Equity	9.45%
Settlement Agreement Annual Increase Net of Current Riders	$ 24.0
Settlement Agreement Amount of Increased Depreciation	6.0
Subsequent Event [Member] | 2019 Arkansas Base Rate Case [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Adjusted Requested Annual Increase	67.0
Settlement Agreement Annual Increase	$ 53.0
Settlement Agreement Return on Common Equity	9.45%
Settlement Agreement Annual Increase Net of Current Riders	$ 24.0
Settlement Agreement Amount of Increased Depreciation	$ 6.0