Rate Matters West Companies (Details) - USD ($) $ in Millions		1 Months Ended	6 Months Ended
		Jul. 25, 2019	Jun. 30, 2019	Dec. 31, 2018
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress			$ 4,944.5	$ 4,393.9
AEP Texas Inc. [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress			963.0	836.2
Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress			101.7	94.0
Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress			209.4	$ 199.3
AEP Texas Interim Transmission and Distribution Rates [Member]
Public Utilities, General Disclosures [Line Items]
AEP Texas Cumulative Revenues Subject to Review			1,200.0
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			1,200.0
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
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
Texas Storm Cost Securitization [Member]
Public Utilities, General Disclosures [Line Items]
Annual Recovery of Storm Costs through Base Rates			1.0
AEP Texas Total Storm-Related Costs			210.0
Requested Distribution-Related System Restoration Costs			230.0
Distribution-Related System Restoration Costs			264.6
Estimated Carrying Costs	[1]		26.9
Up-front Qualified Costs			4.4
Total Distribution-Related System Restoration Costs			295.9
Insurance Proceeds and Government Grants			(3.1)
Excess ADIT	[2]		(63.5)
Securitization Request for Distribution Related Assets			229.3
Debt Carrying Costs Recorded as Reduction to Interest Expense			16.0
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]
Annual Recovery of Storm Costs through Base Rates			1.0
AEP Texas Total Storm-Related Costs			210.0
Requested Distribution-Related System Restoration Costs			230.0
Distribution-Related System Restoration Costs			264.6
Estimated Carrying Costs	[1]		26.9
Up-front Qualified Costs			4.4
Total Distribution-Related System Restoration Costs			295.9
Insurance Proceeds and Government Grants			(3.1)
Excess ADIT	[2]		(63.5)
Securitization Request for Distribution Related Assets			229.3
Debt Carrying Costs Recorded as Reduction to Interest Expense			16.0
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			$ 1,000.0
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			617.0
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			617.0
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%
Subsequent Event [Member] | 2019 Arkansas Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Annual Rate Increase		$ 20.0
Staff Recommended Return on Common Equity		9.50%
Subsequent Event [Member] | 2019 Arkansas Base Rate Case [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Staff Recommended Annual Rate Increase		$ 20.0
Staff Recommended Return on Common Equity		9.50%
Subsequent Event [Member] | Minimum [Member] | 2019 Arkansas Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Annual Rate Increase		$ 21.0
Intervenor Recommended Return on Common Equity		9.00%
Subsequent Event [Member] | Minimum [Member] | 2019 Arkansas Base Rate Case [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Annual Rate Increase		$ 21.0
Intervenor Recommended Return on Common Equity		9.00%
Subsequent Event [Member] | Maximum [Member] | 2019 Arkansas Base Rate Case [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Annual Rate Increase		$ 25.0
Intervenor Recommended Return on Common Equity		9.20%
Subsequent Event [Member] | Maximum [Member] | 2019 Arkansas Base Rate Case [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Annual Rate Increase		$ 25.0
Intervenor Recommended Return on Common Equity		9.20%

[1] Amount includes $16 million of debt carrying costs recorded as a reduction to Interest Expense in the second quarter of 2019.

[2] As part of the financing order, AEP Texas agreed to offset a portion of their Excess ADIT that is not subject to rate normalization requirements against the total distribution-related system restoration costs.