The 2013 reversal of previously recorded regulatory disallowances.

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AEP's share of ETT's cumulative revenues, subject to review, based upon interim rate increases received from 2009 through 2015.

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Amount of requested increase related to environmental controls to be installed at certain plants.

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Amount of increased depreciation expense requested.

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Amount of interim rates implemented in January 2015, subject to refund, as approved by the LPSC in partial settlement agreement.

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Amount of the requested increase related to environmental consumable costs included in the FAC.

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Amount of recovery requested related to Arkansas retail jurisdiction share of environmental costs incurred.

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Base rate increase per the settlement agreement.

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Fuel rate decrease per the settlement agreement.

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Future incremental purchased capacity and energy costs that will be incurred related to the environmental compliance plan.

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Intervenor recommended decrease to annual revenue.

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Intervenor recommended increase to depreciation expense.

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Intervenor recommended return on common equity.

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- Definition

Louisiana jurisdictional share of the Turk Plant.

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No definition available.

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Net increase in Louisiana total rates per the settlement agreement.

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Parents equity ownership interest in ETT.

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Projected capital costs of property, plant and equipment.

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Reduction to the requested revenue increase as approved by the LPSC in the stipulation agreement.

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No definition available.

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Requested annual increase.

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Requested base rate increase.

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Requested revenue requirement.

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Requested total annual increase.

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- Definition

The resulting annual base rate increase subsequent to recent rulings by the PUCT.

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No definition available.

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Return on common equity per the settlement agreement.

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No definition available.

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- Definition

Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Amount of public utility's interim rate increase (decrease) allowed while waiting final decision of regulatory agency.

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Period end amount of total net PPE.

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Percentage of public utility's requested return on equity.

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Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

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Rate Matters - West Companies (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 28, 2016	Mar. 31, 2016	Dec. 31, 2015
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		$ 3,806.3	$ 3,903.9
Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		145.7	315.3
Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress		562.8	$ 751.3
Welsh Plant, Unit 2 [Member]
Public Utilities, General Disclosures [Line Items]
Property, Plant and Equipment, Net		84.0
Welsh Plant, Unit 2 [Member] \| Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Property, Plant and Equipment, Net		$ 84.0
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		$ 468.0
Louisiana 2012 Formula Rate Filing [Member]
Public Utilities, General Disclosures [Line Items]
Louisiana Jurisdictional Share of the Turk Plant		29.00%
Net Increase in Louisiana Total Rates per the Settlement Agreement		$ 2.0
Base Rate Increase per the Settlement Agreement		85.0
Fuel Rate Decrease per the Settlement Agreement		$ 83.0
Return on Common Equity per the Settlement Agreement		10.00%
Reduction To Requested Revenue Increase As Approved In Stipulation Agreement		$ 3.0
Louisiana 2012 Formula Rate Filing [Member] \| Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Louisiana Jurisdictional Share of the Turk Plant		29.00%
Net Increase in Louisiana Total Rates per the Settlement Agreement		$ 2.0
Base Rate Increase per the Settlement Agreement		85.0
Fuel Rate Decrease per the Settlement Agreement		$ 83.0
Return on Common Equity per the Settlement Agreement		10.00%
Reduction To Requested Revenue Increase As Approved In Stipulation Agreement		$ 3.0
Louisiana 2014 Formula Rate Filing [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		5.0
Additional Requested Annual Increase		15.0
Requested Total Annual Increase		20.0
Amount Of Interim Rates Implemented In January 2015 As Approved In Partial Settlement Agreement		15.0
Louisiana 2014 Formula Rate Filing [Member] \| Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		5.0
Additional Requested Annual Increase		15.0
Requested Total Annual Increase		20.0
Amount Of Interim Rates Implemented In January 2015 As Approved In Partial Settlement Agreement		15.0
Louisiana 2015 Formula Rate Filing [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		14.0
Louisiana 2015 Formula Rate Filing [Member] \| Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		14.0
Oklahoma Base Rate Case - 2015 [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		137.0
Requested Base Rate Increase		89.0
Amount Of Increased Depreciation Expense Requested		48.0
Amount Of Increase Related To Environmental Controls		44.0
Amount Of Requested Increase Related To Environmental Consumable Costs In Fuel Adjustment Clause		$ 4.0
Requested Return on Equity		10.50%
Future Incremental Purchased Capacity And Energy Costs Related To Environmental Projects		$ 35.0
Interim Annual Base Rate Increase		75.0
Oklahoma Base Rate Case - 2015 [Member] \| Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Requested Annual Increase		137.0
Requested Base Rate Increase		89.0
Amount Of Increased Depreciation Expense Requested		48.0
Amount Of Increase Related To Environmental Controls		44.0
Amount Of Requested Increase Related To Environmental Consumable Costs In Fuel Adjustment Clause		$ 4.0
Requested Return on Equity		10.50%
Future Incremental Purchased Capacity And Energy Costs Related To Environmental Projects		$ 35.0
Interim Annual Base Rate Increase		75.0
Oklahoma Base Rate Case - 2015 [Member] \| Northeastern Plant, Unit 4 [Member]
Public Utilities, General Disclosures [Line Items]
Property, Plant and Equipment, Net		94.0
Oklahoma Base Rate Case - 2015 [Member] \| Northeastern Plant, Unit 4 [Member] \| Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Property, Plant and Equipment, Net		94.0
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
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
Welsh Plant, Units 1 and 3 - Environmental Projects [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs		900.0
Construction Work in Progress		372.0
Remaining Contractual Construction Obligations		28.0
Amount of Recovery Requested Related to Arkansas Retail Jurisdictional Share of Environmental Costs		69.0
Welsh Plant, Units 1 and 3 - Environmental Projects [Member] \| Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs		900.0
Construction Work in Progress		372.0
Remaining Contractual Construction Obligations		28.0
Amount of Recovery Requested Related to Arkansas Retail Jurisdictional Share of Environmental Costs		69.0
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		606.0
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		606.0
Minimum [Member] \| Oklahoma Base Rate Case - 2015 [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Increase to Annual Revenue and/or Rider		$ 10.0
Intervenor Recommended Return on Common Equity		8.75%
Intervenor Recommended Increase to Depreciation Expense		$ 23.0
Minimum [Member] \| Oklahoma Base Rate Case - 2015 [Member] \| Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Increase to Annual Revenue and/or Rider		$ 10.0
Intervenor Recommended Return on Common Equity		8.75%
Intervenor Recommended Increase to Depreciation Expense		$ 23.0
Maximum [Member] \| Oklahoma Base Rate Case - 2015 [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Increase to Annual Revenue and/or Rider		$ 31.0
Intervenor Recommended Return on Common Equity		9.30%
Intervenor Recommended Increase to Depreciation Expense		$ 46.0
Maximum [Member] \| Oklahoma Base Rate Case - 2015 [Member] \| Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Intervenor Recommended Increase to Annual Revenue and/or Rider		$ 31.0
Intervenor Recommended Return on Common Equity		9.30%
Intervenor Recommended Increase to Depreciation Expense		$ 46.0
Subsequent Event [Member] \| TCC Distribution Cost Recovery Factor [Member]
Public Utilities, General Disclosures [Line Items]
Requested Revenue Requirement	$ 54.0
Subsequent Event [Member] \| TNC Distribution Cost Recovery Factor [Member]
Public Utilities, General Disclosures [Line Items]
Requested Revenue Requirement	$ 16.0
Mercury and Air Toxic Standards [Member] \| Welsh Plant, Units 1 and 3 - Environmental Projects [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs		400.0
Mercury and Air Toxic Standards [Member] \| Welsh Plant, Units 1 and 3 - Environmental Projects [Member] \| Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs		400.0
Environmental Controls Projects [Member] \| Oklahoma Base Rate Case - 2015 [Member] \| Northeastern Plant, Unit 3 and Comanche Plant [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs		219.0
Construction Work in Progress		208.0
Environmental Controls Projects [Member] \| Oklahoma Base Rate Case - 2015 [Member] \| Northeastern Plant, Unit 3 and Comanche Plant [Member] \| Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs		219.0
Construction Work in Progress		$ 208.0