Rate Matters - West Companies (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	$ 3,651.3	$ 3,903.9
Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	127.9	315.3
Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	188.5	$ 751.3
Welsh Plant, Unit 2 [Member]
Public Utilities, General Disclosures [Line Items]
Amount Reclassified as Regulatory Assets Upon Retirement of the Plant	76.0
Welsh Plant, Unit 2 [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Amount Reclassified as Regulatory Assets Upon Retirement of the Plant	$ 76.0
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	$ 545.0
Louisiana 2012 Formula Rate Filing [Member]
Public Utilities, General Disclosures [Line Items]
Louisiana Jurisdictional Share Of Turk Plant	29.00%
Net Increase in Louisiana Total Rates per the Settlement Agreement	$ 2.0
Base Rate Increase per Settlement Agreement	85.0
Fuel Rate Decrease per 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 Turk Plant	29.00%
Net Increase in Louisiana Total Rates per the Settlement Agreement	$ 2.0
Base Rate Increase per Settlement Agreement	85.0
Fuel Rate Decrease per 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 Common Equity	10.50%
Future Incremental Purchased Capacity And Energy Costs Related To Environmental Projects	$ 35.0
Interim Annual Base Rate Increase	$ 75.0
Administrative Law Judge Recommended Return on Common Equity	9.25%
Administrative Law Judge Recommended Environmental Compliance Plan Cost Cap	$ 210.0
Administrative Law Judge Recommended Increase in Depreciation Expense	14.0
Administrative Law Judge Recommended Annual Increase in Revenues	47.0
Commission Staff Recommended Annual Increase in Revenues	32.0
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 Common Equity	10.50%
Future Incremental Purchased Capacity And Energy Costs Related To Environmental Projects	$ 35.0
Interim Annual Base Rate Increase	$ 75.0
Administrative Law Judge Recommended Return on Common Equity	9.25%
Administrative Law Judge Recommended Environmental Compliance Plan Cost Cap	$ 210.0
Administrative Law Judge Recommended Increase in Depreciation Expense	14.0
Administrative Law Judge Recommended Annual Increase in Revenues	47.0
Commission Staff Recommended Annual Increase in Revenues	32.0
Oklahoma Base Rate Case - 2015 [Member] | Northeastern Plant, Unit 4 [Member]
Public Utilities, General Disclosures [Line Items]
Amount Reclassified as Regulatory Assets Upon Retirement of the Plant	87.0
Oklahoma Base Rate Case - 2015 [Member] | Northeastern Plant, Unit 4 [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Amount Reclassified as Regulatory Assets Upon Retirement of the Plant	87.0
SPP Open Access Transmission Tariff Upgrade Costs [Member]
Public Utilities, General Disclosures [Line Items]
Net Unfavorable Impact	7.0
SPP Open Access Transmission Tariff Upgrade Costs [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Net Unfavorable Impact	3.0
SPP Open Access Transmission Tariff Upgrade Costs [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Net Unfavorable Impact	4.0
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
TCC Distribution Cost Recovery Factor [Member]
Public Utilities, General Disclosures [Line Items]
Annual Revenue Requirement Approved in Settlement Agreement	45.0
TNC Distribution Cost Recovery Factor [Member]
Public Utilities, General Disclosures [Line Items]
Annual Revenue Requirement Approved in Settlement Agreement	11.0
Welsh Plant, Units 1 and 3 - Environmental Projects [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs	850.0
Construction Work in Progress	395.0
Remaining Contractual Construction Obligations	14.0
Amount of Recovery Requested Related to Arkansas Retail Jurisdictional Share of Environmental Costs	69.0
Amount of Additional Recovery Requested Related to Arkansas Retail Jurisdictional Share of Environmental Costs	10.0
Total Amount of Recovery Requested Related to Arkansas Retail Jurisdictional Share of Environmental Costs	79.0
Welsh Plant, Units 1 and 3 - Environmental Projects [Member] | Southwestern Electric Power Co [Member]
Public Utilities, General Disclosures [Line Items]
Projected Capital Costs	850.0
Construction Work in Progress	395.0
Remaining Contractual Construction Obligations	14.0
Amount of Recovery Requested Related to Arkansas Retail Jurisdictional Share of Environmental Costs	69.0
Amount of Additional Recovery Requested Related to Arkansas Retail Jurisdictional Share of Environmental Costs	10.0
Total Amount of Recovery Requested Related to Arkansas Retail Jurisdictional Share of Environmental Costs	79.0
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	632.0
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	632.0
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
Environmental Controls Projects [Member] | Oklahoma Base Rate Case - 2015 [Member] | Comanche Plant [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	43.0
Environmental Controls Projects [Member] | Oklahoma Base Rate Case - 2015 [Member] | Comanche Plant [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	43.0
Environmental Controls Projects [Member] | Oklahoma Base Rate Case - 2015 [Member] | Northeastern Plant, Unit 3 [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	180.0
Environmental Controls Projects [Member] | Oklahoma Base Rate Case - 2015 [Member] | Northeastern Plant, Unit 3 [Member] | Public Service Co Of Oklahoma [Member]
Public Utilities, General Disclosures [Line Items]
Construction Work in Progress	180.0
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
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
Mercury and Air Toxic Standards [Member] | Welsh Plant, Units 1 and 3 - Environmental Projects [Member]
Public Utilities, General Disclosures [Line Items]
Completed Project Capital Costs	370.0
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]
Completed Project Capital Costs	$ 370.0