XML 45 R32.htm IDEA: XBRL DOCUMENT v2.4.1.9
Summary of Significant Accounting Policies (Schedule of Estimated Useful Life) (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Building And Improvements [Member]  
Property, Plant and Equipment [Line Items]  
Estimated Useful Lives 30 years
Salvage Value Percentage 0.00%us-gaap_PropertyPlantAndEquipmentSalvageValuePercentage
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_BuildingImprovementsMember
Tractors [Member]  
Property, Plant and Equipment [Line Items]  
Estimated Useful Lives 80 months
Salvage Value Percentage 0.00%us-gaap_PropertyPlantAndEquipmentSalvageValuePercentage
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= wern_TractorsMember
Trailers [Member]  
Property, Plant and Equipment [Line Items]  
Estimated Useful Lives 12 years
Salvage Value 1,000us-gaap_PropertyPlantAndEquipmentSalvageValue
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= wern_TrailersMember
Service And Other Equipment [Member]  
Property, Plant and Equipment [Line Items]  
Salvage Value Percentage 0.00%us-gaap_PropertyPlantAndEquipmentSalvageValuePercentage
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= wern_ServiceAndOtherEquipmentMember
Minimum | Service And Other Equipment [Member]  
Property, Plant and Equipment [Line Items]  
Estimated Useful Lives 3 years
Maximum | Service And Other Equipment [Member]  
Property, Plant and Equipment [Line Items]  
Estimated Useful Lives 10 years