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Summary of Significant Accounting Policies (Schedule of Estimated Useful Life) (Details) (USD $) | 12 Months Ended
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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 | 1,000 us-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

X
- Definition Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18780-107790 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 35 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6539997&loc=d3e1205-110223 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The estimated or actual value of the asset at the end of its useful life or when it is no longer serviceable (cannot be used for its original purpose). + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentSalvageValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Stated as a percentage, the estimated or actual value of the asset at the end of its useful life or when it is no longer serviceable (cannot be used for its original purpose) divided by its [historical] capitalized cost. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentSalvageValuePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=wern_ServiceAndOtherEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=wern_TractorsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=wern_TrailersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |