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v2.4.1.9

Segment Information (Schedule Of Revenue And Long-Lived Assets, By Geographical Areas) (Details) (USD $) In Thousands, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues | $ 553,186 us-gaap_Revenues | $ 551,961 us-gaap_Revenues | $ 542,120 us-gaap_Revenues | $ 492,022 us-gaap_Revenues | $ 517,920 us-gaap_Revenues | $ 511,728 us-gaap_Revenues | $ 506,648 us-gaap_Revenues | $ 492,887 us-gaap_Revenues | $ 2,139,289 us-gaap_Revenues | $ 2,029,183 us-gaap_Revenues | $ 2,036,386 us-gaap_Revenues
Long-lived Assets | 1,013,782 us-gaap_PropertyPlantAndEquipmentNet |  |  |  | 977,518 us-gaap_PropertyPlantAndEquipmentNet |  |  |  | 1,013,782 us-gaap_PropertyPlantAndEquipmentNet | 977,518 us-gaap_PropertyPlantAndEquipmentNet | 993,843 us-gaap_PropertyPlantAndEquipmentNet
United States [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 1,857,624 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = country_US | 1,768,442 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = country_US | 1,772,179 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = country_US
Long-lived Assets | 989,815 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = country_US |  |  |  | 955,543 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = country_US |  |  |  | 989,815 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = country_US | 955,543 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = country_US | 979,798 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = country_US
Mexico [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 187,124 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = country_MX | 172,009 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = country_MX | 172,016 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = country_MX
Long-lived Assets | 23,734 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = country_MX |  |  |  | 21,654 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = country_MX |  |  |  | 23,734 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = country_MX | 21,654 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = country_MX | 13,659 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = country_MX
Other [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 94,541 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = wern_OthersMember | 88,732 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = wern_OthersMember | 92,191 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = wern_OthersMember
Long-lived Assets | 233 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = wern_OthersMember |  |  |  | 321 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = wern_OthersMember |  |  |  | 233 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = wern_OthersMember | 321 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = wern_OthersMember | 386 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = wern_OthersMember
Total Foreign Countries [Member] |  |  |  |  |  |  |  |  |  |  |
Segment Reporting Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 281,665 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = wern_TotalForeignCountriesMember | 260,741 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = wern_TotalForeignCountriesMember | 264,207 us-gaap_Revenues / us-gaap_StatementGeographicalAxis = wern_TotalForeignCountriesMember
Long-lived Assets | $ 23,967 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = wern_TotalForeignCountriesMember |  |  |  | $ 21,975 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = wern_TotalForeignCountriesMember |  |  |  | $ 23,967 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = wern_TotalForeignCountriesMember | $ 21,975 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = wern_TotalForeignCountriesMember | $ 14,045 us-gaap_PropertyPlantAndEquipmentNet / us-gaap_StatementGeographicalAxis = wern_TotalForeignCountriesMember

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- Definition Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.13) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 13 -Subparagraph a -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 8 -Article 7 + Details
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- Definition Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 + Details
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