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Equity Compensation And Employee Benefit Plans (Schedule of Equity Compensation Performance Shares Valuation Assumptions) (Details) (Performance Shares, USD $) In Thousands, except Per Share data, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014
Performance Shares |
Schedule of Share Based Payment Award Performance Shares Valuation Assumptions [Abstract] |
Number of Shares granted | 183 wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardsNonvestedGrantsinPeriod / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Dividends per share (quarterly amounts) | $ 0.05 wern_SharebasedCompensationArrangementbySharebasedPaymentAwardPerformanceSharesFairValueAssumptionsExpectedDividendPaymentsPerShare / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember
Risk-free interest rate | 1.50%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardTypeAxis = us-gaap_PerformanceSharesMember

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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iv) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition The number of grants made during the period on performance awards. + References No definition available. + Details
Name: | wern_EquityCompensationArrangementbySharebasedPaymentAwardPerformanceAwardsNonvestedGrantsinPeriod
Namespace Prefix: | wern_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | wern_ScheduleofShareBasedPaymentAwardPerformanceSharesValuationAssumptionsLineItems
Namespace Prefix: | wern_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Share-based Compensation Arrangement by Share-based Payment Award, Performance Shares Fair Value Assumptions, Expected Dividend Payments Per Share + References No definition available. + Details
Name: | wern_SharebasedCompensationArrangementbySharebasedPaymentAwardPerformanceSharesFairValueAssumptionsExpectedDividendPaymentsPerShare
Namespace Prefix: | wern_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration