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Equity Compensation And Employee Benefit Plans (Schedule Of Equity Compensation Restricted Stock Valuation Assumptions) (Details) (Restricted Stock, USD $) In Thousands, except Per Share data, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Restricted Stock |  |  |
Equity Compensation Arrangement by Equity Compensation Award [Line Items] |  |  |
Number of Restricted Shares granted | 140 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember | 115 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember | 268 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember
Dividends per share (quarterly amounts) | $ 0.05 wern_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendPaymentsPerShare / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember | $ 0.05 wern_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendPaymentsPerShare / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember | $ 0.05 wern_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendPaymentsPerShare / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember
Risk-free interest rate | 1.60%wern_SharebasedCompensationArrangementbySharebasedPaymentAwardRestrictedStockFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember | 1.40%wern_SharebasedCompensationArrangementbySharebasedPaymentAwardRestrictedStockFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember | 0.70%wern_SharebasedCompensationArrangementbySharebasedPaymentAwardRestrictedStockFairValueAssumptionsRiskFreeInterestRate / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockMember

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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + 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 (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

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

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

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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. + References No definition available. + Details
Name: | wern_SharebasedCompensationArrangementbySharebasedPaymentAwardRestrictedStockFairValueAssumptionsRiskFreeInterestRate
Namespace Prefix: | wern_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration