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Commitments and Contingencies - Additional Information (Detail) (USD $)
 0 Months Ended
Mar. 13, 2015
Mar. 28, 2015
Bruno v. Landstar Ranger, Inc.    
Commitments and Contingencies Disclosure [Line Items]    
Verdict against Landstar Ranger, Inc. in the matter of Bruno v. Landstar Ranger Inc. $ 19,250,000us-gaap_LitigationSettlementAmount
/ us-gaap_LitigationCaseAxis
= lstr_LitigationCaseOneMember		  
Verdict percentage of liability 100.00%lstr_VerdictPercentageOfLiability
/ us-gaap_LitigationCaseAxis
= lstr_LitigationCaseOneMember		  
Agreed limited financial exposure 4,500,000us-gaap_LossContingencyDamagesAwardedValue
/ us-gaap_LitigationCaseAxis
= lstr_LitigationCaseOneMember		  
Verdict, Pre-tax charge 4,500,000us-gaap_LossContingencyLossInPeriod
/ us-gaap_LitigationCaseAxis
= lstr_LitigationCaseOneMember		  
Cost of an adverse verdict, per share $ 0.06lstr_LitigationSettlementExpensePerShare
/ us-gaap_LitigationCaseAxis
= lstr_LitigationCaseOneMember		  
Current Investments    
Commitments and Contingencies Disclosure [Line Items]    
Investments providing collateral for letters of credit to guarantee insurance claims   37,174,000us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral
/ us-gaap_InvestmentTypeAxis
= lstr_CurrentInvestmentsMember
Non-Current Investments    
Commitments and Contingencies Disclosure [Line Items]    
Investments providing collateral for letters of credit to guarantee insurance claims   27,059,000us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral
/ us-gaap_InvestmentTypeAxis
= lstr_NonCurrentInvestmentsMember
Total non-current investments   66,954,000us-gaap_LongTermInvestments
/ us-gaap_InvestmentTypeAxis
= lstr_NonCurrentInvestmentsMember
Revolving Credit Facility    
Commitments and Contingencies Disclosure [Line Items]    
Letters of credit outstanding   33,033,000us-gaap_LettersOfCreditOutstandingAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
Guarantee Payment Of Insurance Claims    
Commitments and Contingencies Disclosure [Line Items]    
Letters of credit outstanding   $ 57,810,000us-gaap_LettersOfCreditOutstandingAmount
/ us-gaap_GuaranteeObligationsByNatureAxis
= lstr_GuaranteePaymentOfInsuranceClaimsMember