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Investments - Additional Information (Detail) (USD $) | 12 Months Ended
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Dec. 27, 2014 | Dec. 28, 2013
Schedule of Available-for-sale Securities [Line Items] |  |
Investments maximum maturity period | 5 years | 5 years
Unrealized gains, net of unrealized losses, on the investments in the bond portfolio | $ 163,000 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax | $ 378,000 us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax
Guarantee Payment Of Insurance Claims |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Letters of credit outstanding | 63,761,000 us-gaap_LettersOfCreditOutstandingAmount / us-gaap_GuaranteeObligationsByNatureAxis = lstr_GuaranteePaymentOfInsuranceClaimsMember |
Current Investments |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments providing collateral for letters of credit to guarantee insurance claims | 37,007,000 us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral / us-gaap_InvestmentTypeAxis = lstr_CurrentInvestmentsMember |
Non-Current Investments |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Investments providing collateral for letters of credit to guarantee insurance claims | 33,839,000 us-gaap_AvailableForSaleSecuritiesPledgedAsCollateral / us-gaap_InvestmentTypeAxis = lstr_NonCurrentInvestmentsMember |
Total non-current investments | $ 66,462,000 us-gaap_LongTermInvestments / us-gaap_InvestmentTypeAxis = lstr_NonCurrentInvestmentsMember |

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- Definition Amount before tax of unrealized gain (loss) in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References No definition available. + Details
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- Definition The fair value of available-for-sale securities that serve as collateral for borrowings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5086-111524 + Details
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- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
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- Definition The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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