Commitments and Contingencies - Additional Information (Detail) $ in Thousands	Sep. 29, 2018 USD ($)
Fletes Avella \| Landstar Metro
Commitments and Contingencies Disclosure [Line Items]
Approximate ownership interest acquired by affiliates	21.00%
Fletes Avella \| Landstar Servicios
Commitments and Contingencies Disclosure [Line Items]
Approximate ownership interest acquired by affiliates	21.00%
Revolving Credit Facility
Commitments and Contingencies Disclosure [Line Items]
Letters of credit outstanding	$ 34,370
Guarantee Payment of Insurance Claims
Commitments and Contingencies Disclosure [Line Items]
Letters of credit outstanding	62,457
Current Investments \| Collateral Pledged [Member]
Commitments and Contingencies Disclosure [Line Items]
Investments providing collateral for letters of credit to guarantee insurance claims	40,203
Non-Current Investments
Commitments and Contingencies Disclosure [Line Items]
Total non-current investments	71,489
Non-Current Investments \| Collateral Pledged [Member]
Commitments and Contingencies Disclosure [Line Items]
Investments providing collateral for letters of credit to guarantee insurance claims	$ 29,194

Commitments and Contingencies Disclosure [Line Items]

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

No definition available.

+ 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://fasb.org/us-gaap/role/ref/legacyRef
-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

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

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