Commitments and Contingencies Disclosure [Line Items]

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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=84173941&loc=d3e5086-111524

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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.

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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

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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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Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 20, 2017
Fletes Avella \| Landstar Metro
Commitments and Contingencies Disclosure [Line Items]
Ownership interest acquired by affiliates		30.00%
Fletes Avella \| Landstar Servicios
Commitments and Contingencies Disclosure [Line Items]
Ownership interest acquired by affiliates		30.00%
Revolving Credit Facility
Commitments and Contingencies Disclosure [Line Items]
Letters of credit outstanding	$ 33,115
Guarantee Payment of Insurance Claims
Commitments and Contingencies Disclosure [Line Items]
Letters of credit outstanding	61,186
Current Investments
Commitments and Contingencies Disclosure [Line Items]
Investments providing collateral for letters of credit to guarantee insurance claims	39,014
Non-Current Investments
Commitments and Contingencies Disclosure [Line Items]
Investments providing collateral for letters of credit to guarantee insurance claims	28,970
Total non-current investments	$ 71,611