Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 30, 2017	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	$ 33,124
Guarantee Payment of Insurance Claims
Commitments and Contingencies Disclosure [Line Items]
Letters of credit outstanding	$ 59,436