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Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Corporate income tax rate	21.00%		35.00%
Tax cuts and jobs act of 2017 incomplete accounting revaluation deferred tax liabilities provisional income tax expense (benefit)			$ 20,430,000
Tax cuts and jobs act of 2017 incomplete accounting deemed repatriation foreign earnings and profits provisional income tax expense (benefit)			17,981,000
Tax cuts and jobs act of 2017, incomplete accounting, provisional income tax expense (benefit)			900,000
Tax cuts and jobs act of 2017 incomplete accounting deemed repatriation US federal taxes payable			500,000
Net unrecognized tax benefits		$ 2,403,000	3,670,000
Accrued for estimated interest and penalties		653,000	627,000
Income taxes paid		$ 75,124,000	86,607,000	$ 69,067,000
Landstar Metro
Income Taxes [Line Items]
Ownership in subsidiaries, percentage		79.00%
Landstar Servicios
Income Taxes [Line Items]
Ownership in subsidiaries, percentage		79.00%
Accounting Standards Update 2016-09
Income Taxes [Line Items]
Excess tax benefit from stock-based awards		$ 2,060,000	$ 1,299,000

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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