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Income Taxes - Additional Information (Detail) - USD ($) | 12 Months Ended
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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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