Cover [Abstract] Document Period End Date Entity Current Reporting Status Entity Filer Category Entity Registrant Name Entity Interactive Data Current Entity Common Stock, Shares Outstanding Entity File Number Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Address, Address Line One Entity Address, City or Town Entity Address, Postal Zip Code City Area Code Local Phone Number Document Transition Report Entity Shell Company Entity Small Business Entity Emerging Growth Company Trading Symbol Title of 12(b) Security Security Exchange Name Entity Address, State or Province Document Type Amendment Flag Current Fiscal Year End Date Document Fiscal Year Focus Document Fiscal Period Focus Entity Central Index Key Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Public Float Document Annual Report ICFR Auditor Attestation Flag Auditor Firm ID Auditor Name Auditor Location Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Statement [Line Items] Statement [Line Items] Amortization of right-of-use assets Assets [Abstract] ASSETS Assets Total assets Total assets Assets, Current [Abstract] Current Assets Other Assets, Current Other current assets Assets, Current Total current assets Other Receivables Other receivables, including advances to independent contractors, less allowance of $8,125 and $7,239 Short-term Investments Short-term investments Receivables, Net, Current Trade accounts receivable, less allowance of $7,074 and $8,670 Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Goodwill Goodwill Property, Plant and Equipment, Net Operating property, less accumulated depreciation and amortization of $344,099 and $299,407 Total operating property, net Other Assets, Noncurrent Other assets Liabilities and Equity [Abstract] LIABILITIES AND SHAREHOLDERS' EQUITY Finance Lease, Liability, Noncurrent Long-term debt, excluding current maturities Long-term debt, excluding current maturities Self Insurance Reserve, Noncurrent Insurance claims Stockholders' Equity Attributable to Parent [Abstract] Shareholders' Equity Common Stock, Value, Issued Common stock, $0.01 par value, authorized 160,000,000 shares, issued 68,232,975 and 68,183,702 shares Additional Paid in Capital, Common Stock Additional paid-in capital Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss Treasury Stock, Value Cost of 30,539,235 and 29,797,639 shares of common stock in treasury Cumulative adjustment to retained earnings Retained earnings Stockholders' Equity Attributable to Parent Total shareholders' equity Ending Balance Beginning Balance Deferred Income Taxes and Other Liabilities, Noncurrent Deferred income taxes and other noncurrent liabilities Liabilities, Current [Abstract] Current Liabilities Accounts Payable, Current Accounts payable Bank Overdrafts Cash overdraft Other Liabilities, Current Other current liabilities Finance Lease, Liability, Current Current maturities of long-term debt Current maturities of long-term debt Self Insurance Reserve, Current Insurance claims Dividends Payable, Current Dividends payable Liabilities, Current Total current liabilities Liabilities and Equity Total liabilities and shareholders' equity Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Common Stock, Par or Stated Value Per Share Common stock, par value Common Stock, Shares Authorized Common stock, authorized shares Treasury Stock, Shares Treasury stock, shares Common Stock, Shares, Issued Common stock, issued shares Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Accumulated depreciation and amortization on operating property Less accumulated depreciation and amortization Allowance for Doubtful Accounts, Premiums and Other Receivables Allowance on other receivables Allowance for Doubtful Accounts Receivable, Current Allowance on trade accounts receivable Income Statement [Abstract] Common Stock, Dividends, Per Share, Declared Dividends per common share Operating Income (Loss) Operating income Operating income Net Income (Loss) Attributable to Noncontrolling Interest Less: Net loss attributable to noncontrolling interest Earnings Per Share, Diluted Diluted earnings per share attributable to Landstar System, Inc. and subsidiary Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income before income taxes Costs and Expenses [Abstract] Costs and expenses: Depreciation, Depletion and Amortization, Nonproduction Depreciation and amortization Depreciation and amortization of operating property and intangible assets Costs and Expenses Total costs and expenses Operating Insurance and Claims Costs, Production Insurance and claims Selling, General and Administrative Expense Selling, general and administrative Impairment of Intangible Assets (Excluding Goodwill) Impairment of intangible and other assets Impairment charges of intangible asset Loss on Contract Termination Commission program termination costs Other Cost and Expense, Operating Other operating costs, net of gains on asset sales/dispositions Purchased Transportation Costs Purchased transportation The cost of purchased transportation and transportation-related services of third party capacity providers of various modes for the carriage of customer freight during the period. Sales Commissions and Fees Commissions to agents Income Tax Expense (Benefit) Income taxes Income taxes Weighted Average Number of Shares Outstanding, Diluted Average diluted shares outstanding Interest and Debt Expense Interest and debt expense Interest Income, Operating Investment income Net Income (Loss) Attributable to Parent Net income attributable to Landstar System, Inc. and subsidiary Net income attributable to Landstar System, Inc. and subsidiary Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income Net income Net income (loss) Revenue from Contract with Customer, Excluding Assessed Tax Revenue External revenue Statement of Comprehensive Income [Abstract] Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive income attributable to Landstar System, Inc. and subsidiary Other Comprehensive Income (Loss), Net of Tax [Abstract] Other comprehensive (loss) income: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Other comprehensive (loss) income Other comprehensive income (loss) Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Unrealized holding (losses) gains on available-for-sale investments, net of tax (benefit) expense of ($739), $463, $561 Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Foreign currency translation (losses) gains Other Comprehensive Income (Loss), Securities, Available-for-sale, Tax Unrealized holding (losses) gains on available-for-sale investments, tax (benefit) expense Statement of Cash Flows [Abstract] Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents and restricted cash at beginning of period Cash, cash equivalents and restricted cash at end of period Net Cash Provided by (Used in) Financing Activities [Abstract] FINANCING ACTIVITIES Net Cash Provided by (Used in) Financing Activities NET CASH USED BY FINANCING ACTIVITIES Payments for Repurchase of Common Stock Purchases of common stock Total cost of repurchase of common stock Payments of Debt Issuance Costs Payment for debt issue costs Payments of Dividends Dividends paid Proceeds from (Repayments of) Bank Overdrafts Increase (decrease) in cash overdraft Proceeds from Stock Options Exercised Proceeds from exercises of stock options Payment for Contingent Consideration Liability, Financing Activities Payment of deferred consideration Contigent consideration liability remitted Payments Related to Tax Withholding for Share-based Compensation Taxes paid in lieu of shares issued related to stock-based compensation plans Repayments of Long-term Debt, Long-term Capital Lease Obligations, and Capital Securities Principal payments on finance lease obligations Payments to Noncontrolling Interests Purchase of noncontrolling interest Net Cash Provided by (Used in) Investing Activities [Abstract] INVESTING ACTIVITIES Net Cash Provided by (Used in) Investing Activities NET CASH USED BY INVESTING ACTIVITIES Proceeds from Sale of Property, Plant, and Equipment Proceeds from sales of operating property Payments to Acquire Businesses, Gross Consideration paid for acquisition Purchase consideration Payments to Acquire Marketable Securities Purchases of investments Payments to Acquire Property, Plant, and Equipment Purchases of operating property Expenditures on long-lived assets Proceeds from Sale and Maturity of Marketable Securities Sales and maturities of investments Increase Decrease In Restricted Cash And Investment Net change in other short-term investments Increase decrease in restricted cash and investment. Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect (Decrease) increase in cash, cash equivalents and and restricted cash Net Cash Provided by (Used in) Operating Activities [Abstract] OPERATING ACTIVITIES Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Amortization of Debt Issuance Costs Non-cash interest charges Provision for Doubtful Accounts Provisions for losses on trade and other accounts receivable Increase (Decrease) in Deferred Income Taxes Deferred income taxes, net Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Other Operating Assets Decrease (increase) in other assets Increase (Decrease) in Other Operating Liabilities Increase (decrease) in other liabilities Increase (Decrease) in Receivables (Increase) decrease in trade and other accounts receivable Increase (Decrease) in Accounts Payable Increase (decrease) in accounts payable Increase (Decrease) in Insurance Liabilities (Decrease) increase in insurance claims Gain (Loss) on Disposition of Property Plant Equipment Gains on sales/disposals of operating property Share-based Compensation Stock-based compensation Total cost of the Plans during the period Net Cash Provided by (Used in) Operating Activities NET CASH PROVIDED BY OPERATING ACTIVITIES Effect of Exchange Rate on Cash and Cash Equivalents Effect of exchange rate changes on cash and cash equivalents Statement of Stockholders' Equity [Abstract] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption, Adjustment [Member] Cumulative Effect, Period of Adoption, Adjustment [Member] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] AOCI Attributable to Parent [Member] Accumulated Other Comprehensive (Loss) Income Accumulated Other Comprehensive Income (Loss) Additional Paid-in Capital [Member] Additional Paid-In Capital Common Stock [Member] Common Stock Retained Earnings [Member] Retained Earnings Noncontrolling Interest [Member] Non-controlling Interests Treasury Stock [Member] Treasury Stock at Cost Treasury Stock Shares, Issued Beginning Balance (in shares) Ending Balance (in shares) Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Stock-based compensation Dividends, Common Stock, Cash Dividends Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Ending Balance Beginning Balance Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Purchase noncontrolling interests Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures Issuance of stock related to stock-based compensation plans (in shares) Other Comprehensive Income (Loss), Net of Tax Other comprehensive (loss) income Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures Issuance of stock related to stock-based compensation plans Treasury Stock, Shares, Acquired Purchases of common stock (in shares) Common stock repurchased during period, shares Treasury Stock, Value, Acquired, Cost Method Purchases of common stock Accounting Policies [Abstract] Significant Accounting Policies [Text Block] Significant Accounting Policies Business Combinations [Abstract] Business Combination Disclosure [Text Block] Acquired Business Equity [Abstract] Comprehensive Income (Loss) Note [Text Block] Other Comprehensive Income Investments, Debt and Equity Securities [Abstract] Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Investments Income Tax Disclosure [Abstract] Income Tax Disclosure [Text Block] Income Taxes Property, Plant and Equipment [Abstract] Property, Plant and Equipment Disclosure [Text Block] Operating Property Retirement Benefits [Abstract] Pension and Other Postretirement Benefits Disclosure [Text Block] Retirement Plan Debt Disclosure [Abstract] Debt Disclosure [Text Block] Debt Leases [Abstract] Disclosure Of Leases Of Lessee [Text Block] Leases Disclosure Of leases of lessee. Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Beginning Balance, Weighted Average Remaining Contractual Term (years) Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Share-Based Payment Arrangements Federal Home Loan Banks [Abstract] Stockholders' Equity Note Disclosure [Text Block] Equity Commitments and Contingencies Disclosure [Abstract]