Comprehensive Income (Comprehensive Income Attributable To Landstar System, Inc. And Subsidiary) (Details) (USD $) In Thousands	3 Months Ended	6 Months Ended
Jun. 25, 2011	Jun. 26, 2010	Jun. 25, 2011	Jun. 26, 2010
Comprehensive Income
Net income attributable to Landstar System, Inc. and subsidiary	$ 29,598	$ 24,437	$ 50,217	$ 41,613
Unrealized holding gains on available-for-sale investments	443	63	454	196
Income tax on unrealized holding gains	157	23	161	70
Net unrealized holding gains	286	40	293	126
Foreign currency translation gains (losses)	7	(43)	213	57
Comprehensive income attributable to Landstar System, Inc. and subsidiary	$ 29,891	$ 24,434	$ 50,723	$ 41,796

The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the reporting entity. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, but excludes any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent.

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- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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- Definition

Tax effect of the gross appreciation or the gross loss, net of reclassification adjustment, in the value of the total unsold available-for-sale securities at the end of an accounting period.

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- Definition

Adjustment that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency of the reporting entity, net of tax.

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Appreciation or loss in value (before reclassification adjustment) of the total of unsold securities during the period being reported on, net of tax. Reclassification adjustments include: (1) the unrealized holding gain (loss), net of tax, at the date of the transfer for a debt security from the held-to-maturity category transferred into the available-for-sale category. Also includes the unrealized gain (loss) at the date of transfer for a debt security from the available-for-sale category transferred into the held-to-maturity category; (2) the unrealized gains (losses) realized upon the sale of securities, after tax; and (3) the unrealized gains (losses) realized upon the write-down of securities, after tax.

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