Consolidated Statements Of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 26, 2011
Consolidated Statements Of Income [Abstract]
Revenue	$ 649,023	$ 571,986
Investment income	387	528
Costs and expenses:
Purchased transportation	492,922	431,378
Commissions to agents	50,232	44,171
Other operating costs	6,472	7,944
Insurance and claims	11,095	11,266
Selling, general and administrative	38,799	37,264
Depreciation and amortization	6,740	6,399
Total costs and expenses	606,260	538,422
Operating income	43,150	34,092
Interest and debt expense	724	828
Income before income taxes	42,426	33,264
Income taxes	15,579	12,707
Net income	26,847	20,557
Less: Net loss attributable to noncontrolling interest		(62)
Net income attributable to Landstar System, Inc. and subsidiary	$ 26,847	$ 20,619
Earnings per common share attributable to Landstar System, Inc. and subsidiary	$ 0.57	$ 0.43
Diluted earnings per share attributable to Landstar System, Inc. and subsidiary	$ 0.57	$ 0.43
Average number of shares outstanding:
Earnings per common share	46,800,000	47,870,000
Diluted earnings per share	47,061,000	47,900,000
Dividends paid per common share	$ 0.055	$ 0.050