Consolidated Statements Of Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 25, 2010	Dec. 26, 2009
Consolidated Statements Of Income [Abstract]
Revenue	$ 2,649,082	$ 2,400,170	$ 2,008,796
Investment income	1,705	1,558	1,268
Costs and expenses:
Purchased transportation	2,007,102	1,824,308	1,503,520
Commissions to agents	210,088	181,405	160,571
Other operating costs	28,865	28,826	29,173
Insurance and claims	42,766	49,334	45,918
Selling, general and administrative	152,907	153,080	133,612
Depreciation and amortization	25,814	24,804	23,528
Total costs and expenses	2,467,542	2,261,757	1,896,322
Operating income	183,245	139,971	113,742
Interest and debt expense	3,112	3,623	4,030
Income before income taxes	180,133	136,348	109,712
Income taxes	67,188	49,766	39,762
Net income	112,945	86,582	69,950
Less: Net loss attributable to noncontrolling interest	(62)	(932)	(445)
Net income attributable to Landstar System, Inc. and subsidiary	$ 113,007	$ 87,514	$ 70,395
Earnings per common share attributable to Landstar System, Inc. and subsidiary	$ 2.38	$ 1.77	$ 1.38
Diluted earnings per share attributable to Landstar System, Inc. and subsidiary	$ 2.38	$ 1.77	$ 1.37
Average number of shares outstanding:
Earnings per common share	47,444,000	49,523,000	51,095,000
Diluted earnings per share	47,524,000	49,580,000	51,280,000
Dividends paid per common share	$ 0.21	$ 0.19	$ 0.17