Investments - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended
Dec. 29, 2012 Y	Sep. 28, 2013 Y
Schedule of Available-for-sale Securities [Line Items]
Investments, maximum maturity period, years	5	5
Unrealized gains, net of unrealized losses, on the investments in the bond portfolio	$ 1,407,000	$ 446,000

Net amount of the difference between the fair value and cost of investments in available for sale securities.

No definition available.

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Namespace Prefix:	lstr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant