Note 10 - Business Segments (Detail) - Operating Revenue and Operating Income by Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Operating Revenue	$ 164,474		$ 151,474
Operating Income	12,538		9,519
Truckload Revenue, Net of Fuel Surcharge [Member]
Operating Revenue	94,965		89,198
Truckload Fuel Surcharge Revenue [Member]
Operating Revenue	26,769		25,253
Total Truckload Revenue [Member]
Operating Revenue	121,734		114,451
Logistics Revenue, Net of Intermodal Fuel Surcharge [Member]
Operating Revenue	37,760	[1]	33,436	[1]
Intermodal Fuel Surcharge Revenue [Member]
Operating Revenue	4,980		3,587
Total Logistics Revenue [Member]
Operating Revenue	42,740		37,023
Truckload [Member]
Operating Income	10,000		7,128
Logistics [Member]
Operating Income	$ 2,538		$ 2,391

[1] Logistics revenue is net of $2.1 million and $2.5 million of inter-segment revenue in the three-month periods ended March 31, 2013 and March 31, 2012, respectively, for loads transported by our tractors and arranged by MWL that have been eliminated in consolidation.