Note 10 - Business Segments (Detail) - Operating Revenue and Operating Income by Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Operating Income	$ 9,840		$ 11,111		$ 32,642		$ 30,079
Truckload Revenue, Net of Fuel Surcharge [Member]
Operating Revenue	96,938		92,003		280,284		263,613
Truckload Fuel Surcharge Revenue [Member]
Operating Revenue	25,931		24,849		77,305		72,463
Total Truckload Revenue [Member]
Operating Revenue	122,869		116,852		357,589		336,076
Logistics Revenue, Net of Intermodal Fuel Surcharge [Member]
Operating Revenue	36,408	[1]	35,500	[1]	102,889	[1]	98,221	[1]
Intermodal Fuel Surcharge Revenue [Member]
Operating Revenue	4,329		3,996		11,566		11,042
Total Logistics Revenue [Member]
Operating Revenue	40,737		39,496		114,455		109,263
Total [Member]
Operating Revenue	163,606		156,348		472,044		445,339
Operating Income	9,840		11,111		32,642		30,079
Truckload [Member]
Operating Income	7,938		9,174		26,039		24,097
Logistics [Member]
Operating Income	$ 1,902		$ 1,937		$ 6,603		$ 5,982

[1] Logistics revenue is net of $2.3 million and $7.2 million of inter-segment revenue in the three-month and nine-month periods ended September 30, 2012, respectively, for loads transported by our tractors and arranged by MWL that ha ve been eliminated in consolidation. Inter-segment revenue was $2.3 million and $6.7 million for the three-month and nine-month periods ended September 30, 2011.