Note 17 - Operating Revenue and Operating Income by Segment (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue, Net of Fuel Surcharge [Member] | Truckload [Member]
Operating revenue		$ 348,101	$ 358,458	$ 366,798
Revenues		348,101	358,458	366,798
Revenue, Net of Fuel Surcharge [Member] | Dedicated [Member]
Operating revenue		107,264	56,609	33,526
Revenues		107,264	56,609	33,526
Revenue, Net of Fuel Surcharge [Member] | Intermodal [Member]
Operating revenue		65,877	75,447	71,764
Revenues		65,877	75,447	71,764
Fuel Surcharge Revenue [Member] | Truckload [Member]
Operating revenue		50,260	89,815	98,161
Revenues		50,260	89,815	98,161
Fuel Surcharge Revenue [Member] | Dedicated [Member]
Operating revenue		11,008	13,743	8,794
Revenues		11,008	13,743	8,794
Fuel Surcharge Revenue [Member] | Intermodal [Member]
Operating revenue		11,081	21,645	20,749
Revenues		11,081	21,645	20,749
Truckload [Member]
Operating revenue		398,361	448,273	464,959
Revenues		398,361	448,273	464,959
Operating Income		35,517	39,483	39,290
Dedicated [Member]
Operating revenue		118,272	70,352	42,320
Revenues		118,272	70,352	42,320
Operating Income		12,818	7,136	5,575
Intermodal [Member]
Operating revenue		76,958	97,092	92,513
Revenues		76,958	97,092	92,513
Operating Income		4,832	1,735	4,014
Brokerage [Member] | Marten Transport [Member]
Operating revenue		71,403	57,212	52,746
Revenues		$ 71,403	$ 57,212	52,746
Brokerage [Member] | M W L [Member]
Operating revenue	[1]			6,676
Revenues	[1]			6,676
Brokerage [Member]
Operating revenue		$ 71,403	$ 57,212	59,422
Revenues		71,403	57,212	59,422
Operating Income		3,792	2,652	3,116
Facility [Member]
Total operating income before gain on disposition of facilities		56,959	$ 51,006	$ 51,995
Gain on disposition of facilities		4,104
Operating revenue		664,994	$ 672,929	$ 659,214
Revenues		664,994	672,929	659,214
Operating Income		$ 61,063	$ 51,006	$ 51,995

[1] Brokerage revenue is net of $2.1 million of inter-segment revenue in 2013 for loads transported by our tractors and arranged by MWL that have been eliminated in consolidation. The inter-segment revenue in 2013 relates to loads transported prior to the deconsolidation of MWL effective March 28, 2013.