Note 3 - Segment Information - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues	$ 164,326	$ 158,832	$ 323,070	$ 315,173
Operating income (loss)	3,962	7,316	4,271	14,735
Operating Segments [Member] | Truckload [Member]
Revenues	147,631	144,698	2,932,568	287,452
Operating income (loss)	4,986	8,681	8,888	17,051
Operating Segments [Member] | Other Segments [Member]
Revenues	16,695	14,134	29,814	27,721
Operating income (loss)	1,585	1,489	3,032	3,314
Corporate, Non-Segment [Member]
Operating income (loss)	$ (2,609)	$ (2,854)	$ (7,649)	$ (5,630)