Note 5 - Segment Information - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Revenue	$ 311,839	$ 274,561	$ 920,801	$ 751,775
Operating income	59,059	20,083	109,779	48,925
Operating Segments [Member]
Revenue	311,839	274,561	920,801	751,775
Operating income	59,059	20,083	109,779	48,925
Intersegment Eliminations [Member]
Revenue	1,580	2,494	3,476	4,674
Consolidation, Eliminations [Member]
Revenue	(1,580)	(2,494)	(3,476)	(4,674)
Highway Services [Member] | Operating Segments [Member]
Revenue	117,793	85,289	338,234	251,139
Operating income	30,660	11,064	54,602	27,479
Highway Services [Member] | Intersegment Eliminations [Member]
Revenue	1,580	2,494	3,476	4,674
Dedicated [Member] | Operating Segments [Member]
Revenue	93,423	83,477	279,136	240,791
Operating income	19,416	(659)	24,937	(2,629)
Dedicated [Member] | Intersegment Eliminations [Member]
Revenue	0	0	0	0
Managed Freight [Member] | Operating Segments [Member]
Revenue	78,382	90,072	244,814	213,104
Operating income	8,605	9,251	28,062	21,510
Managed Freight [Member] | Intersegment Eliminations [Member]
Revenue	0	0	0	0
Factoring [Member] | Operating Segments [Member]
Revenue	22,241	15,723	58,617	46,741
Operating income	378	427	2,178	2,565
Factoring [Member] | Intersegment Eliminations [Member]
Revenue	$ 0	$ 0	$ 0	$ 0