Note 5 - Segment Information - Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue	$ 317,377	$ 256,324	$ 608,962	$ 477,213
Operating income	26,873	18,332	50,720	28,843
Operating Segments [Member]
Revenue	317,377	256,324	608,962	477,213
Operating income	26,873	18,332	50,720	28,843
Intersegment Eliminations [Member]
Revenue	1,006	1,734	1,897	2,180
Consolidation, Eliminations [Member]
Revenue	(1,006)	(1,734)	(1,897)	(2,180)
Highway Services [Member] | Operating Segments [Member]
Revenue	121,643	87,369	220,440	165,849
Operating income	14,610	10,225	23,941	16,436
Highway Services [Member] | Intersegment Eliminations [Member]
Revenue	1,006	1,734	1,897	2,180
Dedicated [Member] | Operating Segments [Member]
Revenue	96,767	81,868	185,714	157,314
Operating income	2,882	(191)	5,523	(1,990)
Dedicated [Member] | Intersegment Eliminations [Member]
Revenue	0	0	0	0
Managed Freight [Member] | Operating Segments [Member]
Revenue	80,281	71,635	166,432	123,032
Operating income	8,627	7,316	19,458	12,261
Managed Freight [Member] | Intersegment Eliminations [Member]
Revenue	0	0	0	0
Factoring [Member] | Operating Segments [Member]
Revenue	18,686	15,452	36,376	31,018
Operating income	754	982	1,798	2,136
Factoring [Member] | Intersegment Eliminations [Member]
Revenue	$ 0	$ 0	$ 0	$ 0