Note 10 - Segment Information, Significant Customers, Industry Concentration, and Geographic Areas - Revenue Dollars and Percentages by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating revenues	$ 707,120	$ 486,825	$ 514,177
Motor Carrier [Member]
Operating revenues	$ 698,497	$ 479,110	$ 514,177
Motor Carrier [Member] | Revenue Benchmark [Member] | Geographic Concentration Risk [Member]
Operating Revenues, percentage	100.00%	100.00%	100.00%
Motor Carrier [Member] | UNITED STATES
Operating revenues	$ 474,291	$ 316,542	$ 326,559
Motor Carrier [Member] | UNITED STATES | Revenue Benchmark [Member] | Geographic Concentration Risk [Member]
Operating Revenues, percentage	67.90%	66.10%	63.50%
Motor Carrier [Member] | MEXICO
Operating revenues	$ 223,315	$ 161,412	$ 186,392
Motor Carrier [Member] | MEXICO | Revenue Benchmark [Member] | Geographic Concentration Risk [Member]
Operating Revenues, percentage	32.00%	33.70%	36.30%
Motor Carrier [Member] | CANADA
Operating revenues	$ 891	$ 1,156	$ 1,226
Motor Carrier [Member] | CANADA | Revenue Benchmark [Member] | Geographic Concentration Risk [Member]
Operating Revenues, percentage	0.10%	0.20%	0.20%