Note 6 - Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Revenues from external customers	$ 1,871,999	$ 1,911,767
Segment operating income	110,610	127,776
Segment income before taxes	92,814	119,140
Segment assets	4,629,006	3,969,552	$ 4,364,241
Truck Segment [Member]
Revenues from external customers	1,867,968	1,907,941
Segment operating income	110,708	127,563
Segment income before taxes	92,912	118,927
Segment assets	4,570,652	3,913,928
Other Operating Segment [Member]
Revenues from external customers	4,031	3,826
Segment operating income		213
Segment income before taxes	(98)	213
Segment assets	$ 58,354	$ 55,624