Note 6 - Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Revenues from external customers	$ 1,896,133	$ 1,980,740	$ 5,795,160	$ 5,895,559
Segment operating income	120,754	121,621	355,845	392,256
Segment income before taxes	103,239	107,560	301,114	357,225
Segment assets	4,648,471	4,218,053	4,648,471	4,218,053	$ 4,364,241
Truck Segment [Member]
Revenues from external customers	1,891,777	1,976,395	5,782,578	5,883,127
Segment operating income	120,553	121,675	355,890	391,870
Segment income before taxes	103,038	107,614	301,158	356,839
Segment assets	4,591,223	4,163,261	4,591,223	4,163,261
Other Operating Segment [Member]
Revenues from external customers	4,356	4,345	12,582	12,432
Segment operating income		(54)	(45)	386
Segment income before taxes	201	(54)	(44)	386
Segment assets	$ 57,248	$ 54,792	$ 57,248	$ 54,792