Note 6 - Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Revenues from external customers	$ 2,003,052	$ 1,791,241	$ 3,914,819	$ 3,354,443
Segment operating income	142,859	135,023	270,635	242,522
Segment income before taxes	130,525	140,188	249,665	260,532
Segment assets	4,126,321	3,669,369	4,126,321	3,669,369	$ 3,821,066
Truck Segment [Member]
Revenues from external customers	1,999,028	1,786,927	3,906,969	3,345,979
Segment operating income	142,869	134,506	270,432	241,826
Segment income before taxes	130,535	139,765	249,462
Segment assets	4,070,544	3,615,745	4,070,544	3,615,745
Other Segments [Member]
Revenues from external customers	4,024	4,314	7,850	8,464
Segment operating income		517	203	696
Segment income before taxes	(10)	423	203
Segment assets	$ 55,777	$ 53,624	$ 55,777	$ 53,624