Note 7 - Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Revenues from external customers	$ 1,231,806	$ 1,286,663
Segment operating income (loss)	56,225	35,197
Segment income (loss) before taxes	56,637	31,669
Segment assets	3,008,423	3,242,658	$ 2,985,393
Truck Segment [Member]
Revenues from external customers	1,228,111	1,283,379
Segment operating income (loss)	55,950	35,451
Segment income (loss) before taxes	56,432	31,993
Segment assets	2,958,832	3,203,704
Other Segments [Member]
Revenues from external customers	3,695	3,284
Segment operating income (loss)	275	(254)
Segment income (loss) before taxes	205	(324)
Segment assets	$ 49,591	$ 38,954