Note 8 - Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenues from external customers	$ 1,286,663	$ 1,348,317
Segment operating income (loss)	35,197	56,867
Segment income (loss) before taxes	31,669	49,558
Segment assets	3,242,658	3,422,026	$ 3,407,329
Truck Segment [Member]
Revenues from external customers	1,283,379	1,344,449
Segment operating income (loss)	35,451	56,742
Segment income (loss) before taxes	31,993	49,505
Segment assets	3,203,704	3,384,441
Other Segments [Member]
Revenues from external customers	3,284	3,868
Segment operating income (loss)	(254)	125
Segment income (loss) before taxes	(324)	53
Segment assets	$ 38,954	$ 37,585