Note 7 - Segment Information (Details) - Segment Reporting Information (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues from external customers, by segment	$ 1,193,535	$ 958,667
Segment income (loss) before taxes	27,388	19,615
Segment assets, by segment	2,738,723	2,263,720	2,694,262
Truck Segment [Member]
Segment Reporting Information [Line Items]
Revenues from external customers, by segment	1,189,987	954,407
Segment income (loss) before taxes	27,752	19,759
Segment assets, by segment	2,708,600	2,233,510
Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers, by segment	3,548	4,260
Segment income (loss) before taxes	(364)	(144)
Segment assets, by segment	$ 30,123	$ 30,210