Note 7 - Segment Information (Details) - Segment Reporting Information (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenues from external customers	$ 789,674	$ 835,844	$ 1,546,462	$ 1,613,173
Segment income (loss) before taxes	9,309	28,559	31,409	54,635
Segment assets	1,972,240	1,885,441	1,972,240	1,885,441	1,881,566
Truck Segment [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	784,573	830,773	1,536,803	1,603,681
Segment income (loss) before taxes	8,943	28,574	31,091	54,817
Segment assets	1,945,552	1,858,045	1,945,552	1,858,045
Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues from external customers	5,101	5,071	9,659	9,492
Segment income (loss) before taxes	366	(15)	318	(182)
Segment assets	$ 26,688	$ 27,396	$ 26,688	$ 27,396