Note 18 - Segments - Segment Reporting Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from external customers	$ 4,214,614	$ 4,979,733	$ 4,727,356
Interest income	621	490	239
Interest rate swaps	14,900	13,963	11,437
Depreciation and amortization	51,261	43,859	40,786
Segment operating income	80,728	121,276	141,741
Segment income (loss) from continuing operations before taxes	66,449	107,803	130,543
Segment assets	2,603,047	2,852,008	2,675,875
Goodwill	290,191	285,041	265,145
Expenditures for segment assets	196,965	367,790	263,123
Truck Segment [Member]
Revenues from external customers	4,199,348	4,964,642	4,708,978
Interest income	621	490	239
Interest rate swaps	14,740	13,814	11,278
Depreciation and amortization	50,771	43,355	40,283
Segment operating income	81,483	122,907	142,074
Segment income (loss) from continuing operations before taxes	67,364	109,583	131,035
Segment assets	2,570,016	2,818,255	2,646,018
Goodwill	287,631	282,481	262,585
Expenditures for segment assets	196,704	367,482	262,613
Other Segments [Member]
Revenues from external customers	15,266	15,091	18,378
Interest income
Interest rate swaps	160	149	159
Depreciation and amortization	490	504	503
Segment operating income	(756)	(1,631)	(333)
Segment income (loss) from continuing operations before taxes	(915)	(1,780)	(492)
Segment assets	33,031	33,753	29,857
Goodwill	2,560	2,560	2,560
Expenditures for segment assets	$ 261	$ 308	$ 510