Note 5 - Property and Equipment - Property and Equipment, at Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property, plant, and equipment, gross	$ 631,076	$ 596,071
Revenue Equipment [Member]
Property, plant, and equipment, gross	$ 499,809	468,693
Revenue Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	3 years
Revenue Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	10 years
Office Equipment [Member]
Property, plant, and equipment, gross	$ 8,192	8,189
Office Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	5 years
Office Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	10 years
Land and Land Improvements [Member]
Property, plant, and equipment, gross	$ 25,482	25,184
Land and Land Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	0 years
Land and Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	10 years
Building and Building Improvements [Member]
Property, plant, and equipment, gross	$ 71,324	71,614
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	7 years
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	40 years
Construction in Progress [Member]
Property, plant, and equipment, gross	$ 3,176	1,104
Property, Plant and Equipment, Other Types [Member]
Property, plant, and equipment, gross	$ 23,093	$ 21,287
Property, Plant and Equipment, Other Types [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	2 years
Property, Plant and Equipment, Other Types [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	7 years