Note 4 - Property and Equipment - Property and Equipment, at Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, plant, and equipment, gross	$ 638,770	$ 650,988
Revenue Equipment [Member]
Property, plant, and equipment, gross	$ 504,192	519,797
Revenue Equipment [Member] | Minimum [Member]
Estimated useful lives (Year)	3 years
Revenue Equipment [Member] | Maximum [Member]
Estimated useful lives (Year)	10 years
Office Equipment [Member]
Property, plant, and equipment, gross	$ 3,850	4,585
Office Equipment [Member] | Minimum [Member]
Estimated useful lives (Year)	5 years
Office Equipment [Member] | Maximum [Member]
Estimated useful lives (Year)	10 years
Land and Land Improvements [Member]
Property, plant, and equipment, gross	$ 25,240	25,061
Land and Land Improvements [Member] | Minimum [Member]
Estimated useful lives (Year)	0 years
Land and Land Improvements [Member] | Maximum [Member]
Estimated useful lives (Year)	15 years
Building and Building Improvements [Member]
Property, plant, and equipment, gross	$ 75,134	74,513
Building and Building Improvements [Member] | Minimum [Member]
Estimated useful lives (Year)	7 years
Building and Building Improvements [Member] | Maximum [Member]
Estimated useful lives (Year)	40 years
Construction in Progress [Member]
Property, plant, and equipment, gross	$ 3,121	2,023
Property, Plant and Equipment, Other Types [Member]
Property, plant, and equipment, gross	$ 27,233	$ 25,009
Property, Plant and Equipment, Other Types [Member] | Minimum [Member]
Estimated useful lives (Year)	2 years
Property, Plant and Equipment, Other Types [Member] | Maximum [Member]
Estimated useful lives (Year)	10 years