Note 5 - Property and Equipment (Details) - Property and Equipment, at Cost (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	505,345	$ 462,376
Revenue Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Revenue Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Revenue Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	418,574	372,968
Office Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Office Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	8,248	9,084
Land and Land Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	0 years
Land and Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	10 years
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	18,820	19,009
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	7 years
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	40 years
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	37,217	41,876
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	2,976	1,859
Property, Plant and Equipment, Other Types [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	2 years
Property, Plant and Equipment, Other Types [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives	7 years
Property, Plant and Equipment, Other Types [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, gross	19,510	$ 17,580