Note 15 - Business Segments (Details Textual)	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Number of Operating Segments	5
Number of Reportable Segments	4
Dedicated [Member]
Depreciation, Depletion and Amortization	$ 20,600,000	$ 15,000,000	$ 8,200,000
Dedicated [Member] | Minimum [Member]
Customer Contracts, Term	3 years
Dedicated [Member] | Maximum [Member]
Customer Contracts, Term	5 years
Truckload [Member]
Depreciation, Depletion and Amortization	$ 56,200,000	53,700,000	53,000,000
Intermodal [Member]
Depreciation, Depletion and Amortization	3,900,000	5,400,000	6,000,000
Brokerage [Member]
Depreciation, Depletion and Amortization	$ 1,700,000	$ 1,300,000	$ 993,000