Note 17 - Business Segments (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Number of Operating Segments	5
Number of Reportable Segments	4
Dedicated [Member]
Depreciation, Depletion and Amortization	$ 22.0	$ 20.6	$ 15.0
Dedicated [Member] | Minimum [Member]
Customer Contract Term	3 years
Dedicated [Member] | Maximum [Member]
Customer Contract Term	5 years
Truckload [Member]
Depreciation, Depletion and Amortization	$ 57.2	56.2	53.7
Intermodal [Member]
Depreciation, Depletion and Amortization	4.6	3.9	5.4
Brokerage [Member]
Depreciation, Depletion and Amortization	$ 1.3	$ 1.7	$ 1.3