Note 12 - Business Segments (Details Textual)	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Number of Operating Segments			5
Number of Reportable Segments			4
Dedicated [Member]
Depreciation, Depletion and Amortization	$ 5,600,000	$ 5,200,000	$ 16,400,000	$ 15,300,000
Dedicated [Member] | Minimum [Member]
Customer Contract Term			3 years
Dedicated [Member] | Maximum [Member]
Customer Contract Term			5 years
Truckload [Member]
Depreciation, Depletion and Amortization	14,100,000	14,100,000	$ 43,100,000	41,700,000
Intermodal [Member]
Depreciation, Depletion and Amortization	1,200,000	995,000	3,400,000	2,900,000
Brokerage [Member]
Depreciation, Depletion and Amortization	$ 328,000	$ 400,000	$ 1,000,000	$ 1,300,000