Note 12 - Business Segments (Details Textual)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)
Number of Operating Segments			5
Number of Reportable Segments			4
Dedicated [Member]
Depreciation, Depletion and Amortization	$ 5,400,000	$ 5,100,000	$ 10,800,000	$ 10,000,000
Dedicated [Member] | Minimum [Member]
Customer Contract Term			3 years
Dedicated [Member] | Maximum [Member]
Customer Contract Term			5 years
Truckload [Member]
Depreciation, Depletion and Amortization	14,400,000	13,900,000	$ 29,000,000	27,600,000
Intermodal [Member]
Depreciation, Depletion and Amortization	1,100,000	987,000	2,200,000	1,900,000
Brokerage [Member]
Depreciation, Depletion and Amortization	$ 344,000	$ 376,000	$ 678,000	$ 857,000