Note 3 - Business Acquisition (Details Textual) - USD ($) $ in Thousands		12 Months Ended
	Mar. 20, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Payments to Acquire Businesses, Gross			$ 2,219
Goodwill, Ending Balance		$ 57,708	$ 57,708
Small Truckload Carrier [Member]
Business Combination, Consideration Transferred, Total	$ 10,600
Payments to Acquire Businesses, Gross	2,200
Business Combination, Consideration Transferred, Liabilities Incurred	5,400
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment, Total	5,900
Goodwill, Ending Balance	2,200
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities, Total	5,400
Small Truckload Carrier [Member] | Customer Relationships [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 2,500
Finite-Lived Intangible Asset, Useful Life	7 years
Small Truckload Carrier [Member] | Paid in Three Equal Installments each Anniversary Date [Member]
Payments to Acquire Businesses, Gross	$ 3,000