Note 1 - Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Lease, Right-of-Use Asset	$ 53,400
Operating Lease, Liability, Total	54,793
Operating Lease, Liability, Current	17,875
Operating Lease, Liability, Noncurrent	$ 36,916
Tractors [Member]
Property, Plant and Equipment, Useful Life	5 years
Property, Plant and Equipment, Salvage Value, Percentage	15.00%
Refrigerated Trailers [Member]
Property, Plant and Equipment, Useful Life	7 years
Dry Van Trailers [Member]
Property, Plant and Equipment, Useful Life	10 years
Property, Plant and Equipment, Salvage Value, Percentage	25.00%
Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset		$ 40,100
Operating Lease, Liability, Total		41,000
Operating Lease, Liability, Current		15,300
Operating Lease, Liability, Noncurrent		$ 25,700