Note 1 - Significant Accounting Policies - Segment By Operating Fleet Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Total revenue	$ 243,303	$ 178,631	$ 613,187	$ 501,701
Truckload [Member]
Total revenue	197,053	153,066	522,312	446,322
Truckload [Member] | Covenant Transport, Inc. [Member]
Total revenue	108,223	95,100	309,583	272,387
Truckload [Member] | Southern Refrigerated Transport, Inc. [Member]
Total revenue	47,866	41,382	134,163	123,905
Truckload [Member] | Star Transportation Inc [Member]
Total revenue	19,887	16,584	57,489	50,030
Truckload [Member] | Landair [Member]
Total revenue	21,077		21,077
Managed Freight [Member]
Total revenue	$ 46,250	$ 25,565	$ 90,875	$ 55,379