Note E - Segment Information - Segment Revenue Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue, before fuel surcharge	$ 93,097	$ 98,921	$ 186,700	$ 192,570
Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Revenue, before fuel surcharges, percentage	100.00%	100.00%	100.00%	100.00%
Truckload Services [Member]
Revenue, before fuel surcharge	$ 81,656	$ 86,880	$ 164,575	$ 168,987
Truckload Services [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Revenue, before fuel surcharges, percentage	87.70%	87.80%	88.10%	87.80%
Brokerage and Logistics Services [Member]
Revenue, before fuel surcharge	$ 11,441	$ 12,041	$ 22,125	$ 23,583
Brokerage and Logistics Services [Member] | Sales Revenue, Net [Member] | Product Concentration Risk [Member]
Revenue, before fuel surcharges, percentage	12.30%	12.20%	11.90%	12.20%