Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Revenues	$ 534,644	$ 542,120	$ 1,030,298	$ 1,034,142
Operating Income	52,210	42,330	90,395	65,771
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	417,015	429,390	807,578	832,575
Operating Income	47,312	38,320	83,154	59,100
Value Added Services
Segment Reporting Information [Line Items]
Revenues	103,450	100,501	194,310	185,655
Operating Income	5,004	2,255	7,453	4,110
Other Segment
Segment Reporting Information [Line Items]
Revenues	13,924	12,258	27,909	16,247
Operating Income	(239)	357	(684)	841
Corporate Segment
Segment Reporting Information [Line Items]
Revenues	725	829	1,246	1,387
Operating Income	133	1,398	472	1,720
Subtotal
Segment Reporting Information [Line Items]
Revenues	535,114	542,978	1,031,043	1,035,864
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	$ (470)	$ (858)	$ (745)	$ (1,722)