Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 482,802	$ 495,654
Operating Income	32,487	38,185
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	372,917	390,563
Operating Income	32,359	35,842
Value Added Services
Segment Reporting Information [Line Items]
Revenues	96,577	90,860
Operating Income	5,035	2,449
Other Segment
Segment Reporting Information [Line Items]
Revenues	13,178	13,985
Operating Income	(1,934)	(445)
Corporate Segment
Segment Reporting Information [Line Items]
Revenues	373	521
Operating Income	(2,973)	339
Subtotal
Segment Reporting Information [Line Items]
Revenues	483,045	495,929
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	$ (243)	$ (275)