Segment Information (Disclosure Of Segment Financial Information) (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Revenues	$ 515,897	$ 463,469	$ 985,326	$ 888,544
Operating Income	46,767	35,546	74,209	53,810
Truckload Transportation Services Segment [Member]
Revenues	439,944	394,563	842,290	755,106
Operating Income	44,764	32,087	69,030	46,635
Value Added Services Segment [Member]
Revenues	71,227	65,066	134,800	126,466
Operating Income	3,719	2,346	7,129	5,430
Other Segment [Member]
Revenues	3,234	2,735	5,911	5,047
Operating Income	(1,903)	55	(1,622)	171
Corporate Segment [Member]
Revenues	1,492	1,105	2,325	1,925
Operating Income	$ 187	$ 1,058	$ (328)	$ 1,574