Segment Information (Summary Of Segment Information) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 495,654	$ 492,022
Operating Income	38,185	23,441
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	390,563	403,185
Operating Income	35,842	20,780
Value Added Services
Segment Reporting Information [Line Items]
Revenues	90,860	85,154
Operating Income	2,449	1,855
Other Segment
Segment Reporting Information [Line Items]
Revenues	13,985	3,989
Operating Income	(445)	484
Corporate Segment
Segment Reporting Information [Line Items]
Revenues	521	558
Operating Income	339	322
Subtotal
Segment Reporting Information [Line Items]
Revenues	495,929	492,886
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	$ (275)	$ (864)