Segment Information (Summary Of Segment Information) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 492,022	$ 492,887
Operating Income	23,441	28,693
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	403,185	408,900
Operating Income	20,780	23,615
Value Added Services
Segment Reporting Information [Line Items]
Revenues	85,154	82,510
Operating Income	1,855	3,613
Other Segment
Segment Reporting Information [Line Items]
Revenues	3,989	2,044
Operating Income	484	905
Corporate Segment
Segment Reporting Information [Line Items]
Revenues	558	650
Operating Income	322	560
Subtotal
Segment Reporting Information [Line Items]
Revenues	492,886	494,104
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	$ (864)	$ (1,217)