Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Revenues	$ 534,448	$ 551,961	$ 1,564,746	$ 1,586,103
Operating Income	52,800	41,690	143,195	107,461
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	417,861	428,619	1,225,439	1,261,194
Operating Income	48,747	39,138	131,901	98,238
Value Added Services
Segment Reporting Information [Line Items]
Revenues	102,149	106,490	296,459	292,145
Operating Income	5,021	1,022	12,474	5,132
Other Segment
Segment Reporting Information [Line Items]
Revenues	14,087	16,868	41,996	33,115
Operating Income	(1,354)	404	(2,038)	1,245
Corporate Segment
Segment Reporting Information [Line Items]
Revenues	634	688	1,880	2,075
Operating Income	386	1,126	858	2,846
Subtotal
Segment Reporting Information [Line Items]
Revenues	534,731	552,665	1,565,774	1,588,529
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues	$ (283)	$ (704)	$ (1,028)	$ (2,426)