Goodwill And Intangible Assets (Schedule Of Changes In Gross Carrying Amounts Of Goodwill) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill [Line Items]
Goodwill	$ 520,869	$ 520,765	$ 520,699
Accumulated impairment losses	(183,049)	(183,049)	(183,049)
Total Goodwill	337,820	337,716	337,650
Change in foreign currency exchange rates	104	66
Logistics [Member]
Goodwill [Line Items]
Goodwill	55,544	55,440	55,374
Accumulated impairment losses	(48,236)	(48,236)	(48,236)
Total Goodwill	7,308	7,204	7,138
Change in foreign currency exchange rates	104	66
Truckload [Member]
Goodwill [Line Items]
Goodwill	464,598	464,598	464,598
Accumulated impairment losses	(134,813)	(134,813)	(134,813)
Total Goodwill	329,785	329,785	329,785
Change in foreign currency exchange rates	0	0
Other [Member]
Goodwill [Line Items]
Goodwill	727	727	727
Accumulated impairment losses	0	0	0
Total Goodwill	727	727	727
Change in foreign currency exchange rates	$ 0	$ 0