Goodwill And Intangible Assets (Schedule Of Changes In Gross Carrying Amounts Of Goodwill) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2012
Goodwill [Line Items]
Goodwill	$ 520,765	$ 520,699	$ 521,000
Accumulated impairment losses	(183,049)	(183,049)	(183,049)
Total Goodwill	337,716	337,650	337,951
Change in foreign currency exchange rates	235	66
Logistics [Member]
Goodwill [Line Items]
Goodwill	55,440	55,374	55,675
Accumulated impairment losses	(48,236)	(48,236)	(48,236)
Total Goodwill	7,204	7,138	7,439
Change in foreign currency exchange rates	235	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
Other [Member]
Goodwill [Line Items]
Goodwill	727	727	727
Accumulated impairment losses
Total Goodwill	$ 727	$ 727	$ 727

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 142

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-Subparagraph e

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-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

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-Name Statement of Financial Accounting Standard (FAS)

-Number 142

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-Subparagraph e

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-Number 141R

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-Publisher FASB

-Name Accounting Standards Codification

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

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