Segment Reporting (Operating Income(Loss) (Details) (USD $) In Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Revenues	$ 1,348,549	$ 1,306,263	$ 2,594,176	$ 2,468,174
Inter-segment Revenue Eliminations	53,040	55,950	102,341	126,680
Revenue from External Customers	1,348,549	1,306,263	2,594,176	2,468,174
Operating Income (Loss)	60,165	35,432	96,861	49,832
Other [Member]
Revenues	12,297	14,019	24,294	25,858
Inter-segment Revenue Eliminations	10,437	11,980	21,440	22,982
Revenue from External Customers	1,860	2,039	2,854	2,876
Operating Income (Loss)	(1,408)	66	(785)	1,788
Inter-Segment Eliminations [Member]
Revenues	(53,040)	(55,950)	(102,341)	(126,680)
Freight [Member]
Revenues	839,829	816,965	1,607,570	1,541,968
Inter-segment Revenue Eliminations	12,435	12,934	23,726	25,382
Revenue from External Customers	827,394	804,031	1,583,844	1,516,586
Operating Income (Loss)	39,155	17,226	59,499	14,073
Logistics [Member]
Revenues	394,012	385,775	763,987	740,958
Inter-segment Revenue Eliminations	8,644	5,360	14,805	8,530
Revenue from External Customers	385,368	380,415	749,182	732,428
Operating Income (Loss)	12,095	13,008	20,741	25,864
Truckload [Member]
Revenues	155,451	145,454	300,666	286,070
Inter-segment Revenue Eliminations	21,524	25,676	42,370	69,786
Revenue from External Customers	133,927	119,778	258,296	216,284
Operating Income (Loss)	$ 10,323	$ 5,132	$ 17,406	$ 8,107

The net result for the period of deducting operating expenses from operating revenues.

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- Definition

Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 5
-Section 03
-Paragraph 1

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

+ Details

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- Definition

Amount of revenue from external customers for the reportable segment. Such disclosure is presented if the amount is: (a) included in the measure of segment profit or loss reviewed by the chief operating decision maker or (b) otherwise regularly provided to the chief operating decision maker, even if not included in that measure of segment profit or loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 131
-Paragraph 27
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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- Definition

Amount of revenue from transactions with other operating segments of the same entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 131
-Paragraph 27
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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