Acquisition of Gordon Trucking, Inc. Acquisition pro forma information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Acquisition of Gordon Trucking, Inc. [Abstract]
Business Acquisition, Pro Forma Revenue	$ 961,525	$ 972,340
Business Acquisition, Pro Forma Net Income (Loss)	$ 90,821	$ 64,769

The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(2)-(3)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration