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Significant Accounting Policies Property, Equipment and Depreciation (Details) (USD $) | 12 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Property, Plant and Equipment |  |  |
Amortization Period of Tires | 2 years |  |
Depreciation | $ 57,158,000 | $ 57,226,000 | $ 61,949,000
Communications and Utilities Expense [Member] |  |  |
Property, Plant and Equipment |  |  |
Depreciation | 700,000 | 700,000 |
Tractors [Member] |  |  |
Property, Plant and Equipment |  |  |
Property, Plant, and Equipment, Salvage Value | 15,000 |  |
Trailers [Member] |  |  |
Property, Plant and Equipment |  |  |
Property, Plant, and Equipment, Salvage Value | $ 4,000 |  |
Minimum [Member] | Land Improvements and Buildings [Member] |  |  |
Property, Plant and Equipment |  |  |
Property, Plant and Equipment, Useful Life | 5 years |  |
Minimum [Member] | Furniture and Fixtures [Member] |  |  |
Property, Plant and Equipment |  |  |
Property, Plant and Equipment, Useful Life | 3 years |  |
Minimum [Member] | Shop and Service Equipment [Member] |  |  |
Property, Plant and Equipment |  |  |
Property, Plant and Equipment, Useful Life | 3 years |  |
Minimum [Member] | Revenue Equipment [Member] |  |  |
Property, Plant and Equipment |  |  |
Property, Plant and Equipment, Useful Life | 5 years |  |
Maximum [Member] | Land Improvements and Buildings [Member] |  |  |
Property, Plant and Equipment |  |  |
Property, Plant and Equipment, Useful Life | 30 years |  |
Maximum [Member] | Furniture and Fixtures [Member] |  |  |
Property, Plant and Equipment |  |  |
Property, Plant and Equipment, Useful Life | 5 years |  |
Maximum [Member] | Shop and Service Equipment [Member] |  |  |
Property, Plant and Equipment |  |  |
Property, Plant and Equipment, Useful Life | 10 years |  |
Maximum [Member] | Revenue Equipment [Member] |  |  |
Property, Plant and Equipment |  |  |
Property, Plant and Equipment, Useful Life | 7 years |  |

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- Definition No authoritative reference available. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 -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. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 + Details
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