Significant Accounting Policies Property, Equipment and Depreciation (Details) (USD $)	12 Months Ended
	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