Significant Accounting Policies Property, Equipment and Depreciation (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Property, Plant and Equipment
Amortization Period of Tires	2 years
Percentage of Tractor Fleet Depreciated at 150 Percent	100.00%	68.00%	54.00%	0.00%
Depreciation	$ 57,226,000	$ 61,949,000	$ 58,730,000
Communications and Utilities Expense [Member]
Property, Plant and Equipment
Depreciation	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
Land Improvements and Buildings [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life, Minimum	5
Property, Plant and Equipment, Useful Life, Maximum	30
Furniture and Fixtures [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life, Minimum	3
Property, Plant and Equipment, Useful Life, Maximum	5
Shop and Service Equipment [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life, Minimum	3
Property, Plant and Equipment, Useful Life, Maximum	10
Revenue Equipment [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life, Minimum	5
Property, Plant and Equipment, Useful Life, Maximum	7