Property, Equipment and Depreciation (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Property, Plant and Equipment [Line Items]
Amortization Period of Tires			2 years
Percentage of Tractor Fleet Depreciated at 150%	85.00%		85.00%
Depreciation	$ 13,664,000	$ 15,379,000	$ 26,042,000	$ 31,102,000
Tractors [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment, Salvage Value	15,000		15,000
Trailers [Member]
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment, Salvage Value	4,000		4,000
Communications and Utilities Expense [Member]
Property, Plant and Equipment [Line Items]
Depreciation	$ 167,000		$ 318,000