Property, Equipment, and Depreciation (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Property, Plant and Equipment
Amortization Period of Tires			2 years
Depreciation	$ 15,117,000	$ 14,250,000	$ 47,112,000	$ 42,184,000
Change in Accounting Estimate, Financial Effect	2100		2100
Communications and Utilities Expense [Member]
Property, Plant and Equipment
Depreciation	200,000	200,000	500,000	500,000
Tractors [Member]
Property, Plant and Equipment
Property, Plant, and Equipment, Salvage Value	15,000		15,000
Trailers [Member]
Property, Plant and Equipment
Property, Plant, and Equipment, Salvage Value	$ 4,000		$ 4,000