Property, Equipment, and Depreciation (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Property, Plant and Equipment
Amortization Period of Tires	2 years
Depreciation	$ 15,066,000	$ 13,939,000
Communications and Utilities Expense [Member]
Property, Plant and Equipment
Depreciation	200,000	200,000
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