Property, Equipment, and Depreciation (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Property, Plant and Equipment
Amortization Period of Tires			2 years
Depreciation	$ 16,930,000	$ 13,995,000	$ 31,995,000	$ 27,934,000
Communications and Utilities Expense [Member]
Property, Plant and Equipment
Depreciation	200,000	200,000	300,000	300,000
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