Fair Value Measurements (Details 1) (USD $)			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trucks [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trucks [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Tractors [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Tractors [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trailers [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Revenue earning equipment, Trailers [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Trucks [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Trucks [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Tractors [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Tractors [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Trailers [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member] Revenue earning equipment, Trailers [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Trucks [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Trucks [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Tractors [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Tractors [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Trailers [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member] Revenue earning equipment, Trailers [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Trucks [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Trucks [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Tractors [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Tractors [Member]	Mar. 31, 2013 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Trailers [Member]	Mar. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member] Revenue earning equipment, Trailers [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value											$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 29,161,000	$ 11,459,000	$ 13,229,000	$ 7,321,000	$ 14,943,000	$ 3,514,000	$ 989,000	$ 624,000
Total Losses			4,721,000	3,359,000	3,029,000	2,381,000	1,095,000	471,000	597,000	507,000
Fair Value Measurements (Textuals) (Abstract)
Fair value of total debt	$ 4,020,000,000	$ 3,990,000,000