Fair Value Measurements (Details 1) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Total Losses	$ 11,270,000	$ 26,258,000	$ 52,000,000
Fair Value Measurements (Textual) (Abstract)
Fair value of total debt	3,510,000,000	2,860,000,000
Loss to reflect changes in fair value	11,270,000	26,258,000	52,000,000
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Total Losses	11,270,000	26,258,000
Fair Value Measurements (Textual) (Abstract)
Loss to reflect changes in fair value	11,270,000	26,258,000
Fair Value, Measurements, Nonrecurring [Member] | Revenue earning equipment, Trucks [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Total Losses	6,645,000	13,014,000
Fair Value Measurements (Textual) (Abstract)
Loss to reflect changes in fair value	6,645,000	13,014,000
Fair Value, Measurements, Nonrecurring [Member] | Revenue earning equipment, Tractors [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Total Losses	2,197,000	9,432,000
Fair Value Measurements (Textual) (Abstract)
Loss to reflect changes in fair value	2,197,000	9,432,000
Fair Value, Measurements, Nonrecurring [Member] | Revenue earning equipment, Trailers [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Total Losses	2,428,000	3,812,000
Fair Value Measurements (Textual) (Abstract)
Loss to reflect changes in fair value	2,428,000	3,812,000
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member] | Revenue earning equipment, Trucks [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member] | Revenue earning equipment, Tractors [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member] | Revenue earning equipment, Trailers [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member] | Revenue earning equipment, Trucks [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member] | Revenue earning equipment, Tractors [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member] | Revenue earning equipment, Trailers [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	9,483,000	22,051,000
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Revenue earning equipment, Trucks [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	6,147,000	11,796,000
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Revenue earning equipment, Tractors [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	3,040,000	8,818,000
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | Revenue earning equipment, Trailers [Member]
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets held for sale at fair value	$ 296,000	$ 1,437,000