Leases (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating Leased Assets [Line Items]
Factor which may result in customer being classified as high risk	less than 3 years
Impaired direct financing receivables	$ 0	$ 0
Proceeds from sale-leaseback transaction	130,184,000	37,395,000	0
Rent expense	148,000,000	154,000,000	156,000,000
Contingent rentals from operating leases	319,000,000	303,000,000	294,000,000
Operating Leases [Member]
Operating Leased Assets [Line Items]
Contingent rental income	(1,000,000)	(2,000,000)	(2,000,000)
Direct Financing Leases [Member]
Operating Leased Assets [Line Items]
Contingent rental income	$ (11,000,000)	$ (11,000,000)	$ (12,000,000)
Trucks and Tractors [Member]
Operating Leased Assets [Line Items]
Minimum lease term of revenue earning equipment	3 years
Maximum lease term of revenue earning equipment	7 years
Trailers [Member]
Operating Leased Assets [Line Items]
Maximum lease term of revenue earning equipment	10 years