Credit Facilities (Details) (U.S. Dollar [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Credit Facilities Summary [Line Items]
Line of Credit Facilty -Syndicated warehouse facility	$ 2,500,000
Line of Credit Facilty - U.S. Lease Warehouse Facility	600,000
Line of Credit Facility - Canada Lease Warehouse Facility	803,455
Line of Credit Facility Advances Outstanding [Member]
Credit Facilities Summary [Line Items]
Line of Credit Facilty -Syndicated warehouse facility		621,257
Line of Credit Facilty - U.S. Lease Warehouse Facility
Line of Credit Facility - Canada Lease Warehouse Facility	354,203	181,314
Line of Credit Facility - Medium-term note facility		293,528
Line of Credit Facility - Wachovia Funding Facility		3,292
Credit Facility Totals	$ 354,203	$ 1,099,391