Credit Facilities Prior Year to Date Credit Faciltiy Metrics (Details) (USD $)			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Weighted Average Interest Rate [Member]	Jun. 30, 2011 Weighted Average Interest Rate [Member]	Jun. 30, 2012 Weighted Average Interest Rate [Member]	Jun. 30, 2011 Weighted Average Interest Rate [Member]	Jun. 30, 2012 Average Amount Outstanding [Member]	Jun. 30, 2011 Average Amount Outstanding [Member]	Jun. 30, 2012 Average Amount Outstanding [Member]	Jun. 30, 2011 Average Amount Outstanding [Member]	Jun. 30, 2012 Maximum Amount Outstanding [Member]	Jun. 30, 2011 Maximum Amount Outstanding [Member]	Jun. 30, 2012 Maximum Amount Outstanding [Member]	Jun. 30, 2011 Maximum Amount Outstanding [Member]
Credit Facilities Summary [Line Items]
Unamortized Debt Issuance Expense	$ 7,200,000	$ 6,600,000
Syndicated warehouse facility			0.0133	0.0167	0.0147	0.0166	155,375,000	346,493,000	141,842,000	352,466,000	429,839,000	826,859,000	621,257,000	826,859,000
U.S. Lease Warehouse Facility				$ 0.0158		$ 0.0160		$ 78,656,000		$ 48,453,000		$ 182,749,000		$ 182,749,000