Debt Obligations Portfolio Term Financing (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Line of Credit Facility [Line Items]
Debt Balance	$ 1,049,478	$ 782,634
Securitization Debt [Member]
Line of Credit Facility [Line Items]
Debt Balance	677,118	679,031
Bank Term Financings [Member]
Line of Credit Facility [Line Items]
Debt Balance	347,360	3,603
Portfolio Term Residual Financing [Member]
Line of Credit Facility [Line Items]
Debt Balance	$ 25,000	$ 100,000