Related-Party Transactions - Information on Dealer Loan Portfolio (Details) (Dealer Loan Portfolio, USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Dealer Loan Portfolio
Related Party Transaction [Line Items]
Total serviced portfolio	$ 676,856	$ 513,684
Cash collections due to owner	8,830	6,941
Servicing fees receivable	$ 997	$ 817