Related-Party Transactions - Information on Serviced Auto Loan and Retail Installment Contract Portfolio (Details) (Serviced Auto Loan And Retail Installment, USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Serviced Auto Loan And Retail Installment
Related Party Transaction [Line Items]
Total serviced portfolio	$ 1,096,905	$ 1,175,566
Cash collections due to owner	32,698	32,831
Servicing fees receivable (refundable)	$ 661	$ (3,163)