Loan Loss Allowance and Credit Quality - Summary of Activity in Loan Loss Allowance (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Retail Installment Contracts Acquired Individually
Accounts Notes And Loans Receivable [Line Items]
Balance — beginning of period	$ 2,132,634	$ 1,555,362
Provision for loan losses	656,706	251,641
Charge-offs	(752,565)	(384,726)
Recoveries	407,777	238,335
Balance — end of period	2,444,552	1,660,612
Receivables From Dealers
Accounts Notes And Loans Receivable [Line Items]
Balance — beginning of period	1,090
Provision for loan losses	(55)
Balance — end of period	1,035
Unsecured Short Term Consumer Loans
Accounts Notes And Loans Receivable [Line Items]
Balance — beginning of period	179,350
Provision for loan losses	62,129
Charge-offs	(40,948)
Recoveries	2,659
Balance — end of period	$ 203,190