Loan Loss Allowance and Credit Quality - Summary of Company's TDRs (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable Modifications [Line Items]
Accrued interest	$ 312,040	$ 319,157
Retail Installment Contracts
Financing Receivable Modifications [Line Items]
Total TDR principal	2,812,852	2,604,351
Accrued interest	68,967	70,965
Discount	(80,025)	(70,321)
Origination costs	4,324	4,161
Outstanding recorded investment	2,806,118	2,609,156
Allowance for loan losses	(498,811)	(475,128)
Outstanding recorded investment, net of allowance	2,307,307	2,134,028
Unsecured Consumer Loans
Financing Receivable Modifications [Line Items]
Total TDR principal	9,600	8,391
Discount	(147)	(274)
Origination costs	8	5
Outstanding recorded investment	9,461	8,122
Allowance for loan losses	(3,870)	(2,345)
Outstanding recorded investment, net of allowance	$ 5,591	$ 5,777