Loan Loss Allowance and Credit Quality - Summary of Performing and Non-performing TDRs (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Retail Installment Contracts
Troubled Debt Restructuring Debtor Current Period [Line Items]
Current	$ 2,171,354	$ 1,690,893
31-60 days past due	635,787	556,489
Greater than 60 days past due (non-performing)	344,473	356,969
Total TDRs	3,151,614	2,604,351
Unsecured Consumer Loans
Troubled Debt Restructuring Debtor Current Period [Line Items]
Current	13,008	6,120
31-60 days past due	972	875
Greater than 60 days past due (non-performing)	5,560	1,396
Total TDRs	$ 19,540	$ 8,391