Loan Loss Allowance and Credit Quality - Summary Commercial Loan Credit Quality Indicators for Receivables from Dealers Held for Investment (Details) (Receivables From Dealers, USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Financing Receivable Recorded Investment [Line Items]
Commercial Loan Credit Quality Indicators	$ 85,885	$ 95,835
Pass
Financing Receivable Recorded Investment [Line Items]
Commercial Loan Credit Quality Indicators	83,754	95,835
Special Mention
Financing Receivable Recorded Investment [Line Items]
Commercial Loan Credit Quality Indicators	2,131	0
Substandard
Financing Receivable Recorded Investment [Line Items]
Commercial Loan Credit Quality Indicators	0	0
Doubtful
Financing Receivable Recorded Investment [Line Items]
Commercial Loan Credit Quality Indicators	0	0
Loss
Financing Receivable Recorded Investment [Line Items]
Commercial Loan Credit Quality Indicators	$ 0	$ 0