Loans Held for Investment and Allowance for Loan Losses (Aging Analysis of Term Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-delinquent loans	$ 596,791	$ 486,729
Total unpaid principal balance	651,970	543,790
1-14 calendar days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans	17,698	21,360
15-29 calendar days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans	10,574	8,703
30-59 calendar days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans	10,765	10,347
60-89 calendar days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans	8,621	7,443
90 calendar days past due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past due loans	$ 7,521	$ 9,208