Loans Held for Investment, Allowance for Loan Losses and Loans Held for Sale (Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unpaid principal balance	$ 980,451	$ 543,790
Net deferred origination costs	19,994	8,952
Total loans held for investment	1,000,445	552,742
Term loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unpaid principal balance	864,066	482,596
Lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unpaid principal balance	$ 116,385	$ 61,194