Loans Held for Investment and Allowance for Loan Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unpaid principal balance	$ 1,026,158	$ 980,451
Net deferred origination costs	20,426	19,994
Total loans held for investment	1,046,584	1,000,445
Term loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unpaid principal balance	903,763	864,066
Lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unpaid principal balance	$ 122,395	$ 116,385