Loans and Finance Receivables Held for Investment and Allowance for Credit Losses (Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unpaid principal balance	$ 1,203,322	$ 1,144,954
Net deferred origination costs	24,489	24,453
Total loans and finance receivables held for investment	1,227,811	1,169,407
Term loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unpaid principal balance	937,883	956,755
Lines of credit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unpaid principal balance	253,908	188,199
Other loans and finance receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total unpaid principal balance	$ 11,531	$ 0