Loans and Finance Receivables Held for Investment and Allowance for Credit Losses (Aging Analysis of Term Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Current loans and finance receivables	$ 1,060,465	$ 1,031,449
Total unpaid principal balance	1,185,122	1,144,954
1-14 calendar days past due
Financing Receivable, Past Due [Line Items]
Past due loans	23,798	27,655
15-29 calendar days past due
Financing Receivable, Past Due [Line Items]
Past due loans	15,518	14,665
30-59 calendar days past due
Financing Receivable, Past Due [Line Items]
Past due loans	23,931	21,470
60-89 calendar days past due
Financing Receivable, Past Due [Line Items]
Past due loans	18,162	19,031
90 calendar days past due
Financing Receivable, Past Due [Line Items]
Past due loans	$ 43,248	$ 30,684