Loans and Finance Receivables Held for Investment and Allowance for Credit Losses (Aging Analysis of Term Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Current loans and finance receivables	$ 1,078,904	$ 1,031,449
Total unpaid principal balance	1,203,322	1,144,954
1-14 calendar days past due
Financing Receivable, Past Due [Line Items]
Past due loans	21,951	27,655
15-29 calendar days past due
Financing Receivable, Past Due [Line Items]
Past due loans	15,363	14,665
30-59 calendar days past due
Financing Receivable, Past Due [Line Items]
Past due loans	22,745	21,470
60-89 calendar days past due
Financing Receivable, Past Due [Line Items]
Past due loans	18,624	19,031
90 calendar days past due
Financing Receivable, Past Due [Line Items]
Past due loans	$ 45,735	$ 30,684