Loans Receivable - Aging of the Loans Receivable Balance (Details) - USD ($) $ in Thousands |
9 Months Ended | 12 Months Ended |
|---|---|---|
Sep. 30, 2018 |
Dec. 31, 2017 |
|
| Financing Receivable, Recorded Investment, Past Due [Line Items] | ||
| Past due loans receivable | 14.90% | 14.80% |
| Current loans receivable | 85.10% | 85.20% |
| Balance of Credit Card Loans on Nonaccrual Status | $ 2,016 | $ 2,016 |
| 30-59 days past due | ||
| Financing Receivable, Recorded Investment, Past Due [Line Items] | ||
| Past due loans receivable | 7.00% | 7.10% |
| 60-89 days past due | ||
| Financing Receivable, Recorded Investment, Past Due [Line Items] | ||
| Past due loans receivable | 3.40% | 3.60% |
| 90 or more days past due | ||
| Financing Receivable, Recorded Investment, Past Due [Line Items] | ||
| Past due loans receivable | 4.50% | 4.10% |
| Balance of Loans Receivable 90 or More Days Past Due and Still Accruing Interest and Fees | $ 0 | $ 0 |