Loans Receivable - Components of Loans Receivable, Net (Details) - USD ($) $ in Thousands |
Sep. 30, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|---|
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||
| Loans Receivable, Gross | $ 98,600 | $ 105,941 | |
| Allowance for Loan Losses | (13,138) | (11,454) | $ (6,624) |
| Unamortized Fees | (7,400) | (8,375) | |
| Loans Receivable, Net of Allowances and Unamortized Fees | 78,062 | 86,112 | |
| Credit Card Loans | |||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||
| Loans Receivable, Gross | 90,944 | 89,728 | |
| Acquired Loans | |||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||
| Loans Receivable, Gross | $ 7,656 | $ 16,213 |