Basis and Summary of Significant Accounting Policies - Credit Quality Indicators (Details) |
6 Months Ended | |
|---|---|---|
Jun. 30, 2017 |
Dec. 31, 2016 |
|
| Financing Receivable, Recorded Investment [Line Items] | ||
| Financing receivable, threshold of past dues financing receivable that requires allowance | 24 months | |
| FICO Score, 600 or Less | ||
| Financing Receivable, Recorded Investment [Line Items] | ||
| Financing receivable, percentage of loan portfolio per FICO Score | 1.70% | 1.80% |
| FICO Score, Between 600 and 700 | ||
| Financing Receivable, Recorded Investment [Line Items] | ||
| Financing receivable, percentage of loan portfolio per FICO Score | 77.20% | 78.10% |
| FICO Score, 700 or Greater | ||
| Financing Receivable, Recorded Investment [Line Items] | ||
| Financing receivable, percentage of loan portfolio per FICO Score | 21.10% | 20.10% |