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Loans Held for Investment - By Region (Details) | Dec. 31, 2018 | Dec. 31, 2017
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Loans held for investment by Region [Line Items] |  |
Percentage of Loans concentrated in major states | 39.90% | 40.40%
New York |  |
Loans held for investment by Region [Line Items] |  |
Percentage of Loans held in state | 10.30% | 10.50%
California |  |
Loans held for investment by Region [Line Items] |  |
Percentage of Loans held in state | 9.30% | 9.30%
Pennsylvania |  |
Loans held for investment by Region [Line Items] |  |
Percentage of Loans held in state | 8.50% | 8.50%
New Jersey |  |
Loans held for investment by Region [Line Items] |  |
Percentage of Loans held in state | 6.80% | 6.90%
Illinois |  |
Loans held for investment by Region [Line Items] |  |
Percentage of Loans held in state | 5.00% | 5.20%

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