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Securities - Narrative (Details) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2018 USD ($) investment | Sep. 30, 2017 USD ($) | Sep. 30, 2018 USD ($) investment | Sep. 30, 2017 USD ($) | Dec. 31, 2017 USD ($)
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Proceeds from sale of available-for-sale securities | $ | $ 0 | $ 12,363,748 |  | $ 12,363,748 |
Loss from redemption of securities | $ |  | 1,780 | $ 1,200 | 1,780 |
Gross realized gains, available for sale | $ |  | $ 145,288 |  | $ 145,288 |
Collateral Pledged [Member] |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Restricted securities | $ | $ 109,500,000 |  | $ 109,500,000 |  | $ 97,200,000
US Government-sponsored Enterprises Debt Securities [Member] |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Number of positions | investment | 8 |  | 8 |  |
Municipal securities [Member] |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Number of positions | investment | 32 |  | 32 |  |
Other debt securities [Member] |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Number of positions | investment | 1 |  | 1 |  |
Mortgage-backed securities [Member] |  |  |  |  |
Loans and Leases Receivable Disclosure [Line Items] |  |  |  |  |
Number of positions | investment | 66 |  | 66 |  |

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