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Investment Securities - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items] |  |
Gross realized losses | $ 0.2 |
Gross realized gains |  | $ 0.1
Debt Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Proceeds from sale of securities | $ 12.4 | $ 10.2
Average percent of amortized cost for securities in unrealized loss positions for more than 12 months | 99.30% |

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