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Securities - Narrative (Details) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2019 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2019 USD ($) security institution | Sep. 30, 2018 USD ($) | Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |
Proceeds from sales of securities available for sale | $ 199,875,000 | $ 2,387,000 | $ 212,485,000 | $ 2,387,000 |
Fair Value | 1,238,577,000 |  | $ 1,238,577,000 |  | $ 1,250,777,000
Number of institutions issuing debt | institution |  |  | 150 |  |
Secure government, public and trust deposits |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |
Available for sale securities pledged as collateral | 382,678,000 |  | $ 382,678,000 |  | 619,308,000
Short-term borrowings |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |
Available for sale securities pledged as collateral | 28,041,000 |  | 28,041,000 |  | 18,299,000
Trust preferred securities |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |
Fair Value | $ 9,862,000 |  | $ 9,862,000 |  | $ 10,633,000
Number of securities representing interests in tranches of trusts (tranches) | security |  |  | 2 |  |
Impairments |  |  | $ 0 |  |

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