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Securities (Additional Information) (Details) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2009 USD ($) | Mar. 31, 2019 USD ($) investment | Dec. 31, 2018 USD ($) investment
Debt Securities, Available-for-sale [Line Items] |  |  |
Carrying value of securities pledged to secure repurchase agreements, public and trust deposits and other by law |  | $ 209,016,000 | $ 211,239,000
Original amount in non-controlling investment security in a single banking organization |  | 353,000 | $ 353,000
Additional impairment on equity securities recognized through earnings |  | $ 0 |
Equity Securities |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |
Number of non-controlling investments in a single banking organization | investment |  | 1 | 1
Original amount in non-controlling investment security in a single banking organization | $ 1,350,000 |  |
Other than temporary impairment loss recognized in earnings, non-controlling investment in single banking organization | $ 997,000 |  |

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