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Acquisition - Core Deposit Intangible (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items] |  |  |
Amortization of core deposit intangible | $ 529 | $ 533 | $ 619
Core deposit intangible |  |  |
Future Amortization Expense: |  |  |
2018 | 921 |  |
2019 | 887 |  |
2020 | 853 |  |
2021 | 818 |  |
2022 | 782 |  |
Thereafter | 2,231 |  |
Total | $ 6,492 |  |
Bank of Napa, N.A. (Napa) | Core deposit intangible |  |  |
Acquired Finite-Lived Intangible Assets [Line Items] |  |  |
Core deposit intangible useful life | 10 years |  |
Amortization of core deposit intangible | $ 56 |  |
Future Amortization Expense: |  |  |
2018 | 508 |  |
2019 | 499 |  |
2020 | 488 |  |
2021 | 475 |  |
2022 | 460 |  |
Thereafter | 1,955 |  |
Total | $ 4,385 |  |

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