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Merger Agreement - Narrative (Details) $ in Thousands | Jun. 30, 2021 USD ($) | Apr. 16, 2021 branch shares | Dec. 31, 2020 USD ($)
--- | --- | --- | ---
Business Combination, Separately Recognized Transactions [Line Items] |  |  |
Assets | $ 3,073,818 |  | $ 2,911,926
Deposits | 2,683,575 |  | 2,504,249
Loans at amortized cost | 2,002,767 |  | $ 2,088,556
American River Bank (ARB) Merger | American River Bank (ARB) |  |  |
Business Combination, Separately Recognized Transactions [Line Items] |  |  |
Number of branches | branch |  | 10 |
Assets | 906,100 |  |
Deposits | 787,700 |  |
Loans at amortized cost | $ 434,200 |  |
American River Bank (ARB) Merger | Bank of Marin |  |  |
Business Combination, Separately Recognized Transactions [Line Items] |  |  |
Merger agreement, shares exchange ratio (in shares) | shares |  | 0.575 |

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