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Merger - Business Acquisition, Pro Forma Information (Details) - USD ($) $ in Thousands | 2 Months Ended | 3 Months Ended | 9 Months Ended
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Business Acquisition, Pro Forma Information [Abstract] |  |  |  |  |
Net interest income - Actual |  | $ 27,753 | $ 24,566 | $ 74,318 | $ 73,060
Net income - Actual |  | 5,282 | 7,491 | 23,514 | 22,125
American River Bank (ARB) Merger |  |  |  |  |
Business Acquisition, Pro Forma Information [Abstract] |  |  |  |  |
Net interest income - Pro forma | $ 3,427 | 30,488 | 31,386 | 91,240 | 92,791
Net income - Pro forma | $ 2,993 | 9,953 | 9,182 | 33,422 | 19,638
Total merger-related one-time and conversion costs |  |  |  | 3,600 |
Bank of Marin |  |  |  |  |
Business Acquisition, Pro Forma Information [Abstract] |  |  |  |  |
Total merger-related one-time and conversion costs |  | $ 5,142 | $ 0 | $ 5,359 | $ 0

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- Definition The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
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