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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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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.

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-Publisher FASB
-Name Accounting Standards Codification
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The amount of cash paid during the reporting period for charges associated with the mergers.

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