Benefit Plans	12 Months Ended
Benefit Plans	Dec. 31, 2023
Retirement Benefits [Abstract]
Benefit Plans	Benefit Plans Deferred Compensation Plans We established the Bank of Marin Executive Deferred Compensation Plan, which allows certain key management personnel designated by the Board of Directors of the Bank to defer up to 80% of their salary and 100% of their annual bonus. In addition, we assumed deferred compensation plans for certain members of management and non-employee directors as part of an acquisition in 2021. In 2021, we established a similar Deferred Director Fee Plan, which allows members of the Board of Directors to defer the cash portion of their director compensation. Amounts deferred earn interest equal to the prime rate, as published in the Wall Street Journal, on the first business day of each year, which was 7.50% on January 1, 2023, and 3.25% on January 1, 2022. Benefit payments will generally commence upon separation from service at or after normal retirement age, as elected by the participant. Our deferred compensation obligations under these plans totaled $6.6 million and $7.1 million at December 31, 2023 and 2022, respectively, and are included in interest payable and other liabilities. 401(k) Defined Contribution Plan Our 401(k) Defined Contribution Plan (“401(k) Plan”) is available to all regular employees at least eighteen years of age who complete ninety days of service, and participate in the plan beginning on the first day of the calendar quarter that immediately follows the date the participant meets the age and service requirements. Under the 401(k) Plan, employees can defer between 1% and 50% of their eligible compensation, up to the maximum amount allowed by the Internal Revenue Code. The Bank provides an employer-match of 70% of each participant's contribution, with a maximum of $5 thousand per participant per year. Employer matching contributions to the 401(k) Plan vest at a rate of 20% per year over five years. Employer contributions totaled $871 thousand, $949 thousand and $991 thousand for the years ended December 31, 2023, 2022 and 2021, respectively, and are recorded in salaries and employee benefits expense. Employee Stock Ownership Plan Our Employee Stock Ownership Plan (“ESOP”) is available to all employees under the same eligibility criteria as the 401(k) Plan; however, employee contributions are not permitted. The Board of Directors determines a specific portion of the Bank's profits to be contributed to the ESOP each year either in common stock or in cash for the purchase of Bancorp stock to be allocated to all eligible employees based on a percentage of their salaries, regardless of whether an employee participates in the 401(k) Plan. For all participants, employer contributions vest over a five-year service period. After five years of service, all future employer contributions vest immediately. Bancorp issued shares of common stock and contributed them to the ESOP totaling $1.3 million in 2023, $1.2 million in 2022 and $1.3 million in 2021, based on the quoted market price on the date of contribution. Cash dividends paid on Bancorp stock held by the ESOP are used to purchase additional shares in the open market. All shares of Bancorp stock held by the ESOP are included in the calculations of basic and diluted earnings per share. The Company's contributions to the ESOP are included in salaries and benefits expense. Supplemental Executive Retirement Plans Supplemental executive retirement plans ("SERPs") have been established for a select group of executive management who, upon retirement, will receive 25% of their estimated salary as salary continuation benefit payments that are fixed between five to fifteen years, depending on the executives' service period. Each participant is required to participate in the plan for five years before vesting begins. After five years, the participant vests ratably in the benefit over the remaining service period until age 65. As part of previous acquisitions, we assumed SERPs for certain former executive officers and directors. These plans are unfunded and nonqualified for tax purposes and for purposes of Title I of the Employee Retirement Income Security Act of 1974. At December 31, 2023 and 2022, respectively, our total liability under the SERPs was $4.5 million and $4.7 million recorded in interest payable and other liabilities.