$BMRC
Bank of Marin Bancorp Stock $bmrc

$bmrc Overview Financials Valuation SEC Filings Company Website

2024 Q1 Form 10-K Financial Statement

#000140347524000012 Filed on March 14, 2024

Income Statement

Concept	2024 Q1	2023 Q4	2023
Revenue	$34.15M	$35.42M	$139.5M
YoY Change	-0.59%	3.57%	7.27%
Cost Of Revenue
YoY Change
Gross Profit
YoY Change
Gross Profit Margin
Selling, General & Admin
YoY Change
% of Gross Profit
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$639.0K	$718.0K	$3.448M
YoY Change	-47.92%	-24.1%	91.56%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense	$11.45M	$11.16M	$36.73M
YoY Change	157.46%	1242.84%	1341.07%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$3.929M	$392.0K	$26.04M
YoY Change	-69.49%	-97.78%	-59.0%
Income Tax	$1.007M	-$218.0K	$6.141M
% Of Pretax Income	25.63%	-55.61%	23.59%
Net Earnings	$2.922M	$610.0K	$19.90M
YoY Change	-69.05%	-95.26%	-57.29%
Net Earnings / Revenue	8.56%	1.72%	14.26%
Basic Earnings Per Share	$0.18	$0.04	$1.24
Diluted Earnings Per Share	$0.18	$0.04	$1.24
COMMON SHARES
Basic Shares Outstanding	16.19M shares	16.14M shares	16.01M shares
Diluted Shares Outstanding	16.09M shares	16.05M shares	16.03M shares

Balance Sheet

Concept	2024 Q1	2023 Q4	2023
SHORT-TERM ASSETS
Cash & Short-Term Investments
YoY Change
Cash & Equivalents	$36.31M	$30.45M
Short-Term Investments
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$29.10M	$28.11M	$28.11M
YoY Change	-7.75%	-14.71%	-14.71%
Goodwill	$72.75M	$72.80M
YoY Change	0.0%	0.06%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets			$35.07M
YoY Change			-20.04%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$3.767B	$3.804B	$3.804B
YoY Change	-8.9%	-8.28%	-8.28%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$21.98M	$25.56M	$25.56M
YoY Change	-5.63%	11.4%	11.4%
Accrued Expenses	$24.15M	$22.91M	$22.91M
YoY Change	-5.04%	-14.01%	-14.01%
Deferred Revenue
YoY Change
Short-Term Debt
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$46.13M	$48.47M	$48.47M
YoY Change	-5.33%	-2.25%	-2.25%
LONG-TERM LIABILITIES
Long-Term Debt	$260.0K	$298.0K	$298.0K
YoY Change	-35.32%	-32.12%	-32.12%
Other Long-Term Liabilities
YoY Change
Total Long-Term Liabilities	$260.0K	$298.0K	$298.0K
YoY Change	-35.32%	-32.12%	-32.12%
TOTAL LIABILITIES
Total Short-Term Liabilities	$46.13M	$48.47M	$48.47M
Total Long-Term Liabilities	$260.0K	$298.0K	$298.0K
Total Liabilities	$3.330B	$3.365B	$3.365B
YoY Change	-10.11%	-9.92%	-9.92%
SHAREHOLDERS EQUITY
Retained Earnings	$273.5M	$274.6M
YoY Change	-1.0%	1.4%
Common Stock	$218.3M	$217.5M
YoY Change	1.1%	1.14%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$436.7M	$439.1M	$439.1M
YoY Change
Total Liabilities & Shareholders Equity	$3.767B	$3.804B	$3.804B
YoY Change	-8.9%	-8.28%	-8.28%

Cashflow Statement

Concept	2024 Q1	2023 Q4	2023
OPERATING ACTIVITIES
Net Income	$2.922M	$610.0K	$19.90M
YoY Change	-69.05%	-95.26%	-57.29%
Depreciation, Depletion And Amortization	$639.0K	$718.0K	$3.448M
YoY Change	-47.92%	-24.1%	91.56%
Cash From Operating Activities	$4.326M	$789.0K	$35.66M
YoY Change	-67.82%	-95.17%	-35.49%
INVESTING ACTIVITIES
Capital Expenditures	$161.0K	$9.000K	$1.749M
YoY Change	-88.8%	-99.4%	-22.82%
Acquisitions
YoY Change
Other Investing Activities	$37.79M	$158.2M	$336.4M
YoY Change	173.59%	138.15%	-255.88%
Cash From Investing Activities	$37.63M	$158.2M	$334.7M
YoY Change	204.08%	143.63%	-253.46%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-$36.10M	-251.7M	-385.3M
YoY Change	8.57%	13.68%	176.42%
NET CHANGE
Cash From Operating Activities	$4.326M	789.0K	35.66M
Cash From Investing Activities	$37.63M	158.2M	334.7M
Cash From Financing Activities	-$36.10M	-251.7M	-385.3M
Net Change In Cash	$5.855M	-92.68M	-14.97M
YoY Change	-178.79%	-33.86%	-95.05%
FREE CASH FLOW
Cash From Operating Activities	$4.326M	$789.0K	$35.66M
Capital Expenditures	$161.0K	$9.000K	$1.749M
Free Cash Flow	$4.165M	$780.0K	$33.91M
YoY Change	-65.31%	-94.74%	-36.03%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
CY2023	dei	Document Annual Report DocumentAnnualReport	true
CY2023	dei	Document Period End Date DocumentPeriodEndDate	2023-12-31
CY2023	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2023	dei	Document Transition Report DocumentTransitionReport	false
CY2023	dei	Entity File Number EntityFileNumber	001-33572
CY2023	dei	Entity Registrant Name EntityRegistrantName	Bank of Marin Bancorp
CY2023	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	CA
CY2023	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	20-8859754
CY2023	dei	Entity Address Address Line2 EntityAddressAddressLine2	Suite 100
CY2023	dei	Entity Address City Or Town EntityAddressCityOrTown	Novato
CY2023	dei	Entity Address State Or Province EntityAddressStateOrProvince	CA
CY2023	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	94947
CY2023	dei	City Area Code CityAreaCode	415
CY2023	dei	Local Phone Number LocalPhoneNumber	763-4520
CY2023	dei	Security12g Title Security12gTitle	Common Stock, No Par Value
CY2023	dei	Trading Symbol TradingSymbol	BMRC
CY2023	dei	Security Exchange Name SecurityExchangeName	NASDAQ
CY2023	dei	Entity Well Known Seasoned Issuer EntityWellKnownSeasonedIssuer	No
CY2023	dei	Entity Voluntary Filers EntityVoluntaryFilers	No
CY2023	dei	Entity Current Reporting Status EntityCurrentReportingStatus	Yes
CY2023	dei	Entity Interactive Data Current EntityInteractiveDataCurrent	Yes
CY2023	dei	Entity Filer Category EntityFilerCategory	Accelerated Filer
CY2023	dei	Entity Small Business EntitySmallBusiness	false
CY2023	dei	Entity Emerging Growth Company EntityEmergingGrowthCompany	false
CY2023	dei	Icfr Auditor Attestation Flag IcfrAuditorAttestationFlag	true
CY2023	us-gaap	Net Income Loss NetIncomeLoss	19895000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	33228000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	2575000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	-63000	usd
CY2021	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	-1449000	usd
CY2023	us-gaap	Employee Stock Ownership Plan Esop Compensation Expense EmployeeStockOwnershipPlanESOPCompensationExpense	1315000	usd
CY2022	us-gaap	Employee Stock Ownership Plan Esop Compensation Expense EmployeeStockOwnershipPlanESOPCompensationExpense	1233000	usd
CY2021	us-gaap	Employee Stock Ownership Plan Esop Compensation Expense EmployeeStockOwnershipPlanESOPCompensationExpense	1330000	usd
CY2023	bmrc	Compensation Expense Common Stock For Director Fees CompensationExpenseCommonStockForDirectorFees	398000	usd
CY2022	bmrc	Compensation Expense Common Stock For Director Fees CompensationExpenseCommonStockForDirectorFees	355000	usd
CY2023	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1350000	usd
CY2022	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1489000	usd
CY2021	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1135000	usd
CY2023	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-6897000	usd
CY2022	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-9056000	usd
CY2021	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-5799000	usd
CY2023	bmrc	Accretion Of Discount On Acquired Loans AccretionOfDiscountOnAcquiredLoans	573000	usd
CY2022	bmrc	Accretion Of Discount On Acquired Loans AccretionOfDiscountOnAcquiredLoans	-153000	usd
CY2021	bmrc	Accretion Of Discount On Acquired Loans AccretionOfDiscountOnAcquiredLoans	571000	usd
CY2023	us-gaap	Amortization Of Debt Discount Premium AmortizationOfDebtDiscountPremium	0	usd
CY2022	us-gaap	Amortization Of Debt Discount Premium AmortizationOfDebtDiscountPremium	0	usd
CY2021	us-gaap	Amortization Of Debt Discount Premium AmortizationOfDebtDiscountPremium	1347000	usd
CY2023	us-gaap	Amortization Of Deferred Loan Origination Fees Net AmortizationOfDeferredLoanOriginationFeesNet	836000	usd
CY2022	us-gaap	Amortization Of Deferred Loan Origination Fees Net AmortizationOfDeferredLoanOriginationFeesNet	2716000	usd
CY2021	us-gaap	Amortization Of Deferred Loan Origination Fees Net AmortizationOfDeferredLoanOriginationFeesNet	3155000	usd
CY2023	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	-5893000	usd
CY2022	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	-63000	usd
CY2021	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	-16000	usd
CY2023	bmrc	Depreciation Depletion And Amortization Nonproduction Excluding Amortization Of Intangible Assets DepreciationDepletionAndAmortizationNonproductionExcludingAmortizationOfIntangibleAssets	2098000	usd
CY2022	bmrc	Depreciation Depletion And Amortization Nonproduction Excluding Amortization Of Intangible Assets DepreciationDepletionAndAmortizationNonproductionExcludingAmortizationOfIntangibleAssets	1840000	usd
CY2021	bmrc	Depreciation Depletion And Amortization Nonproduction Excluding Amortization Of Intangible Assets DepreciationDepletionAndAmortizationNonproductionExcludingAmortizationOfIntangibleAssets	1740000	usd
CY2023	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1802000	usd
CY2022	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1229000	usd
CY2022	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-4708000	usd
CY2021	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	2276000	usd
CY2023	us-gaap	Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities	15764000	usd
CY2022	us-gaap	Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities	8691000	usd
CY2021	us-gaap	Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities	12025000	usd
CY2023	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	35659000	usd
CY2021	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	305329000	usd
CY2023	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	0	usd
CY2022	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	243459000	usd
CY2021	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	620236000	usd
CY2023	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	205795000	usd
CY2022	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	10664000	usd
CY2021	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	6632000	usd
CY2023	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	47170000	usd
CY2022	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	47098000	usd
CY2021	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	71682000	usd
CY2023	us-gaap	Interest Expense Negotiable Order Of Withdrawal Now Deposits InterestExpenseNegotiableOrderOfWithdrawalNOWDeposits	1036000	usd
CY2022	us-gaap	Interest Expense Savings Deposits InterestExpenseSavingsDeposits	125000	usd
CY2021	us-gaap	Interest Expense Savings Deposits InterestExpenseSavingsDeposits	94000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	22983000	usd
CY2021Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	23023000	usd
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	22874000	usd
CY2021	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff	5000	usd
CY2021Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	23023000	usd
CY2022	bmrc	Adjustments Related To Tax Withholding And Exercise Of Options For Share Based Compensation AdjustmentsRelatedToTaxWithholdingAndExerciseOfOptionsForShareBasedCompensation	393000	usd
CY2023	dei	Entity Central Index Key EntityCentralIndexKey	0001403475
CY2023	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2023
CY2023	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
CY2023	dei	Amendment Flag AmendmentFlag	false
CY2023Q4	us-gaap	Debt Securities Available For Sale Accrued Interest After Allowance For Credit Loss Statement Of Financial Position Extensible List DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLossStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2023#InterestReceivableAndOtherAssets
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CY2022Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss Statement Of Financial Position Extensible List FinancingReceivableAccruedInterestAfterAllowanceForCreditLossStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2023#InterestReceivableAndOtherAssets
CY2022Q4	us-gaap	Finance Lease Liability Statement Of Financial Position Extensible List FinanceLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2023#DebtAndCapitalLeaseObligations
CY2023Q4	us-gaap	Finance Lease Liability Statement Of Financial Position Extensible List FinanceLeaseLiabilityStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2023#DebtAndCapitalLeaseObligations
CY2023	bmrc	Dividends Cash Dividend Period Restricted Payment Amount Is Determined DividendsCashDividendPeriodRestrictedPaymentAmountIsDetermined	P3Y
CY2022Q4	us-gaap	Finance Lease Right Of Use Asset Statement Of Financial Position Extensible List FinanceLeaseRightOfUseAssetStatementOfFinancialPositionExtensibleList	http://fasb.org/us-gaap/2023#PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization
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CY2023	dei	Entity Address Address Line1 EntityAddressAddressLine1	504 Redwood Blvd.
CY2023	dei	Document Fin Stmt Error Correction Flag DocumentFinStmtErrorCorrectionFlag	false
CY2023	dei	Entity Shell Company EntityShellCompany	false
CY2023Q2	dei	Entity Public Float EntityPublicFloat	269000000	usd
CY2024Q1	dei	Entity Common Stock Shares Outstanding EntityCommonStockSharesOutstanding	16193342	shares
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	30453000	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	45424000	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Excluding Accrued Interest DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest	0	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Excluding Accrued Interest DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest	0	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss	925198000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss	972207000	usd
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CY2023Q4	us-gaap	Bank Owned Life Insurance BankOwnedLifeInsurance	68102000	usd
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CY2022Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset After Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization	8134000	usd
CY2023Q4	us-gaap	Finite Lived Core Deposits Gross FiniteLivedCoreDepositsGross	3766000	usd
CY2022Q4	us-gaap	Finite Lived Core Deposits Gross FiniteLivedCoreDepositsGross	5116000	usd
CY2023Q4	bmrc	Other Real Estate Owned OtherRealEstateOwned	0	usd
CY2022Q4	bmrc	Other Real Estate Owned OtherRealEstateOwned	455000	usd
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CY2022Q4	us-gaap	Interest Receivable And Other Assets InterestReceivableAndOtherAssets	79828000	usd
CY2023Q4	us-gaap	Assets Assets	3803903000	usd
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CY2023Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	1441987000	usd
CY2022Q4	us-gaap	Noninterest Bearing Deposit Liabilities NoninterestBearingDepositLiabilities	1839114000	usd
CY2023Q4	us-gaap	Deposits Negotiable Order Of Withdrawal Now DepositsNegotiableOrderOfWithdrawalNOW	225040000	usd
CY2022Q4	us-gaap	Deposits Negotiable Order Of Withdrawal Now DepositsNegotiableOrderOfWithdrawalNOW	287651000	usd
CY2023Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	233298000	usd
CY2022Q4	us-gaap	Deposits Savings Deposits DepositsSavingsDeposits	338163000	usd
CY2023Q4	us-gaap	Deposits Money Market Deposits DepositsMoneyMarketDeposits	1138433000	usd
CY2022Q4	us-gaap	Deposits Money Market Deposits DepositsMoneyMarketDeposits	989390000	usd
CY2023Q4	us-gaap	Time Deposits TimeDeposits	251317000	usd
CY2022Q4	us-gaap	Time Deposits TimeDeposits	119030000	usd
CY2023Q4	us-gaap	Deposits Deposits	3290075000	usd
CY2022Q4	us-gaap	Deposits Deposits	3573348000	usd
CY2023Q4	us-gaap	Debt And Capital Lease Obligations DebtAndCapitalLeaseObligations	26298000	usd
CY2022Q4	us-gaap	Debt And Capital Lease Obligations DebtAndCapitalLeaseObligations	112439000	usd
CY2023Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	22906000	usd
CY2022Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	26639000	usd
CY2023Q4	us-gaap	Other Liabilities OtherLiabilities	25562000	usd
CY2022Q4	us-gaap	Other Liabilities OtherLiabilities	22946000	usd
CY2023Q4	us-gaap	Liabilities Liabilities	3364841000	usd
CY2022Q4	us-gaap	Liabilities Liabilities	3735372000	usd
CY2023Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		usd
CY2022Q4	us-gaap	Commitments And Contingencies CommitmentsAndContingencies		usd
CY2023Q4	us-gaap	Preferred Stock No Par Value PreferredStockNoParValue	0
CY2022Q4	us-gaap	Preferred Stock No Par Value PreferredStockNoParValue	0
CY2022Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	5000000	shares
CY2023Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	5000000	shares
CY2022Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2023Q4	us-gaap	Preferred Stock Shares Issued PreferredStockSharesIssued	0	shares
CY2023Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	usd
CY2022Q4	us-gaap	Preferred Stock Value PreferredStockValue	0	usd
CY2023Q4	us-gaap	Common Stock No Par Value CommonStockNoParValue	0
CY2022Q4	us-gaap	Common Stock No Par Value CommonStockNoParValue	0
CY2023Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	30000000	shares
CY2022Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	30000000	shares
CY2023Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	16158413	shares
CY2023Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16158413	shares
CY2022Q4	us-gaap	Common Stock Shares Issued CommonStockSharesIssued	16029138	shares
CY2022Q4	us-gaap	Common Stock Shares Outstanding CommonStockSharesOutstanding	16029138	shares
CY2023Q4	us-gaap	Common Stock Value CommonStockValue	217498000	usd
CY2022Q4	us-gaap	Common Stock Value CommonStockValue	215057000	usd
CY2023Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	274570000	usd
CY2022Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	270781000	usd
CY2023Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-53006000	usd
CY2022Q4	us-gaap	Accumulated Other Comprehensive Income Loss Net Of Tax AccumulatedOtherComprehensiveIncomeLossNetOfTax	-73746000	usd
CY2023Q4	us-gaap	Stockholders Equity StockholdersEquity	439062000	usd
CY2022Q4	us-gaap	Stockholders Equity StockholdersEquity	412092000	usd
CY2023Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	3803903000	usd
CY2022Q4	us-gaap	Liabilities And Stockholders Equity LiabilitiesAndStockholdersEquity	4147464000	usd
CY2023	us-gaap	Interest And Fee Income Loans And Leases InterestAndFeeIncomeLoansAndLeases	98505000	usd
CY2022	us-gaap	Interest And Fee Income Loans And Leases InterestAndFeeIncomeLoansAndLeases	93868000	usd
CY2021	us-gaap	Interest And Fee Income Loans And Leases InterestAndFeeIncomeLoansAndLeases	91612000	usd
CY2023	us-gaap	Interest Income Operating InterestIncomeOperating	38660000	usd
CY2022	us-gaap	Interest Income Operating InterestIncomeOperating	34766000	usd
CY2021	us-gaap	Interest Income Operating InterestIncomeOperating	16342000	usd
CY2023	bmrc	Interest Due From Banks And Other InterestDueFromBanksAndOther	2329000	usd
CY2022	bmrc	Interest Due From Banks And Other InterestDueFromBanksAndOther	1407000	usd
CY2021	bmrc	Interest Due From Banks And Other InterestDueFromBanksAndOther	399000	usd
CY2023	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	139494000	usd
CY2022	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	130041000	usd
CY2021	us-gaap	Interest And Dividend Income Operating InterestAndDividendIncomeOperating	108353000	usd
CY2022	us-gaap	Interest Expense Negotiable Order Of Withdrawal Now Deposits InterestExpenseNegotiableOrderOfWithdrawalNOWDeposits	421000	usd
CY2021	us-gaap	Interest Expense Negotiable Order Of Withdrawal Now Deposits InterestExpenseNegotiableOrderOfWithdrawalNOWDeposits	172000	usd
CY2023	us-gaap	Interest Expense Borrowings InterestExpenseBorrowings	11562000	usd
CY2022	us-gaap	Interest Expense Borrowings InterestExpenseBorrowings	91000	usd
CY2023	us-gaap	Interest Expense Trust Preferred Securities InterestExpenseTrustPreferredSecurities	0	usd
CY2022	us-gaap	Interest Expense Trust Preferred Securities InterestExpenseTrustPreferredSecurities	0	usd
CY2021	us-gaap	Interest Expense Trust Preferred Securities InterestExpenseTrustPreferredSecurities	1361000	usd
CY2023	us-gaap	Interest Expense InterestExpense	36733000	usd
CY2023	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	102761000	usd
CY2022	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	127492000	usd
CY2021	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	104951000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	2575000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	-63000	usd
CY2021	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	-1449000	usd
CY2023	bmrc	Provision For Reversal Of Losses On Unfunded Loan Commitments ProvisionForReversalOfLossesOnUnfundedLoanCommitments	-342000	usd
CY2022	bmrc	Provision For Reversal Of Losses On Unfunded Loan Commitments ProvisionForReversalOfLossesOnUnfundedLoanCommitments	-318000	usd
CY2021	bmrc	Provision For Reversal Of Losses On Unfunded Loan Commitments ProvisionForReversalOfLossesOnUnfundedLoanCommitments	-992000	usd
CY2023	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	100528000	usd
CY2022	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	127873000	usd
CY2021	us-gaap	Interest Income Expense After Provision For Loan Loss InterestIncomeExpenseAfterProvisionForLoanLoss	107392000	usd
CY2023	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1802000	usd
CY2022	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1229000	usd
CY2021	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2194000	usd
CY2023	bmrc	Dividend Income Federal Home Loan Bank DividendIncomeFederalHomeLoanBank	1265000	usd
CY2022	bmrc	Dividend Income Federal Home Loan Bank DividendIncomeFederalHomeLoanBank	1056000	usd
CY2021	bmrc	Dividend Income Federal Home Loan Bank DividendIncomeFederalHomeLoanBank	760000	usd
CY2023	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-5893000	usd
CY2022	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-63000	usd
CY2021	us-gaap	Debt And Equity Securities Gain Loss DebtAndEquitySecuritiesGainLoss	-16000	usd
CY2023	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1260000	usd
CY2022	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1849000	usd
CY2021	us-gaap	Noninterest Income Other Operating Income NoninterestIncomeOtherOperatingIncome	1145000	usd
CY2023	us-gaap	Noninterest Income NoninterestIncome	4989000	usd
CY2022	us-gaap	Noninterest Income NoninterestIncome	10905000	usd
CY2021	us-gaap	Noninterest Income NoninterestIncome	10132000	usd
CY2023	us-gaap	Labor And Related Expense LaborAndRelatedExpense	43448000	usd
CY2022	us-gaap	Labor And Related Expense LaborAndRelatedExpense	42046000	usd
CY2021	us-gaap	Labor And Related Expense LaborAndRelatedExpense	41939000	usd
CY2023	bmrc	Occupancy And Equipment OccupancyAndEquipment	8306000	usd
CY2022	bmrc	Occupancy And Equipment OccupancyAndEquipment	7823000	usd
CY2021	bmrc	Occupancy And Equipment OccupancyAndEquipment	7297000	usd
CY2023	bmrc	Data Processing DataProcessing	4057000	usd
CY2022	bmrc	Data Processing DataProcessing	4649000	usd
CY2021	bmrc	Data Processing DataProcessing	5139000	usd
CY2023	us-gaap	Professional Fees ProfessionalFees	3598000	usd
CY2022	us-gaap	Professional Fees ProfessionalFees	3299000	usd
CY2021	us-gaap	Professional Fees ProfessionalFees	4974000	usd
CY2023	bmrc	Deposit Network Fees DepositNetworkFees	2783000	usd
CY2022	bmrc	Deposit Network Fees DepositNetworkFees	258000	usd
CY2021	bmrc	Deposit Network Fees DepositNetworkFees	26000	usd
CY2023	bmrc	Depreciation Depletion And Amortization Nonproduction Excluding Amortization Of Intangible Assets DepreciationDepletionAndAmortizationNonproductionExcludingAmortizationOfIntangibleAssets	2098000	usd
CY2022	bmrc	Depreciation Depletion And Amortization Nonproduction Excluding Amortization Of Intangible Assets DepreciationDepletionAndAmortizationNonproductionExcludingAmortizationOfIntangibleAssets	1840000	usd
CY2021	bmrc	Depreciation Depletion And Amortization Nonproduction Excluding Amortization Of Intangible Assets DepreciationDepletionAndAmortizationNonproductionExcludingAmortizationOfIntangibleAssets	1740000	usd
CY2023	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1878000	usd
CY2022	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	1179000	usd
CY2021	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	889000	usd
CY2023	bmrc	Information Technology InformationTechnology	1569000	usd
CY2022	bmrc	Information Technology InformationTechnology	2197000	usd
CY2021	bmrc	Information Technology InformationTechnology	1550000	usd
CY2023	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1350000	usd
CY2022	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1489000	usd
CY2021	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	1135000	usd
CY2023	us-gaap	Noninterest Expense Directors Fees NoninterestExpenseDirectorsFees	1212000	usd
CY2022	us-gaap	Noninterest Expense Directors Fees NoninterestExpenseDirectorsFees	1107000	usd
CY2021	us-gaap	Noninterest Expense Directors Fees NoninterestExpenseDirectorsFees	957000	usd
CY2023	bmrc	Charitable Contributions Expense CharitableContributionsExpense	717000	usd
CY2022	bmrc	Charitable Contributions Expense CharitableContributionsExpense	709000	usd
CY2021	bmrc	Charitable Contributions Expense CharitableContributionsExpense	587000	usd
CY2023	bmrc	Other Real Estate Owned Expense OtherRealEstateOwnedExpense	48000	usd
CY2022	bmrc	Other Real Estate Owned Expense OtherRealEstateOwnedExpense	359000	usd
CY2021	bmrc	Other Real Estate Owned Expense OtherRealEstateOwnedExpense	5000	usd
CY2023	us-gaap	Other Noninterest Expense OtherNoninterestExpense	8417000	usd
CY2022	us-gaap	Other Noninterest Expense OtherNoninterestExpense	8314000	usd
CY2021	us-gaap	Other Noninterest Expense OtherNoninterestExpense	6400000	usd
CY2023	us-gaap	Noninterest Expense NoninterestExpense	79481000	usd
CY2022	us-gaap	Noninterest Expense NoninterestExpense	75269000	usd
CY2021	us-gaap	Noninterest Expense NoninterestExpense	72638000	usd
CY2023	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	26036000	usd
CY2022	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	63509000	usd
CY2021	us-gaap	Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	44886000	usd
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	6141000	usd
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	16923000	usd
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	11658000	usd
CY2023	us-gaap	Net Income Loss NetIncomeLoss	19895000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	46586000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	33228000	usd
CY2023	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.24
CY2022	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.93
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.32
CY2023	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.24
CY2022	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.92
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.30
CY2023	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	16012000	shares
CY2022	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15921000	shares
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	14340000	shares
CY2023	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	16026000	shares
CY2022	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15969000	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	14422000	shares
CY2023	us-gaap	Net Income Loss NetIncomeLoss	19895000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	46586000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	33228000	usd
CY2023	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	20358000	usd
CY2022	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-88620000	usd
CY2021	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-21281000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-8700000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-63000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-16000	usd
CY2023	bmrc	Other Comprehensive Income Loss Reclassification Adjustment Gain Or Losses Fair Value Hedge OtherComprehensiveIncomeLossReclassificationAdjustmentGainOrLossesFairValueHedge	1359000	usd
CY2022	bmrc	Other Comprehensive Income Loss Reclassification Adjustment Gain Or Losses Fair Value Hedge OtherComprehensiveIncomeLossReclassificationAdjustmentGainOrLossesFairValueHedge	0	usd
CY2021	bmrc	Other Comprehensive Income Loss Reclassification Adjustment Gain Or Losses Fair Value Hedge OtherComprehensiveIncomeLossReclassificationAdjustmentGainOrLossesFairValueHedge	0	usd
CY2023	bmrc	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Investment Transferred From Available For Sale To Held To Maturity Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForInvestmentTransferredFromAvailableForSaleToHeldToMaturityBeforeTax	0	usd
CY2022	bmrc	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Investment Transferred From Available For Sale To Held To Maturity Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForInvestmentTransferredFromAvailableForSaleToHeldToMaturityBeforeTax	14847000	usd
CY2021	bmrc	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Investment Transferred From Available For Sale To Held To Maturity Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForInvestmentTransferredFromAvailableForSaleToHeldToMaturityBeforeTax	0	usd
CY2023	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	1743000	usd
CY2022	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	1580000	usd
CY2021	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	493000	usd
CY2023	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Before Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentBeforeTaxPortionAttributableToParent	29442000	usd
CY2022	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Before Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentBeforeTaxPortionAttributableToParent	-101824000	usd
CY2021	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Before Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentBeforeTaxPortionAttributableToParent	-20772000	usd
CY2023	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	8702000	usd
CY2022	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	-30102000	usd
CY2021	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	-6147000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	20740000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-71722000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-14625000	usd
CY2023	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	40635000	usd
CY2022	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	-25136000	usd
CY2021	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	18603000	usd
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	358253000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	33228000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-14625000	usd
CY2021	bmrc	Stock Issued During Period Value Stock Options Exercised Net Of Shares Surrendered For Cashless Exercises And Tax Withholdings StockIssuedDuringPeriodValueStockOptionsExercisedNetOfSharesSurrenderedForCashlessExercisesAndTaxWithholdings	463000	usd
CY2021	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	90000	usd
CY2021	us-gaap	Stock Issued During Period Value Employee Stock Ownership Plan StockIssuedDuringPeriodValueEmployeeStockOwnershipPlan	1330000	usd
CY2021	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	166000	usd
CY2021	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Stock Options Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition	491000	usd
CY2021	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	481000	usd
CY2021	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.94
CY2021	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	13107000	usd
CY2021	bmrc	Stock Issued During Period Value Nonemployee Director Stock Purchase Plans StockIssuedDuringPeriodValueNonemployeeDirectorStockPurchasePlans	34000	usd
CY2021	bmrc	Stock Issued In Payment Of Director Fees StockIssuedInPaymentOfDirectorFees	217000	usd
CY2021	us-gaap	Stock Issued During Period Shares New Issues StockIssuedDuringPeriodSharesNewIssues	3441235	shares
CY2021	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	124401000	usd
CY2021	us-gaap	Stock Issued During Period Value New Issues StockIssuedDuringPeriodValueNewIssues	124401000	usd
CY2021	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	40722000	usd
CY2021Q4	us-gaap	Stockholders Equity StockholdersEquity	450368000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	46586000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-71722000	usd
CY2022	bmrc	Stock Issued During Period Value Stock Options Exercised Net Of Shares Surrendered For Cashless Exercises And Tax Withholdings StockIssuedDuringPeriodValueStockOptionsExercisedNetOfSharesSurrenderedForCashlessExercisesAndTaxWithholdings	821000	usd
CY2022	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	62000	usd
CY2022	us-gaap	Stock Issued During Period Value Employee Stock Ownership Plan StockIssuedDuringPeriodValueEmployeeStockOwnershipPlan	1233000	usd
CY2022	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	40000	usd
CY2022	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Stock Options Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition	251000	usd
CY2022	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	712000	usd
CY2022	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.98
CY2022	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	15673000	usd
CY2022	bmrc	Stock Issued During Period Value Nonemployee Director Stock Purchase Plans StockIssuedDuringPeriodValueNonemployeeDirectorStockPurchasePlans	16000	usd
CY2022	bmrc	Stock Issued In Payment Of Director Fees StockIssuedInPaymentOfDirectorFees	355000	usd
CY2022	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	877000	usd
CY2022Q4	us-gaap	Stockholders Equity StockholdersEquity	412092000	usd
CY2023	us-gaap	Net Income Loss NetIncomeLoss	19895000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	20740000	usd
CY2023	bmrc	Stock Issued During Period Value Stock Options Exercised Net Of Shares Surrendered For Cashless Exercises And Tax Withholdings StockIssuedDuringPeriodValueStockOptionsExercisedNetOfSharesSurrenderedForCashlessExercisesAndTaxWithholdings	230000	usd
CY2023	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	46000	usd
CY2023	us-gaap	Stock Issued During Period Value Employee Stock Ownership Plan StockIssuedDuringPeriodValueEmployeeStockOwnershipPlan	1315000	usd
CY2023	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	70000	usd
CY2023	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Stock Options Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition	181000	usd
CY2023	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	341000	usd
CY2023	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.00
CY2023	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	16106000	usd
CY2023	bmrc	Stock Issued In Payment Of Director Fees StockIssuedInPaymentOfDirectorFees	398000	usd
CY2023	bmrc	Provision For Reversal Of Losses On Unfunded Loan Commitments ProvisionForReversalOfLossesOnUnfundedLoanCommitments	-342000	usd
CY2022	bmrc	Provision For Reversal Of Losses On Unfunded Loan Commitments ProvisionForReversalOfLossesOnUnfundedLoanCommitments	-318000	usd
CY2021	bmrc	Provision For Reversal Of Losses On Unfunded Loan Commitments ProvisionForReversalOfLossesOnUnfundedLoanCommitments	-992000	usd
CY2021	bmrc	Compensation Expense Common Stock For Director Fees CompensationExpenseCommonStockForDirectorFees	217000	usd
CY2023	us-gaap	Share Based Compensation ShareBasedCompensation	522000	usd
CY2022	us-gaap	Share Based Compensation ShareBasedCompensation	963000	usd
CY2021	us-gaap	Share Based Compensation ShareBasedCompensation	972000	usd
CY2023	bmrc	Write Down Of Other Real Estate Owned WriteDownOfOtherRealEstateOwned	40000	usd
CY2022	bmrc	Write Down Of Other Real Estate Owned WriteDownOfOtherRealEstateOwned	345000	usd
CY2021	bmrc	Write Down Of Other Real Estate Owned WriteDownOfOtherRealEstateOwned	0	usd
CY2021	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2194000	usd
CY2023	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	4149000	usd
CY2022	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-2228000	usd
CY2021	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-5554000	usd
CY2023	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	2378000	usd
CY2022	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	55277000	usd
CY2021	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	45253000	usd
CY2023	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	usd
CY2022	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	319937000	usd
CY2023	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	59316000	usd
CY2022	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	130178000	usd
CY2021	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	110059000	usd
CY2023	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	2807000	usd
CY2022	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	0	usd
CY2021	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	0	usd
CY2023	bmrc	Increase Decrease In Loans Receivable Net IncreaseDecreaseInLoansReceivableNet	16945000	usd
CY2022	bmrc	Increase Decrease In Loans Receivable Net IncreaseDecreaseInLoansReceivableNet	164019000	usd
CY2021	bmrc	Increase Decrease In Loans Receivable Net IncreaseDecreaseInLoansReceivableNet	256856000	usd
CY2023	us-gaap	Proceeds From Sale Of Loans Receivable ProceedsFromSaleOfLoansReceivable	3263000	usd
CY2022	us-gaap	Proceeds From Sale Of Loans Receivable ProceedsFromSaleOfLoansReceivable	0	usd
CY2021	us-gaap	Proceeds From Sale Of Loans Receivable ProceedsFromSaleOfLoansReceivable	0	usd
CY2023	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	0	usd
CY2022	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	4714000	usd
CY2021	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	1943000	usd
CY2023	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	766000	usd
CY2022	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	350000	usd
CY2021	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	2478000	usd
CY2023	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	1749000	usd
CY2022	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	2266000	usd
CY2021	us-gaap	Payments To Acquire Property Plant And Equipment PaymentsToAcquirePropertyPlantAndEquipment	1044000	usd
CY2023	us-gaap	Proceeds From Sale Of Other Real Estate ProceedsFromSaleOfOtherRealEstate	420000	usd
CY2022	us-gaap	Proceeds From Sale Of Other Real Estate ProceedsFromSaleOfOtherRealEstate	0	usd
CY2021	us-gaap	Proceeds From Sale Of Other Real Estate ProceedsFromSaleOfOtherRealEstate	0	usd
CY2023	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	0	usd
CY2022	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	0	usd
CY2021	us-gaap	Cash Acquired From Acquisition CashAcquiredFromAcquisition	140577000	usd
CY2023	us-gaap	Payments To Acquire Real Estate Held For Investment PaymentsToAcquireRealEstateHeldForInvestment	42000	usd
CY2022	us-gaap	Payments To Acquire Real Estate Held For Investment PaymentsToAcquireRealEstateHeldForInvestment	30000	usd
CY2021	us-gaap	Payments To Acquire Real Estate Held For Investment PaymentsToAcquireRealEstateHeldForInvestment	398000	usd
CY2023	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	334691000	usd
CY2022	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-218097000	usd
CY2021	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-340666000	usd
CY2023	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	-283273000	usd
CY2022	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	-235202000	usd
CY2021	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	514279000	usd
CY2023	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-86000000	usd
CY2022	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	112000000	usd
CY2021	us-gaap	Proceeds From Repayments Of Short Term Debt ProceedsFromRepaymentsOfShortTermDebt	-13885000	usd
CY2023	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	148000	usd
CY2022	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	131000	usd
CY2021	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	86000	usd
CY2023	us-gaap	Repayments Of Subordinated Debt RepaymentsOfSubordinatedDebt	0	usd
CY2022	us-gaap	Repayments Of Subordinated Debt RepaymentsOfSubordinatedDebt	0	usd
CY2021	us-gaap	Repayments Of Subordinated Debt RepaymentsOfSubordinatedDebt	4126000	usd
CY2023	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	230000	usd
CY2022	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	821000	usd
CY2021	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	463000	usd
CY2023	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	70000	usd
CY2022	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	40000	usd
CY2021	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	166000	usd
CY2023	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	16106000	usd
CY2022	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	15673000	usd
CY2021	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	13107000	usd
CY2023	us-gaap	Payments For Repurchase Of Equity PaymentsForRepurchaseOfEquity	0	usd
CY2022	us-gaap	Payments For Repurchase Of Equity PaymentsForRepurchaseOfEquity	1250000	usd
CY2021	us-gaap	Payments For Repurchase Of Equity PaymentsForRepurchaseOfEquity	40762000	usd
CY2023	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans	46000	usd
CY2022	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans	78000	usd
CY2021	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans	124000	usd
CY2023	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-385321000	usd
CY2022	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-139397000	usd
CY2021	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	442734000	usd
CY2023	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-14971000	usd
CY2022	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-302217000	usd
CY2021	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	147321000	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	45424000	usd
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	347641000	usd
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	200320000	usd
CY2023Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	30453000	usd
CY2022Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	45424000	usd
CY2021Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	347641000	usd
CY2023	us-gaap	Interest Paid Net InterestPaidNet	34038000	usd
CY2022	us-gaap	Interest Paid Net InterestPaidNet	2560000	usd
CY2021	us-gaap	Interest Paid Net InterestPaidNet	2105000	usd
CY2023	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	8428000	usd
CY2022	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	13730000	usd
CY2021	us-gaap	Income Taxes Paid Net IncomeTaxesPaidNet	12350000	usd
CY2023	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	20358000	usd
CY2022	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	-88620000	usd
CY2021	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax	-21281000	usd
CY2023	bmrc	Available For Sale Securities Transferred To Held To Maturity Securities AvailableForSaleSecuritiesTransferredToHeldToMaturitySecurities	0	usd
CY2022	bmrc	Available For Sale Securities Transferred To Held To Maturity Securities AvailableForSaleSecuritiesTransferredToHeldToMaturitySecurities	357482000	usd
CY2021	bmrc	Available For Sale Securities Transferred To Held To Maturity Securities AvailableForSaleSecuritiesTransferredToHeldToMaturitySecurities	0	usd
CY2023	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	1743000	usd
CY2022	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	1580000	usd
CY2021	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	493000	usd
CY2023	bmrc	Transfer Of Loan To Loans Held For Sale At Fair Value TransferOfLoanToLoansHeldForSaleAtFairValue	3263000	usd
CY2022	bmrc	Transfer Of Loan To Loans Held For Sale At Fair Value TransferOfLoanToLoansHeldForSaleAtFairValue	0	usd
CY2021	bmrc	Transfer Of Loan To Loans Held For Sale At Fair Value TransferOfLoanToLoansHeldForSaleAtFairValue	0	usd
CY2023	bmrc	Repurchase Of Stock Not Yet Settled RepurchaseOfStockNotYetSettled	0	usd
CY2022	bmrc	Repurchase Of Stock Not Yet Settled RepurchaseOfStockNotYetSettled	0	usd
CY2021	bmrc	Repurchase Of Stock Not Yet Settled RepurchaseOfStockNotYetSettled	373000	usd
CY2023	us-gaap	Fair Value Of Assets Acquired FairValueOfAssetsAcquired	0	usd
CY2022	us-gaap	Fair Value Of Assets Acquired FairValueOfAssetsAcquired	0	usd
CY2021	us-gaap	Fair Value Of Assets Acquired FairValueOfAssetsAcquired	757844000	usd
CY2023	us-gaap	Liabilities Assumed1 LiabilitiesAssumed1	0	usd
CY2022	us-gaap	Liabilities Assumed1 LiabilitiesAssumed1	0	usd
CY2021	us-gaap	Liabilities Assumed1 LiabilitiesAssumed1	816558000	usd
CY2023Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	330000	usd
CY2022Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	0	usd
CY2021Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	1930000	usd
CY2023Q4	bmrc	Number Of Retail Branches NumberOfRetailBranches	27	retailbranch
CY2023Q4	bmrc	Number Of Commercial Banking Offices NumberOfCommercialBankingOffices	8	commercialbankingoffice
CY2023Q4	bmrc	Number Of Counties NumberOfCounties	10	county
CY2023	us-gaap	Number Of Operating Segments NumberOfOperatingSegments	1	segment
CY2023	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	1	segment
CY2023	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Accounting Changes and Reclassifications:</span> Certain items in prior financial statements have been reclassified to conform to the current presentation, including the reclassification of the provision for credit losses on unfunded commitments in the second quarter of 2021 from non-interest expense to a separate line item under the provision for credit losses on loans in the consolidated statements of comprehensive income (loss).
CY2023	us-gaap	Use Of Estimates UseOfEstimates	<div style="text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-style:italic;font-weight:700;line-height:120%">Use of Estimates:</span><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%"> </span><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Significant accounting estimates reflected in the consolidated financial statements include the allowance for credit losses, fair value measurements, and goodwill impairment assessment, as discussed in the Notes herein.</span></div>
CY2023Q4	us-gaap	Financing Receivable Threshold Period Past Due Writeoff FinancingReceivableThresholdPeriodPastDueWriteoff	P90D
CY2023	bmrc	Loansand Leases Receivable Nonperforming Number Of Consecutive Payments Considered Sustained Repayment Performance LoansandLeasesReceivableNonperformingNumberOfConsecutivePaymentsConsideredSustainedRepaymentPerformance	6	payment
CY2023Q4	us-gaap	Financing Receivable Threshold Period Past Due Writeoff FinancingReceivableThresholdPeriodPastDueWriteoff	P90D
CY2023	bmrc	Threshold Period Past Due For Write Off Of Deposit Liabilities Reclassified As Loans Receivable ThresholdPeriodPastDueForWriteOffOfDepositLiabilitiesReclassifiedAsLoansReceivable	P60D
CY2022	us-gaap	Gains Losses On Sales Of Assets GainsLossesOnSalesOfAssets	0	usd
CY2021	us-gaap	Gains Losses On Sales Of Assets GainsLossesOnSalesOfAssets	0	usd
CY2023	us-gaap	Gains Losses On Sales Of Assets GainsLossesOnSalesOfAssets	0	usd
CY2023Q4	us-gaap	Goodwill Goodwill	72800000	usd
CY2023	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	usd
CY2021	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	usd
CY2022	us-gaap	Goodwill Impairment Loss GoodwillImpairmentLoss	0	usd
CY2023	us-gaap	Real Estate Owned Valuation Allowance Valuation Increase RealEstateOwnedValuationAllowanceValuationIncrease	40000	usd
CY2022	us-gaap	Real Estate Owned Valuation Allowance Valuation Increase RealEstateOwnedValuationAllowanceValuationIncrease	345000	usd
CY2023	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	16012000	shares
CY2022	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	15921000	shares
CY2021	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	14340000	shares
CY2023	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	3000	shares
CY2022	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	31000	shares
CY2021	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	62000	shares
CY2023	us-gaap	Incremental Common Shares Attributable To Nonvested Shares With Forfeitable Dividends IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends	11000	shares
CY2022	us-gaap	Incremental Common Shares Attributable To Nonvested Shares With Forfeitable Dividends IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends	17000	shares
CY2021	us-gaap	Incremental Common Shares Attributable To Nonvested Shares With Forfeitable Dividends IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends	20000	shares
CY2023	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	16026000	shares
CY2022	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	15969000	shares
CY2021	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	14422000	shares
CY2023	us-gaap	Net Income Loss NetIncomeLoss	19895000	usd
CY2022	us-gaap	Net Income Loss NetIncomeLoss	46586000	usd
CY2021	us-gaap	Net Income Loss NetIncomeLoss	33228000	usd
CY2023	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	1.24
CY2022	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.93
CY2021	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.32
CY2023	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	1.24
CY2022	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.92
CY2021	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.30
CY2023	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	364000	shares
CY2022	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	211000	shares
CY2021	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	97000	shares
CY2023	us-gaap	Advertising Expense AdvertisingExpense	1200000	usd
CY2022	us-gaap	Advertising Expense AdvertisingExpense	1100000	usd
CY2021	us-gaap	Advertising Expense AdvertisingExpense	908000	usd
CY2023Q4	us-gaap	Number Of Interest Rate Derivatives Held NumberOfInterestRateDerivativesHeld	3	interest_rate_swap
CY2023Q4	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest Before Allowance For Credit Loss DebtSecuritiesHeldToMaturityExcludingAccruedInterestBeforeAllowanceForCreditLoss	925198000	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Excluding Accrued Interest DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest	0	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss	925198000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	75000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	110443000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	814830000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest Before Allowance For Credit Loss DebtSecuritiesHeldToMaturityExcludingAccruedInterestBeforeAllowanceForCreditLoss	972207000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Excluding Accrued Interest DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest	0	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss	972207000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	70000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	127038000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	845239000	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Accrued Interest Before Allowance For Credit Loss DebtSecuritiesHeldToMaturityAccruedInterestBeforeAllowanceForCreditLoss	3600000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Accrued Interest Before Allowance For Credit Loss DebtSecuritiesHeldToMaturityAccruedInterestBeforeAllowanceForCreditLoss	3700000	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Excluding Accrued Interest DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest	0	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Excluding Accrued Interest DebtSecuritiesHeldToMaturityAllowanceForCreditLossExcludingAccruedInterest	0	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Amortized Cost Excluding Accrued Interest Before Allowance For Credit Loss DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss	613479000	usd
CY2023Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	3000	usd
CY2023Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	61454000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Amortized Cost Allowance For Credit Loss Excluding Accrued Interest DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest	0	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Excluding Accrued Interest DebtSecuritiesAvailableForSaleExcludingAccruedInterest	552028000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Amortized Cost Excluding Accrued Interest Before Allowance For Credit Loss DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestBeforeAllowanceForCreditLoss	892605000	usd
CY2022Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	34000	usd
CY2022Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	90543000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Amortized Cost Allowance For Credit Loss Excluding Accrued Interest DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest	0	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Excluding Accrued Interest DebtSecuritiesAvailableForSaleExcludingAccruedInterest	802096000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss	2300000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss	3200000	usd
CY2022Q1	us-gaap	Debt Securities Available For Sale Transfer To Held To Maturity Allowance For Credit Loss Expense DebtSecuritiesAvailableForSaleTransferToHeldToMaturityAllowanceForCreditLossExpense	357500000	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss Maturity Allocated And Single Maturity Date Year One DebtSecuritiesHeldToMaturityAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLossMaturityAllocatedAndSingleMaturityDateYearOne	0	usd
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	0	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	101000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	100000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss Maturity Allocated And Single Maturity Date Year One DebtSecuritiesHeldToMaturityAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLossMaturityAllocatedAndSingleMaturityDateYearOne	450000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	446000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	1254000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	1239000	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss Maturity Allocated And Single Maturity Date After Year One Through Five DebtSecuritiesHeldToMaturityAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLossMaturityAllocatedAndSingleMaturityDateAfterYearOneThroughFive	87887000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	84541000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	226669000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	208444000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss Maturity Allocated And Single Maturity Date After Year One Through Five DebtSecuritiesHeldToMaturityAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLossMaturityAllocatedAndSingleMaturityDateAfterYearOneThroughFive	87418000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	83663000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	335813000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	307843000	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss Maturity Allocated And Single Maturity Date After Year5 Through10 DebtSecuritiesHeldToMaturityAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLossMaturityAllocatedAndSingleMaturityDateAfterYear5Through10	304976000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	261654000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	95552000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	85447000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss Maturity Allocated And Single Maturity Date After Year5 Through10 DebtSecuritiesHeldToMaturityAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLossMaturityAllocatedAndSingleMaturityDateAfterYear5Through10	262072000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	222280000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	185997000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	166273000	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss Maturity Allocated And Single Maturity Date After Year10 DebtSecuritiesHeldToMaturityAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLossMaturityAllocatedAndSingleMaturityDateAfterYear10	532335000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	468635000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	291157000	usd
CY2023Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	258037000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss Maturity Allocated And Single Maturity Date After Year10 DebtSecuritiesHeldToMaturityAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLossMaturityAllocatedAndSingleMaturityDateAfterYear10	622267000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	538850000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	369541000	usd
CY2022Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	326741000	usd
CY2023Q4	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss	925198000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	814830000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss	613479000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Excluding Accrued Interest DebtSecuritiesAvailableForSaleExcludingAccruedInterest	552028000	usd
CY2022Q4	us-gaap	Debt Securities Held To Maturity Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesHeldToMaturityExcludingAccruedInterestAfterAllowanceForCreditLoss	972207000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	845239000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Amortized Cost Excluding Accrued Interest After Allowance For Credit Loss DebtSecuritiesAvailableForSaleAmortizedCostExcludingAccruedInterestAfterAllowanceForCreditLoss	892605000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Excluding Accrued Interest DebtSecuritiesAvailableForSaleExcludingAccruedInterest	802096000	usd
CY2023	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	205795000	usd
CY2022	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	10664000	usd
CY2021	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	6632000	usd
CY2023	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	5000	usd
CY2022	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	17000	usd
CY2021	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	1000	usd
CY2023	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	8705000	usd
CY2022	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	80000	usd
CY2021	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	17000	usd
CY2023	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	2807000	usd
CY2022	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	0	usd
CY2021	us-gaap	Proceeds From Sale Of Equity Securities Fv Ni ProceedsFromSaleOfEquitySecuritiesFvNi	0	usd
CY2023	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	2807000	usd
CY2022	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	0	usd
CY2021	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	0	usd
CY2023Q4	us-gaap	Securities Loaned Fair Value Of Collateral SecuritiesLoanedFairValueOfCollateral	938959000	usd
CY2022Q4	us-gaap	Securities Loaned Fair Value Of Collateral SecuritiesLoanedFairValueOfCollateral	234226000	usd
CY2023Q4	bmrc	Marketable Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions MarketableSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions	313	security
CY2022Q4	bmrc	Marketable Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions MarketableSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions	407	security
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	62124000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	676000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	738690000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	109767000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	800814000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	110443000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	1901000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	8000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	549289000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	61446000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	551190000	usd
CY2023Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	61454000	usd
CY2023Q4	bmrc	Available For Sale Securities And Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	64025000	usd
CY2023Q4	bmrc	Availableforsale Securitiesand Heldtomaturity Securities Continuous Unrealized Loss Position Lessthan12 Months Accumulated Loss AvailableforsaleSecuritiesandHeldtomaturitySecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAccumulatedLoss	684000	usd
CY2023Q4	bmrc	Available For Sale Securities And Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	1287979000	usd
CY2023Q4	bmrc	Availableforsale Securitiesand Heldtomaturity Securities Continuous Unrealized Loss Position12 Monthsor Longer Accumulated Loss AvailableforsaleSecuritiesandHeldtomaturitySecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAccumulatedLoss	171213000	usd
CY2023Q4	bmrc	Available For Sale Securities And Held To Maturity Securities Continuous Unrealized Loss Position Fair Value Total AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValueTotal	1352004000	usd
CY2023Q4	bmrc	Availableforsale Securitiesand Heldtomaturity Securities Continuous Unrealized Loss Position Accumulated Loss AvailableforsaleSecuritiesandHeldtomaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	171897000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	359313000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	23733000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	459948000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	103305000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	819261000	usd
CY2022Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	127038000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	354695000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	33887000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	443274000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	56656000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	797969000	usd
CY2022Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	90543000	usd
CY2022Q4	bmrc	Available For Sale Securities And Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	714008000	usd
CY2022Q4	bmrc	Availableforsale Securitiesand Heldtomaturity Securities Continuous Unrealized Loss Position Lessthan12 Months Accumulated Loss AvailableforsaleSecuritiesandHeldtomaturitySecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAccumulatedLoss	57620000	usd
CY2022Q4	bmrc	Available For Sale Securities And Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	903222000	usd
CY2022Q4	bmrc	Availableforsale Securitiesand Heldtomaturity Securities Continuous Unrealized Loss Position12 Monthsor Longer Accumulated Loss AvailableforsaleSecuritiesandHeldtomaturitySecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAccumulatedLoss	159961000	usd
CY2022Q4	bmrc	Available For Sale Securities And Held To Maturity Securities Continuous Unrealized Loss Position Fair Value Total AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValueTotal	1617230000	usd
CY2022Q4	bmrc	Availableforsale Securitiesand Heldtomaturity Securities Continuous Unrealized Loss Position Accumulated Loss AvailableforsaleSecuritiesandHeldtomaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	217581000	usd
CY2023Q4	bmrc	Marketable Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Longer Than12 Months MarketableSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLongerThan12Months	306	security
CY2023Q4	bmrc	Marketable Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than12 Months MarketableSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThan12Months	7	security
CY2023Q4	bmrc	Debt Securities Available For Sale Unrealized Loss Position Allowance For Credit Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAllowanceForCreditLoss	0	usd
CY2022Q4	bmrc	Debt Securities Available For Sale Unrealized Loss Position Allowance For Credit Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAllowanceForCreditLoss	0	usd
CY2023Q4	bmrc	Federal Home Loan Bank Stock Par Value FederalHomeLoanBankStockParValue	100
CY2023Q4	us-gaap	Amortization Method Qualified Affordable Housing Project Investments AmortizationMethodQualifiedAffordableHousingProjectInvestments	2000000	usd
CY2022Q4	us-gaap	Amortization Method Qualified Affordable Housing Project Investments AmortizationMethodQualifiedAffordableHousingProjectInvestments	2500000	usd
CY2023	bmrc	Amortization Method Qualified Affordable Housing Project Investments Tax Credits AmortizationMethodQualifiedAffordableHousingProjectInvestmentsTaxCredits	600000	usd
CY2023	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	503000	usd
CY2023Q4	bmrc	Affordable Housing Program Unfunded Commitments AffordableHousingProgramUnfundedCommitments	344000	usd
CY2023	bmrc	Affordable Housing Credits Investment Impairment Loss AffordableHousingCreditsInvestmentImpairmentLoss	0	usd
CY2022	bmrc	Affordable Housing Credits Investment Impairment Loss AffordableHousingCreditsInvestmentImpairmentLoss	0	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Before Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss	2073720000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Before Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss	2092546000	usd
CY2023Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	25172000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	22983000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest After Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss	2048548000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest After Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss	2069563000	usd
CY2023Q4	bmrc	Financing Receivable Net Deferred Loan Origination Costs Fees FinancingReceivableNetDeferredLoanOriginationCostsFees	2700000	usd
CY2022Q4	bmrc	Financing Receivable Net Deferred Loan Origination Costs Fees FinancingReceivableNetDeferredLoanOriginationCostsFees	1800000	usd
CY2023Q4	bmrc	Certain Loans Acquired In Transfer Without Evidence Of Deteriorated Credit Unrecognized Purchase Discounts CertainLoansAcquiredInTransferWithoutEvidenceOfDeterioratedCreditUnrecognizedPurchaseDiscounts	2000000	usd
CY2022Q4	bmrc	Certain Loans Acquired In Transfer Without Evidence Of Deteriorated Credit Unrecognized Purchase Discounts CertainLoansAcquiredInTransferWithoutEvidenceOfDeterioratedCreditUnrecognizedPurchaseDiscounts	2600000	usd
CY2023Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss FinancingReceivableAccruedInterestAfterAllowanceForCreditLoss	6600000	usd
CY2022Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss FinancingReceivableAccruedInterestAfterAllowanceForCreditLoss	6100000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Year One Originated Current Fiscal Year FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear	183397000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Year Two Originated Fiscal Year Before Current Fiscal Year FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear	291859000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Year Three Originated Two Years Before Current Fiscal Year FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear	320078000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Year Four Originated Three Years Before Current Fiscal Year FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear	264689000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Year Five Originated Four Years Before Current Fiscal Year FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear	239856000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Originated More Than Five Years Before Current Fiscal Year FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear	610122000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Revolving FinancingReceivableExcludingAccruedInterestRevolving	163719000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Before Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss	2073720000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Year One Originated Current Fiscal Year Writeoff FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff	7000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Year Two Originated Fiscal Year Before Current Fiscal Year Writeoff FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff	6000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Year Three Originated Two Years Before Current Fiscal Year Writeoff FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff	1000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Year Four Originated Three Years Before Current Fiscal Year Writeoff FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff	8000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Year Five Originated Four Years Before Current Fiscal Year Writeoff FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff	409000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Originated More Than Five Years Before Current Fiscal Year Writeoff FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff	4000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Revolving Writeoff FinancingReceivableExcludingAccruedInterestRevolvingWriteoff	6000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff	441000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Year One Originated Current Fiscal Year FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear	338104000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Year Two Originated Fiscal Year Before Current Fiscal Year FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear	336584000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Year Three Originated Two Years Before Current Fiscal Year FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear	280304000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Year Four Originated Three Years Before Current Fiscal Year FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear	269247000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Year Five Originated Four Years Before Current Fiscal Year FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear	198510000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Originated More Than Five Years Before Current Fiscal Year FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear	496053000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Revolving FinancingReceivableExcludingAccruedInterestRevolving	173744000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Before Allowance For Credit Loss FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss	2092546000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Nonaccrual FinancingReceivableExcludingAccruedInterestNonaccrual	7992000	usd
CY2023Q4	us-gaap	Financing Receivable Excluding Accrued Interest Nonaccrual No Allowance FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance	3091000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Nonaccrual FinancingReceivableExcludingAccruedInterestNonaccrual	2432000	usd
CY2022Q4	us-gaap	Financing Receivable Excluding Accrued Interest Nonaccrual No Allowance FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance	2432000	usd
CY2022Q4	bmrc	Financing Receivable90 Days Or More Past Due Still Accruing Number Of Loans FinancingReceivable90DaysOrMorePastDueStillAccruingNumberOfLoans	0	loan
CY2023Q4	bmrc	Financing Receivable90 Days Or More Past Due Still Accruing Number Of Loans FinancingReceivable90DaysOrMorePastDueStillAccruingNumberOfLoans	0	loan
CY2023Q4	bmrc	Financing Receivable Nonaccrual Earning Interest On Cash Basis FinancingReceivableNonaccrualEarningInterestOnCashBasis	0	usd
CY2022Q4	bmrc	Financing Receivable Nonaccrual Earning Interest On Cash Basis FinancingReceivableNonaccrualEarningInterestOnCashBasis	0	usd
CY2022	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0	usd
CY2023	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0	usd
CY2021	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0	usd
CY2023	us-gaap	Financing Receivable Accrued Interest Writeoff FinancingReceivableAccruedInterestWriteoff	206000	usd
CY2022	us-gaap	Financing Receivable Accrued Interest Writeoff FinancingReceivableAccruedInterestWriteoff	48000	usd
CY2021	us-gaap	Financing Receivable Accrued Interest Writeoff FinancingReceivableAccruedInterestWriteoff	0	usd
CY2023Q4	bmrc	Weighted Average Ratio Of Loans Value To Collateral Dependent Loans Value WeightedAverageRatioOfLoansValueToCollateralDependentLoansValue	0.70
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Modified Period FinancingReceivableExcludingAccruedInterestModifiedPeriod	2309000	usd
CY2023	bmrc	Financing Receivable Nonaccrual Modified In Period Amount FinancingReceivableNonaccrualModifiedInPeriodAmount	878000	usd
CY2023Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	25172000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	22983000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff	32000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	2575000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Writeoff FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff	441000	usd
CY2023	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Recovery FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery	55000	usd
CY2023Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	25172000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	-63000	usd
CY2023Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization	23148000	usd
CY2022Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization	23746000	usd
CY2022	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Recovery FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery	55000	usd
CY2022Q4	us-gaap	Financing Receivable Allowance For Credit Loss Excluding Accrued Interest FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest	22983000	usd
CY2021	us-gaap	Financing Receivable Excluding Accrued Interest Credit Loss Expense Reversal FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal	-1449000	usd
CY2021	us-gaap	Financing Receivable Allowance For Credit Loss Purchased With Credit Deterioration Increase FinancingReceivableAllowanceForCreditLossPurchasedWithCreditDeteriorationIncrease	1505000	usd
CY2021	us-gaap	Financing Receivable Excluding Accrued Interest Allowance For Credit Loss Recovery FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery	98000	usd
CY2022Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	6445000	usd
CY2021Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	7942000	usd
CY2020Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	6423000	usd
CY2023	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	0	usd
CY2022	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	1525000	usd
CY2021	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	0	usd
CY2023	bmrc	Loans And Leases Receivable Related Parties Acquisition LoansAndLeasesReceivableRelatedPartiesAcquisition	0	usd
CY2022	bmrc	Loans And Leases Receivable Related Parties Acquisition LoansAndLeasesReceivableRelatedPartiesAcquisition	0	usd
CY2021	bmrc	Loans And Leases Receivable Related Parties Acquisition LoansAndLeasesReceivableRelatedPartiesAcquisition	4037000	usd
CY2023	us-gaap	Loans And Leases Receivable Related Parties Proceeds LoansAndLeasesReceivableRelatedPartiesProceeds	613000	usd
CY2022	us-gaap	Loans And Leases Receivable Related Parties Proceeds LoansAndLeasesReceivableRelatedPartiesProceeds	364000	usd
CY2021	us-gaap	Loans And Leases Receivable Related Parties Proceeds LoansAndLeasesReceivableRelatedPartiesProceeds	2518000	usd
CY2023	bmrc	Loans And Leases Receivable Reclassified Due To Change In Borrower Status LoansAndLeasesReceivableReclassifiedDueToChangeInBorrowerStatus	0	usd
CY2022	bmrc	Loans And Leases Receivable Reclassified Due To Change In Borrower Status LoansAndLeasesReceivableReclassifiedDueToChangeInBorrowerStatus	-2658000	usd
CY2021	bmrc	Loans And Leases Receivable Reclassified Due To Change In Borrower Status LoansAndLeasesReceivableReclassifiedDueToChangeInBorrowerStatus	0	usd
CY2023Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	5832000	usd
CY2022Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	6445000	usd
CY2021Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	7942000	usd
CY2023Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset Before Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization	30940000	usd
CY2022Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset Before Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization	31880000	usd
CY2023Q4	us-gaap	Held To Maturity Securities Restricted HeldToMaturitySecuritiesRestricted	287400000	usd
CY2023Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset After Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization	7792000	usd
CY2022Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset After Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization	8134000	usd
CY2023	us-gaap	Depreciation Depreciation	2100000	usd
CY2022	us-gaap	Depreciation Depreciation	1800000	usd
CY2021	us-gaap	Depreciation Depreciation	1700000	usd
CY2023Q4	bmrc	Life Insurance Corporate Or Bank Owned Death Benefits LifeInsuranceCorporateOrBankOwnedDeathBenefits	131800000	usd
CY2023Q4	us-gaap	Life Insurance Corporate Or Bank Owned Amount LifeInsuranceCorporateOrBankOwnedAmount	68100000	usd
CY2022Q4	us-gaap	Life Insurance Corporate Or Bank Owned Amount LifeInsuranceCorporateOrBankOwnedAmount	67100000	usd
CY2023	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1800000	usd
CY2022	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1200000	usd
CY2021	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	2200000	usd
CY2023	bmrc	Proceeds In Excess Of Cash Surrender Values On Bank Owned Life Insurance ProceedsInExcessOfCashSurrenderValuesOnBankOwnedLifeInsurance	313000	usd
CY2022	bmrc	Proceeds In Excess Of Cash Surrender Values On Bank Owned Life Insurance ProceedsInExcessOfCashSurrenderValuesOnBankOwnedLifeInsurance	86000	usd
CY2021	bmrc	Proceeds In Excess Of Cash Surrender Values On Bank Owned Life Insurance ProceedsInExcessOfCashSurrenderValuesOnBankOwnedLifeInsurance	1100000	usd
CY2023Q4	bmrc	Time Deposits Less Than Or Equal To250000 TimeDepositsLessThanOrEqualTo250000	145697000	usd
CY2022Q4	bmrc	Time Deposits Less Than Or Equal To250000 TimeDepositsLessThanOrEqualTo250000	74421000	usd
CY2023Q4	bmrc	Time Deposits250000 Or More TimeDeposits250000OrMore	105620000	usd
CY2022Q4	bmrc	Time Deposits250000 Or More TimeDeposits250000OrMore	44609000	usd
CY2023Q4	us-gaap	Time Deposits TimeDeposits	251317000	usd
CY2022Q4	us-gaap	Time Deposits TimeDeposits	119030000	usd
CY2023	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	4700000	usd
CY2022	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	323000	usd
CY2021	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	246000	usd
CY2023Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	233726000	usd
CY2023Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	6760000	usd
CY2023Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	5510000	usd
CY2023Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	2705000	usd
CY2023Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	2616000	usd
CY2023Q4	us-gaap	Time Deposit Maturities After Year Five TimeDepositMaturitiesAfterYearFive	0	usd
CY2023Q4	us-gaap	Time Deposits TimeDeposits	251317000	usd
CY2023Q4	bmrc	Deferred Tax Assets Unrealized Losseson Availablefor Sale Securities Net DeferredTaxAssetsUnrealizedLossesonAvailableforSaleSecuritiesNet	20993000	usd
CY2022Q4	bmrc	Deferred Tax Assets Unrealized Losseson Availablefor Sale Securities Net DeferredTaxAssetsUnrealizedLossesonAvailableforSaleSecuritiesNet	29458000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	7775000	usd
CY2023Q4	bmrc	Time Deposits Certificate Of Deposit Account Registry Service Cdars TimeDepositsCertificateOfDepositAccountRegistryServiceCDARS	46162000	usd
CY2023Q4	bmrc	Time Deposits Certificate Of Deposit Account Registry Service Cdars One Way TimeDepositsCertificateOfDepositAccountRegistryServiceCDARSOneWay	2164000	usd
CY2022Q4	bmrc	Time Deposits Certificate Of Deposit Account Registry Service Cdars TimeDepositsCertificateOfDepositAccountRegistryServiceCDARS	11031000	usd
CY2022Q4	bmrc	Time Deposits Certificate Of Deposit Account Registry Service Cdars One Way TimeDepositsCertificateOfDepositAccountRegistryServiceCDARSOneWay	2162000	usd
CY2023Q4	bmrc	Deposits Money Market Deposits Insured Cash Sweep Ics DepositsMoneyMarketDepositsInsuredCashSweepICS	245577000	usd
CY2023Q4	bmrc	Deposits Money Market Deposits Insured Cash Sweep Ics One Way DepositsMoneyMarketDepositsInsuredCashSweepICSOneWay	0	usd
CY2022Q4	bmrc	Deposits Money Market Deposits Insured Cash Sweep Ics DepositsMoneyMarketDepositsInsuredCashSweepICS	100749000	usd
CY2022Q4	bmrc	Deposits Money Market Deposits Insured Cash Sweep Ics One Way DepositsMoneyMarketDepositsInsuredCashSweepICSOneWay	0	usd
CY2023Q4	bmrc	Deposits Money Market Deposits Demand Deposit Marketplace DepositsMoneyMarketDepositsDemandDepositMarketplace	132276000	usd
CY2023Q4	bmrc	Deposits Money Market Deposits Demand Deposit Marketplace One Way DepositsMoneyMarketDepositsDemandDepositMarketplaceOneWay	0	usd
CY2022Q4	bmrc	Deposits Money Market Deposits Demand Deposit Marketplace DepositsMoneyMarketDepositsDemandDepositMarketplace	62219000	usd
CY2022Q4	bmrc	Deposits Money Market Deposits Demand Deposit Marketplace One Way DepositsMoneyMarketDepositsDemandDepositMarketplaceOneWay	0	usd
CY2023Q4	bmrc	Total Network Deposits Reciprocal TotalNetworkDepositsReciprocal	424015000	usd
CY2023Q4	bmrc	Total Network Deposits One Way TotalNetworkDepositsOneWay	2164000	usd
CY2022Q4	bmrc	Total Network Deposits Reciprocal TotalNetworkDepositsReciprocal	173999000	usd
CY2022Q4	bmrc	Total Network Deposits One Way TotalNetworkDepositsOneWay	2162000	usd
CY2023Q4	us-gaap	Deposit Liabilities Reclassified As Loans Receivable1 DepositLiabilitiesReclassifiedAsLoansReceivable1	320000	usd
CY2022Q4	us-gaap	Deposit Liabilities Reclassified As Loans Receivable1 DepositLiabilitiesReclassifiedAsLoansReceivable1	247000	usd
CY2023Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	23600000	usd
CY2022Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	11200000	usd
CY2023Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	298000	usd
CY2022Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	439000	usd
CY2023Q4	bmrc	Borrowings And Other Obligations BorrowingsAndOtherObligations	26298000	usd
CY2023	bmrc	Borrowings And Other Obligations Average Balance BorrowingsAndOtherObligationsAverageBalance	221623000	usd
CY2023Q4	bmrc	Borrowings And Other Obligations Average Rate BorrowingsAndOtherObligationsAverageRate	0.0515
CY2022Q4	bmrc	Borrowings And Other Obligations BorrowingsAndOtherObligations	112439000	usd
CY2022	bmrc	Borrowings And Other Obligations Average Balance BorrowingsAndOtherObligationsAverageBalance	2295000	usd
CY2022Q4	bmrc	Borrowings And Other Obligations Average Rate BorrowingsAndOtherObligationsAverageRate	0.0390
CY2021Q4	bmrc	Borrowings And Other Obligations BorrowingsAndOtherObligations	419000	usd
CY2021	bmrc	Borrowings And Other Obligations Average Balance BorrowingsAndOtherObligationsAverageBalance	892000	usd
CY2021Q4	bmrc	Borrowings And Other Obligations Average Rate BorrowingsAndOtherObligationsAverageRate	0.0108
CY2023	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	3132	shares
CY2022	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	11505	shares
CY2021	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	27929	shares
CY2023	bmrc	Adjustments Related To Tax Withholding And Exercise Of Options For Share Based Compensation AdjustmentsRelatedToTaxWithholdingAndExerciseOfOptionsForShareBasedCompensation	86000	usd
CY2021	bmrc	Adjustments Related To Tax Withholding And Exercise Of Options For Share Based Compensation AdjustmentsRelatedToTaxWithholdingAndExerciseOfOptionsForShareBasedCompensation	1085000	usd
CY2023	bmrc	Sharebased Compensation Arrangementsby Sharebased Payment Award Options Tax Withholding And Exercisesin Period Weighted Average Exercise Price SharebasedCompensationArrangementsbySharebasedPaymentAwardOptionsTaxWithholdingAndExercisesinPeriodWeightedAverageExercisePrice	27.57
CY2022	bmrc	Sharebased Compensation Arrangementsby Sharebased Payment Award Options Tax Withholding And Exercisesin Period Weighted Average Exercise Price SharebasedCompensationArrangementsbySharebasedPaymentAwardOptionsTaxWithholdingAndExercisesinPeriodWeightedAverageExercisePrice	34.13
CY2021	bmrc	Sharebased Compensation Arrangementsby Sharebased Payment Award Options Tax Withholding And Exercisesin Period Weighted Average Exercise Price SharebasedCompensationArrangementsbySharebasedPaymentAwardOptionsTaxWithholdingAndExercisesinPeriodWeightedAverageExercisePrice	38.85
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	371584	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	29.92
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	2262000	usd
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y1M13D
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	55861	shares
CY2021	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	36.39
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	8.84
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod	2008	shares
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice	42.50
CY2021	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	60056	shares
CY2021	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	23.01
CY2021	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	885000	usd
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	365381	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	31.97
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	2326000	usd
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y6M25D
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber	315744	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice	30.85
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue	2264000	usd
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1	P5Y1M24D
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	365381	shares
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	31.97
CY2021Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	2326000	usd
CY2021	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y6M25D
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	39094	shares
CY2022	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	34.16
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	8.49
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod	23760	shares
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice	37.48
CY2022	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	51010	shares
CY2022	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	23.01
CY2022	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	617000	usd
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	329705	shares
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	33.22
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	813000	usd
CY2022	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y7M2D
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber	287228	shares
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice	32.81
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue	813000	usd
CY2022	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1	P5Y1M24D
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	329705	shares
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	33.22
CY2022Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	813000	usd
CY2022	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y7M2D
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	10040	shares
CY2023	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	32.54
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	8.49
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod	23804	shares
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice	35.06
CY2023	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	12164	shares
CY2023	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	20.25
CY2023	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	88000	usd
CY2021	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	13107000	usd
CY2023	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	1.00
CY2022	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.98
CY2021	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.94
CY2023Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	274600000	usd
CY2023Q4	us-gaap	Stockholders Equity StockholdersEquity	439100000	usd
CY2023Q4	bmrc	Dividends Cash Dividend Amount Retained Earnings Available For Dividend Payments Under Restriction DividendsCashDividendAmountRetainedEarningsAvailableForDividendPaymentsUnderRestriction	6100000	usd
CY2023	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Period Increase Decrease DebtSecuritiesHeldToMaturityAllowanceForCreditLossPeriodIncreaseDecrease	0	usd
CY2023Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	303777	shares
CY2023Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	33.22
CY2023Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	1000	usd
CY2023	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P4Y10M9D
CY2023Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber	283578	shares
CY2023Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice	33.46
CY2023Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue	1000	usd
CY2023	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1	P4Y7M24D
CY2023	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	522000	usd
CY2022	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	962000	usd
CY2021	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	972000	usd
CY2023	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	146000	usd
CY2022	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	257000	usd
CY2021	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	213000	usd
CY2023Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	1300000	usd
CY2023	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P2Y2M12D
CY2023	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	2000	usd
CY2022	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	3000	usd
CY2021	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	87000	usd
CY2023	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	16106000	usd
CY2022	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	15673000	usd
CY2023Q4	us-gaap	Cash Cash	7200000	usd
CY2022	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss Period Increase Decrease DebtSecuritiesHeldToMaturityAllowanceForCreditLossPeriodIncreaseDecrease	0	usd
CY2023Q1	bmrc	Deferred Compensation Arrangementwith Individual Deferred Interest Earned Percent DeferredCompensationArrangementwithIndividualDeferredInterestEarnedPercent	0.0750
CY2022Q1	bmrc	Deferred Compensation Arrangementwith Individual Deferred Interest Earned Percent DeferredCompensationArrangementwithIndividualDeferredInterestEarnedPercent	0.0325
CY2023Q4	us-gaap	Deferred Compensation Arrangement With Individual Recorded Liability DeferredCompensationArrangementWithIndividualRecordedLiability	6600000	usd
CY2022Q4	us-gaap	Deferred Compensation Arrangement With Individual Recorded Liability DeferredCompensationArrangementWithIndividualRecordedLiability	7100000	usd
CY2023	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent Of Match DefinedContributionPlanEmployerMatchingContributionPercentOfMatch	0.70
CY2023	bmrc	Defined Contribution Plan Employer Matching Contribution Maximum Amount DefinedContributionPlanEmployerMatchingContributionMaximumAmount	5000	usd
CY2023	bmrc	Defined Benefit Plan Percentage Of Salary Paid Upon Retirement DefinedBenefitPlanPercentageOfSalaryPaidUponRetirement	0.25
CY2023	bmrc	Defined Benefits Plan Period Before Ratable Vesting Begins DefinedBenefitsPlanPeriodBeforeRatableVestingBegins	P5Y
CY2023	bmrc	Defined Benefits Plan Period Before Ratable Vesting Begins DefinedBenefitsPlanPeriodBeforeRatableVestingBegins	P5Y
CY2023	bmrc	Defined Benefits Plan Age Ratable Vesting Ends DefinedBenefitsPlanAgeRatableVestingEnds	P65Y
CY2023Q4	us-gaap	Defined Benefit Plan Amounts Recognized In Balance Sheet DefinedBenefitPlanAmountsRecognizedInBalanceSheet	4500000	usd
CY2022Q4	us-gaap	Defined Benefit Plan Amounts Recognized In Balance Sheet DefinedBenefitPlanAmountsRecognizedInBalanceSheet	4700000	usd
CY2023	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	3234000	usd
CY2022	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	10670000	usd
CY2021	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	6627000	usd
CY2023	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	2823000	usd
CY2022	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	6687000	usd
CY2021	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	4815000	usd
CY2023	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	6057000	usd
CY2022	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	17357000	usd
CY2021	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	11442000	usd
CY2023	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	319000	usd
CY2022	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-441000	usd
CY2021	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	274000	usd
CY2023	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-235000	usd
CY2022	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	7000	usd
CY2021	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-58000	usd
CY2023	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	84000	usd
CY2022	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-434000	usd
CY2021	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	216000	usd
CY2023	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	6141000	usd
CY2022	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	16923000	usd
CY2021	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	11658000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	7229000	usd
CY2023Q4	bmrc	Operating Lease And Finance Lease Liability OperatingLeaseAndFinanceLeaseLiability	6860000	usd
CY2022Q4	bmrc	Operating Lease And Finance Lease Liability OperatingLeaseAndFinanceLeaseLiability	8002000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions	3289000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions	3481000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	1709000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	1751000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	1136000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	1239000	usd
CY2023Q4	bmrc	Deferred Tax Asset Fair Value Adjustment Loans Receivable DeferredTaxAssetFairValueAdjustmentLoansReceivable	695000	usd
CY2022Q4	bmrc	Deferred Tax Asset Fair Value Adjustment Loans Receivable DeferredTaxAssetFairValueAdjustmentLoansReceivable	905000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	632000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	697000	usd
CY2023Q4	us-gaap	Deferred Tax Assets State Taxes DeferredTaxAssetsStateTaxes	593000	usd
CY2022Q4	us-gaap	Deferred Tax Assets State Taxes DeferredTaxAssetsStateTaxes	1396000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	179000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	236000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	74000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	194000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	43935000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	54588000	usd
CY2023Q4	bmrc	Operating Lease And Finance Lease Right Of Use Asset OperatingLeaseAndFinanceLeaseRightOfUseAsset	6092000	usd
CY2022Q4	bmrc	Operating Lease And Finance Lease Right Of Use Asset OperatingLeaseAndFinanceLeaseRightOfUseAsset	7465000	usd
CY2023Q4	bmrc	Deferred Tax Liabilities Deferred Loan Origination Costs DeferredTaxLiabilitiesDeferredLoanOriginationCosts	1435000	usd
CY2022Q4	bmrc	Deferred Tax Liabilities Deferred Loan Origination Costs DeferredTaxLiabilitiesDeferredLoanOriginationCosts	1476000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	1113000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	1512000	usd
CY2023Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	226000	usd
CY2022Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	279000	usd
CY2023Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	8866000	usd
CY2022Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	10732000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	35069000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	43856000	usd
CY2023Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	1100000	usd
CY2022Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	usd
CY2023Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	usd
CY2023	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2022	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2021	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2023	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.079
CY2022	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.083
CY2021	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.084
CY2023	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Interest On Municipal Securities And Loans EffectiveIncomeTaxRateReconciliationTaxExemptIncomeInterestOnMunicipalSecuritiesAndLoans	0.031
CY2022	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Interest On Municipal Securities And Loans EffectiveIncomeTaxRateReconciliationTaxExemptIncomeInterestOnMunicipalSecuritiesAndLoans	0.019
CY2021	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Interest On Municipal Securities And Loans EffectiveIncomeTaxRateReconciliationTaxExemptIncomeInterestOnMunicipalSecuritiesAndLoans	0.025
CY2023	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Earnings On Bank Owned Life Insurance EffectiveIncomeTaxRateReconciliationTaxExemptIncomeEarningsOnBankOwnedLifeInsurance	0.015
CY2022	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Earnings On Bank Owned Life Insurance EffectiveIncomeTaxRateReconciliationTaxExemptIncomeEarningsOnBankOwnedLifeInsurance	0.004
CY2021	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Earnings On Bank Owned Life Insurance EffectiveIncomeTaxRateReconciliationTaxExemptIncomeEarningsOnBankOwnedLifeInsurance	0.010
CY2023	bmrc	Effective Income Tax Rate Reconciliation Non Deductible Acquisition Related Expenses EffectiveIncomeTaxRateReconciliationNonDeductibleAcquisitionRelatedExpenses	0
CY2022	bmrc	Effective Income Tax Rate Reconciliation Non Deductible Acquisition Related Expenses EffectiveIncomeTaxRateReconciliationNonDeductibleAcquisitionRelatedExpenses	0
CY2021	bmrc	Effective Income Tax Rate Reconciliation Non Deductible Acquisition Related Expenses EffectiveIncomeTaxRateReconciliationNonDeductibleAcquisitionRelatedExpenses	0.006
CY2023	bmrc	Effective Income Tax Rate Reconciliation Non Deductible Executive Compensation EffectiveIncomeTaxRateReconciliationNonDeductibleExecutiveCompensation	0
CY2022	bmrc	Effective Income Tax Rate Reconciliation Non Deductible Executive Compensation EffectiveIncomeTaxRateReconciliationNonDeductibleExecutiveCompensation	0
CY2021	bmrc	Effective Income Tax Rate Reconciliation Non Deductible Executive Compensation EffectiveIncomeTaxRateReconciliationNonDeductibleExecutiveCompensation	0.004
CY2023	bmrc	Effective Income Tax Rate Reconciliation Tax Credit Affordable Housing EffectiveIncomeTaxRateReconciliationTaxCreditAffordableHousing	0.006
CY2022	bmrc	Effective Income Tax Rate Reconciliation Tax Credit Affordable Housing EffectiveIncomeTaxRateReconciliationTaxCreditAffordableHousing	0.002
CY2021	bmrc	Effective Income Tax Rate Reconciliation Tax Credit Affordable Housing EffectiveIncomeTaxRateReconciliationTaxCreditAffordableHousing	0.004
CY2023	bmrc	Effective Income Tax Rate Reconciliation Deduction Share Based Compensation And Excess Tax Benefits EffectiveIncomeTaxRateReconciliationDeductionShareBasedCompensationAndExcessTaxBenefits	-0.002
CY2022	bmrc	Effective Income Tax Rate Reconciliation Deduction Share Based Compensation And Excess Tax Benefits EffectiveIncomeTaxRateReconciliationDeductionShareBasedCompensationAndExcessTaxBenefits	0
CY2021	bmrc	Effective Income Tax Rate Reconciliation Deduction Share Based Compensation And Excess Tax Benefits EffectiveIncomeTaxRateReconciliationDeductionShareBasedCompensationAndExcessTaxBenefits	0.001
CY2023	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.003
CY2022	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.002
CY2021	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.004
CY2023	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.236
CY2022	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.266
CY2021	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.260
CY2023Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	20316000	usd
CY2022Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	24821000	usd
CY2023Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	22906000	usd
CY2022Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	26639000	usd
CY2023Q4	us-gaap	Finance Lease Right Of Use Asset Before Accumulated Amortization FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization	608000	usd
CY2022Q4	us-gaap	Finance Lease Right Of Use Asset Before Accumulated Amortization FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization	616000	usd
CY2023Q4	bmrc	Finance Lease Right Of Use Asset Accumulated Depreciation FinanceLeaseRightOfUseAssetAccumulatedDepreciation	319000	usd
CY2022Q4	bmrc	Finance Lease Right Of Use Asset Accumulated Depreciation FinanceLeaseRightOfUseAssetAccumulatedDepreciation	187000	usd
CY2023Q4	us-gaap	Finance Lease Right Of Use Asset FinanceLeaseRightOfUseAsset	289000	usd
CY2022Q4	us-gaap	Finance Lease Right Of Use Asset FinanceLeaseRightOfUseAsset	429000	usd
CY2023Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	298000	usd
CY2022Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	439000	usd
CY2023	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	437000	usd
CY2022	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	6116000	usd
CY2021	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	2376000	usd
CY2023	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	7000	usd
CY2022	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	151000	usd
CY2021	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	444000	usd
CY2023	us-gaap	Operating Lease Cost OperatingLeaseCost	5493000	usd
CY2022	us-gaap	Operating Lease Cost OperatingLeaseCost	5356000	usd
CY2021	us-gaap	Operating Lease Cost OperatingLeaseCost	4823000	usd
CY2023	us-gaap	Variable Lease Cost VariableLeaseCost	0	usd
CY2022	us-gaap	Variable Lease Cost VariableLeaseCost	0	usd
CY2021	us-gaap	Variable Lease Cost VariableLeaseCost	0	usd
CY2023	bmrc	Operating Lease Cost Net OperatingLeaseCostNet	5493000	usd
CY2022	bmrc	Operating Lease Cost Net OperatingLeaseCostNet	5356000	usd
CY2021	bmrc	Operating Lease Cost Net OperatingLeaseCostNet	4823000	usd
CY2023	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	147000	usd
CY2022	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	127000	usd
CY2021	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	96000	usd
CY2023	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	7000	usd
CY2022	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	3000	usd
CY2021	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	2000	usd
CY2023	bmrc	Finance Lease Cost FinanceLeaseCost	154000	usd
CY2022	bmrc	Finance Lease Cost FinanceLeaseCost	130000	usd
CY2021	bmrc	Finance Lease Cost FinanceLeaseCost	98000	usd
CY2023	us-gaap	Lease Cost LeaseCost	5647000	usd
CY2022	us-gaap	Lease Cost LeaseCost	5486000	usd
CY2021	us-gaap	Lease Cost LeaseCost	4921000	usd
CY2023Q4	bmrc	Lessee Operating Lease Lease Not Yet Commenced Liability LesseeOperatingLeaseLeaseNotYetCommencedLiability	2000000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	4753000	usd
CY2023Q4	us-gaap	Finance Lease Liability Payments Due Next Twelve Months FinanceLeaseLiabilityPaymentsDueNextTwelveMonths	155000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	4112000	usd
CY2023Q4	us-gaap	Finance Lease Liability Payments Due Year Two FinanceLeaseLiabilityPaymentsDueYearTwo	108000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	3373000	usd
CY2023Q4	us-gaap	Finance Lease Liability Payments Due Year Three FinanceLeaseLiabilityPaymentsDueYearThree	38000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	3096000	usd
CY2023Q4	us-gaap	Finance Lease Liability Payments Due Year Four FinanceLeaseLiabilityPaymentsDueYearFour	5000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	2710000	usd
CY2023Q4	us-gaap	Finance Lease Liability Payments Due Year Five FinanceLeaseLiabilityPaymentsDueYearFive	0	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	7308000	usd
CY2023Q4	us-gaap	Finance Lease Liability Payments Due After Year Five FinanceLeaseLiabilityPaymentsDueAfterYearFive	0	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	25352000	usd
CY2023Q4	us-gaap	Finance Lease Liability Payments Due FinanceLeaseLiabilityPaymentsDue	306000	usd
CY2023Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	2446000	usd
CY2023Q4	us-gaap	Finance Lease Liability Undiscounted Excess Amount FinanceLeaseLiabilityUndiscountedExcessAmount	8000	usd
CY2023Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	22906000	usd
CY2023Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	298000	usd
CY2023Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P7Y3M18D
CY2023Q4	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P2Y2M12D
CY2023Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0240
CY2023Q4	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.0207
CY2023Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	287000	usd
CY2023Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	0	usd
CY2023Q4	us-gaap	Derivative Fair Value Of Derivative Asset Amount Not Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral	287000	usd
CY2023Q4	us-gaap	Derivative Collateral Obligation To Return Securities DerivativeCollateralObligationToReturnSecurities	0	usd
CY2023Q4	us-gaap	Derivative Collateral Obligation To Return Cash DerivativeCollateralObligationToReturnCash	0	usd
CY2023Q4	us-gaap	Derivative Fair Value Of Derivative Asset Amount Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral	287000	usd
CY2022Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	602000	usd
CY2022Q4	us-gaap	Derivative Asset Fair Value Gross Liability DerivativeAssetFairValueGrossLiability	0	usd
CY2022Q4	us-gaap	Derivative Fair Value Of Derivative Asset Amount Not Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountNotOffsetAgainstCollateral	602000	usd
CY2022Q4	us-gaap	Derivative Collateral Obligation To Return Securities DerivativeCollateralObligationToReturnSecurities	0	usd
CY2022Q4	us-gaap	Derivative Collateral Obligation To Return Cash DerivativeCollateralObligationToReturnCash	0	usd
CY2022Q4	us-gaap	Derivative Fair Value Of Derivative Asset Amount Offset Against Collateral DerivativeFairValueOfDerivativeAssetAmountOffsetAgainstCollateral	602000	usd
CY2023Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	1361000	usd
CY2023Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	0	usd
CY2023Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Not Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral	1361000	usd
CY2023Q4	us-gaap	Derivative Collateral Right To Reclaim Securities DerivativeCollateralRightToReclaimSecurities	287000	usd
CY2023Q4	us-gaap	Derivative Collateral Right To Reclaim Cash DerivativeCollateralRightToReclaimCash	330000	usd
CY2023Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral	744000	usd
CY2022Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	0	usd
CY2022Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	0	usd
CY2022Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Not Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral	0	usd
CY2022Q4	us-gaap	Derivative Collateral Right To Reclaim Securities DerivativeCollateralRightToReclaimSecurities	0	usd
CY2022Q4	us-gaap	Derivative Collateral Right To Reclaim Cash DerivativeCollateralRightToReclaimCash	0	usd
CY2022Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral	0	usd
CY2023	bmrc	Provision For Reversal Of Losses On Unfunded Loan Commitments ProvisionForReversalOfLossesOnUnfundedLoanCommitments	-342000	usd
CY2022	bmrc	Provision For Reversal Of Losses On Unfunded Loan Commitments ProvisionForReversalOfLossesOnUnfundedLoanCommitments	-318000	usd
CY2021	bmrc	Provision For Reversal Of Losses On Unfunded Loan Commitments ProvisionForReversalOfLossesOnUnfundedLoanCommitments	-992000	usd
CY2023	dei	Auditor Name AuditorName	Moss Adams LLP
CY2023	dei	Auditor Location AuditorLocation	Portland, OR
CY2023	dei	Auditor Firm AuditorFirmId	659

Files In Submission

Name	View Source	Status
0001403475-24-000012-index-headers.html	Edgar Link	pending
0001403475-24-000012-index.html	Edgar Link	pending
0001403475-24-000012.txt	Edgar Link	pending
0001403475-24-000012-xbrl.zip	Edgar Link	pending
bmrc-20231231.htm	Edgar Link	pending
bmrc-20231231.xsd	Edgar Link	pending
bmrc-20231231_g1.jpg	Edgar Link	pending
bmrc-ex1401_20231231x10k.htm	Edgar Link	pending
bmrc-ex2301_20231231x10k.htm	Edgar Link	pending
bmrc-ex3101_20231231x10k.htm	Edgar Link	pending
bmrc-ex3102_20231231x10k.htm	Edgar Link	pending
bmrc-ex3201_20231231x10k.htm	Edgar Link	pending
bmrc-ex971_20231231x10k.htm	Edgar Link	pending
Financial_Report.xlsx	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
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bmrc-20231231_def.xml	Edgar Link	unprocessable
bmrc-20231231_lab.xml	Edgar Link	unprocessable
bmrc-20231231_pre.xml	Edgar Link	unprocessable
FilingSummary.xml	Edgar Link	unprocessable
bmrc-20231231_htm.xml	Edgar Link	completed
R17.htm	Edgar Link	pending
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report.css	Edgar Link	pending
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bmrc-20231231_cal.xml	Edgar Link	unprocessable

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$BMRC
Bank of Marin Bancorp Stock $bmrc

2024 Q1 Form 10-K Financial Statement

#000140347524000012 Filed on March 14, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$BMRC Bank of Marin Bancorp Stock $bmrc

2024 Q1 Form 10-K Financial Statement

#000140347524000012 Filed on March 14, 2024

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$BMRC
Bank of Marin Bancorp Stock $bmrc