$BMRC
Bank of Marin Bancorp Stock $bmrc

$bmrc Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-K Financial Statement

#000140347521000015 Filed on March 15, 2021

Income Statement

Concept	2019 Q4	2018	2017 Q4
Revenue		$95.08M
YoY Change		24.13%
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	$750.0K	$2.100M	$690.0K
YoY Change	1.35%	10.53%	13.11%
% of Gross Profit
Operating Expenses
YoY Change
Operating Profit
YoY Change
Interest Expense		$3.536M
YoY Change		102.75%
% of Operating Profit
Other Income/Expense, Net
YoY Change
Pretax Income	$12.39M	$43.42M	$6.530M
YoY Change	-4.62%	50.55%	-27.28%
Income Tax	$3.310M	$10.80M	$2.420M
% Of Pretax Income	26.72%	24.86%	37.06%
Net Earnings	$9.080M	$32.62M	$1.110M
YoY Change	-6.0%	104.19%	-80.49%
Net Earnings / Revenue		34.31%
Basic Earnings Per Share		$2.35
Diluted Earnings Per Share	$662.8K	$2.33	$84.67K
COMMON SHARES
Basic Shares Outstanding	13.59M shares	13.86M shares	6.178M shares
Diluted Shares Outstanding		14.03M shares

Balance Sheet

Concept	2019 Q4	2018	2017 Q4
SHORT-TERM ASSETS
Cash & Short-Term Investments	$753.1M		$687.0M
YoY Change	15.17%
Cash & Equivalents	$183.4M		$203.5M
Short-Term Investments	$569.7M		$483.5M
Other Short-Term Assets
YoY Change
Inventory
Prepaid Expenses
Receivables
Other Receivables
Total Short-Term Assets
YoY Change
LONG-TERM ASSETS
Property, Plant & Equipment	$6.070M	$7.400M	$8.612M
YoY Change	-17.71%	-13.95%	1.08%
Goodwill	$30.14M		$30.14M
YoY Change	0.0%		368.3%
Intangibles
YoY Change
Long-Term Investments
YoY Change
Other Assets	$8.200M	$10.40M	$8.800M
YoY Change		18.18%	-42.48%
Total Long-Term Assets
YoY Change
TOTAL ASSETS
Total Short-Term Assets
Total Long-Term Assets
Total Assets	$2.707B	$2.521B	$2.468B
YoY Change	7.39%	2.14%	21.97%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$17.30M	$19.60M	$16.00M
YoY Change	-11.73%	22.5%	16.79%
Accrued Expenses	$12.60M
YoY Change
Deferred Revenue
YoY Change
Short-Term Debt
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$29.90M	$19.60M	$16.00M
YoY Change	52.55%	22.5%	16.79%
LONG-TERM LIABILITIES
Long-Term Debt	$2.900M	$2.600M	$5.700M
YoY Change	11.54%	-54.39%	1.79%
Other Long-Term Liabilities	$1.200M	$400.0K	$700.0K
YoY Change	200.0%	-42.86%	-22.22%
Total Long-Term Liabilities	$4.100M	$3.000M	$6.400M
YoY Change	36.67%	-53.13%	-1.54%
TOTAL LIABILITIES
Total Short-Term Liabilities	$29.90M	$19.60M	$16.00M
Total Long-Term Liabilities	$4.100M	$3.000M	$6.400M
Total Liabilities	$2.370B	$2.205B	$2.171B
YoY Change	7.53%	1.54%	21.09%
SHAREHOLDERS EQUITY
Retained Earnings	$203.2M		$155.5M
YoY Change	12.94%		6.2%
Common Stock	$129.1M		$144.0M
YoY Change	-8.19%		64.74%
Preferred Stock
YoY Change
Treasury Stock (at cost)
YoY Change
Treasury Stock Shares
Shareholders Equity	$336.8M	$316.4M	$297.0M
YoY Change
Total Liabilities & Shareholders Equity	$2.707B	$2.521B	$2.468B
YoY Change	7.39%	2.14%	21.97%

Cashflow Statement

Concept	2019 Q4	2018	2017 Q4
OPERATING ACTIVITIES
Net Income	$9.080M	$32.62M	$1.110M
YoY Change	-6.0%	104.19%	-80.49%
Depreciation, Depletion And Amortization	$750.0K	$2.100M	$690.0K
YoY Change	1.35%	10.53%	13.11%
Cash From Operating Activities	$9.730M	$42.11M	$6.510M
YoY Change	-10.16%	56.26%	26.9%
INVESTING ACTIVITIES
Capital Expenditures	-$120.0K	-$910.0K	-$290.0K
YoY Change	-58.62%	-36.36%	-25.64%
Acquisitions
YoY Change
Other Investing Activities	-$116.1M	-$224.4M	$42.18M
YoY Change	52.9%	-2525.95%	-286.31%
Cash From Investing Activities	-$116.2M	-$225.3M	$41.88M
YoY Change	52.51%	-2983.69%	-281.85%
FINANCING ACTIVITIES
Cash Dividend Paid
YoY Change
Common Stock Issuance & Retirement, Net
YoY Change
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	107.4M	$13.87M	6.030M
YoY Change	-349.13%	-88.44%	-119.95%
NET CHANGE
Cash From Operating Activities	9.730M	$42.11M	6.510M
Cash From Investing Activities	-116.2M	-$225.3M	41.88M
Cash From Financing Activities	107.4M	$13.87M	6.030M
Net Change In Cash	900.0K	-$169.3M	54.42M
YoY Change	-100.83%	-209.42%	-213.07%
FREE CASH FLOW
Cash From Operating Activities	$9.730M	$42.11M	$6.510M
Capital Expenditures	-$120.0K	-$910.0K	-$290.0K
Free Cash Flow	$9.850M	$43.02M	$6.800M
YoY Change	-11.42%	51.59%	23.19%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2020	dei	Document Fiscal Year Focus DocumentFiscalYearFocus	2020
CY2020	dei	Document Fiscal Period Focus DocumentFiscalPeriodFocus	FY
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CY2020	bmrc	Dividends Cash Dividend Period Restricted Payment Amount Is Determined DividendsCashDividendPeriodRestrictedPaymentAmountIsDetermined	P3Y
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CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-31
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	001-33572
CY2020	dei	Entity Registrant Name EntityRegistrantName	Bank of Marin Bancorp
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	CA
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	20-8859754
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	504 Redwood Blvd.
CY2020	dei	Entity Address Address Line2 EntityAddressAddressLine2	Suite 100
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	Novato
CY2020	dei	Entity Address State Or Province EntityAddressStateOrProvince	CA
CY2020	dei	Entity Address Postal Zip Code EntityAddressPostalZipCode	94947
CY2020	dei	City Area Code CityAreaCode	415
CY2020	dei	Local Phone Number LocalPhoneNumber	763-4520
CY2020	dei	Security12g Title Security12gTitle	Common Stock, No Par Value, and attached Share Purchase Rights
CY2020	dei	Trading Symbol TradingSymbol	BMRC
CY2020	dei	Security Exchange Name SecurityExchangeName	NASDAQ
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CY2019	us-gaap	Noninterest Expense Directors Fees NoninterestExpenseDirectorsFees	735000	USD
CY2018	us-gaap	Noninterest Expense Directors Fees NoninterestExpenseDirectorsFees	700000	USD
CY2020	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	474000	USD
CY2019	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	361000	USD
CY2018	us-gaap	Federal Deposit Insurance Corporation Premium Expense FederalDepositInsuranceCorporationPremiumExpense	756000	USD
CY2020	us-gaap	Other Noninterest Expense OtherNoninterestExpense	5484000	USD
CY2019	us-gaap	Other Noninterest Expense OtherNoninterestExpense	5812000	USD
CY2018	us-gaap	Other Noninterest Expense OtherNoninterestExpense	5274000	USD
CY2020	us-gaap	Noninterest Expense NoninterestExpense	60028000	USD
CY2019	us-gaap	Noninterest Expense NoninterestExpense	57970000	USD
CY2018	us-gaap	Noninterest Expense NoninterestExpense	58266000	USD
CY2020	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	40587000	USD
CY2019	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	45894000	USD
CY2018	us-gaap	Income Loss From Continuing Operations Before Income Taxes Minority Interest And Income Loss From Equity Method Investments IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments	43417000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10345000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	11653000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10795000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	30242000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	34241000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	32622000	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.24
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.51
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.35
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.22
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.48
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.33
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	13525000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	13620000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	13864000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	13617000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	13794000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	14029000	shares
CY2020	us-gaap	Net Income Loss NetIncomeLoss	30242000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	34241000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	32622000	USD
CY2020	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	11891000	USD
CY2019	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	11839000	USD
CY2018	us-gaap	Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax	-1707000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	915000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	55000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Sale Of Securities Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax	-79000	USD
CY2020	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
CY2019	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
CY2018	bmrc	Other Comprehensive Income Loss Reclassification Adjustment From Aoci For Investment Transferred From Available For Sale To Held To Maturity Before Tax OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForInvestmentTransferredFromAvailableForSaleToHeldToMaturityBeforeTax	278000	USD
CY2020	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	524000	USD
CY2019	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	445000	USD
CY2018	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	516000	USD
CY2020	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Before Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentBeforeTaxPortionAttributableToParent	11500000	USD
CY2019	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Before Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentBeforeTaxPortionAttributableToParent	12229000	USD
CY2018	us-gaap	Other Comprehensive Income Availableforsale Securities Adjustment Before Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentBeforeTaxPortionAttributableToParent	-1390000	USD
CY2020	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	3402000	USD
CY2019	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	3624000	USD
CY2018	us-gaap	Other Comprehensive Income Availableforsale Securities Tax Portion Attributable To Parent OtherComprehensiveIncomeAvailableforsaleSecuritiesTaxPortionAttributableToParent	-412000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	8098000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	8605000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-978000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	38340000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	42846000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	31644000	USD
CY2018	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	7012000	USD
CY2018Q4	us-gaap	Stockholders Equity StockholdersEquity	316407000	USD
CY2018Q4	us-gaap	Stockholders Equity Note Stock Split Conversion Ratio1 StockholdersEquityNoteStockSplitConversionRatio1	2
CY2017Q4	us-gaap	Stockholders Equity StockholdersEquity	297025000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	32622000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-978000	USD
CY2018	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	538000	USD
CY2018	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	39000	USD
CY2018	us-gaap	Stock Issued During Period Value Employee Stock Ownership Plan StockIssuedDuringPeriodValueEmployeeStockOwnershipPlan	1173000	USD
CY2018	us-gaap	Stock Issued During Period Value Restricted Stock Award Gross StockIssuedDuringPeriodValueRestrictedStockAwardGross	0	USD
CY2018	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	45000	USD
CY2018	us-gaap	Stock Issued During Period Value Restricted Stock Award Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardForfeitures	0	USD
CY2018	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Stock Options Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition	651000	USD
CY2018	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	1013000	USD
CY2018	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.64
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	8860000	USD
CY2018	bmrc	Stock Issued During Period Value Nonemployee Director Stock Purchase Plans StockIssuedDuringPeriodValueNonemployeeDirectorStockPurchasePlans	37000	USD
CY2018	bmrc	Stock Issued In Payment Of Director Fees StockIssuedInPaymentOfDirectorFees	204000	USD
CY2019	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	54000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	34241000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	8605000	USD
CY2019	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	669000	USD
CY2019	us-gaap	Stock Issued During Period Value Employee Stock Ownership Plan StockIssuedDuringPeriodValueEmployeeStockOwnershipPlan	1245000	USD
CY2019	us-gaap	Stock Issued During Period Value Restricted Stock Award Gross StockIssuedDuringPeriodValueRestrictedStockAwardGross	0	USD
CY2019	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	220000	USD
CY2019	us-gaap	Stock Issued During Period Value Restricted Stock Award Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardForfeitures	0	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Stock Options Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition	495000	USD
CY2019	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	1017000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.80
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	10958000	USD
CY2019	bmrc	Stock Issued During Period Value Nonemployee Director Stock Purchase Plans StockIssuedDuringPeriodValueNonemployeeDirectorStockPurchasePlans	24000	USD
CY2019	bmrc	Stock Issued In Payment Of Director Fees StockIssuedInPaymentOfDirectorFees	231000	USD
CY2019	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	15022000	USD
CY2019Q4	us-gaap	Stockholders Equity StockholdersEquity	336788000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	30242000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	8098000	USD
CY2020	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	1304000	USD
CY2020	us-gaap	Stock Issued During Period Value Employee Stock Purchase Plan StockIssuedDuringPeriodValueEmployeeStockPurchasePlan	72000	USD
CY2020	us-gaap	Stock Issued During Period Value Employee Stock Ownership Plan StockIssuedDuringPeriodValueEmployeeStockOwnershipPlan	1289000	USD
CY2020	us-gaap	Stock Issued During Period Value Restricted Stock Award Gross StockIssuedDuringPeriodValueRestrictedStockAwardGross	0	USD
CY2020	us-gaap	Adjustments Related To Tax Withholding For Share Based Compensation AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation	73000	USD
CY2020	us-gaap	Stock Issued During Period Value Restricted Stock Award Forfeitures StockIssuedDuringPeriodValueRestrictedStockAwardForfeitures	0	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Stock Options Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition	319000	USD
CY2020	us-gaap	Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition	884000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.92
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	12506000	USD
CY2020	bmrc	Stock Issued During Period Value Nonemployee Director Stock Purchase Plans StockIssuedDuringPeriodValueNonemployeeDirectorStockPurchasePlans	43000	USD
CY2020	bmrc	Stock Issued In Payment Of Director Fees StockIssuedInPaymentOfDirectorFees	217000	USD
CY2020	us-gaap	Stock Repurchased During Period Value StockRepurchasedDuringPeriodValue	7208000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	358253000	USD
CY2018Q4	us-gaap	Stockholders Equity Note Stock Split Conversion Ratio1 StockholdersEquityNoteStockSplitConversionRatio1	2
CY2020	us-gaap	Net Income Loss NetIncomeLoss	30242000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	34241000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	32622000	USD
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	4594000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	900000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	0	USD
CY2020	bmrc	Provision For Reversal Of Losses On Off Balance Sheet Commitments ProvisionForReversalOfLossesOnOffBalanceSheetCommitments	1570000	USD
CY2019	bmrc	Provision For Reversal Of Losses On Off Balance Sheet Commitments ProvisionForReversalOfLossesOnOffBalanceSheetCommitments	129000	USD
CY2018	bmrc	Provision For Reversal Of Losses On Off Balance Sheet Commitments ProvisionForReversalOfLossesOnOffBalanceSheetCommitments	0	USD
CY2020	bmrc	Noncash Contribution Expense To Employee Stock Ownership Plan NoncashContributionExpenseToEmployeeStockOwnershipPlan	1289000	USD
CY2019	bmrc	Noncash Contribution Expense To Employee Stock Ownership Plan NoncashContributionExpenseToEmployeeStockOwnershipPlan	1245000	USD
CY2018	bmrc	Noncash Contribution Expense To Employee Stock Ownership Plan NoncashContributionExpenseToEmployeeStockOwnershipPlan	1173000	USD
CY2020	bmrc	Compensation Expense Common Stock For Director Fees CompensationExpenseCommonStockForDirectorFees	301000	USD
CY2019	bmrc	Compensation Expense Common Stock For Director Fees CompensationExpenseCommonStockForDirectorFees	301000	USD
CY2018	bmrc	Compensation Expense Common Stock For Director Fees CompensationExpenseCommonStockForDirectorFees	227000	USD
CY2020	us-gaap	Share Based Compensation ShareBasedCompensation	1203000	USD
CY2019	us-gaap	Share Based Compensation ShareBasedCompensation	1512000	USD
CY2018	us-gaap	Share Based Compensation ShareBasedCompensation	1664000	USD
CY2020	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	853000	USD
CY2019	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	887000	USD
CY2018	us-gaap	Amortization Of Intangible Assets AmortizationOfIntangibleAssets	921000	USD
CY2020	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-1354000	USD
CY2019	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-1633000	USD
CY2018	us-gaap	Accretion Amortization Of Discounts And Premiums Investments AccretionAmortizationOfDiscountsAndPremiumsInvestments	-2695000	USD
CY2020	bmrc	Accretion Of Discount On Acquired Loans AccretionOfDiscountOnAcquiredLoans	165000	USD
CY2019	bmrc	Accretion Of Discount On Acquired Loans AccretionOfDiscountOnAcquiredLoans	353000	USD
CY2018	bmrc	Accretion Of Discount On Acquired Loans AccretionOfDiscountOnAcquiredLoans	807000	USD
CY2020	us-gaap	Amortization Of Debt Discount Premium AmortizationOfDebtDiscountPremium	69000	USD
CY2019	us-gaap	Amortization Of Debt Discount Premium AmortizationOfDebtDiscountPremium	68000	USD
CY2018	us-gaap	Amortization Of Debt Discount Premium AmortizationOfDebtDiscountPremium	1025000	USD
CY2020	us-gaap	Amortization Of Deferred Loan Origination Fees Net AmortizationOfDeferredLoanOriginationFeesNet	-5040000	USD
CY2019	us-gaap	Amortization Of Deferred Loan Origination Fees Net AmortizationOfDeferredLoanOriginationFeesNet	348000	USD
CY2018	us-gaap	Amortization Of Deferred Loan Origination Fees Net AmortizationOfDeferredLoanOriginationFeesNet	-183000	USD
CY2020	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	915000	USD
CY2019	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	55000	USD
CY2018	us-gaap	Gain Loss On Sale Of Investments GainLossOnSaleOfInvestments	876000	USD
CY2020	us-gaap	Depreciation Depreciation	2149000	USD
CY2019	us-gaap	Depreciation Depreciation	2228000	USD
CY2018	us-gaap	Depreciation Depreciation	2143000	USD
CY2020	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	973000	USD
CY2019	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1196000	USD
CY2018	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	913000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	5135000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	329000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	-1148000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	-631000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	70000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Liabilities IncreaseDecreaseInOtherOperatingLiabilities	902000	USD
CY2020	us-gaap	Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities	10603000	USD
CY2019	us-gaap	Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities	6692000	USD
CY2018	us-gaap	Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities	9485000	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	40845000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	40933000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	42107000	USD
CY2020	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	0	USD
CY2019	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	3549000	USD
CY2018	us-gaap	Payments To Acquire Held To Maturity Securities PaymentsToAcquireHeldToMaturitySecurities	1988000	USD
CY2020	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	97544000	USD
CY2019	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	110934000	USD
CY2018	us-gaap	Payments To Acquire Available For Sale Securities Debt PaymentsToAcquireAvailableForSaleSecuritiesDebt	235873000	USD
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	33756000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	66081000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	16972000	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	28144000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	23005000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Held To Maturity Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities	22891000	USD
CY2020	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	114991000	USD
CY2019	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	86044000	USD
CY2018	us-gaap	Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities	57662000	USD
CY2020	bmrc	Proceeds From Sale Of Equity Securities Fvni ProceedsFromSaleOfEquitySecuritiesFVNI	0	USD
CY2019	bmrc	Proceeds From Sale Of Equity Securities Fvni ProceedsFromSaleOfEquitySecuritiesFVNI	0	USD
CY2018	bmrc	Proceeds From Sale Of Equity Securities Fvni ProceedsFromSaleOfEquitySecuritiesFVNI	956000	USD
CY2020	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	249337000	USD
CY2019	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	77827000	USD
CY2018	us-gaap	Payments For Proceeds From Loans And Leases PaymentsForProceedsFromLoansAndLeases	84598000	USD
CY2020	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	941000	USD
CY2019	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	2997000	USD
CY2018	us-gaap	Payments To Acquire Life Insurance Policies PaymentsToAcquireLifeInsurancePolicies	0	USD
CY2020	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
CY2019	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	1533000	USD
CY2018	us-gaap	Proceeds From Life Insurance Policies ProceedsFromLifeInsurancePolicies	0	USD
CY2020	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	981000	USD
CY2019	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	542000	USD
CY2018	us-gaap	Payments To Acquire Productive Assets PaymentsToAcquireProductiveAssets	907000	USD
CY2018	us-gaap	Proceeds From Federal Home Loan Bank Borrowings ProceedsFromFederalHomeLoanBankBorrowings	7000000	USD
CY2020	us-gaap	Payments For Proceeds From Federal Home Loan Bank Stock PaymentsForProceedsFromFederalHomeLoanBankStock	176000	USD
CY2019	us-gaap	Payments For Proceeds From Federal Home Loan Bank Stock PaymentsForProceedsFromFederalHomeLoanBankStock	616000	USD
CY2018	us-gaap	Payments For Proceeds From Federal Home Loan Bank Stock PaymentsForProceedsFromFederalHomeLoanBankStock	0	USD
CY2020	us-gaap	Payments To Acquire Real Estate Held For Investment PaymentsToAcquireRealEstateHeldForInvestment	1355000	USD
CY2019	us-gaap	Payments To Acquire Real Estate Held For Investment PaymentsToAcquireRealEstateHeldForInvestment	952000	USD
CY2018	us-gaap	Payments To Acquire Real Estate Held For Investment PaymentsToAcquireRealEstateHeldForInvestment	418000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-173443000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-20754000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	-225303000	USD
CY2020	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	167760000	USD
CY2019	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	161649000	USD
CY2018	us-gaap	Increase Decrease In Deposits IncreaseDecreaseInDeposits	26170000	USD
CY2020	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	1304000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	669000	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	537000	USD
CY2020	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	73000	USD
CY2020	us-gaap	Repayments Of Subordinated Debt RepaymentsOfSubordinatedDebt	0	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	220000	USD
CY2018	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	45000	USD
CY2020	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	0	USD
CY2019	us-gaap	Repayments Of Federal Home Loan Bank Borrowings RepaymentsOfFederalHomeLoanBankBorrowings	7000000	USD
CY2019	us-gaap	Repayments Of Subordinated Debt RepaymentsOfSubordinatedDebt	0	USD
CY2018	us-gaap	Repayments Of Subordinated Debt RepaymentsOfSubordinatedDebt	4137000	USD
CY2020	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	172000	USD
CY2019	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	168000	USD
CY2018	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	0	USD
CY2020	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	12506000	USD
CY2019	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	10958000	USD
CY2018	us-gaap	Payments Of Dividends Common Stock PaymentsOfDividendsCommonStock	8860000	USD
CY2020	us-gaap	Payments For Repurchase Of Equity PaymentsForRepurchaseOfEquity	6898000	USD
CY2019	us-gaap	Payments For Repurchase Of Equity PaymentsForRepurchaseOfEquity	15062000	USD
CY2018	us-gaap	Payments For Repurchase Of Equity PaymentsForRepurchaseOfEquity	6869000	USD
CY2020	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans	115000	USD
CY2019	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans	78000	USD
CY2018	us-gaap	Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans	76000	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	149530000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	128988000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	13872000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	16932000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	149167000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-169324000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	183388000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	34221000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	203545000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	200320000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	183388000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	34221000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	2948000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	4659000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	2599000	USD
CY2020	us-gaap	Income Taxes Paid IncomeTaxesPaid	13065000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	12738000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	8380000	USD
CY2020	bmrc	Increase Decrease In Unrealized Gain Loss On Available For Sale Securities Net Of Tax IncreaseDecreaseInUnrealizedGainLossOnAvailableForSaleSecuritiesNetOfTax	11891000	USD
CY2019	bmrc	Increase Decrease In Unrealized Gain Loss On Available For Sale Securities Net Of Tax IncreaseDecreaseInUnrealizedGainLossOnAvailableForSaleSecuritiesNetOfTax	11839000	USD
CY2018	bmrc	Increase Decrease In Unrealized Gain Loss On Available For Sale Securities Net Of Tax IncreaseDecreaseInUnrealizedGainLossOnAvailableForSaleSecuritiesNetOfTax	-1707000	USD
CY2020	bmrc	Stock Issued In Payment Of Director Fees And To Esop StockIssuedInPaymentOfDirectorFeesAndToESOP	1289000	USD
CY2019	bmrc	Stock Issued In Payment Of Director Fees And To Esop StockIssuedInPaymentOfDirectorFeesAndToESOP	1245000	USD
CY2018	bmrc	Stock Issued In Payment Of Director Fees And To Esop StockIssuedInPaymentOfDirectorFeesAndToESOP	1173000	USD
CY2020	bmrc	Cumulative Effect Of Change In Accounting Principle CumulativeEffectOfChangeInAccountingPrinciple	-1216000	USD
CY2019	bmrc	Cumulative Effect Of Change In Accounting Principle CumulativeEffectOfChangeInAccountingPrinciple	0	USD
CY2018	bmrc	Cumulative Effect Of Change In Accounting Principle CumulativeEffectOfChangeInAccountingPrinciple	0	USD
CY2020	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	524000	USD
CY2019	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	445000	USD
CY2018	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	516000	USD
CY2020	bmrc	Repurchase Of Stock Not Yet Settled RepurchaseOfStockNotYetSettled	413000	USD
CY2019	bmrc	Repurchase Of Stock Not Yet Settled RepurchaseOfStockNotYetSettled	103000	USD
CY2018	bmrc	Repurchase Of Stock Not Yet Settled RepurchaseOfStockNotYetSettled	143000	USD
CY2020	bmrc	Stock Issued In Payment Of Director Fees StockIssuedInPaymentOfDirectorFees	217000	USD
CY2019	bmrc	Stock Issued In Payment Of Director Fees StockIssuedInPaymentOfDirectorFees	231000	USD
CY2018	bmrc	Stock Issued In Payment Of Director Fees StockIssuedInPaymentOfDirectorFees	204000	USD
CY2020	bmrc	Availableforsale Securities Transferredto Heldtomaturity Securities AvailableforsaleSecuritiesTransferredtoHeldtomaturitySecurities	0	USD
CY2019	bmrc	Availableforsale Securities Transferredto Heldtomaturity Securities AvailableforsaleSecuritiesTransferredtoHeldtomaturitySecurities	0	USD
CY2018	bmrc	Availableforsale Securities Transferredto Heldtomaturity Securities AvailableforsaleSecuritiesTransferredtoHeldtomaturitySecurities	27422000	USD
CY2020	bmrc	Subscription In Low Income Housing Tax Credit Investment SubscriptionInLowIncomeHousingTaxCreditInvestment	0	USD
CY2019	bmrc	Subscription In Low Income Housing Tax Credit Investment SubscriptionInLowIncomeHousingTaxCreditInvestment	0	USD
CY2018	bmrc	Subscription In Low Income Housing Tax Credit Investment SubscriptionInLowIncomeHousingTaxCreditInvestment	3000000	USD
CY2020Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	0	USD
CY2019Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	4806000	USD
CY2018Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	5971000	USD
CY2020	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	Accounting Changes and Reclassifications - Certain items in prior financial statements have been reclassified to conform to the current presentation.
CY2020Q3	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	22113000	USD
CY2020Q3	us-gaap	Off Balance Sheet Credit Loss Liability OffBalanceSheetCreditLossLiability	1697000	USD
CY2020	us-gaap	Use Of Estimates UseOfEstimates	<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, income taxes, and fair value measurements (including fair values of acquired assets and assumed liabilities at acquisition dates) as discussed in the Notes herein.</span>
CY2020Q4	us-gaap	Financing Receivable Threshold Period Past Due Writeoff FinancingReceivableThresholdPeriodPastDueWriteoff	P90D
CY2020	bmrc	Loansand Leases Receivable Nonperforming Number Of Consecutive Payments Considered Sustained Repayment Performance LoansandLeasesReceivableNonperformingNumberOfConsecutivePaymentsConsideredSustainedRepaymentPerformance	6	payment
CY2020Q4	us-gaap	Financing Receivable Threshold Period Past Due Writeoff FinancingReceivableThresholdPeriodPastDueWriteoff	P90D
CY2020	bmrc	Threshold Period Past Due For Write Off Of Deposit Liabilities Reclassified As Loans Receivable ThresholdPeriodPastDueForWriteOffOfDepositLiabilitiesReclassifiedAsLoansReceivable	P60D
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Policy For Uncollectible Amounts FinancingReceivableAllowanceForCreditLossesPolicyForUncollectibleAmounts	<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%">Allowance for Credit Losses on Loans ("ACL")</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%">is a valuation account that is deducted from the amortized cost basis at the balance sheet date to present the net amount of loans expected to be collected. Amortized cost does not include accrued interest, which management elected to exclude from the estimate of expected credit losses (refer to the </span><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-style:italic;font-weight:400;line-height:120%">Past-Due and Non-Accrual Loan Policy</span><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%"> section above). Management estimates the allowance quarterly using relevant available information, from internal and external sources, relating to past events, current conditions, and reasonable and supportable forecasts. Credit loss experience provides the basis for the estimation of expected credit losses. </span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The ACL model utilizes a discounted cash flow ("DCF") method to measure the expected credit losses on loans collectively evaluated that are sub-segmented by loan pools with similar credit risk characteristics, which are generally comprised of federal regulatory reporting codes (i.e., Call codes). Pooled segments include the following:</span></div><div style="text-align:justify"><span><br/></span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Loans secured by real estate:</span></div><div style="padding-left:36pt;text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">- 1-4 family residential construction loans</span></div><div style="padding-left:36pt;text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">- Other construction loans and all land development and other land loans</span></div><div style="padding-left:36pt;text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">- Secured by farmland (including residential and other improvements)</span></div><div style="padding-left:36pt;text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">- Revolving, open-end loans secured by 1-4 family residential properties and extended under lines</span></div><div style="padding-left:36pt;text-align:justify;text-indent:18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">of credit</span></div><div style="padding-left:36pt;text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">- Closed-end loans secured by 1-4 family residential properties, secured by first liens</span></div><div style="padding-left:36pt;text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">- Closed-end loans secured by 1-4 family residential properties, secured by junior liens</span></div><div style="padding-left:36pt;text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">- Secured by multifamily (5 or more) residential properties</span></div><div style="padding-left:36pt;text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">- Commercial real estate loans secured by owner-occupied non-farm nonresidential properties</span></div><div style="padding-left:36pt;text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">- Commercial real estate loans secured by other non-farm nonresidential properties</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Loans to finance agricultural production and other loans to farmers</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Commercial and industrial loans</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Loans to individuals for household, family and other personal expenditures (i.e., consumer loans)</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Municipal entities</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Non-profit organizations</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Other loans (overdraft credit lines)</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The DCF method incorporates assumptions for probability of default ("PD"), loss given default ("LGD"), and prepayments and curtailments over the contractual terms of the loans. Under the DCF method, the ACL reflects the difference between the amortized cost basis and the present value of the expected cash flows using the loan's effective rate. We elected to report the change in present values from one reporting period to the next due to the </span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">passage of time and changes in the estimate of future expected cash flows through the provision for credit losses, rather than though interest income. </span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">In determining the PD for each pooled segment, the Bank utilized regression analyses to identify certain economic drivers that were considered highly correlated to historical Bank or peer loan default experience. As a result, management chose the California unemployment rate as the primary economic forecast driver for all segments, except for municipal loans. In addition, the annual percentage change in the California gross domestic product was used in the commercial and industrial loan segment and the annual percentage change in California retail sales was used in the owner-occupied and investor-owned commercial real estate segments. For municipal loans, the ACL model utilized a constant default rate obtained from a nationally recognized default rate st</span><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">udy, which is updated annually. A third party provides LGD estimates for each segment based on a banking industry Frye-Jacobs Risk Index approach. </span><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The ACL model incorporates a one-year reasonable and supportable forecast of economic factors, updated quarterly, which is provided by a well-recognized economics advisory company. For periods beyond the forecast horizon the economic factors revert to historical averages on a straight-line basis over a one-year period.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Expected credit losses are estimated over the contractual term of the loans, adjusted for expected prepayments and curtailments, when appropriate. The pooled loans' contractual loan terms exclude extensions, renewals, and modifications unless one or more of the following applies: 1) management has a reasonable expectation at the reporting date that a troubled debt restructuring will be executed with an individual borrower, 2) the extension or renewal options are included in the original or modified contract, or 3) an existing troubled debt restructuring is within six months of maturity.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Loans that do not share the same risk characteristics as pooled loans are evaluated individually for credit loss and generally include all non-accrual loans, collateral dependent loans, and certain troubled debt restructured loans and loans graded substandard or worse as determined by management.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="background-color:#ffffff;color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Management considers whether adjustments to the quantitative portion of the ACL are needed for differences in segment-specific risk characteristics or to reflect the extent to which it expects current conditions and reasonable and supportable forecasts of economic conditions to differ from the conditions that existed during the historical period included in the development of PD and LGD. </span><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Qualitative internal and external risk factors include, but are not limited to, the following:</span></div><div style="margin-top:6pt;padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Changes in the nature and volume of the loan portfolio</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Changes in the volume and severity of past due loans, the volume of non-accruals loans, and the volume and severity of adversely classified or graded loans</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">The existence and effect of individual loan and loan segment concentrations</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Changes in lending policies and procedures, including changes in underwriting standards and collection, charge-off, and recovery practices not considered elsewhere</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Changes in the experience, ability, and depth of lending management and other relevant staff</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Changes in the quality of our systematic loan review processes</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Changes in economic and business conditions, and developments that affect the collectability of the portfolio</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">Changes in the value of underlying collateral, where applicable</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">The effect of other external factors such as legal and regulatory requirements on the level of estimated credit losses in the portfolio</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">The effect of acquisitions of other loan portfolios on our infrastructure, including risk associated with entering new geographic areas as a result of such acquisitions</span></div><div style="padding-left:36pt;text-align:justify;text-indent:-18pt"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;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%;padding-left:14.5pt">The presence of specialized lending segments in the portfolio</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">While we believe we use the best information available to determine the allowance for credit losses, our results of operations could be significantly affected if circumstances differ substantially from the assumptions used in determining the allowance. Our ACL model is sensitive to changes in unemployment rate forecasts and certain other assumptions that could result in material fluctuations in the allowance for credit losses and adversely affect our financial condition and results of operations.</span></div><div style="text-align:justify"><span><br/></span></div><div style="text-align:justify"><span style="color:#000000;font-family:'Arial',sans-serif;font-size:10pt;font-weight:400;line-height:120%">For further information regarding the allowance for loan losses, see Note 3, Loans and Allowance for Loan Losses.</span></div>
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	13525000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	13620000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	13864000	shares
CY2020	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	69000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	148000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	136000	shares
CY2020	us-gaap	Incremental Common Shares Attributable To Nonvested Shares With Forfeitable Dividends IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends	23000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Nonvested Shares With Forfeitable Dividends IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends	26000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Nonvested Shares With Forfeitable Dividends IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends	29000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	13617000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	13794000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	14029000	shares
CY2020	us-gaap	Net Income Loss NetIncomeLoss	30242000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	34241000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	32622000	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.24
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.51
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.35
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.22
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.48
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.33
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	148000	shares
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	35000	shares
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	139642000	USD
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	44000	shares
CY2018Q4	us-gaap	Stockholders Equity Note Stock Split Conversion Ratio1 StockholdersEquityNoteStockSplitConversionRatio1	2
CY2020	us-gaap	Advertising Expense AdvertisingExpense	769000	USD
CY2019	us-gaap	Advertising Expense AdvertisingExpense	775000	USD
CY2018	us-gaap	Advertising Expense AdvertisingExpense	666000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Amortized Cost Before Other Than Temporary Impairment HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment	109036000	USD
CY2020Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	0	USD
CY2020Q4	bmrc	Debt Securities Held To Maturity After Allowance For Credit Loss DebtSecuritiesHeldToMaturityAfterAllowanceForCreditLoss	109036000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	6149000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	0	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	115185000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Amortized Cost Before Other Than Temporary Impairment HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment	137413000	USD
CY2019Q4	us-gaap	Debt Securities Held To Maturity Allowance For Credit Loss DebtSecuritiesHeldToMaturityAllowanceForCreditLoss	0	USD
CY2019Q4	bmrc	Debt Securities Held To Maturity After Allowance For Credit Loss DebtSecuritiesHeldToMaturityAfterAllowanceForCreditLoss	137413000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Gain HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain	2378000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	149000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	373038000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	19393000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	80000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	392351000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	423923000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax	8748000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax	411000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Allowance For Credit Loss DebtSecuritiesAvailableForSaleAllowanceForCreditLoss	0	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	432260000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	246000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	250000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	11530000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	11687000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount	1807000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities Within One Year Fair Value HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue	1811000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost	6699000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities Within One Year Fair Value AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue	6706000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	7550000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	7961000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	59028000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	62397000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount	2256000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After One Through Five Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	2296000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost	48706000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After One Through Five Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue	49619000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	52113000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	55872000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	144908000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	154089000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount	56221000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Five Through Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	57544000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost	208806000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue	214277000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	49127000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	51102000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	157572000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	164178000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Net Carrying Amount HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount	77129000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Debt Maturities After Ten Years Fair Value HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue	77991000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Amortized Cost AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost	159712000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Maturities After Ten Years Fair Value AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue	161658000	USD
CY2020Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	109036000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	115185000	USD
CY2020Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	373038000	USD
CY2018	bmrc	Availableforsale Securities Transferredto Heldtomaturity Securities Unrealized Gain Loss AvailableforsaleSecuritiesTransferredtoHeldtomaturitySecuritiesUnrealizedGainLoss	278000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	392351000	USD
CY2019Q4	us-gaap	Held To Maturity Securities HeldToMaturitySecurities	137413000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Fair Value HeldToMaturitySecuritiesFairValue	139642000	USD
CY2019Q4	us-gaap	Available For Sale Debt Securities Amortized Cost Basis AvailableForSaleDebtSecuritiesAmortizedCostBasis	423923000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	432260000	USD
CY2018	bmrc	Availableforsale Securities Transferredto Heldtomaturity Securities AvailableforsaleSecuritiesTransferredtoHeldtomaturitySecurities	27400000	USD
CY2020	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	524000	USD
CY2019	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	445000	USD
CY2018	bmrc	Amortization Of Net Unrealized Loss On Available For Sale Securities Transferred To Held To Maturity AmortizationOfNetUnrealizedLossOnAvailableForSaleSecuritiesTransferredToHeldToMaturity	516000	USD
CY2019	bmrc	Availableforsale Securities Transferredto Heldtomaturity Securities AvailableforsaleSecuritiesTransferredtoHeldtomaturitySecurities	0	USD
CY2020	bmrc	Availableforsale Securities Transferredto Heldtomaturity Securities AvailableforsaleSecuritiesTransferredtoHeldtomaturitySecurities	0	USD
CY2020	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	33756000	USD
CY2019	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	66081000	USD
CY2018	us-gaap	Proceeds From Sale Of Available For Sale Securities Debt ProceedsFromSaleOfAvailableForSaleSecuritiesDebt	16972000	USD
CY2020	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	916000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	214000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Gain DebtSecuritiesAvailableForSaleRealizedGain	27000	USD
CY2020	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	1000	USD
CY2019	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	159000	USD
CY2018	us-gaap	Debt Securities Available For Sale Realized Loss DebtSecuritiesAvailableForSaleRealizedLoss	106000	USD
CY2019Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Securities Pledged PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged	127962000	USD
CY2020Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Securities Pledged PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged	132431000	USD
CY2020Q4	bmrc	Marketable Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions MarketableSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions	10	security
CY2019Q4	bmrc	Availableforsale Securitiesand Heldtomaturity Securities Continuous Unrealized Loss Position12 Monthsor Longer Accumulated Loss AvailableforsaleSecuritiesandHeldtomaturitySecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAccumulatedLoss	172000	USD
CY2019Q4	bmrc	Marketable Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions MarketableSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions	40	security
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	9918000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	25000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	1790000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	55000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	11708000	USD
CY2020Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	80000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	14203000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	60000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	7798000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	89000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Continuous Unrealized Loss Position Fair Value HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue	22001000	USD
CY2019Q4	us-gaap	Held To Maturity Securities Accumulated Unrecognized Holding Loss HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss	149000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months	81958000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss	328000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger	10552000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss	83000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position DebtSecuritiesAvailableForSaleUnrealizedLossPosition	92510000	USD
CY2019Q4	us-gaap	Debt Securities Available For Sale Unrealized Loss Position Accumulated Loss DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss	411000	USD
CY2019Q4	bmrc	Available For Sale Securities And Held To Maturity Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue	96161000	USD
CY2019Q4	bmrc	Availableforsale Securitiesand Heldtomaturity Securities Continuous Unrealized Loss Position Lessthan12 Months Accumulated Loss AvailableforsaleSecuritiesandHeldtomaturitySecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAccumulatedLoss	388000	USD
CY2019Q4	bmrc	Available For Sale Securities And Held To Maturity Securities Continuous Unrealized Loss Position Fair Value Total AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValueTotal	114511000	USD
CY2019Q4	bmrc	Available For Sale Securities And Held To Maturity Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue	18350000	USD
CY2019Q4	bmrc	Availableforsale Securitiesand Heldtomaturity Securities Continuous Unrealized Loss Position Accumulated Loss AvailableforsaleSecuritiesandHeldtomaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLoss	560000	USD
CY2020Q4	bmrc	Marketable Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Longer Than12 Months MarketableSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLongerThan12Months	5	security
CY2020Q4	bmrc	Marketable Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions Less Than12 Months MarketableSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThan12Months	5	security
CY2020Q4	bmrc	Federal Home Loan Bank Stock Par Value FederalHomeLoanBankStockParValue	100
CY2018	bmrc	Equity Securities Fvni Number Of Shares Sold EquitySecuritiesFVNINumberOfSharesSold	6500	shares
CY2018	us-gaap	Equity Securities Fv Ni Realized Gain EquitySecuritiesFvNiRealizedGain	956000	USD
CY2020Q4	us-gaap	Amortization Method Qualified Affordable Housing Project Investments AmortizationMethodQualifiedAffordableHousingProjectInvestments	3500000	USD
CY2019Q4	us-gaap	Amortization Method Qualified Affordable Housing Project Investments AmortizationMethodQualifiedAffordableHousingProjectInvestments	4100000	USD
CY2020	bmrc	Amortization Method Qualified Affordable Housing Project Investments Tax Credits AmortizationMethodQualifiedAffordableHousingProjectInvestmentsTaxCredits	654000	USD
CY2020	us-gaap	Amortization Method Qualified Affordable Housing Project Investments Amortization AmortizationMethodQualifiedAffordableHousingProjectInvestmentsAmortization	550000	USD
CY2020Q4	bmrc	Affordable Housing Program Unfunded Commitments AffordableHousingProgramUnfundedCommitments	821000	USD
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	2088556000	USD
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	1843286000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	22874000	USD
CY2019Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	16677000	USD
CY2020Q4	us-gaap	Notes Receivable Net NotesReceivableNet	2065682000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	2705000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	2085851000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	2088556000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	9233000	USD
CY2020Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	9233000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Past Due FinancingReceivableRecordedInvestmentPastDue	1648000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Current FinancingReceivableRecordedInvestmentCurrent	1841638000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Net Of Deferred Income LoansAndLeasesReceivableNetOfDeferredIncome	1843286000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	226000	USD
CY2019Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	226000	USD
CY2019Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	0	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment90 Days Past Due And Still Accruing FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing	0	USD
CY2019Q4	bmrc	Financing Receivable Nonaccrual Earning Interest On Cash Basis FinancingReceivableNonaccrualEarningInterestOnCashBasis	0	USD
CY2020Q4	bmrc	Financing Receivable Nonaccrual Earning Interest On Cash Basis FinancingReceivableNonaccrualEarningInterestOnCashBasis	0	USD
CY2018	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0	USD
CY2020	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0	USD
CY2019	us-gaap	Financing Receivable Nonaccrual Interest Income FinancingReceivableNonaccrualInterestIncome	0	USD
CY2020	us-gaap	Financing Receivable Accrued Interest Writeoff FinancingReceivableAccruedInterestWriteoff	36000	USD
CY2019Q4	us-gaap	Notes Receivable Net NotesReceivableNet	1826609000	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	-4900000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Deferred Income LoansAndLeasesReceivableDeferredIncome	983000	USD
CY2020Q4	bmrc	Certain Loans Acquired In Transfer Without Evidence Of Deteriorated Credit Unrecognized Purchase Discounts CertainLoansAcquiredInTransferWithoutEvidenceOfDeterioratedCreditUnrecognizedPurchaseDiscounts	815000	USD
CY2019Q4	bmrc	Certain Loans Acquired In Transfer Without Evidence Of Deteriorated Credit Unrecognized Purchase Discounts CertainLoansAcquiredInTransferWithoutEvidenceOfDeterioratedCreditUnrecognizedPurchaseDiscounts	958000	USD
CY2020Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss FinancingReceivableAccruedInterestAfterAllowanceForCreditLoss	8800000	USD
CY2019Q4	us-gaap	Financing Receivable Accrued Interest After Allowance For Credit Loss FinancingReceivableAccruedInterestAfterAllowanceForCreditLoss	7700000	USD
CY2020Q4	us-gaap	Financing Receivable Originated In Current Fiscal Year FinancingReceivableOriginatedInCurrentFiscalYear	578922000	USD
CY2020Q4	us-gaap	Financing Receivable Originated In Fiscal Year Before Latest Fiscal Year FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear	275977000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Two Years Before Latest Fiscal Year FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear	275069000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear	180349000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Four Years Before Latest Fiscal Year FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear	138246000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Five Or More Years Before Latest Fiscal Year FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear	428702000	USD
CY2020Q4	us-gaap	Financing Receivable Revolving FinancingReceivableRevolving	211291000	USD
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	2088556000	USD
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	1843286000	USD
CY2020Q4	bmrc	Weighted Average Ratio Of Loans Value To Collateral Dependent Loans Value WeightedAverageRatioOfLoansValueToCollateralDependentLoansValue	0.56
CY2020Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	12506000	USD
CY2019Q4	us-gaap	Financing Receivable Modifications Recorded Investment FinancingReceivableModificationsRecordedInvestment	11333000	USD
CY2020Q4	bmrc	Financing Receivable Modifications Recorded Investment Nonaccrual Status FinancingReceivableModificationsRecordedInvestmentNonaccrualStatus	7400000	USD
CY2019Q4	bmrc	Financing Receivable Modifications Recorded Investment Nonaccrual Status FinancingReceivableModificationsRecordedInvestmentNonaccrualStatus	58000	USD
CY2020	bmrc	Financing Receivable Modifications Removal From Troubled Debt Restructuring Number Of Contracts FinancingReceivableModificationsRemovalFromTroubledDebtRestructuringNumberOfContracts	0	loan
	bmrc	Loan Modifications Under Cares Act During Period LoanModificationsUnderCARESActDuringPeriod	269	loan
	bmrc	Loans And Leases Receivable Net Of Deferred Income Modified Under Cares Act During Period LoansAndLeasesReceivableNetOfDeferredIncomeModifiedUnderCARESActDuringPeriod	402900000	USD
	bmrc	Loan Modifications Under Cares Act During Period Subsequently Resumed Payments LoanModificationsUnderCARESActDuringPeriodSubsequentlyResumedPayments	222	loanProductionOffice
	bmrc	Loans And Leases Receivable Net Of Deferred Income Modified Under Cares Act During Period Subsequently Resumed Payments LoansAndLeasesReceivableNetOfDeferredIncomeModifiedUnderCARESActDuringPeriodSubsequentlyResumedPayments	324200000	USD
	bmrc	Loan Modifications Under Cares Act During Period Subsequently Fully Paid LoanModificationsUnderCARESActDuringPeriodSubsequentlyFullyPaid	18	loanProductionOffice
	bmrc	Loans And Leases Receivable Net Of Deferred Income Modified Under Cares Act During Period Subsequently Fully Paid LoansAndLeasesReceivableNetOfDeferredIncomeModifiedUnderCARESActDuringPeriodSubsequentlyFullyPaid	7700000	USD
CY2020Q4	bmrc	Loan Modifications Under Cares Act Additional Relief Number Of Borrowing Relationships LoanModificationsUnderCARESActAdditionalReliefNumberOfBorrowingRelationships	21	borrowingRelationship
CY2020Q4	bmrc	Loan Modifications Under Cares Act Additional Relief LoanModificationsUnderCARESActAdditionalRelief	29	loan
CY2020Q4	bmrc	Loans And Leases Receivable Net Of Deferred Income Modified Under Cares Act Additional Relief LoansAndLeasesReceivableNetOfDeferredIncomeModifiedUnderCARESActAdditionalRelief	71000000.0	USD
CY2020	us-gaap	Financing Receivable Modifications Number Of Contracts2 FinancingReceivableModificationsNumberOfContracts2	5	contract
CY2020	us-gaap	Financing Receivable Modifications Pre Modification Recorded Investment2 FinancingReceivableModificationsPreModificationRecordedInvestment2	2203000	USD
CY2020	us-gaap	Financing Receivable Modifications Post Modification Recorded Investment2 FinancingReceivableModificationsPostModificationRecordedInvestment2	2195000	USD
CY2020	bmrc	Financing Receivable Modifications Contracts Modified During Period Recorded Investment FinancingReceivableModificationsContractsModifiedDuringPeriodRecordedInvestment	2121000	USD
CY2018	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	0	USD
CY2020	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	0	USD
CY2019	us-gaap	Financing Receivable Modifications Subsequent Default Recorded Investment1 FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1	0	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	16677000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5450000	USD
	us-gaap	Allowance For Loan And Lease Losses Write Offs AllowanceForLoanAndLeaseLossesWriteOffs	30000	USD
	us-gaap	Allowance For Loan And Lease Loss Recovery Of Bad Debts AllowanceForLoanAndLeaseLossRecoveryOfBadDebts	16000	USD
CY2020Q3	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	22113000	USD
CY2020Q4	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	-856000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	1000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses Recovery FinancingReceivableAllowanceForCreditLossesRecovery	14000	USD
CY2020Q4	us-gaap	Financing Receivable Allowance For Credit Losses FinancingReceivableAllowanceForCreditLosses	22874000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	15821000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	900000	USD
CY2019	us-gaap	Allowance For Loan And Lease Losses Write Offs AllowanceForLoanAndLeaseLossesWriteOffs	78000	USD
CY2019	us-gaap	Allowance For Loan And Lease Loss Recovery Of Bad Debts AllowanceForLoanAndLeaseLossRecoveryOfBadDebts	34000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	16677000	USD
CY2017Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	15767000	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	0	USD
CY2018	us-gaap	Allowance For Loan And Lease Losses Write Offs AllowanceForLoanAndLeaseLossesWriteOffs	5000	USD
CY2018	us-gaap	Allowance For Loan And Lease Loss Recovery Of Bad Debts AllowanceForLoanAndLeaseLossRecoveryOfBadDebts	59000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Allowance LoansAndLeasesReceivableAllowance	15821000	USD
	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	5500000	USD
CY2020Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Loans Receivable Pledged For Federal Home Loan Bank Debt PledgedFinancialInstrumentsNotSeparatelyReportedLoansReceivablePledgedForFederalHomeLoanBankDebt	1165000000	USD
CY2019Q4	us-gaap	Pledged Financial Instruments Not Separately Reported Loans Receivable Pledged For Federal Home Loan Bank Debt PledgedFinancialInstrumentsNotSeparatelyReportedLoansReceivablePledgedForFederalHomeLoanBankDebt	1133000000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	8333000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	10635000	USD
CY2017Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	11852000	USD
CY2020	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	0	USD
CY2019	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	0	USD
CY2018	us-gaap	Loans And Leases Receivable Related Parties Additions LoansAndLeasesReceivableRelatedPartiesAdditions	863000	USD
CY2020	us-gaap	Loans And Leases Receivable Related Parties Proceeds LoansAndLeasesReceivableRelatedPartiesProceeds	1910000	USD
CY2019	us-gaap	Loans And Leases Receivable Related Parties Proceeds LoansAndLeasesReceivableRelatedPartiesProceeds	2320000	USD
CY2018	us-gaap	Loans And Leases Receivable Related Parties Proceeds LoansAndLeasesReceivableRelatedPartiesProceeds	2080000	USD
CY2020	bmrc	Loans And Leases Receivable Reclassified As Unrelated Party Loan LoansAndLeasesReceivableReclassifiedAsUnrelatedPartyLoan	0	USD
CY2019	bmrc	Loans And Leases Receivable Reclassified As Unrelated Party Loan LoansAndLeasesReceivableReclassifiedAsUnrelatedPartyLoan	18000	USD
CY2018	bmrc	Loans And Leases Receivable Reclassified As Unrelated Party Loan LoansAndLeasesReceivableReclassifiedAsUnrelatedPartyLoan	0	USD
CY2020Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	6423000	USD
CY2019Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	8333000	USD
CY2018Q4	us-gaap	Loans And Leases Receivable Related Parties LoansAndLeasesReceivableRelatedParties	10635000	USD
CY2020Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset Before Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization	25750000	USD
CY2019Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset Before Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization	26443000	USD
CY2020Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization	20831000	USD
CY2019Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization	20373000	USD
CY2020Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset After Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization	4919000	USD
CY2019Q4	us-gaap	Property Plant And Equipment And Finance Lease Right Of Use Asset After Accumulated Depreciation And Amortization PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization	6070000	USD
CY2020	us-gaap	Depreciation Depreciation	2100000	USD
CY2019	us-gaap	Depreciation Depreciation	2200000	USD
CY2018	us-gaap	Depreciation Depreciation	2100000	USD
CY2020Q4	bmrc	Life Insurance Corporate Or Bank Owned Death Benefits LifeInsuranceCorporateOrBankOwnedDeathBenefits	91300000	USD
CY2020Q4	us-gaap	Life Insurance Corporate Or Bank Owned Amount LifeInsuranceCorporateOrBankOwnedAmount	43600000	USD
CY2019Q4	us-gaap	Life Insurance Corporate Or Bank Owned Amount LifeInsuranceCorporateOrBankOwnedAmount	41600000	USD
CY2020	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	973000	USD
CY2019	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	1200000	USD
CY2018	us-gaap	Bank Owned Life Insurance Income BankOwnedLifeInsuranceIncome	913000	USD
CY2020Q4	us-gaap	Time Deposits Less Than100000 TimeDepositsLessThan100000	28016000	USD
CY2019Q4	us-gaap	Time Deposits Less Than100000 TimeDepositsLessThan100000	29931000	USD
CY2020Q4	bmrc	Time Deposits100000 To250000 TimeDeposits100000To250000	38773000	USD
CY2019Q4	bmrc	Time Deposits100000 To250000 TimeDeposits100000To250000	39377000	USD
CY2020Q4	bmrc	Time Deposits250000 Or More TimeDeposits250000OrMore	30644000	USD
CY2019Q4	bmrc	Time Deposits250000 Or More TimeDeposits250000OrMore	28502000	USD
CY2020Q4	us-gaap	Time Deposits TimeDeposits	97433000	USD
CY2019Q4	us-gaap	Time Deposits TimeDeposits	97810000	USD
CY2020	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	554000	USD
CY2019	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	595000	USD
CY2018	us-gaap	Interest Expense Time Deposits InterestExpenseTimeDeposits	542000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year One TimeDepositMaturitiesYearOne	71852000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Two TimeDepositMaturitiesYearTwo	9552000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Three TimeDepositMaturitiesYearThree	6382000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Four TimeDepositMaturitiesYearFour	4045000	USD
CY2020Q4	us-gaap	Time Deposit Maturities Year Five TimeDepositMaturitiesYearFive	5602000	USD
CY2020Q4	us-gaap	Time Deposit Maturities After Year Five TimeDepositMaturitiesAfterYearFive	0	USD
CY2020Q4	us-gaap	Time Deposits TimeDeposits	97433000	USD
CY2020Q4	us-gaap	Held To Maturity Securities Restricted HeldToMaturitySecuritiesRestricted	131100000	USD
CY2020Q4	bmrc	Time Deposits Certificate Of Deposit Account Registry Service Cdars TimeDepositsCertificateOfDepositAccountRegistryServiceCDARS	7622000	USD
CY2020Q4	bmrc	Time Deposits Certificate Of Deposit Account Registry Service Cdars One Way TimeDepositsCertificateOfDepositAccountRegistryServiceCDARSOneWay	2434000	USD
CY2019Q4	bmrc	Time Deposits Certificate Of Deposit Account Registry Service Cdars TimeDepositsCertificateOfDepositAccountRegistryServiceCDARS	5011000	USD
CY2019Q4	bmrc	Time Deposits Certificate Of Deposit Account Registry Service Cdars One Way TimeDepositsCertificateOfDepositAccountRegistryServiceCDARSOneWay	7453000	USD
CY2020Q4	bmrc	Deposits Money Market Deposits Insured Cash Sweep Ics DepositsMoneyMarketDepositsInsuredCashSweepICS	0	USD
CY2020Q4	bmrc	Deposits Money Market Deposits Insured Cash Sweep Ics One Way DepositsMoneyMarketDepositsInsuredCashSweepICSOneWay	110929000	USD
CY2020Q4	bmrc	Deposits Money Market Deposits Demand Deposit Marketplace DepositsMoneyMarketDepositsDemandDepositMarketplace	30544000	USD
CY2020Q4	bmrc	Deposits Money Market Deposits Demand Deposit Marketplace One Way DepositsMoneyMarketDepositsDemandDepositMarketplaceOneWay	60000000	USD
CY2019Q4	bmrc	Deposits Money Market Deposits Demand Deposit Marketplace DepositsMoneyMarketDepositsDemandDepositMarketplace	41636000	USD
CY2019Q4	bmrc	Deposits Money Market Deposits Insured Cash Sweep Ics DepositsMoneyMarketDepositsInsuredCashSweepICS	56681000	USD
CY2019Q4	bmrc	Deposits Money Market Deposits Insured Cash Sweep Ics One Way DepositsMoneyMarketDepositsInsuredCashSweepICSOneWay	27220000	USD
CY2019Q4	bmrc	Deposits Money Market Deposits Demand Deposit Marketplace One Way DepositsMoneyMarketDepositsDemandDepositMarketplaceOneWay	0	USD
CY2020Q4	bmrc	Total Networkdeposits Reciprocal TotalNetworkdepositsReciprocal	38166000	USD
CY2020Q4	bmrc	Total Networkdeposits One Way TotalNetworkdepositsOneWay	173363000	USD
CY2019Q4	bmrc	Total Networkdeposits Reciprocal TotalNetworkdepositsReciprocal	103328000	USD
CY2019Q4	bmrc	Total Networkdeposits One Way TotalNetworkdepositsOneWay	34673000	USD
CY2020Q4	us-gaap	Deposit Liabilities Reclassified As Loans Receivable1 DepositLiabilitiesReclassifiedAsLoansReceivable1	219000	USD
CY2019Q4	us-gaap	Deposit Liabilities Reclassified As Loans Receivable1 DepositLiabilitiesReclassifiedAsLoansReceivable1	155000	USD
CY2020Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	28100000	USD
CY2019Q4	us-gaap	Related Party Deposit Liabilities RelatedPartyDepositLiabilities	39600000	USD
CY2013Q4	bmrc	Business Combinations Numberof Debt Instruments Acquired BusinessCombinationsNumberofDebtInstrumentsAcquired	2	debenture
CY2020Q4	us-gaap	Junior Subordinated Debenture Owed To Unconsolidated Subsidiary Trust JuniorSubordinatedDebentureOwedToUnconsolidatedSubsidiaryTrust	4000000.0	USD
CY2018Q4	us-gaap	Stockholders Equity Note Stock Split Conversion Ratio1 StockholdersEquityNoteStockSplitConversionRatio1	2
CY2020	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	10001	shares
CY2019	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	7795	shares
CY2018	us-gaap	Shares Paid For Tax Withholding For Share Based Compensation SharesPaidForTaxWithholdingForShareBasedCompensation	46794	shares
CY2020	bmrc	Adjustments Related To Tax Withholding And Exercise Of Options For Share Based Compensation AdjustmentsRelatedToTaxWithholdingAndExerciseOfOptionsForShareBasedCompensation	398000	USD
CY2019	bmrc	Adjustments Related To Tax Withholding And Exercise Of Options For Share Based Compensation AdjustmentsRelatedToTaxWithholdingAndExerciseOfOptionsForShareBasedCompensation	326000	USD
CY2018	bmrc	Adjustments Related To Tax Withholding And Exercise Of Options For Share Based Compensation AdjustmentsRelatedToTaxWithholdingAndExerciseOfOptionsForShareBasedCompensation	1698000	USD
CY2020	bmrc	Sharebased Compensation Arrangementsby Sharebased Payment Award Options Tax Withholding And Exercisesin Period Weighted Average Exercise Price SharebasedCompensationArrangementsbySharebasedPaymentAwardOptionsTaxWithholdingAndExercisesinPeriodWeightedAverageExercisePrice	39.83
CY2019	bmrc	Sharebased Compensation Arrangementsby Sharebased Payment Award Options Tax Withholding And Exercisesin Period Weighted Average Exercise Price SharebasedCompensationArrangementsbySharebasedPaymentAwardOptionsTaxWithholdingAndExercisesinPeriodWeightedAverageExercisePrice	41.84
CY2018	bmrc	Sharebased Compensation Arrangementsby Sharebased Payment Award Options Tax Withholding And Exercisesin Period Weighted Average Exercise Price SharebasedCompensationArrangementsbySharebasedPaymentAwardOptionsTaxWithholdingAndExercisesinPeriodWeightedAverageExercisePrice	36.28
CY2017Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	517936	shares
CY2017Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	20.42
CY2017Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	7075000	USD
CY2017	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y4M2D
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	74096	shares
CY2018	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	33.97
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	7.17
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod	9140	shares
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice	28.25
CY2018	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	157192	shares
CY2018	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	13.93
CY2018	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	3462000	USD
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	425700	shares
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	25.01
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	6910000	USD
CY2018	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y10M6D
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber	311050	shares
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice	22.57
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue	5809000	USD
CY2018	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1	P4Y11M8D
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	425700	shares
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	25.01
CY2018Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	6910000	USD
CY2018	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y10M6D
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	53370	shares
CY2019	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	44.01
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	9.37
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod	13580	shares
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice	38.88
CY2019	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	48108	shares
CY2019	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	16.11
CY2019	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	1247000	USD
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	417382	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	28.01
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	7112000	USD
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y6M
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber	333870	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice	25.34
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue	6581000	USD
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1	P4Y9M3D
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber	417382	shares
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice	28.01
CY2019Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue	7112000	USD
CY2019	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2	P5Y6M
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross	44632	shares
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice	39.18
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue	6.84
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod	17222	shares
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures And Expirations In Period Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice	40.31
CY2020	us-gaap	Stock Issued During Period Shares Stock Options Exercised StockIssuedDuringPeriodSharesStockOptionsExercised	73208	shares
CY2020	us-gaap	Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice	22.26
CY2020	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Exercises In Period Total Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue	1370000	USD
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
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Number ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber	315377	shares
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Exercise Price ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice	28.05
CY2020Q4	us-gaap	Share Based Compensation Arrangement By Share Based Payment Award Options Vested And Expected To Vest Exercisable Aggregate Intrinsic Value ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableAggregateIntrinsicValue	2254000	USD
CY2020	us-gaap	Sharebased Compensation Arrangement By Sharebased Payment Award Options Vested And Expected To Vest Exercisable Weighted Average Remaining Contractual Term1 SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageRemainingContractualTerm1	P4Y6M10D
CY2020	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	1200000	USD
CY2019	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	1500000	USD
CY2018	us-gaap	Allocated Share Based Compensation Expense AllocatedShareBasedCompensationExpense	1700000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	341000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	389000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Tax Benefit From Compensation Expense EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense	404000	USD
CY2020Q4	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized	652000	USD
CY2020	us-gaap	Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1	P1Y8M12D
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	120000	USD
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	145000	USD
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Share Based Compensation Excess Tax Benefit Amount EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount	484000	USD
CY2020	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	12506000	USD
CY2019	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	10958000	USD
CY2018	us-gaap	Dividends Common Stock Cash DividendsCommonStockCash	8860000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.92
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.80
CY2018	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	0.64
CY2020Q4	us-gaap	Retained Earnings Accumulated Deficit RetainedEarningsAccumulatedDeficit	219700000	USD
CY2020Q4	us-gaap	Stockholders Equity StockholdersEquity	358300000	USD
CY2020Q4	bmrc	Dividends Cash Dividend Amount Retained Earnings Available For Dividend Payments Under Restriction DividendsCashDividendAmountRetainedEarningsAvailableForDividendPaymentsUnderRestriction	30600000	USD
CY2020Q4	us-gaap	Cash Cash	5300000	USD
CY2020Q4	bmrc	Dividends Cash Dividend Amount Retained Earnings Available For Dividend Payments Under Restriction DividendsCashDividendAmountRetainedEarningsAvailableForDividendPaymentsUnderRestriction	30600000	USD
CY2017Q3	bmrc	Shareholder Rights Plan Percentage Of Share Ownership Defining Acquiring Person ShareholderRightsPlanPercentageOfShareOwnershipDefiningAcquiringPerson	0.10
CY2020Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	5000000	shares
CY2020Q4	us-gaap	Preferred Stock No Par Value PreferredStockNoParValue	0
CY2018Q2	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	25000000.0	USD
CY2020Q1	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	25000000.0	USD
CY2020	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	203709	shares
CY2019	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	356000	shares
CY2018	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	171217	shares
	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	730926	shares
CY2020	bmrc	Stock Repurchased During Period Share Price StockRepurchasedDuringPeriodSharePrice	7.2
CY2019	bmrc	Stock Repurchased During Period Share Price StockRepurchasedDuringPeriodSharePrice	15.0
CY2018	bmrc	Stock Repurchased During Period Share Price StockRepurchasedDuringPeriodSharePrice	7.0
	bmrc	Stock Repurchased During Period Share Price StockRepurchasedDuringPeriodSharePrice	29.2
CY2020Q1	us-gaap	Stock Repurchase Program Remaining Authorized Repurchase Amount1 StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1	1500000	USD
CY2018Q2	us-gaap	Stock Repurchase Program Authorized Amount1 StockRepurchaseProgramAuthorizedAmount1	25000000.0	USD
CY2020Q1	bmrc	Deferred Compensation Arrangementwith Individual Deferred Interest Earned Percent DeferredCompensationArrangementwithIndividualDeferredInterestEarnedPercent	0.0475
CY2019Q1	bmrc	Deferred Compensation Arrangementwith Individual Deferred Interest Earned Percent DeferredCompensationArrangementwithIndividualDeferredInterestEarnedPercent	0.0550
CY2020Q4	us-gaap	Deferred Compensation Arrangement With Individual Recorded Liability DeferredCompensationArrangementWithIndividualRecordedLiability	4700000	USD
CY2019Q4	us-gaap	Deferred Compensation Arrangement With Individual Recorded Liability DeferredCompensationArrangementWithIndividualRecordedLiability	4400000	USD
CY2020	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent Of Match DefinedContributionPlanEmployerMatchingContributionPercentOfMatch	0.70
CY2020	bmrc	Defined Contribution Plan Employer Matching Contribution Maximum Amount DefinedContributionPlanEmployerMatchingContributionMaximumAmount	5000	USD
CY2020	bmrc	Defined Benefit Plan Percentage Of Salary Paid Upon Retirement DefinedBenefitPlanPercentageOfSalaryPaidUponRetirement	0.25
CY2020	bmrc	Defined Benefits Plan Period Before Ratable Vesting Begins DefinedBenefitsPlanPeriodBeforeRatableVestingBegins	P5Y
CY2020	bmrc	Defined Benefits Plan Period Before Ratable Vesting Begins DefinedBenefitsPlanPeriodBeforeRatableVestingBegins	P5Y
CY2020	bmrc	Defined Benefits Plan Age Ratable Vesting Ends DefinedBenefitsPlanAgeRatableVestingEnds	P65Y
CY2020Q4	us-gaap	Defined Benefit Plan Amounts Recognized In Balance Sheet DefinedBenefitPlanAmountsRecognizedInBalanceSheet	-3200000	USD
CY2019Q4	us-gaap	Defined Benefit Plan Amounts Recognized In Balance Sheet DefinedBenefitPlanAmountsRecognizedInBalanceSheet	-3000000.0	USD
CY2020	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	7108000	USD
CY2019	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	7838000	USD
CY2018	us-gaap	Current Federal Tax Expense Benefit CurrentFederalTaxExpenseBenefit	7289000	USD
CY2020	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	4895000	USD
CY2019	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	5183000	USD
CY2018	us-gaap	Current State And Local Tax Expense Benefit CurrentStateAndLocalTaxExpenseBenefit	4722000	USD
CY2020	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	12003000	USD
CY2019	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	13021000	USD
CY2018	us-gaap	Current Income Tax Expense Benefit CurrentIncomeTaxExpenseBenefit	12011000	USD
CY2020	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-964000	USD
CY2019	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-907000	USD
CY2018	us-gaap	Deferred Federal Income Tax Expense Benefit DeferredFederalIncomeTaxExpenseBenefit	-898000	USD
CY2020	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-694000	USD
CY2019	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-461000	USD
CY2018	us-gaap	Deferred State And Local Income Tax Expense Benefit DeferredStateAndLocalIncomeTaxExpenseBenefit	-318000	USD
CY2020	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1658000	USD
CY2019	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1368000	USD
CY2018	us-gaap	Deferred Income Tax Expense Benefit DeferredIncomeTaxExpenseBenefit	-1216000	USD
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10345000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	11653000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	10795000	USD
CY2020Q4	bmrc	Operating Lease And Finance Lease Liability OperatingLeaseAndFinanceLeaseLiability	8018000	USD
CY2019Q4	bmrc	Operating Lease And Finance Lease Liability OperatingLeaseAndFinanceLeaseLiability	3792000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	7584000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Allowance For Doubtful Accounts DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts	5252000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions	2343000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Pensions DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsPensions	2188000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	1660000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	1914000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	1103000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities	1067000	USD
CY2020Q4	us-gaap	Deferred Tax Assets State Taxes DeferredTaxAssetsStateTaxes	1017000	USD
CY2019Q4	us-gaap	Deferred Tax Assets State Taxes DeferredTaxAssetsStateTaxes	1015000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	658000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Tax Deferred Expense Compensation And Benefits Share Based Compensation Cost DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost	623000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	635000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Property Plant And Equipment DeferredTaxAssetsPropertyPlantAndEquipment	562000	USD
CY2020Q4	bmrc	Deferred Tax Asset Fair Value Adjustment Loans Receivable DeferredTaxAssetFairValueAdjustmentLoansReceivable	254000	USD
CY2019Q4	bmrc	Deferred Tax Asset Fair Value Adjustment Loans Receivable DeferredTaxAssetFairValueAdjustmentLoansReceivable	299000	USD
CY2020Q4	bmrc	Deferred Tax Assets Interest Received On Nonaccrual Loans DeferredTaxAssetsInterestReceivedOnNonaccrualLoans	23000	USD
CY2019Q4	bmrc	Deferred Tax Assets Interest Received On Nonaccrual Loans DeferredTaxAssetsInterestReceivedOnNonaccrualLoans	12000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	100000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Other DeferredTaxAssetsOther	154000	USD
CY2020Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	16467000	USD
CY2019Q4	us-gaap	Deferred Income Tax Liabilities DeferredIncomeTaxLiabilities	8716000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	6928000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Liabilities Net DeferredTaxAssetsLiabilitiesNet	8162000	USD
CY2020Q4	us-gaap	Deferred Tax Assets Operating Loss Carryforwards DeferredTaxAssetsOperatingLossCarryforwards	1700000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2020Q4	us-gaap	Deferred Tax Assets Valuation Allowance DeferredTaxAssetsValuationAllowance	0	USD
CY2020Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	23395000	USD
CY2019Q4	us-gaap	Deferred Tax Assets Gross DeferredTaxAssetsGross	16878000	USD
CY2020Q4	bmrc	Operating Lease And Finance Lease Right Of Use Asset OperatingLeaseAndFinanceLeaseRightOfUseAsset	7589000	USD
CY2019Q4	bmrc	Operating Lease And Finance Lease Right Of Use Asset OperatingLeaseAndFinanceLeaseRightOfUseAsset	3314000	USD
CY2020Q4	bmrc	Net Unrealized Gains On Securities Availablefor Sale NetUnrealizedGainsOnSecuritiesAvailableforSale	5237000	USD
CY2019Q4	bmrc	Net Unrealized Gains On Securities Availablefor Sale NetUnrealizedGainsOnSecuritiesAvailableforSale	1738000	USD
CY2020Q4	bmrc	Deferred Tax Liabilities Deferred Loan Origination Costs DeferredTaxLiabilitiesDeferredLoanOriginationCosts	1945000	USD
CY2019Q4	bmrc	Deferred Tax Liabilities Deferred Loan Origination Costs DeferredTaxLiabilitiesDeferredLoanOriginationCosts	1619000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	1133000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Goodwill And Intangible Assets Intangible Assets DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsIntangibleAssets	1385000	USD
CY2020Q4	bmrc	Deferred Tax Liabilities Unaccreted Debt Discount DeferredTaxLiabilitiesUnaccretedDebtDiscount	398000	USD
CY2019Q4	bmrc	Deferred Tax Liabilities Unaccreted Debt Discount DeferredTaxLiabilitiesUnaccretedDebtDiscount	418000	USD
CY2020Q4	bmrc	Deferred Tax Liabilities Accretion Loans And Investment Securities DeferredTaxLiabilitiesAccretionLoansAndInvestmentSecurities	33000	USD
CY2019Q4	bmrc	Deferred Tax Liabilities Accretion Loans And Investment Securities DeferredTaxLiabilitiesAccretionLoansAndInvestmentSecurities	70000	USD
CY2020Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	132000	USD
CY2019Q4	us-gaap	Deferred Tax Liabilities Other DeferredTaxLiabilitiesOther	172000	USD
CY2020	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2019	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2018	us-gaap	Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate	0.210
CY2020	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.081
CY2019	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.082
CY2018	us-gaap	Effective Income Tax Rate Reconciliation State And Local Income Taxes EffectiveIncomeTaxRateReconciliationStateAndLocalIncomeTaxes	0.080
CY2020	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Interest On Municipal Securities And Loans EffectiveIncomeTaxRateReconciliationTaxExemptIncomeInterestOnMunicipalSecuritiesAndLoans	0.024
CY2019	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Interest On Municipal Securities And Loans EffectiveIncomeTaxRateReconciliationTaxExemptIncomeInterestOnMunicipalSecuritiesAndLoans	0.018
CY2018	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Interest On Municipal Securities And Loans EffectiveIncomeTaxRateReconciliationTaxExemptIncomeInterestOnMunicipalSecuritiesAndLoans	0.024
CY2020	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Earnings On Bank Owned Life Insurance EffectiveIncomeTaxRateReconciliationTaxExemptIncomeEarningsOnBankOwnedLifeInsurance	0.005
CY2019	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Earnings On Bank Owned Life Insurance EffectiveIncomeTaxRateReconciliationTaxExemptIncomeEarningsOnBankOwnedLifeInsurance	0.006
CY2018	bmrc	Effective Income Tax Rate Reconciliation Tax Exempt Income Earnings On Bank Owned Life Insurance EffectiveIncomeTaxRateReconciliationTaxExemptIncomeEarningsOnBankOwnedLifeInsurance	0.004
CY2020	bmrc	Effective Income Tax Rate Reconciliation Tax Credit Affordable Housing EffectiveIncomeTaxRateReconciliationTaxCreditAffordableHousing	0.005
CY2019	bmrc	Effective Income Tax Rate Reconciliation Tax Credit Affordable Housing EffectiveIncomeTaxRateReconciliationTaxCreditAffordableHousing	0.004
CY2018	bmrc	Effective Income Tax Rate Reconciliation Tax Credit Affordable Housing EffectiveIncomeTaxRateReconciliationTaxCreditAffordableHousing	0.005
CY2020	bmrc	Effective Income Tax Rate Reconciliation Deduction Share Based Compensation And Excess Tax Benefits EffectiveIncomeTaxRateReconciliationDeductionShareBasedCompensationAndExcessTaxBenefits	0.002
CY2019	bmrc	Effective Income Tax Rate Reconciliation Deduction Share Based Compensation And Excess Tax Benefits EffectiveIncomeTaxRateReconciliationDeductionShareBasedCompensationAndExcessTaxBenefits	0.001
CY2018	bmrc	Effective Income Tax Rate Reconciliation Deduction Share Based Compensation And Excess Tax Benefits EffectiveIncomeTaxRateReconciliationDeductionShareBasedCompensationAndExcessTaxBenefits	0.006
CY2020	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	0
CY2019	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.009
CY2018	us-gaap	Effective Income Tax Rate Reconciliation Other Adjustments EffectiveIncomeTaxRateReconciliationOtherAdjustments	-0.002
CY2020	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.255
CY2019	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.254
CY2018	us-gaap	Effective Income Tax Rate Continuing Operations EffectiveIncomeTaxRateContinuingOperations	0.249
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	25612000	USD
CY2020Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	25612000	USD
CY2019Q4	us-gaap	Operating Lease Right Of Use Asset OperatingLeaseRightOfUseAsset	11002000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	27062000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	27062000	USD
CY2019Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	12615000	USD
CY2020Q4	bmrc	Finance Lease Right Of Use Asset Gross FinanceLeaseRightOfUseAssetGross	365000	USD
CY2019Q4	bmrc	Finance Lease Right Of Use Asset Gross FinanceLeaseRightOfUseAssetGross	379000	USD
CY2020Q4	bmrc	Finance Lease Right Of Use Asset Accumulated Depreciation FinanceLeaseRightOfUseAssetAccumulatedDepreciation	307000	USD
CY2019Q4	bmrc	Finance Lease Right Of Use Asset Accumulated Depreciation FinanceLeaseRightOfUseAssetAccumulatedDepreciation	170000	USD
CY2020Q4	us-gaap	Finance Lease Right Of Use Asset FinanceLeaseRightOfUseAsset	58000	USD
CY2019Q4	us-gaap	Finance Lease Right Of Use Asset FinanceLeaseRightOfUseAsset	209000	USD
CY2020Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	58000	USD
CY2019Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	212000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	18633000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	1661000	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	18000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Finance Lease Liability RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability	31000	USD
CY2020	bmrc	Right Of Use Operating Lease Assets Reclassified From Other Liabilities RightOfUseOperatingLeaseAssetsReclassifiedFromOtherLiabilities	0	USD
CY2019	bmrc	Right Of Use Operating Lease Assets Reclassified From Other Liabilities RightOfUseOperatingLeaseAssetsReclassifiedFromOtherLiabilities	1967000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	4498000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	4144000	USD
CY2020	us-gaap	Variable Lease Cost VariableLeaseCost	5000	USD
CY2019	us-gaap	Variable Lease Cost VariableLeaseCost	0	USD
CY2020	bmrc	Operating Lease Cost Net OperatingLeaseCostNet	4503000	USD
CY2019	bmrc	Operating Lease Cost Net OperatingLeaseCostNet	4144000	USD
CY2020	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	169000	USD
CY2019	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	172000	USD
CY2020	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	3000	USD
CY2019	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	8000	USD
CY2020	bmrc	Finance Lease Cost FinanceLeaseCost	172000	USD
CY2019	bmrc	Finance Lease Cost FinanceLeaseCost	180000	USD
CY2020	us-gaap	Lease Cost LeaseCost	4675000	USD
CY2019	us-gaap	Lease Cost LeaseCost	4324000	USD
CY2018	us-gaap	Lease And Rental Expense LeaseAndRentalExpense	4600000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	4612000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Next Twelve Months FinanceLeaseLiabilityPaymentsDueNextTwelveMonths	42000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	4424000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Two FinanceLeaseLiabilityPaymentsDueYearTwo	13000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	4004000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Three FinanceLeaseLiabilityPaymentsDueYearThree	4000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	3302000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Four FinanceLeaseLiabilityPaymentsDueYearFour	0	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	2877000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Five FinanceLeaseLiabilityPaymentsDueYearFive	0	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	9869000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due After Year Five FinanceLeaseLiabilityPaymentsDueAfterYearFive	0	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	29088000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due FinanceLeaseLiabilityPaymentsDue	59000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	2026000	USD
CY2020Q4	us-gaap	Finance Lease Liability Undiscounted Excess Amount FinanceLeaseLiabilityUndiscountedExcessAmount	1000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	27062000	USD
CY2020Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	58000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P7Y9M18D
CY2020Q4	us-gaap	Finance Lease Weighted Average Remaining Lease Term1 FinanceLeaseWeightedAverageRemainingLeaseTerm1	P1Y4M24D
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0180
CY2020Q4	us-gaap	Finance Lease Weighted Average Discount Rate Percent FinanceLeaseWeightedAverageDiscountRatePercent	0.0235
CY2020Q4	us-gaap	Hedged Asset Fair Value Hedge HedgedAssetFairValueHedge	15745000	USD
CY2019Q4	us-gaap	Hedged Asset Fair Value Hedge HedgedAssetFairValueHedge	17900000	USD
CY2020Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	1753000	USD
CY2019Q4	us-gaap	Hedged Asset Fair Value Hedge Cumulative Increase Decrease HedgedAssetFairValueHedgeCumulativeIncreaseDecrease	944000	USD
CY2020	us-gaap	Interest And Fee Income Loans And Leases InterestAndFeeIncomeLoansAndLeases	84674000	USD
CY2019	us-gaap	Interest And Fee Income Loans And Leases InterestAndFeeIncomeLoansAndLeases	84331000	USD
CY2018	us-gaap	Interest And Fee Income Loans And Leases InterestAndFeeIncomeLoansAndLeases	79527000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	1912000	USD
CY2020Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	0	USD
CY2020Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	1912000	USD
CY2020Q4	us-gaap	Derivative Collateral Right To Reclaim Securities DerivativeCollateralRightToReclaimSecurities	0	USD
CY2020Q4	us-gaap	Derivative Collateral Right To Reclaim Cash DerivativeCollateralRightToReclaimCash	1912000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral	0	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Liability DerivativeFairValueOfDerivativeLiability	1178000	USD
CY2019Q4	us-gaap	Derivative Liability Fair Value Gross Asset DerivativeLiabilityFairValueGrossAsset	0	USD
CY2019Q4	us-gaap	Derivative Liabilities DerivativeLiabilities	1178000	USD
CY2019Q4	us-gaap	Derivative Collateral Right To Reclaim Securities DerivativeCollateralRightToReclaimSecurities	0	USD
CY2019Q4	us-gaap	Derivative Collateral Right To Reclaim Cash DerivativeCollateralRightToReclaimCash	1178000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Liability Amount Offset Against Collateral DerivativeFairValueOfDerivativeLiabilityAmountOffsetAgainstCollateral	0	USD
CY2020Q4	bmrc	Increase Decrease In Unfunded Loan Commitments IncreaseDecreaseInUnfundedLoanCommitments	36900000	USD

Files In Submission

Name	View Source	Status
0001403475-21-000015-index-headers.html	Edgar Link	pending
0001403475-21-000015-index.html	Edgar Link	pending
0001403475-21-000015.txt	Edgar Link	pending
0001403475-21-000015-xbrl.zip	Edgar Link	pending
bmrc-20201231.htm	Edgar Link	pending
bmrc-20201231.xsd	Edgar Link	pending
bmrc-20201231_cal.xml	Edgar Link	unprocessable
bmrc-20201231_def.xml	Edgar Link	unprocessable
bmrc-20201231_g1.jpg	Edgar Link	pending
bmrc-20201231_htm.xml	Edgar Link	completed
bmrc-20201231_lab.xml	Edgar Link	unprocessable
bmrc-20201231_pre.xml	Edgar Link	unprocessable
bmrc-ex1007_20201231x10k.htm	Edgar Link	pending
bmrc-ex1013_20201231x10k.htm	Edgar Link	pending
bmrc-ex1402_20201231x10k.htm	Edgar Link	pending
bmrc-ex2301_20201231x10k.htm	Edgar Link	pending
bmrc-ex3101_20201231x10k.htm	Edgar Link	pending
bmrc-ex3102_20201231x10k.htm	Edgar Link	pending
bmrc-ex3201_20201231x10k.htm	Edgar Link	pending
FilingSummary.xml	Edgar Link	unprocessable
Financial_Report.xlsx	Edgar Link	pending
MetaLinks.json	Edgar Link	pending
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report.css	Edgar Link	pending
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$BMRC
Bank of Marin Bancorp Stock $bmrc

2019 Q4 Form 10-K Financial Statement

#000140347521000015 Filed on March 15, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$BMRC Bank of Marin Bancorp Stock $bmrc

2019 Q4 Form 10-K Financial Statement

#000140347521000015 Filed on March 15, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$BMRC
Bank of Marin Bancorp Stock $bmrc