XML 55 R45.htm IDEA: XBRL DOCUMENT v3.21.2

Loans and Allowance for Credit Losses on Loans - Troubled Debt Restructuring Narrative (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) loan borrowingRelationship	Sep. 30, 2020 loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans removed from TDR designation | loan		0
Unfunded commitments for TDR loans	$ 242
Financing receivable, loan modifications under CARES Act, payment relief, number of borrowing relationships | borrowingRelationship	2
Financing receivable, loan modifications under CARES Act, payment relief | loan	5
Financing receivable, modified under CARES Act, payment relief	$ 23,600
Financing receivable, weighted average loan-to-value ratio, modified under CARES Act, remaining payment relief	33.00%
Commercial loans | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of loans removed from TDR designation | loan	1
Loans removed from TDR designation, amortized cost	$ 2
Unfunded commitments for TDR loans	$ 600

X

- Definition

Financing Receivable, Loan Modifications Under CARES Act, Payment Relief

+ References

No definition available.

+ Details

Name:	bmrc_FinancingReceivableLoanModificationsUnderCARESActPaymentRelief
Namespace Prefix:	bmrc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Financing Receivable, Loan Modifications Under CARES Act, Payment Relief, Number Of Borrowing Relationships

+ References

No definition available.

+ Details

Name:	bmrc_FinancingReceivableLoanModificationsUnderCARESActPaymentReliefNumberOfBorrowingRelationships
Namespace Prefix:	bmrc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Financing Receivable, Modifications, Removal From Troubled Debt Restructuring, Amortized Cost

+ References

No definition available.

+ Details

Name:	bmrc_FinancingReceivableModificationsRemovalFromTroubledDebtRestructuringAmortizedCost
Namespace Prefix:	bmrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Financing Receivable, Modifications, Removal From Troubled Debt Restructuring, Number Of Contracts

+ References

No definition available.

+ Details

Name:	bmrc_FinancingReceivableModificationsRemovalFromTroubledDebtRestructuringNumberOfContracts
Namespace Prefix:	bmrc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Financing Receivable, Modified Under CARES Act, Payment Relief

+ References

No definition available.

+ Details

Name:	bmrc_FinancingReceivableModifiedUnderCARESActPaymentRelief
Namespace Prefix:	bmrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Financing Receivable, Weighted Average Loan-To-Value Ratio, Modified Under CARES Act, Remaining Payment Relief

+ References

No definition available.

+ Details

Name:	bmrc_FinancingReceivableWeightedAverageLoanToValueRatioModifiedUnderCARESActRemainingPaymentRelief
Namespace Prefix:	bmrc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of unfunded portion of contractual agreement to lend funds to borrower for financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18794-111554

+ Details

Name:	us-gaap_LoansAndLeasesReceivableImpairedCommitmentToLend
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=bmrc_CommercialAndIndustrialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: