XML 48 R52.htm IDEA: XBRL DOCUMENT v3.20.1

Loans and Allowance for Loan Losses - Troubled Debt Restructuring by Class (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment of loans removed from TDR resignation	$ 3,000	$ 247,000
Recorded investment in Troubled Debt Restructurings	11,333,000	14,406,000
Acquired loans included in TDR	0	0
TDR loans on non-accrual status, value	$ 58,000	65,000
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans removed from TDR resignation | loan	1
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in Troubled Debt Restructurings	$ 1,223,000	1,506,000
Commercial real estate | Commercial real estate, owner-occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in Troubled Debt Restructurings	6,998,000	6,993,000
Commercial real estate | Commercial real estate, investor
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in Troubled Debt Restructurings	1,770,000	1,821,000
Commercial real estate | Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in Troubled Debt Restructurings	0	$ 2,688,000
Residential loans | Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans removed from TDR resignation | loan		1
Recorded investment in Troubled Debt Restructurings	$ 251,000	$ 251,000
Residential loans | Other residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans removed from TDR resignation | loan	1
Recorded investment in Troubled Debt Restructurings	$ 452,000	462,000
Consumer loans | Installment and other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recorded investment in Troubled Debt Restructurings	$ 639,000	$ 685,000

X

- Definition

Financing Receivable, Modifications, Recorded Investment, Nonaccrual Status

+ References

No definition available.

+ Details

Name:	bmrc_FinancingReceivableModificationsRecordedInvestmentNonaccrualStatus
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, Modifications, Removal From Troubled Debt Restructuring, Recorded Investment

+ References

No definition available.

+ Details

Name:	bmrc_FinancingReceivableModificationsRemovalFromTroubledDebtRestructuringRecordedInvestment
Namespace Prefix:	bmrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Troubled Debt Restructuring, Loans Acquired

+ References

No definition available.

+ Details

Name:	bmrc_TroubledDebtRestructuringLoansAcquired
Namespace Prefix:	bmrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=118939409&loc=d3e18845-111554

+ Details

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
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:

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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