XML 77 R65.htm IDEA: XBRL DOCUMENT
v3.22.4

Loans and Allowance for Credit Losses - Concentrations of Credit Narrative (Details) - USD ($) $ in Thousands | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | ---
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Loans, at amortized cost | $ 2,092,546 | $ 2,255,645
Commercial real estate |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Percentage of loans by class to all loans | 74.00% | 70.00%
Loans secured by real estate |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Percentage of loans by class to all loans | 90.00% | 86.00%
Loans secured by real estate | Commercial | Small Business Administration Paycheck Protection Program |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Loans, at amortized cost | $ 107,700 |

X
- Definition Loans and Leases Receivable, Ratio of Class to All Loans + References No definition available. + Details
Name: | bmrc_LoansAndLeasesReceivableRatioOfClassToAllLoans
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_FinancingReceivableAllowanceForCreditLossesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919230-210447 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 3B -URI https://asc.fasb.org/extlink&oid=124255953&loc=SL120267963-210447 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_RealEstateLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_UnusualOrInfrequentItemAxis=bmrc_SmallBusinessAdministrationPaycheckProtectionProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |