XML 51 R42.htm IDEA: XBRL DOCUMENT
v3.23.2

Loans and Allowance for Credit Losses on Loans - Loans Outstanding and Aging Analysis (Details) - USD ($) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | $ 2,102,796,000 |  | $ 2,102,796,000 |  | $ 2,092,546,000
Loans past due more than 90 days still accruing | 0 |  | 0 |  | 0
Financing receivable, nonaccrual, earning interest on cash basis | 0 |  | 0 |  | 0
Financing receivable, nonaccrual, interest income | 0 | $ 0 | 0 | $ 0 |
Financing receivable, accrued interest, writeoff |  |  | 14,000 | $ 8,000 |
Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 2,102,796,000 |  | 2,102,796,000 |  | 2,092,546,000
Non-accrual loans | 2,112,000 |  | 2,112,000 |  | 2,432,000
Non-accrual loans with no allowance | 2,112,000 |  | 2,112,000 |  | 2,432,000
Total past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 2,362,000 |  | 2,362,000 |  | 1,342,000
30-59 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 546,000 |  | 546,000 |  | 420,000
60-89 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 528,000 |  | 528,000 |  | 244,000
90 days or more past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 1,288,000 |  | 1,288,000 |  | 678,000
Current | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 2,100,434,000 |  | 2,100,434,000 |  | 2,091,204,000
Commercial loans | Commercial and industrial |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 183,157,000 |  | 183,157,000 |  | 173,547,000
Commercial loans | Commercial and industrial | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 183,157,000 |  | 183,157,000 |  | 173,547,000
Non-accrual loans | 0 |  | 0 |  | 0
Non-accrual loans with no allowance | 0 |  | 0 |  | 0
Commercial loans | Commercial and industrial | Total past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 436,000 |  | 436,000 |  | 267,000
Commercial loans | Commercial and industrial | 30-59 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 3,000
Commercial loans | Commercial and industrial | 60-89 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 436,000 |  | 436,000 |  | 0
Commercial loans | Commercial and industrial | 90 days or more past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 264,000
Commercial loans | Commercial and industrial | Current | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 182,721,000 |  | 182,721,000 |  | 173,280,000
Commercial real estate loans | Commercial owner-occupied |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 344,951,000 |  | 344,951,000 |  | 354,877,000
Commercial real estate loans | Commercial owner-occupied | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 344,951,000 |  | 344,951,000 |  | 354,877,000
Non-accrual loans | 457,000 |  | 457,000 |  | 1,563,000
Non-accrual loans with no allowance | 457,000 |  | 457,000 |  | 1,563,000
Commercial real estate loans | Commercial owner-occupied | Total past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 164,000 |  | 164,000 |  | 0
Commercial real estate loans | Commercial owner-occupied | 30-59 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 0
Commercial real estate loans | Commercial owner-occupied | 60-89 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 0
Commercial real estate loans | Commercial owner-occupied | 90 days or more past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 164,000 |  | 164,000 |  | 0
Commercial real estate loans | Commercial owner-occupied | Current | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 344,787,000 |  | 344,787,000 |  | 354,877,000
Commercial real estate loans | Commercial non-owner occupied |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 1,196,158,000 |  | 1,196,158,000 |  | 1,191,889,000
Commercial real estate loans | Commercial non-owner occupied | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 1,196,158,000 |  | 1,196,158,000 |  | 1,191,889,000
Non-accrual loans | 906,000 |  | 906,000 |  | 0
Non-accrual loans with no allowance | 906,000 |  | 906,000 |  | 0
Commercial real estate loans | Commercial non-owner occupied | Total past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 1,277,000 |  | 1,277,000 |  | 0
Commercial real estate loans | Commercial non-owner occupied | 30-59 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 371,000 |  | 371,000 |  | 0
Commercial real estate loans | Commercial non-owner occupied | 60-89 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 0
Commercial real estate loans | Commercial non-owner occupied | 90 days or more past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 906,000 |  | 906,000 |  | 0
Commercial real estate loans | Commercial non-owner occupied | Current | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 1,194,881,000 |  | 1,194,881,000 |  | 1,191,889,000
Commercial real estate loans | Construction |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 108,986,000 |  | 108,986,000 |  | 114,373,000
Commercial real estate loans | Construction | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 108,986,000 |  | 108,986,000 |  | 114,373,000
Non-accrual loans | 0 |  | 0 |  | 0
Non-accrual loans with no allowance | 0 |  | 0 |  | 0
Commercial real estate loans | Construction | Total past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 0
Commercial real estate loans | Construction | 30-59 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 0
Commercial real estate loans | Construction | 60-89 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 0
Commercial real estate loans | Construction | 90 days or more past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 0
Commercial real estate loans | Construction | Current | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 108,986,000 |  | 108,986,000 |  | 114,373,000
Residential loans | Home equity |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 85,587,000 |  | 85,587,000 |  | 88,748,000
Residential loans | Home equity | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 85,587,000 |  | 85,587,000 |  | 88,748,000
Non-accrual loans | 749,000 |  | 749,000 |  | 778,000
Non-accrual loans with no allowance | 749,000 |  | 749,000 |  | 778,000
Residential loans | Home equity | Total past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 433,000 |  | 433,000 |  | 977,000
Residential loans | Home equity | 30-59 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 124,000 |  | 124,000 |  | 319,000
Residential loans | Home equity | 60-89 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 91,000 |  | 91,000 |  | 244,000
Residential loans | Home equity | 90 days or more past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 218,000 |  | 218,000 |  | 414,000
Residential loans | Home equity | Current | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 85,154,000 |  | 85,154,000 |  | 87,771,000
Residential loans | Other residential |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 118,646,000 |  | 118,646,000 |  | 112,123,000
Residential loans | Other residential | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 118,646,000 |  | 118,646,000 |  | 112,123,000
Non-accrual loans | 0 |  | 0 |  | 0
Non-accrual loans with no allowance | 0 |  | 0 |  | 0
Residential loans | Other residential | Total past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 93,000
Residential loans | Other residential | 30-59 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 93,000
Residential loans | Other residential | 60-89 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 0
Residential loans | Other residential | 90 days or more past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 0
Residential loans | Other residential | Current | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 118,646,000 |  | 118,646,000 |  | 112,030,000
Consumer loans | Installment and other consumer loans |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 65,311,000 |  | 65,311,000 |  | 56,989,000
Consumer loans | Installment and other consumer loans | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 65,311,000 |  | 65,311,000 |  | 56,989,000
Non-accrual loans | 0 |  | 0 |  | 91,000
Non-accrual loans with no allowance | 0 |  | 0 |  | 91,000
Consumer loans | Installment and other consumer loans | Total past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 52,000 |  | 52,000 |  | 5,000
Consumer loans | Installment and other consumer loans | 30-59 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 51,000 |  | 51,000 |  | 5,000
Consumer loans | Installment and other consumer loans | 60-89 days past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 1,000 |  | 1,000 |  | 0
Consumer loans | Installment and other consumer loans | 90 days or more past due | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | 0 |  | 0 |  | 0
Consumer loans | Installment and other consumer loans | Current | Financial asset, other than financial asset acquired with credit deterioration |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans, at amortized cost | $ 65,259,000 |  | $ 65,259,000 |  | $ 56,984,000

X
- Definition Financing Receivable, Nonaccrual, Earning Interest On Cash Basis + References No definition available. + Details
Name: | bmrc_FinancingReceivableNonaccrualEarningInterestOnCashBasis
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 writeoff of accrued interest on financing receivable recognized by reversing interest income. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3D -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3D + Details
Name: | us-gaap_FinancingReceivableAccruedInterestWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest, of financing receivable 90 days or more past due and still accruing. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 16 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-16 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterest90DaysOrMorePastDueStillAccruing
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479344/326-20-45-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-5 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost excluding accrued interest, of financing receivable on nonaccrual status. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 16 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-16 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrual
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost excluding accrued interest, of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 16 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-16 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestNonaccrualNoAllowance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of interest income on financing receivable on nonaccrual status. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 16 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-16 + Details
Name: | us-gaap_FinancingReceivableNonaccrualInterestIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_CreditLossStatusAxis=us-gaap_FinancialAssetOtherThanFinancialAssetAcquiredWithCreditDeteriorationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables30To59DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivables60To89DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancingReceivablesEqualToGreaterThan90DaysPastDueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablesPeriodPastDueAxis=us-gaap_FinancialAssetNotPastDueMember
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_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_CommercialRealEstateLoanNonOwnerOccupiedMember
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: |