XML 67 R55.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Loans and Allowance for Loan Losses - Troubled Debt Restructuring Modifications (Details) | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($) contract | Dec. 31, 2016 USD ($) contract | Dec. 31, 2015 USD ($) contract
Financing Receivable, Modifications [Line Items] |  |  |
Number of Contracts Modified | contract |  | 4 |
Pre-Modification Outstanding Recorded Investment |  | $ 1,985,000 |
Post-Modification Outstanding Recorded Investment |  | 2,115,000 |
Post-Modification Outstanding Recorded Investment at Period End |  | 2,063,000 |
Total of TDR loans charged-off within previous 12 months | $ 0 | $ 0 | $ 0
Consumer loans | Installment and other consumer |  |  |
Financing Receivable, Modifications [Line Items] |  |  |
Number of Contracts Modified | contract | 1 | 1 |
Pre-Modification Outstanding Recorded Investment | $ 50,000 | $ 68,000 |
Post-Modification Outstanding Recorded Investment | 50,000 | 67,000 |
Post-Modification Outstanding Recorded Investment at Period End | $ 47,000 | $ 66,000 |
Commercial | Commercial real estate, investor |  |  |
Financing Receivable, Modifications [Line Items] |  |  |
Number of Contracts Modified | contract |  | 2 |
Pre-Modification Outstanding Recorded Investment |  | $ 1,830,000 |
Post-Modification Outstanding Recorded Investment |  | 1,826,000 |
Post-Modification Outstanding Recorded Investment at Period End |  | $ 1,752,000 |
Commercial | Commercial and industrial |  |  |
Financing Receivable, Modifications [Line Items] |  |  |
Number of Contracts Modified | contract |  |  | 7
Pre-Modification Outstanding Recorded Investment |  |  | $ 3,271,000
Post-Modification Outstanding Recorded Investment |  |  | 3,251,000
Post-Modification Outstanding Recorded Investment at Period End |  |  | $ 2,811,000
Residential loans | Home equity |  |  |
Financing Receivable, Modifications [Line Items] |  |  |
Number of Contracts Modified | contract |  | 1 |
Pre-Modification Outstanding Recorded Investment |  | $ 87,000 |
Post-Modification Outstanding Recorded Investment |  | 222,000 |
Post-Modification Outstanding Recorded Investment at Period End |  | $ 245,000 |

X
- Definition The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings at end of period. + References No definition available. + Details
Name: | bmrc_FinancingReceivableModificationsContractsModifiedDuringPeriodRecordedInvestment
Namespace Prefix: | bmrc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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 Number of financing receivables that have been modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Post-modification amount of investment in financing receivables modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Pre-modification amount of investment in financing receivables modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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: |

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_CommercialRealEstateLoanInvestorMember
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_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: |