XML 36 R35.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans and Allowance for Loan Losses - Credit Quality of Loans (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]    
Total loans $ 1,346,484us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome [1] $ 1,363,351us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome [1]
Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 5,072us-gaap_NotesReceivableNet
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 5,192us-gaap_NotesReceivableNet
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Pass    
Financing Receivable, Recorded Investment [Line Items]    
Total loans 1,286,367us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 1,293,968us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Pass | Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 2,202us-gaap_NotesReceivableNet
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 2,210us-gaap_NotesReceivableNet
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Total loans 25,988us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 33,146us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Special Mention | Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 1,031us-gaap_NotesReceivableNet
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 1,140us-gaap_NotesReceivableNet
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Substandard    
Financing Receivable, Recorded Investment [Line Items]    
Total loans 34,129us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 36,237us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Substandard | Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 1,839us-gaap_NotesReceivableNet
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 1,842us-gaap_NotesReceivableNet
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Commercial and industrial    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 196,240bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember		 209,899bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
Total loans 196,442us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember		 [1] 210,223us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember		 [1]
Commercial and industrial | Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 202us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 324us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Commercial and industrial | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 181,842bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 197,659bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Commercial and industrial | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 9,424bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 6,776bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Commercial and industrial | Substandard    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 4,974bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 5,464bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Commercial real estate, owner-occupied    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 232,708bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember		 227,989bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember
Total loans 235,337us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember		 [1] 230,605us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember		 [1]
Commercial real estate, owner-occupied | Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 2,629us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 2,616us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Commercial real estate, owner-occupied | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 211,551bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 205,820bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Commercial real estate, owner-occupied | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 10,281bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 10,406bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Commercial real estate, owner-occupied | Substandard    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 10,876bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 11,763bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateOwnerOccupiedFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Commercial real estate, investor    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 651,684bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember		 671,325bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember
Total loans 653,848us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember		 [1] 673,499us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember		 [1]
Commercial real estate, investor | Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 2,164us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 2,174us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Commercial real estate, investor | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 640,656bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 651,548bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Commercial real estate, investor | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 3,853bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 13,304bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Commercial real estate, investor | Substandard    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 7,175bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 6,473bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_CommercialRealEstateInvestorFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Construction    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 57,040bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember		 48,402bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember
Total loans 57,050us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember		 [1] 48,413us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember		 [1]
Construction | Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 10us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 11us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Construction | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 50,305bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 41,710bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Construction | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 1,078bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 1,008bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Construction | Substandard    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 5,657bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 5,684bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConstructionLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Home equity    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 113,210bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		 110,721bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
Total loans 113,277us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		 [1] 110,788us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember		 [1]
Home equity | Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 67us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 67us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Home equity | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 111,227bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 107,933bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Home equity | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 321bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 322bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Home equity | Substandard    
Financing Receivable, Recorded Investment [Line Items]    
Loans excluding purchased credit-impaired loans 1,662bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 2,466bmrc_LoansAndLeasesReceivableNetOfDeferredIncomeExcludingPurchasedCreditImpairedLoans
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Other residential    
Financing Receivable, Recorded Investment [Line Items]    
Total loans 73,375us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_OtherResidentialFinancingReceivableMember		 [1],[2] 73,035us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_OtherResidentialFinancingReceivableMember		 [1],[2]
Other residential | Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 0us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_OtherResidentialFinancingReceivableMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 0us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_OtherResidentialFinancingReceivableMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Other residential | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Total loans 71,768us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_OtherResidentialFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 70,987us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_OtherResidentialFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Other residential | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Total loans 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_OtherResidentialFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_OtherResidentialFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Other residential | Substandard    
Financing Receivable, Recorded Investment [Line Items]    
Total loans 1,607us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_OtherResidentialFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 2,048us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= bmrc_OtherResidentialFinancingReceivableMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Installment and other consumer    
Financing Receivable, Recorded Investment [Line Items]    
Total loans 17,155us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 [1] 16,788us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember		 [1]
Installment and other consumer | Receivables Acquired with Deteriorated Credit Quality    
Financing Receivable, Recorded Investment [Line Items]    
Purchase credit-impaired 0us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember		 0us-gaap_NotesReceivableNet
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityAxis
= us-gaap_ReceivablesAcquiredWithDeterioratedCreditQualityMember
Installment and other consumer | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Total loans 16,816us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 16,101us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Installment and other consumer | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Total loans 0us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 190us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Installment and other consumer | Substandard    
Financing Receivable, Recorded Investment [Line Items]    
Total loans $ 339us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 $ 497us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
[1] Amounts include net deferred loan costs of $651 thousand and $487 thousand at March 31, 2015 and December 31, 2014, respectively. Amounts are also net of unaccreted purchase discounts on non-PCI loans of $4.2 million and $4.4 million at March 31, 2015 and December 31, 2014, respectively.
[2] Our residential loan portfolio does not include sub-prime loans, nor is it our practice to underwrite loans commonly referred to as "Alt-A mortgages", the characteristics of which are loans lacking full documentation, borrowers having low FICO scores or higher loan-to-value ratios.