XML 49 R39.htm IDEA: XBRL DOCUMENT
v3.25.2

Investment Securities - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) - USD ($) $ in Thousands | Jun. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Total pledged investment securities | $ 929,071 | $ 941,122
Total investment securities pledged to the State of California |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Total pledged investment securities | 329,662 | 290,564
Secure public deposits in compliance with the Local Agency Security Program |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Total pledged investment securities | 326,962 | 288,385
Collateral for trust deposits |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Total pledged investment securities | 1,200 | 1,284
Collateral for Wealth Management and Trust Services checking account |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Total pledged investment securities | 1,500 | 895
Bankruptcy trustee deposits pledged with Federal Reserve Bank |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Total pledged investment securities | 2,142 | 651
Pledged to FHLB Securities-Backed Credit Program |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Total pledged investment securities | 274,290 | 284,148
Pledged to the Federal Reserve Discount Window |  |
Financial Instruments Owned and Pledged as Collateral [Line Items] |  |
Total pledged investment securities | $ 322,977 | $ 365,759

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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.6-04(11)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479170/946-210-S99-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 860 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481444/860-30-45-1 + Details
Name: | us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of the securities pledged as collateral against securities loaned. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147483444/210-20-55-12 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (d)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483466/210-20-50-3 + Details
Name: | us-gaap_SecuritiesLoanedFairValueOfCollateral
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_InvestmentTypeAxis=bmrc_PledgedToStateOfCaliforniaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=bmrc_PublicDepositsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=bmrc_TrustDepositsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=bmrc_CheckingAccountWealthManagementAndTrustServicesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=bmrc_BankruptcyTrusteeDepositsPledgedWithFederalReserveBankMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=bmrc_FHLBSecuritiesBackedCreditProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=bmrc_FederalReserveDiscountWindowMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |