XML 65 R53.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Summary of Significant Accounting Policies - Accounting Standards Not Yet Effective (Details) $ in Millions | Jan. 31, 2021 USD ($) Contract
--- | ---
Accounting Policies [Abstract] |
Number of interest rate swap contract | Contract | 4
Derivative notional amount | $ | $ 13.0

X
- Definition Number Of Interest Rate Swap Contract + References No definition available. + Details
Name: | bmrc_NumberOfInterestRateSwapContract
Namespace Prefix: | bmrc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959 + Details
Name: | us-gaap_DerivativeNotionalAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant