XML 43 R33.htm IDEA: XBRL DOCUMENT v3.10.0.1

Investment Securities - Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	$ 170,652	$ 151,032
Held to maturity, Fair Value	166,127	151,032
Held-to-maturity, Gross Unrealized Gains	235	619
Held-to-maturity, Gross Unrealized Losses	(4,760)	(619)
Total	397,268	334,285
Available-for-sale, at fair value	388,137	332,467
Available-for-sale, Gross Unrealized Gains	132	574
Available-for-sale, Gross Unrealized Losses	(9,263)	(2,392)
Total investment securities, Amortized Cost	567,920	485,317
Total investment securities, Fair Value	554,264	483,499
Total investment securities, Gross Unrealized Gains	367	1,193
Total investment securities, Gross Unrealized Losses	(14,023)	(3,011)
MBS pass-through securities issued by FHLMC and FNMA
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	94,203	100,376
Held to maturity, Fair Value	90,824	100,096
Held-to-maturity, Gross Unrealized Gains	0	234
Held-to-maturity, Gross Unrealized Losses	(3,379)	(514)
Total	90,082	65,559
Available-for-sale, at fair value	87,590	65,262
Available-for-sale, Gross Unrealized Gains	17	126
Available-for-sale, Gross Unrealized Losses	(2,509)	(423)
SBA-backed securities
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	8,882	0
Held to maturity, Fair Value	8,743	0
Held-to-maturity, Gross Unrealized Gains	0	0
Held-to-maturity, Gross Unrealized Losses	(139)	0
Total	24,620	25,979
Available-for-sale, at fair value	23,954	25,982
Available-for-sale, Gross Unrealized Gains	0	58
Available-for-sale, Gross Unrealized Losses	(666)	(55)
CMOs issued by FNMA
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	11,881	0
Held to maturity, Fair Value	11,766	0
Held-to-maturity, Gross Unrealized Gains	0	0
Held-to-maturity, Gross Unrealized Losses	(115)	0
Total	21,026	35,340
Available-for-sale, at fair value	20,571	35,125
Available-for-sale, Gross Unrealized Gains	7	33
Available-for-sale, Gross Unrealized Losses	(462)	(248)
CMOs issued by FHLMC
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	34,668	31,010
Held to maturity, Fair Value	33,591	30,938
Held-to-maturity, Gross Unrealized Gains	0	2
Held-to-maturity, Gross Unrealized Losses	(1,077)	(74)
Total	123,359	70,514
Available-for-sale, at fair value	120,411	69,889
Available-for-sale, Gross Unrealized Gains	1	3
Available-for-sale, Gross Unrealized Losses	(2,949)	(628)
CMOs issued by GNMA
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	3,730	0
Held to maturity, Fair Value	3,713	0
Held-to-maturity, Gross Unrealized Gains	0	0
Held-to-maturity, Gross Unrealized Losses	(17)	0
Total	12,641	17,953
Available-for-sale, at fair value	12,222	17,785
Available-for-sale, Gross Unrealized Gains	2	26
Available-for-sale, Gross Unrealized Losses	(421)	(194)
Debentures of government- sponsored agencies
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Total	32,395	12,940
Available-for-sale, at fair value	32,139	12,938
Available-for-sale, Gross Unrealized Gains	0	3
Available-for-sale, Gross Unrealized Losses	(256)	(5)
Privately issued CMOs
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Total	431	1,432
Available-for-sale, at fair value	435	1,431
Available-for-sale, Gross Unrealized Gains	4	1
Available-for-sale, Gross Unrealized Losses	0	(2)
Obligations of state and political subdivisions
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	17,288	19,646
Held to maturity, Fair Value	17,490	19,998
Held-to-maturity, Gross Unrealized Gains	235	383
Held-to-maturity, Gross Unrealized Losses	(33)	(31)
Total	89,699	98,027
Available-for-sale, at fair value	87,788	97,491
Available-for-sale, Gross Unrealized Gains	77	298
Available-for-sale, Gross Unrealized Losses	(1,988)	(834)
Corporate bonds
Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]
Total	3,015	6,541
Available-for-sale, at fair value	3,027	6,564
Available-for-sale, Gross Unrealized Gains	24	26
Available-for-sale, Gross Unrealized Losses	$ (12)	$ (3)

X

- Definition

Available-for-sale Securities and Held-to-maturity Securities, Amortized Cost Basis

+ References

No definition available.

+ Details

Name:	bmrc_AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesAmortizedCostBasis
Namespace Prefix:	bmrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Fair Value of Available-for-sale Securities and Held-to-maturity Securities.

+ References

No definition available.

+ Details

Name:	bmrc_AvailableForSaleSecuritiesAndHeldToMaturitySecuritiesFairValue
Namespace Prefix:	bmrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Available-for-sale Securities and Held-to-maturity Securities, Accumulated Gross Unrealized Gain

+ References

No definition available.

+ Details

Name:	bmrc_AvailableforsaleSecuritiesandHeldtomaturitySecuritiesAccumulatedGrossUnrealizedGain
Namespace Prefix:	bmrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Available-for-sale Securities and Held-to-maturity Securities, Accumulated Gross Unrealized Loss

+ References

No definition available.

+ Details

Name:	bmrc_AvailableforsaleSecuritiesandHeldtomaturitySecuritiesAccumulatedGrossUnrealizedLoss
Namespace Prefix:	bmrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Schedule of Available-for-sale Securities and Held-to-maturity Securities [Line Items]

+ References

No definition available.

+ Details

Name:	bmrc_ScheduleOfAvailableForSaleSecuritiesAndHeldToMaturitySecuritiesLineItems
Namespace Prefix:	bmrc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount, before other-than-temporary impairment (OTTI) accretion, of investment in debt securities measured at amortized cost (held-to-maturity).

+ References

No definition available.

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=bmrc_SmallBusinessAdministrationSBABackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_FederalNationalMortgageAssociationCertificatesAndObligationsFNMAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_FederalHomeLoanMortgageCorporationCertificatesAndObligationsFHLMCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_GovernmentNationalMortgageAssociationCertificatesAndObligationsGNMAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByPrivateEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateBondSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: