Name:	fmcb_FinancingReceivableModifiedWeightedAverageInterestRate
Namespace Prefix:	fmcb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Period of weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	fmcb_FinancingReceivableModifiedWeightedAverageTerm
Namespace Prefix:	fmcb_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

Name:	fmcb_NonAccrualLoansAndLeasesAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Number of financing receivables that have been modified by troubled debt restructurings.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Amortized cost of financing receivable modified during period for debtor experiencing financial difficulty.

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amortized cost of financing receivable with payment default in current period and modified within previous 12 months preceding payment default for debtor experiencing financial difficulty.

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-Topic 310
-SubTopic 10
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
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-Topic 310
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