XML 137 R123.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Derivative Financial Instruments - Schedule of Effects of Interest Rate Swap Agreements on Consolidated Statements of Income (Detail) - Designated as Hedging Instrument [Member] - Interest Rate Swap [Member] - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Effects of derivatives on consolidated statement of income | $ 687 | $ 144
Loans, Including Fees [Member] |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Effects of derivatives on consolidated statement of income | 59 | 40
Other [Member] |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Effects of derivatives on consolidated statement of income | 687 | 144
Interest Income [Member] |  |
Derivative Instruments and Hedging Activities Disclosures [Line Items] |  |
Effects of derivatives on consolidated statement of income | $ 746 | $ 184

X
- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4A -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A + Details
Name: | us-gaap_DerivativeGainLossOnDerivativeNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Details
Name: | us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=fmao_InterestAndFeeIncomeLoansAndLeasesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=fmao_InterestIncomeOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=fmao_InterestAndDividendIncomeOperatingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |