XML 62 R52.htm IDEA: XBRL DOCUMENT
v3.23.2

Loans (CECL) - Additional Information (Detail) - Geneva in 2019 and Ossian State Bank in 2021 [Member] - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2022 | Jun. 30, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Accretable yield related to acquisition | $ 6,300 | $ 5,800
Reclassification from nonaccretable difference | $ 138 |

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_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The aggregate excess of a loan's cash flows expected to be collected over the investor's initial investment in the loan for loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481906/310-30-15-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481696/310-30-50-2 + Details
Name: | us-gaap_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesAccretableYield
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Change in the estimate of cash flows expected to be collected, after acquisition of a loan, which results in an increase in accretable yield (for example, if actual cash flows are significantly greater than previously expected). This relates to loans accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 15 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481906/310-30-15-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481696/310-30-50-2 + Details
Name: | us-gaap_CertainLoansAcquiredInTransferAccountedForAsDebtSecuritiesAccretableYieldReclassificationsFromNonaccretableDifference
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=fmao_BankOfGenevaAndOssianStateBankMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |