XML 79 R72.htm IDEA: XBRL DOCUMENT
v3.25.3

Federal Funds Purchased and Securities Sold Under Agreements to Repurchase - Additional Information (Detail) - USD ($) | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Fees And Commissions Income [Abstract] |  |
Federal funds purchased | $ 0 | $ 0

X
- Definition Fees And Commissions Income [Abstract] + References No definition available. + Details
Name: | fmao_FeesAndCommissionsIncomeAbstract
Namespace Prefix: | fmao_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of short term borrowing where a bank borrows, at the federal funds rate, from another bank. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(13)(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 + Details
Name: | us-gaap_FederalFundsPurchased
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant