Fair Value of Instruments - Estimated Fair Values and Related Carrying or Notional Amounts (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Financial Assets:
Cash and Cash Equivalents	$ 45,101	$ 24,295	$ 27,584	$ 19,263
Securities - available-for-sale	246,070	248,492
Other Securities	3,717fmao_OtherSecurities	3,717fmao_OtherSecurities
Loans, net	608,732us-gaap_LoansReceivableNet	616,021us-gaap_LoansReceivableNet
Financial Liabilities:
Non-interest bearing Deposits	156,994	164,009
Time Deposits	191,462us-gaap_TimeDeposits	195,500us-gaap_TimeDeposits
Total deposits	776,687us-gaap_Deposits	762,560us-gaap_Deposits
Federal funds purchased and securities sold under agreement to repurchase	51,741	55,962
Dividends payable	963	965
Carrying Amount [Member]
Financial Assets:
Cash and Cash Equivalents	45,101	24,295
Securities - available-for-sale	246,070	248,492
Other Securities	3,717	3,717
Loans, net	608,732	616,021
Interest receivable	3,998	3,578
Total Assets	907,618	896,103
Financial Liabilities:
Interest bearing Deposits	428,231	403,051
Non-interest bearing Deposits	156,994	164,009
Time Deposits	191,462	195,500
Total deposits	776,687	762,560
Federal funds purchased and securities sold under agreement to repurchase	51,741	55,962
Interest payable	213	207
Dividends payable	963	965
Total Liabilities	829,604	819,694
Fair Value [Member]
Financial Assets:
Cash and Cash Equivalents	45,101	24,295
Securities - available-for-sale	246,070	248,492
Other Securities	3,717	3,717
Loans, net	617,945	625,377
Interest receivable	3,998	3,578
Total Assets	916,831	905,459
Financial Liabilities:
Interest bearing Deposits	428,242	403,801
Non-interest bearing Deposits	156,994	164,009
Time Deposits	192,262	196,545
Total deposits	777,498	764,355
Federal funds purchased and securities sold under agreement to repurchase	51,741	55,962
Interest payable	213	207
Dividends payable	963	965
Total Liabilities	830,415	821,489
Level 1 [Member]
Financial Assets:
Cash and Cash Equivalents	45,101	24,295
Securities - available-for-sale	33,871	25,393
Total Assets	78,972	49,688
Level 2 [Member]
Financial Assets:
Securities - available-for-sale	204,362	215,168
Total Assets	204,362	215,168
Financial Liabilities:
Non-interest bearing Deposits	156,994	164,009
Total deposits	156,994	164,009
Dividends payable	963	965
Total Liabilities	157,957	164,974
Level 3 [Member]
Financial Assets:
Securities - available-for-sale	7,837	7,931
Other Securities	3,717	3,717
Loans, net	617,945	625,377
Interest receivable	3,998	3,578
Total Assets	633,497	640,603
Financial Liabilities:
Interest bearing Deposits	422,806	403,801
Time Deposits	197,698	196,545
Total deposits	620,504	600,346
Federal funds purchased and securities sold under agreement to repurchase	51,741	55,962
Interest payable	213	207
Total Liabilities	$ 672,458	$ 656,515

Accrued interest payable.

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Accrued interest receivable.

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Other Securities consists of Federal Home Loan Bank of Cincinnati and Indianapolis stock and Farmer Mac stock. These stocks are carried at cost and are held to enable the Bank to conduct business with the entities. The Federal Home Loan Banks sell and purchase their stock at par; therefore cost approximates market value. The Federal Home Loan Bank of Cincinnati stock is held as collateral security for all indebtedness of the Bank to the Federal Home Loan Bank.

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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-Publisher FASB

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Amount of debt securities categorized neither as held-to-maturity nor trading.

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The sum of cash and cash equivalents plus Federal Funds Sold. Cash and cash equivalents consist of short term, highly liquid investments that are readily convertible to known amounts of cash and are so near their maturity that they present negligible risk of changes in value due to changes in interest rates -- usually with an original maturity less than 90 days.

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-Glossary Cash Equivalents

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding.

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Amount after offset of short term borrowing where a bank borrows, at the federal funds rate, from another bank and securities that an entity sells and agrees to repurchase at a specified date for a specified price.

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The aggregate of all domestic and foreign interest-bearing deposit liabilities.

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Fair value of financial and nonfinancial obligations.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans held for sale. Excludes loans and leases covered under loss sharing agreements.

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The aggregate amount of all domestic and foreign noninterest-bearing deposits liabilities held by the entity.

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Amount of deposits that cannot be withdrawn before a set date without penalty or for which notice of withdrawal is required. Time deposits include, but are not limited to, certificates of deposits, individual retirement accounts and open accounts.

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