Accrued interest payable.

No definition available.

Name:	fmao_AccruedInterestPayable
Namespace Prefix:	fmao_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Accrued interest receivable.

+ References

No definition available.

+ Details

Name:	fmao_AccruedInterestReceivable
Namespace Prefix:	fmao_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	fmao_FinancialAssetsAbstract
Namespace Prefix:	fmao_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	fmao_FinancialLiabilitiesAbstract
Namespace Prefix:	fmao_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

Name:	fmao_OtherSecurities
Namespace Prefix:	fmao_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7534914&loc=d3e22054-111558

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15E

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 14

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Chapter V

-Subsection I

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 8, 9, 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.1,2,3)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_CashCashEquivalentsAndFederalFundsSold
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.12)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-DEP

-Paragraph 37, 38, 39

-IssueDate 2006-05-01

-Chapter 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_Deposits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

+ Details

Name:	us-gaap_DividendsPayableCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value of financial assets, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

+ Details

Name:	us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The fair value of financial liabilities, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

+ Details

Name:	us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount of Federal Home Loan Bank (FHLB) loans (advances) to member financial institutions.

+ References

No definition available.

+ Details

Name:	us-gaap_FederalHomeLoanBankAdvances
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Total of loans held-for-sale and held-in-portfolio net of unearned income, allowance for loan and lease losses, if any, unamortized loan origination and other fees and costs, and purchased premiums or discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Subparagraph a

-Article 9

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(a))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LoansReceivableNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.(a),16(a)(1))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Subparagraph a(1)

-Article 7

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 13

-Subparagraph 2, 3

-Article 9

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

-Subparagraph a

-Article 5

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.13)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_ShortTermBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Fair Value of Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Jul. 09, 2010
Financial Assets:
Cash and Cash Equivalents	$ 29,629	$ 43,143	$ 38,404
Other Securities	4,365	4,365
Financial Liabilities:
Total Deposits	734,831	739,382		27,749
Dividends payable	931	890
Level 1 [Member]
Financial Assets:
Cash and Cash Equivalents	29,629
Securities - available for sale	31,511
Other Securities
Loans, net
Interest receivable
Total Assets	61,140
Financial Liabilities:
Total Deposits
Short-term debt
Federal Home Loan Bank advances
Interest payable
Dividends payable
Total Liabilities
Level 1 [Member] \| Interest bearing Deposits [Member]
Financial Liabilities:
Total Deposits
Level 1 [Member] \| Non-interest bearing Deposits [Member]
Financial Liabilities:
Total Deposits
Level 1 [Member] \| Time Deposits [Member]
Financial Liabilities:
Total Deposits
Level 2 [Member]
Financial Assets:
Cash and Cash Equivalents
Securities - available for sale	301,494
Other Securities
Loans, net
Interest receivable
Total Assets	301,494
Financial Liabilities:
Total Deposits	87,559
Short-term debt
Federal Home Loan Bank advances
Interest payable
Dividends payable	931
Total Liabilities	88,490
Level 2 [Member] \| Interest bearing Deposits [Member]
Financial Liabilities:
Total Deposits
Level 2 [Member] \| Non-interest bearing Deposits [Member]
Financial Liabilities:
Total Deposits	87,559
Level 2 [Member] \| Time Deposits [Member]
Financial Liabilities:
Total Deposits
Level 3 [Member]
Financial Assets:
Cash and Cash Equivalents
Securities - available for sale	20,450
Other Securities	4,365
Loans, net	490,764
Interest receivable	4,614
Total Assets	520,193
Financial Liabilities:
Total Deposits	651,490
Short-term debt	54,847
Federal Home Loan Bank advances	12,943
Interest payable	318
Dividends payable
Total Liabilities	719,598
Level 3 [Member] \| Interest bearing Deposits [Member]
Financial Liabilities:
Total Deposits	372,026
Level 3 [Member] \| Non-interest bearing Deposits [Member]
Financial Liabilities:
Total Deposits
Level 3 [Member] \| Time Deposits [Member]
Financial Liabilities:
Total Deposits	279,464
Carrying Amount [Member]
Financial Assets:
Cash and Cash Equivalents	29,629	43,143
Securities - available for sale	353,455	327,519
Other Securities	4,365	4,365
Loans, net	486,170	501,124
Interest receivable	4,614	3,481
Total Assets	878,233	879,632
Financial Liabilities:
Total Deposits	734,831	739,382
Short-term debt	54,847	52,440
Federal Home Loan Bank advances	11,611	16,662
Interest payable	318	342
Dividends payable	931	890
Total Liabilities	802,538	809,716
Carrying Amount [Member] \| Interest bearing Deposits [Member]
Financial Liabilities:
Total Deposits	369,588	363,189
Carrying Amount [Member] \| Non-interest bearing Deposits [Member]
Financial Liabilities:
Total Deposits	87,354	84,568
Carrying Amount [Member] \| Time Deposits [Member]
Financial Liabilities:
Total Deposits	277,889	291,625
Fair Value [Member]
Financial Assets:
Cash and Cash Equivalents	29,629	43,143
Securities - available for sale	353,455	327,519
Other Securities	4,365	4,365
Loans, net	490,764	504,629
Interest receivable	4,614	3,481
Total Assets	882,827	883,137
Financial Liabilities:
Total Deposits	739,049	741,975
Short-term debt	54,847	52,440
Federal Home Loan Bank advances	12,943	16,638
Interest payable	318	342
Dividends payable	931	890
Total Liabilities	808,088	812,285
Fair Value [Member] \| Interest bearing Deposits [Member]
Financial Liabilities:
Total Deposits	372,026	363,727
Fair Value [Member] \| Non-interest bearing Deposits [Member]
Financial Liabilities:
Total Deposits	87,559	85,517
Fair Value [Member] \| Time Deposits [Member]
Financial Liabilities:
Total Deposits	$ 279,464	$ 292,731