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Securities - Additional Information (Detail) (USD $) | 12 Months Ended | 3 Months Ended
--- | --- | ---
Dec. 31, 2014 | Mar. 31, 2015
Schedule of Available-for-sale Securities [Line Items] |  |
Investments with a carrying value and fair value |  | 176,900,000 us-gaap_PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged
Increase decrease in investments with a carrying value and fair value | $ 8,000 fmao_IncreaseDecreasePledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged |
Minimum [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Underwater security |  | 10 years
Loss position existed |  | 3 years

X
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- Definition Change in Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party. + References No definition available. + Details
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- Definition Maturity period for under water securities. + References No definition available. + Details
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- Definition Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=34720971&loc=SL6224234-111729 + Details
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