XML 96 R64.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Loans - Loans Individually Evaluated for Impairment by Portfolio Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013
Residential [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | $ 301 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember | $ 300 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember
Unpaid Principal Balance | 326 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember | 300 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember
Related Allowance | 36 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember | 78 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember
Average Recorded Investment | 170 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember | 342 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember
Interest Income Recognized | 7 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember | 15 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember
Interest Income Recognized Cash Basis | 7 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember | 13 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember
Agricultural Real Estate [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment |  | 88 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember
Unpaid Principal Balance |  | 88 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember
Related Allowance |  | 9 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember
Average Recorded Investment | 108 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember | 72 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember
Interest Income Recognized | 7 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember |
Agricultural [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 25 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgriculturalLoanMember |
Unpaid Principal Balance | 25 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgriculturalLoanMember |
Related Allowance | 25 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgriculturalLoanMember |
Average Recorded Investment | 2 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = fmb_AgriculturalLoanMember |
Commercial Real Estate [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 1,180 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember | 1,675 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember
Unpaid Principal Balance | 1,180 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember | 2,022 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember
Related Allowance | 111 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember | 295 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember
Average Recorded Investment | 823 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember | 1,148 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember
Interest Income Recognized | 28 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember | 43 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember
Interest Income Recognized Cash Basis | 26 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember | 3 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember
Commercial [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 326 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember | 377 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember
Unpaid Principal Balance | 326 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember | 377 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember
Related Allowance | 204 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember | 134 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember
Average Recorded Investment | 825 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember | 1,752 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember
Interest Income Recognized | 45 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember | 2 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember
Interest Income Recognized Cash Basis | 18 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember | 1 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember
Consumer [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 11 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ConsumerLoanMember |
Unpaid Principal Balance | 11 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ConsumerLoanMember |
Related Allowance | 11 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ConsumerLoanMember |
Average Recorded Investment | 1 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_ConsumerLoanMember |
With No Related Allowance Recorded [Member] | Residential [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 204 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 18 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
Unpaid Principal Balance | 229 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 18 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
Average Recorded Investment | 52 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 138 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
Interest Income Recognized | 1 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 10 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
Interest Income Recognized Cash Basis | 1 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 10 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
With No Related Allowance Recorded [Member] | Agricultural Real Estate [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Average Recorded Investment | 93 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember |
Interest Income Recognized | 7 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember |
With No Related Allowance Recorded [Member] | Commercial Real Estate [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 471 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 906 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
Unpaid Principal Balance | 471 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 906 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
Average Recorded Investment | 740 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 630 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
Interest Income Recognized | 7 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 21 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
Interest Income Recognized Cash Basis | 5 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 3 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
With No Related Allowance Recorded [Member] | Commercial [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Average Recorded Investment | 319 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember | 203 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember
Interest Income Recognized | 45 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember |
Interest Income Recognized Cash Basis | 18 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithNoRelatedAllowanceRecordedMember |
With a Specific Allowance Recorded [Member] | Residential [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 97 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 282 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Unpaid Principal Balance | 97 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 282 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Related Allowance | 36 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 78 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Average Recorded Investment | 118 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 204 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Interest Income Recognized | 6 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 5 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Interest Income Recognized Cash Basis | 6 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 3 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_ResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
With a Specific Allowance Recorded [Member] | Agricultural Real Estate [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment |  | 88 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Unpaid Principal Balance |  | 88 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Related Allowance |  | 9 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Average Recorded Investment | 15 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 72 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = fmb_AgricultureRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
With a Specific Allowance Recorded [Member] | Agricultural [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 25 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgriculturalLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember |
Unpaid Principal Balance | 25 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgriculturalLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember |
Related Allowance | 25 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = fmb_AgriculturalLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember |
Average Recorded Investment | 2 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = fmb_AgriculturalLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember |
With a Specific Allowance Recorded [Member] | Commercial Real Estate [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 709 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 769 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Unpaid Principal Balance | 709 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 1,116 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Related Allowance | 111 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 295 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Average Recorded Investment | 83 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 518 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Interest Income Recognized | 21 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 22 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Interest Income Recognized Cash Basis | 21 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember |
With a Specific Allowance Recorded [Member] | Commercial [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 326 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 377 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Unpaid Principal Balance | 326 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 377 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Related Allowance | 204 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 134 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Average Recorded Investment | 506 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember | 1,549 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Interest Income Recognized |  | 2 fmb_ImpairedFinancingReceivablesInterestIncomeRecognized / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
Interest Income Recognized Cash Basis |  | 1 fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis / us-gaap_FinancialInstrumentAxis = us-gaap_CommercialLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember
With a Specific Allowance Recorded [Member] | Consumer [Member] |  |
Financing Receivable, Impaired [Line Items] |  |
Recorded Investment | 11 fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember |
Unpaid Principal Balance | 11 fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember |
Related Allowance | 11 fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod / us-gaap_FinancialInstrumentAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember |
Average Recorded Investment | $ 1 fmb_FinancingReceivableAverageRecordedInvestment / us-gaap_FinancialInstrumentAxis = us-gaap_ConsumerLoanMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = fmb_WithSpecificAllowanceRecordedMember |

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- Definition Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses. + References No definition available. + Details
Name: | fmb_FinancingReceivableAverageRecordedInvestment
Namespace Prefix: | fmb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Impaired financing receivable recorded investment during period. + References No definition available. + Details
Name: | fmb_ImpairedFinancingReceivableRecordedInvestmentDuringPeriod
Namespace Prefix: | fmb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Impaired financing receivable related allowance during period. + References No definition available. + Details
Name: | fmb_ImpairedFinancingReceivableRelatedAllowanceDuringPeriod
Namespace Prefix: | fmb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Impaired financing receivables interest income recognized. + References No definition available. + Details
Name: | fmb_ImpairedFinancingReceivablesInterestIncomeRecognized
Namespace Prefix: | fmb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Impaired Financing Receivables Interest Income Recognized Cash Basis + References No definition available. + Details
Name: | fmb_ImpairedFinancingReceivablesInterestIncomeRecognizedCashBasis
Namespace Prefix: | fmb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Impaired financing receivable unpaid principal balance during period. + References No definition available. + Details
Name: | fmb_ImpairedFinancingReceivableUnpaidPrincipalBalanceDuringPeriod
Namespace Prefix: | fmb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | us-gaap_FinancingReceivableImpairedLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_FinancialInstrumentAxis=fmb_AgriculturalLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FinancialInstrumentAxis=fmb_AgricultureRealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CommercialLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ConsumerLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ResidentialRealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fmb_WithNoRelatedAllowanceRecordedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=fmb_WithSpecificAllowanceRecordedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |