Name:	FMBM_AvailableForSaleSecuritiesCarryingValue
Namespace Prefix:	FMBM_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Custom Element.

No definition available.

Name:	FMBM_BankOwnedLifeInsuranceFairValue
Namespace Prefix:	FMBM_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Custom Element.

No definition available.

Name:	FMBM_DepositsCarryingAmount
Namespace Prefix:	FMBM_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Custom Element.

No definition available.

Name:	FMBM_InterestPayableFairValue
Namespace Prefix:	FMBM_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Custom Element.

No definition available.

Name:	FMBM_InterestReceivableEstimatedFairValue
Namespace Prefix:	FMBM_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Custom Element.

No definition available.

Name:	FMBM_LoansHeldForInvestmentNetCarryingAmount
Namespace Prefix:	FMBM_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Custom Element.

No definition available.

Name:	FMBM_LoansHeldForInvestmentNetFairValue
Namespace Prefix:	FMBM_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Custom Element.

No definition available.

Name:	FMBM_LongtermDebtCarryingAmount
Namespace Prefix:	FMBM_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Custom Element.

No definition available.

Name:	FMBM_ShortTermDebtCarryingValue
Namespace Prefix:	FMBM_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Custom Element.

No definition available.

Name:	FMBM_ShortTermDebtEstimatedFairValue
Namespace Prefix:	FMBM_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

Name:	us-gaap_AssetsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a nonrecurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

No definition available.

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

The carrying amount of assets an investment adviser manages on behalf of investors.

No definition available.

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

Fair value of investment in available-for-sale debt securities with a single maturity date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 3
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-Subparagraph (d)
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Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The carrying amount of a life insurance policy on an officer, executive or employee for which the reporting entity (a bank) is entitled to proceeds from the policy upon death of the insured or surrender of the insurance policy.

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

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

No definition available.

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

The recorded value, at the acquisition date, of loans for which the income recognition model was not applied. This relates to loans accounted for as available-for-sale debt securities acquired during the period, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Name:	us-gaap_CertainLoansAcquiredInTransferAccountedForAsAvailableForSaleDebtSecuritiesAcquiredDuringPeriodNotAccountedForUsingIncomeRecognitionModelAtAcquisitionAtCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

No definition available.

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

Amount of interest payable on debt, including, but not limited to, trade payables.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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

Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Name:	us-gaap_InterestReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

Name:	us-gaap_LiabilitiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Aggregation of the liabilities reported on the balance sheet measured at fair value on a nonrecurring basis by the entity.

No definition available.

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

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

No definition available.

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

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

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

Carrying amount of liabilities associated with financial assets accounted for as secured borrowings recognized in the transferor's statement of financial position at the end of each period presented.

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)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729