Name:	fbss_CommercialLoansClassifiedAsSubstandardDeemedNotToBeImpaired
Namespace Prefix:	fbss_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Amount of balance in impaired loans collateralized by commercial buildings, residential real estate or land.

No definition available.

Name:	fbss_ImpairedFinancingReceivableRecordedInvestmentCollateralized
Namespace Prefix:	fbss_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Name:	fbss_ImpairedFinancingReceivableRelatedAllowanceAbstract
Namespace Prefix:	fbss_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of allowance for credit losses related to recorded investment, with related allowances.

No definition available.

Name:	fbss_ImpairedFinancingReceivableWithNoRelatedAllowanceRelatedAllowance
Namespace Prefix:	fbss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of allowance for credit losses related to recorded investment with related allowance.

No definition available.

Name:	fbss_ImpairedFinancingReceivableWithRelatedAllowanceRelatedAllowance
Namespace Prefix:	fbss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The increase (decrease) during the reporting period of amounts due from note holders for outstanding impaired loans.

No definition available.

Name:	fbss_IncreaseDecreaseInImpairedLoansReceivable
Namespace Prefix:	fbss_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the increase (decrease) in the number of impaired loans during the reporting period.

No definition available.

Name:	fbss_IncreaseDecreaseInNumberOfImpairedLoans
Namespace Prefix:	fbss_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number of loans restructured from new loans.

No definition available.

Name:	fbss_NumberOfLoansRestructuredFromNewLoans
Namespace Prefix:	fbss_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number of performing loans from new loans added during period.

No definition available.

Name:	fbss_NumberOfPerformingLoansFromNewLoans
Namespace Prefix:	fbss_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5258-111524

Name:	us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

Name:	us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953550-111524

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

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

Amount of allowance for credit losses related to recorded investment.

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

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

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

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

Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses.

Name:	us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses.

Name:	us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

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

Amount of unpaid principal balance of impaired financing receivables for which there is no related allowance for credit losses.

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

Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses.

Name:	us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired.

Name:	us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of investment in impaired financing receivables for which there is a related allowance for credit losses.

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

Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.