XML 29 R50.htm IDEA: XBRL DOCUMENT v2.4.1.9
Note 6 - Loans Held for Investment (Details) - Impaired Loans (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Financing Receivable, Impaired [Line Items]      
Interest income recognized on impaired loans with no related allowance recorded $ 233us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod $ 976us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod  
Interest income recognized on impaired loans with an allowance recorded 42us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod 151us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod  
Totals:      
Contractual unpaid principal balance 489,441us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance   462,986us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
Interest income recognized on impaired loans 275us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod 1,127us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod  
Recorded Investment [Member] | Residential Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Recorded investment with no related allowance recorded 1,109us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 1,505us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded investment with an allowance recorded   235us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Totals:      
Recorded investment 1,109us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 1,740us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded Investment [Member] | Commercial Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Recorded investment with no related allowance recorded 11,817us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 12,331us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded investment with an allowance recorded 1,501us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 1,530us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded Investment [Member] | Commercial Construction [Member]      
Financing Receivable, Impaired [Line Items]      
Recorded investment with no related allowance recorded 103us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialConstructionMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 103us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialConstructionMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded Investment [Member] | Commercial Lots and Raw Land [Member]      
Financing Receivable, Impaired [Line Items]      
Recorded investment with no related allowance recorded 2,818us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 2,951us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded investment with an allowance recorded 39us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 416us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded Investment [Member] | Commercial and Industrial [Member]      
Financing Receivable, Impaired [Line Items]      
Recorded investment with no related allowance recorded 45us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 46us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded investment with an allowance recorded 244us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		    
Recorded Investment [Member] | Consumer Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Recorded investment with no related allowance recorded 340us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 192us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded investment with an allowance recorded 130us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 132us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded Investment [Member] | Consumer Lots and Raw Land [Member]      
Financing Receivable, Impaired [Line Items]      
Recorded investment with no related allowance recorded 57us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 59us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded investment with an allowance recorded 560us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 643us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded Investment [Member] | Home Equity Lines of Credit [Member]      
Financing Receivable, Impaired [Line Items]      
Recorded investment with no related allowance recorded 79us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 58us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded investment with an allowance recorded   25us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded Investment [Member] | Consumer Other [Member]      
Financing Receivable, Impaired [Line Items]      
Recorded investment with no related allowance recorded 45us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerOtherMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 46us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerOtherMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded Investment [Member] | Commercial [Member]      
Totals:      
Recorded investment 16,567us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 17,377us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded Investment [Member] | Consumer [Member]      
Totals:      
Recorded investment 1,211us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 1,155us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded Investment [Member]      
Financing Receivable, Impaired [Line Items]      
Recorded investment with no related allowance recorded 16,413us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 17,291us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Recorded investment with an allowance recorded 2,474us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 2,981us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Totals:      
Recorded investment 18,887us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		 20,272us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RecordedInvestmentMember		  
Contractual Unpaid Principal Balance [Member] | Residential Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Contractual unpaid principal balance with no related allowance recorded 1,405us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 1,802us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual unpaid principal balance with an allowance recorded   235us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Totals:      
Contractual unpaid principal balance 1,405us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 2,037us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual Unpaid Principal Balance [Member] | Commercial Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Contractual unpaid principal balance with no related allowance recorded 11,861us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 12,361us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual unpaid principal balance with an allowance recorded 1,559us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 1,569us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual Unpaid Principal Balance [Member] | Commercial Construction [Member]      
Financing Receivable, Impaired [Line Items]      
Contractual unpaid principal balance with no related allowance recorded 103us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialConstructionMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 103us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialConstructionMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual Unpaid Principal Balance [Member] | Commercial Lots and Raw Land [Member]      
Financing Receivable, Impaired [Line Items]      
Contractual unpaid principal balance with no related allowance recorded 2,818us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 2,958us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual unpaid principal balance with an allowance recorded 39us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 418us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual Unpaid Principal Balance [Member] | Commercial and Industrial [Member]      
Financing Receivable, Impaired [Line Items]      
Contractual unpaid principal balance with no related allowance recorded 45us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 46us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual unpaid principal balance with an allowance recorded 244us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		    
Contractual Unpaid Principal Balance [Member] | Consumer Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Contractual unpaid principal balance with no related allowance recorded 344us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 192us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual unpaid principal balance with an allowance recorded 130us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 132us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual Unpaid Principal Balance [Member] | Consumer Lots and Raw Land [Member]      
Financing Receivable, Impaired [Line Items]      
Contractual unpaid principal balance with no related allowance recorded 57us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 59us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual unpaid principal balance with an allowance recorded 560us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 643us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual Unpaid Principal Balance [Member] | Home Equity Lines of Credit [Member]      
Financing Receivable, Impaired [Line Items]      
Contractual unpaid principal balance with no related allowance recorded 80us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 58us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual unpaid principal balance with an allowance recorded   25us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual Unpaid Principal Balance [Member] | Consumer Other [Member]      
Financing Receivable, Impaired [Line Items]      
Contractual unpaid principal balance with no related allowance recorded 45us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerOtherMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 46us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerOtherMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual Unpaid Principal Balance [Member] | Commercial [Member]      
Totals:      
Contractual unpaid principal balance 16,669us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 17,455us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual Unpaid Principal Balance [Member] | Consumer [Member]      
Totals:      
Contractual unpaid principal balance 1,216us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 1,155us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual Unpaid Principal Balance [Member]      
Financing Receivable, Impaired [Line Items]      
Contractual unpaid principal balance with no related allowance recorded 16,758us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 17,625us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Contractual unpaid principal balance with an allowance recorded 2,532us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 3,022us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Totals:      
Contractual unpaid principal balance 19,290us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		 20,647us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_ContractualUnpaidPrincipalBalanceMember		  
Related Allowance [Member] | Residential Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Related Allowance   185us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Totals:      
Related allowance   185us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Related Allowance [Member] | Commercial Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Related Allowance 135us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 167us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Totals:      
Related allowance 135us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 167us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Related Allowance [Member] | Commercial Lots and Raw Land [Member]      
Financing Receivable, Impaired [Line Items]      
Related Allowance 30us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 251us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Totals:      
Related allowance 30us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 251us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Related Allowance [Member] | Commercial and Industrial [Member]      
Financing Receivable, Impaired [Line Items]      
Related Allowance 224us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		    
Totals:      
Related allowance 224us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		    
Related Allowance [Member] | Consumer Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Related Allowance 19us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 19us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Totals:      
Related allowance 19us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 19us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Related Allowance [Member] | Consumer Lots and Raw Land [Member]      
Financing Receivable, Impaired [Line Items]      
Related Allowance 95us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 165us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Totals:      
Related allowance 95us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 165us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Related Allowance [Member] | Home Equity Lines of Credit [Member]      
Financing Receivable, Impaired [Line Items]      
Related Allowance   5us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Totals:      
Related allowance   5us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Related Allowance [Member] | Commercial [Member]      
Financing Receivable, Impaired [Line Items]      
Related Allowance 389us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 418us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Totals:      
Related allowance 389us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 418us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Related Allowance [Member] | Consumer [Member]      
Financing Receivable, Impaired [Line Items]      
Related Allowance 114us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 189us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Totals:      
Related allowance 114us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 189us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Related Allowance [Member]      
Financing Receivable, Impaired [Line Items]      
Related Allowance 503us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 792us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
Totals:      
Related allowance 503us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		 792us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_RelatedAllowanceMember		  
YTD Average Recorded Investment [Member] | Residential Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
YTD average recorded investment with no related allowance recorded 1,307us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 1,268us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD average recorded investment with an allowance recorded   47us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
Totals:      
YTD average recorded investment 1,307us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 1,315us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD Average Recorded Investment [Member] | Commercial Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
YTD average recorded investment with no related allowance recorded 12,074us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 13,851us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD average recorded investment with an allowance recorded 1,516us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 2,638us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD Average Recorded Investment [Member] | Commercial Construction [Member]      
Financing Receivable, Impaired [Line Items]      
YTD average recorded investment with no related allowance recorded 103us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialConstructionMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 1,793us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialConstructionMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD Average Recorded Investment [Member] | Commercial Lots and Raw Land [Member]      
Financing Receivable, Impaired [Line Items]      
YTD average recorded investment with no related allowance recorded 2,884us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 3,623us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD average recorded investment with an allowance recorded 227us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 152us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD Average Recorded Investment [Member] | Commercial and Industrial [Member]      
Financing Receivable, Impaired [Line Items]      
YTD average recorded investment with no related allowance recorded 45us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 48us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD average recorded investment with an allowance recorded 122us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		    
YTD Average Recorded Investment [Member] | Consumer Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
YTD average recorded investment with no related allowance recorded 266us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 258us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD average recorded investment with an allowance recorded 131us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 139us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD Average Recorded Investment [Member] | Consumer Lots and Raw Land [Member]      
Financing Receivable, Impaired [Line Items]      
YTD average recorded investment with no related allowance recorded 59us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 477us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD average recorded investment with an allowance recorded 602us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 584us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD Average Recorded Investment [Member] | Home Equity Lines of Credit [Member]      
Financing Receivable, Impaired [Line Items]      
YTD average recorded investment with no related allowance recorded 69us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 46us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD average recorded investment with an allowance recorded   15us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD Average Recorded Investment [Member] | Consumer Other [Member]      
Financing Receivable, Impaired [Line Items]      
YTD average recorded investment with no related allowance recorded 45us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerOtherMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 76us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerOtherMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD Average Recorded Investment [Member] | Commercial [Member]      
Totals:      
YTD average recorded investment 16,971us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 22,105us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD Average Recorded Investment [Member] | Consumer [Member]      
Totals:      
YTD average recorded investment 1,172us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 1,595us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD Average Recorded Investment [Member]      
Financing Receivable, Impaired [Line Items]      
YTD average recorded investment with no related allowance recorded 16,852us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 21,440us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
YTD average recorded investment with an allowance recorded 2,598us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 3,575us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
Totals:      
YTD average recorded investment 19,450us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		 25,015us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis
= fsbk_YTDAverageRecordedInvestmentMember		  
Residential Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Interest income recognized on impaired loans with no related allowance recorded 18us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember		 74us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember		  
Interest income recognized on impaired loans with an allowance recorded   11us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember		  
Totals:      
Interest income recognized on impaired loans 18us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember		 85us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ResidentialRealEstateLoansMember		  
Commercial Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Interest income recognized on impaired loans with no related allowance recorded 172us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember		 721us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember		  
Interest income recognized on impaired loans with an allowance recorded 27us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember		 74us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialRealEstateLoansMember		  
Commercial Construction [Member]      
Financing Receivable, Impaired [Line Items]      
Interest income recognized on impaired loans with no related allowance recorded 1us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialConstructionMember		 5us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialConstructionMember		  
Commercial Lots and Raw Land [Member]      
Financing Receivable, Impaired [Line Items]      
Interest income recognized on impaired loans with no related allowance recorded 36us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember		 159us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember		  
Interest income recognized on impaired loans with an allowance recorded   29us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialLotsAndRawLandMember		  
Commercial and Industrial [Member]      
Financing Receivable, Impaired [Line Items]      
Interest income recognized on impaired loans with no related allowance recorded 1us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember		 2us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember		  
Interest income recognized on impaired loans with an allowance recorded 6us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialAndIndustrialMember		    
Consumer Real Estate Loans [Member]      
Financing Receivable, Impaired [Line Items]      
Interest income recognized on impaired loans with no related allowance recorded 3us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember		 6us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember		  
Interest income recognized on impaired loans with an allowance recorded 2us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember		 6us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerRealEstateLoansMember		  
Consumer Lots and Raw Land [Member]      
Financing Receivable, Impaired [Line Items]      
Interest income recognized on impaired loans with no related allowance recorded 1us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember		 4us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember		  
Interest income recognized on impaired loans with an allowance recorded 7us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember		 31us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerLotsAndRawLandMember		  
Home Equity Lines of Credit [Member]      
Financing Receivable, Impaired [Line Items]      
Interest income recognized on impaired loans with no related allowance recorded   3us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_HomeEquityLinesOfCreditMember		  
Consumer Other [Member]      
Financing Receivable, Impaired [Line Items]      
Interest income recognized on impaired loans with no related allowance recorded 1us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerOtherMember		 2us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerOtherMember		  
Commercial [Member]      
Totals:      
Interest income recognized on impaired loans 243us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember		 990us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_CommercialMember		  
Consumer [Member]      
Totals:      
Interest income recognized on impaired loans $ 14us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember		 $ 52us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fsbk_ConsumerMember