v2.4.1.9
Investment (Details Textual) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Jul. 03, 2013
Income (Loss) from Equity Method Investments $ (734,000)us-gaap_IncomeLossFromEquityMethodInvestments $ (2,073,000)us-gaap_IncomeLossFromEquityMethodInvestments  
Equity Method Investment, Realized Gain (Loss) on Disposal (734,000)us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal (2,073,000)us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal  
Qualstar [Member]      
Equity Method Investment, Ownership Percentage     18.30%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ dei_LegalEntityAxis
= bkfg_QualstarMember
Investment Owned, Balance, Shares (in shares) 3,020,568us-gaap_InvestmentOwnedBalanceShares
/ dei_LegalEntityAxis
= bkfg_QualstarMember
2,594,748us-gaap_InvestmentOwnedBalanceShares
/ dei_LegalEntityAxis
= bkfg_QualstarMember
 
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum 24.65%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum
/ dei_LegalEntityAxis
= bkfg_QualstarMember
21.18%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum
/ dei_LegalEntityAxis
= bkfg_QualstarMember
 
Investment Owned, at Fair Value (in dollars) 649,000us-gaap_InvestmentOwnedAtFairValue
/ dei_LegalEntityAxis
= bkfg_QualstarMember
902,000us-gaap_InvestmentOwnedAtFairValue
/ dei_LegalEntityAxis
= bkfg_QualstarMember
 
Investment Owned, Face Amount (in dollars) 4,000,000us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue
/ dei_LegalEntityAxis
= bkfg_QualstarMember
   
Income (Loss) from Equity Method Investments 3,000us-gaap_IncomeLossFromEquityMethodInvestments
/ dei_LegalEntityAxis
= bkfg_QualstarMember
53,000us-gaap_IncomeLossFromEquityMethodInvestments
/ dei_LegalEntityAxis
= bkfg_QualstarMember
 
Equity Method Investment, Realized Gain (Loss) on Disposal 791,000us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal
/ dei_LegalEntityAxis
= bkfg_QualstarMember
2,073,000us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal
/ dei_LegalEntityAxis
= bkfg_QualstarMember
 
Incremental Investment Proportionate to Net Assets 2,600,000bkfg_IncrementalInvestmentProportionateToNetAssets
/ dei_LegalEntityAxis
= bkfg_QualstarMember
   
Interlink Electronics [Member]      
Investment Owned, Balance, Shares (in shares) 335,293us-gaap_InvestmentOwnedBalanceShares
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= bkfg_InterlinkElectronicsIncMember
   
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum 11.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= bkfg_InterlinkElectronicsIncMember
   
Investment Owned, at Fair Value (in dollars) 2,199,000us-gaap_InvestmentOwnedAtFairValue
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= bkfg_InterlinkElectronicsIncMember
   
Investment Owned, Face Amount (in dollars) 5,500,000us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= bkfg_InterlinkElectronicsIncMember
   
Income (Loss) from Equity Method Investments 89,000us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= bkfg_InterlinkElectronicsIncMember
   
Equity Method Investment, Realized Gain (Loss) on Disposal 57,000us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= bkfg_InterlinkElectronicsIncMember
   
Incremental Investment Proportionate to Net Assets $ 1,600,000bkfg_IncrementalInvestmentProportionateToNetAssets
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= bkfg_InterlinkElectronicsIncMember