XML 60 R34.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans Receivable - Impaired Loans By Segment (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Impaired Financing Receivable, Recorded Investment [Abstract]        
Recorded Investments (Loan Balance Less Charge-Off), No Allowance Recorded $ 7,077us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment   $ 5,776us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment  
Recorded Investments (Loan Balance Less Charge-Off), Allowance Recorded 7,394us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment   8,957us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment  
Recorded Investments (Loan Balance Less Charge-Off) 14,471us-gaap_ImpairedFinancingReceivableRecordedInvestment   14,733us-gaap_ImpairedFinancingReceivableRecordedInvestment  
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]        
Unpaid Principal Balance, No Allowance Recorded 8,069us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance   6,689us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance  
Unpaid Principal Balance, Allowance Recorded 7,682us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance   9,704us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance  
Unpaid Principal Balance 15,751us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance   16,393us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance  
Related Allowance 529us-gaap_ImpairedFinancingReceivableRelatedAllowance   583us-gaap_ImpairedFinancingReceivableRelatedAllowance  
Impaired Financing Receivable, Average Recorded Investment [Abstract]        
Average Investment in Impaired Loans, No Allowance Recorded 7,164us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment 9,493us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment    
Average Investment in Impaired Loans, Allowance Recorded 7,397us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment 7,693us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment    
Average Investment in Impaired Loans 14,561us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment 17,186us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment    
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]        
Interest Income Recognized, No Allowance Recorded 140us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod 136us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod    
Interest Income Recognized, Allowance Recorded 116us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod 187us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod    
Interest Income Recognized 256us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod 323us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod    
Interest income recognized on impaired loans 124us-gaap_LoansAndLeasesReceivableImpairedTroubledDebtInterestIncome 156us-gaap_LoansAndLeasesReceivableImpairedTroubledDebtInterestIncome    
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Allowance for Loan Losses, Collectively Evaluated for Impairment 7,454us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment   7,489us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment  
Allowance for Loan Losses, Individually Evaluated for Impairment 529us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1   583us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1  
Allowance for Loan Losses 7,983us-gaap_LoansAndLeasesReceivableAllowance 8,182us-gaap_LoansAndLeasesReceivableAllowance 8,072us-gaap_LoansAndLeasesReceivableAllowance 7,974us-gaap_LoansAndLeasesReceivableAllowance
Loans Receivable, Ending Balance, Collectively Evaluated for Impairment 482,029us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment   489,095us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment  
Total Loans 496,500us-gaap_LoansAndLeasesReceivableGrossCarryingAmount   503,828us-gaap_LoansAndLeasesReceivableGrossCarryingAmount  
One to four family        
Impaired Financing Receivable, Recorded Investment [Abstract]        
Recorded Investments (Loan Balance Less Charge-Off), No Allowance Recorded 4,032us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  4,103us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Recorded Investments (Loan Balance Less Charge-Off), Allowance Recorded 3,296us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  3,507us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Recorded Investments (Loan Balance Less Charge-Off) 7,328us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  7,610us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]        
Unpaid Principal Balance, No Allowance Recorded 4,765us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  4,720us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Unpaid Principal Balance, Allowance Recorded 3,410us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  4,113us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Unpaid Principal Balance 8,175us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  8,833us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Related Allowance 191us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  170us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Impaired Financing Receivable, Average Recorded Investment [Abstract]        
Average Investment in Impaired Loans, No Allowance Recorded 4,026us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
4,071us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
   
Average Investment in Impaired Loans, Allowance Recorded 3,336us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
3,213us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
   
Average Investment in Impaired Loans 7,362us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
7,284us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
   
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]        
Interest Income Recognized, No Allowance Recorded 113us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
86us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
   
Interest Income Recognized, Allowance Recorded 52us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
113us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
   
Interest Income Recognized 165us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
199us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
   
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Allowance for Loan Losses, Collectively Evaluated for Impairment 3,555us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  3,238us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Allowance for Loan Losses, Individually Evaluated for Impairment 191us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  170us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Allowance for Loan Losses 3,746us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
3,758us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
3,408us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
3,667us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
Loans Receivable, Ending Balance, Collectively Evaluated for Impairment 240,470us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  234,300us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Total Loans 247,798us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
  241,910us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
 
Commercial        
Impaired Financing Receivable, Recorded Investment [Abstract]        
Recorded Investments (Loan Balance Less Charge-Off), No Allowance Recorded 2,503us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  977us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Recorded Investments (Loan Balance Less Charge-Off), Allowance Recorded 3,114us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  4,788us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Recorded Investments (Loan Balance Less Charge-Off) 5,617us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  5,765us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]        
Unpaid Principal Balance, No Allowance Recorded 2,651us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  1,032us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Unpaid Principal Balance, Allowance Recorded 3,113us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  4,883us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Unpaid Principal Balance 5,764us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  5,915us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Related Allowance 153us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  277us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Impaired Financing Receivable, Average Recorded Investment [Abstract]        
Average Investment in Impaired Loans, No Allowance Recorded 2,507us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
1,856us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
   
Average Investment in Impaired Loans, Allowance Recorded 3,191us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
1,371us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
   
Average Investment in Impaired Loans 5,698us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
3,227us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
   
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]        
Interest Income Recognized, No Allowance Recorded 11us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
27us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
   
Interest Income Recognized, Allowance Recorded 40us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
39us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
   
Interest Income Recognized 51us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
66us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
   
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Allowance for Loan Losses, Collectively Evaluated for Impairment 1,740us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  2,077us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Allowance for Loan Losses, Individually Evaluated for Impairment 153us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  277us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Allowance for Loan Losses 1,893us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
1,919us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
2,354us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
1,774us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
Loans Receivable, Ending Balance, Collectively Evaluated for Impairment 172,721us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  184,895us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Total Loans 178,338us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
  190,660us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
 
Consumer        
Impaired Financing Receivable, Recorded Investment [Abstract]        
Recorded Investments (Loan Balance Less Charge-Off), No Allowance Recorded 231us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  383us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Recorded Investments (Loan Balance Less Charge-Off), Allowance Recorded 828us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  535us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Recorded Investments (Loan Balance Less Charge-Off) 1,059us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  918us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]        
Unpaid Principal Balance, No Allowance Recorded 296us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  579us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Unpaid Principal Balance, Allowance Recorded 933us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  557us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Unpaid Principal Balance 1,229us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  1,136us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Related Allowance 157us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  120us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Impaired Financing Receivable, Average Recorded Investment [Abstract]        
Average Investment in Impaired Loans, No Allowance Recorded 320us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
3,566us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
   
Average Investment in Impaired Loans, Allowance Recorded 712us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
2,962us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
   
Average Investment in Impaired Loans 1,032us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
6,528us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
   
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]        
Interest Income Recognized, No Allowance Recorded 5us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
23us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
   
Interest Income Recognized, Allowance Recorded 17us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
18us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
   
Interest Income Recognized 22us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
41us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
   
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Allowance for Loan Losses, Collectively Evaluated for Impairment 1,332us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  1,558us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Allowance for Loan Losses, Individually Evaluated for Impairment 157us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  120us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Allowance for Loan Losses 1,489us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
1,950us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
1,678us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
2,015us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
Loans Receivable, Ending Balance, Collectively Evaluated for Impairment 48,764us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  49,843us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Total Loans 49,823us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
  50,761us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Construction and land        
Impaired Financing Receivable, Recorded Investment [Abstract]        
Recorded Investments (Loan Balance Less Charge-Off), No Allowance Recorded 311us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  313us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Recorded Investments (Loan Balance Less Charge-Off), Allowance Recorded 156us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  127us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Recorded Investments (Loan Balance Less Charge-Off) 467us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  440us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]        
Unpaid Principal Balance, No Allowance Recorded 357us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  358us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Unpaid Principal Balance, Allowance Recorded 226us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  151us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Unpaid Principal Balance 583us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  509us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Related Allowance 28us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  16us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Impaired Financing Receivable, Average Recorded Investment [Abstract]        
Average Investment in Impaired Loans, No Allowance Recorded 311us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
   
Average Investment in Impaired Loans, Allowance Recorded 158us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
147us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
   
Average Investment in Impaired Loans 469us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
147us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
   
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]        
Interest Income Recognized, No Allowance Recorded 11us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
0us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
   
Interest Income Recognized, Allowance Recorded 7us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
17us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
   
Interest Income Recognized 18us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
17us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
   
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Allowance for Loan Losses, Collectively Evaluated for Impairment 403us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  381us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Allowance for Loan Losses, Individually Evaluated for Impairment 28us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  16us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Allowance for Loan Losses 431us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
324us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
397us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
297us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
Loans Receivable, Ending Balance, Collectively Evaluated for Impairment 20,074us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  20,057us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Total Loans 20,541us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
  20,497us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
 
Unallocated        
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]        
Allowance for Loan Losses, Collectively Evaluated for Impairment 424us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
  235us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
 
Allowance for Loan Losses, Individually Evaluated for Impairment 0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
  0us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
 
Allowance for Loan Losses 424us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
231us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
235us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
221us-gaap_LoansAndLeasesReceivableAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
Loans Receivable, Ending Balance, Collectively Evaluated for Impairment 0us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
  0us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
 
Total Loans $ 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember
  $ 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_UnallocatedFinancingReceivablesMember