XML 42 R36.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans Receivable - Credit Quality Indicators by Class of Loan (Details) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Jun. 30, 2014
Financing Receivable, Recorded Investment [Line Items]    
Loans $ 496,500us-gaap_LoansAndLeasesReceivableGrossCarryingAmount $ 503,828us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans 450,506us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 458,624us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Watch    
Financing Receivable, Recorded Investment [Line Items]    
Loans 28,030us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= fnwb_WatchMember		 26,027us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= fnwb_WatchMember
Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans 4,219us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 5,234us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Sub-standard    
Financing Receivable, Recorded Investment [Line Items]    
Loans 13,745us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 13,943us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Doubtful    
Financing Receivable, Recorded Investment [Line Items]    
Loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
Non-performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans 5,840us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 5,964us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember
Performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans 490,660us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PerformingFinancingReceivableMember		 497,864us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PerformingFinancingReceivableMember
Real estate loans    
Financing Receivable, Recorded Investment [Line Items]    
Loans 470,800us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember		 475,800us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
One to four family    
Financing Receivable, Recorded Investment [Line Items]    
Loans 247,798us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 241,910us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
One to four family | Olympic Peninsula | Real estate loans    
Financing Receivable, Recorded Investment [Line Items]    
Loans 166,251us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember		 167,910us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember
One to four family | Olympic Peninsula | Real estate loans | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans 154,502us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember		 156,484us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember
One to four family | Olympic Peninsula | Real estate loans | Watch    
Financing Receivable, Recorded Investment [Line Items]    
Loans 4,898us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= fnwb_WatchMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember		 4,154us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= fnwb_WatchMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember
One to four family | Olympic Peninsula | Real estate loans | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans 2,037us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember		 2,114us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember
One to four family | Olympic Peninsula | Real estate loans | Sub-standard    
Financing Receivable, Recorded Investment [Line Items]    
Loans 4,814us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember		 5,158us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember
One to four family | Olympic Peninsula | Real estate loans | Doubtful    
Financing Receivable, Recorded Investment [Line Items]    
Loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember
One to four family | Olympic Peninsula | Real estate loans | Non-performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans 3,095us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember		 3,223us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember
One to four family | Olympic Peninsula | Real estate loans | Performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans 163,156us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PerformingFinancingReceivableMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember		 164,687us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PerformingFinancingReceivableMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OlympicPeninsulaMember
One to four family | Other locations | Real estate loans    
Financing Receivable, Recorded Investment [Line Items]    
Loans 81,547us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember		 74,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember
One to four family | Other locations | Real estate loans | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans 79,417us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember		 72,809us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember
One to four family | Other locations | Real estate loans | Watch    
Financing Receivable, Recorded Investment [Line Items]    
Loans 1,065us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= fnwb_WatchMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember		 203us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= fnwb_WatchMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember
One to four family | Other locations | Real estate loans | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans 177us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember		 605us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember
One to four family | Other locations | Real estate loans | Sub-standard    
Financing Receivable, Recorded Investment [Line Items]    
Loans 888us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember		 383us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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= us-gaap_SubstandardMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember
One to four family | Other locations | Real estate loans | Doubtful    
Financing Receivable, Recorded Investment [Line Items]    
Loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
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= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember
One to four family | Other locations | Real estate loans | Non-performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans 313us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember		 320us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember
One to four family | Other locations | Real estate loans | Performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans 81,234us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PerformingFinancingReceivableMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember		 73,680us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PerformingFinancingReceivableMember
/ us-gaap_StatementGeographicalAxis
= fnwb_OtherLocationsMember
Commercial    
Financing Receivable, Recorded Investment [Line Items]    
Loans 178,338us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 190,660us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
Commercial | Real estate loans    
Financing Receivable, Recorded Investment [Line Items]    
Loans 122,828us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember		 128,028us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
Commercial | Real estate loans | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans 106,276us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 111,319us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Commercial | Real estate loans | Watch    
Financing Receivable, Recorded Investment [Line Items]    
Loans 9,767us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= fnwb_WatchMember		 9,471us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= fnwb_WatchMember
Commercial | Real estate loans | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans 1,475us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 1,570us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Commercial | Real estate loans | Sub-standard    
Financing Receivable, Recorded Investment [Line Items]    
Loans 5,310us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember		 5,668us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
Commercial | Real estate loans | Doubtful    
Financing Receivable, Recorded Investment [Line Items]    
Loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember		 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
Commercial | Real estate loans | Non-performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans 1,750us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember		 1,913us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_NonperformingFinancingReceivableMember
Commercial | Real estate loans | Performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans 121,078us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnwb_RealEstateLoanMember
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Consumer | Consumer other    
Financing Receivable, Recorded Investment [Line Items]    
Loans 4,851us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
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Consumer | Consumer other | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans 4,416us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Consumer | Consumer other | Watch    
Financing Receivable, Recorded Investment [Line Items]    
Loans 223us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Consumer | Consumer other | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans 43us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Consumer | Consumer other | Sub-standard    
Financing Receivable, Recorded Investment [Line Items]    
Loans 169us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Consumer | Consumer other | Doubtful    
Financing Receivable, Recorded Investment [Line Items]    
Loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Consumer | Consumer other | Non-performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans 48us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Consumer | Consumer other | Performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans 4,803us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Construction and land    
Financing Receivable, Recorded Investment [Line Items]    
Loans 20,541us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Construction and land | Construction    
Financing Receivable, Recorded Investment [Line Items]    
Loans 8,788us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Construction and land | Construction | Pass    
Financing Receivable, Recorded Investment [Line Items]    
Loans 8,560us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Construction and land | Construction | Watch    
Financing Receivable, Recorded Investment [Line Items]    
Loans 228us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Construction and land | Construction | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Construction and land | Construction | Sub-standard    
Financing Receivable, Recorded Investment [Line Items]    
Loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Construction and land | Construction | Doubtful    
Financing Receivable, Recorded Investment [Line Items]    
Loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Construction and land | Construction | Non-performing    
Financing Receivable, Recorded Investment [Line Items]    
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Construction and land | Construction | Performing    
Financing Receivable, Recorded Investment [Line Items]    
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Construction and land | Land and development    
Financing Receivable, Recorded Investment [Line Items]    
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Construction and land | Land and development | Pass    
Financing Receivable, Recorded Investment [Line Items]    
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Construction and land | Land and development | Watch    
Financing Receivable, Recorded Investment [Line Items]    
Loans 670us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Construction and land | Land and development | Special Mention    
Financing Receivable, Recorded Investment [Line Items]    
Loans 130us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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Construction and land | Land and development | Sub-standard    
Financing Receivable, Recorded Investment [Line Items]    
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Construction and land | Land and development | Doubtful    
Financing Receivable, Recorded Investment [Line Items]    
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Construction and land | Land and development | Non-performing    
Financing Receivable, Recorded Investment [Line Items]    
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Construction and land | Land and development | Performing    
Financing Receivable, Recorded Investment [Line Items]    
Loans $ 11,597us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
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