XML 23 R37.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans Receivable - Impaired Loans By Segment (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 6 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Jun. 30, 2014
Impaired Financing Receivable, Recorded Investment [Abstract]          
Recorded Investments (Loan Balance Less Charge-Off), No Allowance Recorded $ 6,420us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment   $ 6,420us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment   $ 5,776us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
Recorded Investments (Loan Balance Less Charge-Off), Allowance Recorded 5,783us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment   5,783us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment   8,957us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
Recorded Investments (Loan Balance Less Charge-Off) 12,203us-gaap_ImpairedFinancingReceivableRecordedInvestment   12,203us-gaap_ImpairedFinancingReceivableRecordedInvestment   14,733us-gaap_ImpairedFinancingReceivableRecordedInvestment
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]          
Unpaid Principal Balance, No Allowance Recorded 7,277us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance   7,277us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance   6,689us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
Unpaid Principal Balance, Allowance Recorded 6,034us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance   6,034us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance   9,704us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
Unpaid Principal Balance 13,311us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance   13,311us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance   16,393us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
Related Allowance 470us-gaap_ImpairedFinancingReceivableRelatedAllowance   470us-gaap_ImpairedFinancingReceivableRelatedAllowance   583us-gaap_ImpairedFinancingReceivableRelatedAllowance
Impaired Financing Receivable, Average Recorded Investment [Abstract]          
Average Investment in Impaired Loans, No Allowance Recorded 7,061us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment 9,073us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment 7,112us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment 9,283us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment  
Average Investment in Impaired Loans, Allowance Recorded 5,990us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment 8,541us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment 6,694us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment 8,117us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment  
Average Investment in Impaired Loans 13,051us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment 17,614us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment 13,806us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment 17,400us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment  
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]          
Interest Income Recognized, No Allowance Recorded 119us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod 222us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod 178us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod 296us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod  
Interest Income Recognized, Allowance Recorded 114us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod 109us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod 177us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod 191us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod  
Interest Income Recognized 233us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod 331us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod 355us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod 487us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod  
Interest income recognized on impaired loans 112us-gaap_LoansAndLeasesReceivableImpairedTroubledDebtInterestIncome 140us-gaap_LoansAndLeasesReceivableImpairedTroubledDebtInterestIncome 235us-gaap_LoansAndLeasesReceivableImpairedTroubledDebtInterestIncome 296us-gaap_LoansAndLeasesReceivableImpairedTroubledDebtInterestIncome  
One to four family          
Impaired Financing Receivable, Recorded Investment [Abstract]          
Recorded Investments (Loan Balance Less Charge-Off), No Allowance Recorded 3,849us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   3,849us-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 3,297us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   3,297us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   3,507us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
Recorded Investments (Loan Balance Less Charge-Off) 7,146us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   7,146us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   7,610us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 [1]
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]          
Unpaid Principal Balance, No Allowance Recorded 4,508us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   4,508us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   4,720us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
Unpaid Principal Balance, Allowance Recorded 3,463us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   3,463us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   4,113us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
Unpaid Principal Balance 7,971us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   7,971us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   8,833us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember
Related Allowance 195us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		   195us-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 3,893us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 5,202us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 3,959us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 4,637us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		  
Average Investment in Impaired Loans, Allowance Recorded 3,304us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 4,186us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 3,321us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 3,699us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		  
Average Investment in Impaired Loans 7,197us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 9,388us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 7,280us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 8,336us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		  
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]          
Interest Income Recognized, No Allowance Recorded 83us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 138us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 109us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 156us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		  
Interest Income Recognized, Allowance Recorded 70us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 61us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 105us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 86us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		  
Interest Income Recognized 153us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 199us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 214us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		 242us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ResidentialPortfolioSegmentMember		  
Commercial          
Impaired Financing Receivable, Recorded Investment [Abstract]          
Recorded Investments (Loan Balance Less Charge-Off), No Allowance Recorded 2,090us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   2,090us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   977us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
Recorded Investments (Loan Balance Less Charge-Off), Allowance Recorded 1,642us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   1,642us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   4,788us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
Recorded Investments (Loan Balance Less Charge-Off) 3,732us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   3,732us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   5,765us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 [1]
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]          
Unpaid Principal Balance, No Allowance Recorded 2,148us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   2,148us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   1,032us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
Unpaid Principal Balance, Allowance Recorded 1,642us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   1,642us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   4,883us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
Unpaid Principal Balance 3,790us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   3,790us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   5,915us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember
Related Allowance 142us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		   142us-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 2,662us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 3,235us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 2,584us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 2,546us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Average Investment in Impaired Loans, Allowance Recorded 1,802us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 3,257us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 2,496us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 2,314us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Average Investment in Impaired Loans 4,464us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 6,492us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 5,080us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 4,860us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]          
Interest Income Recognized, No Allowance Recorded 18us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 40us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 47us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 95us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Interest Income Recognized, Allowance Recorded 20us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 26us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 40us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 69us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Interest Income Recognized 38us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 66us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 87us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		 164us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_CommercialPortfolioSegmentMember		  
Consumer          
Impaired Financing Receivable, Recorded Investment [Abstract]          
Recorded Investments (Loan Balance Less Charge-Off), No Allowance Recorded 170us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   170us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   383us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
Recorded Investments (Loan Balance Less Charge-Off), Allowance Recorded 606us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   606us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   535us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
Recorded Investments (Loan Balance Less Charge-Off) 776us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   776us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   918us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 [1]
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]          
Unpaid Principal Balance, No Allowance Recorded 265us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   265us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   579us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
Unpaid Principal Balance, Allowance Recorded 667us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   667us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   557us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
Unpaid Principal Balance 932us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   932us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   1,136us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember
Related Allowance 99us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		   99us-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 196us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 629us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 258us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 2,097us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		  
Average Investment in Impaired Loans, Allowance Recorded 722us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 900us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 717us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 1,931us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		  
Average Investment in Impaired Loans 918us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 1,529us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 975us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 4,028us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		  
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]          
Interest Income Recognized, No Allowance Recorded 3us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 38us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 6us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 38us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		  
Interest Income Recognized, Allowance Recorded 14us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 14us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 21us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 24us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		  
Interest Income Recognized 17us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 52us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 27us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= us-gaap_ConsumerPortfolioSegmentMember		 62us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ 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		   311us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   313us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
Recorded Investments (Loan Balance Less Charge-Off), Allowance Recorded 238us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   238us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   127us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
Recorded Investments (Loan Balance Less Charge-Off) 549us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   549us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   440us-gaap_ImpairedFinancingReceivableRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 [1]
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]          
Unpaid Principal Balance, No Allowance Recorded 356us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   356us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   358us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
Unpaid Principal Balance, Allowance Recorded 262us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   262us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   151us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
Unpaid Principal Balance 618us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   618us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   509us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember
Related Allowance 34us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		   34us-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 310us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 7us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 311us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 3us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		  
Average Investment in Impaired Loans, Allowance Recorded 162us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 198us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 160us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 173us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		  
Average Investment in Impaired Loans 472us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 205us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 471us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 176us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		  
Impaired Financing Receivable, Interest Income, Accrual Method [Abstract]          
Interest Income Recognized, No Allowance Recorded 15us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 6us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 16us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 7us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		  
Interest Income Recognized, Allowance Recorded 10us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 8us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 11us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 12us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		  
Interest Income Recognized $ 25us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 $ 14us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 $ 27us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		 $ 19us-gaap_ImpairedFinancingReceivableInterestIncomeAccrualMethod
/ fnwb_FinancingReceivablePortfolioSegmentAxis
= fnwb_ConstructionandLandPortfolioSegmentMember		  
[1] Loans individually evaluated for impairmentThere were no new TDR loans, or renewals or modifications of existing TDR loans during the three and six months ended December 31, 2014.There were no new TDR loans with payment defaults of more than 30 days during the three and six months ended December 31, 2013.There were no TDR loans that were modified within the 12 months prior to December 31, 2014, and for which there was a payment default during the three and six months ended December 31, 2014.