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LOANS RECEIVABLE (Details 1) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Financing Receivable, Recorded Investment [Line Items]      
Total loans $ 376,060us-gaap_LoansAndLeasesReceivableGrossCarryingAmount $ 369,325us-gaap_LoansAndLeasesReceivableGrossCarryingAmount $ 369,837us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Special use properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 36,494us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
30,376us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
31,461us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
Retail properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 17,703us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
17,346us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
23,283us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
Office Buildings [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 24,333us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
24,468us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
20,931us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
Industrial and warehouse properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 24,416us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
24,875us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
29,625us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
Investor owned one to four family and multi family [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 29,838us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
25,461us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
17,029us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
Consumer Loan [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 37,518us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
36,844us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
 
Pass [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 362,079us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
355,336us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
 
Pass [Member] | Special use properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 34,073us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
27,925us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
 
Pass [Member] | Retail properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 17,157us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
17,092us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
 
Pass [Member] | Office Buildings [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 23,655us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
23,503us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
 
Pass [Member] | Industrial and warehouse properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 23,260us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
23,707us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
 
Pass [Member] | Investor owned one to four family and multi family [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 28,303us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
23,793us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
 
Pass [Member] | Consumer Loan [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 36,982us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
36,348us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
 
Special Mention [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 6,258us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
6,538us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
 
Special Mention [Member] | Special use properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 1,429us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
1,445us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
 
Special Mention [Member] | Retail properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 398us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
104us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
 
Special Mention [Member] | Office Buildings [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 34us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
319us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
 
Special Mention [Member] | Industrial and warehouse properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 1,135us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
1,145us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
 
Special Mention [Member] | Investor owned one to four family and multi family [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 897us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
1,027us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
 
Special Mention [Member] | Consumer Loan [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 206us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
207us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
 
Substandard [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 7,723us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
7,451us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
 
Substandard [Member] | Special use properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 992us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
1,006us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
 
Substandard [Member] | Retail properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 148us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
150us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
 
Substandard [Member] | Office Buildings [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 644us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
646us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
 
Substandard [Member] | Industrial and warehouse properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 21us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
23us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
 
Substandard [Member] | Investor owned one to four family and multi family [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 638us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
641us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
 
Substandard [Member] | Consumer Loan [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 330us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
289us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
 
Substandard [Member] | Accruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 2,438us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
2,346us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
 
Substandard [Member] | Accruing Credit Risk Profile [Member] | Special use properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 982us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
996us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
 
Substandard [Member] | Accruing Credit Risk Profile [Member] | Retail properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 148us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
150us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
 
Substandard [Member] | Accruing Credit Risk Profile [Member] | Office Buildings [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 98us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
100us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
 
Substandard [Member] | Accruing Credit Risk Profile [Member] | Industrial and warehouse properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
 
Substandard [Member] | Accruing Credit Risk Profile [Member] | Investor owned one to four family and multi family [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 249us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
252us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
 
Substandard [Member] | Accruing Credit Risk Profile [Member] | Consumer Loan [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 143us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
74us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
 
Substandard [Member] | NonAccruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 5,285us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
5,105us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
 
Substandard [Member] | NonAccruing Credit Risk Profile [Member] | Special use properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 10us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
10us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
 
Substandard [Member] | NonAccruing Credit Risk Profile [Member] | Retail properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
 
Substandard [Member] | NonAccruing Credit Risk Profile [Member] | Office Buildings [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 546us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
546us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
 
Substandard [Member] | NonAccruing Credit Risk Profile [Member] | Industrial and warehouse properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 21us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
23us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
 
Substandard [Member] | NonAccruing Credit Risk Profile [Member] | Investor owned one to four family and multi family [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 389us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
389us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
 
Substandard [Member] | NonAccruing Credit Risk Profile [Member] | Consumer Loan [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 187us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
215us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
 
Doubtful [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
 
Doubtful [Member] | Special use properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OtherPropertyMember
 
Doubtful [Member] | Retail properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_RetailSiteMember
 
Doubtful [Member] | Office Buildings [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_OfficeBuildingMember
 
Doubtful [Member] | Industrial and warehouse properties [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= us-gaap_IndustrialPropertyMember
 
Doubtful [Member] | Investor owned one to four family and multi family [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= nvsl_InvestorOwnedOneToFourFamilyAndMultiFamilyMember
 
Doubtful [Member] | Consumer Loan [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis
= us-gaap_ConsumerLoanMember
 
Commercial Business Loans [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 24,353us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
25,801us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
24,250us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
Commercial Business Loans [Member] | Pass [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 22,183us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
23,535us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
 
Commercial Business Loans [Member] | Special Mention [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 615us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
707us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
 
Commercial Business Loans [Member] | Substandard [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 1,555us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
1,559us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
 
Commercial Business Loans [Member] | Substandard [Member] | Accruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 799us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
755us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
 
Commercial Business Loans [Member] | Substandard [Member] | NonAccruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 756us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
804us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
 
Commercial Business Loans [Member] | Doubtful [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialLoanMember
 
Multi-Family and Commercial Real Estate [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 132,784us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
122,526us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
 
Multi-Family and Commercial Real Estate [Member] | Pass [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 126,448us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
116,020us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
 
Multi-Family and Commercial Real Estate [Member] | Special Mention [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 3,893us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
4,040us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
 
Multi-Family and Commercial Real Estate [Member] | Substandard [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 2,443us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
2,466us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
 
Multi-Family and Commercial Real Estate [Member] | Substandard [Member] | Accruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 1,477us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
1,498us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
 
Multi-Family and Commercial Real Estate [Member] | Substandard [Member] | NonAccruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 966us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
968us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
 
Multi-Family and Commercial Real Estate [Member] | Doubtful [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= us-gaap_CommercialRealEstateMember
 
One to four family [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 177,874us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
180,739us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
184,531us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
One to four family [Member] | Pass [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 174,397us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
177,598us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
 
One to four family [Member] | Special Mention [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 725us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
731us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
 
One to four family [Member] | Substandard [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 2,752us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
2,410us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
 
One to four family [Member] | Substandard [Member] | Accruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 19us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
19us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
 
One to four family [Member] | Substandard [Member] | NonAccruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 2,733us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
2,391us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
 
One to four family [Member] | Doubtful [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_OneToFourFamilyMember
 
Construction And Land Development [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 3,531us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
3,415us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
 
Construction And Land Development [Member] | Pass [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 2,069us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
1,835us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
 
Construction And Land Development [Member] | Special Mention [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 819us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
853us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
 
Construction And Land Development [Member] | Substandard [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 643us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
727us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
 
Construction And Land Development [Member] | Substandard [Member] | Accruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
 
Construction And Land Development [Member] | Substandard [Member] | NonAccruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 643us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
727us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
 
Construction And Land Development [Member] | Doubtful [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_ConstructionMember
 
Total Multi family and commercial real estate member [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 132,784us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
122,526us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
 
Total Multi family and commercial real estate member [Member] | Pass [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 126,448us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
116,020us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
 
Total Multi family and commercial real estate member [Member] | Special Mention [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 3,893us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
4,040us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
 
Total Multi family and commercial real estate member [Member] | Substandard [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 2,443us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
2,466us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
 
Total Multi family and commercial real estate member [Member] | Substandard [Member] | Accruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 1,477us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
1,498us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_AccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
 
Total Multi family and commercial real estate member [Member] | Substandard [Member] | NonAccruing Credit Risk Profile [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans 966us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
968us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ nvsl_CreditRiskProfileAxis
= nvsl_NonaccruingCreditRiskProfileMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SubstandardMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
 
Total Multi family and commercial real estate member [Member] | Doubtful [Member]      
Financing Receivable, Recorded Investment [Line Items]      
Total loans $ 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember
$ 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_DoubtfulMember
/ us-gaap_MortgageLoansOnRealEstateLoanTypeAxis
= nvsl_TotalMultiFamilyAndCommercialRealEstateMemberMember