XML 90 R60.htm IDEA: XBRL DOCUMENT v2.4.1.9
Note 5 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans (Details) - Loans by Credit Quality Indicator (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans $ 591,198us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment $ 583,610us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
Construction, 1-4 Family Residential [Member] | Real Estate Construction [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 14,222us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_Construction14FamilyResidentialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 17,702us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_Construction14FamilyResidentialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Construction, 1-4 Family Residential [Member] | Real Estate Construction [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans   163us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_Construction14FamilyResidentialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Construction, 1-4 Family Residential [Member] | Real Estate Construction [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 2,265us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_Construction14FamilyResidentialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 45us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_Construction14FamilyResidentialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
Construction Other [Member] | Real Estate Construction [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 29,047us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ConstructionOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 27,971us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ConstructionOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Construction Other [Member] | Real Estate Construction [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans   29us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ConstructionOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Construction Other [Member] | Real Estate Construction [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 28us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ConstructionOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 15us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ConstructionOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
Equity Lines [Member] | Consumer Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 15,861us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_EquityLinesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 16,146us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_EquityLinesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Equity Lines [Member] | Consumer Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 59us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_EquityLinesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 16us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_EquityLinesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Equity Lines [Member] | Consumer Real Estate [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 60us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_EquityLinesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		  
Closed-end First Liens [Member] | Consumer Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 78,806us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 82,767us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Closed-end First Liens [Member] | Consumer Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 1,566us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 1,007us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Closed-end First Liens [Member] | Consumer Real Estate [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 1,412us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 1,275us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
Closed-end Junior Liens [Member] | Consumer Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 4,258us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndJuniorLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 4,813us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndJuniorLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Closed-end Junior Liens [Member] | Consumer Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 21us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndJuniorLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 109us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndJuniorLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Closed-end Junior Liens [Member] | Consumer Real Estate [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 95us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndJuniorLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 3us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndJuniorLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
Investor-owned Residential Real Estate [Member] | Consumer Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 42,781us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_InvestorOwnedResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 38,071us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_InvestorOwnedResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Investor-owned Residential Real Estate [Member] | Consumer Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 688us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_InvestorOwnedResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 105us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_InvestorOwnedResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Investor-owned Residential Real Estate [Member] | Consumer Real Estate [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 614us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_InvestorOwnedResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 407us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_InvestorOwnedResidentialRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
Multifamily Real Estate [Member] | Commercial Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 73,611us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_MultifamilyRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 67,573us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_MultifamilyRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Multifamily Real Estate [Member] | Commercial Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 1,397us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_MultifamilyRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		  
Multifamily Real Estate [Member] | Commercial Real Estate [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 850us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_MultifamilyRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 958us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_MultifamilyRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
Commercial Real Estate, Owner Occupied [Member] | Commercial Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 125,643us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 134,137us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Commercial Real Estate, Owner Occupied [Member] | Commercial Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 202us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 2,206us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Commercial Real Estate, Owner Occupied [Member] | Commercial Real Estate [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 2,855us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 701us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
Commercial Real Estate, Other [Member] | Commercial Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 90,821us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 89,340us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Commercial Real Estate, Other [Member] | Commercial Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 1,177us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 1,209us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Commercial Real Estate, Other [Member] | Commercial Real Estate [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 582us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 3,063us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOtherMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
Commercial and Industrial [Member] | Commercial Non Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 31,247us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 29,987us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Commercial and Industrial [Member] | Commercial Non Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 97us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 878us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Commercial and Industrial [Member] | Commercial Non Real Estate [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 1,390us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 295us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
States & Political Subdivisions [Member] | Public Sector and IDA [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 41,361us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_StatesPoliticalSubdivisionsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_PublicSectorAndIdaMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 24,220us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_StatesPoliticalSubdivisionsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_PublicSectorAndIdaMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Credit Card Receivable [Member] | Consumer Non Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 5,705us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= us-gaap_CreditCardReceivablesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 6,354us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= us-gaap_CreditCardReceivablesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Automobile [Member] | Consumer Non Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 11,505us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_AutomobileMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 11,428us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_AutomobileMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Automobile [Member] | Consumer Non Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 93us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_AutomobileMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 253us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_AutomobileMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Automobile [Member] | Consumer Non Real Estate [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 128us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_AutomobileMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 34us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_AutomobileMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
Other Consumer Loans [Member] | Consumer Non Real Estate [Member] | Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 10,745us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_OtherConsumerLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 10,253us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_OtherConsumerLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Other Consumer Loans [Member] | Consumer Non Real Estate [Member] | Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans   17us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_OtherConsumerLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Other Consumer Loans [Member] | Consumer Non Real Estate [Member] | Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 6us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_OtherConsumerLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 60us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_OtherConsumerLoansMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember
Real Estate Construction [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 45,562us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember		 45,925us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_RealEstateConstructionMember
Consumer Real Estate [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 146,220us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember		 144,719us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
Commercial Real Estate [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 297,138us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		 299,187us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
Commercial Non Real Estate [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 32,735us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember		 31,160us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember
Public Sector and IDA [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 41,361us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_PublicSectorAndIdaMember		 34,220us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_PublicSectorAndIdaMember
Consumer Non Real Estate [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 28,182us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember		 28,399us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerNonRealEstateMember
Pass [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 575,613us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember		 570,762us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_PassMember
Special Mention [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans 5,300us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember		 5,992us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_InternalCreditAssessmentAxis
= us-gaap_SpecialMentionMember
Classified Excluding Impaired [Member]    
Financing Receivable, Recorded Investment [Line Items]    
Non-impaired gross loans $ 10,285us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember		 $ 6,856us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
/ us-gaap_InternalCreditAssessmentAxis
= nksh_ClassifiedExcludingImpairedMember