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Note 5 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans (Details) - Past Due and Nonaccrual Loans (USD $) In Thousands, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | $ 2,447 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue | $ 2,956 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue
90 or more days past due | 2,302 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue | 6,268 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue
90 or more days past due and still accruing | 207 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing | 190 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing
Nonaccrual loans (including impaired nonaccruals) | 9,287 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus | 6,584 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
Construction Residential [Member] | Real Estate Construction [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due |  | 45 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ConstructionResidentialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_RealEstateConstructionMember
Construction Other [Member] | Real Estate Construction [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | 28 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ConstructionOtherMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_RealEstateConstructionMember | 45 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ConstructionOtherMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_RealEstateConstructionMember
Equity Lines [Member] | Consumer Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | 25 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_EquityLinesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember |
Closed-end First Liens [Member] | Consumer Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | 719 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndFirstLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember | 903 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndFirstLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember
90 or more days past due | 185 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndFirstLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember | 252 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndFirstLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember
90 or more days past due and still accruing | 80 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndFirstLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember | 128 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndFirstLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember
Nonaccrual loans (including impaired nonaccruals) | 105 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndFirstLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember | 308 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndFirstLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember
Closed-end Junior Liens [Member] | Consumer Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | 74 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndJuniorLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember | 10 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndJuniorLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember
90 or more days past due | 1 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndJuniorLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember |
90 or more days past due and still accruing | 1 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_ClosedEndJuniorLiensMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember |
Investor-owned Residential Real Estate [Member] | Consumer Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | 336 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_InvestorOwnedResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember |
90 or more days past due | 45 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_InvestorOwnedResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember |
Nonaccrual loans (including impaired nonaccruals) | 59 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_InvestorOwnedResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerRealEstateMember |
Investor-owned Residential Real Estate [Member] | Commercial Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due |  | 422 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_InvestorOwnedResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember
90 or more days past due |  | 91 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_InvestorOwnedResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember
Nonaccrual loans (including impaired nonaccruals) |  | 91 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_InvestorOwnedResidentialRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember
Multifamily Real Estate [Member] | Commercial Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | 850 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_MultifamilyRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember | 430 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_MultifamilyRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember
90 or more days past due | 868 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_MultifamilyRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember | 3,278 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_MultifamilyRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember
Nonaccrual loans (including impaired nonaccruals) | 2,735 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_MultifamilyRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember | 3,278 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_MultifamilyRealEstateMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember
Commercial Real Estate, Owner Occupied [Member] | Commercial Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due |  | 604 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialRealEstateOwnerOccupiedMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember
90 or more days past due | 1,066 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialRealEstateOwnerOccupiedMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember | 2,519 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialRealEstateOwnerOccupiedMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember
90 or more days past due and still accruing | 102 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialRealEstateOwnerOccupiedMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember |
Nonaccrual loans (including impaired nonaccruals) | 2,573 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialRealEstateOwnerOccupiedMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember | 2,756 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialRealEstateOwnerOccupiedMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember
Commercial Real Estate, Other [Member] | Commercial Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due |  | 32 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialRealEstateOtherMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember
90 or more days past due | 70 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialRealEstateOtherMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember |
Nonaccrual loans (including impaired nonaccruals) | 3,066 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialRealEstateOtherMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialRealEstateLoansMember |
Commercial and Industrial [Member] | Commercial Non Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | 153 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialNonRealEstateMember | 196 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialNonRealEstateMember
90 or more days past due | 43 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialNonRealEstateMember | 43 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialNonRealEstateMember
Nonaccrual loans (including impaired nonaccruals) | 749 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialNonRealEstateMember | 128 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_CommercialAndIndustrialMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_CommercialNonRealEstateMember
Credit Card Receivable [Member] | Consumer Non Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | 3 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CreditCardReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember | 3 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CreditCardReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember
90 or more days past due | 4 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CreditCardReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember | 13 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CreditCardReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember
90 or more days past due and still accruing | 4 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CreditCardReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember | 13 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = us-gaap_CreditCardReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember
Automobile [Member] | Consumer Non Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | 205 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_AutomobileMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember | 217 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_AutomobileMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember
90 or more days past due | 20 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_AutomobileMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember | 26 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_AutomobileMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember
90 or more days past due and still accruing | 20 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_AutomobileMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember | 2 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_AutomobileMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember
Nonaccrual loans (including impaired nonaccruals) |  | 23 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_AutomobileMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember
Other Consumer Loans [Member] | Consumer Non Real Estate [Member] |  |
Financing Receivable, Recorded Investment, Past Due [Line Items] |  |
30 – 89 days past due | 54 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_OtherConsumerLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember | 49 nksh_FinancingReceivableRecordedInvestment30To89DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_OtherConsumerLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember
90 or more days past due |  | 46 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_OtherConsumerLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember
90 or more days past due and still accruing |  | $ 47 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis = nksh_OtherConsumerLoansMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = nksh_ConsumerNonRealEstateMember

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