XML 43 R61.htm IDEA: XBRL DOCUMENT v2.4.1.9
Note 5 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans (Details) - Troubled Debt Restructurings (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Financing Receivable, Modifications [Line Items]    
Number of contracts 5us-gaap_FinancingReceivableModificationsNumberOfContracts2 6us-gaap_FinancingReceivableModificationsNumberOfContracts2
Pre-modification outstanding principal balance $ 5,761us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2 $ 4,401us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Post-modification outstanding principal balance 5,843us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 [1] 4,576us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 [1]
Closed-end First Liens [Member] | Consumer Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of contracts 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember		 2us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
Pre-modification outstanding principal balance 126us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember		 453us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
Post-modification outstanding principal balance 143us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember		 [1] 525us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndFirstLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember		 [1]
Multifamily Real Estate [Member] | Commercial Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of contracts 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_MultifamilyRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		  
Pre-modification outstanding principal balance 2,484us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_MultifamilyRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		  
Post-modification outstanding principal balance 2,484us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_MultifamilyRealEstateMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		 [1]  
Commercial Real Estate, Owner Occupied [Member] | Commercial Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of contracts 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
Pre-modification outstanding principal balance 184us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		 154us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
Post-modification outstanding principal balance 208us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		 [1] 239us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		 [1]
Commercial Real Estate, Non Owner Occupied [Member] | Commercial Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of contracts 2us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateNonOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		 1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateNonOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
Pre-modification outstanding principal balance 2,967us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateNonOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		 3,500us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateNonOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
Post-modification outstanding principal balance 3,008us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateNonOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		 [1] 3,500us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialRealEstateNonOwnerOccupiedMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember		 [1]
Closed-end Junior Liens [Member] | Consumer Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of contracts   1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndJuniorLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
Pre-modification outstanding principal balance   262us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndJuniorLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
Post-modification outstanding principal balance   267us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_ClosedEndJuniorLiensMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember		 [1]
Commercial and Industrial [Member] | Commercial Non Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of contracts   1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember
Pre-modification outstanding principal balance   32us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember
Post-modification outstanding principal balance   $ 45us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= nksh_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialNonRealEstateMember		 [1]
Consumer Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of contracts   2us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_ConsumerRealEstateMember
Commercial Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Number of contracts   1us-gaap_FinancingReceivableModificationsNumberOfContracts2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= nksh_CommercialRealEstateLoansMember
[1] Post-modification outstanding recorded investment considers amounts immediately following the modification. Amounts do not reflect balances at the end of the period.