75000 - Document - Document And Entity Information
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75010 - Statement - Consolidated Balance Sheets
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75020 - Statement - Consolidated Balance Sheets (Parentheticals)
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75030 - Statement - Consolidated Statements of Income
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75040 - Statement - Consolidated Statements of Comprehensive Income
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75050 - Statement - Consolidated Statements of Comprehensive Income (Loss) (Parentheticals)
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75060 - Statement - Consolidated Statements of Changes in Stockholders' Equity
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75070 - Statement - Consolidated Statements of Changes in Stockholders' Equity (Parentheticals)
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75080 - Statement - Consolidated Statements of Cash Flow
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75090 - Disclosure - Cybersecurity Risk Management, Strategy and Governance
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995455 - Disclosure - Note 1 - Summary of Significant Accounting Policies
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995465 - Disclosure - Note 2 - Restriction on Cash
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995475 - Disclosure - Note 3 - Securities
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995485 - Disclosure - Note 4 - Related Party Transactions
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995495 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets
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995505 - Disclosure - Note 6 - Premises and Equipment
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995515 - Disclosure - Note 7 - Deposits
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995525 - Disclosure - Note 8 - Employee Benefit Plans
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995535 - Disclosure - Note 9 - Income Taxes
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995545 - Disclosure - Note 10 - Restrictions on Dividends
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995555 - Disclosure - Note 11 - Minimum Regulatory Capital Requirement
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995565 - Disclosure - Note 12 - Condensed Financial Statements of Parent Company
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995575 - Disclosure - Note 13 - Financial Instruments With Off-balance Sheet Risk
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995585 - Disclosure - Note 14 - Concentrations of Credit Risk
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995595 - Disclosure - Note 15 - Fair Value Measurements
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995605 - Disclosure - Note 16 - Components of Accumulated Other Comprehensive Loss
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995615 - Disclosure - Note 17 - Goodwill and Other Intangibles
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995625 - Disclosure - Note 18 - Revenue Recognition
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995635 - Disclosure - Note 19 - Leases
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995645 - Disclosure - Note 20 - Stock Based Compensation
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995655 - Disclosure - Note 21 - Earnings Per Share
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995665 - Disclosure - Note 22 - Business Combination
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995675 - Disclosure - Significant Accounting Policies (Policies)
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995685 - Disclosure - Note 3 - Securities (Tables)
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995695 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets (Tables)
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995705 - Disclosure - Note 6 - Premises and Equipment (Tables)
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995715 - Disclosure - Note 7 - Deposits (Tables)
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995725 - Disclosure - Note 8 - Employee Benefit Plans (Tables)
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995735 - Disclosure - Note 9 - Income Taxes (Tables)
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995745 - Disclosure - Note 11 - Minimum Regulatory Capital Requirement (Tables)
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995755 - Disclosure - Note 12 - Condensed Financial Statements of Parent Company (Tables)
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995765 - Disclosure - Note 13 - Financial Instruments With Off-balance Sheet Risk (Tables)
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995775 - Disclosure - Note 15 - Fair Value Measurements (Tables)
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995785 - Disclosure - Note 16 - Components of Accumulated Other Comprehensive Income (Loss) (Tables)
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995795 - Disclosure - Note 17 - Goodwill and Other Intangibles (Tables)
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995805 - Disclosure - Note 18 - Revenue Recognition (Tables)
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995815 - Disclosure - Note 19 - Leases (Tables)
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995825 - Disclosure - Note 20 - Stock Based Compensation (Tables)
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995835 - Disclosure - Note 21 - Earnings Per Share (Tables)
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995845 - Disclosure - Note 22 - Business Combination (Tables)
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995855 - Disclosure - Note 1 - Summary of Significant Accounting Policies (Details Textual)
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995865 - Disclosure - Note 3 - Securities (Details Textual)
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995875 - Disclosure - Note 3 - Securities - Securities Available-for-sale (Details)
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995885 - Disclosure - Note 3 - Securities - Securities by Contractual Maturity (Details)
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995895 - Disclosure - Note 3 - Securities - Securities in a Continuous Loss Position (Details)
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995905 - Disclosure - Note 3 - Securities - Realized Gains and Losses From Calls of Securities (Details)
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995915 - Disclosure - Note 4 - Related Party Transactions (Details Textual)
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995925 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets (Details Textual)
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995935 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Allowance for Loan Losses (Details)
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995945 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Loans and Allowance for Loan Losses by Evaluation Method (Details)
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995955 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Ratios of Allowance for Loan Losses (Details)
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995965 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Past Due and Nonaccrual Loans (Details)
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995975 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Details of the Collateral Dependent Loan (Details)
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995985 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Loans by Credit Quality Indicators (Details)
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995995 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Financing Receivable, Troubled Debt Restructurings (Details)
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996005 - Disclosure - Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Allowance for Credit Losses on Unfunded Commitments (Details)
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996015 - Disclosure - Note 6 - Premises and Equipment (Details Textual)
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996025 - Disclosure - Note 6 - Premises and Equipment - Premises and Equipment (Details)
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996035 - Disclosure - Note 7 - Deposits (Details Textual)
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996045 - Disclosure - Note 7 - Deposits - Maturities of Time Deposits (Details)
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996055 - Disclosure - Note 8 - Employee Benefit Plans (Details Textual)
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996065 - Disclosure - Note 8 - Employee Benefit Plans - Defined Benefit Plan Activity (Details)
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996075 - Disclosure - Note 8 - Employee Benefit Plans- Components of Actuarial (Gain) Loss (Details)
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996085 - Disclosure - Note 8 - Employee Benefit Plans - Fair Value Measurements (Details)
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996095 - Disclosure - Note 8 - Employee Benefit Plans - Expected Future Benefit Payments (Details)
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996105 - Disclosure - Note 9 - Income Taxes (Details Textual)
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996115 - Disclosure - Note 9 - Income Taxes - Allocation of Income Tax Expense (Details)
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996125 - Disclosure - Note 9 - Income Taxes - Reconciliation of Expected Income Tax Expense With Reported Income Tax Expense (Details)
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996135 - Disclosure - Note 9 - Income Taxes - Components of Net Deferred Tax Assets (Details)
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996145 - Disclosure - Note 10 - Restrictions on Dividends (Details Textual)
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996155 - Disclosure - Note 11 - Minimum Regulatory Capital Requirement (Details Textual)
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996165 - Disclosure - Note 11 - Minimum Regulatory Capital Requirement - Minimum Capital Requirements (Details)
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996175 - Disclosure - Note 12 - Condensed Financial Statements of Parent Company - Condensed Balance Sheets (Details)
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996185 - Disclosure - Note 12 - Condensed Financial Statements of Parent Company - Condensed Statements of Income (Details)
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996195 - Disclosure - Note 12 - Condensed Financial Statements of Parent Company - Condensed Statements of Cash Flows (Details)
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996205 - Disclosure - Note 13 - Financial Instruments With Off-balance Sheet Risk (Details Textual)
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996215 - Disclosure - Note 13 - Financial Instruments With Off-balance Sheet Risk - Financial Instruments Outstanding Representing Credit Risk (Details)
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996225 - Disclosure - Note 14 - Concentrations of Credit Risk (Details Textual)
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996235 - Disclosure - Note 15 - Fair Value Measurements (Details Textual)
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996245 - Disclosure - Note 15 - Fair Value Measurements - Assets and Liabilities at Fair Value on Recurring Basis (Details)
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996255 - Disclosure - Note 15 - Fair Value Measurements - Impaired Loans and Other Real Estate Owned Measured at Fair Value on Nonrecurring Basis (Details)
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996265 - Disclosure - Note 15 - Fair Value Measurements - Financial Instruments (Details)
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996275 - Disclosure - Note 16 - Components of Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Details)
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996285 - Disclosure - Note 16 - Components of Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Details) (Parentheticals)
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996295 - Disclosure - Note 16 - Components of Accumulated Other Comprehensive Income (Loss) - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Details)
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996305 - Disclosure - Note 17 - Goodwill and Other Intangibles (Details Textual)
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996315 - Disclosure - Note 17 - Goodwill and Other Intangibles - Components of Goodwill and Other Intangible Assets (Details)
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996325 - Disclosure - Note 17 - Goodwill and Other Intangibles - Schedule of Finite-Lived Intangible Assets, Future Amortization Expense (Details)
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996335 - Disclosure - Note 18 - Revenue Recognition - Noninterest Income (Details)
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996345 - Disclosure - Note 19 - Leases (Details Textual)
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996355 - Disclosure - Note 19 - Leases - Lease Information and Expenses (Details)
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996365 - Disclosure - Note 19 - Leases - Lease Liability Maturity Schedule (Details)
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996375 - Disclosure - Note 19 - Leases - Lease Liability Maturity Schedule (Details) 2
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996385 - Disclosure - Note 20 - Stock Based Compensation (Details Textual)
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996395 - Disclosure - Note 20 - Stock Based Compensation - Summary of Nonvested Shares (Details)
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996405 - Disclosure - Note 21 - Earnings Per Share - Schedule of Earnings Per Share (Details)
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996415 - Disclosure - Note 22 - Business Combination - (Details Textual)
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996425 - Disclosure - Note 22 - Business Combination - Schedule of Business Acquisitions (Details)
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Book value of available-for-sale securities that were called during the period.
Sale of Available for Sale Securities, book value
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value
Vested and released, weighted average grant date fair value (in dollars per share)
Business Combination, Acquisition-Related Cost, Expense
Merger-related expense
us-gaap_IncreaseDecreaseInInterestPayableNet
Accrued interest payable
Proceeds from Sale of Property, Plant, and Equipment
Proceeds from Sale of Property, Plant, and Equipment, Total
Proceeds from sale of premises and equipment
Retirement Plan Type [Axis]
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Percentage
Financing Receivables [Text Block]
Allowance for Credit Losses on Loans and Nonperforming Assets
Concentration Risk Type [Axis]
Loans charged against the allowance for credit losses
Charge-offs
Financing Receivable, Allowance for Credit Loss, Writeoff, Total
Loans charged against the allowance for credit losses
us-gaap_DefinedBenefitPensionPlanLiabilitiesCurrent
Benefit obligation
us-gaap_FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear
Originated three years prior
Deferred tax assets:
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]
Entity Incorporation, State or Country Code
Preferred stock, shares issued (in shares)
Defined Benefit Plan, Plan Assets, Contributions by Employer
Employer contribution
Supplemental Disclosures of Noncash Activities
Supplemental Disclosure of Noncash Activities
Fair value, due in one year or less, available for sale securities
Financing Receivable Portfolio Segment [Axis]
Plan Name [Axis]
Temporarily impaired securities, 12 months or more fair value
Entity Current Reporting Status
us-gaap_OtherCommitment
Other Commitment
Class of Financing Receivable [Axis]
US Government Agencies Debt Securities [Member]
Fair Value, Inputs, Level 2 [Member]
Common stock, shares authorized (in shares)
Finite-Lived Intangible Asset, Expected Amortization, Year Four
2029
Unrealized holding gain (loss) on available for sale securities, tax
us-gaap_AssetsFairValueAdjustment
Assets, Fair Value Adjustment
Product and Service [Axis]
Document Fiscal Period Focus
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
2031 - 2035
Represents the number days of delinquent loans for interest accrual to be discontinued.
nksh_NumberOfDaysOfDelinquentLoansNonaccrualOfInterest
Number of Days of Delinquent Loans Nonaccrual of Interest (Year)
Expected return on plan assets
Prepaid benefit cost included in other assets
Prepaid pension cost included in other assets
Entity Shell Company
Refers to information regarding insurance and investment.
Insurance and Investment [Member]
Minimum pension liability adjustment
Segment Reporting, Policy [Policy Text Block]
Segment Reporting
Cash and Cash Equivalent
Total cash and cash equivalents
Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets
us-gaap_DefinedBenefitPlanBenefitObligation
Projected benefit obligation at end of year
Projected benefit obligation at beginning of year
Condensed Financial Information Disclosure [Abstract]
Amount of asset (liability), recognized in statement of financial position, for overfunded defined benefit pension and other postretirement plans.
nksh_AssetsLiabilitiesForPlanBenefitsDefinedBenefitPlan
Deferred tax liabilities
Note 18 - Revenue Recognition - Noninterest Income (Details)
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
2027
Cybersecurity Risk Management, Strategy, and Governance [Abstract]
Common stock, shares issued (in shares)
Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag]
Cybersecurity Risk Board of Directors Oversight [Text Block]
Asset Class [Domain]
Statement [Table]
Changes Measurement [Member]
Right-of-use assets obtained in exchange for operating lease liabilities commencing during the period
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability
Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Allowance for Credit Losses on Unfunded Commitments (Details)
Accrued interest receivable
Age required to diversify allocated Employee Stock Ownership Plan (ESOP) shares.
nksh_AgeOfEmployeesRequiredToDiversifyAllocatedEsopShares
Age of Employees Required to Diversify Allocated ESOP Shares (Year)
us-gaap_LoansAndLeasesReceivableRelatedPartiesAdditions
Loans and Leases Receivable, Related Parties, Additions
us-gaap_LoansAndLeasesReceivableRelatedPartiesProceeds
Loans and Leases Receivable, Related Parties, Proceeds
Cash paid in acquisition
Payments to Acquire Businesses, Gross
Cash consideration (2)
Offsetting Assets [Table]
us-gaap_FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear
Originated five years prior
Represents reported by FCB.
Reported by FCB [Member]
Defined Benefit Plan Benefit Obligation Actuarial Gain Loss Due to Change in Rate of Compensation Increase
Defined benefit plan benefit obligation actuarial gain loss due to change in rate of compensation increase.
Loss due to change in rate of compensation increase
Statement [Line Items]
Aggregate amortization expense
Aggregate amortization expense.
Business Combination [Domain]
Tier 1 capital (to risk weighted assets), actual, amount
The maximum number of days consumer loans are past due for losses on such loans to be written off.
nksh_MaximumNumberOfDaysConsumerLoansArePastDueForLossesToBeChargedOff
Maximum Number of Days Consumer Loans are Past Due for Losses to be Charged Off (Day)
Entity Filer Category
Reclassification, Comparability Adjustment [Policy Text Block]
Reclassifications
Derivative Asset, Measurement Input
This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This element represents the fair value of other real estate owned by bank.
Other real estate owned net of valuation allowance
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement
Settlement gain
Settlement gain
us-gaap_LiabilitiesAndStockholdersEquity
Total liabilities and stockholders’ equity
Recoveries
Credit Concentration Risk [Member]
us-gaap_NoninterestIncome
Total noninterest income
Long-Lived Tangible Asset [Axis]
Fair Value, by Balance Sheet Grouping [Table Text Block]
Cybersecurity Risk Third Party Oversight and Identification Processes [Flag]
Financial Instruments Disclosure [Text Block]
Tier 1 capital (to average assets), actual, amount
us-gaap_MortgageLoansOnRealEstateCostOfMortgagesSold
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Cost of Mortgage Sold
us-gaap_DeferredTaxAssetsValuationAllowance
Deferred Tax Assets, Valuation Allowance
Notes Tables
Notes Tables
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent
Computed "expected" income tax expense, Percent
Nondeductible interest expense, Amount
Tax-exempt interest income, Amount
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount, Total
Gross loans
Loans, gross
Loans
Total loans
Cybersecurity Risk Management Third Party Engaged [Flag]
Documents Incorporated by Reference [Text Block]
Goodwill
Goodwill
Goodwill, Net Carrying Amount
Goodwill
Goodwill
Goodwill
Reported income tax expense, Percent
Effective Income Tax Rate Reconciliation, Percent
Income Taxes Paid
Income taxes paid
Derivative Liability, Measurement Input
Amount of increase in allowance for credit loss on financing receivable from loan acquired from business combination or acquisition.
FCB acquisition
Note 19 - Leases - Lease Information and Expenses (Details)
Amortized cost, due after ten years, available for sale securities
us-gaap_StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithoutRegulatoryApproval
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval
us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsGoodwill
Goodwill
Proceeds from Sale of Other Assets, Investing Activities
Proceeds from sale of repossessed assets
us-gaap_DefinedBenefitPlanPlanAssetsBenefitsPaid
Benefits paid
Percentage of unallocated surplus.
nksh_UnallocatedSurplusPercent
Unallocated Surplus Percent
Significant Accounting Policies [Text Block]
Summary of Significant Accounting Policies
Property, Plant and Equipment [Line Items]
Ratio of ACLL to the end of period loans, net of deferred fees and costs
Estimated useful life
Finite-Lived Intangible Asset, Useful Life
Concentration Risk [Table]
Number of financing receivables that have been modified by troubled debt restructurings.
Commercial Real Estate, Owner Occupied [Member]
us-gaap_RiskWeightedAssets
Banking Regulation, Risk-Weighted Assets, Actual
us-gaap_DepositsFairValueDisclosure
Deposits
Cybersecurity Risk Management, Strategy, and Governance [Table]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Equity Securities [Member]
Amount of actuarial gain loss with asset return for benefit obligation of defined benefit plan.
nksh_DefinedBenefitPlanBenefitObligationActuarialGainLossWithAssetReturn
Actuarial (gain) loss with asset return
Actuarial gain with asset return
Special Mention [Member]
Concentration Risk Disclosure [Text Block]
Percentage Of Ownership Acquired
The percentage of ownership of common stock or equity participation in the investee accounted for under the acquistion.
Percentage of ownership acquired
Represents ratio of net charge-offs to average loans, net of unearned income and deferred fees.
Ratio of net charge-offs to average loans, net of deferred fees and costs
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount [Abstract]
Nondeductible or nontaxable items
Investments Classified by Contractual Maturity Date [Table Text Block]
Basic net income per common share (in dollars per share)
Disaggregation of Revenue [Table Text Block]
Equity Funds [Member]
Retirement Benefits [Text Block]
Discount rate used for disclosure
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property
(Gain) loss on disposal of premises and equipment, net
Amount of deferred tax liability attributable to discount accretion of securities.
nksh_DeferredTaxLiabilitiesDiscountAccretionOfSecurities
Discount accretion of securities
Nonaccruals, no allowance
Core deposit intangible, Additions
Finite-Lived Intangible Assets Acquired
Core deposit intangible additional
Retirement Plan Type [Domain]
amortized cost
Financing Receivable, Modified, Accumulated
Financing Receivable, Revolving, Converted to Term Loan, Writeoff
Revolving loans converted to term, write offs
Adjustments to reconcile net income to net cash provided by operating activities:
us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive
Twelve months ending December 31, 2030
Maximum Loan amount indicated as risk graded
Maximum loan amount indicated as risk graded.
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Deposits
The amount of deposits assumed (as defined) which have been recognized as of the acquisition date.
Deposits
us-gaap_CashUninsuredAmount
Cash, Uninsured Amount
Interest on interest-bearing deposits
Interest Income, Deposits with Financial Institutions, Total
Financing Receivable, Allowance for Credit Loss [Line Items]
Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.
nksh_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment
Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan due to mortality table. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.
nksh_DefinedBenefitPlanBenefitObligationActuarialGainLossDueToChangesInMortality
Gain due to change in mortality table
Proceeds from calls, sales and maturities of securities available for sale
Parent Company [Member]
Conversion Expense
Conversion expense.
Core system conversion expense
Accounting Standards Update [Axis]
Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Details of the Collateral Dependent Loan (Details)
Stockholders’ equity:
Entity Small Business
Interest Income
Valuation, Market Approach [Member]
Retained earnings
Retained Earnings (Accumulated Deficit)
Funded status at the end of the year
Financing Receivable, Nonaccrual [Table Text Block]
Disclosure of accounting policy for rate lock commitments.
Rate Lock Commitments [Policy Text Block]
Rate Lock Commitments
Entity Well-known Seasoned Issuer
Note To Financial Statement Details Textual
Note To Financial Statement Details Textual
Share-Based Payment Arrangement [Text Block]
Disaggregation of Income Statement Expense, Caption [Line Items]
us-gaap_PaymentsOfDividends
Cash dividends paid
Assets acquired
Noncash or Part Noncash Acquisition, Value of Assets Acquired
Noncash or Part Noncash Acquisition, Value of Assets Acquired, Total
Amendment Flag
Interest and dividends on securities – taxable
Interest on securities - taxable
Product and Service [Domain]
Represents restricted stock award.
Restricted Stock Award [Member]
Computed "expected" income tax expense, Amount
Earnings Per Share, Policy [Policy Text Block]
Earnings Per Common Share
Number of days loans secured by residential or commercial real estate are past due for losses to be written off.
nksh_NumberOfDaysLoansSecuredByResidentialOrCommercialRealEstateArePastDueForLossesToBeCargedOff
Number of Days Loans Secured by Residential Or Commercial Real Estate Are Past Due for Losses to Be Carged Off (Day)
Defined Benefit Plan, Equity Securities, US [Member]
Concentration Risk [Line Items]
The shortfall in plan assets.
Fair value of assets
Liabilities and Stockholders’ Equity
Entity Address, Postal Zip Code
us-gaap_NetCashProvidedByUsedInOperatingActivities
Net cash provided by operating activities
Ratio of minimum Tier 1 risk-based capital to risk-weighted assets required for capital requirement as defined by regulatory framework.
Tier 1 capital (to risk weighted assets), minimum capital requirement, ratio
Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description
Cybersecurity Risk Role of Management [Text Block]
us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Defined Contribution Plan, Employer Discretionary Contribution Amount
Disaggregation of Income Statement Expense, Caption [Table]
Number of renewed leases
Number of renewed leases
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block]
us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree
Twelve months ending December 31, 2028
us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
Accumulated depreciation
us-gaap_DividendIncomeOperating
Dividends from subsidiaries
Financing Receivable, Held-for-Investment [Policy Text Block]
Loans
Valuation Technique Fair Value of Collateral Method [Member]
Valuation technique fair value of collateral method.
Valuation Technique, Fair Value of Collateral Method [Member]
Collection of loan participations
Portion at Fair Value Measurement [Member]
Portion at Fair Value Measurement [Member] [Default]
Entity Address, Address Line One
us-gaap_DeferredIncomeTaxLiabilities
Total deferred tax liabilities
Marketable Securities [Table]
Fair Value Hierarchy and NAV [Axis]
Earnings Per Share [Abstract]
Income Tax, Policy [Policy Text Block]
Income Taxes
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag]
Supplemental Disclosures of Cash Flow Information
Represents commercial real estate other.
Commercial Real Estate Other [Member]
Derivative Asset
Goodwill and Intangible Assets Disclosure [Text Block]
Goodwill and Other Intangibles
Tier 1 capital (to average assets), actual, ratio
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
2029
Amount of gain (loss) due to demographic changes from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.
nksh_DefinedBenefitPlanBenefitObligationActuarialGainLossDueToDemographicChanges
Loss (gain) due to change in discount rate
Interest on securities – nontaxable
Net change in other deposits
Fair Value Measurements, Nonrecurring [Table Text Block]
Represents residential real estate loans.
Residential Real Estate Loans [Member]
us-gaap_OperatingLeaseRightOfUseAsset
Right-of-use asset
us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition
Debt Securities, Available-for-Sale, Unrealized Loss Position
Defined Benefit Plan, Plan Assets, Category [Domain]
us-gaap_DeferredTaxAssetsGross
Total deferred tax assets
Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block]
Financing Receivable, Originated, More than Five Years before Current Fiscal Year, Writeoff
Originated more than five years prior, write-offs
Payments to Acquire Debt Securities, Available-for-Sale
Purchases of available for sale securities
Franchise taxes
Document Type
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Goodwill and Intangible Assets, Policy [Policy Text Block]
Goodwill
Loans, individually evaluated
Income taxes paid
Income taxes
Collaborative Arrangement and Arrangement Other than Collaborative [Axis]
Commitments to Extend Credit [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Domain]
Entity Central Index Key
Tier 1 capital (to average assets), minimum to be well capitalized, amount
Debt Securities, Available-for-Sale [Table Text Block]
us-gaap_TimeDepositMaturitiesAfterYearFive
Thereafter
Investments, Debt and Equity Securities [Abstract]
Maturities of Time Deposits [Abstract]
Interest-bearing deposits
us-gaap_LoansAndLeasesReceivableRelatedParties
Loans and Leases Receivable, Related Parties
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax
Amortization of prior service cost
Valuation Approach and Technique [Axis]
us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect
Net change in cash and cash equivalents
The allowance for credit loss for loans recognized as of the acquisition date.
nksh_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAllowanceForCreditLossOnLoans
Allowance for credit losses on loans
Summary of Significant Accounting Policies [Line Items]
Summary of significant accounting policies.
Condensed Balance Sheet [Table Text Block]
us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)
Goodwill and Core Deposit Intangible Assets [Line Items]
Goodwill and core deposit intangible assets.
Accretion of fair value of acquired loans
Accretion of fair value of acquired loans.
Common stock, par value (in dollars per share)
Accounting Standards Update [Domain]
Common equity tier 1 capital (to risk weighted assets), actual, amount
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed, Total
Liabilities assumed
Net change in other liabilities
Other liabilities
Securities available-for-sale, amortized costs
Amortized cost, total securities available for sale
Securities available-for-sale, fair values
Securities available for sale, at fair value
Fair value, total securities available for sale
Securities available for sale
The minimum amount of common equity tier 1 capital required for capital adequacy purposes under the regulatory framework for prompt corrective action.
Common equity tier 1 capital (to risk weighted assets), minimum capital requirement, ratio
Noninterest Income:
Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Loans and Allowance for Loan Losses by Evaluation Method (Details)
Document Financial Statement Error Correction [Flag]
Represents collectively evaluated for impairment.
Collectively Evaluated [Member]
Deferred Tax Liabilities Fair Value Adjustments For Acquired Assets
Deferred tax liabilities fair value adjustments for acquired assets.
Fair value adjustments for acquired assets
Supplemental Cash Flow Elements [Abstract]
Cash payments for:
Reclassification out of Accumulated Other Comprehensive Income [Axis]
Estimate of Fair Value Measurement [Member]
Hedge Funds [Member]
Financial Instrument Performance Status [Domain]
Net change in time deposits
Interest Income, Federal Funds Sold
Interest on federal funds sold
Current Fiscal Year End Date
Fair Value Assets And Liabilities Measured On Recurring Basis [Table]
Fair value assets and liabilities measured on recurring basis table.
Actual return on plan assets
Value of loans transferred to repossessed assets.
Loans transferred to repossessed assets
Unrealized holding gain on securities available for sale
us-gaap_GainsLossesOnSalesOfOtherRealEstate
Gain on other real estate owned
Gain on sale of OREO (2)
Number of shares of common stock unvested.
Common stock, shares unvested (in shares)
Advertising Cost [Policy Text Block]
Advertising
Unallocated Financing Receivables [Member]
Unallocated Financing Receivables [Member]
Entity Address, State or Province
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Nonvested, shares (in shares)
Nonvested, shares (in shares)
Data processing and ATM
Data processing
Financial Instrument Performance Status [Axis]
Schedule of Business Acquisitions, by Acquisition
Business Combination [Table Text Block]
Schedule of Business Acquisitions, by Acquisition [Table Text Block]
Preferred stock, shares outstanding (in shares)
us-gaap_ComprehensiveIncomeNetOfTax
Total Comprehensive Income
Securities available-for-sale, gross unrealized gains
Deferred Tax Liabilities Core Deposit Intangibles
Deferred tax liabilities core deposit intangibles.
Core deposit intangibles
Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Financing Receivable, Troubled Debt Restructurings (Details)
Consulting Agreement [Member]
Consulting Agreement [Member]
Dilutive shares for restricted stock awards: (in shares)
Credit Card Receivable [Member]
us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet
Accrued interest receivable
The gross realized loss on available-for-sale securities that were called during the period.
Sale of Available for Sale Securities, gross loss
Internal Credit Assessment [Axis]
Period of restrictions on banking or savings institution's ability to pay dividends.
nksh_PeriodOfRestrictionOnRetainedNetIncomeWithoutPriorApproval
Period of Restriction on Retained Net Income Without Prior Approval (Year)
Other, net, Amount
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Amount
Professional services
Comprehensive Income, Policy [Policy Text Block]
Comprehensive Income
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]
Amount of gain loss due to asset return for benefit obligation of defined benefit plan
nksh_DefinedBenefitPlanBenefitObligationGainLossDueToAssetReturn
Gain due to asset return
Amount of liability (asset), recognized in statement of financial position, for defined benefit pension plan. Excludes other postretirement benefit plan.
nksh_LiabilityAssetDefinedBenefitPensionPlan
Other assets
us-gaap_TimeDepositMaturitiesYearFive
2030
Other Comprehensive Income, Net of Tax
Financing Receivable, Allowance for Credit Loss, Purchased with Credit Deterioration, Increase
Merger adjustment
Financing receivables that are more than 29 days past due but fewer than 90 days past due.
Financing Receivables 30 to 89 Days Past Due [Member]
Marketable Securities, Policy [Policy Text Block]
Securities
Property, Plant and Equipment [Abstract]
Total interest expense
Interest Expense, Operating
us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss
Net interest income after (recovery of) provision for credit losses
Gain on Sale of Other Real Estate Owned [Member]
Gain on sale of other real estate owned.
Gain on Sale of OREO [Member]
Product and Service, Other [Member]
Proceeds from Sale of Debt Securities, Available-for-Sale
Proceeds from Sale of Debt Securities, Available for Sale
Common equity tier 1 capital (to risk weighted assets), actual, ratio
The period during which the mortgagor defaults after the sale of loans to the investor.
nksh_PotentialDefaultPeriodAfterSaleOfLoansToInvestor
Potential Default Period After Sale of Loans to Investor (Month)
Related Party Transaction [Axis]
Represents residential closed-end junior liens.
Closed End Junior Liens [Member]
AOCI Attributable to Parent [Member]
Derivative Liability
Finite-Lived Intangible Assets, Major Class Name [Domain]
Cash [Member]
us-gaap_GoodwillImpairmentLoss
Goodwill, Impairment Loss
Finite-Lived Intangible Asset, Expected Amortization, after Year Five
Thereafter
Net (gain) loss
Unrecognized net actuarial (gain) loss
Unrecognized net actuarial gain
us-gaap_BusinessCombinationConsiderationTransferred1
Business Combination, Consideration Transferred
Total purchase price consideration
The gross realized gain on available-for-sale securities that were called during the period.
Sale of Available for Sale Securities, gross gain
Noninterest-bearing demand deposits
Preferred stock, no par value, 5,000,000 shares authorized; none issued and outstanding
Preferred stock, no par value, 5,000,000 shares authorized; none issued and outstanding
Core deposit intangible
Business Combination, Recognized Asset Acquired, Identifiable Intangible Asset, Excluding Goodwill
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total
Core deposit intangible
Defined Benefit Plan, Equity Securities, Non-US [Member]
us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetTransitionAssetsObligationsAfterTax
Deferred tax (liability) asset
Reclassification out of Accumulated Other Comprehensive Income [Domain]
Payment of Outstanding and vested options settlement amount under business acquisition.
nksh_BusinessAcquisitionOutstandingAndVestedOptionsSettlementPayment
Business Acquisition, Outstanding and Vested Options Settlement Payment
Minimum [Member]
Granted, weighted average grant date fair value (in dollars per share)
us-gaap_RevenueNotFromContractWithCustomerExcludingInterestIncome
Noninterest Income (out-of-scope of Topic 606)
Financial Instrument [Axis]
us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue
Increase in cash value of bank-owned life insurance
SBA Fees
Deferred Tax Asset, SBA Fees
Deferred tax asset, SBA fees.
us-gaap_FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear
Originated two years prior
Other comprehensive income (loss), tax
Note 17 - Goodwill and Other Intangibles - Schedule of Finite-Lived Intangible Assets, Future Amortization Expense (Details)
Statement - statement - note - 12 - goodwill - and - other - intangibles - schedule - of - finitelived - intangible - assets - future - amortization - expense - details
Amortization of Intangible Assets
Intangible asset amortization
Amortization of core deposit intangible
Net unrealized loss on securities available for sale
Deferred Tax Asset, Debt Securities, Available-for-Sale, Unrealized Loss
Fair Value, Inputs, Level 3 [Member]
Fair Value, Nonrecurring [Member]
Total identifiable assets acquired
Business Combination, Recognized Asset Acquired, Asset
us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment
Premises and equipment
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]
Business Combination [Policy Text Block]
Business Combinations
Note 16 - Components of Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Details)
us-gaap_TimeDepositMaturitiesYearFour
2029
Amortization of fair value of acquired time deposits and leases
Amortization of fair value of acquired time deposits and leases.
Amortization of fair value of acquired time deposits and leases
Related Party Transactions [Abstract]
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities
Accrued expense
Income Tax Reconciliation Nondeductible merger related expenses
Income Tax Reconciliation Nondeductible merger related expenses
Nondeductible merger related expenses, Amount
Interest Expense
Other income
Other Income
Financial Asset Acquired and No Credit Deterioration [Member]
Commitments and contingencies
Service cost (1)
Service cost
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
Nonvested, weighted average grant date fair value (in dollars per share)
Nonvested, weighted average grant date fair value (in dollars per share)
Net pension gain (losses) arising during the period, tax
Net pension gain arising during the period, net of taxes
Lease liability
Goodwill, measurement adjustments
Auditor Firm ID
Loans, collectively evaluated
Deferred tax liability
Amount before allocation of valuation allowances of deferred tax asset (liability) attributable to deductible temporary differences from pension and other postretirement benefits.
Credit Loss Status [Axis]
us-gaap_EmployeeStockOwnershipPlanESOPNumberOfAllocatedShares
Employee Stock Ownership Plan (ESOP), Number of Allocated Shares (in shares)
Concentration Risk Benchmark [Axis]
us-gaap_DebtSecuritiesAvailableForSaleRestricted
Debt Securities, Available-for-Sale, Restricted
Number of loans acquired in business acquisition.
Number of loans
Number of loans
us-gaap_InterestAndDividendIncomeOperating
Total interest income
us-gaap_FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear
Originated more than five years prior
us-gaap_InterestIncomeExpenseNet
Net interest income
us-gaap_ProfitLoss
Income before equity (deficit) in undistributed net income of subsidiaries
Total Loans
Commercial real estate loans totaling
Financing Receivable, before Allowance for Credit Loss, Total
Business Combination, Recognized Asset Acquired, Cash and Cash Equivalent
Cash and cash equivalents
Loans 90 or more days past due and accruing
Nondeductible merger related expenses, Percent
Effective Income Tax Rate Reconciliation, Nondeductible Expense, merger related expenses, Percent
Effective Income Tax Rate Reconciliation, Nondeductible Expense, merger related expenses, Percent
Cybersecurity Risk Management Positions or Committees Responsible [Text Block]
us-gaap_RestrictedInvestmentsAtFairValue
Restricted stock, at cost
Common shares, basic (in shares)
Weighted Average Number of Shares Outstanding, Basic, Total
Weighted average number of common shares outstanding, basic (in shares)
Common shares weighted average outstanding, basic (in shares)
Goodwill, Acquired During Period
Goodwill addition
Amount of deferred fees and costs on loans recognized as of the acquisition date.
nksh_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredFeesAndCostsOnLoans
Deferred fees and costs on loans
Gain (Loss) on Securities [Table Text Block]
Scenario [Axis]
us-gaap_CashSurrenderValueFairValueDisclosure
Bank-owned life insurance
Note 19 - Leases - Lease Liability Maturity Schedule (Details)
Document Information [Line Items]
Scenario, Adjustment [Member]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]
us-gaap_DeferredTaxLiabilitiesLeasingArrangements
Lease accounting
Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table]
Temporarily impaired securities, 12 months or more unrealized loss
Long-Lived Tangible Asset [Domain]
us-gaap_InterestPayableCurrentAndNoncurrent
Accrued interest payable
Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]
us-gaap_LoansReceivableFairValueDisclosure
Loans, net
Tier 1 capital (to risk weighted assets), actual, ratio
Related Party Transactions Disclosure [Text Block]
Related Party Transactions
Percentage of Interest-Bearing Domestic Deposits to Deposits
Total deposits
us-gaap_DefinedBenefitPlanActuarialGainLoss
Actuarial loss (gain)(3)
Actuarial loss (gain)
Duration of interest only payment.
Commercial real estate owner-occupied (Month)
Stockholders’ equity
Balance
Balance
Total stockholders’ equity
Reclassification adjustment for gain included in net income, tax
Income tax benefit
Income tax benefit
Statement of Stockholders' Equity [Abstract]
Investments in subsidiaries
us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax
Unrealized holding gain on available for sale securities, tax
Valuation Approach and Technique [Domain]
Use of Estimates, Policy [Policy Text Block]
Use of Estimates
Interest on other deposits
Schedule of Nonvested Share Activity [Table Text Block]
Credit Loss, Financial Instrument [Policy Text Block]
Allowance for Credit Losses on Loans
Internal Credit Assessment [Domain]
Business Combination, Recognized Asset Acquired, Property, Plant, and Equipment
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment, Total
Premises and equipment
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Related allowance
Balance
Balance
Less allowance for credit losses
Related allowance, Total
Less: allowance for credit losses on loans
Less: allowance for credit losses on loans
Condensed Income Statement [Table Text Block]
Fair Value Disclosures [Text Block]
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from leases.
Lease accounting
Effective Income Tax Rate Reconciliation Nondeductible, Amortization of municipal bond premiums
Effective Income Tax Rate Reconciliation Nondeductible, Amortization of municipal bond premiums
Amortization of municipal bond premiums, Amount
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Information related to payments for architectural plans.
Payments for Architectural Plans [Member]
Extended Maturity [Member]
Tier 1 capital (to risk weighted assets), minimum to be well capitalized, amount
us-gaap_IncomeLossFromEquityMethodInvestments
(Equity) deficit in undistributed net income of subsidiaries
Equity (deficit) in undistributed net income of subsidiaries
(Equity) deficit in undistributed net income of subsidiaries
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]
Total capital (to risk weighted assets), minimum to be well capitalized, amount
Condensed Financial Information of Parent Company Only Disclosure [Text Block]
Plan Name [Domain]
us-gaap_IncreaseDecreaseInOtherOperatingAssets
Other assets
Increase Decrease In Borrowings
Increase decrease in borrowings.
Net change in borrowings
us-gaap_PaymentsForOriginationOfMortgageLoansHeldForSale
Payment for Origination, Loan, Mortgage, Held-for-Sale
Origination of mortgage loans held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Entity [Domain]
Building [Member]
Premises
Fair value, due after ten years, available for sale securities
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Text Block]
Valuation allowance on other real estate owned
Loan Restructuring Modification [Axis]
Schedule of Expected Benefit Payments [Table Text Block]
Cybersecurity Risk Management Expertise of Management Responsible [Text Block]
Proceeds from disposal of other real estate owned
Related Party, Type [Axis]
us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable
Net change in refundable income taxes due from subsidiaries
us-gaap_FinancingReceivableOriginatedInCurrentFiscalYear
Originated current year
Tabular disclosure of components of actuarial loss (gain) related to defined benefit plans.
Schedule of Defined Benefit Plans, Components of Actuarial (Gain) Loss [Table Text Block]
Collateral Held [Axis]
Pension Plan [Member]
Cash and due from banks
Financing Receivable, Past Due [Table Text Block]
Property, Plant and Equipment, Policy [Policy Text Block]
Premises and Equipment
Regulatory Capital Requirements under Banking Regulations [Text Block]
us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax
Net gain
Restrictions on Dividends, Loans and Advances [Text Block]
Entity Address, City or Town
Stock repurchase, shares (in shares)
us-gaap_DepositLiabilitiesReclassifiedAsLoansReceivable1
Deposit Liabilities Reclassified as Loans Receivable
Price of a single share for cash payment of fractional shares and option settlement under business acquisition.
nksh_BusinessAcquisitionSharePriceForCashPaymentOfFractionalSharesAndOptionSettlement
Business Acquisition, Share Price for Cash Payment of Fractional Shares and Option Settlement (in dollars per share)
Security Exchange Name
Deferred Tax Assets, Discount Accretion of Securities
Deferred tax assets, discount accretion of securities
Discount accretion of securities
Refers to financing receivable related to other consumer loans portion of consumer non-real estate portfolio.
Other Consumer Loans [Member]
Premises and Equipment
Noninterest Expense
Deferred Tax Liabilities Defined Benefit Pension Plan
Deferred tax liabilities defined benefit pension plan.
Defined benefit pension plan
Common equity tier 1 capital (to risk weighted assets), minimum to be well capitalized, amount
us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest
Income before income tax expense
Common Stock Including Additional Paid in Capital [Member]
Savings deposits
Interest on borrowings
Concentration Risk Type [Domain]
Gain (Loss) on Disposition of Other Assets
Loss on disposal of repossessed assets
Measurement Input Type [Domain]
Deposits [Abstract]
Financial Asset, Not Past Due [Member]
Core Deposits [Member]
Core Deposits
Interest paid on deposits and borrowed funds
Interest on deposits and borrowings
Measurement Basis [Axis]
Statistical Measurement [Domain]
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Line Items]
Line items represent fair value assets and liabilities measured on nonrecurring basis.
us-gaap_AllocatedShareBasedCompensationExpense
Share-Based Payment Arrangement, Expense
Document Period End Date
Federal Home Loan Bank Branch [Axis]
Fair Value Hierarchy and NAV [Domain]
us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax
Unrealized holding gain (loss) on securities available for sale
Unrealized holding gain on securities available for sale
ICFR Auditor Attestation Flag
us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid
Benefits paid
Loss on disposal of premises and equipment, net
Gain (Loss) on Disposition of Property Plant Equipment
Gain (Loss) on Disposition of Property Plant Equipment, Total
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), after Tax
Prior service cost
Credit Loss Status [Domain]
Gain on sale of mortgage loans held for sale
Gain on sale of mortgage loans held for sale
Statement of Financial Position [Abstract]
Restricted Stock Units (RSUs) [Member]
Employees Restricted Stock Units ("RSUs") [Member]
Restricted Stock Units ("RSUs") [Member]
Cumulative Effect, Period of Adoption, Adjustment [Member]
Revenue [Policy Text Block]
Revenue Recognition
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Line items represent fair value assets and liabilities measured on recurring basis.
Reclassification out of Accumulated Other Comprehensive Income [Member]
Class of Stock [Axis]
us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionNumberOfPositions
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions
Financing receivable net of deferred fees and costs
Financing receivable net of deferred fees and costs.
Loans, net of deferred fees and costs
us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss
Debt Securities, Available-for-Sale, Realized Gain (Loss)
Loss on sale of securities available for sale, net
Cybersecurity Risk Management, Strategy, and Governance [Line Items]
Financial Asset, Aging [Domain]
us-gaap_Liabilities
Total liabilities
Portfolio segment of the company's total financing receivables related to consumer real estate receivables.
Consumer Real Estate Portfolio Segment [Member]
Consumer Real Estate Portfolio Segment [Member]
Consumer Real Estate Loans
Financial Instruments [Domain]
Schedule of Fair Value, off-Balance-Sheet Risks [Table Text Block]
Collateral Pledged [Member]
Note 16 - Components of Accumulated Other Comprehensive Income (Loss) - Components of Accumulated Other Comprehensive Income (Loss) (Details) (Parentheticals)
Note 21 - Earnings Per Share - Schedule of Earnings Per Share (Details)
Portfolio segment of the company's total financing receivables related to consumer non real estate receivables.
Consumer Non Real Estate Portfolio Segment [Member]
Consumer Non Real Estate Portfolio Segment [Member]
Consumer Non-real Estate Loans
us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets
Expected return on plan assets
us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo
Twelve months ending December 31, 2027
Financing Receivable Credit Quality Indicators [Table Text Block]
us-gaap_AdvertisingExpense
Advertising Expense
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Life Insurance, Percent
BOLI income, Percent
BOLI income, Percent
Restricted Stock [Member]
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from SBA fees.
Unvested stock-based compensation
Off balance sheet liability, amount
Temporarily impaired securities, less than 12 months unrealized loss
Common shares, diluted (in shares)
Weighted Average Number of Shares Outstanding, Diluted, Total
Common shares weighted average outstanding, fully diluted (in shares)
Weighted average number of common shares outstanding, diluted
Entity File Number
us-gaap_RelatedPartyDepositLiabilities
Related Party Deposit Liabilities
Unrealized holding gain (loss) on available for sale securities net of tax of $4,315 in 2023 and ($22,403) in 2022
Unrealized holding gain on available for sale securities net of tax of $124 and $4,315 for the periods ended December 31, 2024 and 2023, respectively
Unrealized holding gain on available for sale securities net of tax of $5,617 and $124 for the periods ended December 31, 2025 and 2024, respectively
Amount of asset (liability), recognized in statement of financial position, for defined benefit pension and other postretirement plans, including deferred tax assets.
Total amounts recognized in the Consolidated Balance Sheet
Deferred Tax Assets Fair Value Adjustments To Acquired Assets
Deferred tax assets fair value adjustments to acquired assets.
Fair value adjustments to acquired assets
Other assets
Nonaccruals, with allowance
Measurement Input Type [Axis]
us-gaap_OtherExpenses
Other expenses
Defined Benefit Plan, Expected Future Benefit Payment [Abstract]
Fiduciary and Trust [Member]
Cumulative Effect, Period of Adoption [Axis]
Cash and Cash Equivalents Disclosure [Text Block]
Restriction on Cash
Total capital (to risk weighted assets), minimum capital requirement, ratio
Realized securities loss, net
Realized securities loss, net
Financial Asset, Aging [Axis]
Offsetting Assets [Line Items]
Interest-bearing demand deposits
Loans to state, city, or local US governments or the agencies operated by state, city, or local governments. Political subdivisions of US states would include, for example, county, borough, city, or municipal governments.
States Political Subdivisions [Member]
us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
Income before income tax benefit and equity (deficit) in undistributed net income of subsidiaries
Scenario [Domain]
The gross realized gain (loss) on available-for-sale securities that were called during the period.
Sale of Available for Sale Securities, net gain (loss)
US Treasury Securities [Member]
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized (in shares)
Portfolio segment of the company's total financing receivables related to public sector and IDA receivables.
Public Sector and IDA Portfolio Segment[Member]
Public Sector and IDA Portfolio Segment [Member]
Public Sector and IDA Loans
Information related to loans held for sale.
Loans Held-for-sale [Member]
Tax Jurisdiction of Domicile [Extensible Enumeration]
Collateralized Mortgage-Backed Securities [Member]
Noninterest Income
Noninterest Income (in-scope of Topic 606)
Amount of cash inflow from repayments of mortgage-backed securities.
Proceeds from repayments of mortgage-backed securities
Total amortizing core deposit intangible
Finite-Lived Intangible Assets, Net
Finite-Lived Intangible Assets, Net, Ending Balance
Finite-Lived Intangible Assets, Net, Beginning Balance
Gain on sale of private equity investment
Gain on sale of private equity investment
Realized securities gains, net
Total capital (to risk weighted assets), minimum to be well capitalized, ratio
Tabular disclosure of collateral dependent loan.
Financing Receivable, Collateral Dependent Loan [Table Text Block]
Intangible Assets, Gross (Excluding Goodwill)
Intangible Assets, Gross (Excluding Goodwill), Total
Core deposit intangible, gross
Core deposit intangible
Tax-exempt interest income, Percent
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Tax-exempt interest income, Percent
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Tax-exempt interest income, Percent
us-gaap_DebtSecuritiesAvailableForSaleAccruedInterestAfterAllowanceForCreditLoss
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss
Represents Interest Rate Loan Contract.
Interest Rate Loan Contract [Member]
us-gaap_PropertyPlantAndEquipmentUsefulLife
Property, Plant and Equipment, Useful Life (Year)
Depreciable lives
Financing receivable classified as equity lines.
Equity Lines [Member]
New Accounting Pronouncements, Policy [Policy Text Block]
Recent Accounting Pronouncements
Lessee, Operating Lease, Liability, to be Paid, Maturity [Table Text Block]
Other, net, Percent
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent
us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period (Year)
Comprehensive Income (Loss) Note [Text Block]
Business Combination, Recognized Liability Assumed, Liability
Total identifiable liabilities assumed
nksh_InterestBearingDepositsFairValueDisclosure
For banks and other depository institutions (including Federal Reserve Banks, if applicable). Fair value of interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet.
Interest-bearing deposits
Information on the loan portfolio.
Commercial Real Estate, Loan Portfolio [Member]
Allowance for credit losses and unearned fee income
Allowance for credit losses and deferred fees and costs
Depreciation of premises and equipment
Depreciation
Depreciation, Total
Net unrealized gain on securities available for sale
Deferred Tax Liabilities, Net Unrealized Gain on Securities Available for Sale
Deferred tax liabilities, net unrealized gain on securities available for sale.
Represents Frontier Community Bank.
Frontier Community Bank [Member]
FCB [Member]
Reported Value Measurement [Member]
Represents individually evaluated for impairment.
Individually Evaluated [Member]
us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax
Total recognized
Common stock, shares outstanding (in shares)
Gain (loss) related to the settlement of bank owned life insurance.
nksh_GainLossOnBoliSettlement
BOLI settlement
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)
Amortization of prior service cost
Cybersecurity Risk Management Processes Integrated [Flag]
Document Transition Report
us-gaap_DeferredTaxAssetsLiabilitiesNet
Net deferred tax assets
Cash outflow for shareholder elections and fractional shares.
nksh_PaymentForShareholderElectionsAndFractionalShares
Payment for Shareholder Elections and Fractional Shares
Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Allowance for Loan Losses (Details)
Maximum amount of consideration can be paid in cash under business acquisition as percentage.
nksh_BusinessAcquisitionCashPaymentMaximumPercentageOfConsideration
Business Acquisition, Cash Payment, Maximum Percentage of Consideration (in dollars per share)
Lessee, Operating Leases [Text Block]
Valuation Technique, Discounted Cash Flow [Member]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]
Note 16 - Components of Accumulated Other Comprehensive Income (Loss) - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Details)
Summary of Significant Accounting Policies [Table]
Summary of Significant Accounting Policies [Table]
Statement of Cash Flows [Abstract]
Current Federal Tax Expense (Benefit)
Current federal tax expense
Federal Home Loan Bank Branch [Domain]
us-gaap_EmployeeStockOwnershipPlanESOPCashContributionsToESOP
Employee Stock Ownership Plan (ESOP), Cash Contributions to ESOP
Restrictions on Dividends [Table]
Restrictions on Dividends [Table]
Minimum period of time between issuance of loans commitment and closing and sale of loans.
nksh_PeriodOfTimeBetweenIssuanceOfLoanCommitmentAndClosingAndSaleOfLoansLowerRange
Period of Time Between Issuance of Loan Commitment and Closing and Sale of Loans Lower Range (Day)
Finite-Lived Intangible Assets [Line Items]
Earnings Per Share [Text Block]
Computer Equipment [Member]
Cybersecurity Risk Management Processes Integrated [Text Block]
Net income
Net Income
Net Income
Revolving, write offs
Financing Receivable, Revolving, Writeoff
Pension and Other Postretirement Plans, Pensions, Policy [Policy Text Block]
Pension Plan
us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax
Amount recognized
us-gaap_ConcentrationRiskCreditRiskFinancialInstrumentMaximumExposure
Concentration Risk, Credit Risk, Financial Instrument, Maximum Exposure
Measurement input using pull-through rate.
Measurement Input, Pull-through Rate [Member]
Operating lease expense
Financing receivable deferred fees and costs
Financing receivable deferred fees and costs.
Less deferred fees and costs
Information related to securities called.
Securities Called [Member]
Intangible Assets, Net (Excluding Goodwill)
Core deposit intangible, net
Core deposit intangible, Net Carrying Amount
Core deposit intangible
Core deposit intangible
Cash paid for amounts included in lease liabilities
Provision for (recovery of) credit losses
(Recovery of) provision for credit losses
Note 9 - Income Taxes - Components of Net Deferred Tax Assets (Details)
Assets
The cash inflow associated with calls (requests of early payments) on securities not classified as either held-to-maturity securities or trading securities which are classified as available-for-sale securities.
Sale of Available for Sale Securities, proceeds
The amount of loan discount for non-credit factors (as defined) recognized as of the acquisition date.
nksh_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLoanDiscountForNoncreditFactors
Discount for non-credit factors
Document Fiscal Year Focus
Financing Receivable, Modified [Table Text Block]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
Concentration Risk Benchmark [Domain]
Cash Flows from Investing Activities
Retirement Benefits [Abstract]
Unfunded Loan Commitment [Member]
Represents residential closed-end first liens.
Closed End First Liens [Member]
Tier 1 capital (to average assets), minimum to be well capitalized, ratio
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]
Securities
Proceeds from Sale of Productive Assets
Proceeds from Sale of Productive Assets, Total
Proceeds from sale of premises and equipment
Deferred Federal Income Tax Expense (Benefit)
Deferred federal tax expense (benefit)
Stock based compensation
Tax-exempt interest income, Amount
Income Tax Reconciliation Nondeductible Expense Tax Exempt Income
Income Tax Reconciliation Nondeductible Expense Tax Exempt Income
Defined benefit plan, description
Defined Benefit Plan, Description
Finite-Lived Intangible Asset, Expected Amortization, Year One
2026
Financial Asset Acquired with Credit Deterioration [Member]
Represents acquired loans.
Acquired Loans [Member]
Acquired Loans
Originated four years prior, write offs
Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff
us-gaap_OtherLiabilities
Other liabilities
Fair Value Disclosures [Abstract]
Stock Issued During Period, Value, Acquisitions
Acquisition of Frontier Community Bank
us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths
Twelve months ending December 31, 2026
Net income, basic
Business Combination, Recognized Asset Acquired to Liability Assumed, Excess (Less)
Provisional fair value of net assets acquired
Fair value of net assets acquired
Derivative Instrument [Axis]
us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive
Thereafter
Interest cost (2)
Interest cost
Share-Based Payment Arrangement [Abstract]
us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount
Deposit Liabilities Disclosures [Text Block]
us-gaap_ConcentrationRiskPercentage1
Concentration Risk, Percentage
Tabular disclosure of maturities of time deposits (including certificates of deposits, individual retirement accounts and open accounts) held by the entity.
Scheduled Maturities of Time Deposits [Table Text Block]
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
2026
Banking Regulation, Regulatory Capital Requirement, Compliance [Table]
Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Loans by Credit Quality Indicators (Details)
us-gaap_Revenues
Revenues
us-gaap_NetCashProvidedByUsedInInvestingActivities
Net cash (used in) provided by investing activities
Restrictions on Dividends [Line Items]
Restrictions on dividends.
Pass [Member]
Title of 12(b) Security
Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan due to change in discount rate. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.
nksh_DefinedBenefitPlanBenefitObligationActuarialGainLossDueToChangesInDiscountRate
(Gain) loss due to demographic changes
Condensed Financial Statements, Captions [Line Items]
Amortized cost, due after one year through five years, available for sale securities
Related Party, Type [Domain]
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Life Insurance, Amount
BOLI income
BOLI income, Amount
BOLI income, Amount
Income Tax Disclosure [Text Block]
Measurement input using current reference price.
Measurement Input, Current Reference Price [Member]
us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLoss
Debt Securities, Available-for-Sale, Allowance for Credit Loss
Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff
Gross Charge-Offs
Financing receivable classified as construction, 1-4 family residential.
Construction, 1-4 Family Residential [Member]
us-gaap_AccruedLiabilitiesFairValueDisclosure
Accrued interest payable
Document Information [Table]
Tabular disclosure of realized gain (loss) on called securities.
Schedule of Realized Gain (Loss) on Called Securities [Table Text Block]
Total capital (to risk weighted assets), minimum capital requirement, amount
Consolidated Entities [Axis]
Legal Entity [Axis]
Effective Income Tax Rate Reconciliation, Nondeductible Expense Amortization of municipal bond premiums percent
Effective Income Tax Rate Reconciliation, Nondeductible Expense Amortization of municipal bond premiums percent
Amortization of municipal bond premiums, Percent
Fair value, due after one year through five years, available for sale securities
Net change in:
Business Acquisition, Share Price (in dollars per share)
Business Combination, Price Per Share
Property, Plant and Equipment [Table Text Block]
Fair value, plan assets
Fair value of plan assets at end of year
Fair value of plan assets at beginning of year
Number of new leases
Number of new leases
Fair Value Assets And Liabilities Measured On Nonrecurring Basis [Table]
Fair value assets and liabilities measured on nonrecurring basis table.
Tabular disclosure of ratios for allowance for loan losses.
Schedule of Ratios for Allowance for Loan Losses [Table Text Block]
Portfolio segment of the company's total financing receivables related to real estate construction receivables.
Real Estate Construction Portfolio Segment[Member]
Real Estate Construction Portfolio Segment [Member]
Real Estate Construction Loans
Time deposits
Total time deposits
us-gaap_TimeDepositMaturitiesYearThree
2028
Income Tax Disclosure [Abstract]
Tier 1 capital (to average assets), minimum capital requirement, ratio
Fair Value, Recurring and Nonrecurring [Table]
Business Combination [Text Block]
Business Combination
Business Combination Disclosure [Text Block]
Total capital (to risk weighted assets), actual, ratio
Commercial Mortgage-Backed Securities [Member]
Measurement Frequency [Domain]
Trading Symbol
Intangible Asset, Finite-Lived [Table]
Property, Plant and Equipment Disclosure [Text Block]
Premises and Equipment
us-gaap_IncreaseDecreaseOfRestrictedInvestments
Net change in restricted stock
Related Party Transaction [Table]
Represents investor owned residential real estate.
Investor Owned Residential Real Estate [Member]
Years of plan participation required to diversify Employee Stock Ownership Plan (ESOP).
nksh_YearsOfPlanParticipationRequiredToDiversifyAllocatedEsopShares
Years of Plan Participation Required to Diversify Allocated ESOP Shares (Year)
Amortized cost, due in one year or less, available for sale securities
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Percent
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Percent, Total
Nondeductible interest expense, Percent
Condensed Financial Statements [Table]
Director [Member]
Tier 1 capital (to risk weighted assets), minimum to be well capitalized, ratio
Loans:
Refers to financing receivable related to residential portion of construction portfolio.
Construction Residential [Member]
Portfolio segment of the company's total financing receivables related to commercial receivables, non real estate.
Commercial Non Real Estate Segment [Member]
Commercial Non Real Estate Segment [Member]
Commercial Non-real Estate Loans
Financing Receivable, Allowance for Credit Loss [Table Text Block]
Number of days that all loans and receivables are not received within certain number of days after the payment due date or statement date, at which point they are considered past due.
nksh_NumberOfDaysPastDue
Number of Days Past Due (Day)
Cash Flows from Financing Activities
Fair Value, Recurring [Member]
us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue
Total undiscounted cash flows
Accounting Standards Update 2016-13 [Member]
Accounting Standards Update 2016-13 [Member]
us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount
Less: discount
Disclosure of accounting policy for trust assets and income.
Trust Assets and Income [Policy Text Block]
Trust Assets and Income
Financing Receivable Portfolio Segment [Domain]
Percentage of allocated Employee Stock Ownership Plan shares that can diversified.
nksh_PercentageOfAllocatedEsopSharesThatCanBeDiversified
Percentage of Allocated ESOP Shares That Can be Diversified
us-gaap_FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged1
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged
Equity Components [Axis]
Revolving
Equity Component [Domain]
Asset Class [Axis]
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement
Defined Benefit Plan, Benefit Obligation, (Increase) Decrease for Settlement, Total
Recognized net actuarial gain due to settlement
Represents loans in process.
Loans in Process [Member]
Other operating expenses
Document Annual Report
Commercial and Industrial and Other Consumer Loan [Member]
Commercial and Industrial and Other Consumer Loan [Member]
Commercial and Industrial and Other Consumer Loan.
Financing Receivable, Real Estate Acquired Through Foreclosure [Policy Text Block]
Other Real Estate Owned
Bank-owned life insurance (BOLI)
Bank-owned life insurance ("BOLI")
Business Combination [Axis]
Operating Lease, Liability, Statement of Financial Position [Extensible Enumeration]
Amortized cost, due after five years through ten years, available for sale securities
Automobile Loan [Member]
Originated five years prior, write offs
Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff
Rate of compensation increase
Refers to information regarding standby letters of credit.
Standby Letters of Credit 1 [Member]
Interest on time deposits
Note 13 - Financial Instruments With Off-balance Sheet Risk - Financial Instruments Outstanding Representing Credit Risk (Details)
us-gaap_NotesReceivableNet
Loans, net
Discount on acquired loans
Type of Borrower [Axis]
Note 11 - Minimum Regulatory Capital Requirement - Minimum Capital Requirements (Details)
Statement of Comprehensive Income [Abstract]
Recoveries on loans charged off
Repayments of Bank Debt
Repayment of borrowings
Maximum [Member]
Refers to a category of financing receivables with frequent or persistent delinquency exceeding 75 days or that have a higher level of weakness in the borrower's financial condition. Classified loans have regulatory risk ratings of "substandard" and "doubtful."
Classified Excluding Impaired [Member]
Statistical Measurement [Axis]
Finite-Lived Intangible Assets, Accumulated Amortization
Core deposit intangible, accumulated amortization
Core deposit intangible, accumulated amortization
us-gaap_TimeDepositMaturitiesYearOne
2026
Common stock of $1.25 par value and additional paid-in capital. Authorized 10,000,000 shares; issued and outstanding 6,368,410 (including 5,039 unvested) shares as of December 31, 2025 and 6,363,371 (including 4,961 unvested) shares as of December 31, 2024
Net income, diluted
Financing Receivable, Allowance for Credit Loss [Table]
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]
Financing Receivable, Year One, Originated, Current Fiscal Year, Writeoff
Originated current year, write offs
Cash and Cash Equivalents [Abstract]
Represents Stock Incentive Plan 2023.
Stock Incentive Plan 2023 [Member]
Goodwill and Core Deposit Intangible Assets [Table]
Goodwill and Core Deposit Intangible Assets.
us-gaap_RelatedPartyTransactionAmountsOfTransaction
Related Party Transaction, Amounts of Transaction
us-gaap_DeferredTaxLiabilitiesPrepaidExpenses
Defined benefit pension plan, prepaid portion
BOLI income
Net operating loss of FCB, acquired
Deferred Tax Assets, Operating Loss Carryforwards
Deferred Tax Assets, Operating Loss Carryforwards, Total
Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]
Statement - statement - note - 12 - goodwill - and - other - intangibles - components - of - goodwill - and - other - intangible - assets - details
Note 17 - Goodwill and Other Intangibles - Components of Goodwill and Other Intangible Assets (Details)
Financing Receivable, Held-for-Sale [Policy Text Block]
Loans Held for Sale
Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Ratios of Allowance for Loan Losses (Details)
Related to a debt restructuring stipulating that only interest payments are required for a certain period.
Interest Only Payments [Member]
Marketable Securities [Line Items]
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]
us-gaap_TimeDepositsAtOrAboveFDICInsuranceLimit
Time Deposits, at or Above FDIC Insurance Limit
Entity Public Float
Preferred stock, shares authorized (in shares)
Finite-Lived Intangible Assets by Major Class [Axis]
Credit and Debit Card [Member]
Related Party Transaction [Line Items]
Revenue from Contract with Customer [Text Block]
Business Combination [Table]
Entity Registrant Name
Securities available-for-sale, gross unrealized losses
Entity Voluntary Filers
Sale of mortgage loans held for sale
Proceeds from sale of mortgage loans held for sale
Finite-Lived Intangible Asset, Expected Amortization, Year Two
2027
Accumulated Other Comprehensive Income (Loss) [Table]
Cybersecurity Risk Management Positions or Committees Responsible [Flag]
Consolidated Entities [Domain]
Finite-Lived Intangible Asset, Expected Amortization, Year Three
2028
Income tax expense
Applicable income tax benefit
Applicable income tax benefit
Total income tax expense, Amount
us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage
Measurement Frequency [Axis]
Payments to Acquire Productive Assets
Payments to Acquire Productive Assets, Total
Purchases of premises and equipment
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
2030
Age of an employee to be eligible for the Employee Stock Ownership Plan (ESOP).
nksh_AgeAttainedToBeEligibleForESOP
Age Attained to be Eligible for ESOP (Year)
us-gaap_StockRepurchasedDuringPeriodValue
Stock repurchase
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]
Income
Entity Common Stock, Shares Outstanding
Interest Rate Lock Commitments [Member]
US States and Political Subdivisions Debt Securities [Member]
Amount of deferred income tax (benefit) expense attributable to defined benefit plans.
nksh_OtherComprehensiveIncomeLossDeferredIncomeTaxExpenseBenefit
Deferred income tax expense
Accumulated other comprehensive loss, net
Deferred compensation and other liabilities
Commercial Real Estate Portfolio Segment [Member]
Commercial Real Estate Portfolio Segment [Member]
Commercial Real Estate Loans
Federal Income Tax Expense (Benefit), Continuing Operations
Total federal income tax expense
Commitments and Contingencies, Policy [Policy Text Block]
Loss Contingencies
Note 3 - Securities - Securities Available-for-sale (Details)
Class of Financing Receivable, Type of Borrower [Domain]
Granted, shares (in shares)
Employees Restricted Stock Units Awarded
us-gaap_Assets
Total assets
Property, Plant and Equipment [Table]
Performing Financial Instruments [Member]
Class of Financing Receivable [Domain]
Income Statement [Abstract]
Represents information pertaining to National Bank of Blacksburg (NBB), a wholly-owned subsidiary.
National Bank of Blacksburg [Member]
Consulting agreement amount for transition and advisory services
Consulting agreement amount for transition and advisory services
Consulting Agreement Amount for Transition and Advisory Services
Share-Based Payment Arrangement [Policy Text Block]
Stock Based Compensation
us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses
Recognized net actuarial loss
Preferred stock, par value (in dollars per share)
Deferred tax (benefit) expense
Deferred income tax expense (benefit)
Deferred tax expense (benefit)
Represents forward sale commitment.
Forward Sale Commitment [Member]
Deferred tax liability
Liability, Defined Benefit Plan
Liability, Defined Benefit Plan, Total
Deferred tax liability
Represents accrued interest receivable on loans.
nksh_AccruedInterestReceivableLoans
Accrued Interest Receivable, Loans
Tier 1 capital (to average assets), minimum capital requirement, amount
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period
Vested and released, shares (in shares)
Vested and released, shares (in shares)
Schedule of Allocation of Plan Assets [Table Text Block]
Refers to information regarding commercial real estate loans.
Commercial Real Estate Loans [Member]
Business Combination [Abstract]
Amount of minimum Tier 1 risk-based capital required for capital requirement as defined by regulatory framework.
Tier 1 capital (to risk weighted assets), minimum capital requirement, amount
Fully diluted net income per common share (in dollars per share)
Diluted net income per common share
Nonaccruals
Finite-Lived Intangible Asset, Expected Amortization, Year Five
2030
Deposit Account [Member]
The total amount recognized in net periodic benefit cost and other comprehensive income.
Total recognized in net periodic benefit cost and other comprehensive income
Total recognized in net periodic benefit and other comprehensive income
us-gaap_DividendsCommonStock
Cash dividend
Expenses
City Area Code
us-gaap_RestrictedInvestments
Restricted Investments
Other comprehensive income (loss), net of tax
Other comprehensive income (loss), net of tax
Other comprehensive income, net of tax
Other comprehensive income, net of tax
The common equity tier 1 risk based capital ratio (common equity tier 1 capital divided by risk weighted assets) required to be categorized as "well capitalized", in the regulatory framework for prompt corrective action.
Common equity tier 1 capital (to risk weighted assets), minimum to be well capitalized, ratio
Provision for credit losses
Provision for (recovery of) credit losses
Recovery of credit losses
Defined benefit pension plan
Auditor Name
Schedule of Defined Benefit Plans Disclosures [Table Text Block]
Total deposits
us-gaap_Deposits
The amount of loan discount for credit risk (as defined) recognized as of the acquisition date.
nksh_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLoanDiscountForCreditRisk
Discount for credit risk
Federal Home Loan Bank of Atlanta [Member]
Core Deposit Intangibles
Intangible Assets, Finite-Lived, Policy [Policy Text Block]
Refundable income taxes
Schedule of Intangible Assets and Goodwill [Table Text Block]
Schedule of Intangible Assets and Goodwill [Table Text Block]
Business Combination [Line Items]
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Other Liabilities
The amount of other liabilities assumed (as defined) which have been recognized as of the acquisition date.
Other liabilities
Defined Benefit Plan [Table]
Interest and fees on loans
Revolving loans converted to term
Supplemental Disclosures of Noncash Transactions Included In Acquisition
Noncash or Part Noncash Acquisition, Net Nonmonetary Assets Acquired (Liabilities Assumed) [Abstract]
Note 5 - Allowance for Credit Losses on Loans and Nonperforming Assets - Past Due and Nonaccrual Loans (Details)
Maximum period of time between issuance of loans commitment and closing and sale of loans.
nksh_PeriodOfTimeBetweenIssuanceOfLoanCommitmentsAndClosingAndSaleOfLoansUpperRange
Period of Time Between Issuance of Loan Commitments and Closing and Sale of Loans Upper Range (Day)
College Housing and Professional Office Buildings [Member]
Refers to information regarding college housing and professional office buildings.
us-gaap_LoansHeldForSaleFairValueDisclosure
Mortgage loans
Mortgage loans held for sale
The amount of gross amount of loan (as defined) recognized as of the acquisition date.
Loans, gross
Loans, gross
Weighted average remaining lease term (in years) (Year)
us-gaap_TimeDepositMaturitiesYearTwo
2027
us-gaap_LeaseCost
Total lease expense
Borrowings
Business Combination, Recognized Liability Assumed, Financial Liability
Cash and Cash Equivalents, Policy [Policy Text Block]
Cash and Cash Equivalents
Stock consideration(1)
Business Combination, Consideration Transferred, Equity Interest
Premises and equipment, net
Premises and equipment, net
Lease liabilities arising from obtaining right-of-use assets during the period
Common equity tier 1 capital (to risk weighted assets), minimum capital requirement, amount
us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
2028
Impairment of Intangible Assets, Finite-Lived
Impairment of intangible assets
us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations
Cash and cash equivalents at end of period
Cash and cash equivalents at beginning of period
Discount rate used for net periodic pension cost
Finite Lived Intangible Asset, Expected Amortization, Year Six
Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in sixth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).
2031
Retained Earnings [Member]
Refers to financing receivable related to other portion of construction portfolio.
Construction, Other [Member]
us-gaap_EmployeeBenefitsAndShareBasedCompensation
Employee Benefits and Share-Based Compensation
Equity-based compensation expense
Stock based compensation expense
Federal funds sold
Federal Funds Sold
Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.
nksh_FinancingReceivableTroubledDebtRestructuringSubsequentDefaultNumberOfContracts
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts
This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This element represents the fair value of accrued interest receivable.
nksh_AccruedInterestReceivableFairValueDisclosure
Accrued interest receivable
Other income
Refers to the Multi family real estate as individual assets.
Multifamily Real Estate [Member]
Temporarily impaired securities, less than 12 months, fair value
Weighted average discount rate
Fair Value, Inputs, Level 1 [Member]
Notes to Financial Statements
Disclosure Text Block Abstract
Notes to Financial Statements
us-gaap_NetCashProvidedByUsedInFinancingActivities
Net cash used in financing activities
Collateral Held [Domain]
Lease, Cost [Table Text Block]
Nondeductible or nontaxable items
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Percent [Abstract]
us-gaap_FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear
Originated four years prior
Auditor Location
Fair value, due after five years through ten years, available for sale securities
Derivative Contract [Domain]
us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax
Realized loss on available for sale securities, net of tax, reclassified out of accumulated other comprehensive loss
Reclassification adjustment for loss included in net income, net of tax of $700 in 2023
Reclassification adjustment for loss included in net income, net of tax of $700 in 2023
Realized loss on available for sale securities, net of tax, reclassified out of accumulated other comprehensive loss
Restricted stock, at cost
Condensed Cash Flow Statement [Table Text Block]
Corporate Debt Securities [Member]
Securities
Business Combination, Recognized Asset Acquired, Investment in Debt and Equity Securities, Current
Entity Interactive Data Current
Book Value Per Common Share
Book value per common share.
Book value per common share
Defined Benefit Plan, Plan Assets, Category [Axis]
Deferred tax liabilities:
Cash Flows from Operating Activities
Furniture and Fixtures [Member]
Furniture and Equipment
Contribution to defined benefit plan
Proceeds From Contribution to Defined Benefit Plan
Proceeds from contribution to defined benefit plan.
Loan Restructuring Modification [Domain]
us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments
Amortization of premiums and accretion of discounts on securities, net
The minimum number of days consumer loans are past due for losses on such loans to be written off.
nksh_MinimumNumberOfDaysConsumerLoansArePastDueForLossesToBeChargedOff
Minimum Number of Days Consumer Loans are Past Due for Losses to be Charged Off (Day)
Business Combination, Consideration Transferred, Equity Interest, Share Issued, Number of Shares
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares (in shares)
Total capital (to risk weighted assets), actual, amount
Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff
Originated three years prior, write offs
Cash dividend, per share (in dollars per share)
Dividends declared per common share
Cumulative Effect, Period of Adoption [Domain]
Deferred Tax Assets, Directors Gifts Not Spent
Deferred tax assets, directors gifts not spent.
Directors gifts not spent
For banks and other depository institutions: Includes fair value of cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.
nksh_CashAndDueFromBanksFairValueDisclosure
Cash and due from banks
Entity Tax Identification Number
Share Price
Share Price (in dollars per share)
us-gaap_PaymentsForProceedsFromOtherLoansAndLeases
Loan originations and principal collections, net
Represents information pertaining to the lease of a small office space to a related party.
Small Office Space Lease to Related Party [Member]
us-gaap_CashDividendsPaidToParentCompanyByConsolidatedSubsidiaries
SEC Schedule, 12-04, Cash Dividends Paid to Registrant, Consolidated Subsidiaries
Occupancy, furniture and fixtures
us-gaap_PaymentsToAcquireLoansReceivable
Purchase of loan participations
Represents commercial and industrial loans.
Commercial and Industrial [Member]
us-gaap_ConstructionInProgressGross
Construction in Progress, Gross
Life Settlement Contracts, Policy [Policy Text Block]
Bank Owned Life Insurance
Local Phone Number
Related Party Transaction [Domain]
Mortgage loans held for sale
Financing Receivable, Held-for-Sale, Not Part of Disposal Group, after Valuation Allowance
Accumulated Other Comprehensive Income (Loss) [Line Items]
us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost
Net periodic benefit
Short-term lease expense
us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax
Net pension gain arising during the period, net of tax
Net pension gain, net of tax
Net pension gain arising during the period, net of tax of $255 in 2025 and $701 in 2024
Auditor Opinion [Text Block]
Financing Receivable, Current, Allowance for Credit Loss [Table Text Block]
Cash Acquired from Acquisition
Cash acquired in the acquisition, net of cash paid
FDIC assessment
us-gaap_NoninterestExpense
Total noninterest expense
Liability for agreement to continue an employee's salary after termination of employment including retirement, death, disability, or other event. For example, a company may agree to continue a disabled employee's salary for six months.
nksh_AccruedExpensesForSalaryContinuationPlan
Accrued Expenses for Salary Continuation Plan
Goodwill and Intangible Asset Impairment [Abstract]
Accounting Policies [Abstract]
Other assets
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Other Assets
Amount of other assets acquired at the acquisition date.
Unrealized holding gain on available for sale securities, net of tax
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member]
Percentage of Interest-Bearing Domestic Deposits to Deposits, Other Time Deposit
Other deposit
us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour
Twelve months ending December 31, 2029
Class of Stock [Domain]
Salaries and employee benefits
us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent
Entity Emerging Growth Company
Represents FCB common share.
FCB Common Share [Member]
FCB Common Share [Member]
Federal.
Federal [Member]