XML 87 R76.htm IDEA: XBRL DOCUMENT
v3.26.1

Note 8 - Employee Benefit Plans- Components of Actuarial (Gain) Loss (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024
Retirement Benefits [Abstract] |  |
(Gain) loss due to demographic changes | $ (123) | $ 727
Loss (gain) due to change in discount rate | 931 | (2,691)
Loss due to change in rate of compensation increase | 0 | 1,122
Actuarial loss (gain) | 808 | (842)
Gain due to asset return | (2,060) | (2,364)
Actuarial gain with asset return | $ (1,252) | $ (3,206)

X
- Definition Defined benefit plan benefit obligation actuarial gain loss due to change in rate of compensation increase. + References No definition available. + Details
Name: | nksh_DefinedBenefitPlanBenefitObligationActuarialGainLossDueToChangeInRateOfCompensationIncrease
Namespace Prefix: | nksh_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition 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. + References No definition available. + Details
Name: | nksh_DefinedBenefitPlanBenefitObligationActuarialGainLossDueToChangesInDiscountRate
Namespace Prefix: | nksh_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition 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. + References No definition available. + Details
Name: | nksh_DefinedBenefitPlanBenefitObligationActuarialGainLossDueToDemographicChanges
Namespace Prefix: | nksh_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of actuarial gain loss with asset return for benefit obligation of defined benefit plan. + References No definition available. + Details
Name: | nksh_DefinedBenefitPlanBenefitObligationActuarialGainLossWithAssetReturn
Namespace Prefix: | nksh_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of gain loss due to asset return for benefit obligation of defined benefit plan + References No definition available. + Details
Name: | nksh_DefinedBenefitPlanBenefitObligationGainLossDueToAssetReturn
Namespace Prefix: | nksh_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_CompensationAndRetirementDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of gain (loss) 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. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanActuarialGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration