XML 56 R46.htm IDEA: XBRL DOCUMENT
v3.23.1

Note 5 - Fair Value Measurements - Change in Fair Value Measurement Impacts Net Income (Details) - Valuation, Market Approach [Member] | Mar. 31, 2023
--- | ---
Pull-through Rate [Member] | Weighted Average [Member] | Interest Rate Contract [Member] |
Derivative asset (liability) | 0.8130
Pull-through Rate [Member] | Weighted Average [Member] | Forward Contract [Member] |
Derivative asset (liability) | 0.8130
Current Reference Price [Member] | Weighted Average [Member] | Interest Rate Contract [Member] |
Derivative asset (liability) | (1.0124)
Current Reference Price [Member] | Weighted Average [Member] | Forward Contract [Member] |
Derivative asset (liability) | (1.0124)
Current Reference Price [Member] | Minimum [Member] | Interest Rate Contract [Member] |
Derivative asset (liability) | 1.0083
Current Reference Price [Member] | Minimum [Member] | Forward Contract [Member] |
Derivative asset (liability) | 1.0083
Current Reference Price [Member] | Maximum [Member] | Interest Rate Contract [Member] |
Derivative asset (liability) | 1.0222
Current Reference Price [Member] | Maximum [Member] | Forward Contract [Member] |
Derivative asset (liability) | 1.0222

X
- Definition Value of input used to measure net derivative asset (liability). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
Name: | us-gaap_DerivativeAssetLiabilityNetMeasurementInput
Namespace Prefix: | us-gaap_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_ValuationTechniqueAxis=us-gaap_MarketApproachValuationTechniqueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MeasurementInputTypeAxis=nksh_PullthroughRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_WeightedAverageMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=nksh_ForwardContractMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MeasurementInputTypeAxis=nksh_CurrentReferencePriceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |