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Note 22 - Business Combination - (Details Textual) - USD ($) $ / shares in Units, $ in Thousands | Jun. 01, 2024 | May 31, 2024
--- | --- | ---
Share Price (in dollars per share) |  | $ 30.76
FCB [Member] |  |
Percentage of ownership acquired | 100.00% |
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares (in shares) | 464,855 |
Business Acquisition, Share Price (in dollars per share) | $ 30.76 |
Business Acquisition, Cash Payment, Maximum Percentage of Consideration (in dollars per share) | $ 10 |
Payment for Shareholder Elections and Fractional Shares | $ 1,769 |
Business Acquisition, Outstanding and Vested Options Settlement Payment | $ 281 |
FCB [Member] | FCB Common Share [Member] |  |
Business Acquisition, Share Price for Cash Payment of Fractional Shares and Option Settlement (in dollars per share) | $ 14.48 |

X
- Definition Maximum amount of consideration can be paid in cash under business acquisition as percentage. + References No definition available. + Details
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Namespace Prefix: | nksh_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Payment of Outstanding and vested options settlement amount under business acquisition. + References No definition available. + Details
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Namespace Prefix: | nksh_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Price of a single share for cash payment of fractional shares and option settlement under business acquisition. + References No definition available. + Details
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Namespace Prefix: | nksh_
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X
- Definition Cash outflow for shareholder elections and fractional shares. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the acquistion. + References No definition available. + Details
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Namespace Prefix: | nksh_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of shares of equity interests issued or issuable to acquire entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 805 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(4) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479581/805-30-50-1 + Details
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Balance Type: | na
Period Type: | duration

X
- Definition Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | dtr-types:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Price of a single share of a number of saleable stocks of a company. + References No definition available. + Details
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Data Type: | dtr-types:perShareItemType
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- Details
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Namespace Prefix: |
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- Details
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Period Type: |