XML 49 R42.htm IDEA: XBRL DOCUMENT
v3.25.3

Note 3 - Loans and Allowance for Credit Losses - Loans and Allowance for Loan Losses by Evaluation Method (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024 | Sep. 30, 2024 | Dec. 31, 2023
--- | --- | --- | --- | ---
Allowance for loan losses | $ 10,579 | $ 10,262 | $ 10,328 | $ 9,094
Loans, individually evaluated | 10,699 | 10,521 |  |
Loans, collectively evaluated | 1,006,246 | 978,092 |  |
Loans | 1,016,945 | 988,613 |  |
Individually Evaluated [Member] |  |  |  |
Allowance for loan losses | 90 | 80 |  |
Collectively Evaluated [Member] |  |  |  |
Allowance for loan losses | 10,489 | 10,182 |  |
Real Estate Construction Portfolio Segment [Member] |  |  |  |
Allowance for loan losses | 425 | 348 | 461 | 408
Loans, individually evaluated | 0 | 0 |  |
Loans, collectively evaluated | 46,381 | 50,798 |  |
Loans | 46,381 | 50,798 |  |
Real Estate Construction Portfolio Segment [Member] | Individually Evaluated [Member] |  |  |  |
Allowance for loan losses | 0 | 0 |  |
Real Estate Construction Portfolio Segment [Member] | Collectively Evaluated [Member] |  |  |  |
Allowance for loan losses | 425 | 348 |  |
Consumer Real Estate Portfolio Segment [Member] |  |  |  |
Allowance for loan losses | 3,888 | 3,926 | 3,956 | 3,162
Loans, individually evaluated | 473 | 497 |  |
Loans, collectively evaluated | 324,124 | 307,358 |  |
Loans | 324,597 | 307,855 |  |
Consumer Real Estate Portfolio Segment [Member] | Individually Evaluated [Member] |  |  |  |
Allowance for loan losses | 27 | 31 |  |
Consumer Real Estate Portfolio Segment [Member] | Collectively Evaluated [Member] |  |  |  |
Allowance for loan losses | 3,861 | 3,895 |  |
Commercial Real Estate Portfolio Segment [Member] |  |  |  |
Allowance for loan losses | 4,360 | 4,299 | 4,261 | 3,576
Loans, individually evaluated | 10,226 | 10,024 |  |
Loans, collectively evaluated | 480,742 | 468,054 |  |
Loans | 490,968 | 478,078 |  |
Commercial Real Estate Portfolio Segment [Member] | Individually Evaluated [Member] |  |  |  |
Allowance for loan losses | 63 | 49 |  |
Commercial Real Estate Portfolio Segment [Member] | Collectively Evaluated [Member] |  |  |  |
Allowance for loan losses | 4,297 | 4,250 |  |
Commercial Non Real Estate Segment [Member] |  |  |  |
Allowance for loan losses | 760 | 655 | 659 | 682
Loans, individually evaluated | 0 | 0 |  |
Loans, collectively evaluated | 53,532 | 51,844 |  |
Loans | 53,532 | 51,844 |  |
Commercial Non Real Estate Segment [Member] | Individually Evaluated [Member] |  |  |  |
Allowance for loan losses | 0 | 0 |  |
Commercial Non Real Estate Segment [Member] | Collectively Evaluated [Member] |  |  |  |
Allowance for loan losses | 760 | 655 |  |
Public Sector and IDA Portfolio Segment [Member] |  |  |  |
Allowance for loan losses | 307 | 336 | 338 | 333
Loans, individually evaluated | 0 | 0 |  |
Loans, collectively evaluated | 54,332 | 57,171 |  |
Loans | 54,332 | 57,171 |  |
Public Sector and IDA Portfolio Segment [Member] | Individually Evaluated [Member] |  |  |  |
Allowance for loan losses | 0 | 0 |  |
Public Sector and IDA Portfolio Segment [Member] | Collectively Evaluated [Member] |  |  |  |
Allowance for loan losses | 307 | 336 |  |
Consumer Non Real Estate Portfolio Segment [Member] |  |  |  |
Allowance for loan losses | 792 | 648 | 570 | 583
Loans, individually evaluated | 0 | 0 |  |
Loans, collectively evaluated | 47,135 | 42,867 |  |
Loans | 47,135 | 42,867 |  |
Consumer Non Real Estate Portfolio Segment [Member] | Individually Evaluated [Member] |  |  |  |
Allowance for loan losses | 0 | 0 |  |
Consumer Non Real Estate Portfolio Segment [Member] | Collectively Evaluated [Member] |  |  |  |
Allowance for loan losses | 792 | 648 |  |
Unallocated Financing Receivables [Member] |  |  |  |
Allowance for loan losses | 47 | 50 | $ 83 | $ 350
Unallocated Financing Receivables [Member] | Individually Evaluated [Member] |  |  |  |
Allowance for loan losses | 0 | 0 |  |
Unallocated Financing Receivables [Member] | Collectively Evaluated [Member] |  |  |  |
Allowance for loan losses | $ 47 | $ 50 |  |

X
- Definition Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11B -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-11B Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph c -Publisher SEC Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph a -Subparagraph (1) -Publisher SEC Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph a -Subparagraph (3) -Publisher SEC Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(4)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479344/326-20-45-1 Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(7)(2)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amortized cost, before allowance for credit loss, fee, and loan in process, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481990/310-10-45-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-5 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(7)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 + Details
Name: | us-gaap_FinancingReceivableBeforeAllowanceForCreditLossAndFee
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable collectively evaluated for credit loss. Excludes financing receivable individually evaluated for credit loss. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 4 -Subparagraph (SAB Topic 6.L.5.a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480418/310-10-S99-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11C -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-11C + Details
Name: | us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable individually evaluated for credit loss. Excludes financing receivable collectively evaluated for credit loss. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 4 -Subparagraph (SAB Topic 6.L.5.a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480418/310-10-S99-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11C -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481962/310-10-50-11C + Details
Name: | us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_ClassOfFinancingReceivableTypeOfBorrowerAxis=nksh_IndividuallyEvaluatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ClassOfFinancingReceivableTypeOfBorrowerAxis=nksh_CollectivelyEvaluatedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=nksh_RealEstateConstructionPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=nksh_ConsumerRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=nksh_CommercialNonRealEstateSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=nksh_PublicSectorAndIDAPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=nksh_ConsumerNonRealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_UnallocatedFinancingReceivablesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |