XML 48 R37.htm IDEA: XBRL DOCUMENT
v3.26.1

Note 3 - Securities (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2025
Notes Tables |
Debt Securities, Available-for-Sale [Table Text Block] |
December 31, 2025 |  | Amortized Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized Losses |  |  | Fair Value |
U.S. government agencies and corporations |  | $ | 312,353 |  |  | $ | - |  |  | $ | 24,298 |  |  | $ | 288,055 |
States and political subdivisions |  |  | 177,453 |  |  |  | - |  |  |  | 23,736 |  |  |  | 153,717 |
Mortgage-backed securities |  |  | 210,918 |  |  |  | 129 |  |  |  | 3,406 |  |  |  | 207,641 |
Corporate debt securities |  |  | 5,505 |  |  |  | - |  |  |  | 541 |  |  |  | 4,964 |
Total securities available for sale |  | $ | 706,229 |  |  | $ | 129 |  |  | $ | 51,981 |  |  | $ | 654,377 |
December 31, 2024 |  | Amortized Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized Losses |  |  | Fair Value |
U.S. government agencies and corporations |  | $ | 351,136 |  |  | $ | - |  |  | $ | 40,012 |  |  | $ | 311,124 |
States and political subdivisions |  |  | 178,106 |  |  |  | - |  |  |  | 32,372 |  |  |  | 145,734 |
Mortgage-backed securities |  |  | 143,747 |  |  |  | 24 |  |  |  | 5,473 |  |  |  | 138,298 |
Corporate debt securities |  |  | 6,507 |  |  |  | - |  |  |  | 764 |  |  |  | 5,743 |
U.S. treasury |  |  | 1,000 |  |  |  | - |  |  |  | 1 |  |  |  | 999 |
Total securities available for sale |  | $ | 680,496 |  |  | $ | 24 |  |  | $ | 78,622 |  |  | $ | 601,898 |
Investments Classified by Contractual Maturity Date [Table Text Block] |
December 31, 2025 |  | Amortized Cost |  |  | Fair Value |
Available for Sale: |  |  |  |  |  |
Due in one year or less |  | $ | 23,709 |  |  | $ | 23,484 |
Due after one year through five years |  |  | 229,721 |  |  |  | 218,251 |
Due after five years through ten years |  |  | 221,520 |  |  |  | 195,181 |
Due after ten years |  |  | 231,279 |  |  |  | 217,461 |
Total securities available for sale |  | $ | 706,229 |  |  | $ | 654,377 |
Gain (Loss) on Securities [Table Text Block] |
|  | Less Than 12 Months |  |  | 12 Months or More |
December 31, 2025 |  | Fair Value |  |  | Gross Unrealized Losses |  |  | Fair Value |  |  | Gross Unrealized Losses |
U.S. government agencies and corporations |  | $ | - |  |  | $ | - |  |  | $ | 288,055 |  |  | $ | 24,298 |
States and political subdivisions |  |  | 1,680 |  |  |  | 364 |  |  |  | 151,652 |  |  |  | 23,372 |
Mortgage-backed securities |  |  | 55,986 |  |  |  | 223 |  |  |  | 99,446 |  |  |  | 3,183 |
Corporate debt securities |  |  | - |  |  |  | - |  |  |  | 4,964 |  |  |  | 541 |
Total temporarily impaired securities |  | $ | 57,666 |  |  | $ | 587 |  |  | $ | 544,117 |  |  | $ | 51,394 |
|  | Less Than 12 Months |  |  | 12 Months or More |
December 31, 2024 |  | Fair Value |  |  | Gross Unrealized Losses |  |  | Fair Value |  |  | Gross Unrealized Losses |
U.S. government agencies and corporations |  | $ | - |  |  | $ | - |  |  | $ | 311,124 |  |  | $ | 40,012 |
States and political subdivisions |  |  | 885 |  |  |  | 118 |  |  |  | 144,849 |  |  |  | 32,254 |
Mortgage-backed securities |  |  | 5,336 |  |  |  | 28 |  |  |  | 115,011 |  |  |  | 5,445 |
Corporate debt securities |  |  | - |  |  |  | - |  |  |  | 5,743 |  |  |  | 764 |
U.S. treasury |  |  | - |  |  |  | - |  |  |  | 999 |  |  |  | 1 |
Total temporarily impaired securities |  | $ | 6,221 |  |  | $ | 146 |  |  | $ | 577,726 |  |  | $ | 78,476 |
Schedule of Realized Gain (Loss) on Called Securities [Table Text Block] |
|  | Sale of Available for Sale Securities |
For the Year Ended December 31, |  | Proceeds |  |  | Book Value |  |  | Gross Gain |  |  | Gross Loss |  |  | Net Loss |
2024 |  |  | 9,279 |  |  |  | 9,279 |  |  |  | - |  |  |  | - |  |  |  | - |

X
- Definition Tabular disclosure of realized gain (loss) on called securities. + References No definition available. + Details
Name: | nksh_ScheduleOfRealizedGainLossOnCalledSecuritiesTableTextBlock
Namespace Prefix: | nksh_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-9 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-3 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-2 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-2 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-2 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (aa) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-2 Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (aaa) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-2 Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-2 Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-3 Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-3 Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-3 Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-3 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of realized and unrealized gain (loss) on investment in security. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(9)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(7)(c)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2 + Details
Name: | us-gaap_GainLossOnInvestmentsTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of maturities of an entity's investments as well as any other information pertinent to the investments. + References No definition available. + Details
Name: | us-gaap_InvestmentsClassifiedByContractualMaturityDateTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

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