| Document And Entity Information | Jun. 01, 2024 |
| Document Information [Line Items] | |
| Entity, Registrant Name | NATIONAL BANKSHARES, INC. |
| Document, Type | 8-K |
| Document, Period End Date | Jun. 01, 2024 |
| Entity, Incorporation, State or Country Code | VA |
| Entity, File Number | 0-15204 |
| Entity, Tax Identification Number | 54-1375874 |
| Entity, Address, Address Line One | 101 Hubbard Street |
| Entity, Address, City or Town | Blacksburg |
| Entity, Address, State or Province | VA |
| Entity, Address, Postal Zip Code | 24060 |
| City Area Code | 540 |
| Local Phone Number | 951-6300 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | NKSH |
| Security Exchange Name | NASDAQ |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0000796534 |
