| Document and Entity Information | Jan. 23, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jan. 23, 2024 |
| Entity Registrant Name | NATIONAL BANKSHARES, INC. |
| Entity Incorporation State Country Code | VA |
| Entity File Number | 0-15204 |
| Entity Tax Identification Number | 54-1375874 |
| Entity Address Address Line 1 | 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 | true |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock |
| Trading Symbol | NKSH |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Current Fiscal Year End Date | --12-31 |
| Amendment Flag | false |
| Entity Central Index Key | 0000796534 |
