| Document And Entity Information | Oct. 23, 2020 |
| Document Information [Line Items] | |
| Entity, Registrant Name | National Presto Industries, Inc. |
| Document, Type | 8-K |
| Document, Period End Date | Oct. 23, 2020 |
| Entity, Incorporation, State or Country Code | WI |
| Entity, File Number | 1-2451 |
| Entity, Tax Identification Number | 39-0494170 |
| Entity, Address, Address Line One | 3925 North Hastings Way |
| Entity, Address, City or Town | Eau Claire |
| Entity, Address, State or Province | WI |
| Entity, Address, Postal Zip Code | 54703 |
| City Area Code | 715 |
| Local Phone Number | 839-2121 |
| 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 | NPK |
| Security Exchange Name | NYSE |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0000080172 |
