| Cover | May 18, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 18, 2021 |
| Entity File Number | 1-2451 |
| Entity Registrant Name | National Presto Industries, Inc. |
| Entity Central Index Key | 0000080172 |
| Entity Tax Identification Number | 39-0494170 |
| Entity Incorporation, State or Country Code | WI |
| 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 | 54703-3703 |
| 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, $1.00 par value |
| Trading Symbol | NPK |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
