Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2024	Mar. 04, 2025	Jun. 30, 2024
Document Information [Line Items]
Entity Central Index Key	0000080172
Entity Registrant Name	NATIONAL PRESTO INDUSTRIES INC
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2024
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2024
Document Transition Report	false
Entity File Number	1-2451
Entity Incorporation, State or Country Code	WI
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	54703-3703
City Area Code	715
Local Phone Number	839-2121
Title of 12(b) Security	$1.00 par value common stock
Trading Symbol	NPK
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 385,752,731
Entity Common Stock, Shares Outstanding		7,143,484
Auditor Name	RSM US LLP
Auditor Location	Milwaukee, Wisconsin
Auditor Firm ID	49