Document And Entity Information (USD $)
12 Months Ended
Dec. 31, 2011
Mar. 02, 2012
Jun. 30, 2011
Document And Entity Information [Abstract]
Document Type 10-K
Amendment Flag false
Document Period End Date Dec. 31, 2011
Document Fiscal Period Focus FY
Document Fiscal Year Focus 2011
Entity Registrant Name NATIONAL PRESTO INDUSTRIES INC
Entity Central Index Key 0000080172
Current Fiscal Year End Date --12-31
Entity Filer Category Accelerated Filer
Entity Common Stock, Shares Outstanding 6,875,001
Entity Well-known Seasoned Issuer No
Entity Public Float $ 490,468,015
Entity Current Reporting Status Yes
Entity Voluntary Filers No