Document And Entity Information
6 Months Ended
Jul. 01, 2012
Aug. 01, 2012
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jul. 01, 2012  
Document Fiscal Period Focus Q2  
Document Fiscal Year Focus 2012  
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   6,884,038