XML 37 R1.htm IDEA: XBRL DOCUMENT v3.19.3
Document And Entity Information - USD ($)
 12 Months Ended
Sep. 28, 2019
Oct. 24, 2019
Mar. 30, 2019
Document Information [Line Items]      
Entity Registrant Name INSTEEL INDUSTRIES INC    
Entity Central Index Key 0000764401    
Trading Symbol iiin    
Current Fiscal Year End Date --09-28    
Entity Filer Category Accelerated Filer    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Well-known Seasoned Issuer No    
Entity Emerging Growth Company false    
Entity Small Business false    
Entity Common Stock, Shares Outstanding (in shares)   19,260,725  
Entity Public Float     $ 289,144,525
Entity Shell Company false    
Document Type 10-K    
Document Period End Date Sep. 28, 2019    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Amendment Flag false    
Title of 12(b) Security Common Stock