XML 12 R1.htm IDEA: XBRL DOCUMENT v3.10.0.1
Document And Entity Information - shares
 3 Months Ended
Dec. 29, 2018
Jan. 16, 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 Emerging Growth Company false  
Entity Small Business false  
Entity Common Stock, Shares Outstanding (in shares)   19,223,017
Document Type 10-Q  
Document Period End Date Dec. 29, 2018  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q1  
Amendment Flag false