XML 13 R1.htm IDEA: XBRL DOCUMENT v3.6.0.2
Document And Entity Information - shares
 3 Months Ended
Dec. 31, 2016
Jan. 18, 2017
Document Information [Line Items]    
Entity Registrant Name INSTEEL INDUSTRIES INC  
Entity Central Index Key 0000764401  
Trading Symbol iiin  
Current Fiscal Year End Date --10-01  
Entity Filer Category Accelerated Filer  
Entity Current Reporting Status Yes  
Entity Voluntary Filers No  
Entity Well-known Seasoned Issuer No  
Entity Common Stock, Shares Outstanding (in shares)   18,985,236
Document Type 10-Q  
Document Period End Date Dec. 31, 2016  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q1  
Amendment Flag false