v3.19.2
Document and Entity Information Document - shares
9 Months Ended
May 31, 2019
Jun. 24, 2019
Entity Information [Line Items]    
Document Type 10-Q  
Document Period End Date May 31, 2019  
Entity Registrant Name SCHNITZER STEEL INDUSTRIES, INC.  
Amendment Flag false  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Entity Central Index Key 0000912603  
Current Fiscal Year End Date --08-31  
Entity Filer Category Large Accelerated Filer  
Entity Emerging Growth Company false  
Entity Small Business false  
Entity Shell Company false  
Entity Current Reporting Status Yes  
Class A Common Stock    
Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   26,578,576
Class B Common Stock    
Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   200,000