v3.10.0.1
Document and Entity Information Document - shares
3 Months Ended
Nov. 30, 2018
Jan. 07, 2019
Entity Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Nov. 30, 2018  
Document Fiscal Year Focus 2019  
Current Fiscal Year End Date --08-31  
Entity Registrant Name SCHNITZER STEEL INDUSTRIES INC  
Entity Central Index Key 0000912603  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Document Fiscal Period Focus Q1  
Class A Common Stock    
Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   26,826,217
Class B Common Stock    
Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   200,000