v3.19.3.a.u2
Document and Entity Information Document - shares
3 Months Ended
Nov. 30, 2019
Jan. 06, 2020
Entity Information [Line Items]    
Document Type 10-Q  
Document Period End Date Nov. 30, 2019  
Entity Registrant Name SCHNITZER STEEL INDUSTRIES, INC.  
Amendment Flag false  
Document Fiscal Year Focus 2020  
Trading Symbol SCHN  
Document Fiscal Period Focus Q1  
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  
Entity File Number 000-22496  
Entity Tax Identification Number 93-0341923  
Entity Address, Address Line One 299 SW Clay Street  
Entity Address, Address Line Two Suite 350  
Entity Address, City or Town Portland  
Entity Address, State or Province OR  
Entity Address, Postal Zip Code 97201  
City Area Code 503  
Local Phone Number 224-9900  
Entity Incorporation, State or Country Code OR  
Title of 12(b) Security Class A Common Stock, $1.00 par value  
Security Exchange Name NASDAQ  
Document Quarterly Report true  
Document Transition Report false  
Entity Interactive Data Current Yes  
Class A Common Stock    
Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   26,943,066
Class B Common Stock    
Entity Information [Line Items]    
Entity Common Stock, Shares Outstanding   200,000