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Cover Page - USD ($)
 12 Months Ended
Aug. 31, 2021
Oct. 20, 2021
Feb. 28, 2021
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Aug. 31, 2021    
Document Fiscal Year Focus 2021    
Document Fiscal Period Focus FY    
Entity Registrant Name THE GREENBRIER COMPANIES, INC.    
Trading Symbol GBX    
Security Exchange Name NYSE    
Entity Central Index Key 0000923120    
Current Fiscal Year End Date --08-31    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Title of 12(b) Security Common Stock    
Entity Common Stock, Shares Outstanding   32,484,998  
Entity Public Float     $ 1,502,646,519
Document Annual Report true    
Document Transition Report false    
Entity File Number 1-13146    
Entity Emerging Growth Company false    
Entity Small Business false    
ICFR Auditor Attestation Flag true    
Entity Shell Company false    
Entity Incorporation, State or Country Code OR    
Entity Tax Identification Number 93-0816972    
Entity Address, Address Line One One Centerpointe Drive    
Entity Address, Address Line Two Suite 200    
Entity Address, City or Town Lake Oswego    
Entity Address, State or Province OR    
Entity Address, Postal Zip Code 97035    
City Area Code 503    
Local Phone Number 684-7000    
Documents Incorporated by Reference

Certain portions of the registrant’s definitive Proxy Statement prepared in connection with the Annual Meeting of Shareholders to be held on January 7, 2022 are incorporated by reference into Parts II and III of this Report.