| Document and Entity Information | Jul. 07, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | GREENBRIER COMPANIES INC |
| Amendment Flag | false |
| Entity Central Index Key | 0000923120 |
| Current Fiscal Year End Date | --08-31 |
| Document Type | 8-K |
| Document Period End Date | Jul. 7, 2021 |
| Entity Incorporation State Country Code | OR |
| Entity File Number | 001-13146 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock without par value |
| Trading Symbol | GBX |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
