XML 74 R57.htm IDEA: XBRL DOCUMENT
v3.25.3

Summary of Significant Accounting Policies - Estimated Useful Lives (Detail) | Aug. 31, 2025
--- | ---
Building and improvements | Minimum |
Property Plant and Equipment Estimated Useful Lives [Line Items] |
Property, Plant and Equipment useful life | 15 years
Building and improvements | Maximum |
Property Plant and Equipment Estimated Useful Lives [Line Items] |
Property, Plant and Equipment useful life | 25 years
Machinery and Equipment | Minimum |
Property Plant and Equipment Estimated Useful Lives [Line Items] |
Property, Plant and Equipment useful life | 3 years
Machinery and Equipment | Maximum |
Property Plant and Equipment Estimated Useful Lives [Line Items] |
Property, Plant and Equipment useful life | 15 years
Other | Minimum |
Property Plant and Equipment Estimated Useful Lives [Line Items] |
Property, Plant and Equipment useful life | 3 years
Other | Maximum |
Property Plant and Equipment Estimated Useful Lives [Line Items] |
Property, Plant and Equipment useful life | 10 years

X
- Definition Property Plant and Equipment Estimated Useful Lives [Line Items] + References No definition available. + Details
Name: | gbx_PropertyPlantAndEquipmentEstimatedUsefulLivesLineItems
Namespace Prefix: | gbx_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingAndBuildingImprovementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_MachineryAndEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |