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Lease Commitments - Supplemental Cash Flow Information Related to Leases (Detail) $ in Thousands | 12 Months Ended
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Aug. 31, 2021 USD ($)
Cash Flow Operating Activities Lessee [Abstract] |
Operating cash flows from operating leases | $ 12,603
ROU assets obtained in exchange for new operating lease liabilities | 1,141
ROU assets disposed of for lease terminations | $ (12,053)

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- Definition Right of use asset disposed of for lease terminations. + References No definition available. + Details
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- Definition Right of use asset obtained in exchange for operating lease liabilities. + References No definition available. + Details
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Namespace Prefix: | gbx_
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- References No definition available. + Details
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Data Type: | xbrli:stringItemType
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- Definition Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918643-209977 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (g)(1) -URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918686-209980 + Details
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