XML 113 R92.htm IDEA: XBRL DOCUMENT
v3.21.2

Earnings Per Share - Reconciliation of Shares Used in Computation of Basic and Diluted Earnings Per Common Share (Parenthetical) (Detail) - shares | 12 Months Ended |
--- | --- | ---
Aug. 31, 2021 | Aug. 31, 2020 | Aug. 31, 2019 | Apr. 30, 2021
Restricted Stock |  |  |  |
Earnings Per Share Disclosure [Line Items] |  |  |  |
Anti-dilutive shares excluded from calculation | 0 | 0 | 0 |
2.875% Convertible senior notes, due 2024 |  |  |  |
Earnings Per Share Disclosure [Line Items] |  |  |  |
Debt instrument, interest rate | 2.875% | 2.875% | 2.875% |
2.875% Convertible senior notes, due 2028 |  |  |  |
Earnings Per Share Disclosure [Line Items] |  |  |  |
Debt instrument, interest rate | 2.875% |  |  | 2.875%
2.25% Convertible senior notes, due 2024 |  |  |  |
Earnings Per Share Disclosure [Line Items] |  |  |  |
Debt instrument, interest rate | 2.25% | 2.25% | 2.25% |

X
- Definition Earnings Per Share Disclosure [Line Items] + References No definition available. + Details
Name: | gbx_EarningsPerShareDisclosureLineItems
Namespace Prefix: | gbx_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257 + Details
Name: | us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis=us-gaap_RestrictedStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=gbx_TwoPointEightSevenFiveConvertibleSeniorNotesDue2024Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=gbx_TwoPointEightSevenFiveConvertibleSeniorNotesDue2028Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=gbx_TwoPointTwoFiveConvertibleSeniorNotesDue2024Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |