Debt instrument maturity month and year.

No definition available.

Name:	gbx_DebtInstrumentMaturityMonthAndYear
Namespace Prefix:	gbx_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Increase in debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	gbx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Indicates (true false) whether accounting standards update was adopted.

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- Definition

Date accounting standards update was adopted, in YYYY-MM-DD format.

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- Definition

Aggregate number of common shares reserved for future issuance.

+ References

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- Definition

The value of the financial instrument(s) that the original debt is being converted into in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Notes Payable, Net - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions		12 Months Ended
	Jul. 29, 2022	Aug. 31, 2022	Feb. 09, 2022	Aug. 31, 2021	Aug. 31, 2020
Debt Instrument [Line Items]
Debt instrument amount outstanding		$ 1,290,200,000		$ 915,500,000
ASU 2020-06
Debt Instrument [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]		true
Change in Accounting Principle, Accounting Standards Update, Adoption Date		Sep. 01, 2021
Other Term Loan Due February 2023 to February 2027
Debt Instrument [Line Items]
Unsecured debt		$ 1,200,000
2026 Term Loan
Debt Instrument [Line Items]
Senior term debt		$ 291,900,000
Debt instrument, maturity month and year		2026-08
Periodic Principal Payment		$ 3,650,000
Balloon payment		$ 222,600,000
Swap agreement interest rate		75.00%
Debt instrument amount outstanding		$ 280,900,000
2026 Term Loan \| SOFR
Debt Instrument [Line Items]
Debt instrument, percentage points added to the reference rate		1.50%
2026 Term Loan \| SOFR Adjustment
Debt Instrument [Line Items]
Debt instrument, percentage points added to the reference rate		0.10%
2027 Term Loan
Debt Instrument [Line Items]
Senior term debt	$ 200,000,000	$ 275,000,000.0
Debt instrument, maturity month and year	2023-01	2027-08
Additional term loan	$ 75,000,000
Additional debt available as a delayed draw	$ 75,000,000
Periodic Principal Payment		$ 2,400,000
Balloon payment		$ 219,900,000
Swap agreement interest rate		100.00%
Debt instrument amount outstanding		$ 268,000,000.0
2027 Term Loan \| SOFR
Debt Instrument [Line Items]
Debt instrument, percentage points added to the reference rate		1.375%
2027 Term Loan \| SOFR Adjustment
Debt Instrument [Line Items]
Debt instrument, percentage points added to the reference rate		0.10%
2.875% Convertible senior notes, due 2028
Debt Instrument [Line Items]
Debt instrument, effective interest rate		5.75%
Debt instrument, interest rate		2.875%		2.875%
Description of long term debt		Convertible senior notes, due 2028 (2028 Convertible Notes), bear interest at a fixed rate of 2.875%, paid semiannually in arrears on April 15th and October 15th.
Frequency of payments		semiannually
Debt instrument, maturity date		Apr. 15, 2028
Convertible notes initial conversion rate, shares per $1,000 principal amount		0.180317
Debt instrument, convertible, principal amount		$ 1,000
Convertible notes conversion rate, per share		$ 55.46
Number of shares reserved for future issuance		8.8
2.875% Convertible senior notes, due 2028 \| Redemption on or After April 15, 2025
Debt Instrument [Line Items]
Debt instrument, convertible, latest date		Jan. 15, 2028
Debt instrument redemption start date		Apr. 15, 2025
Debt instrument redemption end date		Apr. 15, 2028
Debt instrument, convertible, threshold percentage of stock price trigger		130.00%
Debt instrument redemption description		Additionally, the Company may elect to call the notes on or after April 15, 2025 and on or before the 40th trading day prior to April 15, 2028, at a cash redemption price described in the 2028 Notes Indenture if the stock price exceeds 130% of the conversion price during certain trading days as defined in the 2028 Notes Indenture.
2.875% Convertible senior notes, due 2024
Debt Instrument [Line Items]
Debt instrument, effective interest rate		4.99%
Debt instrument, interest rate		2.875%		2.875%	2.875%
Description of long term debt		Convertible senior notes, due 2024 (2024 Convertible Notes), bear interest at a fixed rate of 2.875%, paid semi-annually in arrears on February 1st and August 1st.
Frequency of payments		semi-annually
Debt instrument, maturity date		Feb. 01, 2024
Convertible notes initial conversion rate, shares per $1,000 principal amount		0.166234
Debt instrument, convertible, principal amount		$ 1,000
Convertible notes conversion rate, per share		$ 60.16
Number of shares reserved for future issuance		1.1
GBX Leasing Warehouse Facility
Debt Instrument [Line Items]
Senior term debt		$ 323,300,000	$ 323,300,000
Debt instrument amount outstanding		$ 318,600,000
GBX Leasing Warehouse Facility \| SOFR Adjustment
Debt Instrument [Line Items]
Debt instrument, percentage points added to the reference rate		0.11%