Revolving Notes - Additional Information (Detail)	3 Months Ended
	Nov. 30, 2022 USD ($) Facility CreditFacility	Aug. 31, 2022 USD ($)
Line of Credit Facility [Line Items]
Long-term line of credit	$ 290,500,000	$ 296,600,000
Number of lines of credits | CreditFacility	3
Senior Secured Credit Facilities, Consisting of 4 Components
Line of Credit Facility [Line Items]
Number of senior secured credit facilities | Facility	4
Line of credit facility maximum capacity	$ 1,100,000
Letter of credit facility outstanding amount	6,200,000	6,900,000
Senior Secured Credit Facilities, Consisting of 4 Components | North American
Line of Credit Facility [Line Items]
Long-term line of credit	160,000,000.0	160,000,000.0
Senior Secured Credit Facilities, Consisting of 4 Components | European
Line of Credit Facility [Line Items]
Long-term line of credit	45,500,000	51,600,000
Senior Secured Credit Facilities, Consisting of 4 Components | Mexican
Line of Credit Facility [Line Items]
Long-term line of credit	85,000,000.0	$ 85,000,000.0
Committed Credit Facilities
Line of Credit Facility [Line Items]
Aggregate amount available to draw down	213,400,000
Committed Credit Facilities | North American
Line of Credit Facility [Line Items]
Aggregate amount available to draw down	158,300,000
Committed Credit Facilities | European
Line of Credit Facility [Line Items]
Aggregate amount available to draw down	25,100,000
Committed Credit Facilities | Mexican
Line of Credit Facility [Line Items]
Aggregate amount available to draw down	30,000,000
Revolving Line of Credit, 1st Component of Senior Secured Credit Facilities
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 600,000,000.0
Line of credit maturity date	2026-08
Revolving Line of Credit, 1st Component of Senior Secured Credit Facilities | Prime Rate
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	0.50%
Revolving Line of Credit, 1st Component of Senior Secured Credit Facilities | SOFR
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.50%
Revolving Line of Credit, 1st Component of Senior Secured Credit Facilities | SOFR Adjustment
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	0.10%
GBX Leasing Warehouse Facility
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 350,000,000.0
Line of credit maturity date	2027-08
GBX Leasing Warehouse Facility | SOFR
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.85%
GBX Leasing Warehouse Facility | SOFR Adjustment
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	0.11%
European Line of Credit, 2nd Component of Senior Secured Credit Facilities
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 70,500,000
Long-term line of credit	$ 34,200,000
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | Minimum
Line of Credit Facility [Line Items]
Line of credit maturity date	2023-02
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | Maximum
Line of Credit Facility [Line Items]
Line of credit maturity date	2024-09
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | WIBOR | Minimum
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.20%
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | WIBOR | Maximum
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.60%
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | EURIBOR | Minimum
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.10%
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | EURIBOR | Maximum
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.50%
Mexican Railcar Manufacturing Operations Line of Credit, 3rd Component of Senior Secured Credit Facilities
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 115,000,000.0
Mexican Railcar Manufacturing Operations Line of Credit 1, 3rd Component of Senior Secured Credit Facilities
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 30,000,000.0
Joint venture partner each guaranteed percentage	50.00%
Line of credit facility borrowings outstanding due period	2024-06
Mexican Railcar Manufacturing Operations Line of Credit 1, 3rd Component of Senior Secured Credit Facilities | LIBOR | Minimum
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	3.75%
Mexican Railcar Manufacturing Operations Line of Credit 1, 3rd Component of Senior Secured Credit Facilities | LIBOR | Maximum
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	4.25%
Mexican Railcar Manufacturing Operations Line of Credit 2, 3rd Component of Senior Secured Credit Facilities
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 35,000,000.0
Joint venture partner each guaranteed percentage	50.00%
Line of credit facility borrowings outstanding due period	2023-06
Mexican Railcar Manufacturing Operations Line of Credit 2, 3rd Component of Senior Secured Credit Facilities | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	3.75%
Mexican Railcar Manufacturing Operations Line of Credit 3, 3rd Component of Senior Secured Credit Facilities
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 50,000,000.0
Line of credit facility borrowings outstanding due period	2024-10
Mexican Railcar Manufacturing Operations Line of Credit 3, 3rd Component of Senior Secured Credit Facilities | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	4.25%