Revolving Notes - Additional Information (Detail) - USD ($)	6 Months Ended
	Feb. 29, 2024	Aug. 31, 2023
Line of Credit Facility [Line Items]
Long-term line of credit	$ 300,800,000	$ 297,100,000
Notional covering percentage of outstanding balance	99.00%
European
Line of Credit Facility [Line Items]
Line of credit, guaranteed amount	$ 32,500,000
Mexican
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 96,000,000
Minimum | European
Line of Credit Facility [Line Items]
Line of credit maturity date	2024-06
Minimum | Mexican
Line of Credit Facility [Line Items]
Line of credit facility borrowings outstanding due period	2024-06
Maximum | European
Line of Credit Facility [Line Items]
Line of credit maturity date	2025-11
Maximum | Mexican
Line of Credit Facility [Line Items]
Line of credit facility borrowings outstanding due period	2027-01
WIBOR | Minimum | European
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.20%
WIBOR | Maximum | European
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.60%
EURIBOR | European
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.90%
Senior Secured Credit Facilities
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 1,400,000,000
Letter of credit facility outstanding amount	7,100,000	4,900,000
Senior Secured Credit Facilities | North American
Line of Credit Facility [Line Items]
Long-term line of credit	55,000,000
Senior Secured Credit Facilities | European
Line of Credit Facility [Line Items]
Long-term line of credit	31,600,000	47,200,000
Senior Secured Credit Facilities | Mexican
Line of Credit Facility [Line Items]
Long-term line of credit	125,000,000	110,000,000
Committed Credit Facilities
Line of Credit Facility [Line Items]
Aggregate amount available to draw down	329,300,000
Committed Credit Facilities | North American
Line of Credit Facility [Line Items]
Aggregate amount available to draw down	214,600,000
Committed Credit Facilities | European
Line of Credit Facility [Line Items]
Aggregate amount available to draw down	43,700,000
Committed Credit Facilities | Mexican
Line of Credit Facility [Line Items]
Aggregate amount available to draw down	71,000,000
Revolving Line of Credit, 1st Component of Senior Secured Credit Facilities | North American
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 600,000,000
Line of credit maturity date	2026-08
Revolving Line of Credit, 1st Component of Senior Secured Credit Facilities | European
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 75,300,000
Revolving Line of Credit, 1st Component of Senior Secured Credit Facilities | Prime Rate | North American
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	0.75%
Revolving Line of Credit, 1st Component of Senior Secured Credit Facilities | SOFR | North American
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.75%
Revolving Line of Credit, 1st Component of Senior Secured Credit Facilities | SOFR Adjustment | North American
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	0.10%
GBX Leasing
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 550,000,000
Line of credit maturity date	2027-08
Long-term line of credit	$ 89,200,000	$ 139,900,000
GBX Leasing | SOFR
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.85%
GBX Leasing | SOFR Adjustment
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	0.11%
Mexican Railcar Manufacturing Joint Venture Line of Credit, 4 Component of Senior Secured Credit Facilities | Mexican
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 196,000,000
Mexican Railcar Manufacturing Operations Line of Credit 1, 4 Component of Senior Secured Credit Facilities | LIBOR | Mexican
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, 4 Component of Senior Secured Credit Facilities | SOFR | Mexican
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	2.22%
Mexican Railcar Manufacturing Operations Line of Credit 3, 4 Component of Senior Secured Credit Facilities | Mexican
Line of Credit Facility [Line Items]
Joint venture partner each guaranteed percentage	50.00%