Revolving Notes - Additional Information (Detail)	6 Months Ended	12 Months Ended
	Feb. 28, 2021 USD ($) Facility CreditFacility	Aug. 31, 2020 USD ($)
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 115,400,000
Long-term Line of Credit	$ 275,839,000	$ 351,526,000
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	3
Line of credit facility maximum capacity	$ 738,800,000
Letter of credit facility outstanding amount	27,900,000	28,700,000
Borrowings	210,000,000.0	275,000,000.0
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	2024-06
Revolving Line of Credit, 1st Component of Senior Secured Credit Facilities | LIBOR
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 | Prime Rate
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	0.50%
European Line of Credit, 2nd Component of Senior Secured Credit Facilities
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity	$ 68,800,000
Long-term Line of Credit	35,000,000.0
Letter of credit facility outstanding amount	$ 34,800,000	46,500,000
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | Minimum
Line of Credit Facility [Line Items]
Line of credit maturity date	2021-06
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | Maximum
Line of Credit Facility [Line Items]
Line of credit maturity date	2022-09
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	1.50%
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | EURIBOR
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.10%
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	$ 70,000,000.0
Letter of credit facility outstanding amount	31,000,000.0	$ 30,000,000.0
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
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
Line of credit facility borrowings outstanding due period	2021-06
Joint venture partner each guaranteed percentage	50.00%
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	$ 5,000,000.0
Line of credit facility borrowings outstanding due period	2022-09
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	2.95%