Revolving Notes - Additional Information (Detail)	1 Months Ended	3 Months Ended
	Sep. 30, 2018	Nov. 30, 2018 USD ($) CreditFacility Facility	Aug. 31, 2018 USD ($)
LIBOR
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	1.50%
Prime Rate
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate	0.50%
Senior Secured Credit Facilities, Consisting of 3 Components
Line of Credit Facility [Line Items]
Number of senior secured credit facilities | CreditFacility		3
Line of credit facility maximum capacity		$ 689,000,000
Letter of credit facility outstanding amount		72,400,000	$ 72,200,000
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
Line of credit maturity date		2023-09
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		$ 39,000,000
Letter of credit facility outstanding amount		$ 22,200,000	$ 27,700,000
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | Minimum
Line of Credit Facility [Line Items]
Line of credit maturity date		2019-02
European Line of Credit, 2nd Component of Senior Secured Credit Facilities | Maximum
Line of Credit Facility [Line Items]
Line of credit maturity date		2020-09
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		1.10%
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		1.30%
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 Joint Venture Line of Credit, 3rd Component of Senior Secured Credit Facilities
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity		$ 50,000,000
Number of lines of credits | Facility		2
Mexican Railcar Manufacturing Joint Venture 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
Line of credit facility borrowings outstanding due period		2019-01
Mexican Railcar Manufacturing Joint Venture Line of Credit 1, 3rd Component of Senior Secured Credit Facilities | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, percentage points added to the reference rate		2.00%
Mexican Railcar Manufacturing Joint Venture Line of Credit 2, 3rd Component of Senior Secured Credit Facilities
Line of Credit Facility [Line Items]
Line of credit facility maximum capacity		$ 20,000,000
Line of credit facility borrowings outstanding due period		2019-07
Joint venture partner each guaranteed percentage		50.00%
Mexican Railcar Manufacturing Joint Venture 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		2.00%