Commitments and Contingencies - Additional Information (Detail)		9 Months Ended	168 Months Ended
	Jun. 08, 2016 USD ($) Segment	May 31, 2016 USD ($)	Dec. 31, 2014 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Remedial investigation and feasibility study			$ 110,000,000
Bank and third party warranty and performance guarantee facilities		$ 3,200,000
Equity method investment, percentage of ownership interest		50.00%
Payment to acquire equity method investments		$ 5,300,000
Expected loan to unconsolidated joint venture		3,750,000
Note receivable		35,200,000
Loan to unconsolidated joint venture		1,250,000
Mexican Railcar Manufacturing Joint Venture Credit Facility
Commitments and Contingencies Disclosure [Line Items]
Debt outstanding		900,000
Guarantee obligations		400,000
Performance Guarantee
Commitments and Contingencies Disclosure [Line Items]
Letter of credit facility outstanding amount		$ 81,300,000
GBW Railcar Services Holdings, LLC
Commitments and Contingencies Disclosure [Line Items]
Equity method investment, percentage of ownership interest		50.00%
Subsequent Event | Portland Harbor Site
Commitments and Contingencies Disclosure [Line Items]
Discount rate	7.00%
Subsequent Event | Portland Harbor Site | Minimum
Commitments and Contingencies Disclosure [Line Items]
Period for remedial action	4 years
Undiscounted costs for remedial alternatives	$ 642,000,000
Net present value of remedial alternatives	$ 451,000,000
Subsequent Event | Portland Harbor Site | Maximum
Commitments and Contingencies Disclosure [Line Items]
Period for remedial action	62 years
Undiscounted costs for remedial alternatives	$ 10,200,000,000
Net present value of remedial alternatives	$ 9,400,000,000
Subsequent Event | Area Of Willamette River Adjacent to the Company's Portland, Oregon Manufacturing Facility
Commitments and Contingencies Disclosure [Line Items]
Period for remedial action	7 years
Number of sediment decision units | Segment	13
Period for monitoring	30 years
Subsequent Event | Area Of Willamette River Adjacent to the Company's Portland, Oregon Manufacturing Facility | Minimum
Commitments and Contingencies Disclosure [Line Items]
Undiscounted costs for remedial alternatives	$ 1,100,000,000
Net present value of remedial alternatives	$ 746,000,000
Accuracy of cost estimate	(30.00%)
Subsequent Event | Area Of Willamette River Adjacent to the Company's Portland, Oregon Manufacturing Facility | Maximum
Commitments and Contingencies Disclosure [Line Items]
Undiscounted costs for remedial alternatives	$ 1,200,000,000
Net present value of remedial alternatives	$ 811,000,000
Accuracy of cost estimate	50.00%