Acquisitions - Identified Intangible Assets (Detail) - American Railcar Industries $ in Thousands	3 Months Ended
	Nov. 30, 2019 USD ($)
Business Acquisition [Line Items]
Identified intangible assets subject to amortization	$ 35,571
Other identified intangible assets not subject to amortization	860
Total identified intangible assets	36,431
Trademarks and patents
Business Acquisition [Line Items]
Identified intangible assets subject to amortization	$ 19,500
Identified intangible assets subject to amortization,Useful Life	9 years
Customer and supplier relationships
Business Acquisition [Line Items]
Identified intangible assets subject to amortization	$ 16,071
Identified intangible assets subject to amortization,Useful Life	7 years