Revenue Recognition - Additional information (Detail) $ in Millions	3 Months Ended
Nov. 30, 2018 USD ($)
Revenue From Contract With Customers [Line Items]
Revenue recognized from contract with customers liability	$ 5.3
Railcar Sales
Revenue From Contract With Customers [Line Items]
Expected revenue recognized in the reminder of fiscal year	1,100.0
Services
Revenue From Contract With Customers [Line Items]
Expected revenue recognized in the reminder of fiscal year	$ 138.7
Expected performance percentage	60.00%
Maximum
Revenue From Contract With Customers [Line Items]
Repair service period	90 days

Repair services completion period.

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- Definition

Revenue From Contract With Customers [Line Items]

+ References

No definition available.

+ Details

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- Definition

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130556-203045

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Percentage of remaining performance obligation to total remaining performance obligation not recognized as revenue.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130556-203045

+ Details

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- Details

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- Details

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- Details

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