Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Maximum amount of loss due to credit risk	$ 659
Maximum length of time hedged in cash flow hedges	3 years
Maximum maturity period of significant portion of forward and option contracts outstanding	12 months
Typical maturity period of other risk management derivatives	Less than 12 months
Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net unrealized gain (loss) from cash flow hedges recognized in other comprehensive (loss) income	$ (34,260)	$ 39,692	$ 27,578
Net unrealized gain (loss) from cash flow hedges recognized in other comprehensive (loss) income , net of taxes	(31,908)	$ 36,765	$ 20,911
Foreign currency cash flow hedge, reclassified into earnings during fiscal year 2019	$ (16,592)

A description of typical maturity period of other risk management derivatives.

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The value of maximum amount of loss due to credit risk.

+ References

No definition available.

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- Definition

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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Maximum length of time over which the entity is hedging its exposure to the variability in future cash flows for forecasted transactions, excluding those forecasted transactions related to the payment of variable interest on existing financial instruments, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

+ References

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Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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