Derivative Financial Instruments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, (Loss) Gain [Line Items]
Maximum amount of loss due to credit risk	$ 11,373
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
Net unrealized gain (loss) from cash flow hedges recognized in other comprehensive income (loss) , net of taxes	$ 19,228	$ (31,908)	$ 36,765
Typical maturity period of other risk management derivatives	Less than 12 months
Foreign Exchange Contracts [Member]
Derivative Instruments, (Loss) Gain [Line Items]
Net unrealized gain (loss) from cash flow hedges recognized in other comprehensive income (loss)	$ 20,035	(34,260)	39,692
Net unrealized gain (loss) from cash flow hedges recognized in other comprehensive income (loss) , net of taxes	19,228	$ (31,908)	$ 36,765
Foreign currency cash flow hedge, reclassified into earnings during fiscal year 2020	$ 5,085

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

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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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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.

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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.

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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).

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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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