Stock Option and Incentive Plan - Additional Information (Detail) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Awards granted under the Equity Incentive Plan
Maximum number of shares authorized to be granted		70,550	67,550
Stock option awards, term	10 years
Total intrinsic value of options exercised	$ 27,023	$ 31,220	$ 13,081
Value of restricted shares vested	28,682	$ 28,727	$ 28,430
Aggregate intrinsic value of stock options outstanding	58,644
Aggregate intrinsic value of stock options exercisable	$ 38,482
Minimum [Member]
Awards granted under the Equity Incentive Plan
Awards granted under the Equity Incentive Plan, vesting period	3 years
Maximum [Member]
Awards granted under the Equity Incentive Plan
Awards granted under the Equity Incentive Plan, vesting period	4 years

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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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Number of shares authorized for issuance under share-based payment arrangement.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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