Share-based Compensation - Assumptions Used to Estimate the Fair Value of Each Stock Option on the Date of Grant Using a Black-Scholes Option Pricing Model (Detail) - Stock Option - $ / shares |
12 Months Ended | ||
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Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2019 |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Expected term (in years) | 4 years 25 days | 4 years 10 days | 3 years 11 months 23 days |
| Risk-free rate of return | 0.30% | 1.60% | 2.90% |
| Expected volatility | 25.10% | 18.70% | 20.20% |
| Expected dividend yield | 0.60% | 0.70% | 0.70% |
| Fair value per option granted (in dollars per share) | $ 39.51 | $ 29.37 | $ 25.89 |
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- Definition The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition The risk-free interest rate assumption that is used in valuing an option on its own shares. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition 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. No definition available.
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Details
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