Share-Based Compensation - Schedule of Fair Value Assumptions (Details)	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Stock options
Fair value assumptions for share-based compensation awards
Average risk-free interest rate	1.63%	2.79%	2.14%
Expected dividend yield	2.08%	2.27%	1.75%
Expected volatility	24.00%	23.00%	22.00%
Expected term (years)	4 years 10 months 24 days	5 years	5 years
Performance shares
Fair value assumptions for share-based compensation awards
Average risk-free interest rate	1.58%	2.77%	1.88%
Expected dividend yield	2.06%	2.24%	1.72%
Expected volatility	25.00%	23.00%	22.00%

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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.

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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.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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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.

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-Name Accounting Standards Codification
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