Share-Based Compensation - Schedule of Fair Value Assumptions (Details)	12 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Stock options
Fair value assumptions for share-based compensation awards
Average risk-free interest rate	2.14%	1.85%	1.76%
Expected dividend yield	1.75%	2.21%	2.78%
Expected volatility	22.00%	24.00%	29.00%
Expected term (years)	5 years	5 years 1 month	5 years 1 month
Performance shares
Fair value assumptions for share-based compensation awards
Average risk-free interest rate	1.88%	1.35%	1.21%
Expected dividend yield	1.72%	2.20%	2.75%
Expected volatility	22.00%	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 share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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