Stock-Based Compensation Plans - Summary of Fair Value Assumptions Used for Share Based Awards (Details) - $ / shares		12 Months Ended
May 12, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value per share (USD per share)		$ 5.56	$ 7.44
Risk-free interest rate		2.20%	1.70%
Expected dividend yield		0.90%	0.90%
Expected volatility		23.30%	22.80%
Expected term		5 years 10 months 17 days	7 years 5 months 12 days
Minimum risk free interest rate	1.10%
Maximum risk free interest rate	1.90%
Minimum expected volatility rate	21.50%
Maximum expected volatility rate	24.40%
Performance awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate		1.70%	1.20%
Expected dividend yield		1.00%	1.00%
Expected volatility		24.20%	21.00%
Expected term		3 years	1 year 10 months 25 days
Minimum risk free interest rate		1.60%	0.90%
Maximum risk free interest rate		1.80%	1.50%
Minimum expected volatility rate			18.90%
Maximum expected volatility rate			22.40%

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.

+ References

+ Details

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- Definition

The estimated measure of the maximum 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.

+ References

No definition available.

+ Details

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- Definition

The estimated measure of the minimum 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.

+ References

No definition available.

+ Details

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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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+ Details

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- Definition

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

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No definition available.

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- Definition

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

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No definition available.

+ Details

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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.

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No definition available.

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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Fair Value

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No definition available.

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