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Stock-based Compensation Plans (Schedule of Share-based Compensation, Effect on Statement of Operations) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Decrease in operating income	$ 5.5	$ 6.4	$ 8.6
Effect on net income or loss	$ (4.0)	$ (4.0)	$ (4.8)
Effect on earnings or loss per basic share	$ (0.03)	$ (0.03)	$ (0.03)
Effect on earnings or loss per diluted share	$ (0.03)	$ (0.03)	$ (0.03)

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- Definition

Share-based Compensation, Increase (Decrease) in Earnings Per Share, Basic

+ References

No definition available.

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- Definition

Share-based Compensation, Increase (Decrease) in Earnings Per Share, Diluted

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- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901

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-Topic 718
-SubTopic 10
-Section S99
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-Paragraph 2
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- Definition

Amount, after tax, of expense for award under share-based payment arrangement.

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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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