Share-Based Compensation - Restricted Stock Plan Table (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019
Shares Available for Grant
Shares Available for Grant, Beginning (in shares)	1,156,902
Shares Available for Grant, Granted	299,858
Shares Available for Grant, Forfeited	4,410
Shares Available for Grant, Ending (in shares)	861,454	1,156,902
Number of Shares Outstanding
Number of Shares Outstanding, Beginning (in shares)	350,778
Number of Shares Outstanding, Granted	299,858
Number of Shares Outstanding, Vested (in shares)	(161,880)
Number of Shares Outstanding, Forfeited (in shares)	(4,410)
Number of Shares Outstanding, Ending (in shares)	484,346	350,778
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning (in dollar per share)	$ 40.06
Weighted Average Grant Date Fair Value, Granted (in dollar per share)	44.94
Weighted Average Grant Date Fair Value, Vested (in dollar per share)	40.26
Weighted Average Grant Date Fair Value, Forfeited (in dollar per share)	44.23
Weighted Average Grant Date Fair Value, Ending (in dollars per share)	$ 42.97	$ 40.06
Stock Option Activity, Additional Disclosures
Weighted Average Remaining Term (in years)	1 year 4 months 13 days	1 year 4 months 9 days
Aggregate Intrinsic Value	$ 24.8	$ 14.4

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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Number of shares under non-option equity instrument agreements that were cancelled as a result of occurrence of a terminating event.

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Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Increase (decrease) in the number of shares under non-option equity instrument agreements.

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Intrinsic value of outstanding award under share-based payment arrangement. Excludes share and unit options.

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