Common Stock (Schedule of Transactions for Nonvested RSUs) (Details) - USD ($) $ / shares in Units, shares in Thousands	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Weighted Average Grant Date Fair Value
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 2.1
Restricted Stock Units (RSUs) [Member]
Number of Share Units
Nonvested (in shares)	371
Granted (in shares)	242
Vested (in shares)	(234)
Forfeited (in shares)	(42)
Nonvested (in shares)	337	371
Weighted Average Grant Date Fair Value
Nonvested (usd per share)	$ 95.76
Granted (usd per share)	101.74
Vested (usd per share)	78.08
Forfeited (usd per share)	95.14
Nonvested (usd per share)	$ 112.41	$ 95.76
Total vest date fair value of shares that vested	$ 18,100,000	$ 16,600,000	$ 21,900,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 19,300,000

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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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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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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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