Common Stock (Schedule of Weighted Average Fair Value per Share of Stock Options and Related Valuation Assumptions) (Details) - USD ($)	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Valuation assumptions:
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year 8 months 12 days
Share-based Payment Arrangement, Option [Member]
Share-based Payment Arrangement, Disclosure [Abstract]
Weighted average fair value per share (usd per share)	$ 23.86	$ 24.80	$ 25.28
Valuation assumptions:
Risk-free interest rate	0.40%	1.60%	3.00%
Expected dividend yield	0.90%	0.80%	0.80%
Expected volatility	32.30%	27.70%	30.50%
Weighted average expected life (years)			4 years 8 months 12 days
Employee Stock
Valuation assumptions:
Weighted average expected life (years)	4 years 8 months 12 days	4 years 8 months 12 days
Restricted Stock Units (RSUs) [Member]
Valuation assumptions:
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 20,800,000

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

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- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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