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

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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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Amount of tax benefit from exercise of option under share-based payment arrangement.

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Amount of cash inflow from exercise of option under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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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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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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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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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Price of a single share of a number of saleable stocks of a company.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Share-Based Compensation (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant	4,341,614
Closing stock price (in dollars per share)	$ 297.86
Cash received from option exercises	$ 34.1	$ 68.1	$ 76.2
Total tax benefit realized from stock option exercises	15.4
Excess tax benefit from stock option exercises	$ 14.2
Deferred Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units/shares granted	203,000
Weighted-average grant date fair value (in dollars per share)	$ 252.53
Cash payments made for deferred stock units	$ 4.8	1.9	2.2
Unrecognized compensation costs	$ 52.7
Unrecognized compensation costs, period for recognition, years	2 years
Fair value of deferred stock units paid	$ 65.4	$ 19.2	$ 38.5
Deferred Stock Units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting or deferral period	2 years
Deferred Stock Units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting or deferral period	5 years
Director Deferred Stock Units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period after service in which to elect payment	10 years
Market-Based Deferred Stock Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting or deferral period	3 years
Number of units/shares granted	80,215	114,929	105,268
Weighted-average grant date fair value (in dollars per share)	$ 275.19	$ 229.61	$ 202.50
Time-Based Deferred Stock Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of units/shares granted	123,448	169,666	143,379
Weighted-average grant date fair value (in dollars per share)	$ 230.92	$ 168.68	$ 162.11
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting or deferral period	3 years
Exercisable period from grant date	10 years
Weighted average remaining contractual terms, outstanding	2 years 8 months 12 days
Weighted average remaining contractual terms, exercisable	2 years 8 months 12 days
Aggregated intrinsic value, outstanding	$ 189.0
Aggregated intrinsic value, exercisable	189.0
Intrinsic value of stock options exercised	65.7	$ 87.2	$ 90.4
Cash received from option exercises	34.1
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs	0.0
Fair value of vested restricted stock	$ 6.1	$ 2.6	$ 2.2
Restricted Stock \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting or deferral period	1 year
Restricted Stock \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting or deferral period	4 years