Share-Based Compensation - Summary of Performance Share and Restricted Stock Unit Activity (Details) - $ / shares shares in Thousands	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Performance shares
Performance Shares (in thousands)
Outstanding at beginning of period (in shares)	124
Granted (in shares)	44
Adjustment for performance results achieved (in shares)	(2)
Vested and issued (in shares)	(31)	(28)	(145)
Forfeited (in shares)	(16)
Outstanding at end of period (in shares)	119	124
Wtd. Avg. Grant Date Share Fair Value
Outstanding at beginning of period (in dollars per share)	$ 204.92
Granted (in dollars per share)	298.10	$ 265.04	$ 155.04
Adjustment for performance results achieved (in dollars per share)	219.04
Vested and issued (in dollars per share)	219.04
Forfeited (in dollars per share)	217.93
Outstanding at end of period (in dollars per share)	$ 232.94	$ 204.92
Vesting period	3 years
Restricted stock and restricted stock units
Performance Shares (in thousands)
Outstanding at beginning of period (in shares)	163
Granted (in shares)	254
Vested and issued (in shares)	(42)
Forfeited (in shares)	(24)
Outstanding at end of period (in shares)	351	163
Wtd. Avg. Grant Date Share Fair Value
Outstanding at beginning of period (in dollars per share)	$ 182.66
Granted (in dollars per share)	265.32	$ 200.36	$ 170.75
Vested and issued (in dollars per share)	188.87
Forfeited (in dollars per share)	205.15
Outstanding at end of period (in dollars per share)	$ 239.89	$ 182.66

Adjustment for performance results achieved.

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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 the adjustment of target vested shares to the actual performance results achieved.

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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 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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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 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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