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Stock-Based Compensation Plans Performance Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Minimum
Share-based Payment Award [Line Items]
Total Award Range	0.00%
Maximum
Share-based Payment Award [Line Items]
Total Award Range	260.00%
Earnings-Based Restricted Stock Units
Share-based Payment Award [Line Items]
Nonvestsed restricted stock awards	231,466	259,542
Granted	170,077
Vested	(191,131)
Forfeited	(7,022)
Grant date value per share	$ 87.37	$ 83.20	$ 70.46
Granted, Weighted Average Exercise Price	85.53
Vested, Weighted Average Exercise Price	80.09
Forfeited, Weighted Average Exercise Price	$ 87.24
Fair value of restricted stock awards vested	$ 16.4	$ 14.1
Market-based performance shares
Share-based Payment Award [Line Items]
Nonvestsed restricted stock awards	458,551	494,105
Granted	154,904
Performance achievement	201,886
Vested	(392,344)
Forfeited	0
Grant date value per share	$ 135.83	$ 120.69
Granted, Weighted Average Exercise Price	143.63	$ 156.05	$ 163.63
Vested, Weighted Average Exercise Price	102.90
Forfeited, Weighted Average Exercise Price	$ 0
Expected Term	3 years	3 years	3 years
Expected Volatility Rate	22.50%	29.10%	27.70%
Risk Free Interest Rate	4.50%	4.10%	0.90%
Expected Dividend Rate	0.00%	0.00%	0.00%
Fair value of restricted stock awards vested	$ 31.7		$ 6.6

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Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Performance modification

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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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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 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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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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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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