Employee Benefit Plans - Time-Based Restricted Stock Unit Equity Awards (Details) - Restricted Stock Units (RSUs) [Member] $ / shares in Units, $ in Millions	12 Months Ended
Sep. 30, 2022 USD ($) grant_recipient $ / shares shares	Sep. 30, 2021 USD ($) grant_recipient $ / shares shares	Sep. 30, 2020 USD ($) grant_recipient $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value \| $	$ 120.1	$ 131.3	$ 95.6
Number of Restricted Stock Units
Outstanding at beginning of year, shares \| shares	3,817,265	4,725,701	4,889,534
Granted, shares \| shares	1,153,124	856,615	1,657,935
Vested, shares \| shares	(1,402,642)	(1,644,263)	(1,651,840)
Cancelled, shares \| shares	(101,653)	(120,788)	(169,928)
Outstanding at end of year, shares \| shares	3,466,094	3,817,265	4,725,701
Weighted Average Grant Date Fair Value
Outstanding at beginning of year, weighted average grant date fair value, per share \| $ / shares	$ 46.16	$ 34.79	$ 33.01
Granted, weighted average grant date fair value, per share \| $ / shares	74.96	83.13	35.98
Vested, weighted average grant date fair value, per share \| $ / shares	41.44	33.26	30.85
Cancelled, weighted average grant date fair value, per share \| $ / shares	51.22	39.16	33.24
Outstanding at end of year, weighted average grant date fair value, per share \| $ / shares	$ 57.50	$ 46.16	$ 34.79
Additional information - restricted stock units
Share-based compensation expense \| $	$ 63.6	$ 56.5	$ 50.6
Unrecognized compensation expense \| $	$ 147.6
Weighted average period over which unrecognized compensation cost is expected to be recognized	2 years 7 months 6 days
Minimum [Member]
Additional information - restricted stock units
Vesting period	3 years
Maximum [Member]
Additional information - restricted stock units
Vesting period	5 years
Fiscal 2022 Grant
Additional information - restricted stock units
RSU grant recipients \| grant_recipient	1,200
Fiscal 2021 Grant
Additional information - restricted stock units
RSU grant recipients \| grant_recipient		1,030
Fiscal 2020 Grant [Member]
Additional information - restricted stock units
RSU grant recipients \| grant_recipient			960

The number of recipients of a share-based compensation grant.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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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 cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

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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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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