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Share-based Payments - Restricted stock units and PEP units activity (Details) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2022
Other disclosures |  |  |
Compensation expense related to share-based payments | $ 61.5 | $ 45.9 | $ 38.5
Unrecognized compensation expense | $ 68.7 | $ 48.3 |
Recognition period of unrecognized compensation expense | 3 years | 3 years |
Restricted Stock Units |  |  |
Units |  |  |
Outstanding at beginning (in units) | 800,000 | 1,000,000.0 | 1,300,000
Granted (in units) | 300,000 | 300,000 | 300,000
Vested (in shares) | (300,000) | (400,000) | (500,000)
Cancelled (in shares) |  | (100,000) | (100,000)
Outstanding at ending (in units) | 800,000 | 800,000 | 1,000,000.0
Weighted Average Grant-Date Fair Value |  |  |
Outstanding at beginning (in USD per unit) | $ 68.34 | $ 53.05 | $ 38.88
Granted (in USD per unit) | 92.30 | 83.64 | 74.30
Vested (in USD per unit) | 50.14 | 44.35 | 29.44
Cancelled (in USD per unit) | 77.32 | 62.09 | 49.74
Outstanding at ending (in USD per unit) | $ 83.96 | $ 68.34 | $ 53.05
PEP Units |  |  |
Units |  |  |
Outstanding at beginning (in units) | 700,000 | 700,000 | 1,200,000
Granted (in units) | 200,000 | 200,000 | 200,000
PEP units earned (unearned) (in shares) | 200,000 | 200,000 | 600,000
Vested (in shares) | (400,000) | (400,000) | (1,300,000)
Outstanding at ending (in units) | 700,000 | 700,000 | 700,000
Weighted Average Grant-Date Fair Value |  |  |
Outstanding at beginning (in USD per unit) | $ 75.54 | $ 60.60 | $ 37.22
Granted (in USD per unit) | 104.66 | 94.64 | 85.46
PEP units earned (unearned) (in USD per share) | 52.50 | 43.19 | 27.90
Vested (in USD per unit) | 52.50 | 43.19 | 27.90
Cancelled (in USD per unit) | 89.76 | 71.71 | 56.64
Outstanding at ending (in USD per unit) | $ 95.38 | $ 75.54 | $ 60.60

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- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479830/718-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(03) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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- Definition 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. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(03) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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- Definition 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). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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