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Derivative Financial Instruments and Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023 | Jun. 30, 2022 | Sep. 30, 2021
Derivative [Line Items] |  |  |  |  |
Gain recorded representing decrease in fair value | $ 2.5 | $ 7.2 |  |  |
Interest Rate Swap | Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional value |  |  |  |  | $ 400.0
Fixed interest rate (as percent) |  |  |  |  | 1.283%
Material losses recognized in income | 0.0 | 0.0 | $ 0.0 |  |
Interest Rate Cap | Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional value |  |  |  | $ 300.0 |
Fixed interest rate (as percent) |  |  |  | 3.465% |
Derivative, basis spread on variable rate (as percent) |  |  |  | 3.465% |
FY 2025 Fourth Quarter Acquisition |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Maximum value of contingent consideration issued | 17.7 |  |  |  |
February 2023 | United States of America, Dollars | Interest Rate Swap | Cash Flow Hedging | Designated as Hedging Instrument |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional value | $ 400.0 | $ 400.0 |  |  |
Fixed interest rate (as percent) | 1.283% | 1.283% |  |  |

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