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Derivatives - Details of Derivatives Held to Manage Foreign Currency Risk (Detail) | Sep. 30, 2025 USD ($) | Sep. 30, 2025 EUR (€) | Sep. 30, 2024 USD ($) | Sep. 30, 2024 EUR (€) | Sep. 30, 2016
--- | --- | --- | --- | --- | ---
3.4% Notes [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Interest rate on borrowing |  | 3.40% | 3.40% | 3.40% | 3.40% |
3.4% Notes [Member] | Fixed Rate Debt [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Interest rate on borrowing |  |  |  |  |  | 3.40%
Net Investment Hedge [Member] | 3.4% Notes [Member] | Cross Currency Swaps [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Notional Amount |  | $ 250,000,000 | € 223,000,000 | $ 250,000,000 | € 223,000,000 |
Net Investment Hedge [Member] | 3.4% Notes [Member] | Fixed Rate Debt [Member] | Cross Currency Swaps [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Interest rate on borrowing |  | 3.40% | 3.40% | 3.40% | 3.40% |
Not Designated as Hedging Instrument [Member] | Forward Foreign Currency Contracts [Member] |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Notional Amount | [1] | $ 184,000,000 |  | $ 138,000,000 |  |
[1] | At September 30, 2025, the Company’s forward foreign exchange contracts were denominated in Euro, Indonesian rupiah, Czech koruna, and Colombian peso.

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