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DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Non-U.S. currency translation (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax	$ (6,569)	$ 10,137
Accumulated other comprehensive income (loss)	73,972	224,888	$ 315,244	$ 477,570
Foreign currency translation adjustments
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Accumulated other comprehensive income (loss)	$ (45,155)	$ (38,586)

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Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses.

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Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest.

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