Captive Insurance Collateral - Schedule of Maturities of Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Due within one year	$ 75,361
Due after one year through five years	1,977
Due after five years through ten years	0
Total	$ 77,338	$ 74,851

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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