Marketable Securities - Fair Value of Available-for-Sale Marketable Securities by Type of Security (Detail) - USD ($) $ in Thousands	Jun. 30, 2026	Sep. 30, 2025
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 178,617	$ 156,521
Gross Unrealized Gains	0	47
Gross Unrealized Losses	(543)	(2)
Fair Value	178,074	156,566
U.S. Treasury Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	178,617	156,521
Gross Unrealized Gains	0	47
Gross Unrealized Losses	(543)	(2)
Fair Value	$ 178,074	$ 156,566

Amortized cost 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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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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