Supplemental Balance Sheet Information - Amortized Cost, Unrealized Holding Gains and (Losses) and Fair Value of Available-for-sale Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 2,017	$ 9,718
Unrealized Gains		2
Unrealized Losses	(10)	(1)
Fair Value	2,007	9,719
Current Assets	2,007	7,717
Noncurrent Assets		2,002
Commercial paper and corporate bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,017	9,718
Unrealized Gains		2
Unrealized Losses	(10)	(1)
Fair Value	2,007	9,719
Current Assets	$ 2,007	7,717
Noncurrent Assets		$ 2,002

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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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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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