Summary of Significant Accounting Policies and Supplemental Balance Sheet Information - Amortized Cost, Unrealized Holding Gains and (Losses) and Fair Value of Available-for-sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 3,936
Unrealized Losses	(3)
Fair Value	3,933	$ 0
Commercial paper and corporate bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	3,936
Unrealized Losses	(3)
Fair Value	$ 3,933