Summary of Significant Accounting Policies and Select Balance Sheet Information - Amortized Cost, Unrealized Holding Gains and (Losses) and Fair Value of Available-for-sale Securities (Detail) - USD ($)	Sep. 30, 2022	Sep. 30, 2021
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		$ 9,718,000
Unrealized Gains		2,000
Unrealized Losses		(1,000)
Fair Value	$ 0	9,719,000
Current Assets		7,717,000
Noncurrent Assets		2,002,000
Commercial paper and corporate bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		9,718,000
Unrealized Gains		2,000
Unrealized Losses		(1,000)
Fair Value		9,719,000
Current Assets		7,717,000
Noncurrent Assets		$ 2,002,000

Summary of Significant Accounting Policies and Select Balance Sheet Information - Amortized Cost, Unrealized Holding Gains and (Losses) and Fair Value of Available-for-sale Securities (Detail) - USD ($)

Sep. 30, 2022

Sep. 30, 2021

Schedule Of Available For Sale Securities [Line Items]

$ 9,718,000

2,000

(1,000)

$ 0

9,719,000

Current Assets

7,717,000

Noncurrent Assets

2,002,000

Commercial paper and corporate bonds [Member]

Schedule Of Available For Sale Securities [Line Items]

9,718,000

2,000

(1,000)

9,719,000

7,717,000

$ 2,002,000

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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