Fair Value Measurements - Assets Categorized on Basis of Various Levels (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Sep. 30, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market fund deposits	$ 57,462	$ 54,225
Mutual fund investments	10	9
Cash and cash equivalents	57,462	54,225
Investments in marketable securities	10	9
Total	57,472	54,234
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market fund deposits	57,462	54,225
Mutual fund investments	10	9
Cash and cash equivalents	57,462	54,225
Investments in marketable securities	10	9
Total	$ 57,472	$ 54,234