Fair Value Measurements - Assets Categorized on Basis of Various Levels (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market fund deposits	$ 50,597	$ 11,554
Mutual fund investments	10	10
Cash and cash equivalents	50,597	11,554
Investments in marketable securities	10	10
Total	50,607	11,564
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market fund deposits	50,597	11,554
Mutual fund investments	10	10
Cash and cash equivalents	50,597	11,554
Investments in marketable securities	10	10
Total	$ 50,607	$ 11,564