Fair Value Measurements - Assets Categorized on Basis of Various Levels (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market fund deposits	$ 19,871	$ 21,816
Mutual fund investments	9	9
Total	19,880	21,825
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market fund deposits	19,871	21,816
Mutual fund investments	9	9
Total	$ 19,880	$ 21,825