Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Assets and Liabilities Measured at Fair Value on a Recurring Basis [Member] - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	$ 15,027	$ 48,947
Liabilities measured at fair value	817
Available-for-sale investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	9,719	30,313
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	15,027	48,947
Significant Other Observable Inputs (Level 2) [Member] | Available-for-sale investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	9,719	30,313
Level 3 Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities measured at fair value	817
Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	5,308	18,634
Cash equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	5,308	$ 18,634
Contingent consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities measured at fair value	817
Contingent consideration [Member] | Level 3 Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities measured at fair value	$ 817