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, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	$ 48,947	$ 49,306
Liabilities measured at fair value		3,200
Available-for-sale securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	30,313	24,931
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	48,947	49,306
Significant Other Observable Inputs (Level 2) [Member] | Available-for-sale securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	30,313	24,931
Level 3 Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities measured at fair value		3,200
Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	18,634	24,375
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	$ 18,634	24,375
Contingent consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities measured at fair value		3,200
Contingent consideration [Member] | Level 3 Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities measured at fair value		$ 3,200