Fair Value Measurements - Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2022	Sep. 30, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Commercial Notes	$ 25,336
Marketable securities	0	$ 126,728
Short-term investments	225,490	57,430
Long-term investments	159,540	196,643
Certificate of deposits	50,000	50,000
Contingent consideration	0	0
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Commercial Notes	0
Marketable securities	0	126,728
Short-term investments	0	0
Long-term investments	0	0
Certificate of deposits	50,000	50,000
Contingent consideration	0	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Commercial Notes	25,336
Marketable securities	0	0
Short-term investments	225,490	57,430
Long-term investments	159,540	196,643
Certificate of deposits	0	0
Contingent consideration	0	0
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Commercial Notes	0
Marketable securities	0	0
Short-term investments	0	0
Long-term investments	0	0
Certificate of deposits	0	0
Contingent consideration	$ 0	$ 0