Fair Value Measurements - Fair Value Measurements for Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($)	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market instruments	$ 82,924,000		$ 39,262,000
U.S. government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	27,423,000	$ 1,973,000
Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	104,311,000	41,727,000
Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	319,690,000	271,333,000
Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Certificate of deposits	0	50,000,000
Level 1 | Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market instruments	82,924,000		39,262,000
Level 1 | U.S. government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	27,423,000	1,973,000
Level 1 | Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 1 | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 1 | Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Certificate of deposits	0	50,000,000
Level 2 | Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market instruments	0		0
Level 2 | U.S. government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 2 | Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	104,311,000	41,727,000
Level 2 | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	319,690,000	271,333,000
Level 2 | Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Certificate of deposits	0	0
Level 3 | Money market instruments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market instruments	0		$ 0
Level 3 | U.S. government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 3 | Commercial notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 3 | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Held to maturity securities	0	0
Level 3 | Certificate of deposits
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Certificate of deposits	$ 0	$ 0