Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Cash equivalents, fair value	$ 383,794	$ 392,592
Debt Securities, Available-for-sale, Amortized Cost	387,121	398,852
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	(40)	(100)
Fair value	387,081	398,752
Debt Securities, Available-for-sale, Current	3,287	6,160
Debt Securities, Available-for-sale, Noncurrent	0	0
Equity Securities, FV-NI	6,170	5,068
Investments, Fair Value Disclosure	393,251	403,820
Equity Securities, FV-NI, Current	0	0
Short-term Investments	3,287	6,160
Equity Securities, FV-NI, Noncurrent	6,170	5,068
Long-term investments	6,170	5,068
Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Cash equivalents, fair value	383,794	392,592
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	3,227	4,412
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	(40)	(88)
Municipal Bonds And Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	100	1,108
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax	0	(9)
U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		740
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(3)
Fair Value, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Equity Securities, FV-NI	6,170	5,068
Equity Securities, FV-NI, Current	0	0
Equity Securities, FV-NI, Noncurrent	6,170	5,068
Fair Value, Recurring \| Money Market Funds \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Cash equivalents, fair value	383,794	392,592
Fair Value, Recurring \| Corporate Debt Securities [Member] \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value	3,187	4,324
Debt Securities, Available-for-sale, Current	3,187	4,324
Debt Securities, Available-for-sale, Noncurrent	0	0
Fair Value, Recurring \| Municipal Bonds And Notes [Member] \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value	100	1,099
Debt Securities, Available-for-sale, Current	100	1,099
Debt Securities, Available-for-sale, Noncurrent	$ 0	0
Fair Value, Recurring \| U.S. Government Agency Securities \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value		737
Debt Securities, Available-for-sale, Current		737
Debt Securities, Available-for-sale, Noncurrent		$ 0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as noncurrent.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as noncurrent.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

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Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

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