Fair Value Assets - Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	$ 437,273	$ 392,592
Debt Securities, Available-for-sale, Amortized Cost	437,273	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	0	(100)
Debt Securities, Available-for-Sale	437,273	398,752
Debt Securities, Available-for-sale, Current	0	6,160
Debt Securities, Available-for-sale, Noncurrent	0	0
Equity Securities, FV-NI	8,580	5,068
Equity Securities, FV-NI, Current	0	0
Equity Securities, FV-NI, Noncurrent	8,580	5,068
Investments, Fair Value Disclosure	445,853	403,820
Short-term investments	0	6,160
Long-term investments	8,580	5,068
Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	437,273	392,592
Corporate Bonds And Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		4,412
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(88)
Municipal Bonds And Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Securities, Available-for-sale, Amortized Cost		1,108
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax		0
Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax		(9)
US Government Agencies Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [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 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities, FV-NI	8,580	5,068
Equity Securities, FV-NI, Current	0	0
Equity Securities, FV-NI, Noncurrent	8,580	5,068
Fair Value, Recurring [Member] \| Level 1 \| Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value	$ 437,273	392,592
Fair Value, Recurring [Member] \| Level 2 \| Corporate Bonds And Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value		0
Debt Securities, Available-for-Sale		4,324
Debt Securities, Available-for-sale, Current		4,324
Debt Securities, Available-for-sale, Noncurrent		0
Fair Value, Recurring [Member] \| Level 2 \| Municipal Bonds And Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value		0
Debt Securities, Available-for-Sale		1,099
Debt Securities, Available-for-sale, Current		1,099
Debt Securities, Available-for-sale, Noncurrent		0
Fair Value, Recurring [Member] \| Level 2 \| US Government Agencies Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents, fair value		0
Debt Securities, Available-for-Sale		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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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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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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