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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
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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

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- Definition 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. + References No definition available. + Details
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