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Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands | Jun. 30, 2023 | Sep. 30, 2022
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Cash equivalents, fair value | $ 186,499 | $ 287,932
Cost or amortized cost | 200,610 | 422,699
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (229) | (1,787)
Fair value | 200,381 | 420,912
Debt Securities, Available-for-sale, Current | 13,109 | 126,554
Debt Securities, Available-for-sale, Noncurrent | 773 | 6,426
Equity Securities, FV-NI | 5,114 | 3,118
Equity Securities, FV-NI, Current | 0 | 0
Equity Securities, FV-NI, Noncurrent | 5,114 | 3,118
Available-for-sale Securities | 205,495 | 424,030
Available-for-sale Securities, Current | 13,109 | 126,554
Long-term investments | 5,887 | 9,544
Fair Value, Recurring |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Equity Securities, FV-NI | 5,114 | 3,118
Equity Securities, FV-NI, Current | 0 | 0
Equity Securities, FV-NI, Noncurrent | 5,114 | 3,118
Money Market Funds |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Cash equivalents, fair value | 186,499 | 276,294
Money Market Funds | Fair Value, Recurring | Level 1 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Cash equivalents, fair value | 186,499 | 276,294
Corporate Debt Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Cost or amortized cost | 7,271 | 50,828
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (144) | (950)
Corporate Debt Securities [Member] | Fair Value, Recurring | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Cash equivalents, fair value |  | 912
Fair value | 7,127 | 49,878
Debt Securities, Available-for-sale, Current | 6,354 | 44,356
Debt Securities, Available-for-sale, Noncurrent | 773 | 4,610
Municipal Bonds And Notes [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Cost or amortized cost | 2,156 | 5,018
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (31) | (102)
Municipal Bonds And Notes [Member] | Fair Value, Recurring | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Fair value | 2,125 | 4,916
Debt Securities, Available-for-sale, Current | 2,125 | 3,812
Debt Securities, Available-for-sale, Noncurrent | 0 | 1,104
U.S. Government Securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Cost or amortized cost | 2,899 | 84,734
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (34) | (660)
U.S. Government Securities | Fair Value, Recurring | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Cash equivalents, fair value |  | 10,120
Fair value | 2,865 | 84,074
Debt Securities, Available-for-sale, Current | 2,865 | 73,954
Debt Securities, Available-for-sale, Noncurrent | 0 | 0
U.S. Government Agency Securities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Cost or amortized cost | 1,785 | 5,825
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (20) | (75)
U.S. Government Agency Securities | Fair Value, Recurring | Level 2 |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items] |  |
Cash equivalents, fair value |  | 606
Fair value | 1,765 | 5,750
Debt Securities, Available-for-sale, Current | 1,765 | 4,432
Debt Securities, Available-for-sale, Noncurrent | $ 0 | $ 712

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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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