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Investments (Tables) | 12 Months Ended
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Sep. 30, 2025
Investments, Debt and Equity Securities [Abstract] |
Schedule of Short-term, Long-term Investments and Marketable Securities | The Company’s investments consisted of the following:
| As of September 30, 2025
| (in thousands)
| Adjusted Basis |  | Gross Unrealized Gains |  | Gross Unrealized Losses |  | Fair Value
Available-for-sale securities | $ | 689,882 |  |  | $ | 2,956 |  |  | $ | (20) |  |  | $ | 692,818 |
Total current investments | $ | 689,882 |  |  | $ | 2,956 |  |  | $ | (20) |  |  | $ | 692,818 |
| As of September 30, 2024
| (in thousands)
| Adjusted Basis |  | Gross Unrealized Gains |  | Gross Unrealized Losses |  | Fair Value
Available-for-sale securities | $ | 577,465 |  |  | $ | 837 |  |  | $ | (26) |  |  | $ | 578,276 |
Total current investments | $ | 577,465 |  |  | $ | 837 |  |  | $ | (26) |  |  | $ | 578,276 |
Schedule of Contract Maturity of Available for Sale Securities | The following table summarizes the contract maturity of the available-for-sale securities as of:
| September 30, 2025 |  | September 30, 2024
| (in thousands)
Within one year | $ | 224,328 |  |  | $ | 578,276 |
After one to two years | 468,490 |  |  | — |
After two to three years | — |  |  | — |
Total | $ | 692,818 |  |  | $ | 578,276 |

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