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Stock-Based Compensation - Narrative (Details) - USD ($) |  | 3 Months Ended | 6 Months Ended |  |
--- | --- | --- | --- | --- | ---
Oct. 01, 2023 | Mar. 31, 2025 | Mar. 31, 2024 | Mar. 31, 2025 | Mar. 31, 2024 | Sep. 30, 2024 | Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Common stock, share reserve for issuance (in shares) |  | 2,282,102 |  | 2,282,102 |  |  |
Granted (in shares) |  |  |  | 0 | 0 |  |
Number of options outstanding (in shares) |  | 1,525,717 |  | 1,525,717 |  | 1,978,516 |
Stock-based compensation expense |  | $ 15,081,000 | $ 16,588,000 | $ 29,257,000 | $ 34,273,000 |  |
Restricted stock units |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Share-based payment award (in shares) |  | 5,933,743 |  | 5,933,743 |  | 4,913,312 |
Stock-based compensation expense |  | $ 15,100,000 | 16,000,000.0 | $ 29,200,000 | 32,200,000 |  |
Unrecognized pre-tax compensation expense |  | 97,900,000 |  | $ 97,900,000 |  |  |
Weighted average period to recognize pre-tax compensation expense |  |  |  | 1 year 9 months 18 days |  |  |
Options |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Intrinsic value of options exercised |  | 3,700,000 | 2,500,000 | $ 4,600,000 | 3,100,000 |  |
Stock-based compensation expense |  | $ 3,000.0 | 600,000 | $ 100,000 | 2,100,000 |  |
2013 Plan |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Shares reserve for issuance (in shares) |  | 2,391,211 |  | 2,391,211 |  |  |
Number of shares forfeited (in shares) |  |  |  | 166,023 |  |  |
Number of options outstanding (in shares) |  | 891,211 |  | 891,211 |  |  |
2013 Plan | Restricted stock units |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Share-based payment award (in shares) |  | 1,500,000 |  | 1,500,000 |  |  |
2021 Plan |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Number of shares authorized (in shares) |  |  |  |  |  |  | 8,000,000
Number of shares forfeited (in shares) |  |  |  | 331,638 |  |  |
Granted (in shares) |  |  |  | 6,215,559 |  |  |
Number of options outstanding (in shares) |  | 32,151 |  | 32,151 |  |  |
2021 Plan | Restricted stock units |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Share-based payment award (in shares) |  | 3,939,734 |  | 3,939,734 |  |  |
Inducement Awards |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Number of shares authorized (in shares) |  | 832,950 |  | 832,950 |  |  |
Common stock, share reserve for issuance (in shares) |  | 392,611 |  | 392,611 |  |  |
Granted (in shares) |  |  |  | 507,340 |  |  |
Number of options outstanding (in shares) |  | 602,355 |  | 602,355 |  |  |
Inducement Awards | Restricted stock units |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Share-based payment award (in shares) |  | 151,500 |  | 151,500 |  |  |
Visirna ESOP |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |
Number of shares authorized (in shares) | 20,000,000 |  |  |  |  |  |
Granted (in shares) | 7,500,000 |  |  |  |  |  |
Stock-based compensation expense |  | $ 900,000 | $ 1,200,000 | $ 1,900,000 | $ 3,200,000 |  |

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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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