Summary of Significant Accounting Policies - Anti-dilutive Securities Excluded from the Computation of Diluted Net Loss (Detail) - shares shares in Thousands |
6 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Employee Stock Option | ||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||
| Antidilutive securities excluded from computation of earnings per share, amount | 6,740 | 6,025 |
| Unvested rTSRUs [Member] | ||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||
| Antidilutive securities excluded from computation of earnings per share, amount | 104 | 93 |
| Unvested PSUs [Member] | ||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||
| Antidilutive securities excluded from computation of earnings per share, amount | 104 | 93 |
| Unvested Restricted Stock [Member] | ||
| Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] | ||
| Antidilutive securities excluded from computation of earnings per share, amount | 420 | 427 |