Segment Information - Schedule Of Disaggregated Amounts That Comprise Research and Development Expenses (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Segment Reporting Information [Line Items] | ||||
| Total research and development expenses | $ 68,282 | $ 47,951 | $ 133,262 | $ 88,650 |
| Direct Research and Development Expenses | 4D-150 | ||||
| Segment Reporting Information [Line Items] | ||||
| Total research and development expenses | 43,557 | 19,134 | 86,280 | 31,907 |
| Unallocated Personnel Costs (Including Stock-based Compensation) | ||||
| Segment Reporting Information [Line Items] | ||||
| Total research and development expenses | 15,996 | 17,871 | 30,526 | 35,099 |
| All Other Costs | ||||
| Segment Reporting Information [Line Items] | ||||
| Total research and development expenses | $ 8,729 | $ 10,946 | $ 16,456 | $ 21,644 |