Fair Value Measurements - Summary of Changes of Liabilities for Sale of Future Royalties (Details) - BVF Partners L.P. - BVF Agreement - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | ||
| Beginning balance | $ 21 | $ 19 |
| Interest accretion | 0 | 1 |
| Ending balance | $ 21 | $ 20 |