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, 2023	Jun. 30, 2022
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 17	$ 5
Cash received		5
Interest accretion	1	1
Ending balance	$ 18	$ 11