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, 2024	Jun. 30, 2023
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 19	$ 17
Interest accretion	1	1
Ending balance	$ 20	$ 18

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration