License and Collaboration Agreements - Schedule Of Revenues Earned Under License and Collaboration Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues	$ 108,019	$ 21,359	$ 114,412	$ 110,371
Other		42	38	119
Total license and royalty revenue	103,841	18,465	108,931	105,514
Zolgensma and Itvisma Royalties [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues	3,841	18,423	8,893	35,416
AbbVie development milestone [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues	100,000		100,000
Nippon Shinyaku Licenses [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues				69,979
Nippon Shinyaku Services [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues	3,720	2,720	4,731	4,494
Other [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues	458	174	750	363
Total Service Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues	$ 4,178	$ 2,894	$ 5,481	$ 4,857