License and Collaboration Agreements - Schedule Of Revenues Earned Under License and Collaboration Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues	$ 9,162	$ 29,733	$ 123,574	$ 140,104
Other		19	38	138
Total license and royalty revenue	5,244	23,605	114,175	129,119
Zolgensma and Itvisma Royalties [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues	5,244	23,586	14,137	59,002
AbbVie development milestone [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues			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	3,309	5,932	8,040	10,426
Other [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues	609	196	1,359	559
Total Service Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues	$ 3,918	$ 6,128	$ 9,399	$ 10,985