License and Collaboration Agreements - Schedule Of License Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
License Revenue [Line Items]
Other license revenue		$ 31		$ 31
Interest income from licensing	$ 40	153	$ 110	247
Novartis Gene Therapies [Member]
License Revenue [Line Items]
Total license and royalty revenue	18,965	28,417	35,091	49,956
Interest income from licensing	7	71	15	76
Zolgensma Royalties [Member]
License Revenue [Line Items]
Total license and royalty revenue	$ 18,965	$ 28,386	$ 35,091	$ 49,925