License and Collaboration Agreements - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Nov. 25, 2024	Mar. 31, 2025	Mar. 31, 2024	Nov. 25, 2025	Dec. 31, 2024
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Product revenues, net		$ 611,523	$ 359,484
Collaboration and other		133,333	53,980
Loss (gain) on strategic investments		$ 90,728	(931)
Common stock, shares		198,000,000			198,000,000
Development Milestone and Upfront Fee Recognized as Research and Development Expense		$ 583,800	0
ELEVIDYS [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Product revenues, net		$ 611,523	359,484
Arrowhead Pharmaceuticals Inc [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Warrants with an exercise price		$ 0.001
Arrowhead Pharmaceuticals Inc [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense		$ 2,300
Collaborative Arrangement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment for option exercise		111,800
Collaborative Arrangement | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent research milestone payments		30,800
Development Milestone and Upfront Fee Recognized as Research and Development Expense		12,600,000
Collaborative Arrangement | Roche Holding A.G. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration and other		112,000	48,000
Deferred revenue		369,900			$ 455,300
Deferred Revenue, Current		44,900			130,300
Research and development expense		28,500	$ 21,700
Collaboration Receivable		55,200			$ 34,600
Licensing And Collaboration Agreement [Member] | Arrowhead Pharmaceuticals Inc [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up front payment for license and collaboration agreement	$ 500,000
Investment in license agreement		241,400		$ 325,000
Loss (gain) on strategic investments		$ 89,500
Term of installment fee		five years
License agreement fee		$ 250,000
Annual Installment Fee		50,000
Upfront Fee To Be Paid On Certain Enrollment Achievement		300,000
Common stock, shares				11,900,000
Research and development expense		583,600
Development Milestone and Upfront Fee Recognized as Research and Development Expense		$ 10,300,000