v3.26.1
LICENSE AND COLLABORATION AGREEMENTS - Additional Information (Detail) - USD ($)
$ in Thousands
 1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Product revenues, net   $ 328,689 $ 513,123 $ 659,204 $ 1,124,646  
Collaboration and other   72,562 97,968 472,850 231,301  
Loss on strategic investments   $ 448 (36,721) $ 2,160 54,007  
Common stock, shares   198,000,000   198,000,000   198,000,000
ELEVIDYS [Member]            
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Product revenues, net   $ 98,125 281,851 $ 200,090 656,836  
Roche Collaboration Agreement [Member]            
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Collaboration and other       325,000 112,000  
Arrowhead Pharmaceuticals Inc [Member]            
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Research and development expense   6,300 6,500 14,800 8,800  
Collaborative Arrangement | Maximum [Member]            
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Development Milestone and Upfront Fee Recognized as Research and Development Expense       12,100,000    
Collaborative Arrangement | Roche Holding A.G. [Member]            
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Collaboration and other     63,500 365,000 175,500  
Deferred revenue   220,300   220,300   $ 527,300
Deferred Revenue, Current   110,100   110,100   443,400
Research and development expense   7,200 $ 25,700 15,400 54,200  
Collaboration Receivable   45,000   45,000   104,100
Collaborative Arrangement | Roche Collaboration Agreement [Member]            
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Collaboration and other       40,000    
Collaborative Arrangement | NationWide Children Hospital [Member]            
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Milestone Payment Received $ 63,500          
Collaborative Arrangement | Arrowhead Pharmaceuticals Inc [Member]            
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Research and development expense         $ 583,600  
Equity Investment Agreement [Member] | Arrowhead Pharmaceuticals Inc [Member]            
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Investment in license agreement   241,400   241,400    
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   $ 325,000   $ 325,000    
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   11,900,000    
Development Milestone and Upfront Fee Recognized as Research and Development Expense       $ 10,300,000    
Licensing And Collaboration Agreement [Member] | Second Arrowhead DM One Milestone [Member]            
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]            
Cash   $ 200,000   $ 200,000