v3.26.3
Commitments and Contingencies - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
May 19, 2025
Sep. 30, 2026
Jun. 30, 2026
Dec. 31, 2025
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Contingencies And Commitments [Line Items]                    
Research and development expense   $ 71,888     $ 58,902 $ 207,614 $ 201,280      
Letters of credit secured by cash held in restricted depository account   377     3,514 377 3,514      
Total liability associated with the contingent loss   18,200   $ 14,500   18,200        
Restricted cash   7,629   7,629 $ 8,006 7,629 8,006      
Deferred Finance Costs, Share Lending Arrangement, Issuance Costs               $ 221,800 $ 221,800 $ 221,800
Contingent payments   0       0        
Acquired in-process research and development           1,648 $ 96,253      
Accrued expenses   82,018   89,407   82,018        
Sirius Therapeutics [Member]                    
Contingencies And Commitments [Line Items]                    
Research and development expense   5,400       10,400        
Contingent payments   0       0        
Future development regulatory and sales milestone payment $ 300,000                  
Acquired in-process research and development   12,500       12,500        
Accrued expenses   12,500       12,500        
Sirius Therapeutics [Member] | Maximum [Member]                    
Contingencies And Commitments [Line Items]                    
Future development regulatory and sales milestone payment           300,000        
Option payments           20,000        
Milestones aggregate payment $ 87,500         75,000        
Letter of Credit [Member]                    
Contingencies And Commitments [Line Items]                    
Letters of credit secured by cash held in restricted depository account   8,000   11,500   8,000        
2015 Collaboration Agreement [Member] | Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member]                    
Contingencies And Commitments [Line Items]                    
Milestone payment receivable   395,000       395,000        
Intellectual Property [Member]                    
Contingencies And Commitments [Line Items]                    
Research and development expense     $ 3,800 13,000            
Location, Statement of Financial Position, Balance [Axis]: us-gaap:PrepaidExpenseAndOtherAssetsCurrent                    
Contingencies And Commitments [Line Items]                    
Letters of credit secured by cash held in restricted depository account   $ 400   $ 3,900   $ 400