v3.26.1
Revenues - Additional Information (Details) - USD ($)
$ in Millions
 1 Months Ended 3 Months Ended 12 Months Ended
Apr. 30, 2026
Dec. 31, 2021
Mar. 31, 2026
Dec. 31, 2025
Jun. 30, 2025
Mar. 31, 2025
Dec. 31, 2020
Dec. 31, 2023
Disaggregation of Revenue [Line Items]                
Contract with customer, liability     $ 79 $ 78        
Total transaction price         $ 256      
Contract with customer, liability, cumulative catch-up adjustment to revenue, change in measure of progress and change in estimate of transaction price         143      
Deferred revenue, non-refundable payment   $ 725            
Total revenues     17     $ 28    
License and development services                
Disaggregation of Revenue [Line Items]                
Total transaction price         $ 192      
Total revenues     12     20    
Access right and option continuation periods                
Disaggregation of Revenue [Line Items]                
Total revenues     3     6    
Gilead Collaboration | Other | Over time                
Disaggregation of Revenue [Line Items]                
Total revenues     2     0    
Gilead Collaboration | License and development services | Over time                
Disaggregation of Revenue [Line Items]                
Total revenues     8     20    
Taiho Collaboration | License and development services | Over time                
Disaggregation of Revenue [Line Items]                
Total revenues     2          
Gilead | R&D services                
Disaggregation of Revenue [Line Items]                
Total revenues     8     20    
Gilead | Access right and option continuation periods                
Disaggregation of Revenue [Line Items]                
Current and future programs exclusive access period             10 years  
Contingent milestone payments receivable             $ 300  
Option continuation payment receivable upon sixth anniversary of agreement             $ 100  
Gilead | Access right and option continuation periods | Subsequent event                
Disaggregation of Revenue [Line Items]                
Total revenues $ 18              
Gilead | Rights to certain studies                
Disaggregation of Revenue [Line Items]                
Contract with customer, liability     14          
Gilead | R&D Activities for Inflammation Programs                
Disaggregation of Revenue [Line Items]                
Total revenues     $ 2     $ 2    
Gilead | Revenue Benchmark | Customer Concentration Risk                
Disaggregation of Revenue [Line Items]                
Percentage of revenues     88.00%     100.00%    
STAR-221 Development Activities | Taiho Collaboration Agreement                
Disaggregation of Revenue [Line Items]                
Contract with customer, liability               $ 35
Taiho Pharmaceutical Co., Ltd                
Disaggregation of Revenue [Line Items]                
Total transaction price       15        
Taiho Pharmaceutical Co., Ltd | Taiho Agreement                
Disaggregation of Revenue [Line Items]                
Contract with customer, liability       7        
Payment for option exercise       $ 15