v3.26.3
Revenues - Additional Information (Details) - USD ($)
$ in Millions
 1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Dec. 31, 2021
Mar. 31, 2027
Sep. 30, 2026
Jun. 30, 2026
Dec. 31, 2025
Sep. 30, 2025
Jun. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2023
Dec. 31, 2020
Dec. 31, 2017
Disaggregation of Revenue [Line Items]                        
Contract with customer, liability     $ 48   $ 78     $ 48        
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     9     $ 26   67 $ 214      
License and development services                        
Disaggregation of Revenue [Line Items]                        
Total transaction price             $ 192          
Total revenues     8     20   36 192      
Access right and option continuation periods                        
Disaggregation of Revenue [Line Items]                        
Total revenues     0     3   24 14      
Gilead Collaboration | License and development services | Over time                        
Disaggregation of Revenue [Line Items]                        
Total revenues     6     20   21 192      
Taiho Collaboration Agreement                        
Disaggregation of Revenue [Line Items]                        
Milestone payments       $ 30                
Taiho Collaboration | License and development services | Over time                        
Disaggregation of Revenue [Line Items]                        
Total revenues     2     0   8 0      
Taiho Collaboration | Other | Over time                        
Disaggregation of Revenue [Line Items]                        
Total revenues     1         10        
Casdatifan Collaboration | License and development services | Over time                        
Disaggregation of Revenue [Line Items]                        
Total revenues     1         2        
Gilead | R&D services                        
Disaggregation of Revenue [Line Items]                        
Total revenues     6     20   21 192      
Gilead | Access right and option continuation periods                        
Disaggregation of Revenue [Line Items]                        
Total revenues       $ 18                
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 | Rights to certain studies                        
Disaggregation of Revenue [Line Items]                        
Contract with customer, liability     14         14        
Gilead | R&D Activities for Inflammation Programs                        
Disaggregation of Revenue [Line Items]                        
Total revenues     $ 1     $ 3   $ 7 $ 8      
Gilead | Revenue Benchmark | Customer Concentration Risk                        
Disaggregation of Revenue [Line Items]                        
Percentage of revenues     78.00%     100.00%   82.00% 100.00%      
STAR-221 Development Activities | Taiho Collaboration Agreement                        
Disaggregation of Revenue [Line Items]                        
Contract with customer, liability                   $ 35    
Milestone payments                   $ 28    
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   15              
Taiho Pharmaceutical Co., Ltd | Taiho Agreement | Maximum                        
Disaggregation of Revenue [Line Items]                        
Contingent milestone payments receivable         $ 145             $ 145
Taiho Pharmaceutical Co., Ltd | Taiho Agreement | Maximum | Forecast                        
Disaggregation of Revenue [Line Items]                        
Remaining milestone payments   $ 15