v3.26.1
DEBT - Bank borrowings (Details)
€ in Millions, ¥ in Millions, $ in Millions
1 Months Ended 3 Months Ended 12 Months Ended
Mar. 31, 2026
CNY (¥)
Mar. 31, 2026
USD ($)
Nov. 30, 2025
CNY (¥)
Jul. 31, 2025
CNY (¥)
Mar. 31, 2024
CNY (¥)
Aug. 31, 2022
EUR (€)
Dec. 31, 2025
CNY (¥)
Dec. 31, 2025
CNY (¥)
Dec. 31, 2024
CNY (¥)
Dec. 31, 2025
USD ($)
Dec. 31, 2024
EUR (€)
Long-term facility entered in August 2022                      
DEBT                      
Term of debt instrument           3 years          
Maximum borrowing amount | €           € 220          
Long-term debt, current portion | €                     € 99
Term facility entered in August 2022 | RMB                      
DEBT                      
Maximum borrowing amount | €           110          
Revolving credit facility entered in August 2022                      
DEBT                      
Maximum borrowing amount | €           € 70          
Syndicated loan contract entered in march 2024                      
DEBT                      
Term of debt instrument         5 years            
Maximum borrowing amount         ¥ 400            
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]               us-gaap:PrimeRateMember      
Percentage points added to the reference rate               0.55%      
Credit facility drew down amount                 ¥ 340    
Repayment of line of credit facility               ¥ 40 15    
Outstanding loan amount             ¥ 285 ¥ 285 ¥ 325    
Interest rate (as a percent)             2.55% 2.55% 2.90% 2.55% 2.90%
Syndicated loan contract entered in march 2024 | Buildings                      
DEBT                      
Amount pledged as collateral for the loan             ¥ 478 ¥ 478 ¥ 510    
Syndicated loan contract entered in march 2024 | Land use rights                      
DEBT                      
Amount pledged as collateral for the loan             67 67 ¥ 69    
Loan facility entered in July 2025                      
DEBT                      
Term of debt instrument       1 year              
Maximum borrowing amount       ¥ 2,000              
Credit facility drew down amount       ¥ 1,400              
Interest rate (as a percent)       1.80%              
Long-term debt             1,400 1,400      
Loan facility entered in July 2025 | Deposits                      
DEBT                      
Amount pledged as collateral for the loan             ¥ 1,406 1,406      
Term loan and revolving credit facility entered in November 2025                      
DEBT                      
Term of debt instrument     12 months                
Maximum borrowing amount     ¥ 300                
Expected extension term     36 months                
Credit facility drew down amount               0      
Term loan and revolving credit facility entered in November 2025 | Subsequent Event                      
DEBT                      
Credit facility drew down amount | $   $ 180                  
Uncommitted revolving loan facility                      
DEBT                      
Term of debt instrument             1 year        
Expected extension term             36 months        
Credit facility drew down amount               ¥ 0      
Uncommitted revolving loan facility one                      
DEBT                      
Maximum borrowing amount | $                   $ 100  
Uncommitted revolving loan facility two                      
DEBT                      
Maximum borrowing amount | $                   $ 50  
Uncommitted revolving loan facility three | Subsequent Event                      
DEBT                      
Credit facility drew down amount ¥ 833