v3.25.4
FINANCIAL RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Derivative Instruments - Net Asset (Liability) Position (Details)
$ in Millions, $ in Millions
Dec. 31, 2025
CAD ($)
$ / $
Dec. 31, 2025
USD ($)
$ / $
Dec. 31, 2024
CAD ($)
$ / $
Dec. 31, 2024
USD ($)
$ / $
Dec. 31, 2023
CAD ($)
Disclosure of detailed information about hedging instruments [line items]          
Current derivative financial assets $ 99   $ 336    
Non-current derivative financial assets 746   997    
Current derivative financial liabilities (49)   (64)    
Non-current derivative financial liabilities (699)   (845)    
Net mark-to market asset (liability), fair value 97   425   $ (538)
Net mark-to market asset, current 50   273    
Net mark-to market asset, non-current 47   152    
Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Net mark-to market asset (liability), fair value 97   $ 425    
Debt derivatives          
Disclosure of detailed information about hedging instruments [line items]          
Exchange rate, assets | $ / $     1.4282 1.4282  
Exchange rate, liabilities | $ / $     1.4421 1.4421  
Net mark-to market asset (liability), fair value $ 0   $ 5   (101)
Debt derivatives | United States of America, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, assets       $ 666  
Notional amount, liabilities       $ 696  
Debt derivatives | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, assets     952    
Notional amount, liabilities     1,004    
Net mark-to market asset (liability), fair value     $ 357    
Debt derivatives | Cash flow hedges          
Disclosure of detailed information about hedging instruments [line items]          
Exchange rate, assets | $ / $ 1.2373 1.2373 1.2510 1.2510  
Exchange rate, liabilities | $ / $ 1.3449 1.3449 1.3127 1.3127  
Current derivative financial assets $ 34   $ 224    
Non-current derivative financial assets 101   133    
Net mark-to market asset (liability), fair value 135   352   (470)
Debt derivatives | Cash flow hedges | United States of America, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, assets   $ 8,559   $ 11,116  
Notional amount, liabilities   $ 7,763   $ 6,550  
Debt derivatives | Cash flow hedges | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, assets 10,590   13,906    
Fair value, assets 135        
Notional amount, liabilities $ 10,440   8,598    
MLSE interest rate swap | Cash flow hedges          
Disclosure of detailed information about hedging instruments [line items]          
Exchange rate, liabilities | $ / $ 0 0      
MLSE interest rate swap | Cash flow hedges | United States of America, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, liabilities   $ 0      
MLSE interest rate swap | Cash flow hedges | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, liabilities $ 300        
Expenditure derivative instruments:          
Disclosure of detailed information about hedging instruments [line items]          
Exchange rate, liabilities | $ / $ 1.3386 1.3386      
Current derivative financial liabilities $ (10)        
Non-current derivative financial liabilities (15)        
Net mark-to market asset (liability), fair value (17)   $ 0    
Expenditure derivative instruments: | United States of America, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, liabilities   $ 886      
Expenditure derivative instruments: | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, liabilities 1,186        
Fair value, liabilities $ (25)        
Expenditure derivative instruments: | Cash flow hedges          
Disclosure of detailed information about hedging instruments [line items]          
Exchange rate, assets | $ / $ 1.3275 1.3275 1.3362 1.3362  
Exchange rate, liabilities | $ / $ 1.3816 1.3816      
Current derivative financial assets     $ 105    
Non-current derivative financial assets     27    
Net mark-to market asset (liability), fair value $ (8)   132   (15)
Expenditure derivative instruments: | Cash flow hedges | United States of America, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, assets   $ 1,122   $ 1,590  
Notional amount, liabilities   $ 1,261      
Expenditure derivative instruments: | Cash flow hedges | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, assets 1,489   2,125    
Notional amount, liabilities $ 1,742        
Net mark-to market asset (liability), fair value     $ 132    
Equity derivative instruments          
Disclosure of detailed information about hedging instruments [line items]          
Exchange rate, assets | $ / $ 0 0      
Exchange rate, liabilities | $ / $ 0 0 0 0  
Non-current derivative financial assets $ 0        
Current derivative financial liabilities (28)   $ (54)    
Non-current derivative financial liabilities     0    
Net mark-to market asset (liability), fair value 28   (54)   48
Equity derivative instruments | United States of America, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, assets   $ 0      
Notional amount, liabilities   $ 0   $ 0  
Equity derivative instruments | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, assets 173        
Fair value, assets 28        
Notional amount, liabilities $ 84   320    
Net mark-to market asset (liability), fair value     (54)    
Subsidiary equity derivative instruments          
Disclosure of detailed information about hedging instruments [line items]          
Exchange rate, assets | $ / $ 1.3827 1.3827      
Exchange rate, liabilities | $ / $ 1.3846 1.3846      
Current derivative financial liabilities $ 0        
Non-current derivative financial liabilities (35)        
Net mark-to market asset (liability), fair value (35)   $ 0    
Subsidiary equity derivative instruments | United States of America, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, assets   $ 750      
Notional amount, liabilities   $ 4,100      
Subsidiary equity derivative instruments | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, assets 1,037        
Notional amount, liabilities 5,677        
Fair value, liabilities $ (35)        
Virtual power purchase agreement          
Disclosure of detailed information about hedging instruments [line items]          
Exchange rate, liabilities | $ / $ 0 0 0 0  
Current derivative financial liabilities $ (2)   $ (2)    
Non-current derivative financial liabilities (4)   (8)    
Net mark-to market asset (liability), fair value (6)   (10)   $ 0
Virtual power purchase agreement | United States of America, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, liabilities   $ 0   $ 0  
Virtual power purchase agreement | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Notional amount, liabilities 0   0    
Net mark-to market asset (liability), fair value (6)   (10)    
Before Offset Amount          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets 845   1,333    
Fair value, liabilities (748)   (908)    
Before Offset Amount | Debt derivatives          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets 0        
Fair value, liabilities 0        
Current derivative financial assets     7    
Non-current derivative financial assets     0    
Current derivative financial liabilities     (2)    
Non-current derivative financial liabilities     0    
Before Offset Amount | Debt derivatives | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets     7    
Fair value, liabilities     (2)    
Before Offset Amount | Debt derivatives | Cash flow hedges          
Disclosure of detailed information about hedging instruments [line items]          
Current derivative financial assets 47   224    
Non-current derivative financial assets 740   970    
Current derivative financial liabilities (13)   (5)    
Non-current derivative financial liabilities (632)   (837)    
Before Offset Amount | Debt derivatives | Cash flow hedges | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets 787   1,194    
Fair value, liabilities (645)   (842)    
Before Offset Amount | MLSE interest rate swap | Cash flow hedges          
Disclosure of detailed information about hedging instruments [line items]          
Current derivative financial liabilities 0        
Non-current derivative financial liabilities (7)        
Before Offset Amount | MLSE interest rate swap | Cash flow hedges | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, liabilities (7)        
Before Offset Amount | Expenditure derivative instruments:          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets 0        
Current derivative financial liabilities (3)        
Non-current derivative financial liabilities (14)        
Before Offset Amount | Expenditure derivative instruments: | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, liabilities (17)        
Before Offset Amount | Expenditure derivative instruments: | Cash flow hedges          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, liabilities     0    
Current derivative financial assets 15   105    
Non-current derivative financial assets 5   27    
Before Offset Amount | Expenditure derivative instruments: | Cash flow hedges | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets 20   132    
Fair value, liabilities (28)        
Before Offset Amount | Equity derivative instruments          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets     0    
Current derivative financial assets 37        
Non-current derivative financial assets 0        
Current derivative financial liabilities (9)   (54)    
Non-current derivative financial liabilities 0   0    
Before Offset Amount | Equity derivative instruments | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets 37        
Fair value, liabilities (9)   (54)    
Before Offset Amount | Equity derivative instruments | Cash flow hedges          
Disclosure of detailed information about hedging instruments [line items]          
Current derivative financial liabilities (22)        
Non-current derivative financial liabilities (6)        
Before Offset Amount | Subsidiary equity derivative instruments          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets     0    
Current derivative financial assets 0        
Non-current derivative financial assets 1        
Current derivative financial liabilities 0        
Non-current derivative financial liabilities (36)        
Before Offset Amount | Subsidiary equity derivative instruments | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets 1        
Fair value, liabilities (36)        
Before Offset Amount | Virtual power purchase agreement          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, assets 0   0    
Current derivative financial liabilities (2)   (2)    
Non-current derivative financial liabilities (4)   (8)    
Before Offset Amount | Virtual power purchase agreement | Canada, Dollars          
Disclosure of detailed information about hedging instruments [line items]          
Fair value, liabilities $ (6)   (10)    
Net mark-to market asset (liability), fair value     $ (10)