v3.25.4
FINANCIAL RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Changes in Fair Value of Derivatives (Details) - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year $ 425 $ (538)
Proceeds received from settlement of derivatives (52,856) (27,690)
Payment on derivatives settled 52,731 27,534
Increase (decrease) in fair value of derivatives (203) 1,119
Derivative instruments, end of year 97 425
Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year 425  
Derivative instruments, end of year 97 425
Debt derivatives    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year 5 (101)
Proceeds received from settlement of derivatives (16,346) (25,846)
Payment on derivatives settled 16,379 25,746
Increase (decrease) in fair value of derivatives (38) 206
Derivative instruments, end of year 0 5
Debt derivatives | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year 357  
Derivative instruments, end of year   357
Expenditure derivative instruments:    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year 0  
Proceeds received from settlement of derivatives (63)  
Payment on derivatives settled 63  
Increase (decrease) in fair value of derivatives (17)  
Derivative instruments, end of year (17) 0
Expenditure derivative instruments: | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market liability (25)  
Equity derivative instruments    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year (54) 48
Proceeds received from settlement of derivatives 0 0
Payment on derivatives settled 60 0
Increase (decrease) in fair value of derivatives 22 (102)
Derivative instruments, end of year 28 (54)
Equity derivative instruments | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year (54)  
Derivative instruments, end of year   (54)
Subsidiary equity derivative instruments    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year 0  
Proceeds received from settlement of derivatives (29,447)  
Payment on derivatives settled 29,379  
Increase (decrease) in fair value of derivatives 33  
Derivative instruments, end of year (35) 0
Subsidiary equity derivative instruments | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market liability (35)  
Virtual power purchase agreement    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year (10) 0
Proceeds received from settlement of derivatives 0 (1)
Payment on derivatives settled 3 2
Increase (decrease) in fair value of derivatives 1 (11)
Derivative instruments, end of year (6) (10)
Virtual power purchase agreement | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year (10)  
Derivative instruments, end of year (6) (10)
Cash flow hedges | Debt derivatives    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year 352 (470)
Proceeds received from settlement of derivatives (5,018) (203)
Payment on derivatives settled 4,939 196
Increase (decrease) in fair value of derivatives (138) 829
Derivative instruments, end of year 135 352
Cash flow hedges | Expenditure derivative instruments:    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year 132 (15)
Proceeds received from settlement of derivatives (1,982) (1,640)
Payment on derivatives settled 1,908 1,590
Increase (decrease) in fair value of derivatives (66) 197
Derivative instruments, end of year (8) 132
Cash flow hedges | Expenditure derivative instruments: | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year 132  
Derivative instruments, end of year   132
Before Offset Amount    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market asset 1,333  
Mark-to-market liability (748) (908)
Before Offset Amount | Debt derivatives    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market liability 0  
Before Offset Amount | Debt derivatives | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market asset 7  
Mark-to-market liability   (2)
Before Offset Amount | Expenditure derivative instruments: | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market liability (17)  
Before Offset Amount | Equity derivative instruments    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market asset 0  
Before Offset Amount | Equity derivative instruments | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market liability (9) (54)
Before Offset Amount | Subsidiary equity derivative instruments    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market asset 0  
Before Offset Amount | Subsidiary equity derivative instruments | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market liability (36)  
Before Offset Amount | Virtual power purchase agreement    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market asset 0  
Before Offset Amount | Virtual power purchase agreement | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Derivative instruments, beginning of year (10)  
Derivative instruments, end of year   (10)
Mark-to-market liability (6) (10)
Before Offset Amount | Cash flow hedges | Debt derivatives | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market asset 1,194  
Mark-to-market liability (645) (842)
Before Offset Amount | Cash flow hedges | Expenditure derivative instruments:    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market liability   $ 0
Before Offset Amount | Cash flow hedges | Expenditure derivative instruments: | Canada, Dollars    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market asset 132  
Mark-to-market liability (28)  
Before Offset Amount | Cash flow hedges | Debt Derivatives, Including Interest Rate Swap    
Disclosure of detailed information about financial instruments [line items]    
Mark-to-market liability $ (652)