v3.26.3
FINANCIAL INSTRUMENTS - Unrealized Risk Management Positions (Detail) - CAD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Disclosure Of Recurring Fair Value Measurement Of Assets And Liabilities [Line Items]    
Risk management net asset (liability) $ 28 $ 10
Power Swap Contracts    
Disclosure Of Recurring Fair Value Measurement Of Assets And Liabilities [Line Items]    
Risk management net asset (liability) 5  
Level 2 of fair value hierarchy    
Disclosure Of Recurring Fair Value Measurement Of Assets And Liabilities [Line Items]    
Risk management asset 192 46
Risk management liability 164 36
Risk management net asset (liability) 28 10
Level 2 of fair value hierarchy | Commodity price risk | Crude Oil, Natural Gas, Condensate and Refined Products    
Disclosure Of Recurring Fair Value Measurement Of Assets And Liabilities [Line Items]    
Risk management asset 170 27
Risk management liability 141 30
Risk management net asset (liability) 29 (3)
Level 2 of fair value hierarchy | Commodity price risk | Power Swap Contracts    
Disclosure Of Recurring Fair Value Measurement Of Assets And Liabilities [Line Items]    
Risk management asset 5 2
Risk management liability 0 0
Risk management net asset (liability) 5 2
Level 2 of fair value hierarchy | Commodity price risk | Renewable Power Contracts    
Disclosure Of Recurring Fair Value Measurement Of Assets And Liabilities [Line Items]    
Risk management asset 17 17
Risk management liability 9 6
Risk management net asset (liability) 8 11
Level 2 of fair value hierarchy | Currency risk | Foreign Exchange Rate Contracts    
Disclosure Of Recurring Fair Value Measurement Of Assets And Liabilities [Line Items]    
Risk management asset 0 0
Risk management liability 14 0
Risk management net asset (liability) $ (14) $ 0