v3.26.1
Property, Plant and Equipment - ASOP Asset Swap Transaction Narrative (Details) - CAD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Nov. 01, 2025
Dec. 31, 2025
Dec. 31, 2025
Disclosure of detailed information about property, plant and equipment [line items]      
Remeasurement gain $ 4,989    
ASOP Mines      
Disclosure of detailed information about property, plant and equipment [line items]      
Proportion of ownership interest in subsidiary 100.00%    
AOSP Mines and Scotford And Quest      
Disclosure of detailed information about property, plant and equipment [line items]      
Remeasurement gain $ 17    
Discount rate applied to cash flow projections   18.00% 18.00%
ASOP Mines      
Disclosure of detailed information about property, plant and equipment [line items]      
Remaining ownership percentage acquired 0.10    
Disposal of business, ownership interest 90.00%    
Non-cash gain $ 4,508    
Loss (gain) on disposal of asset, after tax 3,471    
Fair value, net of asset retirement obligation, purchase consideration and previously held interests (13,323)    
Gain on remeasurement recorded in the transaction   $ 8,815 $ 8,815
Fair value, net of asset retirement obligation, net $ 1,480    
Scotford and Quest      
Disclosure of detailed information about property, plant and equipment [line items]      
Disposal of business, ownership interest 10.00%    
Proportion of ownership interest in subsidiary 80.00%    
Non-cash gain $ 464    
Loss (gain) on disposal of asset, after tax 357    
Fair value, net of asset retirement obligation, purchase consideration and previously held interests (1,475)    
Gain on remeasurement recorded in the transaction   1,011 1,011
Fair value, net of asset retirement obligation, net $ (1,475)    
AOSP Asset Swap Transaction      
Disclosure of detailed information about property, plant and equipment [line items]      
Revenue of acquiree since acquisition date   143  
Revenue net of blending, production, transportation and feedstock since acquisition date   46 115
Earnings before tax since acquisition   19 97
Depletion, depreciation and amortization since acquisition date   $ 24  
Revenue of combined entity as if combination occurred at beginning of period     804
Depletion, depreciation and amortization     145
Corridor Pipeline Lease      
Disclosure of detailed information about property, plant and equipment [line items]      
Transport expense     154
Interest expense, depletion, depreciation and amortization     $ 136