v3.26.1
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Schedule of Significant Unobservable Inputs Used in the Fair Value Measurement of Level 3 Derivative Instruments (Details)
$ in Millions
Mar. 31, 2026
CAD ($)
$ / MMBTU
$ / bbl
$ / MWh
Dec. 31, 2025
CAD ($)
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ (1,828) $ (823)
Fair Value    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ (1,828) (823)
Level 3    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ 13  
Level 3 | Fair Value    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ 13 $ 188
Commodity Options | Level 3 | Market Approach Valuation Technique | Minimum Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 3  
Commodity Options | Level 3 | Market Approach Valuation Technique | Maximum Price/ Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 74  
Commodity Options | Level 3 | Market Approach Valuation Technique | Weighted Average Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 53  
Natural gas | Commodity Contracts - Financial | Level 3 | Market Approach Valuation Technique | Minimum Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 3.25  
Natural gas | Commodity Contracts - Financial | Level 3 | Market Approach Valuation Technique | Maximum Price/ Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 9  
Natural gas | Commodity Contracts - Financial | Level 3 | Market Approach Valuation Technique | Weighted Average Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 4.5  
Natural gas | Commodity Contracts - Financial | Level 3 | Fair Value | Market Approach Valuation Technique    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ 5  
Natural gas | Commodity Contracts - Physical | Level 3 | Market Approach Valuation Technique | Minimum Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 0.77  
Natural gas | Commodity Contracts - Physical | Level 3 | Market Approach Valuation Technique | Maximum Price/ Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 17.66  
Natural gas | Commodity Contracts - Physical | Level 3 | Market Approach Valuation Technique | Weighted Average Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 3.73  
Natural gas | Commodity Contracts - Physical | Level 3 | Fair Value | Market Approach Valuation Technique    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ 17  
Natural gas | Commodity Options | Level 3 | Market Approach Valuation Technique | Minimum Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 3.77  
Natural gas | Commodity Options | Level 3 | Market Approach Valuation Technique | Maximum Price/ Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 15.14  
Natural gas | Commodity Options | Level 3 | Market Approach Valuation Technique | Weighted Average Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) 8.49  
Natural gas | Commodity Options | Level 3 | Fair Value | Market Approach Valuation Technique    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ 124  
Crude | Commodity Contracts - Financial | Level 3 | Market Approach Valuation Technique | Minimum Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / bbl 81.37  
Crude | Commodity Contracts - Financial | Level 3 | Market Approach Valuation Technique | Maximum Price/ Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / bbl 145.47  
Crude | Commodity Contracts - Financial | Level 3 | Market Approach Valuation Technique | Weighted Average Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / bbl 110.32  
Crude | Commodity Contracts - Financial | Level 3 | Fair Value | Market Approach Valuation Technique    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ (24)  
Crude | Commodity Contracts - Physical | Level 3 | Market Approach Valuation Technique | Minimum Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / bbl 63.91  
Crude | Commodity Contracts - Physical | Level 3 | Market Approach Valuation Technique | Maximum Price/ Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / bbl 148.51  
Crude | Commodity Contracts - Physical | Level 3 | Market Approach Valuation Technique | Weighted Average Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / bbl 124.5  
Crude | Commodity Contracts - Physical | Level 3 | Fair Value | Market Approach Valuation Technique    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ (78)  
Power | Commodity Contracts - Financial | Level 3 | Market Approach Valuation Technique | Minimum Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / MWh 27.08  
Power | Commodity Contracts - Financial | Level 3 | Market Approach Valuation Technique | Maximum Price/ Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / MWh 162.93  
Power | Commodity Contracts - Financial | Level 3 | Market Approach Valuation Technique | Weighted Average Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / MWh 80.68  
Power | Commodity Contracts - Financial | Level 3 | Fair Value | Market Approach Valuation Technique    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ (12)  
Power | Commodity Contracts - Physical | Level 3 | Market Approach Valuation Technique | Minimum Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / MWh 27  
Power | Commodity Contracts - Physical | Level 3 | Market Approach Valuation Technique | Maximum Price/ Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / MWh 152.72  
Power | Commodity Contracts - Physical | Level 3 | Market Approach Valuation Technique | Weighted Average Price/Volatility    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Price volatility (in $/MMBTU, $/barrel, $ / MW/H, percent) | $ / MWh 73.54  
Power | Commodity Contracts - Physical | Level 3 | Fair Value | Market Approach Valuation Technique    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ (19)