v3.26.3
RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Schedule of Significant Unobservable Inputs Used in the Fair Value Measurement of Level 3 Derivative Instruments (Details)
$ in Millions
Sep. 30, 2026
CAD ($)
$ / MWh
$ / MMBTU
$ / bbl
Dec. 31, 2025
CAD ($)
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ (1,678) $ (823)
Fair Value    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ (1,678) (823)
Level 3    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ 185  
Level 3 | Fair Value    
Significant unobservable inputs used in the fair value measurement of Level 3 derivative instruments    
Fair Value | $ $ 185 $ 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) 38  
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) 96  
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) 75  
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) 3.06  
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) 8.55  
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) 4.46  
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 | $ $ 8  
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) 0.83  
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) 16.2  
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) 4.3  
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 | $ $ 5  
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) 1.37  
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) 16.31  
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) 4.32  
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 | $ $ 121  
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 81.15  
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 131.14  
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 112.96  
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 | $ $ 35  
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 61.21  
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 145.42  
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 118.84  
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 | $ $ 40  
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 31.51  
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 202.39  
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 86.66  
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 | $ $ (3)  
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 45.73  
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 184.88  
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 97.42  
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 | $ $ (21)