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Risk Management Activities - Effect of Hedges (Details)
MWh in Thousands, $ in Millions, $ in Millions
12 Months Ended
Dec. 31, 2024
CAD ($)
MWh
Dec. 31, 2023
CAD ($)
MWh
Dec. 31, 2024
USD ($)
MWh
Dec. 31, 2023
USD ($)
MWh
Disclosure of detailed information about hedging instruments [line items]        
Fair value asset   $ 5    
Fair value liability $ 7      
Physical power sales | Cash flow hedges | Commodity risk management        
Disclosure of detailed information about hedging instruments [line items]        
Notional amount (MMWH) | MWh 2,628 5,966 2,628 5,966
Fair value liability $ 45 $ (205)    
Gain (loss) on hedge ineffectiveness 114 (114)    
Foreign-denominated Debt | Net Investment Hedge | Currency risk        
Disclosure of detailed information about hedging instruments [line items]        
Fair value asset 431 489    
Gain (loss) on hedge ineffectiveness $ 0 $ 0    
Foreign-denominated Debt | Net Investment Hedge | Currency risk | USD        
Disclosure of detailed information about hedging instruments [line items]        
Notional amount     $ 300 $ 370