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Risk Management Activities - Effect of Hedges (Details)
MWh in Thousands, $ in Millions, $ in Millions
12 Months Ended
Dec. 31, 2023
CAD ($)
MWh
Dec. 31, 2022
CAD ($)
MWh
Dec. 31, 2023
USD ($)
MWh
Dec. 31, 2022
USD ($)
MWh
Disclosure of detailed information about hedging instruments [line items]        
Fair value asset   $ 3    
Fair value liability $ 5      
Physical power sales | Cash flow hedges | Commodity risk management        
Disclosure of detailed information about hedging instruments [line items]        
Notional amount (MMWH) | MWh 5,966 9,295 5,966 9,295
Fair value liability $ (205) $ (347)    
Gain (loss) on hedge ineffectiveness (114) (594)    
Foreign-denominated Debt | Net Investment Hedge | Currency risk        
Disclosure of detailed information about hedging instruments [line items]        
Fair value asset 489 502    
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     $ 370 $ 370