XML 160 R132.htm IDEA: XBRL DOCUMENT v3.20.4
Risk Management Activities - Effect of Hedges (Details)
MWh in Millions, $ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2020
CAD ($)
Dec. 31, 2019
CAD ($)
Dec. 31, 2020
USD ($)
MWh
Dec. 31, 2020
CAD ($)
MWh
Dec. 31, 2019
USD ($)
MWh
Dec. 31, 2019
CAD ($)
MWh
Disclosure of detailed information about hedging instruments [line items]            
Hedging instrument, assets       $ 2   $ 7
Physical power sales | Cash flow hedges | Commodity risk management            
Disclosure of detailed information about hedging instruments [line items]            
Notional amount purchased | MWh     16 16 19 19
Hedging instrument, assets       $ 573   $ 678
Gain (loss) on hedge ineffectiveness $ (33) $ 47        
Interest rate swap | Cash flow hedges | Interest rate risk | U.S. Dollars            
Disclosure of detailed information about hedging instruments [line items]            
Notional amount     $ 150      
Gain (loss) on hedge ineffectiveness 3          
Hedging instrument, liabilities       (3)    
Interest rate swap | Cash flow hedges | Interest rate risk | Canada, Dollars            
Disclosure of detailed information about hedging instruments [line items]            
Notional amount       75    
Gain (loss) on hedge ineffectiveness 4          
Hedging instrument, liabilities       (4)    
Foreign-denominated debt | Net Investment Hedge | Currency risk            
Disclosure of detailed information about hedging instruments [line items]            
Hedging instrument, assets       $ 472   $ 483
Gain (loss) on hedge ineffectiveness $ 11 $ 21        
Foreign-denominated debt | Net Investment Hedge | Currency risk | U.S. Dollars            
Disclosure of detailed information about hedging instruments [line items]            
Notional amount     $ 370   $ 370