v3.26.1
Fair Value of Financial Instruments and Risk Management - Schedule of Fair Value of Assets and Liabilities (Details) - CAD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Assets    
Other investments $ 200 $ 190
Assets, fair value 300 282
Liabilities    
Liabilities, fair value (201) (174)
Level 1    
Assets    
Other investments 200 190
Assets, fair value 200 190
Liabilities    
Liabilities, fair value 0 0
Level 2    
Assets    
Other investments 0 0
Assets, fair value 100 92
Liabilities    
Liabilities, fair value (201) (174)
Level 3    
Assets    
Other investments 0 0
Assets, fair value 0 0
Liabilities    
Liabilities, fair value 0 0
Energy contracts subject to regulatory deferral    
Assets    
Derivative assets 43 51
Liabilities    
Derivative liabilities (157) (149)
Energy contracts subject to regulatory deferral | Level 1    
Assets    
Derivative assets 0 0
Liabilities    
Derivative liabilities 0 0
Energy contracts subject to regulatory deferral | Level 2    
Assets    
Derivative assets 43 51
Liabilities    
Derivative liabilities (157) (149)
Energy contracts subject to regulatory deferral | Level 3    
Assets    
Derivative assets 0 0
Liabilities    
Derivative liabilities 0 0
Energy contracts not subject to regulatory deferral    
Assets    
Derivative assets 18 4
Liabilities    
Derivative liabilities (1) (2)
Energy contracts not subject to regulatory deferral | Level 1    
Assets    
Derivative assets 0 0
Liabilities    
Derivative liabilities 0 0
Energy contracts not subject to regulatory deferral | Level 2    
Assets    
Derivative assets 18 4
Liabilities    
Derivative liabilities (1) (2)
Energy contracts not subject to regulatory deferral | Level 3    
Assets    
Derivative assets 0 0
Liabilities    
Derivative liabilities 0 0
Total return swaps and interest rate contracts    
Assets    
Derivative assets 39  
Total return swaps and interest rate contracts | Level 1    
Assets    
Derivative assets 0  
Total return swaps and interest rate contracts | Level 2    
Assets    
Derivative assets 39  
Total return swaps and interest rate contracts | Level 3    
Assets    
Derivative assets 0  
Cross-currency interest rate swaps and foreign exchange contracts    
Liabilities    
Derivative liabilities (43)  
Cross-currency interest rate swaps and foreign exchange contracts | Level 1    
Liabilities    
Derivative liabilities 0  
Cross-currency interest rate swaps and foreign exchange contracts | Level 2    
Liabilities    
Derivative liabilities (43)  
Cross-currency interest rate swaps and foreign exchange contracts | Level 3    
Liabilities    
Derivative liabilities $ 0  
Total return swaps and foreign exchange contracts    
Assets    
Derivative assets   37
Total return swaps and foreign exchange contracts | Level 1    
Assets    
Derivative assets   0
Total return swaps and foreign exchange contracts | Level 2    
Assets    
Derivative assets   37
Total return swaps and foreign exchange contracts | Level 3    
Assets    
Derivative assets   0
Interest rate contracts and cross-currency interest rate swaps    
Liabilities    
Derivative liabilities   (23)
Interest rate contracts and cross-currency interest rate swaps | Level 1    
Liabilities    
Derivative liabilities   0
Interest rate contracts and cross-currency interest rate swaps | Level 2    
Liabilities    
Derivative liabilities   (23)
Interest rate contracts and cross-currency interest rate swaps | Level 3    
Liabilities    
Derivative liabilities   $ 0