v3.26.1
Common shares - Common Share Activities (Detail) - CAD ($)
shares in Thousands, $ in Millions
3 Months Ended 12 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Increase (Decrease) in Stockholders' Equity [Roll Forward]      
Common stock beginning balance, (in shares) 483,593    
Common stock, ending balance, (in shares) 483,593   483,593
Common stock beginning balance [1] $ 895    
Common stock, ending balance [1] $ 895   $ 895
Common Stock      
Increase (Decrease) in Stockholders' Equity [Roll Forward]      
Common stock beginning balance, (in shares) 483,593 509,045 509,045
Purchases at stated value, (in shares) 0   (25,452)
Common stock, ending balance, (in shares) 483,593   483,593
Common stock beginning balance $ 895 $ 942 $ 942
Purchases at stated value 0 $ 0 (47)
Common stock, ending balance $ 895   $ 895
[1]
Number of common shares authorized (millions).1,1001,100
Number of common shares outstanding (millions).484484