v3.26.3
SHARE CAPITAL AND WARRANTS - Additional Information (Details) - CAD ($)
$ / shares in Units, shares in Thousands, $ in Millions
 1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Oct. 30, 2026
Sep. 30, 2026
Mar. 31, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Dec. 31, 2025
Nov. 03, 2026
Nov. 07, 2025
Dec. 31, 2024
Disclosure of classes of share capital [Line Items]                    
Maximum percentage of preferred stock upon issuance or outstanding of common stock         20.00%          
NCIB, shares redeemed, amount   $ 1,472   $ 918 $ 2,847 $ 1,281        
Stock Option Plan                    
Disclosure of classes of share capital [Line Items]                    
Shares available for future issuance (in shares)   22,200     22,200          
Common shares                    
Disclosure of classes of share capital [Line Items]                    
Purchase of Common Shares Under NCIB (in shares)         71,718   89,438      
NCIB, shares authorized for repurchase (in shares)               126,500    
Shares outstanding (in shares)   1,816,557     1,816,557   1,883,400     1,825,038
Common shares | Renewed NCIB                    
Disclosure of classes of share capital [Line Items]                    
Purchase of Common Shares Under NCIB (in shares)         71,700          
NCIB, shares repurchased, price per share (in CAD per share)         $ 38.87          
NCIB, shares redeemed, amount         $ 2,800          
NCIB, reduction to retained earnings         2,100          
Average carrying value         2,100          
Taxes paid         $ 59          
Common shares | Renewed NCIB | Potential ordinary share transactions                    
Disclosure of classes of share capital [Line Items]                    
Number of shares authorized (in shares)                 120,300  
Purchase of Common Shares Under NCIB (in shares) 9,200                  
NCIB, shares redeemed, amount $ 415                  
NCIB, shares authorized for repurchase (in shares) 31,900                  
Preferred Shares                    
Disclosure of classes of share capital [Line Items]                    
Shares outstanding (in shares)   0     0   12,000     26,000
Retained earnings     $ 187              
Preferred Shares | Series 1 Preferred Shares                    
Disclosure of classes of share capital [Line Items]                    
Shares outstanding (in shares)     10,700              
Preferred Shares | Series 2 First Preferred Shares                    
Disclosure of classes of share capital [Line Items]                    
Shares outstanding (in shares)     1,300              
Preferred Shares | Series 1 And 2 First Preferred Shares                    
Disclosure of classes of share capital [Line Items]                    
NCIB, shares redeemed, amount     $ 300              
Preferred Shares, Price Per Share     $ 25.00              
Common Share Warrants                    
Disclosure of classes of share capital [Line Items]                    
Shares outstanding (in shares)   0     0   1,172     3,643
Exercise price of warrants issued (in CAD per share)         $ 6.54