v3.25.4
Long-term debt - Narrative (Details)
$ in Millions, $ in Millions
 3 Months Ended 12 Months Ended
Feb. 12, 2026
CAD ($)
Dec. 08, 2025
CAD ($)
Aug. 28, 2025
CAD ($)
Aug. 19, 2025
CAD ($)
Jun. 12, 2025
CAD ($)
Mar. 27, 2025
CAD ($)
Mar. 27, 2025
USD ($)
Feb. 18, 2025
CAD ($)
Jun. 30, 2025
CAD ($)
Mar. 31, 2025
CAD ($)
Dec. 31, 2025
CAD ($)
Dec. 31, 2024
CAD ($)
Aug. 28, 2025
USD ($)
Aug. 20, 2025
CAD ($)
Aug. 20, 2025
USD ($)
Aug. 14, 2025
CAD ($)
Aug. 01, 2025
CAD ($)
Aug. 01, 2025
USD ($)
Jun. 30, 2025
USD ($)
Mar. 27, 2025
USD ($)
Feb. 18, 2025
USD ($)
May 24, 2024
CAD ($)
Feb. 15, 2024
CAD ($)
Feb. 15, 2024
USD ($)
Disclosure of detailed information about borrowings [line items]                                                
Gain (loss) on debt redemption                 $ 91 $ 266 $ 249 $ 0                        
Early repayments of non-current borrowings         $ 602 $ 903 $ 633                                  
Ziply Fiber                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings                                 $ 2,680 $ 1,940            
Series M-41 Medium Term Note Debentures                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings   $ 750                                            
Borrowings, principal amount, repurchased   750                                            
Gain (loss) on debt redemption   $ (1)                                            
Series M-41 Medium Term Note Debentures | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)   3.55%                                            
Secured Fiber Network Revenue Term Notes | Ziply Fiber                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings     $ 2,192                   $ 1,594                      
Borrowings, principal amount, repurchased     2,300                   $ 1,672                      
Gain (loss) on debt redemption     $ (109)                                          
Secured Fiber Network Revenue Funding Notes | Ziply Fiber                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings                           $ 509 $ 367                  
Borrowings, principal amount, repurchased                           $ 509 $ 367                  
Series M-55 Medium Term Note Debentures                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings       $ 90                                        
Borrowings, principal amount, repurchased       6                                        
Gain (loss) on debt redemption       1                                        
Notional amount       $ 7                                        
Series M-55 Medium Term Note Debentures | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)       4.05%                                        
Series M-64 Medium Term Note Debentures                                                
Disclosure of detailed information about borrowings [line items]                                                
Notional amount                               $ 400                
Series M-64 Medium Term Note Debentures | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)                               3.65%                
Series M-65 Medium Term Note Debentures                                                
Disclosure of detailed information about borrowings [line items]                                                
Notional amount                               $ 500                
Series M-65 Medium Term Note Debentures | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)                               4.30%                
Series M-66 Medium Term Note Debentures                                                
Disclosure of detailed information about borrowings [line items]                                                
Notional amount                               $ 600                
Series M-66 Medium Term Note Debentures | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)                               4.70%                
Series M-67 Medium Term Note Debentures                                                
Disclosure of detailed information about borrowings [line items]                                                
Notional amount                               $ 500                
Series M-67 Medium Term Note Debentures | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)                               5.25%                
Total non-committed credit facilities | Bell Mobility Inc.                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings, principal amount, repurchased                 $ 819                   $ 600          
Series M-39 Medium-term notes                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings         500                                      
Borrowings, principal amount, repurchased         $ 105                                      
Series M-39 Medium-term notes | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)         4.35%                                      
Series M-45 Medium-term notes                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings         $ 500                                      
Borrowings, principal amount, repurchased         $ 100                                      
Series M-45 Medium-term notes | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)         4.45%                                      
Series M-51 Medium-term notes                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings         $ 119 1,250                                    
Borrowings, principal amount, repurchased         $ 35 1,131                                    
Early repayments of non-current borrowings           $ 896                                    
Series M-51 Medium-term notes | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)         3.50% 3.50%                           3.50%        
Series M-55 Medium-term notes                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings         $ 550                                      
Borrowings, principal amount, repurchased         $ 460                                      
Series M-55 Medium-term notes | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)         4.05%                                      
Series US-2 Notes                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings           $ 856                           $ 600        
Borrowings, principal amount, repurchased           $ 249                           $ 174        
Series US-2 Notes | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)           4.30%                           4.30%        
Series US-4 Notes                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings           $ 713                           $ 500        
Borrowings, principal amount, repurchased           $ 112                           $ 79        
Series US-4 Notes | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)           3.65%                           3.65%        
Series US-5 Notes                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings           $ 856                           $ 600        
Borrowings, principal amount, repurchased           $ 261                           $ 183        
Series US-5 Notes | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)           2.15%                           2.15%        
Series US-6 Notes                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings           $ 927                           $ 650        
Borrowings, principal amount, repurchased           $ 273                           $ 191        
Series US-6 Notes | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)           3.20%                           3.20%        
Series US-7 Notes                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings           $ 1,070                           $ 750        
Borrowings, principal amount, repurchased           $ 310                           $ 217        
Series US-7 Notes | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)           3.65%                           3.65%        
Fixed-to-Fixed Rate Junior Subordinated Notes, Series C                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings           $ 1,250                                    
Borrowings, interest rate, reset term           5 years 5 years                                  
Borrowings, interest rate, term           5 years 5 years                                  
Borrowings, redemption price, percentage           100.00% 100.00%                                  
Fixed-to-Fixed Rate Junior Subordinated Notes, Series C | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)           5.625%                           5.625%        
Fixed-to-Fixed Rate Junior Subordinated Notes, Series C | Government of Canada Yield                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings, adjustment to interest rate basis           2.95%                           2.95%        
Fixed-to-Fixed Rate Junior Subordinated Notes, Series A                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings               $ 1,416                         $ 1,000      
Borrowings, interest rate, term               5 years                                
Fixed-to-Fixed Rate Junior Subordinated Notes, Series A | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)               6.875%                         6.875%      
Borrowings, interest rate, reset term               5 years                                
Fixed-to-Fixed Rate Junior Subordinated Notes, Series A | U.S. Treasury Rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings, adjustment to interest rate basis               2.39%                         2.39%      
Fixed-to-Fixed Rate Junior Subordinated Notes, Series B                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings               $ 1,771                         $ 1,250      
Borrowings, interest rate, reset term               5 years                                
Borrowings, interest rate, term               5 years                                
Borrowings, redemption price, percentage               100.00%                                
Fixed-to-Fixed Rate Junior Subordinated Notes, Series B | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)               7.00%                         7.00%      
Fixed-to-Fixed Rate Junior Subordinated Notes, Series B | U.S. Treasury Rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings, adjustment to interest rate basis               2.363%                         2.363%      
Series M-61 Medium Term Notes Debentures                                                
Disclosure of detailed information about borrowings [line items]                                                
Notional amount                                           $ 400    
Series M-61 Medium Term Notes Debentures | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)                                           5.60%    
Series M-63 Medium Term Notes Debentures                                                
Disclosure of detailed information about borrowings [line items]                                                
Notional amount                                           $ 1,100    
Series M-63 Medium Term Notes Debentures | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)                                           5.15%    
Series US -9 Medium Term Notes Debentures                                                
Disclosure of detailed information about borrowings [line items]                                                
Notional amount                                             $ 942 $ 700
Series US -9 Medium Term Notes Debentures | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)                                             5.20% 5.20%
Series US -10 Medium Term Notes Debentures                                                
Disclosure of detailed information about borrowings [line items]                                                
Notional amount                                             $ 1,009 $ 750
Series US -10 Medium Term Notes Debentures | Fixed interest rate                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent)                                             5.55% 5.55%
Fixed-to-Fixed Rate Junior Subordinated Notes, Series D | Public Offering                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings $ 750                                              
Borrowings, interest rate, term 5 years                                              
Fixed-to-Fixed Rate Junior Subordinated Notes, Series D | Fixed interest rate | Public Offering                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent) 5.375%                                              
Borrowings, interest rate, reset term 5 years                                              
Fixed-to-Fixed Rate Junior Subordinated Notes, Series D | Government of Canada Yield | Public Offering                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings, adjustment to interest rate basis 2.388%                                              
Fixed-to-Fixed Rate Junior Subordinated Notes, Series E | Public Offering                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings $ 750                                              
Borrowings, interest rate, term 5 years                                              
Borrowings, redemption price, percentage 100.00%                                              
Fixed-to-Fixed Rate Junior Subordinated Notes, Series E | Fixed interest rate | Public Offering                                                
Disclosure of detailed information about borrowings [line items]                                                
Interest rate (as a percent) 5.875%                                              
Borrowings, interest rate, reset term 5 years                                              
Fixed-to-Fixed Rate Junior Subordinated Notes, Series E | Government of Canada Yield | Public Offering                                                
Disclosure of detailed information about borrowings [line items]                                                
Borrowings, adjustment to interest rate basis 2.44%                                              
Bottom of range                                                
Disclosure of detailed information about borrowings [line items]                                                
Number of days between invoice date and payment due date for trade payables that are not part of supplier finance arrangements                     30 days                          
Top of range                                                
Disclosure of detailed information about borrowings [line items]                                                
Number of days between invoice date and payment due date for trade payables that are not part of supplier finance arrangements                     60 days                          
Financial liabilities that are part of supplier finance arrangements                                                
Disclosure of detailed information about borrowings [line items]                                                
Supplier finance arrangement, term                     5 years