v3.26.1
PROPERTY, PLANT AND EQUIPMENT - Cost (Details) - CAD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year $ 3,034.3  
Balance at the end of year 3,039.2 $ 3,034.3
Property, plant and equipment    
Changes in the net carrying amount of fixed assets    
Net of credits received on investment 35.2 26.7
Deferred subsidies used 17.3 2.8
Increase in government credits receivable in large investment projects 6.2 67.5
Land, buildings and leasehold improvements    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year 123.0  
Balance at the end of year 116.1 123.0
Furniture and equipment    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year 241.1  
Balance at the end of year 295.1 241.1
Telecommunication networks    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year 2,503.7  
Balance at the end of year 2,422.2 2,503.7
Projects under development    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year 166.5  
Balance at the end of year 205.8 166.5
Cost    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year 9,904.5 9,667.1
Additions 488.0 446.0
Net change in additions financed with non-cash balances 5.7 (54.5)
Retirement, disposals and other (154.7) (154.1)
Balance at the end of year 10,243.5 9,904.5
Cost | Land, buildings and leasehold improvements    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year 236.7 237.2
Additions 0.7 0.9
Reclassification 0.5 0.9
Retirement, disposals and other (2.4) (2.3)
Balance at the end of year 235.5 236.7
Cost | Furniture and equipment    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year 1,309.5 1,311.1
Additions 118.8 52.1
Net change in additions financed with non-cash balances (7.5) (3.2)
Reclassification 9.2 8.9
Retirement, disposals and other (58.0) (59.4)
Balance at the end of year 1,372.0 1,309.5
Cost | Telecommunication networks    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year 8,191.8 7,959.4
Additions 200.7 247.3
Net change in additions financed with non-cash balances 8.0 (69.1)
Reclassification 124.5 146.6
Retirement, disposals and other (94.8) (92.4)
Balance at the end of year 8,430.2 8,191.8
Cost | Projects under development    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year 166.5 159.4
Additions 167.8 145.7
Net change in additions financed with non-cash balances 5.2 17.8
Reclassification (134.2) (156.4)
Retirement, disposals and other 0.5  
Balance at the end of year 205.8 166.5
Accumulated amortization and impairment losses    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year (6,870.2) (6,514.2)
Retirement, disposals and other (146.1) (179.2)
Balance at the end of year (7,204.3) (6,870.2)
Accumulated amortization and impairment losses | Land, buildings and leasehold improvements    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year (113.7) (106.2)
Retirement, disposals and other (2.1) (2.3)
Balance at the end of year (119.4) (113.7)
Accumulated amortization and impairment losses | Furniture and equipment    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year (1,068.4) (1,090.1)
Retirement, disposals and other (56.7) (91.7)
Balance at the end of year (1,076.9) (1,068.4)
Accumulated amortization and impairment losses | Telecommunication networks    
Changes in the net carrying amount of fixed assets    
Balance at the beginning of year (5,688.1) (5,317.9)
Retirement, disposals and other (87.3) (85.2)
Balance at the end of year $ (6,008.0) $ (5,688.1)