v3.26.1
long-term debt - Long-term debt maturities (Details) - CAD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Jun. 30, 2024
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases $ 2,975.0 $ 3,314.0  
Total 56,687.0 57,627.0  
Composite long-term debt      
long-term debt      
Total 29,483.0    
Total 22,556.0    
Total 52,039.0    
Canadian Dollars      
long-term debt      
Total 19,378.0    
Total 12,250.0    
Total 31,628.0    
Canadian Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 16,913.0    
Future cash outflows in respect of associated interest and like carrying costs 11,500.0    
Undiscounted contractual maturities 28,413.0    
Canadian Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 2,465.0    
Future cash outflows in respect of associated interest and like carrying costs - Finance leases 750.0    
Undiscounted contractual maturities - Finance leases 3,215.0    
U.S. Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 10,523.0    
Future cash outflows in respect of associated interest and like carrying costs 10,145.0    
Undiscounted contractual maturities 20,668.0    
U.S. Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 196.0    
Future cash outflows in respect of associated interest and like carrying costs - Finance leases 68.0    
Undiscounted contractual maturities - Finance leases 264.0    
U.S. Dollars | Derivative Liability Receive      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities (10,919.0)    
Future cash outflows in respect of associated interest and like carrying costs - Derivative Liabilities (3,386.0)    
Undiscounted contractual maturities - Derivative Liabilities, Receive (14,305.0)    
U.S. Dollars | Derivative Liability Pay      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities 10,027.0    
Future cash outflows in respect of associated interest and like carrying costs - Derivative Liabilities 3,390.0    
Undiscounted contractual maturities - Derivative Liabilities, Pay 13,417.0    
U.S. Dollars | Composite long-term debt      
long-term debt      
Total 9,827.0    
Total 10,217.0    
Total 20,044.0    
Other currencies | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 278.0    
Future cash outflows in respect of associated interest and like carrying costs - Finance leases 89.0    
Undiscounted contractual maturities - Finance leases 367.0    
First year      
long-term debt      
Total 6,314.0 7,716.0  
First year | Composite long-term debt      
long-term debt      
Total 2,613.0    
First year | Canadian Dollars      
long-term debt      
Total 522.0    
First year | Canadian Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments     $ 321.0
First year | Canadian Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 201.0    
First year | U.S. Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 2,094.0    
First year | U.S. Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 21.0    
First year | U.S. Dollars | Derivative Liability Receive      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities (2,094.0)    
First year | U.S. Dollars | Derivative Liability Pay      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities 2,038.0    
First year | U.S. Dollars | Composite long-term debt      
long-term debt      
Total 2,059.0    
First year | Other currencies | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 32.0    
2 years hence      
long-term debt      
Total 4,777.0 4,507.0  
2 years hence | Composite long-term debt      
long-term debt      
Total 1,973.0    
2 years hence | Canadian Dollars      
long-term debt      
Total 424.0    
2 years hence | Canadian Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 50.0    
2 years hence | Canadian Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 374.0    
2 years hence | U.S. Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 1,563.0    
2 years hence | U.S. Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 34.0    
2 years hence | U.S. Dollars | Derivative Liability Receive      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities (1,564.0)    
2 years hence | U.S. Dollars | Derivative Liability Pay      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities 1,459.0    
2 years hence | U.S. Dollars | Composite long-term debt      
long-term debt      
Total 1,492.0    
2 years hence | Other currencies | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 57.0    
3 years hence      
long-term debt      
Total 3,690.0 3,801.0  
3 years hence | Composite long-term debt      
long-term debt      
Total 2,366.0    
3 years hence | Canadian Dollars      
long-term debt      
Total 2,286.0    
3 years hence | Canadian Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 1,952.0    
3 years hence | Canadian Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 334.0    
3 years hence | U.S. Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 33.0    
3 years hence | U.S. Dollars | Composite long-term debt      
long-term debt      
Total 33.0    
3 years hence | Other currencies | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 47.0    
4 years hence      
long-term debt      
Total 2,898.0 2,926.0  
4 years hence | Composite long-term debt      
long-term debt      
Total 1,745.0    
4 years hence | Canadian Dollars      
long-term debt      
Total 1,669.0    
4 years hence | Canadian Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 1,404.0    
4 years hence | Canadian Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 265.0    
4 years hence | U.S. Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 37.0    
4 years hence | U.S. Dollars | Composite long-term debt      
long-term debt      
Total 37.0    
4 years hence | Other currencies | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 39.0    
5 years hence      
long-term debt      
Total 2,988.0 3,239.0  
5 years hence | Composite long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities 1,905.0    
5 years hence | Canadian Dollars      
long-term debt      
Total 1,871.0    
5 years hence | Canadian Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 1,652.0    
5 years hence | Canadian Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 219.0    
5 years hence | U.S. Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 39.0    
5 years hence | U.S. Dollars | Derivative Liability Receive      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities (995.0)    
5 years hence | U.S. Dollars | Derivative Liability Pay      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities 962.0    
5 years hence | U.S. Dollars | Composite long-term debt      
long-term debt      
Total 6.0    
5 years hence | Other currencies | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 28.0    
5 years hence to 10 years      
long-term debt      
Total 11,107.0 11,033.0  
5 years hence to 10 years | Composite long-term debt      
long-term debt      
Total 6,908.0    
5 years hence to 10 years | Canadian Dollars      
long-term debt      
Total 5,714.0    
5 years hence to 10 years | Canadian Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 5,251.0    
5 years hence to 10 years | Canadian Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 463.0    
5 years hence to 10 years | U.S. Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 1,279.0    
5 years hence to 10 years | U.S. Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 32.0    
5 years hence to 10 years | U.S. Dollars | Derivative Liability Receive      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities (3,553.0)    
5 years hence to 10 years | U.S. Dollars | Derivative Liability Pay      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities 3,364.0    
5 years hence to 10 years | U.S. Dollars | Composite long-term debt      
long-term debt      
Total 1,122.0    
5 years hence to 10 years | Other currencies | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 72.0    
Thereafter      
long-term debt      
Total 24,913.0 $ 24,405.0  
Thereafter | Composite long-term debt      
long-term debt      
Total 11,973.0    
Thereafter | Canadian Dollars      
long-term debt      
Total 6,892.0    
Thereafter | Canadian Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 6,283.0    
Thereafter | Canadian Dollars | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases 609.0    
Thereafter | U.S. Dollars | Long-term debt      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments 5,587.0    
Thereafter | U.S. Dollars | Derivative Liability Receive      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities (2,713.0)    
Thereafter | U.S. Dollars | Derivative Liability Pay      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Derivative Liabilities 2,204.0    
Thereafter | U.S. Dollars | Composite long-term debt      
long-term debt      
Total 5,078.0    
Thereafter | Other currencies | Lease liabilities      
long-term debt      
Future cash outflows in respect of composite long-term debt principal repayments - Leases $ 3.0