v3.26.1
Debt - Components (Detail)
$ in Millions, $ in Millions
Jun. 30, 2026
USD ($)
Jun. 30, 2026
CAD ($)
Dec. 31, 2025
USD ($)
Dec. 31, 2025
CAD ($)
Debt        
Debt $ 23,356   $ 22,907  
Debt issuance costs, discounts and other (150)   (156)  
Current portion of long-term debt 1,075   711  
Long-term debt, less current portion 22,281   22,196  
Commercial Paper Program [Member]        
Debt        
Debt $ 1,068   $ 1,090  
Weighted average interest rate 3.95% 3.95% 4.05% 4.05%
Senior Notes, Aggregate [Member]        
Debt        
Debt $ 17,483   $ 17,498  
Weighted average interest rate 4.27% 4.27% 4.28% 4.28%
Senior Notes, Aggregate [Member] | Minimum [Member]        
Debt        
Interest rate (as a percent) 1.15% 1.15% 1.15% 1.15%
Senior Notes, Aggregate [Member] | Maximum [Member]        
Debt        
Interest rate (as a percent) 7.75% 7.75% 7.75% 7.75%
Canadian Senior Notes maturing September 2026        
Debt        
Debt $ 352 $ 500 $ 364 $ 500
Interest rate (as a percent) 2.60% 2.60% 2.60% 2.60%
Canadian Senior Notes maturing July 2033        
Debt        
Debt $ 493 $ 700    
Interest rate (as a percent) 3.944% 3.944%    
Tax Exempt Bonds [Member]        
Debt        
Debt $ 2,827   $ 2,827  
Weighted average interest rate 3.33% 3.33% 3.41% 3.41%
Tax Exempt Bonds [Member] | Minimum [Member]        
Debt        
Interest rate (as a percent) 0.70% 0.70% 0.70% 0.70%
Tax Exempt Bonds [Member] | Maximum [Member]        
Debt        
Interest rate (as a percent) 4.60% 4.60% 4.60% 4.60%
Financing leases and other [Member]        
Debt        
Debt $ 1,283   $ 1,284  
Weighted average interest rate 4.90% 4.90% 4.83% 4.83%