v3.25.4
Debt (Schedule of Debt) (Details)
$ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2025
CAD ($)
Dec. 31, 2025
USD ($)
Nov. 12, 2025
Sep. 22, 2025
Jun. 10, 2025
Dec. 31, 2024
CAD ($)
Dec. 31, 2024
USD ($)
Sep. 18, 2024
May 02, 2024
Debt Instrument [Line Items]                  
Commercial paper $ 124 $ 90       $ 721 $ 501    
Finance leases 5         7      
Equipment loans and other 1,365         1,489      
Total debt, gross 22,218         21,901      
Fair value hedging adjustment (11)         0      
Net unamortized discount and debt issuance costs (1,001)         (1,007)      
Total debt 21,206         20,894      
Less: Current portion of long-term debt 906         1,166      
Total long-term debt 20,300         19,728      
Notes and Debentures                  
Debt Instrument [Line Items]                  
Total debt, gross $ 20,724         19,684      
Canadian National Series, 2.80%, 10-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 2.80% 2.80%              
Term of issuance 10 years                
Maturity Sep. 22, 2025                
Total debt, gross $ 0         350      
Canadian National Series, 2.75%, 10-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 2.75% 2.75%              
Term of issuance 10 years                
Maturity Mar. 01, 2026                
Total debt, gross $ 686 $ 500       719 500    
Canadian National Series, 6.90%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 6.90% 6.90%              
Term of issuance 30 years                
Maturity Jul. 15, 2028                
Total debt, gross $ 652 $ 475       683 475    
Canadian National Series, 3.20%, 10-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.20% 3.20%              
Term of issuance 10 years                
Maturity Jul. 31, 2028                
Total debt, gross $ 350         350      
Canadian National Series, 3.00%, 10-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.00% 3.00%              
Term of issuance 10 years                
Maturity Feb. 08, 2029                
Total debt, gross $ 350         350      
Canadian National Series, 4.60%, 5-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.60% 4.60%             4.60%
Term of issuance 5 years                
Maturity May 02, 2029                
Total debt, gross $ 700         700      
Canadian National Series, 4.15%, 7-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.15% 4.15%              
Term of issuance 7 years                
Maturity May 10, 2030                
Total debt, gross $ 550         550      
Canadian National Series, 3.50%, 5-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.50% 3.50%     3.50%        
Term of issuance 5 years                
Maturity Jun. 10, 2030                
Total debt, gross $ 500         0      
Canadian National Series, 4.20%, 5-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.20% 4.20% 4.20%            
Maturity Mar. 12, 2031                
Total debt, gross $ 412 $ 300       0 300    
Canadian National Series, 7.38%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 7.38% 7.38%              
Term of issuance 30 years                
Maturity Oct. 15, 2031                
Total debt, gross $ 274 $ 200       288 200    
Canadian National Series, 3.85%, 10-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.85% 3.85%              
Term of issuance 10 years                
Maturity Aug. 05, 2032                
Total debt, gross $ 1,098 $ 800       1,151 800    
Canadian National Series, 4.40%, 10-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.40% 4.40%              
Term of issuance 10 years                
Maturity May 10, 2033                
Total debt, gross $ 400         400      
Canadian National Series, 5.85%, 10-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 5.85% 5.85%              
Term of issuance 10 years                
Maturity Nov. 01, 2033                
Total debt, gross $ 412 $ 300       431 300    
Canadian National Series, 6.25%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 6.25% 6.25%              
Term of issuance 30 years                
Maturity Aug. 01, 2034                
Total debt, gross $ 686 $ 500       719 500    
Canadian National Series, 4.38%, 10-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.38% 4.38%   2.80%       4.38%  
Term of issuance 10 years                
Maturity Sep. 18, 2034                
Total debt, gross $ 1,029 $ 750       1,079 750    
Canadian National Series, 4.20%, 10-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.20% 4.20%     4.20%        
Term of issuance 10 years                
Maturity Jun. 10, 2035                
Total debt, gross $ 500         0      
Canadian National Series, 4.75%, 10-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.75% 4.75% 4.75%            
Term of issuance 10 years                
Maturity Nov. 12, 2035                
Total debt, gross $ 549 $ 400       0 400    
Canadian National Series, 6.20%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 6.20% 6.20%              
Term of issuance 30 years                
Maturity Jun. 01, 2036                
Total debt, gross $ 618 $ 450       647 450    
Canadian National Series, 6.71%, Puttable Reset Securities                  
Debt Instrument [Line Items]                  
Interest rate 6.71% 6.71%              
Maturity Jul. 15, 2036                
Total debt, gross $ 343 $ 250       360 250    
Canadian National Series, 6.38%, 30-year Debentures                  
Debt Instrument [Line Items]                  
Interest rate 6.38% 6.38%              
Term of issuance 30 years                
Maturity Nov. 15, 2037                
Total debt, gross $ 412 $ 300       431 300    
Canadian National Series, 3.50%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.50% 3.50%              
Term of issuance 30 years                
Maturity Nov. 15, 2042                
Total debt, gross $ 343 $ 250       360 250    
Canadian National Series, 4.50%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.50% 4.50%              
Term of issuance 30 years                
Maturity Nov. 07, 2043                
Total debt, gross $ 343 $ 250       360 250    
Canadian National Series, 3.95%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.95% 3.95%              
Term of issuance 30 years                
Maturity Sep. 22, 2045                
Total debt, gross $ 400         400      
Canadian National Series, 3.20%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.20% 3.20%              
Term of issuance 30 years                
Maturity Aug. 02, 2046                
Total debt, gross $ 892 $ 650       935 650    
Canadian National Series, 3.60%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.60% 3.60%              
Term of issuance 30 years                
Maturity Aug. 01, 2047                
Total debt, gross $ 500         500      
Canadian National Series, 3.65%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.65% 3.65%              
Term of issuance 30 years                
Maturity Feb. 03, 2048                
Total debt, gross $ 823 $ 600       863 600    
Canadian National Series, 3.60%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.60% 3.60%              
Term of issuance 30 years                
Maturity Jul. 31, 2048                
Total debt, gross $ 450         450      
Canadian National Series, 4.45%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.45% 4.45%              
Term of issuance 30 years                
Maturity Jan. 20, 2049                
Total debt, gross $ 892 $ 650       935 650    
Canadian National Series, 3.60%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.60% 3.60%              
Term of issuance 30 years                
Maturity Feb. 08, 2049                
Total debt, gross $ 450         450      
Canadian National Series, 3.05%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 3.05% 3.05%              
Term of issuance 30 years                
Maturity Feb. 08, 2050                
Total debt, gross $ 450         450      
Canadian National Series, 2.45%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 2.45% 2.45%              
Term of issuance 30 years                
Maturity May 01, 2050                
Total debt, gross $ 823 $ 600       863 600    
Canadian National Series, 4.40%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.40% 4.40%              
Term of issuance 30 years                
Maturity Aug. 05, 2052                
Total debt, gross $ 961 $ 700       1,007 700    
Canadian National Series, 4.70%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.70% 4.70%              
Term of issuance 30 years                
Maturity May 10, 2053                
Total debt, gross $ 800         800      
Canadian National Series, 6.13%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 6.13% 6.13%              
Term of issuance 30 years                
Maturity Nov. 01, 2053                
Total debt, gross $ 412 $ 300       431 300    
Canadian National Series, 5.10%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 5.10% 5.10%             5.10%
Term of issuance 30 years                
Maturity May 02, 2054                
Total debt, gross $ 550         550      
Canadian National Series, 4.00%, 30-year Notes                  
Debt Instrument [Line Items]                  
Interest rate 4.00% 4.00%              
Term of issuance 50 years                
Maturity Sep. 22, 2065                
Total debt, gross $ 100         100      
Illinois Central Series, 7.70%, 100-year debentures                  
Debt Instrument [Line Items]                  
Interest rate 7.70% 7.70%              
Term of issuance 100 years                
Maturity Sep. 15, 2096                
Total debt, gross $ 172 $ 125       180 $ 125    
BC Rail series, non-interest bearing 90-year subordinated notes                  
Debt Instrument [Line Items]                  
Term of issuance 90 years                
Maturity Jul. 14, 2094                
Total debt, gross $ 842         842      
Net unamortized discount and debt issuance costs (825)         (826)      
LTD other disclosures                  
Discounted debt $ 17         $ 16      
Imputed interest rate 5.75% 5.75%       5.75% 5.75%    
Equipment Loan                  
Debt Instrument [Line Items]                  
Equipment loans and other $ 1,329         $ 1,449      
Other Equipment Loan                  
Debt Instrument [Line Items]                  
Equipment loans and other $ 36         $ 40      
LTD other disclosures                  
Weighted average interest rate 2.30% 2.30%       2.35% 2.35%