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Long-Term Debt Senior Notes (Details) - Senior Notes [Member] - USD ($)
$ in Millions
12 Months Ended
Apr. 22, 2020
Dec. 31, 2020
Debt Instrument [Line Items]    
Redemption option senior notes, price expressed as a percent of principal amount   100.00%
KCS [Member] | 3.50% Senior Notes due May 1, 2050 [Member]    
Debt Instrument [Line Items]    
Debt instrument, face amount $ 550.0  
Debt instrument, maturity date May 01, 2050  
Debt instrument, stated interest rate 3.50%  
Debt instrument, unamortized discount $ 4.4  
Debt instrument, yield to maturity 3.543%  
KCSM [Member]    
Debt Instrument [Line Items]    
Additional redemption option KCSM senior notes, price expressed as percent of principal amount   100.00%
Debt instrument, stated interest rate   3.00%