Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended		3 Months Ended		9 Months Ended								0 Months Ended										0 Months Ended		0 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 KCSR [Member]	Sep. 30, 2010 KCSR [Member]	Sep. 30, 2011 KCSR [Member]	Sep. 30, 2010 KCSR [Member]	Jul. 12, 2011 KCSR [Member] Federal Funds Rate Plus Percent [Member]	Jul. 12, 2011 KCSR [Member] One-Month LIBOR Plus Percent [Member]	Jul. 12, 2011 KCSR [Member] LIBOR Plus Percent [Member]	Jul. 12, 2011 KCSR [Member] Base Rate [Member] Swing Line Facility [Member]	Jul. 12, 2011 KCSR [Member] Letter of Credit [Member] New Revolving Credit Facility [Member]	Jul. 12, 2011 KCSR [Member] Swing Line Facility [Member] New Revolving Credit Facility [Member]	Jul. 12, 2011 KCSR [Member] New Term Loan Credit Facility [Member]	Jul. 12, 2011 KCSR [Member] New Revolving Credit Facility [Member]	Jul. 12, 2011 KCSR [Member] Prior Revolving Credit Facility [Member]	Jul. 12, 2011 KCSR [Member] Prior Term Loan Credit Facility [Member]	Sep. 30, 2011 KCSM [Member] Federal Funds Rate Plus Percent [Member]	Sep. 30, 2011 KCSM [Member] One-Month LIBOR Plus Percent [Member]	Sep. 30, 2011 KCSM [Member] LIBOR Plus Percent [Member]	Sep. 30, 2011 KCSM [Member] Base Rate [Member] Swing Line Facility [Member]	Sep. 30, 2011 KCSM [Member] Letter of Credit [Member] New Revolving Credit Facility [Member]	Sep. 30, 2011 KCSM [Member] Swing Line Facility [Member] New Revolving Credit Facility [Member]	Sep. 30, 2011 KCSM [Member] New Revolving Credit Facility [Member]	Sep. 30, 2011 KCSM [Member] Prior Revolving Credit Facility [Member]	Jun. 07, 2011 7 5/8% Senior Notes Due December 1, 2013 [Member]	Jun. 07, 2011 7 3/8% Senior Notes Due June 1, 2014 [Member]	May 20, 2011 6 1/8% Senior Unsecured Notes Due June 15, 2021 [Member]	Sep. 01, 2011 Locomotive Loan Agreements [Member] locomotives trusts agreements payments
Debt instrument, maturity date																Jan. 15, 2017			Apr. 28, 2013									Dec. 01, 2013	Jun. 01, 2014	Jun. 15, 2021	Dec. 15, 2020
Gross amount of debt purchased and redeemed by the company																												$ 32.4	$ 165.0
Principal amount of debt																														200.0	18.2
Debt retirement costs	(3.9)	(10.3)	(1.9)	(14.2)	(49.3)	(3.9)	0	(3.9)	(15.8)
Interest rate, stated percentage																												7.625%	7.375%	6.125%	9.31%
Redemption price percentage at the end of the fifth year																														103.063%
Redemption price percentage at the end of the sixth year																														102.042%
Redemption price percentage at the end of the seventh year																														101.021%
Redemption price percentage at the end of the eighth year																														100.00%
Percentage of principal amount that may be redeemed prior to maturity date																														35.00%
Redemption price percentage prior to maturity date																														106.125%
Date Senior Notes are redeemable at KCSM's option																														Jun. 15, 2014
Outstanding debt balance																300.0			305.8
Credit facility maximum borrowing capacity														25.0	15.0		200.0	125.0						15.0	15.0	200.0	100.0
Reduction of principal balance																			$ 5.8
Credit facility expiration date																	7/15/2016	4/28/2013								9/30/2016
Percentage points added to the reference rate										0.50%	1.00%									0.50%	1.00%
Minimum margin percent											0.25%	1.25%	0.25%								0.25%	1.25%	0.25%
Maximum margin percent											1.50%	2.50%	1.50%								1.50%	2.50%	1.50%
Number of loan agreements																															5
Percentage of purchase price financed																															88.00%
Number of locomotives																															75
Number of irrevocable trusts																															5
Number of principal payments																															38