Equity (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended		26 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jan. 01, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 4,468.9	$ 4,252.1	$ 4,404.5	$ 4,224.7
Cumulative-effect adjustment	[1]						$ 2.5
Net income		134.7	120.5	281.6	228.6
Other comprehensive loss		(1.8)	(0.6)	(1.0)	(0.7)
Dividends on common stock		(34.9)	(35.6)	(69.9)	(71.2)
Share repurchases		(64.7)	(8.2)	(120.4)	(59.2)	$ (500.0)
Options exercised and stock subscribed, net of shares withheld for employee taxes		(0.1)	(1.4)	0.1	(1.1)
Excess tax benefit from share-based compensation		0.0	(0.1)	0.0	(0.4)
Share-based compensation		5.7	5.0	10.5	11.1
Ending balance		4,507.8	4,331.7	4,507.8	4,331.7	4,507.8
$25 Par Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends on $25 par preferred stock				(0.1)	(0.1)
Kansas City Southern Stockholders' Equity [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		4,154.0	3,941.4	4,089.9	3,914.3
Cumulative-effect adjustment	[1]						$ 2.5
Net income		134.4	120.1	281.0	227.9
Other comprehensive loss		(1.8)	(0.6)	(1.0)	(0.7)
Dividends on common stock		(34.9)	(35.6)	(69.9)	(71.2)
Share repurchases		(64.7)	(8.2)	(120.4)	(59.2)
Options exercised and stock subscribed, net of shares withheld for employee taxes		(0.1)	(1.4)	0.1	(1.1)
Excess tax benefit from share-based compensation		0.0	(0.1)	0.0	(0.4)
Share-based compensation		5.7	5.0	10.5	11.1
Ending balance		4,192.6	4,020.6	4,192.6	4,020.6	4,192.6
Kansas City Southern Stockholders' Equity [Member] | $25 Par Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends on $25 par preferred stock				(0.1)	(0.1)
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		314.9	310.7	314.6	310.4
Net income		0.3	0.4	0.6	0.7
Ending balance		$ 315.2	$ 311.1	$ 315.2	$ 311.1	$ 315.2

[1] The Company recognized a $2.5 million net cumulative-effect adjustment to equity as of January 1, 2017, due to the adoption of ASU 2016-09, Improvements to Employee Share-Based Payment Accounting. For additional discussion, see Note 1 - Basis of Presentation.