Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 619.1	$ 540.8	$ 629.4
Other comprehensive income (loss):
Unrealized gain (loss) on interest rate derivative instruments, net of tax of $7.5 million, $(4.9) million and $1.0 million	28.1	(18.9)	2.6
Reclassification adjustment from cash flow hedges included in net income, net of tax of $0.5 million and less than $0.1 million	1.9	0.2	0.0
Foreign currency translation adjustments	(0.5)	0.5	0.1
Other comprehensive income (loss)	29.5	(18.2)	2.7
Comprehensive income	648.6	522.6	632.1
Less: comprehensive income attributable to noncontrolling interest	2.1	1.9	2.0
Comprehensive income attributable to Kansas City Southern and subsidiaries	$ 646.5	$ 520.7	$ 630.1