Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities:
Net cash provided	$ 160.3	$ 162.5
Investing activities:
Capital expenditures	(122.1)	(178.0)
Purchase or replacement of equipment under operating leases	(4.6)	(53.7)
Property investments in MSLLC	(6.6)	(1.9)
Proceeds from repayment of loans to affiliates	0.0	0.0
Loans to affiliates	0.0
Contribution to consolidated affiliates	(0.1)
Other investing activities	(3.1)	(0.2)
Net cash used for investing activities	(136.5)	(233.8)
Financing activities:
Proceeds from short-term borrowings	4,194.8	3,842.1
Repayment of short-term borrowings	(4,221.0)	(4,079.6)
Proceeds from issuance of long-term debt	0.0	30.0
Repayment of long-term debt	(7.7)	(7.3)
Dividends paid	(35.8)	(31.0)
Shares repurchased	(51.0)	0.0
Proceeds from loans from affiliates	0.0
Repayment of loans from affiliates	0.0	0.0
Contribution from affiliates	0.0
Other financing activities	(8.2)	7.5
Net cash used for financing activities	(121.2)	(238.3)
Cash and cash equivalents:
Net decrease during each period	(97.4)	(309.6)
At beginning of year	136.6	348.0
At end of period	39.2	38.4
Condensed Consolidating Financial Information KCS [Member] | Parent [Member]
Operating activities:
Net cash provided	110.2	(1.5)
Investing activities:
Capital expenditures	0.0	0.0
Purchase or replacement of equipment under operating leases	0.0	0.0
Property investments in MSLLC	0.0	0.0
Proceeds from repayment of loans to affiliates	4,297.1	25.8
Loans to affiliates	(4,194.8)
Contribution to consolidated affiliates	(96.8)
Other investing activities	0.0	(0.2)
Net cash used for investing activities	5.5	25.6
Financing activities:
Proceeds from short-term borrowings	4,194.8	0.0
Repayment of short-term borrowings	(4,221.0)	0.0
Proceeds from issuance of long-term debt		0.0
Repayment of long-term debt		0.0
Dividends paid	(35.8)	(31.0)
Shares repurchased	(51.0)
Proceeds from loans from affiliates	0.0
Repayment of loans from affiliates	0.0	0.0
Contribution from affiliates	0.0
Other financing activities	(0.3)	7.5
Net cash used for financing activities	(113.3)	(23.5)
Cash and cash equivalents:
Net decrease during each period	2.4	0.6
At beginning of year	0.2	0.2
At end of period	2.6	0.8
Condensed Consolidating Financial Information KCS [Member] | Guarantor Subsidiaries [Member]
Operating activities:
Net cash provided	98.6	53.2
Investing activities:
Capital expenditures	(85.3)	(103.4)
Purchase or replacement of equipment under operating leases	(4.6)	0.0
Property investments in MSLLC	0.0	0.0
Proceeds from repayment of loans to affiliates	0.0	0.0
Loans to affiliates	0.0
Contribution to consolidated affiliates	(0.1)
Other investing activities	(4.9)	(0.1)
Net cash used for investing activities	(94.9)	(103.5)
Financing activities:
Proceeds from short-term borrowings	0.0	3,842.1
Repayment of short-term borrowings	0.0	(3,779.6)
Proceeds from issuance of long-term debt		0.0
Repayment of long-term debt		(0.9)
Dividends paid	0.0	0.0
Shares repurchased	0.0
Proceeds from loans from affiliates	4,194.8
Repayment of loans from affiliates	(4,297.1)	(25.8)
Contribution from affiliates	96.8
Other financing activities	(1.0)	0.2
Net cash used for financing activities	(6.5)	36.0
Cash and cash equivalents:
Net decrease during each period	(2.8)	(14.3)
At beginning of year	10.2	29.5
At end of period	7.4	15.2
Condensed Consolidating Financial Information KCS [Member] | Non-Guarantor Subsidiaries [Member]
Operating activities:
Net cash provided	49.9	113.6
Investing activities:
Capital expenditures	(36.8)	(74.6)
Purchase or replacement of equipment under operating leases	0.0	(53.7)
Property investments in MSLLC	(6.6)	(1.9)
Proceeds from repayment of loans to affiliates	0.0	0.0
Loans to affiliates	0.0
Contribution to consolidated affiliates	(0.1)
Other investing activities	1.8	(0.3)
Net cash used for investing activities	(41.7)	(130.5)
Financing activities:
Proceeds from short-term borrowings	0.0	0.0
Repayment of short-term borrowings	0.0	(300.0)
Proceeds from issuance of long-term debt		30.0
Repayment of long-term debt		(6.4)
Dividends paid	(96.7)	(2.8)
Shares repurchased	0.0
Proceeds from loans from affiliates	0.0
Repayment of loans from affiliates	0.0	0.0
Contribution from affiliates	0.1
Other financing activities	(8.6)	0.2
Net cash used for financing activities	(105.2)	(279.0)
Cash and cash equivalents:
Net decrease during each period	(97.0)	(295.9)
At beginning of year	126.2	318.3
At end of period	29.2	22.4
Condensed Consolidating Financial Information KCS [Member] | Consolidating Adjustments [Member]
Operating activities:
Net cash provided	(98.4)	(2.8)
Investing activities:
Capital expenditures	0.0	0.0
Purchase or replacement of equipment under operating leases	0.0	0.0
Property investments in MSLLC	0.0	0.0
Proceeds from repayment of loans to affiliates	(4,297.1)	(25.8)
Loans to affiliates	4,194.8
Contribution to consolidated affiliates	96.9
Other investing activities	0.0	0.4
Net cash used for investing activities	(5.4)	(25.4)
Financing activities:
Proceeds from short-term borrowings	0.0	0.0
Repayment of short-term borrowings	0.0	0.0
Proceeds from issuance of long-term debt		0.0
Repayment of long-term debt		0.0
Dividends paid	96.7	2.8
Shares repurchased	0.0
Proceeds from loans from affiliates	(4,194.8)
Repayment of loans from affiliates	4,297.1	25.8
Contribution from affiliates	(96.9)
Other financing activities	1.7	(0.4)
Net cash used for financing activities	103.8	28.2
Cash and cash equivalents:
Net decrease during each period	0.0	0.0
At beginning of year	0.0	0.0
At end of period	0.0	0.0
Condensed Consolidating Financial Information KCSR [Member] | Parent [Member]
Operating activities:
Net cash provided	110.2	(1.5)
Investing activities:
Capital expenditures	0.0	0.0
Purchase or replacement of equipment under operating leases	0.0	0.0
Property investments in MSLLC	0.0	0.0
Proceeds from repayment of loans to affiliates	4,297.1	25.8
Loans to affiliates	(4,194.8)
Contribution to consolidated affiliates	(96.8)
Other investing activities	0.0	(0.2)
Net cash used for investing activities	5.5	25.6
Financing activities:
Proceeds from short-term borrowings	4,194.8	0.0
Repayment of short-term borrowings	(4,221.0)	0.0
Proceeds from issuance of long-term debt		0.0
Repayment of long-term debt		0.0
Dividends paid	(35.8)	(31.0)
Shares repurchased	(51.0)
Proceeds from loans from affiliates	0.0
Repayment of loans from affiliates	0.0	0.0
Contribution from affiliates	0.0
Other financing activities	(0.3)	7.5
Net cash used for financing activities	(113.3)	(23.5)
Cash and cash equivalents:
Net decrease during each period	2.4	0.6
At beginning of year	0.2	0.2
At end of period	2.6	0.8
Condensed Consolidating Financial Information KCSR [Member] | KCSR [Member]
Operating activities:
Net cash provided	97.8	52.8
Investing activities:
Capital expenditures	(85.1)	(102.6)
Purchase or replacement of equipment under operating leases	(4.6)	0.0
Property investments in MSLLC	0.0	0.0
Proceeds from repayment of loans to affiliates	0.0	0.0
Loans to affiliates	0.0
Contribution to consolidated affiliates	0.0
Other investing activities	(4.9)	0.1
Net cash used for investing activities	(94.6)	(102.5)
Financing activities:
Proceeds from short-term borrowings	0.0	3,842.1
Repayment of short-term borrowings	0.0	(3,779.6)
Proceeds from issuance of long-term debt		0.0
Repayment of long-term debt		(0.8)
Dividends paid	0.0	0.0
Shares repurchased	0.0
Proceeds from loans from affiliates	4,194.8
Repayment of loans from affiliates	(4,297.1)	(25.8)
Contribution from affiliates	96.7
Other financing activities	(0.9)	0.0
Net cash used for financing activities	(6.5)	35.9
Cash and cash equivalents:
Net decrease during each period	(3.3)	(13.8)
At beginning of year	10.1	29.0
At end of period	6.8	15.2
Condensed Consolidating Financial Information KCSR [Member] | Guarantor Subsidiaries [Member]
Operating activities:
Net cash provided	0.8	0.4
Investing activities:
Capital expenditures	(0.2)	(0.8)
Purchase or replacement of equipment under operating leases	0.0	0.0
Property investments in MSLLC	0.0	0.0
Proceeds from repayment of loans to affiliates	0.0	0.0
Loans to affiliates	0.0
Contribution to consolidated affiliates	(0.1)
Other investing activities	0.0	(0.2)
Net cash used for investing activities	(0.3)	(1.0)
Financing activities:
Proceeds from short-term borrowings	0.0	0.0
Repayment of short-term borrowings	0.0	0.0
Proceeds from issuance of long-term debt		0.0
Repayment of long-term debt		(0.1)
Dividends paid	0.0	0.0
Shares repurchased	0.0
Proceeds from loans from affiliates	0.0
Repayment of loans from affiliates	0.0	0.0
Contribution from affiliates	0.1
Other financing activities	(0.1)	0.2
Net cash used for financing activities	0.0	0.1
Cash and cash equivalents:
Net decrease during each period	0.5	(0.5)
At beginning of year	0.1	0.5
At end of period	0.6	0.0
Condensed Consolidating Financial Information KCSR [Member] | Non-Guarantor Subsidiaries [Member]
Operating activities:
Net cash provided	49.9	113.6
Investing activities:
Capital expenditures	(36.8)	(74.6)
Purchase or replacement of equipment under operating leases	0.0	(53.7)
Property investments in MSLLC	(6.6)	(1.9)
Proceeds from repayment of loans to affiliates	0.0	0.0
Loans to affiliates	0.0
Contribution to consolidated affiliates	(0.1)
Other investing activities	1.8	(0.3)
Net cash used for investing activities	(41.7)	(130.5)
Financing activities:
Proceeds from short-term borrowings	0.0	0.0
Repayment of short-term borrowings	0.0	(300.0)
Proceeds from issuance of long-term debt		30.0
Repayment of long-term debt		(6.4)
Dividends paid	(96.7)	(2.8)
Shares repurchased	0.0
Proceeds from loans from affiliates	0.0
Repayment of loans from affiliates	0.0	0.0
Contribution from affiliates	0.1
Other financing activities	(8.6)	0.2
Net cash used for financing activities	(105.2)	(279.0)
Cash and cash equivalents:
Net decrease during each period	(97.0)	(295.9)
At beginning of year	126.2	318.3
At end of period	29.2	22.4
Condensed Consolidating Financial Information KCSR [Member] | Consolidating Adjustments [Member]
Operating activities:
Net cash provided	(98.4)	(2.8)
Investing activities:
Capital expenditures	0.0	0.0
Purchase or replacement of equipment under operating leases	0.0	0.0
Property investments in MSLLC	0.0	0.0
Proceeds from repayment of loans to affiliates	(4,297.1)	(25.8)
Loans to affiliates	4,194.8
Contribution to consolidated affiliates	96.9
Other investing activities	0.0	0.4
Net cash used for investing activities	(5.4)	(25.4)
Financing activities:
Proceeds from short-term borrowings	0.0	0.0
Repayment of short-term borrowings	0.0	0.0
Proceeds from issuance of long-term debt		0.0
Repayment of long-term debt		0.0
Dividends paid	96.7	2.8
Shares repurchased	0.0
Proceeds from loans from affiliates	(4,194.8)
Repayment of loans from affiliates	4,297.1	25.8
Contribution from affiliates	(96.9)
Other financing activities	1.7	(0.4)
Net cash used for financing activities	103.8	28.2
Cash and cash equivalents:
Net decrease during each period	0.0	0.0
At beginning of year	0.0	0.0
At end of period	$ 0.0	$ 0.0