Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities:
Net income	$ 379.4	$ 331.9	$ 180.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	198.8	186.2	184.9
Deferred income taxes	197.3	120.7	106.2
Equity in net earnings of unconsolidated affiliates	(19.3)	(18.2)	(19.7)
Share-based compensation	10.7	8.5	8.8
Excess tax benefit from share-based compensation	(31.5)	(0.2)	(1.2)
Deferred compensation	7.3	19.5	1.6
Elimination of deferred statutory profit sharing liability	(47.8)	0	0
Distributions from unconsolidated affiliates	19.8	18.1	19.5
Gain on insurance recoveries related to hurricane damage	0	(25.6)	0
Cash payments related to hurricane damage	0	(3.3)	(27.8)
Insurance proceeds related to hurricane damage	0	40.2	8.2
Debt retirement costs	20.1	38.7	68.3
Changes in working capital items:
Accounts receivable	(21.5)	(1.5)	(20.2)
Materials and supplies	(9.3)	(7.2)	6.3
Other current assets	(15.1)	(26.8)	(4.8)
Accounts payable and accrued liabilities	(3.0)	(7.5)	22.0
Other, net	(12.7)	(35.5)	(35.8)
Net cash provided by operating activities	673.2	638.0	496.3
Investing activities:
Capital expenditures	(540.0)	(495.0)	(287.3)
Acquisition of an intermodal facility, net of cash acquired	0	0	(25.0)
Property investments in MSLLC	(35.2)	(33.3)	(25.2)
Contributions from noncontrolling interest	7.8	10.0	0
Insurance proceeds related to hurricane damage	0	12.4	1.8
Proceeds from disposal of property	14.7	10.0	8.3
Other, net	0.8	(14.5)	15.9
Net cash used for investing activities	(551.9)	(510.4)	(311.5)
Financing activities:
Proceeds from issuance of long-term debt	329.6	550.0	480.7
Repayment of long-term debt	(375.9)	(653.3)	(839.7)
Proceeds from common stock issuance	0	0	214.9
Debt costs	(22.1)	(36.6)	(65.1)
Proceeds from employee stock plans	1.9	2.1	2.1
Excess tax benefit from share-based compensation	31.5	0.2	1.2
Dividends paid	(86.1)	(3.0)	(11.0)
Net cash used for financing activities	(121.1)	(140.6)	(216.9)
Cash and cash equivalents:
Net increase (decrease) during each period	0.2	(13.0)	(32.1)
At beginning of year	72.4	85.4	117.5
At end of year	72.6	72.4	85.4
Non-cash investing and financing activities:
Capital expenditures accrued but not yet paid at end of year	44.4	61.7	57.1
Capital lease obligations incurred	13.8	0.7	3.7
Non-cash asset acquisitions	13.2	116.1	7.3
Cash payments:
Interest paid, net of amounts capitalized	97.9	125.0	153.0
Income tax payments, net of refunds	$ 1.9	$ 0.9	$ 1.6