Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income	$ 504.3	$ 353.3	$ 379.4
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	258.1	223.3	198.8
Deferred income taxes	140.1	111.2	197.3
Equity in net earnings of unconsolidated affiliates	(21.1)	(18.8)	(19.3)
Share-based compensation	10.0	13.6	10.7
Excess tax benefit from share-based compensation	0.7	(4.2)	(31.5)
Elimination of deferred statutory profit sharing liability	0	0	(47.8)
Distributions from unconsolidated affiliates	25.5	12.5	19.8
Debt retirement costs	6.6	119.2	20.1
Changes in working capital items:
Accounts receivable	17.2	(14.4)	(21.5)
Materials and supplies	9.2	7.1	(9.3)
Other current assets	(10.0)	(1.8)	(15.1)
Accounts payable and accrued liabilities	(21.8)	0.3	(3.0)
Other, net	(12.8)	(3.0)	(5.4)
Net cash provided by operating activities	906.0	798.3	673.2
Investing activities:
Capital expenditures	(668.2)	(594.8)	(517.1)
Purchase or replacement of equipment under operating leases	(302.1)	(211.8)	(22.9)
Property investments in MSLLC	(26.7)	(31.6)	(35.2)
Proceeds from disposal of property	9.9	8.2	14.7
Other, net	4.2	(3.3)	8.6
Net cash used for investing activities	(982.9)	(833.3)	(551.9)
Financing activities:
Proceeds from short-term borrowings	15,368.8	0	0
Repayment of short-term borrowings	(14,920.2)	0	0
Proceeds from issuance of long-term debt	175.0	1,918.4	329.6
Repayment of long-term debt	(508.0)	(1,343.2)	(375.9)
Dividends paid	(116.6)	(71.2)	(86.1)
Debt costs	(4.9)	(117.8)	(22.1)
Excess tax benefit from share-based compensation	(0.7)	4.2	31.5
Proceeds from employee stock plans	2.0	1.5	1.9
Net cash provided by (used for) financing activities	(4.6)	391.9	(121.1)
Cash and cash equivalents:
Net increase (decrease) during each year	(81.5)	356.9	0.2
At beginning of year	429.5	72.6	72.4
At end of year	348.0	429.5	72.6
Non-cash investing and financing activities:
Capital expenditures and purchase or replacement of equipment under operating lease accrued but not yet paid at end of year	83.2	50.1	44.4
Capital lease obligations incurred	9.1	0	13.8
Non-cash asset acquisitions	5.9	56.7	13.2
Dividends accrued but not yet paid at end of year	31.0	23.8	0
Cash payments:
Interest paid, net of amounts capitalized	72.5	84.1	97.9
Income tax payments, net of refunds	$ 62.9	$ 99.2	$ 1.9