Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Net income	$ 713.6	$ 364.7	$ 826.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	295.4	283.0	266.4
Stock-based compensation expense	31.1	41.3	61.1
Excess tax benefits from stock-based compensation	0.0	(1.0)	(13.3)
Provision (benefit) for deferred income taxes	(337.4)	321.4	116.6
Net gains on railcar lease fleet sales owned more than one year at the time of sale	(83.5)	(13.5)	(166.1)
Gains on disposition of property and other assets	(3.1)	(3.9)	(12.7)
Non-cash interest expense	31.8	28.5	30.1
Other	(1.2)	(3.4)	(2.5)
Changes in assets and liabilities:
(Increase) decrease in receivables	88.1	(16.0)	(0.8)
(Increase) decrease in inventories	32.6	273.3	128.5
(Increase) decrease in restricted cash	0.0	0.0	(9.4)
(Increase) decrease in other assets	(21.1)	18.6	(40.9)
Increase (decrease) in accounts payable	19.3	(60.7)	(78.6)
Increase (decrease) in accrued liabilities	13.8	(104.9)	(169.6)
Increase (decrease) in other liabilities	(17.8)	(37.2)	4.9
Net cash provided by operating activities	761.6	1,090.2	939.7
Investing activities:
(Increase) decrease in short-term marketable securities	(84.8)	(149.8)	(9.9)
Proceeds from railcar lease fleet sales owned more than one year at the time of sale	360.7	37.7	514.6
Proceeds from disposition of property and other assets	11.3	16.0	8.2
Capital expenditures – leasing, net of sold lease fleet railcars owned one year or less with a net cost of $79.9, $92.0, and $295.9	(608.3)	(799.1)	(833.8)
Capital expenditures – manufacturing and other	(104.4)	(134.3)	(196.0)
Acquisitions, net of cash acquired	(47.5)	0.0	(46.2)
Divestitures	0.0	0.0	51.3
Other	0.3	6.8	0.5
Net cash required by investing activities	(472.7)	(1,022.7)	(511.3)
Financing activities:
Proceeds from issuance of common stock, net	0.0	0.0	0.3
Excess tax benefits from stock-based compensation	0.0	1.0	13.3
Payments to retire debt	(375.4)	(162.5)	(587.2)
Proceeds from issuance of debt	534.1	0.0	242.4
(Increase) decrease in restricted cash	(17.0)	17.6	48.3
Shares repurchased	(79.4)	(34.7)	(115.0)
Dividends paid to common shareholders	(72.6)	(66.7)	(64.9)
Purchase of shares to satisfy employee tax on vested stock	(14.4)	(16.3)	(27.5)
Distributions to noncontrolling interest	(48.7)	(26.4)	(39.2)
Other	(0.3)	(2.1)	(0.8)
Net cash required by financing activities	(73.7)	(290.1)	(530.3)
Net increase (decrease) in cash and cash equivalents	215.2	(222.6)	(101.9)
Cash and cash equivalents at beginning of period	563.4	786.0	887.9
Cash and cash equivalents at end of period	$ 778.6	$ 563.4	$ 786.0