Financial Statements for Guarantors of the Senior Notes - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities:
Net income	$ 30.1	$ 41.6
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	1.1	(26.4)
Equity in earnings of subsidiaries, net of taxes	0.0	0.0
Other	(157.1)	58.6
Net Cash Provided by (Used in) Operating Activities, Continuing Operations	(125.9)	73.8
Cash Provided by (Used in) Operating Activities, Discontinued Operations	0.0	99.9
Net Cash Provided by (Used in) Operating Activities	(125.9)	173.7
Investing activities:
(Increase) decrease in short-term marketable securities	0.0	98.7
Proceeds from railcar lease fleet sales owned more than one year	29.4	15.5
Proceeds from dispositions of property and other assets	7.3	1.9
Capital expenditures – leasing	(465.0)	(318.2)
Capital expenditures – manufacturing and other	(11.5)	(8.2)
(Increase) decrease in investment in partially-owned subsidiaries	0.0	0.0
Other	1.3	0.8
Net Cash Provided by (Used in) Investing Activities, Continuing Operations	(438.5)	(209.5)
Cash Provided by (Used in) Investing Activities, Discontinued Operations	0.0	(32.0)
Net cash (used in) provided by investing activities	(438.5)	(241.5)
Financing activities:
Payments to retire debt	(214.8)	(26.5)
Proceeds from issuance of debt	649.7	0.9
Shares repurchased	(15.0)	(49.3)
Dividends paid to common shareholders	(17.3)	(19.5)
Purchase of shares to satisfy employee tax on vested stock	(0.5)	(0.1)
Distributions to noncontrolling interest	(0.4)	(5.8)
Distributions to controlling interest in partially-owned subsidiaries	0.0	0.0
Change in intercompany financing between entities	0.0	0.0
Other	0.0	(3.0)
Net cash provided (used in) by financing activities	401.7	(103.3)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(162.7)	(171.1)
Cash, cash equivalents, and restricted cash at beginning of period	350.8	973.8
Cash, cash equivalents, and restricted cash at end of period	188.1	802.7
Reportable legal entities | Parent
Operating activities:
Net income	30.6	40.2
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0.9	1.4
Equity in earnings of subsidiaries, net of taxes	(54.2)	(81.3)
Other	(24.2)	(17.2)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations		(56.9)
Cash Provided by (Used in) Operating Activities, Discontinued Operations		(1.4)
Net Cash Provided by (Used in) Operating Activities	(46.9)	(58.3)
Investing activities:
(Increase) decrease in short-term marketable securities		98.7
Proceeds from railcar lease fleet sales owned more than one year	0.0	0.0
Proceeds from dispositions of property and other assets	0.0	0.0
Capital expenditures – leasing	0.0	0.0
Capital expenditures – manufacturing and other	(0.6)	(1.4)
(Increase) decrease in investment in partially-owned subsidiaries	0.0	0.0
Other	0.0	0.0
Net Cash Provided by (Used in) Investing Activities, Continuing Operations		97.3
Cash Provided by (Used in) Investing Activities, Discontinued Operations		0.0
Net cash (used in) provided by investing activities	(0.6)	97.3
Financing activities:
Payments to retire debt	(150.0)	0.0
Proceeds from issuance of debt	400.0	0.0
Shares repurchased	(25.0)	(49.3)
Dividends paid to common shareholders	(17.3)	(19.5)
Purchase of shares to satisfy employee tax on vested stock	(0.5)	(0.1)
Distributions to noncontrolling interest	0.0	0.0
Distributions to controlling interest in partially-owned subsidiaries	0.0	0.0
Change in intercompany financing between entities	(251.4)	(126.3)
Other		0.0
Net cash provided (used in) by financing activities	(44.2)	(195.2)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(91.7)	(156.2)
Cash, cash equivalents, and restricted cash at beginning of period	154.7	763.9
Cash, cash equivalents, and restricted cash at end of period	63.0	607.7
Reportable legal entities | Combined Guarantor Subsidiaries
Operating activities:
Net income	42.7	40.4
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0.0	0.0
Equity in earnings of subsidiaries, net of taxes	(15.4)	(13.8)
Other	(184.8)	29.3
Net Cash Provided by (Used in) Operating Activities, Continuing Operations		55.9
Cash Provided by (Used in) Operating Activities, Discontinued Operations		0.0
Net Cash Provided by (Used in) Operating Activities	(157.5)	55.9
Investing activities:
(Increase) decrease in short-term marketable securities		0.0
Proceeds from railcar lease fleet sales owned more than one year	0.4	15.5
Proceeds from dispositions of property and other assets	0.0	0.4
Capital expenditures – leasing	(448.0)	(297.2)
Capital expenditures – manufacturing and other	(7.3)	(2.9)
(Increase) decrease in investment in partially-owned subsidiaries	0.3	3.9
Other	0.0	0.0
Net Cash Provided by (Used in) Investing Activities, Continuing Operations		(280.3)
Cash Provided by (Used in) Investing Activities, Discontinued Operations		0.0
Net cash (used in) provided by investing activities	(454.6)	(280.3)
Financing activities:
Payments to retire debt	0.0	(0.9)
Proceeds from issuance of debt	0.0	0.0
Shares repurchased	0.0	0.0
Dividends paid to common shareholders	0.0	0.0
Purchase of shares to satisfy employee tax on vested stock	0.0	0.0
Distributions to noncontrolling interest	0.0	0.0
Distributions to controlling interest in partially-owned subsidiaries	0.0	0.0
Change in intercompany financing between entities	610.9	231.3
Other		0.0
Net cash provided (used in) by financing activities	610.9	230.4
Net (decrease) increase in cash, cash equivalents, and restricted cash	(1.2)	6.0
Cash, cash equivalents, and restricted cash at beginning of period	4.1	1.6
Cash, cash equivalents, and restricted cash at end of period	2.9	7.6
Reportable legal entities | Combined Non-Guarantor Subsidiaries
Operating activities:
Net income	20.7	50.5
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0.2	(27.8)
Equity in earnings of subsidiaries, net of taxes	(5.0)	(5.3)
Other	58.5	55.9
Net Cash Provided by (Used in) Operating Activities, Continuing Operations		73.3
Cash Provided by (Used in) Operating Activities, Discontinued Operations		101.3
Net Cash Provided by (Used in) Operating Activities	74.4	174.6
Investing activities:
(Increase) decrease in short-term marketable securities		0.0
Proceeds from railcar lease fleet sales owned more than one year	29.0	0.0
Proceeds from dispositions of property and other assets	7.3	1.5
Capital expenditures – leasing	(17.0)	(21.0)
Capital expenditures – manufacturing and other	(3.6)	(3.9)
(Increase) decrease in investment in partially-owned subsidiaries	0.0	0.0
Other	1.3	0.8
Net Cash Provided by (Used in) Investing Activities, Continuing Operations		(22.6)
Cash Provided by (Used in) Investing Activities, Discontinued Operations		(32.0)
Net cash (used in) provided by investing activities	17.0	(54.6)
Financing activities:
Payments to retire debt	(64.8)	(25.6)
Proceeds from issuance of debt	249.7	0.9
Shares repurchased	10.0	0.0
Dividends paid to common shareholders	0.0	0.0
Purchase of shares to satisfy employee tax on vested stock	0.0	0.0
Distributions to noncontrolling interest	(0.4)	(5.8)
Distributions to controlling interest in partially-owned subsidiaries	0.3	3.9
Change in intercompany financing between entities	(356.0)	(111.3)
Other		(3.0)
Net cash provided (used in) by financing activities	(161.2)	(140.9)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(69.8)	(20.9)
Cash, cash equivalents, and restricted cash at beginning of period	192.0	208.3
Cash, cash equivalents, and restricted cash at end of period	122.2	187.4
Eliminations
Operating activities:
Net income	(63.9)	(89.5)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0.0	0.0
Equity in earnings of subsidiaries, net of taxes	74.6	100.4
Other	(6.6)	(9.4)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations		1.5
Cash Provided by (Used in) Operating Activities, Discontinued Operations		0.0
Net Cash Provided by (Used in) Operating Activities	4.1	1.5
Investing activities:
(Increase) decrease in short-term marketable securities		0.0
Proceeds from railcar lease fleet sales owned more than one year	0.0
Proceeds from dispositions of property and other assets	0.0	0.0
Capital expenditures – leasing	0.0
Capital expenditures – manufacturing and other	0.0	0.0
(Increase) decrease in investment in partially-owned subsidiaries	(0.3)	(3.9)
Other	0.0	0.0
Net Cash Provided by (Used in) Investing Activities, Continuing Operations		(3.9)
Cash Provided by (Used in) Investing Activities, Discontinued Operations		0.0
Net cash (used in) provided by investing activities	(0.3)	(3.9)
Financing activities:
Payments to retire debt	0.0	0.0
Proceeds from issuance of debt	0.0	0.0
Shares repurchased	0.0	0.0
Dividends paid to common shareholders	0.0	0.0
Purchase of shares to satisfy employee tax on vested stock	0.0	0.0
Distributions to noncontrolling interest	0.0	0.0
Distributions to controlling interest in partially-owned subsidiaries	(0.3)	(3.9)
Change in intercompany financing between entities	(3.5)	6.3
Other		0.0
Net cash provided (used in) by financing activities	(3.8)	2.4
Net (decrease) increase in cash, cash equivalents, and restricted cash	0.0	0.0
Cash, cash equivalents, and restricted cash at beginning of period	0.0	0.0
Cash, cash equivalents, and restricted cash at end of period	$ 0.0	$ 0.0