Financial Statements for Guarantors of the Senior Notes - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 162.3	$ 30.1
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0.2	1.1
Equity in earnings of subsidiaries, net of taxes	0.0	0.0
Other	11.3	(156.0)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations	173.8	(124.8)
Cash Provided by (Used in) Operating Activities, Discontinued Operations	(0.2)	(1.1)
Net Cash Provided by (Used in) Operating Activities	173.6	(125.9)
Investing activities:
Proceeds from railcar lease fleet sales owned more than one year	68.5	29.4
Proceeds from dispositions of property and other assets	9.8	7.3
Capital expenditures – leasing	(129.2)	(465.0)
Capital expenditures – manufacturing and other	(14.0)	(11.5)
(Increase) decrease in investment in partially-owned subsidiaries		0.0
Other	0.3	1.3
Net cash (used in) provided by investing activities	(64.6)	(438.5)
Financing activities:
Payments to retire debt	(471.4)	(214.8)
Proceeds from issuance of debt	452.4	649.7
Shares repurchased	(35.4)	(15.0)
Dividends paid to common shareholders	(22.7)	(17.3)
Purchase of shares to satisfy employee tax on vested stock	0.0	(0.5)
Distributions to noncontrolling interest	0.0	(0.4)
Distributions to controlling interest in partially-owned subsidiaries		0.0
Change in intercompany financing between entities	0.0	0.0
Net cash (used in) provided by financing activities	(77.1)	401.7
Net decrease in cash, cash equivalents, and restricted cash	31.9	(162.7)
Cash, cash equivalents, and restricted cash at beginning of period	277.6	350.8
Cash, cash equivalents, and restricted cash at end of period	309.5	188.1
Reportable legal entities | Parent
Operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	161.7	30.6
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0.2	0.9
Equity in earnings of subsidiaries, net of taxes	(54.9)	(54.2)
Other	(199.6)	(23.3)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations	(92.6)	(46.0)
Cash Provided by (Used in) Operating Activities, Discontinued Operations	(0.2)	(0.9)
Net Cash Provided by (Used in) Operating Activities	(92.8)	(46.9)
Investing activities:
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)	(0.6)
(Increase) decrease in investment in partially-owned subsidiaries		0.0
Other	0.0	0.0
Net cash (used in) provided by investing activities	(0.6)	(0.6)
Financing activities:
Payments to retire debt	(175.0)	(150.0)
Proceeds from issuance of debt	180.0	400.0
Shares repurchased	(35.4)	(25.0)
Dividends paid to common shareholders	(22.7)	(17.3)
Purchase of shares to satisfy employee tax on vested stock		(0.5)
Distributions to noncontrolling interest		0.0
Distributions to controlling interest in partially-owned subsidiaries		0.0
Change in intercompany financing between entities	191.1	(251.4)
Net cash (used in) provided by financing activities	138.0	(44.2)
Net decrease in cash, cash equivalents, and restricted cash	44.6	(91.7)
Cash, cash equivalents, and restricted cash at beginning of period	155.1	154.7
Cash, cash equivalents, and restricted cash at end of period	199.7	63.0
Reportable legal entities | Combined Guarantor Subsidiaries
Operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	40.7	42.7
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0.0	0.0
Equity in earnings of subsidiaries, net of taxes	(8.5)	(15.4)
Other	210.7	(184.8)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations	242.9	(157.5)
Cash Provided by (Used in) Operating Activities, Discontinued Operations	0.0	0.0
Net Cash Provided by (Used in) Operating Activities	242.9	(157.5)
Investing activities:
Proceeds from railcar lease fleet sales owned more than one year	278.1	0.4
Proceeds from dispositions of property and other assets	0.5	0.0
Capital expenditures – leasing	(442.2)	(448.0)
Capital expenditures – manufacturing and other	(7.2)	(7.3)
(Increase) decrease in investment in partially-owned subsidiaries		0.3
Other	0.0	0.0
Net cash (used in) provided by investing activities	(170.8)	(454.6)
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
Distributions to noncontrolling interest		0.0
Distributions to controlling interest in partially-owned subsidiaries		0.0
Change in intercompany financing between entities	(66.6)	610.9
Net cash (used in) provided by financing activities	(66.6)	610.9
Net decrease in cash, cash equivalents, and restricted cash	5.5	(1.2)
Cash, cash equivalents, and restricted cash at beginning of period	0.1	4.1
Cash, cash equivalents, and restricted cash at end of period	5.6	2.9
Reportable legal entities | Combined Non-Guarantor Subsidiaries
Operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	9.4	20.7
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0.0	0.2
Equity in earnings of subsidiaries, net of taxes	(4.8)	(5.0)
Other	5.1	58.7
Net Cash Provided by (Used in) Operating Activities, Continuing Operations	9.7	74.6
Cash Provided by (Used in) Operating Activities, Discontinued Operations	0.0	(0.2)
Net Cash Provided by (Used in) Operating Activities	9.7	74.4
Investing activities:
Proceeds from railcar lease fleet sales owned more than one year	359.5	29.0
Proceeds from dispositions of property and other assets	9.3	7.3
Capital expenditures – leasing	(256.1)	(17.0)
Capital expenditures – manufacturing and other	(6.2)	(3.6)
(Increase) decrease in investment in partially-owned subsidiaries		0.0
Other	0.3	1.3
Net cash (used in) provided by investing activities	106.8	17.0
Financing activities:
Payments to retire debt	(296.4)	(64.8)
Proceeds from issuance of debt	272.4	249.7
Shares repurchased	0.0	10.0
Dividends paid to common shareholders	0.0	0.0
Purchase of shares to satisfy employee tax on vested stock		0.0
Distributions to noncontrolling interest		(0.4)
Distributions to controlling interest in partially-owned subsidiaries		0.3
Change in intercompany financing between entities	(110.7)	(356.0)
Net cash (used in) provided by financing activities	(134.7)	(161.2)
Net decrease in cash, cash equivalents, and restricted cash	(18.2)	(69.8)
Cash, cash equivalents, and restricted cash at beginning of period	122.4	192.0
Cash, cash equivalents, and restricted cash at end of period	104.2	122.2
Eliminations
Operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(49.5)	(63.9)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	0.0	0.0
Equity in earnings of subsidiaries, net of taxes	68.2	74.6
Other	(4.9)	(6.6)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations	13.8	4.1
Cash Provided by (Used in) Operating Activities, Discontinued Operations	0.0	0.0
Net Cash Provided by (Used in) Operating Activities	13.8	4.1
Investing activities:
Proceeds from railcar lease fleet sales owned more than one year	(569.1)	0.0
Proceeds from dispositions of property and other assets	0.0	0.0
Capital expenditures – leasing	569.1	0.0
Capital expenditures – manufacturing and other	0.0	0.0
(Increase) decrease in investment in partially-owned subsidiaries		(0.3)
Other	0.0	0.0
Net cash (used in) provided by investing activities	0.0	(0.3)
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
Distributions to noncontrolling interest		0.0
Distributions to controlling interest in partially-owned subsidiaries		(0.3)
Change in intercompany financing between entities	(13.8)	(3.5)
Net cash (used in) provided by financing activities	(13.8)	(3.8)
Net decrease 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