Financial Statements for Guarantors of the Senior Notes - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Net income	$ 47.7	$ 36.8	$ 30.1	$ 28.3	$ 65.5	$ 41.6	$ 114.6	$ 135.4
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent							2.3	(54.4)
Equity in earnings of subsidiaries, net of taxes	0.0			0.0			0.0	0.0
Other							47.1	98.5
Net Cash Provided by (Used in) Operating Activities, Continuing Operations							164.0	179.5
Cash Provided by (Used in) Operating Activities, Discontinued Operations							0.0	140.4
Net Cash Provided by (Used in) Operating Activities							164.0	319.9
Investing activities:
Decrease in short-term marketable securities							0.0	319.5
Proceeds from railcar lease fleet sales owned more than one year							175.0	123.4
Proceeds from dispositions of property and other assets							19.5	6.9
Capital expenditures – leasing							(854.3)	(675.8)
Capital expenditures – manufacturing and other							(63.3)	(30.0)
(Increase) decrease in investment in partially-owned subsidiaries							0.0	0.0
Other							(0.2)	(1.9)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations							(723.3)	(257.9)
Cash Provided by (Used in) Investing Activities, Discontinued Operations							0.0	(53.1)
Net cash (used in) provided by investing activities							(723.3)	(311.0)
Financing activities:
Payments to retire debt							(1,360.8)	(738.9)
Proceeds from issuance of debt							2,010.2	561.3
Shares repurchased							(154.9)	(156.1)
Dividends paid to common shareholders							(60.8)	(58.1)
Purchase of shares to satisfy employee tax on vested stock							(8.0)	(11.5)
Distributions to noncontrolling interest							(2.1)	(10.3)
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	(3.2)
Net cash (used in) provided by financing activities							423.6	(416.8)
Net decrease in cash, cash equivalents, and restricted cash							(135.7)	(407.9)
Cash, cash equivalents, and restricted cash at beginning of period			350.8			973.8	350.8	973.8
Cash, cash equivalents, and restricted cash at end of period	215.1			565.9			215.1	565.9
Reportable legal entities | Parent
Operating activities:
Net income	49.0			27.7			116.0	132.0
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent							2.1	12.6
Equity in earnings of subsidiaries, net of taxes	(75.6)			(63.8)			(195.4)	(247.7)
Other							(17.2)	(39.5)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations								(142.6)
Cash Provided by (Used in) Operating Activities, Discontinued Operations								(12.6)
Net Cash Provided by (Used in) Operating Activities							(94.5)	(155.2)
Investing activities:
Decrease in short-term marketable securities								319.5
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	0.2
Capital expenditures – leasing							0.0	0.0
Capital expenditures – manufacturing and other							(4.0)	(11.6)
(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								308.1
Cash Provided by (Used in) Investing Activities, Discontinued Operations								0.0
Net cash (used in) provided by investing activities							(4.0)	308.1
Financing activities:
Payments to retire debt							(750.0)	(647.6)
Proceeds from issuance of debt							825.0	0.0
Shares repurchased							(154.9)	(156.1)
Dividends paid to common shareholders							(60.8)	(58.1)
Purchase of shares to satisfy employee tax on vested stock							(8.0)	(11.5)
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							179.9	289.6
Other								0.0
Net cash (used in) provided by financing activities							31.2	(583.7)
Net decrease in cash, cash equivalents, and restricted cash							(67.3)	(430.8)
Cash, cash equivalents, and restricted cash at beginning of period			154.7			763.9	154.7	763.9
Cash, cash equivalents, and restricted cash at end of period	87.4			333.1			87.4	333.1
Reportable legal entities | Combined Guarantor Subsidiaries
Operating activities:
Net income	66.3			45.1			159.9	141.6
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent							0.0	0.0
Equity in earnings of subsidiaries, net of taxes	(6.0)			(8.0)			(32.0)	(35.2)
Other							(159.3)	29.0
Net Cash Provided by (Used in) Operating Activities, Continuing Operations								135.4
Cash Provided by (Used in) Operating Activities, Discontinued Operations								0.0
Net Cash Provided by (Used in) Operating Activities							(31.4)	135.4
Investing activities:
Decrease in short-term marketable securities								0.0
Proceeds from railcar lease fleet sales owned more than one year							1,184.6	707.8
Proceeds from dispositions of property and other assets							6.3	3.8
Capital expenditures – leasing							(911.4)	(611.9)
Capital expenditures – manufacturing and other							(31.7)	(9.9)
(Increase) decrease in investment in partially-owned subsidiaries							1.6	7.1
Other							0.0	0.0
Net Cash Provided by (Used in) Investing Activities, Continuing Operations								96.9
Cash Provided by (Used in) Investing Activities, Discontinued Operations								0.0
Net cash (used in) provided by investing activities							249.4	96.9
Financing activities:
Payments to retire debt							0.0	(1.8)
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							(219.8)	(161.9)
Other								0.0
Net cash (used in) provided by financing activities							(219.8)	(163.7)
Net decrease in cash, cash equivalents, and restricted cash							(1.8)	68.6
Cash, cash equivalents, and restricted cash at beginning of period			4.1			1.6	4.1	1.6
Cash, cash equivalents, and restricted cash at end of period	2.3			70.2			2.3	70.2
Reportable legal entities | Combined Non-Guarantor Subsidiaries
Operating activities:
Net income	6.6			27.2			42.7	134.6
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent							0.2	(67.0)
Equity in earnings of subsidiaries, net of taxes	(8.1)			(7.3)			(19.7)	(20.2)
Other							257.5	132.9
Net Cash Provided by (Used in) Operating Activities, Continuing Operations								180.3
Cash Provided by (Used in) Operating Activities, Discontinued Operations								153.0
Net Cash Provided by (Used in) Operating Activities							280.7	333.3
Investing activities:
Decrease in short-term marketable securities								0.0
Proceeds from railcar lease fleet sales owned more than one year							180.0	63.3
Proceeds from dispositions of property and other assets							13.2	2.9
Capital expenditures – leasing							(1,132.5)	(711.6)
Capital expenditures – manufacturing and other							(27.6)	(8.5)
(Increase) decrease in investment in partially-owned subsidiaries							0.0	0.0
Other							(0.2)	(1.9)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations								(655.8)
Cash Provided by (Used in) Investing Activities, Discontinued Operations								(53.1)
Net cash (used in) provided by investing activities							(967.1)	(708.9)
Financing activities:
Payments to retire debt							(610.8)	(89.5)
Proceeds from issuance of debt							1,185.2	561.3
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							(2.1)	(10.3)
Distributions to controlling interest in partially-owned subsidiaries							(1.6)	7.1
Change in intercompany financing between entities							49.1	(135.5)
Other								(3.2)
Net cash (used in) provided by financing activities							619.8	329.9
Net decrease in cash, cash equivalents, and restricted cash							(66.6)	(45.7)
Cash, cash equivalents, and restricted cash at beginning of period			192.0			208.3	192.0	208.3
Cash, cash equivalents, and restricted cash at end of period	125.4			162.6			125.4	162.6
Eliminations
Operating activities:
Net income	(74.2)			(71.7)			(204.0)	(272.8)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent							0.0	0.0
Equity in earnings of subsidiaries, net of taxes	89.7			79.1			247.1	303.1
Other							(33.9)	(23.9)
Net Cash Provided by (Used in) Operating Activities, Continuing Operations								6.4
Cash Provided by (Used in) Operating Activities, Discontinued Operations								0.0
Net Cash Provided by (Used in) Operating Activities							9.2	6.4
Investing activities:
Decrease in short-term marketable securities								0.0
Proceeds from railcar lease fleet sales owned more than one year							(1,189.6)	(647.7)
Proceeds from dispositions of property and other assets							0.0	0.0
Capital expenditures – leasing							1,189.6	647.7
Capital expenditures – manufacturing and other							0.0	0.0
(Increase) decrease in investment in partially-owned subsidiaries							(1.6)	(7.1)
Other							0.0	0.0
Net Cash Provided by (Used in) Investing Activities, Continuing Operations								(7.1)
Cash Provided by (Used in) Investing Activities, Discontinued Operations								0.0
Net cash (used in) provided by investing activities							(1.6)	(7.1)
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							1.6	(7.1)
Change in intercompany financing between entities							(9.2)	7.8
Other								0.0
Net cash (used in) provided by financing activities							(7.6)	0.7
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	0.0	0.0
Cash, cash equivalents, and restricted cash at end of period	$ 0.0			$ 0.0			$ 0.0	$ 0.0