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Segment Information - Financial information for segments (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
External Revenue	$ 509.2		$ 736.0		$ 1,124.4	$ 1,340.8
Revenues, Total	509.2		736.0		1,124.4	1,340.8
Operating Profit (Loss)	(307.3)		107.0		(234.3)	198.8
Asset Impairment Charges	(369.4)		0.0		(369.4)	0.0
Restructuring Charges	0.3		0.0		5.8	0.0
Other Nonoperating Expense	52.3		55.3		110.4	107.0
Income Tax Expense (Benefit)	(71.8)		14.1		(219.4)	23.0
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0.0		(0.8)		(0.2)	(1.9)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(287.8)	$ 162.3	36.8	$ 30.1	(125.5)	66.9
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues	0.0				0.0	0.0
Intersegment Eliminations [Member] \| Consolidated Subsidiaries, Leasing [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues	(156.0)		(328.9)		(346.4)	(599.0)
Revenues, Total	(156.0)		(328.9)		(346.4)	(599.0)
Operating Profit (Loss)	(11.0)		(41.6)		(30.9)	(68.8)
Intersegment Eliminations [Member] \| Consolidated Subsidiaries, Excluding Leasing [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues	(2.5)		(3.3)		(6.0)	(8.4)
Revenues, Total	(2.5)		(3.3)		(6.0)	(8.4)
Operating Profit (Loss)	(0.5)		0.2		(1.3)	(0.2)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues, Total	509.2		736.0		1,124.4	1,340.8
Rail Products Group [Member]
Segment Reporting Information [Line Items]
External Revenue	247.3		392.2		564.5	737.8
Rail Products Group [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues	158.3		331.0		350.5	602.9
Rail Products Group [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues, Total	405.6		723.2		915.0	1,340.7
Operating Profit (Loss)	7.9		66.3		33.0	115.4
Restructuring Charges	0.0				2.6
Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
External Revenue	192.6		276.9		428.7	477.1
Railcar Leasing and Management Services Group [Member] \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues	0.2		0.2		0.4	0.4
Railcar Leasing and Management Services Group [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues, Total	192.8		277.1		429.1	477.5
Operating Profit (Loss)	82.9		104.8		175.8	190.6
Restructuring Charges	0.0				0.0
All Other
Segment Reporting Information [Line Items]
External Revenue	69.3		66.9		131.2	125.9
All Other \| Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenues	0.0		1.0		1.5	4.1
All Other \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues, Total	69.3		67.9		132.7	130.0
Operating Profit (Loss)	7.3		7.9		16.6	16.0
Restructuring Charges	0.3				3.4
Operating Segments [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Profit (Loss)	98.1		179.0		225.4	322.0
Corporate, Non-Segment [Member] \| Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Profit (Loss)	(24.2)		$ (30.6)		(52.3)	$ (54.2)
Restructuring Charges	$ 0.0				$ 6.6