Segment Information - Financial information for segments (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
External Revenue	$ 459.4			$ 813.6			$ 1,583.8	$ 2,154.4
Total Revenues	459.4			813.6			1,583.8	2,154.4
Operating Profit (Loss)	72.9			120.3			(161.4)	319.1
Impairment of long-lived assets	0.0			0.0			(369.4)	0.0
Restructuring activities, net	4.7			0.0			10.5	0.0
Other (income) expense	53.7			54.0			164.1	161.0
Provision (benefit) for income taxes	(6.7)			18.2			(226.1)	41.2
Loss from discontinued operations, net of benefit for income taxes of $—, $0.1, $0.1, and $0.6	0.0			(0.4)			(0.2)	(2.3)
Net income (loss)	25.9	$ (287.8)	$ 162.3	47.7	$ 36.8	$ 30.1	(99.6)	114.6
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	0.0						0.0	0.0
Intersegment Eliminations [Member] | Consolidated Subsidiaries, Leasing [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	(166.0)			(314.0)			(512.4)	(913.0)
Total Revenues	(166.0)			(314.0)			(512.4)	(913.0)
Operating Profit (Loss)	(2.6)			(40.7)			(33.5)	(109.5)
Intersegment Eliminations [Member] | Consolidated Subsidiaries, Excluding Leasing [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	(2.3)			(4.2)			(8.3)	(12.6)
Total Revenues	(2.3)			(4.2)			(8.3)	(12.6)
Operating Profit (Loss)	1.0			(0.1)			(0.3)	(0.3)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	459.4			813.6			1,583.8	2,154.4
Rail Products Group [Member]
Segment Reporting Information [Line Items]
External Revenue	213.1			418.8			777.6	1,156.6
Rail Products Group [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	168.1			316.3			518.6	919.2
Rail Products Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	381.2			735.1			1,296.2	2,075.8
Operating Profit (Loss)	3.2			65.4			36.2	180.8
Restructuring activities, net	2.2						4.8
Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
External Revenue	183.7			326.2			612.4	803.3
Railcar Leasing and Management Services Group [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	0.2			0.2			0.6	0.6
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	183.9			326.4			613.0	803.9
Operating Profit (Loss)	89.7			115.7			265.5	306.3
Restructuring activities, net	1.4						1.4
All Other
Segment Reporting Information [Line Items]
External Revenue	62.6			68.6			193.8	194.5
All Other | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	0.0			1.7			1.5	5.8
All Other | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	62.6			70.3			195.3	200.3
Operating Profit (Loss)	7.3			3.9			23.9	19.9
Restructuring activities, net	0.1						3.3
Operating Segments [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Profit (Loss)	100.2			185.0			325.6	507.0
Corporate, Non-Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Profit (Loss)	(21.0)			$ (23.9)			(73.3)	$ (78.1)
Restructuring activities, net	$ 1.0						$ 7.6