Segment Information - Financial information for segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
External Revenue	$ 398.8	$ 615.2
Total Revenues	398.8	615.2
Operating Profit (Loss)	60.2	73.0
Restructuring Charges	0.3	(5.5)
Other (income) expense	52.5	58.1
Provision (benefit) for income taxes	6.0	(147.6)
Loss from discontinued operations, net of provision (benefit) for income taxes of $0.4 and $(0.1)	(0.4)	(0.2)
Net income	1.3	162.3
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	398.8	615.2
Operating Profit (Loss)	84.8	127.3
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	0.0
Intersegment Eliminations [Member] | Consolidated Subsidiaries, Leasing [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	(111.3)	(190.4)
Total Revenues	(111.3)	(190.4)
Operating Profit (Loss)	(1.8)	(19.9)
Intersegment Eliminations [Member] | Consolidated Subsidiaries, Excluding Leasing [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	(2.5)	(3.5)
Total Revenues	(2.5)	(3.5)
Operating Profit (Loss)	(0.4)	(0.8)
Railcar Leasing and Management Services Group [Member]
Segment Reporting Information [Line Items]
External Revenue	183.3	236.1
Operating Profit (Loss)	78.3	92.9
Restructuring Charges	0.0	0.0
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	183.5	236.3
Operating Profit (Loss)	78.3	92.9
Railcar Leasing and Management Services Group [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	0.2	0.2
Rail Products Group [Member]
Segment Reporting Information [Line Items]
External Revenue	147.4	317.2
Operating Profit (Loss)	(8.8)	25.1
Restructuring Charges	(0.3)	(2.6)
Rail Products Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	261.0	509.4
Rail Products Group [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	113.6	192.2
All Other
Segment Reporting Information [Line Items]
External Revenue	68.1	61.9
Operating Profit (Loss)	15.3	9.3
Restructuring Charges	0.7	3.7
All Other | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total Revenues	68.1	63.4
All Other | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue	0.0	1.5
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating Profit (Loss)	(22.7)	(28.1)
Restructuring Charges	$ (0.1)	$ (6.6)