Segment Information - Financial information for segments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
External Revenue	$ 615.2	$ 604.8
Total revenues	615.2	604.8
Operating Profit (Loss)	73.0	91.8
Restructuring Charges	5.5	0.0
Other Nonoperating Expense	58.1	51.7
Provision (benefit) for income taxes	(147.6)	8.9
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(0.2)	(1.1)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	162.3	30.1
Intersegment
Segment Reporting Information [Line Items]
Intersegment Revenues	0.0	0.0
Intersegment | Eliminations – Lease subsidiary
Segment Reporting Information [Line Items]
Intersegment Revenues	(190.4)	(270.1)
Total revenues	(190.4)	(270.1)
Operating Profit (Loss)	(19.9)	(27.2)
Intersegment | Eliminations – Other
Segment Reporting Information [Line Items]
Intersegment Revenues	(3.5)	(15.5)
Total revenues	(3.5)	(15.5)
Operating Profit (Loss)	(0.8)	(0.4)
Total
Segment Reporting Information [Line Items]
Total revenues	615.2	604.8
Rail Group
Segment Reporting Information [Line Items]
External Revenue	317.2	345.6
Rail Group | Intersegment
Segment Reporting Information [Line Items]
Intersegment Revenues	192.2	282.3
Rail Group | Total
Segment Reporting Information [Line Items]
Total revenues	509.4	627.9
Operating Profit (Loss)	25.1	47.1
Restructuring Charges	2.6
Railcar Leasing and Management Services Group
Segment Reporting Information [Line Items]
External Revenue	236.1	200.2
Railcar Leasing and Management Services Group | Intersegment
Segment Reporting Information [Line Items]
Intersegment Revenues	0.2	0.2
Railcar Leasing and Management Services Group | Total
Segment Reporting Information [Line Items]
Total revenues	236.3	200.4
Operating Profit (Loss)	92.9	85.8
Restructuring Charges	0.0
All Other
Segment Reporting Information [Line Items]
External Revenue	61.9	59.0
All Other | Intersegment
Segment Reporting Information [Line Items]
Intersegment Revenues	1.5	3.1
All Other | Total
Segment Reporting Information [Line Items]
Total revenues	63.4	62.1
Operating Profit (Loss)	9.3	10.1
Restructuring Charges	(3.7)
Total | Total
Segment Reporting Information [Line Items]
Operating Profit (Loss)	127.3	143.0
Corporate | Total
Segment Reporting Information [Line Items]
Total revenues	0.0	0.0
Operating Profit (Loss)	(28.1)	$ (23.6)
Restructuring Charges	$ 6.6