Property, Plant, and Equipment - Components of property, plant, and equipment (Details) - USD ($) $ in Millions	Sep. 30, 2020		Dec. 31, 2019
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	$ 9,153.9		$ 9,272.5
Less: accumulated depreciation	(2,216.0)		(2,161.9)
Property, Plant and Equipment, Net	6,937.9		7,110.6
Intersegment Eliminations [Member]
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	(1,063.8)		(1,135.8)
NegativeAccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	237.0		232.0
Property, Plant and Equipment, Net	(826.8)		(903.8)
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member]
Property, Plant and Equipment, Net [Abstract]
Property, Plant and Equipment, Net	7,330.3	[1]	7,605.6
Manufacturing and Corporate [Member]
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	1,089.5		1,040.4
Less: accumulated depreciation	(655.1)		(631.6)
Property, Plant and Equipment, Net	434.4		408.8
Manufacturing and Corporate [Member] | Land
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	28.6		28.4
Manufacturing and Corporate [Member] | Buildings and improvements
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	416.2		402.2
Manufacturing and Corporate [Member] | Machinery and other
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	556.3		546.7
Manufacturing and Corporate [Member] | Construction in progress
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	88.4		63.1
Wholly-owned subsidiaries | Railcar Leasing and Management Services Group [Member] | Operating Segments [Member]
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	6,882.6		6,957.9
Less: accumulated depreciation	(1,190.1)		(1,139.0)
Property, Plant and Equipment, Net	5,692.5	[1]	5,818.9
Wholly-owned subsidiaries | Railcar Leasing and Management Services Group [Member] | Machinery and other | Operating Segments [Member]
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	13.9		13.7
Wholly-owned subsidiaries | Railcar Leasing and Management Services Group [Member] | Equipment on lease | Operating Segments [Member]
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	6,868.7		6,944.2
Partially-owned subsidiaries
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	1,929.5		2,065.3
Less: accumulated depreciation	(513.9)		(527.7)
Partially-owned subsidiaries | Railcar Leasing and Management Services Group [Member] | Operating Segments [Member]
Property, Plant and Equipment, Net [Abstract]
Property, Plant and Equipment, Net	1,637.8	[1]	1,786.7
Partially-owned subsidiaries | Railcar Leasing and Management Services Group [Member] | Equipment on lease | Operating Segments [Member]
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,929.5 and $2,065.3	2,245.6		2,410.0
Less: accumulated depreciation	$ (607.8)		$ (623.3)

[1] See Note 10 for further information regarding impairment of long-lived assets recorded in the nine months ended September 30, 2020.