Property, Plant, and Equipment - Components of property, plant, and equipment (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,940.9 and $1,931.6	$ 9,097.7	$ 9,193.0
Less: accumulated depreciation	(2,297.6)	(2,189.6)
Property, Plant and Equipment, Net	6,800.1	7,003.4
Intersegment Eliminations [Member]
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,940.9 and $1,931.6	(1,044.7)	(1,064.7)
NegativeAccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment	262.1	244.4
Property, Plant and Equipment, Net	(782.6)	(820.3)
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member]
Property, Plant and Equipment, Net [Abstract]
Property, Plant and Equipment, Net	7,198.1	7,422.2
Manufacturing and Corporate [Member]
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,940.9 and $1,931.6	946.1	979.4
Less: accumulated depreciation	(561.5)	(577.9)
Property, Plant and Equipment, Net	384.6	401.5
Manufacturing and Corporate [Member] | Land
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,940.9 and $1,931.6	22.0	23.2
Manufacturing and Corporate [Member] | Buildings and improvements
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,940.9 and $1,931.6	423.8	428.6
Manufacturing and Corporate [Member] | Machinery and other
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,940.9 and $1,931.6	481.6	485.1
Manufacturing and Corporate [Member] | Construction in progress
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,940.9 and $1,931.6	18.7	42.5
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 $1,940.9 and $1,931.6	6,937.4	7,030.1
Less: accumulated depreciation	(1,334.0)	(1,234.2)
Property, Plant and Equipment, Net	5,603.4	5,795.9
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 $1,940.9 and $1,931.6	20.1	19.5
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 $1,940.9 and $1,931.6	6,917.3	7,010.6
Partially-owned subsidiaries
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,940.9 and $1,931.6	1,940.9	1,931.6
Less: accumulated depreciation	(561.4)	(525.7)
Partially-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 $1,940.9 and $1,931.6	2,258.9	2,248.2
Less: accumulated depreciation	(664.2)	(621.9)
Property, Plant and Equipment, Net	$ 1,594.7	$ 1,626.3