Property, Plant, and Equipment - Components of property, plant, and equipment (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,927.9 and $1,917.6	$ 9,482.4	$ 9,272.6
Less: accumulated depreciation	(2,491.2)	(2,385.8)
Property, Plant and Equipment, Net	6,991.2	6,886.8
Intersegment Eliminations [Member]
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,927.9 and $1,917.6	(1,063.5)	(1,050.7)
Property, Plant and Equipment, Net	(758.7)	(763.3)
Negative Accumulated Depreciation PP&E- Deferred Profit	304.8	287.4
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member]
Property, Plant and Equipment, Net [Abstract]
Property, Plant and Equipment, Net	7,406.4	7,309.4
Manufacturing and Corporate [Member]
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,927.9 and $1,917.6	793.5	823.9
Less: accumulated depreciation	(450.0)	(483.2)
Property, Plant and Equipment, Net	343.5	340.7
Manufacturing and Corporate [Member] | Land
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,927.9 and $1,917.6	16.2	15.7
Manufacturing and Corporate [Member] | Buildings and improvements
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,927.9 and $1,917.6	374.8	384.6
Manufacturing and Corporate [Member] | Machinery and other
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,927.9 and $1,917.6	388.6	405.5
Manufacturing and Corporate [Member] | Construction in progress
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,927.9 and $1,917.6	13.9	18.1
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 $1,927.9 and $1,917.6	7,510.1	7,269.0
Less: accumulated depreciation	(1,594.4)	(1,480.9)
Property, Plant and Equipment, Net	5,915.7	5,788.1
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 $1,927.9 and $1,917.6	25.9	21.7
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 $1,927.9 and $1,917.6	7,484.2	7,247.3
Partially-owned subsidiaries
Property, Plant and Equipment, Net [Abstract]
Property, plant, and equipment, at cost, including partially-owned subsidiaries of $1,927.9 and $1,917.6	1,927.9	1,917.6
Less: accumulated depreciation	(635.0)	(599.0)
Partially-owned subsidiaries | Railcar Leasing and Management Services Group [Member] | Operating Segments [Member]
Property, Plant and Equipment, Net [Abstract]
Less: accumulated depreciation	(751.6)	(709.1)
Property, Plant and Equipment, Net	1,490.7	1,521.3
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 $1,927.9 and $1,917.6	$ 2,242.3	$ 2,230.4