Property, Plant, and Equipment - Components of property, plant, and equipment - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	$ 8,385.2	$ 7,981.0
Less: accumulated depreciation	(2,250.5)	(2,014.2)
Property, plant, and equipment, net	6,134.7	5,966.8
Operating Segments
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, net	6,935.4	6,764.9
Net deferred profit on railcars sold to Leasing Group
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	(974.9)	(948.2)
Less: accumulated depreciation	174.2	150.1
Property, plant, and equipment, net	(800.7)	(798.1)
Partially-owned subsidiaries
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	1,985.9	1,979.8
Less: accumulated depreciation	(418.0)	(364.9)
Partially-owned subsidiaries | Operating Segments | Leasing Group
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, net	1,822.7	1,879.6
Partially-owned subsidiaries | Operating Segments | Equipment on lease | Leasing Group
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	2,315.5	2,309.4
Less: accumulated depreciation	(492.8)	(429.8)
Wholly-owned subsidiaries | Operating Segments | Leasing Group
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	4,998.3	4,683.7
Less: accumulated depreciation	(858.3)	(760.1)
Property, plant, and equipment, net	4,140.0	3,923.6
Wholly-owned subsidiaries | Operating Segments | Machinery and other | Leasing Group
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	10.7	10.7
Wholly-owned subsidiaries | Operating Segments | Equipment on lease | Leasing Group
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	4,987.6	4,673.0
Manufacturing/Corporate
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	2,046.4	1,936.1
Less: accumulated depreciation	(1,073.7)	(974.4)
Property, plant, and equipment, net	972.7	961.7
Manufacturing/Corporate | Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	122.1	103.3
Manufacturing/Corporate | Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	668.1	642.6
Manufacturing/Corporate | Machinery and other
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	1,223.6	1,151.1
Manufacturing/Corporate | Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, at cost	32.6	39.1
Manufacturing/Corporate | Operating Segments
Property, Plant and Equipment [Line Items]
Property, plant, and equipment, net	$ 972.7	$ 961.7