Segment Information - Financial information for segments (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Segment Reporting [Line Items]
External Revenue		$ 492.0	$ 585.4
Revenues, Total		492.0	585.4
Depreciation and amortization		72.6	74.3
Selling, engineering, and administrative expenses		50.7	50.0
Gain (Loss) on Sale of Property, Plant and Equipment, Railroad Transportation Equipment		(22.0)	(5.9)
Operating Profit (Loss)		101.1	99.8
Other (income) expense		66.0	63.4
Provision for income taxes		8.5	7.4
Loss from discontinued operations, net of benefit for income taxes of $0.6 and $0.6		(1.8)	(1.9)
Net income		24.8	27.1
Assets		8,330.7		$ 8,424.4
Operating Segment Assets		8,590.9		8,614.5
Segment Reporting, Long-Lived Asset, Expenditure for Addition		157.3	129.4
Operating Segments [Member]
Segment Reporting [Line Items]
Revenues, Total		585.8	707.9
Operating Profit (Loss)		130.3	130.4
Intersegment Eliminations [Member]
Segment Reporting [Line Items]
Intersegment Revenues		93.8	122.5
Revenues, Total		(93.8)	(122.5)
Operating Profit (Loss)		(3.5)	(6.2)
Assets		(568.4)		(575.1)
Leasing & Services
Segment Reporting [Line Items]
External Revenue		285.3	287.2
Depreciation and amortization		64.9	66.5
Segment Reporting, Long-Lived Asset, Expenditure for Addition		153.3	122.5
Leasing & Services | Operating Segments [Member]
Segment Reporting [Line Items]
Revenues, Total		285.8	287.4
Selling, engineering, and administrative expenses	[1]	17.5	18.7
Gain (Loss) on Sale of Property, Plant and Equipment, Railroad Transportation Equipment	[1]	(22.0)	(5.9)
Segment Reporting, Other Segment Item, Amount	[2]	81.8	71.0
Operating Profit (Loss)		108.2	104.5
Assets		7,702.8		7,676.5
Leasing & Services | Operating Segments [Member] | Railroad Transportation Equipment [Member]
Segment Reporting [Line Items]
Depreciation and amortization	[1],[3]	59.2	61.1
Maintenance and compliance expense (5)	[1],[3],[4]	41.1	38.0
Leasing & Services | Intersegment Eliminations [Member]
Segment Reporting [Line Items]
Intersegment Revenues		0.5	0.2
Rail Products Group [Member]
Segment Reporting [Line Items]
External Revenue		206.7	298.2
Depreciation and amortization		6.9	7.0
Segment Reporting, Long-Lived Asset, Expenditure for Addition		2.7	6.6
Rail Products Group [Member] | Operating Segments [Member]
Segment Reporting [Line Items]
Revenues, Total		300.0	420.5
Cost of Revenue	[1],[5]	270.4	387.7
Selling, engineering, and administrative expenses	[1]	7.5	6.9
Segment Reporting, Other Segment Item, Amount	[2]	0.0	0.0
Operating Profit (Loss)		22.1	25.9
Assets		888.1		938.0
Rail Products Group [Member] | Intersegment Eliminations [Member]
Segment Reporting [Line Items]
Intersegment Revenues		93.3	122.3
Corporate Segment [Member]
Segment Reporting [Line Items]
Depreciation and amortization		0.8	0.8
Operating Profit (Loss)		(25.7)	(24.4)
Segment Reporting, Long-Lived Asset, Expenditure for Addition		1.3	$ 0.3
Corporate Segment and Other Operating Segment | Operating Segments [Member]
Segment Reporting [Line Items]
Assets		$ 308.2		$ 385.0

[1] Significant expense categories and amounts align with the segment-level information that is regularly provided to and reviewed by the CODM. Intersegment expenses are included within the amounts shown.

[2] Other segment items for each reportable segment include: –Railcar Leasing and Services Group: the remaining operating costs for our maintenance services and digital and logistics services businesses, including materials, labor, and overhead costs; other operating costs for the lease fleet, including equipment rental, property taxes, and freight and storage expenses; and gains or losses on dispositions of other property. –Rail Products Group: (gains) or losses on dispositions of other property.

[3] Company-owned railcars include wholly-owned railcars, partially-owned railcars, and railcars under leased-in arrangements.

[4] Maintenance and compliance expense is reported at cost with respect to the services performed by our maintenance services business to support the railcars in our lease fleet.

[5] Cost of revenues in the Rail Products Group primarily includes materials, labor, and overhead, including depreciation and amortization.