Railcar Leasing and Services Group - Selected Income Statement Information (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues		$ 798.8	$ 821.3	$ 2,449.8	$ 2,185.4
Cost of revenues		629.3	679.5	1,936.6	1,819.2
Selling, engineering, and administrative expenses		60.5	49.1	174.1	153.3
Lease portfolio sales		11.4	3.1	36.2	46.4
Gain (Loss) on Disposition of Other Assets		2.0	4.4	4.2	6.8
Operating Income (Loss)		122.4	100.2	379.5	268.3
Depreciation and amortization expense (4)				220.2	219.9
Railroad Transportation Equipment [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Depreciation and amortization expense (4)	[1],[2]	$ 59.7	58.7	$ 179.7	179.5
Depreciation, Depletion, and Amortization, Percent Change	[1],[2]	1.70%		0.10%
Maintenance and compliance expense (5)	[1],[3]	$ 29.7	33.7	$ 95.1	101.3
Maintenance Costs, Percent Change	[1],[3]	(11.90%)		(6.10%)
Other fleet operating costs	[1],[4]	$ 8.5	7.7	$ 24.3	25.1
Other fleet operating costs, Percent Change	[1],[4]	10.40%		(3.20%)
Interest expense (7)	[1],[5]	$ 59.1	57.9	$ 176.9	169.7
Interest Expense, Percent Change	[1],[5]	2.10%		4.20%
Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues		$ 798.8	821.3	$ 2,449.8	2,185.4
Operating Income (Loss)		164.1	125.2	486.6	374.3
Leasing & Services | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues		$ 289.5	261.7	$ 856.1	762.9
Revenues, Percent Change		10.60%		12.20%
Cost of revenues	[6]	$ 168.9	156.9	$ 495.9	471.3
Cost of revenues, Percent Change	[6]	7.60%		5.20%
Selling, engineering, and administrative expenses		$ 18.7	16.6	$ 56.8	48.7
Selling, Engineering, and Administrative Expense, Percent Change		12.70%		16.60%
Lease portfolio sales		$ 11.4	3.1	$ 36.2	46.4
Gain (Loss) on Disposition of Other Assets		1.9	4.5	3.9	7.2
Operating Income (Loss)		$ 115.2	$ 95.8	$ 343.5	$ 296.5
Operating Income (Loss), Percent Change		20.30%		15.90%
Operating Profit Margin		39.80%	36.60%	40.10%	38.90%
Operating Profit Margin, excluding Lease portfolio sales		35.90%	35.40%	35.90%	32.80%
Leasing & Services | Operating Segments [Member] | Sustainable Railcar Conversions
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Depreciation and amortization expense (4)			$ 0.1		$ 5.6
Leasing & Services | Leasing and Management [Member] | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues		$ 213.1	204.7	$ 644.0	603.2
Revenues, Percent Change		4.10%		6.80%
Leasing & Services | Maintenance services | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues	[7]	$ 66.5	39.1	$ 180.7	113.6
Revenues, Percent Change	[7]	70.10%		59.10%
Leasing & Services | Digital & Logistics Services | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenues		$ 9.9	$ 17.9	$ 31.4	$ 46.1
Revenues, Percent Change		(44.70%)		(31.90%)

[1] Includes wholly-owned railcars, partially-owned railcars, and railcars under leased-in arrangements.

[2] Depreciation and amortization expense includes $0.1 million and $5.6 million for the three and nine months ended September 30, 2023, respectively, related to the disposal of certain railcar components associated with our sustainable railcar conversion program. Additionally, amortization of deferred profit on railcars sold from the Rail Products Group to the Leasing Group is included in depreciation and amortization expense, resulting in the recognition of depreciation expense based on our original manufacturing cost of the railcars.

[3] 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.

[4] Other fleet operating costs include freight, storage, rent, and ad valorem taxes.

[5] Interest expense is not a component of operating profit and includes the effect of hedges.

[6] Includes depreciation and amortization expense, maintenance and compliance expense, and other fleet operating costs related to our lease fleet, as well as operating costs for our maintenance services and digital and logistics services businesses.

[7] Revenues related to services performed by the maintenance services business to support our lease fleet of Company-owned railcars are eliminated within the Railcar Leasing & Services Group and are excluded from the totals reported on this line.