Railcar Leasing and Management Services Group - Selected consolidating income statement information for the Leasing Group (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2021		Sep. 30, 2020	Sep. 30, 2021		Sep. 30, 2020
Revenues:
Revenues		$ 503.5		$ 459.4	$ 1,273.8		$ 1,583.8
Operating profit (2):
Total operating profit		92.2		72.9	219.8		(161.4)
Select expense information:
Depreciation (3)					206.3		199.5
Selling, engineering, and administrative expenses		54.3		51.2	166.4		172.3
Loss on extinguishment of debt		0.0		0.0	11.7		5.0
Sustainable Railcar Conversions
Select expense information:
Depreciation (3)		4.7			7.3
Reduced Depreciation [Member]
Select expense information:
Depreciation (3)					7.0
Operating Segments [Member]
Revenues:
Revenues		503.5		459.4	1,273.8		1,583.8
Operating profit (2):
Total operating profit		120.9		100.2	302.8		325.6
Railcar Leasing and Management Services Group [Member]
Operating profit (2):
Total operating profit					268.7		265.5
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member]
Revenues:
Revenues		$ 185.5		183.9	$ 554.1		613.0
Revenues, Percent Change		0.90%			(9.60%)
Operating profit (2):
Total operating profit		$ 109.3		$ 89.7	$ 268.7		$ 265.5
Operating Income (Loss), Percent Change		21.90%			1.20%
Operating Profit Margin		58.90%		48.80%	48.50%		43.30%
Select expense information:
Depreciation (3)	[1]	$ 58.7	[2]	$ 51.5	$ 170.5	[2]	$ 159.1
Depreciation, Depletion, and Amortization, Percent Change	[1]	14.00%			7.20%
Maintenance and compliance	[1]	$ 22.8		18.5	$ 73.7		67.4
Maintenance Costs, Percent Change	[1]	23.20%			9.30%
Operating lease expense	[1]	$ 1.9		2.1	$ 5.3		8.1
Operating Leases, Rent Expense, Percent Change	[1]	(9.50%)			(34.60%)
Selling, engineering, and administrative expenses	[1]	$ 11.6		11.7	$ 36.1		39.0
Selling, Engineering, and Administrative Expense, Percent Change	[1]	(0.90%)			(7.40%)
Interest (4)		$ 39.9	[3]	47.0	$ 142.6	[3]	149.2
Interest Expense, Percent Change	[3]	(15.10%)			(4.40%)
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member] | Leasing and Management [Member]
Revenues:
Revenues		$ 185.5		183.9	$ 554.1		558.6
Revenues, Percent Change		0.90%			(0.80%)
Operating profit (2):
Total operating profit		$ 76.4		$ 86.8	$ 223.0		$ 247.8
Operating Income (Loss), Percent Change		(12.00%)			(10.00%)
Operating Profit Margin		41.20%		47.20%	40.20%		44.40%
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member] | Railcar Owned One Year or Less [Member]
Revenues:
Revenues	[4]	$ 0.0		$ 0.0	$ 0.0		$ 54.4
Revenues, Percent Change	[4]				(100.00%)
Railcar Leasing and Management Services Group [Member] | Operating Segments [Member] | Sales of Leased Railcars [Domain]
Operating profit (2):
Total operating profit	[4]	$ 32.9		$ 2.9	$ 45.7		$ 17.7
Operating Income (Loss), Percent Change	[4]				158.20%
Operating Profit Margin		10.20%		44.60%	11.10%		9.20%

[1] 2) Operating profit includes: depreciation; maintenance and compliance; rent; and selling, engineering, and administrative expenses. Amortization of deferred profit on railcars sold from the Rail Products Group to the Leasing Group is included in the operating profit of the Leasing Group, resulting in the recognition of depreciation expense based on our original manufacturing cost of the railcars. Interest expense is not a component of operating profit and includes the effect of hedges.

[2] (3) Depreciation expense increased $4.7 million and $7.3 million for the three and nine months ended September 30, 2021, respectively, as a result of the disposal of certain railcar components associated with our sustainable railcar conversion program. Additionally, depreciation expense related to our small cube covered hopper railcars decreased by approximately $7.0 million for the nine months ended September 30, 2021 relative to the nine months ended September 30, 2020 as a result of the impairment charge recorded in the second quarter of 2020 related to these railcars.

[3] Interest expense for the nine months ended September 30, 2021 includes $11.7 million of loss on extinguishment of debt associated with the refinancing of our partially-owned subsidiaries' debt. See Note 7 for more information. Interest expense for the nine months ended September 30, 2020 includes $5.0 million of loss on extinguishment of debt associated with the early redemption of debt.

[4] (1) Beginning in the fourth quarter of 2020, we made a prospective change in the presentation of sales of railcars from the lease fleet. Therefore, all railcar sales for the three and nine months ended September 30, 2021 are presented as a net gain or loss from the disposal of a long-term asset regardless of the age of railcar that is sold. See Note 1 for more information.