Railcar Leasing and Management Services Group - Schedule of proceeds from leased railcars (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Property Subject to or Available for Operating Lease [Line Items]
Lease portfolio sales				$ 404.5
Operating profit on lease portfolio sales		$ 92.2	$ 72.9	219.8	$ (161.4)
Railcar Leasing and Management Services Group [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating profit on lease portfolio sales				268.7	265.5
Operating Segments [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating profit on lease portfolio sales		120.9	100.2	302.8	325.6
Operating Segments [Member] | Railcar Leasing and Management Services Group [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating profit on lease portfolio sales		$ 109.3	$ 89.7	$ 268.7	$ 265.5
Operating Profit Margin		58.90%	48.80%	48.50%	43.30%
Operating Segments [Member] | Sales of Leased Railcars [Domain] | Railcar Leasing and Management Services Group [Member]
Property Subject to or Available for Operating Lease [Line Items]
Lease portfolio sales		$ 322.1	$ 6.5	$ 410.9	$ 193.1
Operating profit on lease portfolio sales	[1]	$ 32.9	$ 2.9	$ 45.7	$ 17.7
Operating Profit Margin		10.20%	44.60%	11.10%	9.20%

[1] (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.