Railcar Leasing and Management Services Group - Schedule of proceeds from leased railcars (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Property Subject to or Available for Operating Lease [Line Items]
Lease portfolio sales				$ 88.8
Operating profit on lease portfolio sales		$ 67.4	$ (307.3)	127.6	$ (234.3)
Railcar Leasing and Management Services Group [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating profit on lease portfolio sales				159.4	175.8
Operating Segments [Member]
Property Subject to or Available for Operating Lease [Line Items]
Operating profit on lease portfolio sales		97.1	98.1	181.9	225.4
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		$ 81.1	$ 82.9	$ 159.4	$ 175.8
Operating Profit Margin		43.80%	43.00%	43.20%	41.00%
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		$ 71.5	$ 73.8	$ 88.8	$ 186.6
Operating profit on lease portfolio sales	[1]	$ 11.1	$ 4.4	$ 12.8	$ 14.8
Operating Profit Margin		15.50%	6.00%	14.40%	7.90%

[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 six months ended June 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.