Railcar Leasing and Management Services Group - Schedule of proceeds from leased railcars (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Property Subject to or Available for Operating Lease [Line Items]
Proceeds from sale leased railcars	$ 112.8	$ 42.7
Sales-type Lease, Revenue	0.0
Total operating profit	73.0	91.8
Railcar Leasing and Management Services Group | Railcars owned one year or less at the time of sale (1)
Property Subject to or Available for Operating Lease [Line Items]
Proceeds from sale leased railcars	44.3	13.3
Railcar Leasing and Management Services Group | Railcars owned more than one year at the time of sale
Property Subject to or Available for Operating Lease [Line Items]
Proceeds from sale leased railcars	68.5	29.4
Operating Segments | Railcar Leasing and Management Services Group
Property Subject to or Available for Operating Lease [Line Items]
Total operating profit	$ 92.9	$ 85.8
Operating Profit Margin	39.30%	42.80%
Operating Segments | Railcar Owned One Year or Less [Member] | Railcar Leasing and Management Services Group
Property Subject to or Available for Operating Lease [Line Items]
Total operating profit	$ 1.7	$ 0.8
Operating Profit Margin	3.80%	6.00%
Operating Segments | Railcar Owned Greater than One Year [Member] | Railcar Leasing and Management Services Group
Property Subject to or Available for Operating Lease [Line Items]
Total operating profit	$ 8.7	$ 7.9
Operating Profit Margin	12.70%	26.90%
Operating Segments | Sales of Leased Railcars [Domain] | Railcar Leasing and Management Services Group
Property Subject to or Available for Operating Lease [Line Items]
Total operating profit	$ 10.4	$ 8.7
Operating Profit Margin	9.20%	20.40%