Railcar Leasing and Management Services Group - Schedule of proceeds from leased railcars (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Property Subject to or Available for Operating Lease [Line Items]
Proceeds from sale leased railcars	$ 15.5	$ 0.0
Railcar Leasing and Management Services Group | Railcars owned one year or less at the time of sale
Property Subject to or Available for Operating Lease [Line Items]
Proceeds from sale leased railcars	0.0	0.0
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	15.5	0.0
Rail Group
Property Subject to or Available for Operating Lease [Line Items]
Proceeds from sale leased railcars	$ 0.0	$ 0.0